JP2008053341A - Wafer processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for processing a wafer that can form a processing trench at a boundary between a device region and an external circumferential extra region without giving any damage on a device region of wafer. <P>SOLUTION: The wafer processing method that can form a separation trench at the boundary of the device region and external circumferential extra region of the wafer 100 includes a wafer placing step for placing the wafer on a chuck table 36, a center displacement detecting step for detecting displacement from coordinates of the rotation center of the chuck table by detecting a plurality of areas at the external circumferential edge of the wafer placed on the chuck table with an imaging means and then obtaining the coordinates of the center of wafer, a center aligning step for aligning the wafer center and chuck table center by relatively moving the chuck table and wafer in accordance with displacement, and a laser processing step to form a seperation trench at the boundary by rotating the chuck table while the boundary is irradiated with a laser beam from a laser beam irradiating means 52. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wafer processing method including a device region having a plurality of devices formed on a surface and a peripheral surplus region surrounding the device region, and forming a processing groove at a boundary between the peripheral surplus region. .

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers with gallium nitride compound semiconductors laminated on the surface of a sapphire substrate are also divided into individual optical devices such as light emitting diodes and laser diodes by cutting along the streets, and are widely used in electrical equipment. ing.

As described above, the wafer to be divided is formed to have a predetermined thickness by grinding or etching the back surface before cutting along the street. In recent years, it has been required to form a wafer with a thickness of 100 μm or less in order to reduce the weight and size of electrical equipment.
However, if the thickness of the wafer is formed to be 100 μm or less, the wafer is likely to be damaged, and it is difficult to handle the wafer.

  In order to solve the above-mentioned problem, the present applicant grinds the region corresponding to the device region on the back surface of the wafer to form the thickness of the device region to a predetermined thickness, and leaves the outer peripheral portion on the back surface of the wafer. Japanese Patent Application No. 2005-165395 has proposed a method of processing a wafer capable of forming a rigid wafer by forming an annular reinforcing portion.

  By the way, when the wafer described above is divided along the street, the annular reinforcing portion needs to be obstructed and removed. In order to remove the annular reinforcing portion, a cutting device including a chuck table for holding a workpiece and a cutting means having a cutting blade for cutting the workpiece held on the chuck table is used. Can be considered. That is, a rotating cutting blade is positioned at the boundary between the device region and the outer peripheral surplus region of the wafer held on the chuck table, and a predetermined cutting feed is applied to the cutting blade to perform cutting while rotating the chuck table.

  Thus, when the above-described cutting apparatus is used for cutting while rotating the chuck table holding the wafer, the cutting blade has a straight advance, so that when the cutting blade is cut into an arc, a large load acts on the cutting blade and the wafer. For this reason, there is a problem that not only the cutting blade is broken, but also the device region of the thinly formed wafer is damaged.

  The present invention has been made in view of the above facts, and the main technical problem thereof is that a processing groove can be formed at the boundary between the device region and the outer peripheral surplus region without damaging the device region of the wafer. It is to provide a method for processing a wafer.

In order to solve the main technical problem, according to the present invention, a chuck table having a holding surface for holding a wafer and configured to be rotatable, and a machining feed for moving the chuck table in a machining feed direction (X-axis direction). Means, index feed means for moving the chuck table in the index feed direction (Y-axis direction) orthogonal to the machining feed direction (X-axis direction), transport means for transporting the wafer to the chuck table, and the chuck table A plurality of devices on the surface using a laser processing apparatus comprising a laser beam irradiation means having a condenser for irradiating a laser beam to a wafer held on the wafer and an imaging means for imaging the wafer held on the chuck table. The device region of the wafer having a formed device region and an outer peripheral surplus region surrounding the device region A wafer processing method of forming isolation trenches in the boundary portion of the outer peripheral marginal region,
A wafer mounting step of transporting the wafer by the transport means and placing the wafer on a holding surface of the chuck table;
A center shift for detecting a plurality of positions on the outer peripheral edge of the wafer placed on the holding surface of the chuck table by the imaging means to obtain the coordinates of the center of the wafer and detecting a shift from the coordinates of the rotation center of the chuck table. A detection process;
The chuck table and the wafer are moved relative to each other in accordance with the deviation between the center of the wafer detected by the center deviation detection step and the center of rotation of the chuck table, and the center of the wafer and the center of the chuck table are positioned. A center alignment step to match,
Rotating the chuck table while irradiating a laser beam from the laser beam irradiating means at the boundary between the device region and the outer peripheral surplus region of the wafer placed on the holding surface of the chuck table and subjected to the center alignment step A laser processing step of forming a separation groove at the boundary between the device region of the wafer and the outer peripheral surplus region,
A wafer laser processing method is provided.

The center alignment step includes a wafer holding step for holding a wafer immediately above the wafer on which the center shift detection step has been performed, and a wafer detected by the center shift detection step by operating the processing feed means and the index feed means. The center deviation correction step for correcting the deviation in the X axis direction and the Y axis direction between the center of the chuck table and the center of rotation of the chuck table, and the wafer holding step held on the holding surface of the chuck table on which the center deviation correction step was performed. A wafer re-placement step of placing the wafer again.
Based on the deviation between the center of the wafer detected by the center deviation detection step and the center of rotation of the chuck table before the wafer placement step of placing the wafer to be processed next on the holding surface of the chuck table. It is desirable to perform the center misalignment correction step.
In the wafer, the back surface corresponding to the device region is ground, and an annular reinforcing portion is formed on the back surface corresponding to the outer peripheral surplus region.

  According to the present invention, since the separation groove is formed by irradiating the boundary between the device region of the wafer and the outer peripheral surplus region, the load is not applied to the wafer so as to be cut along the boundary by the cutting blade. It can be cut without damaging the device area. Further, according to the present invention, the center of the wafer held on the holding surface of the chuck table and the center of rotation of the chuck table coincide with each other by performing the center misalignment detection step and the center alignment step. And the separation groove can be formed accurately along the boundary between the outer peripheral area and the outer peripheral surplus area.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a wafer laser processing method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view of a semiconductor wafer as a wafer to be processed by the wafer laser processing method according to the present invention. A semiconductor wafer 100 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 350 μm. A plurality of streets 101 are formed in a lattice shape on the surface 100a, and a plurality of streets partitioned by the plurality of streets 101 are provided. A device 102 such as an IC or LSI is formed in the region. The semiconductor wafer 100 configured as described above includes a device region 104 in which the device 102 is formed, and an outer peripheral surplus region 105 that surrounds the device region 104.

  When the semiconductor wafer 100 is cut along the street 101 and divided into individual semiconductor chips, a region corresponding to the device region 104 on the back surface of the semiconductor wafer 100 is ground to form a thickness of the device region 104. At the same time, an annular reinforcing portion is formed in a region corresponding to the outer peripheral surplus region 105 on the back surface of the semiconductor wafer 100. In order to perform such processing, first, as shown in FIG. 2, the protective member 110 is attached to the surface 100 a of the semiconductor wafer 100 (protective member attaching step). Therefore, the back surface 100b of the semiconductor wafer 100 is exposed.

  When the protective member attaching step is performed, a region corresponding to the device region 104 on the back surface 100b of the semiconductor wafer 100 is ground to form a thickness of the device region 104 to a predetermined thickness, and the back surface 100b of the semiconductor wafer 100 is formed. The reinforcement part formation process which leaves the area | region corresponding to the outer periphery excess area | region 105 in this, and forms an annular | circular reinforcement part is implemented. This reinforcement part formation process is implemented by the grinding apparatus shown in FIG.

  A grinding apparatus 1 shown in FIG. 3 includes a chuck table 11 that holds a wafer as a workpiece, and a grinding means 12 that grinds the processed surface of the wafer held on the chuck table 11. The chuck table 11 sucks and holds the wafer on the upper surface and is rotated in the direction indicated by the arrow 11a in FIG. The grinding means 12 includes a spindle housing 121, a rotary spindle 122 rotatably supported by the spindle housing 121 and rotated by a rotary drive mechanism (not shown), a mounter 123 attached to the lower end of the rotary spindle 122, and the mounter And a grinding wheel 124 attached to the lower surface of 123. The grinding wheel 124 includes a disk-shaped base 125 and a grinding wheel 126 that is annularly mounted on the lower surface of the base 125, and the base 125 is attached to the lower surface of the mounter 123.

  In order to perform the reinforcing portion forming step using the grinding apparatus 1 described above, the protective member 110 side of the semiconductor wafer 100 conveyed by the wafer carrying means (not shown) is placed on the upper surface (holding surface) of the chuck table 11. The semiconductor wafer 100 is sucked and held on the chuck table 11. Here, the relationship between the semiconductor wafer 100 held on the chuck table 11 and the annular grinding wheel 126 constituting the grinding wheel 124 will be described with reference to FIG. The rotation center P 1 of the chuck table 11 and the rotation center P 2 of the annular grinding wheel 126 are eccentric, and the outer diameter of the annular grinding wheel 126 is the boundary line between the device region 104 and the outer peripheral surplus region 105 of the semiconductor wafer 100. The diameter is set to be smaller than the diameter of the boundary line 106 and larger than the radius of the boundary line 106, and the annular grinding wheel 126 passes through the rotation center P 1 of the chuck table 11 (the center of the semiconductor wafer 100).

  Next, as shown in FIGS. 3 and 4, while rotating the chuck table 11 in the direction indicated by the arrow 11a at 300 rpm, the grinding wheel 124 is rotated in the direction indicated by the arrow 124a at 6000 rpm, and the grinding wheel 124 is moved downward. The grinding wheel 126 is moved and brought into contact with the back surface of the semiconductor wafer 100. Then, the grinding wheel 124 is ground by a predetermined amount at a predetermined grinding feed speed. As a result, on the back surface of the semiconductor wafer 100, as shown in FIG. 5, the region corresponding to the device region 104 is ground and removed to form a circular recess 104b having a predetermined thickness (for example, 60 μm), and the outer peripheral surplus In the illustrated embodiment, a region corresponding to the region 105 remains 350 μm thick and is formed in the annular reinforcing portion 105b (annular reinforcing portion forming step).

  As described above, the region corresponding to the device region 104 is ground and removed on the back surface of the semiconductor wafer 100 to form the concave portion 104b having a predetermined thickness (for example, 60 μm), and the region corresponding to the outer peripheral surplus region 105 is left to be annular. If the reinforcing portion 105b is formed, the back surface corresponding to the device region 104 is etched, the back surface is coated with a metal film, a via hole is formed, and the like, and then the device region 104 is moved to the street. Although it cut | disconnects along 101 and divides | segments into each semiconductor chip, the cyclic | annular reinforcement part 105b becomes an obstacle. Therefore, it is necessary to cut the boundary between the device region 104 and the outer peripheral surplus region 105 in the semiconductor wafer 100 and remove the annular reinforcing portion 105b. However, when the boundary between the device region 104 and the outer peripheral surplus region 105 in the semiconductor wafer 100 is cut by the cutting blade of the cutting device, the cutting blade and the semiconductor wafer are cut when the cutting blade is cut into an arc shape as described above. There is a problem that a large load is applied to 100 and not only the cutting blade is broken, but also the device region 104 of the thinly formed semiconductor wafer 100 is damaged.

Therefore, in the present invention, the boundary between the device region 104 and the outer peripheral surplus region 105 in the semiconductor wafer 100 is cut by laser processing.
Here, a laser processing apparatus for performing the laser processing will be described with reference to FIGS.
The laser processing apparatus 2 shown in FIG. 6 includes an apparatus housing 20 having a substantially rectangular parallelepiped shape. In the apparatus housing 20, a stationary base 21 shown in FIG. 7 and a chuck for holding a workpiece, which is disposed on the stationary base 21 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X. The table mechanism 3 and the laser beam irradiation unit support mechanism 4 disposed on the stationary base 21 so as to be movable in the indexing feed direction (Y-axis direction) indicated by the arrow Y perpendicular to the direction indicated by the arrow X (X-axis direction). The laser beam irradiation unit 5 is arranged on the laser beam unit support mechanism 4 so as to be movable in the direction indicated by the arrow Z (Z-axis direction).

  The chuck table mechanism 3 includes a pair of guide rails 31, 31 disposed on the stationary base 21 in parallel along the machining feed direction (X-axis direction) indicated by an arrow X, and the guide rails 31, 31. The first sliding block 32 is movably disposed in the machining feed direction indicated by the arrow X, and the arrow Y orthogonal to the machining feed direction (X-axis direction) indicated by the arrow X on the first sliding block 32. A second slide block 33 movably arranged in the indexing feed direction (Y-axis direction) shown in FIG. 2, a cover table 35 supported on the second slide block 33 by a cylindrical member 34, and a workpiece A chuck table 36 as holding means is provided. The chuck table 36 includes a suction chuck 361 that serves as a workpiece holding surface formed of a porous material, and suction means (not shown), for example, a disk-shaped semiconductor wafer as a workpiece on the suction chuck 361. Is supposed to be held by. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame described later.

  The first sliding block 32 is provided with a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and in the index feed direction indicated by an arrow Y on the upper surface thereof. A pair of guide rails 322 and 322 formed in parallel with each other are provided. The first sliding block 32 configured in this way is processed by the arrow X along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. It is configured to be movable in the feed direction. The chuck table mechanism 3 in the illustrated embodiment includes a machining feed means 37 for moving the first sliding block 32 along the pair of guide rails 31 and 31 in the machining feed direction indicated by the arrow X. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 21, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, when the male screw rod 371 is driven to rotate forward and backward by the pulse motor 372, the first sliding block 32 is moved along the guide rails 31, 31 in the machining feed direction indicated by the arrow X.

  The laser processing apparatus 2 in the illustrated embodiment includes a processing feed amount detection means 374 for detecting the processing feed amount of the chuck table 36. The processing feed amount detection means 374 includes a linear scale 374a disposed along the guide rail 31, and a read head disposed along the linear scale 374a along with the first sliding block 32 disposed along the first sliding block 32. 374b. In the illustrated embodiment, the reading head 374b of the feed amount detecting means 374 sends a pulse signal of one pulse every 1 μm to the control means described later. Then, the control means to be described later detects the machining feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 372 is used as the drive source of the machining feed means 37, the machining feed amount of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 372. Can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. By counting, the machining feed amount of the chuck table 36 can also be detected.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the indexing and feeding direction indicated by the arrow Y. The chuck table mechanism 3 in the illustrated embodiment is for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the index feed direction indicated by the arrow Y. First index feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, when the male screw rod 381 is driven to rotate forward and reversely by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the index feed direction indicated by the arrow Y.

  The laser processing apparatus 2 in the illustrated embodiment includes index feed amount detection means 384 for detecting the index processing feed amount of the second sliding block 33. The index feed amount detecting means 384 includes a linear scale 384a disposed along the guide rail 322 and a read head disposed along the linear scale 384a along with the second sliding block 33 disposed along the second sliding block 33. 384b. In the illustrated embodiment, the reading head 384b of the feed amount detection means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. Then, the control means described later detects the index feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 382 is used as the drive source of the first indexing and feeding means 38, the drive table of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 382. The index feed amount can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. It is possible to detect the index feed amount of the chuck table 36 by counting.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41 and 41 arranged in parallel along the indexing feed direction indicated by the arrow Y on the stationary base 21, and the arrow Y on the guide rails 41 and 41. The movable support base 42 is provided so as to be movable in the direction indicated by. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the direction indicated by the arrow Z on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41, 41 in the index feed direction indicated by the arrow Y. is doing. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 21, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and backward by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the index feed direction indicated by the arrow Y.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 52 attached to the unit holder 51. The unit holder 51 is provided with a pair of guided grooves 511 and 511 that are slidably fitted to a pair of guide rails 423 and 423 provided in the mounting portion 422. By being fitted to the guide rails 423 and 423, the guide rails 423 and 423 are supported so as to be movable in the direction indicated by the arrow Z.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a moving means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the direction indicated by the arrow Z (Z-axis direction). The moving means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a drive source such as a pulse motor 532 for rotationally driving the male screw rod. By driving the male screw rod (not shown) in the forward and reverse directions by the motor 532, the unit holder 51 and the laser beam irradiation means 52 are moved along the guide rails 423 and 423 in the direction indicated by the arrow Z (Z-axis direction). In the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 532 forward, and the laser beam irradiation means 52 is moved downward by driving the pulse motor 532 in reverse. Yes.

  The illustrated laser beam application means 52 includes a cylindrical casing 521 arranged substantially horizontally. The laser beam irradiation means 52 is oscillated by the pulse laser beam oscillation means 522 disposed at the tip of the casing 521 and the pulse laser beam oscillation means 522 and the transmission optical system 523 disposed in the casing 521 as shown in FIG. And a condenser 524 for irradiating the workpiece held on the chuck table 36 with the pulsed laser beam. The pulse laser beam oscillation means 522 is composed of a pulse laser beam oscillator 522a composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 522b attached thereto. This repetition frequency setting means 522b is controlled by the control means described later. The transmission optical system 523 includes an appropriate optical element such as a beam splitter.

  Returning to FIG. 7 and continuing the description, an imaging means 6 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed at the tip of the casing 521 constituting the laser beam irradiation means 52. The image pickup means 6 is composed of an image pickup device (CCD) or the like, and sends the picked up image signal to the control means 7.

  The control means 7 is constituted by a computer, and a central processing unit (CPU) 81 that performs arithmetic processing according to a control program, a read only memory (ROM) 72 that stores a control program and the like, and a design value of a workpiece to be described later. A readable / writable random access memory (RAM) 73 that stores data, calculation results, and the like, a counter 74, an input interface 75, and an output interface 76 are provided. Detection signals from the machining feed amount detection means 374, the index feed amount detection means 384, the imaging means 6 and the like are input to the input interface 75 of the control means 7. A control signal is output from the output interface 76 of the control means 8 to the pulse motor 372, pulse motor 382, pulse motor 432, pulse motor 532, laser beam irradiation means 52, display means 8, and the like. The random access memory (RAM) 83 includes a first storage area 73a for storing the coordinates of the center of the chuck table 36 and other storage areas.

  Returning to FIG. 6, the description will be continued. In the cassette mounting area 13 a of the apparatus housing 20, a cassette mounting table 13 for mounting a cassette for storing a workpiece is disposed. The cassette mounting table 13 is configured to be movable in the vertical direction by lifting means (not shown). On the cassette mounting table 13, a cassette 14 that houses the semiconductor wafer 100 as a workpiece is placed. Here, the semiconductor wafer 100 accommodated in the cassette 14 will be described with reference to FIG. As described above, the semiconductor wafer 100 that has been subjected to the annular reinforcing portion forming step is adhered to the surface of the protective tape T having the back surface 100b attached to the annular frame F. And the said protection member 110 stuck on the surface 100a of the semiconductor wafer 100 is peeled (frame support process). As described above, the semiconductor wafer 100 is accommodated in the cassette 13 with the back surface 100b attached to the surface of the protective tape T attached to the annular frame F.

  Returning to FIG. 6, the description will be continued. The laser processing apparatus 2 in the illustrated embodiment is a semiconductor wafer 100 (protective tape on an annular frame F) housed in a cassette 14 placed on a cassette placement table 13. A transporting means 16 for transporting the semiconductor wafer 10 transported to the temporary table 15 onto the chuck table 33, and a chuck table. A cleaning means 18 for cleaning the semiconductor wafer 100 laser-processed on the semiconductor wafer 36 and a cleaning / conveying means 19 for transporting the semiconductor wafer 100 laser-processed on the chuck table 36 to the cleaning means 18 are provided.

The laser processing apparatus 2 in the illustrated embodiment is configured as described above, and a separation groove is formed at the boundary between the device region 104 and the outer peripheral surplus region 105 in the semiconductor wafer 100 using the laser processing apparatus 2 hereinafter. The wafer processing method will be described with reference to FIGS. 6, 7, and 10 to 12.
A semiconductor wafer 100 (supported by an annular frame F via a protective tape T) accommodated in a predetermined position of the cassette 14 placed on the cassette placement table 13 is moved by an elevator means (not shown). The placement table 13 is positioned at the carry-out position by moving up and down. Next, the unloading means 16 moves forward and backward, and the semiconductor wafer 100 positioned at the unloading position is unloaded onto the temporary placement table 15. The semiconductor wafer 100 carried out to the temporary placement table 15 is conveyed to the suction chuck 361 (holding surface) of the chuck table 36 positioned at the workpiece holding position shown in FIGS. And placed (wafer placing step). When the semiconductor wafer 100 is placed on the holding surface of the chuck table 36, a suction means (not shown) is operated to suck and hold the semiconductor wafer 100 on the chuck table 36 as shown in FIG. The support frame F that supports the semiconductor wafer 100 via the protective tape T is fixed by the clamp 362. The outer diameter of the chuck table 36 is 4 to 6 mm smaller than the inner diameter of the annular reinforcing portion 105 b formed on the back surface 100 b of the semiconductor wafer 100. Accordingly, a gap of 2 to 3 mm is formed between the inner peripheral surface of the annular reinforcing portion 105 b and the outer peripheral surface of the chuck table 36.

  As described above, the center of the semiconductor wafer 100 held on the chuck table 36 needs to coincide with the center of the chuck table 36. If the center of the semiconductor wafer 100 attached to the protective tape T attached to the annular frame F coincides with the center of the annular frame F, the center of the semiconductor wafer 100 held on the chuck table 36 is By being conveyed to the chuck table 36 by the conveying means 16, it is configured to coincide with the center of rotation of the chuck table 36. However, when the semiconductor wafer 100 is attached to the protective tape T attached to the annular frame F by a tape applicator, the center of the annular frame F and the center of the semiconductor wafer 100 may slightly shift. Therefore, in a state where the semiconductor wafer 100 is held on the chuck table 36, it is confirmed whether or not the center of the semiconductor wafer 100 coincides with the rotation center of the chuck table 36. If the center of the semiconductor wafer 100 is the chuck table 36. If it does not coincide with the center of rotation, it is necessary to perform a center alignment operation for matching the centers of the two.

Next, a center alignment process for aligning the center of the semiconductor wafer 100 and the rotation center of the chuck table 36 held on the chuck table 36 will be described.
As described above, when the semiconductor wafer 100 is held on the chuck table 36 positioned at the workpiece holding position, the chuck table 36 is moved to the alignment position directly below the imaging means 6. The semiconductor wafer 100 held on the chuck table 36 is at the coordinate position shown in FIG. Then, as shown in FIG. 11, the imaging means 6 images three locations (A, B, C) on the outer peripheral edge of the semiconductor wafer 100, and sends image information to the control means 7. The control means 7 stores the coordinates of three locations (A, B, C) in a random access memory (RAM) 83 based on the image information from the imaging means 6. Next, the control means 7 obtains a point Pw where the perpendiculars from the midpoints of the straight lines AB and BC intersect each other from the coordinates of the three locations (A, B, C), and these coordinates are obtained from the semiconductor wafer 100. The data is stored in a random access memory (RAM) 83 as the center. Then, the control means 7 shifts the rotational axis coordinate Pc of the chuck table 36 stored in the first storage area 73a of the random access memory (RAM) 83 and the central coordinate Pw of the semiconductor wafer 100 in the X-axis direction. (x) and a deviation (y) in the Y-axis direction are obtained (center deviation detection step) and stored in a random access memory (RAM) 83.

  As described above, if the deviation (x) in the X-axis direction and the deviation (y) in the Y-axis direction between the coordinate Pc of the rotation center of the chuck table 36 and the center coordinate Pw of the semiconductor wafer 100 are detected, the chuck table 36 is Move to work piece holding position. Then, the suction holding of the semiconductor wafer 100 is released, and the fixing of the support frame F by the clamp 362 is released. Next, the conveying means 17 is moved directly above the chuck table 36 positioned at the workpiece holding position to hold the semiconductor wafer 100 (wafer holding step). Next, the machining feed means 37 is operated to move the chuck table 36 by the deviation (x) in the X-axis direction, and the first index feed means 38 is operated to move the chuck table 36 to the Y-axis. It moves by the deviation (y) in the direction (center deviation correction step). If the center misalignment correction step is performed in this manner to correct the misalignment (x) in the X-axis direction and the misalignment (y) in the Y-axis direction between the rotation center Pc of the chuck table 36 and the center Pw of the semiconductor wafer 100, cleaning is performed. By placing the semiconductor wafer 100 held by the transfer means 19 on the holding surface of the chuck table 36 again (wafer re-placement step), the center of the semiconductor wafer 100 is positioned at the rotation center of the chuck table 36. In this way, when the center of the semiconductor wafer 100 is positioned at the center of rotation of the chuck table 36, a suction means (not shown) is operated to suck and hold the semiconductor wafer 100 on the chuck table 36, and the semiconductor wafer 100 is held. The support frame F supported via the protective tape T is fixed by the clamp 362.

  As described above, if the center alignment process for aligning the center of the semiconductor wafer 100 held on the chuck table 36 and the center of rotation of the chuck table 36 is performed, the device region 104 of the semiconductor wafer 100 and the outer peripheral surplus A laser processing step for forming a separation groove at the boundary with the region 105 is performed. That is, the chuck table 36 holding the semiconductor wafer 100 is moved to a processing area directly below the condenser 524. Then, as shown in FIG. 12A, the boundary line 106 between the device region 104 and the outer peripheral surplus region 105 of the semiconductor wafer 100 is positioned directly below the condenser 524. Next, the chuck table 36 is rotated at a predetermined rotation speed in the direction indicated by the arrow 36a while the laser beam irradiation means 52 is operated to irradiate a pulsed laser beam having a wavelength that absorbs the silicon wafer from the condenser 524. Let me. As a result, as shown in FIG. 12B, a separation groove 107 is formed in the semiconductor wafer 100 along the boundary line 106 between the device region 104 and the outer peripheral surplus region 105, and the outer peripheral surplus region 105 (annular reinforcing portion) is formed. 105b) is removed. In this laser processing step, the device region 104 can be cut without being damaged so as to be cut along the boundary line 106 with a cutting blade, and the center of the semiconductor wafer 100 held on the chuck table 36 and the chuck can be cut. Since the rotation center of the table 36 coincides as described above, the separation groove 107 can be accurately formed along the boundary line 106 between the device region 104 and the outer peripheral surplus region 105.

In addition, the said laser processing process is performed on the following processing conditions, for example.
Laser light source: YVO4 laser or YAG laser Wavelength: 355 nm
Repetition frequency: 10 kHz
Average output: 6.5W
Condensing spot: φ20μm
Rotation speed of chuck table: 120 degrees / second

  The laser processing step is performed to form the separation groove 107 along the boundary line 106 between the device region 104 and the outer peripheral surplus region 105 of the semiconductor wafer 100, thereby removing the outer peripheral surplus region 105 (annular reinforcing portion 105b). Then, the semiconductor wafer 100 is cut along the streets 101 to shift to a cutting process for dividing the semiconductor wafer 100 into individual semiconductor chips. This cutting step may be performed by the laser processing apparatus 2 or may be performed by a dicing apparatus such as a cutting apparatus.

  If the laser processing step (and the cutting step) is performed as described above, the chuck table 36 is moved to the workpiece holding position. Then, the suction holding of the semiconductor wafer 100 is released, and the fixing of the support frame F by the clamp 362 is released. Next, the cleaning / conveying means 19 is operated to transport the semiconductor wafer 100 from which the outer peripheral surplus area 105 (annular reinforcing portion 105b) has been removed to the cleaning means 18. The semiconductor wafer 100 conveyed to the cleaning means 18 is cleaned here. The semiconductor wafer 100 cleaned by the cleaning means 18 is transported to the temporary table 15 by the transport means 17 after drying. Then, the semiconductor wafer 100 is stored in a predetermined position of the cassette 14 by the unloading means 16.

  Note that the chuck table 36 returned to the workpiece holding position as described above is stored in the random access memory (RAM) 83 until the semiconductor wafer to be processed next is conveyed. It is desirable to carry out the above-described center misalignment correction step based on the X-axis direction misalignment (x) and the Y-axis direction misalignment (y) between the rotation center coordinate Pc of 36 and the center coordinate Pw of the semiconductor wafer 100. As described above, by performing the center misalignment correction step, the probability that the center of the semiconductor wafer 100 to be processed next is positioned as the rotation center of the chuck table 36 is increased. That is, since the semiconductor wafer 100 attached to the protective tape T attached to the annular frame F by the tape applicator has the same deviation tendency in the case of the same lot, the center deviation correction process is performed. This increases the probability that the center of the semiconductor wafer 100 is positioned as the center of rotation of the chuck table 36.

The perspective view of the semiconductor wafer as a wafer processed by the processing method of the wafer by this invention. The perspective view which shows the state which affixed the protection member on the surface of the semiconductor wafer shown in FIG. The perspective view of the grinding device for grinding the back surface of the semiconductor wafer shown in FIG. Explanatory drawing of the reinforcement part formation process implemented with the grinding apparatus shown in FIG. Sectional drawing of the semiconductor wafer in which the reinforcement part formation process shown in FIG. 5 was implemented. The perspective view of the laser processing apparatus for performing the laser processing process in the processing method of the wafer by this invention. The principal part perspective view of the laser processing apparatus shown in FIG. FIG. 7 is a configuration block diagram of a laser beam irradiation means equipped in the laser processing apparatus shown in FIG. 6. Explanatory drawing of the frame support process in the processing method of the wafer by this invention. Explanatory drawing of the wafer mounting process in the processing method of the wafer by this invention. Explanatory drawing of the center shift | offset | difference detection process in the processing method of the wafer by this invention. Explanatory drawing of the laser processing process in the processing method of the wafer by this invention.

Explanation of symbols

1: Grinding device 11: Chuck table of grinding device 12: Grinding means 2: Laser processing device 21: Stationary base 3: Chuck table mechanism 36: Chuck table 37: Processing feed means 38: First indexing feed means 4: Laser beam Irradiation unit support mechanism 43: Second index feeding means 5: Laser beam irradiation unit 52: Laser beam irradiation means 524: Condenser 6: Imaging means 7: Control means 8: Display means 14: Cassette 15: Unloading means 17: Conveyance means 18: Cleaning means 19: Cleaning conveyance means 100: Semiconductor wafer 101: Street 102: Device 104: Device area 105: Peripheral surplus area 110: Protection member F: Ring frame T: Protection tape

Claims (4)

A chuck table having a holding surface for holding a wafer and configured to be rotatable, a machining feed means for moving the chuck table in the machining feed direction (X-axis direction), and the chuck table in the machining feed direction (X-axis direction) Indexing feeding means for moving in the indexing feeding direction (Y-axis direction) orthogonal to the wafer, transport means for transporting the wafer to the chuck table, and a condenser for irradiating the wafer held by the chuck table with a laser beam A laser processing apparatus including a laser beam irradiation means and an imaging means for imaging a wafer held on the chuck table, and a device area having a plurality of devices formed on a surface thereof and a peripheral excess area surrounding the device area And forming a separation groove at the boundary between the device region of the wafer and the outer peripheral surplus region A processing method,
A wafer mounting step of transporting the wafer by the transport means and placing the wafer on the chuck table holding surface;
Center deviation detection for detecting a plurality of positions on the outer peripheral edge of the wafer placed on the chuck table holding surface by the imaging means to obtain the coordinates of the center of the wafer and detecting a deviation from the coordinates of the rotation center of the chuck table Process,
The chuck table and the wafer are moved relative to each other in accordance with the deviation between the center of the wafer detected by the center deviation detection step and the center of rotation of the chuck table, and the center of the wafer and the center of the chuck table are positioned. A center alignment step to match,
Rotating the chuck table while irradiating a laser beam from the laser beam irradiating means at the boundary between the device region and the outer peripheral surplus region of the wafer placed on the holding surface of the chuck table and subjected to the center alignment step A laser processing step of forming a separation groove at the boundary between the device region of the wafer and the outer peripheral surplus region,
A wafer laser processing method characterized by the above.   The center alignment step is detected by the center misalignment detection step by operating the wafer holding step of holding the wafer immediately above the wafer on which the center misalignment detection step has been performed, and operating the processing feed means and the index feed means. Center misalignment correcting step for correcting misalignment between the center of the wafer and the rotation center of the chuck table in the X-axis direction and the Y-axis direction, and the wafer holding step on the holding surface of the chuck table on which the center misalignment correcting step has been performed. A wafer laser processing method according to claim 1, further comprising a wafer re-placement step of placing the wafer held in step 1 again.   Next, before performing the wafer placing step of placing the wafer to be processed on the holding surface of the chuck table, the deviation between the center of the wafer detected by the center deviation detecting step and the rotation center of the chuck table is detected. The wafer laser processing method according to claim 2, wherein the center misalignment correction step is performed based on the method.   4. The wafer laser processing method according to claim 1, wherein the wafer has a back surface corresponding to the device region ground and an annular reinforcing portion formed on the back surface corresponding to the outer peripheral surplus region. 5.

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