JPH0733144Y2 - Pressure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a pressure detecting device.

2. Description of the Related Art A semiconductor substrate having a thin portion and a pressure-sensitive element made of a semiconductor material formed in the thin portion are provided, and the strain applied to the thin portion due to the pressure applied to the thin portion is electrically generated by the pressure-sensitive element. A pressure detection device of the type that converts it into a signal and outputs the signal is known, and is used for various purposes.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In such a pressure detecting device, it is desired to further improve the sensitivity of the pressure sensitive element in order to improve the pressure detecting performance.

Means for Solving the Problems As a result of various investigations by the present inventor, when a pressure-sensitive element made of a semiconductor material is irradiated with light during pressure detection, the sensitivity of the pressure-sensitive element is improved and pressure detection performance is favorable. I have found a fact that can be improved to.

The present invention was made based on such knowledge,
The gist of the invention resides in that the pressure detecting device of the above-mentioned type is provided with a light emitting means for radiating light toward the pressure sensitive element made of a semiconductor material.

According to the pressure detecting device having such a configuration, the light-emitting element irradiates the pressure-sensitive element made of a semiconductor material with light during pressure detection, thereby improving the electrical conversion efficiency of pressure in the pressure-sensitive element. Therefore, the pressure detection performance was able to be improved suitably. It is presumed that this is because the structure of the electron energy band of the atoms constituting the pressure sensitive element was changed by the light energy, and the mobility of carriers in the pressure sensitive element was increased.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 10 is a pulse wave sensor which is an example of a pressure detecting device to which the present invention is applied. The pulse wave sensor 10 includes a pressing member 14 having a bottomed hole 12, a semiconductor substrate 16 made of single crystal silicon or the like fixed to the pressing member 14 so as to cover the opening of the bottomed hole 12, and a pressing member. 14 is attached to the bottom of the bottomed hole 12 and is attached to the pressure-sensitive diode 26 described later.
A plurality of (three in FIG. 1) LEDs 18 for irradiating infrared light (monochromatic light) having a wavelength of about 800 nm are provided. On the surface of the semiconductor substrate 16 opposite to the LED 18 side, a large number (6 in FIG. 1) of recesses 20 are formed at predetermined intervals in a state of being arranged in one direction.
The rubber 22 is embedded in each of the insides of the semiconductor substrate 20, and the surface of the thin portion 24 located at the bottom of the recess 20 of the semiconductor substrate 16 on the LED 18 side is pressure-sensitive due to impurity diffusion or the like as shown in FIG. Each diode 26 is formed. The thickness of the thin portion 24 is extremely thin, for example, 15 μm,
1 and 2 are drawn thicker than they actually are for the sake of convenience.

The pulse wave sensor 10 is pressed by a predetermined pressing means (not shown) on the artery on the surface of the living body on the side of the semiconductor substrate 16 such that the arrangement direction of the pressure sensitive diodes 26 is substantially orthogonal to the artery. As a result, the pressure vibration of the pulse wave generated from the artery is transmitted to the thin portion 24 via the rubber 22, and strain is generated in the thin portion 24 according to the pressure vibration, and the pressure sensitive diode 26 is passed through an electrode (not shown). An electric signal corresponding to the pressure oscillation is output from the pressure-sensitive diode 26 to the microcomputer (not shown) by changing the current that has been preliminarily applied to the strain, and the pulse wave is detected based on the electric signal that is sequentially input. Will be done. Therefore, in the present embodiment, the pressure sensitive diode 26 constitutes a pressure sensitive element. In addition,
In the above pulse wave sensor 10, normally, all pressure-sensitive diodes are used.
The optimum one is selected from 26, and the pulse wave is detected by the optimum pressure-sensitive diode.

In the pulse wave sensor 10 configured as described above, the LE
When the D18 is turned on and the light from the LED 18 is applied to the pressure sensitive diode 26, for example, as shown in FIG. 3, the electric conversion effect of the pressure in the pressure sensitive diode 26 is improved as compared with the conventional case where light is not applied. Then, the pressure detection performance was suitably improved. As a result, the pulse wave sensor 10 was able to detect the pulse wave more accurately. The reason why the sensitivity of the pressure-sensitive diode 26 is increased by irradiating the pressure-sensitive diode 26 with light is that the energy of the light changes the structure of the electron energy band of the atoms constituting the pressure-sensitive diode 26.
That is, since light energy is absorbed by electrons in the so-called valence band of the electron energy band and the electrons are moved to the so-called conduction band of the energy band, the mobility of carriers in the pressure-sensitive diode 26 is increased. Is estimated to be Therefore, the wavelength and intensity of the light emitted from the LED 18 are determined in advance so that light energy capable of moving electrons in the valence band to the conduction band is necessary and sufficient.

In the above-described embodiment, the pressure sensitive element made of a semiconductor material is composed of the pressure sensitive diode 26, but it is not always necessary and may be composed of a pressure sensitive transistor, a pressure sensitive resistor or the like.

Further, in the above-described embodiment, the recess 20 of the semiconductor substrate 16 is located outside the bottomed hole 12 and the thin portion 24 is located inside the bottomed hole 12, and within the recess 20. On rubber
22 is buried, but not necessarily, rubber
Position the recess 20 inside without providing 22 and thin section
The thin portion 24 may be located outside and the thin portion 24 may be directly pressed against the surface of the living body.

Further, in the above-mentioned embodiment, the light emitting means is composed of the LED 18, but it is not always necessary and other light emitting means other than the semiconductor element can be used.

Further, in the above-described embodiment, in addition to irradiating the pressure sensitive diode 26 with light by the LED 18, the pressure in the bottomed hole 12 of the pressing member 14 closed by the semiconductor substrate 16 may be increased to a predetermined positive pressure. Alternatively, the thin portion 24 may be pre-strained by applying a negative pressure or the like. By doing so, the mobility of carriers in the pressure-sensitive diode 26 can be further increased by the distortion, and the sensitivity of the pressure-sensitive diode 26 can be further improved.

The case where the present invention is applied to the pulse wave sensor has been described above, but the present invention can also be applied to other pressure detection devices.

For example, FIG. 4 is a diagram showing an example of a pressure detecting device used to detect the pressure of gas, and 28 is a case. The case 28 is a bottomed cylindrical member 32 having a pressure introduction port 30 at the bottom, and is fixed to the opening side end of the cylindrical member 32 to hermetically close the opening side of the cylindrical member 23. And a plate member 34. A pedestal 36 is airtightly fixed to a portion of the plate-shaped member 34 on the side of the cylindrical member 32, which is located inside the cylindrical member 32, and a surface of the pedestal 36 opposite to the plate-shaped member 34 side. A semiconductor substrate 38 is hermetically fixed to the. A recess is formed on the surface of the semiconductor substrate 38 on the pedestal 36 side.
40 is formed, and this recess 40 is communicated with the atmosphere through a hole 42 provided in the pedestal 36 and a hole 44 provided in the plate member 34. The bottom of the recess 40 of the semiconductor substrate 38 is a thin portion 46, and a pressure sensitive diode 48 is formed on the surface of the thin portion 46 opposite to the pedestal 36 side. As a result, when the pressure to be measured is introduced into the case 28 from the pressure introducing hole 30, an electric signal is sent from the pressure sensitive diode 48 to the microcomputer (not shown) based on the strain generated in the thin portion 46 according to the pressure. The pressure to be measured will be determined from the relationship output in advance and determined in advance based on this electrical signal. The LED 18 is provided on the inner surface of the bottom of the cylindrical member 32.
For example, two pressure sensors are attached to the pressure sensitive diode 48 by irradiating the pressure sensitive diode 48 with light from the LEDs 18 during pressure detection. Note that, also in this embodiment,
A pressure-sensitive transistor or a pressure-sensitive resistor may be used as the pressure-sensitive element, and when the temperature at the time of pressure detection is relatively high, the thin-walled part of the single-crystal semiconductor substrate without impurities is directly sensed. It can also be used as a piezoresistor.

In addition, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a view showing a pulse wave sensor which is an example of a pressure detecting device to which the present invention is applied, and is a view in which a part is cut away. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a diagram showing the electric conversion efficiency of pressure detected by the pulse wave sensor of FIG. 1 and is a diagram compared with the conventional one. FIG. 4 is a sectional view showing another example of the pressure detecting device to which the present invention is applied. 10: Pulse wave sensor (pressure detection device) 16, 38: Semiconductor substrate 18: LED (light emitting means) 24, 46: Thin portion 26, 48: Pressure sensitive diode (pressure sensitive element)

Claims (1)

[Scope of utility model registration request] 1. A semiconductor substrate having a thin portion, and a pressure-sensitive element made of a semiconductor material formed in the thin portion, wherein strain applied to the thin portion causes strain in the thin portion. A pressure detection device of a type in which an element converts the signal into an electric signal and outputs the electric signal, wherein the pressure detection device is provided with a light emitting means for irradiating light toward the pressure sensitive element.