JP5214332B2 - Wafer cutting method - Google Patents

Description

  The present invention relates to a wafer cutting method in which a wafer is cut by a cutting apparatus having two cutting means.

  Semiconductor wafers in which a plurality of electronic circuits such as IC and LSI are formed on a silicon substrate, and various plate materials such as various ceramic substrates, resin substrates, and glass substrates used for electronic components are individually processed by a dicing device (cutting device). Divided into chips, it is widely used in various electronic devices.

  In the dicing apparatus, cutting is performed by cutting a cutting blade including superabrasive grains mounted on the tip of a spindle into a workpiece such as a wafer while rotating at high speed. In recent years, dicing machines with two spindles have been proposed, and a method called step cutting, in which two types of cutting blades are mounted, is widely used especially in semiconductor device manufacturing processes that require high precision and high quality. Has been.

  In step cutting, a cutting groove having a predetermined depth is formed with a first cutting blade, and then the wafer is divided into individual chips by cutting the center of the bottom of the cutting groove with a second cutting blade. In step cutting, a wafer with a predetermined thickness is cut twice, so that the amount of cutting when cutting with each cutting blade is compared to the method of cutting with one cutting blade at a time (single cut) It is possible to reduce the processing load at the time of cutting and to perform cutting with good processing quality.

  In this step cut, it is important that the second cutting blade does not cut the position outside the cutting groove formed by the first cutting blade. Use a cutting blade with a thick blade.

  On the other hand, in the dicing machine, cutting is performed by positioning the reference line of the camera of the machine at the center of the planned cutting line of the wafer called street. And the distance (index value) from one street to the next.

  The dicing machine detects the registered target pattern, detects the planned cutting line based on the distance from the registered target pattern, and automatically performs cutting by feeding the cutting blade with the registered index value. Do.

  In the cutting process, an operation (hairline alignment) of aligning the reference line of the camera mounted on the dicing apparatus and the center line of the cutting blade in advance is performed. Specifically, this hairline alignment work is performed by once processing a groove on the surface of the wafer with a cutting blade, imaging the processed groove, performing image processing, detecting the center of the processed groove, By calculating the amount of deviation from the reference line position of the camera and adding or subtracting this deviation amount to the coordinate position, the origin position that matches the center position of the machining groove and the reference line position of the camera can be stored in the device. Is going.

  The two cutting blades are mounted on different spindles, but thermal expansion occurs in each spindle as it rotates at high speed. Even when the cutting blade and the reference line are aligned at the start of cutting, this thermal expansion causes a shift in the position of the cutting blade. Therefore, it is necessary to align the cutting blade with the reference line of the camera during processing.

  On the other hand, in a wafer with poor pattern accuracy, even if the cutting blade is index-fed at a predetermined index value, the street and the cutting blade are misaligned, so the cutting position must be corrected during processing.

In the correction of the machining position, the target pattern corresponding to the next scheduled cutting line is detected, and the next scheduled cutting line is machined based on the distance from the target pattern registered in advance to the planned cutting line (street). A method of correcting the position is adopted.
Japanese Patent No. 3280736 Japanese Patent No. 2892459 JP-A-11-121403

  However, in the conventional step cutting method, the first cutting blade and the second cutting blade are positioned at the center of the street based on the target pattern, respectively, so that the second cutting blade is formed by the first cutting blade. Located in the center of the groove.

  However, in a cutting line in which the first cutting blade does not cut the center of the street due to thermal expansion of the spindle or the like, the second cutting blade cuts a position off the cutting groove formed by the first cutting blade. There is a risk.

  The present invention has been made in view of the above points, and an object of the present invention is to cut a wafer capable of preventing the second cutting blade from being positioned outside the cutting groove cut by the first cutting blade. Is to provide a method.

According to the present invention, a chuck table for holding a wafer, a first cutting means on which a first cutting blade for cutting the wafer held on the chuck table is rotatably mounted, and the first cutting blade A second cutting means rotatably mounted with a second cutting blade thinner than the thickness, a processing feed means for processing and feeding the chuck table relative to the first and second cutting means, a first indexing means for feeding in a direction of processing feed direction and Cartesian indexing the cutting means of the first, second to indexing feed the cutting means of the second in the direction of the processing-feed direction and Cartesian Using a cutting apparatus comprising index feed means, a wafer area where the first cutting blade is positioned, and an imaging means for detecting the wafer area where the second cutting blade is positioned A wafer cutting method for cutting a wafer in which a plurality of devices are partitioned by a plurality of division lines formed in a lattice shape along the division line, and one of the division lines by the imaging unit. The first cutting blade is positioned on the one scheduled division line, and the wafer is processed and fed by the processing feeding means to form a first cutting groove of a predetermined depth in the wafer, and the first While the first cutting means is indexed and fed by the one index feed means at the intervals of the scheduled division lines of the wafer, the first cutting grooves are sequentially formed on the planned division lines, and one of the first cutting grooves is formed. One is detected by the imaging means, and the second cutting blade is positioned in the one first cutting groove to form a second cutting groove in the first cutting groove. While the indexing-feed at intervals of the second indexing means by said second cutting means wafers the dividing lines of sequentially forming a second cutting grooves in the cutting groove of the first, comprising the steps, In the step of sequentially forming the first cutting grooves, the imaging means is periodically or arbitrarily positioned in one of the first cutting grooves formed in the division planned line, and the first cutting grooves are formed. A groove position confirmation process for confirming whether one is formed at an appropriate position on the division line of the wafer, and if the first cutting groove is not formed at an appropriate position, the deviation amount is detected and And a control data creating step for creating control data for controlling the first indexing and feeding means by correcting an interval between the divided lines to be cut, and sequentially forming the second cutting grooves, Control data preparation work A wafer cutting method is provided , comprising the step of controlling the second indexing and feeding means to position the second cutting blade in the first cutting groove in accordance with the control data created by the process. The

  According to the present invention, the first cutting groove formed by the first cutting blade is detected at a predetermined timing and the position thereof is stored. Therefore, when cutting with the second cutting blade, the first cutting groove Cutting can be performed with the second cutting blade positioned at the center. Therefore, it is possible to prevent the outside of the first cutting groove from being cut by the second cutting blade, and it is possible to prevent damage to the device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a cutting device (dicing device) 2 suitable for carrying out the wafer cutting method of the present invention is shown.

  The cutting device 2 is a two-spindle type cutting device that sucks and holds a workpiece on the chuck table 4, and the chuck table 4 reciprocates in the cutting feed direction (X-axis direction) while indexing feed direction (Y-axis direction). And the work of the first cutting means 6 and the second cutting means 8 moving in the cutting feed direction (Z-axis direction).

  For example, when dicing the semiconductor wafer W, the semiconductor wafer W held on the annular frame F via the dicing tape T is placed on the chuck table 4 and sucked and held as shown in FIG.

  The chuck table 4 is movable in the X-axis direction by the cutting feed means 10, and a first alignment means 12 having a first camera (first imaging means) 13 formed integrally with the first cutting means 6. The wafer W sucked and held by the chuck table 4 by the second alignment means 14 having the second camera (second imaging means) 15 formed integrally with the second cutting means 8 is a region to be cut. After the street is detected and the street and the cutting blade are aligned in the Y-axis direction, cutting is performed.

  The cutting feed means 10 includes a pair of X-axis guide rails 16 disposed in the X-axis direction, an X-axis movement base 18 slidably supported by the X-axis guide rails 16, and an X-axis movement base 18. The X-axis ball screw 20 is screwed into a nut portion (not shown) formed on the X-axis.

The support base 24 that rotatably supports the chuck table 4 is fixed to the X-axis moving base 18, and is driven by the X-axis pulse motor 22 to rotate the X-axis ball screw 20. It is moved in the X-axis direction.

  On the other hand, the first cutting means 12 and the second cutting means 14 are supported by the guide means 26 so as to be indexable in the Y-axis direction. The guide means 26 includes a vertical column 28 disposed in the Y-axis direction orthogonal to the X-axis so as not to prevent movement of the chuck table 4 and a pair of Y disposed in the Y-axis direction on the side surface of the vertical column 28. A shaft guide rail 30, a first ball screw 32 and a second ball screw 34 arranged in parallel with the Y axis guide rail 30, and a first Y axis pulse motor connected to the first ball screw 32. 36 and a second Y-axis pulse motor 38 connected to the second ball screw 34.

  The Y-axis guide rail 30 supports the first support member 40 and the second support member 42 so as to be slidable in the Y-axis direction, and is provided in the first support member 40 and the second support member 42. Nuts (not shown) are screwed into the first ball screw 32 and the second ball screw 34, respectively.

  Driven by the first Y-axis pulse motor 36 and the second Y-axis pulse motor 38 and the first ball screw 32 and the second ball screw 34 rotate, respectively, the first support member 40 and the second The support members 42 are independently moved in the Y-axis direction.

  The positions of the first support member 40 and the second support member 42 in the Y-axis direction are measured by the linear scale 44 and used for precise control of the Y-axis direction positions. Although it is possible to provide a linear scale separately for each support member, it is better to measure the positions of both the first support member 40 and the second support member 42 with a single linear scale 44. It is possible to precisely control the distance between.

  A first moving member 46 to which the first cutting means 6 is attached is attached to the first support member 40 so as to be slidable in the vertical direction (Z-axis direction). The first Z-axis pulse motor When 48 is driven, the first moving member 46 is moved in the Z-axis direction.

  Similarly, a second moving member 50 to which the second cutting means 8 is attached is attached to the second support member 42 so as to be slidable in the vertical direction (Z-axis direction). By driving the shaft pulse motor 52, the second moving member 50 is moved in the Z-axis direction.

  Next, the configuration of the first cutting means 6 will be described with reference to FIGS. Referring to FIG. 2, an exploded perspective view showing the relationship between the spindle 56 and the blade mount 60 attached to the spindle 56 is shown.

  A spindle 56 that is rotationally driven by a servo motor (not shown) is rotatably accommodated in the spindle housing 54 of the first cutting means 6. The spindle 56 has a tapered portion 56a and a small distal end portion 56b, and a male screw 58 is formed on the small distal end portion 56b.

  Reference numeral 60 denotes a blade mount including a boss part (convex part) 62 and a fixing flange 64 formed integrally with the boss part 62, and a male screw 66 is formed on the boss part 62. Further, the blade mount 60 has a mounting hole 67.

  In the blade mount 60, the mounting hole 67 is inserted into the small diameter portion 56b and the tapered portion 56a of the spindle 56, and the nut 68 is screwed into the male screw 58 to be tightened, so that the distal end portion of the spindle 56 is shown in FIG. Attached to.

  FIG. 3 is an exploded perspective view showing a mounting relationship between the spindle 56 to which the blade mount 60 is fixed and the first cutting blade 70. The first cutting blade 70 is called a hub blade, and is configured by electrodepositing a cutting edge 76 in which diamond abrasive grains are dispersed in a nickel base material on the outer periphery of a circular base 72 having a circular hub 74.

  The mounting hole 78 of the first cutting blade 70 is inserted into the boss portion 62 of the blade mount 60, and the fixing nut 80 is screwed and tightened to the male screw 66 of the boss portion 62, thereby making the first cutting blade as shown in FIG. 70 is attached to the spindle 56.

  The second cutting means 8 is configured in substantially the same manner as the first cutting means 6 described above, and description thereof is omitted to avoid duplication. It should be noted that the thickness of the first cutting blade 70 of the first cutting means 6 is thicker than the thickness of the second cutting blade 84 of the second cutting means 8 shown in FIG. Reference numeral 82 denotes a spindle of the second cutting means 8, and a second cutting blade 84 is attached to the tip of the spindle.

  When a new first cutting blade 70 is mounted on the blade mount 60 fixed to the spindle 56, the operation of aligning the reference line of the first imaging means (first camera) 13 and the center line of the first cutting blade 70 in advance (hairline) ).

  Specifically, this hairline alignment operation is performed by once processing a groove on the surface of the workpiece with the first cutting blade 70 and imaging the processed groove with the first imaging means 13. The center of the machining groove is detected, the amount of deviation between the center position of the groove and the reference line position of the first image pickup means 13 is calculated, and the amount of deviation is added to or subtracted from the coordinate position. This is done by causing the cutting device 2 to store the origin position that matches the reference line position of the image pickup means 13. The hairline matching operation of the second cutting blade 84 attached to the second cutting means 8 is performed in the same manner.

  Next, a wafer cutting method according to an embodiment of the present invention for cutting the semiconductor wafer W by the above-described cutting apparatus 2 having two spindles will be described in detail with reference to FIGS. The wafer cutting method of the present invention is a cutting method by so-called step cut.

  As shown in FIG. 5, 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 large number of devices D are 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. Thus, the wafer W is supported by the frame F via the dicing tape T. Each device D is formed with a target pattern 86 that serves as a reference for alignment during alignment.

  Since a predetermined pattern is baked on the semiconductor wafer W by photolithography well known in the semiconductor process, a large number of devices D are formed on the wafer W at a predetermined pitch (index value) P as shown in FIG. It is organized.

  The image used for pattern matching at the time of alignment in which the first alignment means 12 detects a street to be cut needs to be acquired in advance before cutting. Therefore, when the wafer W is positioned directly below the first imaging unit 13, the first imaging unit 13 images the surface of the wafer W and displays the captured image on a display unit (not shown).

  Hereinafter, an outline of alignment by the first imaging unit 13 will be described. The operator of the cutting apparatus 2 images the planned cutting area with the first imaging unit 13 and searches for a target pattern 86 that is a pattern matching target while slowly moving the image displayed on the display unit. This target pattern uses, for example, a characteristic part of a circuit in the device D.

  When the operator determines the target pattern 86, an image including the target pattern 86 is stored in a memory provided in the first alignment means 12 of the cutting apparatus 2. Further, the distance d1 between the target pattern 86 and the center line of the street S1 is obtained by a coordinate axis or the like and the value is also stored in the memory.

  When cutting along the street of the wafer W, the first alignment unit 13 performs pattern matching between the stored image of the target pattern 86 and the image actually captured and acquired by the first imaging unit 13. 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.

  When the pattern matching at two points is completed, the straight line connecting the two target patterns 86 is parallel to the street S1, and the first cutting means 6 is moved by the distance between the target pattern 86 and the center line of the street S1. By moving in the Y-axis direction, the street S1 to be cut and the first cutting blade 70 are aligned.

  In a state where the street to be cut and the first cutting blade 70 are aligned, the chuck table 4 is moved in the X-axis direction, and the first cutting means 6 is moved while rotating the first cutting blade 70 at a high speed. When the predetermined amount is lowered, the aligned street is cut as shown in FIG. 7A, and the first cutting groove 88 is formed in the wafer W.

  By driving the first Y-axis pulse motor 36 with a predetermined pulse, the first cutting grooves 88 are sequentially formed in the first street S1 while indexing and feeding the first cutting means 6 with the index value P. The first cutting groove 88 is formed shallow as shown in FIG. Reference numeral 92 denotes, for example, a low dielectric constant insulator film (low-k film).

  In the present invention, one of the first cutting grooves 88 formed by the first cutting blade 70 is imaged by the second imaging means 15 of the second cutting means 8, and the second cutting blade 84 of the second cutting means 8 is Alignment positioned at the center of one cutting groove 88 is performed.

  With this alignment, the second cutting blade 84 is moved in the X-axis direction while the second cutting blade 84 is aligned with the center of the first cutting groove 88, and the second cutting means 84 is rotated at a high speed while the second cutting blade 84 is rotated at a high speed. When 8 is lowered by a predetermined amount, a second cutting groove 90 is formed at the center of the first cutting groove 88 as shown in FIG.

  By driving the second Y-axis pulse motor 38 with a predetermined pulse, the second cutting means 90 is sequentially inserted into the first cutting groove 88 while the second cutting means 8 is indexed and fed by the index value P. Form.

  In order to improve the throughput, the formation of the first cutting groove 88 by the first cutting blade 70 and the formation of the second cutting groove 90 by the second cutting blade 84 are the alignment of the second cutting blade 84 by the second alignment means 14. It is preferable to carry out at the same time after completion.

  If cutting of the wafer W is continued, the first cutting groove 88 may not be formed at an appropriate position on the street S1 of the wafer W due to thermal expansion of the first spindle 56 or the like. Therefore, in the present embodiment, preferably, in the first cutting groove forming step, the first cutting groove 88 is imaged by the first imaging means 13, and the first cutting groove 88 is formed at the center position of the street S1 of the wafer W. A groove position confirmation step is performed to confirm whether or not Preferably, the groove position confirmation step is periodically performed at a predetermined timing. Alternatively, the groove position confirmation step may be performed at an arbitrary timing.

  If the first cutting groove 88 is not formed at the center position of the street S1, the amount of deviation from the center position is detected, and the street S1 in which the first cutting groove 88 is formed and the street S1 to be cut next are detected. The control data creation step of creating the control data for controlling the driving of the first Y-axis pulse motor 36 by correcting the interval is performed.

  Next, in the second cutting groove forming step, the driving of the second Y-axis pulse motor 38 is controlled according to the control data created in the control data creating step, and the second cutting blade 84 is moved to the first cutting groove 88. Position in the center of

  When the reference line of the first image pickup means 13 and the position of the first cutting blade 70 are shifted due to the processing of the wafer W, hairline alignment is performed to match the first cutting blade 70 with the reference line of the first image pickup means 13. It is preferable to do this.

  Similarly, when the reference line of the second image pickup means 15 and the position of the second cutting blade 84 are displaced, it is preferable to perform hairline alignment that matches the second cutting blade 84 with the reference line of the second image pickup means 15. .

  As an alternative, when the position of the reference line and the cutting blade is misaligned, at least the second imaging means 15 immediately before the first cutting groove 88 cut by the first cutting blade 70 is cut by the second cutting blade 84. Hairline alignment is performed to align the position of the second cutting blade 84 with the reference line.

  FIG. 7B schematically shows a case where the first cutting groove 88 and the second cutting groove 90 are misaligned by the conventional cutting method. In the conventional cutting method, the first cutting blade 70 and the second cutting blade 84 are positioned at the center of the street based on the distance d1 from the target pattern 86 to the center of the street. Cutting.

  Therefore, it is assumed that the first cutting groove 88 is formed at a distance d2 from the target pattern 86 as shown in FIG. 9A due to thermal expansion of the spindle 56 of the first cutting means 6 or distortion of the pattern. . Reference numeral 94 denotes the center position of the street.

  In this case, the spindle 82 of the second cutting means 8 is not significantly affected by thermal expansion or the like, and the formation of the second cutting groove 90 by the second cutting blade 84 is shown in FIGS. 9B and 9C. Thus, it may be formed at an appropriate position.

  As a result, since the first cutting groove 88 is formed at an inappropriate position, even if the second cutting groove 90 is formed at an appropriate position, FIGS. 9B and 9C. In some cases, the second cutting groove 90 may be formed at a position away from the first cutting groove 88. This is because in the conventional cutting method, the first cutting groove 88 and the second cutting groove 90 are not associated with the formation method.

  In the wafer cutting method according to the embodiment of the present invention, the first cutting groove 88 is detected by the second imaging means 15 and the second cutting blade 84 is positioned at the center of the first cutting groove 88. It is possible to prevent the cut portion from being cut by the second cutting blade 84 and to prevent the device D from being damaged.

  In the cutting apparatus shown in FIG. 1, both the first cutting means 6 and the second cutting means 8 include the first and second alignment means 12 and 14, but the two cutting means 6 and 8 are different from each other. One alignment means may be shared.

1 is a perspective view of a cutting device suitable for carrying out the wafer cutting method of the present invention. It is a disassembled perspective view which shows the relationship between a spindle and the blade mount which should be fixed to a spindle. It is a disassembled perspective view which shows the relationship between a blade mount and the cutting blade which should be mounted | worn with a blade mount. It is a perspective view in the state where a cutting blade was attached to a spindle. It is a perspective view which shows the wafer integrated with the flame | frame. It is an enlarged plan view which shows the relationship between the device formed in the grid | lattice form with the predetermined pitch, and a street. FIG. 7A is a schematic plan view for explaining the cutting method of the present invention, and FIG. 7B is a schematic view showing a state in which the second cutting groove is formed outside the first cutting groove by the conventional cutting method. FIG. FIG. 8A is a plan view showing the first and second cutting grooves formed by the method of the present invention, and FIG. 8B is a cross-sectional view taken along line 8B-8B in FIG. 8A. FIG. 9A is a plan view showing a state where the first cutting groove is formed at a position deviated from the center of the street, and FIG. 9B is a diagram showing a state where the second cutting groove is formed at a position deviated from the first cutting groove. 9C is a cross-sectional view taken along the line 9C-9C of FIG. 9B.

Explanation of symbols

4 chuck table 6 first cutting means 8 second cutting means 12 first alignment means 13 first imaging means (first camera)
14 Second alignment means 15 Second imaging means (second camera)
70 First cutting blade 84 Second cutting blade 86 Target pattern 88 First cutting groove 90 Second cutting groove

Claims (1)

A chuck table for holding the wafer; a first cutting means on which a first cutting blade for cutting the wafer held on the chuck table is rotatably mounted; and a second thickness thinner than the thickness of the first cutting blade. A second cutting means on which the cutting blade is rotatably mounted, a processing feed means for processing and feeding the chuck table relative to the first and second cutting means, a first indexing means for feeding in the direction of exchange indexing the cutting means of the first and second indexing means for indexing feed the cutting means of the second in the direction of the processing-feed direction and Cartesian, Formed in a lattice pattern using a cutting apparatus having a wafer area where the first cutting blade is positioned and an imaging means for detecting the wafer area where the second cutting blade is positioned A plurality of wafer devices are partitioned by a plurality of dividing lines have been a method of cutting the wafer of cutting along the dividing lines,
By detecting one of the scheduled division lines by the imaging means, positioning the first cutting blade on the one scheduled division line, and processing and feeding the wafer by the processing feeding means, the wafer has a predetermined depth. Forming a first cutting groove;
While the first indexing means is indexing and feeding the first cutting means at an interval of the scheduled division lines of the wafer, the first cutting grooves are sequentially formed in the scheduled division lines,
One of the first cutting grooves is detected by the imaging means, and the second cutting blade is positioned in the first cutting groove to form a second cutting groove in the first cutting groove;
The second cutting groove is sequentially formed in the first cutting groove while the second indexing means is indexing and feeding the second cutting means at an interval of the division planned lines of the wafer.
With each process ,
The step of sequentially forming the first cutting groove includes:
The imaging means is periodically or arbitrarily positioned in one of the first cutting grooves formed on the planned dividing line, and one of the first cutting grooves is formed at an appropriate position on the planned dividing line of the wafer. A groove position confirmation process for confirming whether or not
When the first cutting groove is not formed at an appropriate position, a control for detecting the amount of deviation and correcting the interval between the divided lines to be cut next to control the first index feeding means. Including a control data creation process for creating data,
The step of sequentially forming the second cutting grooves includes:
Wafer cutting comprising the step of positioning the second cutting blade in the first cutting groove by controlling the second indexing and feeding means in accordance with the control data created in the control data creating step Method.

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