KR20130103357A - Laser machining method and laser machining apparatus - Google Patents

Abstract

PURPOSE: A laser process method and a laser process apparatus are provided to form, on a workpiece on which a first member formed by a first material and a second member formed by a second material are connected, a laser process hole through which a laser beam approach from a first member to a second member. CONSTITUTION: A laser process method comprises the following steps of: detecting the wavelength of plasma generated by a laser beam emitted on a first member and a second member; continuing the emission of pulse laser beam with a first output when only the plasma light with the wavelength of a first member is detected; and stopping the continued emission after the determined shot-emission with the pulse laser beam with a second output higher than the first output. A first material forming the first member contains lithium tantalite. In the first output, the energy per one pulse is set as 40 μj. In the second output, the energy per one pulse is set as 80 μj.

Description

LASER MACHINING METHOD AND LASER MACHINING APPARATUS}

The present invention provides a laser processing method and a laser for forming a laser processing hole that reaches a second member from a first member in a workpiece to which a first member formed of a first material and a second member formed of a second material are connected. It relates to a processing apparatus.

In a semiconductor device manufacturing process, a plurality of regions are defined by a line to be divided, which is called a street arranged in a lattice pattern on the surface of a semiconductor wafer which is substantially a disk, and devices such as ICs and LSIs are formed in the divided regions. Subsequently, the semiconductor wafer is cut along the street to divide the region where the device is formed to manufacture individual semiconductor chips.

A module structure in which a plurality of devices are stacked and a bonding pad provided in a stacked device is connected is put to practical use in order to make the device more compact and highly functional. This module structure is a structure in which a through hole (via hole) is formed at a point 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 through hole (via hole) (for example, a patent document). 1).

The through hole (via hole) provided in the semiconductor wafer mentioned above is formed by the drill. By the way, the through hole (via hole) formed in the semiconductor wafer has a problem that the diameter is small (90 micrometers-300 micrometers), and the drilling by a drill does not have good productivity.

In order to solve the above problem, a plurality of devices are formed on the substrate surface and a bonding pad is formed on the device, and via holes that reach the bonding pads by irradiating a pulsed laser beam from the back side of the substrate are efficiently formed. The punching method of the said wafer is proposed (for example, refer patent document 2).

In addition, when the via laser beam is irradiated from the back surface side of the substrate to form a via hole reaching the bonding pad, the material is converted into plasma by irradiation of the laser beam, and the laser is detected by detecting a spectrum inherent in the material emitted by the plasma. The laser processing apparatus which determines that the light beam reached the bonding pad containing a metal is proposed (for example, refer patent document 3).

Patent Document 1: JP-A-2003-163323 Patent Document 2: JP-A-2007-67082 Patent Document 3: Japanese Unexamined Patent Publication No. 2009-125756

The wavelength of the pulsed laser beam has a low absorption rate with respect to the metal forming the bonding pad, and a wavelength having a high absorption rate is selected for a substrate material such as silicon or lithium tantalate forming the substrate. When forming via holes reaching the bonding pads by irradiating the pulsed laser beams, when the via holes formed in the substrate reach the bonding pads and the pulsed laser beams are irradiated to the bonding pads, the bonding pads containing metal melt and scatter, and the via holes are formed. There is a problem that the fine particles of the metal adhere to the inner wall of the lowering of the device quality.

This invention is made | formed in view of the said fact, The main technical subject is the 1st member from the 2nd member to the to-be-processed object to which the 1st member formed by the 1st material and the 2nd member formed by the 2nd material were connected. It is providing the laser processing method and laser processing apparatus which can suppress that the microparticles | fine-particles of the 2nd material which forms a 2nd member adhere to the inner wall of a laser processing hole at the time of forming the reaching laser processing hole.

In order to solve the said main technical subject, according to this invention, the laser which reaches | attains the 2nd member from a 1st member to the to-be-worked object to which the 1st member formed by the 1st material and the 2nd member formed by the 2nd material were connected. As a laser processing method for forming a processing hole,

Detecting the wavelength of the plasma generated by irradiating the laser beam to the first member and the second member, and continuing to irradiate the pulsed laser beam having the first output when only the plasma light having the wavelength of the first member is detected. When the plasma light having the wavelength of the second member is detected, the laser processing method is stopped after irradiating a predetermined shot with a pulsed laser beam having a second output higher than the first output.

The first material forming the first member is made of lithium tantalate, the first output is set to 40 μJ of energy per pulse, and the second output is set to 80 μJ of energy per pulse.

Moreover, according to this invention, it is equipped with the workpiece holding means which hold | maintains a workpiece, and the laser beam irradiation means which irradiates a laser beam to the workpiece hold | maintained by this workpiece holding means, This laser beam irradiation means is a laser beam Laser beam oscillation means for oscillating the light source, output adjustment means for adjusting the output of the laser beam oscillated by the laser beam oscillation means, and concentrating the laser beam whose output is adjusted by this output adjustment means to hold the workpiece. A laser processing apparatus comprising: a light collector for irradiating a workpiece held in the

Plasma detection means for detecting a wavelength of plasma generated by irradiating a workpiece with laser beam from the laser beam irradiation means, and control means for controlling the laser beam irradiation means based on a detection signal from the plasma detection means. And

The plasma detecting means includes: a beam splitter for splitting plasma light into a first path and a second path, a first band pass filter disposed in the first path and passing only a wavelength of a plasma emitted by the first material; A first photodetector that receives the light passing through the one band pass filter and outputs a light intensity signal to the control means; and a second which is disposed in the second path and passes only the wavelength of the plasma emitted by the second material. A band pass filter and a second photo detector for receiving light passing through the second band pass filter and outputting a light intensity signal to the control means;

The control means is configured to operate the laser beam irradiation means to irradiate a workpiece with a pulsed laser beam and perform laser processing that reaches the second member from the first member of the workpiece. 2, based on the light intensity signal output from the photodetector, when the light intensity signal is output only from the first photodetector, the output adjusting means is controlled to be the first output to continue irradiation of the pulsed laser beam, and When the light intensity signal is output from the second photodetector, controlling the output adjusting means so as to have a second output higher than the first output so as to control the laser beam irradiation means to stop after a predetermined shot irradiation of the pulsed laser beam. A laser processing apparatus is provided.

In the laser processing method of forming the laser processing hole which reaches the 2nd member from a 1st member in the to-be-processed object to which the 1st member formed by the 1st material which concerns on this invention and the 2nd member formed by the 2nd material were connected, Detecting the wavelength of the plasma generated by irradiating the laser beam to the first member and the second member, and continuing to irradiate the pulsed laser beam having the first output when only the plasma light having the wavelength of the first member is detected. When the plasma light having the wavelength of the second member is detected, the pulse laser beam having the first output is stopped because the pulse laser beam having the second output higher than the first output is stopped after a predetermined shot is irradiated. Even if the second member melts and scatters by being irradiated to, and the fine particles of the second member adhere to the inner wall of the laser processing hole formed in the first member, When the laser beam reaches the second member, the output of the pulsed laser beam is changed to a second output higher than the first output, so that the fine particles of the second member attached to the inner wall of the laser processing hole are blown off and released to the outside. As a result, it can suppress that the microparticles | fine-particles of a 2nd member adhere to the inner wall of a laser processing hole.

Moreover, the laser processing apparatus which concerns on this invention WHEREIN: The said plasma detection means which detects the wavelength of the plasma which generate | occur | produces by irradiating a workpiece with a laser beam from a laser beam irradiation means, and based on the detection signal from a plasma detection means, And a control means for controlling the laser beam irradiation means, wherein the plasma detection means includes only a beam splitter for splitting the plasma light into the first path and the second path, and the wavelength of the plasma disposed in the first path and emitted by the first material. A first band pass filter through which the light passes through the first band pass filter, a first photo detector that receives the light passing through the first band pass filter, and outputs a light intensity signal to the control means, and a wavelength of plasma disposed in the second path and emitted by the second material A second band pass filter passing through the bay and light passing through the second band pass filter to receive the light intensity signal; And a second photodetector for outputting to the means, wherein the control means operates the laser beam irradiation means to irradiate the workpiece with the pulsed laser beam and to perform laser processing that reaches the second member from the first member of the workpiece. In this case, based on the light intensity signals output from the first photodetector and the second photodetector, when the light intensity signal is output only from the first photodetector, the output adjustment means is controlled so as to be the first output so that the pulsed laser beam The laser beam irradiation means is controlled so that the output adjustment means is controlled so as to have a second output higher than the first output when the light intensity signal is output from the second photodetector and stops after a predetermined shot irradiation of the pulsed laser beam. In order to control, the second member is melted and irradiated by the pulsed laser beam having the first output to the second member. Even if the fine particles of the second member adhere to the inner wall of the laser processing hole formed in the first member, if the pulse laser beam reaches the second member, the output of the pulse laser beam is changed to a second output higher than the first output. Since it irradiates, the microparticles | fine-particles of the 2nd member adhering to the inner wall of a laser processing hole are blown off and discharged to the outside, As a result, it can suppress that the microparticles | fine-particles of a 2nd member adhere to the inner wall of a laser processing hole.

1 is a perspective view of a laser machining apparatus constructed in accordance with the present invention;
FIG. 2 is a block diagram of a configuration of laser beam irradiation means equipped in the laser processing apparatus shown in FIG. 1. FIG.
FIG. 3 is a block diagram showing the configuration of a plasma detection means equipped in the laser processing apparatus shown in FIG. 1. FIG.
FIG. 4 is a block diagram showing the configuration of the control means of the laser processing apparatus shown in FIG. 1. FIG.
5 is a plan view of a semiconductor wafer as a workpiece.
FIG. 6 is an enlarged plan view of a part of the semiconductor wafer illustrated in FIG. 5. FIG.
FIG. 7 is a perspective view showing a state in which the semiconductor wafer shown in FIG. 5 is bonded to a surface of a protective tape attached to an annular frame. FIG.
FIG. 8 is an explanatory diagram showing a relationship between coordinates in a state where the semiconductor wafer shown in FIG. 5 is held at a predetermined position of a chuck table of the laser processing apparatus shown in FIG. 1.
9 is an explanatory diagram of a drilling step performed by the laser processing apparatus shown in FIG. 1.
10 is an explanatory diagram of a drilling step performed by the laser processing apparatus shown in FIG. 1.
FIG. 11 is a view illustrating plasma generated when a pulsed laser beam is irradiated to a bonding pad including copper and an output voltage of a first photodetector for detecting light intensity of a plasma generated when a pulsed laser beam is irradiated onto a lithium tantalate substrate. Diagram showing an output voltage of a second photodetector for detecting light intensity.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of the laser processing method and laser processing apparatus which concern on this invention is described in detail with reference to an accompanying drawing.

1 shows a perspective view of a laser machining apparatus constructed in accordance with the present invention. The laser processing apparatus 1 shown in FIG. 1 is arrange | positioned so that a movable base 2 and this stop base 2 can be moved to the processing feed direction (X-axis direction) shown by the arrow X are to be processed. Laser beam irradiation unit support mechanism (4) disposed on the chuck table mechanism (3) for holding a cylinder and movable in the indexing feed direction (Y-axis direction) indicated by an arrow Y orthogonal to the X-axis direction on the stationary base (2). And the laser beam irradiation unit 5 disposed in the laser beam irradiation unit support mechanism 4 so as to be movable in the condensing point position adjusting direction (Z-axis direction) indicated by the arrow Z.

The chuck table mechanism 3 has a pair of guide rails 31 and 31 arranged in parallel on the stationary base 2 along the X-axis direction, and on the guide rails 31 and 31 in the X-axis direction. The first sliding block 32 arranged to be movable in the direction of the movement, the second sliding block 33 arranged to be movable in the Y-axis direction on the first sliding block 32, and the second sliding block 33. ), A cover table 35 supported by the cylindrical member 34, and a chuck table 36 as a work holding means. The chuck table 36 has an adsorption chuck 361 formed of a porous material, and is held on the adsorption chuck 361 by suction means not shown, for example, a disk-shaped semiconductor wafer that is a workpiece. The chuck table 36 configured in this way is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. Moreover, the clamp 362 for fixing the annular frame mentioned later is arrange | positioned at the chuck table 36. As shown in FIG.

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 a lower surface thereof, and has a Y-axis direction on the upper surface thereof. A pair of guide rails 322 and 322 formed in parallel are provided. The 1st sliding block 32 comprised in this way is X along a pair of guide rails 31 and 31 by fitting the guide grooves 321 and 321 to a pair of guide rails 31 and 31. FIG. It is comprised so that a movement to an axial direction is possible. The chuck table mechanism 3 in the illustrated embodiment is an X-axis direction moving means (process feed means) for moving the first sliding block 32 along the pair of guide rails 31, 31 in the X-axis direction. (37)]. The processing conveying means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, a pulse motor 372 for rotationally driving the male screw rod 371, and the like. It includes the driving source of. One end of the male thread rod 371 is rotatably supported by a bearing block 373 fixed to the stop base 2, and the other end thereof is electrically connected to an output shaft of the pulse motor 372. have. The male screw rod 371 is screwed into a through female screw hole formed in a female screw block (not shown) provided to protrude from the lower surface of the central portion of the first sliding block 32. Accordingly, the first sliding block 32 is moved in the X-axis direction along the guide rails 31 and 31 by driving the external thread rod 371 forward and reverse rotation by the pulse motor 372.

The laser processing apparatus in the illustrated embodiment includes an 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 the linear scale 374a together with the first sliding block 32 disposed on the first sliding block 32. And a reading head 374b that moves along. In the illustrated embodiment, the leading head 374b of the X-axis direction position detecting means 374 sends a pulse signal of one pulse every 1 μm to a control means described later. The control means, which will be described later, detects the position of the chuck table 36 in the X-axis direction by counting the input pulse signals. In addition, when the pulse motor 372 is used as a drive source of the said process feed means 37, the drive pulse of the control means mentioned later which outputs a drive signal to the pulse motor 372 is counted, The machining feed amount, that is, the position in the X-axis direction may be detected. In addition, when a servo motor is used as a drive source of the said process feed means 37, the pulse signal output by the rotary encoder which detects the rotation speed of a servo motor is sent to the control means mentioned later, and the pulse signal input by the control means is sent. By counting, the machining feed amount of the chuck table 36, that is, the position in the X-axis direction can be detected.

The second sliding block 33 has a pair of guide grooves 331 and 331 fitting to a pair of guide rails 322 and 322 provided on an upper surface of the first sliding block 32 on a lower surface thereof. It is formed, and it is comprised so that a movement to a Y-axis direction by fitting these guide grooves 331,331 to a pair of guide rails 322,322 is carried out. 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 in the first sliding block 32. 1st Y-axis direction moving means (1st indexing feed means 38) is provided. The first indexing transfer means 38 includes 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. Drive sources such as One end of the male thread rod 381 is rotatably supported by a bearing block 383 fixed to an upper surface of the first sliding block 32, and the other end thereof is electrically connected to an output shaft of the pulse motor 382. It is. The male screw rod 381 is screwed into a through female screw hole formed in a female screw block (not shown) provided to protrude from the lower surface of the center portion of the second sliding block 33. Therefore, the second sliding block 33 is moved in the Y-axis direction along the guide rails 322 and 322 by driving the external thread rod 381 forward and reverse rotation by the pulse motor 382.

The laser processing apparatus in the illustrated embodiment includes a Y-axis direction position detecting unit 384 for detecting the indexing feed amount of the second sliding block 33, that is, the Y-axis direction position. The Y-axis direction position detecting means 384 includes a linear scale 384a disposed along the guide rail 322 and the second sliding block 33 and the linear scale 3 together with the second sliding block 33. And a leading head 384b moving along 384a. In the illustrated embodiment, the leading head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of one pulse every 1 μm to a control means described later. The control means described later detects the indexing feed amount of the chuck table 36, that is, the position in the Y-axis direction, by counting the input pulse signal. In addition, when the pulse motor 382 is used as a drive source of the said 1st indexing feed means 38, the chuck table by counting the drive pulse of the control means mentioned later which outputs a drive signal to the pulse motor 382 The indexing feed amount of 36, that is, the position in the Y-axis direction may be detected. When a servo motor is used as the drive source of the first indexing transfer means 38, a pulse signal output by a rotary encoder detecting the rotational speed of the servo motor is sent to a control means to be described later, and the pulse input by the control means. By counting the signals, the indexing feed amount of the chuck table 36, i.e., the position in the Y-axis direction, can be detected.

The laser beam irradiation unit support mechanism 4 is provided on a pair of guide rails 41 and 41 arranged in parallel on the stationary base 2 along the Y-axis direction, and on the guide rails 41 and 41. The movable support base 42 arrange | positioned so that a movement to the direction shown by the arrow Y is provided. The movable support base 42 includes a movable support portion 421 disposed on the guide rails 41 and 41 so as to be movable, 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 are provided in one side in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes second Y-axis direction moving means for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. [Second Indexing Feeder 43] is provided. The second indexing feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41 and 41 and a pulse motor 432 for rotationally driving the male screw rod 431. Drive sources such as The male screw rod 431 is rotatably supported by a bearing block (not shown), one end of which is fixed to the stationary base 2, and the other end thereof is electrically 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 to protrude from the lower surface of the center portion of the movable support portion 421 constituting the movable support base 42. For this reason, the movable support base 42 is moved to the Y-axis direction along the guide rails 41 and 41 by driving the external thread rod 431 forward rotation and reverse rotation 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 guide grooves 511 and 511 which are slidably fitted to the pair of guide rails 423 and 423 provided in the mounting portion 422. By fitting the grooves 511, 511 to the guide rails 423, 423, they are supported to be movable in the Z-axis direction.

The laser beam irradiation unit 5 in the illustrated embodiment is a Z-axis movement means (condensing point position adjustment) for moving the unit holder 51 along the pair of guide rails 423, 423 in the Z-axis direction. Means (53). The light collecting point position adjusting means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a driving source such as a pulse motor 532 for rotationally driving the male screw rod. The unit holder 51 and the laser beam irradiation means 52 are guided along the guide rails 423 and 423 by driving the male screw rod (not shown) by the pulse motor 532. Will move in the axial direction. In addition, in the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 532 forward rotation, and the laser beam irradiation means 52 is driven by reverse rotation driving the pulse motor 532. ) To move downward.

The laser beam irradiation means 52 includes a cylindrical casing 521 substantially horizontally arranged, a pulsed laser beam oscillation means 6 disposed in the casing 521 as shown in FIG. 2, and a pulse. The laser beam oscillation means 6 has passed the acoustooptic deflection means 7 as an optical deflection means for deflecting the optical axis of the laser beam oscillated in the processing feed direction (X-axis direction), and this acoustooptical deflection means 7 The condenser 8 which irradiates the workpiece W hold | maintained by the said chuck table 36 with the pulse laser beam is provided.

The said pulse laser beam oscillation means 6 is comprised from the pulse laser beam oscillator 61 containing a YAG laser oscillator or a YVO4 laser oscillator, and the repetition frequency setting means 62 attached to this. The pulse laser beam oscillator 61 oscillates the pulse laser beam LB of 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 pulse laser beam oscillator 61 and the repetition frequency setting means 62 of these pulse laser beam oscillation means 6 are controlled by the control means mentioned later.

The acoustooptical deflection means 7 includes an acoustooptical element 71 which deflects the optical axis of the pulsed laser beam LB oscillated by the pulsed laser beam oscillation means 6 in the processing feed direction (X-axis direction), and An RF oscillator 72 that generates an RF (radio frequency) applied to the acoustooptical device 71, and an RF that amplifies the power of the RF generated by the RF oscillator 72 and applies it to the acoustooptical device 71. Amplifier 73, deflection angle adjusting means 74 for adjusting the frequency of the RF generated by the RF oscillator 72, and output adjusting means 75 for adjusting the amplitude of the RF generated by the RF oscillator 72 ). The acoustooptical device 71 may adjust an angle of deflecting the optical axis of the laser beam in response to the frequency of the RF applied, and may adjust the output of the laser beam in response to the amplitude of the RF applied. As the optical deflection means, an electro-optical deflection means using an electro-optical element may be used instead of the acoustooptic deflection means 7. The deflection angle adjusting means 74 and the output adjusting means 75 described above are controlled by the control means described later.

In addition, the laser beam irradiation means 52 in the illustrated embodiment, when RF of a predetermined frequency is applied to the acousto-optic element 71, as shown by the broken line in FIG. 2, the acoustooptical element 71. The laser beam absorbing means 76 for absorbing the laser beam deflected by the laser beam is provided.

The condenser 8 is attached to the front end of the casing 521, and has a direction changing mirror 81 for converting the pulsed laser beam deflected by the acousto-optical deflection means 7 downward, and this direction changing mirror. A condensing lens 82 including a telecentric lens for condensing the laser beam converted by direction 81 is provided.

The laser beam irradiation means 52 in the illustrated embodiment is configured as described above, and the operation thereof will be described below with reference to FIG. 2.

When a voltage of, for example, 5 V is applied to the deflection angle adjusting means 74 of the acoustooptical deflection means 7, and an RF of a frequency corresponding to 5 V is applied to the acoustooptical element 71, The pulsed laser beam oscillated from the pulsed laser beam oscillation means 6 has its optical axis deflected as shown by the dashed-dotted line in FIG. In addition, when the voltage of 10 V is applied to the deflection angle adjusting means 74 from the control means described later, and the RF of the frequency corresponding to 10 V is applied to the acousto-optic element 71, pulsed laser beam oscillation means. The pulsed laser beam oscillated from (6) has its optical axis deflected as shown by a solid line in FIG. 2, and is a predetermined amount from the condensing point Pa to the left in FIG. 2 in the processing feed direction (X-axis direction). The light is focused on the displaced light collecting point Pb. On the other hand, when a voltage of, for example, 15 V is applied to the deflection angle adjusting means 74, and RF of a frequency corresponding to 15 V is applied to the acousto-optic element 71, pulsed laser beam oscillation means. The pulsed laser beam oscillated from (6) has its optical axis deflected as shown by the dashed-dotted line in FIG. 2, and is moved from the condensing point Pb to the left side in FIG. 2 in the processing feed direction (X-axis direction). The light is collected at the light collecting point Pc displaced by a predetermined amount. In addition, a voltage of, for example, 0 V is applied to the deflection angle adjusting means 74 of the acoustooptic deflection means 7, and RF of a frequency corresponding to 0 V is applied to the acoustooptical element 71. In this case, the pulsed laser beam oscillated from the pulsed laser beam oscillation means 6 is guided to the laser beam absorbing means 76 as shown by the broken line in FIG. 2. In this way, the laser beam deflected by the acoustooptical element 71 is deflected in the processing feed direction (X-axis direction) corresponding to the voltage applied to the deflection angle adjusting means 74.

With continued description with reference to FIG. 1 again, the laser processing apparatus in the illustrated embodiment is attached to the casing 521 of the laser beam irradiation means 52 constituting the laser beam irradiation unit 5, and the laser beam The plasma detection means 9 which detects the plasma which generate | occur | produces by irradiating a workpiece with a laser beam from the irradiation means 52 is provided. As shown in FIG. 3, the plasma detection means 9 is irradiated with the workpiece W held by the chuck table 36 by the laser beam irradiated from the light collector 8 of the laser beam irradiation means 52. Plasma light receiving means 91 for receiving the plasma generated by the light and the beam splitter 92 for splitting the plasma light received by the plasma light receiving means 91 into the first optical path 92a and the second optical path 92b. ) And a first band pass filter 93 disposed in the first optical path 92a and having a wavelength passing only light having a first set wavelength (the wavelength emitted by the first material forming the first member of the workpiece described later). A first photodetector 94 which receives the light passing through the first band pass filter 93 and outputs a light intensity signal, a direction changing mirror 95 disposed on the second optical path 92b, The wavelength of the plasma light direction-converted by this direction conversion mirror 95 is the second set wavelength (the blood A second band pass filter 196 that passes only light of a wavelength emitted by a second material forming a second member of water and light passing through the second band pass filter 96 to output a light intensity signal; The second photodetector 97 is provided. The plasma light receiving means 91 includes a condenser lens 911 and a lens case 912 for accommodating the condenser lens 911, and the lens case 912 is irradiated with a laser beam as shown in FIG. 1. It is attached to the casing 521 of the means 52. As shown in FIG. 1, the angle adjusting knob 913 is disposed in the lens case 912, so that the installation angle of the condenser lens 911 can be adjusted. In the illustrated embodiment, the first band pass filter 93 is configured to pass light having a wavelength in the range of 660 nm to 680 nm in order to pass only the wavelength (670 nm) of lithium tantalate plasma light. . In the illustrated embodiment, the second band pass filter 96 allows light having a wavelength in the range of 500 nm to 540 nm to pass only the wavelength (515 mm) of copper plasma light. The plasma detection means 9 in the illustrated embodiment is configured as described above, and the first photodetector 94 and the second band pass filter 96 that receive light passing through the first band pass filter 93. The second photodetector 97 which has received the light passing through) outputs a voltage signal corresponding to the intensity of the received light to the control means described later.

Referring to FIG. 1 again, the laser processing apparatus in the illustrated embodiment is arranged at the front end of the casing 521 and picks up the processing region to be laser processed by the laser beam irradiation means 52. An imaging means 11 is provided. This imaging means 11 includes an infrared illuminating means for irradiating infrared rays to a workpiece, in addition to a normal imaging element (CCD) for imaging with visible light, an optical system for capturing infrared rays irradiated by the infrared illuminating means, It consists of an image pick-up element (infrared CCD) etc. which output the electric signal corresponding to the infrared ray captured by this optical system, and sends the picked-up image signal to the control means mentioned later.

The laser processing apparatus in the illustrated embodiment includes the control means 20 shown in FIG. 4. The control means 20 is comprised by the computer, The central processing unit (CPU) 201 which performs arithmetic processing according to a control program, the read-only memory (ROM) 202 which stores a control program, etc., mentioned later A recordable and readable random access memory (RAM) 203, a counter 204, an input interface 205, and an output interface 206 for storing control maps and design data of a workpiece, calculation results, and the like, Equipped. In the input interface 205 of the control means 20, the X-axis direction position detecting means 374, the Y-axis direction detecting means 384, the first photodetector 94 and the first of the plasma detecting means 9 are formed. 2 The detection signal from the photodetector 97, the imaging means 11, etc. is input. The pulse motor 372, the pulse motor 382, the pulse motor 432, the pulse motor 532, and the laser beam irradiation means 52 are configured from the output interface 206 of the control means 20. Control the pulse laser beam oscillator 61 of the pulse laser beam oscillation means 6, the repetition frequency setting means 62, and the deflection angle adjusting means 74 of the acoustooptical deflection means 7, the output adjusting means 75 and the like. Output the signal. On the other hand, the random access memory (RAM) 203 has a first storage area 203a for storing the relationship between the material forming the workpiece and the wavelength of the plasma, or a second for storing data of the design value of the wafer, which will be described later. The storage area 203b and other storage areas are provided.

The laser processing apparatus in embodiment shown is comprised as mentioned above, and the action is demonstrated below.

5 shows a plan view of the wafer 30 as a workpiece to be laser processed. In the illustrated embodiment, the wafer 30 illustrated in FIG. 5 includes a plurality of division scheduled lines arranged in a lattice form on the surface 300a of the lithium tantalate substrate 300 (first member) having a thickness of 300 μm ( A plurality of areas are partitioned by 301, and devices 302 are formed in the partitioned areas, respectively. Each device 302 has the same structure. A plurality of bonding pads 303 (303a to 303j (second members)) are formed on the surface of the device 302, respectively, as shown in FIG. The bonding pads 303 (303a to 303j) as the second member are formed of copper in the illustrated embodiment. In the illustrated embodiment, the X-direction positions are the same for 303a and 303f, 303b and 303g, 303c and 303h, 303d and 303i, and 303e and 303j. The plurality of bonding pads 303 (303a to 303j) are provided with processing holes (via holes) reaching the bonding pads 303 from the back surface 300b, respectively. In the device 302, the interval A in the X-direction (left and right direction in FIG. 6) of the bonding pads 303 and 303a to 303j, and the scheduled to be divided lines in the bonding pads 303 formed in each device 302 Bonding pads adjacent to each other in the X-direction (left and right direction in FIG. 6), ie, the gap B between the bonding pads 303e and the bonding pads 303a are set at the same interval in the illustrated embodiment. In addition, the division C is scheduled in the interval C in the Y direction (up and down direction in FIG. 6) of the bonding pads 303 (303a to 303j) in each device 302 and the bonding pads 303 formed in each device 302. Bonding pads adjacent to each other in the Y direction (up and down directions in FIG. 6) with the line 301 interposed therebetween, that is, the distance D between the bonding pads 303f, the bonding pads 303a, the bonding pads 303j, and the bonding pads 303e. Are set at equal intervals in the illustrated embodiment. With respect to the wafer 30 configured as described above, the number of devices 302 arranged in each of the rows E1 ... En and each of the columns F1 ... Fn shown in FIG. 5 and the above-described intervals A, B, C, D, and X , The Y coordinate value, the data of the design value is stored in the second storage area 203b of the random access memory (RAM) 203.

Embodiment of laser processing which forms a laser processing hole (via hole) in the bonding pads 303 [303a-303j] of each device 302 formed in the wafer 30 using the above-mentioned laser processing apparatus is demonstrated. do.

As shown in FIG. 7, the wafer 30 adheres the surface 300a to a protective tape 50 made of a synthetic resin sheet such as polyolefin attached to the annular frame 40. Accordingly, the back surface 300b of the wafer 30 is on the upper side. Thus, the wafer 30 supported by the protective tape 50 in the annular frame 40 arrange | positions the protective tape 50 side on the chuck table 36 of the laser processing apparatus shown in FIG. do. Then, the wafer 30 is sucked and held on the chuck table 36 via the protective tape 50 by operating suction means (not shown). Therefore, the wafer 30 is held with the rear surface 300b upward. In addition, the annular frame 40 is fixed by the clamp 362.

As described above, the chuck table 36 which sucks and holds the wafer 30 is located directly under the imaging means 11 by the processing transfer means 37. When the chuck table 36 is located directly under the imaging means 11, the wafer 30 on the chuck table 36 is in a state located at the coordinate position shown in FIG. 8. In this state, an alignment operation is performed to determine whether or not the grid-shaped division scheduled lines 301 formed on the wafer 30 held on the chuck table 36 are arranged in parallel in the X-axis direction and the Y-axis direction. do. That is, the imaging means 11 picks up the wafer 30 held by the chuck table 36, and performs alignment processing by performing image processing such as pattern matching. At this time, although the surface 300a on which the division scheduled line 301 of the wafer 30 is formed is located on the lower side, since the lithium tantalate substrate 300 forming the wafer 30 is a transparent body, the wafer 30 is formed. From the back surface 300b of the image, the division scheduled line 301 can be imaged.

Next, the chuck table 36 is moved to place the device 302 at the leftmost end in FIG. 8 of the highest row E1 in the device 302 formed on the wafer 30 directly below the imaging unit 11. Position it. Then, in the electrodes 303 (303a to 303j) formed in the device 302, the upper left electrode 303a in FIG. 8 is positioned directly under the imaging means 11. If the imaging means 11 detected the electrode 303a in this state, the coordinate value a1 is sent to the control means 20 as a 1st process feed start position coordinate value. And the control means 20 stores this coordinate value a1 in the random access memory (RAM) 203 as a 1st process feed start position coordinate value (process feed start position detection process). At this time, since the light collectors 8 of the imaging means 11 and the laser beam irradiation means 52 are arranged at predetermined intervals in the X-axis direction, the X coordinate value is determined by the imaging means 11 and the light collector 8. The interval plus the value is stored.

Thus, if the 1st process feed start position coordinate value a1 in the device 302 of the uppermost row E1 is detected in FIG. 8, the chuck table 36 will be moved to the Y-axis direction by the space | interval of the division planned line 301. Indexing and moving in the X-axis direction, the device 302 at the leftmost end in the second row E2 from the top in FIG. 8 is positioned immediately below the imaging means 11. Further, in the electrodes 303 (303a to 303j) formed in the device 302, the upper left electrode 303a in FIG. 8 is positioned directly under the imaging unit 11. If the imaging means 11 detected the electrode 303a in this state, this coordinate value a2 is sent to the control means 20 as a 2nd process feed start position coordinate value. And the control means 20 stores this coordinate value a2 in the random access memory (RAM) 203 as a 2nd process feed start position coordinate value. At this time, since the light collectors 8 of the imaging means 11 and the laser beam irradiation means 52 are arranged at predetermined intervals in the X-axis direction as described above, the X coordinate value is determined by the imaging means 11 and the light collector. The value obtained by adding the interval (8) is stored. Subsequently, the control means 20 repeatedly executes the above-described indexing feed and the machining feed start position detecting process up to the lowest row En in FIG. 8, and executes the machining feed start position coordinate values of the device 302 formed in each row ( a3 to an) are detected and stored in the random access memory (RAM) 203. In the illustrated embodiment, in the plurality of devices 302 formed on the wafer 30, the device 302 at the leftmost end of the lowest row En in FIG. 8 is set as the measurement device, and the processing transfer of the measurement device is performed. The starting position coordinate value an is stored in the random access memory (RAM) 203 as the measurement position coordinate value an.

If the above-described processing transfer start position detecting step has been performed, a drilling step of drilling a laser processing hole (via hole) is performed on the back surface of each electrode 303 (303a to 303J) formed in each device 302 of the wafer 30. do. In the drilling process, first, the processing feed means 37 is operated to move the chuck table 36, and the first machining feed start position coordinate value a1 stored in the random access memory (RAM) 203 is lasered. It is located just below the light collector 8 of the light irradiation means 52. Thus, the state in which the 1st process feed start position coordinate value a1 is located just under the condenser 8 is a state shown in FIG. From the state shown in FIG. 9A, the control means 20 carries out the said process feed means so that the chuck table 36 may be processed and conveyed at the predetermined movement speed in the direction shown by the arrow X1 in FIG. While controlling 37, the laser beam irradiation means 52 is operated to irradiate the pulsed laser beam from the light collector 8. Moreover, the condensing point P of the laser beam irradiated from the condenser 8 is matched with the upper surface vicinity of the wafer 30. At this time, the control means 20 is based on the detection signal from the leading head 374b of the X-axis direction detection means 374, the deflection angle adjusting means 74 and the output adjusting means of the acoustooptical deflection means 7 A control signal for controlling 75) is output.

On the other hand, the RF oscillator 72 outputs RF corresponding to the control signal from the deflection angle adjusting means 74 and the output adjusting means 75. The power of RF output from the RF oscillator 72 is amplified by the RF amplifier 73 and applied to the acoustooptical device 71. As a result, the acoustooptical device 71 deflects the optical axis of the pulsed laser beam oscillated from the pulsed laser beam oscillation means 6 in a range from the position indicated by the dashed-dotted line in FIG. 2 to the position indicated by the dashed-dotted line in FIG. Synchronize with the moving speed. As a result, the pulse laser beam of predetermined output can be irradiated to the 1st process feed start position coordinate value a1.

When performing the above-mentioned drilling process, the control means 20 counts the number of shots of the pulsed laser beam which the laser beam oscillation means 6 oscillates by the counter 204, and the plasma detection means 9 makes A light intensity signal is input from the one photodetector 94. Here, the light intensity signal output from the first photo detector 94 will be described. When a pulsed laser beam is irradiated onto the lithium tantalate substrate 300 constituting the wafer 30, a plasma having a wavelength of 670 nm is generated. Plasma having a wavelength of 670 nm is condensed by the condensing lens 911 of the plasma light receiving means 91 constituting the plasma detection means 9, as shown in FIG. Pass through to reach the first photodetector 94.

FIG. 11A shows the output voltage of the first photodetector 94 which detects the light intensity of the plasma generated when the lithium tantalate substrate 300 is irradiated with the pulse laser beam described above. In Fig. 11A, the horizontal axis represents the number of shots of the pulsed laser beam, and the vertical axis represents the voltage value (V). In the embodiment shown in FIG. 11A, when the number of shots of the pulsed laser beam is about 80 to 85 shots, the voltage value is about 2.5 V, and when the number of shots of the pulsed laser beam exceeds 85 shots, the punching process is near the end. The voltage value drops sharply.

FIG. 11B shows the output voltage of the second photodetector 97 for detecting the light intensity of the plasma generated when the bonding pad 303 made of copper is irradiated with a pulsed laser beam. In Fig. 11B, the horizontal axis represents the number of shots of the pulsed laser beam, and the vertical axis represents the voltage value (V). In the embodiment shown in FIG. 11B, the voltage value starts to increase from 80 to 85 shots of the pulsed laser beam. When the output voltage of the second photodetector 97 starts to increase, it means that a through hole is formed in the lithium tantalate substrate 300 and a pulse laser beam begins to be irradiated onto the bonding pad 303.

As described above, based on the output voltages from the first photodetector 94 and the second photodetector 97, the control means 20 controls the output of the pulsed laser beam as follows. That is, when the output voltage is inputted only from the first photodetector 94, irradiation of the pulsed laser beam having the first output is continued, and when the output voltage is input from the second photodetector 97, The laser beam irradiation means 52 is controlled to stop the pulsed laser beam having a high second output after a predetermined shot irradiation. Specifically, when the output voltage is input only from the first photodetector 94, the output adjusting means 75 is controlled to be the first output (average output 2W, pulse energy 40 µJ) to irradiate the pulsed laser beam. Subsequently, when the output voltage is input from the second photodetector 97, the output adjusting means 75 is controlled so as to have a second output higher than the first output (average output 4 W, pulse energy of 80 µJ). The laser beam irradiation means 52 is controlled to stop after irradiating the laser beam with a predetermined shot (10 shots). In addition, when the output of a pulse laser beam is controlled to the 2nd output (average output 4W, pulse energy 80microJ) higher than a 1st output, the output voltage from the 2nd photodetector 97 will be 05V, for example. A viewpoint (a viewpoint where the number of shots of a pulse laser beam is 100 shots) is good, and 10 shots are irradiated from this viewpoint. In this way, the pulsed laser beam reaches the bonding pad 303 and the pulsed laser beam is irradiated onto the bonding pad 303 made of copper, thereby melting and scattering the bonding pad 303 made of copper, thereby forming the lithium tantalate substrate 300. Even if the fine particles of copper adhere to the inner wall of the laser processing hole formed in the hole), if the pulse laser beam reaches the bonding pad 303, the output of the pulse laser beam is higher than the first output (second output (average output 4 W, pulse energy). Since the fine particles of copper adhered to the inner wall of the laser processing hole are blown off and released to the outside, the fine particles of copper can be suppressed from adhering to the inner wall of the laser processing hole.

In addition, the processing conditions in the said drilling process are set as follows.

Light source: LD excitation Q switch Nd: YVO4

Wavelength: 532 nm

Average output power: 1st average power 2 W

2nd average power 4 W

Pulse energy: 40 μJ of the first pulse energy

Second pulse energy 80 μJ

Repetition frequency: 50 kHz

Pulse width: 10 ps

Condensing spot diameter: φ 15 μm

On the other hand, the control means 20 inputs the detection signal from the leading head 374b of the X-axis direction position detection means 374, and this detection signal is counted by the counter 204. As shown in FIG. And if the count value by the counter 204 reached the coordinate value of the next bonding pad 303, the control means 20 controls the laser beam irradiation means 52, and performs the said drilling process. Subsequently, the control means 20 operates the laser beam irradiation means 52 each time the count value by the counter 204 reaches the coordinate value of the bonding pad 303 to perform the above drilling process. And as shown in FIG.9 (b), the bonding pad 303 formed in the device 302 of the rightmost end of row E1 of the semiconductor wafer 30 at the rightmost end in FIG.9 (b). If the above drilling process has been performed at the position of the electrode 303e, the operation of the processing transfer means 37 is stopped and the movement of the chuck table 36 is stopped. As a result, the processing hole 304 which reaches the bonding pad 303 is formed in the lithium tantalate board | substrate 300 of the semiconductor wafer 30 as shown in FIG.9 (b).

Next, the control means 20 controls the first indexing conveying means 38 to index and convey the light collector 8 of the laser beam irradiation means 52 in the direction perpendicular to the ground in FIG. 9 (b). do. On the other hand, the control means 20 inputs the detection signal from the leading head 384b of the Y-axis direction position detection means 384, and counts this detection signal by the counter 204. Then, if the count value by the counter 204 reaches a value corresponding to the interval C in the Y-axis direction in FIG. 6 of the bonding pad 303, the operation of the first indexing feed means 38 is stopped, The indexing transfer of the light collector 8 of the laser beam irradiation means 52 is stopped. As a result, the light collector 8 is located directly above the bonding pad 303j (see Fig. 6) facing the bonding pad 303e. This state is a state shown in FIG. In the state shown in FIG. 10A, the control means 20 performs the process feed means so that the chuck table 36 is machined at a predetermined movement speed in the direction indicated by the arrow X2 in FIG. 10A. 37), the laser beam irradiation means 52 is operated to perform the above drilling process. And the control means 20 counts the detection signal from the leading head 374b of the X-axis direction position detection means 374 by the counter 204 as mentioned above, and the count value is the bonding pad 303. Each time the control means 20 operates the laser beam irradiation means 52 to carry out the above drilling process. And as shown in FIG.10 (b), if the said drilling process was performed in the position of the bonding pad 303f formed in the device 302 of the leftmost end of row E1 of the semiconductor wafer 30, the said process transfer The operation of the means 37 is stopped and the movement of the chuck table 36 is stopped. As a result, the laser processing hole 304 is formed in the lithium tantalate substrate 300 of the semiconductor wafer 30 in the back surface side of the bonding pad 303 as shown to FIG. 10 (b).

As described above, if the laser processing hole 304 is formed on the back surface side of the bonding pad 303 formed in the device 302 in the E1 row of the semiconductor wafer 30, the control means 20 is the processing transfer means 37. And a first indexing transfer means 38, which are stored in the random access memory (RAM) 203 in a bonding pad 303 formed in the device 302 in row E2 of the semiconductor wafer 30. The second machining feed start position coordinate value a2 is positioned just below the condenser 8 of the laser beam irradiation means 52. And the control apparatus 20 controls the laser beam irradiation means 52, the process feed means 37, and the 1st indexing feed means 38, and is formed in the device 302 of the E2 row of the semiconductor wafer 30. The above-described punching process is performed on the back side of the bonding pad 303. Subsequently, the above-described punching process is also performed on the back side of the bonding pad 303 formed in the device 302 in the E3 to En rows of the semiconductor wafer 30. As a result, the laser processing hole 304 is formed in the lithium tantalate substrate 300 of the semiconductor wafer 30 in the back surface side of the bonding pad 303 formed in each device 302.

On the other hand, in the above drilling process, the pulsed laser beam is applied to the semiconductor wafer 30 in the interval A region and the interval B region in the X-axis direction in FIG. 6 and the interval C region and the region D region in the Y-axis direction in FIG. Do not investigate. In this way, since the pulsed laser beam is not irradiated on the semiconductor wafer 30, the control means 20 applies a voltage of 0 V to the deflection angle adjusting means 74 of the acoustooptic deflection means 7. As a result, RF of a frequency corresponding to 0 V is applied to the acoustooptical device 71, and the pulsed laser beam LB oscillated from the pulsed laser beam oscillation means 6 is lasered as shown by broken lines in FIG. 2. Since it is guided to the light absorbing means 76, it is not irradiated to the semiconductor wafer 30.

As mentioned above, although demonstrated based on embodiment which showed this invention, this invention is not limited only to embodiment, Various modification is possible in the range of the meaning of this invention. For example, in the above-mentioned embodiment, the bonding pad (second member) is formed from the back surface side of the substrate (first member) on the wafer in which the bonding pads (second member) are arranged on a plurality of devices formed on the surface of the substrate (first member), respectively. Although the example which forms the laser processing hole which reaches the member) was demonstrated, it has been demonstrated from the 1st member to the 2nd member to the to-be-processed object by which the 1st member formed by the 1st material and the 2nd member formed by the 2nd material were joined. When forming the reaching laser processing hole, it can apply magnification.

2: stop base 3: chuck table mechanism
36: chuck table 37: processing feed means
374: X axis direction position detecting means 38: First indexing conveying means
384: Y-axis position detection means 4: laser beam irradiation unit support mechanism
42: movable support base 43: second indexing conveying means
5: laser beam irradiation unit 52: laser beam irradiation means
6: pulsed laser beam oscillation means 61: pulsed laser beam oscillator
62: repeating frequency setting means 7: acousto-optical deflection means
71: acousto-optic element 72: RF oscillator
73: RF amplifier 74: deflection angle adjustment means
75: output adjusting means 76: laser beam absorbing means
8: condenser 9: plasma detection means
91: plasma light receiving means 92: beam splitter
93: first band pass filter 94: first photodetector
95: direction change mirror 96: second band pass filter
97: second photodetector 11: imaging means
20: control means 30: wafer
301: Divided line 302: Device
303: bonding pads 304: laser processing holes

Claims (3)

A laser processing method for forming a laser processing hole for reaching a second member from a first member in a workpiece to which a first member formed by a first material and a second member formed by a second material are connected.
Irradiation of the pulse laser beam which has a 1st output, when the wavelength of the plasma which arises by irradiating a laser beam to a 1st member and a 2nd member is detected, and only the plasma light which has the wavelength of a 1st member is detected. And if the plasma light having the wavelength of the second member is detected, the laser processing method stops after irradiating a predetermined shot with a pulsed laser beam having a second output higher than the first output. The method of claim 1, wherein the first material forming the first member comprises lithium tantalate,
And said second output is set at 40 [mu] j of energy per pulse, and said second output is set at 80 [mu] J energy per pulse. A workpiece holding means for holding the workpiece and laser beam irradiation means for irradiating a laser beam to the workpiece held by the workpiece holding means, the laser beam irradiation means for laser beam oscillating means for oscillating a laser beam; And an output adjusting means for adjusting the output of the laser beam oscillated by the laser beam oscillating means, a laser beam whose output is adjusted by the output adjusting means, and irradiating the workpiece held by the workpiece holding means. As a laser processing apparatus provided with the condenser to make,
Plasma detection means for detecting a wavelength of plasma generated by irradiating a workpiece with laser beam from the laser beam irradiation means, and control means for controlling the laser beam irradiation means based on a detection signal from the plasma detection means. And
The plasma detecting means includes: a beam splitter for splitting plasma light into a first path and a second path, a first band pass filter disposed in the first path and passing only a wavelength of a plasma emitted by the first material; A first photodetector for receiving light passing through the one band pass filter and outputting a light intensity signal to the control means; and a second band pass filter disposed only in the second path to pass the wavelength of the plasma emitted by the second material. And a second photodetector for receiving light passing through the second band pass filter and outputting a light intensity signal to the control means.
The control means is configured to operate the laser beam irradiation means to irradiate a workpiece with a pulsed laser beam and perform laser processing that reaches the second member from the first member of the workpiece. 2, based on the light intensity signal output from the photodetector, when the light intensity signal is output only from the first photodetector, the output adjusting means is controlled to be the first output to continue irradiation of the pulsed laser beam, and When the light intensity signal is output from the second photodetector, controlling the output adjustment means to be a second output higher than the first output to control the laser beam irradiation means to stop after a predetermined shot irradiation of the pulsed laser beam. Laser processing device characterized in that.

Images