KR102114504B1 - Laser machining apparatus - Google Patents

Abstract

The present invention provides a laser processing apparatus having a function of confirming whether or not the focusing point position adjusting means is operating by following the positional information of the top surface height of the workpiece held on the chuck table.
A laser beam irradiation means having an objective condensing lens for condensing and irradiating a laser beam onto a work piece held in the chuck table, a height position detecting means for detecting an upper surface height position of the work piece held in the chuck table, and an objective condenser lens A condensing point position adjusting means for moving the chuck table in the Z-axis direction perpendicular to the holding surface of the chuck table, machining feed means for machining-feeding the chuck table in the X-axis direction, and X for detecting the X-axis position of the chuck table A laser processing apparatus comprising an axial position detection means and a control means, the control means actuating the processing transfer means to move the workpiece held in the chuck table in the X-axis direction while operating the height position detecting means to operate the workpiece. Equipped with a storage means for storing the X coordinate based on the height measurement value obtained by measuring the height position of X and the detection signal from the X-axis direction position detection means, and actuate the machining transfer means to operate the workpiece held in the chuck table X. While moving in the axial direction, the focusing point position adjusting means is controlled based on the height measurement value corresponding to the X coordinate stored in the storage means, and the height information detected by the height position detecting means is displayed on the display means in association with the X coordinate.

Description

Laser processing equipment {LASER MACHINING APPARATUS}

The present invention relates to a laser processing apparatus having a function of detecting a position of an upper surface height of a workpiece held on a chuck table holding a workpiece.

In the semiconductor device manufacturing process, a plurality of regions are partitioned by division scheduled lines arranged in a lattice shape on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs and LSIs are formed in the divided regions. Then, by cutting the semiconductor wafer along the street, an area where the device is formed is divided to manufacture individual semiconductor devices. In addition, a plurality of light-emitting layers comprising an n-type semiconductor layer and a p-type semiconductor layer are laminated on surfaces such as a sapphire substrate, a silicon carbide substrate, and a gallium nitride substrate, which are roughly disk-shaped, and are partitioned by a plurality of division scheduled lines formed in a lattice shape. An optical device such as a light emitting diode or a laser diode is formed in a region to form an optical device wafer. Then, each optical device is manufactured by dividing the optical device wafer along a line to be divided.

As a method of dividing along a line to be divided, such as a semiconductor wafer or an optical device wafer, the pulse laser beam is irradiated by placing a condensing point inside an area to be divided using a pulse laser beam having transparency to the wafer. A laser processing method has been tried. In the division method using this laser processing method, a pulsed laser beam having a transmittance wavelength is irradiated to a wafer by aligning a condensing point from one side side of the wafer to the inside, and the modified layer is continuously disposed along the line to be divided inside the wafer. It is formed by, and by applying the external force along the line to be divided in which the strength is lowered by forming the modified layer, the workpiece is divided (for example, see Patent Document 1). When the modified layer is formed inside along the line to be divided formed in the workpiece, it is important to position the converging point of the laser beam at a predetermined depth from the upper surface of the workpiece.

However, since plate-like workpieces, such as semiconductor wafers, have curvature and fluctuations in their thickness, it is difficult to perform uniform laser processing. That is, in the technique of forming a modified layer by placing the light-converging point inside the wafer and irradiating the laser beam along the line to be divided, the light-converging lens having a numerical aperture (NA) of about 0.8 to increase the peak power density of the laser beam Is used, and when the position of the height of the top surface changes because there is a bend (unevenness) on the irradiation surface (upper surface) of the wafer irradiating the laser beam, the light-condensing point of the laser beam is not positioned at an appropriate position, and thus a uniformly modified layer at a predetermined depth position Cannot form.

In order to solve the above-mentioned problem, the position of the top surface height of the line to be divided formed on the wafer held on the chuck table holding the work piece is measured to create the position information of the top surface height of each line to be divided, and a condensing point inside the wafer When a modified layer is formed by irradiating a laser beam along a line to be divided by positioning, condensing point position adjusting means for adjusting a condensing point by the condensing lens based on the image height position information is controlled in correspondence to the top surface height position. The technology so made is disclosed in Patent Document 2, Patent Document 3, and Patent Document 4 below.

Patent Document 1: Japanese Patent No. 3408805 Patent Document 2: Japanese Patent Publication No. 2011-122894 Patent Document 3: Japanese Patent Publication No. 2012-2604 Patent Document 4: Japanese Patent Publication No. 2009-63446

Therefore, even if the light-converging position adjusting means is operated based on the positional information on the top surface of the workpiece held on the chuck table, there is a case that it operates without delay following the positional information on the height. There is a problem that processing accuracy deteriorates because it cannot be positioned.

The present invention has been made in view of the above facts, and its main technical problem is to provide a function of confirming whether or not the focusing point position adjusting means is operating by following the positional information on the height of the upper surface of the workpiece held in the chuck table. It is to provide a laser processing apparatus.

In order to solve the above main technical problem, according to the present invention, a laser having a chuck table having a holding surface for holding a workpiece, and an objective condensing lens for condensing and irradiating laser beams on the workpiece held on the chuck table Light irradiation means, height position detecting means for detecting the height position of the top surface of the workpiece held on the chuck table, and moving the objective condensing lens in a direction perpendicular to the holding surface of the chuck table (Z-axis direction) Condensing point position adjustment means, processing feed means for relatively processing and processing the chuck table and the laser beam irradiation means in the machining feed direction (X-axis direction), and X-axis for detecting the position of the chuck table in the X-axis direction A laser processing apparatus comprising a direction position detecting means, a control means for outputting a control signal to the condensing point position adjusting means, the processing transfer means and the display means,

The control means operates the processing transfer means to move the workpiece held in the chuck table in the X-axis direction while operating the height position detecting means to measure the height position of the workpiece and the height measurement value obtained by X And storage means for storing X coordinates based on the detection signal from the axial position detecting means, and moving the work conveying means to move the workpiece held in the chuck table in the X-axis direction to be stored in the storage means. A laser processing apparatus characterized by controlling the condensing point position adjusting means based on the height measurement value corresponding to the calculated X coordinate, and displaying the height information detected by the height position detecting means in correspondence with the X coordinate on the display means. Is provided.

The control means enables operation of the laser beam irradiating means if the fluctuation width of the height information corresponding to the X coordinate displayed on the display means is an allowable range, and the laser if the fluctuation width of the height information corresponding to the X coordinate is outside the allowable range. The operation of the light irradiation means is disabled.

Further, the control means, while operating the machining feed means, the height position detecting means and the first condensing point position adjusting means, the X coordinate in the height information corresponding to the X coordinate stored in the storage means and the X of the chuck table. A deviation is generated between the coordinates so that the fluctuation width of the height information becomes an allowable range, and the amount of displacement of the X coordinate when the fluctuation width of the height information is within the allowable range is determined as a correction value.

In the laser processing apparatus according to the present invention, the control means is obtained by measuring the height position of the work piece by operating the height position detecting means while moving the work piece held in the chuck table by operating the work feed means. And storage means for storing the X coordinates based on the height measurement value and the detection signal from the X-axis direction position detecting means, and moving the work conveying means to move the workpiece held in the chuck table in the X-axis direction. Because the height convergence position adjusting means is controlled on the basis of the height measurement value corresponding to the X coordinate stored in, and the height information detected by the height position detecting means is displayed on the display means in correspondence with the X coordinate, the blood held in the chuck table is avoided. Since it is possible to confirm whether or not the focusing point position adjusting means is operating by following the positional information on the top surface height of the workpiece, it is possible to position the focusing point of the laser beam at an appropriate position, thereby improving processing precision.

1 is a perspective view of a laser processing apparatus constructed in accordance with the present invention.
FIG. 2 is a block diagram of a position detection device and laser beam irradiation means constituting a position detection and laser irradiation unit equipped in the laser processing device shown in FIG. 1.
FIG. 3 is a block diagram of control means provided in the laser processing apparatus shown in FIG. 1.
4 is a perspective view of a semiconductor wafer as a workpiece.
5 is a perspective view showing a state in which the semiconductor wafer shown in FIG. 4 is adhered to the surface of a protective tape mounted on an annular frame.
FIG. 6 is an explanatory diagram showing a relationship with a coordinate position in a state where the semiconductor wafer shown in FIG. 4 is held at a predetermined position of the chuck table of the laser processing device shown in FIG. 1.
7 is an explanatory view of a height position detection process performed by the height position detection means provided in the laser processing apparatus shown in FIG. 1.
8 is a height position displacement map created in the height position detection process performed by the height position detection means provided in the laser processing apparatus shown in FIG. 1.
FIG. 9 is an explanatory view of an operation confirmation process of the light-converging position adjusting means performed by the laser processing apparatus shown in FIG. 1.
FIG. 10 is an explanatory diagram showing a voltage value corresponding to the X coordinate output by the light receiving element receiving the reflected light from the workpiece in the operation confirmation process of the condensing point position adjusting means shown in FIG. 9.
11 is an explanatory view of a modified layer forming process performed by the laser processing apparatus shown in FIG. 1.

Hereinafter, preferred embodiments of the laser processing apparatus constructed in accordance with 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 installed on the stationary base 2 and the stationary base 2 so as to be movable in the machining feed direction (X-axis direction) indicated by an arrow X to hold the workpiece. The chuck table mechanism 3 and the laser beam irradiation unit support mechanism 4 movably provided in the indexing feed direction (Y-axis direction) indicated by the arrow Y orthogonal to the X-axis direction to the stop base 2, and The laser beam irradiation unit support mechanism 4 is provided with a position detection / laser irradiation unit 5 that is movably installed in a direction of focusing point (Z-axis direction) indicated by an arrow Z.

The chuck table mechanism (3), a pair of guide rails (31, 31) installed in parallel along the X-axis direction on the stop base (2), and the guide rails (31, 31) moved in the X-axis direction Cylindrical on the first sliding block 32 and the second sliding block 33 and the second sliding block 33, which is installed to be movable in the Y-axis direction on the first sliding block 32. A support table 35 supported by the member 34 and a chuck table 36 as a workpiece holding means are provided. This chuck table 36 is provided with an adsorption chuck 361 formed of a porous material, and is drawn on a holding surface, which is an upper surface of the adsorption chuck 361, by a suction means (not shown), for example, a semiconductor wafer of circular shape. It is supposed to be maintained. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) provided in the cylindrical member 34. In addition, a clamp 362 for fixing an annular frame for supporting a workpiece such as a semiconductor wafer through a protective tape is provided on the chuck table 36.

The first sliding block 32 has a pair of guide grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on its lower surface, and is parallel to the upper surface along the Y-axis direction. A pair of guide rails 322 and 322 are formed. In the first sliding block 32 configured as described above, the guide grooves 321 and 321 fit in the pair of guide rails 31 and 31, and thus move in the X-axis direction along the pair of guide rails 31 and 31. It is made possible. The chuck table mechanism 3 in the illustrated embodiment is provided with machining transfer means 37 for moving the first sliding block 32 in the X-axis direction along the pair of guide rails 31 and 31. have. The machining transfer means 37 includes a driving source such as a male screw rod 371 installed in parallel between the pair of guide rails 31 and 31 and a pulse motor 372 for rotationally driving the male screw rod 371. It contains. The male rod 371 is rotatably supported by a bearing block 373 having one end fixed to the stop base 2, and the other end thereof is electrically connected to the output shaft of the pulse motor 372. Further, the male screw rod 371 is screwed to a through female screw hole formed in a female screw block (not shown) protruding from a lower surface of the central portion of the first sliding block 32. Therefore, by driving the male screw rod 371 forward and reverse by a pulse motor 372, the first sliding block 32 is moved along the guide rails 31 and 31 in the X-axis direction.

The laser processing apparatus 1 in the illustrated embodiment is provided with X-axis direction position detection means 374 for detecting the X-axis direction position of the chuck table 36. The X-axis direction position detecting means 374 is a linear scale 374a installed along the guide rail 31 and a linear scale 374a installed in the first sliding block 32 together with the first sliding block 32 It consists of a read head 374b moving along. In the illustrated embodiment, the read head 374b of the X-axis direction position detecting means 374 sends a pulse signal of 1 pulse every 1 µm to control means described later. And the control means mentioned later calculates the machining feed amount of the chuck table 36 by counting the input pulse signal, and finds the position of the chuck table 36 in the X-axis direction. On the other hand, when the pulse motor 372 is used as the driving source of the machining transfer means 37, the driving pulses of the control means, which will be described later, which output the driving signal to the pulse motor 372 are counted, thereby releasing the chuck table 36. It is also possible to detect the machining feed amount. Further, when a servo motor is used as a driving source of the machining transfer means 37, a pulse signal output by a rotary encoder that detects the rotational speed of the servo motor is sent to control means described later, and the pulse signal input by the control means is transmitted. By counting, the machining feed amount of the chuck table 36 can also be detected.

The second sliding block 33 is formed with a pair of guide grooves 331 and 331 fitted to a pair of guide rails 322 and 322 installed on an upper surface of the first sliding block 32 on its lower surface. Thereby, the guide grooves 331 and 331 are configured to be movable in the Y-axis direction by fitting the pair of guide rails 322 and 322. The chuck table mechanism 3 in the illustrated embodiment is for moving the second sliding block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided on the first sliding block 32. A first indexing transfer means 38 is provided. The first indexing transfer means 38 includes a male screw rod 381 installed in parallel between the pair of guide rails 322 and 322, a pulse motor 382 for rotationally driving the male screw rod 381, and the like. It contains a driving source. The male rod 381 is rotatably supported by a bearing block 383 whose one end is fixed to the upper surface of the first sliding block 32, and the other end is electrically connected to the output shaft of the pulse motor 382. It is. On the other hand, the male screw rod 381 is screwed into a through female screw hole formed in a female screw block (not shown) protruding from the lower surface of the central portion of the second sliding block 33. Accordingly, the second sliding block 33 is moved along the guide rails 322 and 322 in the Y-axis direction by driving the male screw rod 381 forward and reverse by a pulse motor 382.

The laser processing apparatus 1 in the illustrated embodiment is provided with Y-axis direction position detecting means 384 for detecting the Y-axis direction position of the chuck table 36. The Y-axis direction position detecting means 384 detects the Y-axis direction position of the second sliding block 33 provided with the chuck table 36. The Y-axis direction position detecting means 384 in the illustrated embodiment is provided on the linear scale 384a and the second sliding block 33 provided along the guide rail 322, and the second sliding block 33 It consists of a read head 384b moving along the linear scale 384a. In the illustrated embodiment, the read head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of 1 pulse every 1 μm to control means described later. Then, the control means, which will be described later, calculates the indexing feed amount of the chuck table 36 by counting the input pulse signal to obtain the Y-axis position of the chuck table 36. On the other hand, when the pulse motor 382 is used as the driving source of the Y-axis direction position detecting means 384, the chuck table ( The indexing transfer amount of 36) can also be detected. Further, when a servo motor is used as a driving source of the machining transfer means 37, a pulse signal output by a rotary encoder that detects the rotational speed of the servo motor is sent to control means described later, and the pulse signal input by the control means is transmitted. By counting, the indexing feed amount of the chuck table 36 can also be detected.

The laser beam irradiation unit support mechanism 4 has a pair of guide rails 41 and 41 provided parallel to the stationary base 2 along the Y-axis direction, and an arrow Y on the guide rails 41 and 41. The movable support base 42 is provided so as to be movable in the direction indicated by. The movable support base 42 is composed of a movable support portion 421 movably installed on the guide rails 41 and 41, and a mounting portion 422 attached to the movable support portion 421. In the mounting portion 422, a pair of guide rails 423 and 423 extending in the Z-axis direction is provided in parallel on one side. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment has second indexing transfer means 43 for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. ). The second indexing transfer means 43 includes a male screw rod 431 installed in parallel between the pair of guide rails 41 and 41, and a pulse motor 432 for rotationally driving the male screw rod 431. It contains a driving source. The male rod 431 is rotatably supported by a bearing block (not shown), one end of which is fixed to the stop base 2, and the other end thereof is electrically connected to the output shaft of the pulse motor 432. Further, the male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) protruding from the lower surface of the central portion of the movable support part 421 constituting the movable support base 42. For this reason, the movable support base 42 is moved along the guide rails 41 and 41 in the Y-axis direction by driving the male screw rod 431 forward and reverse by the pulse motor 432.

The position detection and laser irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and a cylindrical unit housing 52 attached to the unit holder 51. 51) is movably installed along the pair of guide rails 423 and 423 to the mounting portion 422 of the movable support base 42. In the unit housing 52 attached to the unit holder 51, a laser beam is applied to the workpiece held in the chuck table 36 and height position detecting means for detecting the height position of the workpiece held in the chuck table 36. A laser beam irradiation means for irradiating is provided. The height position detecting means and the laser beam irradiation means will be described with reference to FIG. 2.

2, an example of the interference-type height position detection means is shown. The height position detecting means 6 in the illustrated embodiment induces a light-emitting source 61 emitting light having a predetermined wavelength range and light from the light-emitting source 61 to the first path 6a. A first light diverging means 62 for guiding the reflected light that reverses the first path 6a to the second path 6b, and a correction lens for forming the light induced in the first path 6a into parallel light. (63) and second light diverging means (64) for dividing the light formed by the parallel light by the calibration lens (63) into the third path (6c) and the fourth path (6d).

For the light emitting source 61, for example, an LED, SLD, LD, halogen power source, ASE power source, or supercontinuum power source that emits light in a wavelength range of 820 nm to 870 nm can be used. As the first optical branching means 62, a polarization-maintaining fiber coupler, a polarization-maintaining fiber circulator, a single-mode fiber coupler, a single-mode fiber coupler circulator, or the like can be used. In the illustrated embodiment, the second light diverging means 64 is composed of a beam splitter 641 and a direction changing mirror 642. On the other hand, the path from the light-emitting source 61 to the first light diverging means 62 and the first path 6a are constituted by optical fibers.

In the third path 6c, an objective condensing lens 65 for guiding light induced in the third path 6c to a workpiece W held in the chuck table 36, and the objective condensing lens 65 ) And the second light diverging means 64 are provided with a condensing lens 66. The condensing lens 66 converges the parallel light induced in the third path 6c from the second light diverging means 64 to locate the condensing point in the objective condensing lens 65, and from the objective condensing lens 65 Produces light of pseudo as pseudo-parallel light. Thus, by providing a condenser lens 66 between the objective condenser lens 65 and the second light diverging means 64 to generate light from the objective condenser lens 65 as pseudo-parallel light, to the chuck table 36 The first path 6a when the reflected light reflected from the retained workpiece W is reversed through the objective condenser lens 65, the condenser lens 66, the second light diverging means 64 and the calibration lens 63 ) Can be converged to the optical fiber constituting. On the other hand, the objective condenser lens 65 is attached to the lens case 651, and the lens case 651 is vertically illustrated in FIG. 2 by a condensing point position adjusting means 650 made of a voice coil motor or a linear motor. It is to be moved in the direction, i.e., in the direction of the focusing point position adjustment (Z-axis direction) perpendicular to the holding surface of the chuck table 36. The condensing point position adjusting means 650 is controlled by control means described later.

The fourth path 6d is provided with a reflection mirror 67 that reflects the parallel light induced in the fourth path 6d and reverses the reflected light in the fourth path 6d. The reflection mirror 67 is attached to the lens case 651 of the objective condenser lens 65 in the illustrated embodiment.

In the second path 6b, a correction lens 68, a diffraction grating 69, a condensing lens 70, and a line image sensor 71 are provided. The correction lens 68 is reflected by the reflection mirror 67 to reverse the fourth path 6d, the second light diverging means 64, the correction lens 63, and the first path 6a. The reflected light guided from the first light diverging means 62 to the second path 6b, and the objective condensing lens 65 and the condensing lens 66 and the reflection light reflected from the workpiece W held in the chuck table 36 The two light diverging means 64 and the correction lens 63 and the first path 6a are reversed to form reflected light guided from the first light diverging means 62 to the second path 6b as parallel light. The diffraction grating 69 diffracts the interference of the two reflected light formed as parallel light by the calibration lens 68, and the line image sensor 71 through the condensing lens 70 to diffraction signals corresponding to each wavelength Sends to The line image sensor 71 detects the light intensity at each wavelength of the reflected light diffracted by the diffraction grating 69, and sends the detection signal to control means described later.

The control means, which will be described later, obtains a spectral interference waveform from the detection signal by the line image sensor 71, performs waveform analysis based on the spectral interference waveform and the theoretical waveform function, in the third path 6c. The optical path length difference between the optical path length to the workpiece W held in the chuck table 36 and the optical path length to the reflection mirror 67 in the fourth path 6d is determined, and based on the optical path length difference The distance from the surface of the chuck table 36 to the top surface of the workpiece W held on the chuck table 36, that is, the position of the top surface height of the workpiece W is obtained. On the other hand, waveform analysis based on the Fourier transform theory performed based on the spectral interference waveform and the theoretical waveform function is described in, for example, Japanese Patent Laid-Open No. 2011-122894, and detailed description is omitted.

Continuing the explanation based on FIG. 2, the laser beam irradiation means 8 provided in the unit housing 52 (see FIG. 1) of the position detection and laser irradiation unit 5 includes pulse laser beam oscillation means 81. , A dichroic mirror 82 that converts the pulsed laser beam oscillated from the pulsed laser beam oscillation means 81 toward the objective condenser lens 65. The pulse laser beam oscillation means 81 is composed of a pulse laser beam oscillator 811 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 812 attached thereto, for example, having a wavelength of 1064 nm. Pulsed laser light is oscillated. The dichroic mirror 82 is provided between the condensing lens 66 and the objective condensing lens 65 and passes light from the condensing lens 66, but oscillated from the pulse laser beam oscillation means 81 For example, a pulse laser beam having a wavelength of 1064 nm is redirected toward the objective condenser lens 65. Therefore, the pulse laser beam LB oscillated from the pulse laser beam oscillation means 81 is 90-degree-directed converted by the dichroic mirror 82, incident on the objective condenser lens 65, and the objective condenser lens 65 ), And irradiated to the workpiece W held on the chuck table 36. Therefore, the objective condenser lens 65 has a function as an objective condenser lens constituting the laser beam irradiation means 8.

Returning to FIG. 1 and continuing the explanation, the laser processing apparatus 1 in the illustrated embodiment includes a pair of guide rails 423 in which the unit holder 51 is installed in the mounting portion 422 of the movable support base 42. A light collecting point positioning means 53 for moving in the direction perpendicular to the holding surface of the chuck table 36, that is, the light collecting point position adjusting direction (Z axis direction) indicated by the arrow Z along 423 is provided. The condensing point positioning means 53 includes a driving source such as a male screw rod (not shown) provided between a pair of guide rails 423 and 423, and a pulse motor 532 for rotationally driving the male screw rod. Thereafter, the male and female rods (not shown) are driven by the pulse motor 532 to be rotated forward and reverse to move the position detection and laser irradiation unit 5 along the guide rails 423 and 423 in the Z-axis direction. On the other hand, in the illustrated embodiment, the position detection and laser irradiation unit 5 is moved upward by driving the pulse motor 532 forward rotation, and the position detection and laser irradiation unit is driven by driving the pulse motor 532 reverse rotation ( 5) is to be moved downward.

The position detection and laser irradiation unit 5 in the illustrated embodiment detects the position of the light collecting point position adjustment direction (Z-axis direction) of the unit housing 52 constituting the position detection and laser irradiation unit 5. A Z-axis position detection means 54 is provided. The Z-axis direction position detecting means 54 is attached to the unit holder 51 and the linear scale 54a installed parallel to the guide rails 423 and 423, and the linear scale 54a together with the unit holder 51 It consists of a read head (54b) moving along the. In the illustrated embodiment, the read head 54b of the Z-axis direction position detecting means 54 sends a pulse signal of 1 pulse every 0.1 μm to control means described later.

The imaging means 85 is provided at the front end of the unit housing 52 constituting the position detection and laser irradiation unit 5. The imaging means 85 includes, in addition to a normal imaging element (CCD) for imaging with visible light, an infrared illumination means for irradiating infrared light to a workpiece, and an optical system for capturing infrared rays emitted by the infrared illumination means, It consists of an imaging element (infrared CCD) or the like that outputs an electrical signal corresponding to infrared rays captured by the optical system, and sends the captured image signal to control means described later.

The laser processing apparatus 1 in the illustrated embodiment is provided with the control means 9 shown in FIG. 3. The control means 9 is constituted by a computer, a central processing unit (CPU) 91 that performs arithmetic processing according to a control program, a read-only memory (ROM) 92 that stores a control program and the like, which will be described later. A recordable and readable random access memory (RAM) 93, a counter 94, an input interface 95, and an output interface 96 that store data or calculation results of the control map or work piece design values, etc. I have it. In the input interface 95 of the control means 9 configured as described above, the X-axis direction position detection means 374, Y-axis direction position detection means 384, Z-axis direction position detection means 54, and height position detection The detection signal from the line image sensor 71, the imaging means 85, the input means 90, etc. of the means 6 is input. Then, from the output interface 96 of the control means 9, the pulse motor 372, the pulse motor 382, the pulse motor 432, the pulse motor 532, the condensing point position adjustment means 650, The control signal is output to the pulse laser beam oscillator 811 of the laser beam irradiation means 8, the repetition frequency setting means 812, the display means 900, and the like.

The laser processing apparatus 1 in the illustrated embodiment is configured as described above, and its operation will be described below.

4, a perspective view of a semiconductor wafer as a workpiece is shown. The semiconductor wafer 10 shown in FIG. 4 is made of, for example, a silicon wafer having a thickness of 200 µm, and the surface 10a has ICs in a plurality of regions partitioned by a plurality of division scheduled lines 101 formed in a lattice shape. , LSI, and other devices 102 are formed. The semiconductor wafer 10 thus formed is made of a synthetic resin sheet such as polyolefin mounted on an annular frame F as shown in Fig. 5, for example, a surface 10a on a protective tape T having a thickness of 100 µm. The side is adhered (protective tape adhesion process). Therefore, the back surface 10b of the semiconductor wafer 10 is on the upper side.

Using the laser processing apparatus described above, the laser beam is irradiated along the line 101 to be divided of the semiconductor wafer 10, and a modified layer is formed along the line 101 to be divided inside the semiconductor wafer 10. The embodiment of the laser processing to be described will be described. On the other hand, when the modifying layer is formed inside the semiconductor wafer 10, if the thickness of the semiconductor wafer fluctuates, the modifying layer cannot be uniformly formed at a predetermined depth. Therefore, before performing laser processing, the height position of the upper surface of the semiconductor wafer 10 held on the chuck table 36 is measured by the height position detecting means 6 described above.

In order to measure the position of the height of the top surface of the semiconductor wafer 10 held on the chuck table 36, first, of the semiconductor wafer 10 on the chuck table 36 of the laser processing apparatus 1 shown in FIG. 1 described above. The protective tape T is disposed. Then, by operating the suction means (not shown), the semiconductor wafer 10 is sucked and held on the chuck table 36 through the protective tape T (wafer holding process). Therefore, in the semiconductor wafer 10 held on the chuck table 36 via the protective tape T, the back surface 10b is on the upper side. In this way, if the wafer holding process is performed, the chuck table 36 holding the semiconductor wafer 10 by suction is placed under the imaging means 85 by operating the machining transfer means 37.

When the chuck table 36 is located directly under the imaging means 85, an alignment operation is performed by the imaging means 85 and the control means 9 to detect the processing area to be laser-processed on the semiconductor wafer 10. do. That is, the imaging means 85 and the control means 9 are formed of a division scheduled line 101 formed in a predetermined direction of the semiconductor wafer 10 and a semiconductor wafer 10 along the division scheduled line 101. Image processing such as pattern matching for aligning the objective condenser lens 65 of the height position detecting means 6 constituting the position detecting / laser irradiation unit 5 is performed, and alignment of the detection position is performed. . In addition, alignment of the detection position is similarly performed for the division scheduled line 101 formed in a direction orthogonal to a predetermined direction formed on the semiconductor wafer 10. At this time, the surface 10a on which the division scheduled line 101 of the semiconductor wafer 10 is formed is located at the lower side, but as described above, the imaging means 85 uses infrared illumination means and infrared and optical systems for capturing infrared rays. Since an imaging means composed of an imaging element (infrared CCD) or the like for outputting a corresponding electric signal is provided, the division scheduled line 101 can be imaged by transmitting from the back surface 10b.

When alignment is performed as described above, the semiconductor wafer 10 on the chuck table 36 is in a position located at the coordinate position shown in Fig. 6A. 6 (b) shows a state in which the chuck table 36, that is, the line to be divided is rotated 90 degrees from the state shown in FIG. 6 (a).

On the other hand, the transfer start position coordinate value A1 of each division scheduled line 101 formed on the optical device wafer 10 in the state located at the coordinate positions shown in Figs. 6A and 6B. , A2, A3 ... An) and the feed end position coordinate values (B1, B2, B3 ... Bn) and feed start position coordinate values (C1, C2, C3 ... Cn) and feed end position coordinate values ( In D1, D2, D3 ... Dn, the data of the design value is stored in the random access memory (RAM) 93 of the control means 9.

As described above, when the street 101 formed on the semiconductor wafer 10 held on the chuck table 36 is detected and alignment of the detection position is performed, the chuck table 36 is moved to move the FIG. In), the uppermost street 101 is positioned directly below the objective lens 65 of the height position detecting means 6 constituting the position detecting and laser irradiation unit 5. Further, as shown in Fig. 7, the objective lens is the transfer starting position coordinate value A1 (see Fig. 6 (a)), which is one end (left end in Fig. 7) of the street 101 of the semiconductor wafer 10. It is located beneath (65). Then, the height position detecting means 6 is operated, and the chuck table 36 is moved at a feed rate (for example, 200 mm / sec) determined in the direction indicated by the arrow X1 in Fig. 7, and the X-axis direction position detecting means Based on the detection signal from 374, it is moved to the transfer end position coordinate value B1 (height position detection process). As a result, the height position of the upper surface along the uppermost street 101 in FIG. 6 (a) of the semiconductor wafer 10 is measured as described above by the height position detection means 6. This measured height position is stored in the random access memory (RAM) 93 of the control means 9. Then, the control means 9 moves from the start position coordinate value A1 on the top street 101 in the top street 101 in Fig. 6 (a) stored in the random access memory (RAM) 93 to the end position coordinate value. The displacement amount with respect to the reference height position of the height position up to (B1) is obtained, and a height position displacement map shown in Fig. 8 is created and stored in the random access memory (RAM) 93. This height position detection process is performed along all the streets 101 formed on the semiconductor wafer 10, and the height position displacement map is created and stored in a random access memory (RAM) 93.

If the above-described height position detection process has been carried out, according to the height position displacement map obtained the amount of displacement of the measured height position of the semiconductor wafer 10 relative to the reference height position, the condensing point position adjustment means 650 follows and operates. A process of confirming the operation of the condensing point position adjusting means to confirm whether or not is performed. In the operation confirmation step of the condensing point position adjusting means, the detection signal from the X-axis direction position detecting means 374 input to the control means 9 and the height position detecting means when creating the height position displacement map ( In some cases, the height position signal from 6) is not necessarily the signal detected at the same time due to the signal transmission path, etc., and confirm the deviation of this signal, and the response delay of the condensing point position adjusting means 650 To conduct.

The operation confirmation process of the condensing point position adjusting means 650 first moves the chuck table 36 holding the semiconductor wafer 10 on which the height position detection process has been performed, for example in FIG. 6 (a). The street 101 of is placed directly under the objective lens 65 of the height position detecting means 6 constituting the position detecting and laser irradiation unit 5. Then, as shown in Fig. 9, the objective lens is a transfer starting position coordinate value A1 (see Fig. 6 (a)), which is one end (left end in Fig. 9) of the street 101 of the semiconductor wafer 10. It is located beneath (65). Then, the control means 9 operates the focusing point positioning means 53 to position the focusing point position of the objective lens 65 at the reference height position. Next, the control means 9 moves the machining feed means 37 to move the chuck table 36 at a feed speed (for example, 200 mm / sec) determined in the direction indicated by arrow X1 in FIG. 9, The converging point position adjusting means 650 is controlled in response to the displacement amount with respect to the reference height position in the X coordinate of the height position displacement map stored in the random access memory (RAM) 93, and the height position detecting means 6 is used. In operation, the height information detected by the height position detecting means 6 is obtained by correlating with the X coordinate based on the detection signal from the X-axis direction position detecting means 374. Then, the control means 9 obtains the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate, and displays it on the display means 900 as shown in Fig. 10A or 10B.

In the operation confirmation process of the above-mentioned focusing point position adjusting means, the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate displayed on the display means 900 is X in which the height position displacement map is input to the control means 9 The detection signal from the axial position detection means 374 and the height position signal from the height position detection means 6 are created based on the signals detected at the same time, and the operation of the condensing point position adjustment means 650 is also performed. When there is no delay, the operation of the light-converging point position adjusting means 650 properly follows the height position of the semiconductor wafer 10, and as shown in Fig. 10 (a), becomes substantially straight along the X axis. . On the other hand, the height position displacement map is generated based on a signal in which the detection signal from the X-axis direction position detection means 374 input to the control means 9 and the height position signal from the height position detection means 6 are shifted in time. Or, when there is a delay in the operation of the light-converging point position adjusting means 650, the operation of the light-converging point position adjusting means 650 does not properly follow the height position of the semiconductor wafer 10, and is shown in FIG. As shown in), the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate varies greatly. If the fluctuation range of the displacement amount with respect to the reference height position of the height position corresponding to this X coordinate is an allowable range, the control means 9 judges that the control based on the height position displacement map is appropriate and displays it appropriately on the display means 900 . On the other hand, when the fluctuation range of the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate is outside the allowable range, the control means 9 is suitable for the responsiveness of the height position displacement map and / or the converging point position adjustment means 650. It is judged that it is not, and the display means 900 is marked as impossible.

As described above, when it is impossible to display on the display means 900, the operator obtains a correction value corresponding to the fluctuation width of the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate, and performs a correction value detection process. That is, when the operator inputs the correction value detection instruction signal from the input means 90, the control means 9, like the above operation confirmation process, the processing transfer means 37, the height position detection means 6, the condensing point position While operating the adjusting means 650, a shift is generated between the X coordinate in the height position displacement map stored in the random access memory (RAM) 93 and the X coordinate of the chuck table, so that the reference position of the height position is relative to the reference position. The displacement amount of the displacement amount is adjusted to be within the allowable range. Then, the control means 9 determines the amount of displacement (x µm) of the X coordinate when the variation width of the displacement amount with respect to the reference height position of the height position is within the allowable range, as a correction value, and the random access memory (RAM) ( 93) and display on the display means 900.

If the operation confirmation process and the correction value detection process of the condensing point position adjusting means are performed as described above, a modification layer forming process is performed to form a modification layer along the line 101 to be divided inside the semiconductor wafer 10. .

In order to carry out this modified layer formation process, first, the chuck table 36 is moved, and the top line to be divided 101 in FIG. 6 (a) is positioned immediately below the objective condenser lens 65. Then, as shown in Fig. 11 (a), the transfer starting position coordinate value A1 (see Fig. 6 (a)) which is one end of the division scheduled line 101 (the left end in Fig. 11 (a)). ] Is placed directly under the objective condenser lens 65. Then, the converging point P of the pulsed laser beam irradiated from the objective condensing lens 65 constituting the laser beam irradiating means 8 is located at a predetermined depth position from the back surface 10b (upper surface) of the division scheduled line 101. Position it. Next, the laser beam irradiation means 8 is operated to irradiate the semiconductor wafer 10 from the objective lens 65 while irradiating a pulsed laser beam having a transmittance to the semiconductor wafer 10 in the direction indicated by the arrow X1. It moves at a fixed processing feed rate (for example, 200 mm / sec) (modified layer formation process). Then, as shown in Fig. 11B, if the irradiation position of the objective condenser lens 65 reaches the other end of the division scheduled line 101 (the right end in Fig. 11B), the pulse laser beam Is stopped, and movement of the chuck table 36 is stopped. In this modified layer forming process, the control means 9 is based on the height position displacement map in the division scheduled line 101 of the semiconductor wafer 10 stored in the random access memory (RAM) 93, and the light collecting point. By controlling the position adjusting means 650 and moving the objective condensing lens 65 in the Z-axis direction (condensing point position adjusting direction), the line to be divided of the semiconductor wafer 10 as shown in Fig. 11B. It moves in the vertical direction corresponding to the height position of the back surface 10b (top surface) in (101). At this time, when the deviation amount (x µm) (correction value) obtained in the correction value detection step is set, the detection signal from the X-axis direction position detection means 374 is the deviation amount (x µm) (correction value) The corrected value is set as the X coordinate of the chuck table. As a result, inside the optical device wafer 10, as shown in Fig. 11 (b), a modified layer (parallel to the back surface 10b (top surface) at a predetermined depth position from the back surface 10b (top surface)) 110) is formed.

The processing conditions in the modified layer forming step are set as follows, for example.

Light source: LD excitation Q switch Nd: YVO4 pulse laser

Wavelength: 1064 nm

Repetition frequency: 100 kHz

Average power: 0.5 W

Pulse width: 120 ns

Condensing spot diameter: φ1 μm

Processing feed rate: 200 mm / sec

As described above, if the modification layer forming process was performed along all the division scheduled lines 101 extending in the predetermined direction of the semiconductor wafer 10, the chuck table 36 was rotated 90 degrees, with respect to the predetermined direction. The modified layer forming process is performed along each division scheduled line 101 extending in an orthogonal direction. In this way, if the above-described modified layer forming process was performed along all the division scheduled lines 101 formed on the semiconductor wafer 10, the chuck table 36 holding the semiconductor wafer 10 is initially a semiconductor wafer ( 10) is returned to the position where suction is maintained, where suction holding of the semiconductor wafer 10 is released. And the semiconductor wafer 10 is conveyed to the division process by conveying means not shown.

As described above, in the laser processing apparatus 1 in the illustrated embodiment, the control means 9 operates the processing transfer means 37 to move the semiconductor wafer 10 held on the chuck table 36. The X coordinate based on the height measurement value obtained by measuring the height position of the semiconductor wafer 10 by operating the height position detection means 6 while moving in the X-axis direction and the detection signal from the X-axis direction position detection means 374 A random access memory (RAM) 93 serving as a storage means for storing is provided, and the machining transfer means 37 is operated in accordance with a height position displacement map stored in the random access memory (RAM) 93 to operate the chuck table ( 36. The height position detecting means 6 in the X coordinate by controlling the condensing point position adjusting means 650 based on the height measurement value corresponding to the X coordinate while moving the semiconductor wafer 10 held at 36 along the X coordinate By displaying the detected height information on the display means 900, whether or not the light-converging point position adjusting means 650 is operating in accordance with the top surface height position information of the semiconductor wafer 10 held in the chuck table 36. Since it can be confirmed, it is possible to position the light-converging point of the laser beam at an appropriate position, thereby improving processing precision.

As described above, the present invention has been described based on the illustrated embodiment, but the present invention is not limited only to the embodiment, and various modifications are possible within the scope of the spirit of the present invention. For example, in the above-described embodiment, the interference type height position detection means has been exemplified and described as the height position detection means, but the height position detection means is a confocal optical system detection means, a non-focus aberration detection means, a laser displacement meter (triangle method) detection. Sudan and the like can be used.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 2 Stop base
3: Chuck table mechanism 36: Chuck table
37: machining feed means 374: X-axis position detection means
38: first indexing transfer means 4: laser beam irradiation unit support mechanism
42: movable support base 43: second indexing transfer means
5: position detection and laser irradiation unit 6: height position detection means
61: light emitting source 62: first light diverging means
63: correction lens 64: second light diverging means
65: objective condenser lens 650: condensing point position adjustment means
66: condensing lens 67: reflective mirror
68: correction lens 69: diffraction grating
70: condensing lens 71: line image sensor
8: Laser beam irradiation means 81: Pulsed laser beam oscillation means
82: dichroic mirror 9: control means
10: semiconductor wafer

Claims (3)

A laser beam irradiation means having a chuck table having a holding surface for holding a work piece, an objective condensing lens for condensing and irradiating a laser beam onto the work piece held on the chuck table, and a work piece held in the chuck table Height position detecting means for detecting an image height position, condensing point position adjusting means for moving the objective condensing lens in a direction perpendicular to the holding surface of the chuck table (Z-axis direction), the chuck table and the laser beam A machining feed means for relatively machining feed the irradiation means in the machining feed direction (X-axis direction), an X-axis direction position detecting means for detecting the X-axis direction position of the chuck table, and the condensing point position adjusting means and the In the laser processing apparatus including a control means for outputting a control signal to the processing transfer means and the display means,
The control means operates the processing transfer means to move the workpiece held in the chuck table in the X-axis direction while operating the height position detecting means to measure the height position of the workpiece and the height measurement value obtained by X And storage means for storing X coordinates based on the detection signal from the axial position detection means, and operating the machining transfer means to move the workpiece held in the chuck table in the X-axis direction and stored in the storage means. Based on the height measurement value corresponding to the X coordinate, while controlling the condensing point position adjusting means, the displacement amount with respect to the reference height position of the height position corresponding to the X coordinate is displayed on the display means in association with the X coordinate, and the display means When the fluctuation range of the displacement amount corresponding to the displayed X coordinate is within the allowable range, the operation of the laser beam irradiation means is enabled, and when the fluctuation range of the displacement amount corresponding to the X coordinate is outside the allowable range, the laser beam irradiation means Laser processing device characterized in that the operation is disabled. The X coordinate in the displacement amount according to claim 1, wherein the control means operates the processing feed means, the height position detecting means, and the condensing point position adjusting means while the X coordinate stored in the storage means corresponds to the X coordinate stored in the storage means. And, by making a shift between the X coordinates of the chuck table so that the fluctuation range of the displacement amount is within the allowable range, the displacement amount of the X coordinate when the fluctuation range of the displacement amount is within the allowable range is determined as a correction value. Laser processing equipment. delete

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