JP3233136B2 - Semiconductor pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor and, more particularly, to an improvement in the structure of a sensor which does not cause contamination or light deterioration of a semiconductor chip.

[0002]

2. Description of the Related Art FIG . 3 shows the structure of a conventional semiconductor pressure sensor. In a closed case 1, a rectangular block-shaped glass pedestal 2 is fixed on a bottom wall surface, and a silicon semiconductor chip 3 is mounted on the pedestal 2. It is fixed by anodic bonding. The semiconductor chip 3 has a thin diaphragm portion 3 with its lower center portion being concave.
The strain gauge constituting the pressure sensor is diffused and formed on the upper surface of the diaphragm portion 31. The closed space S between the upper surface of the pedestal 2 behind the diaphragm 31 is evacuated.

A pressure introduction hole 15 is formed through the top wall of the case 1, through which atmospheric pressure is introduced into the case 1. However, the diaphragm section 31 is deformed according to the fluctuation of the atmospheric pressure, and a signal output corresponding to the absolute atmospheric pressure is obtained from the strain gauge. Such a structure is disclosed in, for example,
No. 431.

[0004]

By the way, in the above-mentioned conventional sensor structure, pollutants and water in the air reach the semiconductor chip 3 directly from the pressure introducing hole 15 and adhere to the semiconductor chip 3 to easily cause deterioration of characteristics. There was a problem. In addition, light directly enters the semiconductor chip 3 via the pressure introducing hole 15, and there is a possibility that the characteristics may be degraded.

An object of the present invention is to provide a semiconductor pressure sensor which can prevent such contaminants from adhering and which is not deteriorated by an incident light beam.

[0006]

To explain the structure of the present invention, a semiconductor pressure sensor comprises a rectangular semiconductor chip having a strain gauge on the upper surface of a thin diaphragm portion, and the semiconductor chip fixed to the diaphragm portion. A pedestal forming a closed space between the pedestal and a lower case, and a closed case having a closed space having an inner wall surface provided with a region for arranging and fixing the pedestal. The pedestal arrangement region is a concave portion, and the horizontal height of the inner wall surface around the concave portion and the semiconductor chip becomes substantially the same by installing the pedestal in the concave portion. An electrode electrically connected to the semiconductor chip by a bonding wire in two electrode regions on the inner wall surface and adjacent to two opposing sides of a rectangle of the semiconductor chip; Is formed, the pressure introduction hole is formed only through the closed case in a region different from the pedestal arrangement region of the inner wall surface, and the opening of the pressure introduction hole is a surface of the semiconductor chip having the strain gauge. It is arranged so as to face in the same direction as the direction in which it faces and to face the inner wall surface in the closed space, and the opening of the pressure introducing hole has a rectangular shape of the semiconductor chip in the electrode region.
One of the sides is adjacent to the electrode portion.

More specifically, the openings of the pressure introducing holes are arranged side by side with the electrode portions in a direction in which one side of a rectangle of the semiconductor chip extends.

In the above configuration, the pressure introducing hole 15 is formed on the same inner wall surface as the surface on which the semiconductor chip is provided.
Even if contaminants, water, and the like enter through the pressure introducing holes, they directly adhere to or collide with the inner wall surface facing the semiconductor chip. Therefore, the probability of reaching the semiconductor chip is low.

Also, the light incident from the pressure introducing hole is reflected once on the inner wall surface facing the semiconductor chip or is reflected several times on the other inner wall surface to reach the semiconductor chip. The effect is very small.

An electrode portion electrically connected to the semiconductor chip by a bonding wire is formed in an electrode region adjacent to two opposing sides of a rectangle of the semiconductor chip, and an opening of the pressure introducing hole is formed in the electrode region. Since it is formed, a region for opening the pressure introducing hole is not formed in another region, and the size of the closed case is not made larger than necessary.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, a closed case 1 is composed of a lower container 11 and a lid 12 covering the lower container 11 and having an opening edge tightly fixed with a resin bond. Is thick and the inner wall surface 13 is a rectangular recess 131 having a deep center. The recess 131 has guide protrusions 132 projecting inward from four side walls close to the bottom surface.
A rectangular block-shaped glass pedestal 2 is fixed to the bottom of the recess by resin bonding with the outer periphery approaching these convex portions 132. A silicon semiconductor chip 3 of the same diameter is fixed to the upper surface of the pedestal 2 by anodic bonding, and the pedestal 2 has a thermal expansion coefficient close to that of the semiconductor chip 3.

The semiconductor chip 3 has a thin diaphragm portion 31 with a concave lower surface at the center portion, and a strain gauge is formed on the upper surface of the diaphragm portion 31 by diffusion. The closed space S between the upper surface of the pedestal 2 below the diaphragm 31 is evacuated.

The outer peripheral portion of the inner wall surface 13 surrounding the recess 131 is substantially the same height as the upper surface of the semiconductor chip 3, and terminal plates 41, 42,
43 is buried, and these terminal plates 41 to 43 and the semiconductor chip 3 are connected by bonding wires 32. Then, the lower container 11 is placed on the inner wall surface near the terminal plate 41.
A pressure introducing hole 15 penetrating downward is opened, and atmospheric pressure is introduced into the closed case 1.

The surface of the semiconductor chip 3 is covered with a silicon gel 33, and the ends of the terminal plates 41 to 43 extend to the outside of the lower container 11 so that the external terminals 411, 4
21,431.

In the pressure sensor having the above-described structure, the diaphragm 31 of the semiconductor chip 3 depends on the difference between the atmospheric pressure and the vacuum.
Is deformed and the output signal corresponding to the absolute pressure of the atmosphere is
Between 11 and 431.

Since the pressure introducing hole 15 is formed in the outer peripheral portion of the thick lower container 11, a sufficient length is secured, and it is effective that contaminants, water, and the like enter the closed case 1 through this. Is prevented. Even if it enters, the contaminants and the like adhere to the inner wall surface 14 of the lid 12 facing the opening of the pressure introducing hole 15 and hardly reach the semiconductor chip 3.

Also, external light is prevented from directly entering the closed case 1 by the long pressure introducing hole 15, and even if it enters the case 1, the external light is once reflected by the inner wall surface 14 of the lid 12. The sensor function is not impaired even when the semiconductor chip 3 is reached.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a sensor showing an embodiment of the present invention.

FIG. 2 is a partially broken plan view of a sensor.

FIG. 3 is a schematic sectional view of a sensor showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Closed case, 2 ... Pedestal, 3 ... Semiconductor chip, 13 ...
Inner wall, 15… Pressure introduction hole

Claims (2)

(57) [Claims] 1. A rectangular semiconductor chip having a strain gauge on an upper surface of a thin diaphragm portion, a pedestal to which the semiconductor chip is fixed to form a sealed space between the lower surface of the diaphragm portion, and a pedestal. A closed case having a closed space having an inner wall surface provided with an area for arranging and fixing, wherein the pedestal arrangement area is a concave portion on the inner wall surface in the closed case, and the pedestal is installed in the concave portion. As a result, the horizontal height between the inner wall surface around the concave portion and the semiconductor chip is substantially the same, and the rectangular opposite surface of the semiconductor chip is located on the inner wall surface around the concave portion. In two electrode regions adjacent to the side, an electrode portion electrically connected to the semiconductor chip by a bonding wire is formed, and the electrode portion is formed in a region of the inner wall surface different from the pedestal arrangement region. The pressure introducing hole is formed only through the chain case, and the opening of the pressure introducing hole faces in the same direction as the direction of the surface of the semiconductor chip having the strain gauge and on the inner wall surface in the closed space. A semiconductor pressure sensor arranged so as to face each other, wherein an opening of the pressure introducing hole is adjacent to one of the two sides of the rectangle of the semiconductor chip and the electrode portion in the electrode region. . 2. The semiconductor pressure sensor according to claim 1, wherein the opening of the pressure introducing hole is arranged along with the electrode portion in a direction in which the one side of the rectangle of the semiconductor chip extends.