CN203479456U - Micro-machined vacuum sensor - Google Patents
Micro-machined vacuum sensor Download PDFInfo
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- CN203479456U CN203479456U CN201320441949.6U CN201320441949U CN203479456U CN 203479456 U CN203479456 U CN 203479456U CN 201320441949 U CN201320441949 U CN 201320441949U CN 203479456 U CN203479456 U CN 203479456U
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- brachium pontis
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Abstract
The utility model relates to a micro-machined vacuum sensor. The vacuum sensor comprises a first heat-conduction bridge arm and a second heat-conduction bridge arm arranged at the two ends of a micro bridge floor unit. The first heat-conduction bridge arm and the second heat-conduction bridge arm are connected with a first supporting point and a second supporting point through a first connecting pier and a second connecting pier respectively. The first supporting point and the second supporting point are located under the micro bridge floor unit, and gaps are reserved among the first supporting point, the second supporting point and the micro bridge floor unit. A resistance-type temperature-sensitive coating is arranged on the upper surface of the micro bridge floor unit. Bridge floor electrical connection wires are arranged on two opposite sides of the upper surface of the micro bridge floor unit respectively. Bridge arm electrical connection wires, which are connected with the corresponding bridge floor electrical connection wires, are arranged on the first heat-conduction bridge arm and the second heat-conduction bridge arm respectively. The two bridge arm electrical connection wires extend to the corresponding supporting points respectively. According to the micro-machined vacuum sensor, the bridge floor resistance is measured to calculate the vacuum degree of the environment. Meanwhile, the micro-machined vacuum sensor has the advantages of being high in sensitivity, small in size, compatible with a complementary metal-oxide-semiconductor (CMOS) process and the like.
Description
Technical field
The utility model relates to vacuum technique and microcosmic mechanical technique, specifically a kind of micromechanics vacuum transducer for heat-conducted vacuum meter.
Background technology
Heat-conducted vacuum meter is a kind of being positioned in environment to be measured, and measures pyroconductivity between a controlled thermal source and environment to be measured by suitable method, thereby indirectly extrapolates a kind of sensor of the vacuum pressure of environment to be measured.There is the relation of a quantification in the vacuum tightness of the thermal conductance of its method based on thermal source and surrounding environment and environment.Adopting a kind of typical vacuum transducer of this principle is Pirani ga(u)ge, monitors the change in resistance of a heated resistive conductor (such as platinum resistive conductor).When environment is low vacuum, it is many that resistive conductor passes to the heat of environment, heats later temperature rise relatively low, and resistance value raises smaller; It is larger that otherwise resistance raises.In addition, also have a kind of thermocouple vaccum gauge, its principle and Pi Lani vacuum transducer are similar, and just resistance wire is replaced by a thermopair, and the measurement of temperature is by measuring the electromotive force of galvanic couple.
Heat-conducted vacuum meter, because simple in structure, made easily and is widely used in the measurement of middle low vacuum in industry member.Yet, this class vacuum meter has following shortcoming: 1, stock, as platinum because can bring cross-contamination issue can not with existing CMOS process compatible, therefore can not be integrated with existing cmos circuit technique easily, thus the difficulty of cost and the difficulty of miniaturization brought.2, no matter be resistance-type or thermojunction type, the response ratio of its output is lower.For example, as the platinum of resistance-type material, the TCR of its material (Temperature Coefficient of Resistance, temperature-coefficient of electrical resistance, the temperature variant parameter of a kind of measurement material resistance) lower, only have 0.3% left and right, this need to amplify the signal of resistance variations by more complicated, sensitiveer amplifying circuit with regard to meaning.3, no matter be resistance-type or thermojunction type, its volume needing is all larger.Take resistance-type as example, and the bulk resistor of its common materials platinum is lower, obtain suitable resistance, must need long resistance wire, thereby brings larger volume.These drawbacks limit of the above-mentioned type vacuum meter its application in sensor and the higher field of integrated circuit degree of integration.
Therefore, a kind of have a high sensitivity, and volume is little, and the vacuum meter that the material using and technique can compatibility interface circuit technologies (conventionally adopting CMOS technique) has very huge practicality.For example, the sensor of the micromechanics electronic technology (MEMS) extensively adopting is now because its technique is derived from traditional CMOS integrated technique, employing be the integrated production technology of wafer model, there is volume little, high conformity, stable performance, advantage with low cost.As the pressure transducer adopting in current mobile device (as mobile phone, PDA, toy, camera) and automobile, acceleration transducer, what angular-rate sensor (gyro) all adopted is MEMS sensor.Yet the packaging technology of these devices or the packing forms based on traditional encapsulate individual devices after device detection cutting is complete.Obviously, this encapsulation mode based on individual devices and the wafer model in device production process are runed counter to, therefore caused the bottleneck reducing costs.
The trend of modern encapsulation technology is development wafer scale (WLP) encapsulation technology, and its packaging technology is as the organic part of device technology, employing be the technique of wafer form, after encapsulation, can cut out goods.This method can reduce the cost of encapsulation undoubtedly greatly, improves consistance and the reliability of device, and the miniaturization of device.Yet, this packing forms has also brought a lot of technical challenges, one of challenge is wherein how the required online detection unit of encapsulation to be integrated into unit to be packaged, vacuum meter such as the required test package of Vacuum Package rear chamber internal gas pressure, this will ask vacuum meter to have very little size, and and the process compatible of master reference.
Utility model content
The present invention is directed to the problems referred to above, a kind of micromechanics vacuum transducer is provided, this transducer sensitivity is high, small, and with CMOS process compatible.
According to technical scheme of the present invention: a kind of micromechanics vacuum transducer, comprise microbridge face unit, relative two ends, described microbridge face unit are respectively arranged with the first heat conduction brachium pontis and the second heat conduction brachium pontis being connected with described microbridge face unit, the free end of described the first heat conduction brachium pontis connects bridge pier by first and is connected with first strong point, the free end of described the second heat conduction brachium pontis connects bridge pier by second and is connected with second strong point, described first strong point and described second strong point below described microbridge face unit and and described microbridge face unit between there is gap; On the upper surface of described microbridge face unit, be provided with the temperature sensitive coating of resistance-type, the relative both sides of described microbridge face unit upper surface are respectively arranged with bridge floor electrical connection cabling, on described the first heat conduction brachium pontis and described the second heat conduction brachium pontis, be respectively arranged with the brachium pontis electrical connection cabling being connected with corresponding described bridge floor electrical connection cabling, two described brachium pontis electrical connection cablings extend to the corresponding strong point by corresponding connection bridge pier respectively.
The tie point of described the first heat conduction brachium pontis and described the second heat conduction brachium pontis and described microbridge face unit lays respectively at the diagonal position at two ends, described microbridge face unit.
Described gap is of a size of 0.5-5 micron.
Described microbridge face unit is silicon nitride substrate.
The temperature sensitive coating of described resistance-type is Titanium/titanium nitride, vanadium dioxide or α-amorphous silicon.
Described bridge floor electrical connection cabling and described brachium pontis electrical connection cabling are respectively Ti or NiCr alloy.
During test vacuum, first with a little electric current, measure the original resistance of described microbridge face unit, then with suitable large electric current, measure the resistance value of described microbridge face unit, utilize the ratio of above-mentioned two resistance values to calculate vacuum values.
Technique effect of the present invention is: the present invention adopts micro-bridge structure, and adopts temperature sensing material to form bridge floor resistance, calculates the vacuum tightness of environment by measuring bridge floor resistance, have highly sensitive, small, and and the remarkable advantage such as CMOS process compatible.
accompanying drawing explanation
Fig. 1 is structural representation of the present invention.
Fig. 2 is that the thermal conductivity of gas is with the variation diagram of the pressure of gas.
Fig. 3 (a)-Fig. 3 (e) is for making process sequence diagram of the present invention.
Fig. 4 (a), Fig. 4 (b) are for being used the schematic diagram of measurement of vacuum of the present invention.
Fig. 5 is a test result figure of the present invention.
embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is further described.
In Fig. 1～Fig. 5, comprise first strong point 1, first connects bridge pier 2, the first heat conduction brachium pontis 3, brachium pontis electrical connection cabling 4, bridge floor electrical connection cabling 5, the temperature sensitive coating 6 of resistance-type, second strong point 7, second connects bridge pier 8, the second heat conduction brachium pontis 9, both sides 10, microbridge face unit 11, gap 12, silicon nitride film 13, metal connects figure 14, sacrifice layer 15, bridge pier 16, window 17, conduct electricity temperature sensitive figure 18, metal connects 19, metal connects 20, passivation layer 21, resistance 22, electric connecting point 23, electric connecting point 24, peripheral circuit or equipment 25, measuring current 26, voltage 27 etc.
As shown in Figure 1, the utility model is a kind of micromechanics vacuum transducer, comprises microbridge face unit 11, and microbridge face unit 11 is silicon nitride substrate.
11 relative two ends, microbridge face unit are respectively arranged with the first heat conduction brachium pontis 3 and the second heat conduction brachium pontis 9 being connected with microbridge face unit 11.The tie point of the first heat conduction brachium pontis 3 and the second heat conduction brachium pontis 9 and microbridge face unit 11 lays respectively at the diagonal position at 11 two ends, microbridge face unit.The free end of the first heat conduction brachium pontis 3 connects bridge pier 2 by first and is connected with first strong point 1; The free end of the second heat conduction brachium pontis 9 connects bridge pier 8 by second and is connected with second strong point 7.First strong point 1 and second strong point 7 below microbridge face unit 11 and and microbridge face unit 11 between exist 12， gap, gap 12 to be of a size of 0.5-5 micron, different gaps is applicable to different vacuum measuring ranges.First strong point 1 and second strong point 7 can externally be electrically connected (on figure, not showing), are connected to its test circuit.
On the upper surface of microbridge face unit 11, be provided with the temperature sensitive coating 6 of resistance-type, the temperature sensitive coating 6 of resistance-type adopts the material with very big TCR coefficient and minimum low-frequency electronic noise, as Titanium/titanium nitride, vanadium dioxide or α-amorphous silicon.The relative both sides 10 of microbridge face unit 11 upper surfaces are respectively arranged with bridge floor electrical connection cabling 5, on the first heat conduction brachium pontis 3 and the second heat conduction brachium pontis 9, be respectively arranged with 4, two the brachium pontis electrical connection cablings 4 of brachium pontis electrical connection cabling that are connected with corresponding bridge floor electrical connection cabling 5 and by corresponding connection bridge pier, extend to the corresponding strong point respectively.Bridge floor electrical connection cabling 5 and brachium pontis electrical connection cabling 4 are respectively Ti or NiCr alloy.
Microbridge face unit 11 in the utility model has just formed a bridge floor resistance in conjunction with electrical connection.When microbridge face unit 11 is by certain electric current, it forms certain Joule heat power on micro unit resistance, causes the temperature of micro unit to raise.The heat of the micro unit of heating can scatter and disappear with three main channels, and finally stabilised temperature is exactly the heat of electric current generation and passes through these three later results of channel dispersed heat balance, and its finally stabilised temperature depends on the radiating efficiency of these three channels.These three channels are: 1, heat radiation is scattered and disappeared; 2, by the thermal conductance of brachium pontis, scatter and disappear; 3, by and the thermal conductance in the gap of bottom surface scatter and disappear.Wherein heat radiation is scattered and disappeared and the thermal conductance of brachium pontis is scattered and disappeared and is basic fixing, and the vacuum tightness of environment is irrelevant, and scatters and disappears relevant with the vacuum tightness of environment by the thermal conductance of bottom surface.
When the utility model (being that air pressure is very little) under the very high environment of vacuum tightness, when bridge floor passes through certain electric current, at bridge floor, form certain Joule heat, it is by very little with bottom surface gap conductance dispersed heat, cause the temperature rise ratio of bridge floor higher, thereby cause the variation of bridge floor resistance larger.If bridge floor temperature sensing material adopts the material of negative temperature coefficient as amorphous silicon membrane, its resistance presents larger reduction, and the reduction of this resistance can obtain by the electric current of bridge floor and the voltage drop at bridge floor resistance two ends by measuring.Like this, by measuring last equilibrium temperature, can extrapolate the vacuum tightness of environment.And equilibrium temperature can be determined by measuring the resistance of micro unit.The thermal conductance type vacuum meter of this micro-bridge structure has highly sensitive, small, and and the remarkable advantage such as CMOS process compatible, be particularly useful for the vacuum monitoring after the encapsulation of non-refrigeration type far-infrared thermal radiation focal plane arrays (FPA), because the processing procedure of its manufacturing process and thermal radiation sensor is very close, can be in thermal radiation sensor technique integrated thermal conductance type vacuum meter, and without increasing any other process costs.
Principle of work of the present invention is as follows:
From gas kinetics viewpoint, the height of temperature is exactly the size of molecular thermalmotion mean kinetic energy, the macro manifestations that heat transfer process is carried.The methods analyst heat transfer process with stickiness similar phenomena can be used, and the thermal conductivity K of gas and the relation between microscopic quantity mean value v, λ etc. can be obtained
C in formula
vthe specific heat of gas system in isochoric process.
Above formula shows, the thermal conductivity of gas depends on the density p of gas, the specific heat at constant volume c of gas molecule mean speed v, mean free path λ and gas
v.
The relation of the viscosity η of gas and molecule microscopic quantity mean value v, λ etc.
The density p that depends on gas in system, the mean speed v of molecular thermalmotion, and mean free path λ, this tittle is determined by gas self property and status.
Above-mentioned two formulas relatively obtain
K＝ηc
V
Because c
vthe character that is only decided by gas molecule self, is constant, so the fundamental property of K is similar to η.
The viscosity η of gas keeps constant in very wide pressure range, only when pressure is very low, just shows the trend of variation.Under utmost point low pressure, the viscosity of gas is no longer constant, but is directly proportional to pressure.This is because the mean free path of molecule becomes very large under utmost point low pressure, while having surpassed the limit of container, the actual free path of molecule is by container wall, be that in the present invention, the gap of bridge floor and bottom surface limits, can think that the maximal value of mean free path of molecule is exactly the gap of bridge floor in the present invention.At this moment in the amount of tri-decision gas viscosity η of ρ, v and λ, only have ρ to be directly proportional to pressure, so gas viscosity η is directly proportional to pressure.So just can know the pressure of gas by measuring the thermal conductivity of gas.
The variation of the corresponding gas with various pressure of thermal conductivity of the clearance of the 2 μ m that Fig. 2 description is calculated.As can be seen from the figure, the thermal conductivity of air has a more linear variation with gas pressure intensity.
Make processing step of the present invention as shown in Fig. 3 (a)-Fig. 3 (e), specifically describe as follows:
Fig. 3 (a): the substrate of sensor is the silicon substrate to doping content no requirement (NR) deposits a layer thickness by the method for PECVD (plasma strengthen chemical vapor deposition) above and is on substrate
silicon nitride (SiNx) film 13, and then deposition last layer metal is used for making metal and connects.This layer of metal can be but be not limited to Al, Ti/TiN, and thickness is
and then adopt the method for photoetching+metal etch to form metal connection figure 14.
Fig. 3 (b): first make Polyimide coating as the sacrifice layer 15 of sensor, thickness is 1-3 μ m, needs depending on application.The material of this layer of sacrifice layer 15 should be exotic material, can bear follow-up high-temperature technology, as the PECVD SiNx depositing operation of 350 ℃.Then at metal, connect chemical wet etching on figure 14, form bowl-shape bridge pier 16.And then deposit last layer PECVD SiNx as microbridge face of the present invention, and above metal connects figure 14 windowing 17 for after metal connection prepare.Then adopt PECVD method deposition last layer temperature sensing material as amorphous silicon, chemical wet etching is to form the temperature sensitive figure 18 of needed conduction.
Fig. 3 (c): deposit again last layer metal on device as Ti, the smaller materials of thermal conductivity coefficient such as NiCr alloy.The figure that this metal etch forms later plays two effects, and a metal that is the metal that connects bridge pier and bridge pier below is connected figure 14 connects 19, and another is to be connected bridge pier and conducted electricity the metal of temperature sensitive figure 18 and be connected 20 by brachium pontis.
Fig. 3 (d): deposit again the effect that layer of sin x passivation layer 21 plays protection device on device.
Fig. 3 (e): device cutting is carried out plasma gas phase release process later, empties whole Polyimide sacrifice layers 15, and technique completes, and waits to be packaged.
The method that use the present invention carries out vacuum measurement is as shown in Fig. 4 (a), and the present invention is equivalent to a resistance 22, and it has two electric connecting points 23 and 24.While measuring vacuum, by peripheral circuit or equipment 25, inject a measuring current 26, thereby this electric current can form the temperature rise that joule power causes sensor bridge floor on sensor resistance 22, cause the variation of sensor electrical resistance, its variation can realize by the voltage 27 of survey sensor electric connecting point 23 and 24 simultaneously.
For obtaining measurement result more accurately, Injection Current has two values as shown in Fig. 4 (b), is respectively a little electric current I o and a large electric current I
1.While injecting little electric current I o, its joule power on bridge floor is smaller, and the temperature rise of bridge floor is also smaller, so the resistance of measuring (by the voltage and current ratio at calculating device two ends) has reflected the initial resistance of device substantially, and vacuum to be measured is irrelevant.And inject large electric current I
1time, bridge floor temperature rise is large, now the resistance of device and vacuum tightness close relation to be measured.So the comparator device measuring error that change in resistance can abatement device initial resistivity value deviation be brought under large electric current and little electric current both of these case, improves measuring accuracy.
Fig. 5 is the test result of a device producing.The initial resistivity value of this device is about 80k-Ohm, and measuring current is 15 μ A.When vacuum pressure reduces, resistance value is downward trend.This is because Joule heat causes the temperature rise of device bridge floor to strengthen, and the temperature sensing material that device is used has negative temperature effect (rising of material surface electrical resistance temperature and reduce), cause resistance decreasing, within the scope of the vacuum pressure of hundreds of millitorrs (mTorr), present good linearity.
Claims (6)
1. a micromechanics vacuum transducer, it is characterized in that: comprise microbridge face unit (11), relative two ends, described microbridge face unit (11) are respectively arranged with the first heat conduction brachium pontis (3) and the second heat conduction brachium pontis (9) being connected with described microbridge face unit (11), the free end of described the first heat conduction brachium pontis (3) connects bridge pier (2) by first and is connected with first strong point (1), the free end of described the second heat conduction brachium pontis (9) connects bridge pier (8) by second and is connected with second strong point (7), described first strong point (1) and described second strong point (7) be positioned at described microbridge face unit (11) below and and described microbridge face unit (11) between there is gap (12), on the upper surface of described microbridge face unit (11), be provided with the temperature sensitive coating of resistance-type (6), the relative both sides (10) of described microbridge face unit (11) upper surface are respectively arranged with bridge floor electrical connection cabling (5), on described the first heat conduction brachium pontis (3) and described the second heat conduction brachium pontis (9), be respectively arranged with the brachium pontis electrical connection cabling (4) being connected with corresponding described bridge floor electrical connection cabling (5), two described brachium pontis electrical connection cablings (4) extend to the corresponding strong point by corresponding connection bridge pier respectively.
2. according to micromechanics vacuum transducer claimed in claim 1, it is characterized in that: the tie point of described the first heat conduction brachium pontis (3) and described the second heat conduction brachium pontis (9) and described microbridge face unit (11) lays respectively at the diagonal position at two ends, described microbridge face unit (11).
3. according to micromechanics vacuum transducer claimed in claim 1, it is characterized in that: described gap (12) are of a size of 0.5-5 micron.
4. according to micromechanics vacuum transducer claimed in claim 1, it is characterized in that: described microbridge face unit (11) is silicon nitride substrate.
5. according to micromechanics vacuum transducer claimed in claim 1, it is characterized in that: the temperature sensitive coating of described resistance-type (6) is Titanium/titanium nitride, vanadium dioxide or α-amorphous silicon.
6. according to micromechanics vacuum transducer claimed in claim 1, it is characterized in that: described bridge floor electrical connection cabling (5) and described brachium pontis electrical connection cabling (4) are respectively Ti or NiCr alloy.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201320441949.6U CN203479456U (en) | 2013-07-24 | 2013-07-24 | Micro-machined vacuum sensor |
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| CN201320441949.6U CN203479456U (en) | 2013-07-24 | 2013-07-24 | Micro-machined vacuum sensor |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103424224A (en) * | 2013-07-24 | 2013-12-04 | 无锡微奇科技有限公司 | Micro-machined vacuum sensor |
| CN105021345A (en) * | 2014-04-28 | 2015-11-04 | 国家电网公司 | Full silicon structure MENS vacuum sensor |
| CN107976277A (en) * | 2016-10-20 | 2018-05-01 | 中国科学院苏州纳米技术与纳米仿生研究所 | Vacuum transducer based on graphene oxide and preparation method and application |
-
2013
- 2013-07-24 CN CN201320441949.6U patent/CN203479456U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103424224A (en) * | 2013-07-24 | 2013-12-04 | 无锡微奇科技有限公司 | Micro-machined vacuum sensor |
| CN105021345A (en) * | 2014-04-28 | 2015-11-04 | 国家电网公司 | Full silicon structure MENS vacuum sensor |
| CN107976277A (en) * | 2016-10-20 | 2018-05-01 | 中国科学院苏州纳米技术与纳米仿生研究所 | Vacuum transducer based on graphene oxide and preparation method and application |
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Owner name: WUXI YUANCHUANG HUAXIN MICROELECTROMECHANICAL CO., Free format text: FORMER OWNER: WUXI WEIQI SCIENCE + TECHNOLOGY CO., LTD. Effective date: 20150323 Owner name: WUXI WEIQI SCIENCE + TECHNOLOGY CO., LTD. Effective date: 20150323 |
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Effective date of registration: 20150323 Address after: 214200 No. 16 apricot Road, Yixing Economic Development Zone, Wuxi, Jiangsu Patentee after: WUXI YCM CHIP MICRO-ELECTRO-MECHANICAL CO., LTD. Patentee after: Wuxi Weiqi Science & Technology Co., Ltd. Address before: 214000 Jiangsu New District of Wuxi City Branch Park Chinese Sensor Network International Innovation Park B Building 1 floor Patentee before: Wuxi Weiqi Science & Technology Co., Ltd. |
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