WO2018171161A1 - 加速度敏感器及加速度计 - Google Patents

加速度敏感器及加速度计 Download PDF

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WO2018171161A1
WO2018171161A1 PCT/CN2017/104384 CN2017104384W WO2018171161A1 WO 2018171161 A1 WO2018171161 A1 WO 2018171161A1 CN 2017104384 W CN2017104384 W CN 2017104384W WO 2018171161 A1 WO2018171161 A1 WO 2018171161A1
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mass
acceleration sensor
single mode
accelerometer
mode fiber
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PCT/CN2017/104384
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English (en)
French (fr)
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黄庭峰
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京东方科技集团股份有限公司
北京京东方光电科技有限公司
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Priority to US15/767,830 priority Critical patent/US10884019B2/en
Publication of WO2018171161A1 publication Critical patent/WO2018171161A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/093—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by photoelectric pick-up
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/0802—Details

Definitions

  • the present disclosure relates to the field of micro-optical electromechanical technology, and more particularly to an acceleration sensor and an accelerometer.
  • Accelerometers are now widely used in the automotive industry, robotics, wearable devices, engineering vibration measurement, geological exploration, navigation systems, aerospace and other fields, where sensing needs to be caused by falling, tilting, moving, positioning, impact or vibration. Accelerometers are used for products that change slightly.
  • accelerometers are used for products that change slightly.
  • the development of accelerometer has made great progress, the volume is decreasing, the sensitivity, stability and anti-interference ability are continuously improved.
  • Various micro-accelerometers have been widely used. Commercial application.
  • Existing accelerometers generally consist of mass blocks, dampers, elastic components, sensitive components, and adaptive circuits.
  • the working principle of the accelerometer is: in the acceleration environment, the acceleration value is obtained by using Newton's second law by measuring the inertial force of the mass. Therefore, improving the anti-interference performance of the mass is an important factor to improve the performance of the accelerometer.
  • An acceleration sensor for an accelerometer provided by an embodiment of the present disclosure includes a base, a cantilever beam, and a mass fixed on the base by the cantilever beam;
  • the shape of the mass is a center symmetrical shape
  • the cantilever beam includes four L-shaped arms, wherein a long arm of each of the L-shaped arms is coupled to the base, and a short arm of the L-shaped arm is coupled to the mass, and any two adjacent L-arm is axisymmetric Settings.
  • the cantilever beam, the base, and the mass are a unitary structure.
  • the material of the cantilever beam, the base, and the mass is a silicon carbide material.
  • the silicon carbide material is a 6H-SiC single crystal material.
  • the shape of the mass is rectangular, and the connection points of the short arm of each of the L-shaped arms and the mass are adjacent to the four corners of the rectangle, respectively. .
  • the long arm of each of the L-shaped arms has a length of 1700 ⁇ m to 1900 ⁇ m
  • the short arm has a length of 450 ⁇ m to 550 ⁇ m
  • the arm width is 110 ⁇ m to 130 ⁇ m.
  • An embodiment of the present disclosure further provides an accelerometer, including any of the acceleration sensors provided by the embodiments of the present disclosure.
  • the accelerometer provided by the embodiment of the present disclosure further includes: a substrate disposed opposite to and spaced apart from the acceleration sensor, and an outer package structure encapsulating the acceleration sensor and the substrate, located outside the outer package structure a light source, a circulator, a photomultiplier tube, and a signal processing circuit;
  • the substrate has a hollow sleeve extending through a region opposite to the mass in the acceleration sensor; a first single mode fiber disposed within the hollow sleeve, the end of the first single mode fiber relative to the mass Forming an extrinsic Fabry-Perot interference EFPI cavity with the surface of the mass facing the surface of the substrate;
  • the light source is coupled to the first port of the circulator through a second single mode fiber for providing light to the circulator;
  • a second port of the circulator is coupled to the first single mode fiber by a third single mode fiber, and the second port is configured to provide light to the circulator through the first single mode Optical fiber is transmitted to the mass;
  • the third port of the circulator is connected to the photomultiplier tube through a fourth single mode fiber, and the third port is configured to provide reflected light received by the first single mode fiber to the photomultiplier tube;
  • the signal processing circuit is coupled to the photomultiplier tube, and the signal processing circuit is configured to calculate an acceleration based on a signal output by the photomultiplier tube.
  • an anti-reflection film is further disposed on a side of the mass facing away from the substrate.
  • the material of the anti-reflection film is aluminum nitride.
  • the antireflection film has a thickness of ⁇ /8n z , 5 ⁇ /8n z or 9 ⁇ /8n z , where ⁇ is the wavelength of the light source, and n z is the antireflection The refractive index of the film.
  • the light source is a laser light source having a wavelength of 1550 nm.
  • the material of the substrate is Pyrex glass.
  • the material of the outer package structure is alumina ceramic.
  • the first single mode fiber is an uncoated single mode fiber.
  • a display screen connected to the signal processing circuit is further included, and the display screen is used to display the acceleration calculated by the signal processing circuit.
  • FIG. 1 is a schematic structural diagram of an acceleration sensor according to an embodiment of the present disclosure
  • FIG. 2 is a schematic structural diagram of an accelerometer according to an embodiment of the present disclosure
  • FIG. 3 is a schematic diagram of an equivalent mechanical model of an acceleration sensor according to an embodiment of the present disclosure.
  • FIG. 4 is a second schematic structural diagram of an accelerometer according to an embodiment of the present disclosure.
  • 5a to 5h are schematic structural diagrams corresponding to the execution of each step in the manufacture of the speedometer sensor in the accelerometer provided by the embodiment of the present disclosure
  • Fig. 6 is a top plan view showing the speedometer sensor provided with the antireflection film shown in Fig. 5h.
  • An acceleration sensor 1 for an accelerometer includes a base 01, a cantilever beam 02, and a mass block 03 fixed to the base 01 by a cantilever beam 02;
  • the cantilever beam 02, the base 01 and the mass 03 are integrated structures
  • the shape of the mass block 03 is a center symmetrical shape
  • the cantilever beam 02 includes four L-shaped arms 021, wherein the long arms of the L-shaped arms 021 are connected to the base 01, the short arms of the L-shaped arms 021 are connected to the mass block 03, and any two adjacent L-shaped arms 021 are axially oriented. Symmetrical settings.
  • the cantilever beam 02 is composed of four symmetrically disposed L-shaped arms 021, the four L-shaped arms 021 are laterally clamped to each other, so that the lateral interference resistance is strong.
  • the structure is simple and the production difficulty is low.
  • the cantilever beam 02, the base 01, and the mass block 03 may be a unitary structure. This can be formed by trimming the same piece of material, so that there is no need to increase the joining process between the cantilever beam 02 and the base 01 and the mass block 03.
  • the material of the cantilever beam 02, the base 01, and the mass 03 may be a silicon carbide SiC material.
  • SiC silicon carbide
  • the high bond energy of Si-C bond makes SiC more inert, and it is superior in oxidation resistance, chemical corrosion and radiation.
  • SiC is much more than silicon in anti-neutron radiation and is suitable for high-radiation detection applications.
  • the high breakdown field strength of SiC makes it have good pressure resistance and small size; high thermal conductivity makes it high in power density, suitable for working in high temperature environment, and the working temperature of SiC material can exceed 1000 °C.
  • the silicon carbide material can be selected from 6H-SiC. Single crystal material.
  • the shape of the mass block 03 is a square or a rectangle
  • the production cost is low and the formula for deriving the acceleration is relatively simple. Therefore, in the acceleration sensor provided by the embodiment of the present disclosure, as shown in FIG.
  • the shape of 03 may be a rectangle, and the connection points of the short arm of each L-shaped arm 021 and the mass 03 are adjacent to the four corners of the rectangle, respectively.
  • the length l 1 of the long arm of each L-shaped arm 021 is 1700 ⁇ m to 1900 ⁇ m
  • the length l 2 of the short arm is 450 ⁇ m to 550 ⁇ m
  • the arm width w is 110 ⁇ m. 130 ⁇ m.
  • an embodiment of the present disclosure further provides an accelerometer including any of the above-described acceleration sensors provided by the embodiments of the present disclosure. Since the principle of the accelerometer solving the problem is similar to the foregoing one of the acceleration sensors, the implementation of the accelerometer can be referred to the implementation of the aforementioned acceleration sensor, and the repeated description is not repeated.
  • the accelerometer system Since the acceleration is difficult to be directly measured, in practical applications, the accelerometer system is regarded as a second-order continuous time system, which works in the inertial space. According to Newton's laws of mechanics, the acceleration sensor can be equivalent to a mass-spring-damage (mkf) system as shown in Figure 2.
  • the acceleration sensor is fixed to the accelerometer housing and moves relative to the acceleration in the inertial space.
  • the absolute displacement of the accelerometer casing is z f
  • the absolute displacement of the mass is z
  • the displacement of the mass relative to the pedestal is:
  • ⁇ 0 is the inherent resonant frequency of the mass
  • ⁇ is the damping ratio
  • the relationship between the displacement x of the mass relative to the pedestal and the acceleration a can be known, so that the acceleration can be obtained by measuring the relative displacement.
  • the substrate 2 disposed opposite to and spaced apart from the acceleration sensor 1 and the outer package structure of the package acceleration sensor 1 and the substrate 2 may be further included.
  • a light source 4 a circulator 5, a photomultiplier tube 6, a signal processing circuit 7;
  • the substrate 2 has a hollow sleeve 21 extending through a region opposite to the mass 03 in the acceleration sensor 1, and the first single mode fiber is disposed in the hollow sleeve 21, and the end face and mass of the first single mode fiber relative to the mass 03 Block 03 forms an extrinsic Fabry-Perot Interferometric (EFPI) cavity 9 between the surfaces of the substrate 2;
  • EFPI extrinsic Fabry-Perot Interferometric
  • the light source 4 is connected to the first port 51 of the circulator 5 through a second single mode fiber, and the light source 4 is used to supply light to the circulator 5;
  • the second port 52 of the circulator 5 is connected to the first single mode fiber through a third single mode fiber, and the second end The port 52 is used to transmit the light of the light source 4 to the circulator 5 through the first single mode fiber to the mass 03;
  • the third port 53 of the circulator 5 is connected to the photomultiplier tube 6 through a fourth single mode fiber for providing the reflected light received by the first single mode fiber to the photomultiplier tube 6;
  • the signal processing circuit 7 is connected to a photomultiplier tube 6 for calculating an acceleration based on a signal output from the photomultiplier tube 6.
  • the action of the acceleration causes the vibration of the mass 03
  • the vibration of the mass 03 causes the normal displacement of the mass 03
  • the normal displacement of the mass 03 brings the EFPI.
  • the change in cavity length that is, the optical path difference of the interference light
  • the optical path of the accelerometer is as indicated by the arrow in FIG. 3, and the light emitted from the light source 4 enters the circulator 5 from the first port 51 of the circulator 5, exits from the second port 52 of the circulator 5, and passes through the first single.
  • the mode fiber enters the EFPI cavity, and the first single mode fiber exit end surface of the EFPI cavity generates reflected light and transmitted light, and the transmitted light passes through the EFPI cavity to reach the lower surface of the mass block 03, and then returns to the first single mode fiber, and a part of the light is in the first
  • a single mode fiber directly reflects at the air interface.
  • the two reflected lights cancel or constructively interfere based on the optical path difference between the two, and the interference light passes through the third port 53 of the circulator 5 to reach the photomultiplier tube 6 via the fourth single mode fiber. Therefore, the signal processing circuit 7 can calculate the acceleration based on the signal output from the photomultiplier tube 6.
  • the circulator 5 can avoid the problem that interference crosstalk occurs when light is transmitted bidirectionally using other single devices.
  • the light source 4 is a laser light source having a wavelength of 1550 nm.
  • the light source 4 can also adopt a laser light source with a wavelength of 1310 nm. The longer the wavelength of the light source 4, the larger the range of the accelerometer.
  • the first single mode fiber, the second single mode fiber, the third single mode fiber, and the fourth single mode fiber may be a polyimide coating of 9/125SI13-PI155 type.
  • the communication fiber has a core diameter of 9 ⁇ m and a corresponding cutoff wavelength of 1550 nm.
  • the first single-mode fiber disposed in the hollow sleeve 21 may be a 9/125SI13-PI155 type polyimide coated communication fiber, of course, for an increase in operating temperature. Above 500 ° C, the first single mode fiber disposed in the hollow sleeve 21 can The imide coating in the 9/125SI13-PI155 polyimide coated communication fiber is removed, ie the first single mode fiber can be an uncoated single mode fiber.
  • the accelerometer in order to allow the light that has passed through the EFPI cavity 9 to reach the upper surface of the mass block 03 to be transmitted, the light that passes through the EFPI cavity 9 to the upper surface of the mass block 9 is prevented from being
  • the upper surface of the mass 9 is reflected and returned to the first single mode fiber in the hollow sleeve 21, thereby causing interference to the double beam interference light in the first single mode fiber, as shown in Fig. 4, the mass 03 is facing away
  • An anti-reflection film 04 is also provided on the substrate 2 side.
  • the material of the anti-reflection film 04 may be aluminum nitride AlN, because the thermal expansion coefficient of the AlN is closer to that of the SiC, and the thermal mismatch may be reduced.
  • phase difference ⁇ between the reflected beams of the front and rear surfaces of the antireflection film 04 generally satisfies:
  • the amplitude reflection coefficient of the anti-reflection film 04 is:
  • the reflectance of the antireflection film 04 is:
  • n s , n z and n 0 are the refractive indices of SiC, AR coating 04 and air medium, respectively.
  • the reflectance of the AR coating 04 is a function of ⁇ , i.e. the function e n z.
  • the thickness of the anti-reflection film 04 is ⁇ /8n z , 5 ⁇ /8n z or 9 ⁇ /8n z
  • the reflectance of the anti-reflection film 04 is the smallest, wherein ⁇ is the light source 4
  • the wavelength, n z is the refractive index of the AR coating 04.
  • the material of the substrate 2 may be a Pyrex glass, and the material of the outer package structure 3 may be Alumina ceramics are not limited herein.
  • the signal processing circuit 7 includes an operational amplifier, an adjustable resistor, and a filter capacitor.
  • a display screen 8 connected to the signal processing circuit 7 for displaying the calculated acceleration of the signal processing circuit 7 may be further included.
  • the above accelerometer provided by the embodiment of the present disclosure is more stable due to the mechanical properties of the cantilever beam in the acceleration sensor, and the accelerometer uses the combination of EFPI technology and SiC micromachining technology. Accelerometer operating temperature can be improved, while stability, measurement accuracy, environmental adaptability and anti-interference Excellent performance in terms of ability. In the case of vehicle engine turbocharger, gas turbine monitoring, aerospace autopilot and rocket satellite and other vibration parameters test environment is relatively harsh, the accuracy and sensitivity are higher, so it has a wide application prospect.
  • the pattern of the anti-reflection film 04 may be formed on the SiC wafer before forming the cantilever.
  • the pattern of beam 02 and mass block 03 is as follows:
  • the thickness of the SiC wafer is generally about 340 ⁇ m.
  • the thickness of the wafer can be reduced by grinding to a thickness of 80 ⁇ m by using diamond grinding to reduce the difficulty of the subsequent patterning process.
  • An antireflection film 04 having a thickness of about 70 nm is formed on the susceptor 01, wherein the material of the antireflection film 04 is AlN, as shown in Fig. 5a.
  • the antireflection film 04 is patterned, the antireflection film 04 in the region where the mass 03 is to be formed is retained, and the antireflection film 04 in the other regions is removed, as shown in Fig. 5b.
  • the photoresist 05 is coated and patterned as shown in Fig. 5c.
  • the photoresist 05 is coated with a coater and patterned after exposure to ultraviolet light.
  • the susceptor 01 is dry etched by inductively coupled plasma (ICP), wherein the reaction gases are SF 6 and O 2 , and the etching depth is 12 ⁇ m, as shown in Fig. 5d. Shown.
  • ICP inductively coupled plasma
  • Ni mask 06 is electroplated and patterned as shown in Fig. 5f.
  • the susceptor 01 is dry etched by inductively coupled plasma (ICP), wherein the reaction gases are SF 6 and O 2 , and the etching depth is 68 ⁇ m, forming an integral structure of the cantilever beam 02, the mass block 03, and the susceptor 01.
  • ICP inductively coupled plasma
  • the above acceleration sensor and accelerometer include a base and a cantilever beam And a mass fixed to the base by the cantilever beam; the shape of the mass is a center symmetrical shape; the cantilever beam includes four L-shaped arms, wherein the long arm of each L-shaped arm is connected to the base, and the short arm of the L-shaped arm is connected Mass block, and any two adjacent L-shaped arms are arranged in an axisymmetric manner. Since the cantilever beam is composed of four symmetrically disposed L-shaped arms, the four L-shaped arms are mutually clamped laterally, so that the lateral interference resistance is strong, the structure is simple, and the manufacturing difficulty is low.

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Abstract

一种加速度敏感器(1)及加速度计，包括基座(01)、悬臂梁(02)和通过悬臂梁(02)固定在基座(01)上的质量块(03)；质量块(03)的形状为中心对称形状；悬臂梁(02)包括四个L型臂(021)，其中各L型臂(021)的长臂连接基座(01)，L型臂(021)的短臂连接质量块(03)，且任意相邻两个L型臂(021)呈轴对称设置。由于悬臂梁(02)由四个对称设置的L型臂(021)组成，四个L型臂(021)之间横向相互钳制，因而抗横向干扰能力强，且结构简单，制作难度较低。

Description

加速度敏感器及加速度计
本申请要求在2017年3月24日提交中国专利局、申请号为201710183883.8、发明名称为“一种加速度敏感器及加速度计”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开涉及微光机电技术领域，尤指一种加速度敏感器及加速度计。
背景技术
加速度计现已广泛应用于汽车工业、机器人、可穿戴设备、工程测振、地质勘探、导航系统、航空航天等多种领域，凡需要感测由于坠落、倾斜、移动、定位、撞击或振动产生微小变化的产品，都会用到加速度计。当今在微电子机械系统技术不断进步的条件下，加速度计的研发取得了巨大的进步，体积不断减小，灵敏度、稳定性、抗干扰能力不断提高，各种微小型的加速度计已得到广泛的商业化应用。
现有的加速度计一般由质量块、阻尼器、弹性元件、敏感元件和适调电路等部分组成。加速度计的工作原理为：在加速环境中，通过对质量块所受惯性力的测量，利用牛顿第二定律获得加速度值。因此，提高质量块的抗干扰性能是提升加速度计性能的重要因素。
发明内容
本公开实施例提供的一种用于加速度计的加速度敏感器，包括基座、悬臂梁和通过所述悬臂梁固定在所述基座上的质量块；
所述质量块的形状为中心对称形状；
所述悬臂梁包括四个L型臂，其中各所述L型臂的长臂连接所述基座，所述L型臂的短臂连接所述质量块，且任意相邻的两个所述L型臂呈轴对称 设置。
在本公开实施例提供的加速度敏感器中，所述悬臂梁、所述基座以及所述质量块为一体结构。
在本公开实施例提供的加速度敏感器中，所述悬臂梁、所述基座以及所述质量块的材料为碳化硅材料。
在本公开实施例提供的加速度敏感器中，所述碳化硅材料为6H-SiC单晶材料。
在本公开实施例提供的加速度敏感器中，所述质量块的形状为矩形，且各所述L型臂的短臂与所述质量块的连接点分别与所述矩形的四个角相邻。
在本公开实施例提供的加速度敏感器中，各所述L型臂的长臂的长度为1700μm～1900μm，短臂的长度为450μm～550μm，臂宽为110μm～130μm。
本公开实施例还提供了一种加速度计，包括本公开实施例提供的任一种加速度敏感器。
在本公开实施例提供的加速度计中，还包括：与所述加速度敏感器相对且间隔设置的基板，封装所述加速度敏感器与所述基板的外封装结构，位于所述外封装结构外的光源、环形器、光电倍增管和信号处理电路；其中，
所述基板具有贯穿与所述加速度敏感器中的质量块相对区域的空心套管；所述空心套管内设置有第一单模光纤，所述第一单模光纤相对于所述质量块的端面与所述质量块面向所述基板的表面面之间形成非本征型法布里-珀罗干涉EFPI腔；
所述光源通过第二单模光纤与所述环形器的第一端口相连，所述光源用于向所述环形器提供光；
所述环形器的第二端口通过第三单模光纤与所述第一单模光纤相连，所述第二端口用于将所述光源提供给所述环形器的光通过所述第一单模光纤传输至所述质量块；
所述环形器的第三端口通过第四单模光纤与所述光电倍增管相连，所述第三端口用于将所述第一单模光纤接收的反射光提供给所述光电倍增管；
所述信号处理电路与所述光电倍增管相连，所述信号处理电路用于根据所述光电倍增管输出的信号计算加速度。
在本公开实施例提供的加速度计中，所述质量块背向所述基板一侧还设置有增透膜。
在本公开实施例提供的加速度计中，所述增透膜的材料为氮化铝。
在本公开实施例提供的加速度计中，所述增透膜的厚度为λ/8nz、5λ/8nz或9λ/8nz，其中λ为所述光源的波长，nz为所述增透膜的折射率。
在本公开实施例提供的加速度计中，所述光源为波长是1550nm的激光光源。
在本公开实施例提供的加速度计中，所述基板的材料为派热克斯玻璃。
在本公开实施例提供的加速度计中，所述外封装结构的材料为氧化铝陶瓷。
在本公开实施例提供的加速度计中，所述第一单模光纤为无涂层的单模光纤。
在本公开实施例提供的加速度计中，还包括与所述信号处理电路相连的显示屏，所述显示屏用于显示所述信号处理电路计算所得的加速度。
附图说明
图1为本公开实施例提供的加速度敏感器的结构示意图；
图2为本公开实施例提供的加速度计的结构示意图之一；
图3为本公开实施例提供的加速度敏感器的等效力学模型的示意图；
图4为本公开实施例提供的加速度计的结构示意图之二；
图5a至图5h为在制作本公开实施例提供的加速度计中的速度计敏感器时执行各步骤后对应的结构示意图；
图6为图5h所示的设置有增透膜的速度计敏感器的俯视结构示意图。
具体实施方式
为了使本公开的目的、技术方案和优点更加清楚，下面将结合附图对本公开作进一步地详细描述，显然，所描述的实施例仅是本公开一部分实施例，而不是全部的实施例。基于本公开中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其它实施例，都属于本公开保护的范围。
附图中各部件的形状和大小不反映真实比例，目的只是示意说明本公开内容。
本公开实施例提供的一种用于加速度计的加速度敏感器1，如图1所示，包括基座01、悬臂梁02和通过悬臂梁02固定在基座01上的质量块03；
悬臂梁02、基座01以及质量块03为一体结构；
质量块03的形状为中心对称形状；
悬臂梁02包括四个L型臂021，其中各L型臂021的长臂连接基座01，L型臂021的短臂连接质量块03，且任意相邻的两个L型臂021呈轴对称设置。
具体地，在本公开实施例提供的加速度敏感器中，由于悬臂梁02由四个对称设置的L型臂021组成，四个L型臂021之间横向相互钳制，因而抗横向干扰能力强，且结构简单，制作难度较低。
可选地，在本公开实施例提供的加速度敏感器中，悬臂梁02、基座01以及质量块03可以为一体结构。这样可以通过对同一材料块剪裁形成，从而不需要增加悬臂梁02与基座01以及质量块03之间的连接工艺。
可选地，在本公开实施例提供的加速度敏感器中，悬臂梁02、基座01以及质量块03的材料可以为碳化硅SiC材料。这是由于SiC的禁带宽度是Si的2.5倍，Si-C键的高键能使得SiC具有更高惰性，抗氧化、化学腐蚀以及辐射能力均超强。SiC在抗中子辐射方面远超硅数倍，适于高辐射探测应用。此外，SiC的高击穿场强使其耐压性能好、尺寸小；高热导率使其功率密度高，适合工作在高温环境，SiC材料的工作温度可超过1000℃。
由于6H-SiC单晶材料是SiC中机械性能与耐高温性能最为优异的一种，因此，在本公开实施例提供的加速度敏感器中，碳化硅材料可以选取6H-SiC 单晶材料。
可选地，当质量块03的形状为正方形或长方形时，制作成本低且计算加速度时推导公式相对简单，因此，在本公开实施例提供的加速度敏感器中，如图1所示，质量块03的形状可以为矩形，且各L型臂021的短臂与质量块03的连接点分别与矩形的四个角相邻。
可选地，在本公开实施例提供的加速度敏感器中，各L型臂021的长臂的长度l1为1700μm～1900μm，短臂的长度l2为450μm～550μm，臂宽w为110μm～130μm。
基于同一发明构思，本公开实施例还提供了一种加速度计，该加速度计包括本公开实施例提供的上述任一种加速度敏感器。由于该加速度计解决问题的原理与前述一种加速度敏感器相似，因此加速度计的实施可以参见前述加速度敏感器的实施，重复之处不再赘述。
下面详细说明通过加速度敏感器检测加速度的原理。由于加速度难以被直接测量，在实际应用中，将加速度计系统看成一个二阶连续时间系统，工作在惯性空间中。根据牛顿力学定律，可以将加速度敏感器等效为一个如图2所示的质量-弹簧-阻尼(m-k-f)系统。加速度敏感器与加速度计外壳固定，在惯性空间中随加速度的变化发生相对运动。在惯性空间中，加速度计外壳绝对位移为zf，质量块绝对位移为z，质量块相对于基座的位移为：
x＝z-zf     (1.1)
在惯性力、弹簧弹性力和阻尼力相互作用处于力平衡状态时，根据牛顿第二定律可以得出该系统的二阶运动方程为：
Figure PCTCN2017104384-appb-000001
式中m为质量块的质量，km为弹簧刚度、f为阻尼系数。将式(1.1)代入(1.2)，进行整理变换可得：
Figure PCTCN2017104384-appb-000002
式中a为整个系统所受到的加速度。设系统输入变量为a(t)，输出变量为质量块相对于壳体的位移x(t)，在零初始条件下对(1.3)进行拉氏变换，可得系统的传递函数为：
Figure PCTCN2017104384-appb-000003
式中ω0为质量块固有的谐振频率，ζ为阻尼比，根据工程力学知识：
Figure PCTCN2017104384-appb-000004
式中Q为机械品质因素。当加速度输入为固定值，x(t)趋于定值，则式(1.3)变形为：
Figure PCTCN2017104384-appb-000005
由式可知质量块相对于基座的位移x和加速度a之间的函数关系，从而可以通过测量相对位移得到加速度。
下面通过一个具体的实施例说明本公开实施例提供的加速度计的具体实施方式，但是不限于此。
可选地，在本公开实施例提供的加速度计中，如图3所示，还可以包括：与加速度敏感器1相对且间隔设置的基板2，封装加速度敏感器1与基板2的外封装结构3，光源4，环形器5，光电倍增管6、信号处理电路7；其中，
基板2具有贯穿与加速度敏感器1中的质量块03相对区域的空心套管21，且空心套管21内设置有第一单模光纤，第一单模光纤相对于质量块03的端面与质量块03面向基板2的表面之间形成非本征型法布里-珀罗干涉(Extrinsic Fabry-perot Interferometric，EFPI)腔9；
光源4通过第二单模光纤与环形器5的第一端口51相连，光源4用于向环形器5提供光；
环形器5的第二端口52通过第三单模光纤与第一单模光纤相连，第二端 口52用于将光源4提供给环形器5的光通过第一单模光纤传输至质量块03；
环形器5的第三端口53通过第四单模光纤与光电倍增管6相连，用于将第一单模光纤接收的反射光提供给光电倍增管6；
信号处理电路7与光电倍增管6相连，信号处理电路7用于根据光电倍增管6输出的信号计算加速度。
具体地，在本公开实施例提供的上述加速度计中，加速度的作用会引起质量块03的振动，质量块03的振动引起质量块03的法向位移，质量块03的法向位移带来EFPI腔长的改变，亦即干涉光的光程差发生变化，从而干涉光强信号改变。而加速度计中光路传输路径如图3中箭头所指，光源4出射的光自环形器5的第一端口51进入环形器5，从环形器5的第二端口52出射后再经第一单模光纤进入EFPI腔，EFPI腔的第一单模光纤出射端面产生反射光和透射光，透射光经EFPI腔到达质量块03的下表面发生反射后返回经第一单模光纤，一部分光在第一单模光纤与空气界面直接发生反射。两束反射光基于二者之间的光程差发生相消或者相长干涉，干涉光通过环形器5的第三端口53经由第四单模光纤到达光电倍增管6。因此信号处理电路7根据光电倍增管6输出的信号可以计算加速度。
可选地，在本公开实施例提供的加速度计中，环形器5可以避免在使用其他单个器件是双向传输的光发生干涉串扰的问题。
可选地，在本公开实施例提供的加速计中，光源4为波长是1550nm的激光光源.当然光源4也可以采用波长为1310nm的激光光源。光源4的波长越长，加速度计的量程越大。
可选地，当光源4的波长为1550nm时，第一单模光纤、第二单模光纤、第三单模光纤和第四单模光纤可以采用9/125SI13-PI155型聚酰亚胺涂层通信光纤，其芯径是9μm，对应截止波长为1550nm。
可选地，在本公开实施例提供的加速度计中，设置在空心套管21中的第一单模光纤可以是9/125SI13-PI155型聚酰亚胺涂层通信光纤，当然为了工作温度提高到500℃以上，设置在空心套管21中的第一单模光纤可以将 9/125SI13-PI155型聚酰亚胺涂层通信光纤中的酰亚胺涂层去掉，即第一单模光纤可以为无涂层的单模光纤。
较佳地，在本公开实施例提供的加速度计中，为了使经EFPI腔9到达质量块03的上表面的光被透射出去，以避免经EFPI腔9到达质量块9的上表面的光在质量块9的上表面发生反射又返回至空心套管21中的第一单模光纤，从而对第一单模光纤中的双光束干涉光造成干扰，如图4所示，质量块03背向基板2一侧还设置有增透膜04。
可选地，在本公开实施例提供的加速度计中，增透膜04的材料可以为氮化铝AlN，这是由于AlN的热膨胀系数与SiC更为接近，可以降低热失配。
可选地，增透膜04前后表面反射光束之间的相位差δ一般满足：
Figure PCTCN2017104384-appb-000006
式中e为增透膜04的厚度。由菲涅尔公式，可知正入射时增透膜04前表面的反射系数ρ1和增透膜04前表面的反射系数ρ2分别为：
Figure PCTCN2017104384-appb-000007
Figure PCTCN2017104384-appb-000008
根据单层薄膜干涉理论，可知增透膜04的振幅反射系数为：
Figure PCTCN2017104384-appb-000009
若薄膜吸收不计，可得增透薄膜04的反射比为：
Figure PCTCN2017104384-appb-000010
式中ns、nz和n0分别为SiC、增透膜04和空气介质的折射率。
联立式(2.1)～(2.5)，代入已知的SiC和空气介质的折射率值，整理可得增透膜04反射比(正入射)为：
Figure PCTCN2017104384-appb-000011
对于确定的增透膜04折射率nz，增透膜04的反射比是δ的函数，也即nze的函数。利用MATLAB软件对增透膜04反射比与增透膜04折射率与厚度相关性进行仿真，可得nze＝λ/8，5λ/8，9λ/8处反射比最小。
因此，在本公开实施例提供的加速度计中，增透膜04的厚度为λ/8nz、5λ/8nz或9λ/8nz时增透膜04的反射比最小，其中λ为光源4的波长，nz为增透膜04的折射率。
可选地，从制作工艺考虑，增透膜04的厚度越厚，工艺越难，且成本越高，因此当光源4的波长为1550nm时，且增透膜04的材料为氮化铝时，增透膜04的厚度设置为70nm左右。
可选地，为了保证了基板2和外封装结构3的耐高温特性，在本公开实施例提供的加速度计中，基板2的材料可以为派热克斯玻璃，外封装结构3的材料可以为氧化铝陶瓷，在此不作限定。
可选地，在本公开实施例提供加速度计中，信号处理电路7包括运算放大器、可调电阻与滤波电容。
可选地，在本公开实施例提供的加速度计中，如图4所示，还可以包括与信号处理电路7相连的显示屏8，显示屏8用于显示信号处理电路7计算所得的加速度。
本公开实施例提供的上述加速度计，由于加速度敏感器中悬臂梁机械性能更稳定，并且加速度计使用了EFPI技术和SiC微加工技术结合。可实现加速度计工作温度的提高，同时在稳定性、测量精度、环境适应能力及抗干扰 能力方面性能优异。在车载发动机涡轮增压器、燃气涡轮机监测，航空航天自动驾驶与火箭卫星等振动参数测试环境较为恶劣的情形下，精度和灵敏度更高，因此具有广泛的应用前景。
当本公开实施例提供的加速度计中在加速度敏感器的质量块03上还设置有增透膜04时，在制作时，可以先在SiC晶圆上形成增透膜04的图形后再形成悬臂梁02和质量块03的图形，具体步骤如下：
(1)减薄SiC晶圆形成基座。
可选地，SiC晶圆的厚度一般在340μm左右，为了降低SiC晶圆的厚度，可以采用金刚石进行磨削的方式使晶圆厚度从减薄到80μm，以降低之后进行的构图工艺难度。
(2)在基座01上形成厚度为70nm左右增透膜04，其中增透膜04的材料为AlN，如图5a所示。
(3)对增透膜04进行构图，保留将要形成质量块03的区域内的增透膜04，去除其他区域的的增透膜04，如图5b所示。
(4)涂覆光刻胶05并图形化，如图5c所示。
可选地，利用涂胶机涂覆光刻胶05，经紫外曝光后进行图形化。
(5)以图形化的光刻胶05为掩膜，采用感应耦合等离子体(ICP)干法刻蚀基座01，其中反应气体为SF6和O2，刻蚀深度为12μm，如图5d所示。
(6)去除光刻胶05，并将基座01反转，以进行背面刻蚀，如图5e所示。
(7)电镀Ni掩膜06并图形化，如图5f所示。
(8)采用感应耦合等离子体(ICP)干法刻蚀基座01，其中反应气体为SF6和O2，刻蚀深度为68μm，形成悬臂梁02、质量块03和基座01的一体结构图形，如图5g所示。
(9)去除Ni掩膜06，如图5h所示，其中，图5h对应的俯视图如图6所示，图5h为图6沿AA’方向的剖面示意图。
(10)进行清洗和图形检查。
本公开实施例提供的上述加速度敏感器及加速度计，包括基座、悬臂梁 和通过悬臂梁固定在基座上的质量块；质量块的形状为中心对称形状；悬臂梁包括四个L型臂，其中各L型臂的长臂连接基座，L型臂的短臂连接质量块，且任意相邻两个L型臂呈轴对称设置。由于悬臂梁由四个对称设置的L型臂组成，四个L型臂之间横向相互钳制，因而抗横向干扰能力强，且结构简单，制作难度较低。
显然，本领域的技术人员可以对本公开实施例进行各种改动和变型而不脱离本公开实施例的精神和范围。这样，倘若本公开实施例的这些修改和变型属于本公开权利要求及其等同技术的范围之内，则本公开也意图包含这些改动和变型在内。

Claims (16)

  1. 一种加速度敏感器，其中，包括基座、悬臂梁和通过所述悬臂梁固定在所述基座上的质量块；
    所述质量块的形状为中心对称形状；
    所述悬臂梁包括四个L型臂，其中各所述L型臂的长臂连接所述基座，所述L型臂的短臂连接所述质量块，且任意相邻的两个所述L型臂呈轴对称设置。
  2. 如权利要求1所述的加速度敏感器，其中，所述悬臂梁、所述基座以及所述质量块为一体结构。
  3. 如权利要求1所述的加速度敏感器，其中，所述悬臂梁、所述基座以及所述质量块的材料为碳化硅材料。
  4. 如权利要求3所述的加速度敏感器，其中，所述碳化硅材料为6H-SiC单晶材料。
  5. 如权利要求1-4任一项所述的加速度敏感器，其中，所述质量块的形状为矩形，且各所述L型臂的短臂与所述质量块的连接点分别与所述矩形的四个角相邻。
  6. 如权利要求5所述的加速度敏感器，其中，各所述L型臂的长臂的长度为1700μm～1900μm，短臂的长度为450μm～550μm，臂宽为110μm～130μm。
  7. 一种加速度计，其中，包括如权利要求1-6任一项所述的加速度敏感器。
  8. 如权利要求7所述的加速度计，其中，还包括：与所述加速度敏感器相对且间隔设置的基板，封装所述加速度敏感器与所述基板的外封装结构，位于所述外封装结构外的光源、环形器、光电倍增管和信号处理电路；其中，
    所述基板具有贯穿与所述加速度敏感器中的质量块相对区域的空心套管；所述空心套管内设置有第一单模光纤，所述第一单模光纤相对于所述质量块的端面与所述质量块面向所述基板的表面之间形成非本征型法布里-珀罗 干涉EFPI腔；
    所述光源通过第二单模光纤与所述环形器的第一端口相连，所述光源用于向所述环形器提供光；
    所述环形器的第二端口通过第三单模光纤与所述第一单模光纤相连，所述第二端口用于将所述光源提供给所述环形器的光通过所述第一单模光纤传输至所述质量块；
    所述环形器的第三端口通过第四单模光纤与所述光电倍增管相连，所述第三端口用于将所述第一单模光纤接收的反射光提供给所述光电倍增管；
    所述信号处理电路与所述光电倍增管相连，所述信号处理电路用于根据所述光电倍增管输出的信号计算加速度。
  9. 如权利要求8所述的加速度计，其中，所述质量块背向所述基板的一侧设置有增透膜。
  10. 如权利要求9所述的加速度计，其中，所述增透膜的材料为氮化铝。
  11. 如权利要求10所述的加速度计，其中，所述增透膜的厚度为λ/8nz、5λ/8nz或9λ/8nz，其中λ为所述光源的波长，nz为所述增透膜的折射率。
  12. 如权利要求8-11任一项所述的加速度计，其中，所述光源为波长是1550nm的激光光源。
  13. 如权利要求8-11任一项所述的加速度计，其中，所述基板的材料为派热克斯玻璃。
  14. 如权利要求8-11任一项所述的加速度计，其中，所述外封装结构的材料为氧化铝陶瓷。
  15. 如权利要求8-11任一项所述的加速度计，其中，所述第一单模光纤为无涂层的单模光纤。
  16. 如权利要求8-11任一项所述的加速度计，其中，还包括：与所述信号处理电路相连的显示屏，所述显示屏用于显示所述信号处理电路计算所得的加速度。
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