JP2002090244A - Semiconductor pressure sensor and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor and a manufacturing method thereof with high accuracy that deterioration of offset temperature characteristics of a piezoresistance caused by thermal stress is not produced. SOLUTION: In the semiconductor pressure sensor, a cut groove 5 which extends to a region where an electrode 3 is formed is formed on the side face of a semiconductor substrate 1, and thermal stress which is produced between the substrate 1 and the electrode 3 is reduced. The semiconductor pressure sensor forms a cut groove 5 that extends to a region, where an electrode 3 is formed, on the side face of a semiconductor substrate 1 to reduce thermal stress produced between the substrate 1 and the electrode 3.

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 4 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 4, a piezoresistor whose resistance value changes due to distortion of the displacement of the diaphragm 4 is formed. 2 are formed.

When pressure is applied, the diaphragm 4 is displaced,
The resistance value of the piezo resistor 2 changes, and the pressure is detected by detecting this change as a voltage change. A plurality of electrodes 3 (such as aluminum electrodes) are interconnected (not shown in FIG. 6)
Connected to the piezoresistor 2 and has a role of a signal output terminal and a role of a voltage application terminal to the circuit of the piezoresistor 2.

[0004]

However, the thermal stress generated due to the difference in the thermal expansion coefficient between the semiconductor substrate 1 (silicon substrate) and the electrode 3 (aluminum electrode or the like) affects the piezoresistor 2, and the piezoresistor 2 There was a problem that the offset temperature characteristics deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the thermal stress generated between a semiconductor substrate and an electrode, thereby deteriorating the offset temperature characteristic of a piezo resistor. It is an object of the present invention to provide a high-precision semiconductor pressure sensor and a method of manufacturing the same without any problem.

[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 an electrode electrically connected to a piezo resistor and detecting pressure by a change in resistance value of the piezo resistor, a cut groove is formed on a side surface of the semiconductor substrate over a portion where the electrode is formed. It is characterized by having done.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the semiconductor substrate has a silicon active layer formed on a silicon substrate via an oxide film layer.
An I-substrate, wherein the notch is formed by removing a part of an oxide film layer of the SOI substrate.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor pressure sensor according to the second aspect, an opening is formed on a main surface of the SOI substrate on the silicon active layer side around a portion where a diaphragm is to be formed. Is formed, and a portion of the oxide film layer of the SOI substrate is removed by etching from the opening to form the cut groove. Next, the piezo resistor and the piezoresistor are formed on the main surface of the SOI substrate on the silicon active layer side. The electrode is formed, and the main surface of the SOI substrate on the silicon substrate side is etched to form the diaphragm.

According to a fourth aspect of the present invention, in the method for manufacturing a semiconductor pressure sensor according to the second aspect, the piezoresistor and the electrode are formed on a main surface of the SOI substrate on the silicon active layer side, and then the SOI substrate is formed. On the main surface of the substrate on the side of the silicon active layer, an opening is formed in the periphery of a portion where a diaphragm is to be formed, and a part of the oxide film layer of the SOI substrate is removed by etching from the opening. A slit is formed, and then the main surface of the SOI substrate on the silicon substrate side is etched to form the diaphragm.

According to a fifth aspect of the present invention, in the method of manufacturing a semiconductor pressure sensor according to the third or fourth aspect, the opening is formed by dry etching.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor pressure sensor according to an embodiment of the present invention and a method for manufacturing the same will be described 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 sectional view showing the structure of a semiconductor pressure sensor according to a first embodiment of the present invention. The basic structure is the same as that of the conventional example. A thin-walled diaphragm 4 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 4 due to the displacement of the diaphragm 4. A piezoresistor 2 is formed. Upon receiving the pressure, the diaphragm 4 is displaced, and the resistance value of the piezoresistor 2 changes. By detecting this change as a voltage change, the pressure is detected. The plurality of electrodes 3 are piezoresistors 2
And has a role of a signal output terminal and a role of a voltage application terminal to the circuit of the piezoresistor 2.

Here, as shown in FIG. 1, a notch groove 5 is formed over a portion where the electrode 3 is formed, and a structure is formed such that a constricted portion 5a is formed at the portion of the diaphragm 4. The cut groove 5 acts 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 3 (aluminum electrode or the like). The influence can be reduced, and deterioration of the offset temperature characteristic of the piezoresistor 2 can be prevented.

As described above, since the cut groove 5 is formed over the portion where the electrode 3 is formed, the thermal stress generated in the electrode 3 is absorbed, and the influence of the thermal stress on the piezoresistor 2 is reduced. There is an effect that deterioration of the offset temperature characteristic of the piezo resistor 2 can be prevented.

FIG. 2 is a sectional view showing the structure of 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, as the semiconductor substrate 1, an SOI (Si) in which a silicon active layer 7 is formed on a silicon substrate 9 via an oxide film layer (insulating layer) 8.
A constricted portion 5a of the diaphragm 4 is formed of an oxide film layer 8 of an SOI substrate using a substrate 6 (icon on insulator). As in the first embodiment, the cut grooves 5 on both sides of the constricted portion 5a have a function of absorbing thermal stress. In particular, since the oxide film layer 8 can be selected and etched, there is an effect that the cut groove 5 and the constricted portion 5a can be easily formed. Further, in forming the diaphragm 4, the oxide film layer 8 can be used as an etch stop, so that over-etching can be prevented and the manufacturing accuracy can be improved.

FIG. 3 is a process chart showing a first method of manufacturing the semiconductor pressure sensor according to the second embodiment. (A) A photolithography process is performed on the SOI substrate 6 in which a silicon active layer 7 is formed on a silicon substrate 9 via an oxide film layer (insulating layer) 8 and an upper main surface (the silicon active layer 7 side) is anisotropically etched. An opening 10 is formed at a predetermined position of (b). Next, a part of the oxide film layer 8 is removed by etching from the opening 10 to form the cut groove 5 and the constricted portion 5.
A portion 8a to be a is formed (c). Incidentally, hydrofluoric acid is generally used as an etchant for etching the oxide film layer 8. Next, after performing a photolithography process, a piezoresistor 2 is formed by an ion implantation process and a diffusion process (d). Then, an electrode 3 is formed (e). Next, an SG (Silicate Glass) film is deposited as an etching mask on the upper main surface, and a window is opened at a predetermined position on the lower main surface (the silicon substrate 9 side) by a photolithography process and etching. Then, the lower main surface is anisotropically etched to form the diaphragm 4 (f). At this time, the oxide film layer 8 acts as an etch stop, so that the diaphragm 4 can be formed accurately. Finally, individual semiconductor pressure sensors (chips) are obtained by cutting the portions indicated by broken lines in the figure.

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

FIG. 4 is a process chart showing a second method of manufacturing the semiconductor pressure sensor according to the second embodiment. (A) The photolithography process is performed on the SOI substrate 6, and an opening 10 is formed at a predetermined position on the upper main surface by dry etching (b). Next, a part of the oxide film layer 8 is removed by etching from the opening 10 to form the cut groove 5 and a portion 8a to be the constricted portion 5a (c). Hereinafter, the formation process of the piezoresistor 2, the electrode 3, and the diaphragm 4 is the first.
((D) to (f)). In particular, since the opening 10 can be processed vertically by using dry etching, the size of the semiconductor pressure sensor chip can be reduced as compared with the case where anisotropic etching is used.

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

FIG. 5 is a process chart showing a third method of manufacturing the semiconductor pressure sensor according to the second embodiment. After performing a photolithography process on the SOI substrate 6 (a), a piezoresistor 2 is formed by an ion implantation process and a diffusion process (b). Then, the electrode 3 is formed (c). A photolithography process is performed, and an opening 10 is formed at a predetermined position on the upper main surface by anisotropic etching or dry etching (d). Next, a part of the oxide film layer 8 is removed by etching from the opening 10 to form the cut groove 5 and the portion 8a to be the constricted portion 5a (e). Next, an SG film is deposited as an etching mask on the upper main surface, and a window is opened at a predetermined position on the lower main surface by a photolithography process and etching. Then, the lower main surface is anisotropically etched to form the diaphragm 4 (f). At this time,
The oxide film layer 8 acts as an etch stop, and the diaphragm 4 can be formed with high accuracy. Finally, individual semiconductor pressure sensors (chips) are obtained by cutting the portions indicated by broken lines in the figure.

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

[0022]

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 resistance value of a piezo resistor, a notch groove is formed on a side surface of the semiconductor substrate over a portion where the electrode is formed. As a result, a high-precision semiconductor pressure sensor can be provided in which the thermal stress generated between the semiconductor substrate and the electrode is reduced and the offset temperature characteristic of the piezoresistor is not deteriorated.

According to a second aspect of the present invention, the semiconductor substrate is an SOI substrate in which a silicon active layer is formed on a silicon substrate via an oxide film layer, and the cut groove is formed in one of the oxide film layers of the SOI substrate. Since the part is removed, the groove can be easily formed by etching the oxide film layer selectively, and over-etching is prevented by using the oxide film layer as an etch stop in diaphragm formation. As a result, it is possible to improve the manufacturing accuracy.

In the invention according to claim 3, claim 2
The method for manufacturing a semiconductor pressure sensor according to
On the main surface of the substrate on the side of the silicon active layer, an opening is formed in the periphery of a portion where a diaphragm is to be formed, and a part of the oxide film layer of the SOI substrate is removed by etching from the opening. A notch groove is formed, and then the SOI
The piezoresistor and the electrode are formed on the main surface of the substrate on the silicon active layer side, and the diaphragm is formed by etching the main surface of the SOI substrate on the silicon substrate side. There is an effect that the pressure sensor can be easily formed.

According to the fourth aspect of the present invention, the second aspect is provided.
The method for manufacturing a semiconductor pressure sensor according to
The piezoresistor and the electrode are formed on the main surface of the substrate on the silicon active layer side, and then an opening is formed on the main surface of the SOI substrate on the silicon active layer side at a periphery of a portion where a diaphragm is to be formed. Then, a portion of the oxide film layer of the SOI substrate is removed by etching from the opening to form the cut groove, and then the main surface of the SOI substrate on the silicon substrate side is etched to form the diaphragm. Therefore, there is an effect that the semiconductor pressure sensor having the cut groove can be easily formed.

According to the fifth aspect of the present invention, the third aspect is provided.
Alternatively, in the method of manufacturing a semiconductor pressure sensor according to claim 4, the opening is formed by dry etching, so that the opening can be processed vertically, and the size of the semiconductor pressure sensor chip can be reduced. It has the effect of being able to.

[Brief description of the drawings]

FIG. 1 is 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 process chart showing a first method of manufacturing a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 4 is a process chart showing a second method of manufacturing the semiconductor pressure sensor according to the second embodiment of the present invention.

FIG. 5 is a process chart showing a third method of manufacturing the semiconductor pressure sensor according to the second embodiment of the present invention.

FIG. 6 is a sectional view of a conventional semiconductor pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate (silicon substrate) 2 Piezoresistance 3 Electrode 4 Diaphragm 5 Cut groove 5a Neck 6 SOI substrate 7 Silicon active layer (of SOI substrate) 8 Oxide film layer (of SOI substrate) 9 Silicon substrate (of SOI substrate) 10 Aperture

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuo Eda 1048 Kazuma Kadoma, Kadoma-shi, Osaka F-term in Matsushita Electric Works, Ltd. DA04 DA10 EA02 EA06 FA05 FA09

Claims (5)

[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 cut groove is formed on a side surface of the semiconductor substrate, the cut groove extending over a portion where the electrode is formed. 2. The SOI substrate in which the semiconductor substrate has a silicon active layer formed on a silicon substrate via an oxide film layer, and the cut groove is formed by removing a part of the oxide film layer of the SOI substrate. The semiconductor pressure sensor according to claim 1, wherein: 3. An opening is formed in the main surface of the silicon active layer of the SOI substrate around a portion where a diaphragm is to be formed, and one of the oxide film layers of the SOI substrate is etched by etching from the opening. The piezoresistor and the electrode are formed on the main surface of the SOI substrate on the silicon active layer side, and the SOI substrate is formed.
3. The method according to claim 2, wherein the diaphragm is formed by etching a main surface of the substrate on the silicon substrate side. 4. The piezoresistor and the electrode are formed on the main surface of the SOI substrate on the silicon active layer side, and the portion of the SOI substrate on the silicon active layer side where a diaphragm is to be formed is formed. Forming an opening in the periphery,
Removing a part of the oxide film layer of the SOI substrate by etching from the opening to form the cut groove, and then etching the main surface of the SOI substrate on the silicon substrate side to form the diaphragm; 3. The method according to claim 2, wherein
A manufacturing method of the semiconductor pressure sensor according to the above. 5. The method for manufacturing a semiconductor pressure sensor according to claim 3, wherein the opening is formed by dry etching.