Processing device, image capturing method for workpiece, and processing method

Abstract

To propose a novel technique for acquiring a clear photographed image of an imaging object surface when imaging the imaging object surface of a workpiece via a holding table.SOLUTION: A processing device 2 comprises: a holding table 20 in which at least an imaging region is made of a transparent part; an imaging unit (lower side imaging unit 71) which images a wafer W held by the holding table 20 via a tape T through the transparent part; and a processing unit 5 which applies processing on the wafer W held by the holding table 20. The processing device 2 further comprises: a liquid supply unit 6 for supplying liquid 55 to a holding surface 21 of the holding table 20; and a pressure unit which presses an upper surface (rear surface Wb) of the wafer W held by the holding table 20 via the liquid 55 and forms a liquid film 57 between the holding surface and the tape with the liquid 55.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a processing apparatus and a processing method for processing a workpiece held by a holding table. [Background technology]

[0002] Conventionally, as disclosed in Patent Documents 1 and 2, for example, a technology is known in which a holding table that holds a workpiece is made of a transparent material such as a glass plate, and the underside of the workpiece, i.e., the held surface side, is imaged through the holding table.

[0003] The operator then registers a target pattern based on the captured image, and the controller automatically detects the target pattern from within the captured image by pattern matching, and alignment is then performed to adjust the relative position of the workpiece and the processing unit based on this. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-087141 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-082644 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, the captured image of the underside of the workpiece is preferably as clear as possible because it is used for registering and automatically detecting the target pattern that serves as the basis for alignment.

[0006] However, if unevenness is formed on the underside of the workpiece, the unevenness will appear on the underside of the tape (the side opposite the adhesive side of the tape), forming a tiny gap between the backside of the tape and the holding surface, which will cause moire when capturing an image with an imaging camera, making it difficult to obtain a clear image.

[0007] In particular, when the workpiece is held with its underside attached to tape, the tape generally has a matte finish on the side opposite the adhesive surface, which creates a matte finish with fine irregularities, making it difficult to obtain a clear image of the underside of the workpiece due to the influence of these fine irregularities.

[0008] If the captured image is unclear, alignment will not be performed accurately, and there is a risk of machining the wrong position. In addition, captured images are also used to check the machining state after machining, for example, in kerf checks, but if the captured image is unclear, there is a risk that the machining state will not be noticed and machining will continue as is.

[0009] In addition to the potential problems mentioned above, there is also the possibility that unforeseen problems may occur due to unclear captured images, so there is a demand for technology that can reliably capture clear captured images.

[0010] In view of the above problems, the present invention proposes a new technology that enables a clear image of the surface to be imaged when the surface to be imaged of a workpiece is imaged via a holding table. [Means for solving the problem]

[0011] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0012] According to one aspect of the present invention, a processing device is provided 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 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 between the holding surface and the tape with the liquid.

[0013] According to another aspect of the present invention, the pressing unit has a rolling roller that rolls on the upper surface of the workpiece.

[0014] 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 lower surface of the workpiece via the holding table, the liquid film, and the tape.

[0015] According to one aspect of the present invention, a method for processing a workpiece includes an alignment step for performing alignment based on an image captured, and a processing step for processing the workpiece held on the holding table after performing the alignment step.

[0016] According to one aspect of the present invention, a method for processing a workpiece includes an alignment step for performing alignment based on an image captured from above the workpiece, a processing step for processing the workpiece held on the holding table after performing the alignment step, and a confirmation step for confirming the underside of the workpiece based on the captured image. [Effects of the Invention]

[0017] 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 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. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view of one embodiment of a cutting device used in practicing the present invention; [Figure 2] FIG. 2 is a diagram showing an X-axis moving mechanism that moves the holding table in the X-axis direction. [Figure 3] FIG. 3 is a diagram showing the configuration of a holding table. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of a wafer unit. [Figure 5] 1 is a flowchart showing the steps of an imaging method and a processing method according to the present invention. [Figure 6] FIG. 10 is a diagram illustrating a liquid supplying step. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] 1A is a diagram showing an example of a captured image acquired in an imaging step, and FIG. 1B is a diagram showing a reference example of a captured image when imaging is performed without using the present invention. [Figure 11] 1A to 1C are diagrams illustrating processing steps. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a perspective view showing a processing apparatus 2 according to one embodiment of the present invention. Note that the present invention can be applied not only to a processing apparatus configured as a cutting apparatus described below, but also to a laser processing apparatus having a processing unit equipped with an oscillator that generates a laser beam and a condenser that condenses the laser beam on a workpiece.

[0020] As shown in Fig. 1, a holding table 20 is disposed on a base 4 of the processing device 2 so as to be capable of reciprocating in the X-axis direction by a movement mechanism 22 (Fig. 2). A water cover 14 is disposed around the holding table 20, and a bellows 16 that closes the opening of the base 4 is connected to the water cover 14.

[0021] At the front corner of the base 4, a cassette mounting table 8 is provided for mounting a cassette 7 that accommodates a wafer unit U on which a wafer W, which is an object to be processed, is fixed.

[0022] A gate-shaped column 9 is erected 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 provided 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.

[0023] 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 provided movably 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.

[0024] The Z-axis moving block 38 is fitted with a processing unit 5 and an upper imaging unit 6. The processing unit 5 is configured by removably mounting a cutting blade on the tip of a spindle that is driven to rotate by a motor (not shown).

[0025] A liquid supply unit 50 for supplying liquid to the holding surface 21 of the holding table 20 is disposed above the holding table 20 on the movement path of the holding table 20 in the X-axis direction.

[0026] In 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 upper surface of the wafer W, which is the workpiece held on the holding surface 21 of the holding table 20.

[0027] 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 and is spin-cleaned and can be spin-dried.

[0028] FIG. 2 is a diagram showing the X-axis moving mechanism 22 that moves the holding table 20 in the X-axis direction, and the lower imaging unit 70. As shown in FIG.

[0029] The X-axis movement mechanism 22 has an X-axis direction movement stage 23 that holds the holding table 20, and a rotation mechanism 25 that rotates the holding table 20 around the Z axis.

[0030] X-axis direction moving table 23 is configured to be roughly U-shaped in side view and is composed of upper frame 23a, vertical frame 23b, and lower frame 23c. Lower frame 23c is movably placed on a pair of guide rails 22b provided on base 22a in parallel to the X-axis direction, and is screwed with a ball screw (not shown) provided in the X-axis direction between the pair of guide rails 22b. By rotating the ball screw (not shown) with pulse motor 22c, X-axis direction moving table 23 moves in the X-axis direction.

[0031] 3, a cylindrical frame portion 23f that holds the holding table 20 is provided rotatably around the Z axis on the upper frame 23a of the X-axis direction moving platform 23. The cylindrical frame portion 23f is connected to a motor 25c of the rotation mechanism 25 via a belt 25b, and the holding table 20 rotates integrally with the cylindrical frame portion 23f when driven by the motor 25c.

[0032] 3, cylindrical frame portion 23f is provided with cylindrical support portions 23m for supporting the peripheral portion of holding table 20 made of a transparent material such as glass. Around support portion 23m, suction holding portions 20a for suction-holding annular frame F of wafer unit U are provided at multiple locations with intervals.

[0033] 1, a suction and air blow groove 21a is formed in a cross shape on the holding surface 21 of the holding table 20, and by connecting it to a suction source (not shown), it is possible to hold the tape T by suction. In addition, the suction and air blow groove 21a is 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.

[0034] As shown in Figure 3, a suction groove 21b is formed in a circular shape on the holding surface 21 of the holding table 20 at a position closer to the outer periphery of the wafer W, and by connecting the suction groove 21b to a suction source not shown, the tape T is suction-held in the portion of the wafer unit U outside the wafer W.

[0035] As shown in FIG. 3, the holding table 20 may be made entirely of glass material so that the entire area is a transparent portion, or only a portion of the area corresponding to the wafer W may be made transparent.

[0036] 2, a lower imaging unit 70 is movably disposed in the space between the upper frame 23a and the lower frame 23c of the X-axis direction moving platform 23. The lower imaging unit 70 has an imaging camera 71 disposed facing the holding table 20 from below, and a movement mechanism 72 that moves the imaging camera 71 in the Y and X directions.

[0037] 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.

[0038] The imaging camera 71 is a so-called visible light camera, and images the imaged surface of the wafer W through the holding table 20 made of a transparent member and the translucent tape T. The captured image is stored in a controller (not shown). Note that the imaging camera 71 may be configured as an infrared camera, and a non-translucent tape T may be used. In this case, the wafer surface Wa (FIG. 4) may be exposed upward, and an image including the target pattern of the device D (FIG. 4) may be captured by the infrared camera.

[0039] FIG. 4 shows an example of the configuration of the wafer unit U. The wafer W, which is the workpiece, has its 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 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.

[0040] A metal film K is formed on the back surface Wb of the wafer W, and the metal film K is exposed upward. Note that the metal film K may not be formed. Alternatively, the back surface Wb of the wafer W may be attached to a tape T.

[0041] The tape T has a base material and an adhesive surface formed on the surface of the base material, and 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 surface Wa of the wafer W. The back surface (lower surface) of the tape T, which is 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 (like frosted glass). Note that the tape T may also be one that does not have an adhesive surface (glue layer).

[0042] Next, an example of an imaging method and a processing method for a workpiece using the above-described device configuration will be described. Fig. 5 is a flowchart showing the steps constituting the imaging method and processing method according to the present invention.

[0043] <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 by a transparent portion.

[0044] Specifically, the holding table 20 is positioned below the liquid supply part 51 of the liquid supply unit 50 , and the liquid 55 is dripped from the liquid supply part 51 onto the holding surface 21 of the holding table 20 .

[0045] As shown in Fig. 1, liquid supply unit 50 has a gate-shaped frame shape, and as shown in Fig. 6, it is configured with liquid supply section 51 having a plurality of liquid injection ports formed in its horizontal section. Note that liquid supply unit 50 may also be used to clean the surface of a wafer after processing. The liquid is, for example, pure water.

[0046] Furthermore, as shown in FIG. 6, instead of supplying the liquid 55 to the entire holding surface 21 of the holding table 20, it is also possible to supply the liquid only to the central portion of the holding surface 21, and then in a subsequent holding step, the liquid may be spread to the area below the wafer.

[0047] <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.

[0048] Specifically, the holding table 20 is moved from the position of the liquid supply unit 50 (FIG. 1) to a predetermined position, and the wafer unit U is placed on the holding table 20.

[0049] 7, the liquid 55 remains on the holding surface 21 of the holding table 20 due to surface tension, and the entire surface of the holding surface 21 is covered with the liquid 55. Note that a sufficient amount of liquid 55 may remain only in the center of the holding surface 21, rather than on the entire surface as described above.

[0050] <Holding 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.

[0051] 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 configured to have 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.

[0052] The rolling roller 62 is pressed against one end of the upper surface (rear surface Wb) of the wafer W, and the holding table 20 is moved in the X-axis direction to press the rolling roller 62 up to the other end of the wafer W, thereby spreading the liquid 55 present between the holding surface 21 and the tape T and forming a liquid film 57 with a uniform thickness. As a result, the liquid film 57 fills the gap between the rear surface Tb (lower surface) of the tape T and the holding surface 21.

[0053] Alternatively, the holding table 20 may be moved in one direction in the X-axis direction to press the wafer W from one end to the other end with the rolling rollers 62, and then the position of the rolling rollers 62 may be lowered and the holding table 20 may be moved in the other direction in the X-axis direction to press the wafer W from the other end to the one end with the rolling rollers 62. In other words, the wafer W is moved back and forth, which makes it possible to make the thickness of the liquid film 57 more uniform.

[0054] Alternatively, the rolling roller 62 may be pressed against the center of the wafer W, the wafer W may be moved from that position to one end of the wafer W, and then the wafer W may be 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.

[0055] Furthermore, by pressing the rolling rollers 62 against the upper surface (rear surface Wb) of the wafer W, the liquid film 57 spreads without any gaps between the rear surface Tb (lower surface) of the tape T and the holding surface 21, thereby eliminating variations in the upper surface (rear surface Wb) of the wafer W due to unevenness on the rear surface Tb of the tape T. Eliminating variations in the upper surface (rear surface Wb) of the wafer W improves processing quality, as will be described in detail later.

[0056] The unevenness on the back surface Tb (bottom surface) of the tape T is due to the unevenness of the tape T itself caused by the matte finish, or the unevenness of the devices D and the like on the bottom surface (top surface Wa) of the wafer W, which appear on the back surface Tb of the tape T, and 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.

[0057] In addition, 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 drawn toward the holding surface 21, and the tape T is adhered to the holding surface 21 via the liquid film 57.

[0058] In addition to the configuration of the pressing unit 60 described above, for example, it is possible to adopt a configuration in which the rolling rollers 62 move in the X-axis direction, a configuration in which pressing pads are used instead of the rolling rollers 62, or a configuration in which the wafer is pressed by air.

[0059] <Imaging steps> 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.

[0060] Specifically, the imaging camera 71 captures an image of the underside (front surface Wa) of the wafer W through the light-transmitting holding table 20, the liquid film 57, and the tape T. The imaging is performed at multiple locations on the wafer W by moving the holding table 20 and the imaging camera 71 as appropriate, and an alignment step, which will be described later, is performed using the multiple captured images.

[0061] 10(A) shows an example of a captured image, and the presence of the liquid film 57 (FIG. 9) can eliminate 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 influence of 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.

[0062] Figure 10(B) shows an image captured when there is no liquid film 57 (Figure 9) as a comparative example, and shows how moire fringes m occur due to the influence of the fine irregularities of the matte finish on the back surface (lower surface) of the tape and the irregularities on the lower surface (upper surface) of the wafer, causing parts of the image to become unclear.

[0063] <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. 10(A)) 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.

[0064] In this case, 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.

[0065] <Processing steps> As shown in FIG. 11, this is a step in which the wafer W held by the holding table 20 is processed after the alignment step is performed.

[0066] Specifically, a cutting blade 5a provided in the processing unit 5 forms a cutting groove along the street (planned dividing line).

[0067] 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, thereby eliminating variations in the unevenness of the back surface Tb of the tape T.

[0068] In this processing step, the cutting groove is photographed by the imaging camera 71 as needed, and a kerf check is performed to check the processing state based on the photographed image. At this time, since the photographed image is clear, processing defects can be recognized accurately and early, and processing can be stopped and corrective measures can be taken. The kerf check can be performed by an operator checking the photographed image displayed on a display monitor (not shown), or it can be performed automatically by a controller.

[0069] After processing, the tape T of the wafer unit ∪ is peeled off from the holding surface 21 by blowing air from the suction and air blow groove 21a in FIG. 1 or the suction groove 21b in FIG.

[0070] 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 bottom surface (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. Furthermore, by pressing the rolling roller against the workpiece in the holding step, the irregularities on the back surface (bottom surface) of the tape are eliminated, and the resulting irregularities on the workpiece surface (top surface (back surface Wb) of the wafer W) are eliminated, thereby suppressing processing variations in the processing step and improving processing quality.

[0071] In the above embodiment, alignment is performed using an image captured by the imaging camera 71 below the wafer W as shown in Fig. 2, but alignment may be performed based on an image obtained by capturing an image of the wafer W using the upper imaging unit 6 shown in Fig. 1, and a confirmation step may be performed to confirm processing quality such as chipping on the underside (tape T side) of the wafer W based on an image captured by the lower imaging camera 71 (Fig. 2). In this case, processing may be performed while checking processing quality such as chipping. [Explanation of symbols]

[0072] 2 Processing equipment 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 moving table 23a Upper frame 23f Cylindrical frame part 23m holding part 50 Liquid Supply Unit 51 Liquid supply section 55 liquid 57 Liquid film 60 Pressing unit 62 Roller 70 Lower imaging unit 71 Imaging camera 72 Moving mechanism 72c Horizontal moving part D Device Front annular frame K metal film m Moire P Target Pattern S Street T-tape Ta surface Tb back U Wafer Unit W wafer Wa surface Wb back side

Claims

1. 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.

2. The pressing unit comprises: a rolling roller that rolls on the upper surface of the workpiece; 2. The processing device according to claim 1.

3. 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:

4. 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:

5. 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:

Images