JPH11201845A - Semiconductor type pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect the thin diaphragm part of a semiconductor chip displacing depending on the pressure against damage even when a dew is frozen by coating the surface and rear of the diaphragm part with a protective film. SOLUTION: The sensor comprises a semiconductor chip 1 where a strain gauge is formed on the surface of thin diaphragm part 8 displacing depending on the pressure, a base 2 being bonded thereto, and a protective film 7 covering the position for forming diaphragm part 8 on the surface 1a and rear surface 1b sides of the chip 1. The film 7 composed of a silicon get material covers the surface entirely on the surface 1a and covers the inside of a recess 1c made by etching in order to form diaphragm part 8 on the rear surface 1b side. The film 7 protects diaphragm part 8 against damage even when a dew is formed due to ambient temperature variation and frozen later.

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 for detecting pressure by a change in resistance of a plurality of strain gauges formed on a diaphragm made of a semiconductor material such as silicon.

[0002]

2. Description of the Related Art In a semiconductor pressure sensor, a semiconductor material having a predetermined thickness such as silicon is formed into a substantially concave shape to form a thin diaphragm portion, and a plurality of strain gauges are formed on the diaphragm portion on a bridge circuit. The semiconductor chip is formed by forming the semiconductor chip, and the pressure is detected by a change in the resistance value of a bridge circuit of the semiconductor chip.

[0003]

This semiconductor type pressure sensor is used in various environments, for example,
In some cases, the gauge pressure sensor is mounted on a vehicle as a gauge pressure sensor for measuring an intake pressure of a vehicle engine. The ambient temperature of the gauge pressure sensor mounted on the vehicle changes in a range of about −30 ° C. to about 100 ° C., and this temperature change causes dew condensation on the semiconductor chip, and then the ambient temperature decreases. The moisture generated by dew condensation causes the semiconductor chip itself to freeze, and if pressure is applied to the diaphragm of the semiconductor chip in this frozen state, the thin diaphragm may be damaged. Has problems.

[0004] JP-A-8-193899 and JP-A-Hei-4
In Japanese Patent Application Laid-Open No. 370726/1991, when pressure is transmitted from the front side of a semiconductor chip, a silicon-based protective film is formed on the front side of the semiconductor chip. Disclosed are those in which a silicon-based protective material is disposed on a pressure introduction path formed in a pedestal joined to a semiconductor chip and on a back surface side corresponding to a diaphragm portion of the semiconductor chip. The present invention relates to a structure for protecting one of the front and back surfaces of the semiconductor chip from a contaminated medium with respect to the direction of pressure transmission of the medium such as the above, and the diaphragm portion is damaged when the moisture freezes due to the condensation described above. It is not intended to prevent the above, and in semiconductor type pressure sensors (gauge pressure sensors, differential pressure sensors, etc.) mounted on vehicles, etc. Consideration the semiconductor pressure sensor is desired.

Accordingly, the present invention focuses on the above problem, and it is possible to prevent the diaphragm of the semiconductor chip from being damaged even when the dew condensation occurs due to the change in the ambient temperature and then the moisture due to the dew condensation freezes. A possible semiconductor pressure sensor is provided.

[0006]

According to the present invention, in order to solve the above-mentioned problems, a semiconductor chip having a thin diaphragm portion which is displaced in accordance with pressure is covered with a protective film.

A semiconductor chip having a thin diaphragm portion displaced in response to pressure and having a strain gauge formed on one surface of the diaphragm portion; a glass pedestal joined to the semiconductor chip; And a protective film that covers the one surface and the other surface.

The protective film is made of a silicon-based gel material and covers a position on the other surface of the semiconductor chip where the diaphragm is formed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a semiconductor chip 1 having a thin diaphragm portion 8 which is displaced in response to pressure, wherein a strain gauge is formed on the surface (one surface) of the diaphragm portion 8; 1 is a semiconductor pedestal comprising a glass pedestal 2 bonded to the semiconductor chip 1 and a protective film 7 covering the formation positions of the diaphragm portions 8 on the front surface 1a side of the semiconductor chip 1 and the back surface (other surface) 1b side of the semiconductor chip 1 Sensor
By disposing the protective film 7 which is a soft member on the front and back surfaces of the semiconductor chip 1, the semiconductor chip 1 itself does not freeze even when the surrounding environment becomes low, and the displacement of the diaphragm portion 8 is not spoiled. The diaphragm 8 can be prevented from being damaged.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the accompanying drawings. FIG. 1 is a sectional view of a principal part showing a semiconductor type pressure sensor of the present invention, FIG. 2 is a view showing a method of forming a protective film, and FIG. 3 is a sectional view of a principal part showing another embodiment of the present invention.

The semiconductor pressure sensor according to this embodiment is
It comprises a semiconductor chip 1, a glass pedestal 2, a base plate 3, a pressure introducing pipe 4, an electrode lead 5, a case body 6, and a protective film 7 which is a feature of the present invention.

The semiconductor chip 1 is made of silicon, and a thin diaphragm portion 8 is formed by etching a semiconductor material having a predetermined thickness with KOH or the like. The surface (one surface) of the diaphragm portion 8 has A semiconductor strain gauge (not shown) is formed by diffusion so as to form a bridge circuit.

The glass pedestal 2 is made of a material (for example, Pyrex glass) having a thermal expansion coefficient substantially equal to that of the semiconductor chip 1, and is anodic-bonded to the stem 9 of the semiconductor chip 1. Further, at a position where the glass pedestal 2 and the diaphragm portion 8 face each other, a pressure introduction hole 10 for transmitting pressure of gas or the like to the diaphragm portion 8 is formed so as to penetrate the front and back surfaces of the glass pedestal 2. , Base plate 3 of glass pedestal 2
A metallized layer (not shown) for bonding to the base plate 3 is formed on the surface facing the substrate.

The base plate 3 is made of a metal material such as Kovar, for example, and the glass pedestal 2 is joined by solder.
Further, a through hole 11 is formed in the glass pedestal 2 at a position facing the pressure introduction hole 10.

The pressure introduction port 4 is, for example, a base plate 3
A pressure introducing portion (through-hole) 12 is formed, which is made of a metal material equivalent to the above, and communicates with the through-hole 11 of the base plate 3 and the pressure-introducing hole 10 of the glass pedestal 2. The pressure introduction port 4 is hermetically joined to the base plate 3 by means such as welding.

The electrode leads 5 are for taking out the power input to the semiconductor chip 1 and the output of the bridge circuit to the outside. The electrode leads 5 and the base plate 3 are arranged and fixed by a hermetic seal. This electrode lead 5
Are electrically connected to an electrode portion (not shown) formed together with the strain gauge on the semiconductor chip 1 by a conductive material 13 such as gold.

The case body 6 is made of a metal material such as SPC, and is disposed and fixed to the gate plate 3 by means such as welding.
An outside air intake 14 for taking in outside air is formed on the upper surface of the case body 6.

The protective film 7 is made of a silicon-based gel material, and is applied to the surface (one surface) 1a and the back surface (the other surface) 1b of the semiconductor chip 1 where the strain gauge is formed. The protective film 7 is provided in order to prevent the diaphragm portion 8 from being damaged even when dew condensation occurs due to a change in the ambient temperature and the moisture generated by the dew condensation freezes thereafter. The protective film 7 on the surface 1a side of the diaphragm portion 8
The coating is applied so as to cover the entire surface of the semiconductor chip 1, and the protective film 7 on the back surface 1 b side of the diaphragm portion 8 is applied in the concave portion 1 c formed by etching to form the thin diaphragm portion 8. You. In this embodiment, the protective film 7 is made of, for example, “Shin-Etsu Chemical Co., Ltd.
Penetration after curing of “KJR-9014” is 60 to 75 (JIS K 22
20) is used, and the displacement of the diaphragm portion 8 is not impaired.

The above components constitute a can-package type pressure detector which can prevent the diaphragm portion 8 from being damaged by freezing after dew condensation. In the semiconductor pressure sensor having such a configuration, the protection film 7 which is a soft member is
The semiconductor chip 1 itself does not freeze even when the surrounding environment becomes low, and the displacement of the diaphragm portion 8 is not impaired, so that damage to the diaphragm portion 8 can be prevented. Things. Also,
Even when a medium containing a contaminant is detected, the durability does not change from the conventional one.

In the method of forming the protective film 7 applied to the back surface 1b of the diaphragm portion 8 in this embodiment, a silicon gel material is injected from the pressure introducing hole 10 of the glass pedestal 2 by dispensing using a needle or the like. Then, the protective film 7 is formed by defoaming and curing the air bubbles in the silicon-based gel material using a vacuum defoaming device.

Next, a method of forming a protective film (the protective film 7 on the back surface 1b side of the diaphragm portion 8) in consideration of productivity will be described with reference to FIG.

First, a flat silicon wafer 15 having a predetermined thickness is prepared (a), and a predetermined portion of the silicon wafer 15 is etched into a substantially concave shape 1c to form a thin diaphragm portion 8 (b). ).

Next, after strain gauges are formed on the plurality of diaphragm portions 8 by diffusion (not shown), a silicon-based gel material serving as the protective film 7 is filled in the concave portions 1c formed for constituting the diaphragm portions 8. The coating is performed by means such as dispensing or pin transfer (c). Thereafter, the applied air bubbles of the silicon-based gel material are deaerated using a vacuum defoaming device, and the silicon-based gel material is cured to obtain a protective film 7.

Next, a glass substrate 16 having pressure introducing holes 10 corresponding to the respective diaphragm portions 8 formed in the silicon wafer 15 is prepared, and each of the stem 9 portions of the silicon wafer 15 on which the protective film 7 is formed is formed. Anodically bonding the glass substrate 16 to the glass substrate 16 (d), followed by cutting with a dicer or the like to obtain individual semiconductor pressure sensors 17 having the protective film 7 formed on the back surface 1 b side of the diaphragm portion 8. (E).

The protective film 7 applied on the semiconductor chip 1 is applied after the semiconductor chip 7 and the electrode leads 5 are electrically connected by wire bonding. After the application, the protective film 7 is applied to the back surface 1b of the diaphragm portion 8. It is obtained by defoaming and curing the air bubbles of the silicon-based gel material by a vacuum defoaming device as in the case of applying.

In the step of forming the protective film 7, the silicon gel material can be applied and vacuum degassed in the state of the silicon wafer 15, so that the protective film 7 can be formed in the diaphragm portion 8 without complicating the manufacturing process. Can be formed on the back surface 1b side, and the productivity can be improved.

In the above-described step of forming the protective film 7, the silicon-based gel material is applied to the silicon wafer 15, and then the silicon wafer 15 and the glass substrate 16 are anodically bonded. Sometimes both members 1
Since 5 and 16 are heated at 300 ° C. or higher, it is necessary to use a material that does not deteriorate even at the above-mentioned temperature for the protective film 7.

FIG. 3 shows another structure of the present invention. The difference from the above-described embodiment lies in that a semiconductor pressure sensor 17 is provided in a recessed housing 18 and the periphery of the semiconductor pressure sensor 17 is covered with a protective film 7 made of a silicon-based gel material. It is. In such a structure, similarly to the above-described structure, it is possible to prevent the diaphragm 8 of the semiconductor chip 1 from being damaged by freezing.

The present invention is not limited to the pressure detector having the structure of the above-described embodiment. For example, the structure of the pressure detector for detecting a gauge pressure, a differential pressure or the like mounted on a vehicle or the like may be used. The present invention can be applied to a semiconductor pressure sensor in which the front and back surfaces of a semiconductor chip are covered with protective films.

[0030]

The present invention is characterized in that the front and back surfaces of a semiconductor chip having a thin diaphragm portion displaced in response to pressure are covered with a protective film. The diaphragm itself does not freeze, and the displacement of the diaphragm is not damaged, so that the diaphragm can be prevented from being damaged.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is a view showing a method of forming a protective film according to the embodiment.

FIG. 3 is a sectional view of a main part showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 1a Surface (one surface) 1b Back surface (other surface) 2 Glass pedestal 7 Protective film 8 Diaphragm part

Claims (3)

[Claims] 2. A semiconductor pressure sensor comprising: a semiconductor chip having a thin diaphragm portion which is displaced in response to a pressure; 2. A semiconductor chip having a thin diaphragm portion displaced in response to pressure and having a strain gauge formed on one surface of the diaphragm portion, a glass pedestal joined to the semiconductor chip, and the semiconductor chip. And a protective film that covers one surface and the other surface of the semiconductor pressure sensor. 3. The semiconductor device according to claim 1, wherein the protective film is made of a silicon-based gel material and covers a position where the diaphragm is formed on the other surface of the semiconductor chip.
Alternatively, the semiconductor pressure sensor according to claim 2.