JP2018027565A - Substrate processing method and substrate processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate processing method and a substrate processing device which allow a crystal substrate to be processed to be processed into a substrate containing a processing layer for obtaining a hollowed crystal substrate without crack.SOLUTION: The substrate processing method performs a first step for arranging laser light condensing means 12 on a surface 20u to be irradiated of a crystal substrate 20a to be processed, in a non-contact manner; and performs a second step for changing a light-condensing position Bf of laser light B in a circumferential direction and in a thickness direction of a part 20b to be hollowed of the crystal substrate 20a to be processed while condensing the laser light B and forming a processing layer 20b with deteriorated rupture strength to make a substrate 20C containing a processing layer. In the second step, output of laser light entering the laser light condensing means 12 is controlled so that a processing trace 22c generated in the light condensing position Bf of the laser light B extends along a crystal orientation of the crystal substrate 20a to be processed and does not extend along a different crystal orientation of the crystal substrate 20a to be processed, inside the crystal substrate 20a to be processed and in the vicinity of at least one surface of the crystal substrate to be processed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a substrate processing method and a substrate processing apparatus for forming a processing layer by irradiating laser light from the surface of a processing target crystal substrate and condensing the laser light inside the processing target crystal substrate.

  Conventionally, when manufacturing a semiconductor wafer typified by a single crystal silicon (Si) wafer, a cylindrical ingot solidified from a silicon melt melted in a quartz crucible is cut into blocks of an appropriate length. Then, the peripheral edge is ground to a target diameter, and then the block-shaped ingot is sliced into a wafer shape with a wire saw to manufacture a semiconductor wafer (see, for example, Patent Document 1).

  The semiconductor wafer thus manufactured is subjected to various processes such as formation of a circuit pattern in the previous process in order and used for the subsequent process, and the back surface is back-ground processed in the subsequent process to achieve thinning. Accordingly, the thickness is adjusted to about 750 μm to 100 μm or less, for example, about 75 μm or 50 μm.

  A conventional semiconductor wafer is manufactured as described above, and an ingot is cut by a wire saw, and a cutting allowance larger than the thickness of the wire saw is required for cutting, so a thin semiconductor wafer having a thickness of 0.1 mm or less It is very difficult to manufacture and the product rate is not improved.

JP 2005-297156 A

  By the way, when the size of the single crystal substrate is larger than the size to be used, it is efficient if the single crystal substrate can be reused with a good shape and a small size. In addition, this is not limited to a single crystal substrate but often applies to other types of substrates.

  On the other hand, a processing method for dicing the wafer by condensing the laser beam inside the wafer to form a modified region inside the wafer has been proposed. In general, this processing method utilizes the fact that the modified layer extends to the laser beam irradiation side due to heat absorption by the internally focused laser beam. This method is effective for shortening the processing time when dicing, but the crack progresses along the unexpected crystal orientation of the crystal substrate to be processed due to deterioration of the cross-sectional shape due to the progress of cracks in the modified layer. There is concern. Therefore, when the wafer is cut out, there is a concern that problems such as deterioration of the cross-sectional shape, a reduction in processing accuracy, and chipping of the wafer surface may occur.

  In view of the above problems, an object of the present invention is to provide a substrate processing method and a substrate processing apparatus for processing a crystal substrate to be processed into a processed layer-containing substrate for obtaining a cut-out crystal substrate without chipping.

  According to one aspect of the present invention for solving the above-described problem, the first step of disposing laser condensing means for condensing laser light in a non-contact manner on the irradiated surface of the crystal substrate to be processed, and the laser concentration While condensing the laser light inside the crystal substrate to be processed by optical means, the laser light condensing position is changed in the circumferential direction and the thickness direction of the portion to be cut out of the crystal substrate to be processed, and the processed layer having a reduced breaking strength is formed. And a second step of forming the processed layer-containing substrate by forming on the outer peripheral side of the hollowed out portion. In the second step, a processing mark generated at a laser beam condensing position in the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface extends along the crystal orientation of the processing target crystal substrate and is processed. There is provided a substrate processing method for controlling the output of laser light incident on a laser condensing means so as not to extend along different crystal orientations of the substrate.

  According to another aspect of the present invention, a rotating stage that holds and rotates a placed processing target crystal substrate, and a laser beam is collected toward the processing target crystal substrate that is held on the rotating stage. Laser condensing means for irradiating, irradiation axis direction distance changing means for changing the distance between the rotating stage and the laser condensing means, and laser output for changing the output of the laser light incident on the laser condensing means according to the distance Control means. The laser output control means is configured such that a processing mark generated at a laser beam condensing position extends along a crystal orientation of the processing target crystal substrate in the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface. There is provided a substrate processing apparatus for controlling so as not to extend along different crystal orientations.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate processing method and board | substrate processing apparatus which process a process target crystal board | substrate into the process layer containing board | substrate for obtaining the hollow crystal board without a chip | tip can be provided.

It is a typical side view explaining the substrate processing apparatus concerning a 1st embodiment. (A) to (c) is a schematic side view for explaining a process for manufacturing a processed layer-containing substrate by the substrate processing method according to the first embodiment. (A) And (b) is typical sectional side view which shows that the process layer is formed by the board | substrate processing method which concerns on 1st Embodiment, respectively. In a 1st embodiment, it is a typical perspective view explaining cutting out a hollow object part from a processing layer content substrate. FIG. 5 is a schematic side view for explaining an aberration correction adjustment function in the substrate processing apparatus according to the first embodiment. It is typical explanatory drawing explaining that the processing trace is arranged in the processing layer formed with the substrate processing method concerning a 1st embodiment. In Example 1 of Experimental example 1, it is the imaging figure which imaged the fractured surface with the electron microscope. It is a schematic diagram explaining raising the substrate depth direction position of a condensing point by moving the condensing point of a laser beam to the to-be-irradiated surface side gradually in Experimental example 1. FIG. It is the imaging example which imaged the to-be-irradiated surface with the electron microscope in Experimental example 1. FIG. FIG. 10 is a partially enlarged view of FIG. 9. In Example 2 of Experimental example 2, it is the image pick-up figure which imaged the fractured surface with the electron microscope. In Example 2 of Experimental example 2, it is the image pick-up figure which imaged the fractured surface with the electron microscope. In Example 2 of Experimental example 2, it is the image pick-up figure which imaged the fractured surface with the electron microscope. It is a typical side surface sectional view showing the substrate processing method concerning a 2nd embodiment, and the processing layer containing board manufactured by example 3 of an experiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the same or similar components as those already described are denoted by the same or similar reference numerals, and detailed description thereof is omitted as appropriate. The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not something specific. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention.

[First Embodiment]
First, the first embodiment will be described. FIG. 1 is a schematic side view illustrating a substrate processing apparatus according to the present embodiment. 2A to 2C are schematic side views illustrating a process for manufacturing a processed layer-containing substrate by the substrate processing method according to this embodiment. 3A and 3B are schematic side cross-sectional views showing that a processed layer is formed by the substrate processing method according to the present embodiment, respectively. FIG. 4 is a schematic perspective view for explaining the hollowing out of the single crystal substrate from the processed layer-containing substrate in the present embodiment. FIG. 5 is a schematic side view for explaining the aberration correction adjustment function in the substrate processing apparatus according to the present embodiment. FIG. 6 is a schematic explanatory diagram for explaining that the processing marks are arranged in the processing layer formed by the substrate processing method according to the present embodiment.

(Substrate processing equipment)
As shown in FIGS. 1 and 2, the substrate processing apparatus 10 according to this embodiment includes a rotary stage 11 that holds and rotates a processing target crystal substrate 20 a, and a stage surface Su of the rotary stage 11. Irradiation axis direction distance that changes the distance L between the laser condensing unit 12 (for example, a condensing device) that condenses the laser beam B toward the held crystal substrate 20a to be processed and the rotary stage 11 and the laser condensing unit 12. A changing means (not shown) and a laser output control means 14 for changing the output of the laser beam B incident on the laser condensing means 12 according to the distance L are provided. Further, the substrate processing apparatus 10 has a radial distance changing means (a figure for changing the distance r between the rotation center axis Cs of the rotary stage 11 and the irradiation center axis Cb of the laser beam B to the processing target crystal substrate 20a by the laser focusing means 12). Not shown).

  The irradiation axis direction distance changing means may be a mechanism for moving the laser condensing means 12 in the perspective direction relative to the rotary stage 11, or moving the rotary stage 11 in the perspective direction relative to the laser condensing means 12. A mechanism (for example, an X stage or an XY stage) may be used.

  The radial distance changing means may be a moving mechanism that moves the laser condensing means 12 in one direction parallel to the stage surface Su (for example, the X direction in FIGS. 1 and 2). It may be a moving mechanism that moves in one direction parallel to the surface Su (for example, the X direction in FIGS. 1 and 2).

  The laser output control means 14 transmits a control signal for controlling the output of the laser oscillation device J according to the distance L. This laser output control means 14 is such that a processing mark 22c generated near the surface of the processing target crystal substrate (near the surface (near the top surface) or near the back surface (near the bottom surface)) at the laser beam condensing position is The output of the laser beam B incident on the laser condensing means 12 is controlled so that it extends along the crystal orientation of the substrate 20a and does not extend along different crystal orientations of the processing target crystal substrate 20a.

  Here, the processing trace extends along a crystal orientation different from the crystal orientation of the crystal substrate to be processed. For example, when a single crystal silicon wafer having a crystal orientation [100] is used as a substrate material, the processing trace extends along the crystal orientation [100]. Although it is necessary to form processing traces in the substrate thickness direction, in single crystal silicon, cleavage is likely to occur in the [111] and [110] orientations, which have a weaker bonding force, and the processing traces develop along these crystal orientations. That means. As a result, the cut-out cross-section becomes non-uniform, or chipping or cracking occurs.

  In the present embodiment, the laser output control means 14 is incident on the laser condensing means 12 by increasing the output of the laser oscillation device J as the condensing position Bf of the laser light B is closer to the processing target crystal substrate surface. Control is performed so that the output of the laser beam B increases. In the substrate processing apparatus 10 of this embodiment, the vicinity of the processing target crystal substrate surface that controls the increase in output is set as the vicinity of the irradiated surface 20u (front surface) of the laser beam B, which is opposite to the irradiated surface 20u. The laser output control means 14 does not perform such control in the vicinity of the surface, that is, the surface on the rotary stage side (back surface 20v). Even in the vicinity of the back surface 20v, the apparatus configuration may be such that such control is possible by the laser output control means 14 using a changeover switch or the like.

  In this embodiment, the laser condensing unit 12 includes a condensing lens 15 as shown in FIGS. 5 and 6, and a function of correcting aberration caused by the refractive index of the crystal substrate 20a to be processed, that is, aberration. It functions as a correction ring. Specifically, the condensing lens 15 collects laser light that has reached the outer peripheral portion E of the condensing lens 15 more than the laser light that has reached the central portion M of the condensing lens 15 when condensing in the air. The correction is made so that light is condensed on the optical lens side. That is, when the light is condensed, the condensing point EP of the laser light reaching the outer peripheral portion E of the condensing lens 15 is more concentrated than the condensing point MP of the laser light reaching the central portion M of the condensing lens 15. The correction is made so that the position is close to the lens 15.

  The condensing lens 15 includes a first lens 16 that condenses in the air, and a second lens 18 that is disposed between the first lens 16 and the processing target crystal substrate 20a. In the present embodiment, both the first lens 16 and the second lens 18 are lenses that can condense laser light in a conical shape. The length of the condensing point EP and the condensing point MP can be adjusted by adjusting the distance between the first lens 16 and the second lens 18, and the condensing lens 15 is a lens with a correction ring. It has a function.

  As the first lens 16, in addition to a spherical or aspherical single lens, a combination lens can be used in order to secure various aberration corrections and working distances, and the NA is 0.3 to 0.85. It is preferable. As the second lens 18, a lens having an NA smaller than that of the first lens 16, for example, a convex glass lens having a curvature radius of about 3 to 5 mm is preferable from the viewpoint of easy use.

  Instead of the second lens 18, an aberration enhancing material (for example, an aberration enhancing glass plate) of the laser beam B can be arranged.

(Substrate processing method)
Hereinafter, an example in which the processing target crystal substrate 20a is a single crystal substrate will be described, and the substrate processing method according to the present embodiment using the substrate processing apparatus 10 will be described including effects.

  In this embodiment, the 1st process of arrange | positioning the laser condensing means 12 non-contactingly on the to-be-irradiated surface 20u of the process target single crystal substrate 20am is performed. Then, while condensing the laser beam B inside the processing target single crystal substrate 20am by the laser focusing means 12, the condensing position Bf of the laser beam B is changed in the thickness direction of the cut target portion 20b of the processing target single crystal substrate 20am ( The second step of forming the processed layer-containing substrate 20c is performed by forming the processed layer 22 having a reduced breaking strength on the outer peripheral side of the cutout target portion 20b. In the second step, the processing trace 22c generated at the condensing position of the laser beam B in the processing target single crystal substrate and in the vicinity of at least one processing target single crystal substrate surface is along the crystal orientation of the processing target single crystal substrate 20am. The output of the laser beam B incident on the laser condensing means 12 is controlled so as to extend and extend along different crystal orientations of the processing target single crystal substrate 20am.

  Hereinafter, the procedure for forming the processed layer 22 in the second step will be described in detail. When irradiating the processing target single crystal substrate 20am with the laser beam B, the processing target single crystal substrate arranged on the rotary stage 11 so that irradiation can be started from the surface (back surface 20v) opposite to the irradiated surface 20u. The Z-axis direction position of the condensing position Bf at 20 am is determined.

  First, the laser beam B is irradiated along the concentric circle while rotating the rotary stage 11 at least once. Thereafter, the condensing position Bf is moved in the Z-axis direction of the substrate processing apparatus 10 and the laser beam B is similarly irradiated along the concentric circles. At this time, since the movement of the condensing position Bf in the Z-axis direction is the same as the thickness direction of the single crystal substrate 20am to be processed, the processing layer 22 is formed in a short cylindrical shape orthogonal to the irradiated surface 20u. Can be formed.

  By performing this series of operations up to the vicinity of the irradiated surface 20u of the single crystal substrate 20am to be processed, the processed layer 22 can be completed. In order to perform this movement of the condensing position Bf, it is only necessary to move at least one of the laser condensing means 12 or the rotary stage 11.

  The first condensing position Bf on the back surface 20v (bottom surface) side of the processing target single crystal substrate 20am is such that the processing layer 22 formed by irradiation with the laser beam B is cracked or ablated on the back surface 20v of the processing target single crystal substrate 20am. Is set within a predetermined range that does not cause unnecessary damage (particularly damage to the cutout target portion 20b).

  In the processing layer 22, processing marks 22c formed by condensing the laser beam B are regularly arranged at regular intervals. The interval at which the processing marks 22c are formed is determined by the relationship between the oscillation repetition frequency of the laser beam B and the rotation speed of the rotary stage 11, that is, the peripheral speed, in the substrate plane direction (direction parallel to the irradiated surface 20u and the back surface 20v). In the substrate height (depth) direction, it is determined by the amount of movement of the condensing position Bf in the Z-axis direction. The processed layer 22 is obtained as a region where the processing marks 22c are intermittently formed by irradiating the laser beam B at a predetermined interval as described above. At this time, the laser beam B is composed of, for example, a pulse laser beam having a pulse width of 1 μs or less, and a wavelength of 300 nm or more is selected. For example, when the processing target single crystal substrate 20am is a silicon wafer, a YAG laser having a wavelength of 1000 nm or more Are preferably used.

  Then, the laser output is controlled so that the length K in the substrate thickness direction of the processing target crystal substrate 20a is 10 μm or less at the condensing position Bf of the laser beam B. Specifically, the laser output is increased as the condensing position Bf is closer to the irradiated surface 20u. Further, laser irradiation is stopped in the vicinity of the irradiated surface 20u, and no ablation or chipping occurs on the irradiated surface side of the single crystal substrate to be processed.

  Here, in this embodiment, the laser output is adjusted so that the length K in the substrate thickness direction of the processing mark 22c is 10 μm or less, preferably 3 μm to 7 μm at the condensing position Bf in the processing target single crystal substrate. Then, a processing mark 22c having a length K of 10 μm or less (preferably 3 μm to 7 μm) is formed while moving the condensing position Bf stepwise toward the surface side of the processing target single crystal substrate 20am. At that time, the processing mark 22c extends along the crystal orientation (for example, [100] orientation) of the processing target crystal substrate 20a, and a different crystal orientation (for example, [111] orientation or [110] orientation) of the processing target crystal substrate 20a. The processing mark 22c is formed so that the processing mark 22c does not extend along the line. As a result, it is possible to efficiently obtain a cut-out crystal substrate having a good quality in a short time by extending the processing trace 22c in the crystal orientation of the processing target crystal substrate 20a. Therefore, a processing mark having a length K of 10 μm or less (preferably 3 μm to 7 μm) at each condensing position Bf by controlling the output of the laser beam to the condensing position Bf based on the output confirmed in advance. 22c is formed at a predetermined position. When the processing mark length is less than 3 μm (for example, 2 μm), the formed processing marks are difficult to connect in the depth direction, so that it is difficult to perform good drilling.

  Note that the output of the laser beam may be decreased near the back surface 20v in the vicinity of the back surface 20v, and this effect becomes more remarkable.

  In the present embodiment, in the vicinity of the irradiated surface 20u, the output of the laser beam B is increased as the condensing position Bf of the laser beam B is closer to the irradiated surface 20u. In the processed layer portion near the irradiated surface 20u, Compared to other processed layer portions, the processing mark 22c is small, and the distortion generated around the processing mark 22c is small. Therefore, when the user cuts out the hollow portion 20b, it is possible to greatly suppress the occurrence of unnecessary cracks from the processing marks 22c in the vicinity of the irradiated surface 20u and damage to the hollow single crystal substrate 20d.

  Therefore, according to the present embodiment, it is possible to realize the substrate processing apparatus 10 and the substrate processing method that can easily obtain the cut single crystal substrate 20d without chipping (chipping) from the processing target single crystal substrate 20am in a short time. Note that the outer peripheral surface of the obtained single crystal substrate 20d is subjected to processing such as polishing as necessary.

  Here, the vicinity of the irradiated surface 20u refers to a portion in the vicinity of the irradiated surface that can be manually cut out after forming the processed layer 22 without causing unnecessary chipping by the laser light irradiation. Specifically, it is in the range from the irradiated surface (substrate surface) to 100 μm inside, preferably in the range from the substrate surface to 50 μm. By adjusting the output of the laser beam B by the laser output adjusting means within this range, it is necessary to form a processing mark without causing ablation.

  In the case where the size of the single crystal substrate is larger than the size to be used, this single crystal substrate is used as the processing target single crystal substrate 20am, and the hollow single crystal substrate 20d having a size smaller than the processing target single crystal substrate 20am is obtained. By obtaining the single crystal substrate 20am to be processed, the resources can be effectively used.

  In the present embodiment, when the laser condensing means 12 and the back surface 20v of the processing target single crystal substrate 20am are separated, the movement is performed in the same direction as the substrate thickness direction. Therefore, since the processed layer 22 is formed in a short cylindrical shape, the outer periphery of the obtained hollow single crystal substrate 20d is a cylindrical outer peripheral shape, which is easy to use. Here, in this embodiment, in the vicinity of the irradiated surface 20u of the processed layer-containing substrate 20c, distortion and damage generated around the processed mark 22c are small, and in addition, the first step toward the back surface 20v side of the processing target single crystal substrate 20am is performed. The condensing position Bf is set at a substrate thickness position within a predetermined range from the back surface 20v so as not to cause unnecessary damage to the back surface 20v due to cracks, ablation, or the like. Therefore, even if the shape of the processed layer 22 is not simply a shape in which chipping is likely to occur (for example, a tapered shape spreading on the back surface side), but simply a short cylindrical shape, generation of useless cracks from the processed marks 22c is greatly suppressed. ing.

  In the present embodiment, in the second step, the distance between the first lens 16 and the second lens 18 provided in the laser condensing means 12 is made constant, that is, the adjustment of the laser beam B by the aberration correction adjustment function. The state is kept constant. Therefore, only the output of the laser beam B is changed in parameters according to the movement of the condensing position Bf in the Z-axis direction, and these effects can be obtained by controlling with the laser output control means 14. is there. The distance between the first lens 16 and the second lens 18 is set to an appropriate value in consideration of the difficulty of generating unnecessary cracks in the hollowing and the ease of forming the processed layer 22.

  Note that the adjustment of the distance between the first lens 16 and the second lens 18, that is, the adjustment of the laser beam B by the function as an aberration correction ring may be changed while changing the output of the laser beam B. Thereby, the dimension of the machining mark 22c and the distortion around the machining mark 22c can be controlled with higher accuracy.

  Further, the substrate processing apparatus 10 is a radial distance changing means for changing the distance r between the rotation center axis Cs of the rotary stage 11 and the irradiation center axis Cb of the laser beam B to the processing target single crystal substrate 20am by the laser focusing means 12. It has. Therefore, it is possible to easily change the formation position of the processed layer 22 in accordance with the radius of the cut target 20b.

  In FIG. 4, the processing layer 22 is drawn so that the processing marks 22 c are arranged in a line, but actually, the processing layer 22 has a laser beam so that the processing marks 22 c are scattered over a plurality of rows. B may be irradiated. Thereby, the operation | work at the time of cutting out the hollow part 20b from the process layer containing board | substrate 20c becomes still easier.

  Further, in the second step, when increasing the output of the laser beam B, the ratio of the increase amount of the laser output to the decrease amount of the substrate thickness from the irradiated surface 20u to the condensing position Bf is linear (linear function, that is, Constant). Thereby, the output control by the laser output control means 14 is simple.

  In the second step, when increasing the output of the laser beam B, the ratio of the increase amount of the laser output to the decrease amount of the substrate thickness from the irradiated surface 20u to the condensing position Bf becomes closer to the irradiated surface 20u. It may be suppressed (for example, it may be suppressed closer to the irradiated surface 20u by suppressing the increase rate in a quadratic or cubic function manner). Thereby, compared with the case where it increases linearly, it can suppress more effectively that a useless crack generate | occur | produces when punching out the hollow part 20b, and damage arises in the hollow part 20b.

  In the second step, as shown in FIG. 6, the length K in the substrate thickness direction of the processing mark 22c formed on the processing layer 22 by condensing the laser beam B is set to 10 μm or less. As a result, the processing mark 22c tends to easily extend well in the vertical direction (crystal orientation [100]) of the processing target single crystal substrate 20am. That is, by forming the processing trace 22c without extending in a direction other than the vertical direction (crystal orientation [100]), it is possible to obtain a state in which other processing traces are continuously connected along the crystal orientation in the thickness direction. , It is possible to effectively suppress the occurrence of cracks and chippings in the cutout.

  Further, in the description of the substrate processing method according to the present embodiment, the example in which the processing target single crystal substrate 20am is a single crystal substrate has been described, but the substrate processing method according to the present embodiment is not limited to a single crystal substrate. Applicable.

  In the present embodiment, as an example of the substrate processing method, the substrate processing apparatus 10 according to the present embodiment is used to form the processed layer-containing substrate 20c. However, the substrate processing apparatus 10 is not used, and another apparatus is used. Of course, it is also possible to manufacture the processed layer-containing substrate 20c.

<Experimental example 1>
The inventor uses the substrate processing apparatus 10 described in the above embodiment, and forms an object to be processed on the stage surface Su on the rotary stage 11 as an example of the substrate processing method according to the above embodiment (hereinafter referred to as Example 1). The single crystal substrate 20am was fixed by holding a disk-shaped single crystal silicon wafer. At that time, the rotation center axis Cs of the rotary stage 11 and the center axis of the single crystal silicon wafer were matched.

  At that time, a single crystal silicon wafer having a crystal orientation of [100] and having a thickness of 625 μm and having a diameter of 150 mm was set as a processing target single crystal substrate 20am, and a φ50 mm hollow single crystal substrate was obtained and irradiated with laser light.

Irradiation conditions by the laser oscillator are as follows.
Objective lens: 100x with correction ring function, NA is 0.85
(Uses Olympus LCPLN100XR)
Wavelength (nm): 1064
Pulse width (ns): 190
Correction ring adjustment amount: 1.0
(Correction ring scale value)
Repetition frequency (kHz): 500
Irradiation interval (μm): 2.0

The processing conditions were as follows. In the following description, the processing mark depth position is the position in the substrate depth direction, and the laser output is the pulse energy of the laser.
Processing mark depth position (μm) Laser output (μJ)
725-625 2.3
625-580 2.6
580-500 3.4
500-420 4.2
420-360 5.0
360-260 5.7
260-50 9.3
50-0 6.5

  The processed layer containing substrate 20c was formed by forming the short cylindrical processed layer 22 by performing such laser irradiation. The processed layer containing substrate 20c was formed by forming the short cylindrical processed layer 22 by performing such laser irradiation. Then, when the fractured surface formed by hollowing was observed with a microscope (confocal laser microscope), as shown in FIG. 7, a uniform cross-sectional state was shown, and the processing trace was in a crystal orientation different from the crystal orientation [100]. It was not stretched.

  Here, when the position of the condensing point in the substrate depth direction is increased by gradually moving the condensing point of the laser beam to the irradiated surface side (see FIG. 8), the correction ring adjustment amount (correction ring scale value) ) Is not changed, processing marks are not easily formed due to attenuation of spherical aberration and light intensity, that is, attenuation of laser energy per unit area at the focal point. Therefore, in this laser irradiation in this experimental example, the processing is started with the minimum output by adjusting the DF amount and the laser output so that a processing mark 22c having a length of 7 μm can be formed in the deepest part (back side) of the substrate. did.

  And when raising the condensing point of a laser beam with respect to the position of a board | substrate depth direction, the laser output was raised according to the threshold value of the laser output in which processing trace formation is possible. By repeating this work, it was possible to form a processed layer without extending the processing trace in a crystal orientation ([110] or [110]) different from the crystal orientation [100].

  Also, near the substrate surface, the processing trace becomes longer due to the effect of decreasing the light intensity attenuation, and the substrate surface is likely to be ablated or cracked. When located near the irradiation surface, the laser output was reduced. As a result, as shown in FIGS. 9 and 10, the irradiated surface 20u was prevented from being ablated or cracked by the processing marks 22c.

<Experimental example 2>
The inventor uses the substrate processing apparatus 10 described in the above embodiment, and as an example of the substrate processing method according to the above embodiment (hereinafter, referred to as Example 2), on the rotary stage 11 as in Experimental Example 1. The stage-shaped Su was fixed by holding a disk-shaped single crystal silicon wafer as the processing target single crystal substrate 20am. At that time, the rotation center axis Cs of the rotary stage 11 and the center axis of the single crystal silicon wafer were matched.

  At that time, a single crystal silicon wafer having a crystal orientation of [110] and having a thickness of 625 μm and having a diameter of 150 mm was set as a single crystal substrate to be processed 20am, and a single crystal substrate having a diameter of 50 mm was obtained and irradiated with laser light.

The irradiation conditions by the laser oscillator are as follows and are the same as those in Experimental Example 1.
Objective lens: 100x with correction ring function, NA is 0.85
(Uses Olympus LCPLN100XIR)
Wavelength (nm): 1064
Pulse width (ns): 190
Correction ring adjustment amount: 1.0
Repetition frequency (kHz: 500
Irradiation interval (μm): 2.0

  The processing conditions were as follows. As in Experimental Example 1, in the following description, the processing mark depth position is the position in the substrate depth direction, and the laser output is the pulse energy of the laser.

Processing mark depth position (μm) Laser output (μJ)
725-625 2.3
625-580 2.6
580-500 2.6
500-420 3.0
420-360 6.5
360-260 7.5
260-50 9.3
50-0 6.5
The processed layer containing substrate 20c was formed by forming the short cylindrical processed layer 22 by performing such laser irradiation.

  Compared with Experimental Example 1, in this experimental example, when the processing mark depth position is 580 μm to 500 μm and 500 to 420 μm, the length of the processing mark 22 c is shortened by lowering the laser output, and the processing mark depth position is 420 to When the thickness was 360 μm and 360 to 260 μm, the length of the machining mark 22c was increased by increasing the laser output.

  In this experimental example, when the processing mark length was less than 2 μm, the punching was not smooth. When the fractured surface formed by hollowing was observed with a microscope, it was in a state where it was forcibly cleaved (see FIG. 11).

  When the machining mark length was 4 μm to 7 μm, the hollowing was smooth, and the fractured surface formed by the hollowing was observed with a microscope, and as a result, the machining marks in the thickness direction were connected and the fractured surface was smooth (see FIG. 12). . The surface roughness at this time was Rz = 0.667 μm.

  When the processing trace length is longer than 10 μm, or when a part of the external processing trace (adjacent processing trace) overlaps the processing trace, cleavage occurs in the cut section (see FIG. 13). It is determined that this is because the processing marks have been extended in a crystal orientation [111] different from the orientation [100].

[Second Embodiment]
Next, a second embodiment will be described. FIG. 14 is a schematic side cross-sectional view showing a processed layer-containing substrate manufactured by the substrate processing method according to the present embodiment (the irradiation energy of laser light in the substrate thickness direction shows the value in Experimental Example 3). In the present embodiment, as in the first embodiment, an example in which the processing target crystal substrate 20a is a single crystal substrate will be described.

  In the present embodiment, compared to the first embodiment, when the processing layer 22 is formed on the processing target single crystal substrate 20am in the second step, the back surface (bottom surface) side of the processing target single crystal substrate 20am is configured in the processing layer 22. In the processed layer back surface portion 22v, the distance r between the rotation center axis Cs of the rotary stage 11 and the irradiation center axis Cb of the laser condensing means 12 is gradually increased as the distance from the back surface 20v increases. Also, the distance is constant on the irradiated surface 20u side (front side) (see FIG. 14). Then, by gradually expanding in this way, the outer peripheral side of the processed layer rear surface side portion 22v is formed in an R-plane shape (circular arc shape) whose diameter gradually increases as the distance from the back surface 20v of the processing target single crystal substrate 20am increases. doing. As a result, the processed layer back surface portion 22v has a chamfered shape having a radius N (that is, the portion located on the inner peripheral side of the processed layer back surface portion 22v in the cut-out target portion 20b is also an R surface shape). The punched portion 20b has a structure that can be easily broken from the rear surface side portion 22v of the processed layer.

  As the substrate processing apparatus used in the present embodiment, for example, the substrate processing apparatus 10 described in the first embodiment is used, and the distance r is gradually increased by a radial direction distance changing unit (not shown). In this case, it is preferable that a control program for moving the rotary stage 11 in this way is input to the control means (CPU or the like) of the substrate processing apparatus in order to ensure accuracy and ease of processing.

  In the present embodiment, a hollow single crystal substrate 20d in which the rear surface of the substrate is formed into an R-plane shape having a radius N can be easily obtained by hollowing out the hollow portion 20b from the processed layer-containing substrate 20c. Therefore, the chamfering operation of the hollow single crystal substrate 20d can be eliminated or greatly reduced, and the hollow single crystal substrate 20d (wafer) can be easily handled.

  Further, when the laser beam is irradiated in the second step, such a processed layer 22 is formed by connecting the processing traces one by one. Therefore, the time required for forming the processed layer 22 is reduced to the first time. It can be suppressed to a time that is not so different from the embodiment.

  In the processed layer rear surface portion 22v, it is important to connect the processing marks 22c in the radial direction of the cut target portion 20b (wafer) closer to the back surface 20v from the viewpoint of favorably cutting the cut target portion 20b. As it approaches the irradiated surface side (front surface side), it is important to connect the processing marks 22c gradually in the substrate thickness direction. Therefore, by making a measure such as narrowing the line pitch of the machining mark 22c closer to the back surface 20v and gradually increasing the line pitch as it approaches the irradiated surface side (front surface side), the cut-out target portion 20b is further improved. It can be cut out.

  Further, in the present embodiment, the example in which the outer peripheral side of the processed layer back surface side portion 22v is formed in an R-surface shape has been described, but not only the R-surface shape but also a curved convex surface shape may be cut out from the processed layer-containing substrate 20c. 20b can be easily cut out.

  Further, the processed layer back surface portion 22v does not have such a shape, and the processed layer surface side portion constituting the irradiated surface side (front surface side) of the processing target single crystal substrate 20am in the processed layer 22 is formed on the processed layer back surface side. By making the shape like the portion 22v, it is possible to obtain a hollow single crystal substrate 20d in which the substrate surface has an R-plane shape with a radius N.

  Further, in the description of the substrate processing method according to the present embodiment, the example in which the processing target single crystal substrate 20am is a single crystal substrate has been described, but the substrate processing method according to the present embodiment is not limited to a single crystal substrate. Applicable.

<Experimental example 3>
The present inventor processed a single crystal substrate to be processed under the following conditions using an example of the substrate processing method according to the second embodiment, using the substrate processing apparatus 10.

  First, a disk-shaped single crystal silicon wafer was fixed to the stage surface Su on the rotary stage 11 as a processing target single crystal substrate 20am. At that time, the rotation center axis Cs of the rotary stage 11 and the center axis of the single crystal silicon wafer were matched.

Irradiation conditions by the laser oscillator are as follows.
Repetition frequency (kHz): 500
Correction ring adjustment amount: 1.0
(Correction ring scale value)
Processing mark pitch (μm): 2.0
Line pitch (μm): 3.0

The processing conditions were as follows. In the following description, the processing mark depth position is the position in the substrate depth direction, and the laser output is the pulse energy of the laser.
Processing mark depth position (μm) Laser output (μJ)
725-660 2.3
660-580 2.6
580-500 3.4
500-420 4.2
420-360 5.0
360-260 5.7
260-50 9.3
50-5 6.5

  The processed layer containing substrate 20c was formed by forming the processed layer 22 by performing such laser irradiation. In this experimental example, the processed layer 22 was formed so that the cut-out single crystal substrate 20d had a diameter of 12.7 mm and the processed layer rear surface portion 22v had a radius N of 0.3 mm.

  Thereafter, the single crystal substrate 20d was cut out from the processed layer-containing substrate 20c to obtain a wafer. Then, the shape of the chamfered portion 20de (wafer portion forming the inner side of the processed layer rear surface side portion 22v) of the wafer (the hollow single crystal substrate 20d) was measured and observed with an electron microscope.

  As a result of the observation, it was confirmed that the shape of the chamfered portion 20de was almost the target shape. The chamfered portion 20de had irregularities of about 20 μm.

  According to the present invention, it is possible to obtain a substrate having a smaller dimension from the crystal substrate to be processed. Therefore, the thinly cut substrate is, for example, a single crystal substrate and is a Si substrate (silicon substrate). It can be applied to solar cells, and sapphire substrates such as GaN-based semiconductor devices can be applied to light-emitting diodes, laser diodes, etc., and SiC can be applied to SiC-based power devices. It can be applied in a wide range of fields such as transparent electronics field, lighting field and hybrid / electric vehicle field.

DESCRIPTION OF SYMBOLS 10 Substrate processing apparatus 11 Rotating stage 12 Laser condensing means 14 Laser output control means 15 Condensing lens 16 First lens 18 Second lens 20a Processing target crystal substrate 20am Processing target single crystal substrate 20b Drilling target portion 20c Processing layer containing substrate 20d Cut-out single crystal substrate 20u Irradiated surface 20v Back side (substrate back side)
22 Processing layer 22c Processing mark B Laser beam Bf Condensing position Cb Irradiation center axis Cs Rotation center axis E Outer peripheral part EP Condensing point K Substrate thickness direction length L Distance M Central part MP Condensing point Su Stage surface r Distance

Claims (16)

A first step of disposing laser condensing means for condensing laser light in a non-contact manner on the irradiated surface of the crystal substrate to be processed;
While condensing laser light inside the processing target crystal substrate by the laser condensing means, the focusing position of the laser light is changed in the circumferential direction and the thickness direction of the cut target portion of the processing target crystal substrate, and the breaking strength is increased. Including a second step of forming a lowered processed layer on the outer peripheral side of the cut-out target portion to form a processed layer-containing substrate,
In the second step, a processing mark generated at a laser beam condensing position in the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface extends along a crystal orientation of the processing target crystal substrate; The substrate processing method characterized by controlling the output of the laser beam which injects into the said laser condensing means so that it may not extend | stretch along the different crystal orientation of the said process target crystal substrate.   The substrate processing method according to claim 1, wherein the vicinity of the crystal substrate surface to be processed is the vicinity of the irradiated surface. In the second step,
Focus the laser beam on the substrate thickness position within a predetermined range from the back surface of the substrate that is the surface opposite to the irradiated surface,
The substrate processing method according to claim 2, wherein the processing layer is formed by irradiating a laser beam while moving the laser condensing unit away from the back surface of the substrate.   4. The substrate processing method according to claim 3, wherein, in the second step, the laser output is increased in accordance with an increase in a laser output threshold value at which the processing trace can be formed with the movement.   The substrate processing method according to claim 2, wherein the length of the processing mark is 10 μm or less.   6. The substrate processing method according to claim 5, wherein a length of the processing mark is in a range of 3 to 7 [mu] m.   The substrate processing method according to claim 6, wherein a length of the processing mark is in a range of 4 to 7 μm.   The ratio of the increase amount of the output to the decrease amount of the substrate thickness from the irradiated surface to the condensing position is made constant when increasing the output of the laser light in the second step. 4. The substrate processing method according to 2 or 3.   In the second step, when increasing the output of the laser beam, the ratio of the increase in the output to the decrease in the substrate thickness from the irradiated surface to the condensing position is suppressed as it becomes closer to the irradiated surface. The substrate processing method according to claim 2, wherein the substrate processing method is characterized.   The substrate processing method according to claim 2, wherein in the second step, the processing layer is formed in a short cylindrical shape.   11. The method according to claim 2, wherein, in the second step, a length in a substrate thickness direction of a processing mark formed in the processing layer by condensing a laser beam is set to 10 μm or less. Substrate processing method. The laser focusing means has an aberration correction adjustment function,
2. In the second step, after the aberration is corrected to the position of the back surface of the substrate that is the surface opposite to the irradiated surface, the adjustment state of the laser beam by the adjustment function is kept constant. The substrate processing method according to any one of ˜11.   Among the processed layers, the outer peripheral side of the one substrate surface side portion of the processed layer constituting the one processed target single crystal substrate surface side is a curved convex surface whose diameter gradually increases as the distance from the one processed target single crystal substrate surface increases. It is made into the shape, The board | substrate processing method of any one of Claims 1-12 characterized by the above-mentioned. A rotating stage that holds and rotates the processing target crystal substrate;
Laser condensing means for condensing laser light toward the processing target crystal substrate held on the rotating stage;
An irradiation axis direction distance changing means for changing a distance between the rotary stage and the laser focusing means;
Laser output control means for changing the output of the laser light incident on the laser focusing means according to the distance,
The laser output control means is configured such that a processing mark generated at a laser beam condensing position extends along a crystal orientation of the processing target crystal substrate in the processing target crystal substrate and in the vicinity of at least one processing target crystal substrate surface. A substrate processing apparatus, which is controlled so as not to extend along different crystal orientations of a target crystal substrate. The laser output control means includes
The vicinity of the crystal substrate surface to be processed is the vicinity of the irradiated surface,
Focus the laser beam on the substrate thickness position within a predetermined range from the back surface of the substrate that is the surface opposite to the irradiated surface,
The substrate processing apparatus according to claim 14, wherein the laser condensing unit is controlled to move away from the back surface of the substrate so as to irradiate laser light to form the processed layer.   16. The substrate processing apparatus according to claim 15, further comprising a radial distance changing unit that changes a distance between a rotation center axis of the rotary stage and an irradiation center axis of the laser focusing unit to the processing target crystal substrate. .