JPH073647Y2 - Semiconductor pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention is a semiconductor in which a long diaphragm is formed on a semiconductor substrate and a piezoresistive effect according to the pressure applied to the diaphragm is used. Regarding a pressure sensor.

(Prior Art) Conventionally, there is a semiconductor pressure sensor of this type as shown in FIG. In FIG. 4, reference numeral 1 is a square semiconductor substrate made of a silicon single crystal having a plane orientation of (110) plane, and 2 is a long thin diaphragm formed on the semiconductor substrate 1. This diaphragm 2
It is arranged in the central portion such that its length direction is parallel to the edge of the semiconductor substrate 1, and its width direction is along the crystal axis <111> direction of the semiconductor substrate 1.
The diaphragm 2 is provided with a predetermined thickness by forming an elongated groove portion 3 by anisotropic etching from the lower surface side of the semiconductor substrate 1. Reference numeral 4 is a resistance portion formed by diffusion of impurities in the central portion of the diaphragm 2 along the width direction. The semiconductor substrate 1 thus formed is fixed to a base (not shown), and is installed so as to close the groove 3 to form a reference pressure chamber.

When a difference in pressure inside the reference pressure chamber occurs due to a change in external pressure, the diaphragm 2 is deformed, and as a result,
The resistance value of the resistance portion 4 changes due to the piezoresistive effect, and the pressure is measured by electrically detecting the change in the resistance value.

(Problems to be solved by the invention) By the way, in such a semiconductor pressure sensor, when the thickness of the diaphragm 2 is constant, the linearity of the output obtained with respect to the pressure by the length dimension 1 and the width dimension w thereof. The area is decided, for example, the length dimension 1 and the width dimension w.
If the ratio l / w is kept constant and is increased, the output can be increased without changing the linearity of the output with respect to pressure.

However, in the conventional configuration, the length dimension L of the groove 2 including the length dimension 1 of the diaphragm 2 and the lengths of the slopes 3a and 3b formed by anisotropic etching at the upper and lower ends of the groove 3 is the semiconductor. The length A of one side of the substrate 1 is left for strength retention, and is determined as A-2a excluding the dimension a at the bottom. There was a problem that the substrate 1 had to be large.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor pressure sensor capable of increasing the output against pressure and improving the performance thereof without increasing the size of the semiconductor substrate. is there.

[Structure of the Invention] (Means for Solving the Problem) A semiconductor pressure sensor of the present invention is a rectangular semiconductor substrate having a plane orientation of (110) plane and a long thin diaphragm. It is characterized in that it is formed so that the width direction is along the <111> direction and the length direction is along the diagonal line.

(Operation) According to the semiconductor pressure sensor of the present invention, the diaphragm is
Since the length direction is formed so as to be arranged in a diagonal direction with respect to the semiconductor substrate, both the length dimension and the width dimension can be made larger than in the conventional case, and as a result,
The larger area of the diaphragm increases the sensitivity without reducing the linearity region of the output with respect to pressure.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 11 denotes, for example, a rectangular semiconductor substrate having a rectangular shape with a side length A, which is cut out from a silicon single crystal wafer having a plane orientation of (110) plane. . In addition, in the semiconductor substrate 11, among the vertices 11a to 11d, the diagonal direction connecting the vertices 11a and 11c is <111>.
It is cut out so as to be the crystal axis of the direction.
Reference numeral 12 is a thin thin diaphragm having a length dimension l ′ and a width dimension w ′, which is arranged along a diagonal line connecting the vertices 11b and 11d in the length direction, and therefore the vertices 11a and 11c in the width direction. They are arranged along the diagonal direction, that is, the <111> direction.
In this case, the diaphragm 2 is formed by forming the groove portion 13 on the lower surface side of the semiconductor substrate 11 to reduce the thickness of the semiconductor substrate 11. This groove 13 is the second
As shown in FIG. 3 and FIG. 3, it is formed by anisotropically etching with an alkaline solution such as potassium hydroxide using an etching mask 14 having a predetermined shape provided on the lower surface of the semiconductor substrate 11. Both ends 13a with respect to the vertical direction,
13b is an inclined surface, the side surface portions 13c and 13d are surfaces perpendicular to the bottom surface, and all of these surfaces 13a to 13d are (111) surfaces. In order to maintain the strength of the semiconductor substrate 11, the groove portion 13 is provided so as to be located inside by a predetermined dimension a from the outer circumference as in the conventional case. Reference numeral 15 is a resistance portion formed in the central portion of the diaphragm 12, which is formed by a method such as diffusion along the width direction of the diaphragm 12, that is, the <111> direction. Such a semiconductor substrate 11 is fixed to a base (not shown) so as to seal the groove portion 13, so that the groove portion 13 acts as a reference pressure chamber.

According to the above configuration, when a difference occurs between the pressure inside the groove portion 13 as the reference pressure chamber and the external pressure, the diaphragm 12 is deformed by the force due to the pressure difference, and the resistance portion 15 is deformed by this deformation stress. Since the resistance value changes due to the piezoresistive effect, the external pressure can be measured by electrically detecting the change in the resistance value. In this case, since the length dimension l'of the diaphragm 12 is formed longer than the length dimension 1 of the conventional diaphragm 2, the linear region of the change of the resistance portion 13 with respect to the pressure is increased accordingly. That is, since the maximum length dimension l'of the diaphragm 12 is the length dimension L'of the groove portion 13 minus the dimensions of both end portions 13a and 13b, the length dimension L'of the groove portion 13 and the conventional groove portion Three
Comparing with the length dimension L of, the respective dimensions L and L ′ are L = A−2a (1) Therefore, the difference is Becomes Now, assuming that the ratio l '/ w' of the length dimension l'and the width dimension w'of the diaphragm 12 is set to the same value (k) as the conventional ratio l / w, the value of this ratio k is large. Although the dimension represented by the equation (3) also increases, the value of the ratio k is generally set to a large value, and therefore the dimension represented by the equation (3) also has a positive value in the present embodiment, and the length dimension L ′ Is longer than L.

According to the present embodiment as described above, the diaphragm 12 is arranged in the length direction along the diagonal line of the semiconductor substrate 11 and in the width direction in the <111> direction. It is possible to lengthen both the length dimension l'and the width dimension w'of the diaphragm 12, so that the ratio k (= l '
/ w ') becomes the same as the conventional one, and each length dimension can be increased, and the sensitivity can be increased and the semiconductor substrate 11 can be increased without reducing the linearity region of the output against pressure. It is possible to improve the performance without.

[Advantages of the Invention] As described above, according to the semiconductor pressure sensor of the present invention, the diaphragm is arranged so that the width direction of the diaphragm is along the <111> direction and the length direction is along the diagonal line. Since it is arranged in the above, it is possible to make the length dimension of the diaphragm longer than in the conventional case, and therefore it is possible to increase the sensitivity without decreasing the linearity region of the output with respect to pressure without increasing the size of the semiconductor substrate. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIGS. 2 and 3 are longitudinal side views in the length direction and width direction of the diaphragm, respectively, and FIG. 4 is a first example showing a conventional example. It is a figure equivalent figure. In the drawings, 11 is a semiconductor substrate, 12 is a diaphragm, 13 is a groove, and 15 is a resistor.

Claims (1)

[Scope of utility model registration request] 1. A semiconductor pressure sensor in which a long thin diaphragm is formed on a rectangular semiconductor substrate having a plane orientation of (110) plane, wherein the diaphragm has a width direction with respect to the semiconductor substrate. Is arranged along the axis direction <111> and the length direction is arranged along a diagonal line.