阅读说明：本技术 一种低应力声光器件及其制备方法 (Low-stress acousto-optic device and preparation method thereof ) 是由 曹家强 吴中超 王晓新 刘保见 吴畏 陈虹羽 于 2019-11-21 设计创作，主要内容包括：本发明涉及声光器件,具体涉及一种低应力声光器件及其制备方法,包括：压电晶片和声光晶体,声光晶体上表面从下往上依次镀制有Cr、Au金属膜层,压电晶片下表面从上往下依次镀制有Cr、Au金属膜层,声光晶体的Au膜层和压电晶片的Au膜层键合在一起形成Cr、Au、Cr三层金属膜键合层结构。本发明的低应力声光器件采用压电晶片先研磨后键合工艺代替传统的压电晶片先键合后研磨工艺,避免了Au-Au键合残余应力导致的压电晶片研磨开裂现象；本发明改进了Au膜层的制备工艺,Au膜层的应力明显降低,声光晶体和压电晶片键合后声光晶体没有开裂现象。(The invention relates to an acousto-optic device, in particular to a low-stress acousto-optic device and a preparation method thereof, wherein the method comprises the following steps: the piezoelectric chip comprises a piezoelectric chip and an acousto-optic crystal, wherein a Cr metal film layer and an Au metal film layer are sequentially plated on the upper surface of the acousto-optic crystal from bottom to top, a Cr metal film layer and an Au metal film layer are sequentially plated on the lower surface of the piezoelectric chip from top to bottom, and the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric chip are bonded together to form a Cr, Au and Cr three-layer metal film bonding layer structure. The low-stress acousto-optic device adopts the process of grinding the piezoelectric wafer firstly and then bonding the piezoelectric wafer to replace the traditional process of grinding the piezoelectric wafer firstly and then bonding the piezoelectric wafer, thereby avoiding the phenomenon of grinding and cracking of the piezoelectric wafer caused by Au-Au bonding residual stress; the invention improves the preparation process of the Au film layer, obviously reduces the stress of the Au film layer, and ensures that the acousto-optic crystal does not crack after being bonded with the piezoelectric wafer.)

1. A low stress acousto-optic device comprising: the piezoelectric crystal and the acousto-optic crystal are characterized in that Cr and Au metal film layers are sequentially plated on the upper surface of the acousto-optic crystal from bottom to top, Cr and Au metal film layers are sequentially plated on the lower surface of the piezoelectric crystal from top to bottom, and the Au film layers of the acousto-optic crystal and the Au film layers of the piezoelectric crystal are bonded together to form a Cr, Au and Cr three-layer metal film bonding layer structure.

2. The low stress acousto-optic device according to claim 1, wherein the thickness of the Cr layer of the acousto-optic crystal and the piezoelectric wafer is 10 to 30nm, and the thickness of the Au layer of the acousto-optic crystal and the piezoelectric wafer is 100 to 600 nm.

3. A low stress acousto-optic device according to claim 1 wherein the piezoelectric wafer is made of a material comprising: lithium niobate or/and lithium tantalate; the acousto-optic crystal adopts materials comprising: tellurium oxide or/and gallium phosphide.

4. A preparation method of a low-stress acousto-optic device is characterized by comprising the following steps:

s1, coating the photoresist on the lower surface of the gasket by adopting a spin-coating method, and then baking the gasket in an oven at 80-100 ℃ for 20-30 min;

s2, adhering the upper surface of the piezoelectric wafer to the photoresist on the lower surface of the gasket, then sealing the piezoelectric wafer in a vacuum sealing bag, and finally pressing the piezoelectric wafer in isostatic pressing equipment, wherein the working pressure of the pressing is 5-10 Mpa;

s3, putting the pressed piezoelectric wafer into a grinder for grinding and polishing;

s4, sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the acousto-optic crystal, and sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the piezoelectric wafer;

s5, fixing the acousto-optic crystal and the piezoelectric wafer in a film coating machine, and respectively coating a Cr film layer and an Au film layer on the surfaces of the acousto-optic crystal and the piezoelectric wafer in sequence by adopting a magnetron sputtering method;

s6, aligning, contacting, pressurizing and maintaining pressure of the acousto-optic crystal and the piezoelectric wafer through bonding equipment to complete bonding of the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric wafer;

and S7, soaking the bonded device in acetone for 4-6 hours, and taking out the device after the photoresist is completely dissolved in the acetone and the gasket on the piezoelectric wafer falls off and separates.

5. The method of claim 4, characterized by employingWhen the surfaces of the acousto-optic crystal and the piezoelectric wafer are respectively plated with Cr film layers by a magnetron sputtering method, the working gas is argon Ar, the sputtering pressure is 1-3 Pa, and the sputtering power density is 0.5-0.7W/cm²。

6. The method of claim 4, wherein the Au film is prepared by magnetron sputtering, the working gas is Ar, the sputtering pressure is 1-3 Pa, and the sputtering power density is 0.5-0.7W/cm²And after 4-6 min Au film layers are sputtered each time, the sputtering power supply is closed, and the Au film layers are plated after high-purity argon is introduced for 4-6 min.

7. The method of claim 4, wherein the bonding of the Au film layer of the completed acousto-optic crystal and the Au film layer of the piezoelectric wafer comprises: the cross sections of the Au film layer on the acousto-optic crystal and the Au film layer on the piezoelectric wafer are aligned, and bonding is completed by applying pressure through bonding equipment by utilizing the diffusion effect of interface atoms of the Au film layer and the Au film layer.

8. The method according to claim 4, wherein the bonding pressure is 10 to 20MPa, the bonding temperature is 60 to 120 ℃, and the dwell time is 30 to 60 min.

9. The method of claim 4, wherein the spacer is made of the same material as the piezoelectric wafer.

10. The method of claim 4, wherein the photoresist is coated on the pad to a thickness in the range of 2 to 5 μm.

Technical Field

The invention relates to an acousto-optic device, in particular to a low-stress acousto-optic device and a preparation method thereof.

Background

The acousto-optic device is a photoelectric device developed based on acousto-optic effect, and the manufacturing method of the acousto-optic device increasingly adopts Au-Au bonding technology along with the development of the acousto-optic device to the directions of high frequency, high power and the like.

As shown in fig. 1, the conventional Au-Au bonded acousto-optic device structure and the process flow for manufacturing the same include: firstly, respectively preparing an adhesion layer on the surfaces of an acousto-optic crystal and a piezoelectric wafer, wherein the adhesion layer is usually a metal film layer of magnetron sputtering chromium Cr, titanium Ti and the like, and then a layer of Au film layer is magnetron sputtering on the adhesion layer; then the acousto-optic crystal is contacted with the Au film layer of the piezoelectric wafer, and the bonding is completed by heating and pressurizing; and finally, placing the bonded device in a grinding machine, and grinding and polishing the piezoelectric wafer to the designed thickness. The manufacturing process of firstly bonding Au and then grinding the piezoelectric wafer mainly has the following problems:

(1) the prepared Au film has larger stress, and the acousto-optic crystal is easy to crack after being bonded with the piezoelectric wafer, thereby causing the scrapping of devices;

(2) the residual stress after bonding is released in the process of grinding and polishing the piezoelectric wafer, so that the piezoelectric wafer is cracked, and the device is scrapped.

Disclosure of Invention

In order to solve the problems of bonding cracking of the acousto-optic crystal and grinding cracking of the piezoelectric wafer, the invention adopts the process of grinding the piezoelectric wafer firstly and then bonding to replace the traditional process of grinding the piezoelectric wafer firstly, improves the traditional preparation process of the Au film layer and provides the low-stress acousto-optic device and the preparation method thereof.

A low stress acousto-optic device comprising: the piezoelectric chip comprises a piezoelectric chip and an acousto-optic crystal, wherein a Cr metal film layer and an Au metal film layer are sequentially plated on the upper surface of the acousto-optic crystal from bottom to top, a Cr metal film layer and an Au metal film layer are sequentially plated on the lower surface of the piezoelectric chip from top to bottom, and the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric chip are bonded together to form a Cr, Au and Cr three-layer metal film bonding layer structure.

Furthermore, the thickness of Cr film layers of the acousto-optic crystal and the piezoelectric wafer is 10-30 nm, and the thickness of Au film layers of the acousto-optic crystal and the piezoelectric wafer is 100-600 nm.

Further, the piezoelectric wafer is made of materials including: lithium niobate or/and lithium tantalate; the acousto-optic crystal adopts materials comprising: tellurium oxide or/and gallium phosphide.

A preparation method of a low-stress acousto-optic device comprises the following steps:

s1, coating the photoresist on the lower surface of the gasket by adopting a spin-coating method, and then baking the gasket in an oven at 80-100 ℃ for 20-30 min;

s2, adhering the upper surface of the piezoelectric wafer to the photoresist on the lower surface of the gasket, then sealing the piezoelectric wafer in a vacuum sealing bag, and finally pressing the piezoelectric wafer in isostatic pressing equipment, wherein the working pressure of the pressing is 5-10 Mpa;

s3, putting the pressed piezoelectric wafer into a grinder for grinding and polishing;

s4, sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the acousto-optic crystal, and sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the piezoelectric wafer;

s5, fixing the acousto-optic crystal and the piezoelectric wafer in a film coating machine, and respectively coating a Cr film layer and an Au film layer on the surfaces of the acousto-optic crystal and the piezoelectric wafer in sequence by adopting a magnetron sputtering method;

s6, aligning, contacting, pressurizing and maintaining pressure of the acousto-optic crystal and the piezoelectric wafer through bonding equipment to complete bonding of the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric wafer;

and S7, soaking the bonded device in acetone for 4-6 hours, and taking out the device after the photoresist is completely dissolved in the acetone and the gasket on the piezoelectric wafer falls off and separates.

The invention has the beneficial effects that:

(1) the invention improves the preparation process of the Au film layer, so that the stress of the Au film layer is obviously reduced, and the acousto-optic crystal does not crack after being bonded with the piezoelectric wafer;

(2) according to the invention, the piezoelectric wafer is prepared by grinding and then bonding, and because the piezoelectric wafer is ground to the designed thickness before bonding, the piezoelectric wafer does not need to be ground after bonding, so that grinding and cracking of the piezoelectric wafer caused by Au-Au bonding residual stress are avoided.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a schematic diagram of a conventional Au-Au bonded acousto-optic device process flow;

fig. 2 is a schematic view of a low stress acousto-optic device and a process flow for manufacturing the same according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly and completely apparent, the technical solutions in the embodiments of the present invention are described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

The invention relates to a low stress acousto-optic device, which comprises: the piezoelectric chip comprises a piezoelectric chip and an acousto-optic crystal, wherein a Cr metal film layer and an Au metal film layer are sequentially plated on the upper surface of the acousto-optic crystal from bottom to top, a Cr metal film layer and an Au metal film layer are sequentially plated on the lower surface of the piezoelectric chip from top to bottom, and the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric chip are bonded together to form a Cr, Au and Cr three-layer metal film bonding layer structure.

Furthermore, the thickness of Cr film layers of the acousto-optic crystal and the piezoelectric wafer is 10-30 nm, and the thickness of Au film layers of the acousto-optic crystal and the piezoelectric wafer is 100-600 nm.

Further, the piezoelectric wafer is made of materials including: lithium niobate or/and lithium tantalate.

Further, the acousto-optic crystal adopts materials including: tellurium oxide or/and gallium phosphide.

As shown in fig. 2, as a preferred embodiment, the method for manufacturing the low stress acousto-optic device can adopt the following implementation modes:

s1, coating photoresist on the lower surface of the gasket by adopting a spin-coating method, wherein the gasket, the piezoelectric wafer and the used materials are the same, the thickness range of the photoresist coated on the lower surface of the gasket is 2-5 mu m, and then placing the gasket and the piezoelectric wafer into an oven at 80-100 ℃ for baking for 20-30 min;

s2, adhering the upper surface of the piezoelectric wafer to the photoresist on the lower surface of the gasket, then sealing the piezoelectric wafer in a vacuum sealing bag, and finally pressing the piezoelectric wafer in isostatic pressing equipment, wherein the working pressure of the pressing is 5-10 Mpa;

s3, putting the pressed piezoelectric wafer in a grinder to grind and polish to a designed thickness, wherein the designed thickness is usually several micrometers to dozens of micrometers;

s4, sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the acousto-optic crystal, and sequentially adopting acetone, absolute ethyl alcohol and deionized water to clean the piezoelectric wafer;

s5, fixing the acousto-optic crystal and the piezoelectric wafer in a film coating machine, and respectively coating a Cr film layer and an Au film layer on the surfaces of the acousto-optic crystal and the piezoelectric wafer in sequence by adopting a magnetron sputtering method, wherein the coating thickness of the Cr film layer is 10-30 nm, and the coating thickness of the Au film layer is 100-600 nm;

s6, aligning, contacting, pressurizing and maintaining pressure of the acousto-optic crystal and the piezoelectric wafer through bonding equipment to complete bonding of the Au film layer of the acousto-optic crystal and the Au film layer of the piezoelectric wafer;

and S7, soaking the bonded device in acetone for 4-6 hours, and taking out the device after the photoresist is completely dissolved in the acetone and the gasket on the piezoelectric wafer falls off and separates.

Further, when the surfaces of the acousto-optic crystal and the piezoelectric wafer are respectively plated with Cr film layers by adopting a magnetron sputtering method, the working gas is argon Ar, the sputtering pressure is 1-3 Pa, and the sputtering power density is 0.5-0.7W/cm²。

Furthermore, in order to reduce the stress of the Au film layer and improve the traditional preparation process of the Au film layer, the invention comprises the following steps: the sputtering air pressure of the magnetron sputtering Au film layer is increased from the traditional 0.1-0.3 Pa to 1-3 Pa; the sputtering power density of the Au film is reduced by 1.6-1.8W/cm²Reduce the pressure to 0.5 to 0.7W/cm²(ii) a And (3) sputtering the Au film layer in sections, namely, closing a sputtering power supply after sputtering the 4-6 min Au film layer each time, introducing high-purity argon for 4-6 min, and then plating the Au film layer, wherein the Au film layer is circularly plated to the designed thickness of 100-600 nm according to the method.

Further, the bonding of the Au film layer of the completed acousto-optic crystal and the Au film layer of the piezoelectric wafer comprises: the cross sections of the Au film layer on the acousto-optic crystal and the Au film layer on the piezoelectric wafer are aligned, and bonding is completed by applying pressure through bonding equipment by utilizing the diffusion effect of interface atoms of the Au film layer and the Au film layer.

Furthermore, the bonding pressure is 10-20 MPa, the bonding temperature is 60-120 ℃, and the pressure maintaining time is 30-60 min.

The low-stress acousto-optic device adopts the process of grinding the piezoelectric wafer firstly and then bonding the piezoelectric wafer to replace the traditional process of grinding the piezoelectric wafer firstly and then bonding the piezoelectric wafer, thereby avoiding the phenomenon of grinding and cracking of the piezoelectric wafer caused by Au-Au bonding residual stress; the invention improves the preparation process of the Au film layer, obviously reduces the stress of the plated Au film layer by improving the sputtering air pressure of the magnetron sputtering Au film layer, reducing the sputtering power density of the Au film layer and adopting a sectional sputtering Au film layer mode, and has no cracking phenomenon of the acousto-optic crystal after the acousto-optic crystal is bonded with the piezoelectric wafer.

In the description of the present invention, it is to be understood that the terms "upper surface", "lower surface", "bottom-up", "top-down", "upper", "lower", and the like refer to orientations or positional relationships based on those shown in the drawings, which are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be considered as limiting.

The above-mentioned embodiments, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.