JP3004119B2 - 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. Thus, the diaphragm section 31 is deformed in accordance with 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,
-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]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned object.
On the thin-walled diaphragm 13
A semiconductor chip 3 having a strain gauge to the surface, the lower surface of the diaphragm portion 31 the semiconductor chip 3 is fixed
And a closed case 1 having a closed space having an inner wall surface 13 provided with an area 131 for arranging and fixing the pedestal 2. The above-mentioned closure in an area different from the arrangement area 131
The pressure introducing hole 15 is formed only through the case 1.
The opening of the pressure introducing hole 15 is
Asked toward the same direction as the direction toward the surface having the strain gauge
Are arranged so as to face the inner wall surface 14 in the closed space.
It is characterized by being placed.

[0007]

In the above configuration, the pressure introducing hole 15 is formed in the pedestal arrangement region 13 of the inner wall surface 13 where the semiconductor chip 3 is provided.
1 only through the closure case 1 in an area different from
The opening of the pressure introducing hole 15 is a strain gauge of the semiconductor chip 3.
Same direction toward hunger and thirst closing sky to the direction in which the face is the surface having the over-di
Since that is disposed so as to face the inner wall surface 14 in between, it is pollutants or water from the pressure introducing hole 15 is penetrated,
These directly adhere to or collide with the inner wall surface 14 facing the semiconductor chip 3. Therefore, the probability of reaching the semiconductor chip 3 is low.

Also, the light incident from the pressure introducing hole 15 is
The semiconductor chip 3 reflects once on the inner wall surface 14 facing the semiconductor chip 3 or several times on other inner wall surfaces.
, The influence on the element characteristics on the chip 3 is extremely small.

[0009]

1 and 2, a closed case 1 is composed of a lower container 11 and a lid 12 which covers the lower case 11 and whose opening edge is tightly fixed with a resin bond. Thick, inner wall 13 has a rectangular recess 1 with a deep center.
It is 31. The concave portion 131 has guide convex portions 132 projecting inward on four side walls close to the bottom surface. The outer periphery is brought close to these convex portions 132, and a rectangular block-shaped glass pedestal is formed on the concave bottom surface. 2 is bonded and fixed with a resin bond. 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 is changed according to 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 ensured, 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.

External light is also prevented from directly entering the closed case 1 by the long pressure introducing hole 15, and even if it enters the case 1, it 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.

[0016]

The silicon gel 33 covering the semiconductor sensor 3 is not particularly required.

[0018]

As described above, according to the semiconductor pressure sensor of the present invention, the sensor function is not impaired by contaminants or light entering from the pressure introducing hole.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a sensor showing one 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 13 Inner wall surface 15 Pressure introduction hole 2 Pedestal 3 Semiconductor chip

Claims (1)

(57) [Claims] 1. A 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 closed space between the semiconductor chip and a lower surface of the diaphragm portion, and the pedestal arranged and fixed. A closed case having a closed space having an inner wall surface provided with an area for the, 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,
Opening of the pressure introducing hole is arranged so as to face the inner wall surface of the strain gauge in the same direction as the direction toward the surface having an orientation and the closed space of the semiconductor chip, the inner wall surface in said closed casing In the above pedestal arrangement area
Is a concave part, and this concave part is
A side portion extending to the outside and a bottom portion;
A protrusion protruding inward into the recess in a region where the bottom and the bottom connect.
Part, and the base is fixed to the bottom part.
And a semi-conductive member on the inner wall surface in the closed case around the concave portion.
Electrode part electrically connected to body chip by bonding wire
Are formed, and the convex portion formed in the concave portion is
A semiconductor pressure sensor, wherein a space is formed between the pedestal and the side surface of the recess .