JP2013158778A - Method for producing monocrystalline substrate, monocrystalline substrate, and method for producing monocrystalline member with modified layer formed therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a monocrystalline substrate, capable of making, when a relatively large and thin monocrystalline substrate is formed by peeling it from a modified layer formed in a monocrystalline member, the surface roughness Ra of a peeled surface of the monocrystalline substrate less than 1, a monocrystalline substrate obtained thereby, and a method for producing a monocrystalline member with a modified layer formed therein.SOLUTION: The method includes a first step of disposing a condenser lens 15 in a non-contact manner upon the monocrystalline member 10; a second step of concentrating a laser light B inside the monocrystalline member and relatively moving the condenser lens 15 and the monocrystalline member 10 to form a two-dimensional modified layer 12 inside the monocrystalline member; and a third step of forming the monocrystalline substrate by peeling the monocrystalline layer separated by the modified layer 12 from the modified layer 12. Irradiation conditions for laser light are adjusted in the second step, so that the surface roughness Ra of the peeled surface of the monocrystalline substrate formed in the third step is less than 1.

Description

  The present invention relates to a method for producing a single crystal substrate, a single crystal substrate, and a method for producing an internal modified layer-forming single crystal member, and more particularly, to a method for producing a single crystal substrate by thinly and stably cutting a single crystal substrate, and a single crystal The present invention relates to a substrate and a method for producing an internal modified layer-forming single crystal member.

  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.

  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 the product, and the product rate is not improved.

  In recent years, silicon carbide (SiC), which has high hardness and high thermal conductivity, has attracted attention as a next-generation semiconductor. In the case of SiC, ingots can be easily formed with a wire saw because of its higher hardness than Si. In addition, it is not easy to slice the substrate, and it is not easy to thin the substrate by back grinding.

  On the other hand, the condensing point of the laser beam is aligned with the inside of the ingot with the condensing lens, and the ingot is relatively scanned with the laser beam to form a planar modified layer by multiphoton absorption inside the ingot. A substrate manufacturing method and a substrate manufacturing apparatus are disclosed in which a part of the ingot is peeled off using the modified layer as a peeling surface. For example, Patent Document 1 discloses a technique of using a multiphoton absorption of laser light to form a modified layer inside a silicon ingot and peeling the wafer from the silicon ingot using an electrostatic chuck.

JP 2005-277136 A

  However, with the technique of Patent Document 1, it is not easy to uniformly peel off a large-area substrate (silicon substrate). In addition, since the surface roughness of the peeled surface of the obtained single crystal substrate (wafer) is relatively rough, the time taken for lapping (polishing) of the peeled surface is long.

  In view of the above-described problems, the present invention has a surface roughness Ra of the separation surface of the single crystal substrate of less than 1 when a relatively large and thin single crystal substrate is formed by peeling from the modified layer formed on the single crystal member. It is an object of the present invention to provide a method for manufacturing a single crystal substrate, a single crystal substrate, and a method for manufacturing an internal modified layer-forming single crystal member.

  According to an aspect of the present invention for solving the above-described problem, a laser beam is formed on the surface of the single crystal member by the first step of disposing the laser focusing unit on the single crystal member in a non-contact manner and the laser focusing unit. The laser light is condensed inside the single crystal member by irradiating light, and the laser condensing means and the single crystal member are relatively moved so that a two-dimensional modification is made inside the single crystal member. A second step of forming a porous layer, and a third step of forming a single crystal substrate by peeling a single crystal layer separated by the modified layer from the modified layer, the third step There is provided a method for manufacturing a single crystal substrate in which the laser light irradiation conditions are adjusted in the second step so that the surface roughness Ra of the peel surface of the single crystal substrate formed in step 1 is less than 1.

  According to another aspect of the present invention, there is provided a single crystal substrate manufactured by the method for manufacturing a single crystal substrate according to the present invention.

  According to still another aspect of the present invention, an internal modified layer forming single crystal in which a modified layer is formed inside the single crystal member by irradiating the single crystal member with laser light from the surface and condensing the inside. A method for manufacturing a member, comprising: a first step of disposing a laser condensing unit in a non-contact manner on the single crystal member; and the laser condensing unit irradiating a surface of the single crystal member with laser light to The laser beam is condensed inside the crystal member, and the laser condensing means and the single crystal member are relatively moved to form a two-dimensional modified layer inside the single crystal member. And a surface roughness Ra of the peeling surface of the single crystal substrate formed by peeling the single crystal layer separated by the modified layer from the modified layer is less than 1. Internally modified layer forming single adjustment for adjusting the laser light irradiation conditions in the second step Method for producing a member.

  According to the present invention, when a relatively large and thin single crystal substrate is formed by peeling from the modified layer formed on the single crystal member, the surface roughness Ra of the peel surface of the single crystal substrate is less than 1. It is possible to provide a method for manufacturing a single crystal substrate, a single crystal substrate, and a method for manufacturing an internal modified layer-forming single crystal member.

The typical bird's-eye view explaining the manufacturing method of the single crystal substrate concerning one embodiment of the present invention. The typical bird's-eye view explaining the manufacturing method of the single crystal substrate concerning one embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective sectional view for explaining a method for producing a single crystal substrate and an internal modified layer forming single crystal member according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing that a crack is formed inside a single crystal member by laser light irradiation in an embodiment of the present invention. The typical perspective sectional view of having exposed the modification layer to the side wall of the internal modification layer formation single crystal member in one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view for explaining that the single crystal layer is peeled off from the modified layer by bonding a metal substrate to the upper and lower surfaces of the internal modified layer forming single crystal member in one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view for explaining that the single crystal layer is peeled off from the modified layer by bonding a metal substrate to the upper and lower surfaces of the internal modified layer forming single crystal member in one embodiment of the present invention. The typical sectional view explaining the modification of one embodiment of the present invention. The typical sectional view explaining the modification of one embodiment of the present invention. The typical perspective sectional view explaining the modification of one embodiment of the present invention. The partial expanded side view of the single crystal substrate obtained by one Embodiment of this invention. (A) is a side view showing that a laser beam corrected by an aberration correction ring is incident on a condenser lens and is irradiated as a modification of the embodiment of the present invention, and (b) is a part of (a). Enlarged view. Explanatory drawing which shows the experimental condition and measurement result in Experimental example 1. FIG. The optical microscope photograph of the cross section of the single crystal substrate obtained in Example 1A. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 1B. The optical microscope photograph of the cross section of the single crystal substrate obtained in Example 1B. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 1B. The optical microscope photograph of the cross section of the single crystal substrate obtained in Example 1C. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 1C. The optical microscope photograph of the cross section of the single crystal substrate obtained in Example 1D. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 1D. 2 is a laser confocal microscope photograph of a cross section of a single crystal substrate obtained in Example 2. FIG. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 3A. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 3B. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 4A. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 4B. The laser confocal microscope photograph of the cross section of the single crystal substrate obtained in Example 4C. 6 is a laser confocal microscope photograph of a peeled surface of a single crystal substrate obtained in Example 5. FIG. 6 is a laser confocal microscope photograph of a peeled surface of a single crystal part obtained in Example 5. FIG. 6 is a laser confocal microscope photograph of a peeled surface of a single crystal substrate obtained in Example 6. FIG. 6 is a laser confocal microscope photograph of the peeled surface on the single crystal part side obtained in Example 6. FIG. 6 is an SEM observation image of a peeled surface of a single crystal substrate obtained in Example 6. FIG. The SEM observation image of the peeling surface by the side of the single crystal part obtained in Example 6. FIG. 8 is a laser confocal microscope photograph of a peeled surface of a single crystal substrate obtained in Example 7. FIG. 6 is a laser confocal microscope photograph of the peeled surface on the single crystal part side obtained in Example 7. FIG. 6 is an SEM observation image of a peeled surface of a single crystal substrate obtained in Example 6. FIG. SEM observation image of peeled surface on single crystal part side obtained in Example 7 2 is a laser confocal microscope photograph of a peeled surface of a single crystal substrate obtained in Comparative Example 1. FIG. The laser confocal microscope picture of the peeling surface by the side of the single crystal part obtained by the comparative example 1. FIG. SEM observation image of peeled surface of single crystal substrate obtained in Comparative Example 1 The SEM observation image of the peeling surface by the side of the single crystal part obtained by the comparative example 1. FIG. In Experimental example 2, the optical microscope photograph and spectrum figure of the cross section of an internal modified layer formation single crystal member.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Accordingly, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, The layout is not specified as follows. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

  FIG. 1 is a schematic bird's-eye view illustrating that laser light is condensed in the air by a laser condensing unit in one embodiment of the present invention (hereinafter referred to as this embodiment), and FIG. It is a typical bird's-eye view explaining that a laser beam was condensed inside a single crystal member by a laser condensing means by form. FIG. 3 is a schematic cross-sectional structure illustrating the single crystal substrate manufacturing method and the internal modified layer forming single crystal member 11 according to the present embodiment. FIG. 4 is a schematic cross-sectional view showing that a crack 12c is formed inside the single crystal member by irradiation with laser light. FIG. 5 is a schematic perspective sectional view showing that the modified layer 12 formed by condensing the laser beam is exposed on the side wall of the internal modified layer forming single crystal member 11. FIG. 6 is a schematic cross-sectional view for explaining that the single crystal layer is peeled from the modified layer by adhering a metal substrate to the upper and lower surfaces of the internal modified layer forming single crystal member in the present embodiment. FIG. 7 is a schematic cross-sectional view for explaining that the single crystal layer is peeled off from the modified layer by adhering a metal substrate to the upper and lower surfaces of the internal modified layer forming single crystal member in this embodiment. It is explained that the single crystal layer 10u is peeled from the material layer 12.

  The single crystal substrate manufacturing method according to this embodiment includes a first step of disposing the condensing lens 15 on the single crystal member 10 in a non-contact manner as laser condensing means, and the condensing lens 15 on the surface of the single crystal member 10. The laser beam B is irradiated to collect the laser beam B inside the single crystal member 10, and the condensing lens 15 and the single crystal member 10 are relatively moved so as to form a two-dimensional shape inside the single crystal member 10. The second step of forming the modified layer 12 and the single crystal layer 10u separated by the modified layer 12 are peeled off from the interface with the modified layer 12, so that FIG. 7 (see also FIG. 11 described later) is obtained. And a third step of forming a single crystal substrate 10s as shown in the figure. In the second step, the surface roughness Ra of the peeling surface of the single crystal substrate 10s formed in the third step is less than 1. Adjust the laser irradiation conditions.

Here, the surface roughness is expressed by an arithmetic average roughness Ra, and a portion of the measurement length L is extracted from the roughness curve in the direction of the center line, and the center line of the extracted portion is defined as the X axis and the direction of the vertical magnification. Is the Y axis, and the roughness curve is represented by y = f (x), the value of Ra given by the following equation is expressed in units of micrometers (μm).

  In the following description, the single crystal layer 10u is described as being peeled from the interface 10u with the modified layer 12. However, the present invention is not limited to peeling from the interface 10u, and the peeling is performed within the modified layer 12. It may be made to occur.

(Device configuration and first step (arrangement step of laser focusing means))
The condensing lens 15 disposed in a non-contact manner on the single crystal member 10 is configured to correct aberration due to the refractive index of the single crystal member 10. Specifically, as shown in FIG. 1, in the present embodiment, the condensing lens 15 is configured such that when the condensing lens 15 condenses in the air, the laser light that has reached the outer peripheral portion E of the condensing lens 15 is condensed. The laser beam is corrected so as to be condensed on the condensing lens side with respect to the laser light reaching the central portion M. 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 condensed compared to 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.

  More specifically, the condensing lens 15 includes a first lens 16 that condenses in the air, and a second lens 18 disposed between the first lens 16 and the single crystal member 10. . Both the first lens 16 and the second lens 18 are lenses capable of condensing laser light in a conical shape. The depth (interval) D from the surface 10t (irradiated side surface) of the single crystal member 10 on the side irradiated with the laser beam B to the modified layer 12 is mainly set to the first lens 16 and the surface 10t. It is the structure adjusted with the distance L1. Further, the thickness T of the modified layer 12 is adjusted mainly by the distance L2 between the second lens 18 and the surface 10t. Therefore, aberration correction in the air is mainly performed by the first lens 16, and aberration correction in the single crystal member 10 is mainly performed by the second lens 18. In the present embodiment, the focal lengths of the first lens 16 and the second lens 18, and the above-mentioned so that the modified layer 12 having a thickness T of less than 60 μm is formed at a position of a predetermined depth D from the surface 10 t. The distances L1 and L2 are set.

  As the first lens 16, in addition to a spherical or aspherical single lens, a combination lens can be used in order to ensure various aberration corrections and working distances, and the NA is 0.3 to 0.7. 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.

  The laser that has reached the outer peripheral portion E of the condenser lens 15 from the viewpoint of forming the modified layer 12 inside the single crystal member 10 without damaging the surface 10t of the single crystal member 10 by irradiation with the laser beam B. The NA of the condensing lens 15 in the air defined by light and its condensing point EP is preferably 0.3 to 0.85, and more preferably 0.5 to 0.85.

  The size of the single crystal member 10 is not particularly limited. For example, it is preferable that the single crystal member 10 is made of, for example, a thick silicon wafer having a diameter of 300 mm, and the surface 10t irradiated with the laser beam B is flattened in advance.

  The laser beam B is irradiated not on the peripheral surface of the single crystal member 10 but on the surface 10t from the irradiation device (not shown) through the condenser lens 15. When the single crystal member 10 is silicon, 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 900 nm or more, preferably 1000 nm or more is selected. A YAG laser or the like is suitable. Used for.

  The form in which the laser beam is incident on the condenser lens 15 from above is not particularly limited. A laser oscillator may be disposed above the condensing lens 15 to emit light toward the condensing lens 15, or a reflecting mirror may be disposed above the condensing lens 15 to irradiate laser light toward the reflecting mirror. And you may make it the form reflected toward the condensing lens 15 with a reflective mirror.

The laser beam B preferably has a wavelength of light transmittance of 1 to 80% when a single crystal substrate having a thickness of 0.625 mm is irradiated as the single crystal member 10. For example, when a single crystal substrate of silicon is used as the single crystal member 10, since laser light having a wavelength of 800 nm or less has a large absorption, only the surface is processed and the internal modified layer 12 cannot be formed. A wavelength of 900 nm or more, preferably 1000 nm or more is selected. In addition, a CO ₂ laser with a wavelength of 10.64 μm has a light transmittance that is too high, so that it is difficult to process a single crystal substrate. Therefore, a YAG fundamental wave laser or the like is preferably used.

  The reason why the wavelength of the laser beam B is preferably 900 nm or more is that if the wavelength is 900 nm or more, the laser beam B is improved in the transmittance of the single crystal substrate made of silicon, and the modified layer 12 is reliably provided inside the single crystal substrate. It is because it can form. Laser light B is applied to the peripheral portion of the surface of the single crystal substrate or from the central portion of the surface of the single crystal substrate toward the peripheral portion.

(Second step (modified layer forming step))
As a step (second step) of forming the modified layer 12 inside the single crystal member 10 by relatively moving the condenser lens 15 and the single crystal member 10, for example, the single crystal member 10 is moved to the XY stage (FIG. The single crystal member 10 is held by a vacuum chuck, an electrostatic chuck or the like.

  Then, by moving the single crystal member 10 in the X direction or the Y direction on the XY stage, the condenser lens 15 and the single crystal member 10 are moved to the surface of the single crystal member 10 on the side where the condenser lens 15 is disposed. By irradiating the laser beam B while relatively moving in a direction parallel to 10t, a large number of cracks 12c are formed by the laser beam B condensed inside the single crystal member 10. The aggregate of crack portions 12p having the cracks 12c is the modified layer 12 described above. In the present embodiment, the moving direction of the condenser lens 15 is a direction orthogonal to the optical axis of the laser beam B, and the modified layer 12 is orthogonal to the optical axis of the laser beam B (that is, the modified layer 12 The normal direction is parallel to the optical axis of the laser beam B).

  As a result of the formation of the modified layer 12, the internal modified layer forming single crystal member 11 is manufactured. This internal modified layer forming single crystal member 11 includes a modified layer 12 formed inside the single crystal member, a single crystal layer 10u on the upper side of the modified layer 12 (that is, the irradiated side of the laser beam B), A single crystal portion 10d is provided below the material layer 12. The single crystal layer 10 u and the single crystal portion 10 d are formed by dividing the single crystal member 10 by the modified layer 12. In this embodiment, pulsed laser light is irradiated as laser light.

  In forming the modified layer 12, the laser light irradiation conditions are set so that the surface roughness Ra of the peeling surface 10f (see FIGS. 7 and 11) of the single crystal substrate 10s formed in the third step is less than 1. adjust.

  In order to suppress the moving speed of the stage, laser beam deflecting means such as a galvanometer mirror or a polygon mirror may be used to scan the laser light within the irradiation area of the condenser lens 15 in combination. Further, after completion of the formation of the modified layer 12 by performing such internal irradiation, the laser beam B is focused on the surface 10t on the irradiated side of the single crystal member 10, that is, the surface 10t of the single crystal layer 10u. A mark indicating the region is attached, and then the single crystal member 10 is cut (cleaved) based on this mark, and the peripheral portion of the modified layer 12 is exposed and the single crystal layer 10u is peeled off as described later. May be performed.

  In the modified layer 12 formed by such irradiation, a large number of cracks 12c parallel to the irradiation axis BC of the laser beam B are formed as shown in FIG. The size, density, and the like of the crack 12c to be formed are preferably set in consideration of the material of the single crystal member 10 and the like from the viewpoint of easily peeling the single crystal layer 10u from the modified layer 12.

  In order to confirm the crack 12c, the inner modified layer forming single crystal member 11 is cleaved so as to cross the region to be processed by the laser beam B, that is, the modified layer 12, and a cleavage plane (for example, 14a in FIGS. 3 and 5). -D) may be confirmed by observing with a scanning electron microscope or a confocal microscope, but, for example, a Y stage is fed to a single crystal member (for example, a silicon wafer) of the same material under the same irradiation conditions. It may be easily confirmed by performing linear processing inside the member at intervals of 6 to 50 μm, cleaving across the member, and observing the cleavage plane.

(Third step (peeling step))
Thereafter, the modified layer 12 and the single crystal layer 10u are peeled off (third step). In this embodiment, first, the modified layer 12 is exposed on the side wall of the internal modified layer forming single crystal member 11. In order to expose, for example, cleavage is performed along a predetermined crystal plane of the single crystal portion 10d and the single crystal layer 10u. As a result, as shown in FIG. 5, a structure in which the modified layer 12 is sandwiched between the single crystal layer 10u and the single crystal portion 10d is obtained. The surface 10t of the single crystal layer 10u is a surface on the side irradiated with the laser beam B.

  When the modified layer 12 has already been exposed, or when the distance between the peripheral edge of the modified layer 12 and the side wall of the internal modified layer forming single crystal member 11 is sufficiently short, the exposure work is omitted. It is possible.

  Thereafter, as shown in FIG. 6, metal substrates 28 u and 28 d are bonded to the upper and lower surfaces of the internal modified layer forming single crystal member 11, respectively. That is, the metal substrate 28u is bonded to the surface 10t of the single crystal layer 10u with the adhesive 34u, and the metal substrate 28d is bonded to the surface 10b of the single crystal portion 10d with the adhesive 34d. Oxide layers 29u and 29d are formed on the surfaces of the metal substrates 28u and 28d, respectively. In this embodiment, the oxide layer 29u is bonded to the surface 10t, and the oxide layer 29d is bonded to the surface 10b. As the metal substrates 28u and 28d, for example, a SUS peeling auxiliary plate is used. As the adhesive, an adhesive that is used in a normal semiconductor manufacturing process and is used as a so-called wax for fixing a commercially available silicon ingot is used. When the adhesive bonded with this adhesive is immersed in water, the adhesive strength of the adhesive is reduced, so that the adhesive and the adherend (single crystal layer 10u) can be easily separated.

  In this bonding, first, the metal substrate 28u is attached to the surface 10t of the single crystal layer 10u with a temporary fixing adhesive, and the metal substrate 28u is lined and peeled by applying a force.

  The adhesive strength of the temporary fixing adhesive only needs to be stronger than the force necessary for peeling at the interface 11u between the modified layer 12 and the single crystal layer 10u. Depending on the adhesive strength of the temporary fixing adhesive, the size and density of the crack 12c to be formed may be adjusted.

  As the temporary fixing adhesive, for example, an adhesive made of an anaerobic acrylic two-component monomer component that cures using metal ions as a reaction initiator is used. In this case, if the uncured monomer and the cured reaction product are water-insoluble, it is possible to prevent the peeling surface 10f (for example, the peeling surface of the silicon wafer) of the single crystal layer 10u exposed when peeling in water from being contaminated. .

  The application thickness of the temporary fixing adhesive is preferably 0.1 to 1 mm, and more preferably 0.15 to 0.35 mm before curing. If the application thickness of the temporary fixing adhesive is excessively large, it takes a long time to be completely cured, and cohesive failure of the temporary fixing adhesive is likely to occur when the single crystal member (silicon wafer) is cleaved. . Moreover, when application | coating thickness is too small, a long time is required for peeling in water of the cut single crystal member.

  The application thickness of the temporary fixing adhesive may be controlled by using a method of fixing the metal substrates 28u and 28d to be bonded to an arbitrary height, but simply using a shim plate. Can do.

  If the parallelism between the metal substrate 28u and the metal substrate 28d is not sufficiently obtained when bonded, the necessary parallelism may be obtained using one or more auxiliary plates.

  Further, when the metal substrates 28u and 28d are bonded to the upper and lower surfaces of the internal modified layer-forming single crystal member 11 with a temporary fixing adhesive, the single substrates may be bonded one by one or both may be bonded simultaneously.

  When it is desired to strictly control the coating thickness, it is preferable that the metal substrate is bonded to one side and the adhesive is cured, and then the metal substrate is bonded to the other side. In this way, when bonding one surface at a time, the surface to which the temporary fixing adhesive is applied may be the upper surface or the lower surface of the internal modified layer forming single crystal member 11. At that time, in order to suppress the adhesive from adhering to the non-adhesive surface of the single crystal member 10 and curing, a resin film not containing metal ions may be used as the cover layer.

  As long as parallelism and flatness can be obtained as the metal substrate, machining such as a punch hole for fixing the apparatus may be performed. Since the metal substrate to be bonded undergoes a peeling process in water, it is preferable to form a passive layer for the purpose of suppressing contamination of the silicon wafer, and an oxide layer (oxide film) to be formed for the purpose of reducing the tact time of peeling in water. A thinner layer is preferred.

  In order to perform underwater peeling after cleaving the internally processed silicon wafer, it is preferable to perform a metal degreasing treatment that is normally performed on the metal substrate before bonding.

  In order to increase the adhesive strength between the temporary fixing adhesive and the metal substrate, the surface of the metal surface is easily obtained by removing the oxide layer on the metal surface by a mechanical or chemical method and providing an anchor effect. Is preferred. Specific examples of the chemical method include acid cleaning using chemicals and degreasing treatment. Specific examples of the mechanical method include sand blasting and shot blasting, but the method of damaging the surface of a metal substrate with sand paper is the simplest, and the particle size is preferably # 80 to 2000, and metal Considering the surface damage of the substrate, # 150 to 800 is more preferable.

  After the metal substrate is bonded, an upward force Fu is applied to the metal substrate 28u and a downward force Fd is applied to the metal substrate 28d, as shown in FIG. Here, the interface 11u between the modified layer 12 and the single crystal layer 10u is more easily peeled off than the interface 11d between the modified layer 12 and the single crystal portion 10d. For this reason, as shown in FIG. 7, it peels at the interface 11u between the modified layer 12 and the single crystal layer 10u by the forces Fu and Fd. By this peeling, a thin single crystal substrate 10s is obtained by peeling the single crystal layer 10u from the modified layer 12. In the peeled surface 10f of the single crystal substrate 10s thus obtained, the surface roughness Ra is less than 1 (Ra <1) as shown in FIG. 11, for example.

  The method for applying the forces Fu and Fd is not particularly limited. For example, as shown in FIG. 8, the side wall of the internal modified layer forming single crystal member 11 is etched to form grooves 36 in the modified layer 12, and as shown in FIG. The forces Fu and Fd may be generated by press-fitting (for example, a cutter blade). Further, as shown in FIG. 10, an upward force component Fu and a downward force component Fd may be generated by applying a force F from the angular direction to the internal modified layer forming single crystal member 11.

  As described above, in this embodiment, the surface roughness Ra of the peeled surface of the single crystal substrate 10s formed in the third step is less than 1 by adjusting the laser light irradiation conditions in the second step. Therefore, the time required for lapping of the single crystal substrate after peeling can be greatly reduced as compared with the conventional case. Further, since other steps can be omitted as compared with the case where Ra is 1 or more, contamination of the single crystal substrate due to the other steps can be avoided.

  Further, the energy of the laser beam B can be concentrated on the thin thickness portion in the single crystal member 10 by the condenser lens 15 having a large NA. Therefore, the internal modified layer forming single crystal member 11 in which the modified layer (working region) 12 having a small thickness T (length along the irradiation axis BC of the laser beam B) is formed in the single crystal member 10 is manufactured. be able to. Then, it is easy to manufacture the thin single crystal substrate 10 s by peeling the single crystal layer 10 u from the modified layer 12. Further, such a thin single crystal substrate 10s can be easily manufactured in a relatively short time. In addition, since the number of single crystal substrates 10 s can be obtained from the single crystal member 10 by suppressing the thickness of the modified layer 12, the product rate can be improved.

  Further, as the modified layer 12, an aggregate of crack portions 12p parallel to the irradiation axis BC of the laser beam B is formed. Thereby, peeling of the modified layer 12 and the single crystal layer 10u is easy.

  In the step of forming the single crystal substrate 10s, the single crystal substrate 10s is obtained by bonding and peeling the metal substrate 28u having the oxide layer 29u on the surface to the surface of the single crystal layer 10u. Therefore, an adhesive used in a normal semiconductor manufacturing process can be used for bonding to a metal substrate, and a cyanoacrylate adhesive having a strong adhesive force used when bonding an acrylic plate must be used. That's it. Moreover, since the adhesive strength of the adhesive is greatly reduced by being immersed in water after peeling, the single crystal substrate 10s can be easily separated from the metal substrate 28u.

  When adjusting the laser light irradiation conditions in the second step, 1) adjusting the energy of the laser light after passing through the condensing lens 15, and 2) the condensing lens 15 (the first lens 16 and the second lens 18). ), And an aberration correction ring 40 and a condenser lens 45 (both of which will be described later with reference to FIG. 12) are arranged, and light collection by the condenser lens 45 is adjusted by the aberration correction ring 40. 3) Laser 4) Adjusting the irradiation interval (interval between adjacent irradiation positions) of the pulse laser light irradiated as laser light 5) Adjusting the condenser lens 45 and the single crystal member It is effective to adjust any one of these or a combination thereof.

  FIG. 12 is a diagram showing an example of the above 2). FIG. 12A is a side view showing that the laser light corrected by the aberration correction ring 40 is incident on the condenser lens 45 and irradiated, and FIG. It is the elements on larger scale of (a). When adjusting the condensing by the condensing lens 45 by the aberration correction ring 40, for example, as shown in FIG. 12, the laser light incident on the outer peripheral portion of the condensing lens 45 is aligned with the optical axis (center axis) of the condensing lens 45. The crossing position is adjusted so that the laser beam incident on the inner peripheral side is located closer to the condenser lens 45 than the position where the laser beam intersects the optical axis (center axis) of the condenser lens 45.

  In the above description, the example of performing aberration correction has been described. However, as long as the surface roughness Ra of the separation surface 10f of the single crystal substrate 10s is less than 1 by adjusting the laser light irradiation condition in the second step, A configuration without aberration correction is also possible.

  In the present embodiment, the DF value of the condensing lens 45 is adjusted to adjust the distance from the surface 10t, which is the irradiated surface of the single crystal member 10, to the modified layer 12, thereby obtaining a single layer obtained by peeling. It is possible to adjust the thickness of the crystal substrate 10s.

  In this embodiment, a silicon wafer can be used as the internal modified layer forming single crystal member 10 and the modified layer 12 can be formed inside the silicon wafer.

  In the present embodiment, the metal substrates 28u and 28d are attached to the upper and lower surfaces of the internal modified layer forming single crystal member 11, respectively, and the metal substrates 28u and 28d are peeled by applying force to the single crystal substrate. Although it has been described by forming 10 s, it may be removed by removing the modified layer 12 by etching.

  The single crystal member 10 is not limited to a silicon wafer, but an ingot of a silicon wafer, an ingot of single crystal sapphire, SiC, or a wafer cut out from the ingot, or another crystal (GaN, GaAs, InP) on this surface. Etc.) can be applied. Further, the plane orientation of the single crystal member 10 is not limited to (100), and other plane orientations can be used.

<Experimental example 1>
The inventor conducted the following experiment, and the surface of the separation surface 10f of the single crystal substrate 10s obtained by separation in the third step and the surface of the separation surface on the single crystal portion 10u side formed by the separation. The roughness Ra was measured. Experimental conditions and measurement results are shown in FIG. In this experimental example, the aberration correction ring 40 is used when performing aberration correction.

Example 1
In Example 1, a fiber laser A that supplies a laser beam having a wavelength of 1064 nm, an infrared objective lens having a numerical aperture of 0.85 as the condensing lens 45, and the above-described aberration correction ring 40 are used. An experiment was conducted in which a silicon wafer substrate (double-sided mirror (100) having a thickness of 725 μm) as the modified layer-forming single crystal member 10 was irradiated from the substrate surface to be internally processed. As irradiation conditions, the laser irradiation interval was 1 μm, the offset was 10 μm, the DF was 80 μm in air, and the adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate was 0 to 1 mm. As the observation of the state of the internal processing marks, the cross section obtained by cleaving the processing cross section perpendicular to the laser scanning direction was observed with an optical microscope and a laser confocal microscope. In Example 1, Examples 1A to 1D were performed by changing irradiation conditions little by little as follows.

Example 1A
FIG. 14 is an optical micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1A. FIG. 15 is a laser confocal micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1B, and corresponds to a partially enlarged view of FIG.

  In Example 1A, internal processing was performed by irradiating a silicon wafer with laser light at a repetition frequency of 100 kHz, a pulse width of 21 ns, and an output after the objective lens (that is, the intensity of the laser light after passing through the condenser lens 45) of 0.4 W. . The scanning direction of the laser light is the direction from the front side of the paper to the back side of the paper in FIGS. 14 and 15 (this direction is also shown in FIGS. 16 to 27 described later).

  In the six processing marks 48a to 48f shown in FIG. 14, the scale of the aberration correction ring 40 is sequentially adjusted to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm from the left side of the drawing. Formed. Moreover, in FIG. 15, the process traces 48c and 48d are shown.

(Example 1B)
FIG. 16 is an optical micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1B. FIG. 17 is a laser confocal micrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1B, and corresponds to a partially enlarged view of FIG.

  In Example 1B, internal processing was performed by irradiating a silicon wafer with laser light at a repetition frequency of 100 kHz, a pulse width of 21 ns, and an objective lens output of 0.8 W.

  The six processing marks 50a to 50f shown in FIG. 16 are adjusted in order of the scale of the aberration correction ring 40 to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm sequentially from the left side of the drawing. Formed. Moreover, in FIG. 17, the process marks 50c and 50d are shown.

(Example 1C)
FIG. 18 is an optical micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1C. FIG. 19 is a laser confocal micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1C, and corresponds to a partially enlarged view of FIG.

  In Example 1C, internal processing was performed by irradiating a silicon wafer with laser light at a repetition frequency of 200 kHz, a pulse width of 39 ns, and an objective lens output of 0.8 W.

  In the six processing marks 52a to 52f shown in FIG. 18, the scale of the aberration correction ring 40 is sequentially adjusted to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm from the left side of the drawing. Formed. Moreover, in FIG. 19, the process traces 52c and 52d are shown.

(Example 1D)
FIG. 20 is an optical micrograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1D. FIG. 21 is a laser confocal microscope photograph of a cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 1D, and corresponds to a partially enlarged view of FIG.

  In Example 1D, internal processing was performed by irradiating a silicon wafer with laser light at a repetition frequency of 200 kHz, a pulse width of 39 ns, and an objective lens output of 1.6 W.

  In the six processing marks 54a to 54f shown in FIG. 20, the scale of the aberration correction ring 40 is adjusted to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm sequentially from the left side of the drawing. Formed. Moreover, in FIG. 21, the process marks 54c and 54d are shown.

(Example 2)
FIG. 22 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 2.

  In Example 2, a fiber laser A that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 100 kHz, an objective lens output of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 21 ns, an offset of 10 μm, an DF of 20 to 80 μm in air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate of 0 mm. It was. As an observation of the state of the internal processing marks, a cross section obtained by cleaving a processing cross section perpendicular to the laser scanning direction was observed.

(Example 3)
In Example 3, a fiber laser B that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condensing lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  The irradiation conditions were a repetition frequency of 50 kHz, a laser irradiation interval of 2 μm, an objective lens output of 1.6 W, a pulse width of 200 ns, a DF of 80 μm in air, and an adjustment length of 0 mm for the aberration correction ring 40 with respect to the silicon wafer substrate. As an observation of the state of the internal processing marks, a cross section obtained by cleaving a processing cross section perpendicular to the laser scanning direction was observed. In Example 3, Examples 3A and 3B were performed by changing the irradiation conditions little by little as follows.

(Example 3A)
FIG. 23 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 3A. In Example 3A, the offset was 1 μm.

(Example 3B)
FIG. 24 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 3B. In Example 3B, the offset was 5 μm.

Example 4
In Example 4, a fiber laser B that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condensing lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  The irradiation conditions were a repetition frequency of 50 kHz, a laser irradiation interval of 1 μm, an offset of 1 μm, an output after the objective lens of 0.7 W, a pulse width of 200 ns, a DF of 70 μm in air, and an adjustment length of 0 mm for the aberration correction ring 40 with respect to the silicon wafer substrate. . As an observation of the state of the internal processing marks, a cross section obtained by cleaving a processing cross section perpendicular to the laser scanning direction was observed. In Example 4, Examples 4A to 4C were performed by changing the irradiation conditions little by little as follows.

(Example 4A)
FIG. 25 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 4A. In Example 4A, the number of irradiations was one.

(Example 4B)
FIG. 26 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 4B. In Example 4B, the number of irradiations was two.

(Example 4C)
FIG. 27 is a laser confocal photomicrograph of the cross section of the single crystal substrate (silicon wafer) 10s obtained in Example 4C. In Example 4C, the number of irradiations was three.

(Example 5)
FIG. 28 is a laser confocal micrograph of the peeling surface 10f of the single crystal substrate (silicon wafer) 10s obtained in Example 5, and FIG. 29 is the peeling on the single crystal part 10u side obtained in Example 5. It is the laser confocal microscope picture of a surface.

  In Example 5, a fiber laser A that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 200 kHz, an objective lens output of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 39 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of 0.6 mm for the aberration correction ring 40 relative to the silicon wafer substrate. Then, the silicon wafer substrate was internally processed with a laser beam into a 5 mm × 20 mm region.

  Then, the peeled surfaces (exposed surfaces) obtained by bonding and peeling the metal plates to both surfaces of the internally processed silicon wafer substrate via an adhesive were observed with a laser confocal microscope.

(Example 6)
30 is a laser confocal micrograph of the peeling surface of the single crystal substrate (silicon wafer) 10s obtained in Example 6, and FIG. 31 is the peeling surface on the single crystal part 10u side obtained in Example 6. It is a laser confocal microscope photograph of this. 32 is an SEM observation image of the peeled surface of the single crystal substrate 10s obtained in Example 6, and FIG. 33 is an SEM observed image of the peeled surface on the single crystal part 10u side obtained in Example 6. It is.

  In Example 6, a fiber laser A that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is converted into a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 200 kHz, an objective lens output of 1.2 W, a laser irradiation interval of 1 μm, a pulse width of 39 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0.6 mm. Then, the silicon wafer substrate was internally processed with a laser beam into a 5 mm × 20 mm region. And it peeled like Example 5, and the peeling surface of the obtained single crystal substrate was observed with the laser confocal microscope and the scanning electron microscope.

(Example 7)
34 is a laser confocal micrograph of the peeled surface of the single crystal substrate (silicon wafer) 10s obtained in Example 7, and FIG. 35 is the peeled surface on the single crystal part 10u side obtained in Example 7. It is a laser confocal microscope photograph of this. 36 is an SEM observation image of the peeled surface of the single crystal substrate 10s obtained in Example 6, and FIG. 37 is an SEM observed image of the peeled surface on the single crystal part 10u side obtained in Example 7. It is.

  In Example 7, a fiber laser C that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 200 kHz, an objective lens output of 0.6 W, a laser irradiation interval of 1 μm, a pulse width of 60 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of 0.6 mm for the aberration correction ring 40 relative to the silicon wafer substrate. Then, the silicon wafer substrate was internally processed into a 5 mm × 10 mm region with laser light. And it peeled like Example 5, and the peeling surface of the obtained single crystal substrate was observed with the laser confocal microscope and the scanning electron microscope.

(Example 8)
In Example 8, a fiber laser B that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 50 kHz, an output after the objective lens of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, a DF of 80 μm in air, an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm, The silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region. And it peeled similarly to Example 4, and the peeling surface of the obtained single crystal substrate was observed.

Example 9
In Example 9, a fiber laser B that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 50 kHz, an output after the objective lens of 1.6 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm, The silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Example 10)
In Example 10, a fiber laser B that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is converted into a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 100 kHz, an output after the objective lens of 0.5 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm. The number of times of irradiation was set to 2 times, and the silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Example 11)
In Example 11, a fiber laser C that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 200 kHz, an output after the objective lens of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 80 ns, an offset of 2 μm, an DF of 80 μm in terms of air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0.6 mm. Then, the number of times of irradiation was 2, and the silicon wafer substrate was internally processed in a region of 5 mm × 10 mm. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Example 12)
In Example 12, a fiber laser D that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 100 kHz, an objective lens output of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm. The number of times of irradiation was set to 2 times, and the silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Example 13)
In Example 13, a fiber laser D that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 100 kHz, an objective lens output of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm. The number of times of irradiation was set to 2 times, and the silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Comparative Example 1)
38 is a laser confocal micrograph of the peeled surface of the single crystal substrate (silicon wafer) obtained in Comparative Example 1, and FIG. 39 is a laser of the peeled surface on the single crystal part side obtained in Comparative Example 1. It is a confocal microscope picture. 40 is an SEM observation image of the peeling surface of the single crystal substrate obtained in Comparative Example 1, and FIG. 41 is an SEM observation image of the peeling surface on the single crystal part side obtained in Comparative Example 1. .

  In Comparative Example 1, a fiber laser A that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 200 kHz, an output after the objective lens of 1.6 W, a laser irradiation interval of 1 μm, a pulse width of 39 ns, an offset of 1 μm, an DF of 80 μm in terms of air, and an adjustment length of 0.6 mm for the aberration correction ring 40 relative to the silicon wafer substrate. Then, the silicon wafer substrate was internally processed into a 5 mm × 10 mm region with laser light. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Comparative Example 2)
In Comparative Example 2, a fiber laser C that supplies a laser beam having a wavelength of 1064 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 200 kHz, an output after the objective lens of 0.8 W, a laser irradiation interval of 1 μm, a pulse width of 60 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of 0.6 mm for the aberration correction ring 40 relative to the silicon wafer substrate. Then, the silicon wafer substrate was internally processed into a 5 mm × 10 mm region with laser light. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

(Comparative Example 3)
In Comparative Example 3, a fiber laser D that supplies a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 are used as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror with a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  Irradiation conditions include a repetition frequency of 50 kHz, an output after the objective lens of 0.8 W, a laser irradiation interval of 0.5 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, and an adjustment length of 0 mm for the aberration correction ring 40 with respect to the silicon wafer substrate. Then, the silicon wafer substrate was internally processed with a laser beam to a region of 10 mm × 10 mm. And it peeled similarly to Example 5, and the peeling surface of the obtained single crystal substrate was observed.

<Experimental example 2>
The inventor uses a fiber laser B for supplying a laser beam having a wavelength of 1062 nm and an infrared objective lens having a numerical aperture of 0.85 as the condenser lens 45, and the laser beam is sent to a silicon wafer substrate (double-sided mirror having a thickness of 725 μm ( 100)) was applied to conduct internal processing.

  As irradiation conditions, a repetition frequency of 50 kHz, an output after the objective lens of 0.5 W, a laser irradiation interval of 1 μm, a pulse width of 200 ns, an offset of 1 μm, an DF of 80 μm in air, an adjustment length of the aberration correction ring 40 with respect to the silicon wafer substrate is 0 mm, The number of times of irradiation was one, and the silicon wafer substrate was internally processed with a laser beam into a 10 mm × 10 mm region.

  And the backscattering Raman spectrum measurement was performed with respect to the cleaved cross section using LabRAM HR-800 made by HORIBA JOBIN YVON having a He—Ne laser as a light source. The measurement results are shown in FIG.

  As can be seen from FIG. 42, it was confirmed that there was no mechanical damage to the silicon wafer before peeling except for the modified layer 12 that was internally processed with laser light.

  Mechanical damage refers to damage caused by a mechanical external force such as machining. A substrate having mechanical damage is easily broken from the damaged portion, and has lower mechanical strength and lower quality as a substrate than a substrate having no mechanical damage. Mechanical damage can be confirmed by using Raman spectrum measurement, X-ray structural analysis, or the like. In the Raman spectroscopic measurement, knowledge about the completeness of the crystal can be obtained from the broadening of the half-value width of the reference bond. By utilizing this, the position of mechanical damage can be confirmed.

  Since a thin single crystal substrate can be efficiently formed by the present invention, the thinly cut single crystal substrate can be applied to a solar cell as long as it is a Si substrate, and a sapphire substrate such as a GaN-based semiconductor device. Can be applied to light-emitting diodes, laser diodes, etc., and SiC can be applied to SiC-based power devices, etc., in a wide range of fields such as transparent electronics, lighting, and hybrid / electric vehicles. Applicable.

DESCRIPTION OF SYMBOLS 10 Single crystal member, silicon wafer 10u Single crystal layer 10s Single crystal substrate 10t Surface 10f Release surface 11 Internal modified layer forming single crystal member 12 Modified layer 15 Condensing lens (laser condensing means)
40 Aberration correction ring 45 Condenser lens B Laser light

Claims (9)

A first step of disposing laser focusing means in a non-contact manner on the single crystal member;
The laser condensing means irradiates the surface of the single crystal member with laser light to condense the laser light inside the single crystal member, and relatively moves the laser condensing means and the single crystal member. A second step of forming a two-dimensional modified layer inside the single crystal member;
A third step of forming a single crystal substrate by separating a single crystal layer separated by the modified layer from the modified layer;
And adjusting the laser light irradiation conditions in the second step so that the surface roughness Ra of the peel surface of the single crystal substrate formed in the third step is less than 1 A method for manufacturing a substrate.   2. The single crystal substrate according to claim 1, wherein when adjusting the irradiation condition of the laser beam in the second step, the energy of the laser beam after passing through the objective lens provided in the laser focusing unit is adjusted. Production method.   2. The production of a single crystal substrate according to claim 1, wherein when adjusting the irradiation condition of the laser beam in the second step, an aberration correction ring is provided in the laser condensing unit and the adjustment is performed by the aberration correction ring. Method.   2. The method for manufacturing a single crystal substrate according to claim 1, wherein when adjusting the irradiation condition of the laser beam in the second step, the adjustment is performed by the number of irradiation times of the pulsed laser beam irradiated as the laser beam.   2. The method for manufacturing a single crystal substrate according to claim 1, wherein when adjusting the irradiation condition of the laser beam in the second step, an irradiation interval of the pulse laser beam irradiated as the laser beam is adjusted.   2. The method for manufacturing a single crystal substrate according to claim 1, wherein an offset between the laser condensing unit and the single crystal member is adjusted when adjusting the laser light irradiation condition in the second step.   The thickness of the single crystal substrate is adjusted by adjusting the DF value of an objective lens provided in the laser condensing means to adjust the distance from the irradiated surface of the single crystal member to the modified layer. The method for producing a single crystal substrate according to any one of claims 1 to 6.   A single crystal substrate manufactured by the method for manufacturing a single crystal substrate according to claim 1. A method for producing an internal modified layer-forming single crystal member in which a modified layer is formed inside the single crystal member by irradiating the single crystal member with laser light from the surface and condensing inside the single crystal member,
A first step of disposing laser condensing means in a non-contact manner on the single crystal member;
The laser condensing means irradiates the surface of the single crystal member with laser light to condense the laser light inside the single crystal member, and relatively moves the laser condensing means and the single crystal member. A second step of forming a two-dimensional modified layer inside the single crystal member;
With
In the second step, laser light is used in the second step so that the surface roughness Ra of the peeling surface of the single crystal substrate formed by peeling the single crystal layer separated by the modified layer from the modified layer is less than 1. A method for producing an internal modified layer-forming single crystal member, characterized in that the irradiation conditions are adjusted.