Compound semiconductor film resonant cavity structure

Abstract

The utility model discloses a compound semiconductor film resonant cavity structure, which comprises a germanium wafer substrate, a plurality of film resonant cavities distributed in an array are arranged on the top surface of the germanium wafer substrate, and the film resonant cavities are formed on the top surface of the germanium wafer substrate through a photoetching process. An aluminum oxide reflective coating layer is arranged in each thin film resonant cavity close to the middle, sapphire layer high feet with the height of 60 micrometers and the width of 500 micrometers are arranged on the left side and the right side of each aluminum oxide reflective coating layer through the photoetching technology respectively, and the sapphire layer high feet and the aluminum oxide reflective coating layers are of an integrated structure and selectively grow through the MOCVD technology. According to the structure, the integration requirement is met through the miniaturized design and array distribution of the thin film resonant cavity, the MOCVD integrated technology reduces the assembly error, the interface layering problem of traditional epoxy resin pasting is avoided, unification of miniaturization, high sensitivity and high reliability is achieved, and the problem that the sound pressure response sensitivity is insufficient is solved.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic acoustic pressure technology, specifically a compound semiconductor thin film resonant cavity structure. Background Technology

[0002] In the field of fiber optic acoustic pressure technology, traditional acoustic pressure sensing structures suffer from insufficient acoustic pressure response sensitivity due to their use of silicon substrates combined with polymer thin films.

[0003] Existing resonant cavities exhibit low signal-to-noise ratios in response to weak sound pressure signals. Furthermore, the low Young's modulus of the materials makes it difficult to effectively excite resonance with sound pressure energy, resulting in low signal conversion efficiency. The connection method of attaching the sensitive film with epoxy resin is prone to interface delamination during temperature fluctuations, leading to resonant frequency drift. The thin film fabrication process is difficult to control material uniformity, causing fluctuations in the reflection spectrum. In addition, some structures increase the substrate thickness to enhance stability, which in turn hinders the transfer of sound pressure energy, creating a contradiction between stability and sensitivity. Consequently, existing resonant cavity structures are unable to meet the measurement accuracy requirements of scenarios such as medical ultrasound detection and high-precision underwater monitoring in terms of sound pressure response sensitivity, signal conversion accuracy, and structural reliability. Utility Model Content

[0004] To overcome the shortcomings of the prior art, the purpose of this utility model is to provide a compound semiconductor thin film resonant cavity structure.

[0005] The technical solution adopted in this utility model is as follows: a compound semiconductor thin film resonant cavity structure, including a germanium wafer substrate, wherein multiple arrayed thin film resonant cavities are formed on the top surface of the germanium wafer substrate by photolithography. Each thin film resonant cavity has an aluminum oxide reflective coating layer near the center. The left and right sides of the aluminum oxide reflective coating layer are respectively provided with sapphire layer feet with a height of 60μm and a width of 500μm using photolithography. The sapphire layer feet and the aluminum oxide reflective coating layer are an integral structure and are selectively grown by MOCVD technology. The sapphire layer feet on the left are used to input optical signals to the aluminum oxide reflective coating layer, and the sapphire layer feet on the right are used to transmit the reflected and modulated optical signals to an external photodetector.

[0006] In a preferred embodiment, the germanium wafer substrate is 4-8 inches in size and 100-200 μm thick, and the thin film resonant cavities are arranged in a square array, with each cavity measuring 3×3 mm and the spacing between adjacent cavities being 200-500 μm.

[0007] In a preferred embodiment, the alumina reflective coating layer has a size of 1.5×1.5mm and a thickness of 15μm. It is directly bonded to the germanium wafer substrate by magnetron sputtering or electron beam evaporation. The surface roughness is <1nm and the reflectivity is >95%. The magnetron sputtering or electron beam evaporation process parameters are controlled with a thickness error of <±0.5μm and a uniformity deviation of <±1%.

[0008] In a preferred embodiment, the sidewall of the thin-film resonant cavity is prepared by a dry etching process, the sidewall verticality is >85°, and the sidewall roughness is <5nm. The alumina reflective coating layer is deposited at the bottom of the thin-film resonant cavity by a coating process and is bonded to the germanium wafer substrate.

[0009] In a preferred embodiment, the sapphire layer feet on the left and right sides are electrically connected to the aluminum oxide reflective coating layer, and the electrical connection is an ohmic contact connection with a contact resistance of <5Ω.

[0010] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are:

[0011] In this invention, due to the adoption of the above-mentioned scheme, the structure resists temperature fluctuations through a germanium wafer substrate, avoiding resonant frequency drift and solving the problem of insufficient stability of traditional silicon-based substrates; the 15μm thick alumina reflective coating layer, combined with dry etching of the cavity sidewalls, significantly improves the response to weak sound pressure and reduces energy loss, overcoming the defects of difficulty in sound pressure excitation resonance and transmission obstruction; the sapphire layer is grown integrally with the coating layer, resulting in low optical loss and solving the problems of low coupling efficiency and high signal loss in traditional methods; moreover, the coating layer has high uniformity, avoiding reflection spectrum fluctuations and ensuring signal stability; the 3×3mm miniaturized design and array distribution meet integration requirements; the MOCVD integrated process reduces errors, avoids interface delamination, and achieves a balance between miniaturization, high sensitivity, and high reliability, meeting the requirements of high-precision measurement. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0013] Figure 2 This is a side sectional view of the present invention.

[0014] The markings in the diagram are: 1. Germanium wafer substrate; 2. Thin film chip; 3. Alumina reflective coating layer; 4. Pin. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0016] A compound semiconductor thin film resonant cavity structure, reference Figures 1-2 As shown, the structure includes a germanium wafer substrate 1, on the top surface of which multiple arrayed thin-film resonant cavities 2 are formed. The thin-film resonant cavities 2 are formed on the top surface of the germanium wafer substrate 1 by photolithography. The germanium wafer substrate 1 is 4-8 inches in size and 100-200 μm thick. The thin-film resonant cavities 2 are arranged in a square array, with each cavity measuring 3×3 mm and the spacing between adjacent cavities being 200-500 μm. The 4-8 inch germanium wafer substrate 1, with its excellent thermal stability and mechanical properties, provides a stable support foundation for the entire structure, reducing the interference of environmental factors such as temperature fluctuations on sound pressure detection. The precisely sized, square array of thin-film resonant cavities 2, formed by photolithography, meets the integration requirements of fiber optic sound pressure sensors. Furthermore, the array arrangement facilitates mass production and subsequent distributed signal measurement, improving production efficiency and application adaptability.

[0017] Furthermore, an aluminum oxide reflective coating layer 3 is disposed near the center of the interior of each thin-film resonant cavity 2. The aluminum oxide reflective coating layer 3 has a size of 1.5×1.5mm and a thickness of 15μm. It is directly bonded to the germanium wafer substrate 1 by magnetron sputtering or electron beam evaporation. The surface roughness is <1nm, the reflectivity is >95%, and the control precision of the magnetron sputtering or electron beam evaporation process parameters is: thickness error <±0.5μm, uniformity deviation <±1%. The sidewalls of the thin-film resonant cavity 2 are prepared by dry etching. The sidewall perpendicularity is >85°, and the sidewall roughness is <5nm. The aluminum oxide reflective coating layer 3 is disposed at the bottom of the thin-film resonant cavity 2 by a coating process and is bonded to the germanium wafer substrate 1. The alumina reflective coating layer 3, prepared by a set magnetron sputtering or electron beam evaporation process, has a precise thickness (15 μm), low surface roughness (<1 nm), high reflectivity (>95%), and controllable process parameters (thickness error <±0.5 μm, uniformity deviation <±1%), ensuring high reflection efficiency and providing a high-quality optical foundation for the conversion of sound pressure signals into optical signals. The thin film resonant cavity sidewalls prepared by a set dry etching process (verticality >85°, roughness <5 nm), combined with the tight bonding of the coating layer and the germanium wafer substrate 1, can form a stable resonant cavity space. The 15 μm thick coating layer can vibrate stably under the action of sound pressure, improving the sensitivity of sound pressure signal conversion and structural reliability.

[0018] Furthermore, sapphire layer feet 4, each 60 μm high and 500 μm wide, are formed on the left and right sides of the alumina reflective coating layer 3 using photolithography. These sapphire layer feet 4 are electrically connected to the alumina reflective coating layer 3 via ohmic contact with a contact resistance of <5Ω. The sapphire layer feet 4 and the alumina reflective coating layer 3 are integrally formed using MOCVD selective growth. The left sapphire layer foot 4 is used to input optical signals to the alumina reflective coating layer 3, while the right sapphire layer foot 4 is used to transmit the reflected and modulated optical signals. The signal is transmitted to an external photodetector. The sapphire layer with high feet 4 and the alumina reflective coating layer 3 are integrally formed by selective growth using MOCVD technology, which ensures good mechanical strength and low optical loss. The ohmic contact connection enables low-loss signal transmission. The 60μm high and 500μm wide structure, precisely prepared by photolithography, can accurately control the input and output paths of optical signals, improving signal transmission efficiency and accuracy. Furthermore, MOCVD technology ensures material uniformity and interface quality, enhancing the reliability and consistency of the overall structure.

[0019] The implementation principle of this utility model of a compound semiconductor thin film resonant cavity structure is as follows: When external sound pressure is applied to the thin film resonant cavity structure, the sound pressure energy is first transferred to the thin film resonant cavity 2 on the germanium wafer substrate 1. The germanium wafer substrate 1 can resist structural deformation caused by temperature fluctuations and avoid resonance frequency drift. When the sound pressure energy enters the thin film resonant cavity 2, it will drive the internal alumina reflective coating layer 3 to vibrate. The 15μm thick alumina reflective coating layer 3 is prepared by high-precision process, with a flat surface and forming a stable resonant cavity. It can not only produce a significant response to weak sound pressure, but also reduce energy loss through the dry etching of the sidewall of the thin film resonant cavity 2, breaking the contradiction between "stability and sensitivity" and avoiding the defects of traditional structures where sound pressure energy is difficult to excite resonance or is blocked from transmission.

[0020] When the optical signal is transmitted through the high-leg 4 of the left sapphire layer, the optical loss is extremely low because the high-leg 4 of the sapphire layer and the alumina reflective coating layer 3 are grown integrally using MOCVD technology. The precisely positioned structure, coupled with ohmic contact connection, solves the problems of low coupling efficiency and high signal loss of traditional piezoelectric ceramics. When the alumina reflective coating layer 3 vibrates, its high reflectivity characteristics will precisely modulate the phase or intensity of the optical signal. Moreover, due to the high uniformity of the alumina reflective coating layer 3, the problem of spectral fluctuation of traditional thin film reflection is avoided, ensuring stable and accurate signal. The modulated optical signal is output with low loss through the high-leg 4 of the right sapphire layer and is finally converted into an electrical signal by the photodetector. At the same time, the structure meets the integration requirements through the miniaturized design and array distribution of the 3×3mm thin film resonant cavity 2. The MOCVD integrated process reduces assembly errors and avoids the interface delamination problem of traditional epoxy resin bonding. It achieves a unity of miniaturization, high sensitivity and high reliability, meeting the high-precision measurement requirements of medical ultrasound, underwater monitoring and other scenarios.

[0021] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A compound semiconductor thin-film resonant cavity structure, comprising a germanium wafer substrate (1), characterized in that: The top surface of the germanium wafer substrate (1) is provided with multiple arrayed thin film resonant cavities (2). The thin film resonant cavities (2) are formed on the top surface of the germanium wafer substrate (1) by photolithography. Each thin film resonant cavity (2) is provided with an aluminum oxide reflective coating layer (3) near the center. The left and right sides of the aluminum oxide reflective coating layer (3) are respectively provided with sapphire layer feet (4) with a height of 60μm and a width of 500μm by photolithography. The sapphire layer feet (4) and the aluminum oxide reflective coating layer (3) are an integral structure and are selectively grown by MOCVD technology. The sapphire layer feet (4) on the left side are used to input the optical signal to the aluminum oxide reflective coating layer (3), and the sapphire layer feet (4) on the right side are used to transmit the reflected and modulated optical signal to an external photodetector.

2. The compound semiconductor thin film resonant cavity structure as described in claim 1, characterized in that: The germanium wafer substrate (1) is 4-8 inches in size and 100-200 μm thick. The thin film resonant cavity (2) is arranged in a square array with a single cavity size of 3×3 mm and a spacing of 200-500 μm between adjacent cavities.

3. The compound semiconductor thin film resonant cavity structure as described in claim 1, characterized in that: The alumina reflective coating layer (3) has a size of 1.5×1.5mm and a thickness of 15μm. It is directly bonded to the germanium wafer substrate (1) by magnetron sputtering or electron beam evaporation. The surface roughness is <1nm and the reflectivity is >95%. The control accuracy of the magnetron sputtering or electron beam evaporation process parameters is: thickness error <±0.5μm and uniformity deviation <±1%.

4. The compound semiconductor thin film resonant cavity structure as described in claim 1, characterized in that: The sidewall of the thin film resonant cavity (2) is prepared by dry etching process, the sidewall verticality is >85° and the sidewall roughness is <5nm. The aluminum oxide reflective coating layer (3) is set at the bottom of the thin film resonant cavity (2) by coating process and is attached to the germanium wafer substrate (1).

5. The compound semiconductor thin film resonant cavity structure as described in claim 1, characterized in that: The sapphire layer feet (4) on the left and right sides are electrically connected to the aluminum oxide reflective coating layer (3), and the electrical connection is an ohmic contact connection with a contact resistance of <5Ω.

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