JPH10160606A - Semiconductor pressure sensor and fabrication thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance withstand pressure by setting the diameter of a through hole in a glass base, on the side being bonded to a substrate, such that the pressure is spread to a piezoelectric resistor and setting a small diameter on the opposite side. SOLUTION: Thermal oxides 2, 3 are deposited on the surface and rear of a silicon substrate 1 and a mask pattern 15 is formed of a photosensitive resin on the surface side before an implantation layer 16 is formed by implanting dopant ions from an opening 15a. The implantation layer 16 is then heat treated to form a diffusion layer 6 serving as a piezoelectric resistor. A glass base 19 provided, on the upper surface side thereof, with a hole 18 of such size as the pressure is spread to the piezoelectric resistor and, on the lower surface side thereof, with a small hole 17 is then bonded to the substrate 1 by anodic bonding. Since pressure introduction ports are provided by the holes 17, 18 in the glass base 19, strain of the piezoelectric resistor is stabilized. Furthermore, bonding strength is stabilized because the bonding faces of the substrate 1 and the glass base 19 are flat and thereby withstand pressure is enhanced.

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 having a diaphragm structure formed by a semiconductor substrate and a glass pedestal, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a method of manufacturing a semiconductor pressure sensor of this type, as shown in FIG. 2A, a diffusion layer 6 serving as a piezoresistor is formed on the surface side of a silicon substrate 1, and Thermal oxide films 2 and 3 and nitride films 4 and 5 are formed on the front and back surfaces, respectively. Next, in order to form a diaphragm which receives pressure, as shown in FIG. 2B, a portion where the diaphragm is formed is removed from the thermal oxide film 3 and the nitride film 4 formed on the back surface of the silicon substrate 1. An etching window 7 is formed. By etching the silicon substrate 1 from the back side through the etching window 7, the silicon substrate 1 is partially thinned (several μm to several tens μm) as shown in FIG. Form structure 8. Thereafter, the thermal oxide film 3 and the nitride film 4 on the back surface of the silicon substrate 1 are removed by etching as shown in FIG. 2D, and thereafter, a surface electrode 10 is formed as shown in FIG. Die-bonding the chip generated in the package to the package, or FIG.
As described above, the glass pedestal 13 is bonded to the back surface of the silicon substrate 1 by the anodic bonding method.

A semiconductor pressure sensor manufactured in this way transmits a physical quantity (pressure, acceleration, heat, etc.) to be detected to a diaphragm and detects it as a change in the resistance value of a piezo resistor formed thereon.

[0004]

However, in the method of manufacturing a semiconductor pressure sensor as described above, when the diaphragm structure 8 is formed, the etching window 7 is formed as shown in FIG. Sunlight portions 9 are generated in the thermal oxide film 3 and the nitride film 4 used for the etching, and when the thermal oxide film 3 and the nitride film 4 on the back surface side of the silicon substrate 1 are etched, the sunray portions 9 are broken. After the etching is completed, as shown in FIG. 2D, the nitride film 11 is reattached, and when the front electrode 10 is formed, as shown in FIG. Or occur.

[0005] The nitride film 11 and the scratches 1
In the case of No. 2, the anodic bonding of the glass pedestal 13 may result in an incomplete bonding surface 14, which may reduce the bonding strength when a pressure is applied, leading to a failure.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor pressure sensor having high pressure resistance and a method of manufacturing the same.

[0007]

According to a first aspect of the present invention, there is provided a semiconductor pressure sensor, comprising: a semiconductor substrate having a desired diaphragm thickness formed with a piezoresistor; and a through hole for introducing pressure, and joined to the semiconductor substrate. It has a glass pedestal, the through-hole of the glass pedestal, the bonding surface side with the semiconductor substrate has a diameter of such a size that the pressure reaches the piezo resistance,
The opposite surface is characterized in that the diameter is reduced.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor, comprising: forming a diffusion layer having a piezo resistance at a depth equal to or greater than a desired diaphragm thickness on a semiconductor substrate; The opposite side has a glass pedestal formed with a through hole for pressure introduction so as to reduce the diameter, and a surface on which a piezoresistance of the semiconductor substrate is formed. The upper surface of the glass pedestal is bonded by anodic bonding, the surface of the semiconductor substrate that is not bonded to the glass pedestal is polished, and the polished surface is chemically etched to obtain the desired diaphragm thickness. And a mirror surface, and a thermal oxide film and a surface electrode are formed on the mirrored surface of the semiconductor substrate.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a manufacturing process diagram showing a method for manufacturing a semiconductor pressure sensor according to an example of the embodiment of the present invention. FIG. 1 (g) shows a completed semiconductor pressure sensor.

In the method for manufacturing a semiconductor pressure sensor according to the present embodiment, first, as shown in FIG.
The thermal oxide films 2 and 3 having a thickness of about Å are formed, and a mask pattern 15 is formed with a photosensitive resist so that the formation position of the piezoresistor on the surface side is the opening 15a. Then, an injection layer 16 is formed. This implantation layer 16 is heat-treated to form a diffusion layer 6 that becomes a piezoresistive, as shown in FIG. Here, the diffusion layer 6
Is formed about several μm deeper than the diaphragm thickness adjusted to the desired pressure rating. Thereafter, as shown in FIG. 1C, the thermal oxide film 2 on the front side is removed by etching.
At this time, the thermal oxide film 3 on the back side may also be removed.

Next, as shown in FIG. 1 (d), on the upper surface side opposite to the surface side of the silicon substrate 1 on which the diffusion layer 6 serving as the piezoresistor is formed, the size is such that the pressure reaches the piezoresistor. Hole 18 with a diameter of
A glass pedestal 19 having a hole 17 having a smaller diameter and being connected to the recesses 17 and 18 to form a through-hole is formed, and the upper surface of the glass pedestal 19 where the hole 18 is formed and the piezo resistance of the silicon substrate 1 are formed. Is bonded to the surface side on which the diffusion layer 6 to be formed is to be formed by anodic bonding. The through hole formed by the concave portions 17 and 18 has a function as a pressure introduction port. Here, the diameter of the hole 18 is set such that the periphery of the hole 18 extends over the outer diffusion layer 6.

Next, the back side of the silicon substrate 1 is polished, and polishing is stopped at a position which is assumed to be the bottom 20 of the diffusion layer 6 which becomes a piezoresistance, as shown in FIG. From the state, silicon of about several μm is further removed by chemical etching, and the surface 21 is mirror-finished.

Further, as shown in FIG. 1F, an oxide film 23 and a nitride film 22 are formed on the mirror surface on the back surface side of the silicon substrate 1 at a low temperature by a CVD method. A surface electrode 24 is formed as shown in FIG.

According to the semiconductor pressure sensor of this embodiment,
As shown in FIG. 1 (g), the through hole 1 of the glass pedestal 19
Since the pressure introduction ports are formed by the pressure injection ports 7 and 18, the piezoresistive distortion is more stable than in the conventional semiconductor pressure sensor in which the silicon substrate 1 softer than glass is a part of the pressure introduction ports. In addition, the nitride film 11 and the scratch 12
No bonding occurs, and the bonding surface of the semiconductor substrate 1 with the glass pedestal 19 is flat and smooth, so that the bonding strength between the two can be stabilized, and finally the quality can be stabilized.

[0015]

As described above, according to the first and second aspects of the present invention, the semiconductor substrate having a piezoresistor and having a desired diaphragm thickness and a through-hole for introducing pressure are provided. It has a glass pedestal joined to the substrate, the through-hole of the glass pedestal has a diameter such that the bonding surface side with the semiconductor substrate has a diameter large enough to spread the pressure to the piezoresistance, and the opposite surface side Since the semiconductor pressure sensor is formed to have a small diameter, a through hole for introducing pressure is formed in the glass pedestal, and the bonding strength of the bonding surface between the semiconductor substrate and the glass pedestal is stabilized, and a semiconductor having a high pressure resistance is provided. A pressure sensor and a method for manufacturing the same have been provided.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a method for manufacturing a semiconductor pressure sensor according to one embodiment of the present invention.

FIG. 2 is a manufacturing process diagram showing a method for manufacturing a semiconductor pressure sensor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2, 3 Thermal insulation film 4, 5 Nitride film 6 Diffusion layer (piezo resistance) 7 Etching window 8 Diaphragm structure 9 Sunlight part 10 Surface electrode 11 Nitride film 12 Scratches 13 Glass pedestal 14 Joining surface 15 Mask pattern 15a Opening 16 Injection layer 17 hole 18 hole 19 glass pedestal 20 bottom of diffusion layer 21 surface

Claims (2)

[Claims] 1. A semiconductor substrate having a piezoresistor and a desired diaphragm thickness, and a glass pedestal having a through hole for pressure introduction and joined to the semiconductor substrate,
The through-hole of the glass pedestal is characterized in that the bonding surface side with the semiconductor substrate has a diameter that is large enough to spread the pressure to the piezoresistance, and the opposite surface side is formed to have a small diameter. Semiconductor pressure sensor. 2. A piezo-resistance diffusion layer having a depth equal to or greater than a desired diaphragm thickness is formed in a semiconductor substrate, and a bonding surface side with the semiconductor substrate has a diameter large enough to allow pressure to reach the piezo resistance. Then, the opposite surface side forms a glass pedestal having a through hole for pressure introduction so as to reduce the diameter, and the surface on which the piezoresistance of the semiconductor substrate is formed and the upper surface side of the glass pedestal are anodically bonded. Bonding, polishing the side of the semiconductor substrate that is not bonded to the glass pedestal, and further chemically etching the polished surface so as to have the desired diaphragm thickness and mirror surface, A method for manufacturing a semiconductor pressure sensor, wherein a thermal oxide film and a surface electrode are formed on a surface of a semiconductor substrate formed as described above.