Method for dividing a gallium oxide substrate

Abstract

To divide a β-type gallium oxide substrate having a (001) plane as a main surface satisfactorily.SOLUTION: A gallium oxide substrate division method includes the steps of: forming a plurality of dividing grooves 13 along the extending direction of the (100) plane of a β-type gallium oxide substrate 10 having the (001) plane as the main surface; processing the β-type gallium oxide substrate 10 into strips by cutting in a direction perpendicular to the extending direction of the dividing grooves 13; and cleaving strip-shaped β-type gallium oxide substrates 10 along the dividing grooves 13 to separate them into pieces. Therefore, since the plurality of dividing grooves 13 are formed along the cleavage planes, good division can be achieved without causing flaky peeling on the cleavage planes by cleaving the substrate along the dividing grooves 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for dividing a gallium oxide substrate, and more particularly to a method for dividing a β-type gallium oxide substrate. [Background technology]

[0002] Known methods for dividing compound semiconductors are described in Patent Documents 1 and 2. Patent Document 1 discloses a method in which a scriber is used to form scratches of 150 μm to 200 μm in length on the main surface of a substrate, the substrate is diced into strips, and the strips are cleaved along the scratches to separate the substrate. Patent Document 2 discloses a method in which cutting grooves and scribe lines are formed on both sides of the substrate, and the substrate is cleaved along the cutting grooves and scribe lines to separate the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-201783 [Patent Document 2] Special Publication No. 6-11071 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the β-type gallium oxide substrate has a strong cleavage tendency in the (100) plane, there is a problem that flaky peeling occurs on the cleavage plane in the portion where no scratches are formed in the method described in Patent Document 1. In addition, in the case of a β-type gallium oxide substrate having a (001) plane as the main surface, the (100) plane, which is the cleavage plane, is not perpendicular to the main surface but has a certain inclination, so that the method described in Patent Document 2 cannot properly cleave the β-type gallium oxide substrate.

[0005] Another possible method is to simply dice the β-type gallium oxide substrate into a matrix. However, as described above, the (100) cleavage plane is not vertical, and therefore dicing along the extension direction of the cleavage plane will result in chipping due to partial cleavage.

[0006] Therefore, an object of the present invention is to provide a method for effectively dividing a β-type gallium oxide substrate having a (001) principal surface. [Means for solving the problem]

[0007] The method for dividing a β-type gallium oxide substrate according to the present invention is characterized by comprising the steps of: forming a plurality of first division grooves along the extension direction of a (100) plane of a β-type gallium oxide substrate having a (001) plane as its main surface; processing the β-type gallium oxide substrate into strips by cutting in a direction perpendicular to the extension direction of the first division grooves; and cleaving the strip-shaped β-type gallium oxide substrate along the first division grooves to divide it into individual pieces.

[0008] According to the present invention, since a plurality of first division grooves are formed along the cleavage surface, by cleaving along the first division grooves, it is possible to achieve good division without causing flake-like peeling on the cleavage surface.

[0009] In the present invention, the first dividing grooves may be formed by etching, which prevents cracks or chips from occurring in the substrate when the first dividing grooves are formed.

[0010] In the present invention, the first dividing groove may be formed on the back surface located on the opposite side to the element forming surface, which eliminates the need for processing the element forming surface.

[0011] The method for dividing a β-type gallium oxide substrate according to the present invention further includes a step of forming a plurality of second division grooves on the element formation surface along the extension direction of the (100) plane, and the straight line connecting the first division grooves and the second division grooves may have an angle of about 76° with respect to the element formation surface. In this way, the first division grooves and the second division grooves are located on the same cleavage plane, making it possible to more reliably divide the substrate into individual pieces by cleavage. Effect of the Invention

[0012] As described above, according to the present invention, it is possible to satisfactorily separate a β-type gallium oxide substrate having a (001) plane as its principal surface. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram for explaining a method for dividing a β-type gallium oxide substrate according to a first embodiment of the present invention, where FIG. 1(a) is a plan view and FIG. 1(b) is a schematic cross-sectional view taken along line AA shown in FIG. 1(a). [Diagram 2] FIG. 2 is a schematic plan view for illustrating a method for dividing a β-type gallium oxide substrate according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic plan view for illustrating a method for dividing a β-type gallium oxide substrate according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a yz cross section of an individual element 20. As shown in FIG. [Diagram 5] FIG. 5 is a schematic diagram for explaining a method for dividing a β-type gallium oxide substrate according to a second embodiment of the present invention, where FIG. 5(a) is a plan view and FIG. 5(b) is a schematic cross-sectional view taken along line AA shown in FIG. 5(a). [Figure 6] FIG. 6 is a schematic perspective view showing an example in which an element formation surface 11 of a β-type gallium oxide substrate is offset with respect to the (001) plane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] 1 to 3 are schematic diagrams illustrating a method for dividing a β-type gallium oxide substrate according to a first embodiment of the present invention, in which Fig. 1(a), Fig. 2 and Fig. 3 are plan views, and Fig. 1(b) is a schematic cross-sectional view taken along line AA shown in Fig. 1(a).

[0016] First, as shown in FIG. 1, a β-type gallium oxide (Ga2O3) substrate 10 is prepared, on which a plurality of elements 20 are formed on an element formation surface 11, which is the main surface. Although not particularly limited, an example of the elements 20 is a Schottky barrier diode. A Schottky barrier diode using a β-type gallium oxide substrate is an element in which a current flows in the thickness direction of the substrate, and the side on which a drift layer and an anode electrode in Schottky contact therewith are formed is the element formation surface. Gallium oxide has a very large band gap of 4.8 to 4.9 eV and a large dielectric breakdown field of about 8 MV / cm, so that a Schottky barrier diode using gallium oxide is very promising as a switching element for a power device.

[0017] The element formation surface 11 and the rear surface 12 located on the opposite side form a (001) surface (c-surface). In FIG. 1, the (001) surface forms an xy plane, and a plurality of elements 20 are formed in a matrix in the xy direction. A plurality of division grooves 13 extending in the x direction are formed on the rear surface 12 of such a β-type gallium oxide substrate 10 so as to pass between the elements 20 adjacent in the y direction. The x direction is the extension direction of the (100) surface (a-surface) which is the cleavage surface. Etching is preferably used as a method for forming the division grooves 13. If the division grooves 13 are formed by etching, the β-type gallium oxide substrate 10 does not crack or chip during the formation of the division grooves 13. If the thickness of the β-type gallium oxide substrate 10 is about 250 μm, the depth of the division grooves 13 may be about 25 μm. The division grooves 13 are not formed partially, but are formed over the entire width of the β-type gallium oxide substrate 10 in the x direction.

[0018] 2, the β-type gallium oxide substrate 10 is cut along dicing lines 14 extending in the y direction, thereby processing the β-type gallium oxide substrate 10 into a rectangular shape. In other words, the cutting direction is perpendicular to the extension direction of the division grooves 13. The cutting positions are between the elements 20 adjacent in the x direction. As a result, each of the β-type gallium oxide substrates 10 cut into a rectangular shape has a plurality of elements 20 arranged in the y direction, and a division groove 13 is provided on the back surface 12 between the elements 20 adjacent in the y direction.

[0019] 3, the rectangular β-type gallium oxide substrate 10 is cleaved along the division grooves 13 to separate the elements 20. Fig. 4 is a yz cross section of the separated elements 20, and the cleavage plane 15 cleaved along the division grooves 13 has angles of about 76° (76.3° to be precise) and about 104° (103.7° to be precise) with respect to the element formation surface 11 and the back surface 12.

[0020] In this way, according to the method for dividing a β-type gallium oxide substrate according to the present embodiment, since a plurality of division grooves 13 are formed along the extension direction of the (100) plane, which is the cleavage plane, it is possible to obtain a substantially flat cleavage plane 15 by cleaving along the division grooves 13 without causing flaky peeling. In addition, unlike the case of simply dicing the β-type gallium oxide substrate 10 into a matrix shape, chipping does not occur, and the cutting allowance associated with dicing can be reduced, so that the number of chips obtained increases. Moreover, since the division grooves 13 are formed on the back surface 12 opposite to the element formation surface 11, processing of the element formation surface 11 is not required. However, in the present invention, it is not essential to form the division grooves 13 on the back surface 12, and the division grooves 13 may be formed on the element formation surface 11 side.

[0021] Fig. 5 is a schematic diagram for explaining a method for dividing a β-type gallium oxide substrate according to a second embodiment of the present invention, in which Fig. 5(a) is a plan view and Fig. 5(b) is a schematic cross-sectional view taken along line AA shown in Fig. 5(a).

[0022] The second embodiment is different from the first embodiment in that a dividing groove 16 is further formed on the element forming surface 11. The dividing groove 16 extends parallel to the dividing groove 13. However, the dividing grooves 13 and 16 do not overlap in the thickness direction (z direction) and are offset in the y direction by a distance D. The distance D is T×tanθ (θ=13.7°) when the thickness of the β-type gallium oxide substrate 10 is T. Here, the straight line L connecting the dividing groove 13 and the dividing groove 16 has angles of about 76° and about 104° with respect to the element forming surface 11 and the back surface 12. That is, the dividing grooves 13 and 16 are located on the same cleavage plane.

[0023] As a result, if the β-type gallium oxide substrate 10 is cut into strips and then cleaved along the division grooves 13, 16, it becomes possible to more reliably separate the substrates by cleavage.

[0024] The drift layer on which the elements are formed is a thin film formed by epitaxially growing gallium oxide on the top surface of a β-type gallium oxide substrate using reactive sputtering, PLD, MBE, MOCVD, HVPE, or other methods. When epitaxially growing a thin film on the top surface of a β-type gallium oxide substrate using HVPE, it is common to grow it on the (001) plane. However, in the case of a β-type gallium oxide substrate with a (001) surface, there may be an offset angle of about ±1° with respect to the x-axis or y-axis as a range of manufacturing variation. Furthermore, in consideration of the ease of epitaxial growth and deposition properties, it may be grown on a β-type gallium oxide substrate with an offset angle of about several degrees.

[0025] In such a case, as shown in FIG. 6, if the offset angle of the (001) plane with respect to the y-axis is θ2, then the distance D is T×tan(θ+θ2).

[0026] Although a preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention. [Explanation of symbols]

[0027] 10 β-type gallium oxide substrate 11 Element formation surface 12 Back side 13,16 split groove 14 Dicing Line 15 Cleavage plane 20 elements

Claims

1. forming a plurality of first division grooves along the extending direction of a (100) plane of a β-type gallium oxide substrate having a (001) plane as a main surface; A step of processing the β-type gallium oxide substrate into rectangular shapes by cutting in a direction perpendicular to the extension direction of the first division grooves; and dividing the rectangular β-type gallium oxide substrate into individual pieces by cleaving the rectangular β-type gallium oxide substrate along the first division grooves.

2. 2. The method for dividing a β-type gallium oxide substrate according to claim 1, wherein the first division grooves are formed by etching.

3. 3. The method for dividing a β-type gallium oxide substrate according to claim 1, wherein the first division grooves are formed on a back surface located opposite to the element formation surface.

4. forming a plurality of second division grooves on the element formation surface along an extension direction of the (100) plane; 4. The method for dividing a β-type gallium oxide substrate according to claim 3, wherein a straight line connecting the first division groove and the second division groove has an angle of about 76° with respect to the element formation surface.

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