JP2019096908A - Laser processing equipment - Google Patents

Abstract

To provide laser processing equipment capable of obtaining chips of stabilized quality efficiently.SOLUTION: Laser processing equipment includes laser processing means having a spatial light modulator, and simultaneously focusing laser light on multiple positions of different depth from laser light irradiation surface in a work piece, and separated from each other in a direction orthogonal to the thickness direction of the work piece, by using the spatial light modulator, and correcting aberration of laser light, and aberration correction means configured separately from the spatial light modulator, so that the correction amount of aberration can be changed according to the depth of the multiple positions, for preventing insufficient effectiveness of aberration correction by the spatial light modulator.SELECTED DRAWING: Figure 1

Description

  The present invention is a laser that forms a modified region inside the wafer along a line to be cut of the wafer by irradiating the laser light with the focusing point aligned on the inside of the wafer having a plurality of devices formed on the surface. The present invention relates to a processing apparatus and a laser processing method.

  Conventionally, laser processing is performed to form a modified region in the interior of a wafer along a planned cutting line of the wafer by irradiating a laser beam while aligning a condensing point on the inside of a wafer having a plurality of devices formed on the surface. The device is known.

  In the laser processing apparatus, when the laser beam is focused on the inside of the wafer by the focusing lens, defocusing occurs due to the incident height of the light incident on the focusing lens, and the focusing position differs depending on the incident light. Aberration) occurs. If processing is performed in a state where such an aberration occurs, it is difficult for the laser light to be collected inside the wafer, so a crack (crack) extending in the wafer depth direction (wafer thickness direction) from the modified region The length is shortened, and an adverse effect such as an increase in the number of times of processing occurs.

  On the other hand, Patent Document 1 discloses a laser processing apparatus provided with a spatial light modulator that modulates laser light output from one laser light source. In this laser processing apparatus, the laser light is simultaneously condensed by the condenser lens at two different positions in the interior of the wafer and is presented by the spatial light modulator so that the aberration of the laser light in each is reduced. Control of the hologram pattern (modulation pattern) is performed.

JP, 2010-58128, A

  However, in the laser processing apparatus disclosed in Patent Document 1, as the focus position of the laser light is deeper from the laser light irradiation surface of the wafer, the hologram pattern presented by the spatial light modulator becomes denser. The effectiveness of the aberration correction is insufficient. Therefore, when the thickness of the wafer is large, the aberration of the laser light is not sufficiently corrected at each light focusing position, and the crack generated from the modified region can not be sufficiently extended. As a result, the wafer can not be efficiently divided into chips, making it difficult to obtain chips of stable quality.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a laser processing apparatus and a laser processing method capable of efficiently obtaining a chip of stable quality.

  In order to achieve the above object, a laser processing apparatus according to a first aspect of the present invention aligns a focusing point on the inside of a wafer and irradiates a laser beam to the inside of the wafer along a planned cutting line of the wafer. Laser processing apparatus for forming a modified region in the laser light source, the laser light source outputting the laser light, the spatial light modulator modulating the laser light output from the laser light source, and the laser light modulated by the spatial light modulator The condensing lens which condenses the inside of the wafer, the moving means which moves the wafer relative to the laser beam, and the depth from the laser beam irradiation surface in the wafer are different from each other, and the moving direction of the wafer A control unit for controlling the spatial light modulator so that the laser light is simultaneously collected by the condensing lens at a plurality of positions separated from one another, and the spatial light modulator separately Is provided with, an aberration correcting means for correcting such aberrations of the laser beam is equal to or lower than a predetermined aberration at a plurality of positions to align the focal point of the laser beam inside the wafer.

  In the laser processing apparatus according to the second aspect of the present invention, in the first aspect, the aberration correction means corrects the aberration of the laser beam using a correction ring provided on the condenser lens.

  In the laser processing apparatus according to the third aspect of the present invention, in the first aspect, the aberration correction means is constituted by a correction optical system disposed on the optical path of the laser light between the condensing lens and the spatial light modulator. Be done.

  In the laser processing apparatus according to the fourth aspect of the present invention, in any one of the first to third aspects, the control unit is configured to collect the laser light at a first position in the depth direction of the wafer and The spatial light modulator is controlled so that the laser light is focused to a second position different from the position 1 in the depth direction of the wafer.

  In the laser processing apparatus according to a fifth aspect of the present invention, in the fourth aspect, the second position is disposed upstream of the first position in the moving direction of the wafer, and the second position is the first from the laser light irradiation surface of the wafer. It is arranged at a position deeper than the position of 1.

  In the laser processing apparatus according to the sixth aspect of the present invention, in the fourth aspect, the second position is disposed upstream of the first position in the moving direction of the wafer, and the second position is the first from the laser light irradiation surface of the wafer. It is arranged at a position shallower than the position 1).

  In the laser processing apparatus according to the seventh aspect of the present invention, in any one of the first to sixth aspects, when the thickness of the wafer is 775 μm, the depth of the wafer from the laser light irradiation surface is the aberration correction means. Is corrected so as to minimize the aberration of the laser beam at a position near 500 .mu.m.

  The laser processing method according to the eighth aspect of the present invention is a laser that forms a modified region in the inside of a wafer along a line to cut the wafer by irradiating the laser light with the focusing point aligned on the inside of the wafer. A processing method, which is a modulation step of modulating a laser beam output from a laser light source by a spatial light modulator, and focusing of a laser beam modulated by the spatial light modulator onto a wafer by a focusing lens. The step of moving the wafer relative to the laser beam, the laser beam at a plurality of positions different from each other in the moving direction of the wafer, and different in depth from the laser beam irradiation surface inside the wafer Using a control step of controlling the spatial light modulator so that light is collected simultaneously by the condensing lens, and aberration correction means configured separately from the spatial light modulator, Comprising the aberration correction step of correcting such aberration of the laser beam is equal to or lower than a predetermined aberration at a plurality of positions to align the focal point of the laser beam inside the.

  In the laser processing method according to a ninth aspect of the present invention, in the eighth aspect, the aberration correction step corrects the aberration of the laser beam using a correction ring provided in the condenser lens.

  In the laser processing method according to a tenth aspect of the present invention, in the eighth aspect, the aberration correction step uses a correction optical system disposed on the optical path of the laser light between the condensing lens and the spatial light modulator. And correct the aberration of the laser beam.

The laser processing method according to an eleventh aspect of the present invention is the laser processing method according to any of the eighth to tenth aspects, wherein in the controlling step, the laser light is collected at a first position in the depth direction of the wafer The spatial light modulator is controlled so that the laser light is focused to a second position different from the position 1 in the depth direction of the wafer.

  In a laser processing method according to a twelfth aspect of the present invention, in the eleventh aspect, the second position is disposed upstream of the first position in the moving direction of the wafer, and the second position is the first from the laser light irradiation surface of the wafer. It is arranged at a position deeper than the position of 1.

  In the laser processing method according to a thirteenth aspect of the present invention, in the eleventh aspect, the second position is disposed upstream of the first position in the moving direction of the wafer, and the second position is the first from the laser light irradiation surface of the wafer. It is arranged at a position shallower than the position 1).

  In the laser processing method according to a fourteenth aspect of the present invention, in any one of the eighth to thirteenth aspects, the aberration correction step is a depth from the laser light irradiation surface of the wafer when the thickness of the wafer is 775 μm. Is corrected so as to minimize the aberration of the laser beam at a position near 500 .mu.m.

  According to the present invention, it is possible to sufficiently extend the cracks that occur in the wafer depth direction from the modified region formed inside the wafer. Therefore, the wafer can be efficiently divided into chips, and chips of stable quality can be efficiently obtained.

The block diagram which showed the outline of the laser processing apparatus which concerns on one Embodiment of this invention Conceptual diagram showing how the reformed area is formed inside the wafer A conceptual view of how a crack extends in the wafer depth direction from the modified region formed inside the wafer Graph showing relationship between aberration correction amount and total crack length Graph showing relationship between aberration correction amount and crack bottom length The block diagram which showed the outline of the laser processing apparatus which concerns on other embodiment of this invention It is a conceptual diagram showing a mode that a modification field is formed inside a wafer, and a figure for explaining other forms of two positions (focusing position) where laser beam L is condensed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

  FIG. 1 is a schematic view showing a laser processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the laser processing apparatus 1 of the present embodiment mainly includes a wafer moving unit 11, a laser head 20, a control unit 50, and the like.

  The wafer moving unit 11 is provided with a suction stage 13 for holding the wafer W by suction, and an XYZθ table 12 provided on the main body base 16 of the laser processing apparatus 1 for precisely moving the suction stage 13 in the XYZθ directions. The wafer moving unit 11 precisely moves the wafer W in the XYZθ direction in the drawing. The wafer moving unit 11 is an example of a moving unit.

  A back grind tape (hereinafter, BG tape) having an adhesive material is attached to the surface on which the device is formed, and the wafer W is mounted on the suction stage 13 with the back surface facing upward. The thickness of the wafer W is not particularly limited, but is typically 700 μm or more, and more typically 700 to 800 μm.

  The wafer W may be mounted on the suction stage 13 in a state in which a dicing sheet having an adhesive material is attached to one surface and integrated with the frame through the dicing sheet.

  The laser head 20 mainly includes a laser light source 22, a spatial light modulator 28, a condenser lens 38, and the like.

The laser light source 22 outputs laser light L for processing for forming a modified region inside the wafer W according to the control of the control unit 50. As the conditions of the laser light L, for example, the light source is a semiconductor laser pumped Nd: YAG laser, the wavelength is 1.1 μm, the laser light spot cross-sectional area is 3.14 × 10 ^-8 cm ² , the oscillation mode is Q switch The repetition frequency is 80 to 120 kHz, the pulse width is 180 to 280 ns, and the output is 8 W.

  The spatial light modulator 28 is of a phase modulation type, and receives a laser beam L output from the laser light source 22. The spatial light modulator 28 modulates the phase of the laser beam L in each of a plurality of two-dimensionally arranged pixels. The pattern is presented, and the laser light L after the phase modulation is output. This hologram pattern is obtained by superimposing a plurality of Fresnel lens patterns having different focusing positions. Thereby, as described in detail later, the wafer moving directions (processing feed direction) different from each other in depth from the laser beam irradiation surface (the back surface of the wafer W) inside the wafer W and parallel to the X direction in FIG. The laser light L is simultaneously condensed by the condensing lens 38 at two positions separated from each other by M.

As the spatial light modulator 28, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon)
Spatial light modulator (SLM) is used. The operation of the spatial light modulator 28 and the hologram pattern presented by the spatial light modulator 28 are controlled by the control unit 50. The specific configuration of the spatial light modulator 28 and the hologram pattern presented by the spatial light modulator 28 are already known, and thus detailed description thereof is omitted here.

  The focusing lens 38 is an objective lens (infrared objective lens) for focusing the laser beam L on the inside of the wafer W. The numerical aperture (NA) of the focusing lens 38 is, for example, 0.65.

  The condenser lens 38 is provided with a correction ring 40 to correct the aberration of the laser beam L generated inside the wafer W. The correction ring 40 is configured to be manually rotatable, and when the correction ring 40 is rotated in a predetermined direction, the distance between the lens groups constituting the condenser lens 38 is changed, and the laser light irradiation surface of the wafer W is changed. The aberration can be corrected so that the aberration of the laser beam L becomes equal to or less than a predetermined aberration at a position of a predetermined depth from the (rear surface). The correction ring 40 is an example of an aberration correction unit.

  The correction ring 40 may be configured to be electrically rotated by a correction ring driving unit (not shown). In this case, the control unit 50 controls the operation of the correction ring drive unit to rotate the correction ring 40 so as to correct the aberration of the laser light L to a desired state.

  The laser head 20 is provided with a beam expander 24, a λ / 2 wavelength plate 26, a reduction optical system 36 and the like in addition to the above configuration.

  The beam expander 24 expands the laser light L output from the laser light source 22 into an appropriate beam diameter for the spatial light modulator 28. The λ / 2 wavelength plate 26 adjusts the laser light incident polarization plane to the spatial light modulator 28. The reduction optical system 36 is an afocal optical system (both-side telecentric optical system) including a first lens 36 a and a second lens 36 b, and the condensing lens 38 is a laser light L modulated by the spatial light modulator 28. Project to a reduced size.

  Although not shown, the laser head 20 includes an alignment optical system for performing alignment with the wafer W, and an auto for maintaining a constant distance (working distance) between the wafer W and the condenser lens 38. A focus unit etc. are provided.

  The control unit 50 includes a CPU, a memory, an input / output circuit unit, and the like, and controls the operation of each unit of the laser processing apparatus 1. Specifically, the thickness of the wafer W and the feed rate of the wafer W are controlled, and the operation of each part (the wafer moving part 11 and the laser head 20 etc.) is controlled under optimum conditions to form a modified region.

  Further, the control unit 50 controls the operation of the spatial light modulator 28 and causes the spatial light modulator 28 to present a predetermined hologram pattern. Specifically, two different positions within the wafer W (that is, two positions different from each other in the wafer moving direction M parallel to the X direction in FIG. 1 and different in depth from the laser light irradiation surface) The spatial light modulator 28 presents a hologram pattern for modulating the laser light L so that the laser light L is simultaneously condensed by the condensing lens 38. The hologram pattern is derived in advance based on the formation position of the modified region, the wavelength of the laser beam L to be irradiated, the refractive index of the condensing lens 38 or the wafer W, and the like, and is stored in the control unit 50.

  The laser processing apparatus 1 further includes wafer transfer means, an operation plate, a television monitor, and an indicator light, which are not shown.

  Switches and a display device for operating the operation of each part of the laser processing apparatus 1 are attached to the operation plate. The television monitor displays a wafer image captured by a CCD camera (not shown), or displays program contents, various messages, and the like. The indicator light indicates the operation status such as processing end, emergency stop, etc. during processing of the laser processing apparatus 1.

  The operation of the laser processing apparatus 1 of the present embodiment configured as described above will be described. Here, the case of processing a silicon substrate having a thickness of 775 μm as the wafer W will be described as an example.

  First, by rotating the correction ring 40 provided on the condenser lens 38 manually (or electrically), the laser beam L is focused at the position (processing depth of the modified region) for condensing the laser beam L inside the wafer W The aberration correction amount is adjusted so that the aberration of L is equal to or less than a predetermined aberration. In the present specification, the “aberration correction amount” is a value converted to the depth from the laser light irradiation surface of the wafer W. That is, for example, when the aberration correction amount is 500 μm, it means that the aberration of the laser light becomes minimum at a position near the depth of 500 μm from the laser light irradiation surface of the wafer W. In this example, as described in detail later, when the thickness of the wafer W is 775 μm, it is preferable that the aberration correction amount by the correction ring 40 be set to 500 μm.

  Next, after the wafer W to be processed is mounted on the suction stage 13, the alignment of the wafer W is performed using an alignment optical system (not shown).

  Next, while processing and feeding the XYZθ table 12 in the wafer moving direction M (that is, moving the wafer W relative to the laser light L in the wafer moving direction M), the laser head 20 to the wafer W The laser light L is emitted.

  At this time, the beam diameter of the laser light L output from the laser light source 22 is expanded by the beam expander 24, reflected by the first mirror 30, and the polarization direction is changed by the λ / 2 wavelength plate 26 to perform spatial light modulation. Is incident on the

  The laser light L incident on the spatial light modulator 28 is modulated according to a predetermined hologram pattern presented on the spatial light modulator 28. At this time, the control unit 50 performs spatial light modulation on the hologram pattern for modulating the laser light L so that the laser light L is simultaneously condensed by the condensing lens 38 at two different positions in the inside of the wafer W. Control to be displayed on the display unit 28.

  The laser beam L emitted from the spatial light modulator 28 is sequentially reflected by the second mirror 31 and the third mirror 32, passes through the first lens 36a, and is further reflected by the fourth mirror 33 and the fifth mirror 34. The light is reflected, passes through the second lens 36 b, and is incident on the condensing lens 38. As a result, the laser beam L emitted from the spatial light modulator 28 is reduced and projected onto the condenser lens 38 by the reduction optical system 36 including the first lens 36 a and the second lens 36 b. Then, the laser light L incident on the condensing lens 38 is condensed at two different positions inside the wafer W by the condensing lens 38.

  FIG. 2 is a conceptual view showing how a reformed region is formed inside the wafer W. As shown in FIG. As shown in FIG. 2, the laser light L modulated by the spatial light modulator 28 has different depths from the laser light irradiation surface (the back surface of the wafer W) inside the wafer W by the condensing lens 38, and The light is collected simultaneously at two positions separated from each other in the wafer movement direction M. As a result, modified regions P1 and P2 are formed by multiphoton absorption in the vicinity of the respective focusing positions. Further, when the modified regions P1 and P2 are formed, cracks (cracks) K1 and K2 extending from the respective modified regions P1 and P2 in the wafer depth direction (wafer thickness direction) are formed.

  Here, the two positions (focusing positions) where the laser light L is focused will be described in detail. In the present embodiment, the first position Q1 in the wafer depth direction inside the wafer W (left side in FIG. 2) The laser light L is collected at the light collection point), and the laser light is collected at the second position Q2 (light collection point on the right side in FIG. 2) different from the first position Q1 in the wafer depth direction. Ru.

  Furthermore, in the present embodiment, the second position Q2 is disposed on the upstream side (right side in FIG. 2) of the wafer moving direction M with respect to the first position Q1 and the first position from the laser light irradiation surface of the wafer W. It is arranged at a position deeper than the position Q1. The distance in the wafer depth direction is 50 μm as an example of the distance (interval) between the first position Q1 and the second position Q2. Further, the distance in the wafer moving direction M is 30 μm.

  In this state, as the wafer W moves relative to the laser beam L, as shown in FIG. 3, along the movement locus of two focusing points (focusing positions Q1 and Q2) of the laser beam L. The reformed regions P1 and P2 are formed inside the wafer W. As a result, along the line to cut the wafer W, the modified region P1 and the modified region P2 are formed one by one in the wafer W in a state of being overlapped at a predetermined interval.

  As described above, when the modified region P1 and the modified region P2 are formed in a state of being overlapped at a predetermined interval, time delay is caused among the two modified regions P1 and P2 overlapping in the wafer depth direction. By the impact at the time of formation of the formed modified region P1, as shown in FIG. 3, the crack K1 of the modified region P1 and the crack K2 of the modified region P2 are connected, and the crack K2 extending from the modified region P2 is a wafer It extends toward the surface opposite to the laser beam irradiation surface of W (the back surface of the wafer W).

  That is, by modulating the laser light L by the spatial light modulator 28, the laser light L is simultaneously condensed at mutually different positions in the wafer W, thereby reducing the throughput from the surface of the wafer W. The crack can be extended to a desired position between the target surface indicating the position of the final thickness T2 of the wafer W and the surface of the wafer W. 2 and 3, T1 indicates the initial thickness of the wafer W (775 μm in this example).

  When the reformed regions P1 and P2 are formed one by one along the lines to be cut, the XYZθ table 12 is indexed and fed by one pitch in the Y direction, and the reformed regions P1 and P2 are similarly formed in the next line. .

  When the reformed regions P1 and P2 are formed along all the lines to be cut parallel to the X direction, the XYZθ table 12 is rotated by 90 °, and the lines orthogonal to the previous line are similarly similarly modified. , P2 are formed.

  Thereby, the modified regions P1 and P2 are formed along all the lines to be cut. The modified regions P1 and P2 have the same position on the plane (the position seen from the back surface or the front surface of the wafer W) and are both formed along the line to be cut, but the thickness direction of the wafer W Only the position in the depth direction) differs.

  After the reformed regions P1 and P2 are formed along the lines to be cut as described above, the back surface of the wafer W is ground using a grinding device (not shown) to obtain the thickness (initial thickness) T1 of the wafer W. Is processed to a predetermined thickness (final thickness) T2 (for example, 30 to 50 .mu.m).

  After the back surface grinding step, an expand tape (dicing tape) is attached to the back surface of the wafer W, and after the BG tape attached to the front surface of the wafer W is peeled off, tension is applied to the expanded tape attached to the back surface of the wafer W An expansion step is performed to add and stretch.

  As a result, the wafer W is cut starting from the crack extending to the surface side of the wafer W. That is, the wafer W is cut along a line to cut and divided into a plurality of chips.

  As described above, in the present embodiment, the laser light L is simultaneously condensed by the condensing lens 38 at a plurality of positions using the spatial light modulator 28, and the laser light L is corrected using the correction ring 40 of the condensing lens 38. Correction is performed so that the aberration at the position where the light focusing point is aligned becomes equal to or less than the predetermined aberration, the laser light L is efficiently collected at a deep position in the wafer depth direction even when the thickness of the wafer W is thick. It becomes possible to make it light. In addition, the crack generated when the modified regions P1 and P2 overlapping in the wafer depth direction are formed can be sufficiently extended to the surface (surface of the wafer W) opposite to the laser beam irradiated surface of the wafer W. it can. Therefore, the wafer W can be efficiently divided into chips, and chips of stable quality can be efficiently obtained.

  Here, experiments conducted by the present inventors to verify the effects of the present invention will be described.

  In this experiment, the laser processing apparatus 1 of the embodiment described above was used as an example. In addition, as a comparative example, an apparatus having the same configuration as that of Patent Document 1 described above, that is, a spatial light modulator is used to condense laser light at two mutually different positions within the wafer while the respective positions are separated. (1st comparative example) which performs the aberration correction in (1), and the device which performs the aberration correction using the correction ring without using the spatial light modulator (that is, the laser beam is condensed at one light collecting position) (Second comparative example) was used.

  As experimental conditions, for a wafer (silicon substrate) having a thickness of 775 μm, the total crack length (the crack length) generated in the wafer depth direction when the modified region is formed while changing the aberration correction amount with each device The overall length) and the crack lower end length (the length of the crack extending from the lower end of the modified region to the wafer backside) were measured (see FIG. 3).

  FIG. 4 is a graph showing the relationship between the amount of aberration correction and the total crack length. FIG. 5 is a graph showing the relationship between the aberration correction amount and the crack lower end length. In FIG. 4 and FIG. 5, the horizontal axis indicates the aberration correction amount, and the vertical axis indicates the total crack length and the crack lower end length generated by each device.

  As can be seen from FIGS. 4 and 5, in the example, compared with the first comparative example and the second comparative example, the total crack length is longer over all aberration correction amounts, and the crack lower end length is also longer. The results were obtained.

  In particular, when the aberration correction amount is 500 μm, in the example, the total crack length is about 250 μm and the crack lower end length is about 80 μm, which is a very superior result than the first comparative example and the second comparative example It is obtained. From this result, in the laser processing apparatus 1 of the present embodiment, when processing a wafer W having a thickness of 775 μm, the aberration correction amount by the correction ring 40 is 500 μm (that is, the laser light irradiation surface of the wafer W (wafer It is preferable to set to a position where the depth from the back surface of W is 500 μm so as to minimize the aberration). Then, by modulating the laser light by the spatial light modulator 28 so that the laser light L is simultaneously condensed by the condensing lens 38 at two positions different from each other in depth in the vicinity of this depth (500 μm) The crack extending in the wafer depth direction from the modified region formed inside the wafer W can be sufficiently extended. As a result, the wafer can be efficiently divided into chips, and chips of stable quality can be efficiently obtained.

  In the present embodiment, the aberration correction means is configured by the correction ring 40 provided in the condenser lens 38. However, the present invention is not limited to this. For example, as shown in FIG. The correction optical system 42 may be disposed on the optical path of the laser light L between the light source 38 and the spatial light modulator 28. In this case, the aberration of the laser light L generated inside the wafer W can be corrected by changing the distance between the plurality of lens groups constituting the correction optical system 42 by the driving means (not shown). In the example shown in FIG. 6, it is disposed between the condenser lens 38 and the second lens 36b.

  Also, instead of using an objective lens with a correction ring, a correction function is incorporated in advance so that the aberration of the laser light L becomes minimum at a predetermined position in the wafer depth direction inside the wafer W as the condensing lens 38 An objective lens (infrared objective lens) may be used. In this case, although the amount of aberration correction becomes fixed according to the thickness of the wafer W and the condensing position of the laser beam (the processing depth of the modified region), for example, aberration occurs at a position where the amount of aberration correction becomes 500 μm. By using a minimum objective lens, as is apparent from the above-mentioned experimental results, the crack can be sufficiently extended from the modified region in the wafer depth direction.

  In the present embodiment, the laser light L is simultaneously condensed at two different positions in the wafer depth direction inside the wafer W, and the modified regions P1 and P2 are simultaneously formed at the respective condensing positions. After performing the two-step processing, the back surface grinding step of grinding the back surface of the wafer W is performed, and the method of dividing the wafer W into individual chips is adopted, but it is not limited thereto. The laser processing may be performed a plurality of times while changing the position (processing depth of the modified region) of condensing the laser light L in the inside of. At this time, according to the processing depth of the modified region, a correction pattern for correcting the aberration inside the wafer W (in this case, a direction for canceling the correction by the correction ring 40) on the hologram pattern to be presented to the spatial light modulator 28 By superimposing the patterns of (1) and (2), appropriate aberration correction can be performed even on a portion relatively deep from the laser beam irradiation surface of the wafer W.

  Further, in the present embodiment, as shown in FIG. 2, the second position Q2 is a first position relation as an arrangement relationship between two positions (light collection positions) Q1 and Q2 at which the laser light L is collected. A configuration is employed that is disposed upstream of the position Q1 in the wafer movement direction M (right side in FIG. 2) and is disposed deeper than the first position Q1 from the laser beam irradiation surface of the wafer W The configuration is not limited to this, and as shown in FIG. 7, the configuration may be reverse to the configuration shown in FIG. That is, the second position Q2 is disposed on the upstream side (right side in FIG. 2) of the wafer moving direction M than the first position Q1 and is shallower than the first position Q1 from the laser beam irradiation surface of the wafer W. It may be arranged at a position.

  Further, in the present embodiment, the laser light L is modulated by the spatial light modulator 28 so that the laser light L is simultaneously condensed by the condenser lens 38 at two different positions in the inside of the wafer W. The position at which the laser light L is condensed is not limited to two, and may be three or more.

  Further, in the present embodiment, a reflective spatial light modulator (LCOS-SLM) is used as the spatial light modulator 28. However, the present invention is not limited to this, and MEMS-SLM or DMD (deformable mirror device) or the like is used. It may be. Further, the spatial light modulator 28 is not limited to the reflective type, and may be a transmissive type. Furthermore, as the spatial light modulator 28, a liquid crystal cell type or an LCD type may, for example, be mentioned.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples, and it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention. .

  DESCRIPTION OF SYMBOLS 10 ... Laser processing apparatus, 11 ... Wafer moving part, 12 ... XYZθ table, 13 ... Adsorption stage, 20 ... Laser head, 22 ... Laser light source, 24 ... Beam expander, 26 ... λ / 2 wavelength plate, 28 ... Space light Modulator 36: Demagnification optical system 38: Condensing lens 40: Correction ring 42: Correction optical system 50: Controller

Claims (2)

A spatial light modulator is provided, and using the spatial light modulator, the depths from the laser light irradiation surface are different from each other in the inside of the workpiece, and are mutually different in the direction orthogonal to the thickness direction of the workpiece Laser processing means for simultaneously condensing laser light at a plurality of distant positions and correcting aberration of the laser light;
The system is configured separately from the spatial light modulator, and configured to be able to change the correction amount of the aberration according to the depth of the plurality of positions in order to prevent the effect of the correction of the aberration by the spatial light modulator from being insufficient. Aberration correction means, and
Laser processing equipment. The laser processing apparatus according to claim 1, wherein the aberration correction means is an objective lens with a correction ring.

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