JP2002340714A - Semiconductor pressure sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor having an improved sensitivity to external pressures and its manufacturing method. SOLUTION: A semiconductor substrate 1 has a diaphragm 5 free from flexing in the thickness direction and a diffused gage resistors 2 having a resistance value varying in accordance with a stress is formed on the backside of the diaphragm 5. The flexure of the diaphragm 5 more expands the stress exerted on the diffused gage resistors 2 than that in the conventional example, thereby improving the sensitivity to external pressures.

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 and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a semiconductor substrate 1 made of a single-crystal silicon substrate having a thin diaphragm portion 5 which is flexibly formed in a thickness direction by forming a recess 11 on the back surface side. And a plurality of diffusion gauge resistors 2 which are formed on the peripheral surface side of the diaphragm portion 5 and are subjected to stress by bending the diaphragm portion 5 in the thickness direction, and the resistance value changes according to the stress, A plurality of electrodes 4 arranged along the periphery of the surface of the semiconductor substrate 1 ';
And a wiring resistance 3 which is formed in the inside of the substrate and connects the electrode 4 and the diffusion gauge resistance 2 respectively, and a semiconductor pressure sensor for detecting the pressure from the deflection of the diaphragm portion 5 caused by an external pressure is provided. .

[0003]

However, in the above-mentioned conventional semiconductor pressure sensor, there is a problem that the stress applied to each diffusion gauge resistor 2 is relatively small even when the diaphragm portion 5 is bent, and the sensitivity to external pressure is low. Was.

An object of the present invention is to provide a semiconductor pressure sensor having improved sensitivity to an external pressure and a method of manufacturing the same, which aims at solving the above problems.

[0005]

In order to achieve the above-mentioned object, a first aspect of the present invention is to provide a semiconductor substrate in which a thin-walled diaphragm portion is flexibly provided by forming a concave portion on a back surface side, and a diaphragm. A stress is applied by bending of the portion, comprising a resistor whose resistance value changes in accordance with the stress, a semiconductor pressure sensor that detects the pressure from the deflection of the diaphragm portion caused by external pressure, The resistor is formed on the back side of the diaphragm, and when external pressure is applied from the back side of the diaphragm, the back side of the diaphragm bends more than the front side. As compared with the conventional example in which the body is formed on the surface side of the diaphragm, the stress applied to the resistor can be increased, and the sensitivity to external pressure can be improved.

According to a second aspect of the present invention, in the first aspect, an electrode is provided on the semiconductor substrate, and a wiring resistor for electrically connecting the electrode and the resistor is provided in the semiconductor substrate. Characteristically, the provision of the wiring resistance increases the degree of freedom of the position on the semiconductor substrate where the electrodes can be arranged, and for example, the electrodes can be easily arranged on the surface of the semiconductor substrate.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the first or second aspect, wherein an insulating film is formed on a back surface of the semiconductor substrate, and a part of the insulating film is removed. And a step of forming a resistor on the diaphragm through the portion where the insulating film is removed, whereby the entire back surface of the semiconductor substrate excluding the portion where the resistor is formed can be insulated. .

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the first or second aspect, wherein an SOI substrate having an insulating layer therein is used as the semiconductor substrate.
Forming the above-mentioned recess so that the insulating layer is exposed in the substrate to provide a diaphragm portion, removing a part of the exposed insulating layer, and forming the diaphragm through the portion where the insulating layer has been removed; And a step of forming a resistor in the portion, and by using an SOI substrate as the semiconductor substrate, a step of forming an insulating film can be omitted as compared with the invention of claim 3, and a manufacturing process Can be simplified.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the second aspect, wherein an insulating film is formed on both front and back surfaces of the semiconductor substrate, and a part of the insulating film on the back surface of the diaphragm is removed. Performing a step of forming a part of the wiring resistance in the diaphragm portion through the portion where the insulating film has been removed, a step of removing a part of the insulating film on the surface of the semiconductor substrate, and a step of removing the insulating film. Forming the remaining portion of the wiring resistance on the semiconductor substrate through the portion that has been formed, and forming a part of the wiring resistance from the back side of the diaphragm to ensure the wiring resistance to the resistor. The wiring resistance can be easily formed in a desired range on the surface of the semiconductor substrate by forming the remaining portion of the wiring resistance from the surface side of the semiconductor substrate. To Ri, both the front and back surfaces of the semiconductor substrate excluding a portion resistor and the wiring resistance are formed can be insulated.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the second aspect, wherein: a step of forming an insulating film on a surface of a semiconductor substrate; and a step of removing a part of the insulating film; Forming a wiring resistance on the semiconductor substrate through the portion from which the insulating film has been removed,
By forming the wiring resistance from the front side of the semiconductor substrate, the manufacturing process can be simplified as compared with the fifth aspect of the present invention.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) The basic configuration in this embodiment is common to that of the conventional example. Only parts will be described in detail.

In this embodiment, as shown in FIG. 1, similarly to the conventional example, a semiconductor substrate 1 made of a single-crystal silicon substrate provided with a diaphragm portion 5 and a resistor formed around the diaphragm portion 5 as a resistor. 4 diffusion gauge resistors 2
And a plurality of electrodes 4 arranged along the periphery of the surface of the semiconductor substrate 1 and wiring resistors 3 for connecting the electrodes 4 and the diffusion gauge resistors 2 respectively. Is not formed on the front surface side of the diaphragm portion 5 as in the conventional example, but is formed on the back surface side of the diaphragm portion 5. In FIG. 1, a silicon oxide film described later formed on both front and back surfaces of the semiconductor substrate 1 is omitted.

As shown in FIG. 2A, the diaphragm portion 5 does not bend when no external pressure is applied, and has a substantially uniform thickness. However, as shown in FIG. 2 (b), when pressure is applied in the direction from the back side to the front side (the direction indicated by arrow A in the figure), the diaphragm portion 5 makes its thickness non-uniform, It expands and deflects to the side. As a result, the back surface of the diaphragm portion 5 is more flexed than the front surface.

Therefore, in this embodiment, the diffusion gauge resistance 2
Is formed on the back side of the diaphragm portion 5,
The stress applied to the diffusion gauge resistor 2 due to the deflection of the diaphragm portion 5 can be increased as compared with the conventional example, and the sensitivity to external pressure can be improved.

Here, the manufacturing method of this embodiment will be described with reference to FIGS.

First, after a mask is formed on the back side (lower side in the figure) of the semiconductor substrate 1 shown in FIG. 3A by using photolithography, anisotropic etching is performed.
The recess 11 is formed as shown in FIG. Here, the recess 11 is formed such that the substantially rectangular opening surface becomes smaller from the back surface to the front surface side of the semiconductor substrate 1. Further, by forming the concave portion 11, the thin diaphragm portion 5 which can bend in the thickness direction is provided on the semiconductor substrate 1.

Next, as shown in FIG. 3C, a silicon oxide film 6 as an insulating film is formed on both front and back surfaces including the diaphragm portion 5 of the semiconductor substrate 1 by performing thermal oxidation.

Then, a mask is formed by photolithography on the silicon oxide film 6 formed on the back side of the semiconductor substrate 1 and anisotropic etching is performed in the same manner as described above. Four portions of the oxide film 6 are removed. From each of the removed parts, FIG.
As shown in (1), ions constituting the diffusion gauge resistor 2 are implanted and diffused. Thereby, four diffusion gauge resistors 2 are formed on the back surface side of the diaphragm portion 5.

After the diffusion gauge resistor 2 is formed, a mask by photolithography is formed on the back side of the diaphragm portion 5 and anisotropic etching is performed as described above, and the silicon oxide film 6 around the diffusion gauge resistor 2 is removed. Remove. Then, ions forming the wiring resistance 3 are implanted and diffused from the removed portion as shown in FIG. Thereby, a part 3a of the wiring resistance 3 connected to the diffusion gauge resistance 2
Are formed in the diaphragm portion 5. Then, FIG.
As shown in (f), a mask is formed on the surface side of the semiconductor substrate 1 and anisotropic etching is performed in the same manner as described above to remove the silicon oxide film 6 on the surface of the semiconductor substrate 1 excluding the diaphragm 5. Then, ions constituting the wiring resistance 3 are implanted and diffused from the removed portion. Thereby, the wiring resistance 3
Is formed integrally with the part 3a of the wiring resistor 3 in a portion other than the diaphragm portion 5 on the surface side of the semiconductor substrate 1. In other words, the wiring resistance 3 is formed in a range from the diffusion gauge resistance 2 to the peripheral portion where the electrode 4 of the semiconductor substrate 1 is provided by injecting and diffusing ions from the front and back of the semiconductor substrate 1. . By forming such a wiring resistor 3 in the semiconductor substrate 1, the degree of freedom of the position on the semiconductor substrate 1 where the electrode 4 can be disposed is increased, and the diffusion cage resistor 2 is formed.
Is formed on the back surface of the diaphragm portion 5, the electrodes 4 can be easily arranged on the surface of the semiconductor substrate 1 as in the conventional example. Also, as described above, the diaphragm 5
By forming a part 3a of the wiring resistance 3 from the back side of the semiconductor substrate 1, the wiring resistance 3 can be reliably connected to the diffusion gauge resistance 2, and the wiring resistance 3
By forming the remaining portion 3b, the wiring resistor 3 can be easily formed in a desired range on the surface side of the semiconductor substrate 1.

Finally, as shown in FIG. 3 (g),
By forming a mask on the surface of the semiconductor substrate 1 and performing etching, a part of the silicon oxide film 6 on the peripheral surface of the semiconductor substrate 1 is removed at several places, and the electrode 4 is connected to the wiring resistance 3 at each removed part. Arrange so that they are electrically connected.

In this embodiment, since the silicon oxide film 6 is formed on both the front and back surfaces of the semiconductor substrate 1 as described above, the portions where the electrodes 4, the diffusion gauge resistors 2, and the wiring resistors 3 are formed are excluded. The entire front and back surfaces of the semiconductor substrate 1 can be insulated. (Embodiment 2) Since the basic configuration in this embodiment is common to Embodiment 1, the same reference numerals are given to the common parts, and the description thereof will be omitted, and only the characteristic parts of this embodiment will be described in detail. I do.

In the present embodiment, an SOI (Silicon On Insurato) having an insulating layer 8 made of a buried oxide film (silicon oxide film) inside as the semiconductor substrate 1 is used.
r) A substrate is used.

FIGS. 4A to 4E show a manufacturing method of the present embodiment using this SOI substrate as the semiconductor substrate 1.
It will be described based on.

First, as in the first embodiment, a mask is formed on the back side (lower side in the figure) of the semiconductor substrate 1 shown in FIG. As a result, as shown in FIG.
1 and a diaphragm portion 5 are formed. At this time, the recess 11 is formed such that the insulating layer 8 inside the semiconductor substrate 1 is exposed from the bottom surface.

Next, as shown in FIG. 4C, a silicon oxide film 6 is formed on the surface of the semiconductor substrate 1 including the diaphragm portion 5 by thermal oxidation. Here, in the present embodiment, since the SOI substrate is used for the semiconductor substrate 1, it is not necessary to form the silicon oxide film 6 on the back surface of the semiconductor substrate 1 as in the first embodiment, and compared with the first embodiment. The manufacturing process can be simplified.

Then, a part of the peripheral portion of the insulating layer 8 exposed from the back surface of the diaphragm portion 5 is removed by etching at several places, and ions constituting the diffusion gauge resistor 2 are implanted from each of the removed parts, thereby performing thermal diffusion. Let it. As a result, the diffusion gauge resistor 2 is formed on the back surface of the diaphragm 5.

After forming the diffusion gauge resistor 2, FIG.
As shown in (d), a mask is formed on the surface of the semiconductor substrate 1 and etching is performed to remove a part of the silicon oxide film 6 on the surface of the semiconductor substrate 1, and the wiring resistance 3 is formed from the removed portion. Ions are implanted and thermally diffused. Thereby, the wiring resistance 3 is changed from the diffusion gauge resistance 2 to the semiconductor substrate 1.
The electrode 4 is formed so as to be electrically connected to the diffusion gauge resistor 2 in a range reaching the peripheral portion where the electrode 4 is disposed. Further, as described above, in the present embodiment, in order to form the wiring resistance 3, the above-described manufacturing process in which a mask is formed and etching is performed, and then ions are implanted and ions are thermally diffused, as in the first embodiment, is used. By performing the process only on the front surface of the semiconductor substrate 1 without performing the process on the front and back surfaces of the substrate 1, the manufacturing process can be simplified as compared with the first embodiment.

Finally, as shown in FIG.
By forming a mask on the surface of the semiconductor substrate 1 and performing etching, a part of the silicon oxide film 6 on the peripheral portion of the semiconductor substrate 1 is removed at several places, and the electrode 4 is electrically connected to the wiring resistance 3 at each removed part. Are arranged so that they are connected to each other.

[0029]

According to the first aspect of the present invention, there is provided a semiconductor substrate in which a thin-walled diaphragm portion is flexibly provided by forming a concave portion on the back surface, and a stress is applied by flexing the diaphragm portion. A semiconductor pressure sensor for detecting the pressure from deflection of the diaphragm caused by external pressure, the resistor being formed on the back side of the diaphragm. Therefore, when an external pressure is applied from the back surface side of the diaphragm portion, the back surface side of the diaphragm portion bends more than the front side, so that the resistor is compared with the conventional example in which the resistor is formed on the front surface side of the diaphragm portion. As a result, the stress applied to the resistor can be increased, and the sensitivity to external pressure can be improved.

According to a second aspect of the present invention, an electrode is provided on a semiconductor substrate, and a wiring resistance for electrically connecting the electrode and the resistor is provided in the semiconductor substrate. There is an effect that the degree of freedom of the position on the semiconductor substrate where the electrodes can be arranged is increased, and for example, the electrodes can be easily arranged on the surface of the semiconductor substrate.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the first or second aspect, wherein an insulating film is formed on a back surface of the semiconductor substrate, and a part of the insulating film is removed. And a step of forming a resistor in the diaphragm portion through the portion where the insulating film is removed, so that the entire back surface of the semiconductor substrate except for the portion where the resistor is formed can be insulated. is there.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a semiconductor pressure sensor according to the first or second aspect, wherein an SOI substrate having an insulating layer therein is used as the semiconductor substrate.
Forming the above-mentioned recess so that the insulating layer is exposed in the substrate to provide a diaphragm portion, removing a part of the exposed insulating layer, and forming the diaphragm through the portion where the insulating layer has been removed; And a step of forming a resistor in the portion, by using an SOI substrate for the semiconductor substrate,
As compared with the third aspect of the present invention, the step of forming an insulating film can be omitted, and the manufacturing process can be simplified.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the second aspect, wherein an insulating film is formed on both front and back surfaces of the semiconductor substrate, and a part of the insulating film on the back surface of the diaphragm is removed. Performing a step of forming a part of the wiring resistance in the diaphragm portion through the portion where the insulating film has been removed, a step of removing a part of the insulating film on the surface of the semiconductor substrate, and a step of removing the insulating film. Forming the remaining portion of the wiring resistance on the semiconductor substrate through the portion that has been set, so that the wiring resistance is securely connected to the resistor by forming a part of the wiring resistance from the back side of the diaphragm portion. By forming the remaining portion of the wiring resistance from the front side of the semiconductor substrate, the wiring resistance can be easily formed in a desired range on the front side of the semiconductor substrate.
With the insulating film, there is an effect that both the front and back surfaces of the semiconductor substrate except for the portion where the resistor and the wiring resistance are formed can be insulated.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the second aspect, wherein: a step of forming an insulating film on a surface of a semiconductor substrate; and a step of removing a part of the insulating film. Forming a wiring resistance on the semiconductor substrate via the portion from which the insulating film has been removed, so that the wiring resistance is formed from the front surface side of the semiconductor substrate, thereby simplifying the manufacturing process compared to the invention of claim 5. There is an effect that can be made.

[Brief description of the drawings]

FIG. 1 shows a first embodiment, (a) is a side sectional view,
(B) is a top view.

FIG. 2A is a side cross-sectional view of the same semiconductor substrate in a state where no pressure is applied, and FIG. 2B is a side cross-sectional view in a state where a pressure is applied.

FIGS. 3 (a) to 3 (g) are side sectional views for explaining a manufacturing method of the above.

FIGS. 4A to 4E are side sectional views illustrating a manufacturing method according to a second embodiment.

FIG. 5 is a side sectional view showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor substrate 2 diffusion gauge resistance 3 wiring resistance 4 electrode 5 diaphragm 11 recess

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hisamiya Miyajima 1048 Kazuma Kadoma, Kadoma City, Osaka Pref.Matsushita Electric Works, Ltd. F term (reference) 2F055 AA40 BB20 CC02 DD05 EE14 FF11 FF43 GG01 GG16 4M112 AA01 BA01 CA03 CA04 CA13 DA04 DA12 EA03 EA06 FA01

Claims (6)

[Claims] 1. A semiconductor substrate in which a thin diaphragm portion is flexibly provided by forming a recess on the back surface side, and a stress is applied by flexing the diaphragm portion, and a resistance value is increased according to the stress. A semiconductor pressure sensor for detecting the pressure from the deflection of the diaphragm caused by an external pressure, wherein the resistor is formed on the back side of the diaphragm. Sensor. 2. The semiconductor pressure sensor according to claim 1, wherein an electrode is provided on the semiconductor substrate, and a wiring resistor for electrically connecting the electrode and the resistor is provided in the semiconductor substrate. 3. The method for manufacturing a semiconductor pressure sensor according to claim 1, wherein a step of forming an insulating film on a back surface of the semiconductor substrate, a step of removing a part of the insulating film, and a step of removing the insulating film. Forming a resistor on the diaphragm through the part from which the pressure is removed. 4. The method for manufacturing a semiconductor pressure sensor according to claim 1, wherein an SOI substrate having an insulating layer inside is used as the semiconductor substrate, and the concave is formed so that the insulating layer is exposed on the SOI substrate. Forming a place to form a diaphragm portion, removing a part of the exposed insulating layer, and forming a resistor in the diaphragm portion through the portion where the insulating layer is removed. A method for manufacturing a semiconductor pressure sensor, comprising: 5. The method for manufacturing a semiconductor pressure sensor according to claim 2, wherein an insulating film is formed on both front and back surfaces of the semiconductor substrate, and a part of the insulating film on the back surface of the diaphragm is removed. A step of forming a part of the wiring resistance in the diaphragm portion through the part where the insulating film is removed, a step of removing a part of the insulating film on the surface of the semiconductor substrate, and a part where the insulating film is removed Forming a remaining portion of the wiring resistance on the semiconductor substrate. 6. The method for manufacturing a semiconductor pressure sensor according to claim 2, wherein: a step of forming an insulating film on a surface of the semiconductor substrate; a step of removing a part of the insulating film; and a step of removing the insulating film. Forming a wiring resistance on the semiconductor substrate via the set portion.