JP7733495B2 - Processing device, image capturing method for workpiece, and processing method - Google Patents

Description

The present invention relates to a processing device and processing method that processes a workpiece held on a holding table.

Conventionally, as disclosed in Patent Documents 1 and 2, for example, a technology has been known in which a holding table that holds a workpiece is constructed from a transparent member such as a glass plate, and an image of the underside of the workpiece, i.e., the held surface side, is captured through the holding table.

Then, the operator registers the target pattern based on the captured image, and the controller automatically detects the target pattern from within the captured image using pattern matching. Based on this, alignment is performed to adjust the relative position of the workpiece and the processing unit.

JP 2010-087141 A JP 2010-082644 A

As mentioned above, it is desirable for the captured image of the underside of the workpiece to be as clear as possible, as it will be used to register and automatically detect the target pattern that serves as the basis for alignment.

However, if the workpiece has unevenness on its underside, the unevenness will appear on the underside of the tape (the side opposite the adhesive surface of the tape), forming a tiny gap between the backside of the tape and the holding surface. This causes moire when capturing an image with a camera, making it difficult to obtain a clear image.

In particular, when the workpiece is held in place with its underside adhered to tape, the tape generally has a matte finish on the side opposite the adhesive surface, which creates a matte finish with minute irregularities. These minute irregularities can make it difficult to obtain a clear image of the underside of the workpiece.

If the captured image is unclear, alignment may not be performed accurately, and there is a risk that the wrong position may be processed. Captured images are also used to check the processing state after processing, for example, in kerf checks, but if the captured image is unclear, there is a risk that poor processing may not be noticed and processing may continue as is.

In addition to the potential problems mentioned above, there is also the possibility of unexpected problems occurring due to unclear captured images, so there is a demand for technology that can reliably capture clear captured images.

In consideration of the above problems, the present invention proposes a new technology that makes it possible to obtain a clear image of the surface being imaged when imaging the surface of a workpiece via a holding table.

The above is the problem that this invention aims to solve, and next we will explain the means for solving this problem.

One aspect of the present invention provides a processing device that includes a holding table having at least an imaging area formed by a transparent portion, an imaging unit that images a workpiece held on the holding table via tape through the transparent portion, and a processing unit that processes the workpiece held on the holding table, and that also includes a liquid supply unit that supplies liquid to the holding surface of the holding table, and a pressing unit that presses the top surface of the workpiece held on the holding table via the liquid, forming a liquid film with the liquid between the holding surface and the tape.

Furthermore, according to one aspect of the present invention, the pressing unit has a rolling roller that rolls on the top surface of the workpiece.

Furthermore, according to one aspect of the present invention, there is provided a method for processing a workpiece attached to tape, the method comprising: a liquid supplying step of supplying liquid to the holding surface of a holding table, at least the imaging area of which is formed by a transparent portion; a placing step of, after the liquid supplying step, placing the workpiece on the holding surface via the liquid and the tape; a holding step of, after the placing step, pressing the upper surface of the workpiece toward the holding surface to form a liquid film with the liquid between the holding surface and the tape and holding the workpiece with the holding table; and an imaging step of, after the holding step, imaging the underside of the workpiece via the holding table, the liquid film, and the tape.

Furthermore, according to one aspect of the present invention, there is provided a method for processing a workpiece, comprising an alignment step in which alignment is performed based on a captured image, and a processing step in which, after the alignment step has been performed, processing is performed on the workpiece held by the holding table.

Furthermore, according to one aspect of the present invention, there is provided a method for processing a workpiece, comprising: an alignment step for performing alignment based on an image captured from above the workpiece; a processing step for processing the workpiece held by the holding table after the alignment step; and a confirmation step for confirming the underside of the workpiece based on the captured image.

The present invention has the following effects.
That is, according to one aspect of the present invention, even when there are minute irregularities in the matte finish on the back surface of the tape or when there are irregularities on the underside (top surface) of the workpiece, the gaps formed by the irregularities are filled with a liquid film, thereby preventing moire from occurring in the captured image. Also, by pressing the rolling roller against the workpiece in the holding step, the irregularities on the back side of the tape (bottom surface) are eliminated, and the resulting irregularities in the workpiece surface are eliminated, thereby suppressing the irregularities in the processing step and improving the processing quality.

1 is a perspective view of one embodiment of a cutting device used in practicing the present invention; FIG. 4 is a diagram showing an X-axis moving mechanism that moves the holding table in the X-axis direction. FIG. 3 is a diagram showing the configuration of a holding table. FIG. 2 is a diagram showing an example of the configuration of a wafer unit. 1 is a flowchart showing the steps of an imaging method and a processing method according to the present invention. FIG. 10 is a diagram illustrating a liquid supplying step. FIG. FIG. FIG. 10A is a diagram showing an example of a captured image acquired in an imaging step, and FIG. 10B is a diagram showing a reference example of a captured image when imaging is performed without using the present invention. 1A to 1C are diagrams illustrating processing steps.

Embodiments of the present invention will now be described in detail with reference to the drawings. Figure 1 is a perspective view showing a processing device 2 according to one embodiment of the present invention. Note that the present invention can be applied not only to processing devices configured as cutting devices as described below, but also to laser processing devices having a processing unit equipped with an oscillator that generates a laser beam and a condenser that focuses the laser beam on a workpiece.

As shown in Figure 1, a holding table 20 is disposed on the base 4 of the processing device 2 so that it can move back and forth in the X-axis direction by a movement mechanism 22 (Figure 2). A water cover 14 is disposed around the holding table 20, and a bellows 16 that covers the opening of the base 4 is connected to this water cover 14.

A cassette mounting table 8 is provided at the front corner of the base 4 for mounting a cassette 7 containing a wafer unit U to which a wafer W, the workpiece, is fixed.

A gate-shaped column 9 stands on the base 4, and a pair of guide rails 31 extending in the Y-axis direction are fixed to the column 9. A Y-axis moving block 33 is movably mounted on the guide rails 31, and the Y-axis moving block 33 is guided by the guide rails 31 and moves in the Y-axis direction by a Y-axis moving mechanism 30 consisting of a ball screw 32 and a pulse motor 34.

A pair of guide rails 36 extending in the Z-axis direction are fixed to the Y-axis moving block 33. A Z-axis moving block 38 is movably mounted relative to the guide rails 36, and the Z-axis moving block 38 is guided by the guide rails 36 and moves in the Z-axis direction by a Z-axis moving mechanism 40 consisting of a ball screw 42 and a pulse motor 44.

The processing unit 5 and upper imaging unit 6 are attached to the Z-axis moving block 38. The processing unit 5 is configured with a cutting blade detachably attached to the tip of a spindle that is rotated by a motor (not shown).

A liquid supply unit 50 is arranged above the holding table 20 along the movement path of the holding table 20 in the X-axis direction to supply liquid to the holding surface 21 of the holding table 20.

Along the movement path of the holding table 20 in the X-axis direction, a pressing unit 60 is arranged above the holding table 20 to press the top surface of the wafer W, which is the workpiece held on the holding surface 21 of the holding table 20.

A spinner cleaning unit 48 having a spinner table 46 is provided on the base 4, and the workpiece after cutting is held by suction on the spinner table 46, where it is spin-cleaned and can also be spin-dried.

Figure 2 shows the X-axis movement mechanism 22 that moves the holding table 20 in the X-axis direction, and the lower imaging unit 70.

The X-axis movement mechanism 22 has an X-axis movement table 23 that holds the holding table 20, and a rotation mechanism 25 that rotates the holding table 20 around the Z axis.

The X-axis direction moving table 23 is composed of an upper frame 23a, a vertical frame 23b, and a lower frame 23c, and is roughly U-shaped when viewed from the side. The lower frame 23c is movably placed on a pair of guide rails 22b that are arranged parallel to the X-axis direction on the base 22a, and is threadedly engaged with a ball screw (not shown) that is arranged in the X-axis direction between the pair of guide rails 22b. The X-axis direction moving table 23 moves in the X-axis direction by rotating the ball screw (not shown) using the pulse motor 22c.

As shown in Figure 3, a cylindrical frame portion 23f that holds the holding table 20 is rotatably mounted on the upper frame 23a of the X-axis direction moving platform 23 around the Z axis. The cylindrical frame portion 23f is connected to the motor 25c of the rotation mechanism 25 via a belt 25b, and when driven by the motor 25c, the cylindrical frame portion 23f and the holding table 20 rotate together.

As shown in FIG. 3, cylindrical frame portion 23f is provided with cylindrical support portions 23m for supporting the peripheral portion of holding table 20, which is made of a transparent material such as glass. Around support portion 23m, suction holding portions 20a for holding by suction the annular frame F of wafer unit U are provided at multiple spaced locations.

As shown in FIG. 1, a suction and air blow groove 21a is formed in a cross shape on the holding surface 21 of the holding table 20. By connecting it to a suction source (not shown), the tape T can be held by suction. The suction and air blow groove 21a is also connected to an air supply source (not shown), and by releasing air from the suction and air blow groove 21a, the tape T of the wafer unit U is peeled off from the holding surface 21.

As shown in Figure 3, a circular suction groove 21b is formed on the holding surface 21 of the holding table 20 at a position outer than the wafer W. When the suction groove 21b is connected to a suction source (not shown), the tape T is suction-held in the portion of the wafer unit U outer than the wafer W.

As shown in Figure 3, the holding table 20 may be made entirely of glass material, with the entire area being a transparent portion, or only a portion of the area corresponding to the wafer W may be made transparent.

As shown in FIG. 2, a lower imaging unit 70 is movably arranged in the space between the upper frame 23a and lower frame 23c of the X-axis direction moving platform 23. The lower imaging unit 70 has an imaging camera 71 arranged facing the holding table 20 from below, and a movement mechanism 72 that moves the imaging camera 71 in the Y and X directions.

The movement mechanism 72 is composed of an arm portion 72a that supports the imaging camera 71 at its tip, an elevator portion 72b that raises and lowers the arm portion 72a in the Z-axis direction, and a horizontal movement portion 72c that moves the elevator portion 72b horizontally in the Y-axis direction.

The imaging camera 71 is a so-called visible light camera that captures an image of the surface of the wafer W through the holding table 20, which is made of a transparent material, and the translucent tape T. The captured image is stored in a controller (not shown). The imaging camera 71 may also be configured as an infrared camera, and non-translucent tape T may also be used. In this case, the wafer surface Wa (Figure 4) may be exposed upward, and an image including the target pattern of the device D (Figure 4) may be captured with the infrared camera.

FIG. 4 shows an example of the configuration of the wafer unit U.
A wafer W, which is a workpiece, has a surface Wa, on which devices D are regularly arranged, attached to tape T, and is fixed to an annular frame F via the tape T. Streets S (planned division lines) that intersect with each other at right angles are set between the devices D, and cutting grooves are formed along the streets S, as will be described in detail later.

A metal film K is formed on the back surface Wb of the wafer W, and the metal film K is exposed upward. It is also possible for the metal film K not to be formed. The back surface Wb of the wafer W may also be attached to tape T.

Tape T has a base material and an adhesive surface formed on the surface of the base material. The base material and adhesive surface are made translucent so that the lower imaging unit 70 can capture images of the devices D formed on the front surface Wa of the wafer W. The back surface (lower surface) of tape T, opposite the surface on which the adhesive surface is formed, is given a matte finish in which fine irregularities are arranged in a matte finish (frosted glass-like pattern). Tape T without an adhesive surface (glue layer) can also be used.

Next, we will explain an example of a method for imaging and processing a workpiece using the above-mentioned device configuration. Figure 5 is a flowchart showing the steps that make up the imaging method and processing method according to the present invention.

<Liquid Supply Step>
As shown in FIG. 6, this is a step in which the liquid supply unit 50 supplies the liquid 55 to the holding surface 21 of the holding table 20, at least the imaging area of which is configured as a transparent portion.

Specifically, the holding table 20 is positioned below the liquid supply section 51 of the liquid supply unit 50, and liquid 55 is dripped from the liquid supply section 51 onto the holding surface 21 of the holding table 20.

As shown in Figure 1, the liquid supply unit 50 has a gate-shaped frame shape, and as shown in Figure 6, it is configured with a liquid supply section 51 having multiple liquid injection ports formed in its horizontal section. The liquid supply unit 50 may also be used to clean the surface of a wafer after processing. The liquid is, for example, pure water.

Furthermore, as shown in FIG. 6, instead of supplying liquid 55 to the entire holding surface 21 of the holding table 20, it is also possible to supply it only to the center of the holding surface 21, for example, and then in a later holding step, the liquid can be spread to the area below the wafer.

<Placement step>
As shown in FIG. 7, after the liquid supply step is performed, the wafer W is placed on the holding surface 21 via the liquid 55 and the tape T.

Specifically, the holding table 20 is moved from the position of the liquid supply unit 50 (Figure 1) to a predetermined position, and the wafer unit U is placed on the holding table 20.

In the example of Figure 7, the liquid 55 remains on the holding surface 21 of the holding table 20 due to surface tension, and the entire holding surface 21 is covered with the liquid 55. However, instead of covering the entire surface as in this example, a sufficient amount of liquid 55 may remain only in the center of the holding surface 21.

<Retention step>
As shown in Figure 8, after the placing step is performed, the upper surface (back surface Wb) of the wafer W is pressed toward the holding surface 21, a liquid film 57 is formed between the holding surface 21 and the tape T using liquid 55, and the wafer is held by the holding table 20.

Specifically, the holding table 20 on which the wafer unit U is placed is moved below the pressing unit 60. The pressing unit 60 is composed of a rolling roller 62 that rolls on the upper surface (back surface Wb) of the wafer W, and a frame part 64 that rotatably holds the rolling roller 62 and moves up and down.

By pressing the rolling roller 62 against one end of the top surface (back surface Wb) of the wafer W and moving the holding table 20 in the X-axis direction to press the rolling roller 62 to the other end of the wafer W, the liquid 55 present between the holding surface 21 and the tape T is spread to form a liquid film 57 of uniform thickness. As a result, the liquid film 57 fills the space between the back surface Tb (lower surface) of the tape T and the holding surface 21.

Furthermore, by moving the holding table 20 in one direction in the X-axis direction, the rolling rollers 62 can be pressed from one end of the wafer W to the other end, and then the position of the rolling rollers 62 can be lowered and the holding table 20 can be moved in the other direction in the X-axis direction, so that the rolling rollers 62 can press the wafer W from the other end to the one end. In other words, the wafer W is moved back and forth, which can make the thickness of the liquid film 57 more uniform.

Alternatively, the rolling roller 62 can be pressed against the center of the wafer W, the wafer W moved from that position to one end of the wafer W, and then the wafer W returned to its original position and moved from that position to the other end of the wafer W, thereby draining excess liquid from the center of the wafer W and preventing variations in the thickness of the liquid film.

Furthermore, by pressing the rolling roller 62 against the top surface (back surface Wb) of the wafer W, the liquid film 57 spreads seamlessly between the back surface Tb (lower surface) of the tape T and the holding surface 21, eliminating variations in the top surface (back surface Wb) of the wafer W due to unevenness on the back surface Tb of the tape T. This elimination of variations in the top surface (back surface Wb) of the wafer W improves processing quality, as will be described in more detail below.

The unevenness on the back surface Tb (lower surface) of the tape T is due to the unevenness of the tape T itself caused by the matte finish, or the unevenness of devices D and the like on the underside (front surface Wa) of the wafer W, which appear on the back surface Tb of the tape T. These unevennesses form tiny gaps between the back surface Tb of the tape T and the holding surface 21, which are filled with the liquid film 57.

Furthermore, the tape T is sucked from below by the suction grooves 21b formed on the outer periphery of the holding surface 21, so that the tape T is pulled toward the holding surface 21 and adhered to the holding surface 21 via the liquid film 57.

In addition to the configuration of the pressing unit 60 described above, it is also possible to adopt a configuration in which the rolling rollers 62 move in the X-axis direction, a pressing pad is used instead of the rolling rollers 62, or the wafer is pressed with air.

<Imaging step>
As shown in FIG. 9, after the holding step is performed, an image of the lower surface (front surface Wa) of the wafer W is taken via the holding table 20, the liquid film 57, and the tape T.

Specifically, the imaging camera 71 captures an image of the underside (surface Wa) of the wafer W through the light-transmitting holding table 20, the liquid film 57, and the tape T. Images are captured at multiple locations on the wafer W by moving the holding table 20 and the imaging camera 71 as needed, and the alignment step described below is performed using the multiple captured images.

Figure 10 (A) shows an example of a captured image. The presence of the liquid film 57 (Figure 9) eliminates the influence of minute irregularities in the matte finish on the back surface (bottom surface) of the tape and the irregularities on the back surface (bottom surface) of the tape due to the irregularities on the bottom surface (top surface) of the wafer, suppressing the occurrence of moire and clearly capturing the target pattern P used for alignment. This captured image is displayed on a display monitor (not shown) and can be confirmed by the operator.

Figure 10(B) shows, as a comparative example, an image captured when the liquid film 57 (Figure 9) is not present. It shows how moiré fringes (m) occur due to the influence of the minute irregularities of the matte finish on the back surface (bottom surface) of the tape and the irregularities on the bottom surface (top surface) of the wafer, causing parts of the image to become unclear.

<Alignment step>
This is a step in which alignment is performed based on the captured images taken in the holding step. Specifically, a controller (not shown) recognizes the center position of the street S (planned division line) based on the target pattern P (FIG. 10A) of the multiple captured images, and adjusts the angle of the holding table 20 (FIG. 3) using the rotation mechanism 25 (FIG. 3) so that the street S is parallel to the X-axis direction.

At this time, alignment is performed using a clear captured image, which prevents problems such as misrecognition of the target pattern P (Figure 10(A)), and prevents processing defects caused by processing the wrong position in subsequent processing steps.

<Processing steps>
As shown in FIG. 11, after the alignment step is performed, the wafer W held by the holding table 20 is processed.

Specifically, a cutting groove is formed along the street (planned division line) using the cutting blade 5a provided in the processing unit 5.

As described above, in the holding step, the rolling roller 62 is pressed against the upper surface (back surface Wb) of the wafer W, and the liquid film 57 is uniformly spread between the back surface Tb (lower surface) of the tape T and the holding surface 21, eliminating any unevenness in the back surface Tb of the tape T.

During this processing step, the cutting groove is photographed appropriately using the imaging camera 71, and a kerf check is performed to confirm the processing status based on the captured image. Because the captured image is clear, processing defects can be accurately and quickly recognized, making it possible to halt processing and take appropriate measures. The kerf check can be performed by an operator checking the captured image displayed on a display monitor (not shown), or it can be performed automatically by the controller.

After processing, the tape T of the wafer unit ∪ is peeled off from the holding surface 21 by blowing air through the suction and air blow groove 21a in Figure 1 or the suction groove 21b in Figure 3.

As described above, according to the present invention, even when there are minute irregularities in the matte finish on the back surface of the tape or irregularities on the underside (top surface) of the workpiece, the gaps formed by the irregularities are filled with a liquid film, preventing moire from occurring in the captured image. Furthermore, by pressing the rolling roller against the workpiece in the holding step, variations in the irregularities on the back side (bottom side) of the tape are eliminated, and the resulting variations in the workpiece's surface (top surface (back surface Wb) of the wafer W) are also eliminated, thereby suppressing variations in processing in the processing step and improving processing quality.

In addition, in the above embodiment, alignment is performed using the image captured by the imaging camera 71 below the wafer W as shown in Figure 2. However, alignment may be performed based on the image captured by the upper imaging unit 6 shown in Figure 1, and a confirmation step may be performed to confirm the processing quality, such as chipping, on the underside of the wafer W (the tape T side) based on the image captured by the lower imaging camera 71 (Figure 2). In this case, processing may be performed while checking the processing quality, such as chipping.

2 Processing device 5 Processing unit 5a Cutting blade 20 Holding table 21 Holding surface 21a Air blow groove 21b Suction groove 22 X-axis movement mechanism 22a Base 22b Guide rail 22c Pulse motor 23 X-axis direction movement table 23a Upper frame 23f Cylindrical frame portion 23m Holding portion 50 Liquid supply unit 51 Liquid supply portion 55 Liquid 57 Liquid film 60 Pressing unit 62 Rolling roller 70 Lower imaging unit 71 Imaging camera 72 Movement mechanism 72c Horizontal movement portion D Device F Annular frame K Metal film m Moire P Target pattern S Street T Tape Ta Front surface Tb Back surface U Wafer unit W Wafer Wa Front surface Wb Back surface

Claims (5)

a holding table having at least an imaging area formed of a transparent portion;
an imaging unit that images, through the transparent portion, an image of the workpiece held on the holding table via the tape;
a processing unit that processes the workpiece held by the holding table,
a liquid supply unit for supplying liquid to a holding surface of the holding table;
a pressing unit that presses the upper surface of the workpiece held by the holding table via the liquid , the upper surface being exposed on the side opposite the tape , and forms a liquid film between the holding surface and the tape with the liquid. The pressing unit comprises:
a rolling roller that rolls on the upper surface of the workpiece;
2. The processing device according to claim 1. A method for processing a workpiece attached to a tape, comprising:
a liquid supplying step of supplying a liquid to the holding surface of the holding table, at least the imaging area of which is configured by a transparent portion;
a placing step of placing a workpiece on the holding surface via the liquid and the tape after the liquid supplying step is performed;
a holding step of pressing an upper surface of the workpiece, which is exposed on the side opposite to the tape, toward the holding surface after the placing step, to form a liquid film between the holding surface and the tape with the liquid, and holding the workpiece with the holding table;
an imaging step of imaging the underside of the workpiece through the holding table, the liquid film, and the tape after the holding step is performed;
A method for imaging a workpiece, comprising: an alignment step of performing alignment based on the captured image obtained by the method for capturing an image of a workpiece according to claim 3;
a processing step of processing the workpiece held by the holding table after the alignment step is performed;
A method for processing a workpiece, comprising: an alignment step of performing alignment based on an image captured from above the workpiece;
a processing step of processing the workpiece held by the holding table after the alignment step is performed;
a confirmation step of confirming the bottom surface of the workpiece based on the captured image obtained by the workpiece imaging method according to claim 3;
A method for processing a workpiece, comprising: