Wafer stripping method based on lateral laser

Abstract

The invention discloses a wafer stripping method based on lateral laser, and relates to the technical field of wafers, in particular to the technical field of wafer stripping. According to the specific implementation scheme, a to-be-cut crystal ingot is subjected to modification treatment through laser of a first wavelength, and then wafer stripping is carried out at the position, with the same depth as a modified layer, of the side direction of the to-be-cut crystal ingot through laser of a second wavelength, wherein the laser of the second wavelength has the stripping capacity on the modified layer and does not have the modification capacity on a non-modified layer. The wafer stripping efficiency can be improved, and the fragment risk can be reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of wafer technology, and in particular to the field of wafer peeling technology. 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 have emerged. Laser modification and stripping technology uses the internal modification of the laser beam 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. Among them, the laser modification and stripping method mainly includes two steps: 1. Modification step; 2. Stripping step. The existing stripping steps mainly include chemical corrosion method and ultrasonic vibration method.

[0004] However, the existing chemical etching method and ultrasonic vibration method have the problem of low stripping efficiency; in addition, the ultrasonic vibration method also has the problem of easy fragmentation. Summary of the invention

[0005] The present disclosure provides a wafer peeling method based on lateral laser, which is used to improve the efficiency of wafer peeling.

[0006] The present disclosure provides a wafer peeling method based on a lateral laser, the method comprising:

[0007] Modifying the ingot to be cut at a predetermined depth from the end face of the wafer to be cut based on a first laser to obtain a target modified layer, wherein the first laser is used to generate a laser of a first wavelength that is transparent to the wafer to be cut;

[0008] Based on a second laser, a laser lift-off process is performed at a depth that is the same as a predetermined depth from the end face of the wafer to be cut in a lateral direction of the ingot to be cut, to obtain a target wafer, wherein the second laser is used to generate a laser of a second wavelength that has a cutting capability for the modified layer but has no modifying capability for the non-modified portion of the ingot to be cut;

[0009] Wherein, the first wavelength is greater than the second wavelength.

[0010] Optionally, the ingot to be cut is a silicon carbide ingot.

[0011] Optionally, the second laser is an ultraviolet laser.

[0012] Optionally, the wavelength of the ultraviolet laser is 355 nm.

[0013] Optionally, the power of the ultraviolet laser is 15W, the pulse width is 50fs-200fs, and the repetition frequency is 400KHZ-1MHZ.

[0014] Optionally, the pulse width of the ultraviolet laser is 100fs and the repetition frequency is 500KHZ.

[0015] The present disclosure provides a wafer stripping method based on lateral laser, including: modifying the ingot to be cut at a predetermined depth from the end face of the wafer to be cut based on a first laser to obtain a target modified layer, the first laser is used to generate a laser of a first wavelength that is transparent to the wafer to be cut; performing laser stripping at a depth of the same depth as the predetermined depth from the end face of the wafer to be cut based on a second laser to obtain a target wafer, the second laser is used to generate a laser of a second wavelength that has a cutting ability to the modified layer but has no modification ability to the non-modified part of the ingot to be cut; wherein the first wavelength is greater than the second wavelength. That is, the ingot to be cut is first modified by a laser of the first wavelength, and then at the same depth as the modified layer on the side of the ingot to be cut, a laser of the second wavelength that has a stripping ability to the modified layer but has no modification ability to the non-modified layer is used to perform wafer stripping, which can improve the efficiency of wafer stripping and reduce the risk of fragmentation.

[0016] 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

[0017] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure.

[0018] Figure 1 is a schematic flow chart of a wafer peeling method based on a lateral laser provided in an embodiment of the present disclosure;

[0019] Figure 2 Schematic diagram of wafer debonding using a side laser. DETAILED DESCRIPTION

[0020] 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.

[0021] Laser modification and wafer stripping mainly includes two steps: 1. modification step; 2. stripping step. In the modification step, the laser is focused below the surface of the ingot to be cut, and a single or multiple modified layers are scanned inside the ingot; in the stripping step, under the action of external tension, the cracks in the modified layer extend in a direction perpendicular to the wafer surface, so that the wafer is split from the inside to the outside, thereby stripping the wafer from the silicon carbide ingot. The existing stripping methods mainly include chemical corrosion method and ultrasonic vibration method.

[0022] like Figure 1 As shown, an embodiment of the present disclosure provides a wafer peeling method based on a lateral laser, the method comprising:

[0023] Step S101 , modifying a crystal ingot to be cut at a predetermined depth from an end face of a wafer to be cut using a first laser to obtain a target modified layer, wherein the first laser is used to generate a laser of a first wavelength that is transparent to the wafer to be cut.

[0024] Specifically, a laser with a first wavelength generated by a first laser that is transparent to the crystal ingot to be cut can be used to perform laser scanning at a predetermined depth from the crystal ingot to be cut to obtain a target modified layer.

[0025] Specifically, the first laser may be a green laser or an infrared laser. Specifically, it may be an infrared laser that generates a laser with a wavelength of 1064 nm or a laser that generates a laser with a wavelength of 532 nm.

[0026] Step S102, based on a second laser, laser stripping is performed at a depth that is the same as a predetermined depth on the lateral side of the crystal ingot to be cut and the end face of the wafer to be cut to obtain a target wafer, wherein the second laser is used to generate a laser of a second wavelength that has the ability to cut the modified layer but has no modification ability on the non-modified part of the crystal ingot to be cut; wherein the first wavelength is greater than the second wavelength.

[0027] Specifically, after the ingot to be cut is modified, the material nature of the modified layer of the ingot to be cut is changed, and the Mohs hardness of the modified layer is changed to be lower than the Mohs hardness of the non-modified layer. A second wavelength laser having the ability to cut the modified layer but not having the ability to modify the non-modified part of the ingot to be cut can be used to cut the ingot in the lateral direction (such as Figure 2 As shown in the figure, laser stripping is performed at a depth which is the same as the predetermined depth from the end face of the wafer to be cut, thereby obtaining a target wafer.

[0028] The crystal ingot to be cut may be a silicon carbide crystal ingot, or may be other crystal ingots that can be processed using the method disclosed herein.

[0029] Specifically, the second laser may be an ultraviolet laser, and the wavelength of the ultraviolet laser may be 355 nm.

[0030] Specifically, the power of the 355nm wavelength ultraviolet laser used may be 15W, the pulse width may be 50fs-200fs, and the repetition frequency may be 400KHZ-1MHZ.

[0031] Specifically, the pulse width of the ultraviolet laser is 100fs, and the repetition frequency is 500KHZ. Among them, the main function of the 355nm laser is to cut the bonded part inside the ablation layer (modified layer) between the ingot and the wafer, so as to obtain an ingot + a wafer after peeling. When using an ultraviolet fs laser for peeling, firstly, the 355nm laser has a small focusing spot, and the laser with a pulse width of fs has a lower thermal effect than the laser with a pulse width of ns and ps, which can reduce or avoid additional damage to the non-modified layer during peeling.

[0032] Taking silicon carbide ingot as an example, the Mohs hardness of silicon carbide ingot reaches 9.5. It is difficult to cut silicon carbide using ultraviolet laser. However, after the ingot to be cut is modified using a first wavelength laser (such as green laser, infrared laser), the modified layer becomes C, SI and a composite, so that the ultraviolet laser has the ability to cut the modified layer.

[0033] For example, taking a silicon carbide ingot as an example, the laser modification and stripping method of a silicon carbide wafer is as follows:

[0034] 1. The outline of the entire ingot is captured by visual methods to determine the width to be processed. The linear motor drives the ingot to move under the 532nm laser processing head and scans it at a depth of 500 microns from the surface of the wafer to form ablation points of 10 microns to 20 microns and a 5-micron transverse crack in the Y direction to obtain the target modified layer.

[0035] 2. The linear motor drives the crystal ingot to move to the 355nm laser processing head, and the position of the crack is captured by vision. The wafer is driven to rotate by the stage to achieve laser cutting of the wafer.

[0036] 3. Finally, a crystal ingot and a wafer with a specified thickness peeled off from the crystal ingot are formed.

[0037] The embodiment of the present disclosure provides a wafer stripping method based on lateral laser, including: modifying the ingot to be cut at a predetermined depth from the end face of the wafer to be cut based on a first laser to obtain a target modified layer, the first laser is used to generate a laser of a first wavelength that is transparent to the wafer to be cut; performing laser stripping based on a second laser at a depth that is the same as the predetermined depth from the end face of the wafer to be cut on the lateral side of the ingot to be cut, to obtain a target wafer, the second laser is used to generate a laser of a second wavelength that has a cutting ability to the modified layer but has no modification ability to the non-modified part of the ingot to be cut; wherein the first wavelength is greater than the second wavelength. That is, firstly modifying the ingot to be cut with a laser of a first wavelength, and then using a laser of a second wavelength that has a stripping ability to the modified layer but has no modification ability to the non-modified layer at the same depth on the lateral side of the ingot to be cut as the modified layer to perform wafer stripping, which can improve the efficiency of wafer stripping and reduce the risk of fragmentation. Specifically, when the wafer and the ingot are peeled off by ultrasonic vibration, some areas will be separated first and some areas will not be separated in the uneven processing position. The areas that were separated first will continue to vibrate and are easy to break. The method of peeling off based on the side laser disclosed in the present invention can further perform laser burning treatment on the unseparated part from the side of the ingot to be cut, so that the unseparated part can be separated, thereby reducing the risk of fragmentation. In addition, the use of laser to split the unseparated part is also more efficient than the chemical etching method and the ultrasonic vibration method, thereby making the wafer peeling more efficient.

[0038] 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.

[0039] 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 wafer peeling method based on lateral laser, characterized in that: include: Modifying the ingot to be cut at a predetermined depth from the end face of the wafer to be cut based on a first laser to obtain a target modified layer, wherein the first laser is used to generate a laser of a first wavelength that is transparent to the wafer to be cut; Based on the second laser, laser stripping is performed at a depth that is the same as the predetermined depth at the lateral distance from the end face of the wafer to be cut to obtain a target wafer, and the second laser is used to generate a laser of a second wavelength that has the ability to cut the modified layer but has no modification ability for the non-modified part of the ingot to be cut; wherein the first wavelength is greater than the second wavelength.

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

3. The method according to claim 1, characterized in that: The second laser is an ultraviolet laser.

4. The method according to claim 3, characterized in that The wavelength of the ultraviolet laser is 355nm.

5. The method according to claim 4, characterized in that The power of the ultraviolet laser is 15W, the pulse width is 50fs-200fs, and the repetition frequency is 400KHZ-1MHZ.

6. The method according to claim 5, characterized in that The pulse width of the ultraviolet laser is 100fs and the repetition frequency is 500KHZ.

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