Method for laser cutting billets of non-metal materials into wafers

Abstract

The invention relates to methods for cutting billets of brittle non-metal materials into wafers. To enhance cutting quality, a notch is formed inside a billet using focused laser radiation, and the surface of the billet is heated with laser radiation, to which the material is non-transparent, while the laser beam and the material sample are moved relative to one another. The notch is formed from the direction of the end face of the billet using focused laser radiation, to which the material is non-transparent, in the form of local stress raisers situated in succession along the cutting line at a depth equal to the thickness of the wafer to be cut off, and heating is carried out from the direction of the surface of the sample by scanning with a laser beam, the power density and speed of linear movement of which are selected such as to generate tensile stresses in excess of the ultimate tensile strength of the material, at a depth of the material sample equal to the given thickness of the wafer to be cut off.

Description

[0001] METHOD OF LASER CUTTING OF INGOTS OF NON-METALLIC MATERIALS INTO PLATES

[0002] The invention relates to methods for cutting non-metallic materials, in particular silicon carbide, silicon, gallium arsenide, germanium, sapphire and other brittle non-metallic materials into plates.

[0003] In modern technology and industry, thin device wafers made of sapphire and various semiconductor materials, such as silicon carbide, silicon, gallium arsenide, germanium, etc., are widely used in the manufacture of micro- and optoelectronic devices. These wafers are obtained by growing ingots of the specified materials and then cutting these ingots into thin wafers.

[0004] There are various known methods for cutting non-metallic ingots into plates, such as strip cutting, wire cutting, cutting using diamond wheels with an external or internal cutting edge.

[0005] The disadvantages of the above mentioned cutting methods are the high consumption of the source material due to the large cutting width, commensurate with the thickness of the plate, the low productivity of the diamond-abrasive cutting process of the original ingot into plates during cutting with subsequent grinding and polishing, as well as the low quality of cutting, in particular the large depth of the damaged layer.

[0006] A known method for cutting non-metallic ingots into plates is called laser parallel thermal cleavage [Kondratenko V.S., Kudzh S.A. Precision Cutting of Glass and Other Brittle Materials by Laser-Controlled Thermal Cleavage (Review) / / Glass and Ceramics. 2017. No. 3, pp. 5-12]. In this method, laser radiation creates thermal stresses within the material, leading to the formation of a crack propagating parallel to the surface. In order to cut an ingot of material into plates using this method, it is necessary to create an initial defect within the material at an appropriate depth for the initiation of a parallel crack. In glass, such an initial defect is created by concentrating an elastic wave within the material. However, this method is not applicable for cutting hard anisotropic materials such as sapphire, silicon carbide, and others.

[0007] The closest in technical essence to the proposed method is a method for cutting brittle non-metallic materials [RU 2404931, IPC SOZV 33 / 09, 28.08.2009], which includes making a local cut on the edge of a workpiece, heating the cutting line with an elliptical laser beam and subsequent cooling of the heating zone with a coolant during relative movement of the plate and the laser beam with the coolant, wherein, in at least one of the two cutting directions, a cut is made along the entire length of each cut or, at least, at the points of intersection with the cutting lines in the second direction, wherein the cut along the entire length of the cut or at the points of intersection with the cutting lines in the second direction is made before the start of cutting in this direction, wherein the cut is made by scribing with laser radiation in the ultraviolet range.

[0008] The disadvantage of this method is the relatively low cutting quality, caused by the possible inaccuracy of the direction of the crack that occurs during a local cut relative to the required cutting direction.

[0009] The problem solved by the invention is aimed at creating a cutting method that ensures high quality cutting of non-metallic materials into plates.

[0010] The required technical result is to improve the quality of cutting non-metallic materials into plates.

[0011] The stated problem is solved, and the required technical result is achieved by the fact that in the method, which consists in the fact that in the volume of a sample of a non-metallic material a cut is created by focused laser radiation, and then the surface of the ingot is heated by laser radiation, for which the material is opaque, with relative movement of the laser beam and the sample of the material, according to the invention, the cut is created by focused laser radiation, for which the material is transparent, in the form of local stress concentrators sequentially placed along the cutting line at a depth lr equal to the thickness of the plate being cut off, and heating from the side of the surface of the sample of the non-metallic material is carried out by scanning with a beam of laser radiation, the power density and the linear speed of movement of which are selected from the condition of creating tensile stresses that exceed the tensile strength of the material, at a depth of the sample of the material equal to a given thickness of the plate being cut off.

[0012] In a particular case of the implementation of the proposed method, the required technical result is achieved by using either silicon carbide, or silicon, or gallium arsenide, or germanium, or sapphire as a sample material.

[0013] In addition, the required technical result is achieved by the fact that local stress defects are created by focused laser radiation from a pulsed picosecond or femtosecond laser into a spot with a diameter of 10 - 100 µm at a depth of h = 0.1 - 1 mm.

[0014] In addition, the required technical result is achieved by the fact that the outermost local defect is created in the volume of material at a distance from the end of the material sample equal to 0.01 - 1 mm.

[0015] The drawings show: Fig. 1 - a diagram of the creation of a local stress defect in the form of stress concentrators in a sample of material 1 using a focusing lens 2 at a depth / r equal to the required plate thickness, a local stress defect 3 in the form of a stress concentrator; Fig. 2 - a diagram of the sequential creation of local stress defects in a sample of material 1 using a focusing lens 2 at a depth / r equal to the required plate thickness, first a local stress defect 3 and then a second local stress defect 4 in the form of stress concentrators.

[0016] The proposed method is implemented as follows.

[0017] The entire laser cutting process of non-metallic ingots into wafers consists of two sequential operations: in the first stage, local defects (Fig. 2) are sequentially created along the cutting line in the form of several stress concentrators within the material at a depth lr equal to the thickness of the wafer being cut, by focusing laser radiation with a wavelength for which the material is transparent. A picosecond laser with a wavelength of 1030 nm, an output power of up to 100 W, a pulse repetition rate of up to 2000 kHz, and a pulse energy of up to 100 μJ were used to create notches or defects in the form of stress concentrators in materials such as silicon carbide, silicon, gallium arsenide, germanium, and sapphire.

[0018] To increase the reliability of the parallel crack initiation process, it is advisable to extend the cut along the cutting line. This requires two or more localized cuts by moving a focused laser beam from the depths of the material to the end surface. After completing the first stage of the process—namely, creating the defect (notch), the second stage of laser cutting non-metallic ingots into wafers is performed: scanning the ingot surface with a second laser beam at a wavelength for which the material is opaque, starting from the location of the defect (notch). For materials such as silicon carbide, silicon, gallium arsenide, and germanium, laser radiation from a semiconductor laser with a wavelength of 808 nm and a power of 100 W to 1 kW or more is optimal.

[0019] For sapphire, silicon carbide, single-crystal quartz, glass, and some other materials, radiation from a CO2 gas laser with a wavelength of 10.6 µm is optimal. When the surface of a material ingot is heated by such a laser beam, compressive stresses are generated on the surface of the material, which are compensated by tensile stresses concentrated beneath the laser beam at a certain depth within the material, determined by the thermal conductivity of the material and the relative velocity of the laser beam and the material.

[0020] In this case, in order to improve the quality and productivity of cutting, it is advisable to scan the surface of the ingot with a laser beam extended in a direction perpendicular to the scanning direction.

[0021] Preparatory operations:

[0022] 1.1. Fixing the material sample (boule) in a holder with high heat dissipation from the boule and temperature stabilization.

[0023] 1.2. Preparation of the boule surface by applying an anti-reflective and absorbent coating.

[0024] 1.3. Creating local defects in the boule material at a depth close to the specified thickness of the cut-off plate, with local defects at a depth h equal to the specified thickness of the cut-off plate. This is accomplished using picosecond or femtosecond laser radiation and a focusing lens with a large aperture and short focal length f.

[0025] 2. Laser parallel thermal splitting.

[0026] 2.1. Scanning the surface of the boule with laser radiation of a wavelength for which the material is opaque, focused into a linear beam extended in a direction perpendicular to the scanning direction.

[0027] 2.2. The laser radiation power density Q=P / S and the linear velocity v of the relative movement of the laser beam and the boule are selected from the condition of creating tensile stresses that exceed the tensile strength of the material at a depth in the material sample equal to the specified thickness of the cut plate h: v = KQ / h, where K is the proportionality coefficient.

[0028] 3. Separating the plate from the boule.

[0029] 4. Grinding the surface of the boule after removing the cut plate to prepare for the next plate cutting cycle.

[0030] Thus, by improving known methods, the proposed technical solution achieves the required technical result, which consists in improving the quality of cutting non-metallic materials into plates, since the inaccuracy of the direction of the emerging crack relative to the required cutting direction is guaranteed to be eliminated.

Claims

The amended claim was received by the International Bureau on November 11, 2025 (11.11.2025) CLAUSES OF THE INVENTION 1. A method for laser cutting of non-metallic material ingots into plates, according to which a cut is made in the volume of a non-metallic material sample by focused laser radiation, and then the surface of the ingot is heated by laser radiation, for which the material is opaque, with relative movement of the laser beam and the material sample, characterized in that the cut is made from the end face of the non-metallic material sample by focused laser radiation, for which the material is transparent, in the form of local stress concentrators sequentially placed along the cutting line at a depth h equal to the thickness of the plate being cut, and heating from the surface of the non-metallic material sample is carried out by scanning with a laser beam, the power density and linear speed of movement of which are selected from the condition of creating tensile stresses exceeding the tensile strength of the material, at a depth of the material sample,equal to the specified thickness of the plate being cut off, 2. The method according to paragraph 1, characterized in that silicon carbide is used as the sample material.

3. The method according to paragraph 1, characterized in that silicon is used as the sample material.

4. The method according to paragraph 1, characterized in that gallium arsenide is used as the sample material.

5. The method according to item 1, characterized in that germanium is used as the sample material.

6. The method according to item 1, characterized in that sapphire is used as a sample material.

7. The method according to item 1, characterized in that local stress concentrators are created by focused laser radiation at a depth of h=0.1–1 mm.

8. The method according to item 1, characterized in that local stress concentrators are created by focused laser radiation in a spot with a diameter of 10–100 µm from a pulsed picosecond or femtosecond laser.

9. The method according to item 1, characterized in that the outermost of the local stress concentrators is created in the volume of the material at a distance of 0.01–1 mm from the end of the material sample. 7 AMENDED SHEET (ARTICLE 19)

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