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 kind of capacitive pressure transducer

Technical field

The present invention relates to a kind of capacitive pressure transducer, belong to microelectronics technology.

Background technology

Capacitive pressure transducer has that DC characteristic is stable, drift is little, low in energy consumption and the advantage such as temperature coefficient is little, is being used widely aspect the measurements such as pressure, angular velocity, acceleration.

For sensitivity and the linearity that improves capacitive pressure transducer, Shang Yonghong, Haojie Lv etc. are studied and report the structure of different capacitive transducers.In work formerly, mainly realize the improvement of capacitive transducer characteristic by changing electrode plate structure, shape etc.Such as: Shang Yonghong etc. utilize the island membrane structure to replace flat membrane structure, can improve the linearity of capacitive pressure transducer, still, have reduced the sensitivity of sensor node.HaojieLv etc. form the capacitive pressure transducer of groove structure by to the thin groove of parallel plate capacitor pressure transducer bottom crown etching, and it has enlarged the scope of capacitance change dynamometry, and still, its linearity is relatively poor, is unfavorable for the design of follow-up interface circuit.Chen Zhi has just waited by analyzing the deformation behavior of circular and quadrangular membrane, proposes to utilize circular rete that the structure of capacitive pressure transducer is optimized, and can improve its sensitivity.

But, formerly in the capacitive pressure transducer of design, have all the time measurement range, measure the imbalance problem between sensitivity and the linearity.

Summary of the invention

The objective of the invention is in order to propose a kind of capacitive pressure transducer.

The objective of the invention is to be achieved through the following technical solutions.

A kind of capacitive pressure transducer of the present invention comprises 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 also 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 bondings;

Described lower step 6 be a center with the rectangular parallelepiped of circular groove 5, and there is a layer insulating 4 on the surface of lower step 6;

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

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

The thickness of described circular islands 1 is greater than circular membrane 2 thickness, and circular islands 1 material is polysilicon, and circular membrane 2 thickness are 0.3-1 μ m, and the material of circular membrane 2 is polysilicon;

The degree of depth of described circular groove 5 is 0.55 μ m;

Described insulation course 4 is silicon oxy-nitride material, and the thickness that is positioned at the insulation course 4 of groove 5 is 0.2 μ m; Its effect is to prevent step and lower step 6 short circuits;

The material of described circular side wall 3 is polysilicon, and wall thickness is 1 μ m, and height is 0.5 μ m.

Described lower step 6 is silicon materials, and its thickness is 5 μ m, and length is 150 μ m, and wide is 150 μ m.

Beneficial effect

Capacitive pressure transducer of the present invention has high sensitivity, the linearity and larger measurement range.It has been alleviated measurement range in the traditional capacitance pressure transducer, has measured the contradictory problems between sensitivity and the linearity.

Description of drawings

Fig. 1 is the dimensional structure schematic diagram of capacitive pressure transducer of the present invention;

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

Fig. 3 is that capacitive pressure transducer electric capacity of the present invention is with pressure variation relation figure;

Embodiment

A kind of capacitive pressure transducer comprises 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 also 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 bondings;

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

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

The thickness of described circular islands 1 is 0.5 μ m, and the radius of circular islands 1 is 50 μ m, and circular islands 1 material is polysilicon, and circular membrane 2 thickness are 0.4 μ m, and the material of circular membrane 2 is polysilicon; The radius of circular membrane 2 is 65 μ m;

The degree of depth of the recessed circle 5 of described circle is 0.55 μ m, and radius is 40 μ m;

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; Its effect is to prevent step and lower step 6 short circuits;

The material of described circular side wall 3 is polysilicon, and wall thickness is 1 μ m, and height is 0.5 μ m.

The air pressure of described top crown and center amount of deflection ω ₀The pass be:

$\frac{{\mathrm{<figure-callout\; id="4"\; label="pR"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">pR</figure-callout>}}^4}{{\mathrm{<figure-callout\; id="4"\; label="Eh"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">Eh</figure-callout>}}^4}=\frac{1}{A_p}\left(\frac{{\mathrm{\&omega;}}_0}{h}\right)+B_p\left(\frac{{{\mathrm{\&omega;}}_0}^3}{h^3}\right)---\left(1\right)$

In formula, p is the added air pressure of top crown, and E is Young modulus, and h is circular membrane 2 thickness, A _pAnd B _pAdjust coefficient for rigidity, its expression formula is:

$A_P=\frac{3(1-v^2)}{16}(1-\frac{R^4}{r^4}-4\frac{R^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\mathrm{In}\frac{r}{R})---\left(2\right)$

$B_p=\frac{\frac{7-v}{3}(1+\frac{R^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}+\frac{R^4}{r^4})+\frac{{(3-v)}^2}{1+v}-\frac{R^2}{r^2}}{(1-v)(1+\frac{R^4}{r^4})(1+\frac{R^2}{r^2})}---\left(3\right)$

In formula, R is the radius of circular membrane 2, and r is the radius of circular islands 1.According to (3) formula, by designing the radius of different circular islands 1, can optimize air pressure and center amount of deflection ω ₀The linearity, and then can improve electric capacity-pressure and change the linearity;

The radius of described circular membrane 2 is identical with the radius of circular side wall 3;

Doing the used time without ambient pressure, the capacitance C of above-mentioned pressure transducer represents with following formula:

$C=\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a\mathrm{\&pi;}({r_1}^2-{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}^2)}{{\mathrm{\&epsiv;}}_i{g}_1+{\mathrm{\&epsiv;}}_{a}d}+\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a{{\mathrm{\&pi;<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}^2}{{\mathrm{\&epsiv;}}_i(g_1+g_2)+{\mathrm{\&epsiv;}}_{a}d}---\left(4\right)$

In following formula, ε ₀Be the specific inductive capacity of vacuum, ε _iBe the specific inductive capacity of insulation course 4, ε _aBe the specific inductive capacity of air, d is the thickness of insulation course 4, and r1 is the inside radius of circular side wall 3, and r2 is the radius of circular recessed circle 5, and g1 is the height of circular side wall 3, and g2 is the degree of depth in circular recessed garden 5.

When ambient pressure acted on the top crown upper surface, the capacitance of pressure transducer was expressed as:

$C={\&Integral;}_0^{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}2}\frac{{2\mathrm{\&pi;\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a\mathrm{rdr}}{{\mathrm{\&epsiv;}}_{a}d+{\mathrm{\&epsiv;}}_i(g_1+g_2-\mathrm{\&omega;}(r,p))}+{\&Integral;}_{r1}^{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}2}\frac{{2\mathrm{\&pi;\&epsiv;}}_0{\mathrm{\&epsiv;}}_a{\mathrm{\&epsiv;}}_i\mathrm{rdr}}{{\mathrm{\&epsiv;}}_{a}d+{\mathrm{\&epsiv;}}_i(g_1-\mathrm{\&omega;}(r,p))}---\left(5\right)$

In following formula, ω (r, p) is any amount of deflection at radius r place on circular membrane 2.From the formula of (4) (5), can find out, by increasing circular recessed circle 5, its degree of depth g2 has enlarged the space of circular membrane 2 amounts of deflection, is conducive to increase the scope of measurement.

The course of work is:

At first, external atmosphere pressure acts on the upper surface of circular islands 1, and under the atmospheric pressure effect, the position of circular membrane 2 moves down; The position of oblong film 2 moves down, and the distance between upper step and lower step reduces, and according to (5) formula, sensor capacitance increases.

Secondly, under different external atmosphere pressure effects, the position that circular membrane 2 moves down is different, and the distance between upper step and lower step is different, and the electric capacity of sensor is different.

At last, the electric capacity different according to sensor can be measured the atmospheric pressure that acts on circular islands 1, realizes that capacitive pressure transducer is to the measurement of pressure.

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further details.

Embodiment

As depicted in figs. 1 and 2, a kind of capacitive pressure transducer comprises 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 also 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 bondings;

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

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

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, and circular membrane 2 thickness are 0.5 μ m, and the material of circular membrane 2 is polysilicon; The radius of circular membrane 2 is 65 μ m;

The degree of depth of the recessed circle 5 of described circle is 0.55 μ m, and radius is 40 μ m;

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; Its effect is to prevent step and lower step 6 short circuits;

The material of described circular side wall 3 is polysilicon, and wall thickness is 1 μ m, and height is 0.5 μ m.

The air pressure of described top crown and center amount of deflection ω ₀The pass be:

$\frac{{\mathrm{<figure-callout\; id="4"\; label="pR"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">pR</figure-callout>}}^4}{{\mathrm{<figure-callout\; id="4"\; label="Eh"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">Eh</figure-callout>}}^4}=\frac{1}{A_p}\left(\frac{{\mathrm{\&omega;}}_0}{h}\right)+B_p\left(\frac{{{\mathrm{\&omega;}}_0}^3}{h^3}\right)---\left(1\right)$

In formula, p is the added air pressure of top crown, and E is Young modulus, and h is circular membrane 2 thickness, A _pAnd B _pAdjust coefficient for rigidity, its expression formula is:

$A_P=\frac{3(1-v^2)}{16}(1-\frac{R^4}{r^4}-4\frac{R^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\mathrm{In}\frac{r}{R})---\left(2\right)$

$B_p=\frac{\frac{7-v}{3}(1+\frac{R^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}+\frac{R^4}{r^4})+\frac{{(3-v)}^2}{1+v}-\frac{R^2}{r^2}}{(1-v)(1+\frac{R^4}{r^4})(1+\frac{R^2}{r^2})}---\left(3\right)$

In formula, R is the radius of circular membrane 2, and r is the radius of circular islands 1.According to (3) formula, by designing the radius of different circular islands 1, can optimize pressure and center amount of deflection ω ₀The linearity, and then can improve electric capacity-pressure and change the linearity;

The radius of described circular membrane 2 is identical with the radius of circular side wall 3;

Doing the used time without external atmosphere pressure, the capacitance C of above-mentioned pressure transducer represents with following formula:

$C=\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a\mathrm{\&pi;}({r_1}^2-{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}^2)}{{\mathrm{\&epsiv;}}_i{g}_1+{\mathrm{\&epsiv;}}_{a}d}+\frac{{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a{{\mathrm{\&pi;<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}^2}{{\mathrm{\&epsiv;}}_i(g_1+g_2)+{\mathrm{\&epsiv;}}_{a}d}---\left(4\right)$

In following formula, ε ₀Be the specific inductive capacity of vacuum, ε _iBe the specific inductive capacity of insulation course 4, ε _aBe the specific inductive capacity of air in cavity, d is the thickness of insulation course 4, r ₁Be the inside radius of circular side wall 3, r ₂Be the radius of the recessed circle 5 of circle, g ₁Be the height of circular side wall 3, g ₂The degree of depth for the recessed garden 5 of circle.

When external atmosphere pressure acted on circular islands 1, the capacitance of pressure transducer was expressed as:

$C={\&Integral;}_0^{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}2}\frac{{2\mathrm{\&pi;\&epsiv;}}_0{\mathrm{\&epsiv;}}_i{\mathrm{\&epsiv;}}_a\mathrm{rdr}}{{\mathrm{\&epsiv;}}_{a}d+{\mathrm{\&epsiv;}}_i(g_1+g_2-\mathrm{\&omega;}(r,p))}+{\&Integral;}_{r1}^{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000839612100012.png"\; state="\{\{state\}\}">r</figure-callout>}2}\frac{{2\mathrm{\&pi;\&epsiv;}}_0{\mathrm{\&epsiv;}}_a{\mathrm{\&epsiv;}}_i\mathrm{rdr}}{{\mathrm{\&epsiv;}}_{a}d+{\mathrm{\&epsiv;}}_i(g_1-\mathrm{\&omega;}(r,p))}---\left(5\right)$

In following formula, ω (r, p) is any amount of deflection at radius r place on circular membrane 2.From (5) formula, can find out, by increasing circular recessed circle 5, enlarged the space of circular membrane 2 amounts of deflection, it is conducive to increase the scope of measurement.

The course of work is:

At first, external atmosphere pressure acts on the upper surface of circular islands 1, and under the atmospheric pressure effect, the position of circular membrane 2 moves down; The position of oblong film 2 moves down, and the distance between upper step and lower step reduces, and according to (5) formula, sensor capacitance increases.

Secondly, under different external atmosphere pressure effects, the position that circular membrane 2 moves down is different, and the distance between upper step and lower step is different, and the electric capacity of sensor is different.

At last, the electric capacity different according to sensor can be measured the atmospheric pressure that acts on circular islands 1, realizes that capacitive pressure transducer is to the measurement of pressure.

With described capacitive pressure transducer, utilize ANSYS software to carry out experimental analysis.Impressed pressure from 25kPa in the 225kPa scope, obtain result curve figure as shown in Figure 3.Result curve figure shown in Figure 3 is divided into two zones (I, II).Wherein, measurement range corresponding to II district is from 85kPa to 215kPa, and measurement sensitivity is 0.0019pF/kPa, and the linearity is 0.9941.

For this reason, described capacitive pressure transducer has high measurement sensitivity, the linearity and larger measurement range.

The II district of result curve figure shown in Figure 3 is the linear measurement district of described capacitive pressure transducer.

Capacitive pressure transducer of the present invention, design parameter are that circular islands thickness is 0.5 μ m, and radius is 50 μ m; Circular membrane thickness is 0.4 μ m, and radius is 65 μ m; The circular recessed round degree of depth is 0.55 μ m, and radius is 45 μ m; Circular side wall is high is 0.3 μ m; Thickness of insulating layer is 0.2 μ m.When the air pressure that acts on top crown was 100kPa, the electric capacity of described capacitive pressure transducer was 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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