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

Abstract

The invention relates to methods for cutting non-metal materials, particularly brittle heat-resistant materials. Enhanced cutting quality is achieved by forming a notch inside a sample of non-metal material using focused laser radiation, then heating the surface of the billet 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 made in the form of at least two local stress raisers situated along the cutting line at a depth h and at a distance l from one another. Heating is then carried out from the direction of the surface of the sample of non-metal material by scanning with a laser beam.

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 are widely used in the manufacture of micro- and optoelectronic devices: silicon carbide, silicon, gallium arsenide, germanium, sapphire, which 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 include high consumption of the source material due to the large cutting width, which is commensurate with the plate thickness; low productivity of the diamond-abrasive cutting process of the original ingot into plates during cutting, followed by grinding and polishing; and low cutting quality, primarily due to the large depth of the damaged layer.

[0006] Another 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 which laser radiation creates thermal stresses in the bulk of the material, leading to the appearance 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 in the bulk of the material at the appropriate depth for the initiation of a parallel crack. In glass, such an initial defect is created by concentrating an elastic wave in the bulk of the material. However, this method is not applicable for cutting hard anisotropic materials such as sapphire, silicon carbide, and others.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.

[0007] 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.

[0008] The problem solved by the invention is aimed at creating a cutting method that ensures high quality cutting of non-metallic materials into plates.

[0009] The required technical result is to improve the quality of cutting non-metallic materials into plates.

[0010] 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 an incision is made with focused laser radiation, and then the surface of the ingot is heated with 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, an incision is made with focused laser radiation from the side of the surface of the sample of the non-metallic material in the form of at least two local stress concentrators placed along the cutting line at a depth h along the cutting line, located at a distance I from each other, which is selected from the condition of the formation of a crack between the local stress concentrators due to the addition of thermoelastic stresses in places of defects of local stresses, and then heating is carried out from the side of the surface of the sample of the non-metallic material by scanning with a beam of laser radiation,the power density and linear speed of movement of which are selected from the condition of creating tensile stresses at a depth of the material sample equal to the specified thickness of the cut plate h.,

[0011] In a particular case of the implementation of the proposed method, local stress concentrators in the volume of a sample of non-metallic material are created by focused laser radiation with a wavelength for which the material is transparent.

[0012] In addition, the required technical result is achieved by the fact that local stress concentrators are created by focused laser radiation at a depth of h = 0.1 - 1 mm.

[0013] In addition, the required technical result is achieved by creating local stress concentrators by focused laser radiation into a spot with a diameter of 10 - 100 µm from a pulsed picosecond or femtosecond laser.

[0014] In addition, the required technical result is achieved by the fact that local stress concentrators are created at a distance I from each other equal to 0.01 - 0.5 mm.

[0015] The drawing shows a diagram of the application of local stress concentrators in a material sample when implementing the proposed method of laser cutting non-metallic ingots into plates.

[0016] The drawing shows:

[0017] 1 - sample of material;

[0018] 2 - focusing lens L of laser radiation to create local stress concentrators in the material sample at a depth / r equal to the thickness of the plate being cut;

[0019] 3 - local stress concentrators in a material sample, made at a distance I from each other.

[0020] The proposed method is implemented as follows.

[0021] In the volume of a sample of non-metallic material 1, for example silicon carbide, at a depth lr equal to the thickness of the plate being cut off, local stress concentrators are created by focused laser radiation from the side of the surface of the sample of non-metallic material corresponding to the outer surface of the plate being cut off, while at least two local stress concentrators are created, located at a distance l from each other along the cutting line, which is selected from the condition of the formation of a crack between local defects due to the addition of thermoelastic stresses at the locations of the defects of local stresses, and then heating is carried out from the side of the surface of the sample of non-metallic material by scanning with a beam of laser radiation, the power density and linear speed of movement of which are selected from the condition of creating the maximum possible tensile stresses at a depth of the sample of the material equal to the specified thickness h of the plate being cut off.

[0022] In an example of the implementation of the claimed method, silicon carbide is used as a sample material, created in the form of at least two local stress concentrators at a depth of h = 0.1 - 1 mm by focused laser radiation into a spot with a diameter of 10 - 100 μm from a pulsed picosecond or femtosecond laser at a distance I from each other equal to 0.01 - 0.5 mm.

[0023] In general, the sequence of operations of the proposed method (the technological process of the method of laser cutting of ingots of non-metallic materials into plates) is as follows.

[0024] 1. Preparatory operations:

[0025] 1.1. Fixing the material sample (boule) in a holder with high heat dissipation from the boule and temperature stabilization.

[0026] 1.2. Preparation of the boule surface by applying an anti-reflective and absorbent coating.

[0027] 1.3. Creating local stress concentrators within the boule material at a depth close to the specified thickness of the plate being cut, at a depth h equal to the specified thickness of the plate being cut. This is accomplished using picosecond or femtosecond laser radiation and a focusing lens with a large aperture and short focal length f.

[0028] 2. Laser parallel thermal splitting.

[0029] 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.

[0030] 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 conditionally maximum permissible tensile stresses 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. 3. Separating the plate from the boule.

[0031] 4. Grinding the surface of the boule after removing the cut plate to prepare for the next plate cutting cycle.

[0032] 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 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 by laser radiation focused into a spot with a diameter of 10-100 μm from a pulsed picosecond or femtosecond laser, from the side of the surface of the non-metallic material sample in the form of at least two local stress concentrators placed along the cutting line at a depth of h = 0.1-1 mm, wherein the distance between the local stress concentrators is selected from the condition of crack formation between local defects due to the addition of thermoelastic stresses at the locations of these defects and is equal to 0.01-0.5 mm,and then heating is carried out from the surface of the sample of non-metallic material by scanning with a beam of laser radiation, the power density and linear speed of movement of which are selected from the condition of creating tensile stresses at a depth of the sample of material equal to the specified thickness of the plate being cut off. 7 AMENDED SHEET (ARTICLE 19)

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