CN102262107A

CN102262107A - Capacitive relative humidity sensor for micro-electromechanical system

Info

Publication number: CN102262107A
Application number: CN 201110098540
Authority: CN
Inventors: 赵成龙; 黄庆安; 秦明
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2011-04-20
Filing date: 2011-04-20
Publication date: 2011-11-30

Abstract

The invention discloses a capacitive relative humidity sensor for a micro-electromechanical system, which is characterized in that the humidity sensor comprises a substrate (1), an oxidation layer (2), a first capacitor electrode (3) and a second capacitor electrode (4), wherein the substrate (1) is provided with a cavity (5), the oxidation layer (2) is arranged on the substrate (1), and the first capacitor electrode (3) and the second capacitor electrode (4) are respectively arranged on the oxidation layer (2); the first capacitor electrode (3) and the second capacitor electrode (4) are arranged above the cavity (5); the first capacitor electrode (3) comprises a plurality of parallel first electrodes (33) and a first common end (31) for connecting the first electrodes (33) together; and each first electrode (33) is provided with a first free end (32) opposite to the first common end (31), and the first common end (31) is connected with the first free ends (32) through the first electrodes (33). The capacitive relative humidity sensor disclosed by the invention has the advantages of low cost, high precision, high anti-jamming capability and good long-term stability.

Description

The microelectromechanical systems Relative Humidity Sensor

Technical field

The present invention relates to a kind of MEMS(microelectromechanical systems based on standard CMOS (complementary metal oxide semiconductor (CMOS)) technology) Relative Humidity Sensor, especially a kind of MEMS relative humidity sensor that adopts air as the humidity sensitive medium.

Background technology

Moisture measurement has important use in fields such as industrial and agricultural production, national defence aviation, weather forecast, health care, food processing, environmental protection.Humidity sensor has developed a lot of years as the important component part in the humidity measurement system.Develop into the miniature humidity sensor that can adopt standard CMOS process to make at present by traditional humidity sensors such as initial psychrometer, hair hygrometers.The humidity sensor that processes with standard CMOS process has low in energy consumption, advantages such as volume is little, price is low, good product consistency, is the focus of humidity sensor research in recent years.In addition, utilize standard CMOS process easily that humidity sensor and testing circuit monolithic is integrated, can improve the stability and the antijamming capability of Humidity Detection system like this.2004, Chinese Gu Lei has proposed the relative humidity sensor that a kind of CMOS of utilization technology is made, the sensing unit of this humidity sensor is the interdigital capacitor structure, palisade polysilicon heating resistor is placed the below of broach shape electrode, adopt polyimide as the humidity sensitive medium, highly sensitive, the linearity is good, but the hysteresis characteristic of sensor is not fine, and response is slower, heater circuit work can improve the temperature of humidity sensitive unit, and then accelerates the response speed of sensor, but the power consumption of sensor is increased.2006, Chinese Peng Shaohua has proposed a kind of humidity sensor of CMOS process compatible, this humidity sensor adopts polyimide as the humidity sensitive medium, testing circuit and humidity sensitive electric capacity monolithic is integrated, the humidity sensitive changes in capacitance is converted into change in voltage output, be convenient to the rear end detection system and carry out signal sampling and processing, but the humidity sensor response speed of this structure is slower.

Summary of the invention

Technical matters:The technical problem to be solved in the present invention is to propose MEMS Relative Humidity Sensor a kind of and the standard CMOS process compatibility, and it is fast to have response speed, linearity height, advantage such as temperature drift is little, and is simple in structure, and substrate is parasitic little.

Technical scheme:For solving the problems of the technologies described above, the present invention proposes a kind of MEMS Relative Humidity Sensor, this humidity sensor comprises the substrate that is provided with cavity, be located at the oxide layer on the substrate, be separately positioned on first capacitance electrode and second capacitance electrode on the oxide layer, first capacitance electrode and second capacitance electrode are arranged on the cavity top, first capacitance electrode comprises some first parallel electrodes, first common port that first electrode is linked together, each first electrode is provided with first free end relative with first common port, first electrode connects first common port and first free end, second capacitance electrode comprises some second parallel electrodes, second common port that second electrode is linked together, each second electrode is provided with second free end relative with second common port, and second electrode connects second common port and second free end; First free end does not contact with second common port, and second free end does not contact with first common port.

Preferably, be provided with second capacitance electrode between the first adjacent capacitance electrode, be provided with first capacitance electrode between the second adjacent capacitance electrode, first common port of first capacitance electrode and first free end all are fixed on the oxide layer, and second common port and second free end of the second capacitance electrode phase all are fixed on the oxide layer.

Preferably, first capacitance electrode, second capacitance electrode are respectively the aluminium electrode.

Beneficial effect:Processing step of the present invention is simple, utilizes standard CMOS process to combine with the MEMS process technology and makes, and cost is low, the precision height, and strong interference immunity, long-time stability are good.The humidity sensor that the present invention proposes adopts air as the humidity sensitive medium, linearity height, temperature drift is little, the oxide layer corrosion of substrate and top thereof is formed cavity, be air between the above and below of capacitance electrode and the capacitance electrode like this, make the response speed of sensor accelerate, the substrate ghost effect reduces.

Description of drawings

Fig. 1 is the vertical view of MEMS Relative Humidity Sensor provided by the invention, has among the figure: oxide layer 2, the first electrodes 33, the second electrodes 43, first common port, 31, the second common ports, 41, the first free ends, 32, the second free ends 42, first press welding block, 34, the second press welding blocks 44, cavity 5; Fig. 2 is the sectional view of MEMS Relative Humidity Sensor provided by the invention, has among the figure: substrate 1, oxide layer 2, the first capacitance electrodes 3, the second capacitance electrodes 4, cavity 5.

Embodiment

The present invention will be further described below in conjunction with accompanying drawing.

The present invention is a kind of MEMS Relative Humidity Sensor, by substrate, oxide layer, capacitance electrode is formed, oxide layer is located on the substrate, capacitance electrode is located on the oxide layer, capacitance electrode is drawn by press welding block, the oxide layer of corrosion substrate and top thereof, form cavity, make to be air between the above and below of capacitance electrode and the capacitance electrode, capacitance electrode is broach shape electrode and is staggered, the free end of the common port of every group of broach shape electrode and broach shape electrode all is fixed on the oxide layer, to guarantee the physical strength of capacitance electrode.

Referring to Fig. 1-2, the present invention is a kind of MEMS Relative Humidity Sensor, by substrate 1, oxide layer 2, first capacitance electrode 3, second capacitance electrode 4 is formed, oxide layer 2 is located on the substrate 1, first capacitance electrode 3 and second capacitance electrode 4 are located on the oxide layer 2, first capacitance electrode 3 and second capacitance electrode 4 are drawn respectively by first press welding block 34 and second press welding block 44, the oxide layer 2 of corrosion substrate 1 and top thereof, form cavity 5, make the below of the win capacitance electrode 3 and second capacitance electrode 4 also be air, first capacitance electrode 3 and second capacitance electrode 4 are broach shape electrode and are staggered, first free end 32 and second free end 42 of first common port 31 of every group of broach shape electrode and second common port 41 and broach shape electrode all are fixed on the oxide layer 2, to guarantee the physical strength of first capacitance electrode 3 and second capacitance electrode 4.

A kind of MEMS Relative Humidity Sensor provided by the invention, referring to Fig. 1, Fig. 2, this humidity sensor comprises a kind of MEMS Relative Humidity Sensor, this humidity sensor comprises the substrate 1 that is provided with cavity 5, be located at the oxide layer 2 on the substrate 1, be separately positioned on first capacitance electrode 3 and second capacitance electrode 4 on the oxide layer 2, first capacitance electrode 3 and second capacitance electrode 4 are arranged on cavity 5 tops, first capacitance electrode 3 comprises some first parallel electrodes 33, first common port 31 that first electrode 33 is linked together, each first electrode 33 is provided with first free end 32 relative with first common port 31, first electrode 33 connects first common port 31 and first free end 32, second capacitance electrode 4 comprises some second parallel electrodes 43, second common port 41 that second electrode 43 is linked together, each second electrode 43 is provided with second free end 42, the second electrodes 43 relative with second common port 41 and connects second common port 41 and second free ends 42; First free end 32 does not contact with second common port 41, and second free end 42 does not contact with first common port 31.

Be provided with second capacitance electrode 4 between the first adjacent capacitance electrode 3, be provided with first capacitance electrode 3 between the second adjacent capacitance electrode 4, first common port 31 and first free end 32 of first capacitance electrode 3 all are fixed on the oxide layer 2, and second common port 41 and second free end 42 of second capacitance electrode, 4 phases all are fixed on the oxide layer 2.

Wherein, first capacitance electrode 3 is drawn by first press welding block 34, and second capacitance electrode 4 is drawn by second press welding block 44.

First capacitance electrode 3, second capacitance electrode 4 are respectively the aluminium electrode.

Substrate 1 is a body silicon in the present embodiment, oxide layer 2 is a silicon dioxide, first capacitance electrode 3 and second capacitance electrode 4 are the aluminium electrode, the present invention can make of following technology: growth layer of oxide layer 2 on silicon substrate 1, then at silicon substrate 1 back side deposit one deck silicon nitride, restraining barrier as the silicon substrate corrosion, form first capacitance electrode 3 and second capacitance electrode 4 and first press welding block 34 and second press welding block 44 in silicon substrate 1 positive sputtered aluminum and etching, the silicon nitride barrier at the etching silicon chip back side forms the corrosion window of silicon substrate 1, utilize the body silicon anisotropic etching to corrode then from silicon substrate 1 back side to oxide layer 2 directions, the etchant solution of selecting for use to the corrosion rate of oxide layer 2 much smaller than the corrosion rate of this etchant solution to silicon substrate 1, when being corroded to oxide layer 2, silicon substrate 1 thinks that the corrosion of silicon substrate 1 finishes, at this moment in silicon substrate 1, obtain a cavity, the oxide layer 2 of this cavity top eroded just obtain cavity 5, this moment, the below of first capacitance electrode 3 and second capacitance electrode 4 also be an air, the silicon nitride barrier at silicon substrate 1 back side was eroded at last again.

The electric capacity that first capacitance electrode 3 and second capacitance electrode 4 constitute with air as the humidity sensitive medium, when ambient humidity changes, the specific inductive capacity of air can change, thereby make the humidity sensitive capacitance change, utilize capacitive detection circuit the humidity sensitive changes in capacitance to be detected the information that just can obtain ambient humidity again.Owing to be air between the above and below of first capacitance electrode 3 and second capacitance electrode 4 and first capacitance electrode 3 and second capacitance electrode 4, when ambient humidity changed, sensor is response fast.

Claims

1. microelectromechanical systems Relative Humidity Sensor, it is characterized in that: this humidity sensor comprises the substrate (1) that is provided with cavity (5), be located at the oxide layer (2) on the substrate (1), be separately positioned on first capacitance electrode (3) and second capacitance electrode (4) on the oxide layer (2), first capacitance electrode (3) and second capacitance electrode (4) are arranged on cavity (5) top, first capacitance electrode (3) comprises some parallel first electrodes (33), first common port (31) that first electrode (33) is linked together, each first electrode (33) is provided with first free end (32) relative with first common port (31), first electrode (33) connects first common port (31) and first free end (32), second capacitance electrode (4) comprises some parallel second electrodes (43), second common port (41) that second electrode (43) is linked together, each second electrode (43) is provided with second free end (42) relative with second common port (41), and second electrode (43) connects second common port (41) and second free end (42); First free end (32) does not contact with second common port (41), and second free end (42) does not contact with first common port (31).

2. microelectromechanical systems Relative Humidity Sensor according to claim 1, it is characterized in that: be provided with second capacitance electrode (4) between adjacent first capacitance electrode (3), be provided with first capacitance electrode (3) between adjacent second capacitance electrode (4), first common port (31) of first capacitance electrode (3) and first free end (32) all are fixed on the oxide layer (2), and second common port (41) and second free end (42) of second capacitance electrode (4) phase all are fixed on the oxide layer (2).

3. microelectromechanical systems Relative Humidity Sensor according to claim 1 and 2 is characterized in that: first capacitance electrode (3), second capacitance electrode (4) are respectively the aluminium electrode.