The present invention relates to a method of dividing a gallium oxide substrate and, more particularly, to a method of dividing a β-type gallium oxide substrate.
The methods described in Patent Documents 1 and 2 are known as methods of dividing a compound semiconductor. The method disclosed in Patent Document 1 includes forming a scratch having a length of 150 μm to 200 μm on the main surface of a substrate using a scriber, then processing the substrate into strips by dicing, and subsequently cleaving the strip-shaped substrates along the scratches for singulation. The method disclosed in Patent Document 2 includes forming cut grooves and scribe lines on both sides of a substrate and cleaving the substrate along the cut grooves and scribe lines for singulation.
However, since the (100) plane of a β-type gallium oxide substrate is highly cleaved, the method described in Patent Document 1 has the problem that flaky delamination occurs on a cleavage surface in the areas where no scratches are formed. In addition, in the β-type gallium oxide substrate having the (001) plane as the main surface, the (100) plane, which is a cleavage surface, is not perpendicular to the main surface but has a predetermined inclination, so that the method described in Patent Document 2 cannot cleave the β-type gallium oxide substrate correctly.
A method of simply dicing the β-type gallium oxide substrate into a matrix may also be considered; however, as described above, the (100) plane, which is the cleavage surface, is not perpendicular to the main surface, so that when dicing is performed along the extending direction of the cleavage surface, chipping occurs due to partial cleavage.
It is therefore an object of the present invention to provide a method of satisfactorily dividing a β-type gallium oxide substrate having a (001) plane as a main surface.
A method of dividing a β-type gallium oxide substrate according to the present invention includes; a step of forming a plurality of first dividing grooves along the extending direction of the (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 strips by cutting the β-type gallium oxide substrate in a direction perpendicular to the extending direction of the first dividing grooves; and a step of cleaving the strip-shaped β-type gallium oxide substrates along the first dividing grooves for singulation.
According to the present invention, since the plurality of first dividing grooves are thus formed along the cleavage planes, the substrate can be divided satisfactorily without causing flaky peeling on the cleavage surfaces by cleaving the substrate along the first dividing grooves.
In the present invention, the first dividing grooves may be formed by etching. This prevents the substrate from being cracked or chipped at the time of forming the first dividing grooves.
In the present invention, the first dividing grooves may be formed on the back surface located on the side opposite to an element forming surface. This eliminates the need to process the element forming surface.
Further, the method for dividing a β-type gallium oxide substrate according to the present invention may further include a step of forming a plurality of second dividing grooves in the element forming surface along the extending direction of the (100) plane, and a straight line connecting the first and second dividing grooves may have an angle of about 76° with respect to the element forming surface. Thus, since the first and second dividing grooves are positioned on the same cleavage surface, singulation by cleavage can be performed more reliably.
As described above, according to the present invention, it is possible to satisfactorily divide a β-type gallium oxide substrate having a (001) plane as a main surface.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As illustrated in
The element forming surface 11 and a back surface 12 located on the opposite side of the element forming surface 11 constitute a (001) plane (c-plane). In
Then, as illustrated in
Then, as illustrated in
As described above, according to the method of dividing a β-type gallium oxide substrate according to the present embodiment, the plurality of dividing grooves 13 are formed along the extending direction of the (100) plane, which is the cleavage surface, so that cleavage along the makes a dividing grooves 13 it possible to obtain substantially flat cleavage surface 15 without causing flaky peeling or the like. In addition, unlike the simple matrix dicing of the β-type gallium oxide substrate 10, chipping does not occur, and the cutting margin associated with dicing can be reduced, so that the number of chips that can be obtained increases. Moreover, the dividing grooves 13 are formed on the back surface 12 opposite to the element forming surface 11, so that the element forming surface 11 need not be processed. However, in the present invention, forming the dividing grooves 13 on the back surface 12 is not essential, and the dividing grooves 13 may be formed on the element forming surface 11.
The second embodiment differs from the first embodiment in that dividing grooves 16 are additionally formed in the element forming surface 11. The dividing grooves 16 extend parallel to the dividing grooves 13. However, the dividing grooves 13 and 16 do not overlap in the thickness direction (z-direction) and are offset by a distance D in the y-direction. The distance D is found by T×tan θ (θ=13.7°), where T is the thickness of the β-type gallium oxide substrate 10. Here, a straight line L connecting the dividing grooves 13 and 16 has angles of about 76° and about 104° with respect to the element forming surface 11 and the back surface 12, respectively. That is, the dividing grooves 13 and 16 are positioned on the same cleavage surface.
Thus, when the β-type gallium oxide substrate 10 is cut into strips and then cleaved along the dividing grooves 13 and 16, singulation by cleavage can be performed more reliably.
A drift layer in which an element is formed is a thin film obtained by epitaxially growing gallium oxide on the upper surface of a β-type gallium oxide substrate using reactive sputtering, PLD, MBE, MOCVD, HVPE, or the like. When a thin film is epitaxially grown on the upper surface of a β-type gallium oxide substrate using the HVPE method, it will generally be grown on the (001) plane. However, in the case of a β-type gallium oxide substrate whose surface is the (001) plane, there may be an offset angle of about +1° with respect to the x- and y-axes due to manufacturing variations. Furthermore, in consideration of ease of epitaxial growth and deposition properties, the thin film may be grown on a β-type gallium oxide substrate having an offset angle of several degrees.
In such a case, as illustrated in
While the preferred embodiment of the present disclosure has been described, the present disclosure is not limited to the above embodiment, and various modifications may be made within the scope of the present disclosure, and all such modifications are included in the present disclosure.
Number | Date | Country | Kind |
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2021-050286 | Mar 2021 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2022/007590 | 2/24/2022 | WO |