JP2009076773A - Chuck table mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chuck table mechanism which can suppress chipping or cracking of a wafer during cutting. <P>SOLUTION: The chuck table mechanism includes: a chuck table that has a wafer holding section to suck and hold a wafer adhered to the surface of an adhesive tape of which outer periphery is adhered to a circular frame, by means of the adhesive tape; and a clamp to fix the circular frame that supports a wafer held at the wafer holding section, by means of the adhesive tape. The wafer holding section of the chuck table is provided with: a wafer holding area that sucks and holds a wafer area where the wafer occupies on the adhesive tape; and an adhesive tape holding area that surrounds the wafer holding area and sucks and holds the adhesive tape of the outer periphery of the wafer by the specified width. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chuck table mechanism that sucks and holds a workpiece such as a wafer.

  A semiconductor wafer in which a large number of devices such as IC and LSI are formed on the surface and each device is partitioned by a line to be divided (street) is processed by a grinding machine to have a predetermined thickness after the back surface is ground. A division line is cut by a dicing machine (cutting machine) and divided into individual devices, which are used for electric devices such as mobile phones and personal computers.

  The dicing apparatus includes a chuck table for holding a semiconductor wafer, a cutting means for cutting the wafer held on the chuck table, and a machining feed means for machining and feeding the chuck table in a machining feed direction relative to the cutting means. It has.

  The wafer is held on the annular frame via an adhesive tape (dicing tape), and the annular frame is fixed by a clamp arranged around the chuck table, so that the wafer is held on the chuck table via the adhesive tape with the wafer side facing up. The wafer is divided into individual devices by moving the chuck table by the processing feed means with respect to the cutting blade which is sucked and held at a high speed.

In order to avoid the cutting blade from coming into contact with the clamp even if the clamp comes into contact with the annular frame during conveyance of the annular frame, or there is a mechanical malfunction or inadvertent operation mistake, for example, Japanese Utility Model Publication No. 5-7414. As shown in FIG. 4, the clamp fixes the annular frame so as to be pulled down below the upper surface of the chuck table.
Japanese Utility Model Publication No. 5-7414 JP-A-62-53804

  By the way, along with the trend of thinning and thinning of electric products, the chip size (device size) of semiconductors tends to become smaller and thinner, and the thickness of wafers to be diced is becoming thinner than 100 μm. Yes.

  When such a wafer is machined, chipping that crosses the chip and cracks that are derived from the cutting groove to the inside of the chip often occur even if the same processing conditions as before are used. .

  Although various causes can be considered for these occurrences, the inventor of the present application has verified the above-described phenomenon that is often seen in the outer peripheral portion of the wafer. As a result of diligent research, while cutting the wafer with a cutting blade, the annular frame is pulled down and fixed by the clamp, so tension is generated in the adhesive tape, especially the wafer and adhesive tape near the outer periphery of the wafer, It was found that the chip moved radially outward as viewed from the center of the chuck table, and chipping and cracking were likely to occur.

  In order not to apply excessive tension to the periphery of the adhesive tape, an improvement can be expected if the annular frame is not pulled down by the clamp and the position of the clamp is made almost the same height as the chuck table. In a dicing apparatus having a single spindle type, even with such a configuration, it is possible to control so as to avoid contact between the cutting blade and the clamp during cutting.

  However, in a dicing machine having two spindles that are currently increasing, the two cutting blades must be arranged away from each other in the machining feed direction, and the clamp may be equal to or slightly above the upper surface of the chuck table. If it is at a high position, one of the cutting blades will come into contact with the clamp during the cutting process, so it is necessary to move the cutting blade up and down in addition to the conventional process. Will occur.

  The present invention has been made in view of these points, and an object of the present invention is to provide a chuck table mechanism capable of suppressing the occurrence of chipping and cracking during wafer cutting.

  According to the present invention, a chuck table having a wafer holding part for sucking and holding a wafer attached to the surface of an adhesive tape having an outer peripheral edge attached to an annular frame via the adhesive tape, and the wafer holding part A chuck table mechanism for fixing the annular frame for supporting the wafer to be held via the adhesive tape, wherein the wafer holding portion of the chuck table has an adhesive tape attached to the annular frame. A wafer holding area for sucking and holding the wafer area occupied by the wafer on the adhesive tape, and surrounding the wafer holding area, the adhesive tape on the outer periphery of the wafer has a predetermined width. An adhesive tape holding area for sucking and holding the chuck table mechanism. That.

  Preferably, the predetermined width is in the range of 5 to 10 mm, and the suction means of the chuck table is communicated with a vacuum generator whose ultimate vacuum is −90 kPa or more.

  According to the chuck table mechanism of the present invention, the adhesive tape in the outer peripheral area surrounding the wafer area occupied by the wafer on the adhesive tape is held in the adhesive tape holding area of the wafer holding portion of the chuck table. The influence does not reach the wafer region, and it is possible to prevent the chip (device) that has been cut from being chipped or cracked.

  Also, if a vacuum generator with a strong suction force is used as the suction means, the force to suck and hold the adhesive tape is strong, so that the adhesive tape and wafer are prevented from moving radially outward due to the pulling of the clamp. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an external view of a cutting device (dicing device) 2 that includes the chuck table mechanism of the present invention and can divide a wafer into individual chips (devices).

  On the front side of the cutting device 2, there is provided operating means 4 for an operator to input instructions to the device such as machining conditions. In the upper part of the apparatus, there is provided a display means 6 such as a CRT for displaying a guidance screen for an operator and an image taken by an imaging means described later.

  As shown in FIG. 2, on the surface of the wafer W to be diced, the first street S1 and the second street S2 are formed orthogonally, and the first street S1 and the second street S2 A plurality of devices D are partitioned and formed on the wafer W.

  The wafer W is attached to a dicing tape T that is an adhesive tape, and the outer peripheral edge of the dicing tape T is attached to an annular frame F. As a result, the wafer W is supported by the frame F via the dicing tape T, and a plurality of wafers (for example, 25 sheets) are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

  Behind the wafer cassette 8, a loading / unloading means 10 for unloading the wafer W before cutting from the wafer cassette 8 and loading the wafer after cutting into the wafer cassette 8 is disposed. Between the wafer cassette 8 and the loading / unloading means 10, a temporary placement area 12, which is an area on which a wafer to be carried in / out, is temporarily placed, is provided. Positioning means 14 for positioning at a certain position is provided.

  In the vicinity of the temporary placement area 12, transport means 16 having a turning arm that sucks and transports the frame F integrated with the wafer W is disposed, and the wafer W carried to the temporary placement area 12 is Adsorbed by the conveying means 16 and conveyed onto the chuck table 18 and sucked by the chuck table 18, and held on the chuck table 18 by fixing the frame F by a plurality of fixing means (clamps) 19. .

  The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 18 in the X-axis direction, an alignment unit 20 that detects a street to be cut of the wafer W is provided. It is arranged.

  The alignment unit 20 includes an imaging unit 22 that images the surface of the wafer W, and can detect a street to be cut by a process such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display unit 6.

  On the left side of the alignment means 20, a cutting means 24 for cutting the wafer W held on the chuck table 18 is disposed. The cutting means 24 is configured integrally with the alignment means 20, and both move together in the Y-axis direction and the Z-axis direction.

  The cutting means 24 is configured by attaching a cutting blade 28 to the tip of a rotatable spindle 26 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 28 is located on the extended line of the imaging means 22 in the X-axis direction.

  Referring to FIG. 3, a perspective view of the chuck table mechanism 17 according to the embodiment of the present invention is shown. FIG. 4 is a longitudinal sectional view thereof. Reference numeral 30 denotes a columnar support base of the chuck table mechanism 17, and the chuck table 18 is detachably mounted on the upper surface of the support base 30.

  The chuck table 18 includes a chuck table main body 32 formed in a disk shape from a metal material such as stainless steel. A disk-shaped recess 34 is formed on the upper surface of the chuck table body 32, and a disk-shaped suction chuck 38 is fitted to the stepped portion 36 of the disk-shaped recess 34. The suction chuck 38 is formed of a porous member provided with innumerable suction holes formed of porous ceramic or the like. The suction chuck 38 constitutes a wafer holding unit.

  An annular clamp support 40 is formed integrally with the support base 30, and four clamps 19 are attached to the clamp support 40 so as to be separated from each other by 90 degrees in the circumferential direction.

  Each clamp 19 has a pair of guide rails 42 parallel to each other, one end of which is fixed to the clamp support portion 40, a holder 44 movably attached along these guide rails 42, and a rotation to the holder 44. An attached roller 46 and an L-shaped clamp pawl 48 fixed to the roller 46 are included.

  By loosening the adjustment screw 50, the position of the holder 44 is adjusted along the guide rail 42 according to the size of the annular frame F holding the wafer, and the position of the holder 44 is fixed by tightening the adjustment screw 50 after adjustment. . By rotating the roller 46 by an air cylinder (not shown), the clamp pawl 48 is rotated between the release position shown in FIG. 4 and the clamp position shown in FIG.

  An annular suction groove 52 is formed on the upper surface of the support base 30, and the suction groove 52 is connected to a suction passage 56. A suction passage 50 communicating with the recess 34 is formed at a substantially central portion of the chuck table main body 36. When the chuck table 18 is mounted on the support base 30, the suction passage 50 is formed in the support base 30. The suction passage 54 is configured to communicate with the suction passage 54.

  A seal (not shown) is disposed at the joint between the suction passage 50 and the suction passage 54, and a seal (not shown) is also disposed around the annular suction groove 52. The suction passage 54 is connected to a negative pressure suction source (vacuum generator) 62 via a suction pipe 58 and an electromagnetic opening / closing valve 60, and the suction passage 56 is connected to a negative pressure suction source via a suction pipe 64 and an electromagnetic opening / closing valve 66. 62.

  As shown in FIG. 4, the chuck table mechanism 17 includes a cover table 68 that covers the periphery of the support base 30. The cover table 68 has an opening 70 formed at the center thereof, and a flange portion 68 a protruding upward is provided around the opening 70.

  The flange portion 68a of the cover table 68 is positioned inside the skirt portion 40a of the clamp support portion 40 formed integrally with the support base 30, and the cover table 68 is supported in the state shown in FIG. Is done.

  In the state shown in FIG. 4, since the electromagnetic on-off valve 66 is off, the suction pipe 64 is blocked and no negative pressure acts on the annular suction groove 52, so that the chuck table 18 is supported by the support base 30. Can be removed freely.

  Further, since the electromagnetic on-off valve 60 is also off, the suction pipe 58 is shut off, and no negative pressure acts on the concave portion 34 of the chuck table 18, so that the suction chuck 38 is inactive.

  Referring to FIG. 5, a state where the chuck table 18 sucks and holds the wafer W attached to the surface of the adhesive tape (dicing tape) T whose outer peripheral edge is attached to the annular frame F via the adhesive tape T is shown. It is shown.

  The annular frame F is clamped between the holder 44 and the clamp pawl 48 by rotating the roller 46 by an air cylinder (not shown) from the state of FIG. At this time, since the annular frame F is pulled down and clamped by the clamp 19, a large tension is generated on the outer peripheral portion of the adhesive tape T.

  In the state shown in FIG. 5, the electromagnetic open / close valve 66 is excited and turned on, so that the suction pipe 64 is connected to the negative pressure suction source 62 via the electromagnetic open / close valve 66. Therefore, a large negative pressure acts on the annular suction groove 52 and the chuck table 18 is fixed on the support base 30.

  Further, since the electromagnetic on / off valve 60 is excited and turned on, the suction pipe 58 is connected to the negative pressure suction source 62 via the electromagnetic on / off valve 60, and a large negative pressure acts on the recess 34 of the chuck table 18, A suction chuck (wafer holding unit) 38 sucks and holds the wafer W.

  In the chuck table mechanism 17 of the present embodiment, the diameter of the wafer holding portion (suction chuck) 38 of the chuck table 18 is formed to be considerably larger than the diameter of the wafer W, so that the wafer holding portion 38 is formed on the adhesive tape T. A wafer holding area 72 for sucking and holding the wafer area occupied by the wafer W, and an adhesive tape holding area 74 for sucking and holding the adhesive tape T on the outer periphery of the wafer W over a predetermined width by surrounding the wafer holding area 72 are included. . Preferably, this predetermined width is in the range of 5-10 mm.

  As described above, the adhesive tape T in the outer peripheral region surrounding the wafer area occupied by the wafer W on the adhesive tape T is held in the adhesive tape holding area 74 of the wafer holding portion (suction chuck) 38 of the chuck table 18. The effect of pulling down the clamp 19 is absorbed by the adhesive tape T adsorbed and held in the adhesive tape holding area 74 and does not reach the wafer area of the adhesive tape T. It is possible to prevent chipping or cracking in the device.

  Since the diameter of the wafer holding portion of the conventional chuck table is formed to be approximately the same as the diameter of the wafer to be sucked and held, when the annular frame F is pulled down and fixed by the clamp 19, especially near the outer periphery of the wafer The wafer and the adhesive tape T moved radially outward as viewed from the center of the chuck table 18, which caused chipping and cracking to occur easily.

  Furthermore, in this embodiment, a negative pressure suction source having a vacuum level of −90 kPa or more is used as the negative pressure suction source (vacuum generator) 62. If the negative pressure suction source 62 having such a strong suction force is used as the suction means, the force for sucking and holding the adhesive tape T is strong, so that the adhesive tape T and the wafer W are radially outward when the clamp 19 is pulled down. Can be prevented.

  In the cutting apparatus 2 configured as described above, the wafer W accommodated in the wafer cassette 8 is sandwiched by the frame F by the loading / unloading means 10, and the loading / unloading means 10 moves to the rear of the apparatus (Y-axis direction). When the nipping is released in the placing area 12, the placing area 12 is placed in the temporary placing area 12. Then, the wafer W is positioned at a certain position by the positioning means 14 moving in a direction approaching each other.

  Next, the frame F is adsorbed by the transport unit 16, and the wafer W integrated with the frame F is transported to the chuck table 18 and held by the chuck table 18 as the transport unit 16 rotates. Then, the chuck table 18 moves in the X-axis direction, and the wafer W is positioned directly below the alignment means 20.

  The image used for pattern matching at the time of alignment in which the alignment unit 20 detects a street to be cut needs to be acquired in advance before cutting. Therefore, when the wafer W is positioned directly below the alignment unit 20, the imaging unit 22 captures the surface of the wafer W and causes the display unit 6 to display the captured image.

  Hereinafter, an outline of alignment by the imaging unit 22 will be described. The operator of the cutting device 2 operates the operation means 4 to search for a key pattern that is a target for pattern matching while slowly moving the image picked up by the image pickup means 22 and displayed on the display means 6. This key pattern uses, for example, a characteristic part of a circuit in the device D.

  When the operator determines a key pattern, an image including the key pattern is stored in a memory provided in the alignment unit 20 of the cutting apparatus 2. Further, the distance between the key pattern and the center line of the streets S1 and S2 is obtained by a coordinate value or the like, and the value is also stored in the memory.

  Further, by slowly moving the captured image on the screen, an interval between the adjacent streets (street pitch) is obtained by a coordinate value or the like, and the street pitch value is also stored in the memory of the alignment means 20. .

  At the time of cutting along the street of the wafer W, the alignment unit 20 performs pattern matching between the stored key pattern image and the image actually acquired by the imaging unit 22. This pattern matching is performed at at least two points separated from each other along the same street S1 extending in the X-axis direction.

  First, while slowly moving the image picked up at point A on the screen, pattern matching between the stored key pattern and the actual image key pattern is performed, and the screen is fixed in a state where the key pattern is matched.

  When pattern matching is performed from the imaging screen at point A as described above, the chuck table 18 is moved in the X-axis direction, and pattern matching is performed at point B that is considerably separated from point A in the X-axis direction.

  At this time, instead of moving from point A to point B at once, pattern matching is performed, but pattern matching is performed as necessary at a plurality of points in the middle of movement to point B to correct the deviation in the Y-axis direction. It is preferable to slightly rotate the chuck table 18 to perform θ correction and finally perform pattern matching at point B.

  When the pattern matching at the points A and B is completed, the straight line connecting the two key patterns is parallel to the street S1, and the cutting means 24 is moved by the distance between the key pattern and the center line of the street S1. By moving in the Y-axis direction, the street to be cut and the cutting blade 28 are aligned.

  When the street to be cut and the cutting blade 28 are aligned, the chuck table 18 is moved in the X-axis direction, and the cutting means 24 is lowered while rotating the cutting blade 28 at a high speed. The street was cut.

  The cutting process of the wafer W will be further described with reference to FIG. While the cutting blade 28 is rotated at high speed in the direction of arrow 76, the chuck table 18 is moved in the processing feed direction, that is, the X-axis direction indicated by the arrow 78, and the wafer W is cut along the aligned street.

  When the street is cut by the cutting blade 28, the street is cut while jetting cutting water from a cutting water supply nozzle (not shown) toward the cutting blade 28 and the wafer W. The cutting blade 28 is cooled by ejecting cutting water onto the cutting blade 28.

  By performing cutting while feeding the cutting means 24 in the Y-axis direction by the street pitch stored in the memory, all the streets S1 in the same direction are cut. Furthermore, when the chuck table 18 is rotated by 90 ° and then the same cutting as described above is performed, the streets S2 are all cut and divided into individual devices D.

  The wafer W that has been cut is moved in the X-axis direction by the chuck table 18 and is then gripped by the transfer means 25 that can move in the Y-axis direction and transferred to the cleaning device 27. The cleaning device 27 cleans the wafer by rotating the wafer W at a low speed (for example, 300 rpm) while jetting water from the cleaning nozzle.

  After the cleaning, the wafer W is dried at a high speed (for example, 3000 rpm) by blowing air from the air nozzle and drying the wafer W. Then, the wafer W is adsorbed by the conveying means 16 and returned to the temporary storage area 12, and then the loading / unloading means. 10, the wafer W is returned to the original storage location of the wafer cassette 8.

  Next, referring to FIG. 7, cracks or chipping occurred when the wafer was diced when the chuck table mechanism 17 of the embodiment of the present invention was used as compared with the case where the conventional chuck table mechanism was used. The measurement result of a chip is shown. FIG. 7A shows a measurement result when the conventional chuck table mechanism is used, and FIG. 7B shows a measurement result when the chuck table mechanism 17 according to the embodiment of the present invention is used.

  The black square indicates a chip in which a side crack or a corner chip is generated. First, the result of cutting in the direction of arrow X1 and then cutting in the direction of arrow X2 by rotating the chuck table 90 degrees is shown.

  As is apparent from the comparison between FIG. 7A and FIG. 7B, when the wafer W is diced using the chuck table mechanism 17 according to the embodiment of the present invention, a chip in which side cracks or chipped corners are generated. It is understood that the number of is significantly reduced.

It is an appearance perspective view of a cutting device provided with a chuck table mechanism of the present invention. It is a perspective view which shows the wafer integrated with the flame | frame. It is a perspective view of the chuck table mechanism of an embodiment of the present invention. It is a longitudinal cross-sectional view of a chuck table mechanism. It is a longitudinal cross-sectional view of the chuck table mechanism in a state where the wafer is sucked and held. It is a longitudinal cross-sectional view of the chuck table at the time of wafer cutting. FIG. 7A is a diagram showing a result of measuring a chip in which a wafer is diced using a conventional chuck table mechanism and cracks or chips are generated, and FIG. 7B is a diagram showing the chuck table mechanism of the present invention. It is a figure which shows the result of having used the dicing wafer and measuring the chip | tip which the crack or the chip | tip generate | occur | produced.

Explanation of symbols

2 Cutting device 17 Chuck table mechanism 18 Chuck table 19 Clamp 24 Cutting means 26 Spindle 28 Cutting blade 30 Support base 32 Chuck table body 38 Adsorption chuck (wafer holding part)
62 Negative pressure suction source 72 Wafer holding area 74 Adhesive tape holding area

Claims (3)

A chuck table having a wafer holding portion for sucking and holding a wafer attached to the surface of an adhesive tape having an outer peripheral edge attached to an annular frame via the adhesive tape, and a wafer held by the wafer holding portion. A chuck table mechanism comprising a clamp for fixing the annular frame supported via the adhesive tape,
When the wafer holding portion of the chuck table sucks and holds the wafer disposed on the annular frame via an adhesive tape,
A wafer holding area for sucking and holding a wafer area occupied by the wafer on the adhesive tape;
An adhesive tape holding area that surrounds the wafer holding area and sucks and holds the adhesive tape on the outer periphery of the wafer over a predetermined width;
A chuck table mechanism comprising:   The chuck table mechanism according to claim 1, wherein the predetermined width is in a range of 5 to 10 mm.   The chuck table mechanism according to claim 1 or 2, wherein the suction means of the chuck table is communicated with a vacuum generator having a degree of vacuum of -90 kPa or more.

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