JP2730152B2 - Combined pressure and temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor type for simultaneously measuring the pressure and temperature of a measurement medium used for, for example, observing the pressure and temperature state of a refrigerant in an air conditioner system. Pressure and temperature combined measuring device.

2. Description of the Related Art For example, in an air conditioner system, it is required to measure the temperature of the refrigerant together with the pressure of the refrigerant at the entrance and exit of the refrigerant in a heat exchanger. It is desirable to measure the pressure and temperature of the solvent simultaneously. To meet such demands, for example, two measurement holes are formed in the measurement device, and one of the measurement holes is provided with a pressure sensor such as a semiconductor type, and the other measurement hole is provided with a thermocouple or a thermocouple. It has been considered that a temperature sensor such as a thermistor is configured to be attached.

However, forming two measurement holes in this way means that
The size of the apparatus is inevitably increased, and the cost is the same as when two measuring apparatuses are used. Therefore, it is not possible to sufficiently obtain the advantage of integration. In particular, the position of the two separately formed measurement holes is necessarily different, and there is a distance between the pressure and temperature measurement sites. Therefore, in the case where the density of the measurement medium is calculated from the measured pressure and temperature, if the positions of the pressure and temperature measurement sensors are different from each other, a difference in pressure and temperature occurs between the two points. It is difficult to calculate the density of the measurement medium accurately.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and has a problem that is caused by measuring pressure and temperature at different measurement points of a measurement medium as in the related art. So that the pressure and temperature are measured simultaneously at one specified location of the measurement medium, for example, so that the density of the measurement medium can be easily and accurately calculated from the pressure and temperature; It is an object of the present invention to provide a semiconductor type combined pressure / temperature detection device.

Means for Solving the Problems A combined pressure / temperature detection device according to the present invention has been made in view of the above problems, and has at least four Wheatstone bridges formed on a semiconductor substrate that is distorted in response to a pressure change. A semiconductor sensor having a strain gauge formed by a semiconductor diffusion resistor, a means for supplying and setting a constant current to a Wheatstone bridge of the semiconductor sensor, and detecting an output signal from the Wheatstone bridge corresponding to a pressure change acting on the semiconductor substrate. Means for detecting an output signal from the Wheatstone bridge corresponding to a temperature change of the semiconductor substrate, and a temperature-insensitive resistor connected in parallel to a Wheatstone bridge formed by a strain gauge formed on the semiconductor substrate. The semiconductor sensor has a crystal orientation (100) outside a semiconductor substrate. Only located in parts, as well as to the strain gauge is arranged set, a strain gauge dopant concentration "1 ×
A high concentration of 10 ²⁰ cm ^-3 "or more is set.

[Operation] In the pressure / temperature combined detection device configured as described above, for example, four strain gauges are formed on the outer peripheral portion of the semiconductor substrate, and a Wheatstone bridge is formed by the strain gauges. Therefore, when pressure acts on the semiconductor substrate to cause distortion in the semiconductor substrate, a detection signal corresponding to the amount of the distortion, that is, the pressure, can be obtained from the Wheatstone bridge. Further, since the strain gauge has a property that its resistance value changes according to the temperature, a detection signal corresponding to the temperature change can be obtained from the Wheatstone bridge.
In this case, since the strain gauge is set so as to be limited to the outer peripheral portion of the semiconductor substrate, the influence of the occurrence of the strain of the semiconductor substrate caused by the pressure on the temperature detecting section is prevented. The pressure and the temperature can be measured by one semiconductor sensor, and the pressure and the temperature of only one point of the measurement medium can be simultaneously measured and output.

Further, a temperature-insensitive resistor is connected in parallel with the Wheatstone bridge, and the strain gauge dopant concentration is set to “1 ×
The high concentration of 10 ²⁰ cm ^-3 "or more is set, so that the constant current self-sensitivity temperature compensation can be suitably performed, the non-linearity of the temperature detection output can be improved, Will be able to gain.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit configuration of the semiconductor sensor 11. In the semiconductor sensor 11, four strain gauges R _A , R _B , R _C , and R _D are formed on a surface of a semiconductor substrate by a semiconductor diffusion resistor. These strain gauges _{RA to RD} are connected to a well-known Wheatstone bridge.

Here, the semiconductor substrate is set so that one side thereof communicates with the measurement medium chamber, and the pressure of the measurement target acts on this surface. The other surface of the semiconductor substrate is set to face the reference pressure chamber, so that the semiconductor substrate is distorted in response to the pressure fluctuation of the measurement medium. At the same time, when the semiconductor substrate is brought into contact with the measurement medium, the temperature of the semiconductor substrate is set to the measurement medium temperature together with the temperature of the strain gauge.

That is, the resistance of each of the strain gauges _{RA to RD} changes according to the pressure applied to the semiconductor substrate, and at the same time, the resistance varies according to the temperature of the semiconductor substrate. Is set. The strain gauges R _B and R _D set at one diagonal position are set so that the resistance value increases when pressure acts, and the strain gauges R set at the other diagonal position. _A and _RC are set so that the resistance value is reduced by the action of pressure.

Between the power supply Vcc and the ground point GND, resistors R01, R02 and
A series circuit of R03 is formed to set the constant potential V _K and V _M of the connection point K and M of each resistor depending on the voltage dividing. Power supply Vc
c is further given via a resistor R05 to a point A which is a connection point between the strain gauges _RA and _RD of the Wheatstone bridge.
The potential at the point is _supplied to the operational amplifier OP-1 together with the potential VK at the point K. The output from the operational amplifier OP-1 is
Via respective resistors R07 and resistor R08, and a strain gauge R _A
Connection point R _B B, and are respectively supplied to the connection point C of the strain gauges R _C and R _D. That is, the operational amplifier OP-1 and the resistor R05 act as a constant current source of the bridge circuit using the strain gauge, and the resistors R07 and R08 constitute a circuit for roughly adjusting the offset output voltage of the bridge circuit. become.

The output voltage V _{C at} the output point C of the Wheatstone bridge of the strain gauge is supplied to the operational amplifier OP-2. The operational amplifier OP-2 is set to prevent a circuit-side current from flowing into the bridge circuit or vice versa, and an output signal from the operational amplifier OP-2 includes a resistor R09.
Through the supply to the operational amplifier OP-3 together with the output voltage V _C from point B of the bridge circuit. And this operational amplifier
The transistor Tr1 is controlled by the output from the OP-3. The operational amplifier OP-3, the resistor R09 and the transistor Tr1 are connected to the output voltage “V _B −V _C ” of the Wheatstone bridge.
To the current output.

The transistor Tr1 controlled by the output signal from the operational amplifier OP-3 has a collector connected to the power supply Vcc via the resistor R11. The signal of the collector circuit of the transistor Tr1 is supplied to the operational amplifier OP-4. I do.
The operational amplifier OP-4 includes resistors R11, R12, R13
Together constitute the amplifying circuit amplifies the current output from the operational amplifier OP-3 so that the pressure detection signal V _P obtained. Here, the amplification factor of the circuit by the operational amplifier OP-4 is determined by the ratio between the resistor R12 and the resistor R09.

Signal V _D of the D point is a connection point between the strain gauges R _B and R _C of the semiconductor sensor 11 is supplied to the operational amplifier OP-5 with a reference voltage V _M is set at the point M. The operational amplifier OP-5, corresponding to the temperature of point D along with resistor R21 detects a change of the voltage V _D which varies, and converts it into a current output, transistor by an output signal from the operational amplifier OP-5 Tr
Control two. Signal of the collector circuit of the transistor Tr2 to supply with the reference voltage V _K at point K to the operational amplifier OP-6, the operational amplifier OP-6 is the resistance R22, R23, R2
4 together with an amplifier circuit to amplify the output signal from the operational amplifier OP-5. Then, a temperature detection output _VT is obtained.

FIG. 2 shows a part of a circuit for processing a signal relating to pressure, particularly of the composite detecting device thus constructed, and the same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. This circuit is already known and forms a constant current self-compensation circuit.

That is, when the pressure acting on the semiconductor sensor 11 is changed, the potential V _C at the output terminal C of the Wheatstone bridge by strain gauges, and changes in response to this pressure change, the output pressure detection signal as an output signal V _P Will be done.

Considering the semiconductor sensor 11 that obtains such a pressure detection signal, the potential V _{D at the} point _D has the property of changing almost linearly with temperature as shown in FIG.

Therefore, in the composite detector shown in FIG. 1, the operational amplifier is a circuit for converting the potential VD at the point _D into a signal that changes from near the ground potential (GND) to near the power supply potential (Vcc). set circuit OP-5, originally so that the temperature detection signal V _T is obtained from the semiconductor sensor 11 for detecting the pressure.

Here, as a semiconductor sensor for pressure detection using a strain gauge, for example, is known as shown in U.S. Pat.No. 4,320,664 and the like, such a semiconductor sensor 11 for pressure detection, Conventionally, FIG. 4 (A)
And (B). That is,
Silicon (110) that becomes distorted by acting pressure
A configuration in which four strain gauges 112 to 115 are arranged at a central portion and an outer peripheral portion of a diaphragm composed of a substrate 111,
A Wheatstone bridge is formed by the strain gauges 112 to 115.

Given such a semiconductor sensor 11, to so as to detect the temperature change with pressure, voltage V _D of point D of the Wheatstone bridge by strain gauges, it is necessary not to change during the pressure. However, as shown in FIG. 4, when the strain gauges 112 to 115 are arranged at the central portion and the outer peripheral portion of the substrate 111, as shown in FIG. Stress σ1 at the center of
And the stress σ2 of the outer peripheral portion are not always equal. Accordingly, the potential V _D of the D point in this state is to vary with the pressure change, it is impossible to detect the temperature based on the V _D.

For this reason, as shown in FIGS. 5A and 5B, the semiconductor sensor 11 used in this embodiment is provided on the outer periphery of the diaphragm constituted by the silicon (100) substrate 111 with four pieces. Strain gauge 112-115 (R _A , R _B ,
R _C , R _D ) are arranged so that the strain gauges 112 to 115 form a Wheatstone bridge.

When the strain gauges are arranged as described above, FIG.
Even when stress acts on the substrate 111 as shown in (1), the stress σ2 acting on the strain gauge set at each diagonal position of the Wheatstone bridge becomes equal, and the substrate 111
A state that stress is applied to the well, the change in the potential V _D of the D point of the Wheatstone bridge does not occur. Then, the V _D becomes to respond only to changes in temperature, the semiconductor sensor
11 also functions as a temperature sensor.

In the composite detection device as shown in FIG. 1, the temperature detection is performed by the influence of the secondary components of the resistance temperature coefficients of the strain gauges R _A , R _B , R _C and R _D constituting the semiconductor sensor 11. Non-linearity of about ± 1% FS occurs in the output. Therefore, it is necessary to improve this non-linearity in order to obtain more accurate temperature detection characteristics.

FIG. 6 shows an embodiment in which such a temperature detection characteristic is improved. _A temperature-insensitive resistor R06 is connected in parallel with a Wheatstone bridge formed by strain gauges R _A , R _B , R _C and R _D.

If the resistance value of the resistor R06 is made lower than infinity, the non-linearity of the temperature output at that point will be substantially "0". However, the temperature coefficient of resistance also decreases with this change in resistance, so that constant current self-sensitivity temperature compensation cannot be performed.

In order to prevent this, the dopant concentration of the strain gauges R _A , R _B , R _C , and R _D is set to “1 ×
Set to a high concentration state of 10 ²⁰ cm ^-3 "or more.

Other configurations are the same as those in FIG. 1, and thus the same reference numerals as those in FIG.

[Effects of the Invention] As described above, according to the combined pressure / temperature detection device of the present invention, the temperature and the pressure of the measurement medium can be detected by only one semiconductor sensor. The respective measuring points of the temperature can be matched. Therefore, the configuration of the measuring device itself can be reduced in size and simplified, and the cost can be sufficiently reduced as compared with the case where pressure and temperature detecting sensors are separately installed. Therefore, the pressure and temperature measurement sites can be easily applied to a measurement site having a limited volume, and at the same time, the application range can be effectively expanded.

Further, a temperature-insensitive resistor is connected in parallel with the Wheatstone bridge, and the strain gauge dopant concentration is set to “1 ×
The high concentration of 10 ²⁰ cm ^-3 "or more is set, so that the constant current self-sensitivity temperature compensation can be suitably performed, the non-linearity of the temperature detection output can be improved, Will be able to gain.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram for explaining a combined pressure / temperature detection device according to an embodiment of the present invention, FIG. 2 is a diagram showing a pressure detection processing circuit portion of the above device, and FIG. FIG. 4 is a diagram illustrating a state of output of a temperature detection terminal portion in a steady pressure state in this circuit, FIG. 4 is a diagram illustrating a conventionally known semiconductor sensor, (A) is a sensor plan view, and (B) is a diagram. FIG. 5A is a cross-sectional view taken along the line bb of FIG. 5, FIG. 5C is a diagram showing stress characteristics, FIG. 5 is a diagram illustrating a semiconductor sensor used in the present invention, FIG.
(B) is a cross-sectional view taken along the line bb of (A), (C) is a diagram illustrating stress characteristics, and FIG. 6 is a circuit configuration diagram illustrating another embodiment of the present invention. 11 ...... semiconductor _{sensor, 112~115, R A, R B} , R C, R D ...... strain gauge, OP-3 ...... op (current conversion of the pressure detection output), OP-5 ...... operational amplifier (temperature detection Output current conversion).

Claims (1)

(57) [Claims] 1. A semiconductor sensor in which a strain gauge formed by at least four semiconductor diffusion resistors constituting a Wheatstone bridge is formed on a semiconductor substrate which is distorted in response to a pressure change, and a constant current is supplied and set to the Wheatstone bridge of the semiconductor sensor. Means for detecting an output signal from the Wheatstone bridge corresponding to a change in pressure acting on the semiconductor substrate; and means for detecting an output signal from the Wheatstone bridge corresponding to a change in temperature of the semiconductor substrate; A temperature-insensitive resistor connected in parallel to a Wheatstone bridge formed by a strain gauge formed on the semiconductor substrate, wherein the semiconductor sensor is located only at an outer peripheral portion of the semiconductor substrate having a crystal orientation (100), The strain gauge is arranged and set, and the strain gauge dopant concentration is set to “ × 10
^A combined pressure and temperature detection device characterized in that the concentration is set to a high concentration of ²⁰ cm ^-3 "or more.