JPH05126661A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To provide a semiconductor pressure sensor having a good characteristic by forming a moving diaphragm into a flat shape having no step. CONSTITUTION:An n-type semiconductor film 50 is formed on an insulating diaphragm film 48. Impurities such as boron are ion-implanted or thermally diffused at the portion of the multi-crystal silicone film 50 to serve as a distortion gauge 51. This portion becomes a p-type semiconductor region, and it functions as the distortion gauge 51. The region added with no boron functions as a distortion gauge separation section 52. The distortion gauge 51 is formed flat in the pressure receiving region of the diaphragm 48, thus a moving diaphragm 100 is formed into a flat shape having no step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a thin film forming technique,
The present invention relates to improvement of a semiconductor pressure sensor having a diaphragm formed on the surface of a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional semiconductor pressure sensor.

This semiconductor pressure sensor includes a semiconductor substrate 10
A sacrificial film 11 is formed on the main surface of the. The sacrificial layer 11 covers the pressure receiving region of the semiconductor substrate 10 and the vanishing portion 12.
And a diaphragm fixing portion 13 that covers the periphery of the pressure receiving area. The vanishing portion 12 is formed to have an isotropic etching characteristic along the pressure receiving region. Further, the diaphragm fixing portion 13 is formed to have etching resistance.

An insulating diaphragm film 14 having etching resistance is provided so as to cover the sacrificial film 11, and at least one strain gauge 16 is provided at a predetermined position in the pressure receiving region of the diaphragm film 14.

The diaphragm film 14 and the strain gauge 16 are covered with an insulating protective film 18 made of a material having etching resistance. Connection holes 20 reaching both ends of the strain gauge 16 are formed in the insulating protective film 18, and a plurality of electrodes 22 are connected to both ends of the strain gauge 16 via the connection holes 20.

At a predetermined position of the pressure receiving area of the semiconductor pressure sensor, at least one etchant injection port 24 penetrating the insulating protective film 18 and the insulating diaphragm film 14 to reach the disappearing portion 12 is provided. An opening is formed, and a part of the substrate 10 and the entire disappearing portion 12 are removed by etching through the etching solution injection port 24. As a result, the pressure reference chamber 26 surrounded by the substrate 10 and the diaphragm film 14 is formed.

When this pressure sensor is used as an absolute pressure measuring type sensor, all the etching solution inlets 24 are sealed by a sealing member 24a while the pressure reference chamber 26 is kept in a vacuum state. With the above configuration,
The diaphragm film 14 located on the upper surface side of the pressure reference chamber 26
Functions as the movable diaphragm 14a. When pressure is applied to this pressure sensor, the movable diaphragm 14a bends in proportion to the applied pressure, and the resistance of the strain gauge 16 provided in the pressure receiving region changes due to this bending. Therefore, by taking out the resistance change of the strain gauge 16 as a pressure detection signal via the electrode 22, the absolute pressure applied to the surface side of the movable diaphragm 14a can be measured.

[0008]

However, this conventional technique has problems to be solved which will be described in detail below. (A) In the conventional pressure sensor technology, the diaphragm film 14 is used.
The step of the strain gauge 16 formed above is indicated by a dashed line A in the figure.
There is a problem that a step surrounded by is formed on the surface of the movable diaphragm 14a.

That is, in the prior art, the diaphragm film 1
4 is coated with polycrystalline silicon, and boron is added as an impurity to the polycrystalline silicon by thermal diffusion or ion implantation to form a p-type semiconductor, which is then photoetched. The strain gauge 16 is formed by partially removing it.

The step of the strain gauge 16 becomes a factor for forming a step surrounded by the alternate long and short dash line A in the figure on the surface of the movable diaphragm 14a. Therefore, the movable diaphragm 14a
When pressure is applied from the upper surface of the strain gauge, stress concentration occurs at the step portion between the strain gauge 16 and the movable diaphragm 14a. Therefore, when the pressure is applied repeatedly, there is a problem that the step portion may be fatigued and the performance of the sensor may be deteriorated. (B) In the conventional pressure sensor technology, a silicon nitride film is formed as the diaphragm film 14 by low pressure CVD.
Then, a strain gauge 16 made of polycrystalline silicon is formed at a predetermined position in the pressure receiving region of the silicon nitride film under a temperature condition of about 600 ° C.

Therefore, in the temperature range in which the pressure sensor operates, the stepped portion A where the strain gauge 16 is formed is
Non-uniform thermal stress due to the difference in thermal expansion coefficient occurs between the diaphragm film 14 made of a silicon nitride film and the strain gauge 16 made of polycrystalline silicon.

Particularly, when such non-uniform thermal stress occurs in the pressure receiving region, the movable diaphragm 14a is deformed. Furthermore, when the ambient temperature of the sensor changes, the thermal stress changes due to the difference in thermal expansion coefficient between the diaphragm film 14 made of a silicon nitride film and the strain gauge 16 made of polycrystalline silicon. There was a problem that performance deteriorated.

The present invention has been made in view of such conventional problems, and an object thereof is to obtain a semiconductor pressure sensor having good characteristics by forming a movable diaphragm into a flat shape without steps. Especially.

[0014]

In order to achieve the above object, the present invention provides a pressure reference chamber on the main surface side of a semiconductor substrate, and covers the opening of the pressure reference chamber of the semiconductor substrate. In a semiconductor pressure sensor in which an insulating diaphragm film is formed on the main surface side by coating via a diaphragm fixing portion, at least one first conductivity type strain gauge arranged at a predetermined pressure receiving region of the insulating diaphragm film, It is characterized in that a semiconductor film including a strain gauge isolation portion of a second conductivity type that covers the periphery of the strain gauge is formed by coating on the insulating diaphragm film.

The semiconductor pressure sensor of the present invention has a semiconductor substrate, a vanishing portion covering the pressure receiving region of the main surface of the semiconductor substrate, and a diaphragm fixing portion covering the periphery of the pressure receiving region. A sacrificial film formed to have isotropic etching characteristics along the pressure receiving region, and the diaphragm fixing part is formed on the main surface of the semiconductor substrate so as to cover the sacrificial film. And an insulating diaphragm film formed to have etching resistance, at least one first conductivity type strain gauge disposed at a predetermined position in a pressure receiving region of the insulating diaphragm film, and the periphery of the strain gauge. A second conductivity type strain gauge isolation part covering the semiconductor film, and a semiconductor film formed on the main surface of the semiconductor substrate so as to cover the insulating diaphragm film. At least one etchant injection hole formed so as to penetrate the insulating diaphragm film and the semiconductor film to reach the lost part of the sacrificial film, and at least the lost part of the sacrificial film through the etchant injection port. And a pressure reference chamber formed by etching away.

The semiconductor pressure sensor of the present invention will be described in more detail below.

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

In the semiconductor pressure sensor of the present invention, an insulating film 45 having an etching resistance property is formed on the entire surface of the semiconductor substrate 40, if necessary.

A sacrificial film 42 is formed on the surface of the insulating film 45. The sacrificial film 42 is formed to include a vanishing portion 44 that covers the pressure receiving region of the semiconductor substrate 40 and a diaphragm fixing portion 46 that covers the periphery of the pressure receiving region. Moreover, the vanishing portion 44 is formed to have an isotropic etching characteristic along the pressure receiving region, and the diaphragm fixing portion 46 is formed to have an etching resistance characteristic. Then, an insulating diaphragm film 48 made of an etching resistant material is formed on the main surface of the semiconductor substrate 40 so as to cover the sacrificial film 42 over the entire area.

At least one strain gauge 51 is provided at a predetermined position in the pressure receiving area of the insulating diaphragm film 48.
Is provided.

A feature of the present invention is that the strain gauge 51 is formed in the pressure receiving region of the diaphragm film 48 so as not to have a step structure.

Therefore, the insulating diaphragm film 48 is formed.
An n-type or p-type semiconductor film 50 is formed so as to cover at least the entire pressure receiving region. Then, a predetermined position of the pressure receiving region of the semiconductor film 50 is processed so as to have a conductivity type opposite to that of the semiconductor film to form the strain gauge 51, and an unprocessed region is processed by the strain gauge separating portion 52.
Used as.

For example, the semiconductor film 50 is formed by coating a polycrystal silicon film so as to cover the entire area of the insulating diaphragm film 48. At this time, the semiconductor film 50 made of polycrystalline silicon is processed so as to have n-type semiconductor characteristics, and is formed so that only the etching solution injection port 58 is opened.

Then, an impurity such as boron is ion-implanted or thermally diffused into a portion of the polycrystalline silicon film 50 to be the strain gauge 51. As a result, this portion becomes a p-type semiconductor region and functions as the strain gauge 51. The region to which boron is not added functions as the strain gauge separation unit 52. Therefore, the strain gauge 51 is formed flat in the pressure receiving region of the diaphragm film 48 and does not have a step structure having a strain gauge shape unlike the conventional case.

The semiconductor film 50 is preferably formed by coating with an insulating protective film 53 made of a material having etching resistance.

Connection holes 54 reaching both ends of the strain gauge 51 are formed in the insulating protective film 53, and a plurality of electrodes 56 are connected to both ends of the strain gauge 51 through the connection holes 54. The electrode 56 is the diaphragm fixing portion 4
It is preferable to form it in the region of 6.

The insulating protective film 53 and the diaphragm film 4 are provided at predetermined positions in the pressure receiving area of the semiconductor pressure sensor.
At least one etching solution injection port 58 penetrating 8 and reaching the disappearing portion 44 is formed, and all of the disappearing portion 44 is removed by etching through the etching solution injection port 58. As a result, the pressure reference chamber 60 surrounded by the substrate 40 and the diaphragm film 48 is formed, and the laminated film of the diaphragm film 48 and the semiconductor film 50 located on the upper surface side of the pressure reference chamber 60 is the movable diaphragm 100. Function as.

The etching solution injection port 58 is wholly or partly sealed by a sealing member 62, if necessary.

The semiconductor pressure sensor of the present invention is constructed as described above. Next, the case of measuring the absolute pressure and the case of measuring the differential pressure using this sensor will be described.

In the semiconductor pressure sensor of the present invention, the laminated film of the diaphragm film 48 and the semiconductor film 50 located on the upper surface side of the pressure reference chamber 60 functions as the movable diaphragm 100, but as described above, the insulating protective film is used. When 53 is provided, the laminated film including the diaphragm film 48, the semiconductor film 50, and the insulating protective film 53 functions as the movable diaphragm 100.

First, when the pressure sensor of the present invention is used as an absolute pressure measurement type, all the etching solution injection ports 58 are sealed by the sealing member 62 while the pressure reference chamber 60 is kept in a vacuum state. .. As a result, when pressure is applied, the movable diaphragm 100 bends in proportion to the applied absolute pressure, and the resistance of the strain gauge 51 provided in the pressure receiving region changes due to this bending.

For example, one set of strain gauges 51-2 and 51-4 is arranged in the pressure receiving region of the diaphragm film 48, and another set of strain gauges 51-1 and 51-3 is arranged at the periphery of the pressure receiving region. Then, when the resistance of the strain gauge of one set increases, the resistance of the strain gauge of the other set decreases.

Therefore, these two sets of strain gauges 51-1 and
51-3 and 51-4 are bridge-connected via electrodes 56-1, 56-2, 56-3 and 56-4 so that their resistance changes are added, and a power supply is provided to a pair of electrodes facing each other. By connecting, the voltage can be output from the other pair of electrodes in proportion to the absolute pressure applied to the movable diaphragm 100.

At this time, according to the present invention, since the movable diaphragm 100 has a flat structure having no step, the semiconductor pressure sensor of the present invention has the movable diaphragm 1
No stress concentration occurs at 00, and even if it is used for a long time, there is little change over time, and stable operation is achieved.

Further, even if the temperature around the sensor changes, the diaphragm film 48 is caused by the difference in the coefficient of thermal expansion.
Since the thermal stress generated between the semiconductor film 50 and the semiconductor film 50 has a uniform distribution, the semiconductor pressure sensor can operate stably without being affected by the temperature change around the sensor.

When the semiconductor pressure sensor of the present invention is used as a differential pressure measurement type sensor, the movable diaphragm 100 is formed in a rectangular shape as shown in FIGS. 3 and 4, and the movable diaphragm 100 is formed. Is halved in the longitudinal direction. And at least 1 in one of the areas
It suffices to dispose the individual strain gauges 51, dispose the etching solution injection port 58 in the other region, and provide the pressure introduction means 66 for introducing the pressure p ₂ to be compared with the etching solution injection port 58.

As a result, the pressure p ₁ applied to the front side of the movable diaphragm 100 and the pressure p applied to the back side of the movable diaphragm 100.
₂ differential pressure, like the absolute pressure measurement type sensor,
It is possible to accurately measure the resistance change of the strain gauge 51.

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

First, an insulating film 45 having etching resistance is formed to cover the entire main surface of the semiconductor substrate 40, and then,
A sacrificial film 42 having an isotropic etching property is formed on the surface of the insulating film 45.

Next, the peripheral portion of the pressure receiving region of the sacrificial film 42 is processed to have etching resistance. As a result, the pressure receiving region of the sacrificial film 42 is formed as the vanishing portion 44,
The periphery thereof can be formed as the diaphragm fixing portion 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 of polycrystalline silicon, boron having an impurity concentration of 1 × 10 ²⁰ cm ⁻³ or more is ion-implanted or thermally diffused into a region corresponding to the diaphragm fixing portion 46. , P ⁺ -type semiconductor region is heat-treated. 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 on the sacrificial film 42 by coating.

Next, a semiconductor film 50 is formed so as to cover the surface of the diaphragm film 48, and then the semiconductor film 5 is formed.
Only the etching liquid injection port 58 of 0 is formed by photoetching. Then, at least one strain gauge 51 is formed at a predetermined position in the pressure receiving region of the semiconductor film 50,
Further, the periphery of the strain gauge 51 is formed as a strain gauge separating portion 52.

Such processing of the semiconductor film 50 is performed, for example, in a region corresponding to the strain gauge 51 when the semiconductor film 50 is formed using n-type polycrystalline silicon.
For example, boron is added or diffused by ion implantation or thermal diffusion so as to have p-type semiconductor characteristics. At this time, the region to which boron is not added functions as the strain gauge separation unit 52.

The present invention is not limited to this, and the semiconductor film 5 is not limited thereto.
When 0 is formed by using p-type polycrystalline silicon, for example, phosphorus may be added to a region corresponding to the strain gauge 51, diffused, and processed to have n-type semiconductor characteristics. Even in this case, the effect of the present invention does not change.

As described above, according to the present invention, the semiconductor film 5 formed so as to cover the pressure receiving region of the diaphragm film 48.
Since a part of 0 is formed as the strain gauge 51, the movable diaphragm 100 can be formed flat.

Next, an insulating protective film 53 made of an etching resistant material is formed on the semiconductor film 50 by coating.

Next, at least one etching solution injection port 58 is formed in the opening of the semiconductor film 50 so as to penetrate the insulating protective film 53 and the diaphragm film 48 and reach the vanishing portion 44 of the sacrificial film 42. To form. Then, by injecting an etching solution through the etching solution injecting port 58, all of the disappearing portion 44 of the sacrificial film 42 is removed by etching, and the dimension of the disappearing portion 44 is set between the substrate 40 and the diaphragm film 48. A pressure reference chamber 60 having a size corresponding to the above is formed. At this time, since the diaphragm film 48 located on the upper surface side of the pressure reference chamber 60 is formed by using the etching resistant material, it is hardly removed by etching. As a result, the laminated film of the diaphragm film 48, the semiconductor film 50, and the insulating protective film 53 functions as the movable diaphragm 100 with respect to the pressure reference chamber 60.

Here, according to the present invention, the film thickness of the movable diaphragm 100 is a value obtained by adding the film thicknesses of the diaphragm film 48, the semiconductor film 50, and the insulating protective film 53, and thus the known thin film forming technique is used. Diaphragm 1
It is possible to form the film thickness of No. 00 to a desired value set in advance as thinly and accurately.

Further, according to the present invention, after the pressure reference chamber 60 and the movable diaphragm 100 are formed in this manner, the etching solution injection port 58 provided when the pressure reference chamber 60 is formed is formed, if necessary. It seals using the sealing member 62. At this time, when the sensor of the present invention is used as an absolute pressure measurement type, the etching solution injection port 58 is sealed using the sealing member 62 while keeping the pressure reference chamber 60 in vacuum. On the contrary, when the sensor is used as a differential pressure measurement type sensor, a pressure introducing means for introducing the second pressure toward the pressure reference chamber 60 may be provided at the etching solution injection port 58.

Further, in the present invention, since the surface of the semiconductor film 50 is covered with the insulating protective film 53, it is necessary to provide an electrode for taking out a signal from the strain gauge 51 formed on the semiconductor film 50. Therefore, the insulating protective film 53
Connection holes 54 are formed at both ends of the strain gauge 51, and electrodes 56 connected to the strain gauge 51 through the connection holes 54 are formed. Thereby, the resistance change of the strain gauge 51 can be detected via the electrode 56.

In the semiconductor pressure sensor shown in FIGS. 1 and 2, the insulating film 45 is provided between the semiconductor substrate 40 and the sacrificial film 42.
However, the sacrificial film 42 may be formed directly on the surface of the semiconductor substrate 40 without providing the insulating film 45. In this case, as in the conventional example shown in FIG. 6, a part of the semiconductor substrate 10 and the entire disappearing portion 12 are removed by etching, and the pressure reference chamber 26 is formed.

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

According to the present invention, the flat semiconductor film 50 including the strain gauge 51 and the strain gauge isolation portion 52 is formed on the diaphragm film 48. Therefore, the structure of the movable diaphragm 100 is clearly different from that of the conventional semiconductor pressure sensor having the step structure formed by the strain gauge shape.

As described above, in the semiconductor pressure sensor of the present invention, since the diaphragm film 48, the semiconductor film 50, and the insulating protective film 53 which form the movable diaphragm 100 are all formed flat, the movable diaphragm 100 is viewed from the upper surface side. When pressure is applied, the movable diaphragm 100
There is no stress-concentrated part inside. Therefore, even if the pressure is repeatedly applied, the movable diaphragm 100
Does not cause fatigue, and the accuracy of its output characteristics is stabilized for a long time.

[0055]

As described above, according to the present invention,
A flat semiconductor film including strain gauges and strain gauge separation regions can be formed on the diaphragm film to eliminate the step structure inside the movable diaphragm, enabling stable and highly accurate pressure measurement over a long period of time. It is possible to obtain a semiconductor pressure sensor.

[0056]

【Example】

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

In the semiconductor pressure sensor of the embodiment, the semiconductor substrate 40 is formed by using a single crystal silicon substrate. In the entire main surface of the single crystal silicon substrate 40,
As the insulating film 45 having etching resistance, silicon nitride is formed to a film thickness of 100 nm. The sacrificial film 42 is formed so as to cover the entire area of the insulating film 45.

In the embodiment, the sacrificial film 42 is formed by covering the entire surface of the insulating film 45 with polycrystalline silicon to a thickness of 200 nm by low pressure CVD. Then, boron is added as an impurity to the region corresponding to the diaphragm fixing portion 46 of the sacrificial film 42 by thermal diffusion or ion implantation so as to have etching resistance, and then diffused so that the impurity concentration is 1 × 10 ²⁰ cm 2. ^-3 p ⁺ type semiconductor region is formed. As a result, the region where the impurities are added and diffused has a diaphragm fixing portion 4 having etching resistance.
The pressure receiving region that functions as 6 and does not contain impurities functions as the vanishing portion 44 having isotropic etching characteristics.

In this way, the single crystal silicon substrate 40
After the sacrificial film 42 is formed on the main surface of the sacrificial film, silicon nitride is formed on the entire surface of the sacrificial film 42 as a diaphragm film 48 to a film thickness of 100 nm.

Next, as the semiconductor film 50, polycrystalline silicon is formed to a film thickness of 200 nm so as to cover the entire region of the diaphragm film 48. Then, this semiconductor film 50
Using photoetching,
Only the part is opened. In the example, the polycrystalline silicon film used as the semiconductor film 50 is formed to have n-type semiconductor characteristics.

Next, strain gauges 51-1, 51-2, 51-3, 51- are provided at predetermined positions in the pressure receiving region of the semiconductor film 50.
4 is formed. In the embodiment, each strain gauge 51
-1, 51-2, 51-3, and 51-4 are added to the semiconductor film 50 made of polycrystalline silicon processed to have n-type semiconductor characteristics by using boron as an impurity by thermal diffusion or an ion implantation method. , Diffused, and processed to have p-type semiconductor characteristics. And
The region of the semiconductor film 50 to which boron is not added, that is, the periphery of the strain gauges 51-1, 51-2, 51-3, 51-4 functions as the strain gauge separating portion 52. This allows
Each strain gauge 51-1, 51-2, 51-3, 51-4
Are insulated and separated by the n-type strain gauge separator 52.

Further, on the surface of the semiconductor film 50, a silicon nitride film is formed to a thickness of 300 nm as an insulating protective film 53 by using low pressure CVD.

When the insulating film 45, the sacrificial film 42, the diaphragm film 48, the semiconductor film 50 and the insulating protective film 53 are formed on the main surface side of the substrate 40 in this manner, they are then provided in the pressure receiving region. The insulating protective film 53 and the diaphragm film 4 are aligned with the openings of the semiconductor film 50 thus formed.
An etching solution injection port 58 having a diameter of 5 μm which penetrates 8 to reach the disappearance portion 44 is formed by photoetching, and the etching solution is injected toward the disappearance portion 44 through the etching solution injection port 58.

In the embodiment, 10 wt. % Potassium hydroxide (KOH) aqueous solution is used, and when the etching solution is injected from the etching solution injection port 58, etching proceeds around the injection port 58.

That is, when the etching solution is injected from the etching solution injection port 58, the sacrifice film 42 is removed by etching up to the boundary with the diaphragm fixing portion 46 which is processed to have the etching resistance property, and becomes the pressure reference chamber 60. Is formed.

At this time, the insulating film 45 located on the lower surface side of the pressure reference chamber 60 and the diaphragm film 4 located on the upper surface side of the pressure reference chamber 60.
8. Since the insulating protective film 53 is formed by using silicon nitride which is an etching resistant material, it is hardly removed by etching. Further, since the semiconductor film 50 is also covered with the diaphragm film 48 made of silicon nitride and the insulating protective film 53, it is not removed by etching. Therefore, the diaphragm film 48 and the semiconductor film 5
0 and the pressure-sensitive region of the laminated film composed of the insulating protective film 53,
That is, the region facing the vanishing portion 44 functions as the movable diaphragm 100 with respect to the pressure reference chamber 60.

In particular, according to the present invention, the movable diaphragm 100 is formed in a flat shape having no step portion. Accordingly, when pressure is applied from the upper surface side of the movable diaphragm 100, there is no stress concentration portion in the movable diaphragm 100, and even if repeated pressure is applied, the movable diaphragm 100 does not fatigue, The accuracy of the output characteristics will be stable for a long period of time.

Next, in the present embodiment, the sealing member 62 made of a metal or an insulator hermetically seals the etching solution injection port 58 on the insulating protective film 53 by the vacuum deposition or the sputtering, and at the same time, etches. It is deposited to a thickness such that it reaches the surface of the substrate 40 directly below the liquid injection port 58. As a result, the movable diaphragm 100 is fixed by the diaphragm fixing portion 46 and the etching solution injection port 58 sealed by the sealing member 62. Then, after that, an unnecessary portion is removed by photoetching, if necessary, to form the sealing member 62.

By doing so, the pressure reference chamber 6
0 is hermetically sealed while the inside thereof is kept in a vacuum state. The sealing member 62 may be formed so as to seal the etching solution injection port 58 as shown in FIG.

After that, the strain gauge 51 of the insulating protective film 53 is formed.
Both end positions of the contact hole 5 are removed by photoetching.
4 is formed, an aluminum film is covered thereover, and this is formed into an appropriate shape by photoetching to form an electrode 56.

In this embodiment, the movable diaphragm 1
00 diameter and film thickness are 100 μm and 1.6 μm, respectively.
It has been confirmed by experiments that it can be formed with a high accuracy and a small size up to about m, and that it has an output sensitivity of 2 mV / V or more for a pressure of 100 kPa.

Furthermore, in the sensor of this embodiment, 300
Non-linearity to absolute pressure up to kPa is ± 0.3%
F. S. It was confirmed by experiments that it has excellent linearity as follows.

From this, according to the first embodiment,
It can be understood that the movable diaphragm 100 can be formed flat, and a small-sized and highly accurate semiconductor pressure sensor can be realized.

Second Embodiment Next, a second preferred embodiment of the present invention will be described by taking a differential pressure measurement type sensor as an example. The members corresponding to those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

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

The sensor of the embodiment is the single crystal silicon substrate 4
An insulating film 45 made of silicon nitride is formed over the entire main surface of 0 using low pressure CVD to a thickness of 100 nm.
A sacrificial film 42 made of polycrystalline silicon is formed on the insulating film 45.
Is coated to a thickness of 200 nm using low pressure CVD. Then, the periphery of the rectangular disappearance portion 44 is formed as a diaphragm fixing member 46. After that, similarly to the first embodiment, the diaphragm film 48 and the semiconductor film 50 are formed, the strain gauge 51 is processed and formed in the semiconductor film 50, and then the etching solution injection port 58 is provided.

Here, when an etching solution composed of an aqueous solution of potassium hydroxide (KOH) is injected from the etching solution injection port 58, as shown in FIG. 3 and FIG. The reference chamber 60 and the movable diaphragm 100 are formed.

The characteristic feature of this embodiment is that the strain gauge 51 is formed in one side area of the rectangular diaphragm 100 and the etching solution injection port 58 is formed in the other side area. Then, a pressure introduction cap 66 communicating with the etching solution injection port 58 is provided in one side region of the movable diaphragm 100, and a second pressure is applied into the pressure reference chamber 60.

By doing so, according to the semiconductor sensor of this embodiment, the first pressure P ₁ and the second pressure P ₂ are applied to the front surface and the back surface of the movable diaphragm 100, and both are applied to the movable diaphragm 100. A strain proportional to the pressure difference can be generated, and as a result, an electric signal proportional to the pressure difference can be obtained from the strain gauge 51.

3 and 4, the description of the insulating protective film 53, the connection hole 54 and the electrode 56 is omitted for easy understanding, but these members are the same as those of the first embodiment. Similar to the example, it is provided in this embodiment.

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

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

FIG. 5 shows a plan view of a semiconductor pressure sensor according to the third embodiment of the present invention.

In this embodiment, the semiconductor pressure sensor 200 of the present invention described in the first embodiment is formed at a predetermined position on the silicon substrate 40. Further, on the silicon substrate 50, an integrated circuit 300 that amplifies the output from the pressure sensor 200 and performs signal processing, a lead that connects the sensor 200 and the integrated circuit 300, and a plurality of electrodes that connect to the outside. 400 is formed.

As described above, according to the present invention, the semiconductor pressure sensor can be made small enough to be regarded as one of the constituent elements of the integrated circuit. Further, the manufacturing can be performed by the one-sided processing, and moreover, the same manufacturing processing steps as the integrated circuit can be used.

Therefore, it is understood that the present invention is extremely suitable when the semiconductor pressure sensor is integrated with an integrated circuit to manufacture a so-called integrated sensor.

Other Embodiments In the above embodiment, the diaphragm fixing portion 46 is used.
The impurity concentration of boron is 1 × 10 ²⁰ cm ^−3, and the concentration of the etching solution (KOH) is 10 wt. The explanation has been made taking the case of% as an example. However, the present invention is not limited to this, and in short, the impurity concentration of boron in the diaphragm fixing member 46 and the impurity concentration of boron in the diaphragm fixing member 46 are set so that the etching amount is about 1/10 or less with respect to the polycrystalline silicon used in the vanishing portion 44.
The concentration condition of the potassium hydroxide aqueous solution used for removing the disappearing portion 44 by etching may be arbitrarily selected. Even in this case, the same effect as that of the above embodiment can be obtained.

Further, in the above-mentioned embodiment, the case where silicon nitride is used as the diaphragm film 48 and the insulating protective film 53 has been described as an example. However, other than this, for example, alumina (Al ₂ O ₃ ) or sapphire is used. (Al
Other materials such as ₂ O ₃ ), calcium fluoride (CaF ₂ ) and the like can be used as long as they are insulating materials that are stably deposited on the silicon substrate 40 and have an etching rate extremely slower than the etching rate of silicon. is there.

In each of the above embodiments, the semiconductor substrate 40
The case where the insulating film 45 is provided between the sacrificial film 42 and the sacrificial film 42 has been described as an example, but the present invention is not limited to this, and the substrate 4 can be formed without forming the insulating film 45 as in the conventional case shown in FIG.
The sacrificial film 42 may be directly formed on the surface of No. 0. In this case, when the etching liquid is injected from the etching liquid injection port 58, the disappearing portion 44 is laterally etched and removed at a predetermined speed, and at the same time, the silicon substrate 40 is removed.
Is removed by etching to a predetermined depth in the vertical direction, and a cavity serving as the pressure reference chamber 60 is formed as in the conventional example shown in FIG.

As described above, since the semiconductor pressure sensor of the present invention can be made compact and highly accurate, it can be widely used for various purposes. For example, a barometer,
It can be used for various applications such as a sphygmomanometer, a pressure sensor for controlling an automobile engine, an industrial (plant) pressure transmitter, a pressure sensor for measuring a living body, and a pressure sensor for controlling a robot.

[Brief description of drawings]

FIG. 1 is a plan view showing a first preferred embodiment of a semiconductor pressure sensor according to the present invention.

FIG. 2 is a schematic sectional view of the semiconductor pressure sensor shown in FIG.

FIG. 3 is an explanatory plan view showing a second preferred embodiment of the semiconductor pressure sensor according to the present invention.

FIG. 4 is a schematic sectional view of the semiconductor pressure sensor shown in FIG.

FIG. 5 is a schematic explanatory view showing a preferred third embodiment of the present invention.

FIG. 6 is a schematic cross-sectional explanatory view of a conventional semiconductor pressure sensor.

[Explanation of symbols]

40 Semiconductor Substrate 42 Sacrificial Film 44 Disappearing Part 46 Diaphragm Fixing Part 48 Diaphragm Film 50 Semiconductor Film 51 Strain Gauge 52 Strain Gauge Separating Part 53 Insulating Protective Film 56 Electrode 58 Etching Liquid Injection Port 60 Pressure Reference Chamber 62 Sealing Member 100 Movable Diaphragm 200 Semiconductor pressure sensor
TC007001

Claims (2)

[Claims] 1. A pressure reference chamber is provided on a main surface side of a semiconductor substrate, and an insulating diaphragm film is formed on the main surface side of the semiconductor substrate via a diaphragm fixing portion so as to cover an opening of the pressure reference chamber. In the semiconductor pressure sensor described above, at least one first conductivity type strain gauge disposed at a predetermined position of the pressure receiving region of the insulating diaphragm film, and a second conductivity type strain gauge separating portion that covers the periphery of the strain gauge. A semiconductor pressure sensor, comprising a semiconductor film containing the same formed on the insulating diaphragm film by coating. 2. 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, wherein the vanishing portion extends along the pressure receiving region, etc. The diaphragm fixing portion is formed to have an isotropic etching characteristic, and the diaphragm fixing portion is formed on the main surface of the semiconductor substrate so as to cover the sacrificial film and the sacrificial film. An insulating diaphragm film formed to have, at least one first conductivity type strain gauge arranged at a predetermined position in the pressure receiving region of the insulating diaphragm film, and a second conductivity type strain covering the periphery of the strain gauge. A semiconductor film including a gauge separation part and formed on the main surface of the semiconductor substrate so as to cover the insulating diaphragm film; the insulating diaphragm film; At least one etchant injection port formed to penetrate the body film to reach the lost part of the sacrificial film, and at least the lost part of the sacrificial film is removed by etching through the etchant injection port. A semiconductor pressure sensor comprising: a formed pressure reference chamber;