JP2001208628A - Semiconductor pressure sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-accuracy semiconductor pressure sensor and its manufacturing method not causing deterioration in an offset temperature characteristic of piezoresistors. SOLUTION: This semiconductor pressure sensor has a diaphragm 5 with a thin-walled structure undergoing displacement by a pressure, by piezoresistors 3 provided on the diaphragm 5, and electrodes 6 electrically connected to the piezoresistors 3, and detects the pressure based on a change in the resistance value of the piezoresistors 3. This sensor is characterized in that stress absorbing structures 7 are formed between the piezoresistors 3 and the electrodes 6.

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 a pressure by a change in a piezoresistive value.

[0002]

2. Description of the Related Art A sectional view of a conventional semiconductor pressure sensor is shown in FIG.
Shown in In the drawings, the upper main surface of the semiconductor substrate 1 is referred to as an upper main surface, and the lower main surface is referred to as a lower main surface. A diaphragm 5 having a thin structure is formed on the lower main surface of the semiconductor substrate 1 by anisotropic etching. On the upper main surface of the diaphragm 5, a piezoresistor whose resistance value changes due to distortion of the displacement of the diaphragm 5 is formed. 3 are formed.

When pressure is applied, the diaphragm 5 is displaced,
The resistance value of the piezoresistor 3 changes, and the pressure is detected by detecting this change as a voltage change. The plurality of electrodes 6 (such as aluminum electrodes) are connected to the piezoresistor 3 by a wiring 10 (not shown in FIG. 8) and have a role of an output signal terminal and a terminal for applying a voltage to the circuit of the piezoresistor 3.

[0004]

However, the thermal stress generated by the difference in the thermal expansion coefficient between the semiconductor substrate 1 (silicon substrate) and the electrode 6 (such as an aluminum electrode) affects the piezoresistor 3, and the piezoresistor 3 There was a problem that the offset temperature characteristics deteriorated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a high-precision semiconductor pressure sensor which does not deteriorate the offset temperature characteristic of a piezoresistor and a method of manufacturing the same. Is to do.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor substrate, comprising: a diaphragm having a thin structure displaced by pressure; a piezoresistor provided on the diaphragm; In a semiconductor pressure sensor having a piezoresistor and an electrode electrically connected, and detecting a pressure by a change in the resistance value of the piezoresistor, a stress absorbing structure is formed between the piezoresistor and the electrode. It is characterized by the following.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the stress absorbing structure is a groove structure.

According to a third aspect of the present invention, in the semiconductor pressure sensor according to the second aspect, the sectional structure of the groove structure is V-shaped.

According to a fourth aspect of the present invention, in the semiconductor pressure sensor according to the second aspect, the groove structure has a U-shaped cross section.

According to a fifth aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the stress absorbing structure is a step structure.

According to a sixth aspect of the present invention, in the method for manufacturing a semiconductor pressure sensor according to the third or fifth aspect, the semiconductor substrate is anisotropically etched to form the first semiconductor substrate.
Forming a V-shaped groove structure or step structure on the main surface of
A step of forming a diaphragm by forming a concave portion in the second main surface; a step of forming a piezoresistor by injecting and diffusing impurities into the first main surface of the semiconductor substrate; Forming an electrode to be electrically connected.

According to a seventh aspect of the present invention, in the method of manufacturing a semiconductor pressure sensor according to the fourth or fifth aspect, the semiconductor substrate is dry-etched to form a U-shape on the first main surface of the semiconductor substrate. Forming a groove structure or a step structure, forming a piezoresistor by injecting and diffusing impurities into the first main surface of the semiconductor substrate, and forming a second piezoresistor by anisotropically etching the semiconductor substrate. The method includes a step of forming a diaphragm by forming a concave portion on a main surface, and a step of forming an electrode that is electrically connected to the piezoresistor.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor pressure sensor according to an embodiment of the present invention and a method for manufacturing the same will be described below with reference to FIGS. In the semiconductor substrate 1, the upper main surface in the figure is referred to as an upper main surface, and the lower main surface is referred to as a lower main surface.

FIG. 1 is a view showing a semiconductor pressure sensor according to a first embodiment of the present invention. FIG. 1A is a top view showing an upper main surface of a semiconductor substrate 1 (pressure sensor chip).
FIG. 1B is a cross-sectional view showing a cross section of the semiconductor substrate 1 (pressure sensor chip). The basic structure is the same as that of the conventional example, in which a diaphragm 5 having a thin structure is formed on the semiconductor substrate 1 (silicon substrate), and the resistance value changes on the upper main surface of the concave portion of the diaphragm 5 due to the displacement of the diaphragm 5. A piezoresistor 3 is formed. When the pressure is received, the diaphragm 5 is displaced, and the resistance value of the piezoresistor 3 changes. By detecting this change as a voltage change, the pressure is detected. The plurality of electrodes 6 are connected to the piezoresistor 3 by the wiring 10.
And serves as an output signal terminal and a voltage application terminal to the circuit of the piezoresistor 3.

Here, as shown in the sectional view of FIG. 1B, a groove structure 7 having a V-shaped cross section is formed between the piezoresistor 3 and the electrode 6. Also, in the top view of FIG.
A state where the V-shaped groove structure 7 is formed so as to surround the piezoresistor 3 is shown. The V-shaped groove structure 7 functions as a stress absorbing structure for absorbing thermal stress caused by a difference in thermal expansion coefficient between the semiconductor substrate 1 (silicon substrate) and the electrode 6 (aluminum electrode or the like). The effect of thermal stress on the piezoresistor 3 can be reduced, and the offset temperature characteristics of the piezo resistor 3 can be prevented from deteriorating.

As described above, since the V-shaped groove structure 7 is formed between the piezoresistor 3 and the electrode 6, the thermal stress generated in the electrode 6 is absorbed and the heat applied to the piezoresistor 3 is absorbed. The effect of reducing the influence of stress and preventing deterioration of the offset temperature characteristic of the piezoresistor 3 can be achieved.

FIG. 2 is a sectional view of a semiconductor substrate 1 (pressure sensor chip) for showing a semiconductor pressure sensor according to a second embodiment of the present invention. The basic structure is the same as in the first embodiment. In the present embodiment, a groove structure 8 having a U-shaped cross section is formed between the piezoresistor 3 and the electrode 6.
The formation position of the U-shaped groove structure 8 on the upper main surface of the semiconductor substrate 1 conforms to the formation position of the V-shaped groove structure 7 shown in FIG. In the same manner as in the first embodiment, it is possible to absorb the thermal stress generated in the electrode 6 and reduce the effect of the thermal stress on the piezoresistor 3 to prevent the offset temperature characteristic of the piezoresistor 3 from deteriorating. It has the effect of being able to. Also, since the width of the groove is constant in the depth direction,
This has the effect that the stress absorbing effect can be further enhanced.

FIG. 3 is a sectional view of a semiconductor substrate 1 (pressure sensor chip) for showing a semiconductor pressure sensor according to a third embodiment of the present invention. In the present embodiment, a step structure 9 is formed between the piezoresistor 3 and the electrode 6. The formation position of the step structure 9 on the upper main surface of the semiconductor substrate 1 conforms to the formation position of the V-shaped groove structure 7 shown in FIG. Here, the effect that the step structure 9 absorbs the thermal stress generated in the electrode 6 and alleviates the influence of the thermal stress on the piezoresistor 3 and can prevent the offset temperature characteristic of the piezoresistor 3 from deteriorating. Play.

FIG. 4 shows a fourth embodiment of the present invention.
It is a process drawing showing the 1st manufacturing method. Anisotropic etching is performed on the semiconductor substrate 1 (silicon substrate) to form a V-shaped groove structure 7 and a diaphragm 5 (a). Next, the upper main surface of the semiconductor substrate 1 is thermally oxidized to form a silicon oxide film 2 (b). Then, an opening is formed at a predetermined position of the silicon oxide film 2 by a photolithography step and an etching step (c), and a piezoresistor 3 is formed by an ion implantation (impurity implantation) and diffusion step (d). Next, a silicon nitride film 4 is formed on the surface of the silicon oxide film 2 (e). Then, openings are formed at predetermined positions of the silicon nitride film 4 and the silicon oxide film 2 by a photolithography process and an etching process (f), and an electrode 6 (aluminum electrode or the like) is formed (g).

Through the above steps, a semiconductor pressure sensor corresponding to the first embodiment can be manufactured.

FIG. 5 shows a fifth embodiment of the present invention.
It is a process drawing showing the 2nd manufacturing method. Anisotropic etching is performed on the semiconductor substrate 1 (silicon substrate) to form the step structure 9 and the diaphragm 5 (a). Next, the upper main surface of the semiconductor substrate 1 is thermally oxidized to form a silicon oxide film 2 (b). Then, an opening is formed at a predetermined position of the silicon oxide film 2 by a photolithography step and an etching step (c), and a piezoresistor 3 is formed by an ion implantation and diffusion step (d). Next, a silicon nitride film 4 is formed on the surface of the silicon oxide film 2 (e). Then, openings are formed at predetermined positions of the silicon nitride film 4 and the silicon oxide film 2 by a photolithography process and an etching process (f), and an electrode 6 (aluminum electrode or the like) is formed (g).

With the above steps, a semiconductor pressure sensor corresponding to the third embodiment can be manufactured.

FIG. 6 shows a sixth embodiment of the present invention.
It is a process drawing showing the third manufacturing method. Dry etching is performed on the semiconductor substrate 1 (silicon substrate),
A U-shaped groove structure 8 is formed on the upper main surface of (a).
Next, the upper main surface of the semiconductor substrate 1 is thermally oxidized to form a silicon oxide film 2 (b). Then, an opening is formed at a predetermined position of the silicon oxide film 2 by a photolithography step and an etching step (c), and a piezoresistor 3 is formed by an ion implantation and diffusion step (d). Next, a silicon nitride film 4 is formed on the surface of the silicon oxide film 2 (e).
Next, a pattern is formed on the lower main surface of the semiconductor substrate 1 by a photolithography step and an etching step, and anisotropic etching is performed based on the pattern to form a diaphragm 5 (f). Next, openings are formed at predetermined positions of the silicon nitride film 4 and the silicon oxide film 2 by a photolithography process and an etching process (g),
An electrode 6 (such as an aluminum electrode) is formed (h).

Through the above steps, a semiconductor pressure sensor corresponding to the second embodiment can be manufactured.

FIG. 7 shows a seventh embodiment of the present invention.
It is a process drawing showing the fourth manufacturing method. Dry etching is performed on the semiconductor substrate 1 (silicon substrate),
A step structure 9 is formed on the upper main surface of (a). Next, the upper main surface of the semiconductor substrate 1 is thermally oxidized to form a silicon oxide film 2 (b). Then, an opening is formed at a predetermined position of the silicon oxide film 2 by a photolithography step and an etching step (c), and a piezoresistor 3 is formed by an ion implantation and diffusion step (d). Next, a silicon nitride film 4 is formed on the surface of the silicon oxide film 2 (e). Next, a pattern is formed on the lower main surface of the semiconductor substrate 1 by a photolithography step and an etching step, and anisotropic etching is performed based on the pattern to form a diaphragm 5 (f). Next, openings are formed at predetermined positions of the silicon nitride film 4 and the silicon oxide film 2 by a photolithography process and an etching process (g), and an electrode 6 (aluminum electrode or the like) is formed (h).

Through the above steps, a semiconductor pressure sensor similar to the third embodiment in which the step structure 9 is substantially perpendicular to the upper main surface of the semiconductor substrate 1 can be manufactured.

While the embodiment of the present invention has been described above, the step structure 9 has a step in which the portion of the piezoresistor 3 is higher than the portion of the electrode 6 in the embodiment. Alternatively, the structure may be such that the portion of the electrode 6 has a step that is higher than the portion of the piezoresistor 3.

[0028]

As described above, according to the first aspect of the present invention, a diaphragm having a thin structure displaced by pressure, a piezoresistor provided on the diaphragm, and a piezoresistor provided on the semiconductor substrate are provided. In a semiconductor pressure sensor having an electrode that is electrically connected and detecting pressure by a change in the resistance value of the piezo resistor, a stress absorption structure is formed between the piezo resistor and the electrode. Thus, a high-precision semiconductor pressure sensor without deteriorating the offset temperature characteristics can be provided.

According to the second aspect of the present invention, since the stress absorbing structure is a groove structure, there is an effect that thermal stress can be absorbed with a simple structure.

According to the third aspect of the present invention, since the cross-sectional shape of the groove structure is V-shaped, an effect that thermal stress can be absorbed with a simpler structure is achieved.

According to the fourth aspect of the present invention, since the cross-sectional shape of the groove structure is U-shaped, thermal stress can be absorbed with a simple structure and the stress absorbing effect can be improved. It has the effect of being able to.

According to the fifth aspect of the present invention, since the stress absorbing structure is a step structure, there is an effect that thermal stress can be absorbed with a simple structure.

In a sixth aspect of the present invention, a semiconductor substrate is anisotropically etched to form a V-shaped groove structure or a step structure on a first main surface of the semiconductor substrate. Forming a diaphragm by forming a recess in the second main surface, forming a piezoresistor by injecting and diffusing impurities into the first main surface of the semiconductor substrate; And a step of forming an electrode to be electrically connected, so that a semiconductor pressure sensor having a V-shaped groove structure or a step structure according to claim 3 or 5 can be manufactured. This has the effect.

In a seventh aspect of the present invention, as a manufacturing method, a step of dry-etching the semiconductor substrate to form a U-shaped groove structure or a step structure on the first main surface of the semiconductor substrate; Forming a piezoresistor by injecting and diffusing impurities into a first main surface of the semiconductor substrate, and forming a diaphragm by forming a concave portion in the second main surface by anisotropically etching the semiconductor substrate; And a step of forming an electrode for making an electrical connection to the piezoresistor.
Alternatively, the semiconductor pressure sensor having the U-shaped groove structure or the step structure according to claim 5 can be manufactured.

[Brief description of the drawings]

FIG. 1 is a top view and a cross-sectional view of a semiconductor pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor pressure sensor according to a third embodiment of the present invention.

FIG. 4 is a process chart showing a first manufacturing method as a fourth embodiment of the present invention.

FIG. 5 is a process chart showing a second manufacturing method as a fifth embodiment of the present invention.

FIG. 6 is a process chart showing a third manufacturing method as a sixth embodiment of the present invention.

FIG. 7 is a process chart showing a fourth manufacturing method as a seventh embodiment of the present invention.

FIG. 8 is a sectional view of a semiconductor pressure sensor showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor substrate (silicon substrate) 2 silicon oxide film 3 piezoresistive 4 silicon nitride film 5 diaphragm 6 electrode 7 V-shaped groove structure 8 U-shaped groove structure 9 step structure 10 wiring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sumio Akai 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Inventor Kazuo Eda 1048 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Works F Terms (reference) 2F055 AA40 BB20 CC02 DD05 EE14 FF01 GG01 GG15 4M112 AA01 BA01 CA03 CA11 CA13 CA16 DA03 DA10 DA11 DA12 EA02 EA06 EA07 EA11 FA05

Claims (7)

[Claims] 1. A semiconductor substrate comprising: a diaphragm having a thin structure displaced by pressure; a piezo resistor provided on the diaphragm; and an electrode electrically connected to the piezo resistor. A semiconductor pressure sensor for detecting pressure by a change, wherein a stress absorbing structure is formed between the piezoresistor and the electrode. 2. The semiconductor pressure sensor according to claim 1, wherein said stress absorbing structure is a groove structure. 3. The semiconductor pressure sensor according to claim 2, wherein said groove structure has a V-shaped cross section. 4. The semiconductor pressure sensor according to claim 2, wherein said groove structure has a U-shaped cross section. 5. The semiconductor pressure sensor according to claim 1, wherein said stress absorbing structure is a step structure. 6. A semiconductor substrate is anisotropically etched to form a V-shaped groove structure or a step structure on a first main surface of the semiconductor substrate, and to form a concave portion on a second main surface. Forming a diaphragm by performing impurity implantation and diffusion on the first main surface of the semiconductor substrate to form a piezo-resistor; and forming an electrode electrically connected to the piezo-resistor. The method for manufacturing a semiconductor pressure sensor according to claim 3, wherein the method comprises: 7. A step of dry-etching a semiconductor substrate to form a U-shaped groove structure or a step structure on a first main surface of the semiconductor substrate, and forming an impurity on the first main surface of the semiconductor substrate. Implanting and diffusing to form a piezoresistor; anisotropically etching the semiconductor substrate to form a second piezoresistor;
6. The semiconductor pressure sensor according to claim 4, further comprising: a step of forming a diaphragm by forming a concave portion on a main surface of the semiconductor device; and a step of forming an electrode electrically connected to the piezoresistor. Manufacturing method.