JP2012094591A - Processing method of veer hole and laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method of a veer hole by which a veer hole reaching a bonding pad can be formed on a substrate of a wafer without drilling the bonding pad, and to provide a laser processing device.SOLUTION: A processing method of a veer hole forms a veer hole reaching a bonding pad by irradiating a wafer with a pulse laser beam from a rear surface of a substrate. In the wafer, a plurality of devices are formed on the surface of the substrate, and the bonding pads are formed on the devices. The processing method of the veer hole comprises: a thickness measuring step of measuring a thickness of a region where the bonding pad for the substrate is formed; and a laser processing hole generating step of forming a laser processing hole on the substrate by irradiating with the pulse laser beam from the rear surface of the substrate of the wafer. The laser processing hole generating step determines a shot number of the pulse laser beam based on the thickness of the substrate measured by the thickness measuring step and the energy per pulse of the pulse laser beam.

Description

  The present invention provides a via hole that forms a via hole that reaches a bonding pad by irradiating a wafer on which a plurality of devices are formed on the surface of the substrate and a bonding pad is formed on the device by irradiating a pulse laser beam from the back side of the substrate. The present invention relates to a processing method and a laser processing apparatus.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor chips.

  In order to reduce the size and increase the functionality of an apparatus, a module structure in which a plurality of devices are stacked and bonding pads provided on the stacked devices are connected has been put into practical use. This module structure has a structure in which a through hole (via hole) is formed at a position where a bonding pad is provided in a semiconductor wafer, and a conductive material such as aluminum connected to the bonding pad is embedded in the via hole. (For example, refer to Patent Document 1.)

  The via hole provided in the semiconductor wafer described above is formed by a drill. However, the via hole provided in the semiconductor wafer has a diameter as small as 90 to 300 μm, and there is a problem that productivity is poor when drilling with a drill.

  In order to solve the above problem, a via hole reaching a bonding pad by irradiating a wafer having a plurality of devices formed on the surface of the substrate and a bonding pad formed on the device by irradiating a pulse laser beam from the back side of the substrate. There has been proposed a method for perforating a wafer to efficiently form the wafer. (For example, see Patent Document 2.)

JP 2003-163323 A JP 2007-67082 A

  Thus, since the thickness of the substrate is not the same in all regions where a plurality of bonding pads are formed, it is formed on the substrate when forming a via hole reaching the bonding pad by irradiating a pulse laser beam from the back side of the substrate. When the formed via hole reaches the bonding pad, it is difficult to stop the irradiation of the pulsed laser beam, and there is a problem that the bonding hole does not penetrate or the via hole does not reach the bonding pad.

  The present invention has been made in view of the above-described facts, and a main technical problem thereof is a via hole processing method and laser capable of forming a via hole reaching the bonding pad on a wafer substrate without making a hole in the bonding pad. It is to provide a processing apparatus.

In order to solve the above main technical problem, according to the present invention, a wafer having a plurality of devices formed on the surface of the substrate and bonding pads formed on the device is irradiated with a pulsed laser beam from the back side of the substrate. A via hole processing method for forming a via hole reaching a bonding pad,
A thickness measuring step for measuring the thickness of the region of the wafer substrate where the bonding pads are formed;
A laser processing hole forming step of forming a laser processing hole in the substrate by irradiating a pulse laser beam from the back side of the wafer substrate;
The laser processing hole forming step determines the number of shots of the pulse laser beam based on the thickness of the substrate measured by the thickness measurement step and the energy per pulse of the pulse laser beam.
A method for processing a via hole is provided.

Further, according to the present invention, a wafer having a plurality of devices formed on the surface of the substrate and a plurality of bonding pads formed on the device is irradiated with a pulse laser beam from the back side of the substrate to reach the bonding pads. A laser processing apparatus for forming a via hole,
A chuck table for holding a wafer, a laser beam irradiation means for irradiating a wafer held on the chuck table with a pulsed laser beam, a thickness measuring means for measuring the thickness of a wafer substrate, and a wafer measured by the thickness measuring means Control means for controlling the laser beam irradiation means based on the thickness of the substrate,
The thickness measuring means measures the thickness of an area where a plurality of bonding pads are formed on the wafer substrate,
The control means sets the number of shots of the pulse laser beam based on the thickness of the region where the plurality of bonding pads of the wafer substrate sent from the thickness measurement means are formed and the energy per pulse of the pulse laser beam. Create a control map, determine the number of shots of the pulse laser beam based on the control map when activating the laser beam irradiation means to irradiate the region where the bonding pad is formed from the back side of the substrate,
A laser processing apparatus is provided.

  In the via hole processing method and laser processing apparatus according to the present invention, the thickness of the region of the wafer substrate where the bonding pads are formed is measured, and the pulse laser beam is based on the measured thickness and the energy per pulse of the pulse laser beam. The number of shots is set, and when the pulse laser beam is irradiated from the back side of the substrate, the set number of shots is irradiated. Can be formed.

The perspective view of the laser processing apparatus comprised according to this invention. The block diagram of a structure of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The top view of the semiconductor wafer as a wafer. FIG. 4 is an enlarged plan view showing a part of the semiconductor wafer shown in FIG. 3. The perspective view which shows the state which affixed the semiconductor wafer shown in FIG. 3 on the surface of the protective tape with which the cyclic | annular flame | frame was mounted | worn. FIG. 4 is an explanatory diagram showing a relationship with coordinates in a state where the semiconductor wafer shown in FIG. 3 is held at a predetermined position of the chuck table of the laser processing apparatus shown in FIG. Explanatory drawing of the thickness measurement process in the processing method of the via hole by this invention implemented with the laser processing apparatus shown in FIG. The thickness data measured in the thickness measurement process in the processing method of a via hole by the present invention are shown. The figure which shows the control map which set the number of shots of the pulse laser beam irradiated to the area | region in which the bonding pad of the wafer board | substrate was formed in the processing method of the via hole by this invention. Explanatory drawing of the drilling process in the processing method of the via hole by this invention implemented with the laser processing apparatus shown in FIG.

  Hereinafter, preferred embodiments of a method for processing a via hole and a laser processing apparatus according to the present invention will be described in more detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus constructed according to the present invention. A laser processing apparatus shown in FIG. 1 includes a stationary base 2 and a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X and holds a workpiece. A laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in an index feed direction (Y-axis direction) indicated by an arrow Y orthogonal to the direction indicated by the arrow X (X-axis direction); The laser beam irradiation unit support mechanism 4 includes a laser beam irradiation unit 5 disposed so as to be movable in the direction indicated by the arrow Z (Z-axis direction).

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

  The first sliding block 32 has a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on its lower surface, and an index feed direction indicated by an arrow Y on its upper surface ( A pair of guide rails 322 and 322 formed in parallel along the (Y-axis direction) are provided. The first sliding block 32 configured in this way is processed by the arrow X along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. It is configured to be movable in the feed direction (X-axis direction). The chuck table mechanism 3 in the illustrated embodiment includes a machining feed means 37 for moving the first sliding block 32 in the machining feed direction (X-axis direction) indicated by the arrow X along the pair of guide rails 31, 31. It has. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. . One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Accordingly, by driving the male screw rod 371 in the forward and reverse directions by the pulse motor 372, the first sliding block 32 is moved along the guide rails 31 and 31 in the machining feed direction (X-axis direction) indicated by the arrow X. .

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

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

  The laser processing apparatus in the illustrated embodiment includes Y-axis direction position detecting means 384 for detecting the indexing processing feed amount of the second sliding block 33, that is, the Y-axis direction position. The Y-axis direction position detecting means 384 moves along the linear scale 384a together with the linear scale 384a disposed along the guide rail 322 and the second sliding block 33. And a reading head 384b. In the illustrated embodiment, the reading head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. The control means described later counts the input pulse signal to detect the index feed amount of the chuck table 36, that is, the position in the Y-axis direction. When the pulse motor 382 is used as the drive source of the first indexing and feeding means 38, the drive table of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 382. The index feed amount, that is, the position in the Y-axis direction can also be detected. Further, when a servo motor is used as the drive source of the first index feed means 38, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means described later, and the control means inputs By counting the number of pulse signals, the index feed amount of the chuck table 36, that is, the position in the Y-axis direction can be detected.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41, 41 arranged in parallel along the indexing feed direction (Y-axis direction) indicated by an arrow Y on the stationary base 2, and the guide rails 41, 41, A movable support base 42 is provided on 41 so as to be movable in the direction indicated by arrow Y. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in parallel in a direction indicated by an arrow Z (Z-axis direction) on one side surface. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment has a second index for moving the movable support base 42 along the pair of guide rails 41 and 41 in the index feed direction (Y-axis direction) indicated by the arrow Y. A feeding means 43 is provided. The second index feed means 43 includes a drive source such as a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a pulse motor 432 for rotationally driving the male screw rod 431. Contains. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. Therefore, the movable support base 42 is moved along the guide rails 41 and 41 in the indexing feed direction (Y-axis direction) indicated by the arrow Y by driving the male screw rod 431 forward and backward by the pulse motor 432. .

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

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

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

  The laser beam irradiation device 52 is oscillated by a cylindrical casing 521 disposed substantially horizontally, a pulse laser beam oscillation means 6 disposed in the casing 521 as shown in FIG. 2, and a pulse laser beam oscillation means 6. Acousto-optic deflection means 7 for deflecting the optical axis of the laser beam in the machining feed direction (X-axis direction), and a collection for irradiating the workpiece held on the chuck table 36 with the pulsed laser beam that has passed through the acousto-optic deflection means 7 An optical device 8 is provided.

  The pulse laser beam oscillating means 6 comprises a pulse laser beam oscillator 61 comprising a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 62 attached thereto. The pulse laser beam oscillator 61 oscillates a pulse laser beam (LB) having a predetermined frequency set by the repetition frequency setting means 62. The repetition frequency setting means 62 sets the repetition frequency of the pulse laser beam oscillated by the pulse laser beam oscillator 61.

  The acoustooptic deflecting means 7 includes an acoustooptic element 71 that deflects the optical axis of the laser beam (LB) oscillated by the laser beam oscillator 6 in the processing feed direction (X-axis direction), and an RF ( radio frequency), an RF amplifier 73 that amplifies the RF power generated by the RF oscillator 72 and applies it to the acoustooptic device 71, and an RF frequency generated by the RF oscillator 72 is adjusted. A deflection angle adjusting means 74 for adjusting the amplitude of the RF generated by the RF oscillator 72, and an output adjusting means 75 for adjusting the amplitude of the RF. The acoustooptic device 71 can adjust the angle of deflecting the optical axis of the laser beam in accordance with the frequency of the applied RF, and adjust the output of the laser beam in accordance with the amplitude of the applied RF. Can do. The deflection angle adjusting means 74 and the output adjusting means 75 are controlled by a control means described later.

  Further, the laser beam irradiation device 52 in the illustrated embodiment absorbs the laser beam deflected by the acoustooptic device 71 as indicated by a broken line in FIG. 2 when RF of a predetermined frequency is applied to the acoustooptic device 71. A laser beam absorbing means 76 is provided.

  The condenser 8 is attached to the tip of the casing 521, and changes the direction of the pulse laser beam deflected by the acousto-optic deflecting means 7 downward, and the direction changing mirror 81 changes the direction. And a condensing lens 82 for condensing the laser beam.

The laser irradiation means 52 in the illustrated embodiment is configured as described above, and the operation thereof will be described below with reference to FIG.
When, for example, a voltage of 5V is applied to the deflection angle adjusting means 74 of the acoustooptic deflecting means 7 from a control means described later, and an RF having a frequency corresponding to 5V is applied to the acoustooptic element 71, the pulsed laser beam oscillating means 6 is applied. The pulse laser beam oscillated from is deflected as indicated by a one-dot chain line in FIG. In addition, when a voltage of, for example, 10 V is applied to the deflection angle adjusting unit 74 from a control unit which will be described later, and an RF having a frequency corresponding to 10 V is applied to the acousto-optic element 71, the pulse laser beam oscillation unit 6 oscillates. The pulse laser beam is deflected as shown by a solid line in FIG. 2, and is collected at a condensing point Pb displaced from the condensing point Pa by a predetermined amount in the processing feed direction (X-axis direction) to the left in FIG. Lighted. On the other hand, when a voltage of, for example, 15V is applied to the deflection angle adjusting unit 74 from a control unit which will be described later, and an RF having a frequency corresponding to 15V is applied to the acoustooptic device 71, the pulse laser beam oscillation unit 6 oscillates. The optical axis of the pulse laser beam is deflected as indicated by a two-dot chain line in FIG. 2, and the condensing point Pc is displaced from the condensing point Pb by a predetermined amount to the left in FIG. 2 in the processing feed direction (X-axis direction). It is focused on. Further, when a voltage of, for example, 0V is applied to the deflection angle adjusting unit 74 of the acoustooptic deflecting unit 7 from a control unit described later, and an RF having a frequency corresponding to 0V is applied to the acoustooptic device 71, pulse laser beam oscillation is performed. The pulse laser beam oscillated from the means 6 is guided to the laser beam absorbing means 76 as shown by a broken line in FIG. As described above, the laser beam deflected by the acoustooptic device 71 is deflected in the processing feed direction (X-axis direction) corresponding to the voltage applied to the deflection angle adjusting means 74.

  Referring back to FIG. 1, the laser processing apparatus in the illustrated embodiment is disposed adjacent to the condenser 8 and has a thickness for measuring the thickness of the workpiece held on the chuck table 36. Measuring means 9 is provided. As the thickness measuring means 9, it is desirable to use a non-contact type thickness measuring instrument such as a commercially available reflection spectroscopic thickness measuring instrument. That is, the reflection spectroscopic thickness measuring instrument irradiates a workpiece with a laser beam having transparency, and obtains the thickness of the workpiece based on the reflected light reflected from the upper and lower surfaces of the workpiece. The thickness measuring means 9 sends a measurement signal to the control means described later.

  Continuing with the description based on FIG. 1, the laser processing apparatus in the illustrated embodiment includes a control means 20. The control means 20 is constituted by a computer, and a central processing unit (CPU) 201 that performs arithmetic processing according to a control program, a read-only memory (ROM) 202 that stores a control program and the like, a control map and a work piece to be described later. A readable / writable random access memory (RAM) 203 that stores design value data, calculation results, and the like, a counter 204, an input interface 205, and an output interface 206 are provided. Detection signals from the X-axis direction position detection unit 374, the Y-axis direction position detection unit 384, the thickness measurement unit 9, the imaging unit 10, and the like are input to the input interface 205 of the control unit 20. A control signal is output from the output interface 206 of the control means 20 to the pulse motor 372, pulse motor 382, pulse motor 432, pulse motor 532, pulse laser beam irradiation means 52, display means 200, and the like.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
FIG. 3 shows a plan view of a semiconductor wafer 30 as a workpiece to be laser processed. In the semiconductor wafer 30 shown in FIG. 3, a plurality of regions are partitioned by a plurality of division lines 301 arranged in a lattice pattern on the surface 300a of the silicon substrate 300, and devices 302 such as ICs and LSIs are formed in the partitioned regions. Each is formed. All the devices 302 have the same configuration. A plurality of bonding pads 303 (303a to 303j) are formed on the surface of the device 302 as shown in FIG. The bonding pads 303 (303a to 303j) are made of aluminum in the illustrated embodiment. In the illustrated embodiment, 303a and 303f, 303b and 303g, 303c and 303h, 303d and 303i, and 303e and 303j have the same position in the X direction. The design value data of the X and Y coordinate values of the bonding pads 303 (303a to 303j) formed in each device 302 is stored in the random access memory (RAM) 203.

An embodiment of laser processing in which a laser processing hole (via hole) is formed in the bonding pad 303 (303a to 303j) of each device 302 formed on the semiconductor wafer 30 using the laser processing apparatus described above will be described.
As shown in FIG. 5, the semiconductor wafer 30 has a surface 300 a adhered to a protective tape 50 made of a synthetic resin sheet such as polyolefin and attached to an annular frame 40. Accordingly, the back surface 300b of the semiconductor wafer 30 is on the upper side. In this way, the semiconductor wafer 30 supported on the annular frame 40 via the protective tape 50 places the protective tape 50 side on the chuck table 36 of the laser processing apparatus shown in FIG. Then, by operating a suction means (not shown), the semiconductor wafer 30 is sucked and held on the chuck table 36 via the protective tape 50. Therefore, the semiconductor wafer 30 is held with the back surface 300b facing upward. The annular frame 40 is fixed by a clamp 362.

  As described above, the chuck table 36 that sucks and holds the semiconductor wafer 30 is positioned directly below the imaging unit 10 by the processing feed unit 37. When the chuck table 36 is positioned immediately below the imaging means 10, the semiconductor wafer 30 on the chuck table 36 is positioned at the coordinate position shown in FIG. In this state, an alignment process is performed to determine whether or not the grid-like division planned lines 301 formed on the semiconductor wafer 30 held on the chuck table 36 are arranged in parallel to the X-axis direction and the Y-axis direction. . That is, the semiconductor wafer 30 held on the chuck table 36 is imaged by the imaging means 10 and image processing such as pattern matching is performed to perform alignment work. At this time, the surface 300a on which the division line 301 of the semiconductor wafer 30 is formed is positioned on the lower side. However, the imaging unit 10 corresponds to the infrared illumination unit, the optical system that captures infrared rays, and infrared rays as described above. Since the image pickup device is provided with an image pickup device (infrared CCD) that outputs an electrical signal, the division planned line 301 can be picked up from the back surface 300 b of the semiconductor wafer 30. Thus, the semiconductor wafer 30 on the chuck table 36 on which the alignment process has been performed is positioned at the coordinate values shown in FIG.

  Next, a thickness detection step of detecting the thickness of each bonding pad 303 (303a to 303j) formed on each device 302 of the silicon substrate 300 of the semiconductor wafer 30 is performed. In the thickness detection step, first, the processing feed means 37 is operated to move the chuck table 36, and the highest level in the device 302 formed in the semiconductor wafer 30 shown in FIG. The coordinate value of the bonding pad 303a formed on the leftmost device 302 in the row E1 is positioned directly below the thickness measuring means 9. The state where the coordinate value of the bonding pad 303a is positioned directly below the thickness measuring means 9 is the state shown in FIG. From the state shown in FIG. 7, the control means 20 operates the thickness measuring means 9 to measure the thickness of the silicon substrate 300 of the semiconductor wafer 30 at the coordinate value of the bonding pad 303a. That is, the thickness measuring means 9 is composed of a reflection spectroscopic thickness measuring device, and irradiates a laser beam having transparency to the silicon substrate 300 of the semiconductor wafer 30 so that the upper surface (back surface) of the silicon substrate 300 of the semiconductor wafer 30 is irradiated. The thickness of the silicon substrate 300 of the semiconductor wafer 30 is measured based on the reflected light reflected from the lower surface (front surface), and a measurement signal is sent to the control means 20. Then, the control unit 20 stores the measured thickness (t) in the random access memory (RAM) 203. When the measurement of the thickness of the silicon substrate 300 at the coordinate value of the bonding pad 303a is started in this way, the chuck table 36 is moved at a predetermined moving speed in the direction indicated by the arrow X1 in FIG. When the coordinate value where the bonding pad 303b adjacent to the bonding pad 303a is located immediately below the thickness measuring means 9, the thickness of the silicon substrate 300 of the semiconductor wafer 30 that operates the thickness measuring means 9 is measured and measured. A signal is sent to the control means 20.

  By performing the thickness detection step of detecting the thickness of each bonding pad 303 (303a to 303j) formed on each device 302 of the silicon substrate 300 of the semiconductor wafer 30 as described above, the control means 20 can be configured as shown in FIG. As shown in FIG. 4, data regarding the thickness (t) of the silicon substrate 300 at the coordinate values where the bonding pads 303 (303a to 303j) are located is created and stored in the random access memory (RAM) 203.

  If data relating to the thickness (t) of the silicon substrate 300 at the coordinate values where the bonding pads 303 (303a to 303j) are located is created, the control means 20 coordinates the coordinates where the bonding pads 303 (303a to 303j) are located. Determine the number of shots of the pulsed laser beam to irradiate the value. The number of shots is obtained based on the processing amount per shot of the pulse laser beam. That is, when the pulse energy of a pulse laser beam for performing a drilling step for drilling a laser processing hole (via hole) described later is 10 μJ, the silicon substrate 300 of the semiconductor wafer 30 is drilled by 1 μm per shot of the pulse laser beam. When the amount of perforations to be processed per shot of the pulse laser beam is determined in this way, the control means 20 causes the silicon substrate 300 at the coordinate value where each bonding pad 303 (303a to 303j) created in the thickness detection step is located. The number of shots of the pulse laser beam corresponding to the thickness (t) is obtained, and a control map is created as shown in FIG. 9 and stored in the random access memory (RAM) 203.

  Next, a drilling step of drilling laser processed holes 304 (via holes) in the bonding pad 303 (303a to 303j) portions formed in each device 302 of the semiconductor wafer 30 is performed. In the drilling step, first, the processing feed means 37 is operated to move the chuck table 36, and the highest level in the device 302 formed in the semiconductor wafer 30 shown in FIG. The coordinate value of the bonding pad 303a formed on the leftmost device 302 in the row E1 is positioned immediately below the condenser 8 of the laser beam irradiation means 52. FIG. 10A shows a state where the coordinate value where the bonding pad 303a is positioned is positioned directly below the light collector 8. FIG. When the control means 20 controls the machining feed means 37 so as to feed the chuck table 36 at a predetermined moving speed in the direction indicated by the arrow X1 in FIG. 10 (a) from the state shown in FIG. At the same time, the laser beam irradiating means 52 is operated to irradiate a pulsed laser beam from the condenser 8. The condensing point P of the laser beam irradiated from the condenser 8 is set near the upper surface of the semiconductor wafer 30. At this time, the control means 20 outputs control signals for controlling the deflection angle adjusting means 74 and the output adjusting means 75 of the acousto-optic deflecting means 7 based on the detection signals from the reading head 374b of the X-axis direction position detecting means 374. Output.

  On the other hand, the RF oscillator 72 outputs RF corresponding to the control signals from the deflection angle adjusting means 74 and the output adjusting means 75. The RF power output from the RF oscillator 72 is amplified by the RF amplifier 73 and applied to the acoustooptic device 71. As a result, the acoustooptic device 71 deflects the optical axis of the pulse laser beam oscillated from the pulse laser beam oscillating means 6 in a range from the position indicated by the one-dot chain line to the position indicated by the two-dot difference line in FIG. The output of the pulse laser beam oscillated from the oscillation means 6 is adjusted. As a result, a pulse laser beam with a predetermined output can be irradiated to the coordinate value where the bonding pad 303a is located.

An example of processing conditions in the drilling step will be described.
Light source: LD excitation Q switch Nd: YVO4
Wavelength: 355nm
Pulse energy: 10μJ
Condensing spot diameter: φ70μm

  When performing the above-described drilling process, the control means 20 deflects the acousto-optic deflection means 7 if the number of shots of the pulsed laser beam at the coordinate value where the bonding pad 303 performing the drilling process is reached. A voltage of 0 V is applied to the angle adjusting means 74, an RF having a frequency corresponding to 0 V is applied to the acoustooptic device 71, and the laser beam absorbing means as shown by the broken line in FIG. Lead to 76. Therefore, the semiconductor wafer 30 held on the chuck table 36 is not irradiated with the pulse laser beam.

  On the other hand, the control means 20 receives a detection signal from the reading head 374 b of the X-axis direction position detection means 374 and counts this detection signal by the counter 204. When the count value by the counter 204 reaches the coordinate value at which the next bonding pad 303 is located, the control means 20 controls the laser beam irradiation means 52 to carry out the perforation process. Thereafter, every time the count value of the counter 204 reaches the coordinate value at which the bonding pad 303 is located, the control means 20 operates the laser beam irradiation means 52 to carry out the drilling step. Then, as shown in FIG. 10B, the perforation process is performed at the position of the rightmost electrode 303e in FIG. 10B in the bonding pad 303 formed in the rightmost device 302 of the E1 row of the semiconductor wafer 30. When the operation has been carried out, the operation of the machining feed means 37 is stopped and the movement of the chuck table 36 is stopped. As a result, a processed hole 304 reaching the bonding pad 303 is formed in the silicon substrate 300 of the semiconductor wafer 30 as shown in FIG. Thus, in the above-described perforating process, the pulse laser beam having the number of shots corresponding to the thickness (t) of the silicon substrate 300 is irradiated, so that the silicon substrate 300 of the semiconductor wafer 30 is applied to the silicon substrate 300 as shown in FIG. A processing hole 304 reaching the bonding pad 303 can be formed without melting the bonding pad 303. As described above, the perforating process is performed on all bonding pads 303 formed on the silicon substrate 300 of the semiconductor wafer 30.

2: Stationary base 3: Chuck table mechanism 31: Guide rail 36: Chuck table 37: Processing feed means 374: X-axis direction position detection means 38: First index feed means 384: Y-axis direction position detection means 4: Laser beam Irradiation unit support mechanism 41: guide rail 42: movable support base 43: second index feeding means 5: laser beam irradiation unit 51: unit holder 52: laser beam irradiation means 6: pulse laser beam oscillation means 61: pulse laser beam oscillator 62: repetition Frequency setting means 7: Acoustooptic deflecting means 71: Acoustooptic element 72: RF oscillator 73: RF amplifier 74: Deflection angle adjusting means 75: Output adjusting means 76: Laser beam absorbing means 8: Condenser 9: Thickness measuring means 10: Imaging means 20: Control means 30: Semiconductor wafer 301: Split planned line 302: Device 303: bonding pad 304: laser processed hole 40: an annular frame 50: Protection Tape

Claims (2)

A via hole processing method that forms a via hole reaching a bonding pad by irradiating a wafer on which a plurality of devices are formed on the surface of the substrate and a bonding pad is formed on the device by irradiating a pulse laser beam from the back side of the substrate. And
A thickness measuring step for measuring the thickness of the area where the bonding pads of the wafer substrate are formed;
A laser processing hole forming step of forming a laser processing hole in the substrate by irradiating a pulse laser beam from the back side of the wafer substrate;
The laser processing hole forming step determines the number of shots of the pulse laser beam based on the thickness of the substrate measured by the thickness measurement step and the energy per pulse of the pulse laser beam.
A method for processing a via hole. Laser processing equipment that forms a via hole that reaches a bonding pad by irradiating a wafer with multiple devices formed on the surface of the substrate and multiple bonding pads formed on the device by irradiating a pulse laser beam from the back side of the substrate. There,
A chuck table for holding a wafer, a laser beam irradiation means for irradiating a wafer held on the chuck table with a pulsed laser beam, a thickness measuring means for measuring the thickness of a wafer substrate, and a wafer measured by the thickness measuring means Control means for controlling the laser beam irradiation means based on the thickness of the substrate,
The thickness measuring means measures the thickness of a region where a plurality of bonding pads are formed on a wafer substrate,
The control means is a control in which the number of shots of the pulse laser beam is set based on the thickness of the region where the plurality of bonding pads are formed on the wafer substrate sent from the thickness measuring means and the energy per pulse of the pulse laser beam. A map is created, and the number of shots of the pulse laser beam is determined based on the control map when the laser beam irradiation means is operated to irradiate the region where the bonding pad is formed from the back side of the substrate.
Laser processing equipment characterized by that.

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