JPH0746068B2 - Pressure sensor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a pressure sensor for converting pressure into an electric signal, and more particularly to a pressure sensor having a reference pressure chamber in a sensor chip.

[Prior art]

As a conventional pressure sensor, for example, there is one as shown in FIG. 5 (for example, described in JP-A-58-63826).

The device shown in FIG. 5 is an absolute pressure type pressure sensor, and the pin 3
The pedestal 4 is adhered to the stem 5 of the hermetic seal provided with the pipe 11 via the second adhesive layer 8, and the pressure sensor chip 1 is further adhered thereto via the first adhesive layer 7.

Further, the input / output pad on the surface of the pressure sensor chip 1 and the pin 3 are bonded by the gold wire 2.

Further, the cap 6 and the stem 5 are adhered to each other by electric discharge machining, soldering, etc.
A vacuum chamber 10 is formed by sealing 12.

In the above structure, the vacuum chamber 10 is evacuated as a reference pressure, and the external pressure is applied from the lower part of the pressure sensor chip 1 through the pipe 11.

[Problems to be Solved by the Invention] In the conventional pressure sensor as described above, particularly in the absolute pressure type pressure sensor, it is necessary to form a vacuum chamber serving as a reference pressure, and moreover, the stem 5 and the pressure sensor chip 1 are formed. Since it is necessary to reduce the thermal stress due to the difference in the expansion coefficient, it must be mounted by taking into consideration such as selecting a material having a close thermal expansion coefficient as the pedestal 4, the first adhesive layer 7, and the second adhesive layer 8. Therefore, there is a problem that mounting the pressure sensor chip 1 requires a lot of cost, and as a result, the pressure sensor becomes expensive.

The present invention has been made in order to solve the problems of the conventional techniques as described above, and an object thereof is to provide a pressure sensor that can be easily mounted and can be manufactured at low cost.

[Means for solving problems]

In order to achieve the above object, in the present invention, the reference pressure chamber is formed at the same time when the sensor portion is formed on the substrate.

That is, in the present invention, a plurality of grooves provided on the surface of the substrate, at least one ridge whose both surfaces are separated from the surrounding substrate by the groove, and a member for sealing the top of the groove on one side of the ridge. A conversion means for converting the displacement generated in the ridges according to the pressure difference between the hollow area and the outside into an electric signal by forming a groove whose top is hermetically sealed to the outside. It is configured to include.

With the above-mentioned configuration, in the present invention,
Since the air pressure in the cavity area (for example, a vacuum of 10 Torr or less) can be used as the reference pressure, it is not necessary to separately form the reference pressure chamber outside the sensor chip.
Therefore, a pressure sensor having a large number of reference pressure chambers can be manufactured at the same time by the badge processing of Si wafers, etc., and the mounting becomes easy and the cost can be reduced.

Example of Invention

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

In FIG. 1, three grooves 102, 103 and 104 are provided in the vicinity of the surface of a silicon substrate 101, whereby ridges 106 and 107 are formed between the grooves. Also ridges 106 and 1
The top of the groove 104 with respect to 07 is sealed by a lid 105, so that the groove 104 serves as a hollow region that is formed airtight to the outside, that is, a reference pressure chamber. Also ridges 106 and 107
The electrodes 10 are provided on the surfaces facing each other (both sides of the groove 104).
8 and 109 are formed.

Next, the operation will be described.

FIG. 2 is a diagram showing a pressure sensitive portion of the pressure sensor of the present invention.

In FIG. 2, the internal pressure (reference pressure) of the reference pressure chamber is
P ₀ , depth d, width w, length (length in the direction perpendicular to the paper surface)
Is 1 and the thickness of the ridge between the reference pressure chamber and the atmospheric chamber is t. The thickness t may be different between the two ridges. Also, with the electrodes formed on both sides of the reference pressure chamber,
An electrostatic capacitance having an area S = d × l is formed at intervals of w.

In the above structure, when a pressure difference is generated between the reference pressure chamber and the atmosphere chamber, the ridge is bent, and as a result, the width w changes and the capacitance between both electrodes changes. The applied pressure can be detected by converting this capacitance change into an electric signal. Therefore, the absolute pressure can be detected only by the structure shown in FIG. 2, and it is not necessary to provide another reference pressure chamber, so that the mounting is very simple.

The above operation will be described in more detail with reference to FIG.

For example, when the atmospheric pressure is equal to the reference pressure chamber and is P ₀ , there is no ridge deflection as shown in FIG. 3 (A), and the capacitance C ₀ is C ₀ = ε ₀ · d · l / w. Become. The external pressure changes and P
Then, the ridge is bent as shown in (B). At this time, the ridge spacing, that is, the electrode spacing is W (x, p). However,
As shown in FIG. 3B, the x-axis is taken in the depth direction,
The midpoint is the origin. This W (x, p) is an amount determined by the deflection of the ridge, and is a function of the material, size, pressure difference between the inside and outside of the ridge.

That W (x) = F (t , d, P 0, p, t 1 ...) to become.

In the above equation, the dimensions, reference pressure, etc. are values that are appropriately designed according to the application and specifications. As a result, the electrostatic capacitance C (P) when the external pressure is P is as follows.

If the reference pressure, the material of the ridges, the size of the reference pressure chamber, etc. are determined as can be seen from the above equation, it can be seen that the capacitance is determined only by the external pressure P.

Next, the manufacturing process of the pressure sensor of FIG. 1 will be described with reference to FIG.

First, in (A), after forming an oxide film 117 on the silicon substrate 101 by a method such as thermal oxidation, a diffusion layer 116 is formed by a method such as ion implantation or diffusion.

Next, in (B), the oxide film 117 is selectively removed by photoetching, and the remaining oxide film is used as a mask.
The silicon substrate 101 is vertically etched by reactive ion etching to form the grooves 102, 103, 104. The depth of the groove is, for example, about 5 μm. Like this 3
By forming the book groove, two ridges 106 and 107 are formed.

Next, an impurity diffusion layer 118 of the same type as the diffusion layer 116 formed in (A) above is formed on the wall surface of the groove.

Next, in (C), the diffusion layer 118 formed at the bottom of the groove.
Etch by reactive ion etching until completely removed. This divides the diffusion layer 118 and forms the electrodes 108 and 109.

Next, in (D), a metal, a dielectric, or the like is formed on the substrate surface by a method such as vapor deposition under a predetermined pressure, and a portion other than the upper portion of the reference pressure chamber is removed by photoetching to remove the lid. Form 105. At this time, by appropriately setting the width and depth of the groove 104 serving as the reference pressure chamber, and by using a method such as oblique vapor deposition, the deposit can be formed into the groove 10.
It is possible to prevent the inside of the groove 4 from entering and to keep the inside of the groove at the pressure when the lid 105 is formed.

It should be noted that, in the embodiments described so far, three grooves are formed, two ridges are formed thereby, and the groove between them is used as the reference pressure chamber. However, two grooves are formed. The reference pressure chamber can also be formed by forming one ridge between them and providing a lid on the top of either one of the grooves.

〔The invention's effect〕

As described above, in the present invention, the pressure detecting portion is provided on the surface of the substrate and the reference pressure chamber is formed at the same time. Since the sensor can be manufactured, and therefore the mounting becomes extremely easy, the excellent effect that the cost can be reduced can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 and FIG.
FIG. 4 is a diagram for explaining the operation of the present invention, FIG. 4 is a manufacturing process diagram of the present invention, and FIG. 5 is a sectional view of an example of a conventional device. <Explanation of symbols> 101 ... Silicon substrate, 102, 103, 104 ... Groove 105 ... Lid, 106, 107 ... Ridges 108, 109 ... Electrodes

Claims (1)

[Claims] 1. A plurality of grooves provided on the surface of a substrate, at least one ridge whose both surfaces are separated from the surrounding substrate by the groove, and a member for sealing the top of the groove on one side of the ridge, The top portion is a cavity region hermetically sealed with respect to the outside, and conversion means is provided for converting the displacement generated in the ridges according to the pressure difference between the cavity region and the outside into an electric signal. Pressure sensor.