Methods for removing epitaxial regenerated substrates from silicon carbide epitaxial wafers

Abstract

This invention discloses a method for removing epitaxial regenerated substrates from silicon carbide epitaxial wafers, comprising: (1) measuring the total thickness, maximum flatness, and thickness at multiple points on the epitaxial layer of the epitaxial wafer; (2) calculating the average epitaxial thickness and the thinning thickness; (3) performing a first thinning treatment on the epitaxial layer sequentially using a coarse grinding wheel and a second thinning treatment on the epitaxial layer using a fine grinding wheel, or directly performing a second thinning treatment on the epitaxial layer using a fine grinding wheel; (4) rinsing both sides of the thinned epitaxial wafer using a double-sided brushing machine; and (5) simultaneously performing at least one chemical mechanical polishing (CMP) on multiple epitaxial wafers to completely remove the epitaxial layer from each epitaxial wafer. The method of this invention enables more efficient and precise removal of the epitaxial layer, retains the substrate thickness, and improves the processing efficiency and quality of CMP, achieving the reuse of regenerated substrates from defective epitaxial wafers.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide epitaxial technology, and in particular to a method for removing epitaxial regeneration substrate from silicon carbide epitaxial wafers. Background Technology

[0002] If the silicon carbide homoepitaxial growth is unqualified, the epitaxial layer needs to be removed and then chemical mechanical polishing (CMP) is performed to restore it to a quality equivalent to the original substrate.

[0003] The existing method for removing defective epitaxial wafers involves first performing single-sided grinding, then single-sided initial polishing, and finally CMP treatment. Single-sided grinding involves fixing the epitaxial wafer on a mold, applying pressure, and using an abrasive on a metal disk to grind and cut the wafer. Single-sided grinding has low precision, is difficult to control, results in poor surface quality, and easily introduces deep scratches. Furthermore, grinding technology lacks uniformity; when processing multiple wafers, the combination of epitaxial wafer thicknesses is very demanding, and the processing efficiency is low. If the ground epitaxial wafer is then subjected to CMP treatment, it requires a long time to remove the damaged layer. Moreover, because the thickness of the substrate varies, the thickness of the epitaxial wafer also varies, resulting in different thinning requirements for each epitaxial wafer, leading to low overall processing efficiency.

[0004] Therefore, it is necessary to provide a method that can process more efficiently and accurately remove epitaxial regenerated substrates, so as to minimize the thickness of the damaged layer, retain the substrate thickness, and improve the processing efficiency and quality of CMP, thereby realizing the reuse of regenerated substrates of defective epitaxial wafers. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing epitaxial regenerated substrates from silicon carbide epitaxial wafers, which can process the removal of epitaxial regenerated substrates more efficiently and accurately, minimize the thickness of the damaged layer, retain the substrate thickness, and improve the processing efficiency and quality of CMP, thereby realizing the reuse of regenerated substrates from defective epitaxial wafers.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer is provided, for removing the epitaxial layer generated on the substrate of the epitaxial wafer. The method includes the following steps:

[0007] (1) Provide an epitaxial wafer, measure the total thickness of the epitaxial wafer, its maximum flatness and the thickness of multiple points on its epitaxial layer, wherein the maximum flatness is the height difference between the highest and lowest positions on the side of the substrate on which the epitaxial layer is grown;

[0008] (2) The average thickness of the epitaxial layer at multiple points is taken to calculate the average epitaxial thickness, and the sum of the average epitaxial thickness and the maximum flatness is calculated to obtain the thinning thickness of the epitaxial wafer.

[0009] (3) Based on the average thickness of the epitaxial layer, the epitaxial layer is subjected to a first thinning process by passing a coarse grinding wheel and a second thinning process by passing a fine grinding wheel, or the epitaxial layer is subjected to a second thinning process directly by passing the fine grinding wheel; wherein the mesh number of the coarse grinding wheel is less than the mesh number of the fine grinding wheel.

[0010] (4) The two sides of the thinned epitaxial wafer are rinsed by a double-sided brushing machine;

[0011] (5) After rinsing, the epitaxial wafers with the thickness of the substrate within a preset range are attached to the ceramic disk of a chemical mechanical polishing device, and then the epitaxial wafers are simultaneously subjected to at least one chemical mechanical polishing to completely remove the epitaxial layer of each epitaxial wafer.

[0012] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, the following steps are included before step (5):

[0013] Calculate the thickness of the substrate, wherein the thickness of the substrate is equal to the total thickness of the epitaxial wafer minus the thinning thickness.

[0014] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, step (3) specifically comprises:

[0015] When the average thickness of the epitaxial layer is greater than 30 μm, the epitaxial layer is first thinned by the coarse grinding wheel, and then the epitaxial layer is thinned by the fine grinding wheel.

[0016] When the average thickness of the epitaxial layer is less than or equal to 30 μm, the epitaxial layer is subjected to the second thinning process using the fine grinding wheel.

[0017] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, "performing the second thinning treatment on the epitaxial layer using the fine abrasive wheel" specifically means:

[0018] The epitaxial layer is subjected to a first cut by a first fine grinding wheel and / or a second cut by a second fine grinding wheel, wherein the mesh count of the first fine grinding wheel is smaller than that of the second fine grinding wheel.

[0019] Preferably, in one embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, when the average thickness of the epitaxial layer is greater than 30 μm, step (3) above specifically comprises:

[0020] First, the epitaxial layer is subjected to the first thinning treatment using the coarse grinding wheel to remove 70% to 90% of its thickness. Then, the epitaxial layer is cut using the first fine grinding wheel or the second fine grinding wheel to remove 10% to 30% of its thickness; or

[0021] First, the epitaxial layer is subjected to the first thinning process using the coarse grinding wheel to remove 60% to 80% of the thickness of the epitaxial layer. Then, the epitaxial layer is subjected to the first cutting process using the first fine grinding wheel to remove 10% to 30% of the thickness of the epitaxial layer. Finally, the epitaxial layer is subjected to the second cutting process using the second fine grinding wheel to remove 10% of the thickness of the epitaxial layer.

[0022] Preferably, in another embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, step (3) specifically comprises:

[0023] When the average thickness of the epitaxial layer is greater than 10 μm and less than or equal to 30 μm, the epitaxial layer is first cut using only the first fine grinding wheel; or the epitaxial layer is first cut using the first fine grinding wheel to remove 70% to 90% of its thickness, and then the epitaxial layer is second cut using the second fine grinding wheel to remove 10% to 30% of its thickness.

[0024] When the average thickness of the epitaxial layer is less than or equal to 10 μm, the epitaxial layer is subjected to a second cutting using the second fine grinding wheel.

[0025] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention, the coarse grinding wheel has a mesh size of 1000~3000 and a feed speed greater than or equal to 0.5μm / s; the first fine grinding wheel has a mesh size of 5000~10000 and a feed speed of 0.1~0.5μm / s; and the second fine grinding wheel has a mesh size of 20000~50000 and a feed speed of 0.01~0.1μm / s.

[0026] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, step (4) includes the following steps:

[0027] (41) The rotation speed of the epitaxial wafer is set to 2000 rpm, and the nylon brush of the double-sided brushing machine is used in conjunction with two fluids to repeatedly brush one side of the epitaxial wafer from the edge to the center 2 to 5 times at a rotation speed of 2000 rpm. The diameter of the nylon brush is 0.04 to 0.1 mm and the bristle length is 10 to 20 mm.

[0028] (42) Flip the epitaxial wafer and repeat the brushing step in step (41);

[0029] (43) Spin dry the epitaxial wafer.

[0030] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, step (5) includes the following steps:

[0031] (51) A plurality of epitaxial wafers with a thickness within a preset range are attached to the ceramic disk;

[0032] (52) The ceramic disc and the workstation are rotated at a speed of 20~60 rpm and a speed of 100~300 g / cm. 3 Under pressure, the material interacts with the polishing pad and alumina polishing liquid of the chemical mechanical polishing equipment to perform chemical mechanical polishing on multiple epitaxial wafers with sub-damaged surfaces to remove a 1-5 μm damaged layer, resulting in a surface roughness Ra value of 0.1-0.2 nm for the epitaxial wafers.

[0033] Preferably, in the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer of the present invention, step (5) further includes the following steps:

[0034] (53) The ceramic disc and the workstation are rotated at a speed of 20~60 rpm and a speed of 100~300 g / cm. 3 Under pressure, the material interacts with the polishing pad and silicon oxide polishing slurry of the chemical mechanical polishing equipment to further perform chemical mechanical polishing on multiple epitaxial wafers to remove a damaged layer of 0.5~2μm, resulting in a surface roughness Ra value of 0.1~0.15nm for the epitaxial wafers.

[0035] Compared with existing technologies, the method for removing the epitaxial regeneration substrate from silicon carbide epitaxial wafers in this invention performs thinning treatments according to different average epitaxial thicknesses of the epitaxial wafer. Specifically, for epitaxial wafers with larger average thicknesses, a first thinning treatment is performed sequentially using a coarse grinding wheel, followed by a second thinning treatment using a fine grinding wheel. For epitaxial wafers with smaller average thicknesses, a second thinning treatment is performed directly using a fine grinding wheel. Firstly, selecting different thinning methods based on different average epitaxial thicknesses can save unnecessary process steps, improve processing efficiency, and reduce brush wheel wear. Secondly, the method uses a combination of coarse and fine grinding wheels for... The thinning process results in a mirror-like surface with some scattering patterns on the epitaxial wafer. The surface roughness is low, comparable to polishing, and no deep scratches are visually introduced. Furthermore, the flatness, warpage, and curvature values ​​are all lower than those after existing grinding methods. Therefore, the thinning process of this invention has high precision, which can shorten the subsequent processing time and improve the processing efficiency and quality of CMP. Finally, CMP is performed using alumina polishing slurry and / or silicon oxide polishing slurry, which can accurately remove the epitaxial layer while preserving the substrate as much as possible, restoring the substrate to its initial state, and allowing for normal epitaxial growth. This enables the reuse of the substrate from defective epitaxial wafers. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention.

[0037] Figure 2 yes Figure 1 The sub-flowchart of step S04.

[0038] Figure 3 yes Figure 1 The sub-flowchart of step S06.

[0039] Figure 4 This is a partial structural schematic diagram of the biaxial thinning machine used in this invention.

[0040] Figure 5 This is a partial structural schematic diagram of the chemical mechanical polishing equipment used in this invention.

[0041] Figure 6 yes Figure 5 A structural diagram from another angle.

[0042] Figure 7 This is a cross-sectional view of the epitaxial wafer whose epitaxial layer is to be removed in this invention. Detailed Implementation

[0043] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which similar element reference numerals represent similar elements. It should be noted that the directional descriptions involved in the present invention, such as up, down, left, right, front, and rear, indicating directions or positional relationships, are based on the directions or positional relationships shown in the drawings and are only for the convenience of describing the technical solutions of this application or / and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "first," "second," etc., described are only used to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0044] The method for removing epitaxial regeneration substrate from silicon carbide epitaxial wafers provided by the present invention is used to remove the epitaxial layer of unqualified epitaxial wafers, so that they are finally restored to the same quality as the original substrate, so as to realize the regeneration and reuse of the substrate.

[0045] Please refer to the following first. Figure 1 As shown, the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer provided by the present invention includes the following steps:

[0046] S01. Provide an epitaxial wafer, measure the total thickness of the epitaxial wafer, its maximum flatness, and the thickness of multiple points on its epitaxial layer, wherein the maximum flatness is the height difference between the highest and lowest positions on the side of the substrate on which the epitaxial layer is grown;

[0047] S02. The average thickness of multiple points on the epitaxial layer is taken to calculate its average epitaxial thickness. The sum of the average epitaxial thickness and the maximum flatness is calculated to obtain the thinning thickness of the epitaxial wafer.

[0048] Continue reading Figure 7 As shown, the thickness value h obtained in step S01 is... i ( i =1, 2, ..., n The average value is taken to calculate the average epitaxial thickness h of the epitaxial wafer. Since removing the epitaxial layer 32 requires removing all epitaxial layers 32 on the substrate 31, the thinning thickness h0 in this invention is greater than or equal to the sum of the average epitaxial thickness h and the maximum flatness TTV.MAX, that is, h0≥h+TTV.MAX. In one specific embodiment, the thinning thickness h0 is taken as the sum of the average epitaxial thickness h and the maximum flatness TTV.MAX, that is, h0=h+TTV.MAX.

[0049] S03. Based on the average thickness of the epitaxial layer, the epitaxial layer is subjected to a first thinning process by passing a coarse grinding wheel and a second thinning process by passing a fine grinding wheel, or the epitaxial layer is subjected to a second thinning process by passing a fine grinding wheel; wherein the mesh number of the coarse grinding wheel is less than the mesh number of the fine grinding wheel;

[0050] See Figure 4 As shown, the thinning technology is an upgrade of existing grinding technology. Specifically, the thinning technology uses a biaxial thinning machine 10, on which the epitaxial wafer 30 is fixed on a porous ceramic adsorption stage 12. A grinding wheel 11, made of diamond powder and resin, etc., rapidly cuts the surface of the epitaxial wafer 30 under high-speed rotation, resulting in high efficiency and high precision. The structure and working principle of other parts of the biaxial thinning machine 10 are conventional methods well known to those skilled in the art and will not be described in detail.

[0051] In this invention, when the average epitaxial thickness h is large, specifically greater than a preset value, the epitaxial layer is thinned sequentially using a coarse grinding wheel and a fine grinding wheel. This allows for precise removal of the epitaxial layer while preserving the substrate as much as possible, resulting in high processing accuracy. Conversely, when the average epitaxial thickness h is small, specifically less than or equal to the aforementioned preset value, only the fine grinding wheel is used to thin the epitaxial layer, reducing processing steps and improving processing efficiency. In other words, this invention differentiates between the thickness of the epitaxial layer and employs different methods and steps to remove it, effectively improving both processing accuracy and efficiency.

[0052] In one specific embodiment of the present invention, when the average epitaxial thickness h is greater than 30 μm, the epitaxial layer is first thinned using a coarse grinding wheel, and then a second thinning process is performed using a fine grinding wheel. These two thinning processes precisely remove the epitaxial layer while preserving as much of the substrate as possible, resulting in finer processing. When the average epitaxial thickness h is less than or equal to 30 μm, the second thinning process is performed directly using a fine grinding wheel to remove the epitaxial layer, reducing processing steps and thus improving processing efficiency.

[0053] S04. The two sides of the thinned epitaxial wafer are rinsed using a double-sided brushing machine;

[0054] S05. Calculate the thickness of the substrate of the epitaxial wafer, wherein the thickness of the substrate is equal to the total thickness of the epitaxial wafer minus the thinning thickness;

[0055] See details Figure 7 As shown, the substrate thickness h c =H-h0, by calculating the substrate thickness h c This is so that the substrate thickness h can be reduced during subsequent chemical mechanical polishing. cChemical mechanical polishing is performed on 30 epitaxial wafers within a preset range in the same batch to improve processing efficiency.

[0056] S06. After rinsing, a plurality of epitaxial wafers with a substrate thickness within a preset range are attached to a ceramic disk of a chemical mechanical polishing (CMP) device. Then, the plurality of epitaxial wafers are simultaneously subjected to at least one CMP polishing to completely remove the epitaxial layer of each epitaxial wafer.

[0057] See Figure 5-6 As shown, CMP technology is the final process in epitaxial wafer polishing. Specifically, the epitaxial wafer 30 is attached to the ceramic disk 22 of the chemical mechanical polishing equipment 20. Then, under the pressure of the cylinder 21, the epitaxial wafer 30 interacts with the polishing liquid and polishing pad 23, which can remove the damaged layer on the surface of the epitaxial wafer 30 and reduce the surface roughness. Only through good CMP processing can the epitaxial wafer 30 be restored to a quality equivalent to the original substrate, and can a better epitaxial growth be achieved when it is reused.

[0058] In this invention, the thickness h of the substrate is... c Multiple epitaxial wafers 30 are attached to a ceramic disk 22 within a preset range. The preset range refers to a certain range with similar thickness values. Multiple epitaxial wafers 30 are chemically and mechanically polished at one time. Compared with the existing single-wafer processing method, the efficiency of chemical mechanical polishing is greatly improved.

[0059] The structure and working principle of the other parts of the chemical mechanical polishing equipment 20 involved in this invention are conventional methods well known to those skilled in the art, and will not be described in detail here.

[0060] The following is combined Figure 4 , Figure 7 As shown, in the method for removing the epitaxial regeneration substrate from a silicon carbide epitaxial wafer of the present invention, the step S03 above, "performing the epitaxial layer through a fine grinding wheel to perform the second thinning treatment," specifically refers to:

[0061] The epitaxial layer is subjected to a first cut using a first fine grinding wheel and / or a second cut using a second fine grinding wheel, wherein the mesh size of the first fine grinding wheel is smaller than that of the second fine grinding wheel. In other words, the steps for the second thinning process using fine grinding wheels can be further refined according to different needs. Specifically, the epitaxial layer can be cut twice sequentially using the first and second fine grinding wheels to achieve finer processing and remove as much of the epitaxial layer as possible; however, this also increases the number of processing steps. Alternatively, the epitaxial layer can be cut only once using either the first or second fine grinding wheel to reduce the number of processing steps and improve processing efficiency.

[0062] Continue to combine Figure 4 , Figure 7As shown, in a specific embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention, step S03 specifically includes the following:

[0063] When the average thickness of the epitaxial layer is greater than 30 μm, one approach is to first perform the first thinning process on the epitaxial layer using the coarse grinding wheel to remove 70% to 90% of the thickness of the epitaxial layer, and then use the first fine grinding wheel or the second fine grinding wheel to cut the epitaxial layer to remove 10% to 30% of the thickness of the epitaxial layer. This approach, through two thinning processes using coarse and fine grinding wheels, can accurately remove the epitaxial layer while retaining the substrate as much as possible. At the same time, the appropriate processing steps ensure processing efficiency. Another approach is to first perform the first thinning treatment on the epitaxial layer using the coarse grinding wheel to remove 60% to 80% of the epitaxial layer thickness, then perform the first cutting on the epitaxial layer using the first fine grinding wheel to remove 10% to 30% of the epitaxial layer thickness, and finally perform the second cutting on the epitaxial layer using the second fine grinding wheel to remove 10% of the epitaxial layer thickness. This approach involves three thinning treatments using the coarse grinding wheel, the first fine grinding wheel, and the second fine grinding wheel, resulting in a more meticulous process that can more accurately remove the epitaxial layer and remove it as thoroughly as possible. However, this approach increases the number of process steps and the transfer time is longer, thus reducing efficiency compared to the previous approach.

[0064] The epitaxial wafer thinned by a combination of coarse and fine grinding wheels has lower values ​​for flatness, warpage, and curvature than those obtained by grinding in existing technologies. The thinned epitaxial wafer has a mirror-like morphology with some scattering patterns, and its surface roughness is low, comparable to polishing. Visually, no deep scratches are introduced, indicating high precision in the thinning process. Therefore, it can shorten the processing time of subsequent processes and improve the efficiency and quality of subsequent CMP processing.

[0065] When the average thickness of the epitaxial layer is greater than 10 μm and less than or equal to 30 μm, one method is to use only the first fine grinding wheel to perform a first cut on the epitaxial layer to completely remove it. This method involves fewer processing steps. Another method is to first use the first fine grinding wheel to perform a first cut on the epitaxial layer to remove 70% to 90% of its thickness, and then use the second fine grinding wheel to perform a second cut to remove 10% to 30% of its thickness. This method uses two different mesh sizes of fine grinding wheels for two thinning processes, resulting in more detailed processing, but the processing time is also longer than the first method.

[0066] When the average thickness of the epitaxial layer is less than or equal to 10 μm, since the thickness of the epitaxial layer is small, the purpose of removing the epitaxial layer can be achieved simply by using the second fine grinding wheel to perform a second cut on the epitaxial layer. This results in fewer processing steps and more meticulous processing.

[0067] In one specific embodiment of the present invention, the coarse grinding wheel preferably has a mesh size of 1000-3000 and a feed rate greater than or equal to 0.5 μm / s; the first fine grinding wheel preferably has a mesh size of 5000-10000 and a feed rate of 0.1-0.5 μm / s; and the second fine grinding wheel preferably has a mesh size of 20000-50000 and a feed rate of 0.01-0.1 μm / s. It is understood that the mesh size and feed rate of the coarse grinding wheel, the first fine grinding wheel, and the second fine grinding wheel are not limited to those in this embodiment and can be flexibly set according to specific requirements.

[0068] The following is combined Figures 1-7 As shown in Table 1 below, different embodiments of the thinning step (i.e., step S03 above) in the method for removing the epitaxial regenerated substrate from the silicon carbide epitaxial wafer of the present invention will be described respectively. Other steps are as described above, so they will not be described again.

[0069]

[0070] Table 1

[0071] Example 1:

[0072] First, a coarse grinding wheel (#1000~3000) is used to perform the first thinning process on the epitaxial layer at a feed rate greater than or equal to 0.5 μm / s, removing 60%~80% of the thickness of the epitaxial layer. Then, a first fine grinding wheel (#5000~10000) is used to perform the first cutting process on the epitaxial layer at a feed rate of 0.1~0.5 μm / s, removing 10%~30% of the thickness of the epitaxial layer. Finally, a second fine grinding wheel is used to perform the second cutting process on the epitaxial layer at a feed rate of 0.01~0.1 μm / s, removing 10% of the thickness of the epitaxial layer. This method involves three thinning processes. The advantage is that the machining is more detailed and can remove the epitaxial layer more accurately, especially suitable for removing thicker epitaxial layers. The disadvantage is that the process steps are increased, the transfer time is longer, and the processing efficiency is reduced.

[0073] Example 2:

[0074] Using the same coarse grinding wheel and under the same conditions as in Example 1, the epitaxial layer undergoes the first thinning process to remove 70% to 90% of its thickness. Then, using a #30000 second fine grinding wheel at a feed rate of 0.01 to 0.1 μm / s, the epitaxial layer undergoes a second cutting process to remove 10% to 30% of its thickness. This method, using a coarse grinding wheel and a second fine grinding wheel for two thinning processes, can accurately remove the epitaxial layer while preserving as much of the substrate as possible. Compared to the method in Example 1, it reduces the number of processing steps and thus improves processing efficiency. However, its disadvantage is that the #30000 grinding wheel experiences greater wear.

[0075] Example 3:

[0076] The epitaxial layer is subjected to the first thinning process in the same manner as in Example 2 above, to remove 70% to 90% of the thickness of the epitaxial layer. Then, the epitaxial layer is subjected to the first cutting process using a #5000 to 10000 first fine grinding wheel at a feed rate of 0.1 to 0.5 μm / s, to remove 10% to 30% of the thickness of the epitaxial layer, thus completing the entire thinning process. This method is the same as in Example 2, and compared to the method in Example 1, it reduces the number of processing steps, thereby improving processing efficiency. However, its disadvantage is that the mesh count of the first fine grinding wheel is smaller than that of the second fine grinding wheel. In other words, the precision of the first cutting process is slightly lower than that of the second cutting process. Therefore, the processing time in the subsequent CMP process is longer than that in Example 2.

[0077] The methods described in Examples 1 to 3 above are preferably applicable to epitaxial wafers with an average epitaxial thickness greater than 30 μm, that is, they are more suitable for removing epitaxial layers with relatively large thicknesses.

[0078] Example 4:

[0079] First, the epitaxial layer is subjected to a first cutting process using a #5000~10000 fine grinding wheel at a feed rate of 0.1~0.5 μm / s to remove 70%~90% of its thickness. Then, the epitaxial layer is subjected to a second cutting process using a #30000 fine grinding wheel at a feed rate of 0.01~0.1 μm / s to remove 10%~30% of its thickness. This method uses two types of fine grinding wheels for two cutting processes, which has the advantage of fine machining. However, its disadvantage is that directly using fine grinding wheels for cutting results in a longer thinning time and greater wheel wear.

[0080] Example 5:

[0081] Using a first fine grinding wheel of #5000~10000, at a feed rate of 0.1~0.5μm / s, the epitaxial layer is subjected to a first cutting process to remove all of it. Compared with the method in Example 4 above, this method has the advantage of fewer processing steps, but its disadvantage is that it only uses a fine grinding wheel for one cutting process, resulting in a longer thinning time and greater grinding wheel wear. The accuracy of the first cutting process is slightly lower than that of the second cutting process. Therefore, the subsequent CMP process takes longer than that in Example 4.

[0082] The methods described in Examples 4-5 above are preferably applicable to epitaxial wafers with an average epitaxial thickness greater than 10 μm and less than or equal to 30 μm.

[0083] Example 6:

[0084] When the average thickness of the epitaxial layer is less than or equal to 10 μm, due to the small thickness of the epitaxial layer, the epitaxial layer is removed entirely by a second cutting process using only the second fine grinding wheel at a feed rate of 0.01~0.1 μm / s. The advantage of this method is fewer processing steps and more detailed processing, but its disadvantages are that the second fine grinding wheel has a larger mesh size, resulting in a longer thinning time and greater wheel wear.

[0085] Based on the descriptions of Embodiments 1 to 6 above, in the present invention, when performing thinning processing, different thinning methods and steps are selected according to different average epitaxial thicknesses (that is, different thicknesses of epitaxial layers), instead of using the same steps for all thicknesses of epitaxial layers. This not only ensures that epitaxial layers of various thicknesses can be removed, but also saves processing steps and improves processing efficiency.

[0086] The following is combined Figures 1-2 As shown, in a specific embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention, step S04 specifically includes the following steps:

[0087] S41. The rotation speed of the epitaxial wafer is set to 2000 rpm. The nylon brush of the double-sided brushing machine, in conjunction with the two fluids, repeatedly brushes one side of the epitaxial wafer from the edge to the center 2 to 5 times at a rotation speed of 2000 rpm. The diameter of the nylon brush is 0.04 to 0.1 mm and the bristle length is 10 to 20 mm.

[0088] Understandably, the diameter and bristle length of the nylon brush are not limited to those in this embodiment, and other specifications of nylon brushes can be selected as needed.

[0089] S42. Flip the epitaxial wafer over and repeat the brushing step of step S41 to rinse the other side of the epitaxial wafer.

[0090] S43. Spin dry the epitaxial wafer.

[0091] The following is combined Figure 1 , Figure 3 As shown, in one embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention, step S06 specifically includes the following steps:

[0092] S61. A plurality of epitaxial wafers with a thickness within a preset range are attached to the ceramic disk;

[0093] In this invention, performing CMP treatment simultaneously on multiple epitaxial wafers with similar substrate thicknesses can improve the efficiency of chemical mechanical polishing.

[0094] S62, keep the ceramic disc and the workstation at a rotational speed of 20~60 rpm and a speed of 100~300 g / cm. 3 Under pressure, the epitaxial wafers are subjected to chemical mechanical polishing with a polishing pad and alumina polishing slurry to remove a 1-5 μm damaged layer, resulting in a surface roughness Ra of 0.1-0.2 nm.

[0095] Continue reading Figure 3 As shown, in a more preferred embodiment of the method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer according to the present invention, step S06 further includes the following steps:

[0096] S63, keep the ceramic disc and the workstation at a rotational speed of 20~60 rpm and a speed of 100~300 g / cm. 3 Under pressure, the material interacts with the polishing pad and silicon oxide polishing slurry of the chemical mechanical polishing equipment to further perform chemical mechanical polishing on multiple epitaxial wafers to remove a damaged layer of 0.5~2μm, resulting in a surface roughness Ra value of 0.1~0.15nm for the epitaxial wafers.

[0097] Specifically, if normal epitaxial growth still cannot be achieved on the regenerated substrate after the CMP treatment in step S62, a silicon oxide CMP treatment in step S63 needs to be added to further remove the damaged layer by 0.5~2μm, thereby further reducing the surface roughness of the regenerated substrate.

[0098] Recombined Figures 1-7 As shown, a specific embodiment of the method for removing epitaxial regenerated substrate using the silicon carbide epitaxial wafer of the present invention will be described.

[0099] First, the thinning thickness h0 is calculated to be 30 μm using the method described in step S02 above. Then, a #2000 coarse grinding wheel is selected at a feed rate of 0.5 μm / s to perform the first thinning process, reducing the epitaxial layer by 22 μm. Next, a #8000 fine grinding wheel is selected at a feed rate of 0.2 μm / s to perform the first cutting process (i.e., the second thinning process), reducing the epitaxial layer by 8 μm, thus completing the thinning process. Next, a nylon brush with a diameter of 0.08 mm and a bristle length of 12 mm is used to brush the thinned epitaxial wafer on both sides. After brushing, CMP treatment is performed, specifically using a 250 g / cm³ brush. 3 The pressure and rotation speed of the device are 40 rpm, which causes the epitaxial wafer to react with the alumina polishing slurry to remove the 3 μm damaged layer. At this time, the original silicon carbide epitaxial wafer is restored to the substrate. After being processed by the method of this invention, the surface roughness Ra of the regenerated substrate can reach 0.1~0.15 nm, and the cumulative length of the scratches is less than or equal to one diameter of the substrate, realizing the reuse of the regenerated substrate of the defective epitaxial wafer.

[0100] In summary, the method for removing the epitaxial regeneration substrate from a silicon carbide epitaxial wafer of the present invention performs thinning treatment according to different average epitaxial thicknesses of the epitaxial wafer. Specifically, for epitaxial wafers with larger average thicknesses, a first thinning treatment is performed sequentially using a coarse grinding wheel, followed by a second thinning treatment using a fine grinding wheel. For epitaxial wafers with smaller average thicknesses, a second thinning treatment is performed directly using a fine grinding wheel. Firstly, selecting different thinning methods based on different average epitaxial thicknesses can save unnecessary process steps, improve processing efficiency, and reduce brush wheel wear. Secondly, the use of a combination of coarse and fine grinding wheels for thinning... The thinning process results in a mirror-like epitaxial wafer with some scattering patterns. The surface roughness is low, comparable to polishing, and no deep scratches are visually introduced. Furthermore, its flatness, warpage, and curvature values ​​are all lower than those after existing grinding methods. Therefore, the thinning process of this invention has high precision, which can shorten the subsequent processing time and improve the processing efficiency and quality of CMP. Finally, CMP is performed using alumina polishing slurry and / or silicon oxide polishing slurry, which can accurately remove the epitaxial layer while preserving the substrate as much as possible, restoring the substrate to its initial state, and allowing for normal epitaxial growth. This enables the reuse of the substrate from defective epitaxial wafers.

[0101] The devices and equipment involved in the method of this invention are all conventional devices in the art and are conventional working methods well known to those skilled in the art, and will not be described in detail here.

[0102] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for removing an epitaxial regrown substrate from a silicon carbide epitaxial wafer for removing a non-qualified epitaxial layer formed on a substrate of the epitaxial wafer, characterized by, The method comprises the following steps: (1) providing an epitaxial wafer, measuring the total thickness of the epitaxial wafer, the maximum flatness thereof and the thickness of a plurality of points on the epitaxial layer thereof, wherein the maximum flatness is the height difference between the highest position and the lowest position on the side of the substrate on which the epitaxial layer is grown; (2) averaging the thickness of the plurality of points on the epitaxial layer to calculate the average thickness of the epitaxial layer, and calculating the sum of the average thickness of the epitaxial layer and the maximum flatness to obtain the thinning thickness of the epitaxial wafer; (3) according to the average thickness of the epitaxial layer, sequentially performing a first thinning treatment on the epitaxial layer by a coarse grinding wheel and a second thinning treatment on the epitaxial layer by a fine grinding wheel, or directly performing the second thinning treatment on the epitaxial layer by the fine grinding wheel; wherein the mesh number of the coarse grinding wheel is smaller than that of the fine grinding wheel; (4) flushing both sides of the epitaxial wafer after the thinning treatment by a double-sided brushing machine; (5) calculating the thickness of the substrate, wherein the thickness of the substrate is equal to the total thickness of the epitaxial wafer minus the thinning thickness; (6) attaching a plurality of the epitaxial wafers after the flushing and the thickness of the substrate within a preset range to a ceramic disc of a chemical mechanical polishing device, and then simultaneously performing at least one chemical mechanical polishing on the plurality of epitaxial wafers to completely remove the epitaxial layer of each epitaxial wafer.

2. The method of removing an epitaxial regrown substrate from a silicon carbide epitaxial wafer of claim 1, wherein, The step (3) is specifically: when the average thickness of the epitaxial layer is greater than 30 μm, first performing the first thinning treatment on the epitaxial layer by the coarse grinding wheel, and then performing the second thinning treatment on the epitaxial layer by the fine grinding wheel; when the average thickness of the epitaxial layer is less than or equal to 30 μm, performing the second thinning treatment on the epitaxial layer by the fine grinding wheel.

3. The method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer as described in claim 2, characterized in that, The "performing the second thinning treatment on the epitaxial layer by the fine grinding wheel" is specifically: performing a first cutting on the epitaxial layer by a first fine grinding wheel and / or performing a second cutting on the epitaxial layer by a second fine grinding wheel, wherein the mesh number of the first fine grinding wheel is smaller than that of the second fine grinding wheel.

4. The method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer as described in claim 3, characterized in that, When the average thickness of the epitaxial layer is greater than 30 μm, the step (3) is specifically: first performing the first thinning treatment on the epitaxial layer by the coarse grinding wheel to remove 70% to 90% of the thickness of the epitaxial layer, and then performing cutting on the epitaxial layer by the first fine grinding wheel or the second fine grinding wheel to remove 10% to 30% of the thickness of the epitaxial layer; or first performing the first thinning treatment on the epitaxial layer by the coarse grinding wheel to remove 60% to 80% of the thickness of the epitaxial layer, then performing a first cutting on the epitaxial layer by the first fine grinding wheel to remove 10% to 30% of the thickness of the epitaxial layer, and then performing a second cutting on the epitaxial layer by the second fine grinding wheel to remove 10% of the thickness of the epitaxial layer.

5. The method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer as described in claim 3, characterized in that, The step (3) is specifically: When the average thickness of the epitaxial layer is greater than 10 μm and less than or equal to 30 μm, only the first fine grinding wheel is used to cut the epitaxial layer; or the first fine grinding wheel is used to cut the epitaxial layer to remove 70-90% of the thickness of the epitaxial layer, and then the second fine grinding wheel is used to cut the epitaxial layer to remove 10-30% of the thickness of the epitaxial layer. When the average thickness of the epitaxial layer is less than or equal to 10 μm, the second fine grinding wheel is used to cut the epitaxial layer.

6. The method of removing an epitaxial regrown substrate from a silicon carbide epitaxial wafer as recited in any one of claims 3-5, wherein, The coarse grinding wheel has a mesh number of 1000-3000 and a feeding speed of greater than or equal to 0.5 μm / s; the first fine grinding wheel has a mesh number of 5000-10000 and a feeding speed of 0.1-0.5 μm / s; The second fine grinding wheel has a mesh number of 20000-50000 and a feeding speed of 0.01-0.1 μm / s.

7. The method of claim 1, wherein the silicon carbide epitaxial wafer is a 4H- SiC wafer. The step (4) comprises the following steps: (41) the rotation speed of the epitaxial wafer is 2000 rpm, and one side of the epitaxial wafer is repeatedly washed from the edge to the center by the nylon brush of the double-sided brush washing machine at a rotation speed of 2000 rpm and in cooperation with two fluids, wherein the diameter of the nylon brush is 0.04-0.1 mm, and the length of the bristles is 10-20 mm; (42) the epitaxial wafer is turned over, and the washing step in step (41) is repeated; (43) the epitaxial wafer is spun dry.

8. The method of claim 1, wherein the silicon carbide epitaxial wafer is a bulk silicon carbide wafer. The step (5) comprises the following steps: (51) the epitaxial wafers with the thickness of the substrate within a preset range are attached to the ceramic disc; (52) The ceramic disk and the station are made to act with the polishing pad of the chemical mechanical polishing equipment and the alumina polishing liquid under the rotation speed of 20-60 rpm and the pressure of 100-300 g / cm 3 The surface sub-damaged multiple epitaxial wafers are chemically mechanically polished to remove the damage layer 1-5 μm, so that the surface roughness Ra value of the epitaxial wafer is 0.1-0.2 nm.

9. The method for removing the epitaxial regenerated substrate from a silicon carbide epitaxial wafer as described in claim 8, characterized in that, The step (5) further comprises the following steps: (53) continuing the chemical mechanical polishing of the plurality of the epitaxial wafers by the polishing pad of the chemical mechanical polishing apparatus and the silica polishing liquid at a rotation speed of 20 to 60 rpm and a pressure of 100 to 300 g / cm 3 to remove the damage layer by 0.5 to 2 μm and to make the surface roughness Ra value of the epitaxial wafer 0.1 to 0.15 nm.

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