JPH0894472A - Pressure sensor, manufacture thereof and gas meter and hemomanometer employing it - Google Patents

Abstract

PURPOSE: To obtain a pressure sensor excellent in sensor characteristics by enhancing the machining accuracy of a diaphragm. CONSTITUTION: A silicon wafer is subjected, on one side thereof, to dry etching to form a circular gap 4 and a protrusion 15 on the peripheral edge thereof. The silicon wafer is subjected, on the other side thereof, to anisotropic etching to form a thin film part 12 wider than the gap 4 thus producing a silicon frame 1 in which a circular diaphragm 2 is formed. A glass cover 3 is applied to the upper surface of the frame 1 and anode bonded thereto thus producing a pressure sensor A. Since the position, size and shape of the diaphragm 2 are determined by the circular gap 4 formed through dry etching, a highly accurate diaphragm 2 can be produced with regard to the position and size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, a method for manufacturing the pressure sensor, a gas meter and a blood pressure monitor equipped with the pressure sensor. More specifically, the present invention relates to a pressure sensor that measures the pressure of a fluid such as air or liquid, a method for manufacturing the pressure sensor, and a gas meter and a sphygmomanometer including the pressure sensor.

[0002]

2. Description of the Related Art Conventionally, as a capacitance type semiconductor pressure sensor, there is one disclosed in, for example, Japanese Patent Laid-Open No. 3-239938. The pressure sensor H is shown in FIGS.
The top view and sectional drawing of are shown. Square frame-shaped frame 51
A thin film-shaped diaphragm 52 is disposed substantially at the center of the diaphragm 52. The diaphragm 52 is formed by dry etching a silicon wafer from one side to form a large gap 53, and then from the side opposite to the surface on which the gap 53 is formed. Anisotropic etching is performed using an etching solution to form a deep truncated pyramid-shaped recess, which is integrally formed with the frame 51. A movable electrode 54 is formed on the upper surface of the diaphragm 52, and a correction capacitance electrode 57 is formed in the gap 53 region around the movable electrode 54.

A glass cover 55 is superposed on the upper surface of the frame 51, and its peripheral portion is bonded to the frame 51 by an anodic bonding method or the like. A fixed electrode 56 is formed on the inner surface of the cover 55 so as to face the movable electrode 54.
A detection capacitor is formed between the movable electrode 54 and the fixed electrode 56, and the detection capacitor is drawn out from a pair of electrode pads 59, 59 on the upper surface of the frame 51. Further, another correction capacitance electrode 58 is formed around the fixed electrode 56 so as to face the correction capacitance electrode 57 around the movable electrode 54, and the correction capacitor is formed between the correction capacitance electrodes 57 and 58. Are drawn out from a pair of separate electrode pads 60, 60 on the upper surface of the frame 51.

However, when the pressure of a fluid such as air or liquid is applied to the lower surface of the diaphragm 52, the diaphragm 52 is displaced in the thickness direction thereof in proportion to the magnitude of the applied pressure, and the movable electrode 54 and The amount of the gap with the fixed electrode 56 changes. When the gap amount changes, the capacitance value of the detection capacitor changes, and the pressure applied by detecting the capacitance value by a detection circuit (not shown) connected to the electrode pads 59, 59. You can know the size of. At the same time, the capacitance of the correction capacitor is measured by a correction circuit (not shown) connected to the electrode pads 60, 60, and the capacitance of the detection capacitor detected in accordance with the change in the capacitance of the correction capacitor is detected. By correcting the value of the electrostatic capacitance, it is possible to reduce the measurement error due to changes in the ambient temperature.

[0005]

However, in this pressure sensor, the diaphragm is deeply anisotropically etched (wet etching) from the side opposite to the surface on which the gap is formed in the silicon wafer in which the gap is formed.
Since the upper surface of the truncated pyramid-shaped recess on the lower surface of the silicon wafer is smaller than the gap area and is accommodated within the gap region in plan view, the silicon wafer may have different thicknesses or plane orientations. The influence of the selection ratio at the time of isotropic etching, the angle deviation of the mask alignment, etc. was great, and the size of the diaphragm was inaccurate.

Further, since the shape of the diaphragm is determined by the truncated pyramidal recess formed by deep anisotropic etching, the shape of the diaphragm becomes rectangular, and if the displacement due to the applied pressure is centrally symmetric. However, the sensor characteristics such as linearity were poor.

Further, in the case of a pressure sensor in which glass and silicon are bonded together, there is a difference in the coefficient of thermal expansion between glass and silicon, which causes distortion due to temperature changes, and the temperature characteristics of the pressure sensor are poor. In addition, during anodic bonding, strain during bonding is concentrated in the gap portion, and compressive stress acts on the diaphragm, causing the diaphragm to be distorted.

The present invention has been made in view of the drawbacks of the above conventional examples, and an object of the present invention is to provide a pressure sensor having excellent sensor characteristics by solving the above problems. It is in.

[0009]

The pressure sensor of the present invention comprises:
A deep concave portion is provided in a semiconductor substrate, a thin film portion serving as a movable electrode is formed on the bottom surface of the concave portion, and a fixed substrate having a fixed electrode and the semiconductor substrate are bonded to each other, and a side surface of the thin film portion opposite to the concave portion and a fixed electrode. In a pressure sensor in which and are opposed to each other across a gap, the gap is contained in the thin film portion in a plan view.

This gap may be provided in the semiconductor substrate or in the fixed substrate. At this time, it is preferable to form the gap in a circular shape.

Further, it is preferable that a region facing the gap has a low impurity concentration and a region other than the region has a high impurity concentration on the surface of the semiconductor substrate on the gap side, and a substantially annular convex portion is provided around the gap. It may be formed.

It is preferable that the gap and the fixed electrode are substantially circular, and the ratio of the area of the fixed electrode to the area of the gap is 0.4 to 0.7.

Also, the fixed electrode is fixed to the fixed electrode by crimping the wiring part drawn from the fixed electrode to the outer peripheral part of the fixed substrate and the wiring part drawn from the pad part provided on the outer peripheral part of the semiconductor substrate. In the pressure sensor electrically drawn to the pad portion, the film thickness of the crimping portion of the wiring portion on the fixed electrode side and the wiring portion on the pad portion side,
It is preferable to make it thicker than the film thickness of other wiring portions.

It is preferable that the crimping portion is located outside the thin film portion of the semiconductor substrate, and a groove for inserting the wiring portion is provided in the semiconductor substrate or the fixed substrate in which the gap is formed. It is preferable to form the groove at the same depth as the gap.

Further, a recess deeper than the gap may be formed outside the gap of the semiconductor substrate in which the gap is formed, and the pad portion and the wiring portion thereof may be provided on the insulating film formed in the recess. it can.

In these pressure sensors, another semiconductor substrate is bonded to the surface of the fixed substrate opposite to the surface on which the semiconductor substrate is bonded, and the bonding regions on both surfaces of the fixed substrate with the semiconductor substrates are bonded. Should be approximately equal.

The first method of manufacturing the pressure sensor of the present invention comprises:
A thin film portion is formed by deep anisotropic etching on one surface of the semiconductor substrate, and a gap having a smaller area than the thin film portion is formed by shallow dry etching on the other surface of the semiconductor substrate. It is characterized in that a fixed substrate having a fixed electrode is anodically bonded to the surface on the side of the gap.

According to a second method of manufacturing the pressure sensor of the present invention, the thin film portion is formed by deep anisotropic etching of the surface of the semiconductor substrate, and the thin film portion is formed by shallow etching of the surface of the fixed substrate. It is characterized in that a gap having a smaller area is formed, a fixed electrode is formed in this gap, and then the semiconductor substrate and the fixed substrate are anodically bonded so that the thin film portion of the semiconductor substrate and the gap of the fixed substrate face each other. I am trying.

The gas meter and blood pressure monitor of the present invention are characterized by including the pressure sensor of the present invention.

[0020]

In the pressure sensor of the present invention, depending on the shape of the gap formed on the semiconductor substrate or the fixed substrate,
Since the size and shape of the diaphragm are determined, the size and shape of the diaphragm can be manufactured accurately.

At this time, if the shape of the diaphragm is circular, the diaphragm is isotropically deformed, and the linearity of the pressure sensor becomes good. In addition, there is no misalignment of mask alignment.

On the surface of the semiconductor substrate on the side of the gap, the region facing the gap has a low impurity concentration, and the other regions have a high impurity concentration, so that the residual stress of the die duff diaphragm is reduced and at the same time, the semiconductor substrate of the semiconductor substrate is reduced. The electric resistance can be reduced.

Further, by forming a substantially annular convex portion around the gap, during anodic bonding between the semiconductor substrate and the fixed substrate, anodic bonding progresses outward from the convex portion around the gap, and strain is concentrated in the gap portion. Can be prevented.

Further, the diaphragm and the fixed electrode are substantially circular, and the ratio of the area of the fixed electrode to the area of the gap is 0.
If it is set to 4 to 0.7, the sensor sensitivity to the displacement of the diaphragm becomes optimum, and the linearity of the sensor output can be enhanced by using the region of the diaphragm where the deformation is relatively small as the sensor electrode.

Further, if the thickness of the portion of the fixed electrode side wiring portion that is crimped to the pad portion wiring portion is made larger than the thickness of the other wiring portion, the fixed substrate and the semiconductor substrate are crimped. Thus, the fixed electrode side wiring portion and the pad side wiring portion can be connected to each other, and the fixed electrode can be reliably pulled out to the pad portion of the semiconductor substrate.

If the crimping portion is located outside the thin film portion of the semiconductor substrate, the thin film portion is less likely to be stressed when the crimping portion is crimped, and the thin film portion can be protected.

Further, if the groove for inserting the wiring portion provided on the fixed substrate or the semiconductor substrate is set to have the same depth as the gap in the gap, the influence of the groove on the displacement of the diaphragm can be reduced. .

If a concave portion deeper than the gap is formed outside the gap and a pad portion or a wiring portion for drawing out the fixed electrode is provided on the insulating film provided in the concave portion, the fixed electrode and the movable electrode can be formed. The stray capacitance generated in parallel with the inter-sensor capacitance can be reduced.

Further, if the fixed substrate is sandwiched by the semiconductor substrates and the bonding regions on both surfaces of the fixed substrate are made equal to each other, the warp and distortion of the sensor can be prevented and the temperature characteristics can be improved.

According to the method of manufacturing the pressure sensor of the present invention,
The pressure sensor of the present invention in which a gap is formed in the thin film portion in plan view can be easily manufactured.

The pressure sensor of the present invention can be used in a gas meter, a blood pressure monitor, etc., and can accurately measure gas pressure, blood pressure, etc.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a pressure sensor A according to an embodiment of the present invention.
FIG. In the pressure sensor A, a glass cover 3 is superposed on the upper surface of a silicon frame 1 on which a circular diaphragm 2 is supported, and its peripheral portion is bonded to the frame 1 by anodic bonding or the like. The diaphragm 2 has a thin film portion 1 formed by forming a recess 19.
A circular gap 4 is formed substantially at the center of the frame 2, so that the frame 2 and the frame 1 are integrally formed.
The upper surface of the diaphragm 2 is a circular movable electrode 5 having conductivity, and is drawn out from the electrode pad 6 (FIG. 4) on the upper surface of the frame 1. A circular fixed electrode 7 is formed on the inner surface of the cover 3 so as to face the movable electrode 5 concentrically with the movable electrode 5, and is electrically connected to a lead wire 8 on the inner surface of the cover 3. The lead wire 8 is the frame 1
The fixed electrode 7 is electrically connected by pressure bonding with another lead wiring 10 electrically connected to the electrode pad 9 on the upper surface.
Are led out from the electrode pad 9. The crimping portion 8a of the lead-out wiring 8 is made thicker than the wiring portion other than the crimping portion 8a, and is made of a metal having a low yield point such as Au or Al.

A wiring groove 11 is provided on the upper surface of the frame 1, and is formed in the thin film portion 12 at a depth substantially equal to the gap 4, and in the area outside the thin film portion 12 area, the gap 4 is formed. Formed deeper than. An insulating film 13 is formed in the exposed region of the frame 1 from the wiring groove 11 formed deeper than the gap 4, and the electrode pads 6 and 9 and the lead wiring 10 are formed on the insulating film 13. Has been done.

A pressure introducing passage 14 for introducing a reference pressure such as atmospheric pressure is provided in the gap 4 on both sides of the gap 4 on the upper surface of the frame 1 (in a direction substantially orthogonal to the wiring groove 11), and a peripheral portion of the gap 4 is provided. Is provided with a substantially annular convex portion 15.

2, 3 and 4 show a method of manufacturing the frame 1 of the pressure sensor A, FIG. 5 shows a method of manufacturing the cover 3, and each step is shown in plan and sectional views. is there. Hereinafter, the method of manufacturing the pressure sensor A will be described in detail with reference to the drawings. First, as shown in FIG. 2A, the pressure introducing passage 14 having the same depth as the gap 4 to be formed later is formed in the silicon wafer 21 which becomes the frame 1. Next, a predetermined region where the insulating film 13 is formed is etched deeper than the gap 4 to form a notch 22 having a plane convex shape (FIG. 2B). Then, the convex portion 1 on the upper surface of the frame 1
The outer peripheral area of the area where 5 is formed is removed by a predetermined thickness (thickness corresponding to the height of the convex portion 15) by dry etching to form a circular protruding portion 23 on the silicon wafer 21 (FIG. 2C). ). After the dopant such as phosphorus is diffused over the entire surface of the silicon wafer 21 to increase the surface concentration (see FIG. 2).
(D)) The protrusion 23 region of the silicon wafer 21 is dry-etched into a circular shape so that the peripheral portion of the protrusion 23 is left to form the convex portion 15 and the gap 4 and the wiring groove 11. (FIG.3 (e)). Here, in order to reduce the extraction resistance of the movable electrode 5, the silicon wafer 2
In order to improve conductivity, the impurities were diffused into the silicon substrate at a high concentration, but when the impurities were diffused into the silicon substrate, residual stress was generated inside. Therefore, the impurity implantation depth is made shallower than the depth of the gap 4, and the impurity implantation layer is removed in the region of the diaphragm 2 by etching during the formation of the gap 4 to expose the original layer of the silicon wafer 21. In this way, high-concentration impurities remain only around the diaphragm 2,
Since the diaphragm 2 has a low impurity concentration, the diaphragm 2 having a small residual stress and a small strain can be obtained.

Next, a mask 24 made of silicon nitride is formed into a circular shape at a predetermined position on the lower surface of the silicon wafer 21 (FIG. 3 (f)), and then the gap 4 is formed as shown in FIG. 3 (g).
The insulating film 1 is formed in the notch 22 that is etched deeper than
3 is formed. A contact hole 25 with the electrode pad 6 is opened in the insulating film 13 (FIG. 3 (h)), and the electrode pad 6 and the lead wiring 10 integrated with the electrode pad 9 are formed on the insulating film 13 (FIG. 4). (I)). Finally, anisotropic etching is performed from the back surface of the silicon wafer 21 with a KOH aqueous solution or the like to form the concave portion 19 and the thin film portion 12 in a region wider than the gap 4 region, and the frame in which the circular diaphragm 2 is formed. 1 is produced (FIG. 4 (j)).

Next, a method of manufacturing the cover 3 will be described. First, as shown in FIG. 5A, a region substantially facing the insulating film 13 region of the glass substrate 25 is removed by etching with an HF aqueous solution to form a notch 26. Next, in the region where the fixed electrode 7 and the lead wiring 8 are formed, the Cr film 2 is formed.
7 is vapor-deposited, and an Au film 28 is vapor-deposited thereon (FIG. 5B). Finally, the crimping part 8 of the lead wire 8
The Au film 28 is removed leaving a, the fixed electrode 7 and the lead wiring 8 are formed, and the cover 3 is formed (FIG. 5).
(C)). The pressure sensor A can be manufactured by stacking the frame 1 and the cover 3 thus manufactured and bonding them by anodic bonding.

In this pressure sensor A, since the area of the gap 4 is smaller than the area of the thin film portion 12, the shape and size of the diaphragm 2 are formed by dry etching on the thin film portion 12 formed by anisotropic etching. It is determined by the shape and size of the gap 4. The formation of the gap 4 by dry etching is different from the formation of the thin recess 19 by anisotropic (wet) etching.
Since the pattern can be formed in an arbitrary pattern with high accuracy, the diaphragm 2 can be formed with high accuracy, and an angular deviation of mask alignment does not occur. Further, since the diaphragm 2 has a circular shape, the diaphragm 2 is isotropically displaced by the applied pressure, and the linearity of the pressure sensor A can be improved.

Further, since the mask shape is circular and anisotropic etching is performed, it is possible to prevent under-etching due to an angular deviation due to a photolithography process, and the thin film portion 12 is accurately formed at a predetermined position. can do.

Since the fixed electrode 7 is also formed in a circular shape, the fixed electrode 7 does not have an angular deviation, and the sensor characteristics of the pressure sensor A can be improved. Especially the movable electrode 5
Since they are arranged concentrically with each other, an angular deviation between them and the movable electrode 5 is unlikely to occur.

Further, since the crimping portion 8a of the lead-out wiring 8 on the cover 3 side is formed thicker than the other wiring portions, it can be securely crimped to the lead-out wiring 10 on the frame 1 side. Moreover, since the surface of the crimping portion 8a is formed of a metal such as Au having a low yield point, the frame 1 and the cover 3 can be joined together without a gap. Furthermore, since the crimping portion 8a is located outside the thin film portion 12, stress during the crimping is unlikely to be applied to the thin film portion 12, and damage to the thin film portion 12 can be prevented.

Since the wiring groove 11 on the upper surface of the frame 1 is formed at the same depth as the gap 4 in the region of the thin film portion 12, the pressure introduced into the gap 4 causes the wiring groove 1
It is evenly transmitted to the inside of 1, and does not affect the displacement of the diaphragm 2. At this time, if the wiring groove 11 is formed in a direction perpendicular to the <110> plane direction of the silicon wafer, the region passing through the thin film portion 12 can be minimized. Moreover, since the wiring groove 11 in the region outside the thin film portion 12 is formed deeper than the gap 4, the movable electrode 5
The stray capacitance generated in parallel with the detection capacitor (sensor capacitance) formed between the fixed electrode 8 and the fixed electrode 8 can be made extremely small. In addition, this deeply formed wiring groove 11
Since the insulating film 13 is formed on the frame 1, a MOS capacitance is generated between the lead wire 10 or the electrode pad 9 on the frame 1 side and the frame 1. However, by thickening the insulating film 13, the MOS capacitance is increased. Could be kept as low as about 1.5 pF.

Further, in this pressure sensor A, since the annular convex portion 15 is formed on the peripheral edge of the gap 4, the convex portion 15 is formed at the time of anodic bonding between the frame 1 and the cover 3.
To the outer peripheral direction of the cover 3 gradually. As a result, the strain generated at the time of anodic bonding is not concentrated in the gap 4 portion, and the pressure sensor A with less strain of the diaphragm 2 can be manufactured.

FIG. 6 shows the sensor capacitance characteristic of the pressure sensor A thus manufactured. As shown in FIG. 6, good linearity was obtained between the reciprocal of the detected capacitance (1 / C) and the pressure.

FIG. 7 shows the relationship between the depth of the gap and the sensitivity (capacitance C). The depth of the gap and the sensitivity are in inverse proportion to each other. In particular, the depth is preferably 1.5 μm or less.

Further, FIG. 8 shows the relationship between the diameter ratio of the fixed electrode to the gap and the linearity. Where "1 / capacity"
The output non-linearity is the maximum deviation (absolute value of 1 / C) from the case where the sensor capacitance characteristic is a perfect straight line in the sensor capacitance characteristic diagram shown in FIG. 6 (E in FIG. 6).
The smaller the "1 / capacity" output nonlinearity is, the better the linearity is. As can be seen from FIG. 8, when the ratio of the diameter of the fixed electrode to the diameter of the gap is about 0.7, the "1 / capacitance" output nonlinearity becomes minimum, and the ratio is reduced from 0.65 to 0.8. Is desirable in terms of sensor capacitance characteristics. In other words, it is desirable to convert the area ratio of the fixed electrode to the area of the gap to 0.4 to 0.7.

Next, FIG. 9 shows the relationship between the maximum displacement of the diaphragm (ratio to the gap depth) and the sensitivity and linearity. Here, the linearity (% FS) represents the reciprocal of the maximum deviation (E in FIG. 6) from the case where the sensor capacitance characteristic is a perfect straight line in the sensor capacitance characteristic diagram shown in FIG. It is represented by the ratio (%) of the maximum displacement to the sensor capacity at the time of maximum displacement (at the maximum pressure in the operating pressure range). As can be seen from the line (a), the sensitivity of the pressure sensor increases as the ratio of the maximum displacement of the diaphragm to the gap depth increases, but if the ratio of the maximum displacement of the diaphragm to the gap depth increases,
As can be seen from the line B, the linearity drops sharply. Therefore, it is preferable to adjust the thickness of the diaphragm so that the maximum displacement of the diaphragm is approximately 0.7 or less.

If the silicon frame 1 and the glass cover 3 are joined together, distortion occurs due to the difference in thermal expansion coefficient, and the temperature stability of the pressure sensor is poor. FIG. 10 shows temperature characteristics when the thickness of the glass cover (ratio to the thickness of the frame) is changed. The thicker the cover, the better the temperature stability. It is preferable that the thickness of the cover is approximately three times or more the thickness of the frame. The temperature characteristic (% FS) means that the value of 1 / capacitance difference Δ (1 / C) between zero pressure (differential pressure) and maximum pressure at the reference temperature T ₀ is A, T
And difference of 1 / capacitance at reference temperature T ₀ (1 / C)
With the value B of, that is, B / A expressed in%. The smaller the temperature characteristic (% FS), the better the temperature stability.

FIG. 11 shows a schematic sectional view of a pressure sensor B which is another embodiment of the present invention. Pressure sensor B
In FIG. 3, a silicon plate 16 is further joined to the upper surface of the glass cover 3. By using the three-layer structure of silicon / glass / silicon in this way,
The temperature stability of the pressure sensor B can be improved.
At this time, like the pressure sensor C shown in FIG. 12, a circular gap 17 having the same area is formed on the inner surface of the plate 16 at a position facing the gap 4 of the frame 1, and the cover 3 is formed.
If the frame 1 and the plate 16 are bonded to the upper and lower surfaces with substantially the same bonding area, warpage and distortion of the pressure sensor C can be reduced, and the pressure sensor C having excellent temperature stability can be obtained. Further, as in the pressure sensor D shown in FIG. 13, a circular hole 18 is formed on the upper surface of the cover 3 so that the joint areas of the cover 3 and the frame 1 are substantially equal.
A plate 16 having openings at corresponding positions in the gap 4
May be joined together.

14A and 14B are a plan view and a sectional view of a pressure sensor E which is another embodiment of the present invention.
A substantially U-shaped groove 31 is formed on the outer periphery of the gap 4 of the frame 1.
Are provided in a concave shape, and a pair of correction capacitance electrodes 32 and 32 are formed on the inner surface of the bottom of the groove 31 and the cover 3 facing the bottom. The correction capacitance electrodes 32 and 32 are a pair of electrodes on the upper surface of the frame 1. It is pulled out from the pads 33, 33 to the outside. In this way, if a correction capacitor is formed in the outer peripheral area of the gap 4 to perform temperature correction and the like, more accurate pressure measurement becomes possible. Since the groove 31 can be formed at the same time as the gap 4 by dry etching, the manufacturing process does not increase or is complicated, and the correction capacitor can be easily provided. Also, FIG.
As in the pressure sensor F shown in FIG. 5, by providing the pressure introducing passage 34 that is connected to the groove 31 and the gap 4 from the side surface of the pressure sensor F, the relative permittivity in the groove 31 and the relative permittivity in the gap 4 are provided. Can be made equal, and the measurement error (error due to correction) due to the difference in relative permittivity can be reduced.

FIG. 16 is a sectional view of a pressure sensor G which is still another embodiment of the present invention, in which the gap 4
Is formed on the cover 3 side. Although a detailed description of the structure of the pressure sensor G is omitted, the frame 1 has a concave portion 19 formed by anisotropically etching one surface of the silicon wafer to form a thin film portion 12 larger than the gap 4. Have The upper surface of the thin film portion 12 has conductivity and serves as the movable electrode 5. Gap 4
Is formed into a circular shape by etching a glass substrate, and the fixed electrode 7 is formed on the inner surface thereof. As described above, by attaching the cover 3 having the gap 4 formed thereon to the frame 1 having the thin film portion 12 formed thereon, the diaphragm 2 can be accurately formed at a predetermined position. Of course, even in such a pressure sensor, a silicon plate (not shown) having an equal bonding area may be bonded to the upper surface of the cover 3.

The pressure sensor of the present invention can be used for a gas meter, a blood pressure monitor and the like. FIG. 17 is a configuration diagram of a gas meter K according to the present invention, in which the gas meter K measures a gas amount (total gas amount) 72 and a gas pipe 71.
A flow sensor 73 for measuring the flow rate of gas flowing inside (gas flow rate per unit time), a pressure sensor 74 according to the present invention for measuring the gas pressure in the gas pipe 71, a seismograph 75 for detecting an earthquake, and the like. ing. The total amount of gas flowing in the gas pipe 71 is measured by the measuring unit 72 and displayed on a display unit (not shown) such as a meter. Further, the gas flow rate and gas pressure in the gas pipe 71 are measured by the flow rate sensor 73 and the pressure sensor 74, respectively, and the controller 76
Is constantly monitored by If a gas leak occurs, the flow rate of gas flowing through the gas pipe 71 increases abnormally. Also, if you forget to turn off the gas appliances, the gas will continue to flow for an abnormal time. Furthermore, the gas pressure flowing through the gas pipe 71 is reduced before and after the gas leak and the restoration of the gas pipe construction. In the gas meter K, when the controller 76 detects an abnormality in the gas flow rate or a decrease in the gas pressure, the warning lamp 78 is turned on to notify the alarm, and the shutoff valve 77 is closed. Further, even when an earthquake is detected by the seismograph 75, the warning lamp 78 is turned on to notify the alarm, and the shutoff valve 77 is closed. In this way, when an abnormality occurs in the gas flow rate or gas pressure, the gas pipe 71 can be automatically closed to prevent the risk of explosion or the like. In particular, when the pressure sensor 74 of the present invention is used, it is possible to detect a slight pressure drop because it has excellent sensor characteristics, and there are few measurement errors, so there are few malfunctions, and safety is taken into consideration. A high gas meter L can be provided. Further, as shown in FIG. 17, the shut-off valve 77 is closed or a warning lamp 78 is detected by detecting an external signal 79 from a gas alarm device installed in a room or an incomplete combustion alarm device installed in a gas appliance.
May be turned on.

FIG. 18 is a block diagram of a sphygmomanometer according to the present invention. A sphygmomanometer L is a capacitance type pressure sensor 8 according to the present invention.
1, control unit 84 including cuff 82, pump 83 and CPU
Etc. A pressure guiding pipe 85 is connected between the cuff 82 and the pressure sensor 81. A pump 83 is connected to the pressure guiding pipe 85, and air can be sent from the pump 83 to the cuff 82. When measuring the blood pressure, first, the cuff 82 is wrapped around the upper arm of the measurement subject, the age and sex of the measurement subject are input from the input unit 86 such as a keyboard as necessary, and the blood pressure monitor L is started. . When the control unit 84 receives the start signal from the input unit 86, it closes the control valve 88, activates the pump 83, sends air to the cuff 82 until a predetermined pressure is reached, and tightens the upper arm portion. Cuff 8
The pressure applied to No. 2 is constantly detected by the pressure sensor 81, and when the pressure reaches a certain level, the control unit 84 causes the pump 8 to operate.
Stop 3. Next, the control unit 84 opens the control valve 88 to gradually remove the air in the cuff 82 to reduce the pressure. At this time, the pressure applied to the pressure sensor 81 via the pressure guiding tube 85 becomes smaller while changing periodically with the pressure of the blood flow flowing through the upper arm. Therefore, the change in the pressure applied to the pressure sensor 81 via the pressure guiding tube 85 is controlled by the control unit 84.
The maximum blood pressure, the minimum blood pressure, and the pulse rate can be obtained by detecting with. When the minimum blood pressure is obtained, the control unit 84 fully opens the control valve 88 to discharge the air in the cuff 82 to the atmospheric pressure. The obtained systolic blood pressure and diastolic blood pressure are displayed on the output unit 87 including a display or the like, or by referring to the input age or the like, it is possible to call attention to an abnormal value or the like as necessary. In this sphygmomanometer, the sensor characteristic of the pressure sensor is good, and the sphygmomanometer can be made reliable.

[0054]

According to the present invention, a diaphragm having a predetermined size and shape can be accurately formed at a predetermined position.

At this time, if the shape of the diaphragm is circular, the diaphragm is deformed isotropically and the linearity of the pressure sensor is improved. In addition, there is no misalignment of mask alignment.

Further, on the surface of the semiconductor substrate on the gap side, the region facing the gap has a low impurity concentration, and the other regions have a high impurity concentration, so that the residual stress of the diaphragm is reduced and at the same time, the semiconductor substrate of the semiconductor substrate is reduced. The electric resistance can be reduced.

Furthermore, by forming a substantially annular convex portion around the gap, during anodic bonding between the semiconductor substrate and the fixed substrate, anodic bonding progresses outward from the convex portion around the gap, and strain is generated in the gap portion. Don't concentrate

If the diaphragm and the fixed electrode are made substantially circular, they will be deformed isotropically and the linearity of the pressure sensor will be improved. In particular, it is most desirable in terms of sensor characteristics to set the ratio of the area of the fixed electrode to the area of the gap to 0.4 to 0.7.

Further, by making the pressure-bonding portion of the wiring portion on the fixed electrode side thicker than the other wiring portions, it is possible to reliably connect to the wiring portion on the semiconductor substrate side, and the fixed electrode is connected to the electrode pad of the semiconductor substrate. It can be pulled out reliably.

If the crimping portion is located outside the thin film portion of the semiconductor substrate, the thin film portion is less likely to be stressed when the crimping portion is crimped, and the thin film portion can be protected.

Further, if the groove for inserting the wiring portion provided on the fixed substrate or the semiconductor substrate is made to have the same depth as the gap within the gap, the influence of the groove on the displacement of the diaphragm can be reduced. .

If a concave portion deeper than the gap is formed outside the gap and a pad portion or a wiring portion for drawing out the fixed electrode is provided on the insulating film provided in the concave portion, the fixed electrode and the movable electrode can be formed. The stray capacitance generated in parallel with the inter-sensor capacitance is reduced, and the sensor characteristics can be improved.

Further, by sandwiching the fixed substrate between the semiconductor substrates and making the bonding regions on both sides of the fixed substrate equal to the bonding regions of the semiconductor substrate, warpage and distortion of the sensor can be prevented and the temperature characteristics can be improved.

According to the manufacturing method of the present invention, the pressure sensor of the present invention having excellent sensor characteristics can be easily manufactured.

By using the pressure sensor of the present invention for a gas meter, a blood pressure monitor or the like, it is possible to provide a reliable gas meter or blood pressure monitor.

[Brief description of drawings]

FIG. 1 is a partially broken exploded perspective view showing a pressure sensor according to an embodiment of the present invention.

2 (a), (b), (c), and (d) are views for explaining a method of manufacturing the frame of the pressure sensor of the above.

3 (e) (f) (g) (h) are continuation diagrams of the same as above.

FIG. 4 (i) (j) is a continuation diagram of the above.

5 (a), (b) and (c) are views for explaining a method of manufacturing the cover of the pressure sensor of the above.

FIG. 6 is a sensor capacitance characteristic diagram of the pressure sensor of the above.

FIG. 7 is a diagram showing the relationship between the depth of the gap and the sensitivity (sensor capacitance) in the pressure sensor of the present invention.

FIG. 8 is a diagram showing the relationship between the diameter ratio of the fixed electrode to the gap and the non-linearity of the sensor capacitance in the pressure sensor of the present invention.

FIG. 9 is a diagram showing a relationship between a maximum displacement amount of a diaphragm and sensitivity and linearity in the pressure sensor of the present invention.

FIG. 10 is a diagram showing a relationship between a cover thickness and temperature characteristics in the pressure sensor of the present invention.

FIG. 11 is a schematic sectional view showing a pressure sensor which is another embodiment of the present invention.

FIG. 12 is a schematic sectional view showing a pressure sensor which is still another embodiment of the present invention.

FIG. 13 is a schematic sectional view showing a pressure sensor which is still another embodiment of the present invention.

14A and 14B are a plan view and a cross-sectional view showing a pressure sensor which is still another embodiment of the present invention.

FIG. 15 is a plan view showing a pressure sensor which is still another embodiment of the present invention.

FIG. 16 is a schematic sectional view showing a pressure sensor which is still another embodiment of the present invention.

FIG. 17 is a configuration diagram showing a gas meter according to the present invention.

FIG. 18 is a configuration diagram showing a sphygmomanometer according to the present invention.

19A and 19B are a plan view and a cross-sectional view showing a conventional pressure sensor.

[Explanation of symbols]

 2 diaphragm 4 gap 8 lead-out wiring on cover side 8a crimping portion 10 lead-out wiring on frame side 12 thin film portion formed by anisotropic etching 14 pressure introducing path 15 convex portion 31 groove 32 electrode for correction capacitance

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area H01L 29/84 B

Claims (16)

[Claims] 1. A deep recess is formed in a semiconductor substrate, a thin film portion serving as a movable electrode is formed on a bottom surface of the recess, and a fixed substrate having a fixed electrode is bonded to the semiconductor substrate to form a recess of the thin film portion. A pressure sensor in which an opposite side surface and a fixed electrode are opposed to each other with a gap therebetween, wherein the gap is set to be accommodated in the thin film portion in a plan view. 2. The pressure sensor according to claim 1, wherein the gap is provided in the semiconductor substrate. 3. The pressure sensor according to claim 1, wherein the gap is provided on a fixed substrate. 4. The pressure sensor according to claim 1, 2 or 3, wherein the gap has a circular shape. 5. The surface of the semiconductor substrate on the gap side has a low impurity concentration in a region facing the gap and a high impurity concentration in the other regions. The pressure sensor described. 6. A substantially annular convex portion is formed around the gap.
The pressure sensor described in. 7. The gap and the fixed electrode are both substantially circular, and the ratio of the area of the fixed electrode to the area of the gap is 0.4 to 0.7. The pressure sensor according to claim 1, 2, 3, 5 or 6. 8. The fixed electrode is fixed to the fixed electrode by crimping a wiring part drawn from the fixed electrode to the outer peripheral part of the fixed substrate and a wiring part drawn from a pad part provided on the outer peripheral part of the semiconductor substrate. In the pressure sensor electrically drawn to the pad portion, the film thickness of the pressure-bonded portion of the fixed electrode side wiring portion with the pad portion side wiring portion is larger than the film thickness of other wiring portions. Claims 1, 2, 3, 4, 5,
The pressure sensor according to 6 or 7. 9. The fixed electrode is formed by crimping a wiring part drawn from the fixed electrode to the outer peripheral part of the fixed substrate and a wiring part drawn from a pad part provided on the outer peripheral part of the semiconductor substrate. The pressure sensor electrically drawn to a pad part WHEREIN: The said crimping | compression-bonding part is located in the outer side of the thin film part of the said semiconductor substrate, 1, 2, 3, 4, 5 ,.
The pressure sensor according to 6, 7, or 8. 10. The fixed electrode is formed by crimping a wiring portion drawn from the fixed electrode to the outer peripheral portion of the fixed substrate and a wiring portion drawn from a pad portion provided on the outer peripheral portion of the semiconductor substrate. In the pressure sensor electrically drawn to the pad portion, a groove for inserting the wiring portion is provided in the semiconductor substrate or the fixed substrate in which the gap is formed, and the groove is formed at the same depth as the gap in the gap. Claims 1, 2, 3, 4, 5, 6, 7,
The pressure sensor according to 8 or 9. 11. The fixed electrode is fixed to the fixed electrode by crimping a wiring part drawn from the fixed electrode to the outer peripheral part of the fixed substrate and a wiring part drawn from a pad part provided on the outer peripheral part of the semiconductor substrate. In the pressure sensor electrically drawn to the pad portion, a concave portion deeper than the gap is formed outside the gap of the semiconductor substrate having the gap, and the pad portion and the pad portion are formed on the insulating film formed in the concave portion. The wiring portion is provided, and the wiring portion is provided.
The pressure sensor according to 6, 7, 8, 9 or 10. 12. Another semiconductor substrate is bonded to the surface of the fixed substrate opposite to the surface to which the semiconductor substrate is bonded, so that the bonding areas on both surfaces of the fixed substrate are substantially equal to each other. Claims 1, 2, 3, 4,
The pressure sensor according to 5, 6, 7, 8, 9, 10 or 11. 13. A thin film portion is formed by deep anisotropic etching on one surface of a semiconductor substrate, and a gap having a smaller area than the thin film portion is formed by shallow dry etching on the other surface of the semiconductor substrate. After that, a method of manufacturing a pressure sensor, characterized in that a fixed substrate having a fixed electrode is anodically bonded to the gap side surface of the semiconductor substrate. 14. A thin film portion is formed by deeply anisotropically etching a surface of a semiconductor substrate, and a surface of the fixed substrate is shallowly etched to form a gap having an area smaller than that of the thin film portion. A method for manufacturing a pressure sensor, comprising: forming a fixed electrode on a substrate; and then anodic bonding the semiconductor substrate and the fixed substrate so that a thin film portion of the semiconductor substrate and a gap of the fixed substrate face each other. 15. The method according to claim 1, 2, 3, 4, 5, 6, 7,
A gas meter comprising the pressure sensor according to 8, 9, 10, 11 or 12. 16. The method according to claim 1, 2, 3, 4, 5, 6, 7,
A sphygmomanometer comprising the pressure sensor according to 8, 9, 10, 11 or 12.