CN100500359C - Laser beam processing machine - Google Patents

Abstract

A laser beam processing machine comprising a chuck table for holding a workpiece, a laser beam application means for applying a pulse laser beam to the workpiece held on the chuck table, and a processing-feed means for processing-feeding the chuck table and the laser beam application means relative to each other, wherein the machine further comprises a feed amount detection means for detecting the processing-feed amount of the chuck table and a control means for controlling the laser beam application means based on a detection signal from the feed amount detection means, and the control means outputs an application signal to the laser beam application means for each predetermined processing-feed amount based on a signal from the feed amount detection means.

Description

Laser beam processing machine

technical field

The present invention relates to a laser beam processing machine which applies a laser beam along a dividing line formed on a workpiece.

Background technique

In the manufacturing process of semiconductor devices, the substantially disk-shaped semiconductor wafer front is divided into a plurality of regions by dividing lines called "streets" arranged in a lattice pattern, and in each divided region, such as IC or LSI circuits. The semiconductor wafer is diced along dicing lines to separate it into a number of regions each having a circuit on each region to produce individual semiconductor chips. Also, an optical device wafer having a GaN-based compound semiconductor layer on the front side of a sapphire substrate is diced along a dicing line to be diced into optical devices such as light emitting diodes or laser diodes widely used in electrical equipment.

The dicing along the above-mentioned dividing line of the semiconductor wafer or the optical device is generally performed using a dicing machine called a "dicer". The dicing machine includes: a chuck table for holding a workpiece such as a semiconductor wafer or an optical device wafer; a cutting device for cutting the workpiece held on the chuck table; and a cutting feeding device for Used to move the chuck table and cutting unit relative to each other. The cutting device has a spindle unit including a rotating shaft, a cutting blade mounted on the rotating shaft, and a driving mechanism for rotationally driving the rotating shaft. The cutting disc comprises a disc-shaped base and an annular cutting edge, and diamond abrasive grains with a diameter of about 3 μm are fixed on the base by electroforming to form an annular cutting edge on the peripheral portion of the side wall of the base and make it form about to a thickness of 20 μm.

Due to the high Mohs hardness of sapphire substrates, silicon carbide substrates, etc., it is not always easy to cut using the above-mentioned dicing blades. Further, since the thickness of the dicing sheet is about 20 μm, the dividing lines for dividing the devices must have a thickness of about 50 μm. Therefore, in the case of a device size of 300 μm×300 μm, the area ratio of the dicing line to the device is 14%, thereby reducing productivity.

As an apparatus for dividing a plate-shaped workpiece such as a semiconductor wafer, a laser processing method using a pulsed laser beam whose wavelength can pass through the workpiece and whose focus is set inside the divided region has also been attempted, such as disclosed in Japanese Patent No. 3408805 like that. In the division method using this laser processing technology, the workpiece is divided by applying a pulsed laser beam in the infrared range that can transmit the workpiece to the workpiece, from the surface of the workpiece with its focus set to the inside of the workpiece in the A damaged layer is continuously formed inside the workpiece along the split line, and an external force is applied along the split line, the strength of which has decreased due to the formation of the damaged layer.

A laser beam processing machine for carrying out the above-mentioned laser processing has a chuck table for holding a workpiece, a laser beam applying device for applying a pulsed laser beam to the workpiece held on the chuck table, and a device for operating the chuck. The processing feed device that performs relative processing feed between the table and the laser beam application device.

The chuck table of the above-mentioned laser beam processing machine was subjected to processing feed at the feed speed shown in FIG. 11 . In FIG. 11 , the horizontal axis shows the machining feed amount of the chuck table, and the vertical axis shows the machining feed speed of the chuck table. As shown in FIG. 11, the machining feed speed of the chuck table increases from the machining feed start position (m0) and reaches a predetermined machining feed speed (V) at the first machining feed position (m1). Then, the chuck table moves at a predetermined machining feed speed (V), and when its machining feed speed reaches the second machining feed position (m2), the machining feed speed starts to decrease, and at the machining feed Give the end position (m3) to zero (0). However, it is necessary to apply the pulsed laser beam under the condition that the processing feed speed of the chuck table is constant, so that uniform laser processing can be performed along the dividing line of the workpiece. Thus, a pulsed laser beam is applied between a first machining feed position (m1) and a second machining feed position (m2), and the chuck table is moved between these two positions at a predetermined uniform machining feed rate (V) to move. Therefore, the region where the laser processing is actually performed is the region between the first processing feed position (m1) and the second processing feed position (m2), and is located between the processing feed start position (m0) and the first processing feed position. The area where the chuck table accelerates between the positions (m1) and the area where the chuck table decelerates between the second machining feed position (m2) and the machining feed end position (m3) is not performed. The laser-processed ineffective travel area, thereby reducing productivity and prolonging the movement stroke of the chuck table, hinders the miniaturization of the device.

Contents of the invention

It is an object of the present invention to provide a laser beam processing machine capable of performing uniform machining by applying a pulsed laser beam to a workpiece over the entire area from the machining feed start position of the chuck table to the machining feed end position. processing.

To achieve the above objects, according to the present invention, there is provided a laser beam processing machine comprising a chuck table for holding a workpiece, a laser beam for applying a pulsed laser beam to the workpiece held on the chuck table an application device, and a processing feed device for causing the chuck table and the laser beam application device to perform processing feed relative to each other, wherein,

The laser beam processing machine also includes a feed amount detecting device for detecting a processing feed amount of the chuck table and a control device for controlling the laser beam applying device according to a detection signal from the feed amount detecting device; as well as

The control means outputs an application signal for each predetermined processing feed amount to the laser beam applying means based on the signal from the feed amount detection means.

In addition, according to the present invention, there is also provided a laser beam processing machine including: a chuck table for holding a workpiece, a laser beam application device for applying a pulsed laser beam to the workpiece held on the chuck table. device, and a processing feeding device for making the chuck table and the laser beam applying device carry out processing feeding relative to each other, wherein when the chuck table is processing feeding, the processing feeding device is at Control the machining feed speed of the chuck table during the process from the machining feed start position to the first machining feed amount, so that it accelerates to a predetermined machining feed speed, and from the first machining feed amount to Maintain the predetermined processing feed speed at a constant speed during the second processing feed amount, and decelerate the processing feed speed to zero during the process from the second predetermined processing feed amount to the end position of the processing feed, wherein ,

The laser beam processing machine also includes a feed amount detecting device for detecting a processing feed amount of the chuck table and a control device for controlling the laser beam applying device according to a detection signal from the feed amount detecting device; as well as

The control device includes storage means for storing a control map for setting laser beam processing conditions according to a processing feed rate corresponding to a processing feed from the chuck table applied by the processing feed device. The machining feed amount from the start position to the machining feed end position is given, and an application signal of the machining conditions set by the control map is output to the laser beam applying means based on the signal from the feed amount detection means.

The above-mentioned control chart is a frequency control chart which sets the repetition frequency of the laser beam according to the machining feed speed corresponding to the machining feed start position of the chuck table to the machining feed applied by the machining feed device. Machining feed at the end position.

According to the present invention, since the chuck table holding the workpiece moves a predetermined amount of machining feed every time, even in the acceleration movement area and the deceleration movement area where the machining feed speed of the chuck table is not constant, the pulsed laser beam Emitted from the laser beam application device, the pulsed laser beam is applied to the workpiece at equal time intervals, and uniform processing is performed from the processing feed start position to the processing feed end position. Therefore, the area from the machining feed start position to the machining feed end position becomes the machining area and there is no idle stroke of the chuck table, so that the machining time can be shortened and the size of the entire apparatus can be reduced.

Furthermore, in the present invention, since the above-mentioned control means includes storage means for storing a processing control map for setting laser beam processing conditions in accordance with a processing feed rate corresponding to the processing feed rate applied by the above-mentioned processing feed means The processing feed amount of the chuck table from the processing feed start position to the processing feed end position, and the control device outputs the processing conditions set by the control chart to the laser beam application device based on the signal from the above feed amount detection device Even in the accelerated movement area and the decelerated movement area where the machining feed rate of the chuck table is not constant, the pulsed laser beam based on the machining conditions of the machining feed rate is applied to the workpiece, whereby, Uniform machining is possible from the machining feed start position to the machining feed end position. Therefore, the area from the machining feed start position to the machining feed end position becomes the machining area and there is no idle stroke of the chuck table, so that the machining time can be shortened and the size of the entire apparatus can be reduced.

Description of drawings

Fig. 1 is the perspective view of the laser beam processing machine that forms according to the present invention;

Fig. 2 is a block diagram, which schematically shows the structure of the laser beam applying device arranged in the laser beam processing machine shown in Fig. 1;

Fig. 3 is a schematic diagram explaining the focal spot diameter of the laser beam from the laser beam applying device shown in Fig. 2;

4 is a perspective view showing a semiconductor wafer as a workpiece;

5(a) and 5(b) are schematic diagrams showing the coordinate relationship of the semiconductor wafer shown in FIG. 4, wherein the semiconductor wafer is held at a predetermined position on the chuck table of the laser beam processing machine shown in FIG. 1 ;

Fig. 6 is a schematic diagram, which has shown the dividing line detection step that is implemented by the laser beam processing machine shown in Fig. 1;

7(a) and 7(b) are schematic diagrams showing the laser beam application steps implemented by the laser beam processing machine shown in FIG. 1;

8 is a schematic diagram showing the relationship between the processing feed amount and the processing feed speed of the chuck table provided in the laser beam processing machine shown in FIG. 1 and the processing area;

Fig. 9 is a schematic diagram of a frequency control map, which is stored in the control device provided in the laser beam processing machine shown in Fig. 1;

FIG. 10 is a schematic diagram of an energy control map stored in a control device provided in the laser beam processing machine shown in FIG. 1; and

11 is a schematic diagram showing the relationship between the machining feed amount and the machining feed speed of the chuck table provided in the laser beam machining machine shown in FIG. 1 and the machining area in the prior art machining method.

Detailed ways

Preferred embodiments of the laser beam processing machine constructed according to the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a perspective view of a laser beam processing machine constructed in accordance with the present invention. The laser beam processing machine shown in FIG. 1 comprises: a fixed base 2, a chuck table mechanism 3, a laser beam applying unit support mechanism 4, and a laser beam applying unit 5, and the chuck table mechanism 3 is installed in such a manner On the fixed base 2, so that it can move along the processing feed direction indicated by the arrow X and hold the workpiece, the laser beam application unit support mechanism 4 is installed on the fixed base 2 in such a way that it can move along the direction indicated by the arrow X. The direction indicated by X moves vertically to the indexing feed direction indicated by arrow Y, and the laser beam applying unit 5 is mounted on the laser beam applying unit support mechanism 4 in such a way that it can move in the direction indicated by arrow Z .

The above-mentioned chuck table mechanism 3 includes: a pair of guide rails 31 and 31, which are installed on the fixed base 2, and arranged parallel to each other along the processing feed direction indicated by the arrow X; the first slider 32, which is arranged in such a way Installed on the guide rails 31 and 31 so that it can move in the processing feed direction indicated by the arrow X; the second slider 33, which is installed on the first slider 32 in such a way that it can move in the direction of the arrow X Move on the index feed direction indicated by Y; support table 35, which is supported on the second slide block 33 by cylindrical element 34; and chuck table 36 as a workpiece holding device. The chuck table 36 has a chuck 361 made of a porous material and a disk-shaped semiconductor wafer as a workpiece held on the chuck 361 by a suction device not shown. The chuck table 36 is rotated by a pulse motor (not shown) mounted in the cylindrical member 34 .

Above-mentioned first slide block 32 has a pair of to-be-guided grooves 321 and 321 installed on the above-mentioned two guide rails 31 and 31 on its bottom surface, and has indexing feeding direction indicated by arrow Y on its top surface. A pair of guide rails 322 and 322 are formed in parallel. The first slider constructed as described above is so constructed that by installing the grooves to be guided 321 and 321 on the pair of guide rails 31 and 31, respectively, the slider is allowed to move along the direction of machining feed indicated by the arrow X. The pair of guide rails 31 and 31 moves. The chuck table mechanism 3 in the exemplary embodiment includes a machining feed device 37 for moving the first slider 32 in the machining feeding direction indicated by the arrow X along the pair of guide rails 31 and 31 . The machining feeding device 37 includes a male threaded rod 371 disposed between and parallel to the aforementioned pair of guide rails 31 and 31 , and a drive source such as a pulse motor 372 for rotationally driving the male threaded rod 371 . One end of the male threaded rod 371 is rotatably supported in a bearing seat 373 fixed on the above-mentioned fixed base 2 , and the other end is drivingly connected with the output shaft of the above-mentioned pulse motor 372 . The male threaded rod 371 is screwed into a threaded through hole formed in a female threaded block (not shown) protruding from the bottom surface of the middle portion of the first slider 32 . Therefore, by driving the male threaded rod 371 in the forward or reverse direction using the pulse motor 372, the first slider 32 is moved along the guide rails 31 and 31 in the machining feed direction indicated by the arrow X.

The laser beam processing machine in this exemplary embodiment includes a feed amount detection device 374 for detecting the feed amount of the chuck table 36 described above. The feed amount detection device 374 includes a linear scale 374a arranged along the guide rail 31 and a reading head 374b mounted on the slider 32 and moving along the linear scale 374a together with the first slider 32 . In this exemplary embodiment, the reading head 374b of the feed amount detection device 374 sends out a pulse signal every time the chuck table 36 moves 0.1 μm toward the control device which will be described later. A control device to be described later calculates an input pulse signal to detect the machining feed amount of the chuck table 36 . When the pulse motor 372 is used as the driving source of the above-mentioned processing feeding device 37, the processing feeding of the chuck table 36 can be detected by calculating the driving pulse for outputting a driving signal to the pulse motor 372 described later. quantity. When a servo motor is used as the driving source of the above-mentioned processing feeding device 37, a pulse signal from a rotary encoder that detects the number of revolutions of the servo motor is supplied to the control device, and the pulse signal input to the control device is calculated to obtain The machining feed rate of the chuck table 36 is detected.

Above-mentioned second slide block 33 has a pair of to-be-guided grooves 331 and 331 to be fitted in the pair of guide rails 322 and 322 provided on the top face of above-mentioned first slide block 32 at its bottom surface, and second slide block 33 It is constructed so that it moves in the index feed direction indicated by arrow Y by fitting the grooves to be guided 331 and 331 into the pair of guide rails 322 and 322 , respectively. The chuck table mechanism 3 in this exemplary embodiment has a first index feeding device 38 for indexing along the pair of guide rails 322 and 322 provided on the first slider 32 at the index indicated by the arrow Y. Move the second slider 33 in the given direction. The first index feeding device 38 includes a male threaded rod 381 disposed between and parallel to the above-mentioned pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male threaded rod 381. . One end of the male threaded rod 381 is rotatably supported in a bearing seat 383 fixed on the top surface of the first slider 32 , and the other end is drivingly connected with the output shaft of the pulse motor 382 . The male threaded rod 381 is screwed into a threaded through hole formed in a female threaded block (not shown) protruding from the bottom surface of the middle portion of the second slider 33 . Therefore, by driving the male threaded rod 381 in the forward or reverse direction using the pulse motor 382, the second slider 33 can be moved along the guide rails 322 and 322 in the index feed direction indicated by the arrow Y.

The above-mentioned laser beam applying unit support mechanism 4 includes: a pair of guide rails 41 and 41, which are installed on the fixed base 2 and arranged parallel to each other along the indexing feeding direction indicated by the arrow Y, and a movable support base 42, which uses this It is mounted on the guide rails 41 and 41 in such a way that it can move in the direction indicated by the arrow Y. The movable supporting base 42 includes a movable supporting part 421 movably installed on the guide rails 41 and 41 and a mounting part 422 installed on the movable supporting part 421 . The mounting portion 422 has, on one side thereof, a pair of guide rails 423 and 423 extending parallel to each other in the direction indicated by the arrow Z. As shown in FIG. The laser beam application unit support mechanism 4 in this exemplary embodiment has a second index feeding device 43 for making the movable support base 42 move along the pair of guide rails 41 and 41 in the index feeding direction indicated by arrow Y move up. The second index feeding device 43 includes a male threaded rod 431 disposed between and parallel to the above-mentioned pair of guide rails 41 and 41, and a drive source such as a pulse motor 432 for rotationally driving the male threaded rod. 431. One end of the male threaded rod 431 is rotatably supported in a bearing seat (not shown) fixed on the above-mentioned fixed base 2 , and the other end is drivingly connected with the output shaft of the above-mentioned pulse motor 432 . The male threaded rod 431 is screwed into a threaded through hole formed in a female threaded block (not shown) protruding from the bottom surface of the middle portion of the movable support portion 421 constituting the movable support base 42 . Therefore, by driving the male threaded rod 431 in the forward or reverse direction using the pulse motor 432, the movable support base 42 can be moved along the guide rails 41 and 41 in the index feed direction indicated by the arrow Y.

The laser beam application unit 5 in this exemplary embodiment includes a unit holder 51 and a laser beam application device 52 fixed to the unit holder 51 . The unit holder 51 has a pair of guide grooves 511 and 511 to be slidably installed in the pair of guide rails 423 and 423 provided on the above-mentioned mounting portion 422, and the unit holder is supported in such a manner that It is made possible to move in the direction indicated by the arrow Z by fitting the grooves to be guided 511 and 511 into the above-mentioned guide rails 423 and 423, respectively.

This exemplary laser beam applying device 52 has a cylindrical housing 521 which is fixed to the above-mentioned unit holder 51 and extends substantially horizontally. As shown in FIG. 2 , a pulsed laser beam oscillation device 522 and an optical transmission system 523 are installed in a housing 521 . A pulsed laser beam oscillator 522a using a YAG laser oscillator or a YVO4 laser oscillator and a repetition rate adjusting device 522b connected to the pulsed laser beam oscillator 522a constitute the pulsed laser beam oscillator 522. The repetition frequency adjusting means 522b adjusts the vibration repetition frequency of the pulsed laser beam oscillator 522a in accordance with a control signal from a control means described later. The optical delivery system 523 includes suitable optical elements such as beam splitters or the like. A condenser 524 for accommodating a condenser lens (not shown) composed of a known lens combination is directly connected to the end of this housing 521 .

The laser beam generated by the vibration of the above-mentioned pulsed laser beam oscillation device 522 reaches the light collector 524 through the optical transmission system 523, and the laser beam is applied from the light collector 524 to the laser beam held on the above-mentioned chuck table 36 with a predetermined focal spot diameter D. on the workpiece. When as shown in Fig. 3, when the objective lens 524a of concentrator 524 applies the pulsed laser beam that shows normal distribution, this focal spot diameter D is given by the expression D (μm)=4*λ*f/(π ×W), where λ is the wavelength (μm) of the pulsed laser beam, W is the diameter (mm) of the pulsed laser beam entering the objective lens 524a, and f is the focal length (mm) of the objective lens 524a.

Returning to FIG. 1 , the image acquisition device 6 is connected to the front end of the casing 521 constituting the above-mentioned laser beam application device 52 . In addition to a common capture device (CCD) for capturing images of visible light radiation in this exemplary embodiment, the image capture device 6 includes an infrared radiation device for applying infrared radiation to the workpiece, and for collecting images generated by the infrared radiation device. An optical system for emitting infrared radiation and an image capture device (infrared CCD) for outputting electrical signals corresponding to the infrared radiation collected by the optical system. The image signal is supplied to an unshown control device.

The laser beam applying unit 5 in this exemplary embodiment has a moving device 53 for moving the unit holder 51 in the direction indicated by the arrow Z along the pair of guide rails 423 and 423 . The moving device 53 includes a male screw rod (not shown) provided between the pair of guide rails 423 and 423 and a driving source such as a pulse motor 532 for rotationally driving the male screw rod. The male threaded rod (not shown) is driven forward or reverse by using the pulse motor 532 to move the unit holder 51 and the laser beam application device 52 in the direction indicated by the arrow Z along the guide rails 423 and 423 . In this exemplary embodiment, the pulse motor 532 is driven forward to move the laser beam applying device 52 upward, and the pulse motor 532 is driven backward to move the laser beam applying device 52 downward.

The laser beam processing machine in this exemplary embodiment has a control device 10 . This control device 10 is made up of computer, and this computer comprises: Central Processing Unit (CPU) 101, it is used for carrying out arithmetic operation processing according to control program; Read Only Memory (ROM) 102, it is used for storing control program etc.; Read/write random access memory (RAM) 103 for storing calculation results; calculator 104 , input interface 105 and output interface 106 . Detection signals from the above-mentioned feed amount detection device 374 , image acquisition device 6 , etc. are input into the input interface 105 of the control device 10 . Control signals are output from the output interface 106 of the control device 10 to the pulse motor 372 , the pulse motor 382 , the pulse motor 532 , the laser beam applying device 52 , and the like.

The laser beam processing machine in this exemplary embodiment is constituted as described above, and its operation will be described below.

Fig. 4 is a perspective view of a semiconductor wafer as a workpiece to be processed by a laser beam. The semiconductor wafer 20 shown in FIG. 4 is composed of a silicon wafer, and has a plurality of regions divided by a plurality of dividing lines 201 provided on its front surface 20a in a lattice pattern, and circuits 202 such as ICs or LSIs are formed on each in a split area.

Next, a description will be given of a first embodiment of laser processing, which forms damage along the dividing line 201 inside the semiconductor wafer 20 by applying a laser beam along the dividing line 201 of the above-mentioned semiconductor wafer 20 using the above-mentioned laser beam processing machine. layer.

First, the semiconductor wafer 20 is placed on the chuck table 36 of the above-mentioned laser beam processing machine shown in FIG. On stage 36. The processing feeder 37 moves the chuck table 36 holding the semiconductor wafer 20 by suction to a position directly below the image pickup device 6 .

After the chuck table 36 is positioned directly under the image pickup device 6 , the image pickup device 6 and the control device 10 perform calibration work of detecting the laser beam processing area of the semiconductor wafer 20 . That is, the image pickup device 6 and the control device 10 perform image processing such as pattern matching so that the dividing line 201 formed in a predetermined direction of the semiconductor wafer 20 is aligned with the laser beam along which the laser beam is applied. The condenser 524 of the application unit 52 is used to calibrate the laser beam application position. This alignment of the laser beam application position is also performed on the dividing line 201 formed on the semiconductor wafer 20 in a direction perpendicular to the aforementioned predetermined direction. Although the front surface 20a of the semiconductor wafer 20 on which the dividing line 201 is formed faces downward here, since the infrared irradiation device, the optical system for capturing infrared radiation, and the electric power corresponding to the infrared radiation are provided as described above, The signal image acquisition device (infrared CCD) constitutes the image acquisition device 6, so that the image of the dividing line 201 can be acquired through the back surface 20b.

After the calibration work as described above is performed, the semiconductor wafer 20 on the chuck table 36 is positioned in the state of the coordinate position shown in FIG. 5( a ). FIG. 5( b ) shows a state where the chuck table 36 , that is, the semiconductor wafer 20 is rotated by 90° from the position shown in FIG. 5( a ).

After performing detection of the dividing line formed on the semiconductor wafer 20 held on the chuck table 36 and aligning the laser beam application position as described above, the chuck table is moved so that in FIG. 5(a) The uppermost dividing line 201 extending in a predetermined direction (left-right direction in FIG. 5 ) is moved to a position directly below the image pickup device 6 . Further, then, as shown in FIG. 6 , one end (the left end in FIG. 6 ) of the above-mentioned dividing line 201 is positioned directly below the image acquisition device 6 . In this state, after one end (the left end in FIG. 6 ) of the dividing line 201 is detected by the image acquisition device 6, its coordinate value (A1 in FIG. 5(a)) is provided to the control device 10 as the processing step. Coordinate values for the starting position. Subsequently, the chuck table 36 is moved in the direction indicated by the arrow X1, so that the other end (the right end in FIG. 6 ) of the dividing line 201 is moved to a position directly below the image capture device 6 . The image acquisition device 6 detects the other end of the dividing line 201, and provides its coordinate value (B1 in FIG. 5(a)) to the control device 10 as the coordinate value of the processing feed end position. The control device 10 temporarily stores the coordinate value (A1) of the machining feed start position and the coordinate value (B1) of the machining feed end position of the dividing line 201 in a random access memory (RAM) 103 (dividing line detection step) . Therefore, the random access memory (RAM) 103 serves as a storage device for storing the coordinate values of the machining feed start position and the machining feed end position of the dividing line detected by the image acquisition device 6 .

After the coordinate value of the processing feed start position and the coordinate value of the processing feed end position of the uppermost dividing line 201 in Fig. 5 (a) are detected as described above, in the indexing feed direction indicated by the arrow Y The chuck table 36 moves a distance equivalent to the distance between the dividing lines 201, thereby moving the second dividing line 201 from the top in FIG. The above-mentioned dividing line detection step is carried out on the second dividing line 201 from the uppermost to detect the coordinate value (A2) of the machining feed start position and the coordinate value (A2) of the machining feeding end position of the second dividing line 201 from the uppermost. coordinate values (B2), and temporarily store them in random access memory (RAM) 103. Subsequently, the above-mentioned index feed step and dividing line detection step are repeatedly executed until the lowermost dividing line 201 in FIG. and the coordinate values (B1 to Bn) of the machining feed end position and temporarily store them in the random access memory (RAM) 103.

After performing the above-described dividing line detection step on the dividing line 201 extending in a predetermined direction, the chuck table 36, that is, the semiconductor wafer 20 is rotated by 90° to be positioned at the position shown in FIG. 5( b ). superior. Thereafter, the above-mentioned dividing line detecting step is carried out to the dividing line 201 extending in a direction perpendicular to the dividing line 201 extending in the above-mentioned predetermined direction (left-right direction in FIG. The coordinate values (C1 to Cn) of the machining feed start position and the coordinate values (D1 to Dn) of the machining feed end position are temporarily stored in a random access memory (RAM) 103 . For the coordinate values (A1 to An) of the processing feed start position and the coordinate values (B1 to Bn) of the processing feed end position of the dividing line 201 extending along a predetermined direction formed on the semiconductor wafer 20 and along the direction perpendicular to the predetermined For the coordinate values (C1 to Cn) of the processing feed start position and the coordinate values (D1 to Dn) of the processing feed end position of the dividing line 201 extending in the Read Only Memory (ROM) 102 or Random Access Memory (RAM) 103, so as to omit the above-mentioned dividing line detection step.

Next is performed a step of applying a pulsed laser beam along the dividing line 201 formed on the semiconductor wafer 20 to form a damaged layer.

In the damage layer forming step, the chuck table 36 is first moved so that the uppermost dividing line 201 in FIG. And, as shown in FIG. 7(a), the coordinate value of the machining feed start position (see FIG. 5(a)), that is, one end of the dividing line 201 (the left end in FIG. 7(a)) is positioned at the condenser 524 directly below. Then, while a pulsed laser beam of a wavelength capable of penetrating the semiconductor wafer 20 as a workpiece is applied from the condenser 524, the chuck table 36, ie, the semiconductor wafer 20 is process-feeded in the direction indicated by arrow X1 in FIG. When the other end (the right end in Fig. 7 (a)), that is, the coordinate value (B1) of the processing feed end position of the dividing line 201 arrives at the application position of the light collector 524 of the laser beam application device 52, as shown in Fig. 7 ( As shown in b), the application of the pulsed laser beam is discontinued, and the movement of the chuck table 36, ie, the semiconductor wafer 20, is stopped. In this damaged layer forming step, the focal point P of the pulsed laser beam is set at a position close to the front surface 20 a (bottom surface) of the semiconductor wafer 20 . Accordingly, the damaged layer 210 is exposed to the front surface 20a of the semiconductor wafer 20 and is formed inwardly from the front surface 20a. The damaged layer 210 is formed as a melted and resolidified layer (ie, a layer that is melted and then solidified again), and its strength is reduced.

In the above-mentioned damage layer forming step, the processing feed speed of the chuck table, that is, the semiconductor wafer 20 is changed as shown in FIG. 8 . Fig. 8 corresponds to Fig. 11, and the horizontal axis shows the processing feed rate of the chuck table, and the vertical axis shows the processing feed speed of the chuck table. As shown in FIG. 8, the machining feed speed of the chuck table is accelerated from the machining feed start position (m0) and reaches a predetermined speed (V) at the first machining feed position (m1). After the chuck table moves at a predetermined speed (V) and reaches the second machining feed position (m2), its feed speed decreases and becomes zero at the machining feed end position (m3). The processing feed amount from the processing feed start position (m0) to the processing feed end position (m3) is based on the coordinate value (A1 to An) to the coordinate value (B1 to Bn) of the machining feed end position and the coordinate value (C1 to Cn) of the machining feed start position of the dividing line 201 extending in a direction perpendicular to the predetermined direction to the machining feed The coordinate values (D1 to Dn) given to the end position vary depending on the distance. However, the length from the machining feed start position (m0) to the first machining feed position (m1) is fixed regardless of the length of the dividing line when the machining feed speed is uniformly increased, and from the second machining feed The length from the position (m2) to the machining feed end position (m3) is fixed regardless of the length of the dividing line when the machining feed speed is uniformly reduced. Therefore, the area that changes according to the length of the dividing line is the area from the first machining feed position (m1) to the second machining feed position (m2).

As shown in Figure 8, the chuck table is accelerated between the machining feed start position (m0) and the first machining feed position (m1), and the chuck table is moved between the second machining feed position (m2) and Move at a gradually decreasing speed between the processing feed end positions (m3), and the chuck table moves at a predetermined processing speed at a constant speed between the first processing feed position (m1) and the second processing feed position (m2) , and the machining speed between the machining feed start position (m0) and the first machining feed position (m1) and the machining speed between the second machining feed position (m2) and the machining feed end position (m3) The speed is lower than the predetermined processing speed. Therefore, when the repetition frequency of the pulsed laser beam is set according to the predetermined machining speed between the first machining feed position (m1) and the second machining feed position (m2), the applied pulse of the laser beam is in the above-mentioned accelerated movement region and slow movement areas become too large.

Then, in the first embodiment of the present invention, a laser beam pulse is applied every time the processing feed amount of the chuck table 36, ie, the semiconductor wafer 20, reaches a predetermined value. That is to say, the control device receives a pulse signal, which is a detection signal of the reading head 374b of the feed detection device 374 . The control device 10 counts input pulses by a calculator 104 , and when the number of pulses becomes, for example, 10, an application signal is output to the laser beam application device 52 . Therefore, in this exemplary embodiment, the reading head 374b outputs a pulse signal every time the chuck table 36, that is, the semiconductor wafer 20 moves 0.1 μm, and each time the chuck table 36, that is, the semiconductor wafer 20 A laser beam pulse is applied along the dividing line 201 of the semiconductor wafer 20 by moving 1 μm. Therefore, even in the accelerated movement area from the machining feed start position (m0) to the first machining feed position (m1) and the deceleration area from the second machining feed position (m2) to the machining feed end position (m3) (The processing feed speed of the chuck table 36, that is, the semiconductor wafer 20 is not constant in these regions), and the pulsed laser beam will also be applied at regular time intervals along the dividing line 201 of the semiconductor wafer 20, thereby realizing Uniform machining from machining feed start position (m0) to machining feed end position (m3). Therefore, since the entire area from the processing feed start position (m0) to the processing feed end position (m3) becomes the processing area, there is no invalidation of the chuck table 36, that is, the semiconductor wafer 20, in this embodiment. stroke, which can shorten the processing time and reduce the size of the whole device.

In addition, when the pulse motor 372 is used as the driving source of the above-mentioned processing feeding device 37, the processing feeding amount of the chuck table 36 can be detected by calculating the driving pulse of the control device 10, which outputs to the pulse motor 372 A driving signal is used to apply a laser beam pulse every time the chuck table 36, that is, the processing feed amount of the semiconductor wafer 20, reaches a predetermined value. That is, in the present exemplary embodiment, the processing feeding device 37 is designed to move the chuck table 36 by 0.1 μm each time a driving pulse is applied to the pulse motor 372 . Therefore, when the predetermined machining feed speed (V) is 100 mm/sec, the control device 10 outputs 1,000,000 driving pulses per second to the pulse motor 372 . And, the control device 10 counts the drive pulses output to the pulse motor 372 by the calculator 104 , and sends an application signal to the laser beam application device 52 when the number of pulses becomes 10. Therefore, a laser beam pulse is applied along the dividing line 201 of the semiconductor wafer 20 every time the chuck table 36 , ie, the semiconductor wafer 20 is processed by 1 μm.

For example, the processing conditions in the above damage layer forming step are set as:

Light source: LD excitation Q-switched Nd: YVO4 laser

Wavelength: Pulsed laser with a wavelength of 1,064nm

Energy: 3(J/sec)

Focal spot diameter: 1μm

Machining feed rate: 100mm/sec between the first machining feed position (m1) and the second machining feed position (m2)

When the semiconductor wafer 20 is thick, the damage layer shaping process is performed by changing the focal point P multiple times to gradually form a plurality of damage layers 210 . The damage layer 210 may be formed only inside without being exposed on the front side 20a and the back side 20b.

The above-described damage layer forming step is performed along all the dividing lines 201 formed in a predetermined direction of the semiconductor wafer 20 . Then, the chuck table 36, that is, the semiconductor wafer 20 is rotated by 90° so that the above-mentioned damaged layer forming step is performed along the dividing line 201 extending in a direction perpendicular to the above-mentioned dividing line 201 formed in the predetermined direction of the semiconductor wafer 20.

A second embodiment of the present invention will be described below.

In the second embodiment, there is a frequency control map prepared in advance such as shown in FIG. This corresponds to the machining feed amount from the machining feed start position to the machining feed end position controlled by the machining feed device 37 as shown in FIG. 7 . In FIG. 9, the horizontal axis shows the processing feed amount of the chuck table, and the vertical axis shows the repetition frequency of the pulsed laser beam corresponding to each processing feed amount. In the frequency control diagram shown in Figure 9, the chuck table moves from the first processing feed position (m1) to the second processing feed position (m2) at a uniform processing feed rate, such as 100mm/sec, And the repetition frequency (F) of the pulsed laser beam between the two positions is set to be, for example, 100 kHz. Pulses for the acceleration movement range from the machining feed start position (m0) to the first machining feed position (m1) and the deceleration range from the second machining feed position (m2) to the machining feed end position (m3) The repetition frequency of the laser beam is set as follows.

If the uniform acceleration motion of the chuck table 36 from the machining feed start position (m0) to the first machining feed position (m1) is represented by A (mm/s ² ), from the first machining feed position (m1) to The uniform motion of the second machining feed position (m2) is represented by V (mm/s), the time required from the machining feed start position (m0) to the first machining feed position (m1), that is, the chuck works The time required for the machining feed speed of the table to change from 0 (mm/s) to V (mm/s) is represented by t, and the The repetition frequency of the pulsed laser beam in the uniform moving region is represented by F (Hz), then the repetition of the pulsed laser beam in the accelerated moving region from the processing feed start position (m0) to the first processing feed position (m1) The frequency f(Hz) is given by the expression f(Hz)=(F×A×t)/V. And, if the uniformly decelerated motion from the second machining feed position (m2) to the machining feed end position (m3) is represented by B (mm/s ² ), and moving from the second machining feed position (m2) to the machining The time required to feed the end position (m3), that is, the time required for the processing feed speed of the chuck table to change from V (mm/s) to 0 (mm/s) is represented by t, then the second processing feed The frequency f(Hz) of the pulsed laser beam in the deceleration movement region from the feed position (m2) to the machining feed end position (m3) is given by the expression f(Hz)=(F×B×t)/V.

The frequency control map thus prepared is stored in a read only memory (ROM) 102 or a random access memory (RAM) 103 of the control device 10 as a control map for setting machining conditions. The control means 10 controls the repetition frequency adjusting means 522b of the pulsed laser beam oscillating means 522 of the laser beam applying means 52 based on the frequency control map in the above-mentioned damaged layer forming step.

That is to say, as mentioned above, in the above-mentioned damaged layer forming step, the control device 10, according to the pulse signal, that is, the detection signal of the reading head 374b of the feed amount detection device 374 (or the driving source for the processing feed device 37 The driving pulse signal when the pulse motor 372 is used or the pulse signal from the rotary encoder when the driving source of the processing feeding device 37 is a servo motor) controls the processing feeding amount of the chuck table 36, that is, the semiconductor wafer 20. The control device 10 controls the repetition rate adjusting device 522b of the pulsed laser beam oscillating device 522 so that the chuck table 36, that is, the semiconductor wafer 20, moves from the processing feed start position (m0) to the first processing feed position (m1). ), generate a pulsed laser beam with a repetition rate corresponding to the rate of increasing uniform acceleration shown in FIG. 9 . When the chuck table 36, that is, the semiconductor wafer 20, arrives at the first processing feed position (m1), the control device 10 controls the repetition rate adjustment device 522b of the pulsed laser beam oscillation device 522 to generate a pulsed laser beam, and the pulsed laser beam The preset wavelength of the beam in the region of constant velocity movement from the first machining feed position (m1) to the second machining feed position (m2) is 100 kHz. When the chuck table 36, that is, the semiconductor wafer 20, reaches the second processing feed position (m2), the control device 10 controls the repetition rate adjustment device 522b of the pulsed laser beam oscillation device 522, so that the chuck table 36, that is, When the semiconductor wafer 20 moves from the second processing feed position (m2) to the processing feed end position (m3), pulsed laser beams are generated at a repetition rate corresponding to the speed shown in FIG. 9 at a uniform deceleration.

In this way, in the second embodiment of the present invention, since the repetition frequency of the pulsed laser beam is controlled according to the frequency control map, in this frequency control map, according to the process feed start position from the chuck table 36 to the process feed The processing feed speed corresponding to each processing feed amount at the end position controls the repetition frequency of the pulsed laser beam, which is applied to the semiconductor wafer 20 at regular time intervals along the dividing line 201, thereby starting from the processing feed Uniform machining can be performed from the position to the end position of the machining feed. Therefore, in the second embodiment, the area from the machining feed start position (m0) to the machining feed end position (m3) is the machining area, and there is no ineffective travel of the chuck table 36, that is, the semiconductor wafer 20. , so that the processing time can be shortened and the size of the entire device can be reduced.

In the first and second embodiments described above, the number of pulses of the pulsed laser beam is controlled in accordance with the processing feed speed of the chuck table. However, it is also possible to uniformize the energy of the pulsed laser beam applied to a unit distance along the dividing line formed on the semiconductor wafer. That is, FIG. 10 shows an energy control map in which the machining feed corresponding to the machining feed amount from the machining feed start position to the machining feed end position of the chuck table 36 The energy of the pulsed laser beam is set as the processing condition for the speed. In FIG. 10, the horizontal axis shows the processing feed amount of the chuck table, and the vertical axis shows the energy of the pulsed laser beam corresponding to each processing feed amount. In the energy control diagram shown in Figure 10, the chuck table moves from the first processing feed position (m1) to the second processing feed position (m2) at a constant speed of, for example, 100mm/sec, and between the two The energy (P) between positions is set to be, for example, 3 (J/sec). And, the acceleration movement area from the machining feed start position (m0) to the first machining feed position (m1) and the deceleration movement area from the second machining feed position (m2) to the machining feed end position (m3) The energy of the pulsed laser beam was set as follows.

If the uniform acceleration motion of the chuck table from the machining feed start position (m0) to the first machining feed position (m1) is represented by A (mm/s ² ), from the first machining feed position (m1) to the first machining feed position The uniform motion of the second machining feed position (m2) is represented by V (mm/s), the time required to move from the machining feed start position (m0) to the first machining feed position (m1), that is, the chuck table The time required for the machining feed speed to reach V (mm/s) from 0 (mm/s) is represented by t, and the uniform speed from the first machining feed position (m1) to the second machining feed position (m2) The energy of the pulsed laser beam in the moving region is represented by P(J/sec), then the energy p(J/sec ) is obtained by the expression p(J/sec)=(P×A×t)/V. And, if the uniform deceleration motion from the second machining feed position (m2) to the machining feed end position (m3) is represented by B (mm/s ² ), moving from the second machining feed position (m2) to the machining feed The time required for the end position (m3), that is, the time required for the processing feed speed of the chuck table to drop from V (mm/s) to 0 (mm/s), is represented by t, then from the second processing The energy p (J/sec) of the pulsed laser beam in the deceleration movement area from the feed position (m2) to the processing feed end position (m3) is given by the expression p (J/sec)=(P×B×t)/ V draws.

The energy control map thus prepared is stored in a read only memory (ROM) 102 or a random access memory (RAM) 103 of the control device 10 . The control device 10 controls the pulsed laser beam oscillating device 522 of the laser beam applying device 52 according to the energy control map in the damage layer forming step described above.

That is to say, as mentioned above, in the above-mentioned damaged layer forming step, the control device 10 is based on the pulse signal, that is, the detection signal of the reading head 374b of the feed amount detection device 374 (or the drive for processing the feed device 37 The drive pulse signal when the source is the pulse motor 372 or the pulse signal from the rotary encoder when the drive source for the processing feeding device 37 is a servo motor) controls the processing feed amount of the chuck table 36, that is, the semiconductor wafer 20 . The control device 10 controls the repetition frequency adjusting device 522b of the pulsed laser beam oscillating device 522 so that the chuck table 36, that is, the semiconductor wafer 20, moves from the processing feed start position (m0) to the first processing feed position (m1). , a pulsed laser beam having energy corresponding to the speed increasing at a uniform acceleration as shown in FIG. 10 is generated. When the chuck table 36, that is, the semiconductor wafer 20, arrives at the first processing feed position (m1), the control device 10 controls the pulsed laser beam oscillation device 522 to generate a pulsed laser beam. The preset energy in the constant speed moving region from the feed position (m1) to the second processing feed position (m2) is 3 (J/sec). And, when the chuck table 36, that is, the semiconductor wafer 20, arrives at the second processing feeding position (m2), the control device 10 controls the pulsed laser beam oscillation device 522, so that when the chuck table 36, that is, the semiconductor wafer 20, moves from When the second machining feed position (m2) is moved to the machining feed end position (m3), a pulsed laser beam having energy corresponding to the speed decreasing at a uniform deceleration as shown in FIG. 10 is generated.

Thus, in this embodiment using the energy control map shown in FIG. The energy of the pulsed laser beam for each processing feed amount is controlled so that the energy of the pulsed laser beam applied to a unit distance along the dividing line 201 of the semiconductor wafer 20 is uniform from the processing feed start position to the processing feed end position of. Therefore, also in this embodiment, the area from the processing feed start position (m0) to the processing feed end position (m3) is a processing area, and there is no chuck table 36, that is, the semiconductor wafer 20. Lost travel, which can shorten the processing time and reduce the size of the entire device.

Claims (3)

1. A laser beam processing machine comprising a chuck table for holding a workpiece, a laser beam applying device for applying a pulse laser beam to the workpiece held on the chuck table, and a processing feed device for causing the chuck table and the laser beam applying device to perform processing feed relative to each other,

the laser beam processing machine further comprises a feed amount detecting means for detecting a processing feed amount of the chuck table and a control means for controlling the laser beam applying means in accordance with a detection signal from the feed amount detecting means; and

the control means outputs an application signal for each predetermined processing feed amount to the laser beam application means in accordance with the signal from the feed amount detection means.

2. A laser beam processing machine comprising a chuck table for holding a workpiece, a laser beam applying device for applying a pulse laser beam to the workpiece held on the chuck table, and a processing feed device for causing the chuck table and the laser beam applying device to perform processing feed relative to each other, wherein at the time of processing feed to the chuck table, the processing feed device controls a processing feed speed of the chuck table in a process from a processing feed start position to a first predetermined processing feed amount so as to accelerate to a predetermined processing feed speed and maintains the predetermined processing feed speed at a constant speed in a process from the first predetermined processing feed amount to a second predetermined processing feed amount, and decelerates to zero in a process from the second predetermined processing feed amount to a processing feed end position, wherein,

the laser beam processing machine further comprises a feed amount detecting means for detecting a processing feed amount of the chuck table and a control means for controlling the laser beam applying means in accordance with a detection signal from the feed amount detecting means; and

the control means includes storage means for storing a control map for setting the processing conditions of the laser beam in accordance with a processing feed speed corresponding to a processing feed amount applied by the processing feed means from a processing feed start position to a processing feed end position of the chuck table, and outputs an application signal of the processing conditions set by the control map to the laser beam application means in accordance with a signal from the feed amount detection means.

3. The laser beam processing machine according to claim 2, wherein the control map is a frequency control map which sets a repetition frequency of the laser beam in accordance with a processing feed speed corresponding to a processing feed amount applied from a processing feed start position to a processing feed end position of the chuck table by the processing feed means.

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