JPH03202739A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make it possible to measure pressure excellently by forming the periphery of a movable diaphragm as a flat shape having no irregularities. CONSTITUTION:A sacrifice film 42 is formed so as to cover the main surface of a semiconductor substrate 40 and constituted so as to contain a disappearing part 44 covering the pressure receiving region of the substrate 40 and a diaphragm fixing part 46 covering the surrounding part of the pressure receiving region. The disappearing part 44 is formed so as to have an isotropic etching characteristic along the pressure receiving region. The fixed part 46 is formed so as to have an etching resisting characteristic. An insulating diaphragm film 48 comprising an etching resisting material is formed so as to cover the film 42 along the entire main surface of the substrate 40. The film 48 is formed flatly along the entire surface of the film 42. An etching-liquid injecting port 58 is formed at a specified position so as to penetrate the film 48. A pressure reference chamber 60 surrounded with the substrate 40 and the film 48 is formed. The film 48 function as a movable diaphragm 100. Since the film is formed flatly at a peripheral part A of the pressure receiving region, the supporting state of the diaphragm 100 is stabilized, and the sensor is operated stably for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor pressure sensor, and particularly to an improvement in a semiconductor pressure sensor in which a diaphragm is formed on the surface of a semiconductor substrate using a thin film formation technique.

[Prior art] 12th rl! J shows the configuration of a conventional semiconductor pressure sensor.

In this semiconductor pressure sensor, a pressure-receiving region on the main surface of a semiconductor substrate 1o is coated with a vanishing film 12 having a predetermined planar shape and having isotropic etching characteristics. The main surface of the semiconductor substrate 1o is coated with an insulating diaphragm film 14 made of an etching-resistant material so as to cover the vanishing film 12 over the entire main surface. At least one strain gauge 16 is provided. The diaphragm 7114 and the strain gauge 16 are further covered with an insulating protective film 18 made of a material having etching-resistant properties, and the insulating protective film 18 has connection holes located at both ends of the strain cage 16. 20 is formed. Via this connection hole 2o, both ends of the strain gauge 16 are connected to
A plurality of electrodes 22 are connected.

The insulating protective film 18. At least one etching liquid inlet 24 is formed to penetrate through the diaphragm membrane 14 and reach the vanishing film 12, and a portion of the substrate 10 and all of the vanishing film 1112 are etched through the etching fluid inlet 24. Etched away. Thereby, a pressure reference chamber 26 surrounded by the substrate 1o and the diaphragm membrane 14 is formed.

When the pressure sensor is used as an absolute pressure measurement type sensor, all etching liquid inlets 24 are sealed with sealing members 24a while maintaining the pressure reference chamber 26 in a vacuum state.

With the above configuration, the diaphragm membrane 14 located on the upper surface side of the pressure reference chamber 26 is connected to the movable diaphragm 14.
It functions as a.

When pressure is applied to this pressure sensor, the movable diaphragm 14a is deflected in proportion to the applied pressure, and due to this deflection, the strain gauge 1 provided in the pressure receiving area
6 resistance changes. Therefore, by extracting the detection signal of the strain gauge 16 via the electrode 22, the absolute pressure applied to the surface side of the movable diaphragm 14a can be measured.

[Problems to be Solved by the Invention] However, this prior art has problems to be solved as detailed below.

(a) In the conventional pressure sensor technology, after processing the vanishing film 12 made of polycrystalline silicon into a predetermined shape, the vanishing film 1
A diaphragm film 14 made of silicon nitride having etching resistance is formed on the substrate 10 so as to cover the substrate 10 .

Therefore, the peripheral portion of the movable diaphragm 14 is supported by the substrate 10 via the stepped structure A as surrounded by the dashed line in the figure. Therefore, when pressure is applied from the upper surface of the movable diaphragm 14a, the supporting strength of the diaphragm is weak and the supporting state changes, which poses a problem that the measurement accuracy of the strain gauge 16 may be reduced.

In particular, this prior art has the problem that when the semiconductor pressure sensor is used repeatedly, the step structure A portion of the movable diaphragm 14a tends to fatigue, making it difficult to accurately measure pressure over a long period of time.

(b) In the conventional pressure sensor technique shown in FIG. 12, a pressure reference chamber 26 is formed by etching away a portion of the substrate 10 and the disappearing film 12.

In response to this, the present inventors have investigated forming the pressure reference chamber 26 by etching only the vanishing film 12 without etching the substrate 1o. As a result, we found that it is sufficient to cover the surface of the semiconductor substrate 1o with an insulating film 28 made of an etching-resistant material, as shown by the dashed line in the figure, and to sequentially stack the vanishing film 12, diaphragm film 14, etc. on top of this. I found it.

However, for example, the semiconductor substrate 1 made of silicon, etc.
When a silicon nitride film is formed as a diaphragm 11114 on the silicon substrate 1o by low pressure CVD, tensile internal stress is generated between the silicon nitride film and the silicon substrate 1o due to a difference in coefficient of thermal expansion. In this case, when the disappearing film 14 between the silicon nitride film 14 and the semiconductor substrate 10 is removed by etching to form the pressure reference chamber 26, a bending moment is generated at the stepped portion A around the movable diaphragm 14a. The diaphragm 14a is the semiconductor substrate 1
It deforms to the 0 side.

Therefore, when the pressure reference chamber 26 is formed by etching away only the vanishing film 12, the movable diaphragm 1
There was a problem in that 4a was deformed toward the substrate side by the bending moment and came into contact with the insulating film 28, so that it did not function as a pressure sensor.

The present invention was made in view of such conventional problems, and its purpose is to obtain a semiconductor pressure sensor with good characteristics by making the periphery of a movable diaphragm flat with no steps. It is in.

[Means and effects for solving the problems] In order to achieve the above object, the present invention includes: a semiconductor substrate; a vanishing portion that covers a pressure receiving region on the main surface of the semiconductor substrate; and a diaphragm fixing portion that covers the periphery of the pressure receiving region. the vanishing portion is formed to have isotropic etching characteristics along the pressure receiving region; the diaphragm fixing portion includes a sacrificial film formed to have etching resistance; and a sacrificial film covering the sacrificial film. an insulating diaphragm film coated on the main surface of the semiconductor substrate and formed to have etching resistance; one etching liquid inlet; a pressure reference chamber formed by etching and removing at least the disappearing portion of the sacrificial film through the etching liquid inlet; and a pressure reference chamber formed at a predetermined position in the pressure receiving area of the insulating diaphragm membrane. and at least one strain gauge.

Below, the semiconductor pressure sensor of the present invention will be explained in more detail.

FIG. 1 shows a plan view showing the basic structure of a semiconductor pressure sensor according to the present invention, and FIG. 2 shows a cross-sectional view thereof.

In the semiconductor pressure sensor of the present invention, a sacrificial film 42 is formed on the main surface of a semiconductor substrate 40 to cover it.

A feature of the present invention is that the sacrificial film 42 is configured to include a vanishing portion 44 that covers a pressure-receiving region of the semiconductor substrate 40 and a diaphragm fixing portion 46 that covers the periphery of the pressure-receiving region, and that the sacrificial film 42 includes: The diaphragm fixing portion is formed to have isotropic etching characteristics along the pressure receiving region, and the diaphragm fixing portion is formed to have etching resistance characteristics.

The sacrificial film 42 having such characteristics is formed, for example, by covering the main surface of the semiconductor substrate 40 with a polycrystalline silicon film. At this time, this polycrystalline silicon film,
By ion-implanting or diffusing impurities such as boron, phosphorus, or nitrogen into a portion to become the diaphragm fixing portion 46, this portion is formed as the diaphragm fixing portion 46 having etching-resistant properties. A portion where no impurity is implanted or diffused, that is, a portion surrounded by the diaphragm fixing portion 46, functions as a vanishing portion 44 having isotropic etching characteristics along the pressure receiving region.

Further, the main surface of the semiconductor substrate 40 is coated with an insulating diaphragm film 48 made of an etching-resistant material so as to cover the sacrificial film 42 over the entire main surface, and the pressure receiving area of the diaphragm film 48 is located at a predetermined position. is provided with at least one strain gauge 50. At this time, the diaphragm film is formed flat over the entire surface of the sacrificial film 42, and does not have a stepped structure around the pressure receiving area unlike the conventional method.

In the present invention, it is preferable that the diaphragm film 48 and strain gauge 50 be further covered with an insulating protective film 52 made of a material having etching-resistant properties.

Connection holes 54 reaching both ends of the strain gauge 50 are formed in the insulating protective film 52, and a plurality of electrodes 56 are connected to both ends of the strain gauge 54 via the connection holes 54.

The insulating protective film 52 is placed at a predetermined position in the pressure receiving area of this semiconductor pressure sensor. At least one etching liquid inlet 58 is formed to penetrate through the diaphragm membrane 48 and reach the vanishing part 44, and a part of the substrate 40 and all of the vanishing part 44 are injected through the etching liquid inlet 58. Etched away. As a result, a pressure reference chamber 60 surrounded by the substrate 40 and the diaphragm membrane 48 is formed, and the diaphragm membrane 48 located on the upper surface side of the pressure reference chamber 60 functions as a movable diaphragm 100.

At this time, according to the present invention, the movable diaphragm 10
The diaphragm membrane 48 constituting the pressure receiving area is formed in a flat shape without a stepped structure at the peripheral edge A of the pressure receiving area. As a result, even when pressure is applied from the upper surface of the movable diaphragm 100, the peripheral edge of the movable diaphragm 100 is supported and fixed with sufficient strength by the diaphragm fixing portion 46, and even when used for a long period of time, it is stable with minimal deterioration over time. It will work.

Note that the present invention is not limited to this, and for example, as shown in FIG. 6, by forming an insulating layer 46 having etching-resistant properties between the semiconductor substrate 40 and the sacrificial film 42, only the disappearing portion 44 can be removed. The pressure reference chamber 60 may be formed by removing it by etching.

Further, the etching liquid inlet 58 is completely or partially sealed by a sealing member 62 as required.

The semiconductor pressure sensor of the present invention has the above-described configuration. Next, the case of measuring absolute pressure and the case of measuring differential pressure using this sensor will be explained.

Note that in the semiconductor pressure sensor of the present invention, the pressure reference chamber 60
The diaphragm membrane 48 located on the upper surface side functions as a movable diaphragm 100.
In addition, when the insulating protection film 52 is provided as described above, the laminated film consisting of the diaphragm film 48 and the insulating protection 1152 functions as the movable diaphragm 100.

First, when the pressure sensor of the present invention is used as an absolute pressure measurement type sensor, all etching liquid inlets 58 are sealed with sealing members 62 while maintaining the pressure reference chamber 60 in a vacuum state. Thereby, when pressure is applied, the movable diaphragm 100 deflects in proportion to the applied absolute pressure, and this deflection changes the resistance of the strain gauge 50 provided in the pressure receiving area.

For example, if one set of strain gauges 50-2. The strain applied to a set of strain gauges is a compressive force on one side and a tensile force on the other, and as a result, if the resistance of one set of strain gauges increases, the resistance of the other set of strain gauges will decrease. .

Therefore, these two sets of strain gauges 50-1°50-2.
-50-3.50-4 are bridge-connected through electrodes 56-1.56-2.56-3゜56-4 so that the resistance changes are added, and a power supply is connected to the opposing pair of electrodes. For example, a voltage proportional to the absolute pressure applied to the movable diaphragm 100 can be output from the other pair of electrodes.

At this time, the movable diaphragm 100 of the present invention has a flat shape with no step structure at the part fixed to the diaphragm fixing part 46 located at the peripheral edge A, so that the movable diaphragm 100 has a flat shape with no step structure. It will be supported and fixed with strength. Therefore, even if pressure is repeatedly applied to the surface of the movable diaphragm 100, the peripheral edge of the movable diaphragm 100 is less likely to fatigue as in the conventional case, and even after long-term use, the strain gauge 50 generates an electric current corresponding to the applied pressure. A signal will be output. Therefore, highly accurate pressure measurement is possible over a long period of time.

Furthermore, when the semiconductor pressure sensor of the present invention is used as a sensor for measuring differential pressure, the movable diaphragm 100 is formed into a rectangular shape, as shown in FIGS. 3 and 4, for example, and the movable diaphragm 100 Divide into thirds lengthwise. At least one strain gauge 50 is arranged in one region, and an etching liquid inlet 58 is arranged in the other region.
The etching liquid inlet 58 may be provided with a pressure introducing means for introducing a comparative pressure P2 into the etching liquid inlet 58.

In addition to this, when the semiconductor pressure sensor of the present invention is used as a differential pressure measurement type sensor, a plurality of etching liquid inlets 58 are provided, and some of them are sealed using a sealing member 60. and the rest is formed to be open. and,
It is sufficient to provide a pressure introducing means for introducing the pressure P2 for comparison into the opened etching liquid inlet 58 toward the pressure reference chamber 60.

This makes it possible to accurately measure the differential pressure between the front and back surfaces of the movable diaphragm 100 as a change in resistance of the strain gauge 50, similar to the absolute pressure type sensor.

Further, the semiconductor pressure sensor of the present invention is not limited to the type in which a pressure reference chamber 60 is formed by etching away both a part of the substrate 40 and the disappearing portion 40, as shown in FIGS. 1 to 4. For example, as shown in FIG. 6, only the disappearing portion 44 may be removed by etching to form the pressure reference chamber 60.

In this case, if there is a stepped structure around the movable diaphragm 100 as in the conventional case, the movable diaphragm 100 will come into contact with the surface of the substrate 40 and will no longer function as a pressure sensor, but in the present invention, the diaphragm 1148 Since the overall shape can be made flat, there is no step structure at the periphery of the movable diaphragm 100. Therefore, there is no problem of initial deflection due to internal tension stress of the movable diaphragm 100 as in the prior art, and it is possible to stably operate the movable diaphragm 100 without contacting the substrate 40.

Manufacturing Method Next, an example of a method for manufacturing the semiconductor pressure sensor according to the present invention will be specifically described.

According to this method, first, a sacrificial portion 42 having isotropic etching characteristics is formed to cover a pressure-receiving region of the main surface of a semiconductor substrate 40 .

Here, for example, when the pressure reference chamber 60 is formed as shown in FIGS. 1 and 2, a sacrificial film 42 having isotropic etching characteristics is formed over the entire peripheral surface of the semiconductor substrate 28.
Form a coating.

Further, when forming the pressure reference chamber 60 as shown in FIG. 6, for example, an insulating film 64 made of an etching-resistant material is first formed over the entire main surface of the semiconductor substrate 40, and then the insulating film 64 is formed by coating the entire main surface of the semiconductor substrate 40. A sacrificial film 42 is formed on the film 64 to cover it.

After the sacrificial film 40 is formed to cover the sacrificial film 40 in this manner, the peripheral portion of the pressure receiving area of the sacrificial film 42 is treated to have etching resistance. As a result, the pressure-receiving region of the sacrificial film 42 is formed as the vanishing section 44, and the periphery thereof is formed as the diaphragm fixing section 46. Such processing of the sacrificial film 42 can be performed by various means as necessary. For example, when the sacrificial film 42 is formed using polycrystalline silicon, the area corresponding to the diaphragm fixing part 46 may be For example, boron, phosphorus, or nitrogen may be added and diffused by ion implantation or thermal diffusion to provide etching resistance. For example, when boron is used as an impurity, it may be formed as heat-treated polycrystalline silicon in a P1 type half region having an impurity concentration of I x 10 "cm" or more.

As a result, the diaphragm fixing portion 46 exhibits sufficient etching resistance.

Next, an insulating diaphragm film 48 made of an etching-resistant material is formed to cover the sacrificial film 42 thus formed. At least one strain gauge 50 is provided at a predetermined position in the pressure receiving area of the diaphragm membrane 48, and an insulating protective film 52 made of an etching-resistant material is formed over the strain gauge 50 and the diaphragm membrane 48.

In this way, the sacrificial film 42. After coating the diaphragm film 48 and the insulating protective film 52, the insulating protective film 52 and the diaphragm 1 are then coated at a predetermined position in the pressure receiving area.
At least one etching liquid inlet 58 is formed to penetrate through the etching solution 148 and reach the disappearing portion 44 of the sacrificial film 42 .

A characteristic feature of the present invention is that by injecting an anisotropic etching liquid through the etching liquid inlet 58 formed in this manner, all of the disappearing portion 44 of the sacrificial film 42 and, if necessary, the semiconductor substrate can be etched. Etching and removing a part of 4o,
The purpose is to form the pressure reference chamber 6o and to form the movable diaphragm 100 that covers it, and the process will be described in detail below.

1st OrI! J shows the etching characteristics of each member, characteristic curve A represents the lateral etching characteristics when a polycrystalline silicon film is used as the vanishing part 44 of the sacrificial film 42, and characteristic curve B represents the etching characteristics of the semiconductor. The characteristic curve C represents the vertical etching characteristics when a single crystal silicon substrate is used as the substrate 40.
This represents the lateral etching characteristics when boron is ion-implanted or diffused into a polycrystalline silicon film.

Furthermore, FIG. 11 shows the progress of etching when anisotropic etching liquid is injected through the etching liquid inlet 58, (a) shows the state before anisotropic etching, and (b) shows the state before anisotropic etching. (c) represents the initial state of etching.
(d) represents an intermediate state in which etching has progressed, and (d) represents a state in which etching has been completed.

First, when an anisotropic etching liquid is injected from the etching liquid inlet 58, isotropic etching progresses in the disappearing portion 44 from the state shown in FIG. 11(a) to the states shown in FIG. 11(b) and (C). I will do it. Then, the disappearing portion 44 gradually disappears from the center to enlarge the opening, and the opening area expands in the lateral direction with time according to the characteristic curve A shown in FIG.

Furthermore, in the single crystal silicon substrate 40 exposed due to the disappearance of the disappearance part 44, anisotropic etching progresses according to the opening area of the disappearance part 44, and etching is performed in the vertical direction according to the characteristic curve B shown in FIG.

Here, if the opening area of the disappearing portion 44 is constant, the etching depth of the single crystal silicon substrate 40 will stop at the depth where the (111) plane intersects the left and right inclined planes. In the invention, since the opening area of the vanishing part 44 increases continuously over time, the first
As shown in FIG. 1(c), etching also progresses in the vertical direction of the polycrystalline silicon substrate 40.

Then, as shown in FIG. 11(d), when all of the disappearing portion 44 is etched away, the etching characteristics in the lateral direction are as follows from the characteristic curve A of the disappearing portion 44 shown in FIG.
The characteristic curve changes to characteristic curve C of the diaphragm fixing portion 46 of the sacrificial film 42, thereby reducing the etching rate in the lateral direction to several tens of minutes.

As a result, when the etching reaches the state shown in FIG. 11(d), the opening area in the lateral direction hardly expands, and the etching depth of the single-crystal silicon substrate 40 is such that the sloped surface is It almost stops at the depth where it intersects the (111) plane.

That is, in the present invention, the disappearing portion 44 of the sacrificial film 46
The shape of the pressure reference chamber 60 determines the processing dimensions of the pressure reference chamber 60, and even if etching is continued further, this shape will hardly change.

By the way, in the above explanation, an example was given in which etching was continued until the etching in the depth direction of the semiconductor substrate 40 almost stopped, but the shape of the cavity of the pressure reference chamber 60 is not essentially important in the present invention. When the movable diaphragm 100 bends due to pressure, it is only necessary to obtain a sufficient gap that does not prevent the bending. Therefore, for example, as shown in FIG. 6, the semiconductor substrate 40 and the sacrificial film 4
2 is coated with an insulating film 64 having etching-resistant properties so that the semiconductor substrate 40 is not etched at all, and the pressure reference chamber 60 is formed by etching away only the disappearing portion 44. However, as long as sufficient space is obtained, the effects of the present invention will not change in any way.

In this manner, according to the present invention, it is possible to form the pressure reference chamber 60 between the substrate 40 and the diaphragm membrane 48, the size of which corresponds to the dimensions of the vanishing portion 44. At this time, according to the present invention, the diaphragm membrane 48 located on the upper surface side of the pressure reference chamber 60 is formed using an etching-resistant material, so that it is rarely removed by etching.

As a result, the laminated film of the diaphragm membrane 48 and the insulating protective film 52 is different from the movable diaphragm 1 with respect to the pressure reference chamber 60.
It will function as 00.

Here, according to the present invention, the diaphragm membrane 48 can be flatly supported and fixed on the diaphragm fixing part 46 of the sacrificial membrane 42 without having any step.

Furthermore, according to the present invention, the film thickness of the movable diaphragm 100 is the sum of the film thicknesses of both the diaphragm film 48 and the insulating protective film 52. It becomes possible to form the film thinly and precisely to a desired value set in advance.

Further, according to the present invention, the pressure reference chamber 60
After forming the movable diaphragm 100, the etching liquid inlet 58 provided when forming the pressure reference chamber 60 is sealed using the sealing member 60, if necessary. At this time, when the sensor of the present invention is formed as an absolute pressure measurement type, the etching liquid inlet 58 is sealed using the sealing member 62 while the pressure J reference chamber 60 is kept in a vacuum.

On the other hand, when used as a differential pressure measurement type sensor, pressure introduction means for introducing the second pressure into the pressure reference chamber 60 may be provided in the etching liquid inlet 58.

Further, in the present invention, since the surface of the strain gauge 54 is covered with the insulating protective film 52, it is necessary to provide an electrode for extracting a signal from the strain gauge 50. For this purpose, connection holes 54 are formed at both ends of the strain gauge in the insulating protective film 52, and the strain gauge 50 is connected through the connection holes 54.
An electrode 56 connected to is formed. This makes it possible to detect changes in resistance of the strain gauge 50 via the electrodes 56.

Comparison with Conventional Example Next, the features of the semiconductor pressure sensor of the present invention will be specifically explained in comparison with the conventional example.

According to the present invention, the diaphragm film 48 and the insulating protective film 52 are formed on the flat sacrificial JII 42 including the vanishing part 44 and the diaphragm fixing part 46. Therefore, the etching liquid is injected from the etching liquid inlet 58 to remove the disappearing portion 44 and remove the movable diaphragm 10.
0, the diaphragm membrane 48 constituting the movable diaphragm 100 has a flat shape fixed by the diaphragm fixing part 46 of the sacrificial membrane 42, and the periphery of the pressure receiving area has a stepped structure. Its structure is clearly different from that of a sensor.

In this way, in the semiconductor pressure sensor of the present invention, the diaphragm membrane 48 constituting the movable diaphragm 100 is supported and fixed in a flat state without having a stepped structure, so that the supporting state of the diaphragm 100 is stabilized and its It is understood that the accuracy of the output characteristics is stable over a long period of time.

In addition, the movable diaphragm 100 of the present invention is free of initial deflection due to internal tensile stress. Thereby, even with the semiconductor pressure sensor of the type shown in FIG. 6, good pressure measurement can be performed.

[Effects of the Invention] As explained above, according to the present invention, the diaphragm membrane can be formed flat and there is no step structure around the movable diaphragm, so high precision pressure measurement can be achieved over a long period of time. In addition, the initial deflection caused by the internal stress of pulling the movable diaphragm can be prevented,
It becomes possible to obtain a semiconductor pressure sensor capable of highly accurate measurement.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail based on the drawings.

First Embodiment FIGS. 1 and 2 show a preferred first embodiment of the semiconductor pressure sensor of the present invention.

In the semiconductor pressure sensor of the embodiment, the semiconductor substrate 40 is formed using a single crystal silicon substrate, and a sacrificial film 42 is formed to cover the entire main surface of the single crystal silicon substrate 40.

In the embodiment, the sacrificial film 42 is formed by coating the entire main surface of the single crystal silicon substrate 40 with polycrystalline silicon to a thickness of 200 nm using low pressure CVD. and,
Boron is added and diffused as an impurity into the region corresponding to the diaphragm fixing part 46 of the sacrificial film 42 by thermal diffusion or ion implantation so as to have etching resistance, and the impurity concentration is increased to I x 10'' (7). -3 P4 type half region is formed.As a result, this impurity-added and diffused region functions as a diaphragm fixing portion 46 having etching-resistant properties, and the pressure-receiving region to which no impurity is added is made of polycrystalline silicon. It functions as a vanishing part 44 having an isotropic etching characteristic.

After the sacrificial film 42 is formed on the main surface of the single crystal silicon substrate 40 in this way, the main surface is covered with the following:
The entire area is covered with silicon nitride as a diaphragm film 48 to a thickness of 1100 nm.

At a predetermined position on the surface of this diaphragm membrane 48,
Strain gauges 50-1.50-2.50-3.50-4 are provided, and in the embodiment, this strain gauge 50 is made by applying polycrystalline silicon to a thickness of 200 mm on the surface of the diaphragm film 48 by low pressure CVD. Then, boron is added and diffused as an impurity to this polycrystalline silicon using thermal diffusion or ion implantation to form a P-type semiconductor, which is then partially removed by photoetching. Ru.

Furthermore, silicon nitride is formed as an insulating protective film 52 to a thickness of 300 mm over the entire surface of the strain gauge 50 and the diaphragm film 48 using low pressure CVD.

When the main surface side of the substrate 40 is coated with the disappearing portion 44, the diaphragm film 48, and the insulating protective film 52 in this way, the insulating protective film 52. The vanishing portion 44 penetrates the diaphragm membrane 48
An etching solution inlet 58 having a diameter of 5 μm is formed using photoetching, and an anisotropic etching solution is injected into the substrate 40 through the etching solution inlet 58.

In the example, as the anisotropic etching solution, 10
A potassium hydroxide (KOH) aqueous solution of ωt % is used, and when this etching solution is injected from the etching solution inlet 58, etching progresses around the inlet 58.

That is, when the etching solution is injected from the etching solution inlet 58, the disappearing portion 44 is etched away in the lateral direction at a predetermined speed as shown in FIGS. 11(b) and 11(C), and at the same time, the silicon substrate 40 is As shown in FIG. 3, the material is etched away vertically to a predetermined depth to form a cavity that will become the pressure reference chamber 60.

At this time, since the diaphragm film 48 and the insulating protective film 52 located on the upper surface side of the pressure reference chamber 60 are formed using an etching-resistant material, that is, silicon nitride,
is rarely etched away. Therefore, the pressure-receiving region of the laminated film consisting of the diaphragm film 48 and the insulating protective film 52, that is, the region where the vanishing portion 44 is provided, functions as the movable diaphragm 100 for the pressure reference chamber 60.

In particular, according to the present invention, the diaphragm membrane 48 is formed in a flat shape with no stepped portions.

Therefore, the movable diaphragm 100 can be supported stably and with sufficient strength on the diaphragm fixing portion 46.

Here, since each strain gauge 50 is covered in a sandwich-like manner by the diaphragm film 48 and the insulating protective film 52, it is not affected by the etching solution.

In this embodiment, once the pressure reference chamber 60 and the movable diaphragm 100 are formed in this way, a metal or an insulator is then deposited on the insulating protective film 52 by vacuum evaporation or sputtering to form the etching liquid inlet 58. It is deposited to a thickness that allows for a hermetically sealed seal. Thereafter, unnecessary portions are removed by photoetching to form the sealing member 62.

By doing so, the pressure reference chamber 60 is hermetically sealed while the inside thereof is maintained in a vacuum state.

Thereafter, both ends of the strain gauge of the insulating protective film 52 are removed by photo-etching to form a connection hole 54, and an aluminum vapor-deposited film is coated thereon and an appropriate shape is formed by photo-etching to form the electrode 56. Form.

With the above configuration, the semiconductor pressure sensor of this embodiment detects the absolute pressure applied from the surface side of the diaphragm 100 as a resistance change of the strain gauge 50, and sends a signal proportional to the absolute pressure via the electrode 56. can be obtained.

In this example, the diameter and film thickness of the diaphragm 100 can be formed as small as 50 μm and 0.5 μm with high accuracy, respectively, and excellent output sensitivity of 2 m V/V or more can be achieved at a pressure of 100 KPa. It was confirmed through experiments that it has.

Furthermore, it was confirmed through experiments that the sensor of the example of this publication has excellent linearity with respect to absolute pressures up to 500 KPa, with nonlinearity of ±0.5% F, S or less.

From this, it can be seen that according to the first embodiment, the diaphragm can be stably supported and fixed with sufficient strength, and a compact and highly sensitive semiconductor pressure sensor can be realized.

Second Embodiment Next, a second preferred embodiment of the present invention will be explained by taking a differential pressure measuring type sensor as an example. Incidentally, members corresponding to those in the first embodiment are given the same reference numerals and their explanations will be omitted.

FIG. 3 is an explanatory plan view showing the sensor of the second embodiment, and FIG. 4 is a schematic explanatory view of its cross section.

In the sensor of the embodiment, rectangular polycrystalline silicon is coated on the surface of a single crystal silicon substrate 40 as a sacrificial film 42, and the pressure receiving area of this sacrificial film 42 is used as a vanishing part 44, and the surrounding area is used as a diaphragm fixing part 46. Form. after that,
As in the first embodiment, the diaphragm membrane 48. Strain gauge 50°, insulating protective film 52 and etching branch injection port 5
8 will be provided.

Here, when an anisotropic etching liquid consisting of an aqueous potassium hydroxide (KOH) solution is injected from the etching inlet 58, the disappearing portion 4 is injected as shown in FIGS.
4, a pressure reference chamber 60 and a movable diaphragm 100 are formed from a rectangular cavity.

A feature of this embodiment is that a strain gauge 50 is formed on one side of the rectangular diaphragm 100, and an etching liquid inlet 58 is formed on the other side. A pressure introduction cap 66 communicating with the etching liquid inlet 58 is provided on the other side of the movable diaphragm 100 to apply a second pressure into the pressure reference chamber 60.

By doing so, according to the semiconductor pressure sensor of this embodiment, the first
A pressure P1 and a second pressure P2 are applied, and a strain proportional to the pressure difference between the two is generated in the movable diaphragm 100.
As a result, it becomes possible to obtain an electrical signal from the strain gauge 50 that is proportional to this differential pressure.

Note that in FIGS. 3 and 4, the insulating protective film 52. Although a description of the connection hole 54 and the electrode 56 is omitted, these members are provided in this embodiment as well as in the first embodiment.

Third Embodiment Next, a third preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows a plan view of the semiconductor pressure sensor according to the third embodiment, and FIG. 6 shows its V[-Vl
A schematic diagram of the cross section is shown. Note that the same reference numerals are given to the members corresponding to those in each of the above embodiments, and the explanation thereof will be omitted.

In the semiconductor pressure sensor of this embodiment, the semiconductor substrate 40
is formed using a single-crystal silicon substrate, and the entire main surface of this substrate 40 is covered with a sacrificial film 42 that includes a vanishing portion 44 and a diaphragm fixing portion 46 .

The feature of this embodiment is that the sacrificial film 42 was formed in accordance with the following procedure.

That is, first, an insulating film 64 made of silicon nitride (Si3N4) is formed to a thickness of 1100 nm over the entire main surface of the substrate 40 using high-pressure CVD, and then a sacrificial film 42 is formed on this insulating film 64 using low-pressure CVD. A coating is formed to a thickness of 200 cm. Then, the region of the sacrificial film 42 corresponding to the diaphragm fixing part 46 is treated to have etching resistance as in the first embodiment, thereby forming the diaphragm fixing part 46 and the disappearing part 44.

In the embodiment, the shape of the disappearing portion 44 is formed into a square shape, and the four corners of the square are formed to have regions 68 that respectively protrude toward the outside.

Further, on the sacrificial film 42, silicon nitride is deposited as a diaphragm film 48 over the entire area using low pressure CVD to a thickness of 10
0■ is coated.

At a predetermined position in the pressure receiving area of this diaphragm membrane 48, a strain gauge 50-1.50 is installed as in the first embodiment.
-2.50-3.50-4 are formed using low pressure CVD and photoetching, and an insulating protective film 5 is formed on the entire surface of the strain gauge 50 and the diaphragm film 48.
2, silicon nitride is made to a film thickness of 300 using low pressure CVD.
It is coated on nIll.

As shown in FIG. 5, the four protruding regions 68 are covered with an insulating protective film 52. Four etching liquid inlets 58 are formed to penetrate through the diaphragm 48 and reach the disappearing portion 44 of the sacrificial film 42, and the etching liquid is injected through these etching liquid inlets 58.

By doing so, in this embodiment, only the disappearing portion 44 is etched away, and the pressure reference chamber 60 and the movable diaphragm 100 are formed.

Thereafter, connection holes are provided at both ends of the strain gauge in the insulating protective film 52, and electrodes 56 are formed through the connection holes 54.

After that, plasma CV is applied to the entire surface of the insulating protective film 52.
Using D, silicon nitride 70 is coated to a thickness of 1 μm.

By doing so, this silicon nitride 70 becomes
It functions as a sealing member 62 for each etching liquid inlet 58, and also serves as passivation for the sensor surface.

In this example, the size of one side of the square-shaped movable diaphragm 100 can be reduced to 80 μm, and the film thickness can be reduced to about 1.4 μm, and furthermore, it has an excellent performance of 3 m V / V or more against a pressure of 100 KPa. It was confirmed through experiments that it has a high output sensitivity.

Further, the deflection of the movable diaphragm 100 having the above-mentioned shape is about 60 n■ against a pressure of 100 KPa. In contrast, the movable diaphragm 100 and the substrate 40 of the embodiment
The distance between the insulating film 64 formed over the entire main surface of the
(2) Therefore, absolute pressures up to 200 KPa can be adequately measured, and experiments have shown that the nonlinearity in this pressure range is 0.3% F, S or less, which is excellent. Confirmed by.

In this way, the third embodiment also supports the movable diaphragm 100 stably and with sufficient strength, and the size and thickness of the movable diaphragm 100 can be made sufficiently small and accurately shaped to realize a compact and highly sensitive sensor. I understand that it is possible.

Further, when an excessive pressure of 300 KPa or more is applied, the movable diaphragm 100 comes into contact with the insulating film 64 and does not bend any further, so it is not destroyed. In other words, it has a good protective structure against excessive pressure.

Fourth Embodiment Next, a fourth preferred embodiment of the present invention will be described. It should be noted that the same reference numerals are given to the members corresponding to each of the above-mentioned embodiments, and the explanation thereof will be omitted.

FIG. 7 shows a plan view of the sensor according to the embodiment shown in FIG. 4, and FIG. 8 shows a schematic cross-sectional view thereof.

In the sensor of this embodiment, as in the third embodiment, an insulating film 64 is formed to cover the main surface of a substrate 40, and a sacrificial film 42 is formed on the entire surface of this insulating film 64. This sacrificial film 42 is treated so that its diaphragm fixing portion 46 has etching resistance as in the first embodiment. In addition, the disappearing part 44 corresponding to the associated area is 10
It is formed into a square shape with a side of 0 μm.

A diaphragm film 48 is formed to cover the entire surface of the sacrificial film 42, and a plurality of strain gauges 50-1.50-2° are provided at predetermined pressure receiving areas of the diaphragm film 48 as shown in FIG. 50-3 and 50-4 are provided. Strain gauge 50-1. The plurality of electrodes 56 connected to both ends of the movable diaphragm 10
0 and extends toward the other end of the substrate 40.

Then, an insulating protective film 52 is formed over the entire surface of the diaphragm membrane 48 on which the strain gauge 50 and the electrode 56 are provided, and an etching solution is further injected onto one end side in the same manner as in the third embodiment. An inlet 58 is formed, and by injecting etching liquid from this etching liquid inlet 58, a square movable diaphragm 100 and a pressure reference chamber 60 are formed.

Thereafter, a film of silicon nitride [1170] is formed to a predetermined thickness on the insulating protective film 52 in the same manner as in the third embodiment, and a sealing member 62 is formed to seal the etching solution inlet 58.
used as.

Then, on the other end side of the substrate 40, a silicon nitride film 7
A connection hole 54 communicating with the electrode 56 is formed in the electrode 56, and a connection terminal 56a is formed therein.

In this way, in this embodiment, the diaphragm 100 is located at one end of the substrate 40, and the connection terminal 56a is located at the other end, and the electrode 56 is not exposed on the movable diaphragm 100 side. Therefore, it is suitable as a sensor for measuring the pressure of various liquids and living organisms.

According to experiments, the semiconductor pressure sensor of this example has a substrate 4
It was confirmed that the size of 0 can be made as small as 150 μm×500 μm. As a result, it is understood that according to this embodiment, an ultra-small semiconductor pressure sensor can be realized.

Fifth example Next, a fifth preferred embodiment of the present invention will be described.

The characteristic feature of this embodiment is that the semiconductor pressure sensor was formed integrally with an integrated circuit, and was used as a so-called integrated semiconductor pressure sensor.

FIG. 9 shows a plan view of a semiconductor pressure sensor according to the fifth embodiment. In this embodiment, the semiconductor pressure sensor 200 of the present invention explained in the first embodiment and the third embodiment is formed at a predetermined position on a silicon substrate 40, and furthermore, a pressure sensor 200 is formed on this silicon substrate 40. An integrated circuit 30 that performs amplification and signal processing of the output from the sensor 200
0, a plurality of electrodes 400 are formed for connecting leads between the sensor 200 and the integrated circuit 300, and connections to the outside.

As described above, according to the present invention, a semiconductor pressure sensor can be formed so small that it can be considered as one of the constituent elements of an integrated circuit, and it can also be manufactured by single-sided processing. Moreover, the same manufacturing process as integrated circuits can be used.

Therefore, it is understood that the present invention is extremely suitable for manufacturing a so-called integrated sensor by integrating semiconductor pressure sensors as an integrated circuit, as shown in this fifth embodiment.

Other Embodiments In the above-mentioned embodiments, the impurity concentration of boron in the diaphragm fixing portion 46 was set to 1.times.10@20 CII+-3, and the concentration of the etching solution (KOH) was set to 10 wt %. However, the present invention is not limited to this, and the point is that the diaphragm fixed portion is etched so that the amount of etching is about one-tenth or less of the polycrystalline silicon used for the disappearing portion 44 and the single crystal silicon used for the substrate 40. The conditions for the boron impurity concentration in 44 and the concentration of the potassium hydroxide aqueous solution used to remove the vanishing portion 44 by etching may be arbitrarily selected. Even in this case, the same effects as those of the embodiments described above can be obtained.

Furthermore, in each of the above embodiments, boron is used as the impurity diffusion element of the diaphragm fixing part 46 to form a P4 type half region. It has been experimentally confirmed that an n-type semiconductor region can be formed using phosphorus and can also be formed to have etching resistance. In addition to this, even when nitrogen is used as an impurity diffusion element,
It can exhibit the same etching resistance properties as when using boron, phosphorus, etc., and in this case boron.

It can exhibit better insulating properties than when phosphorus or the like is used, and has the effect of reliably preventing leakage current from the electrode 56 to the substrate 40.

Further, in each of the above embodiments, the case where a laminated film of the diaphragm film 48 made of silicon nitride and the insulating protective film 52 is used as the movable diaphragm 100 has been explained as an example, but the present invention is not limited to this. Alternatively, a multilayer film sandwiched between upper and lower silicon nitride films can also be used as the movable diaphragm 100. For example, when a thick diaphragm 100 is required, a silicon nitride film - a polycrystalline silicon film - a silicon nitride film is used. A three-layer film is suitable.

Furthermore, in the embodiment, the diaphragm membrane 48.
Although the case where silicon nitride is used as the insulating protective film 52 has been described as an example, it is also possible to use other materials such as alumina (
Al203), sapphire (Al2O2),
Silicon substrate 4 such as calcium fluoride (CaF 2 )
It is also possible to use other insulating materials as long as they are insulating materials that can be stably deposited on the substrate and have an etching rate that is much slower than that of silicon.

Further, in each of the embodiments described above, the case where polycrystalline silicon is used as the strain gauge 50 is explained as an example, but other than this, for example, polycrystalline silicon may be recrystallized to become a single crystal. , it is possible to further improve the sensitivity, and other materials can also be used as long as they can be deposited stably on the diaphragm membrane and can sufficiently exhibit the piezoresistance effect. It is also possible to form

Further, in the embodiment described above, the case where polycrystalline silicon is used as the vanishing portion 44 having isotropic etching characteristics has been described as an example, but the present invention is not limited to this, and the semiconductor substrate 28 and the like are not limited thereto. Other materials can be used as long as they have faster lateral etching characteristics than the interface of the diaphragm film 32; for example, phosphor glass can also be used.

As described above, the semiconductor pressure sensor of the present invention can be made small and highly accurate, and therefore can be used in a wide variety of applications, such as barometers, blood pressure monitors, pressure sensors for automobile engine control, It can be used in various applications such as pressure transmitters for industry (plants), pressure sensors for biological measurements, and pressure sensors for robot control.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing a preferred first embodiment of a semiconductor pressure sensor according to the present invention, and FIGS. 3 and 4 are schematic diagrams showing a preferred second embodiment of the present invention. Figures 5 and 6 are schematic explanatory diagrams showing a third preferred embodiment of the present invention; Figures 7 and 8 are schematic explanatory diagrams showing a preferred fourth embodiment of the present invention; FIG. 9 is an explanatory diagram showing a preferred fifth embodiment of the present invention. FIG. 10 is a characteristic diagram showing the etching characteristics of each part of the semiconductor pressure sensor according to the present invention. FIG. 11 is a diagram showing the etching characteristics of the semiconductor pressure sensor according to the present invention. FIG. 12, an explanatory diagram of a reference chamber forming step in a method for manufacturing a pressure sensor, is a schematic explanatory diagram showing a conventional semiconductor pressure sensor and a method for manufacturing the same. 40... Substrate, 42... Sacrificial film, 44... Vanishing part, 46... Diaphragm fixing part, 48... Diaphragm membrane, 50... Strain gauge, 5
2... Insulating protective film, 56... Electrode, 18... Etching wave injection port, 60... Pressure reference chamber, 62... Sealing member, 100...
...Movable diaphragm 200...Semiconductor pressure sensor 400...Electrode.

Claims (3)

[Claims] (1) A semiconductor substrate, a vanishing part that covers a pressure receiving area on the main surface of the semiconductor substrate, and a diaphragm fixing part that covers the periphery of the pressure receiving area, and the vanishing part has an isotropic structure along the pressure receiving area. The diaphragm fixing portion includes a sacrificial film formed to have etching resistance, and a sacrificial film coated on the main surface of the semiconductor substrate so as to cover the sacrificial film, and formed to have etching resistance. an insulating diaphragm film formed by the insulating diaphragm film; at least one etchant injection port formed to penetrate the insulating diaphragm film and reach the disappearing portion of the sacrificial film; A semiconductor pressure device characterized by comprising: a pressure reference chamber formed by etching away a disappearing portion of a sacrificial film; and at least one strain gauge formed at a predetermined position in a pressure receiving region of the insulating diaphragm film. sensor. (2) In claim (1), an insulating film having etching resistance is formed between the semiconductor substrate and the sacrificial film, and the pressure reference chamber is connected to the sacrificial film through the etching solution inlet. A semiconductor pressure sensor characterized in that it is formed by etching away only the disappearing portion of a film. (3) In either of claims (1) and (2), the diaphragm fixing portion of the sacrificial film is formed using polycrystalline silicon into which boron, phosphorus, or nitrogen is ion-implanted or thermally diffused. Semiconductor pressure sensor.