CN103528567A - Tilt angle sensor based on pressure sensing - Google Patents

Abstract

The invention discloses an inclination sensor based on pressure sensing, which includes a substrate, two micro pressure sensors and a cover plate, a vertical deep groove is arranged in the middle of the substrate, and a pressure elastic membrane is arranged at the bottom of the substrate , the micro-pressure sensor is arranged at a symmetrical position at the bottom of the pressure elastic membrane; liquid is filled in the deep groove and above the pressure elastic membrane, and the cover plate is sealed above the deep groove; an insulating A dielectric membrane, the insulating dielectric membrane covers the pressure elastic membrane and the two micro pressure sensors. The inclination sensor based on pressure sensing provided by the present invention has a clear principle, can be manufactured in batches by using mature silicon processing technology, has low cost, and is easy to integrate with circuits; the micro pressure sensor can use a piezoresistive stress sensor to detect pressure changes , the signal processing is simple; the micro pressure sensor is mainly used to detect the stress difference and has no temperature drift effect.

Description

A Tilt Sensor Based on Pressure Sensing

technical field

The invention relates to an inclination sensor based on pressure sensing, in particular to an inclination sensor with two micro pressure sensors arranged in symmetrical positions manufactured on the basis of micro-machining technology.

Background technique

Level gauges are widely used in many industries today, and are often used in mechanical processing, medical and biochemical systems, precision instrument installation, construction, road engineering, and military ships. The traditional bubble level is the bubble level, which can measure the inclination of the one-dimensional level and the two-dimensional level, but the data is read by the naked eye and cannot be automatically measured, so there will be certain errors in the measurement and the accuracy is low. The main working principle of the new electronic level or inclination sensor is capacitive and inductive. It uses solid swing to realize induction and automatic measurement. It can measure the balance of high-precision mechanical structures, such as lathes and precision instruments. With the development of micro-processing technology, the use of silicon micro-manufacturing technology reduces the size of the device, the structure of the inclinometer is more precise, and can be integrated with the circuit, which can make the measurement more accurate.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides an inclination sensor based on pressure sensing, which detects the unbalanced state of the liquid through two micro-pressure sensors arranged at symmetrical positions. The principle is clear and the structure is simple. .

Technical scheme: in order to achieve the above object, the technical scheme adopted in the present invention is:

An inclination sensor based on pressure sensing, including a substrate, two micro pressure sensors and a cover plate, a vertical bottomless deep groove with a symmetrical cross-sectional shape is provided in the middle of the substrate, and a pressure sensor is provided at the bottom of the substrate Elastic film (ie, pressure sensitive film), the pressure elastic film seals the bottom of the deep groove, and the pressure elastic film is symmetrical to the symmetry line of the deep groove section, and the two micro pressure sensors are respectively arranged at the bottom of the pressure elastic film, The position below the deep groove (preferably set at the edge of the deep groove section, the pressure response at this position is more obvious), and the two micro pressure sensors are symmetrical to the symmetry line of the deep groove section; in the deep groove, the pressure elastic membrane There is a liquid above the pressure elastic membrane. When the position of the pressure elastic membrane is horizontal, there is a gap between the liquid level of the liquid and the upper edge of the deep groove, and the cover plate is sealed above the deep groove; the bottom of the pressure elastic membrane is provided with an insulating medium film The insulating dielectric film covers the pressure elastic film and the two micro-pressure sensors except for the connection position of the metal lead, and the insulating dielectric film is used for protection to realize electrical isolation.

Preferably, the micro pressure sensor is a one-dimensional structural stress detection sensor or a two-dimensional structural stress detection sensor. Preferably, the stress detection sensor made by semiconductor piezoresistive technology is used as the micro pressure sensor, and the two micro pressure sensors are arranged at symmetrical positions on the edge of the pressure elastic film: if a one-dimensional structural stress detection sensor is used, it is generally arranged at the edge of the pressure elastic film. On the two long opposite sides, and the center is symmetrical; if a two-dimensional structural stress detection sensor is used, it is generally arranged on the two opposite sides of the pressure elastic membrane, and the center is symmetrical.

Preferably, the density of the liquid is greater than or equal to the density of water, which increases the force on the pressure elastic membrane at the bottom, makes it easier for the micro pressure sensor to detect pressure changes, and improves the detection sensitivity.

Preferably, the substrate is a silicon wafer or other semiconductor materials.

Preferably, the cover plate is sealed above the deep groove by means of sealant or glass-silicon anode bonding or glass-silicon eutectic bonding.

Preferably, the cover plate is made of silicon, glass, plastic or metal.

Preferably, the substrate has a circular or square structure, and of course it can also be in other shapes, such as a regular polygon.

Preferably, the cross-sectional shape of the deep groove is a circle or a regular polygon, and the number of sides of the regular polygon is preferably an even number.

Preferably, the substrate and the pressure elastic membrane are integrally structured, and a vertical bottomed groove is arranged on the integral structure, and the area surrounded by the vertical side walls of the groove serves as a deep groove, and the groove The part above the cross-section of the bottom surface is used as the substrate, and the part below the cross-section of the bottom surface of the groove is used as the pressure elastic film.

When the sensor in this case is placed horizontally, the liquid generates uniform pressure on the pressure elastic film at the bottom, and the output signals of the two micro pressure sensors are the same. The pressure sensor can detect the pressure difference, which is proportional to the inclination angle. After a certain calibration, it can reflect the inclination angle of the system measured by the sensor.

Beneficial effects: the inclination sensor based on pressure sensing provided by the present invention has a clear principle, can be manufactured in batches by using mature silicon processing technology, has low cost, and is easy to integrate with circuits; the micro pressure sensor can use a piezoresistive stress sensor Detect pressure changes, signal processing is simple; micro pressure sensor is mainly used to detect stress difference, no temperature drift effect.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

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

As shown in Figure 1, it is a kind of inclination sensor based on pressure sensing, which is characterized in that: it includes a substrate 1, two micro pressure sensors 2 and a cover plate 6, and the middle part of the substrate 1 is provided with a vertical symmetric cross-sectional shape To the bottomless deep groove, a pressure elastic film 7 is arranged at the bottom of the substrate 1, the pressure elastic film 7 seals the bottom of the deep groove, and the pressure elastic film 7 is symmetrical to the sectional symmetry line of the deep groove, and the two Two micro-pressure sensors 2 are respectively arranged at the bottom of the pressure elastic membrane 7 and the position below the deep groove, and the two micro-pressure sensors 2 are symmetrical to the sectional symmetry line of the deep groove; There is a liquid 5, when the position of the pressure elastic membrane 7 is horizontal, there is a gap between the liquid level of the liquid 5 and the upper edge of the deep groove, and the cover plate 6 is sealed above the deep groove; an insulating dielectric film is arranged at the bottom of the pressure elastic membrane 7 3. The insulating dielectric film 3 covers the pressure elastic film 7 and the two micro pressure sensors 2 except for the connection position of the metal leads; the micro pressure sensors 2 are led out through the metal leads 4 for driving and measurement.

The micro pressure sensor 2 is a one-dimensional structural stress detection sensor or a two-dimensional structural stress detection sensor; the cover plate 6 is sealed above the deep groove by sealant or glass-silicon anode bonding or glass-silicon eutectic bonding. The substrate 1 has a circular or square structure; the cross-sectional shape of the deep groove is circular or regular polygonal.

The substrate 1 and the pressure elastic film 7 can be designed as an integrated structure, and a vertical bottomed groove is arranged on the integrated structure, and the area surrounded by the vertical side walls of the groove is used as a deep groove. The part above the cross-section of the bottom of the groove is used as the substrate 1 , and the part below the cross-section of the bottom of the groove is used as the pressure elastic film 7 .

When the sensor is placed horizontally, the pressure of the liquid 5 on the pressure elastic membrane 7 is uniform at this time, and the output of the micro pressure sensor 2 placed on the edge of the pressure elastic membrane 7 is equal, and the pressure difference is 0. When the whole sensor is tilted, because the liquid 5 in the deep groove remains horizontal at a steady state, the pressure of the liquid 5 on the bottom pressure elastic membrane 7 will be different due to the difference in liquid height, and the edge of the pressure elastic membrane 7 is placed The output of the micro pressure sensor 2 also produces a difference, and its output voltage is proportional to the pressure difference, and the actual inclination angle can be reflected through subsequent calibration.

The manufacturing process of the inclination sensor based on the pressure sensor in this case is as follows: use silicon as the substrate, make a high-sensitivity strain piezoresistor at a symmetrical position on the surface, make a deep groove by etching the bottom, and make a pressure-sensitive film on the surface of the silicon wafer. The sheet is turned upside down and filled with part of the liquid to seal the surface; the specific production process is as follows:

1. Select N-type (100) silicon as the substrate 1, and then use a thermal oxidation process to form a layer of silicon dioxide on the surface as the insulating dielectric layer 3;

2. Photoetching the silicon oxide insulating dielectric layer 3, and using a buffered hydrofluoric acid solution to etch the silicon oxide insulating dielectric layer 3 to expose the two micro pressure sensor 2 regions, using ion implantation of boron impurities and annealing to form the micro pressure sensor 2;

3. Carry out photolithography again, and use buffered hydrofluoric acid solution to etch the silicon oxide insulating dielectric layer 3 to expose the lead hole, then use magnetron sputtering process to deposit aluminum metal, photolithographically etch the aluminum and use hot phosphoric acid to etch the metal aluminum to form a metal lead 4;

4. Perform photolithography on the back of the substrate 1, etch the silicon oxide to form a silicon groove window, and then use dry deep reactive ion etching or wet tetramethyl hydroxide ammonium to etch the silicon to form a deep groove. At this time, the bottom of the deep groove remains The uncorroded part of the silicon below is used as the pressure sensitive film 7;

5. Place the back side up, and use a precision dropper to pour liquid 5 into the deep groove. The liquid can be water or other heavy-density liquids such as salt water or mercury, etc., do not fill it up;

6. The surface is sealed with a cover plate 6 through a sealant.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (9)

1. An inclination sensor based on pressure sensing, characterized in that: it includes a substrate (1), two micro pressure sensors (2) and a cover plate (6), and the middle part of the substrate (1) is provided with a symmetrical A vertical bottomless deep groove with a cross-sectional shape, a pressure elastic film (7) is arranged at the bottom of the substrate (1), the pressure elastic film (7) seals the bottom of the deep groove, and the pressure elastic film (7) is opposite Symmetrical to the line of symmetry in the cross section of the deep groove, the two micro pressure sensors (2) are respectively arranged at the bottom of the pressure elastic membrane (7) and below the deep groove, and the two micro pressure sensors (2) are relative to the cross section of the deep groove The line of symmetry is symmetrical; liquid (5) is contained in the deep groove above the pressure elastic membrane (7), and when the position of the pressure elastic membrane (7) is horizontal, the liquid level of the liquid (5) and the upper edge of the deep groove There is a gap, the cover plate (6) is sealed above the deep groove; the bottom of the pressure elastic film (7) is provided with an insulating dielectric film (3), and the insulating dielectric film (3) is covered except for the connection position of the metal lead wire Cover the pressure elastic membrane (7) and the two micro pressure sensors (2). 2. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the micro pressure sensor (2) is a one-dimensional structural stress detection sensor or a two-dimensional structural stress detection sensor. 3. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the density of the liquid (5) is greater than or equal to the density of water. 4. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the substrate (1) is a silicon substrate. 5. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the cover plate (6) is sealed above the deep groove by sealant or glass-silicon anode bonding or glass-silicon eutectic bonding . 6. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the cover plate (6) is made of silicon, glass, plastic or metal. 7. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the substrate (1) has a circular or square structure. 8. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the cross-sectional shape of the deep groove is a circle or a regular polygon. 9. The inclination sensor based on pressure sensing according to claim 1, characterized in that: the substrate (1) and the pressure elastic film (7) are integrally structured, and a vertical bottomed A groove, the area surrounded by the vertical side walls of the groove is used as a deep groove, the part above the bottom cross section of the groove is used as a substrate (1), and the part below the bottom cross section of the groove is used as a pressure elastic membrane (7) .

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