CN108955664B - Fully-decoupled annular micro gyroscope based on optical microcavity and processing method thereof - Google Patents

Abstract

The invention discloses a fully decoupled annular micro-gyroscope based on an optical micro-cavity and a processing method thereof. The micro-gyroscope includes a cap and a wafer from top to bottom, and the wafer includes an upper device layer and a lower substrate layer. , the device layer is provided with a number of electrodes, resonators, a first optical microcavity, a second optical microcavity, a first optical waveguide and a second optical waveguide, the electrodes are adjacent to the inner wall of the resonator to form a capacitor, the first optical waveguide and the second optical waveguide are symmetrically distributed on both sides of the resonator, the first optical microcavity and the second optical microcavity are respectively adjacent to the first optical waveguide and the second optical waveguide, and the first optical microcavity and the second optical microcavity are connected to the harmonic oscillator. The present invention adopts an optical detection scheme, and compared with the traditional micro-electromechanical gyroscope, the reliability and measurement accuracy of the gyroscope can reach a higher level.

Description

A fully decoupled annular microgyroscope based on optical microcavity and its processing method

technical field

The invention relates to a micro-optical electromechanical and inertial navigation device and process, in particular to a fully decoupled ring gyroscope based on an optical microcavity and a processing method thereof.

Background technique

MOEMS gyroscope is a new type of gyroscope developed on the basis of MEMS gyroscope. Based on MEMS processing technology, it combines optical detection components with higher sensitivity to realize angular velocity detection. This type of device combines the advantages of small size, light weight, low cost, easy integration, high measurement accuracy of micro-optical devices, and anti-electromagnetic interference capability of MEMS devices. It is a very good high-precision micro gyroscope.

The optical microcavity belongs to the Whispering Gallery Mode (WGM) optical microcavity. The microcavity is characterized in that the photons can be totally reflected at the boundary of the microcavity and have a high Q value. Light with the same resonant frequency of the cavity can be coupled into the cavity. Therefore, it can be regarded as an optical filter. When there is a disturbance in the external environment, the spectral line of the microcavity will change significantly, that is, the filter frequency band will change. This kind of change can calculate the magnitude of the external disturbance.

SUMMARY OF THE INVENTION

Purpose of the invention: In order to overcome the deficiencies of the prior art and realize the miniaturization of the high-precision gyroscope, the present invention provides a fully decoupled annular micro-gyroscope based on an optical micro-cavity and a processing technology thereof.

Technical solution: The present invention provides a fully decoupled annular micro-gyroscope based on an optical microcavity, which includes a cap and a wafer from top to bottom, and the wafer includes an upper device layer and a lower substrate layer. There are several electrodes, resonators, a first optical microcavity, a second optical microcavity, a first optical waveguide and a second optical waveguide. The electrodes are adjacent to the inner wall of the resonator to form a capacitor, the first optical waveguide and the second optical waveguide. The waveguides are symmetrically distributed on both sides of the resonator, the first optical microcavity and the second optical microcavity are respectively adjacent to the first optical waveguide and the second optical waveguide, and both the first optical microcavity and the second optical microcavity are adjacent to the resonator. connected.

Preferably, the resonator is in the shape of a disk, which sequentially includes an inner ring, an inner disk, a middle ring, a middle disk, an outer ring and an outer disk from the inside to the outside. The outer disk is provided with a number of decoupling beams. Adjacent to form a capacitor, and the outer disk is surrounded by an isolation structure.

Preferably, there are four electrodes, which are evenly arranged inside the inner ring of the resonator, and the electrodes and the inner ring of the resonator form a capacitor. sound waves.

Preferably, the optical microcavity is disc-shaped and located at the edge of the resonator, and the optical waveguide is a straight waveguide structure, tangent to the optical microcavity, for input and output of light.

Preferably, the cap is a silicon cap, located directly above the resonator, the cap is provided with a plurality of electrode through holes, which correspond to the electrodes one-to-one, and the electrodes are electrically connected to the metal leads through the electrode through holes to realize electrical signal input.

Preferably, the silicon cap is processed on a silicon wafer, the electrode through hole is a conical hole, and a bonding metal layer is deposited around the lower surface of the silicon cap to realize the bonding between the cap and the wafer.

Preferably, the resonator and the electrodes are processed on the device layer of a SOI wafer, and the optical waveguide and the optical microcavity are processed by LPCVD on the silicon oxide layer deposited on the surface of the device layer of the SOI wafer where the resonator is located.

A processing method of a fully decoupled annular micro-gyroscope based on an optical micro-cavity, comprising the following steps:

(1) Cleaning the wafer, drying, and depositing a light guide layer on the surface of the wafer device layer by low-pressure chemical vapor deposition for the processing of optical waveguides and optical microcavities;

(2) after cleaning and drying the wafer surface of step (1), a layer of adhesive is applied on the surface of the light guide layer, and then a layer of electron beam exposure glue is spin-coated and cured;

(3) the electron beam exposure adhesive layer obtained in step (2) is exposed by electron beam to define the pattern and position of the optical waveguide and the optical microcavity, and then develop and post-bake;

(4) On the basis of step (3), a dry etching process is used to process the light guide layer to obtain an optical waveguide and an optical microcavity, and then remove the residual electron beam exposure glue;

(5) after cleaning and drying the wafer processed in step (4), spray photoresist on the surface of the device layer and solidify, and then use the first mask to transfer the pattern of the electrode and the disc resonator to the photoresist layer;

(6) on the basis of step (5), utilize deep reactive ion etching to process to obtain electrode and resonator, then wet etching, remove part of the buried oxide layer below the disc resonator, then remove residual photoresist;

(7) Take another silicon wafer, clean and dry the surface, spin-coat photoresist on the lower surface, use the second mask to define the pattern of the metal bonding area by photolithography, and then deposit a layer of chromium in sequence For metal and gold layers, lift-off process is used to peel off the bonding area and remove residual photoresist;

(8) Spin-coat photoresist on the upper surface of the cap obtained in step (7), use a third mask to define the pattern of electrode holes by photolithography, and then wet etching to open electrodes on the cap holes, after which the residual photoresist is cleaned;

(9) Bonding the cap of step (8) and the structure obtained in step (5) through a gold-silicon bonding process to obtain a complete photoacoustic wave gyroscope structure.

Preferably, the material of the light guide layer deposited in the step (1) is silicon oxide, silicon nitride, indium phosphide or gallium arsenide.

Preferably, when the material of the light guide layer is silicon oxide, when the light guide layer is deposited in step (1), a low pressure chemical vapor deposition method is used or a silicon thermal oxidation process is used on the surface of the SOI wafer device layer.

Beneficial effects: compared with the prior art, the present invention measures the change of the sound wave by means of the optical microcavity, thereby realizing the measurement of the angular velocity. Due to the optical detection scheme, the reliability and measurement accuracy of the gyroscope can reach a higher level than the traditional MEMS gyroscope. The invention has the advantages of high measurement accuracy, no electromagnetic interference, full decoupling and the like.

Description of drawings

Fig. 1 is the split structure schematic diagram of the present invention;

Fig. 2 is the top view of the harmonic oscillator, optical microcavity and optical waveguide in Fig. 1;

Fig. 3 is the rear schematic view of the cap in Fig. 1;

FIG. 4 is a partial enlarged view of the optical microcavity and the optical waveguide in FIGS. 1 and 2;

Fig. 5 is the sectional view along AA plane in Fig. 1;

Figure 6 is a process flow diagram of the present invention.

In the figure: 1 is the SOI wafer for processing the resonator and electrodes, 2 is the silicon cap, 3 is the disc resonator, 4 is the optical microcavity, 5 is the optical waveguide, 21 is the electrode through hole on the silicon cap, 22 is the bonding metal layer, 31 is the electrode, 32 is the inner ring structure, 33 is the inner disk structure, 34 is the middle ring, 35 is the middle disk, 36 is the outer ring, 37 is the outer disk, 38 is the isolation, 39 is the decoupling beam, 40 (the raised portion in the dashed box in Figure 5) is the anchor point.

Detailed ways

In order to better understand the present invention, the content of the present invention is further clarified below with reference to the accompanying drawings and specific embodiments, but the content of the present invention is not limited to the following embodiments. It should be pointed out that for those skilled in the art, the position of each facility can be adjusted without departing from the principle of the present invention, and these adjustments should also be regarded as the protection scope of the present invention.

A fully decoupled annular micro-gyroscope based on an optical micro-cavity, from top to bottom, includes a cap and a wafer, the wafer includes an upper device layer and a lower substrate layer, and the device layer is provided with a number of electrodes, resonators, The first optical microcavity, the second optical microcavity, the first optical waveguide and the second optical waveguide, the electrodes are adjacent to the inner wall of the resonator to form a capacitor, and the first optical waveguide and the second optical waveguide are symmetrically distributed on the two sides of the resonator. On the side, the first optical microcavity and the second optical microcavity are respectively adjacent to the first optical waveguide and the second optical waveguide, and both the first optical microcavity and the second optical microcavity are connected to the resonator.

The resonator is in the shape of a disc, which sequentially includes an inner ring, an inner disk, a middle ring, a middle disk, an outer ring and an outer disk from the inside to the outside. A capacitor is formed, and the outer disk is surrounded by an isolation structure. There are four electrodes, which are evenly arranged inside the inner ring of the resonator, and the electrodes and the inner ring of the resonator form a capacitor. The optical microcavity is disc-shaped and located at the edge of the resonator, and the optical waveguide is a straight waveguide structure, which is tangent to the optical microcavity and is used for light input and output. The cap is a silicon cap and is located directly above the resonator. The cap is provided with a plurality of electrode through holes, which correspond to the electrodes one by one. The electrodes are electrically connected to the metal leads through the electrode through holes to realize the input of electrical signals. . The silicon cap is processed on a silicon wafer, and is bonded to the resonator through a gold-silicon bonding process. The resonator and the electrode are processed on the device layer of a SOI wafer, and the optical waveguide and the optical microcavity are processed by LPCVD on the silicon oxide layer deposited on the surface of the device layer of the SOI wafer where the resonator is located.

Example 1

As shown in Figures 1-5, a fully decoupled ring micro-gyroscope based on an optical microcavity includes a disc-shaped resonator 3 with decoupling characteristics, a set of electrodes 31 for inputting electrical signals, two An optical microcavity 4 for angular velocity detection, two groups of optical waveguides 5 for light transmission, and a group of silicon caps 2 for encapsulation; resonators and electrodes are processed on the device layer of the SOI wafer 1; The optical waveguide and the optical microcavity are fabricated by LPCVD (low pressure chemical vapor deposition) on the silicon oxide layer deposited on the surface of the resonator 3; the silicon cap 2 is fabricated on a silicon wafer, and is bonded to the resonator by a gold-silicon bonding process. achieve bonding.

The silicon cap for encapsulation is located directly above the resonator, and there are a total of 4 electrode through holes on the cap, which correspond to the electrodes one-to-one. Through the electrode through holes, the metal leads and the electrodes can be interconnected. So as to realize the input of electrical signal. The electrode through hole 21 in the silicon cap 2 is a tapered hole, and a bonding metal layer 22 is deposited around the lower surface thereof to realize the bonding between the cap and the SOI wafer.

The electrode 31 is adjacent to the inner ring 32 of the resonator, and is distributed in a circle, and a capacitor is formed between the inner ring 32 and the inner ring 32. After an electrical signal is input, an electrostatic force can be generated to drive the vibration of each ring and the disk structure to generate sound waves.

The disc-shaped resonator is processed on the device layer of a SOI wafer, including inner disk, middle disk, outer disk, inner ring, middle ring, outer ring, decoupling beam and anchor point, inner ring 32, inner disk 33, middle ring 34, the middle plate 35, the outer ring 36, the outer plate 37, and the decoupling beam 39 are interconnected in turn, so that part of the bulk wave can be prevented from propagating to the outer ring. Referring to Figure 2, the decoupling beam is a thin rod that is connected to the outer ring and the outermost periphery, The full decoupling between the driving and sensitive modes is achieved by decoupling the constraints of the beam and the inner, middle and outer three disks. Referring to FIG. 5 , the anchor point is the bump in the dotted box in the figure, which is located at the bottom of the device layer.

The optical microcavity and the optical waveguide are closely attached to the upper surface of the SOI wafer device layer where the resonator is located. The optical microcavity is a microdisk cavity in the whispering gallery mode, which is disc-shaped and is located on the upper surface of the outer disk of the resonator. It realizes the detection of the deformation and body wave generated by the vibration, that is, the detection of the change of the acoustic wave distribution in the resonator, and then the angular velocity is calculated.

The optical waveguide is a straight waveguide structure, coupled with the optical microcavity 4, and the optical waveguide is tangent to the optical microcavity, and is used to detect the input and output of light.

The working principle of the fully decoupled ring microgyroscope based on the optical microcavity is as follows:

The present invention is a fully decoupled annular micro-gyroscope based on an optical micro-cavity and a processing method thereof. The outside is electrically connected to the electrode through the electrode through hole on the cap, and the metal lead is used to achieve electrical connection with the electrode. There is a stable distribution of body waves inside, and a standing wave is formed inside; when the angular velocity changes, due to the Gothic effect, after the resonator rotates, the wave field distribution of the body wave in the resonator will change. Based on the elastic-light effect, The bulk wave in the medium will cause the shape and refractive index of the optical microcavity in contact with the resonator to change, causing its filtering characteristics to change. Therefore, there is a difference in the shape and refractive index of the optical microcavity before and after the rotation, resulting in its spectral line change. , the transmittance of the detection light after being coupled into the microcavity through the optical waveguide is different, the spectral line of the microcavity can be obtained by sweeping the frequency, and the angular velocity can be calculated by measuring the change of the spectrum.

The optical waveguide is used to detect the input and output of light, as well as the optical coupling between the detection light and the optical microcavity. The detection light is provided by an external narrow-band laser generator as a light source, and the detection light is coupled into the optical microcavity through the optical waveguide, and passes through the optical microcavity. After the cavity is filtered, it returns to the optical waveguide for emission, and finally, the spectrum of the outgoing light is analyzed by an external spectrometer to obtain the spectral lines of the optical microcavity.

As shown in Figure 6, a method for processing a fully decoupled annular micro-gyroscope based on an optical micro-cavity includes the following steps:

(1) Cleaning the SOI wafer, drying, and depositing a light guide layer on the surface of the SOI wafer device layer by low-pressure chemical vapor deposition (LPCVD) method for the processing of optical waveguides and optical microcavities;

(2) after cleaning and drying the SOI wafer surface of step (1), a layer of adhesive is applied on the surface of the light guide layer, and then a layer of electron beam exposure glue (PMMA) is spin-coated and cured;

(3) the electron beam exposure adhesive layer obtained in step (2) is exposed by electron beam to define the pattern and position of the optical waveguide and the optical microcavity, and then develop and post-bake;

(4) On the basis of step (3), a dry etching process is used to process the light guide layer to obtain an optical waveguide and an optical microcavity, and then an acetone solution is used to remove the residual electron beam exposure glue;

(5) after cleaning and drying the wafer processed in step (4), spray photoresist on the surface of the device layer and solidify, and then use the first mask to transfer the pattern of the electrode and the disc resonator to the photoresist layer;

(6) On the basis of step (5), use DRIE (deep reactive ion etching) to process to obtain electrodes and resonators, then use KOH solution, wet etching, remove part of the buried oxide layer below the disc resonator, then, Use acetone solution to remove residual photoresist;

(7) Take another silicon wafer, clean and dry the surface, spin-coat photoresist on the lower surface, use the second mask to define the pattern of the metal bonding area by photolithography, and then deposit a layer of chromium in sequence (Ga) metal and gold (Au) layer, using lift-off process, stripping to obtain bonding area, removing residual photoresist;

(8) Spin-coat photoresist on the upper surface of the cap obtained in step (7), use a third mask to define the pattern of electrode holes by photolithography, and then use KOH solution to wet-etch the cap. The electrode hole is opened on the top, and then the residual photoresist is cleaned;

(9) Bonding the cap of step (8) and the structure obtained in step (5) through a gold-silicon bonding process to obtain a complete photoacoustic wave gyroscope structure.

The fabrication of the gyroscope in the present invention combines electron beam exposure, photolithography technology, MEMS bulk silicon processing technology, surface micro-processing technology and gold-silicon bonding technology.

The invention utilizes the method of detecting the optical cavity spectrum to realize the angular velocity detection, and has both high measurement accuracy and small volume. It has the advantages of no electromagnetic interference and easy mass production. It has a wide range of applications and a good market prospect.

Example 2

It is basically the same as Embodiment 1, the difference is: in the step (1), when the silicon oxide layer is deposited, it can also be used on the surface of the SOI wafer device layer, and is produced by a silicon thermal oxidation process.

Example 3

It is basically the same as Example 1, the difference is: in the steps (1)-(4) of the processing scheme of Example 1, in addition to silicon oxide, silicon nitride, Indium phosphide, gallium arsenide and other materials instead.

Technologies not mentioned in the present invention are all prior art.

The invention provides a fully decoupled annular micro-gyroscope based on an optical micro-cavity and a processing method thereof, including a disc-shaped resonator with decoupling characteristics, an electrode for inputting electrical signals, an optical micro-cavity for realizing angular velocity detection , optical waveguides for light transmission, SOI caps for encapsulation. Both the optical microcavity and the optical waveguide are obtained by low temperature deposition of silicon dioxide. The gyroscope uses the electrostatic drive resonator to generate sound waves, the sound wave distribution changes under the influence of the angular velocity, and then uses the optical microcavity to measure the change of the sound wave, so as to realize the measurement of the angular velocity. Due to the optical detection scheme, the reliability and measurement accuracy of the gyroscope can reach a higher level than the traditional MEMS gyroscope.

The invention belongs to the category of MOMES gyroscope, adopts MEMS technology to realize device measurement and processing, and realizes diagonal velocity detection by means of the above-mentioned optical microcavity. The basic principle is that the disc resonator resonates under the drive of the inner electrode, and the generated bulk wave acts on the optical cavity after the decoupling of the inner and outer discs, resulting in the deformation of the optical cavity and the change of the refractive index of the material. After the rotation, due to the change of the vibration mode, the deformation of the optical cavity and the change of the refractive index also change, resulting in the change of the spectral line of the optical cavity. By detecting the change of the spectral line, the magnitude of the angular velocity can be obtained.

Claims (10)

1. The utility model provides a full decoupling annular micro gyroscope based on optics microcavity which characterized in that: from top to bottom including block and wafer, the wafer includes the device layer on upper strata and the substrate layer of lower floor, and the device layer is equipped with a plurality of electrodes, harmonic oscillator, first optics microcavity, second optics microcavity, first optical waveguide and second optical waveguide, the electrode is adjacent with the harmonic oscillator inner wall, constitutes the electric capacity, and first optical waveguide and second optical waveguide symmetric distribution are in the harmonic oscillator both sides, and first optics microcavity and second optics microcavity are adjacent with first optical waveguide and second optical waveguide respectively, and first optics microcavity and second optics microcavity all link to each other with the harmonic oscillator.

2. The fully decoupled annular micro-gyroscope based on optical microcavities of claim 1, wherein: the harmonic oscillator is disc-shaped and sequentially comprises an inner ring, an inner disc, a middle ring, a middle disc, an outer ring and an outer disc from inside to outside, a plurality of decoupling beams are arranged on the outer disc, the electrodes are adjacent to the inner ring of the harmonic oscillator to form a capacitor, and an isolation structure is arranged around the outer disc.

3. The fully decoupled annular micro-gyroscope based on optical microcavities of claim 2, wherein: the four electrodes are uniformly arranged on the inner side of the harmonic oscillator inner ring, the electrodes and the harmonic oscillator inner ring form a capacitor, and after an electric signal is input, an electrostatic force is generated, so that the rings and the disc structures are driven to vibrate, and sound waves are generated.

4. The fully decoupled annular micro-gyroscope based on optical microcavities of claim 1, wherein: the optical microcavity is disc-shaped and is positioned at the edge of the harmonic oscillator, and the optical waveguide is of a straight waveguide structure, is tangent to the optical microcavity and is used for inputting and outputting light.

5. The fully decoupled annular micro-gyroscope based on optical microcavities of claim 1, wherein: the cap is a silicon cap and is positioned right above the harmonic oscillator, a plurality of electrode through holes are formed in the cap and correspond to the electrodes one to one, and the electrodes are electrically connected with the metal lead wires through the electrode through holes so as to realize the input of electric signals.

6. The fully decoupled annular micro-gyroscope based on optical microcavities of claim 5, wherein: the silicon cap is processed on a silicon wafer, the electrode through hole is a conical hole, and the bonding metal layer is deposited on the periphery of the lower surface of the silicon cap and used for achieving bonding of the cap and the wafer.

7. The full-decoupling annular micro-gyroscope based on the optical microcavity as claimed in claim 1, wherein the harmonic oscillator and the electrode are processed on a device layer of an SOI wafer, and the optical waveguide and the optical microcavity are processed by L PCVD on a silicon oxide layer deposited on the surface of the device layer of the SOI wafer where the harmonic oscillator is located.

8. The method for processing a fully decoupled annular micro-gyroscope according to any of claims 1 to 7, comprising the following steps:

(1) cleaning a wafer, drying, and depositing a light guide layer on the surface of a wafer device layer by adopting a low-pressure chemical vapor deposition method for processing an optical waveguide and an optical microcavity;

(2) cleaning and drying the surface of the wafer in the step (1), coating a layer of adhesive on the surface of the light guide layer, spin-coating a layer of electron beam exposure glue, and curing;

(3) defining patterns and positions of the optical waveguide and the optical microcavity by using electron beam exposure on the electron beam exposure adhesive layer obtained in the step (2), and then carrying out development and post-baking;

(4) on the basis of the step (3), processing the light guide layer by adopting a dry etching process to obtain an optical waveguide and an optical microcavity, and then removing residual electron beam exposure glue;

(5) cleaning and drying the wafer processed in the step (4), spraying photoresist on the surface of the device layer, curing, and transferring the patterns of the electrode and the disc harmonic oscillator to the photoresist layer by using a first mask;

(6) on the basis of the step (5), obtaining an electrode harmonic oscillator by utilizing deep reactive ion etching processing, then carrying out wet etching, removing a part of buried oxide layer below the disc harmonic oscillator, and then removing residual photoresist;

(7) another silicon wafer is taken, cleaned and dried, photoresist is coated on the lower surface in a rotating mode, a second mask is utilized, the pattern of a metal bonding area is defined through photoetching, then a layer of chromium metal and a layer of gold are deposited in sequence, a lift-off process is adopted, the bonding area is obtained through stripping, and residual photoresist is removed;

(8) spin-coating photoresist on the upper surface of the cap obtained in the step (7), defining a pattern of an electrode hole by photoetching by using a third mask, then performing wet etching, forming the electrode hole in the cap, and cleaning the residual photoresist;

(9) and (5) bonding the cap obtained in the step (8) and the structure obtained in the step (5) through a gold-silicon bonding process to obtain a complete photoacoustic wave gyroscope structure.

9. The method for processing the fully decoupled annular micro-gyroscope based on the optical microcavity as claimed in claim 8, wherein: the light guide layer deposited in the step (1) is made of silicon oxide, silicon nitride, indium phosphide or gallium arsenide.

10. The method for processing the fully decoupled annular micro-gyroscope based on the optical microcavity as claimed in claim 9, wherein: when the light guide layer is made of silicon oxide and deposited in the step (1), the light guide layer is produced by adopting a low-pressure chemical vapor deposition method or a silicon thermal oxidation process on the surface of the SOI wafer device layer.

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