JPH027573A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To improve offset temperature characteristics and reduce offset by constituting a gate resistor by connecting a plurality of diffusion resistances in parallel. CONSTITUTION:Three diffusion resistors 21, 22 and 23 are used for constituting a gauge resistance. The diffusion resistors 21, 22 and 23 can be connected by a conductive substance 24 such as aluminum. When resistance per resistor of the diffusion resistors 21, 22 and 23 is RX9 and contact resistance is DELTAR, the resistance of the gauge resistor GR1 is GR1=(RX9+DELTARX2)/3=RX3+DELTARX2/3. On the other hand, for realizing a resistance which is nearly the same as that of the gauge resistance GR1 by connecting a plurality of diffusion resistors. the diffusion resistance may be set to R. In this case, a gauge resistance GR2 is expressed as follows: GR2=(R+DELTARX2)X3=RX3+DELTARX6. Thus, with the contact resistance occupying in a gauge resistance GR, the influence by temperature coefficient of a contact resistance DELTAR differs by 9 times between the series connection and parallel connection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a semiconductor pressure sensor, and more particularly to the structure of a diffused resistor that can improve the offset and the temperature characteristics of the offset.

[Prior Art] Conventionally, this type of semiconductor pressure sensor has four gauge resistors 42 connected to the periphery of a diaphragm 41 through a conductive material 43 to form a Wheatstone bridge, as shown in FIG. It had been formed. Here, the gauge resistor 42 is composed of a diffused resistor formed by diffusing impurities into silicon 44, and the cage resistor 42 is composed of a plurality of diffused resistors 51 connected in series as shown in FIG. Each resistor was connected through a conductive metal 52. When the resistance value of the diffusion resistor 51 changes due to the strain on the diaphragm excited by the pressure of the fluid to be measured, the balance of the Wheatstone bridge changes and an output proportional to the pressure is obtained. 55 is metal 52
This is a contact hole for connecting the resistor and the diffused resistor.

[Problems to be Solved by the Invention] In the configuration of the conventional semiconductor pressure sensor described above, a plurality of diffused resistors are connected in series. The resulting contact resistance value increased in proportion to the number of resistors. The sum of this contact resistance and the actual diffusion resistance value is the gauge resistance value, but because the contact resistance value varies, the offset value of the Wheatstone bridge, which is made up of four gauge resistors, varies depending on the device. There was a problem.

Furthermore, since the contact resistance and the diffused resistance each have different temperature coefficients of resistance, this causes variations in the temperature characteristics of the offset of the Wheatstone bridge.

[Differences between the invention and the prior art] As mentioned above, the conventional gauge resistor has a plurality of diffused resistors connected in series, but the present invention has a difference in that the plurality of diffused resistors are connected in parallel. has.

[Means for Solving the Problems] The present invention is a semiconductor pressure sensor comprising a thin film diaphragm portion and a pressure sensing element, characterized in that a plurality of diffused resistors constituting the pressure sensing element are connected in parallel.

[Example code] Strategy Brigade The present invention will be explained below with reference to Examples.

FIG. 1 is a perspective view showing a semiconductor pressure sensor according to a first embodiment of the present invention, in which a diaphragm 1 receives the pressure of a fluid to be measured and induces strain on silicon 7. In FIG. Gauge resistor 2. around the diaphragm 10. 3. 4. form 5. The gauge resistors 2°3.4.5 are connected by a conductive material 6, such as aluminum, forming a Wheatstone bridge. FIG. 2 shows an example of the configuration of a gauge resistor, in which three diffused resistors 21, 22, and 23 are used. The diffused resistors 21, 22, 23 are connected by a conductive material 24, such as aluminum.

The contact resistance is the diffusion resistance 21 in the contact hole 25.
, 22. This is the resistance of the contact surface between 23 and the conductive substance 24.

The resistance per diffused resistor 21, 22, 23 is RX9
, the resistance value G of the gauge resistance when the contact resistance value is ΔR
R+ becomes as follows.

GR+: (RX9+△RX2)/3=RX3+△R
X2/3 On the other hand, in the conventional semiconductor pressure sensor ζ, a gauge resistor is constructed by connecting a plurality of diffused resistors in series, as shown in FIG. In the case of FIG. 5, the gauge resistor is constructed using three diffused resistors. In order to achieve a resistance value that is approximately the same as the resistance value GR+ of the gauge resistor when diffused resistors are connected in parallel, the diffused resistance value may be set to R. The gauge resistance value Q R2 in this case is as follows: GR2=(R+ΔRX2)X3=R×3+ΔRX6.

Therefore, the contact resistance value that accounts for the gauge resistance value GR is
When three diffused resistors are used, there is a nine-fold difference between the series connection and the parallel connection.

In other words, the influence of the temperature coefficient of contact resistance ΔR is nine times different.

Furthermore, by connecting the diffused resistors in parallel, the average value of the connected diffused resistors becomes the gauge resistance value, which makes it less susceptible to variations in the diffused resistors.

FIG. 3 is a plan view showing the configuration of the gauge resistor in the second embodiment, and is a plan view showing the configuration of the gauge resistor in the second embodiment. 32. 33. I am using 4 pieces of 34. Diffusion resistance 31, 32° 33.34 is
35 conductive substances like aluminum! This is how they are connected.

As in the case of the first embodiment, the diffused resistors 31, 32, 33.
The resistance per 34 wire is RX16, and the contact resistance value is △R.
The resistance value GR3 of the gauge resistor is as follows.

C; R3= (RX 16+△RX2)/4=R×4+
△R/2 On the other hand, in order to wire four diffused resistors in series and achieve a resistance value almost equivalent to the resistance value GR3 of the gauge resistor, the diffused resistance value should be R, and in this case the gauge Resistance value GR
4 becomes GR4=(R+ΔRX2)X4=RX4+ΔRX8.

Therefore, when four diffused resistors are used, the contact resistance value that accounts for the gauge resistance value GR is 16 times different between the series connection and the parallel connection.

In this way, the more resistors are connected in parallel, the more the proportion of the contact resistance value in the gauge resistance value GR decreases, and the less the contact resistance is adversely affected by the temperature coefficient.

Furthermore, since the diffused resistance values of a larger number of wires are averaged, it becomes even more difficult to be affected by variations in the diffused resistances.

[Effects of the Invention] The semiconductor pressure sensor of the present invention has the following effects by configuring the gauge resistor by connecting a plurality of diffused resistors in parallel.

(1) Since the influence of the temperature coefficient of contact resistance can be reduced, the offset temperature characteristics of the semiconductor pressure sensor are improved.

(2) Since the gauge resistance value can be the average value of a plurality of diffused resistance values, variations in the gauge resistance value are reduced and offsets are reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first embodiment of a semiconductor pressure sensor of the present invention, and FIG. 2 is a perspective view of a semiconductor pressure sensor according to the first embodiment. FIG. 5 is a plan view showing the configuration of a gauge resistor of a conventional semiconductor pressure sensor. 1...Diaphragm, 2, 3. 4. 5... Gauge resistance, 6... Conductive material, 7... Silicon, 8... Bat, 21.22.23... Diffused resistance, 24... Conductive Substance, 25... Contact hole, 31.32, 33.34... Diffused resistance, 35 ・ 36 ・ 41 ・ 42 ・ 43 ・ 44 ・ 45 ・ 51 ・ δ2 ・ 55 ・ ・ Conductive material, ・Contact hole, diaphragm, gauge resistor, conductive material, silicon, pad, diffused resistor, conductive material, contact hole.

Claims (1)

[Claims] 1. A semiconductor pressure sensor comprising a thin film diaphragm portion and a pressure sensing element, characterized in that a plurality of diffusion resistors constituting the pressure sensing element are connected in parallel.