JP4714909B2 - Capacitance detection circuit output signal correction method and tilt sensor - Google Patents

Description

  The present invention relates to a tilt sensor that accurately measures the tilt of a processing apparatus that performs wafer processing and precise processing in a semiconductor factory, for example.

  A sensor that electrically measures the magnitude of tilt is called a tilt sensor. Examples of the tilt sensor include a sensor using a laser and a sensor that measures a displacement amount of a mass point. In particular, a device for measuring the amount of displacement of a mass point has a simple structure and is often used for a small one.

As a technique relating to such a tilt sensor for measuring the amount of displacement of the mass point, for example, a technique in which a plurality of comb-shaped electrodes are formed using quartz and the tilt is measured by a change in capacitance between the plurality of electrodes is disclosed in Patent Document 1. Is disclosed. In the device disclosed in Patent Document 1, the change in capacitance is nonlinear, and it may be necessary to correct the change. As a circuit for correcting a nonlinear signal, there is one disclosed in Patent Document 2.
Japanese Patent No. 3944509 Japanese Patent Laid-Open No. 06-167351

  The tilt sensor disclosed in Patent Document 1 is the basis of the present invention. When attention is paid to one comb-shaped electrode, the movable electrode is displaced between a pair of fixed electrodes in accordance with the tilt, and one of the movable electrodes Approaches the corresponding fixed electrode, the other movable electrode moves away from the corresponding fixed electrode.

  That is, two capacitors are in series, and when the distance between the electrodes of one capacitor approaches Δx according to the displacement of the movable electrode, the distance between the electrodes of the other capacitor increases by Δx. Therefore, the capacity of one capacitor increases and the capacity of the other capacitor decreases.

  By the way, this inclination sensor can express the displacement amount x of a movable electrode with respect to inclination (theta) by Formula (1). Here, k is a spring constant.

The two differential capacitors C ₁ and C ₂ are charged with a controllable constant current for a certain period of time so that the average value of the voltages V ₁ and V ₂ after charging of each capacitor becomes equal to a specific reference voltage V _ref. The constant current is controlled. At this time, the output V _{out of the} detection circuit can be generally expressed by Expression (2). Further, the output voltage _Vout of the detection circuit that applies a voltage having an amplitude _Vref to the two capacitors and controls the charge amounts of the respective capacitors to be equal can be expressed as shown in Expression (2). Here, A is a constant.

From the above formulas (1) and (2), the relationship between the output V _{out of the} tilt sensor and the tilt θ can be expressed by formula (3). Here, A ′ is a constant.

Therefore, the output V _{out of the} tilt sensor is non-linear with respect to the tilt θ. However, there are cases where it is desirable that the output be linear depending on the intended use, such as when a change in capacitance is converted into a voltage, and in this case, correction of this nonlinearity becomes a problem.

  Further, the technology disclosed in Patent Document 2 is a method in which the capacitance changes due to the displacement of the diaphragm, and the non-linearity of the capacitance change is canceled by the non-linearity of the capacitance change on the opposite surface of the diaphragm. It is intended to enhance the nature.

  However, this is a configuration similar to the above-mentioned Patent Document 1 from the viewpoint of detecting a change in capacitance, and the idea of sufficiently correcting nonlinearity is not yet presented.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tilt sensor that can be used without correction when the change in capacitance is taken out as voltage conversion by improving the linearity of an output signal and is extremely easy to use.

  In addition, an object of the present invention is that when a displacement electrode disposed opposite to each fixed electrode oscillates between the two fixed electrodes to cause an inclination, one fixed electrode and a displacement opposed thereto are generated. The capacitance of each of the first capacitor formed by the electrode and the second capacitor formed by the other fixed electrode and the displacement electrode facing the first capacitor is changed, and the change in the capacitance is represented by the capacitance. In a tilt sensor that outputs a voltage change converted by a detection circuit, the linearity of the output signal of the capacitance detection circuit can be increased, and the output signal can be used without correction, making the use of the tilt sensor extremely easy. Another object of the present invention is to provide a method for correcting a capacitance detection circuit output signal.

  In order to solve the above-described problems, the tilt sensor according to the present invention has a displacement portion that is located between the pair of fixed portions and is displaced with respect to the fixed portion. The capacitance change of the two capacitors formed between the pair of fixed portions and the displacement portion due to the displacement is converted into a voltage change, and the charge amount of the capacitor is controlled according to each voltage. I made it.

That is, the tilt sensor according to the present invention includes a frame-shaped fixing portion formed of a thin plate, and a displacement portion formed of a thin plate and disposed on the same plane as the fixing portion and within the frame of the fixing portion. A pair of fixed electrodes extending toward the inside of the frame of the fixed portion and the displacement portion, and are respectively disposed between the pair of fixed electrodes so as to face the fixed electrodes. A capacitance detection circuit that converts a capacitance change of each of the two capacitors formed by the pair of displacement electrodes and each of the fixed electrodes and the displacement electrode facing the fixed electrodes into a voltage change; In addition, the capacitance detection circuit outputs the capacitance detection circuit so that the distance between each displacement electrode and the fixed electrode facing the displacement electrode is displaced by a change in direction of gravitational acceleration. The slope is measured by the voltage A tilt sensor capable Rukoto, and a voltage variable multiplying the difference between the voltages generated in each of the two capacitors the capacitance detecting circuit outputs, as the reference voltage to a sum of a predetermined magnitude of voltage The charge to the capacitor is controlled so that the average value of the voltages generated in the two capacitors or a constant multiple thereof is equal to the reference voltage, and the nonlinear component of the output voltage of the capacitance detection circuit is canceled out. A charge control circuit in which the value of the variable is determined is provided.

  According to this configuration, the displacement electrode that is located between the pair of fixed electrodes and is displaced with respect to the fixed electrode is displaced by the direction change of the gravitational acceleration. Along with this, the capacitance of the two capacitors formed between each pair of the fixed electrode and the displacement electrode changes, and the capacitance detection circuit converts this capacitance into a voltage change. The charge control circuit controls the charge charged to each capacitor in proportion to each voltage output from the capacitance detection circuit. Therefore, the displacement part is displaced by a slight acceleration, and the displacement can be detected by a change in the direction of gravitational acceleration between the fixed part and the displacement part, and the displacement of the displacement part can be detected as a voltage change. Even if the rate of change of the capacitor is small, the relationship between the slope and the output voltage can be nonlinearly corrected by increasing the charge amount.

In the present invention, the charge control circuit may calculate a variable multiple of a difference between a voltage generated in each of the control current source that generates current to be supplied to the two capacitors and the two capacitors that are output from the capacitance detection circuit. A reference voltage generation circuit that generates a reference voltage that is the sum of the voltage and a voltage of a predetermined magnitude, and an average value or a constant multiple of the voltage generated in each of the two capacitors is equal to the reference voltage. Thus, it can also be set as the structure provided with the current source control circuit which controls the output current of the said control current source.

According to this configuration, the two capacitors are charged by the capacitance detection circuit so that the output voltage and the reference voltage are equal. Further, the reference voltage changes in proportion to a change in voltage output from the capacitance detection circuit. Accordingly, as the slope θ increases, the rate of change ΔV _out / Δθ of the output voltage V _out of the capacitance detection circuit with respect to the change of the slope θ decreases. Here, do it the reference voltage is controlled so as to increase in proportion to the voltage change of the output voltage V _out, since [Delta] V _{out /} [Delta] [theta] acts so as to compensate for the smaller amount, the linear region of the output voltage V _out as a result It becomes possible to take large.

  In the present invention, the reference voltage generation circuit includes a constant voltage source that generates a constant voltage, an amplifier that amplifies a voltage output from the capacitance detection circuit, and a voltage that is generated by the constant voltage source. A voltage adding circuit that adds the output voltages and outputs the sum as the reference voltage may be provided.

  With this configuration, the reference voltage generation circuit can generate a reference voltage that changes in proportion to a change in voltage output from the capacitance detection circuit.

  Further, in the present invention, a pair of groove portions are formed in a concave shape on one side of the displacement portion, and inserted into the groove portions and in contact with the inside of the groove portion on one side in the frame of the fixed portion. Without extending, a pair of opposing portions are extended toward the inside of the frame, the fixed electrodes are formed on the side surfaces of the opposing sides of the opposing portions, and the displacement electrodes are provided in the groove portions. It can comprise so that it may form in the side surface of the edge | side facing a fixed electrode.

  In the present invention, the displacement part and the fixed part may be coupled by a flexible narrow part formed narrower than the width of the displacement part.

  Moreover, in this invention, you may form the said fixing | fixed part, the said displacement part, and the said narrow part integrally by processing one board | substrate.

  In the present invention, the fixed portion, the displacement portion, and the narrow portion may be integrally formed with a single crystal plate.

Further, the capacitance detection circuit output signal correction method according to the present invention is such that when an inclination is caused by the swing of the displacement electrode disposed opposite to each fixed electrode between the two fixed electrodes, Capacitances of the first capacitor formed by the fixed electrode and the displacement electrode opposed to the first fixed electrode, and the second capacitor formed by the other fixed electrode and the displacement electrode opposed thereto. A capacitance detection circuit that corrects a change in the output signal of the capacitance detection circuit to be linear or substantially linear in a tilt sensor that changes and outputs the change in capacitance to a voltage change by the capacitance detection circuit. a method of correcting the output signal, the charge control circuit, the capacitor and the voltage variable multiplying the difference between the voltages generated in each of the two capacitors detecting circuit outputs, electrodeposition predetermined size A reference voltage to the sum of the so that the average value or a constant multiple thereof of the voltage generated in the two capacitors is equal to the reference voltage, to control the charge to be charged to the capacitor, the output of the capacitance detecting circuit The value of the variable is determined so as to cancel the nonlinear component of the voltage.

  In this manner, the linearity of the output signal of the capacitance detection circuit is enhanced by controlling the charge charged to each capacitor to cancel the nonlinear component of the output voltage of the capacitance detection circuit. Therefore, the output signal of the capacitance detection circuit can be used without correction, and the use of the tilt sensor becomes extremely easy.

In the present invention, the charge control circuit includes a control current source, a reference voltage generation circuit, and a current source control circuit, and each current is supplied to the two capacitors by the control current source. The capacitor is charged, and a voltage obtained by multiplying the difference between the voltages generated in the two capacitors output from the capacitance detection circuit by the reference voltage generation circuit and a constant voltage _Vref0 having a predetermined magnitude The reference voltage that is the sum is generated, and the output of the control current source is set so that an average value or a constant multiple of the voltage generated in each of the two capacitors is equal to the reference voltage by the current source control circuit. By controlling the current, the charge charged in each of the two capacitors may be controlled.

  Thereby, it is possible to control the charge charged in each of the two capacitors so as to cancel the nonlinear component of the output voltage of the capacitance detection circuit.

  In the present invention, the reference voltage generation circuit includes a constant voltage source, an amplifier, and a voltage addition circuit. The constant voltage source generates a constant voltage, and the amplifier detects the capacitance detection circuit. The output voltage may be amplified, and the reference voltage may be generated by adding the voltage output from the amplifier to the voltage generated by the constant voltage source in the voltage adding circuit.

  As a result, the reference voltage output from the reference voltage generation circuit can be changed in proportion to the change in the voltage output from the voltage generation circuit.

  Since the tilt sensor of the present invention is configured as described above, when the fixed portion and the displacement portion are integrally formed, for example, each portion can be configured at a time by etching a quartz plate, etc. Can be increased.

  The displacement with respect to the tilt can be output as a voltage change, and the tilt can be detected by looking at the voltage.

  Then, the charge amount of the capacitor is changed according to the output voltage, and the charge charge of the capacitor is increased even when the capacitance change rate of the capacitor is small with respect to the change of the slope when the slope is large. Thus, the voltage change rate can be increased, and the nonlinearity of the output voltage can be corrected.

  Further, since the nonlinearity of the output voltage is corrected to make it linear, even if the inclination angle to be measured is increased, the relationship between the output voltage and the inclination angle is constant, and the inclination angle can be easily measured.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The tilt sensor according to the first embodiment of the present invention basically has a structure as shown in FIG. In FIG. 1, in the tilt sensor according to the first embodiment, a fixed portion 2 and a displacement portion 3 are formed by etching a substrate 1 such as a crystal. The fixed part 2 is formed in a substantially square frame shape. The displacement part 3 is formed in the frame of the fixed part 2. The displacement portion 3 has a substantially rectangular outer shape, and the groove portions 5 and 5 ′ having the same shape are cut and formed on one side of the displacement portion 3 to form a line-symmetric comb shape as a whole.

  Further, the displacement portion 3 is connected to the fixed portion 2 by the narrow portion 4 at the center of the side facing the side where the groove portions 5 and 5 ′ are formed. This narrow portion 4 is also made by etching one substrate 1 together with the fixed portion 2 and the displacement portion 3. Thus, when acceleration is applied to the fixed portion 2 and the displacement portion 3, the narrow portion 4 is bent by the mass of the displacement portion 3, and the lower end of the displacement portion 3 swings in the direction of arrow A in FIG. .

  Of the sides on the inner peripheral side of the frame of the fixed portion 2, the sides facing the side where the narrow portion 4 is formed are comb-like opposed to be inserted into the grooves 5 and 5 ′ of the fixed portion 2. Portions 6 and 6 ′ are formed to protrude. The facing portions 6 and 6 ′ have the same shape and are arranged symmetrically with respect to the center line of the displacement portion 3.

  As shown in FIG. 2, a first displacement electrode 7 and a second displacement electrode 7 ′ are formed on the side surfaces in the groove portions 5 and 5 ′ of the fixed portion 2 facing the facing portions 6 and 6 ′, respectively. .

  A fixed electrode 8 is formed on the side surface of the facing portion 6 facing the displacement electrode 7, and a fixed electrode 8 ′ is formed on the side surface of the facing portion 6 ′ facing the displacement electrode 7 ′. That is, the fixed electrodes 8 and 8 ′ are formed on the side surfaces of the opposing sides of the facing portions 6 and 6 ′.

  As shown in FIGS. 1 and 2, a conductive thin film 9 is connected to the displacement electrode 7 and the displacement electrode 7 ′, and conductive thin films 10 and 10 ′ are connected to the fixed electrodes 8 and 8 ′, respectively. . The conductive thin film 9 is linearly formed from the fixed portion 2 to the displacement portion 3 through the narrow portion 4, the end on the displacement portion 3 side branches, and each branch is a displacement electrode 7, 7 respectively. It has a configuration connected to '. A circular connection terminal 11 is formed at the end of the conductive thin film 9 on the fixed portion 2 side. On the other hand, each of the conductive thin films 10 and 10 'is formed on the fixed portion 2, and one end is connected to the fixed electrodes 8 and 8', and the circular connection terminals 12 and 12 'are formed on the other end. Yes.

  In the inclination sensor of the present embodiment, when gravitational acceleration is applied, the narrow portion 4 is curved and the lower end of the displacement portion 3 is displaced in any of the directions of arrow A in FIG. As a result, the distance between the displacement electrodes 7 and 7 'and the fixed electrodes 8 and 8' changes, and the capacitance between them changes. By detecting this change in capacitance, the displacement amount of the displacement portion 3 can be detected, and the inclination angle applied to the inclination sensor can be detected by the mass of the displacement portion 3 and the spring constant of the narrow portion 4. it can.

A specific circuit for detecting the tilt angle is shown in FIG. In FIG. 3, the tilt angle detection circuit of the tilt sensor of the present embodiment includes a capacitance detection circuit 20 and a charge control circuit 21. Note that the differential capacitors C ₁ and C ₂ in FIG. 3 are capacitors constituted by the displacement electrode 7 and the fixed electrode 8, and the displacement electrode 7 ′ and the fixed electrode 8 ′, respectively. One end (the connection terminal 11 side) of the differential capacitors C ₁ and C ₂ is grounded.

The capacitance detection circuit 20 includes a changeover switch circuit SW ₅ , an operational amplifier Amp ₁ , differential amplifiers Amp ₂ and Amp ₃ , sample hold circuits S / H ₁ and S / H ₂ , and voltage dividing resistors R ₁ , R ₂ and R _3. It has.

The terminals of the differential capacitors C ₁ and C ₂ corresponding to the connection terminals 12 and 12 ′ are connected to the changeover switch circuit SW ₅ respectively. The changeover switch SW ₅ switches between the differential capacitors C ₁ and C ₂ and the input terminal of the operational amplifier Amp ₁ . The operational amplifier Amp ₁ amplifies the voltage of the input terminal by α and outputs the amplified voltage. The output terminal of the operational amplifier Amp ₁ is connected to the input terminals of the sample and hold circuits S / H ₁ and S / H ₂ . The sample hold circuits S / H ₁ and S / H ₂ hold the voltage input to the input terminal and output the hold voltage to the output terminal. The output terminals of the sample hold circuits S / H ₁ and S / H ₂ are connected to the + side input of the differential amplifier Amp _{2 and} the − side input of the differential amplifier Amp ₃ , respectively. Voltage dividing resistors R ₁ , R ₂ , and R ₃ are arranged in series between the output terminal of the differential amplifier Amp _{2 and} the output terminal of the differential amplifier Amp ₃ . The connection node of the voltage dividing resistors R ₁ and R ₂ is connected to the − side input of the differential amplifier Amp ₂ , and the connection node of the voltage dividing resistors R ₂ and R ₃ is connected to the + side input of the differential amplifier Amp _3. Has been.

Voltages V _out1 and V _out2 are output to the differential amplifiers Amp ₂ and Amp ₃ , respectively. The difference voltage V _out1 −V _out2 between the two terminals becomes the output voltage V _out of the tilt sensor.

On the other hand, the charge control circuit 21 includes a control current source I _C , switch circuits SW ₁ , SW ₂ , SW ₃ , SW ₄ , a differential amplifier Comp, and a reference voltage generation circuit 22. Here, the differential amplifier Comp functions as a “current source control circuit” in the present invention, as will be described later.

Terminal of the differential capacitor _C 1, _{C 2} corresponding to the connection terminals 12 and 12 ', respectively, are connected to the output terminal of the controlled current source _{I C} through the switch circuit _SW 1, SW _2, the differential A constant charge can be applied to the type capacitors C ₁ and C ₂ . Therefore, voltages V ₁ and V ₂ are generated in the differential capacitors C ₁ and C ₂ , respectively. The voltages V ₁ and V ₂ are amplified by the operational amplifier Amp _{1 and the} like, and become voltages of V _out1 and V _out2 .

The terminals of the differential capacitors C ₁ and C ₂ corresponding to the connection terminals 12 and 12 ′ are grounded via the switch circuits SW ₃ and SW ₄ . By connecting the switch circuits SW ₃ and SW ₄ , the charges of the differential capacitors C ₁ and C ₂ can be discharged.

Reference voltage generating circuit 22 generates a reference voltage V _ref for controlling the output of the controlled current source I _C. The output terminal of the reference voltage generation circuit 22 is connected to one input terminal of the differential amplifier Comp. On the other hand, to the other terminal of the differential amplifier Comp, the center tap of the voltage dividing resistors _{R 2,} i.e., the voltage α is _{(V 1 + V 2) /} 2 is input. Differential amplifier Comp may generate a control voltage of the voltage _{α (V 1 + V 2)} / 2 and _{V ref} and the voltage difference α _{(V 1} + V 2) of the / _{2-V ref} and amplify the control current source _{I C} To do. Controlled current source _{I C} outputs a difference voltage α _{(V 1} + V 2) the magnitude of the current proportional to / _{2-V ref.}

FIG. 4 is a configuration diagram of the reference voltage generation circuit 22. The reference voltage generation circuit 22 includes a constant voltage source 23, a differential amplifier 24, and a voltage addition circuit 25. The constant voltage source 23 generates a constant reference voltage _Vref0 . The differential amplifier 24 receives the output voltages V _out1 and V _out2 of the capacitance detection circuit, and outputs a voltage a ′ V _out = a ′ (V _out1 −V _out2 ) that is a ′ times the difference between them. . Voltage addition circuit 25 outputs a 'voltage _{V ref0} + a obtained by adding V _out' V _out reference voltage _{V ref0} and voltage a reference voltage _{V ref.}

  The circuit shown in FIG. 3 operates as follows.

First, the switch circuits SW ₁ and SW ₂ are connected for the time T, respectively, and the differential capacitors C ₁ and C ₂ are charged for the time T by the charging current I _C. As a result, charging voltages V ₁ and V ₂ are generated in the differential capacitors C ₁ and C ₂ , respectively.

Next, the changeover switch circuit SW ₅ is sequentially switched to the differential capacitor C ₁ side and the differential capacitor C ₂ side, and the sample hold circuits S / H ₁ and S / H ₂ are operated by the operational amplifier Amp ₁ . The amplified terminal voltages V _out1 and V _out2 of the differential capacitors C ₁ and C ₂ are sampled and held.

When the sample hold is performed, the switch circuits SW ₃ and SW ₄ are connected for a predetermined time, and the differential capacitors C ₁ and C ₂ are discharged.

On the other hand, the output voltages of the sample and hold circuits S / H ₁ and S / H ₂ are amplified by the differential amplifiers Amp ₂ and Amp ₃ , respectively, and output to the output terminal of the capacitance detection circuit 20. At this time, the output voltage V _out of the capacitance detection circuit 20 is V _out = V _out1 −V _out2 = a · (V ₁ −V ₂ ). Here, a is a constant.

The voltage dividing resistors R ₁ and R ₃ have the same resistance value, and the amplification factors of the differential amplifiers Amp ₂ and Amp ₃ are set to be equal. Thus, the differential amplifier divided voltage of the resistance _{R 2} of the intermediate tap that is input to one input terminal of Comp the amplified differential capacitor _C 1, _{C 2} of the terminal voltage _{V out1, V} the average value of _out2 (V _out1 + V _out2 ) / 2 = α (V ₁ + V ₂ ) / 2. The differential amplifier Comp outputs a difference voltage α (V ₁ + V ₂ ) / 2−V _ref between the average value (V _out1 + V _out2 ) / 2 and the reference voltage V _ref . Controlled current source _{I C} outputs a current proportional to the differential amplifier Comp differential voltage outputs _{α (V 1 + V 2)} / 2-V ref. Accordingly, when the difference voltage α (V ₁ + V ₂ ) / 2−V _ref = 0, the output current I _C becomes zero. Thereby, the control current source I _C is controlled so that the average value of the terminal voltages V _out1 and V _out2 is equal to the reference voltage V _ref .

As will be described later, under this condition, the output voltage V _out becomes V _out = A · x · V _ref . x is the displacement of the movable electrode constituting the differential capacitors C ₁ and C ₂ . The capacitances of the differential capacitors C ₁ and C ₂ are C ₁ = ε · S / (d−x) and C ₂ = ε · S / (d + x). d is the distance between the electrodes when the displacement electrodes 7 and 7 'between the two fixed electrodes 8 and 8' are at the center. ε is the dielectric constant of the differential capacitors C ₁ and C ₂ , and S is the electrode area of the differential capacitors C ₁ and C ₂ .

Next, the operation of tilt detection by the tilt sensor of this embodiment will be described. When the inclination is large to some extent, the distance between the displacement electrode 7 ′ and the fixed electrode 8 ′ becomes small, and the change in capacitance between the electrodes becomes large with respect to the change in the distance. On the other hand, when the inclination increases and approaches 90 degrees, the displacement rate of the displacement electrode 7 ′ decreases with respect to the change rate of the inclination. As a result, the change in the voltages V ₁ and V ₂ due to the voltage of the displacement electrode 7 ′ and the fixed electrode 8 ′ with respect to the inclination, that is, the electric charge charged between the electrodes becomes nonlinear.

The output signals of the voltages V ₁ and V ₂ are amplified to the voltages V _out1 and V _out2 by the operational amplifier Amp ₁ and the differential amplifiers Amp ₂ and Amp ₃ , and the output represented by the expression (4) is provided between the output terminals. A signal V _out is output.

ここで、電圧Ｖ_out1は式（５）で表される。

Here, the voltage _Vout1 is expressed by Expression (5).

ここでＶ_Ｃ1は差動型コンデンサＣ₁の電圧であり、Ａは定数である。

Here, V _C1 is the voltage of the differential capacitor C ₁ , and A is a constant.

Further, the voltage V _out2 is _expressed by Expression (6).

ここでＶ_Ｃ2は差動型コンデンサＣ₂の電圧であり、Ａは定数である。

Here V _C2 is the voltage of the differential capacitor C _2, A is a constant.

The relationship between the output signal V _out1 and the inclination θ of the substrate 1 is

となり、Ｖ_out2と基板１の傾斜θとの関係も同様となる。つまり基板１の傾斜θにより変位部３が変位することによって、出力信号の電圧Ｖ_out1，Ｖ_out2が変化する。即ち、これらの出力信号は基板１の傾斜角度を示している。

Thus, the relationship between V _out2 and the inclination θ of the substrate 1 is the same. That is, when the displacement portion 3 is displaced by the inclination θ of the substrate 1, the voltages V _out1 and V _{out2 of the} output signal change. That is, these output signals indicate the tilt angle of the substrate 1.

As can be seen from the equations (6) and (7), V _out1 or V _out2 is nonlinear with respect to the inclination θ. Therefore, from the equation (4), V _out is also non-linear with respect to the inclination θ.

Considering the relationship between V _out and displacement x, V _out is a series circuit of differential capacitors C ₁ and C ₂ , and the distance d between the electrodes is d + x in the differential capacitor C _1. in type capacitor C ₂ becomes d-x.

This by the voltage V _out charges of the differential capacitor C ₁ and a differential capacitor C ₂ are determined, the output signal V _out becomes linear.

The circuit shown in FIGS. 3 and 4 is used as means for specifically realizing this. In FIG. 3, I _C is a control control current source, and this control current source I _C supplies a current according to a predetermined condition.

In other words, the differential capacitor C ₁ and C ₂ is supplied charging current from the controlled current source I _C, a charge amount to be charged is determined by the current and the switch SW _1, SW ₂ of the on-time of the control current source . Here I _C is the mean value of the charging voltage of each capacitor

と所定の電圧Ｖ_ｒｅｆとが等しくなるように制御されている。この回路の出力Ｖ_outは、式（３）で表すことができる。

And the predetermined voltage V _ref are controlled to be equal. The output V _{out of} this circuit can be expressed by equation (3).

Here, when the comparison voltage V _ref of the comparator is added to a voltage corresponding to the output V _out , for example, a component of a times the output as shown in FIG. 4, the linear region of the output V _out is arbitrarily changed, Correction can be performed.

When this is obtained by calculation, the conventional tilt sensor is nonlinear as shown in equation (3), but the output V _out of the tilt sensor of this embodiment can be expressed as in equation (9).

Here, θ ₀ is defined as the zero point, that is, the angle when the sensor is not tilted, and the angle θ in the above equation (9) is newly rewritten as θ−θ ₀ . In addition, since A'V _ref0 is applied to both terms in the equation (9), if this is omitted, the equation (10) is eventually obtained.

  Here, if the third power or higher term is ignored, it can be expressed as in Expression (11).

Here, if the coefficient of theta ² is 0, the relationship of the output voltage to theta approaches linearly. Therefore, when the coefficient of θ ² is 0, the following expressions (12a) and (12b) are obtained.

  As can be seen from the equations (11), (12a), and (12b), the power of θ disappears and the output voltage approaches linear.

  The present invention provides a tilt sensor that is excellent in mass productivity, can be mass-produced using a semiconductor manufacturing process, has high sensitivity, and an output signal is linear with respect to tilt.

It is a front view which shows Example 1 of the inclination sensor of this invention. It is an enlarged front view which shows a part of inclination sensor of this invention. It is a circuit diagram of the inclination-angle detection circuit of the inclination sensor of this invention. 3 is a configuration diagram of a reference voltage generation circuit 22. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Fixed part 3 Displacement part 4 Narrow part 5, 5 'Groove part 6, 6' Opposing part 7 1st displacement electrode 7 '2nd displacement electrode 8, 8' Fixed electrode 9 Conductive thin film 10, 10 'Conductive thin film 11 Connection terminal 12, 12 ′ Connection terminal 20 Capacity detection circuit 21 Charge control circuit 22 Reference voltage generation circuit 23 Constant voltage source 24 Differential amplifier 25 Voltage addition circuit

Claims (10)

When the displacement electrode disposed opposite to each fixed electrode swings between the two fixed electrodes to cause an inclination, the fixed electrode is formed by one of the fixed electrodes and the displacement electrode facing the fixed electrode. Capacitances of the first capacitor and the second capacitor formed by the other fixed electrode and the displacement electrode opposed to the first capacitor are changed, and the change of the capacitance is detected by the capacitance detection circuit. In the inclination sensor that converts and outputs the change, the capacitance detection circuit output signal correction method that corrects the change in the output signal of the capacitance detection circuit to be linear or substantially linear,
A sum of a voltage obtained by multiplying a voltage difference generated by each of the two capacitors output from the capacitance detection circuit by a variable by a charge control circuit and a voltage having a predetermined magnitude is used as a reference voltage. as the average value, or a constant multiple thereof of the voltage generated is equal to the reference voltage, to control the charge to be charged to the capacitor, the value of the variable so as to cancel the non-linear component of the output voltage of the capacitance detection circuit A method for correcting a capacitance detection circuit output signal, comprising: determining a capacitance detection circuit output signal. The charge control circuit includes a control current source, a reference voltage generation circuit, and a current source control circuit,
The control current source charges each capacitor by supplying current to the two capacitors,
The reference voltage generation circuit generates the reference voltage that is a sum of a voltage obtained by multiplying a difference between voltages generated by the two capacitors output from the capacitance detection circuit by a variable and a voltage having a predetermined magnitude. ,
The current source control circuit controls the output current of the control current source so that an average value of the voltages generated in the two capacitors or a constant multiple thereof is equal to the reference voltage. 2. The method of correcting a capacitance detection circuit output signal according to claim 1, wherein the charge charged in each of the capacitors is controlled. The reference voltage generation circuit includes a constant voltage source, an amplifier, and a voltage addition circuit,
A constant voltage is generated by the constant voltage source,
Amplifying the voltage output from the capacitance detection circuit by the amplifier;
3. The method of correcting a capacitance detection circuit output signal according to claim 2, wherein in the voltage addition circuit, the reference voltage is generated by adding a voltage output from the amplifier to a voltage generated by the constant voltage source. . A frame-shaped fixing part formed of a thin plate;
A displacement portion formed of a thin plate, disposed on the same plane as the fixed portion and within the frame of the fixed portion;
A pair of fixed electrodes extending toward the frame of the fixed portion;
A pair of displacement electrodes formed on the displacement portion and disposed between the pair of fixed electrodes so as to face the fixed electrodes;
A capacitance detection circuit that converts and outputs a change in capacitance of each of the two capacitors composed of the fixed electrodes and the displacement electrode facing the fixed electrodes;
The displacement portion is swingably attached to the fixed portion such that a distance between each displacement electrode and the fixed electrode facing the displacement electrode is displaced by a change in direction of gravitational acceleration.
A tilt sensor capable of measuring a tilt according to a voltage output from the capacitance detection circuit;
The sum of a voltage obtained by multiplying the difference in voltage generated in each of the two capacitors output by the capacitance detection circuit by a variable and a voltage having a predetermined magnitude is used as a reference voltage, and an average of the voltages generated in the two capacitors A charge control circuit that controls the charge charged to the capacitor so that a value or a constant multiple thereof is equal to the reference voltage, and that the value of the variable is determined so as to cancel the nonlinear component of the output voltage of the capacitance detection circuit A tilt sensor comprising: The charge control circuit includes:
A control current source for generating a current to be supplied to the two capacitors;
A reference voltage generation circuit that generates the reference voltage that is a sum of a voltage obtained by multiplying a difference between voltages generated by the two capacitors output from the capacitance detection circuit by a variable and a constant voltage _Vref0 having a predetermined magnitude. When,
A current source control circuit that controls an output current of the control current source so that an average value of a voltage generated in each of the two capacitors or a constant multiple thereof is equal to the reference voltage;
The tilt sensor according to claim 4, further comprising: The reference voltage generation circuit includes:
A constant voltage source that generates a constant voltage;
An amplifier for amplifying the voltage output from the capacitance detection circuit;
A voltage adding circuit that adds the voltage output from the amplifier to the voltage generated by the constant voltage source and outputs the voltage as the reference voltage;
The tilt sensor according to claim 5, further comprising: On one side of the displacement part, a pair of groove parts are cut and formed in a concave shape,
A pair of opposing portions are extended to the inside of the frame of the fixed portion toward the inside of the frame without being inserted into the grooves and in contact with the inside of the grooves.
Each of the fixed electrodes is formed on the side surface of each of the facing portions facing each other,
The inclination sensor according to any one of claims 4 to 6, wherein each displacement electrode is formed on a side surface of each groove portion opposite to each fixed electrode.   The said displacement part and the said fixing | fixed part are couple | bonded by the flexible narrow part formed narrowly with respect to the width | variety of the said displacement part. The inclination sensor according to one.   9. The tilt sensor according to claim 8, wherein the fixed portion, the displacement portion, and the narrow portion are integrally formed by processing a single substrate.   The tilt sensor according to claim 9, wherein the fixed portion, the displacement portion, and the narrow portion are integrally formed of a single crystal plate.

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