POI substrate, surface acoustic wave filter and preparation method thereof

Abstract

The invention discloses a POI substrate, a surface acoustic wave filter and a preparation method thereof, and belongs to the technical field of semiconductor preparation. The POI substrate sequentially comprises a supporting layer, a polycrystalline silicon layer, a first SiO2 layer, a second SiO2 layer and a functional layer from bottom to top, wherein the first SiO2 layer and the second SiO2 layer are in homogeneous bonding connection. The polycrystalline silicon layer prepared by the method is good in size uniformity and compactness, and can effectively inhibit the electrical loss of the substrate; the second SiO2 layer is prepared on the functional layer after ion implantation, on one hand, the second SiO2 layer can be bonded with the first SiO2 layer of the supporting layer, homogeneous bonding of SiO2-SiO2 is achieved, and the bonding strength of bonding is improved, and on the other hand, pre-stripping of the functional layer can be achieved, the subsequent annealing and stripping time is shortened, the production period is shortened, and the production efficiency is improved.

Description

Technical Field

[0001] The present application relates to a POI substrate, a surface acoustic wave filter and a preparation method thereof, and belongs to the technical field of semiconductor preparation. Background Art

[0002] With the rapid development of the fifth generation (5G) wireless system and the substantial increase in data usage, strict requirements are placed on high-frequency and broadband RF devices. In order to achieve rapid data transmission and chip integration, surface acoustic wave filters mainly show the trend of "high frequency, high power, and miniaturization".

[0003] The development of 5G communication technology has put forward higher requirements on the frequency and bandwidth of RF front-end resonators. The frequency of surface acoustic wave (SAW) resonators is limited by the accuracy of photolithography and it is difficult to meet high-frequency application scenarios above 3.5Ghz. With the increase in frequency bands supported by wireless communication equipment, the frequency bands used by wireless communication equipment are becoming more and more dense. In order to improve the quality of communication, reduce interference between frequency bands, and improve the quality of communication, higher requirements are bound to be placed on the performance and size of SAW filters. Therefore, in recent years, more and more SAW filters are using POI substrates.

[0004] The POI substrate includes a functional layer film. In the prior art, lithium niobate (LN) crystals and lithium tantalate (LT) crystals are mostly used to prepare the functional layer film. However, the LN / LT film prepared by the traditional method has technical difficulties such as difficult orientation control, excessively high growth temperature, and stoichiometric ratio segregation caused by lithium (Li) volatilization. As a result, the LN / LT film has poor preferential orientation, high defect density, and is easy to grow into a polycrystalline film, and its performance is far lower than that of the LN / LT single crystal block. Traditionally, mechanical thinning is usually used to reduce the film thickness when preparing LN / LT films. Due to the unevenness of the wafer thickness, this will damage the film surface and the film thickness can only be reduced to about 10 microns, which is not suitable for preparing films below the submicron level.

[0005] In the prior art, the POI substrate has different materials for the substrate layer and the functional layer, and the chemical properties of the surface dangling bonds are quite different, resulting in low interface strength of the bonded body formed by bonding. On the other hand, the difference in thermal expansion coefficients between the substrate layer and the functional layer leads to the introduction of large thermal stress, which is greater than the bonding strength, and is prone to problems such as debonding and cracking, affecting the quality of the POI substrate. In addition, in the prior art, the subsequent annealing and peeling step takes a lot of time, which prolongs the production cycle and reduces production efficiency.

[0006] Therefore, it is necessary to provide a POI substrate and a preparation method thereof, which can achieve stronger bonding strength and shorter annealing and peeling time, and improve the yield and production efficiency of the POI substrate. Summary of the invention

[0007] In order to solve the above problems, a POI substrate, a surface acoustic wave filter and a preparation method thereof are provided. The polycrystalline silicon layer prepared in the present application has good size uniformity and good density, and can effectively suppress the electrical loss of the substrate; a second SiO2 is prepared on the functional layer after ion implantation. 2 layer, on the one hand, can be connected with the first SiO 2 Layer bonding to achieve SiO 2 -SiO 2 Homogeneous bonding increases the bonding strength of the bonding. On the other hand, it can achieve pre-stripping of the functional layer, reduce the time of subsequent annealing and stripping, shorten the production cycle, and improve production efficiency.

[0008] According to one aspect of the present application, a POI substrate is provided, which comprises, from bottom to top, a support layer, a polysilicon layer, a first SiO 2 Layer, second SiO 2 layer and functional layer, the first SiO 2 Layer and second SiO 2 Layer homogeneous bonding connection.

[0009] Specifically, in the present application, the polysilicon layer can effectively suppress the electrical loss of the substrate. 2 The second SiO layer can effectively suppress the leakage of acoustic waves, and the second SiO layer can be prepared on the functional layer after ion implantation. 2 layer, on the one hand, can be connected with the first SiO 2 Layer bonding to achieve SiO 2 -SiO 2 Homogeneous bonding increases the bonding strength of the bonding. On the other hand, it can achieve pre-stripping of the functional layer, reduce the time of subsequent annealing and stripping, shorten the production cycle, and improve production efficiency.

[0010] Optionally, the thickness of the support layer is 300-1000nm; the thickness of the polysilicon layer is 300-1000nm; 2 The thickness of the layer is 300-1000nm; the second SiO 2 The thickness of the layer is 300-1000 nm; the thickness of the functional layer is 300-1000 nm.

[0011] Specifically, the present application provides a support layer, a polysilicon layer, a first SiO 2 Layer, second SiO 2 The thickness of the layers and the functional layers are specifically limited to obtain a POI substrate with stable performance and high bonding strength.

[0012] Optionally, the support layer material is silicon, silicon carbide, gallium nitride, diamond, gallium arsenide or sapphire; the functional layer material is lithium niobate, lithium tetraborate, lanthanum gallium silicate or lithium tantalate.

[0013] According to another aspect of the present application, a method for preparing the above-mentioned POI substrate is also provided, comprising the following steps:

[0014] (1) CVD deposition of polysilicon: placing the support layer in a LPCVD furnace tube, growing a polysilicon layer in a silane atmosphere, and polishing the polysilicon layer;

[0015] (2) PEALD deposition of the first SiO 2 Layer: The support layer with polycrystalline silicon film is placed in the space type PEALD to deposit the first SiO 2 layer, and then placed in CVD for annealing, and the first SiO 2 Polishing of the layer;

[0016] (3) Ion implantation: Place the functional layer in an ion implanter and perform ion implantation;

[0017] (4) PEALD deposition of the second SiO 2 Layer: Place the ion-implanted functional layer in a space-type PEALD to deposit the second SiO 2 layer, and the second SiO 2 Polishing of the layer;

[0018] (5) Wafer bonding: placing the material obtained in step (2) and the material obtained in step (4) in a wafer bonding machine for bonding;

[0019] (6) Annealing and polishing: Annealing and polishing are performed after bonding to obtain a POI substrate.

[0020] Specifically, the present invention first performs ion implantation on the functional layer, and then uses PEALD to deposit a second SiO 2 During the deposition process, the ions in the functional layer form bubbles, which pre-strip the functional layer, reduce the time for subsequent annealing and stripping, and shorten the production cycle.

[0021] Specifically, in step (2) and step (4), the first SiO 2 Layer and second SiO 2 The roughness of the layer after polishing is less than 0.5 nm.

[0022] Optionally, in step (1), the deposition temperature is 580-650° C., the deposition time is 30-120 min, the silane atmosphere flow rate is 200-500 sccm, and the chamber pressure is 20-100 Pa.

[0023] Specifically, the present application specifically defines the process parameters for CVD deposition of polysilicon, so that the obtained polysilicon layer has good size uniformity and film density, and can effectively suppress substrate electrical losses.

[0024] Optionally, in step (2) and step (4), the deposition temperature is 60-100° C., the plasma power is 100-3000 W, the chamber pressure is 20-200 Pa, the silane flow rate is 100-3000 sccm, and the H 2 The flow rate of O is 100-9000sccm; and / or the annealing temperature in step (2) is 400-800°C, and the annealing time is 2-10h.

[0025] Specifically, the present application is directed to depositing a first SiO 2 Layer and second SiO 2 The process parameters of the first SiO layer are specifically defined, and the number of cycles can be controlled to control the 2 Layer and second SiO 2 The thickness of the layer.

[0026] Specifically, step (2) also includes an annealing step, and the annealing temperature and time are limited to increase the SiO 2 The crystallinity of the film is improved, which enhances the bonding strength between the films.

[0027] Optionally, the energy of the ion implantation in step (3) is 120-200 KeV, the beam current of the ion implantation is 0.2-2 mA, and the dose of the ion implantation is 1.0*E 16 -5.0*E 16 .

[0028] Specifically, the present application limits the parameters of ion implantation. The process parameters of ion implantation also determine the thickness of the functional layer. If the ion implantation energy is too high, the degree of substrate damage will increase. If the ion implantation energy is too low, the ion implantation damage layer will be formed within a smaller depth range. The thickness of the functional layer finally peeled off will be lower than the expected value.

[0029] Optionally, in step (5), the power of the plasma is 20-200 W; and / or in step (6), the annealing temperature is 100-300° C., and the annealing time is 10-30 h.

[0030] Specifically, the deposition temperature in step (4) is 60-100°C, and the annealing temperature in step (6) is 100-300°C. Therefore, in step (4), the second SiO 2 During the process of layer deposition, the functional layer can be pre-stripped, which reduces the time of subsequent annealing and stripping and shortens the production cycle.

[0031] According to another aspect of the present application, a method for preparing a surface acoustic wave filter is provided, comprising the following steps:

[0032] Prepare a POI substrate according to the above preparation method;

[0033] A filter structure is prepared on the POI substrate.

[0034] According to another aspect of the present application, a surface acoustic wave filter is provided, comprising a filtering structure and the above-mentioned POI substrate, wherein the filtering structure is arranged on the POI substrate.

[0035] The beneficial effects of this application include but are not limited to:

[0036] 1. According to a POI substrate of the present application, the polysilicon layer prepared in the present application has good size uniformity and good density, and can effectively suppress the electrical loss of the substrate; a second SiO2 is prepared on the functional layer after ion implantation. 2 layer, on the one hand, can be connected with the first SiO 2 Layer bonding to achieve SiO 2 -SiO 2 Homogeneous bonding increases the bonding strength of the bonding. On the other hand, it can achieve pre-stripping of the functional layer, reduce the time of subsequent annealing and stripping, shorten the production cycle, and improve production efficiency.

[0037] 2. According to a method for preparing a POI substrate of the present application, a first SiO 2 Layer and second SiO 2 The deposition thickness of the layer is controllable, the film forming property and uniformity are good, the density is good, and it can be mass-produced; after the functional layer is ion implanted, the second SiO 2 layer, the functional layer can be pre-stripped to reduce the time of subsequent stripping. 2 Layer and second SiO 2 Homogeneous bonding of layers effectively improves bonding strength.

[0038] 3. According to a method for preparing a POI substrate of the present application, this method provides a new solution and scheme for the development of higher performance and integrated SAW devices, which can meet the urgent demand for a new generation of piezoelectric acoustic devices under the development trend of integration and miniaturization of the RF front end, and has broad market application prospects.

[0039] 4. According to a method for preparing a surface acoustic wave filter of the present application, the above-mentioned POI substrate is used to obtain a surface acoustic wave filter with temperature stability and high power handling. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0041] Figure 1 The present invention is a schematic diagram of a process for preparing a POI substrate according to an embodiment of the present application.

[0042] Figure 2 This is a schematic diagram of a POI substrate structure involved in Example 1 of the present application.

[0043] List of parts and reference numerals:

[0044] 1. Support layer; 2. Polysilicon layer; 3. First SiO 2 4. Second SiO 2 Layer; 5. Functional layer. DETAILED DESCRIPTION

[0045] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0046] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels.

[0047] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0048] Example 1

[0049] A method for preparing a POI substrate:

[0050] (1) CVD deposition of polysilicon: a 300 nm thick silicon carbide support layer was placed in an LPCVD furnace tube, and a polysilicon layer was grown in a silane atmosphere at a deposition temperature of 580°C, a deposition time of 30 min, a silane atmosphere flow rate of 200 sccm, a chamber pressure of 20 Pa, and the polysilicon layer was polished to a thickness of 300 nm;

[0051] (2) PEALD deposition of the first SiO 2 Layer: The support layer with polycrystalline silicon film is placed in the space type PEALD to deposit the first SiO 2 layer, the deposition temperature is 60℃, the plasma power is 100W, the chamber pressure is 20Pa, the silane flow rate is 100sccm, and the H 2 O flow rate is 100sccm, and then placed in CVD for annealing, the annealing temperature is 400℃, the annealing time is 2h, and the first SiO 2 The layer was polished to a thickness of 300 nm;

[0052] (3) Ion implantation: The lithium niobate functional layer is placed in an ion implanter for ion implantation. The energy of the ion implantation is 120 KeV, the beam current of the ion implantation is 0.2 mA, and the dose of the ion implantation is 1.0*E 16 ;

[0053] (4) PEALD deposition of the second SiO 2 Layer: Place the ion-implanted functional layer in a space-type PEALD to deposit the second SiO 2 layer, the deposition temperature is 60℃, the plasma power is 100W, the chamber pressure is 20Pa, the silane flow rate is 100sccm, and the H 2 O flow rate is 100 sccm, and the second SiO 2 The layer was polished to a thickness of 300 nm;

[0054] (5) Wafer bonding: placing the material obtained in step (2) and the material obtained in step (4) in a wafer bonding machine for bonding, with the plasma power being 20 W;

[0055] (6) Annealing and polishing: After bonding, annealing and polishing are performed at a temperature of 100° C. for 10 h to obtain a POI substrate in which the thickness of the functional layer is 300 nm.

[0056] Example 2

[0057] A method for preparing a POI substrate:

[0058] (1) CVD deposition of polysilicon: a diamond support layer with a thickness of 1000 nm was placed in an LPCVD furnace tube, and a polysilicon layer was grown in a silane atmosphere at a deposition temperature of 650°C, a deposition time of 120 min, a silane atmosphere flow rate of 500 sccm, a chamber pressure of 100 Pa, and the polysilicon layer was polished to a thickness of 1000 nm;

[0059] (2) PEALD deposition of the first SiO 2 Layer: The support layer with polycrystalline silicon film is placed in the space type PEALD to deposit the first SiO 2 layer, the deposition temperature is 100℃, the plasma power is 3000W, the chamber pressure is 200Pa, the silane flow rate is 3000sccm, and the H 2 O flow rate is 9000sccm, and then placed in CVD for annealing, the annealing temperature is 800℃, the annealing time is 10h, and the first SiO 2 The layer was polished to a thickness of 1000 nm;

[0060] (3) Ion implantation: The lithium tantalate functional layer is placed in an ion implanter for ion implantation. The energy of the ion implantation is 200 KeV, the beam current of the ion implantation is 2 mA, and the dose of the ion implantation is 5.0*E 16 ;

[0061] (4) PEALD deposition of the second SiO 2 Layer: Place the ion-implanted functional layer in a space-type PEALD to deposit the second SiO 2 layer, the deposition temperature is 100℃, the plasma power is 3000W, the chamber pressure is 200Pa, the silane flow rate is 3000sccm, and the H 2 O flow rate is 9000sccm, and the second SiO 2 The layer was polished to a thickness of 1000 nm;

[0062] (5) Wafer bonding: placing the material obtained in step (2) and the material obtained in step (4) in a wafer bonding machine for bonding, with the plasma power being 200 W;

[0063] (6) Annealing and polishing: After bonding, annealing and polishing are performed at a temperature of 300° C. for 30 h to obtain a POI substrate in which the thickness of the functional layer is 1000 nm.

[0064] Example 3

[0065] A method for preparing a POI substrate:

[0066] (1) CVD deposition of polysilicon: A 600 nm thick gallium arsenide support layer was placed in an LPCVD furnace tube, and a polysilicon layer was grown in a silane atmosphere at a deposition temperature of 630°C, a deposition time of 90 min, a silane atmosphere flow rate of 400 sccm, a chamber pressure of 50 Pa, and the polysilicon layer was polished to a thickness of 400 nm;

[0067] (2) PEALD deposition of the first SiO 2 Layer: The support layer with polycrystalline silicon film is placed in the space type PEALD to deposit the first SiO 2 layer, the deposition temperature is 80℃, the plasma power is 500W, the chamber pressure is 100Pa, the silane flow rate is 1000sccm, and the H 2 O flow rate is 5000sccm, and then placed in CVD for annealing, the annealing temperature is 600℃, the annealing time is 5h, and the first SiO 2 The layer was polished to a thickness of 500 nm;

[0068] (3) Ion implantation: Place the lithium tetraborate functional layer in an ion implanter for ion implantation. The energy of ion implantation is 150 KeV, the beam current of ion implantation is 1 mA, and the dose of ion implantation is 3.0*E 16 ;

[0069] (4) PEALD deposition of the second SiO 2 layer: Place the functional layer after ion implantation in a spatial PEALD to deposit the second SiO 2 layer. The deposition temperature is 80 °C, the Plasma power is 500 W, the chamber pressure is 100 Pa, the flow rate of silane is 1000 sccm, and the flow rate of H 2 O is 5000 sccm. Then polish the second SiO 2 layer to a thickness of 500 nm;

[0070] (5) Wafer bonding: Place the materials obtained in step (2) and the materials obtained in step (4) in a wafer bonder for bonding. The power of Plasma is 100 W;

[0071] (6) Annealing and polishing: After bonding, perform annealing and polishing. The annealing temperature is 200 °C and the annealing time is 20 h to obtain a POI substrate, where the thickness of the functional layer is 400 nm.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 3 is that it does not include step (4) PEALD deposition of the second SiO 2 layer, and the rest are the same.

[0074] Comparative Example 2

[0075] The difference between Comparative Example 2 and Example 3 is that it first performs step (4) PEALD deposition of the second SiO 2 layer and then performs step (3) ion implantation, and the rest are the same.

[0076] Comparative Example 3

[0077] The difference between Comparative Example 3 and Example 3 is that it does not include depositing the polysilicon layer in step (1), and the rest are the same.

[0078] Experimental Example 1

[0079] Test the bonding strength of the POI substrates obtained in the above Examples 1-3 and Comparative Examples 1-3. The test method is the crack propagation method for characterizing the surface energy of the bonding interface; measure the yield rate of the POI substrates obtained in Examples 1-3 and Comparative Examples 1-3. The test results are shown in Table 1.

[0080] Table 1 Test Results of Composite Piezoelectric Substrates

[0081] Group <![CDATA[Bond energy (J / m 2 )]]> Yield rate (%) Example 1 1.25 92 Example 2 1.34 93 Example 3 1.56 95 Comparative Example 1 0.80 88 Comparative Example 2 0.75 83 Comparative Example 3 0.68 82

[0082] As shown in Table 1, in Examples 1 to 3, the bonding energy and the yield rate in Examples 1 to 3 are at a relatively high level, and Example 3 is the best example. 2 layer, cannot be separated from the first SiO 2 The layers are homogeneously bonded, so the bonding energy is significantly reduced. In Comparative Example 2, the second SiO 2 The second SiO layer is then ion implanted. 2 The atomic structure of silicon oxide in the first SiO layer is destroyed, so that the bonding energy and the yield rate are affected; in Comparative Example 3, the polysilicon layer is not included, so that the substrate layer and the first SiO 2 The bonding strength of the layers is poor, which in turn affects the overall bonding energy and yield.

[0083] like Figure 1 As shown, the present invention deposits a polysilicon layer by CVD, deposits a first SiO 2 layer, ion implantation, PEALD deposition of the second SiO 2 The POI substrate is obtained by performing the following steps: layer, wafer bonding, annealing and polishing. The structure of the POI substrate is as follows: Figure 2 As shown, the POI substrate has a strong bonding strength.

[0084] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A POI substrate, characterized in that: From bottom to top, it includes a supporting layer, a polysilicon layer, a first SiO2 layer, a second SiO2 layer and a functional layer, wherein the first SiO2 layer is homogeneously bonded to the second SiO2 layer.

2. The POI substrate according to claim 1, characterized in that: The thickness of the support layer is 300-1000nm; the thickness of the polysilicon layer is 300-1000nm; the thickness of the first SiO2 layer is 300-1000nm; the thickness of the second SiO2 layer is 300-1000nm; and the thickness of the functional layer is 300-1000nm.

3. The POI substrate according to claim 1, characterized in that: The support layer material is silicon, silicon carbide, gallium nitride, diamond, gallium arsenide or sapphire; the functional layer material is lithium niobate, lithium tetraborate, lanthanum gallium silicate or lithium tantalate.

4. A method for preparing a POI substrate according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) CVD deposition of polysilicon: placing the support layer in a LPCVD furnace tube, growing a polysilicon layer in a silane atmosphere, and polishing the polysilicon layer; (2) PEALD deposition of the first SiO2 layer: placing the support layer on which the polycrystalline silicon film is deposited in a space-type PEALD process to deposit the first SiO2 layer, then placing the support layer in a CVD process for annealing, and polishing the first SiO2 layer; (3) Ion implantation: Place the functional layer in an ion implanter and perform ion implantation; (4) PEALD deposition of a second SiO2 layer: The functional layer after ion implantation is placed in a spatial PEALD process to deposit a second SiO2 layer, and the second SiO2 layer is polished; (5) Wafer bonding: placing the material obtained in step (2) and the material obtained in step (4) in a wafer bonding machine for bonding; (6) Annealing and polishing: Annealing and polishing are performed after bonding to obtain a POI substrate.

5. The method for preparing a POI substrate according to claim 4, characterized in that: In step (1), the deposition temperature is 580-650° C., the deposition time is 30-120 min, the silane atmosphere flow rate is 200-500 sccm, and the chamber pressure is 20-100 Pa.

6. The method for preparing a POI substrate according to claim 4, characterized in that: In step (2) and step (4), the deposition temperature is 60-100°C, the plasma power is 100-3000W, the chamber pressure is 20-200Pa, the silane flow rate is 100-3000sccm, and the H2O flow rate is 100-9000sccm; and / or the annealing temperature in step (2) is 400-800°C, and the annealing time is 2-10h.

7. The method for preparing a POI substrate according to claim 4, characterized in that: The energy of ion implantation in step (3) is 120-200 KeV, the beam current of ion implantation is 0.2-2 mA, and the dose of ion implantation is 1.0*E 16 -5.0*E 16 .

8. The method for preparing a POI substrate according to claim 4, characterized in that: In step (5), the power of the plasma is 20-200 W; and / or in step (6), the annealing temperature is 100-300° C., and the annealing time is 10-30 h.

9. A method for preparing a surface acoustic wave filter, characterized in that: The following steps are involved: Prepare a POI substrate according to the preparation method according to any one of claims 4 to 8; A filter structure is prepared on the POI substrate.

10. A surface acoustic wave filter, characterized in that: The invention comprises a filter structure and the POI substrate according to any one of claims 1 to 3, wherein the filter structure is arranged on the POI substrate.

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