JPH0239474A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To reduce variations of linear sensor elements by a method wherein a p type diffusion resistance region is connected to a p type diffusion resistance defined at the center of said connection is divided proportionally in a specific ratio. CONSTITUTION:With use of a silicon single crystal slice as a raw material, a silicon oxide film is formed in a diaphragm 1, and thereafter a gauge diffusion resistance 2 is formed on the surface side of the silicon oxide film. Four gauge resistances are disposed at a region surrounding the diaphragm 1, and at the same time connection diffusion resistances 3-8 and lead diffusion regions 9, 10 are formed. Herein, if a size ratio of division lengths d1, d2 of a side which defines positions of connection sections 11, 12 is assumed a proper value ranging 1 to 1.2-6, linearity is made minimum to reduce variations of sensor elements.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a semiconductor pressure sensor that converts pressure into voltage, such as air intake pressure for automobile engine control and atmospheric pressure for high altitude correction, especially a silicon diaphragm diffused resistance type. Regarding.

2. Description of the Related Art In general, when semiconductor pressure sensors are applied to automobiles, it is necessary to improve the absolute value of linearity among the pressure-output characteristics and to eliminate variations among sensor elements. Until now, the absolute value of linearity has been 100±0.
Although it is within the range of 3%, the degree of variation is still not sufficient. The distribution of piezoresistance coefficient 0 stress sensitivity depending on silicon crystal direction is shown in Figs. The idea was that it would be sufficient to simply place a diffused resistor to connect the two. That is, in the (100) plane of FIG. 3, the <001> direction is the piezoresistance coefficient πe, and in the (110) plane of FIG. 4, the <001> direction is the piezoresistance coefficient πe.

The stress sensitivity of π is the direction of zero.

In the (100) plane diaphragm, the elongated directions of the four gauge diffused resistors are arranged in the same <110> direction, and all the gauge resistors are arranged in the peripheral region of the diaphragm. In addition, in the (110) plane diaphragm, all four gauge diffused resistors are arranged in the 110> direction, which is perpendicular to the <001> direction, and two gauge resistors are placed in the central area of the diaphragm, while the other two are placed in the area around the diaphragm.

Problems to be Solved by the Invention The above description of the arrangement of the connecting resistors lacks specificity, and it cannot be said that the arrangement is sufficient for the purpose of reducing variations in linearity between sensor elements. The problem is the conditions to be set.

Means for Solving the Problems The present invention provides that when four P-type gauge diffused resistors are arranged on the front side to form a bridge, two adjacent gauge resistors and a P-type diffused resistor for drawing out an output are arranged on the front side. A P-type diffusion region adjacent to the diffused resistor for mutual connection is connected to the P-type diffused resistor by a narrow diffusion region, and the P-type diffused region is separated at the center of this connecting portion. 1 side to 1.2~
This is a semiconductor pressure sensor with a structure divided into 6 parts.

Function According to the present invention, one side of the P-shaped diffusion region that serves as a connecting portion for drawing output from the bridge has a length proportionally divided by 1:1.2 to the narrow diffusion region that extends the connecting portion.
By setting the value to an appropriate value in the range of 6, it is possible to minimize the degree to which the resistance of the P-type diffusion region itself contributes to the resistance change output due to stress change.

Embodiments The present invention will be described in detail with reference to plan views of embodiments of each apparatus shown in FIGS. 1 and 2. A (100) plane silicon single crystal slice was used as a material, and after a silicon oxide film was formed inside the diaphragm 1, a gauge diffused resistor 2 was formed on the surface side.

The gauge resistor 2 has a width of 15 μm and a length of 250 μm, and five resistors form one gauge resistor. All four gauge resistors were arranged in the peripheral area of the diaphragm 1 so that their longitudinal direction was in the 011> direction. Connecting diffusion resistors 3 to 8 and lead diffusion regions 9 and 10 were formed at the same time as these gauge resistors.

Here, the dimensional ratio d + / of each proportional length d, , d2 of the length of one side that determines the position of the connecting portion 11, 12 shown in FIG.
As an example of d2, a photomask having a ratio of 6.5/3.5 was used. Thereafter, a diaphragm was formed by etching from the back side of the silicon slice. The thickness of the diaphragm was 25μ. Next, a glass pedestal having approximately the same coefficient of thermal expansion was directly bonded to the back side of the silicon slice. After forming an aluminum electrode on the surface side of the silicon slice, the slice was diced and then separated into chips. Each chip was assembled into a metal package with a pipe. At this time, the inside of the cap was evacuated and used as a pressure sensor for an absolute pressure gauge. Then measurements were taken.

Effects of the Invention According to the present invention, when the connecting portions 11 and 12 are provided exactly in the center of the sides of the rectangular connecting resistors 3 and 4, the linearity is 100.
The ratio d+/d2 was 1:1.
When the appropriate value is in the range of 2 to 6, the linearity is minimum, 10
0+O, 1%, and the variation between the sensor elements was significantly improved. This result was determined by analyzing the stress distribution of the diaphragm and by considering the zero stress sensitivity direction of the piezoresistance coefficients πe and π in Figure 2 and the specific pattern of the connecting resistance. ratio d +
This is due to the optimization of /d2.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a (100) simple crystal silicon diaphragm and each diffused resistance pattern, Fig. 2 is a plan view showing a pattern for a <110> plane diaphragm, Fig. 3,
FIG. 4 is a (100)-plane (110)-plane crystal direction dependence distribution diagram showing the stress sensitivity of the piezoresistance coefficients πe and πt of single-crystal silicon. 1...Diaphragm region, 2. R3~Rd...
... Gauge diffused resistance, 3-8... Tie diffused resistance, 9°10... Drawer diffused region, 11.
12...Connected diffusion section.

Claims (1)

[Claims] When forming a bridge by arranging four P-type gauge diffused resistors on the front side, the function is to connect two adjacent gauge resistors and a P-type diffused resistor for drawing out the output adjacently to each other. A P-type diffused resistor region is connected to the P-type diffused resistor only by a thin and short diffused region, and the length of one side of the rectangular P-type diffused resistor separated at the center of this connection is 1 to 1, 2. ~
A semiconductor pressure sensor characterized by proportionally dividing the pressure into 6 parts.