KR-102961427-B1 - Composite substrate and method for manufacturing a composite substrate

Abstract

A composite substrate capable of contributing to the high performance of a SAW filter is provided. A composite substrate according to an embodiment of the present invention comprises a support substrate having an upper surface and a lower surface facing each other, a piezoelectric layer disposed on the upper surface side of the support substrate, and an intermediate layer disposed between the support substrate and the piezoelectric layer, wherein a low-crystallinity region is formed at the end of the upper surface side of the support substrate, the crystallinity is lower than that of the region located on the lower surface side.

Inventors

• 야마데라 다카히로
• 호리 유지

Assignees

• 엔지케이 가부시키가이샤

Dates

Publication Date

20260507

Application Date

20230414

Priority Date

20220627

Claims (7)

1. In a composite substrate, A support substrate having upper and lower surfaces facing each other, and A piezoelectric layer disposed on the upper surface side of the above-mentioned support substrate, and It includes an intermediate layer disposed between the support substrate and the piezoelectric layer, and At the upper end of the support substrate, a low-crystallinity region with lower crystallinity than the region located on the lower side is formed. The above intermediate layer includes a first oxide layer, a silicon film, and a second oxide layer in this order from the support substrate side, and A composite substrate having a thickness of 3 μm or less in the low-crystallinity region.
2. In paragraph 1, A composite substrate having a thickness of 30 nm or more in the low-crystallinity region.
3. delete
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5. In a method for manufacturing a composite substrate for manufacturing the composite substrate described in claim 1, A step of forming a damaged area at the upper end of a support substrate having upper and lower surfaces facing each other, and, A method for manufacturing a composite substrate, comprising the step of bonding a piezoelectric substrate to the upper surface side of the support substrate through an intermediate layer in this order.
6. In paragraph 5, A method for manufacturing a composite substrate, wherein the damaged area is formed by blasting abrasive particles onto the upper surface of the support substrate.
7. In paragraph 5 or 6, A method for manufacturing a composite substrate, wherein the above intermediate layer comprises a silicon film formed by physical vapor deposition.

Description

Composite substrate and method for manufacturing a composite substrate The present invention relates to a composite substrate and a method for manufacturing a composite substrate. In information and communication devices, filters utilizing elastic surface waves (SAW filters) are used to extract electrical signals of arbitrary frequencies. Recently, in the field of information and communication devices, the volume of communication has increased rapidly, and there is a demand for high performance of SAW filters. For example, Non-Patent Literature 1 discloses a SAW filter using a substrate comprising a piezoelectric element, a silicon oxide film, and a silicon substrate. FIG. 1 is a schematic cross-sectional view showing the schematic configuration of a composite substrate according to one embodiment of the present invention. FIG. 2a is a drawing showing an example of a manufacturing process of a composite substrate according to one embodiment. Figure 2b is a drawing that follows Figure 2a. Figure 2c is a drawing that follows Figure 2b. Figure 2d is a drawing that follows Figure 2c. Figure 2e is a drawing that follows Figure 2d. Figure 3 is a cross-sectional view of the composite substrate of Example 1. Figure 4a is an explanatory diagram of the pattern of the coplanar waveguide used to evaluate high-frequency characteristics. Figure 4b is a drawing showing an enlarged view of the part enclosed by the dashed line in Figure 4a. Figure 5 is a graph showing the evaluation results. Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, in order to make the explanation clearer, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the embodiments; however, this is merely an example and does not limit the interpretation of the present invention. A. Composite substrate FIG. 1 is a schematic cross-sectional view showing the schematic configuration of a composite substrate according to one embodiment of the present invention. The composite substrate (100) has a support substrate (10), an intermediate layer (20), and a piezoelectric layer (30) in this order. Specifically, a piezoelectric layer (30) is disposed on the upper surface (10a) side of a support substrate (10) having an upper surface (10a) and a lower surface (10b) facing each other, and an intermediate layer (20) is disposed between the piezoelectric layer (30) and the support substrate (10). A low-crystallinity region (12) is formed at the end of the upper surface (10a) of the support substrate (10). In the low-crystallinity region (12), the crystallinity is lower compared to the region located on the lower surface (10b) of the support substrate (10). The crystallinity of the support substrate (10) can be confirmed, for example, by observation using a transmission electron microscope (TEM). By using such a support substrate, a high-performance elastic surface wave device can be obtained. The low-crystallinity region (12) may be formed partially when viewed from the plane of the support substrate (10), but it is preferable that it be formed over the entire plane of the support substrate (10). The intermediate layer (20) preferably includes a silicon film, for example, from the perspective of obtaining a high-performance elastic surface wave device, and in the illustrated example, the intermediate layer (20) has a multilayer structure including a first oxide layer (22), a silicon film (24), and a second oxide layer (26) from the side of the support substrate (10). Although not illustrated, the composite substrate (100) may have any additional layers. The type, function, number, combination, arrangement, etc. of such layers can be appropriately set according to the purpose. The composite substrate (100) can be manufactured in any suitable shape. In one embodiment, it can be manufactured in the form of a so-called wafer. The size of the composite substrate (100) can be appropriately set according to the purpose. The diameter of the wafer is, for example, 100 mm to 200 mm. A-1. Support substrate The above-mentioned support substrate is typically composed of silicon. The type of silicon constituting the support substrate is not particularly limited, but it is preferably single-crystal silicon. In addition, the silicon constituting the support substrate is preferably high-resistance silicon (e.g., having a volume resistivity of 1000 Ω·cm or more). The silicon constituting the support substrate may be doped with dopants such as phosphorus and boron. It is preferable that the coefficient of thermal expansion of the material constituting the support substrate be smaller than the coefficient of thermal expansion of the material constituting the piezoelectric layer. With such a support substrate, changes in the shape and size of the piezoelectric layer when the temperature changes can be suppressed, thereby su