JP2013161820A - Substrate and method for processing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate having a wide variety in options of laser sources, thin in thickness of an internal processing layer, and efficiently forming an internal processing layer with a small number of laser pulse irradiation, and a method for processing a substrate.SOLUTION: A single crystal substrate 10 includes a modified layer 14 having periodic structures formed therein, the periodic structures having a crystal orientation different from the crystal orientation of the substrate 10 and being connected.

Description

  The present invention relates to a substrate such as a silicon single crystal substrate and a substrate processing method.

  Conventionally, when manufacturing a semiconductor wafer represented by a silicon (Si) wafer, a cylindrical ingot solidified from a silicon melt melted in a quartz crucible is cut into blocks of an appropriate length, The peripheral edge is ground to a target diameter, and then the block ingot is sliced into a wafer shape with a wire saw to manufacture a semiconductor wafer (see, for example, Patent Documents 1 and 2).

  The semiconductor wafer manufactured in this way is subjected to various processes such as circuit pattern formation in the previous process in order and used in the subsequent process. In this subsequent process, the back surface is back-grinded and thinned. 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 with a wire saw, and a cutting allowance larger than the thickness of the wire saw is required for cutting, so a thin semiconductor wafer with a thickness of 0.1 mm or less It was very difficult to manufacture and the product rate was not improved.

  On the other hand, by combining a high numerical aperture condensing lens with an aberration enhancing material made of a glass plate, processing the inside of a silicon wafer with a pulsed laser with a wavelength of 1064 nm, and then bonding it to a rigid substrate and peeling it off A technique for obtaining a thin single crystal silicon substrate is disclosed (see Patent Document 3).

  According to this technique, a processed layer having a thickness of about 100 μm is formed inside the silicon substrate. For this reason, when a large number of thin substrates having a thickness of about 0.1 mm are sliced from the crystalline substrate, there is a limit to the material yield. For example, even if the infrared observation aberration enhancing material for silicon is removed, the thickness of the processed layer cannot be reduced greatly.

  Further, when an objective lens having an NA of about 0.5 is used, the thickness of the processed layer is reduced, but the amount of light is reduced and the processed layer is not sufficiently processed, and actual peeling is difficult. On the other hand, if the number of times of irradiation is increased and processing of the processed layer is sufficiently performed, it is necessary to fill the two-dimensional processing region with 1 μm pitch irradiation, which requires a huge number of irradiation pulses. However, there was a problem of irradiation time in practical use.

  In this specification, a wafer is referred to as a substrate unless otherwise specified.

JP 2008-200772 A JP 2005-297156 A JP 2011-60862 A

  The present invention has been made to solve the above-mentioned problems, and is a substrate and a processing method for forming an internal processing layer by laser light irradiation inside a crystalline substrate, and peeling the internal processing layer as a boundary. An object of the present invention is to provide a substrate and a substrate processing method for efficiently forming an internal processing layer with a wide choice of light sources, a thin internal processing layer, and a small number of laser pulse irradiations.

  In order to solve the above-described problems, a substrate according to the present invention is a single crystal substrate, and the substrate has a periodic structure having a crystal orientation different from the crystal orientation of the substrate formed therein. It has a modified layer, and the periodic structures are connected.

  The periodic structure is formed by irradiating the surface of the substrate with laser light by a laser condensing means, and the laser condensing means is axially symmetric with respect to the optical axis within the substrate. And the light incident on the outer peripheral portion of the laser condensing means is condensed on the laser condensing means side from the light incident on the inner peripheral portion of the laser condensing means. Preferably it is.

  The periodic structure is preferably formed by relatively moving the laser condensing unit and the substrate and irradiating the substrate with laser light by the laser condensing unit.

  The periodic structure is preferably formed by changing the phase of the condensing point of the laser beam on the substrate.

  The modified layer preferably has a predetermined thickness and is formed at a predetermined depth from the surface of the single crystal substrate.

  The modified layer is preferably formed in parallel with the surface of the substrate.

  It is preferable that a plurality of the modified layers are formed in parallel with the surface of the substrate.

  The surface of the substrate is preferably a mirror surface.

  The substrate is preferably a silicon single crystal substrate or a silicon carbide single crystal substrate.

  The substrate processing method according to the present invention includes a step of providing a single-crystal substrate, and irradiating a laser beam toward the surface of the substrate with a laser condensing unit, whereby the crystal orientation of the substrate is inside the substrate. Forming a modified layer in which a periodic structure having a different crystal orientation is formed, and the laser condensing means condenses the laser light axially symmetrically with respect to an optical axis, and Inside, the light incident on the outer peripheral portion of the laser condensing means is configured to condense on the laser condensing means side from the light incident on the inner peripheral portion of the laser condensing means. is there.

  Preferably, the method further includes a step of relatively moving the laser condensing unit and the substrate.

  The periodic structure is preferably formed by changing a phase of a condensing point of the laser beam on the substrate.

  The modified layer preferably has a predetermined thickness and is formed at a predetermined depth from the surface of the single crystal substrate.

  The modified layer is preferably formed in parallel with the surface of the substrate.

  It is preferable that a plurality of the modified layers are formed in parallel with the surface of the substrate.

  The surface of the substrate is preferably a mirror surface.

  The substrate is preferably a silicon single crystal substrate or a silicon carbide single crystal substrate.

  It is preferable that the substrate is cleaved by peeling off the modified layer.

It is a perspective view of a substrate internal processing apparatus. It is a top view of the stage which mounted the board | substrate. It is sectional drawing of the stage which mounted the board | substrate. It is a figure explaining irradiation of the laser beam with respect to a board | substrate. It is a figure which shows 1st Embodiment of irradiation of the laser beam with respect to a board | substrate. It is a figure which shows 2nd Embodiment of irradiation of the laser beam with respect to a board | substrate. It is a reference figure explaining the aberration in a substrate. It is a figure which shows 3rd Embodiment of irradiation of the laser beam with respect to a board | substrate. It is a figure which shows 4th Embodiment of irradiation of the laser beam with respect to a board | substrate. It is a front view which shows a cleaving apparatus. It is a figure explaining peeling a board | substrate from a metal plate in water. It is a figure which shows the specific example of a laser condensing part. It is a figure which shows the other specific example of a laser condensing part. 2 is a photograph showing a cross section of the internal modified layer of Example 1. FIG. 4 is a photograph showing a cross section on the surface side of Example 2. FIG. 3 is a photograph showing a cross section on the back side of Example 2. FIG. 4 is a photograph showing a cross section on the surface side of Example 3. FIG. 6 is a photograph showing a cross section on the back surface side of Example 3. 6 is a photograph showing a cross section on the surface side of Example 4. FIG. 6 is a photograph showing a cross section of the back side of Example 4. 4 is a photograph showing a cross section on the surface side of Comparative Example 1; 4 is a photograph showing a cross section of the back side of Comparative Example 1. 10 is a photograph showing a cross section of the surface side of Comparative Example 2. 10 is a photograph showing a cross section of the back side of Comparative Example 2.

  Next, embodiments of the present invention will be described with reference to the 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. Therefore, 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 embodiments described below 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.

(Configuration of substrate internal processing equipment)
FIG. 1 is a perspective view showing the configuration of the substrate internal processing apparatus 100. The substrate internal processing apparatus 100 includes a stage 110, a stage support unit 120 that supports the stage 110 so as to be movable in the XY directions, and a substrate fixture 130 that is disposed on the stage 110 and fixes the substrate 10. ing.

  The substrate internal processing apparatus 100 includes a laser light source 150 and a laser condensing unit 160, and the laser condensing unit 160 condenses the laser light 190 emitted from the laser light source 150 and irradiates the substrate 10. To do. The laser condensing unit 160 includes an objective lens 170 and a plano-convex lens 180.

  FIG. 2 is a top view showing the substrate 10 placed on the stage 110. FIG. 3 is a cross-sectional view showing the substrate 10 placed on the stage 110.

  The substrate 10 is held on the stage 110 by the substrate fixture 130. The substrate fixture 130 fixes the substrate 10 by a fixing table 125 provided thereon. A normal adhesive layer, mechanical chuck, electrostatic chuck or the like can be applied to the fixed table 125.

  The condensing point P of the laser beam 190 focused and irradiated on the substrate 10 forms a locus 12 having a predetermined shape in a region at a predetermined depth from the surface inside the substrate 10, thereby being horizontal to the surface. A two-dimensional internal reforming layer 14 can be formed in the direction.

  FIG. 4 is a diagram for explaining the formation of the internal modified layer 14 in the substrate 10. In the substrate internal processing apparatus 100, the laser light 190 is irradiated toward the substrate 10 through the objective lens 170 and the plano-convex lens 180 of the laser condensing unit 160 and is condensed inside the substrate 10.

  In the present embodiment, the laser condensing unit 160 is configured such that the laser light 190 emitted from the laser condensing unit 160 is axially symmetric with respect to its optical axis, and the component 190b on the outer peripheral side of the laser light 190 inside the substrate 10. The condensing point P2 at which the light beams intersect with each other is configured to be closer to the laser condensing unit 160 than the condensing point P1 at which the light beams of the components on the inner peripheral side 190a of the laser light 190 intersect.

  In other words, since the surface of the substrate 10 faces the laser condensing unit 160, the condensing point P2 of the component 190b on the outer peripheral side of the laser light 190 is more than the condensing point 190b on the inner peripheral side 190a of the laser light 190. Also, the objective lens 170 and the plano-convex lens 180 are located at a shallow position from the surface of the substrate 10.

  This state can be regarded as a state in which the aberration generated in the laser beam 190 by the substrate 10 is excessively corrected, and can be said to be a “out-of-focus” state in which the focus is excessively corrected. In such a state, the diameter of the laser beam can be substantially reduced within a certain depth range of the substrate 10, and sufficient energy density is ensured for forming the internal modified layer 14 in the region. Can do. In the figure, an internal reforming layer 14 formed in a range t having a constant depth is shown.

  The internal modified layer 14 is made of polycrystalline silicon formed by condensing and irradiating the laser beam 190 on the substrate 10 to change the bonding state by being cooled after the silicon single crystal is melted. It has polycrystalline grains.

  The inner modified layer 14 thus formed has a periodic structure having a polycrystal having a crystal orientation different from the crystal orientation of the silicon single crystal by irradiating the laser beam 190 at periodic intervals. It is. Needless to say, polycrystals having different crystal orientations are composed of silicon of the same element as a silicon single crystal.

The internal modified layer 14 is preferably exposed at the end of the substrate 10 in order to improve the yield in the cleaving process described later. As a method for exposing the internal modified layer 14, the cleavage of crystal orientation may be used, or the laser beam 190 may be used.

  An embodiment in which such a laser condensing unit 160 is used to irradiate the substrate 10 with laser light 190 will be described. FIG. 5 is a diagram illustrating the first embodiment. In FIG. 5, for convenience, the laser condensing unit 160 is represented by the plano-convex lens 180 and the optical axis is described in the horizontal direction, but the laser beam is collected by the entire laser condensing unit 160 including the plano-convex lens 180. Is.

  In the first embodiment, the laser beam 190 condensed by the laser condensing unit 160 is irradiated toward the surface of the substrate 10. The laser beam 190 is refracted by the substrate 10 and is condensed at a position where the component on the outer peripheral side at a position higher from the optical axis is shallower than the surface of the substrate 10 than the component on the inner peripheral side at a position lower than the optical axis. ing. In other words, the light on the outer peripheral side is condensed at a position closer to the laser condensing unit 190 than the light on the inner peripheral side.

  The position of the laser condensing unit 160 with respect to the substrate 10 can be moved by a condensing adjusting unit (not shown). As will be described later, the condensing adjustment unit adjusts the condensing position, condensing shape, and the like of the laser light 190 on the substrate 10 by adjusting the distance between the laser condensing unit 160 and the substrate 10. Such a condensing adjustment part can be easily realized by using a conventional technique.

  FIG. 6 is a diagram for explaining a second embodiment of laser beam irradiation on a substrate. In the second embodiment, the distance between the laser condensing unit 160 and the substrate 10 is larger than that in the first embodiment, and the laser light 190 collected by the laser condensing unit 160 is focused on the surface of the substrate 10. It is adjusted by the condensing adjustment part.

  In the second embodiment, for example, as shown in the first embodiment, before the condensing point is set inside the substrate 10, the position of the laser condensing unit 190 with respect to the substrate 10 is initially set. Can be used for That is, the distance between the laser condensing unit 190 and the surface of the substrate 10 is shortened by a predetermined value from the initial state in which the laser light 190 is focused on the surface of the substrate 10 in the second embodiment by a condensing adjusting unit (not shown). Thereby, a desired condensing point can be formed inside the substrate 10 as in the first embodiment. Such an initial setting can be performed not only on the front surface of the substrate 10 but also on the back surface of the substrate 10.

  FIG. 7 is a reference diagram for explaining the aberration in the substrate. This reference diagram shows aberrations that occur when the laser condensing unit 160 is not provided for comparison with the first embodiment. For example, the case where only a normal objective lens is installed corresponds.

  In FIG. 7A, as in the second embodiment, the laser beam 190 is focused on the surface of the substrate 10 as a focal point. From this state, the substrate 10 is moved in the incident direction along the optical axis so that the laser beam 190 is condensed in the substrate 10. In this case, as shown in FIG. 7B, the component on the outer peripheral side of light having a high height from the optical axis is deeper from the surface of the substrate 10 than the component on the inner peripheral side having a low height from the optical axis. Condensed at the position.

  This state is different from the first embodiment in which the outer peripheral component having a high height from the optical axis is condensed at a position shallower than the inner peripheral component having a low height from the optical axis. The depth of the condensing point on the substrate 10 has an inverse relationship. In other words, the first embodiment in which the component on the outer peripheral side condenses at a position shallower than the component on the inner peripheral side can be realized only by providing the laser condensing unit 160.

  FIG. 8 is a diagram showing a third embodiment of laser beam irradiation on the substrate. In the third embodiment, adjustment is performed by a condensing point adjusting unit (not shown) so that the distance between the laser condensing unit 160 and the surface of the substrate 10 is shortened. It is adjusted so that a condensing point of is formed. Due to this condensing point, the internal modified layer 14 is formed in parallel with the surface of the substrate 10 near the back surface of the substrate 10.

  FIG. 9 is a diagram showing a fourth embodiment of laser beam irradiation on a substrate. In the fourth embodiment, after the internal modified layer 14a is formed near the back surface of the substrate 10 according to the third embodiment, the laser condensing unit 160 and the surface of the substrate 10 are formed by a condensing point adjusting unit (not shown). The condensing point of the laser beam 190 is formed in the substrate 10 near the surface of the substrate 10. Due to this condensing point, the second internal modified layer 14 b is formed near the surface of the substrate 10 in parallel with the surface of the substrate 10. The internal modified layer 14 is not limited to two layers as in the fourth embodiment, and may be a plurality of layers of two or more layers.

(Cleaving the substrate)
FIG. 10 is a front view showing the cleaving device. The substrate 10 on which the internal modified layer 14 is formed according to the third or fourth embodiment is cleaved in the internal modified layer 14 using this cleaving apparatus.

  In the cleaving apparatus 50, the structure 40 in which the first and second metal plates 20 and 21 are bonded to both surfaces of the substrate 10 with an adhesive is placed on the mount 52. The adhesive may be any adhesive that is stronger than the cohesive strength of the polycrystalline grains forming the region near the inner modified layer 14 of the substrate 10. For example, an anaerobic acrylic type resin that cures using metal ions as a reaction initiator. An adhesive 25 composed of a liquid monomer component can be used.

  The structure 40 may be fixed to the gantry 52 using a through hole provided in the second metal plate 21. In this state, a downward pressing force is applied to the first metal plate 20 by the cleaving jig 54. As a result, the substrate 10 receives a reverse force in both directions of the upper surface and the lower surface bonded to the first and second metal plates 20, 21, and when the force exceeds a predetermined threshold, the substrate 10 is divided, The structure 40 is separated into two upper and lower parts.

(Peeling the substrate)
FIG. 11 is a diagram illustrating a method for peeling the substrate 10 from the metal plate 20 in water. The substrate 10 bonded to the metal plates 20 and 21 with the adhesive 25 is immersed in warm water of 80 to 100 ° C. stored in the water tank 60. After a predetermined time has elapsed, the adhesive 25 reacts with water in a predetermined manner, and the adhesive force is lost from the adhesive 25. Therefore, by peeling the adhesive 25 from the substrate 10 in water, the substrate 10 is removed from the metal plates 20, 21. Can be separated.

  By drying the substrate 10 from which the adhesive 25 has been peeled in this way, a final divided substrate can be obtained. In addition, when there are a plurality of internal modified layers 14a and 14b as in the fourth embodiment, it is possible to divide the substrate 10 into a plurality of internal modified layers by repeating the cleaving process of the substrate 10 a plurality of times. it can.

(Specific example of laser focusing unit)
FIG. 12 is a diagram illustrating a specific example of the laser condensing unit. In this specific example, the laser condensing unit 160 is realized by a combination of an objective lens 170 having a high NA and a long working distance, and a plano-convex lens 180 provided on the surface side of the substrate 10, for example.

  Specifically, for internal processing of the substrate 10 made of single crystal silicon having a thickness of 1 mm, a plano-convex lens 180 made of glass having a focal length of 15 mm at a position of 0.14 mm from the surface side of the substrate 10 (Sigma light machine: SLB). -10-15P) and can be combined with an objective lens 170 (Sigma light machine: EPL-10) having NA = 0.3.

  In such a laser condensing unit 160, a condensing point adjustment unit (not shown) adjusts the shape of the condensing point by the distance between the plano-convex lens 80 and the surface of the substrate 10, and the distance between the objective lens 170 and the surface of the substrate 10. It can comprise so that the position of a condensing point may be adjusted.

  FIG. 13 is a diagram illustrating another specific example of the laser condensing unit. In another specific example, this is realized by an infrared objective lens for silicon having a correction ring with NA = 0.5 to 0.9. Specifically, for example, when an Olympus lens LCPLN100XIR is used, the correction ring is set to 0.6 mm when the internal processing layer 14 is provided at a position of 300 μm from the surface of the crystal 10. It can be set so that the light incident on the outer peripheral portion of the condensing unit 160 is condensed on the laser condensing 160 side from the light incident on the inner peripheral portion.

  According to this other embodiment, it is possible to configure with a single objective lens with a correction ring without requiring a plurality of constituent members such as the objective lens 170 and the plano-convex lens 180 as in the above-described embodiments. Becomes simple and easy to operate.

  In another specific example, when the internal modified layer 14 is formed on the surface side of the substrate 10, it is necessary to increase the distance between the laser focusing unit 160 and the surface of the substrate 10. In this case, in order to suppress the influence of the laser beam 190 on the surface of the substrate 10, beam diameter adjusting means such as an iris diaphragm and a beam expander is provided on the incident side of the laser condensing unit 160, and the outer peripheral component of the laser beam 190 is reduced. The amount of light may be reduced.

  In Example 1, a laser light source 150 of the substrate internal processing apparatus 100 having a wavelength of 1064 nm, a repetition frequency of 200 kHz, an output of 1.6 W, and a pulse width of 10 nm was used. In the substrate internal processing apparatus 100, single crystal silicon having a size of 50 × 50 mm, a thickness of 0.7 mm, and a mirror-finished surface on an xy stage 110 movable at a maximum speed of 200 mm / s in the x-axis and y-axis directions, respectively. The substrate 10 made of was placed and fixed.

  As the laser condensing unit 160, an objective lens 200 (an Olympus LCPLN100XIR) with a correction ring 210 of NA = 0.85 was used. Then, the correction ring 210 is set to 0 mm, and the objective lens 200 is observed with respect to the surface of the substrate 10 so that the light irradiated from the objective lens 200 forms a focal point on the surface of the substrate 10 while being observed with the reference light. Was positioned. At this time, the distance between the objective lens 200 and the substrate 10 was 0.6 mm.

  Next, the objective lens 200 was moved 0.06 mm toward the surface of the substrate 10 with this position as a reference. In this state, the setting of the correction ring 210 is set to 0.6 mm, the stage 110 is moved at a speed of 200 mm / s in the x direction, and is further sent 10 μm in the y direction 10 times to repeat from the objective lens 200 to the substrate 10. The laser beam 190 was irradiated in the form of 10 straight lines at intervals of 10 μm.

  The substrate 10 was cleaved at right angles to the linear irradiation direction, and the cross section was observed. As a result, as shown in FIG. 14, it was confirmed that the processing region had a length of 30 μm at a depth of 0.3 mm from the mirror-side surface of the substrate 10 and adjacent processing traces were connected to each other. This processing trace is a change in the single crystal structure to a polycrystalline structure (phase change) due to melting and cooling by laser irradiation, including crystals with a crystal orientation different from the crystal orientation of the single crystal, and a region of the polycrystalline structure Constitutes an internally processed layer 14 having a periodic structure in which are connected.

  Using a fiber laser A having a wavelength of 1064 nm as the laser light source 150, using an infrared objective lens having a repetition frequency of 200 kHz and a numerical aperture of 0.85 as the laser condensing unit 160, an output of 1.6 W after the objective lens, a pulse width of 39 ns, Laser beam 190 toward a region of surface 5 mm × 20 mm of a silicon single crystal substrate 10 having a laser irradiation interval of 1 μm, an offset of 1 μm, an DF of 80 μm in terms of air, a silicon aberration correction ring of 0.6 mm, and a thickness of 725 μm. To form an internal modified layer 14. The surface of the substrate 10 refers to the main surface of the substrate 10 facing the laser condensing unit 160, and the main surface of the substrate 10 opposite to the laser condensing unit 160 is referred to as the back surface.

  Then, a metal plate is bonded to both the front and back surfaces of the substrate 10 via an adhesive, and the substrate 14 is divided using the cleaving device 50 with the internal modified layer 14 as a boundary, and the exposed divided surface is made by JEOL. Observation was performed using a scanning electron microscope (SEM). FIG. 15 is an enlarged photograph of the surface-side divided surface with a scanning electron microscope. FIG. 16 is an enlarged photograph of the rear divided surface with a scanning electron microscope.

  Using a fiber laser B having a wavelength of 1064 nm as the laser light source 150, using an infrared objective lens having a repetition frequency of 200 kHz and a numerical aperture of 0.85 as the laser condensing unit 160, an output of 0.8 W after the objective lens, a pulse width of 39 ns, Laser beam 190 toward the region of surface 5 mm × 20 mm of the silicon single crystal substrate 10 having a laser irradiation interval of 1 μm, an offset of 1 μm, an DF of 80 μm in terms of air, a silicon aberration correction ring of 0.6 mm, and a thickness of 725 μm. Was applied to form an internal processed layer 14.

  In the same manner as in Example 2, the substrate 10 was divided and the divided surfaces were observed. FIG. 17 is an enlarged photograph of the surface-side divided surface with a scanning electron microscope. FIG. 18 is an enlarged photograph of the rear divided surface with a scanning electron microscope.

  Using a fiber laser B having a wavelength of 1064 nm as the laser light source 150, using an infrared objective lens having a repetition frequency of 200 kHz and a numerical aperture of 0.85 as the laser condensing unit 160, an output of 0.8 W after the objective lens, a pulse width of 39 ns, Laser beam 190 toward a region of surface 5 mm × 20 mm of a silicon single crystal substrate 10 having a laser irradiation interval of 1 μm, an offset of 2 μm, an DF of 80 μm in terms of air, a silicon aberration correction ring of 0.6 mm, and a thickness of 725 μm. Was applied to form an internal processed layer 14.

  In the same manner as in Example 2, the substrate 10 was divided and the divided surfaces were observed. FIG. 19 is an enlarged photograph of the divided surface on the surface side with a scanning electron microscope. FIG. 20 is an enlarged photograph of the rear divided surface with a scanning electron microscope.

[Comparative Example 1]
Using a fiber laser A having a wavelength of 1064 nm as the laser light source 150, using an infrared objective lens with a repetition frequency of 200 kHz and a numerical aperture of 0.85 as the laser condensing unit 160, an output of 1.2 W after the objective lens, a pulse width of 39 ns, Laser beam 190 toward a region of surface 5 mm × 10 mm of a silicon single crystal substrate 10 having a laser irradiation interval of 1 μm, an offset of 1 μm, an DF of 80 μm in air equivalent, a silicon aberration correction ring of 0.6 mm and a thickness of 725 μm and double-sided mirror processing (100). Was applied to form an internal processed layer 14.

  In the same manner as in Example 2, the substrate 10 was divided and the divided surfaces were observed. FIG. 21 is an enlarged photograph of the divided surface on the surface side with a scanning electron microscope. FIG. 22 is an enlarged photograph of the rear divided surface with a scanning electron microscope.

[Comparative Example 2]
Using a fiber laser B having a wavelength of 1064 nm as the laser light source 150, an infrared objective lens having a repetition frequency of 200 kHz and a numerical aperture of 0.85 as the laser condensing unit 160, an output of 0.6 W after the objective lens, a pulse width of 60 ns, Laser beam 190 toward a region of surface 5 mm × 10 mm of a silicon single crystal substrate 10 having a laser irradiation interval of 1 μm, an offset of 1 μm, an DF of 80 μm in air equivalent, a silicon aberration correction ring of 0.6 mm and a thickness of 725 μm and double-sided mirror processing (100). Was applied to form an internal processed layer 14.

  In the same manner as in Example 2, the substrate 10 was divided and the divided surfaces were observed. FIG. 23 is an enlarged photograph of the surface-side divided surface with a scanning electron microscope. FIG. 24 is an enlarged photograph of the rear divided surface with a scanning electron microscope.

  As is clear from Examples 1 to 4 and Comparative Examples 1 and 2 described above, in Examples 2 to 4, a processing mark having a periodic structure is formed in the internal processing layer 14 as in Example 1, and a processing region is formed. Is as short as 30 μm and is formed by connecting adjacent processing traces. In Examples 2 to 4, since the internal modified layer 14 having the processing traces formed by being connected in this way is divided, a smooth cross section having a periodic structure can be obtained. Therefore, there is no need for further polishing, and the number of steps required for another process such as a wet process such as chemical etching or laser etching and the influence of impurity contamination associated therewith can be reduced.

  As described above, the inner processing layer 14 formed by connecting adjacent processing traces with a short processing region length as in the first to fourth embodiments is a component on the outer peripheral side of the laser beam 190 inside the substrate 10. This is made possible by using the laser condensing unit 160 configured such that the condensing point of the laser beam is located in the laser condensing unit 160 rather than the condensing point of the inner peripheral component.

  In Comparative Examples 1 and 2, since the adjacent processing traces in the internal modified layer 14 are not connected, the cross section has a coarse particle size. Therefore, this cross section requires an additional polishing step.

In the above embodiment, the silicon single crystal substrate is exemplified. However, the present invention can be similarly applied to, for example, silicon carbide (SiC).

  Since the substrate can be efficiently and thinly formed by the substrate processing apparatus and method of the present invention, the thinly cut substrate can be applied to a solar cell as long as it is a Si substrate. If it is a sapphire substrate, etc., it can be applied to light emitting diodes, laser diodes, etc. If it is SiC, it can be applied to SiC-based power devices, etc., and it is widely used in the fields of transparent electronics, lighting, hybrid / electric vehicles Applicable in the field.

DESCRIPTION OF SYMBOLS 10 Substrate 14 Internal modified layers 20 and 21 Metal plate 25 Adhesive 50 Cleaving device 52 Base 54 Cleaving jig 100 Substrate internal processing device 110 Stage 120 Stage support unit 150 Laser light source 160 Laser condensing unit

Claims (18)

A single crystal substrate,
The substrate, wherein the substrate has a modified layer in which a periodic structure having a crystal orientation different from the crystal orientation of the substrate is formed, and the periodic structures are connected.   The periodic structure is formed by irradiating the surface of the substrate with laser light by a laser condensing means, and the laser condensing means is axially symmetric with respect to the optical axis within the substrate. And the light incident on the outer peripheral portion of the laser condensing means is condensed on the laser condensing means side from the light incident on the inner peripheral portion of the laser condensing means. The substrate according to claim 1, wherein:   The periodic structure is formed by relatively moving the laser condensing unit and the substrate, and irradiating the substrate with laser light by the laser condensing unit. 2. The substrate according to 2.   The substrate according to claim 1, wherein the periodic structure is formed by changing a phase of a condensing point of the laser beam in the substrate.   The substrate according to claim 1, wherein the modified layer has a predetermined thickness and is formed at a predetermined depth from a surface of the single crystal substrate.   The substrate according to claim 1, wherein the modified layer is formed in parallel with a surface of the substrate.   The substrate according to claim 1, wherein a plurality of the modified layers are formed in parallel with the surface of the substrate.   The substrate according to claim 1, wherein the surface of the substrate is a mirror surface.   The substrate according to claim 1, wherein the substrate is a silicon single crystal substrate or a silicon carbide single crystal substrate. Providing a single crystal substrate;
By irradiating the surface of the substrate with laser light by a laser focusing means, a modified layer in which a periodic structure having a crystal orientation different from the crystal orientation of the substrate is formed inside the substrate And a step of
The laser condensing means condenses the laser light symmetrically with respect to the optical axis, and the light incident on the outer peripheral portion of the laser condensing means inside the substrate is an inner peripheral portion of the laser condensing means. A method for condensing light on the laser condensing means side from light incident on the light.   The method according to claim 10, further comprising a step of relatively moving the laser focusing unit and the substrate.   The method according to claim 10, wherein the periodic structure is formed by changing a focusing point of the laser beam on the substrate.   The method according to claim 10, wherein the modified layer has a predetermined thickness and is formed at a predetermined depth from a surface of the single crystal substrate.   The method according to claim 10, wherein the modified layer is formed parallel to a surface of the substrate.   The method according to claim 10, wherein a plurality of the modified layers are formed in parallel with the surface of the substrate.   The method of claim 10, wherein the surface of the substrate is a mirror surface.   The method of claim 10, wherein the substrate is a silicon single crystal substrate or a silicon carbide single crystal substrate.   The method according to claim 10, wherein the substrate is cleaved by peeling off the modified layer.