JPH06213744A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To provide a semiconductor pressure sensor which is not sensitive to the stress even if the direction of a temperature compensation gauge is deflected slightly from the crystal axis exhibiting lowest piezoresistance coefficient and in which differential pressure or pressure signal can be corrected highly accurately. CONSTITUTION:A temperature compensation sensor 8 is formed by connecting two microlines 8a, 8b in zigzag. The two microlines 8a, 8b have identical length and resistance and intersect perpendicularly each other and formed, respectively, in the directions of (010) and (100) axes exhibiting the lowest sensitivity of piezoresistance coefficient in the crystal orientation (001).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor for detecting a differential pressure or pressure.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor pressure sensor of this type, one using a Si (silicon) semiconductor diaphragm is known. In this Si diaphragm type semiconductor pressure sensor, a gauge acting as a piezoresistive region is formed on the surface of a semiconductor substrate by an impurity diffusion or ion implantation technique, and a lead is formed by vapor deposition of Al and a part of the back surface is etched. It is configured by forming a thin portion having a thickness of about 20 μm to 50 μm, that is, a diaphragm by removing it by applying a pressure. When the measured pressure is applied to the front and back surfaces of the diaphragm, the specific resistance of the gauge changes with the deformation of the diaphragm. The output voltage accompanying the resistance change at this time is detected to measure the differential pressure or pressure. Recently, in order to prevent the zero point change of the sensor caused by temperature or static pressure, the static pressure and temperature are detected, and the differential pressure or pressure signal is corrected by these detection signals to increase the differential pressure or pressure. There is known a multi-function type semiconductor pressure sensor capable of performing accurate measurement (eg, Japanese Patent Laid-Open No. 4-113239). In particular, temperature compensation is important because the temperature dependence of the piezoresistive coefficient increases as the impurity concentration of the semiconductor substrate decreases.

FIGS. 4 and 5 show a conventional example of such a multi-function type semiconductor pressure sensor, in which 1 is a back plate, which is a Pyrex glass whose linear expansion coefficient is similar to that of the semiconductor substrate 2. A pressure introducing hole 3 is formed of ceramics or the like and penetrates the upper and lower surfaces, and the semiconductor substrate 2 is electrostatically bonded to the upper surface. The semiconductor substrate 2 is made of (001) -faced n-type single crystal Si, and since the recessed portion 4 provided on the back surface forms a thin portion, a diaphragm 5 for differential pressure sensing is formed. A differential pressure detecting gauge 6 for detecting a differential pressure or pressure is provided on the surface side of 5 and a differential pressure detecting gauge 6 for detecting the pressure is further provided, and the temperature is also formed on the outer peripheral portion of the semiconductor substrate 2 outside the diaphragm 5 for detecting the differential pressure. A temperature compensating gauge 8 is provided. Recessed portion 4 provided on the back surface side of the semiconductor substrate 2
Communicates with the pressure introducing hole 3 and one of the measured pressures P1 is introduced. The differential pressure detection gauge 6 is formed by an impurity diffusion or ion implantation technique and acts as a piezoresistive region (piezoresistive element), and a wheelstone bridge is formed by the leads 9 formed by vapor deposition of Al or the like. The differential pressure signals of the pressures P1 and P2 to be measured applied to the front and back surfaces of the diaphragm 5 are differentially output.
Maximum measured differential pressure or pressure is 140 Kgf / cm
² , about 420 Kgf / cm ² .

The piezoresistive coefficient of the differential pressure detecting gauge 6 is p
For both the n-type and the n-type, it decreases as the doping amount of impurities into the semiconductor substrate increases. Therefore, in order to increase the rate of change of the specific resistance of the differential pressure detection gauge 6 to increase the sensitivity to pressure and obtain a large output voltage, the impurity concentration is set low. Also, the piezoresistance coefficient differs between p-type and n-type,
The p-type is larger, and therefore it is common to provide the p-type resistance layer on the n-type semiconductor. Differential pressure gauge 6
The output voltage depends on the shape of the diaphragm, the wall thickness, the formation position of the differential pressure detection gauge 6, the orientation of the gauge itself, and the like. For example, regarding the direction of the differential pressure detection gauge 6, when the gauge is provided on Si having a crystal plane orientation (001), the direction in which the piezoresistance coefficient is maximum is the <110> crystal axis direction. It is desirable to form the differential pressure detection gauge 6 in the direction.

Like the differential pressure detecting gauge 6, the temperature compensating gauge 8 is formed by an impurity diffusion or ion implantation technique to form a piezoresistive region (piezoresistive element).
The temperature is detected by forming a wheelstone bridge with a lead (not shown) formed by vapor deposition of Al or the like. And this gauge 8
Is a direction showing the minimum sensitivity of the piezoresistance coefficient in the crystal plane orientation (001) on the surface of the thick portion of the semiconductor substrate 2 so as not to be sensitive to the pressures P1 and P2 to be measured applied to the front and back surfaces of the diaphragm 5. 010> (or <100
>) It is formed in the axial direction.

FIG. 6 shows a crystal plane (00
Piezoresistance coefficient πl of p-type piezoresistive element for 1)
3 is a diagram showing the distribution of .pi.t.

[0007]

In the conventional semiconductor pressure sensor described above, the temperature compensating gauge 8 is insensitive to the pressure so that the piezoresistance coefficient in the crystal plane orientation (001) is the minimum (<010 > Or <1
00> axial direction). However, it is difficult to accurately form the temperature compensating gauge 8 in the crystal axis direction in which the piezoresistive coefficient is minimized due to an alignment error during gauge formation. As described above, there is a problem that an error occurs in the output voltage in response to the stress generated at that location, and the differential pressure or the pressure signal cannot be corrected with high accuracy.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is that the orientation of the temperature compensating gauge is slightly from the crystal axis direction in which the piezoresistive coefficient is the minimum. It is an object of the present invention to provide a semiconductor pressure sensor that is insensitive to stress even if it is deviated and is capable of correcting a differential pressure or a pressure signal with high accuracy.

[0009]

To solve the above problems, the present invention provides a semiconductor pressure sensor in which a thin portion is formed on a semiconductor substrate and a gauge acting as a piezoresistive region is provided on one surface of the thin portion. A temperature compensating piezoresistive region is formed on the surface of the thick portion of the semiconductor substrate by connecting two minute line segments that are orthogonal to each other and are in a crystal axis direction having a minimum piezoresistive coefficient in a zigzag shape. is there.

[0010]

If the two minute line segments forming the temperature compensating piezoresistive region that are orthogonal to each other deviate from the crystal axis direction in which the piezoresistive coefficient is the minimum, the piezoresistive coefficient does not become zero and stress occurs. , Produce an output signal accordingly.
This output signal is canceled because the two minute components are orthogonal to each other, and as a result, the output of the temperature compensating piezoresistive region becomes zero, forming a gauge that is insensitive to pressure.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 is a plan view showing an embodiment of a semiconductor pressure sensor according to the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. The same components as those in FIGS. 4 and 5 are designated by the same reference numerals. In this embodiment, static pressure and temperature are detected in addition to differential pressure or pressure, and the differential pressure or pressure signal is corrected by the detection signal of static pressure and temperature to measure the differential pressure or pressure with higher accuracy. The case where the present invention is applied to the multi-functional semiconductor pressure sensor thus obtained is shown. Further, the thickness and size of each part in the drawing are exaggerated for ease of understanding, and are different from actual dimensions. The back plate 1 is formed of Pyrex glass, ceramics, or the like having a thermal expansion coefficient similar to that of the semiconductor substrate 2, and the semiconductor substrate 2 is integrally bonded to the upper surface by electrostatic bonding. The semiconductor substrate 2 is made of (001) -faced n-type single crystal Si, and a thin disk-shaped differential pressure-sensitive or pressure-sensitive diaphragm 5 for pressure detection which is sensitive to differential pressure or pressure by removing the central portion of the back surface thereof. Four static pressure detection pressure sensitive diaphragms 1 which are also provided and which are sensitive to static pressure by being removed on the outer surface of the pressure sensitive diaphragm 5 at regular intervals in the circumferential direction by etching.
1 is provided. On the other hand, on the surface side of the semiconductor substrate 2, a differential pressure detecting gauge 6 for detecting a differential pressure or pressure and a static pressure detecting gauge 12 for detecting a static pressure are provided with the differential pressure or pressure detecting pressure sensitive diaphragm 5 and each static pressure. Pressure-sensitive diaphragm for pressure detection 1
1. The temperature compensating gauges 8 are respectively positioned and provided on the outer peripheral surface of the thick portion 1 and near the outer surface of the thick portion for detecting temperature.
Is provided. At the center of the back plate 1 is formed a pressure introducing hole 3 for guiding one of the pressures P1 to be measured to the back surface side of the diaphragm 5 through a recess 4 formed at the center of the back surface of the semiconductor substrate 2. The four recesses 14 formed on the back surface side of the semiconductor substrate 2 along with the formation of each static pressure detection pressure-sensitive diaphragm 11 are sealed by the back plate 1 to form a reference chamber, which is a vacuum or Maintained at atmospheric pressure.

The differential pressure detecting gauge 6 is diffused or ionized near the peripheral portion where the stress in the radial direction and the circumferential direction generated on the diaphragm 5 at the time of applying a differential pressure or pressure on the upper surface of the pressure sensitive diaphragm 5 is maximum. Four of them are formed by the driving method, and the differential pressure signals are differentially output by being connected to the wheelstone bridge.

The static pressure detecting gauges 12 are formed on the front surface side of the semiconductor substrate 2 on the static pressure detecting pressure sensitive diaphragms 11 so as to be located outside the differential pressure detecting gauges 6, respectively. The static pressure signal is output differentially by being connected to the wheelstone bridge.

The temperature compensating sensor 8 is formed on the outer peripheral portion of the upper surface of the thick portion 15 of the semiconductor substrate 2 by a diffusion or ion implantation method so as to be located outside the static pressure detecting gauge 12 and has a predetermined length. And a resistance value and a gauge portion that acts as a piezo region. In this case, the gauge portions forming the sensor 8 have the same length and the same resistance, are orthogonal to each other, and have crystal plane orientations (00
Orientation showing the minimum sensitivity of the piezoresistive coefficient in 1) <0
Two minute line segments 8 in the 10> axis direction and the <100> axis direction
It is formed by connecting a and 8b in a zigzag shape, thereby forming a temperature sensor that is insensitive to pressure. That is, the two minute line segments 8a and 8b that are orthogonal to each other and form the temperature compensating sensor 8 are correctly formed so as to coincide with the <010> axial direction and the <100> axial direction in which the piezoresistance coefficient is the minimum. In this case, as apparent from FIG. 6, the piezoresistance coefficients πl and πt are zero, so that even if stress occurs, no output is produced as a sensor. on the other hand,
When the two minute line segments 8a and 8b are deviated by an angle θ from the <010> axis direction and the <100> axis direction where the piezoresistance coefficient is the minimum, the piezoresistance coefficients πl and πt do not become zero,
Therefore, when a stress is generated, the resistance value changes accordingly and an output voltage is generated. Here, the resistance values of the minute line segments 8a and 8b are ΔRa and ΔRb, the resistance value of the entire gauge is R, the piezoresistance coefficient is π (πl, πt), and the minute line segments 8a and 8b.
The stress in the vicinity of the <100> axis is σ1, <010
> If the stress in the axial direction is σ2, ΔRa of the minute line segment 8a
/ R is ΔRa / R = π (σ 2 −σ 1), and ΔRb / R of the minute line segment 8 b is ΔRb / R = π (σ 1 −σ 2). Since ΔRa / R and ΔRb / R have opposite signs and the same value, they do not cancel each other out to generate an output. Therefore, even if the piezoresistive coefficient π is not zero and the stress is not zero, it is possible to configure the temperature compensating sensor 8 that is insensitive to pressure.

3 (a) and 3 (b) are views showing other embodiments in which minute line segments of the temperature compensation sensor are connected in a zigzag manner. As long as the directions of the two minute line segments 8a and 8b coincide with the <010> axial direction and the <100> axial direction where the piezoresistance coefficient is the minimum, they may be connected in a zigzag manner. .

In FIG. 1, 20 is a lead, 21 is a power source terminal for differential pressure detection and static pressure detection, 22 is a terminal for differential pressure signal extraction, 23 is a terminal for static pressure signal extraction, and 24 is a power source for temperature compensation. It is a terminal part.

In the above embodiment, the semiconductor substrate 2 is made of n-type silicon, and the gauges 6, 8, 12 which are piezoresistive regions are made of p.
I explained about the case that it is composed of type silicon,
This is because using a piezoresistor made of p-type silicon has better pressure-resistance linearity than n-type,
The (001) plane with the maximum piezoresistive coefficient, <110>
This is because it is possible to take out the outputs in both the forward and reverse directions with good symmetry in the crystal axis direction, but the present invention is not limited to this, and an n-type piezo region may be formed on a p-type substrate. Of course.

[0018]

As described above, in the semiconductor pressure sensor according to the present invention, the temperature compensating piezoresistive elements are zigzag-shaped with two minute line segments in the crystal axis direction which are orthogonal to each other and each have a minimum piezoresistive coefficient. Since it is formed by being connected to the temperature sensor, it is possible to obtain a temperature sensor that is insensitive to stress even if it is deviated from the crystal axis direction, and it is possible to accurately correct the differential pressure or the pressure signal.

[Brief description of drawings]

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

FIG. 2 is a sectional view of the same sensor taken along the line II-II of FIG.

3 (a) and 3 (b) are diagrams showing other embodiments of the temperature compensation sensor, respectively.

FIG. 4 is a plan view of a conventional semiconductor pressure sensor.

FIG. 5 is a sectional view of the sensor.

FIG. 6 is a diagram showing distributions of piezoresistance coefficients πl and πt of a p-type piezoresistive element with respect to a crystal plane (001) of a Si diaphragm.

[Explanation of symbols]

 1 Back Plate 2 Semiconductor Substrate 5 Diaphragm 6 Differential Pressure Detection Gauge 8 Temperature Compensation Gauge 12 Static Pressure Detection Gauge 8a, 8b Fine Line Segment

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[Procedure amendment]

[Submission date] February 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

To solve the above problems, the present invention provides a semiconductor pressure sensor in which a thin portion is formed on a semiconductor substrate and a gauge acting as a piezoresistive region is provided on one surface of the thin portion. A temperature compensating piezoresistive region formed by connecting two minute line segments orthogonal to each other in a zigzag shape is provided on the surface of the thick portion of the semiconductor substrate.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

The temperature compensating sensor 8 is formed on the outer peripheral portion of the upper surface of the thick portion 15 of the semiconductor substrate 2 by a diffusion or ion implantation method so as to be located outside the static pressure detecting gauge 12 and has a predetermined length. And a resistance value and a gauge portion that acts as a piezo region. In this case, the gauge portions forming the sensor 8 have the same length and the same resistance, are orthogonal to each other, and have crystal plane orientations (00
Orientation showing the minimum sensitivity of the piezoresistive coefficient in 1) <0
Two minute line segments 8 in the 10> axis direction and the <100> axis direction
It is formed by connecting a and 8b in a zigzag shape, thereby forming a temperature sensor that is insensitive to pressure. That is, the two minute line segments 8a and 8b that are orthogonal to each other and form the temperature compensating sensor 8 are correctly formed so as to coincide with the <010> axial direction and the <100> axial direction in which the piezoresistance coefficient is the minimum. In this case, as apparent from FIG. 6, since the piezo resistance coefficients πl and πt are zero, even if stress occurs, no output is produced as a sensor. on the other hand,
When the two minute line segments 8a and 8b deviate from the <010> axis direction and the <100> axis direction where the piezoresistance coefficient is the minimum by the angle θ, the piezoresistance coefficients πl and πt do not become zero,
Therefore, when a stress is generated, the resistance value changes accordingly and an output voltage is generated. Here, the resistance values of the minute line segments 8a and 8b are ΔRa and ΔRb, the resistance value of the entire gauge is R, the piezo resistance coefficient is π (πl, πt), and the minute line segments 8a and 8b.
The stress in the <100> axis direction in the vicinity is σ1, <010
> If the stress in the axial direction is σ2, ΔRa of the minute line segment 8a
/ R is ΔRa / R = π (σ2-σ1) and ΔRb / R of the minute line segment 8b is ΔRb / R = π (σ1-σ2). Since ΔRa / R and ΔRb / R have opposite signs and the same value, they do not cancel each other out to produce an output. Therefore, even if the piezo resistance coefficient π is not always zero and the stress is not zero, it is possible to configure the temperature compensation sensor 8 that is insensitive to pressure. That is, the temperature compensation sensor 8 according to the present invention is
Basically, two minute line segments 8a and 8b which are orthogonal to each other
Anything connected in zigzag will do, and always <
010> axis direction and <100> axis direction
You don't have to. However, <010> axial direction and <100> axial direction
If it deviates from the direction, the sensitivity will decrease and the error will increase,
It is preferable to manufacture them so as to match each other.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

[0018]

As described above, in the semiconductor pressure sensor according to the present invention, the temperature compensating piezoresistive elements are directly connected to each other.
Since two minute line segments intersecting each other are formed by connecting in a zigzag shape, a temperature sensor that is insensitive to stress can be obtained even if deviated from the crystal axis direction, and the differential pressure or pressure signal is corrected with high accuracy. be able to.

Claims (1)

[Claims] 1. A semiconductor pressure sensor in which a thin portion is formed on a semiconductor substrate, and a gauge acting as a piezoresistive region is provided on one surface of the thin portion, the thick portion of the semiconductor substrate being perpendicular to each other. A semiconductor pressure sensor comprising a temperature-compensating piezoresistive region formed by connecting two minute line segments in a crystal axis direction having a minimum piezoresistive coefficient in a zigzag shape.