CN103162894A - Capacitive pressure sensor - Google Patents

Abstract

The invention relates to a capacitive pressure sensor and belongs to the field of micro electronic techniques. The capacitive pressure sensor comprises an upper-level board, a lower-level board (6) and a round lateral wall (3). The upper-level board comprises a round island (1) and a round film (2), wherein the round island (1) is a cylinder, the round film (2) is a cylinder, the round island (1) is located above the round film (2), and the round island (1) is fixedly connected with the round film (2) in a bonding mode. The lower-level board (6) is a cuboid with the center provided with a round concave circle (5), an insulation layer is arranged on the surface of the lower-level board (6), and the upper-level board is fixedly connected with the lower-level board (6) in a bonding mode through the round lateral wall (3). The capacitive pressure sensor is high in sensitively, linearity and measurement range, and relieves the problems of the conflict among the measurement range, the measurement sensitivity and the linearity of a traditional capacitive pressure sensor at the same time.

Description

A capacitive pressure sensor

technical field

The invention relates to a capacitive pressure sensor, which belongs to the technical field of microelectronics.

Background technique

Capacitive pressure sensors have the advantages of stable DC characteristics, small drift, low power consumption, and small temperature coefficient, and are widely used in the measurement of pressure, angular velocity, and acceleration.

In order to improve the sensitivity and linearity of capacitive pressure sensors, Shang Yonghong, Haojie Lv et al. studied and reported the structures of different capacitive sensors. In the previous work, the improvement of the characteristics of the capacitive sensor was mainly achieved by changing the structure and shape of the plate. For example: Shang Yonghong et al. used the island membrane structure instead of the flat membrane structure, which can improve the linearity of the capacitive pressure sensor, but reduces the sensitivity of the sensor node. HaojieLv et al etched a thin groove on the lower plate of the parallel plate capacitive pressure sensor to form a capacitive pressure sensor with a groove structure, which expanded the range of capacitance change measurement force, but its linearity is poor, which is not conducive to subsequent Interface circuit design. Chen Zhigang et al. analyzed the deformation characteristics of circular and square membranes, and proposed that the use of circular membranes to optimize the structure of capacitive pressure sensors can improve their sensitivity.

However, in previously designed capacitive pressure sensors, there has always been an imbalance between measurement range, measurement sensitivity, and linearity.

Contents of the invention

The object of the present invention is to propose a capacitive pressure sensor.

The purpose of the present invention is achieved through the following technical solutions.

A capacitive pressure sensor of the present invention comprises an upper board, a lower board 6 and a circular side wall 3;

The upper plate includes a circular island 1 and a circular membrane 2, the circular island 1 is a cylinder, and the circular membrane 2 is also a cylinder; the circular island 1 is located above the circular membrane 2, and the circular island 1 and circular membrane 2 are bonded and fixedly connected;

The lower plate 6 is a cuboid with a circular groove 5 in the center, and the surface of the lower plate 6 has an insulating layer 4;

The radius of the circular island 1 is greater than the radius of the circular groove 5;

The upper-level board and the lower-level board 6 are bonded and fixedly connected through the circular side wall 3 .

The thickness of the circular island 1 is greater than the thickness of the circular film 2, the material of the circular island 1 is polysilicon, the thickness of the circular film 2 is 0.3-1 μm, and the material of the circular film 2 is polysilicon;

The depth of the circular groove 5 is 0.55 μm;

The insulating layer 4 is a silicon oxynitride material, and the thickness of the insulating layer 4 located in the groove 5 is 0.2 μm; its function is to prevent the short circuit between the upper board and the lower board 6;

The material of the circular side wall 3 is polysilicon, the wall thickness is 1 μm, and the height is 0.5 μm.

The lower plate 6 is made of silicon material, with a thickness of 5 μm, a length of 150 μm, and a width of 150 μm.

Beneficial effect

The capacitive pressure sensor of the invention has high sensitivity, linearity and large measurement range. It alleviates the conflicting problems among measurement range, measurement sensitivity and linearity in traditional capacitive pressure sensors.

Description of drawings

Fig. 1 is the dimension structure schematic diagram of capacitive pressure sensor of the present invention;

Fig. 2 is the structural representation of capacitive pressure sensor of the present invention;

Fig. 3 is the capacitive capacity of the capacitive pressure sensor of the present invention varies with pressure;

Detailed ways

A capacitive pressure sensor comprising an upper plate, a lower plate 6 and a circular side wall 3;

The upper plate includes a circular island 1 and a circular membrane 2, the circular island 1 is a cylinder, and the circular membrane 2 is also a cylinder; the circular island 1 is located above the circular membrane 2, and the circular island 1 and circular membrane 2 are bonded and fixedly connected;

The lower plate 6 is a cuboid with a circular concave circle 5 in the center, and the surface of the lower plate 6 has an insulating layer 4;

The upper-level board and the lower-level board 6 are bonded and fixedly connected through the circular side wall 3 .

The thickness of the circular island 1 is 0.5 μm, the radius of the circular island 1 is 50 μm, the material of the circular island 1 is polysilicon, the thickness of the circular film 2 is 0.4 μm, and the material of the circular film 2 is polysilicon; Membrane 2 has a radius of 65 μm;

The circular concave circle 5 has a depth of 0.55 μm and a radius of 40 μm;

The insulating layer 4 is a silicon oxynitride material, and the thickness of the insulating layer 4 located in the circular concave circle 5 is 0.2 μm; its function is to prevent the short circuit between the upper board and the lower board 6;

The material of the circular side wall 3 is polysilicon, the wall thickness is 1 μm, and the height is 0.5 μm.

The relationship between the air pressure of the upper pole plate and the central deflection _ω0 is:

$\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="pR"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">pR</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="Eh"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">Eh</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\frac{{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, p is the air pressure applied by the upper plate, E is Young's modulus, h is the thickness of the circular membrane 2, A _p and B _p are stiffness adjustment coefficients, and their expressions are:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; In</span>}\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{\frac{\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, R is the radius of the circular membrane 2, and r is the radius of the circular island 1. According to formula (3), by designing the radii of different circular islands 1, the linearity of air pressure and central deflection ω ₀ can be optimized, and then the capacitance-pressure variation linearity can be improved;

The radius of the circular membrane 2 is the same as that of the circular side wall 3;

When there is no external air pressure, the capacitance value C of the above-mentioned pressure sensor is expressed by the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the above formula, ε ₀ is the dielectric constant of vacuum, ε _i is the dielectric constant of the insulating layer 4, ε _a is the dielectric constant of air, d is the thickness of the insulating layer 4, and r1 is the inner diameter of the circular side wall 3 Radius, r2 is the radius of the circular concave circle 5, g1 is the height of the circular side wall 3, and g2 is the depth of the circular concave garden 5.

When the external air pressure acts on the upper surface of the upper plate, the capacitance value of the pressure sensor is expressed as:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;\&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; rdr</span>}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;\&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; rdr</span>}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In the above formula, ω(r, p) is the deflection at any radius r on the circular membrane 2 . From formulas (4) and (5), it can be seen that by increasing the depth g2 of the circular concave circle 5, the space for the deflection of the circular membrane 2 is enlarged, which is beneficial to increase the measurement range.

The working process is:

First, the external atmospheric pressure acts on the upper surface of the circular island 1, and under the action of the atmospheric pressure, the position of the circular membrane 2 moves downward; as the position of the circular membrane 2 moves downward, the distance between the upper plate and the lower plate decreases, According to (5), the capacitance of the sensor increases.

Secondly, under the action of different external atmospheric pressures, the downward movement position of the circular membrane 2 is different, the distance between the upper plate and the lower plate is different, and the capacitance of the sensor is different.

Finally, according to the different capacitances of the sensors, the atmospheric pressure acting on the circular island 1 can be measured to realize the measurement of the pressure by the capacitance pressure sensor.

The specific implementation manner of the present invention will be described in further detail below in conjunction with the accompanying drawings.

Example

As shown in Figures 1 and 2, a capacitive pressure sensor includes an upper board, a lower board 6 and a circular side wall 3;

The upper plate includes a circular island 1 and a circular membrane 2, the circular island 1 is a cylinder, and the circular membrane 2 is also a cylinder; the circular island 1 is located above the circular membrane 2, and the circular island 1 and circular membrane 2 are bonded and fixedly connected;

The lower plate 6 is a cuboid with a circular concave circle 5 in the center, and the surface of the lower plate 6 has an insulating layer 4;

The upper-level board and the lower-level board 6 are bonded and fixedly connected through the circular side wall 3 .

The thickness of the circular island 1 is 2 μm, the radius of the circular island 1 is 50 μm, the material of the circular island 1 is polysilicon, the thickness of the circular film 2 is 0.5 μm, and the material of the circular film 2 is polysilicon; 2 has a radius of 65 μm;

The circular concave circle 5 has a depth of 0.55 μm and a radius of 40 μm;

The insulating layer 4 is a silicon oxynitride material, and the thickness of the insulating layer 4 located in the circular concave circle 5 is 0.2 μm; its function is to prevent the short circuit between the upper board and the lower board 6;

The material of the circular side wall 3 is polysilicon, the wall thickness is 1 μm, and the height is 0.5 μm.

The relationship between the air pressure of the upper pole plate and the central deflection _ω0 is:

$\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="pR"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">pR</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; Eh</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\frac{{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, p is the air pressure applied by the upper plate, E is Young's modulus, h is the thickness of the circular membrane 2, A _p and B _p are stiffness adjustment coefficients, and their expressions are:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; In</span>}\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{\frac{\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, R is the radius of the circular membrane 2, and r is the radius of the circular island 1. According to formula (3), by designing the radii of different circular islands 1, the linearity of pressure and central deflection ω ₀ can be optimized, and then the linearity of capacitance-pressure change can be improved;

The radius of the circular membrane 2 is the same as that of the circular side wall 3;

When there is no external atmospheric pressure, the capacitance value C of the above-mentioned pressure sensor is expressed by the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the above formula, _ε0 is the dielectric constant of vacuum, _εi is the dielectric constant of the insulating layer 4, _εa is the dielectric constant of the air in the cavity, d is the thickness of the insulating layer 4, and _r1 is the circular side The inner radius of the wall 3, r ₂ is the radius of the circular concave circle 5, g ₁ is the height of the circular side wall 3, and g ₂ is the depth of the circular concave circle 5.

When the external atmospheric pressure acts on the circular island 1, the capacitance value of the pressure sensor is expressed as:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;\&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; rdr</span>}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;\&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; rdr</span>}}{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In the above formula, ω(r, p) is the deflection at any radius r on the circular membrane 2 . From formula (5), it can be seen that by adding the circular concave circle 5, the space for the deflection of the circular membrane 2 is expanded, which is beneficial to increase the measurement range.

The working process is:

First, the external atmospheric pressure acts on the upper surface of the circular island 1, and under the action of the atmospheric pressure, the position of the circular membrane 2 moves downward; as the position of the circular membrane 2 moves downward, the distance between the upper plate and the lower plate decreases, According to (5), the capacitance of the sensor increases.

Secondly, under the action of different external atmospheric pressures, the downward movement position of the circular membrane 2 is different, the distance between the upper plate and the lower plate is different, and the capacitance of the sensor is different.

Finally, according to the different capacitances of the sensors, the atmospheric pressure acting on the circular island 1 can be measured to realize the measurement of the pressure by the capacitance pressure sensor.

The capacitive pressure sensor was analyzed experimentally using ANSYS software. In the range of applied pressure from 25kPa to 225kPa, the result graph shown in Figure 3 is obtained. The resulting graph shown in Figure 3 is divided into two regions (I, II). Among them, the measurement range corresponding to Zone II is from 85kPa to 215kPa, the measurement sensitivity is 0.0019pF/kPa, and the linearity is 0.9941.

For this reason, the capacitive pressure sensor has high measurement sensitivity, linearity and large measurement range.

Zone II of the result graph shown in FIG. 3 is the linear measurement zone of the capacitive pressure sensor.

The specific parameters of the capacitive pressure sensor of the present invention are that the thickness of the circular island is 0.5 μm, and the radius is 50 μm; the thickness of the circular membrane is 0.4 μm, and the radius is 65 μm; the depth of the circular concave circle is 0.55 μm, and the radius is 45 μm; the circular side The wall height is 0.3 μm; the insulating layer thickness is 0.2 μm. When the air pressure acting on the upper plate is 100kPa, the capacitance of the capacitive pressure sensor is 0.6232pF.

Claims (7)

1. a capacitive pressure transducer, is characterized in that: comprise step, lower step (6) and circular side wall (3);

Described upper step comprises circular islands (1) and circular membrane (2), and circular islands (1) is a right cylinder, and circular membrane (2) is a right cylinder; Circular islands (1) is positioned at the top of circular membrane (2), and circular islands (1) is fixedly connected with circular membrane (2) bonding;

Described lower step (6) be a center with the rectangular parallelepiped of the recessed circle of circle (5), and there is a layer insulating (4) on the surface of lower step (6);

Be fixedly connected with by circular side wall (3) bonding between described upper step and lower step (6).

2. a kind of capacitive pressure transducer according to claim 1, it is characterized in that: the thickness of described circular islands (1) is 2 μ m, and the radius of circular islands (1) is 50 μ m, and circular islands (1) material is polysilicon.

3. a kind of capacitive pressure transducer according to claim 1 and 2, it is characterized in that: circular membrane (2) thickness is 0.5 μ m, and the material of circular membrane (2) is polysilicon; The radius of circular membrane (2) is 65 μ m.

4. a kind of capacitive pressure transducer according to claim 1, it is characterized in that: the degree of depth of the recessed circle of described circle (5) is 0.55 μ m, radius is 40 μ m.

5. a kind of capacitive pressure transducer according to claim 1 is characterized in that: described insulation course (4) is silicon oxy-nitride material, and the thickness that is positioned at the insulation course (4) of circular recessed circle (5) is 0.2 μ m.

6. a kind of capacitive pressure transducer according to claim 1, it is characterized in that: the material of described circular side wall (3) is polysilicon, and wall thickness is 1 μ m, and height is 0.5 μ m.

7. a kind of capacitive pressure transducer according to claim 1, it is characterized in that: the radius of described circular membrane (2) is identical with the radius of circular side wall (3).

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