JPS582464B2 - Semiconductor pressure sensing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring pressure in a liquid or gas, and in particular to a pressure sensing device of the semiconductor type.

The semiconductor-type pressure sensing device disclosed below is suitable for measuring pressure in penetration holes, pipelines, pneumatic or hydraulic systems of aircraft, internal combustion engines, or hydraulic systems in agricultural machinery, or in laboratory conditions. Used to measure ultra-high pressure.

In addition, the present invention is applicable to heavy loads (railway vehicles, mining vehicles).
It is also used to measure force in weighing or controlling motion activities in forging and rolling equipment.

The ability of semiconductor materials to change their resistance in response to the hydrostatic pressure of their environment, such as air, gas, or liquid, is
Are known.

It is also known that this phenomenon is used in the manufacture of pressure gauges, and in particular semiconductor pressure sensing devices made based on n-type single crystal gallium antimonide are also known; The pressure sensing device has two current terminals, and variation in the electrical signal difference between the current terminals is an indicator of pressure change.

(For example, Physical Review Vol. 117 No. 1,
Sagar A., 1960, pp. 98-100.
”Experimental Investment
On of Co-induction Band of
(See “GaSb”).

The conduction band of gallium antimonide changes relative energy differences in response to hydrostatic pressure.

With two minimum values, the change results in a change in the electrical resistance of the pressure sensing device.

However, the conduction band minimum in gallium antimonide moves along the energy scale in response to pressure in one direction, and the sensitivity factor of the instrument to pressure is low (10-
4 bar-1).

In this case, the operating pressure range of such instruments based on gallium antimonide is limited to the range from 0 to 10,000 bar.

The temperature stability of these instruments is insufficient and the temperature component in the sensitivity variation is too high < 0.5 de
It even reaches g-1.

AB1 consists of two semiconductor materials, AB and AC.
Another pressure gauge is known which comprises a solid based on a solid solution called -xCx, in which the first of the semiconductor materials
One has a direct forbidden band, the second one has an indirect forbidden band, and both of these materials have a minimum value of the direct and indirect conduction band, and the AC material in solid solution AB1-xCx. The X value, which is the mole fraction, is AB1-xCx
The direct and indirect energy minima of the solid solution conductor are chosen to be close.

The pressure gauge also includes means electrically coupled to the solid body for measuring changes in electrical resistance of the solid body in response to applied pressure.

(e.g. U.S. Pat. No. 3,270,562, Class 73-39
8, see).

Conventionally known pressure gauges are made based on a solid solution of GaAa1-xPx containing gallium arsenide and gallium phosphide in a specific molar ratio.

The value of X in the solid solution GaAs1-xPx is selected according to the pressure range to be measured.

By choosing solid solutions with different X values, 0
Instruments can be made to measure high or low pressures in the range from 60,000 bar to 60,000 bar.

The pressure sensitivity of such instruments is higher than instruments based on single-crystal gallium antimonide, ranging from 2.times.10@-4 to 4.times.10@-4 over the entire pressure range.

This can be explained by the fact that the conduction band minimum moves in opposite directions on the energy scale in response to pressure.

However, a serious drawback of conventionally known pressure gauges lies in the low stability of their characteristic values with respect to temperature, which is due to the difference between the thermal energy of electrons in the solid solution of GaAs This is due to the change in the ratio to the energy width.

Thus, according to experimental data regarding the dependence of the sensitivity factor on the ratio of the X values at three temperatures: +25°C, -27°C and +90°C, GaAs0.65P0.
The pressure sensitivity of the instrument based on a solid solution of 35 is from 3 x 10-4 bar-1 at -27°C to +90°C.
about 20 such as up to 2.5 x 10-4 bar-
However, this means that the temperature component of the sensitivity change almost reaches 0.15% deg-1, which is a considerably large value.

In a pressure gauge based on GaAsO, 6P0.4, the sensitivity to pressure is 3.6X10-4b at +25°C.
ar to 2 x 10-4 bar-1 at +90°C, which means that the temperature component of the sensitivity change is 0.7%.
It will be deg-1.

This means that if the temperature difference during measurement varies widely,
This considerably limits the technical use of such pressure gauges.

One of the objects of the invention is to reduce errors in pressure measurements during uniform compression of liquids or gases.

Another object of the present invention is to provide a semiconductor pressure sensing device characterized by increased stability of the pressure sensitivity coefficient with respect to temperature.

Another object of the invention is to provide a pressure sensing device that ensures the measurement of hydrostatic pressure over a wide range of operating temperatures.

Yet another object of the invention is to provide a pressure sensing device with high temperature stability of electrical resistance in the operating range.

These and other objects provide that the semiconductor-type pressure sensing device is a solid state 1 having a semiconductor composition of AB1-xCx consisting of two semiconductor materials, the first of which has the same direct forbidden band. the second has an indirect forbidden zone;
Each of the semiconductor materials has direct and indirect energy minima in the conduction band, and the AC in the AB1-xCx composition
The mole fractions of the materials are selected such that the direct and indirect minimum energy values of the conduction band of the AB1-xCx composition with two groups of alternating layers 2 and 3 with different X values are close; Each of the groups has at least one layer 2 or 3
and having a uniform X value in one group,
means for measuring the variation in electrical resistance of a solid body in response to changes in applied pressure, the electrical resistance of the solid body being electrically connected to the solid body, from a minimum value to a maximum value within a composition; Variable X value range and first and second group layers 2
and 3 is selected to compensate for the decrease in sensitivity to applied pressure due to temperature fluctuations in the layers 2 of the first group by increasing the sensitivity in the layers 3 of the second group. be done.

It is desirable to use a semiconductor composition in which the value of X is constant throughout the thickness of each layer.

It is also desirable to use semiconductor compositions in which the value of X in each layer varies from one interface to another throughout the thickness of the layer according to a principle expressed by a fraction of a sine function. That's true.

It is useful for the layer of the semiconductor composition to be doped with shallow energy level impurities to a free carrier concentration sufficient to degenerate the electron gas in the semiconductor composition.

the solid is selected with X ranging from 0.2 to 0.4;
The difference between the maximum and minimum values of It has also proven useful that the ratio of the two groups of layers to the total volume is selected in the range from 1 to 10 and the thickness of each layer is selected in the range from 200 Å to 3000 Å.

Moreover, the semiconductor composition layer of GaAs1-xPx is 2×1018
It may also be doped to a free carrier concentration selected in the range from cm to 7×10 cm.
This is desirable.

The pressure sensing device proposed by the invention has a very high temperature stability with respect to the pressure sensitivity coefficient.

Other objects and advantages of the invention will become apparent from the following description of specific embodiments, taken in conjunction with the accompanying drawings.

Consider the semiconductor pressure sensing device shown schematically in FIG.

The semiconductor type pressure sensing device comprises a solid body 1 based on a solid solution called AB1-xCx consisting of two semiconductor materials AB and AC. has an indirect forbidden zone.

Each of these materials has direct and indirect energy minima in the conduction band.

The solid solution AB1-xCx is of semiconducting composition with two groups, alternating layers 2 and 3.

The first group includes at least one layer 2 having a first average value of
, and the second group has at least one layer 3 with a second average value of X.

The semiconductor composition is based on a solid solution comprising the material ANBV.

Specific examples of such compositions are GaAs1-xPx, AsG
a1-xAx, PIn1-XGa.

In this case, GaAs and InP have a direct forbidden band, and GaP and AlAs have an indirect forbidden band.

The X value, which determines the mole fraction of AC material in the AB1-xCx solid solution, is chosen to approximate the direct and indirect energy minima of the conductors in the AB1-xCx solid solution.

The range of the X-value variation from the minimum value to the maximum value in the semiconductor composition called ABC and the volume ratio of layers 2 and 3 belonging to different groups are determined by It is chosen to compensate for the decrease in sensitivity by increasing the temperature sensitivity in the layers 3 belonging to the second group.

Means for measuring the variation in electrical resistance of the solid body 1 in response to applied pressure is provided as a resistance meter 4.

An ohmic contact 5 bonded over a thickness d to the side surface of the solid body 1 is electrically connected to the input of the resistance meter 4 by means of a conductor 6 .

It is also possible for the layers 2, 3 of the semiconductor composition to be doped with shallow energy level impurities to a sufficient free carrier concentration to degenerate the electron gas in the semiconductor composition.

Tellurium, selenium, and tin are such impurities as A■
It can be used in a solid solution comprising the material B■.

The x value in each layer 2, 3 may be constant throughout the thickness of the layer 2, 3, and in each layer 2, 3 from one interface to the other interface throughout the thickness of each layer 2, 3. It can also be changed to.

Referring to FIG. 2, the X value changes from layer 2 to layer 3 through the thickness d of solid 1 (FIG. 1).

In this (Fig. 2), d1 is each layer 2 belonging to the first group.
, and d2 is the thickness of each layer 3 belonging to the second group.

Across the thickness d1 of layer 2 (FIG. 1), X has a first constant value, and through the thickness d2 of layer 3 (FIG. 2), X has a second constant value.

FIG. 3 shows that the variation of the X value through the thickness d is expressed by a sine wave function.

Here, d1 is the thickness of each layer 2 (FIG. 1) belonging to the first group, and d2 (FIG. 3) is the thickness of each layer 3 (FIG. 1) belonging to the second group.

Throughout the thickness d1 (Fig. 3) of layer 2 (Fig. 1), the X value has a first average value, and from one interface to the other
The principle of value variation is expressed by the first half-wave part of the sinusoidal function.

Through the thickness d2 (Fig. 3) of layer 3 (Fig. 1), the X value has a second average value, and the X value from one interface to the other
The principle of value variation is expressed by the second half-wave part of the sinusoidal function.

Referring to Figure 4, the principle of X-value variation over thickness d is expressed by a portion of a sinusoidal function, where d1 is the thickness of layer 2 (Figure 1) belonging to the first group. d2 is the thickness of layer 3 (FIG. 1) belonging to the second group.

Over the thickness d1 (Fig. 4) of layer 2 (Fig. 1) the X value has a first average value, and over the thickness d2 (Fig. 4) of layer 3 (Fig. 1) the X value has a second average value. has an average value of

The principle of the variation of the X value over the thickness d of layers 2 and 3 is expressed by a portion of a sinusoidal function that changes from the minimum X value at the first interface of layer 2 to the maximum X value at the second interface of layer 3. be done.

This pressure detection device operates as follows.

As the pressure to be measured increases, the electrical resistance of the device also increases, resulting in an individual increase in the potential difference between the contact surfaces 5 (FIG. 1), which is recorded by the resistance meter 4.

The pressure sensitivity S of the pressure sensing device is determined by the following general formula.

Here, Uo: Potential difference between contact surfaces at initial pressure △U: Increment in potential difference between contact surfaces due to pressure change △P: Increase in pressure Conductivity and thickness d1, d2 of layers 2 and 3 are respectively The pressure sensitivity S of the pressure sensing device in the case of equal values is determined by the following equation.

Here, S1: Sensitivity of solid solution in layer 2 S2: Sensitivity of solid solution in layer 3 It is known that solid solution pressure sensitivity depends on the X value,
Since the X-value variation over the thickness d1, d2 of each layer 2, 3 is a sinusoidal function, S1 and S2 integrate this known dependent characteristic within the limits of the X-value variation in layers 2, 3 belonging to each group. can be found by

The pressure sensitivity of this device, which is based on a semiconductor solid solution of two semiconductor materials, can increase or decrease in response to the temperature of the environment.

This is the thermal energy of the electron KT and the solid solution AB1-x
depends on the energy difference ΔE between the direct and indirect minima of the conduction band of Cx.

The value of ΔE also depends on the X value of the solid solution.

When the inequality ΔE>KT holds, the pressure sensitivity increases with increasing temperature.

When the inequality ΔE<KT holds, the pressure sensitivity decreases as the temperature increases.

Therefore, the compositions of layers 2 and 3 ensure that the composition of layer 2 belonging to the first group satisfies the first condition ΔE>KT, and the composition of layer 3 belonging to the second group satisfies the second condition ΔE<KT. selected to do so.

If in layer 2 (Fig. 1) the X value is 0.37 and the sensitivity S1 decreases with increasing temperature in the temperature range from 0°C to 100°C as shown in curve 7 of Fig. 5, In layer 3 (Fig. 1), if the value of has a smaller temperature dependence than in each of layers 2 and 3, as shown by curve 9 in FIG.

Therefore, the decrease in sensitivity to applied pressure in layer 2 (FIG. 1) belonging to the first group is due to the increase in sensitivity to applied pressure in response to humidity fluctuations in layer 3 (FIG. 1) belonging to the second group. be compensated.

This ensures an increased operating temperature range and an improved temperature stability of the pressure sensitivity coefficient.

Moreover, the pressure sensitivity and temperature stability of the pressure sensing device depend on the doping level of the AB1-xCx solid solution.

When the doping level is low, the pressure sensitivity is determined by the electron transfer that can occur over the energy difference ΔE between the direct and indirect minima of the conduction band.

If the impurity doping level is increased to the point where the electron gas degeneration occurs when the free carrier concentration is higher than 1018 cm-3 in the majority of compounds A■B■, then the Fermi level corresponding to the energy EF is in the forbidden band. to the conduction band, and the sensitivity of this device to pressure is determined by the electron transfer that can occur across the energy difference (ΔE-EF).

Electron energy KT grows with increasing temperature,
The possibility of electron transfer across the energy difference (ΔE-EF) remains almost constant since the Fermi level decreases with increasing temperature.

This means that the smaller the energy EF, the larger the energy difference (△E-EF), which ultimately results in a decrease in the possibility of electron transfer due to temperature and a pressure sensing device. and improved temperature sensitivity.

Moreover, in the case of electron gas degeneration, the concentration and mobility of electrons vary little with temperature, which also improves the temperature stability of the resistance of the pressure sensing device.

The ratio of the thicknesses d1, d2 of adjacent layers 2, 3 belonging to different groups and the overall thickness d of the structure are substantial factors influencing the operation of the pressure sensing device.

The absolute values of these conditions are determined by the input impedance requirements of the device.

The absolute values of the thicknesses d1, d2 of the layers 2, 3 are selected taking into account the properties of the particular solid solution on which the pressure sensing device is based.

If a solid solution of GaAs1-xPx is used and is characterized by a significant difference in the crystal lattice parameters of the semiconductor materials gallium arsenide and gallium phosphide, the structure based on this solid solution is , 3 are chosen to be as thin as possible to reduce the periodic structure mismatch dislocation density.

If a solid solution comprising gallium abrasive and aluminum abrasive is used, in which the difference in the lattice parameters of the semiconductor materials is close to zero, the layers 2, 3 are made thicker.

However, in any case, the statistical averaging of uncontrollable deviations of the thickness of layers 2, 3 from a specific thickness and deviations of the aspect of the distribution of solid solution components throughout the thickness of layers 2, 3 Therefore, the large overall number of layers 2, 3 contributes to increasing the reproducibility of the parameters of the pressure sensing device during the manufacturing process.

For a better understanding of the invention, specific examples of embodiments of pressure sensing devices are provided below.

Example 1 A pressure sensing device made on the basis of a GaAs1-xPx solid solution with alternating layers 2, 3 with X values of 0.3 and 0.37, respectively.

The total number of layers 2, 3 is 300, the thickness of layers 2, 3 is uniform and equal to 500 Å, and the layers 2, 3 belong to different groups.
The volume ratio of 3 is 1.

The absolute thickness of the isolated layer 23 of GaAs1-xPx solid solution is selected from the range 200 Å to 3000 Å.

This range is considered optimal.

The reason is that when the thickness of layers 2, 3 is less than 3000 Å, the crystal lattice bonds are usually matched, which eliminates incompatible dislocations.

The thickness of layers 2, 3 should not be less than 200 Å.

The reason is that this involves technical difficulties due to making expensive high-quality periodic structures with periods smaller than 200 Å, making pressure sensing devices more expensive.

The level of impurity doping in layers 2 and 3 is 2×10 18 cm −3 .

Pressure detection device is 10mm x 0.2mm x 0.015mm
A solid 1 has dimensions of .

The contact surface 5 is made of an indium-tin alloy and the conductor 6 is a gold conductor with a diameter of 50-70μ.

The resistance variation was measured with a resistance meter 4 in the pressure range from 0 to 250 bar.

The range of resistance fluctuation of the pressure sensing device is - under constant pressure.
795○ in the temperature range from 77℃ to +130℃
It was recorded from hm to 670○hm.

In other words, the resistance fluctuation is 20% in a temperature range of 207 degrees.
%, and the temperature coefficient of resistance variation is equal to 0.1% deg-1.

The pressure sensitivity versus temperature characteristic of the device is shown in curve 10 of FIG.

Pressure sensitivity is 1.36 x 10-4 bar at -77°C
1.27 x 10-4 bar from -1 to +130°C
Changes to -1.

The sensitivity variation due to temperature in the temperature range of 207 degrees is 7%, and the temperature coefficient of sensitivity variation is 0.033% deg.
-1.

The calculated curve 9 and the experimental curve 10 were sufficiently close for this pressure sensing device.

The pressure sensing device described herein has good temperature resistance stability (temperature coefficient of resistance variation is 0.1% deg-1);
Good pressure sensitivity and temperature stability (temperature coefficient of sensitivity variation is 0.0
33% deg-1).

Semiconductor pressure sensing devices based on GaAs1-xPx solid solutions can be used in compressor installations, the petrochemical industry, ore weighing in mining vehicles, ultra-high pressure (up to 40,000 bar) measurements in laboratories, etc.

Example 2 ASGa1-xA with two types of layers 2 and 3 (Fig. 1)
l A pressure sensing device based on a solid solution, comprising:
The × values are 0.33 and 0.37, respectively.

The solid 1 is composed of two layers 2 each having a thickness of 60,000 Å,
3, and the ratio between the volumes of layers 2, 3 belonging to different groups is equal to 1.

Layers 2 and 3 are doped to a level of 2×10 18 cm −3 .

The pressure detection device is 10mm x O. 2mm x 0.012mm
A solid 1 has dimensions of .

The contact surface 5 is made of nickel and the conductor 6 has a diameter of 50-55
It is a copper conductor of μ.

The resistance is measured with a resistance meter 4 in the pressure range from 0 to 250 bar.

The variation range of the resistance of the device was recorded as from 155 o hm to 147 o hm under constant pressure in the temperature range from 21 °C to 108 °C.

In this temperature range equal to 87 degrees, the resistance variation of the device reaches 5.5%, and the temperature coefficient of resistance variation is 0.07% de
It was equal to g-1.

Pressure sensitivity is 2.43 x 10-4 bar1 at 21°C
to 2.28 x 10-4 bar-1 at 108°C.

Sensitivity variation due to temperature in a temperature range of 87 degrees is 7
%, and the sensitivity variation temperature coefficient was equal to 0.1% deg-1.

Semiconductor pressure sensing devices based on AsGa1-xAlx solid solutions can be used to measure oil pressure in the process of compressing oil wells or ceramic-metal sections.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a semiconductor pressure sensing device according to the invention, FIG. 2 shows a graph of the variation of the x value from one layer to another throughout the thickness of a solid body according to the invention, and FIG. 4 shows a graph in which the x value varies from one layer to another throughout the thickness of the solid according to the invention according to another principle, and FIG. FIG. 5 illustrates the curve of pressure sensitivity versus temperature of the device according to the invention. In the drawings, 1 is a solid body, 2 is a layer belonging to the first group, 3 is a layer belonging to the second group, 4 is a resistance meter, 5 is a contact surface, and 6 is a conductive wire.

Claims (1)

[Scope of Claims] 1. A solid 1 having a semiconductor composition of AB1-xCx consisting of two semiconductor materials, the first of which has a direct forbidden band, and the second of which has an indirect forbidden band. each of the semiconductor materials has direct and indirect energy minima in the conduction band, and each of the semiconductor materials has a direct and indirect energy minimum in the AB1-XCX composition.
．． The mole fraction of the C material is selected such that the direct and indirect minimum energy values of the conduction band of the AB1-xCx composition with two groups of alternating layers 2 and 3 with different X values are close; Each of the two groups comprises at least one layer 2 or 3 and has a uniform X value in the group, and means for measuring variations in the electrical resistance of the solid in response to changes in applied pressure. and electrically connected to the solid body, the semiconductor pressure sensing device comprising:
The range of values and the volume ratio of layers 2 and 3 of the first and second groups is such that the decrease in sensitivity to applied pressure due to temperature fluctuations in layer 2 of the first group is reduced by the increase in sensitivity in layer 3 of the second group. Selected to compensate. Semiconductor type pressure sensing device. 2. A device according to claim 1, wherein the X value in each layer 2, 3 of semiconductor composition is constant throughout the thickness of the layer 23. 3 The X value in each layer 2 and 3 of the semiconductor composition is
2. The device according to claim 1, wherein the device varies from one interface to another throughout the thickness of the interface according to a principle expressed by a fraction of a sine function. 4. The layers 2, 3 of the semiconductor composition are doped with shallow energy level impurities to a free carrier concentration sufficient to degenerate the electron gas in the semiconductor composition. equipment. 5 The solid 1 is of a semiconductor composition of GaAS1-xPx with X selected in the range from 0.2 to 0.4, and the entire volume of the layer 3 of the second group is The ratio to the product is selected to be in the range 1 to 10 and each layer 2,
The thickness of X is selected to be in the range from 200 Å to 3000 Å, and the difference between the maximum and minimum values of X in the semiconductor composition is selected to be in the range from 0.02 to 0.2. Apparatus according to claims 2, 3 or 4. 6 Layers 2 and 3 with a semiconductor composition of GaAs1-xPx are 2×10
6. A device according to claim 5, doped to a free carrier concentration selected in the range from 18 cm-3 to 7x1018 cm-3.