JP2894478B2 - Capacitive pressure sensor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type pressure sensor using a silicon substrate as a diaphragm and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a pressure sensor using silicon, a part of a silicon substrate is etched to form a pressure-sensitive diaphragm.
A glass plate provided with an electrode is provided at a portion facing the pressure-sensitive portion, a capacitor is formed between the diaphragm and the electrode, and a change in capacitance due to a change in pressure is detected.

[0003] Conventional pressure sensors, and two pressure P ₀ when none of the two pressure P ₀ and P ₁ is not a fixed value P
A relative pressure sensor for measuring the differential pressure of ₁ and two pressures P
Two pressures P ₀ when _one of ₀ and P ₁ is a fixed value
There are two types of absolute pressure sensor that measures the pressure difference P ₁ and.

FIG. 7 shows a first example of a conventional capacitance type pressure sensor.
It is sectional drawing of the example of FIG.

A lower electrode 52 of the opposite conductivity type is provided on the upper surface of a silicon substrate 51 of one conductivity type (P type or N type) and single crystal, and the thin portion 5 is etched from below the lower electrode 52.
3. A thick portion 54 is formed to be a pressure-sensitive portion. A field oxide film 55 for isolation is provided next to the pressure-sensitive portion, and a well 56 of the opposite conductivity type is provided in a region surrounded by the field oxide film 55.
, And a signal processing circuit section 58 including a semiconductor element 57 is provided in the well 56. The lower electrode 52 and the signal processing circuit section 58 are connected by wiring (not shown), and a lead wire 59 is connected to the signal processing circuit section 58 to be drawn out. This forms a diaphragm.

The upper glass plate 61 is made of a glass plate such as Pyrex glass. A concave portion is formed in a region of the diaphragm 51 facing the lower electrode 52, and an upper electrode 62 is formed in the concave portion. The connection wiring 63 for connecting the upper electrode 62 to the signal processing circuit section 58 is
2 to the bottom surface of the upper glass plate 61.

The pedestal glass plate 71 is made of a glass plate such as Pyrex glass.
A vent hole 72 is formed in a region facing 4.

A diaphragm is placed on a pedestal glass plate 71, an upper glass plate 61 is placed thereon, the lower electrode 52 and the upper electrode 62 are aligned, heated to about 400 ° C., and applied with a direct current of 600 to 1000 V. Bonding is performed by an anodic bonding method in which a voltage is applied. By this joining, a closed cavity 64 is formed between the lower electrode 52 and the upper electrode 62, and the lower electrode 52 and the upper electrode 62 form a capacitor. The upper electrode 62 is connected to the signal processing circuit section 58 by the connection wiring 63.

Now, let the pressure in the cavity 4 be P₀And Pressure P
₀Is a constant value, which is a reference value. External pressure is P₁To be
And this pressure sensor has a pressure P₀Pressure difference with reference value
(P ₁−P₀) Is detected. The signal processing circuit unit 58
Calculate the absolute pressure from the value of. Therefore, this pressure sensor
Is an absolute pressure sensor.

FIG. 8 shows a second example of a conventional capacitance type pressure sensor.
It is sectional drawing of the example of FIG.

This pressure sensor is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-23993.
No. 8, the silicon substrate 81 is etched from both sides to form a thin portion 82 to be a pressure-sensitive portion. An upper electrode 83 and a correction electrode 8 surrounding the upper electrode 83 at intervals are formed in a concave portion formed on the lower surface of the thin portion 82.
4 is provided, and a signal processing circuit portion 85 is provided in a region adjacent to the thin portion 82, and the upper electrode 83 and the correction electrode 84 are connected to the signal processing circuit portion 85. This forms a diaphragm.

The pedestal glass plate 91 is made of a glass plate such as Pyrex glass and has a diaphragm upper electrode 83.
The lower electrode 92, the correction electrode 93, and these electrodes 92 and 93 are provided in a region facing the
5 is provided. Further, a ventilation hole 95 penetrating the lower electrode 92 from the lower surface of the pedestal glass plate 91 and the signal processing circuit unit 8 from the lower surface of the pedestal glass plate 91.
A hole 96 reaching 5 is provided.

The diaphragm is placed on the pedestal glass plate 91, and the lower electrode 92 and the upper electrode 83 are aligned with each other.
Join by anodic bonding. By this bonding, the lower electrode 92
And the upper electrode 83 form a capacitor.
Is connected to the signal processing circuit unit 85 by the wiring 94. A signal line 98 is inserted into the hole 96 and fixed with a conductive adhesive 97, and the signal line 98 is connected to the signal processing circuit unit 85 and pulled out. Thin part 82 of diaphragm and pedestal glass plate 91
A cavity 86 is formed therebetween. This cavity 86 has the ventilation hole 9
It is connected to 5. This pressure sensor is a relative pressure sensor for measuring the relative pressure since both sides of the thin portion 82 are open.

FIG. 9 is a correlation diagram showing the relationship between the gap between the upper electrode and the lower electrode and the pressure-capacity characteristics in the capacitance type pressure sensor.

In the capacitance type pressure sensor, when the pressure increases, the thin portion of the diaphragm bends, the gap d between the upper electrode and the lower electrode becomes narrower, and the capacitance of the capacitor formed by the upper electrode and the lower electrode becomes the gap d. Increases in inverse proportion to Now, the gap between the upper electrode and the lower electrode pressure of the pressure sensor of d ₁ - Assuming that capacitance characteristic is represented by a line 101, the pressure sensor of d ₁ is smaller than the gap _{d 2 (d 2 <d 1} ) The pressure-capacitance characteristic is represented by a line 102, and the pressure-capacity characteristic of the pressure sensor having a gap d ₃ (d ₃ > d ₁ ) larger than d ₁ is represented by a line 103. Therefore, in the capacitance type pressure sensor, it is important to secure the gap d between the upper electrode and the lower electrode as designed.

FIG. 10 is a correlation diagram showing the relationship between the thickness of the thin portion and the pressure-capacity characteristics in the capacitance type pressure sensor.

In the capacitance type pressure sensor, the thinner the thinner portion of the diaphragm becomes, the more easily the thinner portion is bent at the same pressure, so that the distance between the upper electrode and the lower electrode is easily reduced. The capacity of the capacitor formed by the electrode and the lower electrode tends to be large. In FIG. 10, line 104
Indicates the pressure-capacity characteristics when the thickness of the thin portion is small, and the line 105 indicates the pressure-capacity characteristics when the thickness of the thin portion is large. The greater the pressure, the greater the difference in capacitance between the thinner and thinner parts. Therefore, in order to reduce the variation in the pressure-capacity characteristics, it is necessary to reduce the variation in the thickness of the thin portion.

[0018]

In the conventional pressure sensor described above, the distance between the upper electrode and the lower electrode is formed by etching the silicon substrate, etching the glass plate, or etching both the silicon substrate and the glass plate. The thin portion of the diaphragm was also formed by etching the silicon substrate. Etching for setting the distance between the upper electrode and the lower electrode and the thickness of the thin portion has been controlled by the composition of the etching solution, the temperature, and the etching time. However, in the case of etching, when the gap between the upper electrode and the lower electrode is about 1 to 2 μm, there is a variation of about ± 0.4 μm, and when the thickness of the thin portion is about 10 to 20 μm, ± 0.2 μm. There is a variation of about 3 μm, and it has been extremely difficult to suppress the variation to less than this. For this reason, it is very difficult to keep the sensitivity of the pressure sensor within a narrow range of variation, and if the variation is to be kept within a narrow range, there is a problem that the yield is reduced and the cost is increased.

An object of the present invention is to make it easy to make the distance between the upper electrode and the lower electrode and the thickness of the thin portion of the diaphragm within a narrow range of variation, and to keep the sensitivity of the sensor within the narrow range of variation. It is an object of the present invention to provide a capacitance type pressure sensor which has a structure which can be easily manufactured and which can stably produce a product having uniform sensitivity with good yield, and a method of manufacturing the same.

[0020]

According to the present invention, there is provided a capacitance type pressure sensor according to the present invention, comprising a lower electrode of the opposite conductivity type provided on the upper surface of a single conductivity type single crystal silicon substrate; A diaphragm having a thin portion formed by selectively removing the substrate from the lower surface and a thick portion formed in the thin portion, and an opposite conductivity type provided on the lower surface of a single conductivity type single crystal silicon plate. An upper electrode, and an electrode extraction portion formed by selectively removing the silicon plate from the upper surface until reaching the upper electrode, wherein the upper electrode faces the lower electrode at an interval. An upper electrode plate mounted on an upper surface of a silicon substrate, and disposed between the diaphragm and the upper electrode plate to form a cavity between the upper electrode and the thin portion and to form the upper electrode and the lower electrode An insulating film that keeps an interval between the thin film and a pedestal glass plate that is provided on the lower surface of the diaphragm and forms a cavity between the thin portion and a ventilation hole that communicates with the cavity. I do.

The present invention is characterized in that the thin portion is constituted by a part of the lower electrode of the opposite conductivity type.

The present invention is characterized in that the electrode lead-out portion of the lower electrode is formed in a recess reaching the lower electrode from the lower surface of the silicon substrate.

The present invention is characterized in that the electrode lead-out portion of the lower electrode is formed in a recess reaching the lower electrode from the upper surface of the silicon plate.

The present invention is characterized in that the upper electrode plate has a hole that penetrates a part of the upper electrode from the upper surface of the silicon plate to reach the cavity.

The present invention is characterized in that a signal processing circuit for obtaining a pressure value from a capacitance value detected by the upper electrode and the lower electrode is formed integrally with the upper electrode plate.

The method of manufacturing a capacitance type pressure sensor according to the present invention comprises: (A) a lower electrode forming step of forming a lower electrode of the opposite conductivity type on the upper surface of a single conductivity type single crystal silicon substrate 1;
(B) an upper electrode plate forming step of forming an upper electrode of the opposite conductivity type on a lower surface of a silicon plate of one conductivity type single crystal; (C) a lower electrode of the silicon substrate and an upper electrode of the silicon plate or the upper surface of the silicon plate or the silicon plate An insulating film forming step of forming an insulating film having a predetermined thickness on the lower surface of the substrate; (D) bonding the silicon substrate and the silicon plate by positioning the lower electrode and the upper electrode so as to face each other; Matching process,
(E) The silicon substrate is selectively removed from the lower surface until it reaches the lower electrode to form a thin portion to form a diaphragm, and at the same time, the silicon plate is selectively removed from the upper surface to expose a part of the upper electrode. (F) a pedestal glass plate forming step of selectively etching a glass plate to form ventilation holes;
(G) a laminating step of positioning the ventilation hole of the pedestal glass plate so as to face the thick portion of the diaphragm, and laminating and laminating the diaphragm on the upper surface of the pedestal glass plate. I do.

The present invention is characterized in that the etching step includes an etching for forming a hole reaching the insulating film through a part of the upper electrode facing the thin portion.

The present invention is characterized in that the insulating film is selectively removed through the hole to form a cavity between the thin portion and the upper electrode.

The present invention is characterized in that the insulating film is selectively formed in a region excluding the thin portion.

According to the present invention, the etching step includes an etching step of selectively removing the silicon substrate from the lower surface until the silicon substrate reaches the lower electrode, exposing a part of the lower electrode to form a recess for extracting an electrode. Features.

According to the present invention, the etching step includes an etching step of selectively removing the silicon plate from the upper surface until reaching the lower electrode to expose a part of the lower electrode to form a concave portion for taking out the electrode. Features.

[0032]

According to the present invention, the distance between the upper electrode and the lower electrode is determined by the thickness of the insulating film. When a SiO ₂ film or the like is used for the insulating film, ± 0.01 μm for an insulating film having a thickness of 1-2 μm.
The thickness can be controlled to a desired thickness with the following accuracy. Therefore, the interval between the electrodes can be controlled with this accuracy, and variation in pressure-capacity characteristics can be reduced. Further, in the present invention, the lower electrode is formed of a high impurity region and used as an etch stopper, and the thin portion is formed by selectively removing the lower electrode, so that excessive or insufficient etching can be prevented, and the thin portion can be prevented. The thickness can be controlled with high precision, and variations in pressure-capacity characteristics can be reduced.

According to the present invention, the impurity region whose thickness can be controlled with high precision is used as the lower electrode, and a part of this lower electrode is made to be a thin portion. -Variation in capacitance characteristics can be reduced.

If a concave portion for forming the electrode extraction portion of the lower electrode is provided on the lower surface side of the silicon substrate, etching can be performed at the time of forming the thin portion, and the manufacturing process can be shortened.

If the electrode take-out portion of the lower electrode is provided on the upper surface side of the silicon plate, wiring at the time of assembling and mounting on a printed wiring board becomes easy.

When it is desired to obtain a relative pressure measuring pressure sensor for measuring a pressure difference between two pressures, a hole communicating with a cavity between the upper electrode and the lower electrode is formed in the upper electrode plate.

When the signal processing circuit is formed integrally with the upper electrode plate, the element area can be reduced, the size can be reduced, and the cost can be reduced.

In the method of manufacturing a pressure sensor according to the present invention, the distance between the upper electrode and the lower electrode is determined by the thickness of the insulating film, and the thickness of the thin portion is determined by the thickness of the upper electrode. The thickness of the thin portion is set using the high-concentration impurity region as an etch stopper by utilizing the fact that the etching rate of the high-concentration impurity region is extremely slower than that of the low-concentration impurity region. For this purpose, a lower electrode having a high impurity concentration is first provided on a silicon substrate, an insulating film is formed on one of the silicon substrate and the silicon plate, and the silicon substrate and the silicon plate are bonded and etched. Therefore,
The distance between the upper electrode and the lower electrode and the thickness of the thin portion can be controlled with high accuracy.

In order for the thin portion to move by sensing pressure, a space is required on both sides of the thin portion. When the insulating film is formed over the entire surface of the silicon substrate or the silicon plate and bonded together, the insulating film in contact with the thin portion needs to be removed by etching. Therefore, a hole for introducing an etching solution is formed.

An etching solution is introduced through the holes to selectively remove the insulating film, thereby forming a cavity between the thin portion and the upper electrode.

When the silicon substrate and the silicon substrate are bonded together after the insulating film in contact with the thin portion is selectively removed in advance,
There is no need for etching, and the work becomes easier.

When the concave portion for taking out the lower electrode is formed on the lower surface of the silicon substrate, if the concave portion is formed at the same time as the etching for forming the thin portion, the etching can be completed in one step, thereby reducing the number of steps.

When the concave portion for taking out the lower electrode is formed on the upper surface of the silicon substrate, the concave portion is formed by etching the silicon plate from the upper surface to reach the lower electrode.

[0044]

FIG. 1 is a sectional view of a first embodiment of the present invention.

The silicon substrate 1 has a crystal orientation of [100].
And N-type single crystal silicon having a main surface of
The surface of the silicon substrate 1 is doped with P-type²⁰
cm ^-3By diffusing into the above high concentration, the lower electrode 2 having high conductivity is formed.
Form. Selective etching of silicon substrate 1 to thin section
5, a thick portion 6, and a concave portion 7 are formed. The thin part 5 is
It is composed of a part of the pole 2 and has almost the same thickness as the lower electrode 2.
I do. The thickness of the thick part 6 is 3 to 10 times the thickness of the thin part 5
About. An electrode extraction portion 8 is provided in the concave portion 7. to this
A diaphragm is formed.

The silicon plate 11 has a crystal orientation of [100].
And N-type single crystal silicon having a main surface of
P type impurities are added to the surface of the silicon²⁰
cm ^-3The high conductivity upper electrode 12 diffused to the above high concentration
To form The silicon plate 11 is selectively removed to form the recess 15
a and 15b are formed. A hole 16 is provided in the recess 15a.
The electrode extracting portion 18 is provided in the portion 15b. This allows the upper part
An electrode plate is configured.

The silicon substrate 1 and the silicon plate 11 are aligned so that the upper electrode 12 and the thin portion 5 face each other, and are joined with an insulating film 13 having a thickness of 1 to 2 μm therebetween. The insulating film 13 forms a cavity 17 between the upper electrode 12 and the thin portion 5 and keeps a space between the upper electrode 12 and the lower electrode 2. The cavity 17 needs to completely cover the thin portion 5. Although SiO ₂ film formed by thermal oxidation as an insulating film 13 is best suited for, it can be used SiO ₂ film formed by CVD (chemical vapor deposition) method, phosphosilicate glass, borosilicate glass, Rinhou silicate glass .

The pedestal glass plate 21 has wirings 22 on its surface, and has a ventilation hole 23 at a location where gas can be sent to the diaphragm to apply pressure. The pedestal glass plate 21
It is aligned and bonded to the silicon substrate 1 by anodic bonding or the like. By this bonding, a cavity 24 is formed between the pedestal glass plate 21 and the diaphragm of the silicon substrate 1, the ventilation hole 23 communicates with the cavity 24, and at the same time, the electrode extraction portion 8 of the silicon substrate 1 and the wiring 22 are connected. The metal wire 9 is connected to the wiring 22. The metal wire 19 is connected to the electrode extracting portion 18.

As described with reference to FIG. 9, the distance between the upper electrode 12 and the lower electrode 2 is directly related to the pressure-capacity characteristic of the pressure sensor. In the present invention, this interval is determined by the insulating film 13 such as a SiO ₂ film or the like whose thickness can be controlled with high accuracy. Therefore, this interval can be controlled with high accuracy, and variations in pressure-capacity characteristics are reduced. be able to.

As described with reference to FIG. 10, the thickness of the thin portion 5 is directly related to the pressure-capacity characteristics. In the present invention, utilizing the fact that the etching rate of the high-concentration impurity region is extremely slower than that of the low-concentration impurity region, the lower electrode 2 is formed as a high-concentration impurity region and used as an etch stopper. The thickness of the lower electrode 2 was set. Since the depth (thickness) of the impurity region can be controlled with high precision, the thickness of the thin portion 5 can be controlled with high precision, and variations in pressure-capacity characteristics can be reduced.

In the first embodiment, the hole 16 communicating with the cavity 17 is provided. However, when it is desired to obtain a pressure sensor for measuring absolute pressure by using the cavity 17 as a sealed space, the hole 16 is formed. No need. Accordingly, the concave portion 15a becomes unnecessary.

FIG. 2 is a cross-sectional view showing the order of steps for explaining a method of manufacturing the pressure sensor of FIG.

First, as shown in FIG. 2A, boron is thermally diffused or ion-implanted into the back surface (lower surface) of a single crystal N-type silicon plate 11 having a main surface with a crystal orientation of [100]. Thus, a P-type region is formed to form the upper electrode 12. A substantially circular small region 12a in which boron is not diffused is provided in the center of the upper electrode 12. This is to form an inlet for the etchant when forming the cavity 17 later.
The upper electrode 12 has an impurity concentration of 1 × 10 ²⁰ cm ⁻³ or more in order to lower the electric resistance and to function as an etch stopper described later. The thermal diffusion of boron is performed, for example, by a gas phase diffusion method using BCl ₃ or BBr ₃ , BN
This is performed by a solid phase diffusion method or the like. The ion implantation is performed by, for example, a method using BF ₂ ⁺ . Silicon plate 11
The thickness of the insulating film 13 is 1 to 2 μm
An m ₂ SiO ₂ film is formed. As described with reference to FIG. 9, the thickness of the insulating film 13 is very important because it determines the gap between the lower electrode 2 and the upper electrode 12 and determines the pressure-capacity characteristics. When the SiO ₂ film is formed by the thermal oxidation method, the thickness can be controlled quite accurately, and a desired thickness can be obtained with an accuracy of ± 0.01 μm or less. The insulating film 13 may be formed by a CVD (chemical vapor deposition) method instead of the thermal oxidation method, and the insulating film 13 is not limited to the SiO ₂ film, and may be a glass such as a phosphosilicate glass, a borosilicate glass, or a phosphoborosilicate glass. Can be used. Further, the insulating film 13 may be provided on the surface of the silicon substrate 1.

Next, as shown in FIG. 2B, a P-type region is formed on the surface (upper surface) of an N-type silicon substrate 1 made of a single crystal having a main surface with a crystal orientation of [100]. The lower electrode 2 is used. The lower electrode 2 has an impurity concentration of 1 × 10 ²⁰ cm ⁻³ or more for the same reason as the upper electrode 12. The thickness of the lower electrode 2 is the same as the thickness of the thin portion 5 to be formed later. As described with reference to FIG. 10, the thickness of the thin portion 5 determines the pressure-capacity characteristics and is very important. The thickness of the thin portion 5 is determined by the thickness of the lower electrode 2.
Is determined by the depth of diffusion. However, the depth of diffusion can be controlled with high precision, so that the thickness of the thin portion 5 can be controlled with high precision.

Next, as shown in FIG. 2C, the silicon plate 11 is placed on the silicon substrate 1 and aligned.
The silicon substrate 1 and the silicon plate 11 are bonded together hermetically by anodic bonding.

Next, as shown in FIG. 2D, the SiO ₂ film 3 is used as a mask on the silicon substrate 1 and the silicon plate 11.
14 is selectively formed and etched to form recesses 4, 7, 15
a and 15b are formed. The depth of the recesses 4, 7, 15a, 15b is set to a value obtained by subtracting the difference in thickness between the thick portion 6 and the thin portion 5 from the thickness of the silicon substrate 1. When the SiO ₂ film is used as a mask, the etching solution is TMAH (tetramethyl ammonium hydroxide, (CH ₃ ) ₄ NOH)
Alternatively, hydrazine (N ₂ H ₄ ) is suitable. These etchants is because not so much etched SiO _2.

Next, as shown in FIG.
Only the portion of the SiO ₂ film 3a that will become the lower electrode 2 is removed.
Then, etching is performed until a part of the surface of the upper electrode 12 is exposed, so that the depths of the concave portions 4, 7, 15a, and 15b are increased to form the thin portion 5 and the thick portion 6. The thickness of the thick portion 6 is about 3 to 10 times the thickness of the thin portion 5. This etching is
Utilizing that the etching rate of the high concentration impurity region is extremely slower than that of the low concentration impurity region, the lower electrode 2 and the upper electrode 12 of the high concentration impurity region serve as an etch stopper. Therefore, the surfaces of the lower electrode 2 and the upper electrode 12 can be accurately exposed. The reason why the small region 12a is provided earlier is that the etching is performed on the small region 12a to form the hole 16 so that the insulating film 13 is exposed. Thereby, a diaphragm is formed.

Next, as shown in FIG. 2F, a cavity 17 is formed by introducing an etchant through the hole 16 and etching the insulating film 13. When the insulating film 13 is SiO ₂ , hydrofluoric acid is suitable for the etching solution. Lateral extension of the cavity 17, as shown in FIG. 3, larger than completely encompasses the circle R ₁ a thin portion 5, to be in the range R ₁₂ between the chip smaller circle R ₂ of one pressure sensor I do. The circle R ₂ determines the allowable value of the cavity 17,
It is not so strict that the silicon substrate 1 and the silicon plate 1
It is permissible to the extent that bonding with 1 can be maintained. In the etching of the SiO ₂ film, the etchant easily penetrates from the side surfaces of the silicon substrate 1 and the silicon plate 11, and if it is desired to avoid this, as shown in FIG. It is preferable to provide a polycrystalline silicon film 25 for protection. Lower electrode 2 exposed in recesses 7 and 15b
Then, electrode extraction portions 8 and 18 are formed on the surface of the upper electrode 12 with a metal such as aluminum.

Next, as shown in FIG. 2 (g), wirings 22 are formed on the upper surface of the pedestal glass plate 21, and then ventilation holes 23 are opened using photolithography. Pedestal glass plate 2
A variety of materials can be used for 1, but Pyrex glass or the like is suitable.

Next, as shown in FIG.
The diaphragm of the silicon substrate 1 is placed on the upper surface of the substrate 1 and bonded by an anodic bonding method. This bonding forms a cavity 24 between the pedestal glass plate 21 and the diaphragm. When bonding the pedestal glass plate 21 to the diaphragm,
Positioning is performed so that 3 communicates with the cavity 24 and the wiring 22 and the electrode extraction portion 8 are electrically connected. next,
After separating the chip into individual chips, further separating the silicon substrate 1 and the silicon plate 11 on the metal wire mounting portion, and placing them in a package, the metal wires 9 and 19 are mounted to complete the pressure sensor.

The above-mentioned cavity 17 is formed by bonding the silicon substrate 1 and the silicon plate 11 and then etching the insulating film 13 through the hole 16. After the insulating film is provided on the upper surface of the silicon substrate 1, the cavity 17 is formed. The silicon substrate 1 and the silicon plate 11 can be joined after the insulating film in the region to be 5 is removed by etching. This method is particularly effective for manufacturing a pressure sensor for measuring absolute pressure, in which the hole 17 is not provided and the cavity 17 is made a sealed space to measure absolute pressure. When manufacturing a pressure sensor for measuring absolute pressure, FIG.
The small area 12a shown in (a), FIGS. 2 (d) and 2 (e)
It is not necessary to form the recess 15a shown in FIG. 2 and the hole 16 shown in FIG.

FIG. 5 is a sectional view of a second embodiment of the present invention.

In the second embodiment, the concave portion 7 is formed in the silicon plate 11, and the electrode extraction portion 8 of the lower electrode 2 is provided on the silicon plate 11 side, and the metal wire 9 is attached thereto. To make this possible, the lower electrode 2 is extended longer than in the first embodiment. In this manner, the metal wires 9 and 19 can be taken out from the positions at substantially the same height, and there is an advantage that the metal wire bonding after packaging becomes easy. The other parts are the same as the first embodiment.

As in the first embodiment, when manufacturing a pressure sensor for measuring an absolute pressure by measuring the absolute pressure using the cavity 17 as a sealed space, it is not necessary to form the hole 16. Accordingly, the concave portion 15a becomes unnecessary.

FIG. 6 is a sectional view of a third embodiment of the present invention.

In the third embodiment, the capacitance-
This is an example in which a signal processing circuit unit such as a frequency conversion circuit or a capacitance-pressure conversion circuit is built. In FIG. 6, the diffusion layer 26 and the metal line 27 show a part of the signal processing circuit unit. As described above, if the pressure sensor and the signal processing circuit are formed on the same silicon plate, the degree of integration is increased and the size of the chip can be reduced. The other parts are the same as the first embodiment.

As in the first embodiment, when the absolute pressure measurement pressure sensor for measuring the absolute pressure is manufactured by using the cavity 17 as a sealed space, the hole 16 and the concave portion 15a are unnecessary.

In each of the first to third embodiments, a relative pressure measuring pressure sensor for measuring the difference by applying different pressures from both sides of the diaphragm is used. For example, since the pressure sensor is an absolute pressure measuring pressure sensor, it is obvious that the present invention can be applied to an absolute pressure measuring pressure sensor.

[0069]

As described above, according to the present invention, it is possible to control the distance between the upper electrode and the lower electrode with high accuracy in controlling the thickness.
Since the distance is determined by an insulating film such as an O ₂ film, the distance can be controlled with high accuracy, and a pressure sensor with less variation in pressure-capacitance characteristics can be manufactured with a high yield.

Further, according to the present invention, the impurity region whose thickness can be controlled with high precision is used as the lower electrode, and a part of this lower electrode is formed as a thin portion, so that the thickness of the thin portion can be controlled with high precision. Thus, a pressure sensor having a small variation in pressure-capacity characteristics can be manufactured with a high yield.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

2A to 2C are cross-sectional views illustrating a method of manufacturing the pressure sensor shown in FIG. 1 in a process order.

FIG. 3 is a bottom view for explaining an allowable range of the cavity in FIG. 1;

FIG. 4 is a cross-sectional view illustrating a means for preventing side etching of the SiO ₂ film.

FIG. 5 is a sectional view of a second embodiment of the present invention.

FIG. 6 is a sectional view of a third embodiment of the present invention.

FIG. 7 is a sectional view of a first example of a conventional capacitance type pressure sensor.

FIG. 8 is a sectional view of a second example of a conventional capacitance type pressure sensor.

FIG. 9 is a correlation diagram showing a relationship between a gap between an upper electrode and a lower electrode and a pressure-capacity characteristic in a capacitance type pressure sensor.

FIG. 10 is a correlation diagram showing a relationship between a thickness of a thin portion and a pressure-capacity characteristic in a capacitance type pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Lower electrode 5 Thin part 6 Thick part 8 Electrode taking-out part 9 Metal wire 11 Silicon plate 12 Upper electrode 13 Insulating film 17 Cavity 18 Electrode taking-out part 21 Base glass plate 22 Wiring 23 Vent hole

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01L 9/12

Claims (12)

(57) [Claims] 1. A lower electrode of opposite conductivity type provided on an upper surface of a silicon substrate of one conductivity type, a thin portion formed by selectively removing the silicon substrate from the lower surface until reaching the lower electrode. A diaphragm having a thick portion formed in a thin portion, an upper electrode of the opposite conductivity type provided on a lower surface of a single-conductivity type single crystal silicon plate, and an upper surface of the silicon plate until reaching the upper electrode; An upper electrode plate attached to the upper surface of the silicon substrate such that the upper electrode is opposed to the lower electrode at an interval; and And the upper electrode plate,
An insulating film that forms a cavity between the upper electrode and the thin portion and maintains an interval between the upper electrode and the lower electrode; and an insulating film provided on a lower surface of the diaphragm, between the thin portion. And a pedestal glass plate having a cavity and a vent hole communicating with the cavity. 2. The capacitance-type pressure sensor according to claim 1, wherein the thin portion is constituted by a part of the lower electrode of the opposite conductivity type. 3. The capacitance type pressure sensor according to claim 1, wherein an electrode lead-out portion of said lower electrode is formed in a concave portion reaching from said lower surface of said silicon substrate to said lower electrode. 4. The capacitance type pressure sensor according to claim 1, wherein an electrode extraction portion of said lower electrode is formed in a concave portion reaching from said upper surface of said silicon plate to said lower electrode. 5. The capacitance-type pressure sensor according to claim 1, wherein said upper electrode plate has a hole penetrating a part of said upper electrode from said upper surface of said silicon plate to reach said cavity. 6. The static electrode according to claim 1, wherein a signal processing circuit for obtaining a pressure value from a capacitance value detected by the upper electrode and the lower electrode is formed integrally with the upper electrode plate. Capacitive pressure sensor. 7. A lower electrode forming step of forming a lower electrode of the opposite conductivity type on the upper surface of a single conductivity type single crystal silicon substrate; and An upper electrode plate forming step of forming a mold upper electrode; (C) an insulating film forming step of forming an insulating film having a predetermined thickness on the upper surface of the silicon substrate or the lower surface of the silicon plate; A bonding step of bonding the silicon substrate and the silicon plate by positioning the silicon substrate so that the upper electrode faces each other; and (E) selectively removing the silicon substrate from a lower surface until the silicon substrate reaches the lower electrode. At the same time as forming the diaphragm by forming the thick portion in the thin portion, the silicon plate is selectively removed from the upper surface to expose a part of the upper electrode to form a recess for taking out the electrode. (F) a pedestal glass plate forming step of forming a ventilation hole by selectively etching a glass plate; and (G) positioning the pedestal glass plate so that the ventilation hole of the pedestal glass plate faces a thin portion of the diaphragm. A method for manufacturing a capacitance type pressure sensor, comprising: a laminating step of laminating and laminating the diaphragm on an upper surface of a plate. 8. An etching method according to claim 7, wherein said etching step includes etching to form a hole penetrating a part of the upper electrode facing said thin portion and reaching said insulating film.
A manufacturing method of the capacitance type pressure sensor according to the above. 9. The method according to claim 8, wherein the insulating film is selectively removed through the hole to form a cavity between the thin portion and the upper electrode. . 10. The method according to claim 7, wherein the insulating film is selectively formed in a region excluding the thin portion. 11. The etching step includes selectively removing the silicon substrate from the lower surface until the silicon substrate reaches the lower electrode, exposing a portion of the lower electrode to form a recess for extracting an electrode. The method for manufacturing a capacitance type pressure sensor according to claim 7. 12. The method according to claim 11, wherein the etching step includes selectively removing the silicon plate from an upper surface until reaching the lower electrode to expose a part of the lower electrode to form a concave portion for taking out the electrode. The method for manufacturing a capacitance type pressure sensor according to claim 7.