JPH10242480A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor whose sensitivity can be enhanced without making a chip size large. SOLUTION: Piezoresistive elements 2 are formed on one main face of a silicon wafer 1, two main surfaces are etched anisotropically while a nitride film 4 in which an opening part 5 is formed is used as a mask, and a diaphragm 1a is formed. Then, the two main surfaces of the silicon wafer 1 are etched anisotropically while the nitride film 4 in which opening parts 4a are formed is used as a mask, and slit-shaped groove parts 1b are formed.

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.

[0002]

2. Description of the Related Art FIG. 8 is a schematic sectional view showing a manufacturing process of a conventional semiconductor pressure sensor. In the conventional semiconductor pressure sensor, first, a plane orientation having a thickness of about 300 μm (11
0), a piezoresistive element 2 is formed at a portion where a diaphragm 1a to be described later is formed by performing ion implantation of impurities and annealing on one main surface of the silicon wafer 1; And a nitride film 4 are formed. At this time, two piezoresistive elements 2 are formed substantially at the center of the diaphragm and two at the outer periphery thereof.
Piezoresistive elements 2 and aluminum (A
l) The wiring 6 constitutes a Wheatstone bridge structure.

Next, the opening 5 is formed by etching the oxide film 3 and the nitride film 4 formed on the two main surfaces of the silicon wafer 1 using a photoresist (not shown) patterned into a predetermined shape as a mask. Then, the photoresist is removed by plasma ashing or the like (FIG. 8).
(A)) Oxide film 3 and nitride film 4 in which opening 5 is formed
Is used as a mask, anisotropic etching of the silicon wafer 1 is performed using an alkaline etchant such as an aqueous solution of potassium hydroxide (KOH) to form a thin diaphragm 1a (FIG. 8B).

[0004] Next, the oxide film 3 and the nitride film 4 on the piezoresistive element 2 and the oxide film 3 and the nitride film 4 formed on the two main surfaces of the silicon wafer 1 are removed by etching. An aluminum (Al) layer is formed on the entire surface side on which the resistance element 2 is formed, and etching is performed using a photoresist (not shown) patterned in a predetermined shape as a mask, thereby forming an aluminum (Al) layer.
Patterning the layer to form aluminum (Al) wiring 6
Is formed, and the photoresist is removed (FIG. 8C).
Finally, a glass pedestal 7 having a desired thickness (about 1 mm) required for mounting on a package and having a pressure introducing hole 7a is provided on the two main surfaces of the silicon wafer 1 at locations corresponding to the diaphragm 1a. (FIG. 8D).

[0005]

However, in the semiconductor pressure sensor having the above structure, in order to obtain a required output, it is necessary to adjust the thickness (D) of the diaphragm 1a and the size (L) of the diaphragm 1a. Therefore, as the lower pressure is measured (improved in sensitivity), the thickness (D) of the diaphragm 1a must be reduced and the size (L) of the diaphragm 1a must be increased.

In order to obtain the required size (L) of the diaphragm 1a, a side etching amount (l) corresponding to the thickness of the silicon wafer 1 is taken into consideration.
It is also necessary to secure a bonding margin (A) for bonding with the substrate.

Further, in order to reduce stress caused by a difference in the coefficient of thermal expansion from a package (not shown) to the glass pedestal 7 and from the glass pedestal 7 to the piezoresistive element 2, the thickness of the silicon wafer 1 must be reduced. It is desirable that the thickness be as thick as possible. As a result, there is a problem that the chip size is inevitably increased in order to improve the sensitivity.

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 capable of improving the sensitivity without increasing the chip size. is there.

[0009]

According to the first aspect of the present invention,
In a semiconductor pressure sensor having a semiconductor substrate having a diaphragm and a piezoresistive element formed on the diaphragm, a plurality of slit-shaped grooves are formed on the diaphragm.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, an interval between the adjacent slit-shaped grooves is made narrower from a substantially center to a periphery of the diaphragm. It is a feature.

According to a third aspect of the present invention, in the semiconductor pressure sensor according to the first or second aspect, the depth of the slit-shaped groove portion is increased from a substantially center to a periphery of the diaphragm. It is characterized by having done.

According to a fourth aspect of the present invention, in the semiconductor pressure sensor according to the first to third aspects, the groove is formed on a surface of the diaphragm on which the piezoresistive element is formed. is there.

According to a fifth aspect of the present invention, in the semiconductor pressure sensor according to the first to fourth aspects, the groove is formed on a surface of the diaphragm different from the surface on which the piezoresistive element is formed. Is what you do.

According to a sixth aspect of the present invention, in the semiconductor pressure sensor according to the first to fifth aspects, the groove is formed by anisotropic etching using an alkali-based etchant. Things.

According to a seventh aspect of the present invention, in the semiconductor pressure sensor according to any one of the first to fifth aspects, the groove is formed by R
It is characterized by being formed by IE.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 = FIG. 1 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG. 2 is a view seen from the back surface of the semiconductor pressure sensor according to the embodiment. FIG. 4 is a schematic plan view showing a state in which it is folded. The manufacturing process of the semiconductor pressure sensor according to the present embodiment up to FIG. 1B is the same as the manufacturing process up to FIG. 8B as a conventional example, and the description is omitted here. Description will be made from the manufacturing process (c). The nitride film 4 and the oxide film 3 formed on the two main surfaces of the silicon wafer 1 are removed by CF ₄ plasma etching or the like (FIG. 1).
(C)) A nitride film 4 is formed again on the two main surfaces of the silicon wafer 1 by the CVD method or the like.

An opening 4a is formed by etching the nitride film 4 formed on the two main surfaces of the silicon wafer 1 using a photoresist (not shown) patterned in a predetermined shape as a mask. Is removed. At this time, the opening 4a for etching is
Diaphragm 1 at a position outside piezoresistive element 2 shown in FIG.
The depth of the etching can be determined by adjusting the size of the opening 4a.

Next, using the nitride film 4 in which the opening 4a is formed as a mask, anisotropic etching is performed using an alkaline etchant such as an aqueous solution of potassium hydroxide (KOH) to obtain a slit-like shape. V-shaped groove 1b
Is formed (FIG. 1D), and the nitride film 4 formed on the two main surfaces of the silicon wafer 1 is removed by etching. At this time, the etching is stopped when the entire etched surface of the silicon wafer 1 is formed on the (111) plane. Further, the groove 1b is arranged so as to be in line contrast with the center line of the diaphragm 1a, so that the distortion due to the stress is maximized.

The following steps are the same as the manufacturing steps from (c) shown in FIG. 8 as a conventional example, and the description is omitted here. In FIG. 1, the opening 4a
Although only two are formed, as shown in FIG. 2, actually, as many openings 4a as the number of grooves 1b to be formed are formed.
Is formed.

Accordingly, in this embodiment, the diaphragm 1a of the silicon wafer 1 is provided with a slit-shaped groove 1b.
Is formed so that a portion having a small film thickness is formed on the diaphragm 1a. Therefore, distortion due to stress is increased as compared with the related art, and output sensitivity can be improved.

In this embodiment, the groove 1b is formed by anisotropic etching using a KOH aqueous solution. However, the present invention is not limited to this. For example, RIE (Reactive Ion Etching) may be used. Groove 1 using
b may be formed. In this case, the opening 4a
Regardless of the size, the groove 1b having a desired depth can be formed.

Further, in the present embodiment, the case where the silicon wafer 1 having the (110) plane orientation is used as the silicon wafer 1, but the present invention is not limited to this. The silicon wafer 1 has the (100) plane orientation. The present invention can be applied to a case where a silicon wafer is used.

Embodiment 2 = FIG. 3 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to another embodiment of the present invention, and FIG. It is an approximate top view showing the state where it was seen. In the semiconductor pressure sensor according to the present embodiment, first, an ion implantation of impurities and an annealing process are performed on one main surface of a silicon wafer 1 having a thickness of about 300 μm and a plane orientation of (110), thereby forming a diaphragm 1a to be described later. A piezoresistive element 2 is formed, and an oxide film 3 and a nitride film 4 are formed on both surfaces of the silicon wafer 1 by a CVD method or the like. At this time, two piezoresistive elements 2 are formed at substantially the center of the diaphragm and two at the outer periphery, and a four-piezoresistive element 2 and a wiring 7 described later constitute a Wheatstone bridge structure.

Next, the openings 5a and 5b are formed by etching the oxide film 3 and the nitride film 4 formed on both sides of the silicon wafer 1 using a photoresist (not shown) patterned in a predetermined shape as a mask. Then, the photoresist is removed by plasma ashing or the like (FIG. 3A).

At this time, the opening 5a is formed in a groove 1b to be described later.
The opening 5b is formed on the formation location, and the size of the opening 5b is adjusted so that a later-described diaphragm 1a has a desired size.

Using the oxide film 3 and the nitride film 4 in which the openings 5a and 5b are formed as a mask, potassium hydroxide (K
OH) By performing anisotropic etching of the silicon wafer 1 using an alkaline etchant such as an aqueous solution,
A thin diaphragm 1a is formed, and a slit-like groove 1b is formed on the surface of the silicon wafer 1 on which the piezoresistive elements 2 are formed (FIG. 3B). At this time, the etching of the groove 1b is stopped when the entire etched surface of the silicon wafer 1 is formed with the (111) plane. Further, the groove 1b is arranged so as to be in line contrast with the center line of the diaphragm 1a, so that the distortion due to the stress is maximized.

The following steps are the same as the steps from (c) shown in FIG. 8 as a conventional example, and the description is omitted here. In FIG. 3, the opening 5a is 2
Although only one is formed, actually, as shown in FIG. 4, the number of openings 5a corresponding to the number of grooves 1b to be formed is formed.

Therefore, in this embodiment, the diaphragm 1a of the silicon wafer 1 is provided with the slit-shaped groove 1b.
Is formed so that a portion having a small film thickness is formed on the diaphragm 1a. Therefore, distortion due to stress is increased as compared with the related art, and output sensitivity can be improved.

In the present embodiment, the groove 1b is formed simultaneously with the anisotropic etching when the diaphragm 1a is formed.
Is formed, the strain due to stress can be increased and the output sensitivity can be improved with fewer steps than in the first embodiment.

In this embodiment, the case where the silicon wafer 1 has a plane orientation of (110) plane is used, but the present invention is not limited to this. The present invention can be applied to a case where a silicon wafer is used.

Embodiment 3 = FIG. 5 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to another embodiment of the present invention. A schematic plan view showing a state of the semiconductor pressure sensor according to the present embodiment viewed from the surface is the same as FIG. FIG. 5 according to the present embodiment.
Since the manufacturing process up to (b) is the same as the manufacturing process up to (b) shown in FIG. 8 as a conventional example, the description is omitted here, and the manufacturing process from FIG. The opening 5a is formed by etching the nitride film 4 and the oxide film 3 on the surface of the silicon wafer 1 on which the piezoresistive elements 2 are formed, using a photoresist (not shown) patterned in a predetermined shape as a mask. Then, the photoresist is removed. At this time, the opening 5a is formed on the location where the groove 1b is formed.

The oxide film 3 having the opening 5a formed therein
Then, etching is performed by RIE using the nitride film 4 as a mask until the trench 1b reaches a desired depth (FIG. 5).
(C)). At this time, by disposing the groove portion 1b so as to be in line contrast with the center line of the diaphragm 1a, distortion due to stress is maximized.

The following steps are the same as the steps from (c) shown in FIG. 8 as a conventional example, and the description is omitted here. In FIG. 5, the opening 5a is 2
Although only one is formed, actually, as shown in FIG. 4, the number of openings 5a corresponding to the number of grooves 1b to be formed is formed.

Therefore, in this embodiment, the diaphragm 1a of the silicon wafer 1 is provided with the slit-shaped groove 1b.
Is formed so that a portion having a small film thickness is formed on the diaphragm 1a. Therefore, distortion due to stress is increased as compared with the related art, and output sensitivity can be improved.

In the present embodiment, since the groove 1b is formed by RIE, the groove 1b having a desired depth can be formed regardless of the size of the opening 4a.

In the present embodiment, the case where the silicon wafer 1 has a (110) plane orientation is used as the silicon wafer 1. However, the present invention is not limited to this. The silicon wafer 1 has a (100) plane orientation. The present invention can be applied to a case where a silicon wafer is used.

Embodiment 4 = FIGS. 6A and 6B are schematic views showing a semiconductor pressure sensor according to another embodiment of the present invention. FIG. 6A is a schematic plan view showing a state viewed from above, and FIG. () Is a schematic sectional view taken along line XX 'of (a). Since the manufacturing process of the semiconductor pressure sensor according to the present embodiment is the same as the manufacturing process of the semiconductor pressure sensor shown in FIG. 3 as the second embodiment, only different points will be described. As shown in FIG. 6, the semiconductor pressure sensor according to the present embodiment has a configuration in which the interval between adjacent slit-shaped grooves 1b is reduced from substantially the center to the periphery of the diaphragm 1a.

In the present embodiment, the opening 5a in FIG. 3A is formed on the location where the groove 1b is formed in FIG. 6A.

Therefore, in this embodiment, the diaphragm 1a of the silicon wafer 1 is provided with the slit-shaped groove 1b.
Is formed so that a portion having a small film thickness is formed on the diaphragm 1a. Therefore, distortion due to stress is increased as compared with the related art, and output sensitivity can be improved.

Further, the distance between the adjacent slit-shaped grooves 1b is made narrower toward the periphery of the diaphragm 1a, so that the stress due to the stress at the periphery of the diaphragm 1a further increases, and conversely, the center of the diaphragm 1a is increased. Since the strain due to the stress is reduced in the portion, the sensitivity can be further improved.

Further, in the present embodiment, the case where the silicon wafer 1 having the (110) plane orientation is used has been described. However, the present invention is not limited to this. The silicon wafer 1 has the (100) plane orientation. The present invention can be applied to a case where a silicon wafer is used.

In this embodiment, the groove 1b is formed on the surface of the diaphragm 1a on which the piezoresistive element 2 is formed. However, the present invention is not limited to this, and the piezoresistive element 2 of the diaphragm 1a may be used. The same effect can be obtained even if it is formed on a surface side different from the formed surface.

In this embodiment, the distance between the adjacent grooves 1b is reduced from substantially the center to the periphery of the diaphragm 1a. However, the present invention is not limited to this. The groove 1b may be arranged so that the distortion caused by the stress in the diaphragm 1a increases and the distortion caused by the stress in the central portion of the diaphragm 1a decreases.

Embodiment 5 = FIGS. 7A and 7B are schematic views showing a semiconductor pressure sensor according to another embodiment of the present invention. FIG. 7A is a schematic plan view showing a state viewed from above, and FIG. () Is a schematic sectional view taken along line YY 'of (a). Since the manufacturing process of the semiconductor pressure sensor according to the present embodiment is the same as the manufacturing process of the semiconductor pressure sensor shown in FIG. 3 as the second embodiment, only different points will be described. As shown in FIG. 7, the semiconductor pressure sensor according to the present embodiment has a configuration in which the depth of the slit-like groove 1b is increased from substantially the center to the periphery of the diaphragm 1a.

In the present embodiment, the width of the opening 5a in FIG. 3A is increased toward the periphery of the diaphragm 1a to thereby increase the width of the diaphragm 1a.
From the substantially center to the periphery, the slit-shaped groove 1
b can be made deeper.

Therefore, in this embodiment, the diaphragm 1a of the silicon wafer 1 is provided with the slit-shaped groove 1b.
Is formed so that a portion having a small film thickness is formed on the diaphragm 1a. Therefore, distortion due to stress is increased as compared with the related art, and output sensitivity can be improved.

Further, the depth of the groove 1b is made deeper toward the periphery of the diaphragm 1a, so that the distortion due to the stress becomes larger at the periphery of the diaphragm 1a, and conversely, the stress at the center of the diaphragm 1a becomes larger. Since the distortion is reduced, the sensitivity can be further improved.

Further, in the present embodiment, the case where the silicon wafer 1 having the (110) plane is used as the silicon wafer 1 has been described. However, the present invention is not limited to this. The present invention can be applied to a case where a silicon wafer is used.

In the present embodiment, the groove 1b is formed on the surface of the diaphragm 1a on which the piezoresistive element 2 is formed. However, the present invention is not limited to this, and the piezoresistive element 2 of the diaphragm 1a may be used. The same effect can be obtained even if it is formed on a surface side different from the formed surface.

In this embodiment, the depth of the groove 1b is increased from the substantially center to the periphery of the diaphragm 1a. However, the present invention is not limited to this. The groove 1b may be formed so that the strain due to the stress increases and the strain at the center of the diaphragm 1a decreases.

[0052]

According to a first aspect of the present invention, there is provided a semiconductor pressure sensor having a semiconductor substrate having a diaphragm and a piezoresistive element formed on the diaphragm.
Since a plurality of slit-shaped grooves are formed on the diaphragm, a thin portion is formed on the diaphragm, which increases the distortion due to stress and improves the output sensitivity.
A semiconductor pressure sensor capable of improving sensitivity without increasing the chip size was provided.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, an interval between adjacent slit-shaped grooves is made narrower from substantially the center to the periphery of the diaphragm. The distortion due to the stress is further increased in the peripheral portion, and the distortion due to the stress is decreased in the central portion of the diaphragm, so that the sensitivity can be further improved.

According to a third aspect of the present invention, in the semiconductor pressure sensor according to the first or second aspect, the depth of the slit-shaped groove is made deeper as it goes from substantially the center to the periphery of the diaphragm. However, since the distortion due to the stress becomes larger at the periphery of the diaphragm, and the distortion due to the stress becomes smaller at the center of the diaphragm,
Further, the sensitivity can be improved.

According to a fourth aspect of the present invention, in the semiconductor pressure sensor according to the first to third aspects, the groove is formed on the surface of the diaphragm on which the piezoresistive element is formed.
The groove 1b can be formed at the same time as the diaphragm is formed, and the distortion due to stress can be increased to increase the output sensitivity without increasing the number of steps.

According to a fifth aspect of the present invention, in the semiconductor pressure sensor according to the first to fourth aspects, the groove is formed on a surface of the diaphragm different from the surface on which the piezoresistive element is formed. Since a thin portion is formed, distortion due to stress is increased and output sensitivity is improved.

According to a sixth aspect of the present invention, in the semiconductor pressure sensor according to the first to fifth aspects, the groove is formed by performing anisotropic etching using an alkaline etchant.

According to a seventh aspect of the present invention, in the semiconductor pressure sensor according to the first to fifth aspects, the groove is formed by RIE, so that the groove is formed irrespective of the size of the opening of the mask for etching. A groove having a desired depth can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to one embodiment of the present invention.

FIG. 2 is a schematic plan view showing a state of the semiconductor pressure sensor according to the embodiment as viewed from the back surface.

FIG. 3 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to another embodiment of the present invention.

FIG. 4 is a schematic plan view showing a state of the semiconductor pressure sensor according to the embodiment as viewed from the surface.

FIG. 5 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to another embodiment of the present invention.

FIGS. 6A and 6B are schematic views showing a semiconductor pressure sensor according to another embodiment of the present invention, wherein FIG. 6A is a schematic plan view showing a state viewed from above, and FIG. It is a schematic sectional drawing in X '.

FIGS. 7A and 7B are schematic views showing a semiconductor pressure sensor according to another embodiment of the present invention, wherein FIG. 7A is a schematic plan view showing a state viewed from above, and FIG. It is a schematic sectional drawing in Y '.

FIG. 8 is a schematic sectional view showing a manufacturing process of a semiconductor pressure sensor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 1a Diaphragm 1b Groove part 2 Piezoresistive element 3 Oxide film 4 Nitride film 4a Opening 5,5a, 5b Opening 6 Aluminum (Al) wiring 7 Glass pedestal 7a Pressure introducing hole

Claims (7)

[Claims] 1. A semiconductor pressure sensor comprising a semiconductor substrate having a diaphragm and a piezoresistive element formed on the diaphragm, wherein a plurality of slit-shaped grooves are formed on the diaphragm. Semiconductor pressure sensor. 2. The semiconductor pressure sensor according to claim 1, wherein an interval between the adjacent slit-shaped grooves is narrowed from a substantially center to a periphery of the diaphragm. 3. The semiconductor pressure sensor according to claim 1, wherein the depth of the slit-shaped groove portion is made deeper as it goes from substantially the center to the periphery of the diaphragm. 4. The semiconductor pressure sensor according to claim 1, wherein said groove is formed on a surface of said diaphragm on which said piezoresistive element is formed. 5. The semiconductor pressure sensor according to claim 1, wherein said groove is formed on a surface of said diaphragm that is different from a surface on which said piezoresistive element is formed. 6. The semiconductor pressure sensor according to claim 1, wherein the groove is formed by performing anisotropic etching using an alkaline etchant. 7. The semiconductor pressure sensor according to claim 1, wherein said groove is formed by RIE.