CN109831729A - Compact high sensitivity MEMS capacitive sensor - Google Patents

Compact high sensitivity MEMS capacitive sensor Download PDF

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Publication number
CN109831729A
CN109831729A CN201910092073.0A CN201910092073A CN109831729A CN 109831729 A CN109831729 A CN 109831729A CN 201910092073 A CN201910092073 A CN 201910092073A CN 109831729 A CN109831729 A CN 109831729A
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China
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electrode
layer
electrode layer
unit
capacitive sensor
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CN201910092073.0A
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Chinese (zh)
Inventor
陈曦
卓文军
王俊力
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武汉大学
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Priority to CN201910092073.0A priority Critical patent/CN109831729A/en
Publication of CN109831729A publication Critical patent/CN109831729A/en

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Abstract

The present invention relates to compact high sensitivity MEMS capacitive sensors, including the substrate (10) set gradually from lower to upper, lower separation layer (11), lower electrode layer (12), upper separation layer (13), sacrificial layer (14), vibrating diaphragm layer (15), upper electrode layer (16), insulating layer (17), lower electrode layer (12) and upper electrode layer (16) include at least one electrod-array unit (22), electrod-array unit (22) includes multiple electrodes unit, the edge of the electrode unit (19b) of the electrode unit (19a) and/or upper electrode layer (16) of lower electrode layer (12) has multiple notches (20).Reduce the overlapping area of condenser structure electrode fixed part, so that capacitance variations amplitude is bigger when diaphragm oscillations, impedance transformation caused by institute's energy is more significant after characteristic frequency offset.

Description

Compact high sensitivity MEMS capacitive sensor

Technical field

The invention belongs to silicon micromachining technique fields, and in particular to the micro- capacitive sensing of compact high sensitivity MEMS Device.

Background technique

With the development of Internet of Things, the demand to MEMS sensor is also growing, current to adopt there are many sensor again Environmental factor is detected with capacitance type structure, such as gas sensor, distance measuring sensor, ultrasonic imaging sensor, capacitor Formula microphone etc..

Wherein, the MEMS capacitive gas sensor mainly surface vibration portion on a sensor based on characteristic frequency variation Divide deposition, spin coating gas adsorption material, micro variation can occur for its quality in adsorption and desorption.And working frequency is higher When, such as in supersonic range, small mass change can cause characteristic frequency to change, and keep the vibration frequency of oscillating component inclined From characteristic frequency, Oscillation Amplitude becomes smaller, so that capacitance structure impedance structure be made to change.By the impedance transformation for detecting capacitance structure Amount can extrapolate the quality of institute's adsorbed gas.Therefore, the limiting value that can detect impedance transformation is lower, the gas that can be detected Weight limiting value is lower, i.e. the sensitivity of sensor is higher.

The electrode section of traditional MEMS capacitive gas sensor generallys use circle, the face of upper/lower electrode fixed part Product it is larger, cause vibration when effective coverage it is relatively small, therefore, the sensitivity of sensor is not fine.In addition, MEMS is sensed The size of device is smaller, and the upper limit of gaseous mass range that can be detected is lower, some largely exists and to required precision detecting It wants to exist when high gas certain insufficient.

Summary of the invention

The present invention provides a kind of MEMS capacitive sensor, including set gradually from lower to upper substrate, lower separation layer, Lower electrode layer, upper separation layer, sacrificial layer, vibrating diaphragm layer, upper electrode layer, insulating layer, the lower electrode layer and the upper electrode layer are equal Including at least one electrod-array unit, the electrod-array unit includes multiple electrodes unit, the electrode of the lower electrode layer The edge of the electrode unit of unit and/or the upper electrode layer has multiple notches, reduces condenser structure electrode fixed part Overlapping area so that capacitance variations amplitude is bigger when diaphragm oscillations, impedance caused by institute's energy is converted after characteristic frequency offset It is more significant.

In above-mentioned MEMS capacitive sensor, on the lower electrode layer and the opposite electrode unit of the upper electrode layer The notch be staggered.

In above-mentioned MEMS capacitive sensor, the notch is evenly distributed on the edge of the electrode unit.

In above-mentioned MEMS capacitive sensor, the shape of the notch is round or triangle or rectangle.

In above-mentioned MEMS capacitive sensor, which is characterized in that the notch is inwardly no more than 10um.

It is less than the lower electrode layer in the area of above-mentioned MEMS capacitive sensor, the upper electrode layer electrode unit The area of electrode unit.

In above-mentioned MEMS capacitive sensor, the electrode unit is circle, the upper electrode layer electrode unit Diameter is 2-4um smaller than the diameter of the lower electrode layer electrode unit.

Connecting line between above-mentioned MEMS capacitive sensor, the lower electrode layer electrode unit is powered on described Connecting line between the layer electrode unit of pole is staggered, and reduces overlapping area to the greatest extent.

Successively decrease step by step in the length of above-mentioned MEMS capacitive sensor, the electrod-array unit, it is stepped.

In above-mentioned MEMS capacitive sensor, the lower electrode layer and the upper electrode layer include four electricity Four electrod-array units of pole array element, the lower electrode layer and the upper electrode layer are all connected with into Wheatstone bridge.

The present invention reduces the overlapping area of condenser structure electrode fixed part on the basis of electric bridge compares amplifying circuit, So that when vibration can oscillating component area relative total area it is higher, capacitance variations amplitude when vibration is bigger, inclined in characteristic frequency The transformation of impedance caused by institute's energy is more significant after shifting.The present invention changes the layout of electrod-array unit in upper/lower electrode layer, so that Capacitance structure element number under same area is more, and when being used for gas detection, detection range can be improved.

Detailed description of the invention

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

Fig. 1 shows the structure chart of a part of MEMS capacitive sensor.

Fig. 2 shows a kind of plan views of lower electrode layer electrode unit.

Fig. 3 shows a kind of plan view of upper electrode layer electrode unit.

Fig. 4 shows a kind of plan view of sacrificial layer.

Fig. 5 shows plan view when lower electrode layer, sacrificial layer and upper electrode layer storied placement.

Fig. 6 shows the plan view of electrod-array cellular construction.

Specific embodiment

MEMS capacitive sensor include the substrate 10 set gradually from lower to upper, lower separation layer 11, lower electrode layer 12, Upper separation layer 13, sacrificial layer 14, vibrating diaphragm layer 15, upper electrode layer 16, insulating layer 17.Lower electrode layer 12 and upper electrode layer 16 include At least one electrod-array unit 22, electrod-array unit 22 include multiple electrodes unit 19.

Substrate 10 plays support fixed function, can be used as silicon wafer.Lower separation layer 11 supports lower electrode layer 12, and plays insulation and protect Shield effect, can be SiO2、SiNxEqual insulating materials.Lower electrode layer 12 and upper electrode layer 16 all include the formation of multiple electrodes unit 19 Electrod-array unit 22.Upper electrode layer 16 is located at 12 top of lower electrode layer, an electrode unit 19b face of upper electrode layer 16 One electrode unit 19a of lower electrode layer 12, the two collectively constitutes one can capacitance-type vibration structure.Lower electrode layer 12 and top electrode The material of layer 16 can be the conductive materials such as aluminium, polysilicon.Upper separation layer 13 is used for insulation blocking capacitor array structure, can be SiO2、SiNxEqual insulating materials.14 material of sacrificial layer can select for corrosion such as Al, Cr than high material The vibration of vibrating diaphragm layer 15 provides space.Sacrificial layer 14 is also to be located at right above lower electrode layer 12 in array distribution, and size is smaller In lower electrode layer 12, the electrode unit 19a and top electrode of one lower electrode layer 12 of the cavity face of each sacrificial layer 14 The electrode unit 19b of layer 16.Vibrating diaphragm layer 15 is used to support upper electrode layer 16, positioned at the underface of upper electrode layer 16.Vibrating diaphragm layer 15 It drives upper electrode layer 16 to vibrate together when vibration, etches an etching channels vertically downward in vibrating diaphragm layer 15, enable corrosive liquid Enough enter the sacrificial layer 14 of 15 lower section of corrosion vibrating diaphragm layer by the etching channels.The etching channels can pass through upper electrode layer 16 Electrode unit 19b block.Insulating layer 17 plays insulation protection for protecting upper electrode layer 16.

Fig. 1 shows the structure of a part of MEMS capacitive sensor, wherein the electrode unit 19a of lower electrode layer 12 Multiple notches 20 are all had with the edge of the electrode unit 19b of upper electrode layer 16.It alternatively, can also be only in the electricity of lower electrode layer 12 Notch 20 is arranged in the edge of the electrode unit 19b of pole unit 19a or upper electrode layer 16.Notch 20 on electrode unit 19 can subtract The overlapping area of few condenser structure electrode fixed part, improves the sensitivity and stability of sensor.

With reference to Fig. 1, the notch 20 on lower electrode layer 12 and the opposite electrode unit 19 of upper electrode layer 16 is staggered, and certainly may be used Not to be staggered.With reference to Fig. 2, Fig. 3, notch 20 is evenly distributed on the edge of electrode unit 19.16 electrode unit 19b's of upper electrode layer Area is less than the area of 12 electrode unit 19b of lower electrode layer, for example, when electrode unit 19 is round, 16 circular electric of upper electrode layer The diameter of pole unit 19b is 2-4um smaller than the diameter of 16 circular electrode unit 19a of lower electrode layer, prevents error when lithography alignment Caused dislocation.The shape of notch 20 can be round or triangle or rectangle, naturally it is also possible to be other shapes.Notch 20 Inwardly it is no more than 10um.

With reference to Fig. 5, connecting line 18 and 16 electrode unit 19b of upper electrode layer between 12 electrode unit 19a of lower electrode layer it Between connecting line 21 be staggered, reduce overlapping area to the greatest extent.Wherein, the connecting line between electrode unit can be straight line or interlock Oblique line or curve etc..

With reference to Fig. 6, lower electrode layer 12 and upper electrode layer 16 can be respectively provided with four electrod-array units 22, the i.e. micro- electricity of MEMS There are four capacitors for capacity sensor tool.Four electrod-array units 22 of lower electrode layer 12 and upper electrode layer 16 are connected into respectively Wheatstone bridge amplifies faint original signal.The electrod-array unit 22 of lower electrode layer 12 and upper electrode layer 16 is long Degree successively decreases step by step, stepped, arranges more compact in this way, takes full advantage of space.When four electrod-array units 22 are arranged, Outwardly, shorter top is towards the center of electrode layer, in center position by four electrod-array units for longer bottom It connects, shortens connecting line, the area utilization of array is improved with this.

The top electrode of capacitor array be can vibration film, influenced that vibration can be synchronized by its frequency by institute's power on signal It is dynamic, handle by signal of the voltage comparison method to the capacitor array the two poles of the earth for connecting into Wheatstone bridge available more significant Voltage magnitude variable quantity.

In four independent capacitance arrays, it is in parallel and two capacitor array diaphragm mass that current potential is different is constant, in addition two The electrode quality of a capacitor array can change because adsorbing object (such as gas) detected.In the Wheatstone bridge When being passed through fixed character frequency alternating current, the diaphragm mass of corresponding capacitor array changes, and characteristic frequency will shift, Maximum dynamic displacement reduces, so that the capacitance of capacitor array changes, counterpart impedance is caused to change, can be with by comparing node voltage Amplify surveyed electric signal.

The MEMS capacitive sensor of above-described embodiment can make by the following method:

Step a is existed using chemical vapour deposition technique (CVD), thermal oxidation method or ethyl orthosilicate (TEOS) thermal decomposition method The SiO with a thickness of 200~1000 is prepared in substrate 102Film, the SiO2Film layer is lower separation layer 11.

Step b prepares polysilicon or Al film with a thickness of 100~500, the polysilicon membrane in lower SiO2 film layer Layer is lower electrode layer 12.

Step c uses chemical wet etching (litho-etch) to lower electrode layer 12 according to the pattern of the array of design, several A edge has the electrode unit 19a of notch 20 as an electrod-array unit 22, and four electrod-array units 22 are connected At Wheatstone bridge.

Step d is prepared using chemical vapour deposition technique (CVD) on lower electrode layer 12 with a thickness of 200~1000 SiO2Film, the SiO2Film layer is upper separation layer 13.

Step e, in upper SiO2The Al or Cr with a thickness of 0.5um~1.5um are prepared using magnetron sputtering (FHR) in film layer Etc. corrosion susceptible materials;

Corrosion material is etched into the structure of array arrangement by chemical wet etching method (litho-etch) by step f.

Step g continues to prepare with a thickness of 0.5um~1um's using chemical vapour deposition technique (CVD) on sacrificial layer 14 SiO2Film, as vibrating diaphragm layer 15.

Vibrating diaphragm layer 15 is etched corrosion circular hole, the corrosion circle by chemical wet etching method (litho-etch) by step h Pore size distribution etching channels upper end described in sacrificial layer 14 is simultaneously centered around circular membrane surrounding, using corrosive liquid to sacrificial layer 14 into Row corrosion.

Step i prepares the Al of 0.2um~0.5um using magnetron sputtering (FHR) in vibrating diaphragm layer 15, as upper electrode layer 16, And the corrosion circular hole is sealed up.

Step j etches the electrode with notch 20 by chemical wet etching method (litho-etch) on upper electrode layer 16 Unit 19b, several electrode units 19b connect into favour as an electrod-array unit 22, by four electrod-array units 22 Stone electric bridge.

Step k, using chemical vapour deposition technique (CVD) continue on upper electrode layer 16 preparation with a thickness of 100nm~ The SiNx film of 300nm, as insulating layer 17.

Claims (10)

1. a kind of MEMS capacitive sensor, including set gradually from lower to upper substrate (10), lower separation layer (11), lower electricity Pole layer (12), upper separation layer (13), sacrificial layer (14), vibrating diaphragm layer (15), upper electrode layer (16), insulating layer (17), lower electrode layer (12) and upper electrode layer (16) includes at least one electrod-array unit (22), and electrod-array unit (22) includes multiple electrodes Unit, which is characterized in that the electrode unit (19b) of the electrode unit (19a) and/or upper electrode layer (16) of lower electrode layer (12) Edge has multiple notches (20).
2. MEMS capacitive sensor according to claim 1, which is characterized in that lower electrode layer (12) and upper electrode layer (16) notch (20) on opposite electrode unit is staggered.
3. MEMS capacitive sensor according to claim 1 or 2, which is characterized in that notch (20) is evenly distributed on The edge of the electrode unit.
4. MEMS capacitive sensor according to claim 1, which is characterized in that the shape of notch (20) be it is round, Or triangle or rectangle.
5. MEMS capacitive sensor according to claim 1, which is characterized in that notch (20) is inwardly no more than 10um。
6. MEMS capacitive sensor according to claim 1, which is characterized in that upper electrode layer (16) electrode unit The area of (19b) is less than the area of lower electrode layer (12) electrode unit (19a).
7. MEMS capacitive sensor according to claim 1, which is characterized in that the electrode unit is circle, on The diameter of electrode layer (16) circular electrode unit is 2-4um smaller than the diameter of lower electrode layer (12) circular electrode unit.
8. MEMS capacitive sensor according to claim 1, which is characterized in that lower electrode layer (12) electrode unit Connecting line (21) between connecting line (18) between (19a) and upper electrode layer (16) electrode unit (19b) is staggered.
9. MEMS capacitive sensor according to claim 1, which is characterized in that the length of electrod-array unit (22) Successively decrease step by step, it is stepped.
10. according to claim 1, MEMS capacitive sensor described in 8 or 9, which is characterized in that lower electrode layer (12) and upper Electrode layer (16) includes four electrod-array units (22), four electrod-arrays of lower electrode layer (12) and upper electrode layer (16) Unit (22) is all connected with into Wheatstone bridge.
CN201910092073.0A 2019-01-30 2019-01-30 Compact high sensitivity MEMS capacitive sensor CN109831729A (en)

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CN102730628A (en) * 2012-06-08 2012-10-17 华中科技大学 Preparation method of carbon microelectrode array structure
US20130140655A1 (en) * 2011-12-01 2013-06-06 Industrial Technology Research Institute Mems acoustic transducer and method for fabricating the same
CN103607684A (en) * 2013-11-29 2014-02-26 上海集成电路研发中心有限公司 Capacitive silicon microphone and preparing method thereof
CN103713203A (en) * 2013-12-19 2014-04-09 清华大学 Miniature electric field sensor structure
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CN106454665A (en) * 2015-08-04 2017-02-22 英飞凌科技股份有限公司 System and method for a multi-electrode MEMS device
CN107963608A (en) * 2017-10-26 2018-04-27 江苏西贝电子网络有限公司 It is a kind of using voltage comparison method amplifying circuit of MEMS capacitor arrays and preparation method thereof
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Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1462878A (en) * 2003-06-20 2003-12-24 复旦大学 Sensor of chip contaonong microelectrode array
US20110154649A1 (en) * 2009-12-25 2011-06-30 Canon Kabushiki Kaisha Method of manufacturing capacitive electromechanical transducer
CN102158794A (en) * 2010-01-26 2011-08-17 佳能株式会社 Capacitive electromechanical transducer
US20130140655A1 (en) * 2011-12-01 2013-06-06 Industrial Technology Research Institute Mems acoustic transducer and method for fabricating the same
CN102730628A (en) * 2012-06-08 2012-10-17 华中科技大学 Preparation method of carbon microelectrode array structure
CN104422548A (en) * 2013-08-28 2015-03-18 中芯国际集成电路制造(北京)有限公司 Capacitive pressure sensor and formation method thereof
CN103607684A (en) * 2013-11-29 2014-02-26 上海集成电路研发中心有限公司 Capacitive silicon microphone and preparing method thereof
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US20180120110A1 (en) * 2015-07-01 2018-05-03 Shin Sung C&T Co., Ltd. Mems link mechanism used for gyroscope
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CN109261477A (en) * 2018-10-23 2019-01-25 浙江大学 A kind of micro electronmechanical piezoelectric supersonic wave transducer with etched hole and sectional type top electrode

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