A sapphire substrate, a processing method thereof and a preparation method of a light emitting diode

Abstract

The application discloses a sapphire substrate and a processing method thereof and a preparation method of a light emitting diode. The processing method of the sapphire substrate rotates a sapphire crystal bar by 90 degrees along a circumferential direction from a central axis A perpendicular to an A surface, obtains an M surface of the sapphire crystal bar, then fixes the M surface to a workbench, and cuts the sapphire crystal bar along an M axis direction perpendicular to the M surface to obtain the sapphire substrate. The method cuts the sapphire crystal bar along the M direction, and can obtain a substrate with a concentric circular surface type of nearly 100% after linear cutting, improves the surface type consistency and uniformity of the substrate, and is beneficial to the growth of a subsequent epitaxial layer. In addition, in the cutting process of the sapphire crystal bar, the cleavage characteristics of the M surface are utilized, parameters are optimized and adjusted, the cutting difficulty is reduced, the linear net consumption is reduced, the linear net consumption is reduced by nearly 5% to 20% compared with the prior art, the processing time is saved, and the processing time can be saved by nearly 5% to 20% compared with the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated circuit manufacturing, in particular to a sapphire substrate, a processing method thereof and a preparation method of a light emitting diode. BACKGROUND

[0002] GaN material single crystal growth is difficult and costly. At present, it is mainly obtained by using C-face sapphire substrate epitaxial growth technology with low cost. After epitaxial growth, the substrate is cut into individual cores along a certain lattice direction. Sapphire belongs to hexagonal system and has anisotropic characteristics. The properties of the crystal are different in different directions. The main crystal faces C, A, M and R have different material hardness, and in particular, the material hardness of R face is significantly lower than that of A and M faces. Therefore, the distribution of R face in the cutting direction will have a decisive effect on the formation of the surface profile during the cutting process of the substrate material.

[0003] The traditional cutting technology adopts A face cutting, which is widely used in the industry due to the relatively small difficulty in adjusting the line cutting parameters due to the relatively uniform distribution of R face area on both sides of the center cutting direction. At the same time, the surface profile of the wafer after line cutting presents an S-shaped warping shape in the cutting direction and the line saw direction, and the final product surface profile is easily affected by the in-plane thickness removal difference during subsequent grinding and polishing processing. The consistency of the wafer surface profile is poor, the epitaxial growth experience is poor, and the epitaxial growth quality is uneven. SUMMARY

[0004] In order to solve at least one of the technical problems in the background art, the present application provides a sapphire substrate processing method, a sapphire substrate obtained by the method, and a preparation method of a light emitting diode based on the sapphire substrate. The sapphire substrate processing method cuts a sapphire crystal bar along the M direction to obtain a sapphire substrate with uniform surface profile, and effectively reduces the cutting difficulty and saves the line network consumption.

[0005] According to an embodiment of the present application, a sapphire substrate processing method is provided, which comprises the following steps:

[0006] A sapphire crystal bar is provided, and the sapphire crystal bar is pretreated to mark the A face of the sapphire crystal bar;

[0007] The sapphire crystal bar is rotated 90° along the circumferential direction from the central axis A perpendicular to the A face to obtain the M face of the sapphire crystal bar, and the sapphire crystal bar is fixed along the M face;

[0008] The sapphire crystal bar is cut along the M axis direction perpendicular to the M face to obtain a sapphire substrate.

[0009] Optionally, the pretreatment of the sapphire crystal bar further comprises the following steps:

[0010] rotating the sapphire crystal rod with a C-axis perpendicular to the C face of the sapphire crystal rod as a reference;

[0011] determining an R direction of the sapphire crystal rod and marking the R direction on the sapphire crystal rod;

[0012] fixing the sapphire crystal rod along the R direction, and marking the A face at a position 90° apart from the R direction along the circumferential direction of the sapphire crystal rod.

[0013] Optionally, cutting the sapphire crystal rod along the M-axis direction perpendicular to the M face further comprises:

[0014] calculating the area of the R face of the sapphire crystal rod at different segment positions on the C face;

[0015] adjusting the cutting parameters of the sapphire crystal rod according to the area of the R face at each segment position.

[0016] Optionally, adjusting the cutting parameters of the sapphire crystal rod according to the area of the R face at each segment position further comprises:

[0017] calculating the softening degree of the R face relative to the M face;

[0018] obtaining an adjustment amplitude coefficient of the feeding amount of the cutting machine according to the product of the area ratio of the R face at the current segment position and the softening degree;

[0019] determining a new feeding speed according to the adjustment amplitude coefficient, wherein the new feeding speed = the feeding speed when cutting the same area of the M face + adjustment amplitude coefficient * 2.

[0020] Optionally, the sapphire substrate processing method further comprises: grinding and polishing the sapphire substrate after cutting.

[0021] According to another embodiment of the present application, a sapphire substrate is provided, which is obtained by the sapphire substrate processing method of the present application.

[0022] According to another embodiment of the present application, a preparation method of a light emitting diode is provided, comprising the following steps:

[0023] providing a growth substrate, the growth substrate having a first surface and a second surface, wherein the growth substrate is a sapphire substrate, and the sapphire substrate is obtained by the sapphire substrate processing method of the present application;

[0024] growing an epitaxial layer on the first surface of the growth substrate;

[0025] cutting the sapphire substrate with the epitaxial layer to obtain a plurality of core particles.

[0026] Optionally, growing an epitaxial layer on the growth substrate comprises:

[0027] growing a first semiconductor layer on a first surface of the growth substrate;

[0028] growing a light emitting layer on the first semiconductor layer;

[0029] growing a second semiconductor layer on the light emitting layer;

[0030] wherein the first semiconductor layer and the second semiconductor layer are of opposite conductivity types.

[0031] Compared with the prior art, the sapphire substrate, the processing method thereof and the preparation method of the light emitting diode have at least the following beneficial effects:

[0032] The processing method of the sapphire substrate of the present application obtains the M face of the sapphire crystal bar by rotating the sapphire crystal bar 90° along the circumferential direction from the central axis A perpendicular to the A face of the sapphire crystal bar, then pastes and fixes the M face to the workbench, and cuts the sapphire crystal bar along the M axis direction perpendicular to the M face to obtain the sapphire substrate. This method cuts the sapphire crystal bar along the M direction, and can obtain a substrate of almost 100% concentric circular face type after line cutting, thereby improving the face type consistency and uniformity of the substrate and being beneficial to the growth of the subsequent epitaxial layer. In addition, in the cutting process of the sapphire crystal bar, the cleavage characteristics of the M face are utilized to optimize and adjust the parameters, thereby reducing the cutting difficulty, reducing the line net consumption, reducing the line net consumption by about 5% to 20% compared with the prior art, saving the processing time, and saving the processing time by about 5% to 20% compared with the prior art.

[0033] The epitaxial growth of the sapphire substrate obtained by the above method of the present application can obtain a uniform epitaxial layer, which is beneficial to improve the quality of the epitaxial layer and improve the yield of the subsequent products, such as light emitting diodes. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram of a crystal face structure of a sapphire crystal is shown.

[0035] Figure 2 A schematic diagram of a crystal direction and a crystal face of a sapphire crystal is shown. Figure 3 A schematic diagram of a crystal direction and a crystal face of a sapphire crystal is shown.

[0036] Figure 4 A schematic diagram of the material removal rate of each crystal face in a sapphire crystal bar under different grinding disc speeds is shown.

[0037] Figure 5 A schematic diagram of the distribution of the R face in a sapphire crystal bar in different crystal directions is shown.

[0038] Figure 6A flowchart of a sapphire substrate processing method provided by the first embodiment of the present application.

[0039] Figure 7 and Figure 8 A schematic diagram of a sapphire crystal rod provided by the first embodiment of the present application.

[0040] Figure 9 A schematic diagram of fixing the sapphire crystal rod shown in Figure 8 to a worktable.

[0041] Figure 10 A sapphire substrate obtained by cutting the sapphire crystal rod shown in Figure 9 .

[0042] Figure 11 A flowchart of a light emitting diode preparation method provided by the second embodiment of the present application.

[0043] Figure 12 A structural schematic diagram of growing an epitaxial layer on a sapphire substrate.

[0044] Reference signs:

[0045] 100 sapphire crystal rod 403 cutting path

[0046] 101 notch 500 epitaxial layer

[0047] 200 worktable 501 first semiconductor layer

[0048] 300 sacrificial material 502 second semiconductor layer

[0049] 400 sapphire substrate 503 active layer

[0050] 401 first surface 510 first electrode

[0051] 402 second surface 520 second electrode DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0053] Sapphire belongs to hexagonal system and has obvious anisotropy by itself, such as Figure 1 , Figure 2 and Figure 3As shown, the main crystal faces include C face, A face, M face and R face, and the C face, A face, M face and R face have different material hardness, and in particular, the material hardness of the R face is obviously lower than that of the A and M faces. Figure 4 As shown, the material removal rates of the C face, A face, M face and R face of the sapphire crystal bar under different grinding disc rotating speeds are as follows. Figure 4 As can be seen, under the same rotating speed, the material removal rate of the R face is significantly higher than that of the C face, A face and M face. Figure 5 As shown, the distribution of the R face is as shown in the figure, and therefore the distribution of the R face in the in-cut direction plays a decisive role in the formation of the surface type of the substrate material cutting process.

[0054] To solve the above problems, the present application provides a sapphire substrate processing method, which is specifically described in the following embodiment one.

[0055] Embodiment one

[0056] The embodiment provides a sapphire substrate processing method, as shown in the figure, the method comprises the following steps. Figure 6

[0057] S101: providing a sapphire crystal bar, and pre-treating the sapphire crystal bar to mark the A face of the sapphire crystal bar.

[0058] The sapphire single crystal is obtained by a process of crystal growth and rod extraction. After obtaining the sapphire crystal bar 100, as shown in the figures, the A face of the sapphire crystal bar 100 is marked, specifically, the sapphire crystal bar 100 is rotated with the C axis perpendicular to the C face of the sapphire crystal bar 100 as the reference, the R direction of the sapphire crystal bar 100 is determined, and the R direction is marked on the sapphire crystal bar 100, the sapphire crystal bar 100 is fixed along the R direction, and the A face is marked at a position spaced 90° from the R direction along the circumferential direction of the sapphire crystal bar 100. Figure 7 8 As shown in the figures, in an optional embodiment, a notch 101 is formed in the A face direction to mark the A face. In another optional embodiment, as shown in the figure, the A face of the sapphire crystal bar 100 is added to a plane to mark the A face. Figure 7 Figure 8

[0059] ​​​​S102: Rotate the sapphire crystal rod 90° circumferentially from the central axis A, which is perpendicular to the A surface, to obtain the M surface of the sapphire crystal rod, and fix the sapphire crystal rod along the M surface;

[0060] like Figure 5 As shown, in the sapphire crystal rod 100, the M-plane and the A-plane are in mutually perpendicular directions; therefore, the M-plane can be determined by referring to the A-plane marked on the sapphire crystal rod 100. Figure 8 Taking the A-side as a plane as an example, the sapphire crystal rod 100 is rotated 90° counterclockwise or clockwise from the central axis A-axis perpendicular to the A-side. In this embodiment, rotating 90° clockwise will give the orientation of the M-side.

[0061] S103: Cut the sapphire crystal rod along the M-axis direction perpendicular to the M-plane to obtain a sapphire substrate.

[0062] like Figure 9 As shown, the C-side of the sapphire crystal ingot 100 is fixed to the worktable. Specifically, first, the M-side of the sapphire crystal ingot 100 is bonded to the sacrificial material 300, and then the sacrificial material 300, together with the crystal ingot, is fixed to the worktable. Figure 10 The sapphire ingot 100 is cut using a wire mesh, indicated by arrow Z perpendicular to plane M. The sacrificial material 300 protects the worktable and cutting machine during the cutting process. According to... Figure 5 The distribution of the R-face in the sapphire crystal rod shown includes calculating the area of ​​the R-face at each segment of the sapphire crystal rod 100 before cutting. Specifically, it involves calculating the area of ​​the R-face at different depths along the radial direction of the sapphire crystal rod 100, perpendicular to the M-face. This then calculates the percentage of the R-face area on the entire cut surface, and adjusts the subsequent cutting parameters of the sapphire crystal rod 100 based on the percentage of the R-face area at each segment. Calculations show that the percentage of the R-face area at each segment is between 0% and 80%. Figure 4 As shown, the material removal rates differ across the various faces of the sapphire crystal rod at the same rotational speed, especially the R-face, which exhibits a significantly higher material removal rate than the other three faces at the same rotational speed. The material removal rates of the R-face and M-face at the same rotational speed directly reflect the material's hardness. Therefore, assuming all other conditions remain the same, the ratio of material removal rates can reflect changes in the material's hardness. Figure 4As shown, taking the grinding disc rotation speed of 60 rpm as an example, at this rotation speed, the material removal rate of the M surface is about 8.56 μm / min, and the material removal rate of the R surface is about 23.04 μm / min, thus the degree of softening of the relative hardness of the material of the R surface compared with the M surface is: 1-(8.56 / 23.04)=0.625. The product of the degree of softening of the relative hardness of the R surface and the M surface and the area ratio of the R surface is the adjustment amplitude coefficient of the cutting machine feeding amount, and the new feeding speed = the feeding speed when cutting the M surface of the same area + adjustment amplitude coefficient*2. For example, if the area ratio of the R surface to the cutting area of the whole section in the current section is 80%, the adjustment amplitude coefficient of the cutting machine feeding amount is 0.625*0.8=0.5, at this time, the feeding amount of the cutting machine is adjusted to 2.0 times of the original feeding amount, i.e. the feeding speed is 2.0 times of the original feeding speed; if the area ratio of the R surface to the cutting area of the whole section in the current section is 30%, the adjustment amplitude coefficient of the cutting machine feeding amount is 0.625*0.3=0.2, at this time, the feeding amount of the cutting machine is adjusted to about 1.4 times of the original feeding amount, i.e. the feeding speed is 1.4 times of the original feeding speed. The relationship between the adjustment amplitude coefficient of the feeding amount and the feeding speed (feeding amount) when the area ratio of the R surface is between 0 and 80% is shown in Table 1. In addition, during the cutting of the substrate, the swing angle of the swing head of the cutting machine can also be adjusted, which is mainly limited by the machine, and the adjustable range is between 0 and 12 degrees. The sapphire crystal rod 100 is cut according to the set and adjusted cutting parameters, and the sapphire substrate 400 as shown is obtained. Figure 10

[0063] Table 1 Relationship between cutting feeding amount adjustment amplitude coefficient and feeding speed (feeding amount)

[0064]

[0065]

[0066] As described above, the sapphire crystal rod 100 is cut along the M direction perpendicular to the M surface, and during the cutting, the cutting parameters are adjusted according to the different areas of the R surface in different sections. Because the overall hardness of the M surface is small and the optimized cutting parameters are adopted, the cutting difficulty is reduced, and a sapphire substrate with almost 100% concentric surface type can be obtained, and the surface type difference between the substrates is very small. In addition, the unit consumption of wire can also be saved and the processing time can also be shortened.

[0067] Finally, according to the processing flow of the sapphire substrate, the sapphire substrate obtained by cutting is ground and polished to obtain a sapphire substrate with low warping and high flatness.

[0068] ​This embodiment also provides a sapphire substrate, which is obtained by the method described above. This sapphire substrate has a nearly 100% concentric circular surface, with minimal surface differences between substrates. This is beneficial for improving the uniformity of the epitaxial layers subsequently grown on the sapphire substrate, thereby improving the yield of subsequent devices.

[0069] Example 2

[0070] This embodiment provides a method for fabricating a light-emitting diode, such as... Figure 11 As shown, the method includes the following steps:

[0071] S201: A growth substrate is provided, the growth substrate having a first surface and a second surface, wherein the growth substrate is a sapphire substrate, and the sapphire substrate is obtained by the sapphire substrate processing method provided in the embodiments of the present invention;

[0072] like Figure 12 As shown, with Figure 10 The sapphire substrate 400 shown serves as a growth substrate, having a first surface 401 and a second surface 402, wherein the first surface 401 serves as the surface for growing the epitaxial layer 500.

[0073] S202: An epitaxial layer is grown on the first surface of the growth substrate;

[0074] like Figure 12 As shown, an epitaxial layer 500 is grown on the surface of a sapphire substrate 400. Specifically, a first semiconductor layer 501, an active layer 503, and a second semiconductor layer 502 are sequentially grown on the first surface 401 of the sapphire substrate 400. The first semiconductor layer 501 and the second semiconductor layer 502 are semiconductor layers with opposite conductivity types. For example, the first semiconductor layer 501 is an N-type semiconductor layer, and the second semiconductor layer 502 is a P-type semiconductor layer. Of course, it is also possible for the first semiconductor layer 501 to be a P-type semiconductor layer and the second semiconductor layer 502 to be an N-type semiconductor layer. The active layer 503 is the light-emitting layer of a light-emitting diode. In an optional embodiment, taking a GaN epitaxial layer as an example, the first semiconductor layer 501 can be an N-type GaN layer, such as a Si-doped GaN layer; the active layer 503 can be an InGaN / GaN multiple quantum well; and the second semiconductor layer 502 is a p-type GaN layer, such as a Mg-doped GaN layer.

[0075] Similarly, refer to Figure 12 A first electrode 510 and a second electrode 520 are formed above the first semiconductor layer 501 and the second semiconductor layer 502, respectively. It is understood that the light-emitting diode may also include an insulating protective layer formed on the surface of the epitaxial layer 500.

[0076] S203: cutting the sapphire substrate with the epitaxial layer to obtain a plurality of core particles.

[0077] Specifically, the same wavelength laser light source and different laser energy are used to cut the sapphire substrate 400 along the cutting path 403 of the second surface 402 of the sapphire substrate 400.

[0078] The sapphire substrate used in the embodiment has a surface type of almost 100% concentric circle, and the surface type difference between substrates is very small, thus, the growth uniformity of the epitaxial layer of different batches is improved, and the overall yield of the light emitting diode is improved.

[0079] The specific embodiment is only an explanation of the present application, but not a limitation of the present application, and those skilled in the art can modify the embodiment according to the needs after reading the specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for processing sapphire substrates, characterized in that, Includes the following steps: A sapphire crystal rod is provided, and the sapphire crystal rod is pre-treated by rotating the sapphire crystal rod with the C-axis perpendicular to the C-plane of the sapphire crystal rod as a reference. Determine the R direction of the sapphire crystal rod and mark the R direction on the sapphire crystal rod; fix the sapphire crystal rod along the R direction, and mark surface A at a position 90° away from the R direction along the circumference of the sapphire crystal rod; The sapphire crystal rod is rotated 90° circumferentially from the central axis A, which is perpendicular to the A-plane, to obtain the M-plane of the sapphire crystal rod, and the sapphire crystal rod is fixed along the M-plane. Calculate the area ratio of the R-surface of the sapphire crystal rod at different segments on the C-surface to the total cut area; adjust the cutting parameters of the sapphire crystal rod according to the area ratio of the R-surface at each segment; cut the sapphire crystal rod along the M-axis direction perpendicular to the M-surface to obtain a sapphire substrate. Adjusting the cutting parameters of the sapphire crystal rod based on the area of ​​the R-face at each segment specifically includes: Calculate the degree of softening of the R surface relative to the M surface; Based on the product of the area ratio of the R-surface at the current stage and the degree of softening, the adjustment range coefficient of the cutting machine feed rate is obtained; a new feed rate is determined based on the adjustment range coefficient, wherein the new feed rate = feed rate when cutting the M-surface with the same area + adjustment range coefficient * 2.

2. The sapphire substrate processing method according to claim 1, characterized in that, Also includes: The cut sapphire substrate is then ground and polished.

3. A sapphire substrate, characterized in that, The sapphire substrate is obtained using the sapphire substrate processing method described in claim 1 or 2.

4. A method for fabricating a light-emitting diode, characterized in that, Includes the following steps: A growth substrate is provided, the growth substrate having a first surface and a second surface, wherein the growth substrate is a sapphire substrate, and the sapphire substrate is obtained by the sapphire substrate processing method according to claim 1 or 2. An epitaxial layer is grown on the first surface of the growth substrate; The sapphire substrate having the epitaxial layer is cut to obtain a number of core particles.

5. The method for fabricating a light-emitting diode according to claim 4, characterized in that, The epitaxial layer grown on the growth substrate includes: A first semiconductor layer is grown on the first surface of the growth substrate; A light-emitting layer is grown on top of the first semiconductor layer; A second semiconductor layer is grown on top of the light-emitting layer; The first semiconductor layer has an opposite conductivity type to the second semiconductor layer.

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