JPH08181331A - Dynamic quantity sensor - Google Patents

Abstract

PURPOSE: To obtain a dynamic quantity sensor which approximates the temperature coefficient of an output voltage to zero and is hardly affected by an ambient temperature by a method wherein a p-n junction diode with a negative temperature coefficient of resistance is formed of a first semiconductor layer and of a second semiconductor layer which is formed so as to be situated at its inside and in a contact hole place. CONSTITUTION: A second semiconductor layer 9 which is connected in series with a gage resistance 4 due to a relationship to a first semiconductor layer 8 and constitutes p-n junction diodes 6a, 6b with a negative temperature coefficient of resistance is formed inside the first semiconductor layer 8 so as to be situated in a contact hole 10 formed in an insulating film 7 used to connect a conductor 11 for wiring to the gage resistor 4. The p-n junction diodes 6a, 6b are connected across gage resistors 4c, 4d on the side of a ground GND and the ground GND. Thereby, it is possible to realize a dynamic quantity sensor which can improve the temperature coefficient of an output voltage V0 in the direction to be approximated to zero and is hardly affected by an ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various types of pressure detection, acceleration detection, etc., in which a plurality of gauge resistors made of semiconductor layers formed by an appropriate method such as diffusion, ion implantation, epitaxial growth, etc. are assembled in a bridge circuit. The present invention relates to a mechanical quantity sensor that can be used as a sensor.

[0002]

2. Description of the Related Art For example, JP-A-6-102118, JP-A-160218,
Each of the publications of 207871 discloses a pressure sensor using a mechanical quantity sensor. This type of pressure sensor is designed to generate strain in a gauge resistance by introducing pressure, convert resistance change due to a piezoresistive effect of the gauge resistance into an electric signal of a bridge circuit, and detect a pressure value.

FIG. 5 shows a basic structure of a conventional example.
N having a peripheral thick-walled frame portion 2 that serves as a fixed portion and a thin-walled diaphragm portion (distortion sensitive portion) 3 that receives a central pressure
In the diaphragm portion 3 of the type silicon substrate (semiconductor substrate) 1, four gauge resistors 4 having a piezoresistive effect formed of a p-type region are formed, and these gauge resistors 4 (4a to 4a-4
As shown in FIG. 6, the bridge circuit 5 is assembled and the power supply voltage Vcc is applied to the bridge circuit 5 to change the gauge resistance 4 due to the distortion of the diaphragm portion 3 due to the pressure difference between the front and back sides of the diaphragm portion 3. , The output voltage Vo corresponding to the pressure can be taken out from the bridge circuit 5.

[0004]

Such a pressure sensor has a negative temperature coefficient of the gauge rate, which decreases when the ambient temperature rises, and the bridge circuit 5 also has a negative temperature coefficient of the gauge rate. It is known to have a gauge factor temperature coefficient TCK of, and its value is generally -1600 to -20.
It is about 00 ppm / ° C. Therefore, some kind of temperature compensating means is usually required even in a narrow operating temperature range, and it is necessary to improve the temperature coefficient of the output voltage Vo of the bridge circuit 5 in the direction of approaching zero.

For example, as the temperature compensating means, it is known to connect a diode 6 having a negative temperature coefficient of resistance, as shown in FIG. 7, in which the rising voltage (voltage at which the current flows) decreases when the ambient temperature rises. (See, for example, JP-A-3-228364 and JP-A-228365).

The output voltage Vo in FIG.
The input voltage Vb applied to the bridge circuit 5 obtained by dividing the power supply voltage Vcc in FIG.
Therefore, the output voltage Vo in FIG. 7 is given by Equation 3 below. In equations 1 to 3, R is the combined resistance value of the bridge circuit 5, ΔR is the amount of change in the combined resistance value of the bridge circuit 5 due to distortion, k is the gauge factor of the bridge circuit 5,
ko is the gauge factor of the bridge circuit 5 at the reference temperature, ε
Is the distortion factor, n is the number of diodes 6 connected in series (hereinafter simply referred to as the number), Vf is the forward drop voltage of the diode 6, and V
fo is the forward voltage drop of the diode 6 at the reference temperature,
α indicates the temperature coefficient of the diode 6, and ΔT indicates the temperature difference from the reference temperature.

[0007]

[Equation 1]

[0008]

[Equation 2]

[0009]

(Equation 3)

Therefore, in order to make the temperature coefficient of the output voltage Vo of the bridge circuit 5 zero, it is sufficient to satisfy the following Expression 4 from Expression 3.

[0011]

[Equation 4]

From the equation 4, the following equation 5 can be obtained. For example, TCK = -1800 [ppm / ° C.], Vfo = 0.6
[V], α = −3300 [ppm / ° C.], n = 1, 2,
In the case of 3, Vcc is about 1.7, 3.4, and 5.1 [v], respectively.

[0013]

(Equation 5)

That is, the temperature of the output voltage Vo of the bridge circuit 5 is adjusted by adjusting the power supply voltage Vcc according to the number of the diodes 6 or by selecting the number of the diodes 6 according to the desired power supply voltage Vcc. The coefficient can be brought close to zero.

[0015]

The present invention relates to a specific technique for forming the temperature compensating means, which is formed by a first semiconductor layer formed inside a strain sensitive portion of a semiconductor substrate. A gauge resistor having a negative temperature coefficient of gauge ratio, a wiring conductor formed on an insulating film formed on the surface of the semiconductor substrate and connected to the gauge resistor, and the wiring conductor connected to the gauge resistor. Therefore, a pn junction diode having a negative temperature coefficient of resistance, which is provided at a contact hole portion formed in the insulating film and is connected in series with the gauge resistor, is provided.

Further, the pn junction diode is formed by the first semiconductor layer and the second semiconductor layer formed inside the first semiconductor layer and at the contact hole.

A gauge resistor having a negative gauge coefficient temperature coefficient, which is formed by the p-type or n-type first semiconductor layer formed inside the strain sensitive portion of the n-type or p-type silicon substrate,
A wiring conductor formed on an insulating film formed on the surface of the silicon substrate and connected to the gauge resistor, and the insulation for connecting the inside of the first semiconductor layer and the wiring conductor to the gauge resistor. An n-type or p-type second diode that is formed at a contact hole formed in the film and is connected in series with the gauge resistor in relation to the first semiconductor layer to form a pn junction diode having a negative temperature coefficient of resistance. And a semiconductor layer.

[0018]

Since the pn-junction diode has a negative temperature coefficient of resistance, the input voltage applied to the gauge resistance of the first semiconductor layer formed by dividing the power supply voltage increases by that amount. Even if the gauge rate of resistance decreases, the input voltage applied to the gauge resistance is increased according to the rate of decrease of the gauge rate, so that the temperature coefficient of output voltage can be improved in the direction of approaching zero. It is possible to realize a mechanical quantity sensor that is hardly affected by temperature.

In particular, an element isolation process is used by forming a pn junction diode between the first semiconductor layer and the second semiconductor layer formed inside the first semiconductor layer and at the contact hole. Without using a plurality of pn junction diodes.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The mechanical quantity sensor of the present invention will be described below based on the embodiment shown in FIGS. 1 to 4 applied to a pressure sensor. And omit the detailed explanation.

FIG. 1 is a circuit diagram of an embodiment, in which a pn junction according to the present invention is provided between the grounding GND side gauge resistors 4c and 4d among the gauge resistors 4 constituting the bridge circuit 5 and the grounding GND. The diodes 6a and 6b are connected. However, since the pn junction diodes 6a and 6b operate in parallel, two of them function as one. With this configuration, the temperature coefficient of the output voltage Vo can be improved in the direction of approaching zero, and a mechanical quantity sensor that is less susceptible to the ambient temperature can be realized, as in the case of the conventional example.
In addition, 5 a to 5 e are respective terminals of the bridge circuit 5.

In such a configuration, the pn junction diode 6
Since the direction of (6a, 6b) is unidirectional, there is a limitation that it can be used only under the condition of forward current, but as described above, the width of the potential difference that can be compensated by the number of diodes is necessary. There is no limit theoretically.

Next, a method of manufacturing the pn junction diode 6 will be described. As described above, the diode used as the pn junction diode 6 can be formed by an appropriate method such as diffusion, ion implantation, or epitaxial growth. However, when the gauge resistor 4 is manufactured by diffusion, the same method is used for the pn junction diode 6. This is desirable in terms of manufacturing cost because it can be obtained in a series of steps, and the steps will be described below with reference to FIGS. 2 and 3.

First, the n-type silicon substrate 1, which is a semiconductor substrate, is left with the thick frame portion 2 around the periphery serving as a fixing portion,
A central thin-walled diaphragm portion 3 to be a strain sensitive portion is formed by an appropriate method such as wet etching using an alkaline etching solution such as KOH, and then an insulating film 7 made of silicon dioxide, silicon nitride or the like is provided on the front and back surfaces (cross section). For the shape, refer to FIG.

Next, in the diaphragm portion 3, the insulating film 7 on the surface corresponding to the location of the gauge resistor 4 is removed, and the first semiconductor layer 8 is formed in the silicon substrate 1 using a p-type semiconductor material such as boron. Form. As shown in FIG. 3, most of the first semiconductor layer 8 becomes the gauge resistance 4c, and a part thereof becomes the p-type region of the pn junction diode 6b described later.

Next, after the insulating film 7 is formed again on the entire surface, the insulating film 7 corresponding to the part of the first semiconductor layer 8 in the diaphragm portion 3 is removed, and an n-type film such as phosphorus is formed. By forming the second semiconductor layer 9 in the first semiconductor layer 8 using a semiconductor material, the second semiconductor layer 9 becomes an n-type region of the pn junction diode 6b as shown in FIG.
A pn junction diode 6b is configured with the part of the first semiconductor layer 8 that is the type region. The pn junction diode 6a provided at the location of the gauge resistor 4d is also configured in the same manner.

After forming the insulating film 7 on the entire surface again, a contact hole 10 is provided in the insulating film 7 in order to form the gauge resistance 4 and the pn junction diode 6 into the circuit configuration of FIG. 1, and a predetermined pattern is formed thereon. The wiring conductor 11 made of aluminum or the like is patterned.

As described above, inside the first semiconductor layer 8, the first semiconductor layer 8 is located at the 10 contact holes formed in the insulating film 7 for connecting the wiring conductor 11 to the gauge resistor 4. Pn junction diode 6 connected in series with gauge resistance 4 and having a negative temperature coefficient of resistance
The second semiconductor layer 9 forming a and 6b is provided, and a plurality of pns are formed without using an element isolation process.
It is possible to obtain the junction diodes 6a and 6b (however, since the pn junction diodes 6a and 6b of this embodiment operate in parallel, it is described above that the two pn junction diodes 6a and 6b function as one). Moreover, no large step is generated on the surface of the silicon substrate 1.

Reference numeral 6c is another pn junction diode interposed between the connection midpoint of the gauge resistors 4a and 4b and the power supply voltage Vcc, for the purpose of increasing the number of diodes for temperature compensation. As shown in FIG. 4, p and n type regions are formed in the silicon substrate 1 using the first and second semiconductor layers 8 and 9 to form a pn junction diode 6c. The pn junction diode 6c may be formed as needed.

Although the second semiconductor layer 9 is formed inside the first semiconductor layer 8, it may be provided on the surface of the first semiconductor layer 8.

In addition, the silicon substrate 1 and the second semiconductor layer 9,
The n-type and p-type of the first semiconductor layer 8 are not limited to this, and may be opposite to each other.

Further, in forming the first and second semiconductor layers 8 and 9, it is possible to select and use an appropriate method such as ion implantation and epitaxial growth in addition to the diffusion described in the embodiment.

The present invention can be applied not only to the mechanical quantity sensor having the bridge circuit composed of a plurality of gauge resistors shown in the embodiment but also to the mechanical quantity sensor having a single gauge resistance. In addition to the pressure sensor, the mechanical quantity sensor of the present invention can also be used as other sensors such as an acceleration sensor.

[0034]

According to the present invention, a gauge resistor formed of a first semiconductor layer formed inside a strain sensitive portion of a semiconductor substrate and having a negative gauge coefficient temperature coefficient, and formed on the surface of the semiconductor substrate. A wiring conductor formed on an insulating film and connected to the gauge resistor, and the gauge provided at a contact hole portion formed in the insulating film for connecting the wiring conductor to the gauge resistor. And a pn junction diode having a negative temperature coefficient of resistance connected in series with a resistor, thereby obtaining a mechanical quantity sensor that is not easily affected by ambient temperature in a series of steps without using an element isolation process. Therefore, the process can be simplified and the manufacturing cost can be reduced.

Particularly, by forming the pn junction diode by the first semiconductor layer and the second semiconductor layer formed inside the first semiconductor layer and at the contact hole portion, the pn junction diode is formed. Generation of surface steps can be suppressed, which is advantageous for forming a wiring conductor.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a plan view of the above embodiment.

FIG. 3 is a cross-sectional view of the essential part of the above-described embodiment taken along the line III-III in FIG.

FIG. 4 is a sectional view of the essential part of the above-mentioned embodiment taken along the line IV-IV in FIG.

5A is a cross-sectional view of a main part of a conventional example, and FIG. 5B is a plan view of the same.

FIG. 6 is a circuit diagram of the same.

FIG. 7 is a circuit diagram in which temperature compensating means is added to the conventional example.

[Explanation of symbols]

 1 Silicon substrate (semiconductor substrate) 2 Frame part 3 Diaphragm part (distortion sensitive part) 4 (4a, 4b, 4c, 4d) Gauge resistance 5 Bridge circuit 6 (6a, 6b, 6c) pn junction diode 7 Insulating film 8 1st Semiconductor layer 9 Second semiconductor layer 10 Contact hole 11 Wiring conductor

Claims (3)

[Claims] 1. A gauge resistor formed of a first semiconductor layer formed inside a strain sensitive portion of a semiconductor substrate and having a negative temperature coefficient of gauge factor, and an insulating film formed on the surface of the semiconductor substrate. A wiring conductor formed and connected to the gauge resistor, and a series connection with the gauge resistor provided at a contact hole portion formed in the insulating film for connecting the wiring conductor to the gauge resistor. And a pn junction diode having a negative temperature coefficient of resistance. 2. The pn junction diode is formed by the first semiconductor layer and a second semiconductor layer formed inside the first semiconductor layer and at the contact hole location. The mechanical quantity sensor according to claim 1. 3. A gauge resistor having a negative gauge coefficient temperature coefficient, which is formed by a p-type or n-type first semiconductor layer formed inside a strain sensitive portion of an n-type or p-type silicon substrate, and the silicon substrate. A wiring conductor formed on an insulating film formed on the surface of the insulating film and connected to the gauge resistor, and formed on the insulating film for connecting the inside of the first semiconductor layer and the wiring conductor to the gauge resistor. An n-type or p-type second semiconductor layer which is formed at a contact hole and is connected in series with the first semiconductor layer in series to form a pn junction diode having a negative temperature coefficient of resistance; A mechanical quantity sensor having: