Composite piezoelectric substrate, elastic wave device, and module

Abstract

The utility model discloses a kind of composite piezoelectric substrate, elastic wave device and module, wherein the composite piezoelectric substrate includes: support layer, film thickness difference absorption layer and piezoelectric layer are sequentially laminated;Wherein, the difference between the compressive stress of the film thickness difference absorption layer and the compressive stress of the piezoelectric layer is within ±10% of the compressive stress of the piezoelectric layer.The composite piezoelectric substrate provided in the utility model embodiment can improve the uniformity of piezoelectric layer thickness, so as to improve the yield and characteristics of elastic wave device.

Description

Technical Field

[0001] This utility model relates to the field of electronic device technology, and in particular to a composite piezoelectric substrate, elastic wave device and module. Background Technology

[0002] In some elastic wave devices, such as SAW (surface acoustic wave) devices, a composite piezoelectric substrate is typically formed mainly by a support layer and a piezoelectric layer. In the manufacturing methods of such composite piezoelectric substrates, processes such as ion implantation and smart-cut are costly. Therefore, a common approach is to directly bond the support layer and the piezoelectric layer, followed by grinding and polishing the piezoelectric layer. However, the surface roughness of the support layer and the inherent inhomogeneity of the grinding equipment result in poor uniformity of the piezoelectric layer thickness after grinding, thus affecting the characteristics and yield of the elastic wave device. Therefore, maximizing the uniformity of the piezoelectric layer thickness is a crucial issue. Utility Model Content

[0003] To overcome at least some of the defects and deficiencies of the prior art, this utility model proposes a composite piezoelectric substrate to improve the thickness uniformity of the piezoelectric layer.

[0004] On one hand, the present invention provides a composite piezoelectric substrate comprising a support layer, a film thickness difference absorption layer and a piezoelectric layer stacked sequentially; wherein the difference between the compressive stress of the film thickness difference absorption layer and the compressive stress of the piezoelectric layer is within ±10% of the compressive stress of the piezoelectric layer.

[0005] On the other hand, an elastic wave device provided by this utility model includes a composite piezoelectric substrate as described above, and an IDT electrode, wherein the IDT electrode is located on the main surface of the piezoelectric layer facing away from the thickness difference absorption layer.

[0006] In another aspect, this utility model embodiment provides a module including the aforementioned elastic wave device.

[0007] The above embodiments of this utility model have at least one or more of the following beneficial effects:

[0008] In this embodiment, the difference between the compressive stress of the film thickness difference absorption layer and the compressive stress of the piezoelectric layer in the composite piezoelectric substrate is within ±10% of the compressive stress of the piezoelectric layer. This makes the composite piezoelectric substrate unaffected by the non-uniformity of the support layer thickness, thereby obtaining a piezoelectric layer with uniform thickness. This, in turn, improves the characteristics and yield of the elastic wave device made from the composite piezoelectric substrate. Attached Figure Description

[0009] The specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0010] Figure 1 This is a schematic diagram of the structure of a composite piezoelectric substrate provided in one embodiment of the present invention.

[0011] Figure 2 A schematic diagram of the structure of a composite piezoelectric substrate provided in another embodiment of this utility model.

[0012] Figure 3 for Figure 1 The diagram shows a process flow diagram of one method for fabricating a composite piezoelectric substrate.

[0013] Figure 4 for Figure 1 The diagram shows another method for fabricating the composite piezoelectric substrate.

[0014] Figure 5 This is a schematic diagram of the structure of an elastic wave device provided in one embodiment of the present invention.

[0015] Figure 6 This is a schematic diagram of the structure of an elastic wave device provided in another embodiment of the present invention.

[0016] Figure 7 This is a schematic diagram of the module provided in one embodiment of the present invention.

[0017] Figure 8 This is a schematic diagram of the fabrication method of composite piezoelectric substrate in related technologies.

[0018] Figure 9 This is a schematic diagram of the structure of a composite piezoelectric substrate in related technologies.

[0019] [Explanation of Labels in the Attached Image]

[0020] 1000, Module; 100, Elastic Wave Device; 10, Composite Piezoelectric Substrate; 11, Support Layer; 11A, First Support Material Layer; 11B, Second Support Material Layer; 111, First Interface; 112, Second Interface; 12, Film Thickness Difference Absorption Layer; 12A, First Material Layer; 13, Piezoelectric Layer; 13A, Piezoelectric Material Layer; 14, Intermediate Layer; 21, IDT Electrode; 22, Electrode Pad; 30, Encapsulation Substrate; 41, First Sealing Structure; 42, Second Sealing Structure; 51, Bump; 52, First Conductive Part; 53, First External Terminal Electrode; 54, Second Conductive Part; 55, Second External Terminal Electrode; 60, Gap; 70, Cover; 400, Inductor; 500, Sealing Part; 600, Integrated Circuit Component; 700, Wiring Substrate; 701, External Connection Terminal. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0022] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] It should also be noted that the division of multiple embodiments in this utility model is only for the convenience of description and should not constitute a special limitation. Features in various embodiments can be combined and referenced in each other without contradiction.

[0025] [First Embodiment]

[0026] Figure 1 This utility model provides a composite piezoelectric substrate 10, which may include, for example, a support layer 11, a film thickness difference absorption layer 12, and a piezoelectric layer 13.

[0027] Specifically, the support layer 11, the thickness difference absorption layer 12, and the piezoelectric layer 13 are stacked sequentially from bottom to top. The difference between the compressive stress of the thickness difference absorption layer 12 and the compressive stress of the piezoelectric layer 13 is within ±10% of the compressive stress of the piezoelectric layer 13. The support layer 11 can be, for example, a support substrate layer, and can be made of materials such as single-crystal alumina, sapphire, silicon, aluminum nitride, quartz glass, spinel, etc. The thickness difference absorption layer 12 can be, for example, an adhesive layer, used to bond the support layer 11 and the piezoelectric layer 13 together. The material of the thickness difference absorption layer 12 can be, for example, epoxy resin, silicon dioxide, silicon, silicon nitride, aluminum nitride, polycrystalline silicon, etc. The piezoelectric layer 13 can be, for example, a piezoelectric substrate layer, and can be made of materials such as lithium tantalate, lithium niobate, quartz, etc.

[0028] In prior art, the manufacturing process of composite piezoelectric substrates can be, for example... Figure 8 As shown, sapphire, silicon, aluminum nitride, quartz glass, and other materials are first selected as the first support material layer 11A to form the first support layer. The formed first support layer may, for example, exhibit a thickness non-uniformity of 3 micrometers. Figure 8 As shown in the first step, to reduce the impact of this thickness non-uniformity, the first support material layer 11A needs to be ground and polished. The lower surface of the first support material layer 11A is ground to achieve a completely flat lower surface, thereby obtaining the second support material layer 11B. However, since the upper surface of the second support material layer 11B is relatively rough, it is impossible to deposit or bond on the upper surface. Therefore, the upper surface of the second support material layer 11B needs to be chemically mechanically polished. After polishing, the support layer 11 is obtained. Due to the characteristics of the polishing equipment, it is not possible to perform chemical mechanical polishing on the upper surface of the second support material layer 11B. Even after achieving complete homogenization, the first interface 111 of the support layer 11 will still exhibit a non-uniformity of, for example, 0.3 micrometers. This non-uniformity results in continuous protrusions and pits on the first interface 111, creating a wave-like surface. The 0.3-micrometer non-uniformity refers to a distance of 0.3 micrometers between the highest and lowest points on the first interface, i.e., between the highest point of a protrusion and the lowest point of a pit. This non-uniformity will also cause similar non-uniformity in the piezoelectric layer 13 bonded or deposited on the support layer 11. Figure 9 As shown, in Figure 9 In the diagram, T1' represents the thickness at the location of maximum thickness in piezoelectric layer 13, and T2' represents the thickness at the location of minimum thickness in piezoelectric layer 13. The difference between T1' and T2' is 0.3 micrometers. This 0.3-micrometer thickness non-uniformity can cause stress non-uniformity between the layers of the composite piezoelectric substrate, leading to unstable output charge of piezoelectric layer 13. This, in turn, affects the efficiency of sensing or energy conversion, thereby affecting the characteristics of the elastic wave device.

[0029] To mitigate this impact, specifically the surface non-uniformity caused by the 0.3 micrometer difference, this application employs a thickness difference absorbing layer 12 disposed between the support layer 11 and the piezoelectric layer 13 of the composite piezoelectric substrate 10. The compressive stress of the thickness difference absorbing layer 12 is set such that the difference between the compressive stress of the thickness difference absorbing layer 12 and the compressive stress of the piezoelectric layer 13 is within ±10% of the compressive stress of the piezoelectric layer 13. Subsequently, a piezoelectric layer 13 is disposed on the upper surface of the thickness difference absorbing layer 12. Therefore, the thickness difference absorbing layer 12 can partially offset the stress from the support layer 11 and the piezoelectric layer 13, ensuring that no strain difference occurs between the piezoelectric layer 13 and the thickness difference absorbing layer 12. Furthermore, by setting the relationship between the compressive stress difference between the two, the thickness variation on the upper surface of the bonded piezoelectric layer 13 is reduced, thereby improving the thickness uniformity of the upper surface of the piezoelectric layer 13 and making the piezoelectric layer thickness more uniform. This, in turn, improves the characteristics and yield of the elastic wave device fabricated from the composite piezoelectric substrate 10.

[0030] Specifically, such as Figure 3 As shown, it illustrates a process flow of a fabrication method for the composite piezoelectric substrate 10 of this invention:

[0031] Step S1: As mentioned above, since the second interface 112 of the support layer 11 needs to be flattened, the support layer 11 is obtained by grinding one side of the first support material layer 11A (i.e., the bottom surface of the first support material layer 11A). This achieves complete flatness of the second interface 112, while the first interface 111 of the support layer 11 will have a thickness non-uniformity of, for example, 3 micrometers. Figure 2 As shown, D1 is the distance between the highest and lowest points in the plane containing the upper surface of the support layer 11, and D1 is approximately 3 micrometers.

[0032] Step S2: A first material layer 12A is bonded to the first interface 111 of the support layer 11, and then the surface of the first material layer 12A facing away from the support layer 11 is subjected to chemical mechanical polishing to obtain a thickness difference absorption layer 12. After chemical mechanical polishing, a thickness non-uniformity of 0.3 micrometers will occur on the surface of the thickness difference absorption layer 12 facing away from the support layer 11 (the upper surface of the thickness difference absorption layer 12). Figure 2 As shown, D2 is the distance between the highest and lowest points in the plane containing the upper surface of the film thickness difference absorption layer 12, and D2 is 0.3 micrometers.

[0033] Step S3: Bond the piezoelectric material layer 13A to the surface of the film thickness difference absorption layer 12 facing away from the support layer 11;

[0034] Step S4: Perform chemical mechanical polishing on the surface of the piezoelectric material layer 13A facing away from the film thickness difference absorption layer 12 to obtain the piezoelectric layer 13; as Figure 2As shown, D3 represents the thickness difference of the piezoelectric layer 13, which is the distance between the highest and lowest points in the plane containing the upper surface of the piezoelectric layer 13. D3 is 0.1 micrometers. The difference in compressive stress between the first material layer and the piezoelectric material layer is within ±10% of the compressive stress of the piezoelectric material layer. Since the difference in compressive stress between the film thickness difference absorbing layer 12 and the piezoelectric layer 13 is within ±10% of the compressive stress of the piezoelectric layer 13, the film thickness difference absorbing layer 12 can offset part of the stress from the support layer 11 and the piezoelectric layer 13. This reduces the thickness difference on the upper surface of the film thickness difference absorbing layer 12 to less than 0.3 micrometers. Simultaneously, the piezoelectric layer 13 is bonded to the film thickness difference absorbing layer 12, making the thickness difference of the piezoelectric layer 13 less than 0.3 micrometers, specifically 0.1 micrometers. This further reduces the thickness non-uniformity generated from the support layer 11, resulting in a more uniform thickness of the piezoelectric layer 13.

[0035] The grinding conditions for the chemical mechanical grinding treatment in steps S2 and S4 are the same.

[0036] Of course, composite piezoelectric substrates can also be fabricated through other methods, such as... Figure 4 As shown, it illustrates another method for fabricating the composite piezoelectric substrate 10 of this invention:

[0037] Step S1: As mentioned above, since the second interface 112 of the support layer 11 needs to be flattened, the first support material layer 11A is ground to obtain the support layer 11, which can achieve complete flatness of the second interface 112. However, the first interface 111 of the support layer 11 will have a thickness non-uniformity of, for example, 3 micrometers. Figure 2 As shown, its thickness D1 is 3 micrometers.

[0038] Step S2: A first material layer 12A is deposited on the first interface 111 of the support layer 11, and then the surface of the first material layer 12A facing away from the support layer 11 is subjected to chemical mechanical polishing to obtain the thickness difference absorption layer 12. After chemical mechanical polishing, the surface of the thickness difference absorption layer 12 facing away from the support layer 11 (the upper surface of the thickness difference absorption layer 12) will have a thickness non-uniformity of 0.3 micrometers. Figure 2 As shown, D2 is the distance between the highest and lowest points in the plane containing the upper surface of the film thickness difference absorption layer 12, and D2 is 0.3 micrometers.

[0039] Step S3: Bond the piezoelectric material layer 13A to the surface of the film thickness difference absorption layer 12 facing away from the support layer 11;

[0040] Step S4: Perform chemical mechanical polishing on the surface of the piezoelectric material layer 13A facing away from the film thickness difference absorption layer 12 to obtain the piezoelectric layer 13; the difference in compressive stress between the first material layer and the piezoelectric material layer is within ±10% of the compressive stress of the piezoelectric material layer. The polishing conditions for the chemical mechanical polishing in steps S2 and S4 are the same.

[0041] Furthermore, such as Figures 1-2 As shown, the total thickness variation (TTV) of the piezoelectric layer 13 is less than 0.1 micrometers. Figure 2 As shown, in the piezoelectric layer 13, T1 represents the thickness at the location of the maximum thickness, and T2 represents the thickness at the location of the minimum thickness. The difference between T1 and T2 represents the total thickness variation of the piezoelectric layer, which is less than 0.1 micrometers. Therefore, since the total thickness variation (TTV) of the piezoelectric layer 13 is less than 0.1 micrometers, the 0.3 micrometer non-uniformity transmitted from the thickness difference absorption layer 12 can be offset by the total thickness variation of the piezoelectric layer 13, resulting in a thickness non-uniformity of less than 0.3 micrometers on the upper surface of the piezoelectric layer 13.

[0042] Furthermore, the thickness difference absorption layer 12 and the piezoelectric layer 13 are made of the same material. The materials of the thickness difference absorption layer 12 and the piezoelectric layer 13 may be, for example, one of silicon, silicon dioxide, silicon nitride, aluminum nitride, polycrystalline silicon, polyimide, and epoxy resin.

[0043] Furthermore, such as Figure 2 As shown, the composite piezoelectric substrate 10 further includes, for example, an intermediate layer 14 located between the film thickness difference absorption layer 12 and the piezoelectric layer 13, wherein the sound velocity of the intermediate layer 14 is lower than that of the piezoelectric layer 13. By limiting the sound velocity of the intermediate layer 14 to be lower than that of the piezoelectric layer 13, the resonant characteristics of the composite piezoelectric substrate 10 can be optimized, thereby matching the acoustic impedance between the two.

[0044] Furthermore, the thickness of the piezoelectric layer 13 ranges from 0.08 to 0.12 micrometers. The thickness of the piezoelectric layer 13 can be determined by... Figure 3 and Figure 4 The thickness of the composite piezoelectric substrate after grinding the bonding piezoelectric material layer 13A in step S4 is obtained by comparing the thickness of the composite piezoelectric substrate obtained after grinding the bonding first material layer 12A on the first interface 111 of the support layer 11 in step S2.

[0045] Furthermore, the thickness of the support layer 11 ranges from 100 to 200 micrometers. Since the surface of the first interface 111 of the support layer 11 is not flat, the thickness of the support layer 11 at its maximum thickness location will not exceed 200 micrometers, while the thickness of the support layer 11 at its minimum thickness location exceeds 100 micrometers.

[0046] Furthermore, such as Figures 1-2 As shown, the support layer 11 has a first interface 111 facing the film thickness difference absorption layer 12; the flatness of the first interface 111 is 1 micrometer. The flatness is the distance between the highest and lowest points of the first interface 111, such as... Figure 2 As shown above, the second interface of the support layer 11 needs to be flat. After grinding, the first interface 111 of the support layer 11 will become uneven, for example, it includes continuous protrusions and pits connected to each other, which can form a wavy surface, for example. The distance between the highest point and the lowest point of the wavy surface is the flatness.

[0047] Furthermore, the flatness of the interface between the thickness difference absorption layer 12 and the piezoelectric layer 13 is less than the flatness of the first interface 111. The flatness of the first interface 111 can be, for example, 1 micrometer, and the flatness of the interface between the thickness difference absorption layer 12 and the piezoelectric layer 13 can be, for example, 0.1 micrometer.

[0048] [Second Embodiment]

[0049] like Figure 5 As shown, this embodiment provides an elastic wave device 100, which may include, for example, a composite piezoelectric substrate 10, an IDT electrode 21, an electrode pad 22, a packaging substrate 30, a first sealing structure 41, a bump 51, a first conductive part 52, and a first external terminal electrode 53.

[0050] The composite piezoelectric substrate 10 may be, for example, the composite piezoelectric substrate 10 described in the first embodiment. The encapsulation substrate 30 may be, for example, a multilayer substrate made of resin. A plurality of first external terminal electrodes 53 are formed on the lower surface of the encapsulation substrate 30. The IDT electrode 21 is located on the main surface of the piezoelectric layer 13 facing away from the film thickness difference absorption layer 12. The electrode pads 22 are respectively located on the main surfaces of the composite piezoelectric substrate 10 and the encapsulation substrate 30. The electrode pads 22 are formed of copper or a copper-containing alloy. The IDT electrode 21 may be, for example, formed of aluminum and copper or an alloy of aluminum and copper.

[0051] The bump 51 is formed on the upper surface of the electrode pad 22 on the main surface of the packaging substrate 30. The material of the bump can be one or more of Au, Al, Pt and Ti.

[0052] The electrode pad 22 is electrically connected to the first external terminal electrode 53 through the first conductive part 52.

[0053] The first sealing structure 41 is formed such that it covers the composite piezoelectric substrate 10. A gap 60 may be formed between the encapsulation substrate 30 and the composite piezoelectric substrate 10.

[0054] The elastic wave device 100 made from the composite piezoelectric substrate 10 of this application can improve the characteristics and yield of the elastic wave device 100.

[0055] [Third Embodiment]

[0056] like Figure 6 As shown, this embodiment provides an elastic wave device 100, which may include, for example, a composite piezoelectric substrate 10, an IDT electrode 21, an electrode pad 22, a second sealing structure 42, a bump 51, a second conductive part 54, a second external terminal electrode 55, and a cover 70.

[0057] The composite piezoelectric substrate 10 may be, for example, the composite piezoelectric substrate 10 described in the first embodiment. The cover 70 may be disposed on the main surface of the composite piezoelectric substrate 10. The second sealing structure 42 may be formed at the edge between the composite piezoelectric substrate 10 and the cover 70.

[0058] A plurality of second external terminal electrodes 55 are formed on the lower surface of the cover 70, and the IDT electrode 21 is located on the main surface of the piezoelectric layer 13 facing away from the film thickness difference absorption layer 12. The electrode pad 22 is located on the main surface of the composite piezoelectric substrate 10, and the electrode pad 22 is formed of copper or a copper-containing alloy. The IDT electrode 21 may be formed, for example, of aluminum and copper or an alloy of aluminum and copper.

[0059] The electrode pad 22 is electrically connected to the second external terminal electrode 55 via the second conductive part 54.

[0060] A gap 60 may be formed between the cover 70 and the composite piezoelectric substrate 10.

[0061] The elastic wave device 100 made from the composite piezoelectric substrate 10 of this application can improve the characteristics and yield of the elastic wave device 100.

[0062] [Fourth Embodiment]

[0063] like Figure 7 As shown, this embodiment provides a module 1000, which includes, for example, an elastic wave device 100, an inductor 400, a sealing part 500, an integrated circuit component 600, and a wiring substrate 700.

[0064] The wiring substrate 700 has an elastic wave device 100 disposed on its main surface. The elastic wave device 100 may be the same as that described in the second or third embodiment above. The wiring substrate 700 includes a plurality of external connection terminals 701. The external connection terminals 701 can be mounted to the main printed circuit board of a predetermined mobile communication terminal.

[0065] An inductor 400 is provided on the main surface of the wiring substrate 700 to achieve impedance matching. The inductor 400 may be an integrated passive device (IPD). An integrated circuit component 600 is provided inside the wiring substrate 700. The module 1000 seals the integrated circuit component 600, including the elastic wave device 1, through a sealing portion 500.

[0066] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A composite piezoelectric substrate (10), characterized in that, It includes a support layer (11), a thickness difference absorption layer (12), and a piezoelectric layer (13) stacked in sequence; wherein the difference between the compressive stress of the thickness difference absorption layer (12) and the compressive stress of the piezoelectric layer (13) is within ±10% of the compressive stress of the piezoelectric layer (13).

2. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, The TTV of the piezoelectric layer (13) is less than 0.1 micrometers.

3. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, The thickness difference absorption layer (12) is made of the same material as the piezoelectric layer (13).

4. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, It also includes an intermediate layer (14) located between the film thickness difference absorption layer (12) and the piezoelectric layer (13), wherein the sound velocity of the intermediate layer (14) is lower than that of the piezoelectric layer (13).

5. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, The thickness of the piezoelectric layer (13) ranges from 0.08 to 0.12 micrometers.

6. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, The thickness of the support layer (11) ranges from 100 to 200 micrometers.

7. The composite piezoelectric substrate (10) as described in claim 1, characterized in that, The support layer (11) has a first interface (111) facing the film thickness difference absorption layer (12); the flatness of the first interface (111) is 1 micrometer.

8. The composite piezoelectric substrate (10) as described in claim 7, characterized in that, The flatness of the interface between the film thickness difference absorption layer (12) and the piezoelectric layer (13) is less than that of the first interface (111).

9. An elastic wave device (100), characterized in that, The composite piezoelectric substrate (10) as described in any one of claims 1 to 8 further includes an IDT electrode (21) located on the main surface of the piezoelectric layer (13) facing away from the thickness difference absorption layer (12).

10. A module (1000), characterized in that, It includes the composite piezoelectric substrate (10) as described in any one of claims 1 to 8 or the elastic wave device (100) as described in claim 9.

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