JPS6020692B2 - Semiconductor pressure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor pressure detection device that utilizes the piezoresistance effect of a diffusion layer formed in a semiconductor single crystal substrate.

Heretofore, as this type of pressure detection diffusion layer, one represented by the equivalent circuit shown in FIG. 1 has been known.

In the figure, R, , R2 are pressure sensitive resistance elements made of diffusion layers formed on a semiconductor single crystal substrate. These resistance elements R, R2 exhibit resistance changes in different directions due to pressure, and fixed resistances R3 and R2 that are insensitive to pressure are used.
The half bridge 1 is constructed by roughly putting together the 4 parts. L,r
2 is a zero point adjustment resistor. A drive voltage VB is applied to this half bridge 1 from a reference power supply VE via a drive voltage compensation amplifier 2. At this time, in order to prevent pressure sensitivity from changing due to external temperature fluctuations,
It is necessary to change the bridge drive voltage in response to the external temperature. For this reason, temperature-sensitive resistance elements such as thermistors RT
is used to control the gain of the amplifier 2. For example, when the temperature characteristic of the relative pressure sensitivity △VP/△VP (2500) with the pressure sensitivity of 25oo as 1 is obtained as shown by the solid line in Figure 2, in order to compensate for this, it is necessary to A driving voltage VB must be applied to the bridge.

The solid line in Fig. 2 indicates that the pressure-sensitive resistance element in Fig. This is the temperature characteristic when a half-bridge is configured and driven with a constant voltage of VE = 4V.The dashed line shows that the pressure output is 2500 and the pressure output changes to VE = 4V even when the outside temperature is changed. Bridge drive voltages are shown for compensation to match. The temperature compensation accuracy is determined by how well the bridge drive voltage curve (broken line) is obtained to match the pressure sensitivity fluctuation curve (solid line) in FIG. 2. However, in the conventional configuration, the pressure-sensitive resistive elements R, , R2 and the overflow-sensitive resistive elements R-d are prepared separately, which has the following drawbacks.

First, there is no temperature-sensitive resistance element with characteristics that draw a curve necessary for compensation as shown in FIG. 2, and the error in temperature compensation is large. Second, even if a temperature-sensitive resistance element with ideal temperature characteristics is obtained, the temperature-sensitive resistance element and pressure-sensitive resistance element are prepared separately, making it difficult to match the temperatures of the two. "Compensation errors become large especially when external temperature fluctuations are far away. In view of the above points, the present invention provides a semiconductor pressure detection device that performs extremely accurate temperature compensation for pressure sensitivity. In this invention, ``a pn junction diode is constructed in which a diffusion layer is provided separately from the pressure-sensitive resistance element in the same semiconductor single crystal substrate on which the pressure-sensitive resistance element is provided, and this diode is used as a temperature compensation sensor for the pressure detection circuit. The main idea is to use it as an overflow element.

In this way, if the pressure-sensitive resistance element and the temperature-sensitive element are integrally formed on the same substrate, the temperatures of the two accurately match, and therefore it becomes possible to perform accurate temperature compensation for pressure sensitivity.
Examples of the present invention will be described below.

FIG. 3 shows the structure of a pressure sensor section of one embodiment, and FIG. 4 shows an equivalent circuit of a pressure detection device constructed using this sensor. In Fig. 3, reference numeral 11 is an n-type silicon single crystal substrate, the central part of which is processed into a thin shape to form a pressure-sensitive diaphragm, and the thick peripheral part is bonded with glass or Au-Si alloy. It is adhered to the silicon base turtle 2 for pressure introduction using an agent. From the opposite side of the diaphragm, boron is diffused to form a p-type diffusion layer 3, 132 and a ridge 33. Each of these diffusion layers has a different role. That is, each of the diffusion layers 13, 132 is a pressure sensitive resistance element R whose resistance changes positively and negatively depending on the pressure.
,, used as R2. In addition, the diffusion layer 133 and the substrate 1
A pn junction diode ○ formed between the neck and the neck is used as a chlorine sensitive element. In this way, when a temperature sensing element using a pressure sensitive resistor element and a pn junction diode is fabricated on the same substrate by only one diffusion, the bias relationship is It is necessary to give sufficient consideration to The circuit configuration of FIG. 4 will be explained below, including this point. First, the pressure sensitive resistance element R, ? shown in FIG.
R2 and pressure-insensitive fixed resistors R3 and R4 constitute a half bridge 21 as a pressure detection circuit. r,, [2 is a zero point adjustment resistor. Here, each terminal a to f in FIG. 4 corresponds to each terminal a to f in FIG. 3. Half-bridge 2 "Well, one power supply terminal is connected to the terminal a taken out from the n-type substrate 11 in FIG.
B is applied to the other power supply terminal. Thereby, the diffusion layers 13, ?, used as the pressure sensitive resistance elements R, ? 132 and the substrate 11 is always reverse biased, and the pressure sensitive resistive element R,? R2 is electrically isolated from the substrate box 1. That is, even if the pn junction diode D between the diffusion layer 133 and the substrate 11 is forward biased and used as a temperature sensing element, the temperature sensing element and the pressure sensitive resistance elements R, , R
This will prevent mutual influence between the two. Diode D is forward biased by a positive voltage from constant current source CI as shown in FIG. This diode D is about 3
It shows a potential change of hV, and this potential change is caused by the amplifier 22,
23 to the base of the transistor T, thereby controlling the bridge drive voltage -V8. In Fig. 4, V0 and V- are external power supplies,
E,,E2 are amplifiers 2 made using these external power supplies.
2 and 23, VR is a variable resistor for adjusting the exposure force of diode D, and 24 is a sense amplifier. The fact that pressure sensitivity is compensated for temperature by such a configuration will be explained below with reference to FIGS. 5 and 6.

FIG. 5 shows the temperature fluctuation characteristics of the relative sensitivity when the bridge 21 is driven at a constant voltage of -VB-4V without operating the temperature compensation circuit portion in the configuration shown in FIGS. 3 and 4. This uses a 2 kgf/sensor with a diaphragm diameter of 4 and a diaphragm thickness of 70 cm as a pressure sensor, and the bridge output at a full scale pressure of 2 x 9 f/ is calculated as -△VP=
This is data when the voltage is 9 melon hV. On the other hand, FIG. 6 shows the result of temperature compensation performed by operating the circuit shown in FIG. 6 normally. To explain the specific compensation procedure, first, assume that at 25o0, a full scale pressure output -ΔVP=-91.25 mV was obtained at 1VB=-4V. Next 8
The bridge drive dragon pressure to obtain the same full-scale pressure output at 000 is calculated based on Figure 5.
-VB=-4V, 80g0 -V8=-4.4494
The gains of the amplifiers 22 and 23 and the variable resistance V
Adjust R etc. By just adjusting the temperature at these two points, as shown in FIG. 6, the error with respect to the full-scale pressure output can be kept within ±0.1% between -20°C and 8000°C.
As described above, in the present invention, the temperature sensing element for temperature compensation is integrally formed on the semiconductor substrate constituting the pressure sensor.

Therefore, the temperatures and temperature fluctuations of the pressure-sensitive resistive element and the temperature-sensitive element almost completely match, and temperature compensation for pressure sensitivity can be performed with high accuracy. Especially when external temperature fluctuations are far away.
It is excellent in that accurate temperature compensation can be performed without being affected by the rate of fluctuation. Furthermore, the pressure-sensitive resistance element and the temperature-sensitive element have the same material, manufacturing process, and other backgrounds, so it is easy to match their temperature characteristics, and accurate temperature compensation of pressure sensitivity can be easily performed. Another advantage is that the pressure-sensitive resistance element and the temperature-sensitive element can be easily fabricated by one-time impurity diffusion into a single crystal substrate. This has been made possible by making the circuit a dual power supply system with a positive power supply V+ and a negative power supply V-. In other words, in order to apply the required bias to a pressure-sensitive resistance element and a diode as a sensitive element provided on the same substrate using a single power supply, two Although complex processes such as heavy diffusion are required and the structure is naturally complicated, by using the dual power supply system as explained in the example, the manufacturing process and structure of the pressure sensor section can be simplified. It becomes possible. In the embodiment, an n-type semiconductor substrate is used and a pressure-sensitive resistance element and a temperature-sensitive element are formed by a p-type diffusion layer, but the conductivity types may be reversed. In that case, of course, the bias relationship will be opposite to that of the embodiment. Further, in the embodiment, a pressure detection circuit using a half bridge has been described, but the present invention can be applied not only to a full bridge configuration but also to a pressure detection circuit configuration that does not utilize a bridge.

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit diagram of a conventional semiconductor pressure detection device, Figure 2 is an equivalent circuit diagram of a conventional semiconductor pressure detection device.
The figure is a diagram to explain the temperature compensation operation of pressure sensitivity.
FIG. 3 is a diagram showing the structure of a pressure sensor section according to an embodiment of the present invention, and FIG. 4 is an equivalent circuit diagram of a pressure detection device according to the embodiment.
FIGS. 5 and 6 are diagrams for explaining the temperature compensation operation. 11...N-type silicon single crystal substrate, 13,~1
33... p-type diffusion layer, R,, R2... pressure sensitive resistance element, D
・・・・・・PN junction diode (temperature sensing element), 21.
...Half bridge (pressure detection circuit). Figure 1 Figure 3 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 A pressure-sensitive resistance element consisting of a semiconductor single crystal substrate and a diffusion layer formed by one-time impurity diffusion into this substrate, and a PN constructed between the substrate and another diffusion layer formed in the same process.
A bridge circuit for pressure detection configured using a junction diode and the pressure-sensitive resistance element, and a driving voltage is applied to the bridge circuit in a potential relationship that reverse biases between the diffusion layer of the pressure-sensitive resistance element and the substrate. The present invention is characterized by comprising a bridge drive circuit and a temperature compensation circuit that controls the output drive voltage of the bridge drive circuit in accordance with a change in the forward voltage drop of the pn junction diode to compensate for the temperature of pressure sensitivity. Semiconductor pressure detection device.