JP7735649B2 - Laser Processing Equipment - Google Patents

Description

The present invention relates to a laser processing device that performs laser processing on wafers.

In recent years, in the field of semiconductor device manufacturing, wafers (semiconductor wafers) have become known in which multiple devices are formed using a laminate consisting of a low-dielectric-constant insulating film (low-k film) made of a glassy material and a functional film that forms circuits, laminated on the surface of a substrate such as silicon. Such wafers are divided into multiple devices in a grid pattern by grid-like streets (also known as planned division lines), and individual devices are manufactured by dividing the wafer along the streets.

Known methods for dividing a wafer into multiple devices (chips) include using a high-speed rotating blade and forming modified regions along the streets inside the wafer and applying external force along the streets. However, in the case of wafers that use a low-k film, the material of the low-k film is different from the material of the wafer, so the former method makes it difficult to simultaneously cut the insulating film and substrate with a blade. Furthermore, the latter method makes it difficult to divide the wafer into individual devices with good quality when low-k film is present on the streets.

Patent Document 1 discloses a laser processing device that performs edge cutting processing, which forms two edge cutting grooves (blocking grooves) along the streets of a wafer, and core cutting processing, which forms a core cutting groove (dividing groove) between the two edge cutting grooves. This laser processing device is equipped with a first laser beam application unit that corresponds to the edge cutting processing and a second laser beam application unit that corresponds to the core cutting processing (see Figure 15 of Patent Document 1). By moving the first laser beam application unit and the second laser beam application unit relative to the wafer in one direction in the processing feed direction (e.g., the forward direction), the two edge cutting grooves and the core cutting groove are simultaneously formed (parallel formation) along the same street, thereby removing low-k films, etc.

In such laser processing equipment, the formation position of the two edge-cutting grooves may shift relative to the street, or the formation position of the hollow groove may shift relative to the formation position of the two edge-cutting grooves, due to changes in the offset amount of each part due to temperature fluctuations, errors in the processing feed (straightness errors), and installation errors (assembly errors) and operation errors of each part of the optical system.

Therefore, the laser processing device performs a kerf check by photographing the two edge-cut grooves and the center-cut grooves with various microscopes or cameras at preset times, and measuring the processing position, processing width, and chipping of the two edge-cut grooves and the center-cut grooves based on the captured images.

For example, Patent Document 2 discloses a laser processing device that uses an observation optical system coaxial with the laser processing optical system of the laser processing device to photograph the processed groove (kerf) formed by laser processing, and performs a kerf check based on the photographed image. Furthermore, Patent Document 3 discloses a laser processing device that performs edge cutting and hollowing in different regions within the peripheral excess region of the workpiece, and separately performs kerf checks on the two edge cutting grooves and hollowing grooves formed in each of the peripheral excess regions.

In addition, with laser processing equipment, fluctuations in the laser beam output, abnormalities in the laser beam, foreign matter on the optical path of the optical system, and dirt on the focusing lens can disrupt the laser beam profile at the processing point during laser processing, which can result in a deterioration in the processing quality of the two edge-cut grooves and the hollowed-out grooves.

Patent Document 4 discloses a laser processing device that captures an image of the laser spot (also called the beam plasma or focal point) of the laser light during laser processing, and uses this captured image to detect whether the laser spot is positioned at the desired position.

JP 2009-182019 A Patent No. 6498553 Patent No. 6210902 JP 2017-120820 A

The laser processing device described in Patent Document 2 performs kerf checks using an observation optical system that is coaxial with the laser processing optical system, making it possible to perform so-called real-time kerf checks, in which the kerf of the processed groove is checked in parallel during laser processing. However, when performing edge cutting and hollowing along the street as described in Patent Document 1, the hollowed groove is formed between two already formed edge cutting grooves, so it is not possible to photograph the hollowed groove alone. For this reason, the laser processing device described in Patent Document 2 can perform kerf checks on two edge cutting grooves alone, but cannot perform kerf checks on hollowed grooves alone.

The laser processing device described in Patent Document 3 requires edge cutting and hollowing out of the excess area around the workpiece's periphery when performing a kerf check, making it impossible to perform the real-time kerf check described above. Therefore, even if an abnormality occurs during laser processing, this abnormality cannot be detected immediately.

Furthermore, the laser processing devices described in Patent Documents 2 and 3 only photograph the outer shapes of the processed grooves (two edge-cut grooves and a hollow groove), making it impossible to confirm whether the laser beam itself is operating properly during laser processing. As a result, it is not possible to detect abnormalities that occur during laser processing, and it cannot be said that the positional accuracy and processing quality of the laser processing are adequately maintained.

On the other hand, while the laser processing device described in Patent Document 4 can detect the position of the laser spot of the laser light, it cannot detect abnormalities in the shape of the processed groove simply by photographing and observing the laser spot. For this reason, it cannot be said that the positional accuracy and processing quality of the laser processing are sufficiently maintained.

The present invention was made in consideration of these circumstances, and aims to provide a laser processing device that can further improve the positional accuracy and processing quality of laser processing.

To achieve the objectives of the present invention, a laser processing device performs laser processing to form grooves along the streets by irradiating the streets with laser light from the laser head while moving a table that holds a wafer and a laser head having a focusing lens that focuses laser light on the streets of the wafer held on the table relative to each other in the processing feed direction along the streets of the wafer. The laser processing device also includes a camera that simultaneously captures images of the laser spot of the laser light focused on the street and the grooves through the focusing lens while laser processing is being performed, and a measurement unit that measures the positional accuracy and processing quality of the laser processing based on the images captured by the camera.

This laser processing device allows for simultaneous measurement of laser processing position accuracy and processing quality.

A laser processing device according to another aspect of the present invention includes an illumination light source that emits illumination light; a main optical path that guides laser light and the illumination light emitted from the illumination light source to a condenser lens and into which a first reflected light of the laser light reflected by the street and a second reflected light of the illumination light enter from the condenser lens; and a branching optical element disposed in the main optical path that outputs the first reflected light and the second reflected light that enter the main optical path toward a branching optical path that branches from the main optical path. A camera is disposed in the branching optical path and captures the first reflected light and the second reflected light to generate photographed images of the laser spot and groove. This allows the positional accuracy and processing quality of laser processing to be measured simultaneously.

In another aspect of the present invention, a laser processing device is provided with a light reduction filter that is disposed in the branched optical path and reduces the amount of first reflected light that enters the camera. This makes it possible to prevent overexposure in the captured image.

In a laser processing device according to another aspect of the present invention, the wavelength of the laser light and the wavelength range of the illumination light are different, and the light intensity reduction filter is a band-stop filter that reduces the amount of light corresponding to the wavelength range of the laser light. This makes it possible to prevent overexposure in the captured image.

In another aspect of the present invention, the laser processing device includes an illumination light source that emits illumination light in a wavelength range different from that of laser light; a main optical path that guides the laser light and the illumination light emitted from the illumination light source to a condenser lens and into which a first reflected light of the laser light reflected by a street and a second reflected light of the illumination light enter from the condenser lens; a first branching optical element arranged in the main optical path that outputs the first reflected light that entered the main optical path toward a first branched optical path branched from the main optical path; and a second branching optical element arranged in the main optical path that outputs the second reflected light that entered the main optical path toward a second branched optical path branched from the main optical path. The camera includes a first camera arranged in the first branched optical path that captures the first reflected light, and a second camera arranged in the second branched optical path that captures the second reflected light, with the sensitivity of the first camera set lower than that of the second camera. This prevents blown-out highlights from occurring in captured images.

In another aspect of the laser processing device of the present invention, the laser processing involves edge cutting, which forms two parallel grooves along the street, and hollowing, which forms a groove between the two grooves.The camera simultaneously captures images of the laser spot corresponding to the edge cutting and the grooves through a condenser lens while the edge cutting is being performed, and simultaneously captures images of the laser spot corresponding to the hollow cutting and the grooves through a condenser lens while the hollowing is being performed.

A laser processing device according to another aspect of the present invention includes a first illumination light source that illuminates the street edge cutting processing area through a condenser lens while edge cutting processing is being performed, and a second illumination light source that illuminates the street hollowing processing area through a condenser lens while hollowing processing is being performed.

A laser processing device according to another aspect of the present invention includes a mirror mechanism provided on the optical path of the laser light, the mirror mechanism including a plurality of mirrors and an adjustment mechanism that adjusts at least one of the position and orientation of the plurality of mirrors.

In another aspect of the laser processing device of the present invention, the focusing lens includes a first focusing lens and two second focusing lenses arranged in a row along the processing feed direction with the first focusing lens sandwiched between them; the laser head includes a laser light emitting system that emits two first laser beams corresponding to edge cutting processing and a second laser beam corresponding to center cutting processing as laser beams; and a connection optical system that guides the two first laser beams emitted from the laser light emitting system to the first focusing lens and selectively guides the second laser beam emitted from the laser light emitting system to the two second focusing lenses; when the laser head is moved relative to the table in either the forward direction or the backward direction in the processing feed direction, the connection optical system guides the second laser beam emitted from the laser light emitting system to the second focusing lens located on the other side of the first focusing lens in the forward direction or the backward direction; and a camera is provided for each of the first focusing lens and the two second focusing lenses. This reduces the takt time required for laser processing of wafers.

In another aspect of the laser processing device of the present invention, the laser beam emission system includes a laser light source that emits laser beams, a branching element that branches the laser beam emitted from the laser light source into two beams, a first beam forming element that generates and emits two first laser beams from one of the laser beams branched by the branching element, a second beam forming element that generates and emits a second laser beam from the other laser beam branched by the branching element, and a mirror mechanism provided on the optical path of the laser beam and/or on the optical paths of the two first laser beams and the second laser beam, and the mirror mechanism includes a plurality of mirrors and an adjustment mechanism that adjusts at least one of the position and orientation of the plurality of mirrors.

In another aspect of the laser processing device of the present invention, the condenser lens includes a first condenser lens and two second condenser lenses arranged in a row along the processing feed direction together with the first condenser lens, sandwiching the first condenser lens therebetween; the laser head includes a first laser light emitting system that emits two first laser beams corresponding to edge cutting as laser beams, two second laser light emitting systems that emit second laser beams corresponding to center cutting as laser beams, a first connecting optical system that guides the two first laser beams emitted from the first laser light emitting system to the first condenser lens; and a laser head that is connected to a table. and a second connection optical system that guides the second laser light emitted from one of the second laser light emitting systems to a second condenser lens located on the return side of the processing feed direction relative to the first condenser lens when the laser head is moved relatively in the outgoing direction in the processing feed direction, and that guides the second laser light emitted from the other of the second laser light emitting systems to a second condenser lens located on the return side of the first condenser lens when the laser head is moved relatively in the return direction relative to the table, and cameras are provided for each of the first condenser lens and two second condenser lenses.

A laser processing device according to another aspect of the present invention includes a mirror mechanism provided on the optical paths of two first laser beams and one second laser beam, the mirror mechanism including a plurality of mirrors and an adjustment mechanism that adjusts at least one of the position and orientation of the plurality of mirrors.

The present invention can further improve the positional accuracy and processing quality of laser processing.

1 is a schematic diagram of a laser processing apparatus according to a first embodiment. FIG. 2 is a plan view of a wafer. FIG. 10 is an explanatory diagram for explaining laser processing along odd-numbered streets. FIG. 10 is an explanatory diagram for explaining laser processing along even-numbered streets. This is an explanatory diagram to explain edge cutting and hollowing processing using a laser head that moves relative to the wafer in the forward direction, simultaneous photography of the laser spot and two edge cutting grooves, and simultaneous photography of the laser spot and hollowing grooves. This is an explanatory diagram to explain edge cutting and core cutting processing using a laser head that moves relative to the wafer in the return direction, simultaneous photography of the laser spot and two edge cutting grooves, and simultaneous photography of the laser spot and core cutting grooves. FIG. 2 is a functional block diagram of a control device. 10 is an explanatory diagram for explaining measurement of the positional accuracy of edge cutting processing by a positional accuracy measurement unit. FIG. 10 is an explanatory diagram for explaining measurement of positional accuracy of hollowing by a positional accuracy measuring unit. FIG. 10 is an explanatory diagram for explaining measurement of the processing quality of edge cutting by a processing quality measurement unit. FIG. 10 is an explanatory diagram for explaining measurement of the processing quality of hollowing by a processing quality measurement unit. FIG. 10 is a flowchart showing the flow of laser processing of each street of a wafer by the laser processing device. FIG. 10 is a schematic diagram of a laser head of a laser processing apparatus according to a second embodiment. FIG. 10 is a schematic diagram of a laser head of a laser processing apparatus according to a third embodiment. FIG. 10 is a schematic view of a laser head of a laser processing apparatus according to a fourth embodiment. FIG. 10 is a schematic view of a laser head of a laser processing apparatus according to a fifth embodiment. FIG. 13 is a schematic diagram of a laser head of a laser processing apparatus according to a sixth embodiment. FIG. 13 is a schematic diagram of a laser head of a laser processing apparatus according to a seventh embodiment.

[Overall configuration of the laser processing device of the first embodiment]
Fig. 1 is a schematic diagram of a laser processing apparatus 10 according to a first embodiment. As shown in Fig. 1, the laser processing apparatus 10 performs laser processing (also referred to as laser ablation processing or ablation groove processing) along a plurality of streets C on a wafer 12. Note that the X, Y, and Z directions in the figure are mutually orthogonal, with the X and Y directions being horizontal directions and the Z direction being the up-down direction. Here, the X direction corresponds to the processing feed direction in the present invention, and the Y direction corresponds to the vertical direction in the present invention.

Figure 2 is a plan view of the wafer 12. As shown in Figure 2, the wafer 12 is a laminated body in which a low-k film and a functional film that forms circuits are stacked on the surface of a substrate such as silicon. The wafer 12 is divided into multiple regions by multiple streets C arranged in a grid pattern. Each of these divided regions is provided with a device 16 that constitutes a chip 14.

As indicated by the parenthesized numbers (1) to (4) in the figure, the laser processing device 10 performs laser processing to remove low-k films and other materials from the substrate along each street C along one of the intersecting directions. After completing laser processing of all streets C parallel to one direction, the laser processing device 10 rotates the wafer 12 by 90 degrees and performs laser processing to remove low-k films and other materials along each street C along the other direction.

At this time, in order to reduce the takt time required for laser processing of the wafer 12, the laser processing device 10 alternates the processing feed direction (relative movement direction) when moving the laser head 24 (described below) relative to the wafer 12 in the X direction for each street C.

For example, when laser processing is performed along odd-numbered streets C, such as those indicated by parenthesized numbers (1) and (3) in the figure, the laser head 24, described below, is moved relative to the wafer 12 in one direction in the X direction, that is, the forward direction XA (see FIG. 5). Furthermore, when laser processing is performed along even-numbered streets C, such as those indicated by parenthesized numbers (2) and (4) in the figure, the laser head 24 is moved relative to the wafer 12 in the other direction in the X direction, that is, the backward direction XB (see FIG. 6).

Figure 3 is an explanatory diagram illustrating laser processing along odd-numbered streets C. Figure 4 is an explanatory diagram illustrating laser processing along even-numbered streets C.

As shown in Figures 3 and 4, in this embodiment, edge cutting and hollowing are performed simultaneously (in parallel) as laser processing. Edge cutting is performed using two first laser beams L1, and forms two parallel edge cutting grooves 18 (ablation grooves corresponding to the two first grooves of the present invention) along street C. Hole cutting is performed using one second laser beam L2, which has a larger diameter than the two first laser beams L1, and forms a hollowing groove 19 (ablation groove corresponding to the second groove of the present invention) between the two edge cutting grooves 18 formed by the edge cutting. Note that the two edge cutting grooves 18 and hollowing groove 19 are publicly known technologies (see Patent Document 1), so detailed description thereof will be omitted.

In this way, in the laser processing device 10, whether the laser head 24 is moved relative to the wafer 12 in the forward direction XA (see Figure 5) or in the backward direction XB (see Figure 6), the edge cutting process is performed before the hollowing process.

Returning to Figure 1, the laser processing device 10 simultaneously captures the laser spots SP1 of the two first laser beams L1 and the two edge-cutting grooves 18, and also captures the laser spots SP2 of the second laser beam L2 and the two edge-cutting grooves 18 (including the hollow grooves 19) while laser processing street C.

The laser processing device 10 includes a table 20, a laser head 24, a microscope 26, a relative movement mechanism 28, and a control device 30.

The table 20 holds the wafer 12. The table 20 is moved by the relative movement mechanism 28 in the X direction, which is the processing feed direction parallel to the street C to be processed, and is rotated around the central axis (rotation axis) of the table 20, which is parallel to the Z direction.

The laser head 24 (also referred to as the laser optical system or laser unit) includes a first laser light source 22A, a second laser light source 22B, a first condenser lens 38, and two second condenser lenses 40A and 40B. The laser head 24 irradiates two first laser beams L1 from the first condenser lens 38 toward street C. The laser head 24 also selectively irradiates second laser beams L2 from the two second condenser lenses 40A and 40B toward street C. The laser head 24 is moved in the Y and Z directions by a relative movement mechanism 28.

The microscope 26 is fixed to the laser head 24 and moves integrally with the laser head 24. The microscope 26 photographs the alignment reference formed on the wafer 12 before edge cutting and hollowing processing of the wafer 12. The alignment reference may be a street C, a device 16, or a known alignment mark.

The relative movement mechanism 28 is composed of an XYZ actuator and motor (not shown), and under the control of the control device 30, moves the table 20 in the X direction and rotates it around the rotation axis, and moves the laser head 24 in the Y and Z directions. This allows the relative movement mechanism 28 to move the laser head 24 and microscope 26 relative to the table 20 and wafer 12.

By driving the relative movement mechanism 28, it is possible to align the laser head 24 with the processing start position, which is one end of the street C to be processed, and to relatively move the laser head 24 in the processing feed direction (X direction) along the street C. Furthermore, by driving the relative movement mechanism 28 and rotating the table 20 by 90 degrees, it is possible to selectively make each of the intersecting streets C parallel to the processing feed direction (X direction).

The control device 30 comprehensively controls the operation of each part of the laser processing device 10, such as the laser head 24, microscope 26, and relative movement mechanism 28, and performs operations such as aligning the laser head 24, laser processing for each street C, simultaneously photographing the laser spot SP1 and the two edge-cutting grooves 18, and simultaneously photographing the laser spot SP2 and the hollow groove 19.

[Laser head]
Fig. 5 is an explanatory diagram for explaining edge cutting and center cutting processing by the laser head 24 moved relatively in the forward direction side XA with respect to the wafer 12, simultaneous photography of the laser spot SP1 and the two edge cutting grooves 18, and simultaneous photography of the laser spot SP2 and the center cutting groove 19. Fig. 6 is an explanatory diagram for explaining edge cutting and center cutting processing by the laser head 24 moved relatively in the backward direction side XB with respect to the wafer 12, simultaneous photography of the laser spot SP1 and the two edge cutting grooves 18, and simultaneous photography of the laser spot SP2 and the center cutting groove 19.

Hereinafter, odd-numbered streets C that are the target of processing by the laser head 24 that moves relatively in the forward direction XA with respect to the wafer 12 will be referred to as the "forward path" as appropriate, and even-numbered streets C that are the target of processing by the laser head 24 that moves relatively in the backward direction XB will be referred to as the "backward path" as appropriate.

As shown in Figures 5 and 6, the laser head 24 includes a first laser light source 22A, a second laser light source 22B, steering mirror mechanisms M1A and M1B, a first light forming element 32, a beam splitter 33, a second light forming element 34, a beam splitter 35, a connection switching element 36, a beam splitter 37, a first condenser lens 38, second condenser lenses 40A and 40B, an illumination light source 41, beam splitters 42, 43A, and 43B, and cameras 45, 46A, and 46B. The first laser light source 22A, the second laser light source 22B, the first light forming element 32, and the second light forming element 34 constitute the laser light emission system of the present invention.

Under the control of the control device 30, the first laser light source 22A emits laser light LA with conditions (wavelength, pulse width, repetition frequency, etc.) suitable for edge cutting processing to the first light forming element 32 via a steering mirror mechanism M1A (described below).Under the control of the control device 30, the second laser light source 22B emits laser light LB with conditions (wavelength, pulse width, repetition frequency, etc.) suitable for hollow cutting processing to the second light forming element 34 via a steering mirror mechanism M1B (described below).

The first light forming element 32 may be, for example, a diffractive optical element (DOE). This first light forming element 32 forms two first laser beams L1 corresponding to the edge cutting process from the laser beam LA incident from the first laser light source 22A, and emits the two first laser beams L1 toward the beam splitter 33. As a result, portions of the two first laser beams L1 are reflected by the beam splitter 33 toward the first condenser lens 38. As a result, the two first laser beams L1 are condensed by the first condenser lens 38 onto street C (outbound and return paths), and two laser spots SP1 spaced apart in the Y direction are formed on street C.

Although not shown, the optical paths of the two first laser beams L1 (including the various optical elements arranged along the optical paths) from the first light forming element 32 to the first focusing lens 38 constitute part of the connection optical system of the present invention.

The second light forming element 34 may be, for example, a diffractive optical element or a mask. The second light forming element 34 forms the second laser light L2 corresponding to the hollowing process from the laser light LB incident from the second laser light source 22B. The second laser light L2 forms a single rectangular (or other shape such as circular) laser spot SP2 between the two edge cutting grooves 18 on the wafer 12. The width of this spot in the Y direction is adjusted to match the spacing between the two edge cutting grooves 18. A portion of the second laser light L2 emitted from the second light forming element 34 is reflected by the beam splitter 35 toward the connection switching element 36.

The connection switching element 36 constitutes the connection optical system of the present invention. A known optical switch or the like is used as this connection switching element 36. The connection switching element 36 may also be constituted by an appropriate combination of various optical elements [such as a λ/2 plate, a polarizing beam splitter, a half mirror (beam splitter), and a shutter]. The connection switching element 36 selectively guides the second laser light L2 emitted from the second light forming element 34 to the second condenser lens 40A and the second condenser lens 40B (beam splitter 37 via a steering mirror mechanism M1B). The beam splitter 37 reflects a portion of the second laser light L2 incident from the connection switching element 36 toward the second condenser lens 40B.

The first condenser lens 38 and the second condenser lenses 40A and 40B are arranged in a row along the X direction (processing feed direction). The first condenser lens 38 is arranged between the second condenser lenses 40A and 40B. The second condenser lens 40A is arranged on the return path side XB relative to the first condenser lens 38. The second condenser lens 40B is arranged on the forward path side XA relative to the first condenser lens 38.

The first focusing lens 38 focuses the two first laser beams L1 incident from the first light forming element 32 onto street C (outward and return paths). The second focusing lens 40A focuses the second laser beam L2 incident from the connection switching element 36 onto street C (outward path). The second focusing lens 40B focuses the second laser beam L2 incident from the connection switching element 36 via the beam splitter 37 onto street C (return path).

When the laser head 24 is moved relative to the wafer 12 in either the forward direction side XA or the backward direction side XB, the connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 to one of the second condenser lenses 40A, 40B located on the other side of the forward direction side XA or the backward direction side XB relative to the first condenser lens 38.

Specifically, when the laser head 24 is moved relative to the wafer 12 in the forward direction XA, the connection switching element 36 guides the second laser beam L2 emitted from the second light forming element 34 to the second condenser lens 40A (see FIG. 5). This causes the second laser beam L2 to be focused on street C (forward path) by the second condenser lens 40A. As a result, the relative movement of the laser head 24 in the forward direction XA first performs edge cutting processing along street C (forward path), forming two edge cutting grooves 18, and then performs center cutting processing, forming a center cutting groove 19 between the two edge cutting grooves 18.

Furthermore, when the laser head 24 is moved relative to the wafer 12 in the return direction XB, the connection switching element 36 guides the second laser light L2 emitted from the second light forming element 34 to the second condenser lens 40B (see Figure 6). This causes the second laser light L2 to be focused on street C (return direction) by the second condenser lens 40B. As a result, the relative movement of the laser head 24 in the return direction XB first performs edge cutting processing along street C (return direction), forming two edge cutting grooves 18, and then performs center cutting processing, forming a center cutting groove 19 between the two edge cutting grooves 18.

The illumination light source 41 emits illumination light L3 that illuminates the street C (the two edge-cut grooves 18 and the hollow groove 19) during laser processing. Note that illumination light L3 uses light in a wavelength range (approximately 430 nm) close to the wavelength range (approximately 355 nm) of the laser beams LA and LB in order to suppress the effects of aberrations in the first condenser lens 38 and the second condenser lenses 40A and 40B.

The illumination light L3 emitted from the illumination light source 41 enters the first condenser lens 38 via the beam splitters 42 and 33, and is condensed by the first condenser lens 38 onto the street C (outbound and inbound paths) and the two edge-cutting grooves 18. As a result, the street C (outbound and inbound paths) and the two edge-cutting grooves 18 are illuminated by the illumination light L3 during edge-cutting processing of the street C (outbound and inbound paths).

Furthermore, illumination light L3 emitted from the illumination light source 41 enters the second condenser lens 40A via the beam splitter 43A, 35 and the connection switching element 36, and is focused by the second condenser lens 40A onto street C (outbound path), the two edge-cutting grooves 18, and the cut-out groove 19. Furthermore, illumination light L3 enters the second condenser lens 40B via the beam splitter 43B, 37, and is focused by the second condenser lens 40B onto street C (return path), the two edge-cutting grooves 18, and the cut-out groove 19. As a result, street C, the two edge-cutting grooves 18, and the cut-out groove 19 are illuminated by illumination light L3 during cut-out processing of street C (outbound path and return path).

The main optical path OP1 is composed of the optical path from the first laser light source 22A to the first condenser lens 38 and the optical path from the illumination light source 41 to the first condenser lens 38. The main optical path OP1 guides the first laser light L1 and illumination light L3 to the first condenser lens 38. Also, the main optical path OP1 is entered from the first condenser lens 38 by reflected laser light R1 (corresponding to the first reflected light), which is the reflected light of the first laser light L1 reflected by street C (outbound and return paths), and reflected illumination light R3 (corresponding to the second reflected light), which is the reflected light of the illumination light L3. A portion of each reflected light R1, R3 that enters the main optical path OP1 passes through the beam splitter 33 and enters the beam splitter 42.

The main optical path OP2 is composed of the optical path from the second laser light source 22B to the second condenser lens 40A and the optical path from the illumination light source 41 to the second condenser lens 40A. The main optical path OP2 guides the second laser light L2 and illumination light L3 to the second condenser lens 40A. Also, the main optical path OP2 receives reflected laser light R2 (corresponding to the first reflected light), which is the reflected light of the second laser light L2 reflected on street C (outbound path), and the previously described illumination reflected light R3 from the second condenser lens 40A. A portion of each reflected light R2, R3 that enters the main optical path OP2 passes through the connection switching element 36 and beam splitter 35 and enters the beam splitter 43A.

The main optical path OP3 is composed of the optical path from the second laser light source 22B to the second condenser lens 40B and the optical path from the illumination light source 41 to the second condenser lens 40B. The main optical path OP3 guides the second laser light L2 and illumination light L3 to the second condenser lens 40B. In addition, reflected light R2 and R3 reflected on street C (return path) enter the main optical path OP3 from the second condenser lens 40B. A portion of the reflected light R2 and R3 entering the main optical path OP3 passes through the beam splitter 37 and enters the beam splitter 43B.

Beam splitters 42, 43A, and 43B (including half mirrors) correspond to the branching optical element of the present invention. Beam splitter 42 branches branched optical path BP1 from main optical path OP1. This beam splitter 42 reflects a portion of each reflected light beam R1 and R3 incident from beam splitter 33 toward branched optical path BP1.

Beam splitter 43A branches off branched optical path BP2 from main optical path OP2. This beam splitter 43A reflects a portion of each reflected light beam R2, R3 incident from beam splitter 35 toward branched optical path BP2.

Beam splitter 43B branches off branched optical path BP3 from main optical path OP3. This beam splitter 43B reflects a portion of each reflected light beam R2, R3 incident from beam splitter 37 toward branched optical path BP3.

Cameras 45, 46A, and 46B are electronic cameras equipped with a photographing optical system and image sensor (not shown). Camera 45 is positioned on branched optical path BP1 and captures the reflected light beams R1 and R3 incident on beam splitter 42. As a result, camera 45 simultaneously captures the laser spot SP1 and the two edge-cutting grooves 18 through first condenser lens 38 while edge-cutting processing of street C (outbound and return paths) is being performed. The captured image D1 (image data) of laser spot SP1 and the two edge-cutting grooves 18 simultaneously captured by camera 45 is output from camera 45 to control device 30.

Camera 46A is positioned on branched optical path BP2 and captures the reflected light beams R2 and R3 incident from beam splitter 43A. As a result, while the center cutting process is being performed on street C (outbound path), camera 46A simultaneously captures the laser spot SP2, center cutting groove 19, and the two edge cutting grooves 18 formed earlier through the second condenser lens 40A. The captured image D2A (image data) of the laser spot SP2, the two edge cutting grooves 18, etc. simultaneously captured by camera 46A is output from camera 46A to control device 30.

Camera 46B is positioned on branched optical path BP3 and captures the reflected light beams R2 and R3 incident from beam splitter 43B. As a result, while the center cutting process of street C (return path) is being performed, camera 46B simultaneously captures the laser spot SP2, center cutting groove 19, and the two edge cutting grooves 18 formed earlier through the second condenser lens 40B. The captured image D2B (image data) of the laser spot SP2 and the two edge cutting grooves 18 simultaneously captured by camera 46B is output from camera 46B to control device 30.

When taking pictures using cameras 45, 46A, and 46B, the exposure time may be shortened to obtain an image in which street C appears stationary, or the exposure time may be lengthened to obtain an image in which street C appears to be moving.

[Control device]
FIG. 7 is a functional block diagram of the control device 30. As shown in FIG. 7, the control device 30 is configured by an arithmetic device such as a personal computer, and includes an arithmetic circuit configured with various processors, memories, etc. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). The various functions of the control device 30 may be implemented by a single processor or by multiple processors of the same or different types.

In addition to the first laser light source 22A, second laser light source 22B, microscope 26, relative movement mechanism 28, illumination light source 41, and cameras 45, 46A, and 46B already described, an operation unit 49 is also connected to the control device 30. The operation unit 49 uses a keyboard, mouse, operation panel, operation buttons, etc., and accepts input of various operations by the operator.

By executing a control program (not shown) stored in a memory unit (not shown), the control device 30 functions as an alignment detection unit 50, a laser processing control unit 52, an imaging control unit 54, a measurement unit 56, a correction unit 58, and a notification unit 60. Note that what is described as a "unit" of the control device 30 may also be a "circuit," a "device," or a "equipment." In other words, what is described as a "unit" may be composed of firmware, software, hardware, or a combination of these.

<Alignment detection unit>
The alignment detection unit 50 controls the microscope 26 and the relative movement mechanism 28 to perform alignment detection, which detects the position of each street C on the wafer 12. First, the alignment detection unit 50 drives the relative movement mechanism 28 to adjust the position of the microscope 26 with respect to a predetermined alignment reference on the wafer 12. Next, the alignment detection unit 50 causes the microscope 26 to photograph the alignment reference, thereby acquiring a photographed image of the alignment reference from the microscope 26. Then, based on the photographed image of the alignment reference, the alignment detection unit 50 detects the alignment reference in this photographed image using a known image recognition method, thereby detecting the position of each street C, i.e., performing alignment detection.

<Laser processing control unit>
Based on the alignment detection results by the alignment detection unit 50, the laser processing control unit 52 controls the first laser light source 22A, the second laser light source 22B, the relative movement mechanism 28, and the connection switching element 36 to perform laser processing (edge cutting processing, hollowing processing) for each street C.

Specifically, based on the detection results of the alignment detection unit 50, the laser processing control unit 52 drives the relative movement mechanism 28 to align the optical axis of the first focusing lens 38 of the laser head 24 with the processing start position of Street C (forward and backward passes).

The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser light L2 to the second condenser lens 40A when performing laser processing on Street C (outbound path), and to switch the lens that emits the second laser light L2 to the second condenser lens 40B when performing laser processing on Street C (return path).

The laser processing control unit 52 then emits laser beams LA and LB from the first laser light source 22A and the second laser light source 22B. The laser processing control unit 52 also drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the forward direction XA when performing laser processing on street C (forward direction), and to move the laser head 24 relative to the wafer 12 in the backward direction XB when performing laser processing on street C (return direction). This allows the formation of two edge cutting grooves 18 by edge cutting processing and the formation of a core groove 19 by core cutting processing to be performed simultaneously with an interval between them (see Figures 5 and 6). The laser processing control unit 52 then repeatedly performs the above-described process for each street C.

<Shooting control unit>
The photography control unit 54 controls the illumination light source 41 and the cameras 45, 46A, 46B to control the photography of the images D1, D2A, D2B by the cameras 45, 46A, 46B. Specifically, the photography control unit 54 continuously emits illumination light L3 from the illumination light source 41 during laser processing of the street C (outward and return passes). As a result, the street C, the two edge-cutting grooves 18, and the hollow groove 19 are illuminated by the illumination light L3.

In addition, during laser processing of Street C (outbound), the photography control unit 54 continues to have camera 45 capture the reflected light beams R1 and R3, and camera 46A capture the reflected light beams R2 and R3. As a result, during laser processing of Street C (outbound), the camera 45 simultaneously captures the laser spot SP1 and the two edge-cutting grooves 18, outputs the captured image D1 from camera 45, and the camera 46A simultaneously captures the laser spot SP2 and the two edge-cutting grooves 18, etc., and outputs the captured image D2A from camera 46A, all in parallel.

Furthermore, during laser processing of Street C (returning), the photography control unit 54 continues to have camera 45 capture images of the reflected light beams R1 and R3, and camera 46B capture images of the reflected light beams R2 and R3. As a result, during laser processing of Street C (returning), the simultaneous photography and output of captured image D1 by the aforementioned camera 45, the simultaneous photography of laser spot SP2 and the two edge cutting grooves 18, etc. by camera 46B, and the output of captured image D2B from camera 46B are carried out in parallel.

<Measurement part>
The measuring unit 56 measures the positional accuracy and processing quality of the laser processing (edge cutting processing and hollowing processing) based on the captured images D1, D2A, and D2B output from the cameras 45, 46A, and 46B. This measuring unit 56 functions as a positional accuracy measuring unit 56a and a processing quality measuring unit 56b.

It is assumed that the positional relationship of the optical axes of the first condenser lens 38 and the second condenser lenses 40A, 40B relative to the optical axis of the alignment microscope 26 has been measured and adjusted in advance. That is, adjustments have been made in advance during laser processing so that the Y-direction positions of the optical axis of the first condenser lens 38 (center of field CV1, see Figure 8), the optical axis of the second condenser lenses 40A, 40B (center of field CV2, see Figure 9), and the reference position of street C are aligned.

In addition, by performing edge cutting and hollowing processing separately in advance on the wafer 12 (product wafer) or mirror wafer using the laser processing device 10, the positions and appearances of the laser spots SP1, SP2, the two edge cutting grooves 18, and the hollowing groove 19 in the captured images D1, D2A, and D2B are also measured in advance.

(Measurement of positional accuracy of edge cutting)
8 is an explanatory diagram for explaining measurement of the positional accuracy of edge cutting by the positional accuracy measuring unit 56a. Reference symbol VIIIA in the figure is an example of ideal edge cutting along the center of street C (forward and return passes). Reference symbol VIIIB in the figure is an example of edge cutting misaligned in the Y direction from the center of street C (forward and return passes).

As shown in Figure 8 and the previously described Figure 7, the position accuracy measurement unit 56a measures the position accuracy of the edge cutting process based on the captured image D1 output from the camera 45 during the edge cutting process on Street C (outbound and return paths).

Specifically, the position accuracy measurement unit 56a detects the center position of each of the two laser spots SP1 and the center position of each of the two edge cutting grooves 18 from the captured image D1. Then, the position accuracy measurement unit 56a measures the positional relationship (positional deviation in the Y direction) of the center position of each laser spot SP1 with respect to the field of view center CV1, which corresponds to the optical axis position of the first focusing lens 38. The position accuracy measurement unit 56a also measures the positional relationship (positional deviation in the Y direction) of the center position of each of the two edge cutting grooves 18 with respect to the field of view center CV1.

(Measurement of positional accuracy during hollowing)
FIG. 9 is an explanatory diagram for explaining measurement of the positional accuracy of the hollowing process by the positional accuracy measuring unit 56a. Note that the symbol IXA in the figure is an example of ideal hollowing process along the center of street C (forward and return passes). Also, the symbol IXB in the figure is an example in which the Y-direction positions of the edge cutting process and the hollowing process are misaligned. Furthermore, the upper part of each example is a cross-sectional view of the two edge cutting grooves 18 and the hollowing groove 19, and the lower part of each example is a diagram showing an example of captured images D2A and D2B. Furthermore, the symbol CV2 in the figure is the field of view center, which corresponds to the optical axis position of the second focusing lenses 40A and 40B.

As shown in Figure 9 and the previously described Figure 7, the positional accuracy measurement unit 56a measures the positional accuracy of the hole-cutting process based on the captured image D2A output from camera 46A during hole-cutting process on Street C (outbound path), and measures the positional accuracy of the hole-cutting process based on the captured image D2B output from camera 46B during hole-cutting process on Street C (return path).

Specifically, the position accuracy measurement unit 56a detects the center position of the laser spot SP2 and the Y-direction center positions of the two previously formed edge-cutting grooves 18 (the midpoint positions of the centers of the two edge-cutting grooves 18) from the captured images D2A and D2B. Then, the position accuracy measurement unit 56a measures the positional relationship (positional deviation in the Y direction) between the center position of the laser spot SP2 and the Y-direction center positions of the two edge-cutting grooves 18.

(Measurement of edge cutting quality)
10 is an explanatory diagram for explaining measurement of the processing quality of edge cutting by the processing quality measuring unit 56b. Note that the symbol XA in the figure is an example of ideal edge cutting, the symbol XB in the figure is an example of edge cutting in a state where the two first laser beams L1 are biased, and the symbol XC in the figure is an example of edge cutting in a state where the diameters of the two first laser beams L1 are increased. The upper part of each example is a cross-sectional view of the two edge cutting grooves 18, and the lower part of each example is a diagram showing an example of a captured image D1.

As shown in Figure 10 and the previously described Figure 7, the processing quality measurement unit 56b measures the processing quality of the edge cutting processing based on the captured image D1 output from the camera 45 during the edge cutting processing of Street C (outbound and return paths).

Specifically, the processing quality measurement unit 56b detects the laser spot SP1 from the captured image D1 and measures its shape, size (diameter), and brightness. The processing quality measurement unit 56b also detects the center position of each laser spot SP1 and the center position of each of the two edge-cutting grooves 18 from the captured image D1, and measures the deviation in the Y direction (see symbol XB) of the center position of each laser spot SP1 relative to the center position of each of the two edge-cutting grooves 18.

(Measurement of processing quality of hollowing)
11 is an explanatory diagram for explaining measurement of the machining quality of the hollow cutting by the machining quality measurement unit 56b. The symbol XIA in the figure is an example of ideal hollow cutting, the symbol XIB in the figure is an example of hollow cutting where the machining width in the Y direction is insufficient, and the symbol XIC in the figure is an example of hollow cutting where the machining width in the Y direction is too wide. The upper part of each example is a cross-sectional view of the two edge-cutting grooves 18 and the hollow cutting groove 19, and the lower part of each example is a diagram showing an example of the captured images D2A and D2B.

As shown in Figure 11 and the previously described Figure 7, the processing quality measurement unit 56b measures the processing quality of the hollowing out process based on the captured image D2A output from the camera 46A during the hollowing out process on Street C (outbound path), and measures the processing quality of the hollowing out process based on the captured image D2B output from the camera 46B during the hollowing out process on Street C (return path).

Specifically, the processing quality measurement unit 56b detects the laser spot SP2 from the captured images D2A and D2B, measures its shape, size (diameter), and brightness, and detects the position of the laser spot SP2 within the captured images D2A and D2B (within the field of view).

<Correction section>
7 , the correction unit 58 determines correction values for the Y-direction positions of the edge cutting and hollow cutting based on the measurement of the positional accuracy of the laser processing (edge cutting and hollow cutting) by the position accuracy measurement unit 56a. As a result, the laser processing control unit 52 drives the relative movement mechanism 28 to correct the Y-direction positions of the edge cutting and hollow cutting based on the correction values for the Y-direction positions of the edge cutting and hollow cutting determined by the correction unit 58 during or after laser processing of street C (outward and return passes). As a result, from the middle of laser processing of street C (outward and return passes) or from laser processing of the next street C, the Y-direction positional deviation of the two edge cutting grooves 18 relative to street C and the Y-direction positional deviation of the hollow cutting grooves 19 relative to the two edge cutting grooves 18 are corrected.

In addition, the correction unit 58 determines correction values for the processing conditions for edge cutting and hollow cutting (such as the light intensity of the laser beams LA and LB, the processing width for edge cutting and hollow cutting, and the relative Y-direction positions for edge cutting and hollow cutting) based on the processing quality measurement unit 56b measures for the laser processing (edge cutting and hollow cutting). As a result, during or after laser processing of street C (forward and return passes), the laser processing control unit 52 controls each part of the laser head 24 to correct the processing conditions for edge cutting and hollow cutting based on the correction values for each processing condition determined by the correction unit 58. As a result, the processing conditions are corrected during laser processing of street C (forward and return passes) or from the laser processing of the next street C. In addition, in order to correct the laser processing conditions (symbols XB and XC in FIG. 10, symbols XIB and XIC in FIG. 11), it is possible to provide diaphragm mechanisms on each of the main optical paths OP1 to OP3, adjustment mechanisms (steering mirror mechanisms M1A and M1B) that adjust the position and orientation of the mirrors on the laser optical path, and adjustment mechanisms that adjust the position and orientation of each of the condenser lenses 38, 40A, and 40B.

Returning to Figures 5 and 6, the steering mirror mechanism M1A is provided between the first laser light source 22A and the first light forming element 32, and is composed of two or more steering mirrors 102. By adjusting the angle of each steering mirror 102, the steering mirror mechanism M1A corrects positional deviation and deformation of the laser spot SP1 caused by fluctuations in the emission direction of the laser light LA emitted from the first laser light source 22A. In addition, by driving the steering mirror mechanism M1A using feedback of the measurement results of the position accuracy measurement unit 56a and the processing quality measurement unit 56b, it is possible to correct deviations in the processing position of the laser spot SP1, including factors caused by fluctuations in the position and orientation of the optical system downstream of the steering mirror mechanism M1A.

The steering mirror mechanism M1B is provided between the second laser light source 22B and the second light forming element 34, and, like the steering mirror mechanism M1A, is composed of multiple steering mirrors 102. The steering mirror mechanism M1B adjusts the angle of each steering mirror 102 to correct positional deviation and distortion of the laser spot SP2 (forward direction side XA, return direction side XB) caused by fluctuations in the emission direction of the laser light LB emitted from the second laser light source 22B. Note that the laser spot SP2 (forward direction side XA) is the laser spot SP2 when the processing feed direction is the forward direction side XA, and the laser spot SP2 (return direction side XB) is the laser spot SP2 when the processing feed direction is the return direction side XB.

Furthermore, by driving the steering mirror mechanism M1B using feedback from the measurement results of the position accuracy measurement unit 56a and the processing quality measurement unit 56b, it is possible to correct the deviation in the processing position of the laser spot SP2 (forward direction side XA, return direction side XB), including factors related to fluctuations in the position and orientation of the optical system downstream of the steering mirror mechanism M1B. However, since laser spot SP2 (forward direction side XA) and laser spot SP2 (return direction side XB) cannot be corrected individually and simultaneously, if the processing positions of the two in the Y direction (hereinafter referred to as the Y processing position) are misaligned, the steering mirror mechanism M1B is adjusted according to the processing feed direction (forward direction side XA, return direction side XB).

A steering mirror mechanism M2A may be provided in place of the steering mirror mechanism M1A, and a steering mirror mechanism M2B may be provided in place of the steering mirror mechanism M1B.

The steering mirror mechanism M2A is provided between the first light forming element 32 and the beam splitter 33, and has a configuration similar to the steering mirror mechanisms M1A and M1B. The steering mirror mechanism M2A adjusts the angle of each steering mirror 102 to correct positional deviation and distortion of the laser spot SP1 caused by fluctuations in the position and orientation of the first light forming element 32. In addition, by driving the steering mirror mechanism M2A using feedback from the measurement results of the position accuracy measurement unit 56a and the processing quality measurement unit 56b, it is possible to correct deviations in the processing position of the laser spot SP1, including factors caused by fluctuations in the position and orientation of the optical system downstream of the steering mirror mechanism M2A.

The steering mirror mechanism M2B is provided between the second light forming element 34 and the beam splitter 35 and has a configuration similar to the steering mirror mechanisms M1A and M1B. The steering mirror mechanism M2B adjusts the angle of each steering mirror 102 to correct positional deviation and distortion of the laser spot SP2 (forward direction side XA, backward direction side XB) caused by fluctuations in the position and orientation of the second light forming element 34. Furthermore, by driving the steering mirror mechanism M2B using feedback from the measurement results of the position accuracy measurement unit 56a and the processing quality measurement unit 56b, it is possible to correct deviations in the processing position of the laser spot SP2 (forward direction side XA, backward direction side XB), including factors related to fluctuations in the position and orientation of the optical system downstream of the steering mirror mechanism M2B. However, since laser spot SP2 (forward direction side XA) and laser spot SP2 (return direction side XB) cannot be corrected individually and simultaneously, if the processing positions of the two in the Y direction (hereinafter referred to as Y processing positions) are misaligned, the steering mirror mechanism M2B is adjusted according to the processing feed direction (forward direction side XA, return direction side XB).

Note that misalignment of the Y processing position can be corrected using only the steering mirror mechanism M1A (or steering mirror mechanism M2A) by aligning the Y processing position of laser spot SP1 with the Y processing position of laser spot SP2 (forward direction side XA, backward direction side XB). Conversely, misalignment of the Y processing position can be corrected using only the steering mirror mechanism M1B (or steering mirror mechanism M2B) by aligning the Y processing position of laser spot SP2 (forward direction side XA, backward direction side XB) with the Y processing position of laser spot SP1.

Furthermore, a steering mirror mechanism M3 may be provided between the connection switching element 36 and the beam splitter 37. The steering mirror mechanism M3 has the same configuration as the steering mirror mechanisms M1A to M2B described above. Driving the steering mirror mechanism M3 corrects the positional deviation of the laser spot SP2 (returning direction side XB). Note that the steering mirror mechanism M3 alone cannot correct the positional deviation between the laser spots SP1 and SP2 (returning direction side XB), and must be used in conjunction with the steering mirror mechanism M1A (M2A) or steering mirror mechanism M1B (M2B).

By using the steering mirror mechanism M3, there is no need to change the position and orientation of the steering mirror mechanism M1A (M2A) or steering mirror mechanism M1B (M2B) that precedes the steering mirror mechanism M3, depending on whether the processing feed direction is the outgoing direction XA or the return direction XB.

The above steering mirror mechanisms M1A to M3 can be arranged in the following four patterns.

(First pattern)
The first pattern is a pattern in which only one of the steering mirror mechanism M1A, steering mirror mechanism M2A, steering mirror mechanism M1B, and steering mirror mechanism M2B is arranged. In the first pattern, the position of either the first laser spot SP1 or the second laser spot SP2 is corrected to match the position of the other. Note that if the laser spot shape is distorted on the side where the steering mirror mechanism is not provided, correction is made on the side where the steering mirror mechanism is provided accordingly, which may result in failure to correct the laser spot shape. Furthermore, if there is a positional misalignment between the second condenser lenses 40A and 40B, it is necessary to adjust the steering mirror mechanism for each of the processing feed directions (forward direction side XA and return direction side XB).

(Second pattern)
The second pattern combines one of the steering mirror mechanisms M1A and M2A with one of the steering mirror mechanisms M1B and M2B. The second pattern can correct the positions of both the first laser spot SP1 and the second laser spot SP2, making it easier to prevent distortion of the laser spots. However, it may not be possible to prevent distortion of the shapes of the laser beams L1 and L2 along the optical path. Furthermore, if there is a misalignment between the second condenser lenses 40A and 40B, it is necessary to adjust the steering mirror mechanism for each of the processing feed directions (the forward direction XA and the backward direction XB).

(Third pattern)
The third pattern combines one of the steering mirror mechanisms M1A or M2A, one of the steering mirror mechanisms M1B or M2B, and the steering mirror mechanism M3. This third pattern, like the second pattern, allows for correction of the positions of both the first laser spot SP1 and the second laser spot SP2, making it easier to prevent distortion of the laser spots. Furthermore, the third pattern eliminates the need to adjust the steering mirror mechanism for each of the processing feed directions (the forward direction XA and the backward direction XB) even if there is a misalignment between the second condenser lenses 40A and 40B.

(Fourth pattern)
The fourth pattern is a pattern that includes all of steering mirror mechanisms M1A, M2A, M1B, M2B, and M3. In addition to the advantages of the third pattern, this fourth pattern allows correction of the shapes and positions of the laser beams L1 and L2 at any point on the optical path.

<Notification Department>
Returning to Figure 7, if the positional accuracy and processing quality of the laser processing (edge cutting processing, hollowing processing) do not meet predetermined standards based on the measurement results of the positional accuracy measurement unit 56a and the processing quality measurement unit 56b, the notification unit 60 displays error information on a monitor (not shown) or outputs it as audio from a speaker.

[Action of the laser processing device of the first embodiment]
FIG. 12 is a flowchart showing the flow of laser processing of each street C of the wafer 12 by the laser processing apparatus 10 having the above configuration.

As shown in FIG. 12, when the wafer 12 is held on the table 20, the alignment detection unit 50 drives the relative movement mechanism 28 to move the microscope 26 relative to the wafer 12 to a position where the alignment fiducial (not shown) of the wafer 12 can be photographed, and then causes the microscope 26 to photograph the alignment fiducial. The alignment detection unit 50 then performs alignment detection to detect the position of each street C on the wafer 12 based on the photographed image of the alignment fiducial photographed by the microscope 26 (step S1).

Once alignment detection is complete, the laser processing control unit 52 drives the relative movement mechanism 28 based on the detection results of the alignment detection unit 50 to align the optical axis of the first focusing lens 38 of the laser head 24 with the processing start position of Street C (outbound path) (step S2).

The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser light L2 to the second condenser lens 40A (step S3). Note that steps S2 and S3 may be performed in the reverse order or simultaneously.

Once steps S2 and S3 are completed, the laser processing control unit 52 begins laser processing of street C (outbound path) (step S4). First, the laser processing control unit 52 causes the first laser light source 22A to emit laser light LA. This causes two first laser light beams L1 to be emitted from the first condenser lens 38 via the first light forming element 32, and the two first laser light beams L1 are condensed at the processing start position on street C (outbound path).

The laser processing control unit 52 then drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the forward direction XA, and causes the second laser light source 22B to emit laser light LB when the optical axis of the second condenser lens 40A reaches the above-mentioned processing start position. This causes the second laser light L2 to be emitted from the second condenser lens 40A via the second light forming element 34 and the connection switching element 36, and the second laser light L2 is focused at the processing start position.

The laser processing control unit 52 then drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the forward direction XA (step S5). As a result, as shown in Figures 3 and 5, two edge cutting grooves 18 are formed by edge cutting processing and two hollow grooves 19 are formed by hollow cutting processing at intervals along street C (forward path).

In addition, in conjunction with the start of laser processing, the photography control unit 54 initiates the emission of illumination light L3 from the illumination light source 41, the capture of reflected light R1 and R3 by camera 45, and the capture of reflected light R2 and R3 by camera 46A. This results in simultaneous photography of laser spot SP1 and the two edge-cutting grooves 18 by camera 45, and simultaneous photography of laser spot SP2 and the two edge-cutting grooves 18, etc. by camera 46A (step S6). The measurement unit 56 also acquires the captured image D1 output from camera 45 and the captured image D2A output from camera 46A (step S7).

Then, the position accuracy measurement unit 56a and processing quality measurement unit 56b of the measurement unit 56 measure the position accuracy (see Figure 8) and processing quality (see Figure 10) of the edge cutting process based on the captured image D1, and measure the position accuracy (see Figure 9) and processing quality (see Figure 11) of the hollowing process based on the captured image D2A (step S8).

Then, steps S5 to S8 are repeated until laser processing of Street C (outbound) is completed. As a result, during laser processing of Street C (outbound), simultaneous photography of laser spot SP1 and the two edge-cutting grooves 18 by camera 45, simultaneous photography of laser spot SP2 and the two edge-cutting grooves 18 by camera 46A, etc., and measurement of the positional accuracy and processing quality of the laser processing are carried out in parallel (NO in step S9).

The laser processing control unit 52 stops the emission of laser light LA from the first laser light source 22A when laser spot SP1 reaches the processing end position of street C (outward path), and then stops the emission of laser light LB from the second laser light source 22B when laser spot SP2 reaches the processing end position, and stops driving the relative movement mechanism 28. This completes laser processing of street C (outward path) (YES in step S9).

When laser processing of Street C (outbound pass) is completed, the correction unit 58 determines the correction values for the Y-direction positions of the edge cutting and hollowing processes based on the results of measurement of the positional accuracy of the edge cutting and hollowing processes by the position accuracy measurement unit 56a. This corrects the Y-direction positional deviation of the two edge cutting grooves 18 relative to Street C from the next Street C (return pass), and the Y-direction positional deviation of the hollowing grooves 19 relative to the two edge cutting grooves 18 (step S10).

The correction unit 58 also determines correction values for the processing conditions for edge cutting and hollowing based on the measurement results of the processing quality of edge cutting and hollowing by the processing quality measurement unit 56b. As a result, the processing conditions for edge cutting and hollowing are corrected starting from the next street C (returning path) (step S10).

Furthermore, if the positional accuracy and processing quality of the laser processing (edge cutting processing, hollowing processing) do not meet predetermined standards based on the measurement results of the positional accuracy measurement unit 56a and processing quality measurement unit 56b, the notification unit 60 issues an error notification (step S10). This allows the operator to be prompted to perform maintenance on the laser processing device 10 (cleaning each part of the laser head 24, adjusting the position, etc.).

Instead of performing step S10 after laser processing of street C, step S10 may be performed during laser processing of street C (outward pass). This makes it possible to correct the Y-direction position and processing conditions for laser processing and to notify error information during laser processing of street C (outward pass).

When laser processing of Street C (outbound path) is completed, the laser processing control unit 52 drives the relative movement mechanism 28 to align the optical axis of the first condenser lens 38 with the processing start position of the next Street C (return path) (YES in step S11, step S2). The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser light L2 to the second condenser lens 40B (step S3).

Then, the processes from step S4 to step S10 described above are repeatedly executed. This allows for parallel laser processing of street C (returning), simultaneous photography of laser spot SP1 and the two edge-cutting grooves 18 by camera 45, simultaneous photography of laser spot SP2 and the two edge-cutting grooves 18, etc. by camera 46B, and measurement of the positional accuracy and processing quality of the laser processing. Next, the Y-direction position and processing conditions of the laser processing (edge-cutting and hollow-out processing) are corrected, and error information is reported.

Similarly, the processes from step S2 to step S10 described above are repeated for all streets C (outbound and inbound) parallel to the X direction. Next, the laser processing control unit 52 drives the relative movement mechanism 28 to rotate the table 20 by 90 degrees, thereby making the remaining streets C parallel to the Y direction on the wafer 12 parallel to the X direction. The above-mentioned series of processes are then repeated. As a result, laser processing is performed along each of the grid-like streets C.

[Effects of the first embodiment]
As described above, in the laser processing apparatus 10 of the first embodiment, during laser processing of street C (forward and return passes), simultaneous photography of the laser spot SP1 and the two edge-cutting grooves 18 by the camera 45 and simultaneous photography of the laser spot SP2 and the two edge-cutting grooves 18, etc. by the cameras 46A and 46B can be performed in parallel. This enables real-time kerf checks to immediately detect any abnormalities that may occur during laser processing. Furthermore, it is possible to detect abnormalities (see symbol IXB in FIG. 9 , symbols XB and XC in FIG. 10 , symbol XIC in FIG. 11 , etc.) that cannot be detected by photographing and observing only the processed grooves (the two edge-cutting grooves 18 and the hollow groove 19) or the laser spots SP1 and SP2. As a result, the positional accuracy and processing quality of the laser processing can be further improved.

Second Embodiment
FIG. 13 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the second embodiment. In the first embodiment, the reflected beams R1 and R3 are imaged by the cameras 46A and 46B, and the reflected beams R2 and R3 are imaged by the cameras 46A and 46B. Because the intensity of the laser beams L1 and L2 is greater than the intensity of the illumination beam L3, the intensity of the reflected laser beams R1 and R2 is greater than the intensity of the illumination beam R3. As a result, halation (blown-out highlights) may occur in the captured images D1, D2A, and D2B. In this case, it may be difficult to detect the laser spots SP1 and SP2 and their surrounding background (including the two edge-cutting grooves 18 and the hollow grooves 19) in the captured images D1, D2A, and D2B, or the detection accuracy may be reduced.

13, in the laser processing apparatus 10 of the second embodiment, a band stop filter 80A is provided midway along the branched optical path BP1 in the laser head 24, and a band stop filter 80B is provided midway along the branched optical paths BP2 and BP3 . The laser processing apparatus 10 of the second embodiment has basically the same configuration as the laser processing apparatus 10 of the first embodiment except for the inclusion of the band stop filters 80A and 80B, and therefore, components that are the same in function or configuration as those of the first embodiment are denoted by the same reference numerals and their description will be omitted.

The bandstop filters 80A and 80B correspond to the light intensity reduction filters of the present invention. The bandstop filter 80A reduces the amount of light in the wavelength range corresponding to the two first laser beams L1. The bandstop filter 80B reduces the amount of light in the wavelength range corresponding to the second laser beam L2. As mentioned above, the illumination light L3 is light in a wavelength range close to the wavelength range of the laser beams LA and LB to suppress the effects of aberrations in the first focusing lens 38 and the second focusing lenses 40A and 40B, but is not light in the same (approximately the same) wavelength range as the laser beams LA and LB. Therefore, the bandstop filters 80A and 80B can reduce only the amount of the reflected laser beams R1 and R2 without reducing the amount of the reflected illumination light R3.

As described above, in the second embodiment, the bandstop filters 80A and 80B can reduce only the amount of reflected laser light R1 and R2, preventing the occurrence of the aforementioned blown-out highlights. As a result, the detection accuracy of the laser spots SP1 and SP2 and their surrounding background from within the captured images D1, D2A, and D2B is improved, thereby enabling the positional accuracy and processing quality of the laser processing to be improved even more than in the first embodiment.

In addition, bandstop filter 80A may be provided between beam splitter 33 and beam splitter 42, and bandstop filter 80B may be provided between beam splitter 35 and beam splitter 43A, and between beam splitter 37 and beam splitter 43B.

In addition, instead of providing bandstop filters 80A and 80B, a polarizing filter may be provided as the light intensity reduction filter of the present invention. In this case, the polarization directions of the laser beams LA and LB and the illumination light L3 (when the illumination light source 41 is a laser light source) are made different, and the polarization direction of the polarizing filter is made orthogonal (approximately orthogonal) to the polarization direction of the laser beams LA and LB. This makes it possible to reduce only the light intensity of the reflected laser beams R1 and R2. Furthermore, in this case, light in the same wavelength range as the laser beams LA and LB can be used as the illumination light L3, eliminating the need to consider the effects of aberrations in the first condenser lens 38 and the second condenser lenses 40A and 40B.

[Third embodiment]
Figure 14 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the third embodiment. In Figure 14, the symbol XIVA indicates only the components related to edge cutting within the laser head 24, and the symbol XIVB indicates only the components related to hollowing. In the second embodiment, band-stop filters 80A and 80B are used to prevent overexposure in the captured images D1, D2A, and D2B. In the third embodiment, however, a different method is used to prevent overexposure in the captured images D1, D2A, and D2B. The laser processing apparatus 10 of the third embodiment has basically the same configuration as the laser processing apparatus 10 of the first embodiment. Therefore, components that are functionally or structurally identical to those of the first embodiment are designated by the same reference numerals, and their description will be omitted.

As shown by symbol XIVA in Figure 14, a dichroic mirror 82A (including a dichroic prism) and a beam splitter 82B (including a half mirror) are arranged between the beam splitter 33 and the illumination light source 41 on the main optical path OP1.

The dichroic mirror 82A corresponds to the first branching optical element of the present invention, and branches the first branched optical path BP11 from the main optical path OP1. This dichroic mirror 82A reflects light in the wavelength range corresponding to the two first laser beams L1 and transmits light in other wavelength ranges. As a result, the dichroic mirror 82A reflects the reflected laser light R1 incident from the beam splitter 33 toward the first branched optical path BP11 and transmits the reflected illumination light R3.

Beam splitter 82B corresponds to the second branching optical element of the present invention, and branches off the main optical path OP1 into a second branched optical path BP12. This beam splitter 82B reflects a portion of the reflected illumination light R3 incident from dichroic mirror 82A toward the second branched optical path BP12.

A first camera 451 is disposed on the first branched optical path BP11, and a second camera 452 is disposed on the second branched optical path BP12. The first camera 451 and the second camera 452 are the electronic cameras described above.

The first camera 451 is disposed on the first branched optical path BP11 and captures the reflected laser light R1 incident from the dichroic mirror 82 A. The second camera 452 is disposed on the second branched optical path BP12 and captures the reflected illumination light R3 incident from the beam splitter 82 B.

As shown by symbol XIVB in Figure 14, a dichroic mirror 83A (including a dichroic prism) and a beam splitter 83B (including a half mirror) are disposed between the beam splitter 35 and the illumination light source 41 on the main optical path OP2, and between the beam splitter 37 and the illumination light source 41 on the main optical path OP3. The dichroic mirror 83A corresponds to the first branching optical element of the present invention, and the beam splitter 83B corresponds to the second branching optical element of the present invention.

A dichroic mirror 83A arranged on the main optical path OP2 branches off a first branched optical path BP21 from the main optical path OP2, and a dichroic mirror 83A arranged on the main optical path OP3 branches off a first branched optical path BP31 from the main optical path OP3. These dichroic mirrors 83A reflect light in the wavelength range corresponding to the second laser light L2 and transmit light in other wavelength ranges. As a result, each dichroic mirror 83A reflects the reflected laser light R2 toward the first branched optical paths BP21 and BP31 and transmits the reflected illumination light R3.

Beam splitter 83B located on main optical path OP2 branches off a second branched optical path BP22 from main optical path OP2, and beam splitter 83B located on main optical path OP3 branches off a second branched optical path BP32 from main optical path OP3. These beam splitters 83B reflect a portion of the reflected illumination light R3 incident from dichroic mirror 83A toward the second branched optical paths BP22 and BP32, respectively.

The first camera 46A1 is positioned on the first branched optical path BP21, and the first camera 46B1 is positioned on the first branched optical path BP31. The first cameras 46A1 and 46B1 are the electronic cameras already described, and capture the reflected laser light R2 incident on the dichroic mirror 83A.

The second camera 46A2 is positioned on the second branched optical path BP22, and the second camera 46B2 is positioned on the second branched optical path BP32. The second cameras 46A2 and 46B2 are the electronic cameras already described, and capture the reflected illumination light R3 incident from the beam splitter 83B.

The control device 30 (e.g., measurement unit 56) of the third embodiment generates captured image D1 by combining the image captured by the first camera 451 and the image captured by the second camera 452. Similarly, the control device 30 generates captured image D2A by combining the image captured by the first camera 46A1 and the image captured by the second camera 46A2, and generates captured image D2B by combining the image captured by the first camera 46B1 and the image captured by the second camera 46B2.

Here, the sensitivity of the first camera 451 is set lower than that of the second camera 452. The sensitivity of the first cameras 46A1 and 46B1 is also set lower than that of the second cameras 46A2 and 46B2. This prevents blown-out highlights from occurring in the captured images D1, D2A, and D2B.

As described above, in the third embodiment, the image of the processed grooves (the two edge-cutting grooves 18 and the hollow grooves 19) based on the reflected illumination light R3 is not darkened, and the occurrence of the aforementioned blown-out highlights can be prevented, thereby achieving the same effect as in the second embodiment.

In the third embodiment, the dichroic mirrors 82A and 83A reflect the reflected laser light R1 and R2, but they may also reflect the reflected illumination light R3. In this case, the first cameras 451, 46A1, and 46B1 capture the reflected illumination light R3, and the second cameras 452, 46A2, and 46B2 capture the reflected laser light R1 and R2. Therefore, in this case, the sensitivity of the second cameras 452, 46A2, and 46B2 is set lower than the sensitivity of the first cameras 451, 46A1, and 46B1.

Furthermore, in the third embodiment, if the polarization directions of the two first laser beams L1, the second laser beam L2, and the illumination light L3 are different, a polarizing beam splitter may be provided instead of the dichroic mirrors 82A, 83A and the beam splitters 82B, 83B.

[Fourth embodiment]
Figure 15 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the fourth embodiment. In Figure 15, the symbol XVA indicates only the configuration related to edge cutting within the laser head 24, and the symbol XVB indicates only the configuration related to hollowing. The laser processing apparatus 10 of the fourth embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above embodiments (particularly the third embodiment) except for the fact that a portion of the configuration of the laser head 24 has been changed, so that components that are the same in function or configuration as those of the above embodiments will be assigned the same symbols and their description will be omitted.

As shown by symbol XVA in FIG. 15, the first branched optical path BP11 and the second branched optical path BP12 are connected to camera 45. Also, as shown by symbol XVB in FIG. 15, the first branched optical path BP21 and the second branched optical path BP22 are connected to camera 46A, and the first branched optical path BP31 and the second branched optical path BP32 are connected to camera 46B. As a result, similar to the first embodiment described above, camera 45 captures the reflected light beams R1 and R3 to generate captured image D1, and cameras 46A and 46B capture the reflected light beams R2 and R3, respectively, to generate captured images D2A and D2B.

In the fourth embodiment, a bandstop filter 80A is provided midway along the first branched optical path BP11, and a bandstop filter 80B is provided midway along the first branched optical paths BP21 and BP31. This allows the amount of light only from the reflected laser beams R1 and R2 to be reduced without reducing the amount of light from the reflected illumination beam R3, as in the second embodiment described above.

In addition, in the fourth embodiment, the optical path lengths of the first branched optical path BP11 and the second branched optical path BP12 are made different, the optical path lengths of the first branched optical path BP21 and the second branched optical path BP22 are made different, and the optical path lengths of the first branched optical path BP31 and the second branched optical path BP32 are made different.

Specifically, to reduce the effects of aberrations in the first focusing lens 38 due to differences in the wavelength ranges of the two first laser beams L1 (laser beam LA) and the illumination light L3, the optical path length of the first branched optical path BP11 is adjusted according to the wavelength ranges of the two first laser beams L1, and the optical path length of the second branched optical path BP12 is adjusted according to the wavelength range of the illumination light L3. Furthermore, to reduce the effects of aberrations in the second focusing lenses 40A and 40B due to differences in the wavelength ranges of the second laser beam L2 (laser beam LB) and the illumination light L3, the optical path lengths of the first branched optical paths BP21 and BP31 are adjusted according to the wavelength range of the second laser beam L2, and the optical path lengths of the second branched optical paths BP22 and BP32 are adjusted according to the wavelength range of the illumination light L3.

As described above, in the fourth embodiment, by providing bandstop filters 80A and 80B along the first branched optical paths BP11, BP21, and BP31, it is possible to prevent blown-out highlights in the captured images D1, D2A, and D2B, as in the second embodiment. Furthermore, by adjusting the optical path length of each optical path for each wavelength range of light, it is possible to absorb the effects of aberrations in each condenser lens 38, 40A, and 40B, eliminating the need to set the wavelength range of illumination light L3 to a wavelength range close to that of each laser light L1 and L2.

In the fourth embodiment, too, the dichroic mirrors 82A and 83A may reflect the illumination reflected light R3 onto the first branched optical paths BP11, BP21, and BP31, and the beam splitters 82B and 83B may reflect the laser reflected light R1 and R2 onto the second branched optical paths BP12, BP22, and BP32. In this case, bandstop filters 80A and 80B are provided midway along the second branched optical paths BP12, BP22, and BP32.

Furthermore, in the fourth embodiment, a polarizing filter may be provided instead of the bandstop filters 80A and 80B as described in the second embodiment above, or a polarizing beam splitter may be provided as described in the third embodiment above.

Fifth Embodiment
FIG. 16 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the fifth embodiment. As shown in FIG. 16, the laser processing apparatus 10 of the fifth embodiment has basically the same configuration as the laser processing apparatus 10 of each of the above-described embodiments (particularly the first embodiment), except that it includes a laser light source 22, a branching element 31, and a steering mirror mechanism M0 instead of the first laser light source 22A for edge cutting and the second laser light source 22B for hollow cutting. Therefore, components identical in function or configuration to those of the first embodiment are designated by the same reference numerals and will not be described again. In the fifth embodiment, a steering mirror mechanism M1A is disposed between the branching element 31 and the first light forming element 32, and a steering mirror mechanism M1B is disposed between the branching element 31 and the second light forming element 34.

The laser light source 22 emits laser light L having conditions (wavelength, pulse width, repetition frequency, etc.) suitable for both edge cutting and hollowing processing toward the branching element 31 via the steering mirror mechanism M0.

The steering mirror mechanism M0 has the same configuration as the steering mirror mechanisms M1A to M3 described above. By adjusting the angle of each steering mirror 102, the steering mirror mechanism M0 is used to correct deviations in the machining position and shape of each laser spot SP1, SP2 caused by fluctuations in the position and orientation of the laser light source 22. In this case, the Y machining positions of the three machining points (each laser spot SP1, SP2) move simultaneously, so deviations in the machining position caused by fluctuations in the position and orientation of the optical system downstream of the steering mirror mechanism M0 cannot be corrected.

The branching element 31 may be, for example, a beam splitter. The branching element 31 branches the laser light L emitted from the laser light source 22 into two beams, and emits one of the two beams of laser light L to the first light forming element 32 and the other beam of laser light L to the second light forming element 34. Alternatively, one beam of laser light L may be emitted from the branching element 31 to the first light forming element 32 via a steering mirror mechanism M1A, and the other beam of laser light L may be emitted to the second light forming element 34 via a steering mirror mechanism M1B. As a result, two beams of first laser light L1 are emitted from the first light forming element 32, and a second laser light L2 is emitted from the second light forming element 34, as in the above embodiments.

As described above, in the fifth embodiment, it is sufficient to provide only one type of laser light source 22, which allows for the laser head 24 to be made smaller and less expensive.

Sixth Embodiment
Fig. 17 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the sixth embodiment. In each of the above embodiments, the street C (the two edge-cutting grooves 18 and the hollow groove 19) is illuminated using the illumination light L3 emitted from the same illumination light source 41. However, as shown in Fig. 17, the street C may be illuminated using different first and second illumination light sources 41A and 41B depending on the type of laser processing (edge-cutting processing and hollow-cutting processing).

The laser processing apparatus 10 of the sixth embodiment has basically the same configuration as the laser processing apparatus 10 of the first embodiment, except that it is equipped with a first illumination light source 41A and a second illumination light source 41B instead of the illumination light source 41. Therefore, parts that are the same in function or configuration as those of the first embodiment are given the same reference numerals and their description will be omitted.

The first illumination light source 41A emits illumination light L3A, suitable for observing the edge cutting process, toward the beam splitter 42. As a result, during the edge cutting process of street C, the illumination light L3A illuminates street C and the two edge cutting grooves 18 (the edge cutting process area of street C). Then, the illumination reflected light R3A, which is the reflected light of the illumination light L3A reflected by street C, is captured by the camera 45 together with the previously described laser reflected light R1.

The second illumination light source 41B emits illumination light L3B, suitable for observing the hollowing out process, toward the beam splitters 43A and 43B. As a result, street C and the hollowing out groove 19 (the hollowing out process area of street C) are illuminated by illumination light L3B during hollowing out process of street C. Then, the illumination reflected light R3B, which is the reflected light of illumination light L3B reflected by street C, is captured by the cameras 46A and 46B together with the previously described laser reflected light R2.

By providing different first and second illumination light sources 41A and 41B depending on the type of laser processing, street C can be illuminated using illumination light L3A and L3B in different wavelength ranges (which may partially overlap) for edge cutting and hollowing processing.

In addition, in the laser processing apparatus 10 of the second to fifth embodiments described above, a first illumination light source 41A and a second illumination light source 41B may be provided instead of the illumination light source 41.

Seventh Embodiment
18 is a schematic diagram of the laser head 24 of the laser processing apparatus 10 of the seventh embodiment. In each of the above embodiments, the same second laser light source 22B is used to perform the hollow cutting of the street C on the outward and return paths. However, as shown in FIG. 18, two different second laser light sources 22B1 and 22B2 may be used to perform the hollow cutting of the street C on the outward and return paths.

The laser processing device 10 of the seventh embodiment has basically the same configuration as the laser processing device 10 of the second embodiment described above, except that it is equipped with second laser light sources 22B1 and 22B2, two second light forming elements 34, and polarizing filters 81A, 81B1, and 81B2 instead of the second laser light source 22B, connection switching element 36, and bandstop filters 80A and 80B, and that the arrangement of the steering mirror mechanisms M1B and M2B is partially different. Therefore, components that are functionally or structurally identical to those of the second embodiment described above are designated by the same reference numerals and their description will be omitted.

In the seventh embodiment, the first laser light source 22A and the first light forming element 32 constitute the first laser light emission system of the present invention, and the laser light LA (two first laser lights L1) emitted from the first laser light source 22A is linearly polarized. Furthermore, when the illumination light source 41 is a laser light source, the polarization direction of the illumination light L3 differs from the polarization direction of the laser lights LA and LB.

The second laser light source 22B1 and the second laser light source 22B2 emit laser light LB having different polarization directions or laser light LB having the same polarization direction toward the second light forming element 34. The second laser light source 22B1 and the second light forming element 34, and the second laser light source 22B2 and the second light forming element 34 constitute two second laser light emitting systems of the present invention.

The laser light LB emitted from the second laser light source 22B1 is formed into the second laser light L2 by the second light forming element 34 and then enters the beam splitter 35. As a result, the second laser light L2 is reflected by the beam splitter 35 toward the second condenser lens 40A, and is condensed onto street C (outbound path) by the second condenser lens 40A.

Meanwhile, the laser light LB emitted from the second laser light source 22B2 is formed into second laser light L2 by the second light forming element 34 and then enters the beam splitter 37. As a result, the second laser light L2 is reflected by the beam splitter 37 toward the second condenser lens 40B, and is condensed onto street C (return path) by the second condenser lens 40B.

In the seventh embodiment, the two optical paths of the first laser light L1 (including various optical elements arranged along the optical paths) from the first light forming element 32 to the first condenser lens 38 constitute the first connected optical system of the present invention. Furthermore, the optical path from one side of the second light forming element 34 to the second condenser lens 40A and the optical path from the other side of the second light forming element 34 to the second condenser lens 40B constitute the second connected optical system of the present invention.

By using the second laser light source 22B1 and the second laser light source 22B2 in this way, different second laser light sources 22B1, 22B2 (i.e., second laser light L2 with different polarization directions) can be used on the outbound and return paths to perform the hollowing out process of street C.

The specific processing control is basically the same as in the above embodiments. However, when performing hollow cutting on Street C (outbound path), the second laser light source 22B1 is turned on and the second laser light source 22B2 is turned off, or a shutter is inserted in the optical path of the laser light LB emitted from the second laser light source 22B2. Conversely, when performing hollow cutting on Street C (return path), the second laser light source 22B1 is turned off and the second laser light source 22B2 is turned on, or a shutter is inserted in the optical path of the laser light LB emitted from the second laser light source 22B1. These switching mechanisms also constitute part of the second connection optical system of the present invention.

The polarizing filter 81A has a polarization axis that is perpendicular to the polarization direction of the laser light LA (two first laser lights L1) emitted from the first laser light source 22A, and reduces the amount of reflected laser light R1.

Polarizing filter 81B1 has a polarization axis perpendicular to the polarization direction of laser light LB (second laser light L2) emitted from second laser light source 22B1, and reduces the amount of reflected laser light R2 incident through second focusing lens 40A, etc. Polarizing filter 81B2 has a polarization axis perpendicular to the polarization direction of laser light LB (second laser light L2) emitted from second laser light source 22B2, and reduces the amount of reflected laser light R2 incident through second focusing lens 40B, etc.

As described above, in the seventh embodiment, the amount of reflected laser light R1 and R2 can be reduced by the polarizing filters 81A, 81B1, and 81B2, thereby achieving the same effect as in the second embodiment. Furthermore, by adjusting the polarization direction of the laser light LB emitted from each of the second laser light sources 22B1 and 22B2 and/or the polarization direction of each of the polarizing filters 81B1 and 81B2, the amount of reflected laser light R2 incident on each of the cameras 46A and 46B can be adjusted independently.

In the seventh embodiment, polarizing filters 81A, 81B1, and 81B2 are provided, but polarizing filters 81A, 81B1, and 81B2 may be omitted. In this case, second laser light source 22B1 and second laser light source 22B2 may also be provided in each embodiment other than the fifth embodiment. Also, in the seventh embodiment, as in the sixth embodiment, first illumination light source 41A and second illumination light source 41B may be provided instead of illumination light source 41.

[others]
In each of the above embodiments, the core groove 19 is always formed between two edge cutting grooves 18, so it is not possible to simultaneously photograph a single core groove 19 and the laser spot SP2, but it is also possible to simultaneously photograph a single core groove 19 and the laser spot SP2 by performing core cutting processing alone on the wafer 12 (for example, in the peripheral excess area or at the intersection of street C). In this case, the processing quality of the core cutting processing can be measured based on the positional relationship between the core groove 19 and the laser spot SP2, and the processing conditions for the core cutting processing can be corrected or error information can be reported based on the measurement results.

The laser processing apparatus 10 in each of the above embodiments is equipped with one first condenser lens 38 for edge cutting and two second condenser lenses 40A, 40B for hollow cutting sandwiched between the first condenser lens 38, but the first condenser lens 38 and the second condenser lenses 40A, 40B may be interchanged. In other words, the laser processing apparatus 10 may be equipped with two first condenser lenses for edge cutting and a second condenser lens for hollow cutting disposed between the two first condenser lenses, and the connection of the two first condenser lenses may be switched depending on the processing feed direction.

The laser processing apparatus 10 in each of the above embodiments is equipped with one first condenser lens 38 for edge cutting and two second condenser lenses 40A, 40B for hollow cutting sandwiched between the first condenser lens 38, but the present invention can also be applied to a laser processing apparatus 10 equipped with only one first condenser lens for edge cutting and one second condenser lens for hollow cutting. Furthermore, the laser processing apparatus 10 of the present invention is not limited to those that perform edge cutting and hollow cutting along street C, and the present invention can also be applied to laser processing apparatus 10 that perform various known laser processing along street C.

In each of the above embodiments, the edge cutting and hollow cutting processes are switched on and off by switching the first laser light source 22A and the second laser light source 22B (laser light source 22) on and off. However, the first laser light source 22A and the second laser light source 22B (laser light source 22) may be always on. In this case, the edge cutting and hollow cutting processes are switched on and off by, for example, inserting and removing shutters in the optical paths of the laser beams LA, LB, and L, or inserting and removing shutters in the optical paths of the laser beams L1 and L2, or by a combination of these.

While each of the above embodiments includes a steering mirror mechanism provided on the optical path of the various laser beams, a shift mirror mechanism may be provided instead of the steering mirror mechanism. In other words, the mirror mechanism of the present invention can be configured to include multiple mirrors arranged on the optical path of the various laser beams and an adjustment mechanism that adjusts at least one of the position and orientation of the multiple mirrors.

10 Laser processing apparatus 12 Wafer 14 Chip 16 Device 18 Edge cutting groove 19 Hole groove 20 Table 22 Laser light source 22A First laser light source 22B, 22B1, 22B2 Second laser light source 24 Laser head 26 Microscope 28 Relative movement mechanism 30 Control device 31 Branching element 32 First light forming element 33, 35, 37 Beam splitter 34 Second light forming element 36 Connection switching element 38 First condenser lens 40A, 40B Second condenser lens 41 Illumination light source 41A First illumination light source 41B Second illumination light source 42, 43A, 43B Beam splitter 45, 46A, 46B Camera 451, 46A1, 46B1 First camera 452, 46A2, 46B2 Second camera 49 Operation unit 50 Alignment detection unit 52 Laser processing control unit 54 Photography control unit 56 Measurement unit 56a Position accuracy measurement unit 56b Processing quality measurement unit 58 Correction unit 60 Notification units 80A, 80B Bandstop filters 81A, 81B1, 81B2 Polarizing filters 82A, 83A Dichroic mirrors 82B, 83B Beam splitters BP1, BP2, BP3 Branched optical paths BP11, BP21, BP31 First branched optical path BP12, BP22, BP32 Second branched optical path C Streets CV1, CV2 Field of view centers D1, D2A, D2B Captured images L, LA, LB Laser light L1 First laser light L2 Second laser light L3, L3A, L3B Illumination light OP1 to OP3 Main optical paths R1, R2 Laser reflected light R3, R3A, R3B Illumination reflected light SP1, SP2 Laser spot XA Outward direction side XB Inward direction side M0, M1A, M1B, M2A, M2B, M3 Steering mirror mechanism

Claims (12)

A laser processing apparatus performs laser processing to form grooves along streets by irradiating the streets with laser light from the laser head while moving a table that holds a wafer and a laser head having a condenser lens that condenses laser light onto streets of the wafer held on the table relatively in a processing feed direction along the streets of the wafer,
a camera that simultaneously captures an image of the groove and a laser spot of the laser light focused on the street through the focusing lens while the laser processing is being performed;
a measuring unit that simultaneously measures the positional accuracy and processing quality of the laser processing during the laser processing based on the captured image taken by the camera;
Equipped with
The laser processing device , wherein the processing quality is at least one of the deviation of the center position of the laser spot from the center position of the groove and the processing width of the groove . an illumination light source that emits illumination light;
a main optical path along which the laser light and the illumination light emitted from the illumination light source are guided to the condenser lens, and along which a first reflected light of the laser light and a second reflected light of the illumination light reflected by the street are incident from the condenser lens;
a branching optical element disposed in the main optical path and configured to output the first reflected light and the second reflected light incident on the main optical path toward a branched optical path branched from the main optical path;
Equipped with
The laser processing device according to claim 1 , wherein the camera is disposed on the branched optical path and captures an image of the first reflected light and the second reflected light to generate a photographed image of the laser spot and the groove. The laser processing device of claim 2, further comprising a light-reduction filter disposed in the branched optical path and configured to reduce the amount of the first reflected light incident on the camera. the wavelength of the laser light and the wavelength range of the illumination light are different from each other,
4. The laser processing device according to claim 3, wherein the light intensity reducing filter is a band-stop filter that reduces the intensity of light corresponding to the wavelength range of the laser light. an illumination light source that emits illumination light in a wavelength range different from the laser light;
a main optical path along which the laser light and the illumination light emitted from the illumination light source are guided to the condenser lens, and along which a first reflected light of the laser light and a second reflected light of the illumination light reflected by the street are incident from the condenser lens;
a first branching optical element disposed in the main optical path and configured to output the first reflected light incident on the main optical path toward a first branched optical path branched from the main optical path;
a second branching optical element disposed in the main optical path and configured to output the second reflected light incident on the main optical path toward a second branched optical path branched from the main optical path;
Equipped with
the camera includes a first camera disposed in the first branched optical path and capturing an image of the first reflected light, and a second camera disposed in the second branched optical path and capturing an image of the second reflected light,
2. The laser processing device according to claim 1, wherein the sensitivity of the first camera is set lower than the sensitivity of the second camera. As the laser processing, an edge cutting process is performed to form two grooves parallel to each other along the street, and a hollowing process is performed to form the groove between the two grooves,
The camera simultaneously photographs the laser spot and the groove corresponding to the edge cutting process through the condenser lens while the edge cutting process is being performed, and simultaneously photographs the laser spot and the groove corresponding to the center cutting process through the condenser lens while the center cutting process is being performed,
The processing quality of the edge cutting processing includes the shape, size, and brightness of the laser spot, and a deviation of the center position of the laser spot with respect to the center position of the groove,
The laser processing device according to claim 1 , wherein the processing quality of the hollowing process includes the shape, size, and brightness of the laser spot, and the processing width of the groove . a first illumination source that illuminates the edge-cutting processing area of the street through the condenser lens while the edge-cutting processing is being performed;
a second illumination light source that illuminates the hollowing area of the street through the condenser lens while the hollowing is being performed;
The laser processing device according to claim 6, comprising: a mirror mechanism provided on an optical path of the laser light,
8. The laser processing device according to claim 1, wherein the mirror mechanism includes a plurality of mirrors and an adjustment mechanism that adjusts at least one of the positions and attitudes of the plurality of mirrors. the condenser lens includes a first condenser lens and two second condenser lenses arranged in a row along the processing feed direction together with the first condenser lens with the first condenser lens sandwiched therebetween,
The laser head
a laser beam emitting system that emits, as the laser beams, two first laser beams corresponding to the edge cutting process and a second laser beam corresponding to the hollowing process;
a connecting optical system that guides the two first laser beams emitted from the laser beam emitting system to the first condenser lens and selectively guides the second laser beams emitted from the laser beam emitting system to two second condenser lenses;
Equipped with
the connecting optical system, when the laser head is moved relative to the table in one of the forward direction side and the backward direction side in the processing feed direction, guides the second laser light emitted from the laser light emitting system to the second condenser lens located on the other side of the forward direction side and the backward direction side with respect to the first condenser lens,
8. The laser processing apparatus according to claim 6, wherein the camera is provided for each of the first condenser lens and each of the two second condenser lenses. The laser light emission system
a laser light source that emits the laser light;
a branching element that branches the laser light emitted from the laser light source into two beams;
a first light forming element that generates and emits the two first laser beams from one of the laser beams branched by the branching element;
a second light forming element that generates and emits the second laser light from the other of the laser lights branched by the branching element;
a mirror mechanism provided on at least one of the optical path of the laser light, the optical path of the two first laser lights, and the optical path of the second laser light;
Equipped with
10. The laser processing apparatus according to claim 9, wherein the mirror mechanism includes a plurality of mirrors and an adjustment mechanism that adjusts at least one of the positions and attitudes of the plurality of mirrors. the condenser lens includes a first condenser lens and two second condenser lenses arranged in a row along the processing feed direction together with the first condenser lens with the first condenser lens sandwiched therebetween,
The laser head
a first laser beam emitting system that emits two first laser beams corresponding to the edge cutting process as the laser beams;
two second laser beam emitting systems that emit second laser beams corresponding to the hollowing process as the laser beams;
a first connecting optical system that guides the two first laser beams emitted from the first laser beam emitting system to the first condenser lens;
a second connection optical system that, when the laser head is moved relatively to the table in the forward direction of the processing feed direction, guides the second laser light emitted from one of the second laser light emitting systems to the second condenser lens located on the backward direction side of the processing feed direction with respect to the first condenser lens, and, when the laser head is moved relatively to the table in the backward direction, guides the second laser light emitted from the other of the second laser light emitting systems to the second condenser lens located on the forward direction side of the first condenser lens;
Equipped with
8. The laser processing apparatus according to claim 6, wherein the camera is provided for each of the first condenser lens and each of the two second condenser lenses. a mirror mechanism provided on an optical path of the two first laser beams and an optical path of the second laser beam,
12. The laser processing apparatus according to claim 11, wherein the mirror mechanism includes a plurality of mirrors and an adjustment mechanism that adjusts at least one of the positions and attitudes of the plurality of mirrors.