JPS63170973A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To eliminate the influence of contaminating ions on the surface and to eliminate the influence of a residual stress by a method wherein a gauge is constructed in such a way that it is buried in an epitaxial layer. CONSTITUTION:A diffused layer 25, where an n-type impurity having a small diffusion coefficient is diffused at a high concentration of n<+>, is formed on a p-type single-crystal silicon layer 24; a gauge 23 is formed on the layer by diffusing an impurity of the p-conductivity type. An epitaxial layer 26 of the n-conductivity type is formed on the gauge 23 and the silicon layer 24; low- resistance diffused parts 27, 28 where the impurity of the p-conductivity type is diffused at a high concentration of p<+> are formed from the upper surface on both ends of the gauge 23. Because the gauge is buried in the epitaxial layer, it is possible to eliminate the influence of contaminating ions on the surface.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a semiconductor pressure sensor that detects measured pressure as a change in electrical resistance corresponding to the measured pressure with a gauge formed on a silicon diaphragm, and particularly relates to a semiconductor pressure sensor that detects measured pressure as a change in electrical resistance corresponding to the measured pressure. This invention relates to a semiconductor pressure sensor with an improved configuration of a gauge formed on its diaphragm.

<Prior Art> FIG. 4 is a vertical sectional view showing the structure of a conventional semiconductor pressure sensor.

10 is a diaphragm made of n-type silicon single crystal and has a recess 11;
The strain-generating part 12 has a thin single crystal due to the formation of the strain-generating part 12, and a fixing part 13 around the strain-generating part 12 is formed.

A gauge 14 is installed near the boundary between the strain generating part 12 and the fixed part 13.
However, due to the diffusion of impurities, the conduction type is p-type. The upper surface of the diaphragm 10 is covered with an oxide film (Si 02 ) 15 to protect the gauge 14.

The fixing part 13 is fixed to a silicon substrate 17 having a through hole 16 through which the measurement pressure P is introduced, for example, through a glass thin film or the like by anodic bonding, and the substrate 17 is further bonded to a metal casing 18.

When the measurement pressure P is applied to the diaphragm 10, a strain is generated in the strain-generating portion 12, and this strain is applied to the gauge 14.
The resistance of the gauge 14 changes in response to the measured pressure P. Therefore, the measured pressure can be determined from the change in resistance of the gauge 14.

FIG. 5 is a process diagram showing an outline of the process for manufacturing such a semiconductor pressure sensor.

FIG. 5(A) shows a step of forming a gauge 14 that senses the measured pressure by diffusing, for example, a p-type impurity in a predetermined position of an n-type silicon substrate 19, and covering the gauge 14 with an oxide film 15. ing.

Thereafter, as shown in FIG. 5(B), a recess 11 is formed on the opposite side of the silicon substrate 19 from the side on which the gauge is formed by means such as grinding or etching, thereby forming a strain-generating portion 12.

The diaphragm 10 made as described above is shown in Figure 5 (
As shown in c), it is bonded to the substrate 17 by a bonding method such as anodic bonding.

Next, the diaphragm 10 insulated by the substrate 17 is fixed to a metal housing 18 (FIG. 5(d)).

The semiconductor pressure sensor shown in FIG. 4 is manufactured through the steps outlined above.

<Problems to be Solved by the Invention> However, in such a conventional semiconductor pressure sensor, since the gauge 14 is formed on the surface of the diaphragm 10, it is easily affected by the surface.

For example, contaminants such as alkali ions adhere to the surface, which can cause the gauge to change over time.

In addition, various 'DFQC8tO2 films, St 3 N
4) Residual stress was generated in the gauge during the process of formation, and there was a possibility that a change in this residual stress due to temperature would appear as a change in the resistance value of the gauge.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a method in which impurities of the second conduction type are diffused into the strain-generating portion of a diaphragm made of silicon of the first conduction type. An impurity of the first conduction type, whose diffusion coefficient is larger than that of the impurity of the second conduction type, is diffused into the surface of this diffusion layer to form a diffusion surface, and the impurity is further grown on the diffusion surface. An epitaxial layer, a first conduction type gauge whose resistance value changes due to strain caused by measurement pressure by diffusing impurities on the diffusion surface formed in this epitaxial layer, and a gauge of the first conduction type whose resistance value is changed by strain caused by measurement pressure. and a pair of low resistance diffusion portions of the first conduction type with high concentration.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

Reference numeral 19 denotes a diaphragm made of silicon single crystal and has a recess 20, and the diaphragm 19 has a strain-generating part 21 whose thickness is made thinner by forming the recess 20, and a fixing part 22 around the strain part 21. have.

A gauge 23 is formed inside the diaphragm 19 near the boundary between the strain generating part 21 and the fixed part 13. Further, the lower end of the fixed part 22 of the diaphragm 19 is connected to the silicon substrate 17.
The silicon substrate 17 has a through hole 24 opened to the atmosphere. Measurement pressure P is applied to the strain-generating portion 21.
[ is applied, thereby giving strain to the gauge 23.

FIG. 2 is an enlarged view of the gauge portion in FIG. 1.

24 is a silicon layer of 111 crystal whose conductivity type is p type,
On top of this, a diffusion layer 25 is formed in which n-type impurities having a small diffusion coefficient are diffused at a high concentration n+.

On top of this, an impurity of p-type conductivity is diffused to form a gauge 2
3 is formed.

An epitaxial layer 26 having an n-type conductivity is formed on the gauge 23 and the silicon layer 24, and at both ends of the gauge 23 there are low-resistance diffusion portions 27 in which impurities having a p-type conductivity are diffused at a high concentration p+. .28 is formed from the upper surface. An oxide m29 is formed on this surface, and an aluminum wiring 30.31 connected to a low resistance diffusion part 27.28 is formed above this.

A diaphragm 19 is formed by the silicon layer 24, epitaxial layer 26, and the like.

Next, the procedure for making the semiconductor pressure sensor shown in FIG. 1 will be explained with reference to FIG. 3.

FIG. 3(a) shows a diffusion process in which n-type impurities with a small diffusion coefficient, such as arsenic (AS), are added onto the silicon layer 24.
Diffusion 1 by diffusing antimony (Sb) etc. to high concentration n+
Form i125. Thereafter, an oxide film 32 is formed on this a-expanded layer 25, and a portion of the oxide film 32 is opened.

Next, with the window in FIG. 3(a) open, a p-type impurity having a diffusion coefficient larger than that of n-type impurity, such as boron (B), is diffused to form a p-type layer 33 (FIG. 3(b)). After this, the oxide film 32 is removed. In this case, the p-type layer 33 does not have to be thick enough to form a region.

In the step of FIG. 3(c), 1 m26 of n-type epitaxial layer is grown on the p-type layer 33 grown 1q in FIG. 3(0).

Next, as shown in FIG. 3(d), a low resistance diffusion region 2 in which p-type impurity P+ is diffused at a high temperature of 81 degrees is formed at both ends of the p-type layer 33.
7.28 is formed. The low-resistance diffusion portions 27 and 28 undergo a thermal process in the process of forming them, and at this time the diffusion layer 25 and the P-type layer 33 are also diffused to the epitaxial layer 26 side. In this case, the p-type impurity region has a larger diffusion coefficient than the highly concentrated n-type impurity.
That is, the region of the gauge 23 is mostly formed within the epitaxial layer 26. Therefore, the resistance value of the gauge 23 is confined to a narrow region and kept at a relatively high value.

Next, an oxide film 34 is formed in the oxide film formation process shown in FIG. 3 (BO), and the oxide film 34 formed in FIG. A hole corresponding to part 27.2 is opened and aluminum (AI) is deposited, and a wiring 30131 is formed in this part.

Note that the diffusion in the explanation up to now may be performed by thermal diffusion or by ion implantation. Further, in addition to the gauge, a circuit such as a preamplifier may be mounted on the same board.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the gauge is embedded in the epitaxial layer, so the influence of contaminating ions on the surface can be removed, and Since no retaining II film is formed on the surface, the influence of residual stress generated thereby can also be eliminated.

In addition, since the gauge can be placed inside the diaphragm, it is possible to determine the fJ e l inside the diaphragm.Furthermore, since the gauge is embedded in the diffusion layer with a small diffusion coefficient, it becomes a thin gauge and can be processed through a thermal process. The resistance value of the gauge is also held at a relatively high value.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing one embodiment of the present invention, Fig. 2 is an enlarged view of the vicinity of the gauge in Fig. 1, and Fig. 3 is a process for making the semiconductor pressure sensor of the embodiment in Fig. 1. FIG. 4 is a cross-sectional view showing a longitudinal section of a conventional semiconductor pressure sensor, and FIG. 5 is a process diagram showing the steps for making the semiconductor pressure sensor shown in FIG. 4. 10.19...Diaphragm, 11.20...Concave portion, 12.21...Strain-generating portion, 14.23...Gage,
25... Diffusion layer, 26... Epitaxial layer, 27
．． 28... constant resistance diffusion section, 33... p-type layer. Figure 1 Z4 Figure 2 Figure 4 T-shape

Claims (1)

[Claims] A diffusion layer formed by diffusing an impurity of a second conduction type into the strain-generating part of a diaphragm made of silicon of the first conduction type, and a diffusion coefficient on the surface of this diffusion layer that is higher than that of the impurity of the second conduction type. A large impurity of the first conductivity type is diffused to form a diffusion surface, an epitaxial layer is further grown on this diffusion surface, and an impurity formed on the diffusion surface formed in this epitaxial layer is diffused to form a diffusion surface and a measurement pressure is applied. a semiconductor comprising: a gauge of the first conductivity type whose resistance value changes due to strain; and a pair of low-resistance diffusion portions of the first conductivity type formed in the epitaxial layer and having a high concentration for extracting the resistance of the gauge. pressure sensor.