JP2000193548A - Semiconductor pressure sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor which has a sufficient bonding strength between a semiconductor substrate and a seating and is superior in resistance to environment, and to provide its manufacturing method. SOLUTION: This pressure sensor comprises both a semiconductor substrate 11 with a diaphragm 15 provided by etching a one-surface center part and forming a recessed part 11a, and a semiconductor seating 17 with a pressure introducing hole 17a connected to the recessed part 11a, and is formed by bonding the semiconductor seating 17 to one surface of the semiconductor substrate 11 by an anodic bonding method. In this case, a protective layer 16 is formed on the surface of the recessed part 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm type semiconductor pressure sensor using a semiconductor substrate on which a piezoresistive element for extracting a detected pressure as a potential is formed, and more particularly to a semiconductor pressure sensor excellent in environmental resistance. The present invention relates to a structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, pressure sensors have been widely used in various industrial fields. Above all, the use of semiconductor pressure sensors in in-vehicle relations, home electric appliances and the like is rapidly increasing in terms of reliability, cost, and reduction in size and weight.

[0003] Conventional techniques of semiconductor pressure sensors include:
A structure in which a piezoresistor is formed on one surface of a silicon substrate on which a diaphragm is formed is known. The silicon substrate is bonded to the package via the glass pedestal, and the silicon substrate and the glass pedestal are bonded by an anodic bonding method. Further, the glass pedestal and the package are joined by soldering via a metallized layer.
Due to these physically strong junctions, it is possible to obtain a sensor having no leak in the operating temperature range.

However, since the diaphragm for detecting pressure is made of silicon, when the pressure medium is in an alkaline atmosphere, for example, the silicon diaphragm may be corroded and the sensor device may be destroyed. Therefore, as shown in FIG. 5, a semiconductor pressure sensor in which a silicon oxide film 2 is formed on the back surface of a silicon substrate 1 and then a glass pedestal 3 is joined has been studied.

[0005]

In the above-described semiconductor pressure sensor shown in FIG. 5, since the silicon oxide film 2 is formed on the silicon diaphragm, it is effective for a corrosive medium. However, since the silicon substrate 1 and the glass pedestal 3 are anodically bonded via the silicon oxide film 2, there is a problem that the bonding strength between the silicon substrate 1 and the glass pedestal 3 is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a semiconductor pressure sensor having a sufficient bonding strength between a semiconductor substrate and a pedestal and having excellent environmental resistance. And a method for manufacturing the same.

[0007]

In order to solve the above-mentioned problems, a semiconductor pressure sensor according to the present invention comprises a semiconductor substrate having a diaphragm provided by forming a concave portion by etching a central portion of one surface; A glass pedestal having a pressure introduction hole communicating with the semiconductor substrate, wherein the semiconductor pedestal is joined to one surface of the semiconductor substrate by an anodic bonding method, wherein a protective film is formed on the surface of the concave portion. It is a feature. In this case, it is preferable that the protective film is a silicon nitride film.

Further, according to the method of manufacturing a semiconductor pressure sensor of the present invention, a diaphragm is provided by forming a concave portion by etching a central portion of one surface of a semiconductor substrate, and a glass pedestal having a pressure introducing hole communicating with the concave portion is provided. In the method for manufacturing a semiconductor pressure sensor in which the one surface of the semiconductor substrate is bonded by the anodic bonding method, a step of forming a protective film on the surface of the concave portion is provided. In this case, it is preferable that the protective film is a silicon nitride film.

[0009]

1 to 4 show an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a schematic sectional view of a semiconductor pressure sensor according to the present invention. 2A and 2B are schematic cross-sectional views showing a manufacturing process of a semiconductor pressure sensor according to an embodiment of the present invention. FIG. 2A shows a state in which a silicon oxide film and a silicon nitride film are formed on both surfaces of a silicon substrate. ) Shows a state where a non-mask portion of the silicon oxide film and the silicon nitride film on one side of the silicon substrate is etched, (c) shows a state where a concave portion is formed on the silicon substrate by anisotropic etching,
(D) shows a state in which a protective film is formed in the concave portion, and (e) shows
Indicates a state where a glass pedestal is bonded to a silicon substrate. FIG. 3 is an image diagram illustrating cutting of a pressure sensor chip from a silicon wafer. FIG. 4 is a schematic cross-sectional view showing a state where the pressure sensor chip is mounted on the support base.

In FIG. 1, a semiconductor pressure sensor has a plane orientation (110) or a plane orientation (10) corresponding to a semiconductor substrate.
The diaphragm 15 which is a thin portion is formed by forming the concave portion 11a on one main surface (lower side surface in FIG. 1) of the silicon substrate 11 of (0). Then, the glass pedestal and the silicon substrate 11 are bonded by an anodic bonding method,
1 and sealed in a package 22.

The silicon substrate 11 is formed by forming a pressure receiving surface on one surface, a diaphragm 15 for converting pressure into stress, a strain gauge (not shown), and an electrode (not shown) on a single crystal silicon substrate. A change in pressure is converted into a change in electrical resistance by the effect and output. The electrodes formed on the silicon substrate 11 and the leads 23 provided on the package 22 are connected by bonding wires 25 such as Au wires.

The support 21 is a cylindrical pressure introducing cylinder 21.
b, and a flange-shaped mounting portion provided on one end side of the pressure introducing cylinder 21b. The pressure introducing hole 21a inside the pressure introducing cylinder 21b is
7a.

A method for manufacturing a semiconductor pressure sensor according to the present invention will be described below. First, as shown in FIG. 2A, silicon oxide is applied to both surfaces of a single crystal silicon substrate 11 having, for example, a (110) plane orientation by mirror-polishing both surfaces of two main surfaces and one main surface. A film 12 is formed, and a chemical vapor deposition method (hereinafter, referred to as CVD (Chemical Vapor)) is performed.
The silicon nitride film 13 is formed by, for example, a Deposition method). Then, a diffusion resistance (not shown) and an interlayer insulating film are formed on the two main surfaces (the upper surface in FIG. 2A) by an ion implantation method, a dry etching method, a wet etching method, or the like.

Next, one main surface of the silicon substrate 11 (FIG. 2)
2 (a), a resist mask 14 is formed in a predetermined pattern in a portion other than a region where a diaphragm is to be formed, and then, as shown in FIG.
Using a dry etching technique such as active ion etching, the silicon oxide film 12 and the silicon nitride film 13 in the non-mask portion are removed by etching.

After the resist mask 14 is removed by ashing or the like, anisotropic etching is performed with a non-alkali etchant such as a potassium hydroxide solution at 80 ° C. using the silicon nitride film 13 as a mask.
The concave portion 11a shown in FIG. 3C is formed, and the thin diaphragm 15 is formed.

Further, using the silicon oxide film 12 and the silicon nitride film 13 as masks, nitrogen ions are implanted, and then an annealing process is performed at, for example, 900 ° C.
As shown in (d), a silicon nitride film 16 corresponding to a protective film is formed on the surface of the concave portion 11a on one main surface of the silicon substrate 11. The silicon nitride film 16 protects the silicon substrate 11 from erosion.

Next, the silicon oxide film 12 and the silicon nitride film 13 formed on the back surface of the silicon substrate 11 are removed by etching.

Then, the surface of the glass pedestal 17 for anodic bonding for forming the pressure introducing holes 17a facing the silicon substrate 11 is polished so as to reduce the unevenness of the surface. 11 A metal thin film 1 made of metal by metal evaporation
8 is formed. After that, the surface of the silicon pedestal 17 that has been subjected to the polishing treatment and one main surface of the silicon substrate 11 are aligned so that the pressure introducing hole 17a and the diaphragm 15 are superimposed. As shown, bonding is performed by an anodic bonding method, for example, under the conditions of a DC voltage of 600 V, 400 ° C., and a vacuum atmosphere. Then, as shown in FIG. 3, the silicon wafer 2 is moved along the dicing lane.
A chip is cut out from 4 to obtain a pressure sensor chip 19 with a silicon pedestal.

Further, as shown in FIG. 4, for example, Au-S
Using an n-type solder 20, for example, at 360 ° C., the pressure sensor chip 19 with the silicon pedestal and the support 21 having a gold layer formed on the surface by vapor deposition are solder-bonded in, for example, a nitrogen atmosphere.

After connecting the electrodes of the pressure sensor chip 19 with the silicon pedestal and the leads 23 of the support 21 by wire bonding, a resin is applied to the surface of the silicon substrate 11 and sealed in a package 22 to form a semiconductor. The pressure sensor is completed.

Although the protective film is described as being a silicon nitride film, the present invention is not limited to this, and any material can be used as long as it can protect the silicon substrate 11 from erosion.
Therefore, for example, a silicon oxide film or the like may be used. In the case of a silicon nitride film, there is an advantage that environmental resistance is further improved.

[0022]

Since the semiconductor pressure sensor and the method of manufacturing the same according to the present invention are constructed as described above, according to the first aspect of the present invention, a concave portion is formed by etching a central portion of one surface. A semiconductor pressure sensor comprising: a semiconductor substrate having a diaphragm provided therein; and a glass pedestal having a pressure introduction hole communicating with the concave portion, wherein the semiconductor pedestal is joined to one surface of the semiconductor substrate by an anodic bonding method. Since the protective film is formed in the concave portion, there is an effect that the bonding strength between the semiconductor substrate and the pedestal is sufficient and a semiconductor pressure sensor having excellent environmental resistance can be provided.

According to a second aspect of the present invention, a concave portion is formed by etching a central portion of one surface of a semiconductor substrate, a diaphragm is provided, and a glass pedestal having a pressure introducing hole communicating with the concave portion is provided on the semiconductor substrate. In the method for manufacturing a semiconductor pressure sensor bonded to the one surface of the substrate by the anodic bonding method, the step of forming a protective film in the concave portion is provided, so that the bonding strength between the semiconductor substrate and the pedestal is sufficient,
An advantage is provided in that a method of manufacturing a semiconductor pressure sensor having excellent environmental resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a semiconductor pressure sensor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a manufacturing process of the semiconductor pressure sensor according to one embodiment of the present invention, wherein (a) shows a state in which a silicon oxide film and a silicon nitride film are formed on both surfaces of a silicon substrate, (b) shows a state where a non-mask portion of the silicon oxide film and the silicon nitride film on one side of the silicon substrate is etched, (c) shows a state where a concave portion is formed on the silicon substrate by anisotropic etching, and (d) shows Shows a state in which a protective film is formed in the concave portion, and (e) shows a state in which a glass pedestal is bonded to a silicon substrate.

FIG. 3 is an image diagram illustrating cutting of a pressure sensor chip from a silicon wafer.

FIG. 4 is a schematic cross-sectional view showing how a pressure sensor chip is mounted on a support.

FIG. 5 is a schematic sectional view of a conventional semiconductor pressure sensor.

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 11a recess 15 diaphragm 16 protective film 17 glass pedestal 17a pressure introducing hole

Continued on front page F term (reference) 2F055 AA40 BB20 CC02 DD05 EE14 FF38 FF49 GG01 GG12 HH05 HH11 4M112 AA01 BA01 CA05 CA14 CA15 DA04 DA18 EA03 EA07 EA13 FA08

Claims (2)

[Claims] 1. A semiconductor substrate having a diaphragm formed by forming a concave portion by etching a central portion of one surface, and a glass pedestal having a pressure introducing hole communicating with the concave portion, wherein the semiconductor substrate has A semiconductor pressure sensor in which the semiconductor pedestal is bonded to one surface by an anodic bonding method, wherein a protective film is formed in the recess. 2. A pedestal is formed by etching a central portion of one surface of a semiconductor substrate to form a concave portion, a diaphragm is provided, and a glass pedestal having a pressure introducing hole communicating with the concave portion surface is anodic bonded to the one surface of the semiconductor substrate. A method of manufacturing a semiconductor pressure sensor, comprising: forming a protective film on the surface of the concave portion.