TWI566285B - Wafer processing method and laser processing device - Google Patents

Description

Wafer processing method and laser processing device Field of invention

The present invention relates to a method for processing a wafer in which a wafer is divided into individual elements along a dicing street, and a laser processing apparatus, wherein the wafer is divided into a plurality of regions by a dicing-shaped dicing street and a component is formed in the region. By.

Background of the invention

In the semiconductor device manufacturing process, the surface of the semiconductor wafer having a substantially disk shape is divided into a plurality of regions by a predetermined dividing line which is arranged in a lattice shape and called a dicing street, and an element such as an IC or an LSI is formed in the divided region. Then, the semiconductor wafer is cut along the dicing street, and the region where the component is formed is divided to form each component. In addition, an optical element wafer formed of a sapphire substrate or a lanthanum carbide substrate surface layer gallium nitride-based compound semiconductor is cut and divided into optical elements such as light-emitting diodes and laser diodes along the scribe line, and is widely used. In electrical machines.

A method of dividing a wafer along a dicing street may be a laser processing method in which a pulsed laser beam having a penetrating property to the wafer is used to illuminate the pulsed laser beam at a position where the condensing point is positioned inside the divided region. By using the laser processing method, the light collecting point is positioned inside from the back side of the wafer. A pulsed laser beam having a penetrating wavelength to the wafer is irradiated along the dicing street, and a modified layer is continuously formed along the scribe line inside the wafer, and the strength of the dicing channel is reduced by the formation of the modified layer, and then the cutting is performed The force is applied to separate the wafer into individual components. (Refer to Patent Document 1 as an example.)

Conventional technical literature Patent literature

[Patent Document 1] Japanese Patent Gazette No. 2001-96764

Summary of invention

Further, on the so-called TSV wafer on which the electrode of the element formed on the surface of the wafer reaches the back surface of the wafer, since the electrode protrudes from the back surface of the wafer, the back surface of the wafer is etched. If the back side of the wafer is etched, the back surface is formed to have a thickness in the range of Ra 0.02 to 0.1 μm. Therefore, once the laser light having a penetrating wavelength to the wafer is irradiated from the back side, there is a penetration of the laser light. Partially blocked, unable to form a proper layer of modification.

The present invention has been made in view of the above-mentioned facts, and the main technical object thereof is to provide a laser beam having a transparent wavelength to the wafer from the back side even if the back surface of the wafer is rough, and a suitable modified layer is formed inside. Wafer processing method and laser processing device.

In order to solve the above-mentioned main technical problems, the present invention provides a method for processing a wafer, which is formed by dividing a surface into a grid-shaped cutting path. Forming a modified layer along the scribe line for the inside of the plurality of regions and the wafer in which the component is formed in the region, the processing method includes the following procedure: the surface roughness map is formed by measuring the area corresponding to the scribe line on the back side of the wafer Surface roughness, surface roughness map; and reforming layer forming process, the laser light having a penetrating wavelength to the wafer is irradiated along the scribe line along the back side of the wafer, and is modified along the scribe line inside the wafer. The modified layer forming program controls the output of the irradiated laser light by referring to the surface roughness map and the appropriate output map of the laser light preset with the corresponding surface roughness.

Moreover, according to the present invention, there is provided a laser processing apparatus comprising: a chuck table for holding a workpiece; and a laser light irradiation means for irradiating the wafer held by the chuck table with laser light; a processing feeding means for processing the chuck table and the laser beam irradiation means in the processing feed direction (X-axis direction), and for irradiating the chuck table and the laser beam The indexing feeding means for dividing the feeding direction in the indexing feeding direction orthogonal to the machining feed direction (X-axis direction), and the X-axis for detecting the position of the chuck table in the X-axis direction a direction position detecting means, a Y-axis direction position detecting means for detecting a position of the chuck table in the Y-axis direction, and a signal control output detected based on the X-axis direction position detecting means and the Y-axis direction position detecting means Adjusting means for controlling a control means for adjusting the output of the irradiated laser light by means of the laser light irradiation means; the control means is provided with a memory for storing the processed object according to the processed object a surface roughness map prepared by the surface roughness data of the processing region in the incident surface on the side where the laser light is irradiated, and an appropriate output map of the laser light corresponding to the surface roughness map and the surface roughness, and the processed object The incident surface side is positioned at a condensing point inside the processing region to illuminate the laser beam having a penetrating wavelength to the workpiece, and when the modified layer is formed inside the workpiece, the surface roughness map and the appropriate output map are used to control the Output adjustment means to control the output of the irradiated laser light.

The method for processing a wafer of the present invention comprises: measuring a surface roughness of a region corresponding to a dicing street on a back surface of the wafer, preparing a surface roughness of the surface roughness pattern, and cutting a surface along the back side of the wafer The irradiation of the laser beam with a penetrating wavelength on the wafer, forming a modified layer forming process of the modified layer along the scribe line inside the wafer; the reforming layer forming procedure refers to the surface roughness map and the corresponding surface roughness The pre-set laser light output map controls the output of the irradiated laser light, so that even if the back side of the wafer is roughened, a suitable modified layer can be formed along the scribe line inside the wafer.

Further, the laser processing apparatus of the present invention is provided with a memory for storing a surface roughness map based on surface roughness data of a processing region of an incident surface of a workpiece irradiated with a laser beam, and a surface roughness map corresponding thereto. And an appropriate output map of the laser light with a predetermined surface roughness, and a laser beam having a penetrating wavelength for the workpiece to be irradiated by the spotting point on the incident surface side of the workpiece to be processed on the object to be processed When the modified layer is formed internally, the surface roughness map and the appropriate output map are used to control the output adjustment means to control the output of the irradiated laser light, so that the processed object passes through the laser beam. Even if the incident surface on the irradiation side is roughened, a suitable modified layer can be formed inside the processed region of the workpiece.

1‧‧‧ Laser processing equipment

2‧‧‧Standing abutment

3‧‧‧The chuck mechanism

4‧‧‧Laser light irradiation unit support mechanism

5‧‧‧Laser light irradiation unit

6‧‧‧Photography

8‧‧‧Control means

10‧‧‧Semiconductor wafer

10a‧‧‧ surface

10b‧‧‧back

31‧‧‧ rails

32‧‧‧1st sliding block

33‧‧‧2nd sliding block

34‧‧‧Cylinder components

35‧‧‧ Coverage

36‧‧‧ chuck table

37‧‧‧Processing means of feeding

38‧‧‧1st index feeding means

41‧‧‧rails

42‧‧‧ movable support abutment

43‧‧‧2nd index feeding means

51‧‧‧ unit mount

52‧‧‧Laser light exposure

53‧‧‧ concentrating point position adjustment means

81‧‧‧ central processing unit

82‧‧‧Read-only memory

83‧‧‧Readable and write random access memory

84‧‧‧ counter

85‧‧‧Input interface

86‧‧‧Output interface

101 (a ~ n), 102 (a ~ n) ‧ ‧ cutting road

103‧‧‧ components

104‧‧‧Bumps (electrodes)

110‧‧‧Modified layer

321‧‧‧guided ditch

322‧‧‧rails

331‧‧‧guided ditch

361‧‧‧Adsorption chuck

362‧‧‧ fixture

371‧‧‧Male screw

372‧‧‧pulse motor

373‧‧‧ bearing block

374‧‧‧X-axis position detection means

374a‧‧‧linear scale

374b‧‧‧Reading

381‧‧‧Male screw

382‧‧‧pulse motor

383‧‧‧ bearing block

384‧‧‧Y-axis position detection means

384a‧‧‧linear scale

384b‧‧‧Reading

421‧‧‧Mobile Support Department

422‧‧‧Installation Department

423‧‧‧rails

431‧‧‧Male screw

432‧‧‧pulse motor

511‧‧‧guided ditch

521‧‧‧ casing

522‧‧‧pulse laser oscillating means

522a‧‧‧pulse laser ray oscillator

522b‧‧‧Repetition frequency setting means

523‧‧‧ Output adjustment means

524‧‧ ‧ concentrator

524a‧‧‧ Directional Conversion Mirror

524b‧‧‧ Condenser lens

532‧‧‧pulse motor

F‧‧‧ ring frame

T‧‧‧ cutting tape

P‧‧‧ spotlight

W‧‧‧Processed objects

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a laser processing apparatus constructed in accordance with the present invention.

Fig. 2 is a block diagram showing the structure of a laser beam for illuminating the laser processing apparatus shown in Fig. 1.

Figure 3 is a block diagram showing the control means of the laser processing apparatus shown in Figure 1.

4(a) to 4(b) are perspective views of a semiconductor wafer processed by the wafer processing method of the present invention, and a cross-sectional view showing an enlarged portion of the main portion.

Fig. 5 is a perspective view showing a state in which the semiconductor wafer shown in Fig. 4 is adhered to a dicing tape provided in an annular frame.

6(a) to 6(b) are explanatory views showing a procedure for creating a surface roughness map in the wafer processing method of the present invention.

7(a) to 7(b) are explanatory views showing a procedure for creating a surface roughness map in the wafer processing method of the present invention.

Fig. 8 is an explanatory view showing an appropriate output map of the storage in the memory of the control means provided in the laser processing apparatus shown in Fig. 1.

9(a) to 9(c) are explanatory views of a reforming layer forming program in the wafer processing method of the present invention.

Form for implementing the invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a wafer processing method and a laser processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a laser processing apparatus constructed in accordance with the present invention. The laser processing apparatus 1 shown in FIG. 1 is provided with a stationary base 2, and is disposed on the stationary base 2 so as to be movable in the machining feed direction (X-axis direction) indicated by an arrow X and used to keep processed. The chuck mechanism 3, a laser beam irradiation unit supporting mechanism 4 disposed on the stationary base 2 and movable in the index feeding direction (Y-axis direction) indicated by an arrow Y orthogonal to the X-axis direction And a laser beam irradiation unit 5 disposed on the laser beam irradiation unit supporting mechanism 4 and movable in a direction (Z-axis direction) of the light-converging point position indicated by an arrow Z.

The chuck mechanism 3 includes a guide rail 31 and 31 that are disposed in parallel with each other on the stationary base 2 in the X-axis direction, and a first slider 32 that is disposed on the rails 31 and 31 and movable in the X-axis direction. a second sliding block 33 movable in the Y-axis direction on the first sliding block 32, a covering table 35 supported by the cylindrical member 34 on the second sliding block 33, and a chuck as a workpiece holding means Taiwan 36. The chuck table 36 has a suction chuck 361 formed of a porous material, and the workpiece, such as a disk-shaped semiconductor wafer, is held on the adsorption chuck 361 by an adsorption means (not shown). The chuck table 36 having the above-described configuration is driven to rotate by a pulse motor (not shown) disposed in the cylindrical member 34. Further, a jig 362 for fixing a ring-shaped frame to be described later is disposed in the chuck table 36.

The first slider block 32 is provided on the lower surface thereof to be fitted to the pair of guide rails 31, 31 to be guided by the pair of guide grooves 321, 321 and to have a pair of guide rails 322, 322 formed in parallel in the Y-axis direction. The first slide block 32 having the above-described configuration is fitted to the pair of guide rails 31, 31 by the guide grooves 321, 321 It is movable in the X-axis direction along the pair of guide rails 31, 31. The chuck mechanism 3 of the embodiment shown in the drawing includes a machining feed means 37 for moving the first slider 32 along the pair of rails 31, 31 in the X-axis direction. The machining feed means 37 includes a male screw 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 371. One end of the male screw 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is coupled to an output shaft of the pulse motor 372. Further, the male screw 371 is screwed to the through female screw hole formed in the female screw which is provided on the lower surface of the central portion of the first slider 32 but not shown. Therefore, the male screw 371 can be driven to rotate forward and reverse by the pulse motor 372, and the first slider 32 can be moved along the guide rails 31, 31 in the X-axis direction.

The laser processing apparatus 1 according to the embodiment of the present invention includes an X-axis direction position detecting means 374 for detecting the machining feed amount of the chuck table 36, that is, the X-axis direction position. The X-axis direction position detecting means 374 is composed of a linear scale 374a disposed along the guide rail 31, and a read head 374b disposed on the first slider 32 and moving along the linear scale 374a together with the first slider 32. In the embodiment shown in the figure, the read head 374b of the X-axis direction position detecting means 374 transmits a pulse signal of one pulse per 1 μm to a control means to be described later. The input pulse signal is counted by a control means described later to detect the machining feed amount of the chuck table 36, that is, the X-axis direction position. Further, the pulse motor 372 is used as the drive source of the machining feed means 37, and the machining feed of the chuck table 36 can be detected by counting the drive pulses for outputting the drive signal to the pulse motor 372 and the control means described later. The quantity is also the position in the X-axis direction. Further, a servo motor is used as the driving source of the processing feed means 37, and is used for inspection. The pulse signal output from the rotary encoder that measures the number of rotations of the servo motor is transmitted to a control device to be described later, and the input pulse signal is counted by the control means, and the machining feed amount of the chuck table 36, that is, the X-axis direction position can be detected.

The second sliding block 33 is provided on the lower surface with a pair of guided grooves 331 and 331 for fitting with the pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32, and the guide grooves are guided by the guide grooves 322 and 322. When the 331 and 331 are fitted to the pair of guide rails 322 and 322, they are movable in the Y-axis direction. The chuck mechanism 3 of the embodiment shown in the drawings further includes a first index feeding means 38 for causing the second slider 33 to be disposed on the guide rails 322 and 322 of the first slider 32 on the Y-axis. Move in the direction. The first index feeding means 38 includes a male screw 381 disposed in parallel between the pair of guide rails 322 and 322, and a driving source such as a pulse motor 382 for rotationally driving the male screw 381. One end of the male screw 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first slider 32, and the other end is coupled to an output shaft of the pulse motor 382. Further, the male screw 381 is screwed to the through female screw hole formed in the female screw which is provided on the lower surface of the central portion of the second sliding block 33 but not shown. Therefore, the male screw 381 can be driven to rotate forward and reverse by the pulse motor 382, and the second slider 33 can be moved in the X-axis direction along the guide rails 322 and 322.

The laser processing apparatus according to the embodiment of the present invention includes a Y-axis direction position detecting means 384 for detecting a position in the Y-axis direction which is an indexing machining feed amount of the second slider 33. The Y-axis direction position detecting means 384 is composed of a linear scale 384a disposed along the guide rail 322 and a read head 384b disposed on the second slider 33 and moving along the linear scale 384a together with the second slider 33. The read head 384b of the Y-axis direction position detecting means 384 is shown in the figure. In the embodiment shown, a pulse signal of one pulse is transmitted every 1 μm to a control means to be described later. The input pulse signal is counted by a control means described later to detect the indexing feed amount of the chuck table 36, that is, the Y-axis direction position. Further, the pulse motor 382 is used as the driving source of the first index feeding means 38, and the chuck table 36 can be detected by counting the driving pulse for outputting the driving signal to the pulse motor 382 and the control means described later. The indexing feed amount is also the position in the Y-axis direction. Further, a servo motor is used as a driving source of the first index feeding means 38, and a pulse signal output from a rotary encoder for detecting the number of rotations of the servo motor is transmitted to a control means to be described later, and the control means counts the input. The pulse signal can also detect the indexing feed amount of the chuck table 36, that is, the position in the Y-axis direction.

The laser beam irradiation unit support mechanism 4 includes movable rails 41 and 41 that are disposed in parallel with each other on the stationary base 2 in the Y-axis direction, and movable rails that are disposed on the rails 41 and 41 in the direction indicated by the arrow Y. The base station 42 is supported. The movable support base 42 is composed of a movement support portion 421 disposed on the guide rails 41 and 41 and movable, and a mounting portion 422 attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in parallel in the Z-axis direction on one side surface. The laser beam irradiation unit supporting mechanism 4 of the embodiment shown in the drawing includes a second index feeding section 43 for moving the movable supporting base 42 in the Y-axis direction along the pair of rails 41 and 41. The second index feeding means 43 includes a male screw 431 disposed in parallel between the pair of guide rails 41, 41, and a driving source such as a pulse motor 432 for rotationally driving the male screw 431. One end of the male screw 431 is rotatably supported by a bearing block fixed to the stationary base 2 but not shown, and the other end is rotatably It is coupled to the output shaft of the pulse motor 432. Further, the male screw 431 is screwed to the female screw hole formed in the female screw which is provided below the center portion of the movement support portion 421 which constitutes the movable support base 42 but is not shown. Therefore, the male screw 431 can be driven to rotate forward and reverse by the pulse motor 432, and the movable support base 42 can be moved in the Y-axis direction along the guide rails 41 and 41.

The laser beam irradiation unit 5 of the illustrated embodiment includes a unit holder 51 and a laser beam irradiation means 52 attached to the unit holder 51. The unit fixing base 51 is provided with a pair of guided grooves 511 and 511 which are slidably fitted to the guide rails 423 and 423 provided in one of the mounting portions 422, and the guide grooves 511 and 511 and the guide rails are guided by the unit. The 423 and 423 are fitted to support the movement of the unit holder 51 in the Z-axis direction.

The laser beam irradiation unit 5 of the embodiment shown in the drawings further includes a light collecting point position adjusting means 53 for moving the unit fixing base 51 along the pair of guide rails 423, 423 in the Z-axis direction. The condensing point position adjusting means 53 includes a male screw (not shown) disposed between the pair of guide rails 423, 423, and a driving source such as a pulse motor 532 for rotationally driving the male screw, by means of a pulse motor The 532 drives the male screw (not shown) to rotate forward and reverse, and the unit mount 51 and the laser beam irradiation means 52 are moved in the Z-axis direction along the guide rails 423 and 423. Further, in the illustrated embodiment, the laser beam 532 is rotated forward by the drive pulse motor 532, and the laser beam irradiation means 52 is moved upward, and the laser beam 532 is reversed to move the laser beam irradiation means 52 downward.

The illustrated laser beam illumination means 52 includes a cylindrical sleeve 521 that is fixed to the unit holder 51 and extends in a substantially horizontal direction. This laser light irradiation means 52 will be described with reference to Fig. 2 .

The illustrated laser beam illumination means 52 is provided with a pulsed laser beam oscillating means 522 disposed in the sleeve 521, and an output for adjusting the pulsed laser beam oscillating by the pulsed laser beam oscillating means 522. The output adjustment means 523 and a concentrator 524 for illuminating the workpiece W held by the holding surface of the chuck table 36 by the pulsed laser light which is output and adjusted by the output adjustment means 523.

The pulsed laser ray oscillating means 522 is provided by a pulsed laser ray oscillator 522a for oscillating, for example, a pulsed laser beam having a wavelength of 1064 nm, and a pulsed laser for oscillating the pulsed laser ray oscillator 522a. The repetition frequency setting means 522b of the repetition frequency of the light is constituted. The output adjustment means 523 is configured to adjust the output of the pulsed laser beam oscillated by the pulsed laser beam oscillating means 522 to a predetermined output. The pulsed laser ray oscillator 522a, the repetition frequency setting means 522b, and the output adjustment means 523 of the pulsed laser beam oscillating means 522 are controlled by a control means not described later.

The concentrator 524 is provided with a direction converting mirror 524a for oscillating the pulsed laser beam oscillating means 522 and adjusting the output of the pulsed laser beam by the output adjusting means 523 toward the holding surface of the chuck table 36, and a The condensing lens 524b for illuminating the workpiece W held by the chuck table 36 is irradiated with the pulsed laser light that has been converted by the direction changing mirror 524a. The concentrator 524 of the foregoing configuration is mounted on the front end of the sleeve 521 as shown in FIG.

The front end of the sleeve 521 for constituting the laser light irradiation means 52 is provided with a means for detecting the lightning by the laser light irradiation means 52. The imaging means 6 of the processing area of the shot processing. The imaging means 6 is divided into a general imaging unit (CCD) for capturing visible light, and an infrared illumination means for irradiating the workpiece with infrared rays, an optical system for capturing infrared rays irradiated by the infrared illumination means, and An image pickup unit (infrared CCD) that can respond to an electrical signal of infrared rays captured by an optical system is output, and the captured image signal is transmitted to a control means to be described later.

The laser processing apparatus 1 of the embodiment shown in the drawings further includes a control means 8 shown in FIG. The control means 8 is composed of a computer, and has a central processing unit (CPU) 81 for performing calculation processing according to a control program, a read-only memory (ROM) 82 for storing a control program, etc., and a control chart for storing the latter. A readable and writable random access memory (RAM) 83, a counter 84, an input interface 85, and an output interface 86, such as data of a workpiece design value or a calculation result. The input interface 85 of the control means 8 inputs signals detected by the X-axis direction position detecting means 374, the Y-axis direction position detecting means 384, and the imaging means 6. Then, the pulse motor 372, the pulse motor 382, the pulse motor 432, the pulse motor 532, the pulsed laser ray oscillator 522a of the laser beam irradiation means 52, and the repetition frequency setting means 522b are provided by the output interface 86 of the control means 8. And output control means 523 and the like output control signals.

Next, a wafer processing method performed by the above-described laser processing apparatus 1 will be described.

4(a) and 4(b) are perspective views of a semiconductor wafer processed by the wafer processing method of the present invention and a cross-sectional view showing an enlarged main portion thereof. The semiconductor wafer 10 shown in FIGS. 4(a) and 4(b) is composed of a germanium wafer, and the surface 10a is divided into a plurality of regions by a grid-shaped dicing streets 101 and 102. An element 103 is formed in the middle. A plurality of bumps (electrodes) 104 are formed in a plurality of elements 103 formed on the surface 10a of the semiconductor wafer 10, and the plurality of bumps (electrodes) 104 are buried in a state in which the surface 10a reaches the back surface 10b. The semiconductor wafer 10 thus formed is subjected to an etching treatment on the back surface 10b so that a plurality of bumps (electrodes) 104 are slightly protruded from the back surface 10b. After the etching treatment, the back surface 10b of the semiconductor wafer 10 becomes thick, and the surface roughness is Ra 0.02 to 0.1 μm.

A method of forming a modified layer as a fracture starting point along the dicing streets 101 and 102 inside the optical element wafer 10 by the laser processing apparatus 1 will be described below.

First, as shown in FIG. 5, the surface 10a of the semiconductor wafer 10 is adhered to the surface of the dicing tape T mounted on the annular frame F (wafer adhesion procedure). Therefore, the semiconductor wafer 10 adhered to the surface of the dicing tape T is in a state in which the back surface 10b is located on the upper side.

After the wafer bonding process is performed, a surface roughness pattern forming program is performed to measure the surface roughness of the region corresponding to the dicing street 101 in the back surface 10b of the semiconductor wafer 10, and a surface roughness map is created. For the measurement of the surface roughness of the region corresponding to the scribe lines 101 and 102 in the back surface 10b of the semiconductor wafer 10, for example, Mitutoyo Corporation (Japanese original: Co., Ltd.) can be used. ) Manufactured surface roughness measuring machine SURF TEST SV2100.

An example of a surface roughness map creation program will be described below with reference to Figs. 6 and 7 .

First, as shown in FIG. 6(a), the semiconductor wafer 10 is set to a state in which the dicing street 101 is parallel to the X-axis direction, and is measured along the dicing street 101a to the dicing street 101n. Surface roughness. Next, as shown in FIG. 6(b), the surface roughness of each of the dicing streets 101a to 101n and the XY coordinates is set to prepare a surface roughness map (1).

Next, after the semiconductor wafer 10 is rotated by 90 degrees, the semiconductor wafer 10 is set to a state in which the dicing street 102 is parallel to the X-axis direction as shown in FIG. 7(a), and the surface is measured along the scribe line 102a to the dicing street 102n. Roughness. Next, as shown in Fig. 7(b), the surface roughness of each of the dicing streets 102a to 102n corresponding to the XY coordinates is set to prepare a surface roughness map (2).

The surface roughness map (1) shown in Fig. 6(b) and the surface roughness map (2) shown in Fig. 7(b) are randomly stored in the control means 8 provided in the laser processing apparatus 1 described above. Access memory (RAM) 83. Further, a random access memory (RAM) 83 is stored and an appropriate output map as shown in FIG. 8 is stored, which sets the output of the laser light to a suitable modified layer to form a suitable modified layer. The appropriate output map shown in Fig. 8 shows the surface roughness (μm) on the vertical axis and the pulse energy (μJ) of the pulsed laser light on the horizontal axis. The output of the laser beam which can form a suitable modified layer corresponding to the surface roughness is obtained experimentally.

The surface roughness map (1) shown in FIG. 6(b) and the surface roughness map (2) shown in FIG. 7(b) and the appropriate output map shown in FIG. 8 are stored in the control of the laser processing apparatus 1 described above. After the random access memory (RAM) 83 of the means 8, the dicing tape T side of the semiconductor wafer 10 is placed on the chuck table 36 of the laser processing apparatus 1. Then, the suction means (not shown) is activated, and the semiconductor wafer 10 is sucked and held on the chuck table 36 via the dicing tape T (wafer holding program). Therefore, the semiconductor wafer 10 held on the chuck table 36 is backed. 10b is in the state of the upper side.

The chuck table 36 that has attracted the semiconductor wafer 10 as described above is positioned directly below the image pickup unit 6 by the processing feed means 37. The chuck table 36 is always located directly below the imaging device 6, that is, the imaging device 6 and the control device 8 perform a calibration operation to detect a processing region of the optical device wafer 10 to be subjected to laser processing. That is, the imaging means 6 and the control means 8 perform image processing such as pattern batching so that the dicing streets 101 formed on the semiconductor wafer 10 in a predetermined direction are aligned for the laser beam irradiation means for irradiating the laser beam along the dicing street 101. The concentrator 524 of 52 completes the calibration of the position of the laser beam irradiation (calibration procedure). Further, a calibration procedure is also performed for the dicing streets 102 formed on the semiconductor wafer 10 extending in a direction orthogonal to the predetermined direction. At this time, the surface 10a of the semiconductor wafer 10 on which the dicing streets 101 and 102 are formed is located on the lower side, but the imaging means 6 is as described above by the infrared illumination means and the optical system for capturing infrared rays and for outputting the infrared rays. Since the electrical signal is composed of an imaging unit (infrared CCD) or the like, the scribe lines 101 and 102 can be penetrated by the back surface 10b.

After the calibration procedure is carried out as described above, the chuck table 36 is moved to the laser light irradiation area where the concentrator 524 of the laser light irradiation means 52 is located as shown in Fig. 9 (a), and one end of the predetermined cut track 101 is The left end in Fig. 9(a) is positioned directly below the concentrator 524 of the laser beam illumination means 52. Next, the condensed spot P of the pulsed laser light irradiated by the concentrator 524 is aligned with the intermediate portion of the semiconductor wafer 10 in the thickness direction. In order to position the condensed spot P of the pulsed laser light irradiated by the concentrator 524 at a predetermined position of the semiconductor wafer 10, a method such as that disclosed in Japanese Laid-Open Patent Publication No. 2009-63446 may be employed. The workpiece height position detecting device held by the chuck table detects the height position of the semiconductor wafer 10 held on the chuck table 36, and starts concentrating based on the height position of the upper surface of the semiconductor wafer 10 measured. The dot position adjusting means 53 positions the light collecting point P of the pulsed laser light at a predetermined position. Next, the concentrator 524 of the laser beam illumination means 52 illuminates the pulsed laser light having a penetrating wavelength to the semiconductor wafer 10, and simultaneously causes the chuck table 36 to be processed as indicated by the arrow X1 in Fig. 9(a). The feed direction moves at a predetermined machining feed speed. Next, as shown in FIG. 9(b), if the other end of the scribe line 101 (the right end in FIG. 9(b)) reaches the irradiation position of the concentrator 524 of the laser beam irradiation means 52, the irradiation of the pulsed laser light is stopped. At the same time, the movement of the chuck table 36 is stopped (the reforming layer forming program). In the reforming layer forming program, the control means 8 refers to the surface roughness map (1) shown in FIG. 6(b) stored in the random access memory (RAM) 83 and the appropriate output map shown in FIG. The laser light corresponding to the surface roughness measured by the XY coordinates in the region corresponding to the scribe line 101 in the back surface 10b of the semiconductor wafer 10 is appropriately output (pulse energy). Subsequently, the control means 8 controls the output adjustment means 523 to cause the output of the pulsed laser light oscillating by the pulsed laser beam oscillating means 522 to be appropriately output (pulse energy). In this way, even if the surface roughness of the back surface 10b of the semiconductor wafer 10 is in the range of Ra 0.02 to 0.1 μm, the semiconductor wafer 10 can be along the dicing street 101 as shown in FIGS. 9(b) and 9(c). A suitable modified layer 110 is formed inside.

The processing conditions of the modified layer forming program described above can be set as follows.

Light source: semiconductor excited solid laser (Nd: YAG)

Wavelength: 1064nm

Repeat frequency: 80kHz

Average output: 0.1~0.7W

Pulse energy: 1.25~8.75μJ

Convergence point diameter: Φ1μm

Processing feed rate: 100mm / sec

As described above, after all the dicing streets 101 extending in the predetermined direction in the semiconductor wafer 10 are subjected to the modified layer forming process, the chuck table 36 is rotated by 90 degrees and then orthogonalized along a predetermined direction. Each of the dicing streets 102 formed in the direction performs the aforementioned reforming layer forming process. When the reforming layer forming program is performed along the scribe line 102, the control means 8 refers to the surface roughness map (1) shown in FIG. 7(b) stored in the random access memory (RAM) 83 and as shown in FIG. Appropriately outputting the map, determining the proper output (pulse energy) of the laser light set by the surface roughness measured by the XY coordinate in the region corresponding to the scribe line 102 in the back surface 10b of the semiconductor wafer 10, and controlling the output adjustment means 523 The output of the pulsed laser light oscillating by the pulsed laser oscillating means 522 is brought to an appropriate output (pulse energy). As a result, even if the surface roughness of the back surface 10b of the semiconductor wafer 10 is in the range of Ra 0.02 to 0.1 μm, the semiconductor wafer 10 can be formed with a suitable modified layer along the scribe line 102.

The semiconductor wafer 10 subjected to the reforming layer forming process is sent to a dividing process for dividing the dicing streets 101 and 102 in which the reforming layer 110 is formed inside.

The present invention has been described above with reference to the embodiments shown in the drawings. However, the present invention is not limited to the embodiments, and various modifications can be made without departing from the scope of the invention. For example, the embodiment is directed to a laser processing apparatus that does not have a surface roughness measuring machine, but a laser processing apparatus may also be used. The image information transmitted from the imaging means 6 is transmitted to the surface roughness measuring machine to measure the surface roughness.

10‧‧‧Semiconductor wafer

10b‧‧‧back

36‧‧‧ chuck table

52‧‧‧Laser light exposure

101‧‧‧ cutting road

110‧‧‧Modified layer

524‧‧ ‧ concentrator

P‧‧‧ spotlight

T‧‧‧ cutting tape

Claims (2)

A method for processing a wafer is characterized in that a surface is divided into a plurality of regions formed by a grid-shaped dicing street and a wafer is formed in the region, and a modified layer is formed along the scribe line. The processing method includes the following procedures: The surface roughness map is formed by measuring the surface roughness of the area corresponding to the scribe line on the back side of the wafer to form a surface roughness map; and the reforming layer forming process is performed by dicing the wafer along the back side of the wafer a laser beam having a penetrating wavelength, forming a modified layer along the scribe line inside the wafer; the reforming layer forming process is appropriate according to the surface roughness map and the predetermined surface roughness of the predetermined laser light The output map controls the output of the laser light that is incident on the wafer. A laser processing apparatus is provided with a chuck table for holding a workpiece, a laser beam for irradiating a laser beam to the wafer held by the chuck table, and a laser light for the chuck And a processing feeding means for processing the feeding in the processing feed direction (X-axis direction), and a direction for processing the chuck table and the laser beam irradiation means in the processing feed direction (X-axis direction) is an orthogonal indexing feed direction relative to the indexing feed indexing means, and an X-axis direction position detecting means for detecting the position of the chuck table in the X-axis direction, a Y-axis direction position detecting means for detecting a position of the chuck table in the Y-axis direction, and a control means for controlling the output adjusting means based on the X-axis direction position detecting means and the signal detected by the Y-axis direction position detecting means, lose The adjusting means is provided for the laser light irradiation means for adjusting the output of the irradiated laser light; the control means is provided with a memory for storing in the incident surface on the side irradiated with the laser beam according to the workpiece A surface roughness map prepared by the surface roughness data of the processing region, and an appropriate output map of the laser light corresponding to the surface roughness map and the surface roughness, and positioned by the incident surface side of the workpiece in the processing region The condensing point is used to illuminate the laser beam having a penetrating wavelength to the workpiece, and when the modified layer is formed inside the workpiece, the surface roughness map and the appropriate output map are used to control the output adjustment means to control The output of the laser beam that is incident on the workpiece.