JPH0834315B2 - Semiconductor pressure sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor that can be used when converting a pressure change such as an air intake pressure for engine control of an automobile or an atmospheric pressure for high altitude correction into a voltage change. The present invention relates to a pressure sensor, especially a silicon diaphragm diffusion resistance type.

2. Description of the Related Art Generally, a semiconductor pressure sensor is called a gauge resistance.
Although the individual resistance elements are used in a bridge connection, the characteristics of the individual resistance elements improve the absolute value of the linearity of the pressure-output characteristics, and the resistance value between the resistance elements in the sensor is improved. It is necessary to eliminate variations. Up to now, the absolute value of the linearity is 100 ± 0.3% in the characteristic of each resistance element.
However, the degree of variation in the resistance value between the resistance elements is not yet sufficient. The stress sensitivity distribution of the piezoresistive coefficient depending on the silicon crystal direction is shown in FIGS. 3 and 4, but in the conventional semiconductor pressure sensor using a silicon single crystal substrate for the diaphragm, the piezoresistive coefficient π _l , The so-called diffusion resistance in the role of a conductor for connecting a gauge resistance to a bridge while arranging the gauge resistance in a highly sensitive direction of π _t and considering such a non-sensitive direction is a piezo resistance coefficient π _l Therefore, it is only necessary to dispose at a position where there is no sensitivity of π _t . That is, in the (100) plane of FIG. 3 is <001> direction, and in the (110) plane of FIG. 4 is <001> direction, respectively, piezo-resistance coefficient [pi _l, stress sensitivity of [pi _t is It is the direction of zero.

In the case of a (100) plane silicon diaphragm, in order to realize high sensitivity characteristics, the four gauge resistors are arranged in the same <110> direction in the longitudinal direction, and all the gauge resistors are arranged in the peripheral region of the diaphragm. . Also, (11
With a diaphragm using 0) plane silicon, the longitudinal directions of the four gauge resistors are all <110> perpendicular to the <001> direction.
2 of the gauge resistors are in the central area of the diaphragm, and the other 2 are in the peripheral area of the diaphragm.
Placed respectively.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, the arrangement of the diffusion resistors having the conductor role described above requires that the conditions for setting the positions thereof are set in order to reduce the variation between individual gauge resistors in the semiconductor pressure sensor, that is, the resistance elements. is important.

Means for Solving the Problems According to the present invention, four gauge resistors arranged on the surface of a semiconductor substrate are bridge-connected to each other, and a rectangular shape connected to two adjacent gauge resistors for extracting an output. The first diffusion conductive region is connected to the second diffusion conductive region adjacent to the first diffusion conductive region by a third diffusion conductive region having a narrow width, and the arrangement position of the third diffusion conductive region is set. , The side length of one side of the rectangle of the first diffusion conductive region is d ₁ to d ₂
It is a semiconductor pressure sensor having a structure that is set at positions proportional to the length of (d ₁ = 1.2 to 6, d ₂ = 1).

Effect According to the present invention, one side of the rectangular diffusion region (the first diffusion region) that plays the role of a conductor for extracting the output from the bridge has an electrode region (the second diffusion region) for outputting to the outside. ), And the proportion of the length up to the narrow conductive area is set to a suitable value in the range of 1.2 to 6: 1 with a ratio of d ₁ to d ₂ of the first conductor. The stress change in the resistance of the diffusion region itself can be minimized by the degree of involvement in the so-called output resistance change that is output to the outside as the sensitivity of the sensor.

Embodiments The present invention will be described in more detail with reference to plan views of respective devices of the embodiments shown in FIGS. A (100) plane N-type silicon single crystal substrate (thin plate) is used as a material and is processed into a diaphragm 1 described later. First, a silicon oxide film is formed in this substrate, and then a P-type diffusion region is formed on the surface side. The gauge resistance 2 was formed by selective diffusion. The gauge resistance 2 has a width of 15μ, 1
With a length of 250 μm, five of these are connected in series with each other to form one gauge resistor. Four gauge resistors 2 were arranged in the peripheral region of the diaphragm 1 so that their longitudinal directions were the <01> directions. At the same time as these gauge resistors 2, diffusion regions serving as conductors, so-called connecting diffusion resistors 3 to 8 and electrode regions for taking out an output, so-called extraction diffusion regions 9 and 10 were formed. Here, the dimensional ratio d _{1 of the} proportional distribution lengths d ₁ and d ₂ of the length of one side of the connection diffusion resistance 3 for determining the positions of the narrow conductive regions, so-called connecting portions 11 and 12 shown in FIG. A photomask having a ratio of 6.5 / 3.5 was used as an example of / d ₂ . Then, this silicon substrate was etched from the back surface side to form a predetermined diaphragm 1. Diaphragm 1
Had a thickness of 25μ. Then, a glass pedestal having substantially the same coefficient of thermal expansion was directly bonded to the back side of the silicon substrate to make it convenient to handle in the processing step. After the aluminum electrode was formed on the surface side of the silicon substrate, the substrate was diced and then separated into chips. Each chip was assembled in a metal package with a pipe. At this time, the inside of the cap was evacuated to form a pressure sensor for an absolute pressure gauge.

EFFECTS OF THE INVENTION According to the present invention, when the connecting portions 11 and 12 are provided in the center of one side of the rectangular connecting diffusion resistors 3 and 4, the linearity is 100 ± 0.3.
%, On the other hand, when the ratio d ₁ to d ₂ was set to an appropriate value in the range of 1.2 to 6 to 1, the linearity was 100 ± 0.1%, and the variation among the sensor elements was remarkably improved. . This result is obtained by conducting a stress distribution analysis of the diaphragm.
Considering the direction of zero stress sensitivity of the piezoresistive coefficients π _l and π _t in FIG. 2 and the specific pattern of the connecting resistance,
This is due to the optimization of the ratio d ₁ / d ₂ that determines the connection.

[Brief description of drawings]

FIG. 1 is a plan view showing a (100) plane single crystal silicon diaphragm and each diffusion resistance pattern, and FIG. 2 is a plan view showing a pattern in the case of a <110> plane diaphragm, FIGS.
The figure is a (100) plane (110) plane crystal orientation dependence distribution diagram showing the stress sensitivity of the piezoresistance coefficients π _l and π _t of single crystal silicon. 1 ...... diaphragm region, 2, R _a to R _d ...... gauge resistors, 3
～ 8 …… Connecting diffusion resistance, 9,10 …… Drawing diffusion area, 1
1,12 …… Connecting part.

Claims (1)

[Claims] 1. A rectangular first diffusion conductive region connected to two gauge resistors arranged on the surface of a semiconductor substrate so as to bridge-connect each other and to connect two adjacent gauge resistors for extracting an output. Is connected to a second diffusion conductive region adjacent to this by a third diffusion conductive region having a narrow width, and the arrangement position of the third diffusion conductive region is set to the first diffusion region. For one side of the rectangle of the conductive area, the side length is d ₁ vs. d ₂
A semiconductor pressure sensor characterized in that the pressure is set at a position proportional to the length of (d ₁ = 1.2 to 6, d ₂ = 1).