JP5456510B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus that performs processing such as cutting and groove formation by irradiating a workpiece such as a semiconductor wafer with a laser beam, and more particularly to a laser beam optical axis adjustment technique.

  In the semiconductor device manufacturing process, a large number of rectangular device areas are defined on the surface of a workpiece made of a substantially disk-shaped semiconductor wafer by grid-like division lines, and electronic circuits such as ICs and LSIs are placed in these device areas. Then, after performing necessary processing such as polishing after grinding the back side, each device region is divided into pieces by performing dicing that cuts along the planned dividing line, and a large number of devices ( Semiconductor chip). For dicing a workpiece, a cutting device called a dicer that cuts a workpiece with a cutting blade rotated at a high speed is widely used. However, in recent years, laser processing is performed by irradiating a laser beam to a division line. A method of cutting a workpiece has also been attempted (see Patent Document 1).

  A laser processing apparatus that irradiates a laser beam generally has a configuration in which a laser beam emitted from an oscillator is reflected by a mirror and then focused and irradiated on a workpiece through a condenser lens. In such a configuration, in order to process the target portion with high accuracy, the irradiation angle of the laser beam with respect to the surface of the workpiece needs to be vertical. Therefore, when the apparatus is started up or when the oscillator is replaced, the irradiation angle is adjusted to make the irradiation angle of the laser beam perpendicular to the surface of the workpiece. For safety, the entire device is covered with a light-shielding partition so that the laser beam does not leak to the outside, and the worker wears protective goggles for shielding the laser beam in the light-shielded partition. The current situation is.

JP-A-10-305420

  Therefore, it is extremely time-consuming and cumbersome to install a light-shielding partition or a worker wearing protective goggles every time the laser beam irradiation angle is adjusted, and an improvement measure is desired. It was.

  The present invention has been made in view of the above circumstances, and the main technical problem thereof is that the operation of adjusting the irradiation angle of the laser beam is accurately performed without complicated operations and with the safety of the worker secured. An object of the present invention is to provide a laser processing apparatus that can be used for the following.

  The laser processing apparatus of the present invention is a laser processing apparatus having a holding mechanism that holds a workpiece, and a laser irradiation mechanism that performs laser processing by irradiating the workpiece held by the holding mechanism with a laser beam. The irradiation mechanism includes an oscillator that emits a laser beam, a reflection mirror that reflects the laser beam emitted from the oscillator in a desired direction, and a laser beam reflected by the reflection mirror toward the work held by the holding mechanism. The condensing lens for condensing, and the laser beam disposed on the optical axis of the laser beam between the oscillator and the irradiation position of the laser beam to the workpiece, and the laser beam condensed by the condensing lens is the workpiece An optical axis confirmation unit for confirming that the light is perpendicularly incident on the surface of the optical axis, and surrounds at least the reflection mirror, the condenser lens, and the optical axis confirmation unit The optical axis confirmation unit includes: a fluorescent plate that emits light when irradiated with a laser beam; a laser beam reflected by the reflecting mirror; and a laser beam reflected by a work held by the holding mechanism. A fixed portion on which the fluorescent plate is detachably fixed at a position where the axis passes, an image of light emitted from the fluorescent plate fixed to the fixed portion, and a light emitting point by the laser beam reflected by the reflecting mirror and the workpiece And an imaging unit that can confirm whether or not the emission point of the reflected laser beam matches.

  In the laser processing apparatus of the present invention, the laser beam emitted from the oscillator is guided to the condenser lens by reflecting the reflection mirror, and is condensed and irradiated onto the work held by the holding mechanism by the condenser lens. Laser processing is performed. In the present invention, when a laser beam is emitted from the oscillator in a state where the fluorescent plate of the optical axis confirmation unit is fixed to the fixed unit, the laser beam is applied to the workpiece through the fluorescent plate, further reflects the workpiece and passes through the fluorescent plate. On the fluorescent plate, the part through which the laser beam passes emits light, and the light emission point is imaged and confirmed by the imaging unit. Here, when the laser beam is irradiated perpendicularly to the surface of the workpiece, the laser beam reflected from the workpiece has the same optical axis as the laser beam on the irradiation side, so that the number of emission points on the fluorescent screen is one. Therefore, when the number of light emission points on the fluorescent screen imaged by the imaging unit is one, it is determined that the laser beam is radiating perpendicularly to the surface of the workpiece.

  On the other hand, if it is not vertical, the light emitting points on the fluorescent screen are two points on the irradiation side and the reflection side, and it is confirmed that they are not vertical. In this case, the angle of the laser beam applied to the workpiece is adjusted so that the light emitting point on the fluorescent screen becomes one by adjusting the reflection angle of the laser beam on the reflecting mirror, etc. The irradiation angle is adjusted vertically. In the present invention, the reflection mirror, the condensing lens, and the optical axis confirmation unit are surrounded by the casing, and the laser beam cannot be visually recognized, and the irradiation angle adjustment that makes the irradiation angle to the surface of the workpiece vertical is the imaging of the imaging unit. This can be done while checking. For this reason, the work of adjusting the irradiation angle is carried out in a state where the safety of the worker is sufficiently ensured while the conventional troublesome work of covering the device with a light-shielding partition and wearing the protective goggles by the worker is omitted. Can be done.

The work referred to in the present invention is not particularly limited. For example, a semiconductor wafer made of silicon or gallium arsenide (GaAs), an adhesive member such as DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, Various electronic components such as semiconductor product packages, ceramic and glass, sapphire (Al ₂ O ₃ ) -based or silicon-based inorganic material substrates, LCD drivers for controlling and driving liquid crystal display devices, and processing position accuracy on the micron order are required. And various processed materials.

  According to the present invention, there is an effect that the operation of adjusting the irradiation angle of the laser beam can be accurately performed without complicated work and in a state where the safety of the worker is ensured.

It is a perspective view which shows the workpiece | work (semiconductor wafer) of the laser processing apparatus which concerns on one Embodiment of this invention, Comprising: This wafer has shown the state supported via the adhesive tape on the cyclic | annular flame | frame. 1 is an overall perspective view of a laser processing apparatus according to an embodiment of the present invention, showing a state where an apparatus cover is removed. It is a whole perspective view of the laser processing apparatus of one Embodiment, Comprising: The state which mounted | wore the apparatus cover is shown. It is the III section enlarged view of FIG. It is a perspective view which shows the structure in the housing | casing of the laser irradiation mechanism with which the same laser processing apparatus is equipped. It is the side view seen from the X direction which shows the structure of the laser irradiation mechanism. It is the side view seen from the Y direction which shows the structure of the laser irradiation mechanism. It is a side view which shows a mode that the irradiation position of the X direction of the laser beam with respect to a wafer is adjusted with the X direction adjustment mirror of the laser irradiation mechanism. It is a side view which shows a mode that the irradiation angle of the Y direction of the laser beam with respect to a wafer is adjusted with the angle adjustment mirror of the laser irradiation mechanism. It is a side view which shows a mode that the irradiation angle of the X direction of the laser beam with respect to a wafer is adjusted with the angle adjustment mirror of the laser irradiation mechanism. It is a figure which shows the surface of the fluorescent plate of the optical axis confirmation part in the laser irradiation mechanism, Comprising: The irradiation light of the laser beam which permeate | transmits this fluorescent plate, and the reflected light from a wafer are shown. It is a perspective view which shows the laser irradiation mechanism which concerns on other embodiment of this invention.

Hereinafter, a laser processing apparatus according to an embodiment of the present invention will be described.
[1] Wafer First, a disk-shaped semiconductor wafer (hereinafter referred to as wafer) 1 which is a workpiece in one embodiment shown in FIG. 1 will be described. The wafer 1 is a silicon wafer or the like having a thickness of about 100 to 700 μm, for example, and a large number of rectangular device regions 3 are partitioned on the surface by grid-like division planned lines 2. In each device region 3, an electronic circuit such as an IC or LSI (not shown) is formed. A linear notch 4 called an orientation flat indicating the crystal orientation of the semiconductor is formed at a predetermined location on the peripheral surface of the wafer 1. In the wafer 1, after all the division lines 2 are laser processed by the laser processing apparatus 10 shown in FIG. 2, each device region 3 is separated into a plurality of devices (semiconductor chips).

  As shown in FIG. 1, a wafer 1 is a work unit 7 that is concentrically arranged in a circular opening 5a of an annular frame 5 via an adhesive tape 6 and is integrally supported. 10 is supplied. The adhesive tape 6 has an adhesive surface on one side, and the frame 5 and the back surface of the wafer 1 are attached to the adhesive surface. The frame 5 has rigidity made of a plate material such as metal, and the wafer 1 is transferred together with the work unit 7 by supporting the frame 5.

[2] Laser Processing Device (1) Basic Configuration and Operation of Laser Processing Device Next, the basic configuration of the laser processing device 10 according to one embodiment will be described with reference to FIG. Reference numeral 11 in FIG. 2 denotes a base, and a wall 12 is provided upright at the end of the base 11 on the back side (X2 side). An XY movement table 20 is provided on the base 11 so as to be movable in the horizontal X and Y directions. The XY moving table 20 is provided with a chuck table (holding mechanism) 30 that holds the work unit 7. Above the chuck table 30, a laser irradiation mechanism 40 that performs laser processing by irradiating the wafer 1 held on the chuck table 30 with a laser beam is disposed so as to face the chuck table 30. The laser irradiation mechanism 40 is fixed to the wall portion 12.

  The XY moving table 20 is a combination of an X-axis base 21 provided on the base 11 so as to be movable in the X direction and a Y-axis base 22 provided on the X-axis base 21 so as to be movable in the Y direction. It is configured. The X-axis base 21 is slidably attached to a pair of parallel guide rails 211 that are fixed on the base 11 and extend in the X direction, and is driven by an X-axis drive mechanism 214 that operates a ball screw 213 by a motor 212. It is moved in the X direction. On the other hand, the Y-axis base 22 is slidably attached to a pair of parallel guide rails 221 that are fixed on the X-axis base 21 and extend in the Y direction, and a Y-axis drive that operates a ball screw 223 by a motor 222. It is moved in the Y direction by the mechanism 224.

  A cylindrical chuck base 31 is fixed to the upper surface of the Y-axis base 22, and the chuck table 30 is rotatably supported on the chuck base 31 with the Z direction (vertical direction) as a rotation axis. . The chuck table 30 is of a general well-known vacuum chuck type that sucks and holds a work (in this case, the wafer 1) by a negative pressure action. The chuck table 30 is rotationally driven in one or both directions by a rotational driving means (not shown) accommodated in the chuck base 31. Around the chuck table 30, a plurality of clamps 32 for detachably holding the frame 5 of the work unit 7 are disposed. These clamps 32 are attached to the chuck base 31.

  In the XY movement table 20, when the X-axis base 21 moves in the X direction, it is a processing feed for irradiating the laser beam along the planned division line 2. Then, when the Y-axis base 22 moves in the Y direction, indexing is performed to switch the division planned line 2 to be irradiated with the laser beam. The machining feed direction and the index feed direction may be set oppositely, that is, the Y direction may be set as the machining feed direction, and the X direction may be set as the index feed direction, and is not limited.

  One end of the laser irradiation mechanism 40 is fixed to the front surface of the wall portion 12 on the X1 side, and has a rectangular parallelepiped casing 41 that extends in the X1 direction from the one end toward the upper side of the chuck table 30. An irradiation port 411 that irradiates a laser beam substantially vertically downward is provided at the lower end of the tip of the housing 41 on the X1 side.

  In the housing 41, an oscillator that emits a laser beam, a condensing lens that condenses the laser beam, an optical axis adjusting unit that guides the laser beam emitted from the oscillator to the condensing lens and adjusts the optical axis of the laser beam, Elements constituting the laser irradiation mechanism 40 such as an optical axis confirmation unit for confirming whether or not the optical axis of the laser beam is perpendicularly incident on the surface of the workpiece (wafer 1) are accommodated. Will be described in detail later.

  The laser processing apparatus 10 includes an apparatus cover 13 that is set when the wafer 1 is irradiated with a laser beam. The device cover 13 is a rectangular parallelepiped box that opens downward and on the X2 side, and includes a top plate 131 and side plates 132 that close the X1, Y1, and Y2 sides. Further, a notch 133 into which the housing 41 of the laser irradiation mechanism 40 is fitted is formed in the center of the top plate 131 on the X2 side. The device cover 13 is placed and set on the base 11 as shown in FIG. In this set state, the casing 41 is fitted into the notch 133 and the lower part is covered with the device cover 13. Further, the XY moving table 20 and the chuck table 30 on the base 11 are completely covered with the apparatus cover 13.

  In addition, an alignment unit (not shown) for recognizing the irradiation position of the laser beam by imaging the division planned line 2 of the wafer 1 is provided near the irradiation port 411 at the lower end of the housing 41. Yes. The alignment means includes an illuminating means for illuminating the surface of the wafer 1, an optical system, an image pickup device such as a CCD for picking up an image captured by the optical system, and the like.

  The above is the basic configuration of the laser processing apparatus 10. In this apparatus 10, first, the work unit 7 is held on the chuck table 30, and then the apparatus cover 13 is set, and then the laser beam is applied to the division line 2 of the wafer 1. Irradiation and laser processing are performed.

  The work unit 7 is held on the chuck table 30 by vacuum-operating the chuck table 30 and placing the wafer 1 on the chuck table 30 via an adhesive tape so that the surface is exposed. This is done by holding the clamp 32. Thereafter, the apparatus cover 13 is set. The apparatus cover 13 makes the optical path of the laser beam from the irradiation port 411 to the wafer 1 invisible.

  Laser processing on the planned division line 2 is performed after the planned division line 2 is imaged by the alignment means and the irradiation position of the laser beam is recognized. In the laser processing, the X-axis base 21 of the XY moving table 20 is moved in the X direction, and the laser beam is irradiated from the irradiation port 411 of the laser irradiation mechanism 40 along the planned division line 2 parallel to the X direction. Is done by. In order to make the division line 2 parallel to the X direction, that is, the machining feed direction, the chuck table 30 is rotated to rotate the wafer 1. The selection of the division line 2 to be irradiated with the laser beam is performed by moving the Y-axis base 22 of the XY moving table 20 in the Y direction and processing the Y-direction position of the irradiation position of the laser beam irradiated from the irradiation port 411. This is done by indexing to match the target division line 2.

  In addition, although the laser processing in this embodiment performed along the division | segmentation planned line 2 includes the full cut which cut | disconnects the division | segmentation planned line 2 completely, the process which weakens the division | segmentation planned line 2 is also employ | adopted for this other than that can do. The full cut is performed by an ablation process in which the components of the wafer 1 are melted and evaporated. Further, the weakening process is performed by forming a groove having a certain depth on the surface side of the division line 2 by ablation or forming a fragile altered layer inside the wafer 1. These types of laser processing are selected according to the type (wavelength, output) of the laser beam to be irradiated, the number of irradiations, and the like.

  When laser processing is performed by irradiating all the division lines 2 with laser beam, the laser beam irradiation by the laser irradiation mechanism 40 is stopped, and the vacuum operation of the chuck table 30 is stopped to release the holding of the wafer 1. To do. Then, after removing the device cover 13 and releasing the holding of the frame 5 by the clamp 32, the work unit 7 is picked up from the chuck table 30. Thereafter, the wafer 1 is subjected to a cleaning process and the like, and then transferred to a process of picking up the separated device region 3, that is, a device (semiconductor chip) from the adhesive tape 6. In addition, when the division planned line 2 is fully cut as described above, it is directly moved to the pickup process, but in the case of the weakening process, after dividing the division planned line 2 weakened by applying external force, Moved to pickup process.

(2) Laser irradiation mechanism Next, the laser irradiation mechanism 40 will be described in detail.
In the housing 41, as shown in FIG. 5, an oscillator 42 that emits a laser beam L, a Y-direction adjusting mirror (reflection mirror) 43, and an X-direction adjustment mirror (reflection mirror) that constitute the optical axis adjusting means. 44, an angle adjustment mirror (reflection mirror) 45, a 1 / 2λ wavelength plate 46, a condenser lens 47, an optical axis confirmation unit 48, and the like are accommodated.

  The oscillator 42 generates a laser beam (for example, a pulsed laser beam) according to the laser processing of the wafer 1, and is fixed to the bottom of the end portion on the Y2 side in the housing 41 as shown in FIG. Yes. A horizontal laser beam L is emitted from the oscillator 42 in the Y1 direction. As shown in FIGS. 5 to 7, the laser beam L emitted from the oscillator 42 passes through the ½λ wavelength plate 46 and then is in the order of the Y direction adjusting mirror 43, the X direction adjusting mirror 44, and the angle adjusting mirror 45. After the reflection, the light travels downward, passes through the condenser lens 47, and irradiates the wafer 1 held on the chuck table 30.

  In this case, the Y-direction adjusting mirror 43 is composed of a polarizing beam splitter, and the laser beam L transmitted through the 1 / 2λ wavelength plate 46 is transmitted through the Y-direction adjusting mirror 43 as shown in FIG. L1) and the reflected component (reflected light L2). The laser beam L1 transmitted through the Y-direction adjusting mirror 43 is absorbed by the absorber 49 and stops traveling. On the other hand, the laser beam L2 reflected by the Y direction adjusting mirror 43 is directed to the upper X direction adjusting mirror 44 at an angle of 90 °. A laser beam L1 reflected by the Y-direction adjusting mirror 43 and directed toward the X-direction adjusting mirror 44 is a processing light beam used for laser processing of the wafer 1.

  The 1 / 2λ wavelength plate 46 is rotatably installed, and by rotating, the ratio of the laser beam reflected by the Y-direction adjusting mirror 43 and the ratio of the transmitted laser beam is changed. That is, by rotating the 1 / 2λ wavelength plate 46, the amount of the processing laser beam L (L2) reflected by the Y-direction adjusting mirror 43 is adjusted, and the substantial laser beam output of the laser irradiation mechanism 40 is adjusted. Has been adjusted. In this embodiment, since the Y-direction adjusting mirror 43 also has a laser beam output adjustment function, there is no need to separately provide a laser beam output adjustment mechanism. As a result, the number of parts can be reduced, the weight can be reduced, and the cost can be reduced. Advantages such as reduction can be obtained.

  The laser beam L reflected by the Y direction adjusting mirror 43 upward at an angle of 90 ° is incident on the X direction adjusting mirror 44, reflected in the X1 direction at an angle of 90 °, and then incident on the angle adjusting mirror 45. Reflected downward by the angle adjusting mirror 45 at an angle of approximately 90 °. The laser beam L directed downward by the angle adjustment mirror 45 is condensed by a condenser lens 47 detachably disposed in the irradiation port 411 below the angle adjustment mirror 45 and irradiated onto the wafer 1. . The adjustment mirrors 43, 44, and 45 are respectively provided on moving units 431, 441, and 451 that are fixed at predetermined positions in the housing 41 so as to be movable in a predetermined direction.

  As shown in FIGS. 5 and 6, the Y-direction adjusting mirror 43 can move linearly in the Y direction on the upper surface of the Y-direction moving portion 431 fixed to the bottom of the Y1 side end in the housing 41. It is supported by. The Y-direction moving unit 431 has a Y-direction adjustment dial 432 as an operation member that moves the Y-direction adjustment mirror 43 in the Y direction. The Y-direction adjustment dial 432 protrudes in the Y1 direction from the side surface of the housing 41 and is exposed to the outside. When the Y-direction adjustment dial 432 is pinched and rotated, the Y-direction adjustment mirror 43 is moved to the arrow A in FIG. As shown, it moves linearly in the Y direction. By moving the Y direction adjusting mirror 43 in the Y direction in this way, as shown in FIG. 6 (after the dotted line is moved), the incident / reflection position of the laser beam L in the Y direction on the Y direction adjusting mirror 43. Changes. As a result, the position in the Y direction at the irradiation position of the laser beam L irradiated on the surface of the wafer 1 is adjusted.

  As shown in FIGS. 5 to 7, the X-direction adjusting mirror 44 is positioned above the Y-direction adjusting mirror 43 and fixed to the upper surface of the housing 41 on the side surface on the X1 side of the X-direction moving unit 441. It is supported so as to be linearly movable in the vertical direction. The X-direction moving unit 441 is provided with an X-direction adjusting dial 442 as an operation member that moves the X-direction adjusting mirror 44 in the vertical direction. The X direction adjustment dial 442 protrudes upward from the upper surface of the housing 41 and is exposed to the outside. When the X direction adjustment dial 442 is pinched and rotated, the X direction adjustment mirror 44 is indicated by an arrow B in FIG. In this way, it moves linearly in the vertical direction. By moving the X-direction adjusting mirror 44 in the vertical direction in this way, as shown in FIG. 8 (after the dotted line is moved), the vertical incidence / reflection position of the laser beam L on the X-direction adjusting mirror 44. Changes. Thereby, the incident / reflection position of the laser beam L at the angle adjusting mirror 45 changes in the X direction, and as a result, the position in the X direction at the irradiation position of the laser beam L irradiated on the surface of the wafer 1 is adjusted.

  As shown in FIGS. 5 and 7, the angle adjustment mirror 45 is supported by the end face on the X2 side of the rotational movement unit 451 that is disposed opposite to the X1 side of the X direction adjustment mirror 44 and fixed in the housing 41. Yes. The rotation moving unit 451 includes a support unit 452 fixed to the housing 41, and a horizontal rotation unit supported on the X2 side end surface of the support unit 452 so as to be rotatable in the horizontal direction about the Z direction (vertical direction) as a rotation axis. 453, and an up-and-down rotating unit 454 supported on the end surface on the X2 side of the horizontal rotating unit 453 so as to be rotatable in the up-and-down direction about the Y direction as a rotation axis.

  The horizontal rotating portion 453 rotates and moves in the horizontal direction as indicated by an arrow C in FIG. 5 by pinching and rotating the Y-direction angle adjusting dial 455 provided on the support portion 452. By rotating the horizontal rotating portion 453 in the horizontal direction in this way, as shown in FIG. 9 (after the dotted line is moved), the laser beam L reflected downward by the angle adjusting mirror 45 is reflected in the Y direction. The angle is adjusted. As a result, the irradiation angle in the Y direction of the laser beam L irradiated on the surface of the wafer 1 is adjusted.

  Further, the vertical rotation unit 454 rotates in the vertical direction as indicated by an arrow D in FIG. 5 by pinching and rotating the X-direction angle adjustment dial 456 provided in the horizontal rotation unit 453. . When the vertical rotation unit 454 is rotated in the vertical direction in this way, the reflection angle in the X direction of the laser beam L reflected downward by the angle adjustment mirror 45 as shown in FIG. 10 (after the dotted line has moved). Is adjusted. As a result, the irradiation angle in the X direction of the laser beam L irradiated on the surface of the wafer 1 is adjusted.

  The Y-direction angle adjustment dial 455 protrudes from the side surface of the housing 41 in the Y1 direction and is exposed to the outside. The X-direction angle adjustment dial 456 protrudes upward from the upper surface of the housing 41 and is exposed to the outside. By appropriately rotating the angle adjusting mirrors 455 and 456, the irradiation angle in the X and Y directions of the laser beam L reflected downward by the angle adjusting mirror 45 is adjusted, and as a result, the laser with respect to the wafer 1 as described above is adjusted. The irradiation angle in the X and Y directions of the light beam is adjusted.

  As shown in FIG. 4, the Y-direction adjustment dial 432, the X-direction adjustment dial 442, the Y-direction angle adjustment dial 455, and the X-direction angle adjustment dial 456 are exposed when the device cover 13 is set and can be rotated. It has become. In the present embodiment, a Y-direction adjusting mirror 43, a Y-direction moving unit 431 that moves the mirror 43 in the Y direction, an X-direction adjusting mirror 44, an X-direction moving unit 441 that moves the mirror 44 in the X direction, and angle adjustment. The optical axis adjusting means of the present invention is configured by the mirror 45 and the rotational movement unit 451 that changes the angle of the mirror 45 in the Y direction and the X direction.

  As shown in FIG. 7, the optical axis confirmation unit 48 is disposed between the angle adjustment mirror 45 and the condenser lens 47 in the housing 41. The optical axis confirmation unit 48 includes a rectangular parallelepiped casing 481, a fluorescent plate 482 accommodated in the casing 481, and an imaging unit 483 that images the surface side of the fluorescent plate 482. The casing 481 is formed with upper and lower transmission holes 481a and 481b through which the laser beam L reflected downward by the angle adjusting mirror 45 is transmitted, and the fluorescent plate 482 covers the casing 481 in a state of closing the lower transmission hole 481b. It is fixed. The imaging unit 483 is disposed at a position where the surface of the fluorescent plate 482 can be imaged, and is fixed to the casing 481.

  The laser beam L reflected downward by the angle adjusting mirror 45 passes through the upper transmission hole 481a, the fluorescent plate 482, and the lower transmission hole 481b of the casing 481 and reaches the condenser lens 47. It is focused on. The fluorescent plate 482 has a characteristic of emitting light having a wavelength that can be recognized by the imaging unit 483 when irradiated with the laser beam L. Therefore, the position of the irradiation light transmitted through the laser beam L is emitted in a spot shape. Further, the laser beam L focused and irradiated on the wafer 1 is reflected by the surface of the wafer 1, and the reflected light irradiates the fluorescent plate 482 to emit light at the irradiation position.

  As shown by the broken line in FIG. 10, when the irradiation angle of the laser beam L with respect to the surface of the wafer 1 is vertical, the reflected light from the wafer 1 coincides with the irradiation light, so that the La point in FIG. The fluorescent plate 482 has one light emitting point. On the other hand, as shown by the one-dot chain line in FIG. 10, when the irradiation angle of the laser beam L with respect to the surface of the wafer 1 is not vertical, the reflected light from the wafer 1 does not coincide with the irradiation light, and the Lb point in FIG. Like the Lc point, there are two emission points on the fluorescent screen 482 (the Lb point is irradiation light and the Lc point is reflected light). Such a light emission state on the fluorescent plate 482 is imaged by the imaging unit 483, and the imaging is confirmed by a monitor (not shown).

  The optical axis confirmation unit 48 is handled as one unit for each casing 481, and the casing 481 is detachably set to a fixing unit 484 provided in the housing 41 as shown in FIG. 7. Accordingly, the fluorescent plate 482 is detachably fixed together with the casing 481 at a predetermined position. The optical axis confirmation unit 48 is inserted into and removed from the side opening 412 of the housing 41 and is attached to and detached from the fixing unit 484. The side opening 412 is covered with a detachable cover 413.

(3) Action of Laser Irradiation Mechanism Next, the action of the laser irradiation mechanism 40 will be described. According to this laser irradiation mechanism 40, the following optical axis adjustment can be performed.

(3-1) Adjustment to make the irradiation angle of the laser beam perpendicular to the wafer The irradiation angle of the laser beam L to the surface of the wafer 1 needs to be vertical in order to process the target portion with high accuracy. In this apparatus 10, the irradiation angle with respect to the surface of the wafer 1 is confirmed by the optical axis confirmation unit 48, and the adjustment of the irradiation angle is performed by adjusting the reflection angle of the angle adjustment mirror 45 by the Y direction angle adjustment dial 455 and the X direction angle adjustment dial 456. It can be done by adjusting.

  In the adjustment operation of the irradiation angle, first, the condenser lens 47 is removed from the irradiation port 411. Then, the apparatus cover 13 is set so that the laser beam L does not leak outside. Next, the oscillator 42 is operated to irradiate the wafer 1 held on the chuck table 30 with the laser beam L. Then, the fluorescent plate 482 is imaged by the imaging unit 483, and the imaging is confirmed on the monitor.

  As shown in FIG. 11, the fluorescent plate 482 emits light when the irradiation light of the laser beam L and the reflected light from the wafer 1 are transmitted. If the light emitting point is one place as indicated by the La point in FIG. 11, the reflected light coincides with the irradiated light, and therefore the irradiation angle of the laser beam L with respect to the surface of the wafer 1 is determined to be vertical. The

  However, as shown by the Lb point (irradiation light) and the Lc point (reflection light) in FIG. 11, when there are two emission points on the fluorescent screen 482, the reflected light passes through the same position as the irradiation light. In other words, it is determined that the irradiation angle to the surface of the wafer 1 is not vertical, and it is necessary to perform an adjustment operation to make it vertical. To do this, while checking the monitor, operate the Y-direction angle adjustment dial 455 and the X-direction angle adjustment dial 456 to adjust the angle of the angle adjustment mirror 45 so that the light emitting points of the fluorescent screen 482 approach each other and eventually become one place. Adjust as appropriate.

  According to the present embodiment, the optical axis can be adjusted so that the irradiation angle of the laser beam L to the wafer 1 is vertical while the laser beam L is completely covered by the casing 41 and the apparatus cover 13. This is because the dials 455 and 456 are exposed from the housing 41 and can be operated. For this reason, the conventional troublesome technique in which the apparatus is covered with a light shielding partition to prevent the laser beam from leaking to the outside and an operator wears protective goggles for shielding the laser beam in the light shielding partition. Saving time and effort. The irradiation angle can be easily adjusted in a short time and with sufficient safety for the worker.

  In the present embodiment, since the optical axis confirmation unit 48 is configured as one unit for each casing 481, the relative positions of the fluorescent plate 482 and the imaging unit 483 are appropriately set in a state in which imaging is possible at the time of assembly. If it is set and fixed, there is an advantage that it is not necessary to adjust afterwards and it is easy to use.

  The optical axis confirmation unit 48 is set on the fixing unit 484 only when the irradiation angle of the laser beam L to the wafer 1 is confirmed and adjusted, and is removed from the optical path of the laser beam L during normal laser processing. Further, the optical axis confirmation unit 48 may be configured to be set on the fixing unit 484 by an operator's hand, and the retraction position deviated from the optical path of the laser beam L by the conveying device and the setting position on the fixing unit 484. You may take the structure which conveys between.

  In addition, the optical axis confirmation unit 48 accommodated in the housing 41 is disposed between the angle adjustment mirror 45 and the condenser lens 47 in the one embodiment, but may be in the middle of the optical path of the laser beam L. Any location may be used. When the irradiation angle of the laser beam L with respect to the wafer 1 is not vertical, the farther away from the wafer 1, the larger the fluctuation width of the irradiation light and the reflected light, so that a slight inclination can be detected. The accuracy of the vertical degree of the irradiation angle can be further increased. From this point of view, it is preferable that the optical axis confirmation unit 48 is arranged at a position as far as possible from the wafer 1 in the optical path of the laser beam L.

  Further, the number of optical axis confirmation units 48 is not limited to one. For example, two optical axis confirmation units 48 are arranged in the optical path of the laser beam L, and one is the angle adjustment mirror 45 and the condenser lens as in the above embodiment. 47 is arranged at a location close to the wafer 1 and the other one at a location relatively far from the wafer 1 (for example, between the oscillator 42 and the 1 / 2λ wave plate 46). Also good. Thus, when the optical axis confirmation unit 48 is disposed at two spaced locations in the optical path of the laser beam L, first, a relatively rough primary adjustment is performed by the optical axis confirmation unit 48 on the side closer to the wafer 1, and then By adopting an adjustment method in which a precise secondary adjustment is performed by the optical axis confirmation unit 48 on the side far from the wafer 1, the operation of accurately and highly accurately irradiating the laser beam L onto the wafer 1 is performed. It can be carried out. In some cases, the irradiation angle of the laser beam L to the wafer 1 is significantly inclined and the reflected light may not pass through the optical axis confirmation unit 48 for secondary adjustment on the side far from the wafer 1. In such a situation, reflected light can be passed through the optical axis confirmation unit 48 for secondary adjustment by performing the primary adjustment. That is, the primary adjustment optical axis confirmation unit 48 also has a role of reliably guiding the reflected light to the secondary adjustment optical axis confirmation unit 48.

(3-2) Adjustment of passing the optical axis of the laser beam through the center of the condenser lens In order to process the target portion with high accuracy, the optical axis of the laser beam L emitted from the oscillator 42 is the center of the condenser lens 47. It is also necessary to pass through. In this apparatus 10, the optical axis of the laser beam L incident on the condenser lens 47 is moved and adjusted in the Y direction by operating the Y direction adjusting dial 432 and moving the Y direction adjusting mirror 43 in the Y direction. The Further, by operating the X direction adjustment dial 442 to move the X direction adjustment mirror 44 in the X direction, the optical axis of the laser beam L incident on the condenser lens 47 is moved and adjusted in the X direction. Accordingly, by appropriately operating these two dials 432 and 442, the optical axis of the laser beam L can pass through the center of the condenser lens 47.

  The adjustment operation for passing the optical axis of the laser beam L through the center of the condensing lens 47 in this way is preferably performed after the above irradiation angle adjustment, and the adjustment is performed by attaching the condensing lens 47 to the irradiation port 411. Do. The method for confirming whether or not the optical axis of the laser beam L passes through the center of the condensing lens 47 is arbitrary. For example, the wafer 1 is irradiated with the laser beam L on a test basis, A method of confirming the position of the processing mark with a microscope is employed. Based on the position of the processing mark, the optical axis of the laser beam L is adjusted in the X and Y directions.

  In the present embodiment, the center of the condenser lens 47 can be adjusted so that the optical axis of the laser beam L passes by moving the optical axis of the laser beam L instead of the condenser lens 47. There is no need to move the lens 47. Contrary to the present embodiment, when the condenser lens 47 is moved so that the optical axis of the laser beam L passes through the center of the condenser lens 47, the irradiation position of the laser beam L may change significantly. There is. For this reason, for example, it becomes necessary to reset the irradiation position information of the laser beam L stored in the apparatus, which causes a problem that it becomes complicated. However, according to the embodiment in which the optical axis of the laser beam L is moved without moving the condenser lens 47 as in the present embodiment, the optical axis shift is relatively small, and the trouble of resetting the position information can be saved. There is also a possibility.

(4) Other Embodiments of Laser Irradiation Mechanism FIG. 12 shows another embodiment of the laser irradiation mechanism 40. In this embodiment, the X-direction adjusting mirror 44 and the angle adjusting mirror 45 in the above-described embodiment are configured by one mirror (herein referred to as the angle adjusting mirror 45). In other words, the angle adjustment mirror 45 also serves as the X direction adjustment mirror 44. For this reason, the X direction adjustment mirror 44 is omitted.

  As shown in FIG. 12, the laser beam L emitted from the oscillator 42 is incident on the Y-direction adjusting mirror 43. In this embodiment, the laser beam L incident on the Y-direction adjusting mirror 43- is reflected in the X1 direction, and the angle The light directly enters the adjustment mirror 45. Then, the laser beam L incident on the angle adjusting mirror 45 is reflected downward and applied to the wafer 1.

  The rotational movement unit 451 that supports the angle adjustment mirror 45 so as to be capable of rotational movement is linearly movable in the vertical direction (Z direction) on the side surface on the X2 side of the X-direction movement unit 457 fixed to the housing 41. It is supported. The rotational movement unit 451 moves in the vertical direction as indicated by an arrow E by pinching and rotating the X direction adjustment dial 458 provided in the X direction movement unit 457.

  Although not shown, the X-direction adjustment dial 458 protrudes upward from the upper surface of the housing 41 and is exposed to the outside, and can be operated from the outside of the housing 41. By moving the rotational movement unit 451 in the vertical direction by the X direction adjustment dial 458, the angle adjustment mirror 45 moves in the vertical direction integrally with the rotational movement unit 451. Thereby, the reflection position of the laser beam L in the X direction by the angle adjustment mirror 45 is adjusted, and as a result, the irradiation position of the laser beam L on the wafer 1 in the X direction is adjusted.

  In this embodiment, there is an advantage that the X-direction adjusting mirror 44 in the previous embodiment is omitted, the number of mirrors is reduced, the configuration is simplified, and the cost is reduced.

1 ... Semiconductor wafer (work)
DESCRIPTION OF SYMBOLS 10 ... Laser processing apparatus 13 ... Apparatus cover 20 ... XY movement table 30 ... Chuck table (holding mechanism)
DESCRIPTION OF SYMBOLS 40 ... Laser irradiation mechanism 41 ... Case 42 ... Oscillator 43 ... Y direction adjustment mirror (reflection mirror)
44 ... X direction adjustment mirror (reflection mirror)
45 ... Angle adjustment mirror (reflection mirror)
47 ... Condensing lens 48 ... Optical axis confirmation part 482 ... Fluorescent plate 483 ... Imaging part 484 ... Fixed part L ... Laser beam

Claims (1)

A laser processing apparatus comprising: a holding mechanism that holds a workpiece; and a laser irradiation mechanism that performs laser processing by irradiating the workpiece held by the holding mechanism with a laser beam,
The laser irradiation mechanism is
An oscillator that emits a laser beam, a reflection mirror that reflects the laser beam emitted from the oscillator in a desired direction, and a collector that condenses the laser beam reflected by the reflection mirror toward a work held by the holding mechanism. An optical lens is disposed on the optical axis of the laser beam between the oscillator and the laser beam irradiation point on the workpiece, and the laser beam condensed by the condenser lens is applied to the surface of the workpiece. An optical axis confirmation unit for confirming that the light is vertically incident, and a housing surrounding at least the reflection mirror, the condenser lens, and the optical axis confirmation unit,
The optical axis confirmation unit is
The fluorescent plate is detachably fixed at a position where each optical axis of the fluorescent plate that emits light when irradiated with the laser beam, the laser beam reflected by the reflecting mirror, and the laser beam reflected by the work held by the holding mechanism passes. The light emitting point of the laser beam reflected by the workpiece and the light emitting point reflected by the workpiece are coincident with each other by imaging the light emitted from the fluorescent plate fixed to the fixing unit. An imaging unit that can confirm whether or not,
A laser processing apparatus comprising:

Images