Method for separating gallium oxide substrate

Abstract

[Technical problem] To divide a β-gallium oxide substrate having a (001) plane as a main surface. [Solution means] The present application includes: a step of forming a plurality of division grooves 13 along an extension direction of a (100) plane of a β-gallium oxide substrate 10 having a (001) plane as a main surface; a step of processing the β-gallium oxide substrate 10 into a long strip shape by cutting in a direction perpendicular to the extension direction of the division grooves 13; and a step of performing single wafer processing by cleaving the long strip-shaped β-gallium oxide substrate 10 along the division grooves 13. In this way, since a plurality of division grooves 13 are formed along a cleavage plane, cleaving along the division grooves 13 does not cause thin sheet-shaped peeling on the cleavage plane, and division can be performed well.

Description

Technical Field

[0001] This invention relates to a method for segmenting gallium oxide substrates, and particularly to a method for segmenting β-type gallium oxide substrates. Background Technology

[0002] As a method for dicing compound semiconductors, the methods described in Patent Documents 1 and 2 are known. Patent Document 1 discloses a method in which: after forming scribe lines of 150 μm to 200 μm in length on the main surface of a substrate using a dicing machine, the substrate is cut into a strip shape; further, the strip-shaped substrate is cleaved along the scribe lines to achieve monolithic wafer formation. Patent Document 2 discloses a method in which: cutting grooves and scribe lines are formed on both sides of a substrate, and the substrate is cleaved along the cutting grooves and scribe lines to achieve monolithic wafer formation.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 7-201783

[0006] Patent Document 2: Japanese Patent Publication No. 6-11071 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, due to the strong cleavage of the (100) surface of the β-type gallium oxide substrate, the method described in Patent Document 1 has the following problem: thin sheet-like peeling occurs on the cleavage surface in areas where no scratches are formed. Furthermore, for a β-type gallium oxide substrate with the (001) surface as the main surface, the cleavage surface, i.e., the (100) surface, is not perpendicular to the main surface and has a predetermined tilt angle. Therefore, the method described in Patent Document 2 cannot correctly cleave the β-type gallium oxide substrate.

[0009] In addition, a method of simply cutting the β-type gallium oxide substrate into a matrix shape was also considered. However, as mentioned above, the cleavage plane, i.e. the (100) plane, is not perpendicular. Therefore, if the cutting is carried out along the extension direction of the cleavage plane, a chip gap will be generated due to partial cleavage.

[0010] Therefore, the object of the present invention is to provide a method for effectively dividing a β-type gallium oxide substrate with the (001) surface as the main surface.

[0011] Means for solving technical problems

[0012] The method for dividing a β-type gallium oxide substrate according to the present invention is characterized by comprising: a step of forming a plurality of first dividing grooves along the extension direction of the (100) surface of the β-type gallium oxide substrate with the (001) surface as the main surface; a step of processing the β-type gallium oxide substrate into a strip shape by cutting it in a direction perpendicular to the extension direction of the first dividing grooves; and a step of monolithizing the strip-shaped β-type gallium oxide substrate by cleaving it along the first dividing grooves.

[0013] According to the present invention, since a plurality of first dividing grooves are formed along the cleavage plane, cleavage along the first dividing grooves will not produce thin-sheet peeling on the cleavage plane, and good division can be achieved.

[0014] In this invention, the first dividing groove can be formed by etching. Therefore, no cracks or gaps will be generated in the substrate during the formation of the first dividing groove.

[0015] In this invention, the first dividing groove can also be formed on the back side opposite to the component forming surface. Therefore, it is not necessary to process the component forming surface.

[0016] Furthermore, the slicing method for the β-type gallium oxide substrate of the present invention may also include a step of forming a plurality of second slicing grooves on the device forming surface along the extension direction of the (100) surface, wherein the straight line connecting the first slicing groove and the second slicing groove has an angle of approximately 76° with respect to the device forming surface. Therefore, since the first slicing groove and the second slicing groove are located on the same cleavage plane, cleavage-based monolithization can be performed more reliably.

[0017] Invention Effects

[0018] Thus, according to the present invention, it is possible to effectively divide a β-type gallium oxide substrate with the (001) surface as the main surface. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the slicing method of the β-type gallium oxide substrate according to the first embodiment of the present invention. Figure 1 (a) is a top view. Figure 1 (b) is along Figure 1 The approximate cross-sectional view of line AA shown in (a).

[0020] Figure 2 This is a schematic top view illustrating the slicing method of a β-type gallium oxide substrate according to the first embodiment of the present invention.

[0021] Figure 3 This is a schematic top view illustrating the slicing method of a β-type gallium oxide substrate according to the first embodiment of the present invention.

[0022] Figure 4It is the yz cross section of the monolithic element 20.

[0023] Figure 5 This is a schematic diagram illustrating the slicing method of the β-type gallium oxide substrate according to the second embodiment of the present invention. Figure 5 (a) is a top view. Figure 5 (b) is along Figure 5 The approximate cross-sectional view of line AA shown in (a).

[0024] Figure 6 This is a general perspective view showing an example of an element forming surface 11 of a β-type gallium oxide substrate being offset relative to the (001) surface. Detailed Implementation

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] Figures 1-3 This is a schematic diagram illustrating the slicing method of a β-type gallium oxide substrate according to the first embodiment of the present invention. Here, Figure 1 of (a), Figure 2 and Figure 3 It is a top view. Figure 1 (b) is along Figure 1 The approximate cross-sectional view of line AA shown in (a).

[0027] First, such as Figure 1 As shown, a β-type gallium oxide (Ga2O3) substrate 10 is prepared to form multiple elements 20 on its main surface, i.e., the element forming surface 11. Although there are no particular limitations, a Schottky barrier diode can be used as an example of an element 20. A Schottky barrier diode using a β-type gallium oxide substrate is an element in which current flows along the thickness direction of the substrate, and the side where the drift layer and the anode electrode in Schottky contact are formed is the element forming surface. Gallium oxide has a very large band gap of 4.8–4.9 eV and an insulation breakdown electric field as high as approximately 8 MV / cm; therefore, a Schottky barrier diode using gallium oxide is very promising as a switching element for power devices.

[0028] The component forming surface 11 and the back surface 12 located on its opposite side constitute a (001) surface (c surface). Figure 1In the β-type gallium oxide substrate 10, the (001) surface forms the xy plane, and multiple elements 20 are formed in a matrix shape in the xy direction. On the back surface 12 of such a β-type gallium oxide substrate 10, multiple cleaving grooves 13 extending in the x direction are formed between adjacent elements 20 in the y direction. The x direction is the extension direction of the cleaving surface, i.e., the (100) surface (a surface). As a method for forming the cleaving grooves 13, etching is preferred. If the cleaving grooves 13 are formed by etching, the β-type gallium oxide substrate 10 will not develop cracks or gaps when forming the cleaving grooves 13. If the thickness of the β-type gallium oxide substrate 10 is about 250 μm, the depth of the cleaving grooves 13 can be about 25 μm. The cleaving grooves 13 are not formed partially, but are formed throughout the entire width of the β-type gallium oxide substrate 10 in the x direction.

[0029] Next, as Figure 2 As shown, the β-type gallium oxide substrate 10 is processed into a strip shape by cutting along a cutting line 14 extending in the y-direction. That is, the cutting direction is perpendicular to the extension direction of the dividing groove 13. The cutting position is between adjacent elements 20 in the x-direction. Thus, each of the β-type gallium oxide substrates 10 cut into strip shapes is in a state where multiple elements 20 are arranged in the y-direction, and dividing grooves 13 are provided on the back surface 12 between adjacent elements 20 in the y-direction.

[0030] Then, as Figure 3 As shown, the device 20 is monolithically formed by cleaving the elongated β-type gallium oxide substrate 10 along the segmentation groove 13. Figure 4 The yz section of the monolithic element 20 has an angle of about 76° (76.3° to be exact) and about 104° (103.7° to be exact) relative to the element forming surface 11 and the back surface 12 along the cleavage surface 13.

[0031] Thus, according to the slicing method of the β-type gallium oxide substrate of this embodiment, since multiple slicing grooves 13 are formed along the extension direction of the cleavage surface (100), a generally flat cleavage surface 15 can be obtained by cleaving along the slicing grooves 13 without producing sheet-like peeling. In addition, as in the case where the β-type gallium oxide substrate 10 is simply cut into a matrix shape, no chip gaps are produced, and the cutting allowance accompanying the cutting can be reduced, thereby increasing the number of chips obtained. Moreover, since the slicing grooves 13 are formed on the back surface 12 opposite to the element forming surface 11, it is not necessary to process the element forming surface 11. However, in the present invention, it is not necessary to form the slicing grooves 13 on the back surface 12; the slicing grooves 13 can be formed on the side of the element forming surface 11.

[0032] Figure 5This is a schematic diagram illustrating the slicing method of a β-type gallium oxide substrate according to the second embodiment of the present invention. Here, Figure 5 (a) is a top view. Figure 5 (b) is along Figure 5 (a) shows a rough cross-sectional view of line AA.

[0033] In the second embodiment, the difference from the first embodiment is that a slit groove 16 is also formed on the element forming surface 11. The slit groove 16 extends parallel to the slit groove 13. However, the slit grooves 13 and 16 do not overlap in the thickness direction (z-direction) but are offset by a distance D in the y-direction. With the thickness of the β-type gallium oxide substrate 10 set to T, the distance D is T × tanθ (θ = 13.7°). Here, the straight line L connecting the slit grooves 13 and 16 has angles of approximately 76° and approximately 104° relative to the element forming surface 11 and the back surface 12, respectively. That is, the slit grooves 13 and 16 are located on the same cleavage plane.

[0034] Therefore, by cutting the β-type gallium oxide substrate 10 into a long strip, and then cleaving it along the dividing grooves 13 and 16, monolithization based on cleaving can be performed more reliably.

[0035] The drift layer forming the device is a thin film of gallium oxide epitaxially grown on the upper surface of a β-type gallium oxide substrate using methods such as reactive sputtering, PLD, MBE, MOCVD, and HVPE. When epitaxially growing a thin film on the upper surface of a β-type gallium oxide substrate using HVPE, it is generally grown on the (001) plane. However, when the β-type gallium oxide substrate has a (001) plane, there is sometimes an offset angle of about ±1° relative to the x-axis and y-axis, which is considered a manufacturing deviation. Furthermore, considering the ease of epitaxial growth and stacking, it is sometimes grown on a β-type gallium oxide substrate with an offset angle of several degrees.

[0036] In such a situation, such as Figure 6 As shown, if the offset angle of the (001) surface relative to the y-axis is set to θ2, then the distance D becomes T×tan(θ+θ2).

[0037] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Various modifications can be made without departing from the spirit of the present invention, and these modifications are also included within the scope of the present invention.

[0038] [Symbol Explanation]

[0039] 10: β-type gallium oxide substrate

[0040] 11: Component Forming Surface

[0041] 12: Back

[0042] 13, 16: Dividing slots

[0043] 14: Cutting line

[0044] 15: Cleavage planes

[0045] 20: Components.

Claims

1. A method for slicing a β-type gallium oxide substrate, characterized in that, have: A process of forming multiple first dividing grooves along the extension direction of the (100) surface of a β-type gallium oxide substrate with the (001) surface as the main surface; The process of processing the β-type gallium oxide substrate into a strip shape by cutting it in a direction perpendicular to the extension direction of the first dividing groove; as well as The process of monolithization is performed by cleaving the elongated β-type gallium oxide substrate along the first dividing groove.

2. The method for segmenting a β-type gallium oxide substrate according to claim 1, characterized in that: The first dividing groove is formed by etching.

3. The method for segmenting a β-type gallium oxide substrate according to claim 1 or 2, characterized in that: The first dividing groove is formed on the back side, which is located on the opposite side of the component forming surface.

4. The method for segmenting a β-type gallium oxide substrate according to claim 3, characterized in that, It also includes the step of forming a plurality of second dividing grooves on the element forming surface along the extension direction of the (100) surface. The straight line connecting the first dividing groove and the second dividing groove has an angle of approximately 76° with respect to the element forming surface.

Images