Ingot laser modification process and laser processing equipment

Abstract

This invention discloses a laser ingot refining process and laser processing apparatus, belonging to the field of semiconductor technology. The laser ingot refining process includes the following steps: positioning the focusing points of at least two refining laser beams with transmittance wavelengths at a predetermined depth from a first surface of the ingot; each focusing point forms a corresponding refining section; at least two refining sections are arranged at intervals along the C-surface; cracks propagate from the refining sections along the C-surface; cracks formed in adjacent refining sections connect to each other to form a set of cracks; a cutting laser beam is used to cut between two adjacent sets of cracks to form a cutting section; the two ends of the cutting section are respectively connected to the two sets of cracks. This invention improves production efficiency by increasing the crack width and eliminates the need for a pressing mechanism for peeling, thereby increasing the wafer yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a crystal ingot laser modification process and laser processing device. BACKGROUND

[0002] SiC has superior performance, which can be well applied to power devices or LED devices. The traditional SiC wafer is usually sliced by wire cutting, however, this processing technology causes great loss to the material, and is time-consuming, which greatly affects the cost of silicon carbide.

[0003] In order to solve this problem, the prior art is: the focal point of the laser beam is positioned at a specific depth of the first surface of the single crystal ingot, forming a modification layer parallel to the first surface and a crack propagating from the modification layer along the c surface. In the process of forming the modification layer, the focal point of the laser beam moves along a direction perpendicular to the direction forming the deviation angle between the c axis and the first surface, forming a straight modification layer; then, the focal point is indexed by a certain amount in the direction forming the deviation angle and in the direction downhill to the c surface to form a new modification layer. When the pressing member is rotated in the state of being pressed to the front surface of the single crystal ingot, a torsional stress is generated in the single crystal ingot, and the single crystal ingot is broken from the separation starting point where the modification layer and the crack are formed, and a single crystal wafer can be separated from the hexagonal single crystal ingot.

[0004] However, the width of the crack propagating along the C surface of the modification layer in the prior art is small, which increases the number of reciprocating scans of the laser beam, resulting in low production efficiency. At the same time, in this method, the cracks are inclined, and there is no mutual connection between the parallel cracks, and the method of peeling off by the subsequent pressing mechanism may cause the crack to be brought, resulting in low yield.

[0005] Therefore, it is urgent to provide a crystal ingot laser modification process and laser processing device to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a crystal ingot laser modification process and laser processing device, which increases the width of the crack to improve production efficiency and improves the yield of the wafer.

[0007] In order to achieve the above purpose, the following technical solutions are provided:

[0008] The crystal ingot laser modification process comprises the following steps:

[0009] The focal points of at least two modification laser beams with a transmission wavelength are positioned at a predetermined depth from the first surface of the crystal ingot, each focal point forming a corresponding modification part, and at least two modification parts are arranged at intervals along the C surface, and a crack propagates from the modification part along the C surface, and the cracks formed by adjacent modification parts are connected to each other and form a group of cracks;

[0010] The cutting laser beam cuts between the two adjacent groups of cracks to form a cutting section, and the two ends of the cutting section are connected with the two groups of cracks respectively.

[0011] As an alternative to the laser modification process of the crystal ingot, the focal point of the modification laser beam moves along the set path to form a modification layer inside the crystal ingot.

[0012] As an alternative to the laser modification process of the crystal ingot, at least two of the modification laser beams form a linear modification layer inside the crystal ingot.

[0013] As an alternative to the laser modification process of the crystal ingot, the distance between the focal points of at least two of the modification laser beams is the length that the generated cracks can connect to each other after propagation.

[0014] As an alternative to the laser modification process of the crystal ingot, the cutting laser beam is focused at the midpoint of the overlap between the tail of the previous group of cracks and the head of the current group of cracks, and emits pulsed laser.

[0015] As an alternative to the laser modification process of the crystal ingot, the cutting laser beam cuts in the vertical direction, or the length of the cutting section is the vertical distance between the two groups of cracks.

[0016] As an alternative to the laser modification process of the crystal ingot, the length of each group of cracks formed by connecting adjacent cracks is greater than 500um, and the indexing amount of the modification laser beam is less than the length of the crack.

[0017] A laser processing device processes a crystal ingot using the laser modification process of the crystal ingot as mentioned above, and the laser processing device comprises:

[0018] A laser beam generating unit, comprising a first laser oscillator for generating a modification laser beam and a second laser oscillator for generating a cutting laser beam.

[0019] A base, on which the crystal ingot can be placed.

[0020] As an alternative to the laser processing device, the laser beam generating unit further comprises a laser parameter adjusting member for adjusting the modification laser beam and the cutting laser beam to a set laser parameter.

[0021] As an alternative to the laser processing device, the laser beam generating unit further comprises a first light splitting focusing mirror, at least one second light splitting focusing mirror and a cutting focusing mirror arranged in sequence along the vertical direction, the first light splitting focusing mirror and the second light splitting focusing mirror are located in the light path of the modified laser beam and can focus the modified laser beam into the interior of the crystal ingot, and the cutting focusing mirror is located in the light path of the cutting laser beam and can focus the cutting laser beam into the interior of the crystal ingot.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The crystal ingot laser modification process provided by the present application uses at least two modified laser beams to scan the crystal ingot, forming corresponding modified parts at each light focusing point at the preset depth of the crystal ingot. The cracks on both sides of the at least two modified parts propagate along the C face of the crystal ingot and connect to form a group of cracks. The length of the group of cracks is greater than the length of the crack formed by a single light focusing point in the prior art. By increasing the width of the crack, the number of laser reciprocating scans is reduced, which helps to increase the indexing amount, shorten the processing time, and improve the production efficiency of the wafer. The cutting laser beam forms a cutting part to connect the two adjacent groups of cracks, eliminating the need for a pressing mechanism to peel off, thereby improving the yield of the wafer.

[0024] The laser processing device provided by the present application improves production efficiency by increasing the width of the crack, and eliminates the need for a pressing mechanism to peel off, thereby improving the yield of the wafer. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the contents of the embodiments of the present application and these drawings.

[0026] Figure 1 It is a structure schematic diagram of the crystal ingot before laser processing in the embodiments of the present application.

[0027] Figure 2 It is a schematic diagram of generating multiple groups of cracks in the crystal ingot in the embodiments of the present application.

[0028] Figure 3 It is a structure schematic diagram of the laser processing device in the embodiments of the present application.

[0029] Figure 4 It is a structure schematic diagram of the crystal ingot after processing in the embodiments of the present application.

[0030] Figure 5 It is a structure schematic diagram of the laser beam generating unit in the embodiments of the present application.

[0031] Reference signs:

[0032] 1000, laser beam generating unit; 2000, base station;

[0033] 100, first light splitting and focusing mirror; 200, second light splitting and focusing mirror; 300, cutting focusing mirror; 400, reflecting mirror;

[0034] 1, modified laser beam; 2, cutting laser beam; 3, modified part; 4, cutting part; 5, crystal ingot; 6, crack. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0036] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the present application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used for differentiation in description and cannot be understood as indicating or implying relative importance. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0037] In the description of the present application, it should also be noted that, unless otherwise specified and limited, the terms "provided", "connected" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0039] In order to improve production efficiency and improve the yield of wafers, the embodiment provides a crystal ingot laser modification process and a laser processing device, as follows Figures 1 to 5 The specific content of the embodiment is described in detail. It should be noted that the vertical direction mentioned in the embodiment is the Z direction in Figure 2 The single crack in the embodiment is referred to as a crack, and the plurality of connected cracks are referred to as a scratch.

[0040] As shown in Figure 1 in combination with Figure 2 The crystal ingot laser modification process in the embodiment includes the following steps: positioning at least two focal points of a modification laser beam 1 with a transmission wavelength at a preset depth from a first surface of a crystal ingot 5, each focal point forming a corresponding modification part 3, and at least two modification parts 3 being arranged at intervals along the C surface, and a crack 6 propagating from the modification part 3 along the C surface, and the cracks 6 formed by adjacent modification parts 3 being connected to each other and forming a group of scratches; and cutting a cutting part 4 between two adjacent groups of scratches using a cutting laser beam 2, and the two ends of the cutting part 4 being connected to the two groups of scratches, respectively. Figure 2 In the embodiment, there are three groups of scratches. Further, the preset depth is 0-2000um.

[0041] Briefly, the crystal ingot laser modification process provided by the present application uses at least two modification laser beams 1 to scan the crystal ingot 5, and each focal point at a preset depth of the crystal ingot 5 forms a corresponding modification part 3, and the cracks 6 on both sides of the at least two modification parts 3 propagate along the C surface of the crystal ingot 5 and are connected to form a group of scratches, the length of the group of scratches is greater than the length of the crack formed by a single focal point in the prior art, and the width of the crack is increased to reduce the number of laser reciprocating scans, which helps to increase the indexing amount, shorten the processing time, and improve the production efficiency of the wafer. The cutting laser beam 2 is used to form a cutting part 4 to connect two adjacent groups of scratches, without the need for a pressing mechanism to peel off, thereby improving the yield of the wafer.

[0042] Further, the focal points of the modification laser beam 1 move along a set path to form a modification layer inside the crystal ingot 5. Exemplarily, the set path in the embodiment is linear.

[0043] Further, the at least two modification laser beams 1 form a linear modification layer inside the crystal ingot 5. Understandably, the at least two modification parts 3 corresponding to the at least two modification laser beams 1 form the modification layer, and the width of the modification layer is increased.

[0044] Further, the distance between the focal points of the at least two modification laser beams 1 is the length at which the generated cracks 6 can be connected to each other. Since the cracks 6 on both sides of each modification part 3 propagate along the C surface, by making the distance between the two focal points of the modification parts 3 equal to the length of the generated cracks 6, it is ensured that the cracks 6 are connected to each other and form a group of scratches.

[0045] For example, the cutting laser beam 2 is focused at the midpoint where the tail of the previous set of cracks and the head of the current crack overlap, and pulsed laser light is emitted to form the cutting section 4. The cutting laser beam 2 is positioned so that the focused point begins cutting from the midpoint of the overlap, improving cutting accuracy. If the focused point of the cutting laser beam 2 is positioned too high or too low, the modified section 3 formed by the focused point may be located outside the area defined by the two sets of cracks.

[0046] Optionally, the cutting laser beam 2 cuts in a vertical direction, or the length of the cutting section 4 is the vertical distance between the two sets of cracks. After laser processing, the wafer can be easily separated from the ingot 5 by a suction cup component.

[0047] For example, the length of each group of cracks formed by connecting adjacent cracks 6 is greater than 500 μm, and the displacement of the modifying laser beam 1 is less than the length of the crack. The ingot laser modification process mentioned in this embodiment solves the problem of insufficient crack length 6. Through multi-beam and new optical path design, multiple cracks 6 can be generated simultaneously and connected, so that the total length of the cracks formed by the single connected cracks 6 is increased to greater than 500 μm, which facilitates the increase of the displacement value, speeds up the processing, and further shortens the laser processing time.

[0048] like Figures 3 to 5 As shown, this embodiment also provides a laser processing apparatus. The laser processing apparatus uses the aforementioned ingot laser modification process to process ingot 5. The laser processing apparatus includes a laser beam generating unit 1000 and a base 2000. The laser beam generating unit 1000 includes a first laser oscillator and a second laser oscillator. The first laser oscillator generates a modification laser beam 1, and the second laser oscillator generates a cutting laser beam 2. Ingot 5 can be placed on the base 2000. Optionally, the base 2000 can be moved according to actual usage requirements.

[0049] Furthermore, the laser beam generating unit 1000 also includes a laser parameter adjustment component, which is used to adjust the modified laser beam 1 and the cutting laser beam 2 to the set laser parameters to meet the laser parameter requirements for processing the ingot 5 by the modified laser beam 1 and the cutting laser beam 2.

[0050] Furthermore, the laser beam generating unit 1000 also includes a first beam-splitting focusing mirror 100, at least one second beam-splitting focusing mirror 200, and a cutting focusing mirror 300 arranged sequentially in the vertical direction. The first beam-splitting focusing mirror 100 and the second beam-splitting focusing mirror 200 are located in the optical path of the modified laser beam 1 (wherein the modified laser beam 1 can use a reflecting mirror 400 to change the optical path) and can focus the modified laser beam 1 into the interior of the ingot 5. The cutting focusing mirror 300 is located in the optical path of the cutting laser beam 2 (wherein the cutting laser beam 2 can use a reflecting mirror 400 to change the optical path) and can focus the cutting laser beam 2 into the interior of the ingot 5. (Reference) Figure 5 As shown, the modified laser beam 1 from the first laser oscillator and the cutting laser beam 2 from the second laser oscillator are emitted vertically. The optical paths are adjusted to the horizontal direction by a reflector. The modified laser beam 1 is split into at least two laser beams by a first beam splitter 100 and at least one second beam splitter 200. The second beam splitter 200 can move both horizontally and vertically to adjust the spacing between the focusing points of the two modified sections 3. The cutting focusing mirror 300 can move horizontally or vertically to adjust the position of the focusing point within the ingot 5, allowing the focusing point of the cutting section 4 to move between the two sets of cracks.

[0051] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A laser modification process of a crystal ingot, characterized by, The method comprises the following steps: focusing points of at least two modified laser beams (1) with a transmission wavelength are positioned at a preset depth from a first surface of a crystal ingot (5), each focusing point forming a corresponding modified portion (3), at least two of the modified portions (3) being arranged along a C face, a crack (6) propagating along the C face from the modified portions (3), cracks (6) formed by adjacent modified portions (3) being connected to each other and forming a group of cracks; a cutting laser beam (2) is used to cut between two adjacent groups of cracks to form a cutting portion (4), two ends of the cutting portion (4) being connected to the two groups of cracks, respectively; the cutting laser beam (2) is focused at a midpoint of an overlapping position between a tail of a previous group of cracks and a head of a current group of cracks, and emits pulsed laser light; the laser processing device comprises: a laser beam generating unit (1000) comprising a first laser oscillator for generating a modified laser beam (1) and a second laser oscillator for generating a cutting laser beam (2); a base (2000) on which the crystal ingot (5) can be placed.

2. The crystal ingot laser modification process of claim 1, wherein, The focusing points of the modified laser beams (1) move along a set path to form a modified layer inside the crystal ingot (5).

3. The crystal ingot laser modification process of claim 2, wherein, At least two of the modified laser beams (1) form a linear modified layer inside the crystal ingot (5).

4. The crystal ingot laser modification process of claim 2, wherein, The distance between the focusing points of the at least two modified laser beams (1) is the length at which the generated cracks (6) can be connected to each other after extending.

5. The crystal ingot laser modification process of claim 1, wherein, The cutting laser beam (2) cuts along a vertical direction, or the length of the cutting portion (4) is the vertical distance between the two groups of cracks.

6. The ingot laser modification process of any of claims 1-5, wherein, The length of each group of cracks formed by the adjacent cracks (6) is greater than 500 um, and the displacement of the modified laser beam (1) is less than the length of the cracks.

7. The crystal ingot laser modification process of claim 1, wherein, The laser beam generating unit (1000) further comprises a laser parameter adjusting member for adjusting the modified laser beam (1) and the cutting laser beam (2) to a set laser parameter.

8. The crystal ingot laser modification process of claim 7, wherein, The laser beam generating unit (1000) further comprises a first light splitting and focusing mirror (100), at least one second light splitting and focusing mirror (200), and a cutting focusing mirror (300) arranged in sequence along a vertical direction, the first light splitting and focusing mirror (100) and the second light splitting and focusing mirror (200) being located in the light path of the modified laser beam (1) and being capable of focusing the modified laser beam (1) inside the crystal ingot (5), the cutting focusing mirror (300) being located in the light path of the cutting laser beam (2) and being capable of focusing the cutting laser beam (2) inside the crystal ingot (5).

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