CN105021179A - Micro-hemispherical resonator gyroscope based on borosilicate glass annealing forming and preparing method - Google Patents

Abstract

The invention discloses a micro hemispherical resonant gyroscope based on annealing of borosilicate glass and a manufacturing method thereof. A silicon wafer is used as a base to form a silicon base, and a cylindrical cavity and the center of the cavity are etched on the upper surface of the silicon wafer. The central pillar is connected to the center of the hemispherical resonator to form a suspended structure; at the same time, eight flat-plate electrodes are evenly arranged around the hemispherical resonator on the periphery of the cylindrical cavity on the upper surface of the silicon wafer. The electrodes are composed of four driving electrodes and four detecting electrodes. All the driving electrodes and detecting electrodes are not in contact with the hemispherical resonator, and there is the same gap, and the driving electrodes and detecting electrodes are arranged at intervals in sequence. The glass-metal blown miniature hemispherical resonant gyroscope produced by the invention has the advantages of simple structure, low surface stress, high symmetry, etc., so that it has relatively stable performance and wider application range.

Description

Micro hemispherical resonator gyroscope based on borosilicate glass annealing and manufacturing method

technical field

The invention belongs to the technical field of micro inertial sensors in MEMS, in particular to a micro hemispherical resonant gyroscope based on borosilicate glass annealing and a manufacturing method.

Background technique

With the development of national defense technology and civilian industry, gyroscopes have become very important inertial devices in the fields of attitude control, navigation and positioning. Among them, the hemispherical resonant gyroscope is recognized as the best performance due to its precise scaling factor, satisfactory random drift and bias stability, and insensitivity to the external environment (acceleration, vibration, temperature, etc.). One of the gyro products. The precision of hemispherical resonant gyroscope is even higher than that of fiber optic gyroscope and laser gyroscope, and it also has the advantages of high resolution, wide measurement range, anti-overload, anti-radiation, and anti-interference. The processing and forming of the gyroscope has become an important direction in the extensive research and application development of MEMS technology in recent years.

Inspired by the proven macro hemispherical resonant gyroscope, the 3-DMEMS wine glass hemispherical resonant gyroscope structure applied to clock and inertia detection has become a research hotspot in recent years. With the advent of 3-D precision machining technology, it has become possible to mass-produce such wineglass-style hemispherical resonator gyroscope structures. Since the wine glass structure has obvious advantages in terms of symmetry, low energy loss, and isolation from external vibrations, this structure is likely to become a new generation of MEMS devices with good dynamic performance. However, compared with the macro-machining process, the micro-machining process is more suitable for manufacturing flat and relatively low (10 ^-2 -10 ^-4 order of magnitude) structures. Molding inconsistency, alignment error, high surface roughness, and the spacing of deposited films are the main factors that hinder the realization of high-precision hemispherical resonator gyroscope technology in the current MEMS manufacturing process. Therefore, it is still a technical problem to manufacture smooth, symmetrical and high-aspect-ratio 3-D hemispherical resonator gyroscope structures at the wafer level by micromachining technology.

At present, the existing hemispherical resonator gyroscope preparation technologies at home and abroad are mainly divided into two categories. The first category is the thin film growth method. The Chinese patent "Hemispherical Resonant Micromechanical Gyroscope and Its Processing Technology" (Patent Application No.: 201210231285.0) and the Chinese Patent "Micro Hemispherical Resonant Gyroscope and Its Preparation Method" (Patent Application No.: 201310022146.1) all use thin film growth technology to manufacture hemispheres The characteristics of the resonant gyroscope are: a silicon dioxide film is deposited on the silicon surface, and a hemispherical spherical shell is obtained by isotropic dry etching. The resonant layer is made of polysilicon or silicon dioxide or silicon nitride or diamond. This method of film growth has disadvantages such as large stress, large surface roughness and low yield.

The second type of preparation technology is the glass blowing/gas extraction method. The advantage of this technology is that it mainly adopts the surface micromachining process, the cost is low, and mass production can be realized; in terms of etching glass, the isotropic etching method will cause the distance between the resonator and the electrode to be too wide, while the anisotropic etching method The glass method can only use dry plasma etching. However, the dry etching glass process is limited by the etching depth, surface roughness and low aspect ratio. This is a technical problem that cannot be solved so far by using glass materials.

At present, the Chinese patent "Hemispherical Resonant Microgyroscope Supported Up and Down" (Patent Application No.: 201410390495.3) and the Chinese Patent "Glass Metal Hemispherical Resonant Microgyroscope Supported Up and Down" (Patent Application No.: 201410390485.X) use glass or glass metal The hemispherical resonator is manufactured by pumping technology, and then the formed hemispherical resonator is bonded to the top pillar to form the overall structure of the hemispherical resonator gyroscope. The Chinese patent "A Glass Metal Blowing Micro Hemispherical Resonator Gyroscope and Its Preparation Method" (Application No.: 201410390482.6) and the Chinese Patent "Annular Glass-Enclosed Glass Blowing Micro Hemispherical Resonator Gyroscope" (Application No.: 201410390473.7) also propose glass Hemispherical resonator gyroscopes are manufactured by metal/glass blowing. However, this type of technology has problems such as high requirements for equipment, high surface stress, low yield, low electrode consistency, and difficulty in ensuring symmetry.

Contents of the invention

The object of the present invention is to provide a hemispherical resonant gyroscope with low surface stress, high electrode consistency, high symmetry, simple process and high yield and its manufacturing method based on high-temperature annealing and blowing of borosilicate glass.

The technical solution to realize the object of the present invention is: a micro hemispherical resonator gyroscope based on borosilicate glass annealing and its manufacturing method, a silicon wafer is used as the substrate to form a silicon substrate, and a cylindrical cavity is etched on the upper surface of the silicon wafer The central pillar at the center of the body and the cavity is connected to the center of the hemispherical resonator to form a suspended structure; at the same time, eight flat-plate electrodes are evenly arranged around the hemispherical resonator on the periphery of the cylindrical cavity on the upper surface of the silicon wafer , the eight planar electrodes are composed of four driving electrodes and four detecting electrodes, all the driving electrodes and detecting electrodes are not in contact with the hemispherical resonator, there is the same gap, and the driving electrodes and the detecting electrodes are distributed in sequence.

Compared with the prior art, the present invention has significant advantages: (1) the glass-metal blown miniature hemispherical resonator gyroscope made by the method has the advantages of simple structure, low surface stress and high symmetry, so that it has relatively stable performance and Wider range of applications. (2) Using silicon wafer and glass wafer as the main processing structure, the preparation of the hemispherical resonant gyroscope can be realized only by using MEMS micromachining technology, the process is simple, the cost is low, and mass production can be realized. (3) All photolithography steps are completed before glass blowing, which can not only realize 3-D structure, but also avoid the implementation of difficult graphics processes, such as: 3-D photolithography, shadow mask and laser Ablation technology minimizes the process errors introduced by complex processes. (4) The edge flaws and thermal/mechanical disturbances produced by blown glass are the biggest factors affecting the symmetry of the hemispherical resonator gyroscope. In order to reduce photolithography and etching errors as much as possible, the process scheme proposed by the present invention only uses two photolithography steps, which simplifies the process to the greatest extent, avoids errors, and ensures the symmetry of the structure. (5) Borosilicate glass containing alkali metal ions is selected as the material of the resonator structure layer. Compared with conventional glass substrates (such as soda lime glass and quartz glass), the etching rate of this borosilicate glass is high. , and a more ideal anisotropic etching morphology can be obtained by controlling the mask and etching parameters. (6) The metal mask before etching the glass adopts electroplating technology, which can reduce the surface stress of the resonant layer, minimize the damage to the flatness of the glass before blowing the glass, and improve the yield. (7) Deep etching of glass adopts plasma oxide dry etching technology. Through reasonable control of etching parameters, the etching accuracy and aspect ratio of the capacitance distance between electrodes and resonators can be guaranteed, and complete and smooth etching can be obtained. edge. (8) The use of a flat-plate external electrode structure overcomes the shortcoming that the working area of the driving electrode and the sensitive electrode is too small, and can improve its integration. (9) In the process of releasing silicon, the suspended hemispherical resonator and external electrode structure are formed at the same time of isotropic dry etching, which avoids the crystal orientation that may occur in asymmetric etching.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic diagram of the three-dimensional structure of the miniature hemispherical resonator gyroscope based on annealing and forming of borosilicate glass according to the present invention.

Fig. 2 is a schematic diagram of different angles of the miniature hemispherical resonator gyroscope based on borosilicate glass annealing and forming according to the present invention: (a) top view, (b) front view, (c) 3/4 sectional view.

Fig. 3 is the processing flowchart (central cross-sectional view) of the hemispherical resonator gyroscope of the present invention, wherein, (a)-use silicon wafer as the silicon substrate 1 of the hemispherical resonator gyroscope, (b)-deeply etched cylindrical cavity 4 With the central pillar 5, (c)-glass wafer 6 is anodically bonded to the silicon substrate 1, (d)-deep etching the glass wafer, (e)-high temperature annealing to form a hemispherical resonator, (f)-releasing the silicon substrate 1 , forming a suspended hemispherical harmonic oscillator structure, (g)-covering the metal conductive layer.

Detailed ways

1 and 2, the present invention is based on borosilicate glass annealed miniature hemispherical resonator gyroscope, including:

a silicon substrate 1;

A hemispherical harmonic oscillator 2;

A central pillar 5 connects the hemispherical resonator and the silicon substrate;

Eight planar electrodes 3 arranged on the silicon substrate 1 and uniformly arranged around the hemispherical resonator, the eight planar electrodes 3 are four drive electrodes 3a, 3c, 3e, 3g and four detection electrodes 3b, 3d, 3f , composed of 3h, all driving electrodes, detecting electrodes and the hemispherical resonator are not in contact, and the driving electrodes and detecting electrodes are distributed sequentially at intervals, that is, there is a detecting electrode between every two driving electrodes, and similarly, between every two detecting electrodes is a driving electrode.

The present invention is based on the annealing of borosilicate glass. The central pillar 5 of the miniature hemispherical resonator gyroscope is connected to the center of the hemispherical resonator. structure. The gap between the hemispherical resonator 2 and the eight flat electrodes 3 is 80-120 μm. The structure of the hemispherical harmonic oscillator 2 is a 3-D inverted wine glass type.

The working principle of the miniature hemispherical resonator gyroscope based on the annealing of borosilicate glass in the present invention is: when the driving electrodes 3a, 3c, 3e, and 3g are applied with AC voltage, under the effect of capacitive induction, the diameter of the spherical shell of the hemispherical resonator 2 When the angular velocity is input, under the action of Coriolis force, the mode shape of the hemispherical resonator will precess in the circumferential direction relative to the shell, forming a detection mode, and the detection electrodes 3b, 3d, 3f , 3h through the sensitive signal generated by the capacitive effect, the signal detection is realized.

3, the present invention is based on the manufacturing method of the borosilicate glass annealing miniature hemispherical resonator gyroscope, a silicon chip is used as the substrate to form the silicon substrate 1, and a cylindrical cavity 4 and the center of the cavity are etched on the upper surface of the silicon chip. The central pillar 5 at the center of the hemispherical resonator 5 is connected to the center of the hemispherical resonator to form a suspended structure; at the same time, eight flat-plate electrodes 3 are evenly arranged around the hemispherical resonator 2 on the periphery of the cylindrical cavity 4 on the upper surface of the silicon chip , the eight planar electrodes 3 are composed of four driving electrodes and four detecting electrodes, all the driving electrodes and detecting electrodes are not in contact with the hemispherical resonator 2, and there is the same gap, and the driving electrodes and detecting electrodes are arranged at intervals in sequence. Method concrete steps of the present invention are as follows:

Step 1, as shown in Figure 3 (a), using a silicon wafer as the silicon substrate 1 of the hemispherical resonator gyroscope, as shown in Figure 3 (b), using photolithography technology (the surface of the wafer is first coated with glue, soft baked, then exposed, developing and hardening the film to form a photoresist pattern) to form a cylindrical cavity and a central pillar pattern on the upper surface of the silicon wafer, and then use ICP (Inductively Coupled Plasma Inductively Coupled Plasma) etching technology to deeply etch the cylindrical cavity 4 and the central pillar 5. After that, wash and remove the glue, and peel off the excess metal (Lift-off, solvent stripping method).

Step 2, pre-treat the borosilicate glass wafer 6 in a plasma remover environment (such as an oxygen plasma 200W and argon plasma 400W environment), clean the bonding surface, and remove surface particles; as shown in Figure 3 In (c), the borosilicate glass wafer 6 is anodically bonded to the periphery of the cylindrical cavity 4 of the silicon substrate 1 and the central pillar 5, and at the same time, the inert gas is sealed in the cylindrical cavity 4 to 1 atm. Anodic bonding, also known as electrostatic bonding, is a bonding completed by applying a certain electric field strength to the wafer at 200-500°C, and is generally used for silicon-glass bonding.

Step 3, cleaning the bonded wafer, magnetron sputtering 30-35nm Ti, and then using electroplating method to deposit a metal (such as Al) with a thickness of 4 μm as a mask, during the electroplating process, the substrate is heated (such as lower than 150°C) to reduce residual stress; after electroplating the mask, use photolithography to pattern the surface of the mask, place the wafer after photolithography in a constant temperature water bath of 40-50°C, use dilute nitric acid and glacial acetic acid The mixed solution (such as 6:1 ~ 8:1 dilute nitric acid: glacial acetic acid solution) wet etching mask.

Step 4, as shown in (d) of Figure 3, use plasma oxide dry etching technology (such as using ULVACNLD570 oxide etching machine) to deeply etch the glass layer of the wafer after the wet etching mask to form a glass layer The resonator part 2a of the unit (before annealing and forming) and the plate electrode 3 are cleaned and deglued, and the remaining mask is wet-etched with a mixed solution of dilute nitric acid and glacial acetic acid. In step 4, the plasma oxide dry etching technology is adopted, and the etching parameters are set as follows: C3F8-30sccm, Ar-90sccm as etching gas, balance physical and chemical etching, and ensure smooth etching surface; O ₂ - 90 sccm is plasma cleaning gas, set low pressure 3mT, electromagnetic power 1500W, bias power 50W, so that the etching rate can reach 0.8μm/min, and the aspect ratio close to 8:1 can be obtained, and at the same time, the resonance between the control electrode and the hemisphere is guaranteed The etching accuracy of the sub-capacitor spacing can obtain a complete and smooth etching edge. The deep etching depth of the glass layer of the wafer may be 90-100 μm.

Step 5, in the high temperature environment of the rapid annealing furnace, the inert gas in the cylindrical cavity is heated and expanded due to the difference in internal and external pressure, as shown in (e) of Figure 3, the harmonic oscillator part 2a of the glass layer unit is subjected to surface tension and cavity Viscous deformation occurs under pressure, and a hemispherical resonator 2 (forming a 3-D inverted wine glass type hemispherical resonator) is formed on the surface of the wafer obtained in step 4, and is rapidly cooled to room temperature. The temperature of the high temperature environment of the rapid annealing furnace may be 800-900°C.

Step ₆ , using XeF2 gas to etch the silicon substrate 1 to form a cavity 7 (the cavity formed after releasing the bonding part of the hemispherical resonator and the silicon substrate), as shown in (f) of Figure 3, releasing the hemispherical resonator 2 and the silicon substrate 1 bonding area, forming an independent suspended structure.

Step 7, as shown in (g) of Figure 3, uses magnetron sputtering on the molding structure obtained in step 6 to cover a layer of metal iridium 8 to obtain a conductive layer on the upper surface of the structure to form a miniature hemispherical resonant gyroscope, as shown in Figure 2 ( a), (b), (c) three structures shown in the figure.

The material of the silicon substrate 1 of the present invention is low-resistance doped silicon (less than 1Ω) with good electrical conductivity, and the material of the hemispherical resonator 2 and the plate electrode 3 is borosilicate glass containing alkali metal ions.

The present invention applies the theory of surface tension and pressure driven micron-scale glass blowing to a wafer-scale process. This manufacturing method can process 3-D wine glasses with complete symmetry (vibration frequency difference Δf<1Hz, second-order mode frequency sensitivity Δf _n=2 /f _n=2 <10ppm) and atomic-level smoothness (0.23nm Sa) Type hemispherical harmonic oscillator structure. The micro glass blowing process is completely different from the traditional deposition, molding, and etching processes. The principle is: the structural layer glass undergoes viscous deformation under surface tension and pressure, thereby forming a hemispherical harmonic oscillator structure. During the transient viscous deformation of the structural layer, the surface tension acts on the hemispherical harmonic oscillator structure at the atomic level, which can minimize the surface roughness and incompleteness of the structure. The surface smoothness and symmetry of the structure of this glass annealing forming process is much higher than that of the traditional manufacturing process, and it effectively realizes the manufacture of high-precision wafer-level hemispherical resonant gyroscopes with high consistency.

Claims (10)

1. to anneal a shaping micro hemispherical resonator gyro based on borosilicate glass, it is characterized in that comprising silicon base (1), hemispherical resonator (2), centre strut (5) connects hemispherical resonator and silicon base; Be arranged on silicon base (1) to go up and eight plate electrodes (3) be evenly arranged around hemispherical resonator, these eight plate electrodes (3) are four drive electrode (3a, 3c, 3e, 3g) He four detecting electrode (3b, 3d, 3f, 3h) form, all drive electrodes, detecting electrode all do not contact with hemispherical resonator, and drive electrode and detecting electrode are spaced apart successively, are namely detecting electrodes between every two drive electrodes, equally, be a drive electrode between every two detecting electrodes.

2. according to claim 1ly to anneal shaping micro hemispherical resonator gyro based on borosilicate glass, it is characterized in that centre strut (5) is connected with hemispherical resonator subcenter, between hemispherical resonator (2) and eight plate electrodes (3) in silicon base (1), identical gap is set, forms hanging structure.

3. according to claim 2ly to anneal shaping micro hemispherical resonator gyro based on borosilicate glass, it is characterized in that the gap between hemispherical resonator (2) and eight plate electrodes (3) is 80-120 μm.

4. to anneal shaping micro hemispherical resonator gyro based on borosilicate glass according to claim 1,2 or 3, is characterized in that the structure of hemispherical resonator (2) is that 3-D is inverted wineglass formula.

5. the manufacture method of a shaping micro hemispherical resonator gyro of annealing based on borosilicate glass, a silicon chip is it is characterized in that to form silicon base (1) as substrate, silicon chip upper surface etches the centre strut (5) of a circular cylindrical cavity (4) and cavity circle centre position, this centre strut (5) is connected with hemispherical resonator subcenter, forms hanging structure; Simultaneously, peripheral at the circular cylindrical cavity (4) of silicon chip upper surface, and be evenly arranged eight plate electrodes (3) around hemispherical resonator (2), these eight plate electrodes (3) are made up of four drive electrodes and four detecting electrodes, all drive electrodes, detecting electrode do not contact with hemispherical resonator (2), there is identical gap, and drive electrode and detecting electrode are spaced apart successively.

6. the manufacture method of shaping micro hemispherical resonator gyro of annealing based on borosilicate glass according to claim 5, is characterized in that concrete steps are as follows:

Step 1, silicon base (1) using Silicon Wafer as hemispherical reso nance gyroscope, photoetching technique is utilized to form circular cylindrical cavity and centre strut figure at Silicon Wafer upper surface, then ICP lithographic technique deep etching circular cylindrical cavity (4) and centre strut (5) is used, cleaning is afterwards removed photoresist, and peels off unnecessary metal;

Step 2, by borosilicate glass wafer (6) pre-treatment under equipment for burning-off photoresist by plasma environment, circular cylindrical cavity (4) periphery and the centre strut (5) of borosilicate glass wafer (6) and Silicon Wafer (1) carry out anode linkage, and in circular cylindrical cavity (4), sealed inert gas is to 1atm;

Step 3, the wafer after cleaning bonding, magnetron sputtering Ti, then uses electric plating method plated metal as mask, in electroplating process, heats to reduce unrelieved stress to substrate; After having electroplated mask, utilize photoetching technique graphical in mask surface, the wafer after photoetching is placed in water bath with thermostatic control, use the mixed solution wet etching mask of dust technology and glacial acetic acid;

Step 4, use plasma oxide dry etching technology to the glassy layer deep etching of the wafer after wet etching mask, form the harmonic oscillator part (2a) of glassy layer unit and plate electrode (3) part, then cleaning is removed photoresist, and uses the remaining mask of mixed solution wet etching of dust technology and glacial acetic acid;

Step 5, under quick anneal oven hot environment, the harmonic oscillator part (2a) of glassy layer unit is subject to surface tension and chamber pressure generation viscous yielding, and the crystal column surface obtained in step 4 forms hemispherical resonator (2), and is cooled to room temperature rapidly;

Step 6, uses XeF ₂gas attack silicon base (1) forms cavity (7), releases hemispherical resonator (2) and the bond area of silicon base (1), forms independently hanging structure;

Step 7, on the molding structure using magnetron sputtering to obtain in step 6, covers layer of metal iridium (8), forms micro hemispherical resonator gyro.

7. the manufacture method of the shaping micro hemispherical resonator gyro of annealing based on borosilicate glass according to claim 5 or 6, it is characterized in that the material of silicon base (1) is that low resistance mixes silicon, hemispherical resonator (2) and the material of plate electrode (3) are the borosilicate glass of alkali metal containing ion.

8. the manufacture method of shaping micro hemispherical resonator gyro of annealing based on borosilicate glass according to claim 6, it is characterized in that in step 4, using plasma oxide dry etching technology, etching parameters arranges as follows: C3F8-30sccm, Ar-90sccm is as etching gas, counterbalance Physicochemical etches, and ensures that etched surface is more smooth; O ₂-90sccm is plasma cleaning gas, low pressure 3mT is set, electromagnetic power 1500W, bias power 50W, etch rate is made to reach 0.8 μm/min, and the depth-to-width ratio that can obtain close to 8: 1, ensure that the etching precision of control electrode and hemispherical resonator electric capacity spacing simultaneously, obtain complete, level and smooth etched edge.

9. the manufacture method of shaping micro hemispherical resonator gyro of annealing based on borosilicate glass according to claim 6, is characterized in that in step 4, and the glassy layer deep etching degree of depth of wafer is 90 ~ 100 μm.

10. the manufacture method of shaping micro hemispherical resonator gyro of annealing based on borosilicate glass according to claim 6, is characterized in that the temperature of the quick anneal oven hot environment in step 5 is 800-900 DEG C.