Method for manufacturing wafer based on green laser

Abstract

The invention discloses a method for manufacturing a wafer based on a green laser, and relates to the technical field of chips, in particular to the technical field of wafer manufacturing. According to the specific implementation scheme, a to-be-cut crystal ingot is subjected to modification treatment based on a green laser to form at least one modification layer; and performing wafer stripping based on the modified layer formed by the to-be-cut crystal ingot to obtain at least one wafer. Namely, the crystal ingot to be cut is subjected to modification treatment, the used laser is a green laser which is short in wavelength and has permeability to the crystal ingot, the focusing capacity of laser beams emitted by the green laser is high, light spots after focusing are small, the influence of input heat is small, and loss brought to materials is small.

Description

Technical Field

[0001] The present disclosure relates to the field of chip technology, and in particular to the field of chip manufacturing technology based on green laser. Background Art

[0002] Traditional semiconductor ingot cutting methods mainly include slurry cutting and diamond wire cutting, which first cut the ingot into multiple wafers of specified thickness, and then grind and thin it to a specific thickness. Traditional mechanical cutting technology has problems such as low efficiency and severe damage.

[0003] In recent years, laser modification and stripping has emerged. Laser modification and stripping technology uses the laser beam to modify the internal structure of the material for stripping. It has the advantages of high efficiency, high precision, and low damage. It has gradually become the preferred technology for cutting high-hardness and brittle materials such as silicon carbide.

[0004] However, the existing laser glass modification methods have the problem that the wavelength of the laser light used is relatively long, resulting in large laser focusing spot, large heat impact and high material loss. Summary of the invention

[0005] The present disclosure provides a method, device and electronic equipment for manufacturing wafers based on green laser, which are used to reduce the thermal impact caused by a large laser focus spot and reduce material loss.

[0006] In a first aspect of the present disclosure, a method for manufacturing a wafer based on a green laser is provided, the method comprising:

[0007] Performing a modification process on the ingot to be cut based on a green laser to form at least one modified layer;

[0008] Wafer peeling is performed based on the modified layer formed on the crystal ingot to be cut to obtain at least one wafer.

[0009] Optionally, the green laser is a green laser with a laser light wavelength of 517nm to 547nm.

[0010] Optionally, the green laser is a green laser with a laser light wavelength of 532 nm.

[0011] Optionally, the green laser is a multi-mode green laser.

[0012] Optionally, the green laser is a multi-mode green continuous laser.

[0013] Optionally, the wafer peeling based on at least one modified layer formed on the ingot to be cut comprises:

[0014] Based on one or a combination of chemical etching and ultrasonic vibration methods, wafer peeling is performed based on at least one modified layer formed on the crystal ingot to be cut.

[0015] Optionally, the ingot to be cut is a silicon carbide ingot.

[0016] Optionally, the ingot to be cut is subjected to a modification process based on a green laser to form at least one modified layer, comprising:

[0017] a modification step, controlling the focal point of the laser light of the green laser to be located at a predetermined depth from the end face of the ingot to be cut, and performing interpolation motion to form a spiral burning point, thereby forming a modified layer at a predetermined depth from the end face of the ingot to be cut; the predetermined depth is determined based on the number and thickness of the wafers to be manufactured;

[0018] a depth-changing and re-modifying step, wherein after the previous modification step is completed, the focal point of the laser light of the green laser is changed to be located at a depth from the end face of the ingot to be cut, and the focal point of the laser light of the green laser is controlled to be located at a changed depth from the end face of the ingot to be cut, and an interpolation movement is performed to form a spiral burning point, and a modified layer at a predetermined depth from the end face of the ingot to be cut is formed; the changed depth is determined based on the number and thickness of the wafers to be manufactured;

[0019] The aforementioned step of changing the depth and then modifying is repeated until a predetermined number of modified layers are obtained for the crystal ingot to be cut.

[0020] Optionally, the distance between adjacent spiral lines is 0.08-0.12 mm.

[0021] Optionally, the distance between adjacent spiral lines is 0.1 mm.

[0022] The present disclosure provides a method for manufacturing a wafer based on a green laser, comprising: performing a modification process on a crystal ingot to be cut based on a green laser to form at least one modified layer; performing wafer peeling based on the modified layer formed on the crystal ingot to be cut to obtain at least one wafer. That is, the crystal ingot to be cut is modified, and the laser used is a green laser with a short wavelength and transmittance to the crystal ingot. The laser beam emitted by the green laser has a strong focusing ability, and the spot is smaller after focusing, the input heat effect is smaller, and the loss to the material is small.

[0023] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure.

[0025] Figure 1 is a flow chart of a method for manufacturing a wafer based on a green laser provided by an embodiment of the present disclosure;

[0026] Figure 2 is a schematic diagram of the energy distribution of a single-mode laser;

[0027] Figure 3 is a schematic diagram of the energy distribution of multi-mode lasers;

[0028] Figure 4 It is a schematic diagram of the damage layer caused by single-mode laser and multi-mode laser;

[0029] Figure 5 It is a schematic diagram of the spiral burning point formed by the interpolation motion of the laser. DETAILED DESCRIPTION

[0030] The following is a description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, including various details of the embodiments of the present disclosure to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0031] Embodiment 1

[0032] Figure 1 A method for manufacturing a wafer based on a green laser provided by an embodiment of the present disclosure is shown, the method comprising:

[0033] Step S101, performing a modification process on the ingot to be cut based on a green laser to form at least one modified layer;

[0034] Step S102, performing wafer peeling based on the modified layer formed on the ingot to be cut to obtain at least one wafer.

[0035] The ingot to be cut may be a silicon carbide ingot, a gallium nitride ingot, or other ingots to which the method disclosed herein can be applied. The green laser may be a green continuous laser, a green pulse laser, or other green lasers capable of realizing the functions disclosed herein.

[0036] Laser modification and cutting of crystal ingots usually includes two steps: 1. The peeling starting point formation step, in which the focal point of the laser light of a wavelength that is transparent to the crystal ingot is positioned at a depth from the end face of the ingot corresponding to the thickness of the wafer to be manufactured, and the laser light is irradiated to the ingot to form a modified layer and a peeling starting point; 2. The peeling step, in which the wafer to be manufactured is peeled from the ingot from the peeling starting point. However, the existing laser modification and cutting of crystal ingots uses a longer wavelength of laser, such as the technical solution disclosed in CN116890174A patent, which uses a 1064nm infrared laser.

[0037] Specifically, in the embodiment of the present disclosure, a green laser with a shorter laser wavelength is used to modify the ingot to be cut to form at least one modified layer; then, wafer peeling is performed based on the modified layer formed on the ingot to be cut to obtain at least one wafer.

[0038] Specifically, a green laser modification process may be performed to form a modified layer, and then the stripping process may be performed, or multiple modified layers may be formed by the modification process, and then the stripping process may be performed.

[0039] The disclosed embodiment provides a method for manufacturing a wafer based on a green laser, including: performing a modification process on a crystal ingot to be cut based on a green laser to form at least one modified layer; performing wafer peeling based on the modified layer formed on the crystal ingot to be cut to obtain at least one wafer. That is, the laser used for modifying the crystal ingot to be cut is a green laser with a shorter wavelength and transmittance to the crystal ingot. The laser beam emitted by the green laser has a strong focusing ability, a smaller spot after focusing, a smaller input heat impact, and a smaller loss to the material.

[0040] The present disclosure provides a possible implementation method, wherein the green laser is a green laser having a laser light wavelength of 517 nm to 547 nm.

[0041] Specifically, taking the ingot to be cut as a silicon carbide ingot as an example, the laser modification method is used to cut the silicon carbide ingot. The laser light used needs to have a certain degree of transmittance to silicon carbide, and the spot formed by laser focusing cannot be too large, otherwise there will be problems such as too large laser focus spot, large heat impact, and high material loss. Through experiments by the inventors of the present disclosure, a green laser with a wavelength of 517nm to 547nm can take into account the requirements of both transmittance and the appropriate size of the laser focus spot.

[0042] The embodiment of the present disclosure provides a possible implementation method, wherein the ingot to be cut is a silicon carbide ingot, and the green laser is a green laser with a laser light wavelength of 532 nm.

[0043] According to the experiments of the inventors of this disclosure, the 532nm laser has the ability to penetrate materials, and the focused spot is smaller, causing less damage to the material. For example, according to Spot size = 4M 2 *Wavelength*f / ΠD shows that the focused spot of 532nm is smaller than that of 1064nm. At the same time, because the focused spot is smaller, the thermal impact caused is also smaller than that of 1064nm. The focused spot of 1064nm laser is large, and the thermal impact is large, which causes more damage to the material. More material damage increases the cost on the one hand, and the cost of subsequent grinding consumables on the other hand, which also leads to longer processing time for subsequent grinding.

[0044] The present disclosure provides a possible implementation manner, wherein the green laser is a multi-mode green laser.

[0045] Among them, lasers are devices that use the principle of stimulated radiation to amplify or oscillate light in certain excited substances. The essential difference between single-mode lasers and multi-mode lasers is that the output beam mode of a single-mode laser has only one mode, while the output beam mode of a multi-mode laser has multiple modes. The difference in mode will directly affect the spatial distribution of energy. From the perspective of energy distribution, single-mode lasers present a typical Gaussian distribution, such as Figure 2 As shown in the figure, the three-dimensional graph is a sharp peak, while the multi-mode laser presents a typical flat-top distribution, such as Figure 3 As shown in the figure, the three-dimensional image of an inverted cup has relatively even energy, which can make the processing effect more uniform, reduce the roughness of the separation surface, improve the surface flatness, and reduce the processing time and grinding wheel loss of the subsequent grinding process. In addition, Figure 4 As shown in the figure, it is a schematic diagram of the damage layer caused by single-mode laser and multi-mode laser. The damage caused by single-mode is more in the direction perpendicular to the material surface, while that caused by multi-mode is less.

[0046] The multi-mode green laser used in the embodiment of the present disclosure has a more even energy distribution compared to a single-mode laser, so that the processing effect of the modified layer is more uniform; in addition, the damage to the material is relatively reduced, which reduces material loss and thus reduces costs.

[0047] The present disclosure provides a possible implementation method, wherein the green light laser is a multi-mode green light continuous laser.

[0048] Specifically, the green light laser is a multi-mode green light continuous laser. Compared with a pulsed laser, in the vertical peeling scenario of a silicon carbide wafer, the spot mode of the continuous laser is a flat-top distribution, which can better control the damaged layer of the material.

[0049] The present disclosure provides a possible implementation method, wherein the wafer peeling is performed based on at least one modified layer formed on the ingot to be cut, including:

[0050] Based on one or a combination of chemical etching and ultrasonic vibration methods, wafer peeling is performed based on at least one modified layer formed on the crystal ingot to be cut.

[0051] Specifically, the modified crystal ingot to be cut can be processed by one or a combination of chemical etching and ultrasonic vibration methods to obtain wafers.

[0052] Among them, the chemical etching method, such as using an acidic etching mixed solution to which a polyoxyethylene ether surfactant (such as one or a mixture of Triton X-100, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, isomeric alcohol polyoxyethylene ether) is added, is used to etch the ingot to be cut that forms at least one modified layer to obtain a target wafer. Among them, during the etching process of the laser modified layer by the acidic etching mixed solution, the modified layer is dissolved and part of hydrogen is generated, thereby forming a mixed solution flow channel in the modified layer. By adding a polyoxyethylene ether surfactant, the wettability of the mixed solution is enhanced, the flow of the mixed solution is promoted, and at the same time, the growth of bubbles can be prevented to hinder the contact between the removal object and the mixed solution, thereby improving the ablation efficiency and uniformity of the laser ablation layer.

[0053] Among them, the ultrasonic vibration method can be, for example, the method disclosed in patent CN116890174A.

[0054] The disclosed embodiments solve the problem of how to peel the ingot after it has been modified.

[0055] The present disclosure provides a possible implementation method, which is to perform a modification process on a to-be-cut ingot based on a green laser to form at least one modified layer, including:

[0056] a modification step, controlling the focal point of the laser light of the green laser to be located at a predetermined depth from the end face of the ingot to be cut, and performing interpolation motion to form a spiral burning point, thereby forming a modified layer at a predetermined depth from the end face of the ingot to be cut; the predetermined depth is determined based on the number and thickness of the wafers to be manufactured;

[0057] a depth-changing and re-modifying step, wherein after the previous modification step is completed, the focal point of the laser light of the green laser is changed to be located at a depth from the end face of the ingot to be cut, and the focal point of the laser light of the green laser is controlled to be located at a changed depth from the end face of the ingot to be cut, and an interpolation movement is performed to form a spiral burning point, and a modified layer at a predetermined depth from the end face of the ingot to be cut is formed; the changed depth is determined based on the number and thickness of the wafers to be manufactured;

[0058] The aforementioned step of changing the depth and then modifying is repeated until a predetermined number of modified layers are obtained for the crystal ingot to be cut.

[0059] If a modified layer is formed by green laser modification, and then a stripping process is performed, the modification step may be included. If multiple modified layers are formed by the modification process, and then a stripping process is performed, the modification step may include a depth change and then a modification step, and the aforementioned depth change and then a modification step may be repeated.

[0060] In the field of CNC machine tools, the contour of a part is often diverse, including straight lines, arcs, and arbitrary curves. The cutting tool of a CNC machine tool often cannot move along the actual contour of the curve, but moves approximately along several very small straight lines, and the direction of the movement is generally in the x and y directions. The interpolation methods include: linear interpolation, circular interpolation, parabola interpolation, spline interpolation, etc. Specifically, the interpolation motion described in the present disclosure is the process in which the laser control system determines the laser motion trajectory of the laser according to a certain method.

[0061] Among them, the present invention discloses a method for interpolating motion to form a spiral line burning point, the laser is focused inside the material, the laser ablation points are formed inside the material, and the ablation points are distributed inside the ingot / wafer at a specific interval. In addition, the laser only needs to scan the processed object once, avoiding repeated scanning, causing laser damage superposition, and increasing material loss. For example, Figure 5 As shown, the focal point of the laser light of the green laser is controlled to be located at a certain depth from the end face of the ingot to be cut, and interpolation motion is performed to form a spiral burning point.

[0062] Among them, the thickness of the silicon carbide wafer can be set according to specific needs, such as 500 microns, then the focal point is located at a predetermined depth of about 500 microns from the end face of the ingot to be cut. If it is two modified layers, under the same wafer thickness (500 microns), the corresponding changed depth of the second modified layer is about 1000 microns. If the required wafer thickness is different, such as the first wafer is 500 microns and the second wafer is 600 microns, then the corresponding focal point is located at a predetermined depth of 500 microns from the end face of the ingot to be cut, and the corresponding changed depth of the second modified layer is about 1100 microns.

[0063] Specifically, the distance between adjacent spiral lines is 0.08 to 0.12 mm. Preferably, the distance between adjacent spiral lines is 0.1 mm. Combined with the focused spot size and multi-mode laser: the 0.1 mm spot effect is determined by the size of the focused spot. The size of the focused spot on the two-dimensional plane in the XY direction is about 0.1 mm. Setting a spacing of 0.1 mm can reduce the overlap rate of the spot and speed up the scanning speed. The single-mode spot is generally around 0.02 mm after focusing.

[0064] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0065] The above specific implementations do not constitute a limitation on the protection scope of the present disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for manufacturing a wafer based on a green laser, characterized in that: include: Performing a modification process on the ingot to be cut based on a green laser to form at least one modified layer; Wafer peeling is performed based on the modified layer formed on the crystal ingot to be cut to obtain at least one wafer.

2. The method according to claim 1, characterized in that The green laser is a green laser with a laser light wavelength of 517nm to 547nm.

3. The method according to claim 1, characterized in that The green laser is a green laser with a laser light wavelength of 532nm.

4. The method according to any one of claims 1 to 3, characterized in that: The green laser is a multi-mode green laser.

5. The method according to claim 4, characterized in that: The green laser is a multi-mode green continuous laser.

6. The method according to claim 1, characterized in that The method of performing wafer peeling based on at least one modified layer formed on the ingot to be cut comprises: Based on one or a combination of chemical etching and ultrasonic vibration methods, wafer peeling is performed based on at least one modified layer formed on the crystal ingot to be cut.

7. The method according to claim 1, characterized in that The ingot to be cut is a silicon carbide ingot.

8. The method according to any one of claims 1 to 6, characterized in that: The method comprises: performing a modification process on the ingot to be cut based on a green laser to form at least one modified layer, comprising: a modification step, controlling the focal point of the laser light of the green laser to be located at a predetermined depth from the end face of the ingot to be cut, and performing interpolation motion to form a spiral burning point, thereby forming a modified layer at a predetermined depth from the end face of the ingot to be cut; the predetermined depth is determined based on the number and thickness of the wafers to be manufactured; a depth-changing and re-modifying step, wherein after the previous modification step is completed, the focal point of the laser light of the green laser is changed to be located at a depth from the end face of the ingot to be cut, and the focal point of the laser light of the green laser is controlled to be located at a changed depth from the end face of the ingot to be cut, and an interpolation movement is performed to form a spiral burning point, and a modified layer at a predetermined depth from the end face of the ingot to be cut is formed; the changed depth is determined based on the number and thickness of the wafers to be manufactured; The aforementioned step of changing the depth and then modifying is repeated until a predetermined number of modified layers are obtained for the crystal ingot to be cut.

9. The method according to claim 7, characterized in that: The distance between adjacent spiral lines is 0.08 to 0.12 mm.

10. The method according to claim 7, characterized in that The distance between adjacent spirals is 0.1 mm.

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