Crystal ingot laser modification process and laser processing device

Abstract

The invention discloses a crystal ingot laser modification process and a laser processing device, and belongs to the technical field of semiconductors. The crystal ingot laser modification technology comprises the following steps that light gathering points of at least two modification laser beams with permeable wavelengths are positioned at the position with the preset depth from the first face of a crystal ingot, each light gathering point forms a corresponding modification part, at least two modification parts are arranged at intervals along the C face, cracks spread along the C face from the modification parts, and the cracks are formed in the first face of the crystal ingot. The cracks formed by the adjacent modified parts are mutually connected to form a group of cracks; a cutting laser beam is adopted for cutting between two adjacent groups of cracks to form a cutting part, and the two ends of the cutting part are connected with the two groups of cracks respectively. According to the invention, the production efficiency is improved by increasing the width of the crack, stripping by a pressing mechanism is not needed, and the yield of the wafer is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a crystal ingot laser modification process and a laser processing device. Background Art

[0002] SiC has superior performance and can be well applied to power devices or LEDs. Traditional SiC wafers are usually sliced ​​by wire cutting, but this processing technology causes great loss of materials and is time-consuming, which has a great impact on the cost of silicon carbide.

[0003] In order to solve this problem, the existing technology is: positioning the focal point of the laser beam at a specific depth of the first surface of the single crystal ingot to form a modified layer parallel to the first surface and a crack propagating from the modified layer along the c-plane. In the process of forming the modified layer, the focal point of the laser beam moves in a direction perpendicular to the direction of the deviation angle formed between the c-axis and the first surface to form a linear modified layer; then, the focal point is shifted a certain amount in the direction of the deviation angle and in a downhill direction toward the c-plane to form a new modified layer. When the pressing component is rotated in a state where the pressing component is pressed against the front side of the single crystal ingot, torsional stress is generated in the single crystal ingot, and the single crystal ingot breaks from the separation starting point where the modified layer and the crack are formed, so that a hexagonal single crystal wafer can be separated from the hexagonal single crystal ingot.

[0004] However, in the prior art, the width of the cracks propagating along the C-plane of the modified layer is small, which increases the number of reciprocating scans of the laser beam, resulting in low production efficiency. At the same time, since the cracks in this method are inclined and the parallel cracks are not connected to each other, the subsequent peeling method of the pressing mechanism may cause cracks, resulting in low yield.

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

[0006] The object of the present invention is to provide a crystal ingot laser modification process and a laser processing device, which can improve production efficiency by increasing the width of cracks and improve the yield rate of wafers.

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

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

[0009] Positioning the focal points of at least two modified laser beams having a transmittance wavelength at a preset depth from the first surface of the ingot, each focal point forming a corresponding modified portion, at least two of the modified portions being arranged at intervals along the C surface, cracks propagating from the modified portions along the C surface, and cracks formed in adjacent modified portions being connected to each other to form a group of cracks;

[0010] A cutting laser beam is used to cut between two adjacent groups of cracks to form a cutting portion, and two ends of the cutting portion are respectively connected to the two groups of cracks.

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

[0012] As an optional solution of the ingot laser modification process, at least two modified laser beams form a linear modified layer inside the ingot.

[0013] As an optional solution of the ingot laser modification process, the distance between the focal points of at least two of the modified laser beams is a length that allows the generated cracks to be connected to each other after extension.

[0014] As an optional solution for the ingot laser modification process, the cutting laser beam is focused at the midpoint where the tail of the previous set of cracks and the head of the current crack overlap, and a pulsed laser is emitted.

[0015] As an optional solution for the ingot laser modification process, the cutting laser beam cuts along a vertical direction, or the length of the cutting portion is the vertical distance between two groups of cracks.

[0016] As an optional solution for the ingot laser modification process, the length of each group of cracks formed by connecting adjacent cracks is greater than 500um, and the displacement amount of the modified laser beam is less than the length of the crack.

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

[0018] A laser beam generating unit, comprising a first laser oscillator and a second laser oscillator, wherein the first laser oscillator is used to generate a modified laser beam, and the second laser oscillator is used to generate a cutting laser beam;

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

[0020] As an optional solution of the laser processing device, the laser beam generating unit further includes a laser parameter adjusting component, and the laser parameter adjusting component is used to adjust the reforming laser beam and the cutting laser beam to set laser parameters.

[0021] As an optional solution for the laser processing device, the laser beam generating unit also includes a first beam splitter focusing mirror, at least one second beam splitter focusing mirror and a cutting focusing mirror arranged in sequence along the vertical direction, the first beam splitter focusing mirror and the second beam splitter focusing mirror are located in the optical path of the modified laser beam and can focus the modified laser beam into the interior of the ingot, and the cutting focusing mirror is located in the optical path of the cutting laser beam and can focus the cutting laser beam into the interior of the ingot.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The ingot laser modification process provided by the present invention uses at least two modified laser beams to scan the ingot, and each focal point at a preset depth of the ingot forms a corresponding modified portion. The cracks on both sides of at least two modified portions propagate along the C surface of the ingot and connect to form a group of cracks. The length of the group of cracks is greater than the length of the cracks formed by a single focal point in the prior art. By increasing the width of the cracks, 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 portion is formed by a cutting laser beam to connect two adjacent groups of cracks, and there is no need to use a pressing mechanism for peeling, thereby improving the yield of the wafer.

[0024] The laser processing device provided by the present invention improves production efficiency by increasing the width of cracks, and does not require peeling by a pressing mechanism, thereby improving the yield rate of chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0026] Figure 1 This is a schematic diagram of the structure of the crystal ingot before laser processing in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of multiple groups of cracks generated in a crystal ingot according to an embodiment of the present invention;

[0028] Figure 3 It is a schematic diagram of the structure of a laser processing device in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the structure of the crystal ingot after processing in an embodiment of the present invention;

[0030] Figure 5 Schematic diagram of the structure inside the laser beam generating unit in an embodiment of the present invention.

[0031] Reference numerals:

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

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

[0034] 1. Modified laser beam; 2. Cutting laser beam; 3. Modified part; 4. Cutting part; 5. Ingot; 6. Crack. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0036] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or are the positions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0037] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

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

[0040] like Figure 1 Combination Figure 2 As shown, the ingot laser modification process in this embodiment includes the following steps: positioning the focal points of at least two modified laser beams 1 with a transmittance wavelength at a preset depth from the first surface of the ingot 5, each focal point forms a corresponding modified portion 3, at least two modified portions 3 are arranged at intervals along the C surface, cracks 6 propagate from the modified portion 3 along the C surface, and the cracks 6 formed by adjacent modified portions 3 are connected to each other and form a group of cracks; using a cutting laser beam 2 to cut between two adjacent groups of cracks to form a cutting portion 4, and the two ends of the cutting portion 4 are respectively connected to the two groups of cracks. Figure 2 There are three groups of cracks shown in FIG. Further, the preset depth is 0-2000um.

[0041] In short, the ingot laser modification process provided by the present invention uses at least two modified laser beams 1 to scan the ingot 5, and each focal point at a preset depth of the ingot 5 forms a corresponding modified portion 3. The cracks 6 on both sides of at least two modified portions 3 propagate along the C surface of the ingot 5 and connect to form a group of cracks. The length of this group of cracks is greater than the length of the cracks formed by a single focal point in the prior art. By increasing the width of the cracks, the number of laser reciprocating scans is reduced, which helps to increase the amount of indexing, shorten the processing time, and improve the production efficiency of the wafer. The cutting laser beam 2 is used to form the cutting portion 4, so that two adjacent groups of cracks are connected, and there is no need to use a pressing mechanism for peeling, which improves the yield of the wafer.

[0042] Furthermore, the focal point of the modified laser beam 1 moves along the set path to form a modified layer inside the crystal ingot 5. Exemplarily, the set path in this embodiment is a straight line.

[0043] Further, at least two modified laser beams 1 form a linear modified layer inside the ingot 5. It can be understood that at least two modified portions 3 corresponding to at least two modified laser beams 1 form a modified layer, which increases the width of the modified layer.

[0044] Furthermore, the spacing between the focal points of at least two modified laser beams 1 is the length by which the generated cracks 6 can be connected to each other after stretching. Since the cracks 6 extending on both sides of each modified portion 3 propagate along the C-plane, by making the spacing between the modified portions 3 generated by the two focal points equal to the length by which the generated cracks 6 stretch, it is ensured that the cracks 6 are connected to each other and form a group of cracks.

[0045] Exemplarily, the cutting laser beam 2 is focused at the midpoint of the overlap between the tail of the previous set of cracks and the head of the current crack, and a pulsed laser is emitted to form the cutting portion 4. The focal point formed by the cutting laser beam 2 is made to start cutting from the midpoint of the overlap, thereby improving the cutting accuracy. If the focal point formed by the cutting laser beam 2 is biased upward or downward, it is easy to cause the modified portion 3 where the focal point is generated to be located outside the range 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 portion 4 is the vertical distance between two groups of cracks. After laser processing, the wafer can be easily separated from the ingot 5 by a suction cup member.

[0047] Exemplarily, the length of each group of cracks formed by connecting adjacent cracks 6 is greater than 500um, and the displacement amount of the modified laser beam 1 is less than the length of the crack. The ingot laser modification process mentioned in this embodiment solves the problem that the length of the crack 6 is not long enough. Through multiple beams and a new optical path design, multiple cracks 6 can be generated and connected at the same time, so that the total length of a single connected crack 6 after forming a crack is increased to more than 500um, which is convenient for increasing the value of the displacement amount, speeding up the processing speed, and further shortening the laser processing time.

[0048] like Figures 3 to 5 As shown, this embodiment also provides a laser processing device, which uses the above-mentioned ingot laser modification process to process the ingot 5, and the laser processing device 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 is used to generate a modified laser beam 1, and the second laser oscillator is used to generate a cutting laser beam 2. The ingot 5 can be placed on the base 2000. Optionally, the base 2000 can be moved according to actual use requirements.

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

[0050] Furthermore, the laser beam generating unit 1000 further includes a first beam splitter focusing mirror 100, at least one second beam splitter focusing mirror 200 and a cutting focusing mirror 300 arranged in sequence along the vertical direction. The first beam splitter focusing mirror 100 and the second beam splitter focusing mirror 200 are located in the optical path of the modified laser beam 1 (wherein the modified laser beam 1 can use the reflector 400 to achieve the change of the optical path) and can focus the modified laser beam 1 into 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 the reflector 400 to achieve the change of the optical path) and can focus the cutting laser beam 2 into 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 in the vertical direction, and the optical path is adjusted to the horizontal direction through the reflector, wherein the modified laser beam 1 is divided into at least two laser beams through the first beam splitting and focusing mirror 100 and at least one second beam splitting and focusing mirror 200, and the second beam splitting and focusing mirror 200 can move in the horizontal direction and the vertical direction to adjust the distance between the two focal points of the modified part 3. The cutting focusing mirror 300 can move in the horizontal direction or the vertical direction to adjust the position of the focal point in the ingot 5, so that the focal point of the cutting part 4 can move between the two groups of cracks.

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

Claims

1. The ingot laser modification process is characterized by: The following steps are involved: Positioning the focal points of at least two modified laser beams (1) having a transmission wavelength at a preset depth from the first surface of the ingot (5), each focal point forming a corresponding modified portion (3), at least two of the modified portions (3) being arranged at intervals along the C surface, cracks (6) propagating from the modified portions (3) along the C surface, and cracks (6) formed in adjacent modified portions (3) being connected to each other to form 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), and two ends of the cutting portion (4) are respectively connected to the two groups of cracks.

2. The ingot laser modification process according to claim 1, characterized in that: The focal point of the modified laser beam (1) moves along a set path to form a modified layer inside the crystal ingot (5).

3. The ingot laser modification process according to claim 2, characterized in that: At least two of the modified laser beams (1) form a linear modified layer inside the crystal ingot (5).

4. The ingot laser modification process according to claim 2, characterized in that: The distance between the focal points of at least two of the modified laser beams (1) is a length that allows the generated cracks (6) to be connected to each other after they are extended.

5. The ingot laser modification process according to claim 1, characterized in that: 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 emits a pulsed laser.

6. The ingot laser modification process according to claim 5, characterized in that: The cutting laser beam (2) performs cutting along a vertical direction, or the length of the cutting portion (4) is the vertical distance between two groups of cracks.

7. The ingot laser modification process according to any one of claims 1 to 6, characterized in that: The length of each group of cracks formed by connecting adjacent cracks (6) is greater than 500um, and the displacement amount of the modified laser beam (1) is less than the length of the cracks.

8. A laser processing device, characterized in that: The crystal ingot (5) is processed by the crystal ingot laser modification process according to any one of claims 1 to 7, wherein the laser processing device comprises: A laser beam generating unit (1000) comprising a first laser oscillator and a second laser oscillator, wherein the first laser oscillator is used to generate a modified laser beam (1), and the second laser oscillator is used to generate a cutting laser beam (2); A base (2000) on which the crystal ingot (5) can be placed.

9. The laser processing device according to claim 8, characterized in that: The laser beam generating unit (1000) further comprises a laser parameter adjusting component, wherein the laser parameter adjusting component is used to adjust the modifying laser beam (1) and the cutting laser beam (2) to set laser parameters.

10. The laser processing device according to claim 9, characterized in that: The laser beam generating unit (1000) further comprises a first beam splitter focusing mirror (100), at least one second beam splitter focusing mirror (200) and a cutting focusing mirror (300) arranged in sequence along a vertical direction; the first beam splitter focusing mirror (100) and the second beam splitter focusing mirror (200) are located in the optical path of the modified laser beam (1) and can focus the modified laser beam (1) into the interior of the crystal ingot (5); the cutting focusing mirror (300) is located in the optical path of the cutting laser beam (2) and can focus the cutting laser beam (2) into the interior of the crystal ingot (5).

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