JP5122378B2 - How to divide a plate - Google Patents

Description

  The present invention relates to a method for dividing a plate-like object such as a semiconductor wafer.

  A plate-like object such as a semiconductor wafer on which a plurality of devices such as IC and LSI are formed on the surface is divided into individual devices by a cutting device, and the divided devices are widely used in electric devices such as mobile phones and personal computers. .

  As a cutting device, a device called a dicer having a chuck table for holding a workpiece, a cutting blade for cutting a workpiece held on the chuck table, and a spindle on which the cutting blade is mounted is widely used. Has been.

  The cutting blade has, for example, a cutting blade electrodeposited and fixed with diamond abrasive grains having a particle size of about 3 μm on the outer periphery, and the cutting blade cuts into the work piece while being rotated at a high speed of 20000 to 60000 rpm by the spindle. Cutting is performed.

  In processing by a dicer, a processing position is set by matching a reference line of a camera mounted on a device called a hairline and a planned cutting line. Before machining, the camera reference line and the center line of the cutting blade are aligned (hairline alignment), but the spindle undergoes thermal expansion due to high-speed rotation during processing, so the cutting blade is positioned in the axial direction. Deviation occurs.

  If cutting is performed in a state where the cutting blade and the reference line of the camera are deviated from each other, there is a fear that the device is damaged by cutting the area deviated from the planned cutting line. Therefore, normally, hairline alignment is performed at a predetermined timing during the cutting process. Specifically, a cutting groove formed by cutting is imaged by a camera, and a deviation between the reference line of the camera and the cutting groove is detected and corrected.

  On the other hand, in recent years, in order to improve the processing ability of semiconductor chips such as IC and LSI, inorganic films such as SiOF and BSG (SiOB) and polymer films such as polyimide and parylene are formed on the surface of a semiconductor substrate such as silicon. A semiconductor wafer having a form in which a semiconductor chip is formed by a laminate in which a low dielectric constant insulator film (low-k film) made of an organic film and a functional film for forming a circuit is laminated has been put into practical use. .

  Also, there is a semiconductor wafer configured such that a metal pattern called a test element group (TEG) is partially arranged on a division line of a semiconductor wafer, and the function of the circuit is tested through the metal pattern before dividing the device into devices. It has been put into practical use.

  Since these low-k films and TEG are formed of a material different from that of the semiconductor substrate, it is difficult to cut the semiconductor substrate simultaneously with the cutting blade. In particular, since the low-k film is very brittle like mica, there is a problem that when the cutting is performed with a cutting blade, the low-k film is peeled off from the cut point and the device is damaged. Further, since TEG is made of metal, there is a problem that when cutting with a cutting blade, burrs are generated and the life of the cutting blade is shortened.

In order to solve these problems, the low-k film and TEG on the planned division line are removed by irradiating a pulsed laser beam along the planned division line of the semiconductor wafer, and a cutting blade is positioned in the removed area. A processing apparatus for cutting has been proposed (see Japanese Patent Application Laid-Open No. 2003-320466).
JP 2003-320466 A

  However, when cutting a region where a low-k film or TEG has been removed by laser beam irradiation and a laser processing groove is formed with a cutting blade, the cutting groove by cutting is a laser processing groove. Therefore, there is a problem that it is difficult to detect the cutting groove with the camera from the upper surface of the workpiece.

  The present invention has been made in view of the above points, and the object of the present invention is to detect the cutting groove even when the region where the processing groove is formed by laser beam irradiation is cut with a cutting blade. It is an object of the present invention to provide a method for dividing a plate-like object that can be surely and easily performed and can match a laser-machined groove and a cutting groove.

According to the present invention, a plurality of division lines are formed in a lattice shape on the surface, and a device area in which a device is formed in each of a plurality of areas partitioned by the plurality of division lines and surrounding the device area A plate-like object dividing method for dividing a plate-like object having an outer peripheral surplus area into individual devices, and irradiating a laser beam along the planned division line except for an outer peripheral part of the outer peripheral surplus area. A laser beam irradiation step for forming a laser processing groove, and a cutting blade is used to cut the bottom portion of the laser processing groove and the outer peripheral portion of the outer peripheral surplus region along the laser processing groove formed by the laser beam irradiation step. A cutting step of forming a cutting groove having a narrower groove width than the laser processing groove, and the laser processing groove formed in the laser beam irradiation step, A plate-like object comprising: an alignment step of detecting a positional deviation of the outer peripheral surplus region from the cutting groove formed in the outer peripheral portion and aligning the cutting blade with the laser processing groove. Are provided.
Preferably, in the alignment step, the cutting groove formed in the outer peripheral portion of the outer peripheral surplus area is imaged by an imaging unit including an optical system in which a reference line for alignment of a cutting blade is formed, and the reference A correction value is calculated by detecting a positional deviation between the line and the cutting groove, the reference line is aligned with the laser processing groove, and the correction value is added to the position data of the cutting blade. And each laser processing groove are made to correspond to each step.

  According to the present invention, when the laser processing groove is formed, an unformed region of the laser processed groove remains in the outer peripheral portion of the outer peripheral surplus region. Therefore, when cutting with a cutting blade, hairline alignment is performed in the laser processed groove non-formed region This makes it possible to match the cutting groove with the laser processing groove. Further, since the laser processed groove non-formed region is formed in the outer peripheral portion of the outer peripheral surplus region where the device is not formed, the amount of device taken from one wafer is not reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a laser processing apparatus suitable for carrying out the plate-like object dividing method of the present invention.

  The laser processing apparatus 2 includes a first slide block 6 mounted on a stationary base 4 so as to be movable in the X-axis direction. The first slide block 6 is moved along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, by the machining feed means 12 including the ball screw 8 and the pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing feeding means 22 constituted by the ball screw 18 and the pulse motor 20.

  A chuck table 28 is mounted on the second slide block 10 via a cylindrical support member 26, and the chuck table 28 can be moved in the X-axis direction and the Y-axis direction by the processing feed means 12 and the index feed means 22. . The chuck table 28 is provided with a clamper 30 for clamping a work such as an LED wafer sucked and held by the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 accommodating a laser beam oscillation means 34 is attached to the column 32. The laser beam oscillation means 34 includes a processing laser beam oscillation means and a workpiece edge detection laser beam oscillation means, as will be described in detail later.

  The laser beam for processing and edge detection oscillated from these laser beam oscillating means is condensed by the objective lens of the condenser 36 attached to the tip of the casing 35 and held on the chuck table 28. Irradiate the workpiece.

  At the tip of the casing 35, an image pickup means 38 is arranged which is aligned with the condenser 36 in the X-axis direction and detects a processing region to be laser processed by the processing laser beam irradiation means.

  The image pickup means 38 includes, in addition to an image pickup device such as a normal CCD that picks up an image with visible light, an infrared irradiation means for irradiating the work with infrared rays, an optical system for capturing the infrared rays irradiated by the infrared irradiation means, Infrared imaging means including an infrared imaging element such as an infrared CCD that outputs an electrical signal corresponding to the captured infrared light is included, and the captured image signal is transmitted to a controller (control means) 40 described later.

  The controller 40 includes a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read-only memory (ROM) 44 that stores a control program, and a random read / write that stores arithmetic results. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  Reference numeral 56 denotes a processing feed amount detection means comprising a linear scale 54 disposed along the guide rail 14 and a read head (not shown) disposed on the first slide block 6. Is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes index feed amount detection means comprising a linear scale 58 disposed along the guide rail 24 and a read head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  An image signal picked up by the image pickup means 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation means 34, and the like.

  Next, referring to FIG. 2, there is shown an external perspective view of a cutting device (dicing device) 62 suitable for carrying out the plate-like material dividing method of the present invention.

  On the front side of the cutting device 62, operating means 64 is provided for an operator to input instructions to the device such as machining conditions. In the upper part of the apparatus, there is provided display means 66 such as a CRT on which a guide screen for the operator and an image taken by an imaging means described later are displayed.

  A wafer W which is a kind of plate-like material suitable for applying the method of the present invention is attached to a dicing tape T which is an adhesive tape, and an outer peripheral edge portion 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 68 shown in FIG. The wafer cassette 68 is placed on a cassette elevator 69 that can move up and down.

  Behind the wafer cassette 68 is disposed a loading / unloading means 70 for unloading the wafer W before cutting from the wafer cassette 68 and loading the wafer after cutting into the wafer cassette 68.

  Between the wafer cassette 68 and the carry-in / out means 70, a temporary placement area 72, which is an area on which a wafer to be carried in / out, is temporarily placed, is provided. Positioning means 74 for positioning at a fixed position is provided.

  In the vicinity of the temporary placement area 72, a transport means 76 having a swivel 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 72 is It is sucked by the transport means 76 and transported onto the chuck table 78 and is sucked by the chuck table 78, and is held on the chuck table 78 by fixing the frame F by a plurality of fixing means 79.

  The chuck table 78 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 78 in the X-axis direction, an alignment unit 80 that detects a street to be cut of the wafer W is provided. It is arranged.

  The alignment unit 80 includes an imaging unit 82 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 82 is displayed on the display unit 6. The imaging unit 82 includes an optical system in which a reference line is formed for positioning of the cutting blade.

  On the left side of the alignment means 80, a cutting means 84 for cutting the wafer W held on the chuck table 78 is disposed. The cutting means 84 is configured integrally with the alignment means 80, and both move in conjunction with each other in the Y-axis direction and the Z-axis direction.

  The cutting means 84 is configured by attaching a cutting blade (hub blade) 88 to the tip of a rotatable spindle 86 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 88 is located on the extended line of the image pickup means 82 in the X-axis direction.

  As shown in FIG. 3, on the surface of the semiconductor wafer W to be divided, the first street S1 and the second street S2 are formed orthogonally, and the first street S1 and the second street S2 are formed. A device (semiconductor chip) D is formed in each of a plurality of regions partitioned by.

  The semiconductor wafer W suitable for dividing by the dividing method of the present invention forms a semiconductor chip (device) by a laminated body in which a low dielectric constant insulating film (low-k film) and a functional film for forming a circuit are laminated. Or a semiconductor wafer in which a metal pattern called a test element group (TEG) is partially arranged on a division line (street) of the wafer.

  When this type of semiconductor wafer is cut by a cutting machine equipped with a cutting blade, there is a problem as described in the background art section. It is preferable to divide the wafer into individual devices by a two-stage method of forming a cutting groove with a cutting device. The division method of the present invention employs this two-stage division method.

  Prior to processing by the dividing method of the present invention, as shown in FIG. 4, the semiconductor wafer W is attached to a dicing tape T which is an adhesive tape having an outer peripheral edge attached to an annular frame F. As a result, the wafer W is supported by the frame F via the dicing tape T.

  In order to carry out the dividing method of the present invention, first, the wafer W is supported and fixed on the chuck table 28 by clamping the annular frame F by the clamper 30 of the laser processing apparatus 2 shown in FIG. Next, the processing feed means 12 and the index feed means 22 are driven to position the wafer W directly below the imaging means 38 constituting the alignment means.

  An image used for pattern matching at the time of alignment in which the alignment means detects a street to be laser processed must be acquired in advance before laser processing. Therefore, when the wafer W is positioned immediately below the imaging means 38, the imaging means 38 images the surface of the wafer W and displays the captured image on a display means (not shown).

  When the operator of the laser processing apparatus 2 searches for a key pattern to be a pattern matching target and the operator determines the key pattern, an image including the key pattern is stored in a memory 46 provided in the controller 40 of the laser processing apparatus 2. . Further, the distance between the key pattern and the center line of the streets S 1 and S 2 is obtained by a coordinate value or the like, and the value is also stored in the memory 46.

  Further, by moving the image pickup means 38, an interval between the adjacent streets (street pitch) is obtained by a coordinate axis or the like, and the street pitch value is also stored in the memory 46 of the controller 40.

  When forming the laser processing groove along the street of the wafer W, pattern matching between the image of the stored key pattern and the image actually acquired by the imaging unit 38 is performed by an alignment unit (not shown). This pattern matching is performed in at least two places along the same street.

  When the patterns are matched, the chuck table 28 is rotated by θ to correct the angle, and the index feed means 22 is driven to move the chuck table 28 to the Y axis by the distance between the key pattern and the center line of the street. By moving in the direction, the street where the laser processing groove is to be formed and the condenser 36 are aligned.

  In a state where the street where the laser processing groove is to be formed and the condenser 36 are aligned, the laser beam oscillation means 34 is driven to oscillate the laser beam, and the laser beam is positioned by the condenser 36. The light is condensed on the aligned streets, and the machining feed means 12 is driven to move the chuck table 28 in the X-axis direction.

  Thereby, a laser processing groove is formed in the aligned street. In general, since the size of the beam spot is smaller than the width of the street, it is preferable to form a plurality of laser processing grooves along the street.

  By irradiating a laser beam while indexing the chuck table 28 by the index feed means 22 for each street pitch stored in the memory 46, the laser processing grooves 94 are formed in all the streets S1 in the same direction as shown in FIG. It is formed. Further, when the chuck table 28 is rotated 90 degrees and the same operation as described above is performed, the laser processing grooves 94 are formed in all the streets S2.

  What is important in the dividing method of the present invention is that the laser processed groove 94 is formed in a region excluding the outer peripheral portion 96 of the outer peripheral surplus region 92 of the wafer W. Accordingly, the outer peripheral portion 96 of the outer peripheral surplus region 92 becomes a laser processed groove non-formed region. As described above, when the laser processing groove 94 is formed on the street of the wafer W by the laser beam irradiation, the low-k film and the TEG are removed.

  According to the dividing method of the present invention, the wafer W in which the laser processing grooves 94 are formed in all the streets in this way is formed on the bottom of the laser processing grooves 94 using the cutting device 62 as shown in FIG. Cutting grooves are formed, and the wafer W is divided into individual devices D.

  First, the wafer W in which the laser processing grooves 94 are formed in all the streets as shown in FIG. 5 is sucked and held on the chuck table 78 of the cutting device 62. Next, the chuck table 78 is moved in the X-axis direction so that the wafer W is positioned immediately below the imaging means 82 of the alignment means 80. Next, the periphery of the laser processing groove 94 is imaged by the imaging means 82, and alignment by pattern matching or the like similar to that described in the laser processing apparatus 2 is performed.

  When the patterns are matched, the chuck table 78 is rotated by θ to correct the angle, and the cutting means 84 is moved in the Y-axis direction by the distance between the key pattern and the center line of the laser processing groove 94. Then, the laser processing groove 94 to be cut and the cutting blade 88 are aligned.

  When the laser processing groove 94 to be cut and the cutting blade 88 are aligned, the chuck table 78 is moved in the X-axis direction, and the cutting means 84 is lowered while the cutting blade 88 is rotated at a high speed. The aligned laser processing groove 94 is cut.

  By performing cutting while indexing the cutting means 84 in the Y-axis direction by street pitches stored in the memory, all the laser processing grooves 94 in a predetermined direction are cut. Further, when the same cutting as described above is performed after the chuck table 78 is rotated by 90 degrees, all the laser processing grooves 94 orthogonal to the predetermined direction are also cut, and the wafer W is divided into the individual devices D.

  In the cutting of the wafer W by the cutting device 62, thermal expansion due to high-speed rotation occurs in the spindle 86 along with the cutting, so that the position of the cutting blade 88 is displaced in the Y-axis direction. Therefore, in the dividing method of the present invention, alignment is performed so that the laser processing groove 94 and the cutting blade 88 are matched at a predetermined timing during the cutting process.

  The alignment process for aligning the laser processing groove 94 and the cutting blade 88 is performed by detecting a positional deviation between the cutting groove 98 formed in the laser processing groove non-formed region 96 and the laser processing groove 94 as shown in FIG. To do.

  Specifically, in this alignment step, the cutting groove 98 formed in the laser processing groove non-forming region 96 is imaged by the imaging means 82 having an optical system in which the alignment reference line of the cutting blade 88 is formed. Then, a positional deviation between the cutting blade 88 and the reference line is detected to calculate a correction value.

  Then, the cutting means 84 is moved in the Y-axis direction so that the reference line is aligned with the laser processing groove 94, and the correction value is added to the Y coordinate of the cutting blade 88 to match the cutting blade 88 and the laser processing groove 94. Let

  Thus, the hair groove alignment using the cutting groove 98 formed in the laser processing groove non-forming region 96 can be corrected so that the cutting groove 98 is formed at the center of the laser processing groove 94.

  According to the embodiment of the present invention described above, since the hairline alignment is performed using the cutting groove 98 formed in the laser processing groove non-forming region 96, the cutting groove 98 can be reliably detected by the imaging means 82. Further, since the laser processed groove non-formed region 96 is formed in the outer peripheral portion of the outer peripheral surplus region 92 where no device is formed, the amount of device taken is not reduced.

  In the embodiment described above, hairline alignment in the middle of processing is performed using the cutting groove 98 formed in the laser processing groove non-forming region 96, but cutting is performed without forming the cutting groove in the laser processing groove non-forming region 96. A mark may be provided, and the reference line of the imaging unit 82 and the cutting blade 88 may be matched based on the cut mark.

  Alternatively, the cutting trace and the laser processing groove 94 may be imaged by the imaging unit 82 to calculate a deviation amount, and the cutting blade 88 may be positioned in the laser processing groove 94 in consideration of the deviation amount.

It is a schematic perspective view of the laser processing apparatus suitable for implementing the division | segmentation method of this invention. It is an external appearance perspective view of the cutting device suitable for implementing the division | segmentation method of this invention. It is a surface side perspective view of the wafer used as processing object. It is a perspective view which shows the state with which the wafer was mounted | worn with the annular frame via the dicing tape. It is a perspective view of a wafer showing the state where a laser processing groove was formed in all the streets. It is a perspective view of a wafer showing the state where a cutting groove was formed along all the laser processing grooves.

Explanation of symbols

2 Laser processing apparatus 28 Chuck table 34 Laser beam irradiation means 36 Condenser 38 Imaging means 40 Controller 62 Cutting apparatus 78 Chuck table 80 Alignment means 82 Imaging means 84 Cutting means 86 Spindle 88 Cutting blade 90 Device area 92 Outer peripheral area 94 Laser Machining groove 96 Laser machining groove non-formed area 98 Cutting groove

Claims (3)

A plurality of division lines are formed in a lattice pattern on the surface, and a device area in which devices are formed in a plurality of areas partitioned by the plurality of division lines, and an outer peripheral surplus area surrounding the device area, A plate-like material dividing method for dividing a plate-like material having an individual device,
Excluding the outer peripheral portion of the outer peripheral surplus region, a laser beam irradiation step of forming a laser processing groove by irradiating a laser beam along the division planned line;
A cutting groove having a groove width narrower than that of the laser processing groove by cutting the bottom portion of the laser processing groove and the outer peripheral portion of the outer peripheral surplus region along the laser processing groove formed by the laser beam irradiation step. Cutting process to form,
Position where the laser processing groove formed in the laser beam irradiation step and the cutting groove formed in the outer peripheral portion of the outer peripheral surplus region are misaligned and the cutting blade is aligned with the laser processing groove Combining process,
A method for dividing a plate-like object, comprising: In the alignment step, the cutting groove formed in the outer peripheral portion of the outer peripheral surplus area is imaged by an imaging unit including an optical system in which a reference line for alignment of a cutting blade is formed,
Detecting a positional deviation between the reference line and the cutting groove to calculate a correction value;
Aligning the reference line with the laser processing groove, and adding the correction value to the position data of the cutting blade to match the cutting blade with the laser processing groove;
The method for dividing a plate-like object according to claim 1, comprising each step.   The plate-like product dividing method according to claim 1 or 2, wherein the laser beam irradiation step forms a plurality of laser-processed grooves along the planned dividing line.

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