JP2008200757A - Mems element, and manufacture method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MEMS (Micro Electro Mechanical System) element, having less attachment between a substrate and a movable part, and also to provide a simple manufacture method of it. <P>SOLUTION: The movable part 11 of a MEMS structure 1 comprises: a large movable part 15; and an intermediate movable part 14. A distance d1 between the large movable part 15 and a silicon substrate 3 is longer than a distance d2 between the intermediate movable part 14 and the silicon substrate 3. The large movable part 15 includes a part where displacement quantity toward the silicon substrate 3 is the largest. Though the part where the displacement quantity toward the silicon substrate 3 is the largest has more chances of getting in contact with the silicon substrate, chances of the large movable part 15 to get in contact with the silicon substrate 3 are minimized as the distance between the large movable part 15 and the silicon substrate 3 is longer. The MEMS element 10 in which attachment to the silicon substrate 3 is less likely to occur is thus provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a MEMS element including a MEMS structure having a movable portion that is displaced in a substrate direction, and a method for manufacturing the same.

MEMS (Micro Electro Mechanical System) elements are used in acceleration sensors, video devices, and the like, and the demand for these elements is increasing.
The MEMS element is used for frequency control, switching, mechanical quantity detection, and the like by using the displacement amount of the movable part of the MEMS structure and the electrical variable linked to the displacement amount.
As a method for forming the movable portion, a method is widely used in which a sacrificial layer is formed on a substrate, a movable portion is formed on the sacrificial layer, and then the sacrificial layer is removed to separate the movable portion from the substrate.
Here, when a wet etching method is used to remove the sacrificial layer, pure water that is a substitute liquid for the etching solution enters between the movable portion and the substrate, and when the pure water is dried, the movable portion is The movable part may be fixed to the surface of the substrate by being pulled toward the substrate side.
A method is known in which a movable range restricting projection is formed on the surface of the movable part facing the substrate to prevent the movable part and the substrate surface from sticking to each other (see Patent Document 1).

JP-A-9-18021 (page 6, paragraph numbers [0035] to [0038], FIG. 2)

However, as a method of forming the movable range limiting projection on the surface of the movable portion facing the substrate, the concave portion is formed by etching the sacrificial layer, and then the movable portion is formed on the sacrifice layer, and the movable range is restricted following the concave portion. A method for forming a projection is used. Here, since the shape, height, and the like of the movable range limiting projection are determined by the accuracy of the sacrifice layer etching, high etching control is required. However, it is difficult to control etching regardless of wet or dry etching methods. Further, since the etching is partially performed, a mask and a resist are required, and the manufacturing process becomes long.
An object of the present invention is to provide a MEMS element with less adhesion between a substrate and a movable part and a simple manufacturing method thereof.

The MEMS element of the present invention is a MEMS element in which a movable part of a MEMS structure can be moved by removing a sacrificial layer formed by oxidizing a semiconductor substrate, and the MEMS structure includes a movable part and a movable part. A base portion fixed to the semiconductor substrate, and the movable portion is at an intermediate position between the maximum movable portion including a portion having a maximum amount of displacement in the semiconductor substrate direction, and the base portion and the maximum movable portion. An N-type impurity concentration in a region of the semiconductor substrate facing the maximum movable portion is higher than an N-type impurity concentration in a region of the semiconductor substrate facing the intermediate movable portion, If the distance between the maximum movable part and the semiconductor substrate is d1, and the distance between the intermediate movable part and the semiconductor substrate is d2, d1 and d2 have the following relationship.
d2 <d1

  According to this invention, the movable part of the MEMS structure has the maximum movable part and the intermediate movable part, and the distance d1 between the maximum movable part and the semiconductor substrate is compared with the distance d2 between the intermediate movable part and the semiconductor substrate. Long. The maximum movable portion includes a portion having a maximum amount of displacement in the semiconductor substrate direction. The portion with the largest amount of displacement in the direction of the semiconductor substrate has many opportunities to come into contact with the semiconductor substrate, but since the distance between the largest movable portion and the semiconductor substrate is long, the chance that the largest movable portion comes into contact with the semiconductor substrate is reduced. Therefore, a MEMS element that is less likely to adhere to the semiconductor substrate can be obtained.

  A method for manufacturing a MEMS device according to the present invention is a method for manufacturing a MEMS device comprising a MEMS structure having a base on a semiconductor substrate, wherein the MEMS structure is introduced by introducing an N-type impurity into the semiconductor substrate. The N-type impurity concentration of the region of the semiconductor substrate facing the maximum movable portion including the portion having the maximum displacement amount in the semiconductor substrate direction is opposed to the intermediate movable portion at an intermediate position between the base portion and the maximum movable portion. An impurity region forming step for increasing the N-type impurity concentration in the region of the semiconductor substrate, a sacrificial layer forming step for forming a sacrificial layer on the semiconductor substrate by thermal oxidation, and the MEMS structure on the sacrificial layer. And a step of removing the sacrificial layer by a wet etching method.

According to the present invention, the sacrificial layer formed by thermal oxidation in the region having a high N-type impurity concentration is formed thicker than the region having a low N-type impurity concentration by accelerated oxidation. Since the region having a high N-type impurity concentration is formed corresponding to the maximum movable portion, the distance between the maximum movable portion and the semiconductor substrate is longer than the distance between the intermediate movable portion and the semiconductor substrate. When the sacrificial layer is removed by the wet etching method, the sticking to the semiconductor substrate accompanying the drying of the etching solution or the cleaning solution is likely to occur at the maximum movable portion including the portion having the maximum displacement in the semiconductor substrate direction. Here, since the distance between the maximum movable part and the semiconductor substrate is long, the etching liquid or the cleaning liquid moves between the intermediate movable part and the semiconductor substrate due to surface tension and is dried. Therefore, a method for manufacturing a MEMS element that is less likely to adhere to the semiconductor substrate is obtained.
Note that the step of removing the sacrificial layer includes a step of drying the etching solution or the cleaning solution. The wet etching method may include a step of cleaning the etching solution.

Embodiments and modifications embodying the present invention will be described below with reference to the drawings.
In the drawings of each embodiment and the modified example, the same components are described with the same reference numerals.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing an embodiment of a MEMS device 10 according to the present invention. FIG. 1A is a schematic partial plan view of the MEMS element 10, and FIG. 1B is a schematic partial cross-sectional view taken along the line AA in FIG.

  1A and 1B, the MEMS element 10 includes a MEMS structure 1 and an impurity diffusion region 2. The MEMS element 10 is formed on a silicon substrate 3 that is a semiconductor substrate.

The MEMS structure 1 includes a movable part 11, a base part 12, and a fixed part 13.
The movable portion 11 includes an intermediate movable portion 14 at a position where the distance from the base portion 12 is short, and a maximum movable portion 15 at a position where the distance from the base portion 12 is long. The intermediate movable portion 14 and the maximum movable portion 15 are continuously formed with a step. The intermediate movable portion 14 and the maximum movable portion 15 have a substantially plate shape.
The movable portion 11 and the base portion 12 are also formed continuously with a step, and the base portion 12 is fixed to the silicon substrate 3 by a fixing portion 13. Therefore, the movable part 11, the base part 12, and the fixed part 13 form a cantilever structure.

  In the movable portion 11 having the cantilever structure, the displacement amount at the intermediate movable portion 14 close to the base portion 12 is small due to the rigidity of the movable portion 11, and the displacement amount increases as the distance from the base portion 12 increases. In the present embodiment, the amount of displacement in the direction of the silicon substrate 3 is maximized in the vicinity of the end 18 where the distance from the base 12 is maximized. The maximum movable portion 15 includes a portion having a maximum amount of displacement in the direction of the silicon substrate 3.

If the distance between the maximum movable portion 15 and the silicon substrate 3 is d1, and the distance between the intermediate movable portion 14 and the silicon substrate 3 is d2, d1 and d2 have the following relationship.
d2 <d1
The approximate dimensions of the movable portion 11 are, for example, a length of several tens of μm, a width of several μm, and a thickness of 0. It is about several μm. These values can be freely selected by design.

The impurity diffusion region 2 includes regions 21 and 23 having a high N-type impurity concentration, and a region 22 having a lower N-type impurity concentration than these regions. A region 21 having a high N-type impurity concentration is formed in the silicon substrate 3 facing the maximum movable portion 15. A region 22 having a low N-type impurity concentration is formed in the silicon substrate 3 facing the intermediate movable portion 14. The region 22 may not be implanted with N-type impurities or may be implanted with P-type impurities.
A region of the silicon substrate 3 facing the fixed portion 13 is a region 23 having a high N-type impurity concentration.
The impurity diffusion region 2 can be used as a drive electrode, a counter electrode, or the like as long as it has conductivity. For example, if a region having a high P-type impurity concentration is formed as the region 21 having a high N-type impurity concentration and the region 22 having a low N-type impurity concentration, each region can be used as an independent electrode.

In the present embodiment, the movable portion 11 and the base portion 12 are made of polysilicon containing impurities and have conductivity. The movable portion 11 and the base portion 12 are connected to other power sources, signal lines, elements, and the like (not shown) by wirings 16. Similar to the movable portion 11 and the base portion 12, the wiring 16 is integrally formed of polysilicon containing impurities. On the other hand, the fixing portion 13 is made of silicon oxide.
A region 21 having a high N-type impurity concentration and a region 22 having a low N-type impurity concentration (region having a high P-type impurity concentration) are formed to extend to other power sources, signal lines, elements, etc. not shown as wirings 222 and 211. When connected and used as a drive electrode or the like, it can be configured as an electrode facing the movable portion 11. In this case, the region 22 having a low N-type impurity concentration (region having a high P-type impurity concentration) can shorten the distance d2 that is the distance between the electrodes, and can constitute a counter electrode having a large capacity.

Below, the manufacturing method of the MEMS element 10 concerning this embodiment is demonstrated based on drawing.
FIG. 2 shows a flowchart of the method for manufacturing the MEMS element 10. FIG. 3 shows a schematic cross-sectional view in each step.

  In FIG. 2, the manufacturing method of the MEMS element 10 includes an impurity region forming step S1, a sacrificial layer forming step S2, a MEMS structure forming step S3, which is a step of forming the MEMS structure 1 on the sacrificial layer 20, and a wet etching method. The sacrificial layer removal process S4 which is the process of removing the sacrificial layer 20 by this is included.

Hereinafter, a method for manufacturing the MEMS element 10 will be described in detail with reference to FIG.
FIG. 3A shows the impurity region forming step S1.
In the impurity region forming step S1, phosphorus, which is an impurity, is introduced into the silicon substrate 3 by ion implantation and thermal diffusion to form regions 21 and 23 having a high N-type impurity concentration. The region 21 having a high N-type impurity concentration is formed in a region facing the maximum movable portion 15 of the MEMS element 10 shown in FIG. Also, a region 23 having a high N-type impurity concentration is formed in a region facing the fixing portion 13 shown in FIG. A high N-type impurity concentration is, for example, a concentration of 1 × 10 ¹⁹ or more.
Phosphorus may be implanted at a lower concentration in the region 22 of the silicon substrate 3 facing the intermediate movable portion 14 shown in FIG. 1 than in the region 21 having a higher N-type impurity concentration or not. The low N-type impurity concentration is, for example, a concentration of 1 × 10 ¹⁶ to 10 ¹⁷ .
The N-type impurity concentration in the region 21 of the silicon substrate 3 facing the maximum movable portion 15 may be formed higher than the N-type impurity concentration in the region 22 of the silicon substrate 3 facing the intermediate movable portion 14.
Further, boron or the like that is a P-type impurity may be implanted into the region 22 having a low N-type impurity concentration instead of the N-type impurity.
By increasing the impurity concentration of these regions 21, 22, and 23, it can be used as an electrode such as a drive electrode. In this case, the wirings 222 and 211 shown in FIG. 1 can be formed simultaneously.
By this step, the impurity diffusion region 2 is formed.

FIG. 3B shows a sacrificial layer forming step S2.
The sacrificial layer forming step S2 is performed by heating the silicon substrate 3 in an oxygen-rich atmosphere. In this embodiment, a part of the sacrificial layer 20 is used as the fixing portion 13 shown in FIG.
For example, heating is performed at 900 ° C. for 1 hour in an atmosphere having an oxygen concentration of 95% and a hydrogen concentration of 5%. The silicon substrate 3 is oxidized by heating, but thick silicon oxide is formed in the regions 21 and 23 having a high N-type impurity concentration by accelerated oxidation. In the region 22 having a low N-type impurity concentration, silicon oxide having a thickness of 100 nm is formed, whereas in the regions 21 and 23 having a high N-type impurity concentration, silicon oxide having a thickness of 150 nm to 200 nm is formed. Therefore, as shown in FIG. 3B, sacrificial layers 20 having different thicknesses are formed. The thickness of the sacrificial layer 20 can be changed by changing the concentration of the N-type impurity to be implanted in the impurity region forming step S1. The N-type impurity concentration is changed according to the target thickness.

FIG. 3C shows a MEMS structure etc. forming step S3.
In the MEMS structure etc. forming step S3, the movable portion 11, the base portion 12, and the wiring 16 shown in FIG. The movable part 11, the base part 12, and the wiring 16 are obtained by forming a polysilicon film by a low pressure CVD method. At this time, phosphorus is introduced to obtain conductivity.
The MEMS structure etc. forming step S3 can be performed by a well-known photolithography process.

FIG. 3D shows the sacrificial layer removal step S4.
In the sacrificial layer removal step S4, the sacrificial layer 20 is etched and removed by a wet etching method. At this time, the fixing portion 13 is left to be etched. After the etching, the etching solution is removed with pure water or the like.
The MEMS element 10 is obtained by a manufacturing method including the above manufacturing steps.

The operation of the MEMS element 10 will be described with reference to FIG.
In FIG. 1B, the state when the movable part 11 is displaced in the direction of the silicon substrate 3 is indicated by a dotted line. When the movable part 11 is formed with d1 = d2, the case where the movable part 11 is displaced is indicated by a two-dot chain line.
When the movable portion 11 is displaced when d2 <d1 in the present embodiment, the boundary 17 between the intermediate movable portion 14 and the maximum movable portion 15 or the end 18 of the maximum movable portion 15 comes into contact with the silicon substrate 3. Therefore, it becomes a contact at a point or a line.
On the other hand, when the movable portion 11 in the case of d1 = d2 is deformed, the tip 19 of the movable portion 11 contacts over a large area of the silicon substrate 3.

Hereinafter, effects of the present embodiment will be described.
(1) The movable part 11 of the MEMS structure 1 has a maximum movable part 15 and an intermediate movable part 14, and a distance d1 between the maximum movable part 15 and the silicon substrate 3 is determined between the intermediate movable part 14 and the silicon substrate 3. Long compared to the distance d2. The maximum movable portion 15 includes a portion having a maximum amount of displacement in the direction of the silicon substrate 3. The portion with the maximum displacement in the direction of the silicon substrate 3 has many opportunities to come into contact with the silicon substrate 3, but the distance d1 between the maximum movable portion 15 and the silicon substrate 3 is longer than d2, so that the maximum movable portion 15 is the silicon substrate. 3 can be reduced compared to the case of d1 = d2. Therefore, it is possible to obtain the MEMS element 10 that is not easily fixed to the silicon substrate 3.

  (2) The sacrificial layer 20 by thermal oxidation of the regions 21 and 23 having a high N-type impurity concentration is formed thicker than the region 22 having a low N-type impurity concentration by accelerated oxidation. Since the region 21 with a high N-type impurity concentration is formed corresponding to the maximum movable portion 15, the distance d1 between the maximum movable portion 15 and the silicon substrate 3 is compared with the distance d2 between the intermediate movable portion 14 and the silicon substrate 3. Can be long. When the sacrificial layer 20 is removed by the wet etching method, the adhesion to the silicon substrate 3 due to the drying of the etching solution or the cleaning solution is likely to occur at the maximum movable portion 15 including the portion where the displacement amount in the silicon substrate 3 direction is the maximum. Here, since the distance d1 between the maximum movable portion 15 and the silicon substrate 3 is long, the etching solution or the cleaning solution moves between the intermediate movable portion 14 and the silicon substrate 3 due to surface tension and is dried. Therefore, it is possible to obtain a method for manufacturing the MEMS element 10 that is less likely to adhere to the silicon substrate 3.

(Second Embodiment)
FIG. 4 is a schematic configuration diagram showing an embodiment of the MEMS element 30 according to the present invention. 4A is a schematic partial plan view of the MEMS element 30, and FIG. 4B is a schematic partial cross-sectional view taken along the line BB in FIG. 4A.

  4 (a) and 4 (b), the difference between this embodiment and the first embodiment is that the MEMS structure 1 is formed by integrating the fixing portion 13 and the base portion 12 in the first embodiment. It is a point. In addition, a region 23 having a high N-type impurity concentration is formed in a region other than the region of the silicon substrate 3 where the base 12 and the silicon substrate 3 are in contact.

Hereinafter, a method for manufacturing the MEMS element 30 will be described with reference to FIG.
FIG. 5A shows the impurity region forming step S1.
In the impurity region forming step S1, phosphorus, which is an impurity, is introduced into the silicon substrate 3 by ion implantation and thermal diffusion to form regions 21 and 23 having a high N-type impurity concentration and regions 22 having a low N-type impurity concentration. In the present embodiment, the region 23 having a high N-type impurity concentration is formed outside the region corresponding to the fixed portion 13. In FIG. 5, the fixing portion 13 is formed in a left region toward the paper surface. The type and concentration of impurities can be selected as in the first embodiment.
Furthermore, the difference from the first embodiment is that a mask 31 is formed in a region corresponding to the base 12. The mask 31 is formed by a well-known photolithography process.
A region 24 having a high N-type impurity concentration or a high P-type impurity concentration may be provided in a region facing the base portion 12. In this case, this region can be used as the wiring of the MEMS structure 1 having conductivity.

FIG. 5B shows a sacrificial layer forming step S2.
In the sacrificial layer forming step S2, as in the first embodiment, the sacrificial layer 20 is formed by heating the silicon substrate 3 in an oxygen-rich atmosphere.
In the present embodiment, since the mask 31 is present, the region corresponding to the base 12 is not oxidized. On the other hand, the region on the left side of the mask 31 with respect to the paper surface is oxidized.

FIG. 5C shows a mask removal process.
In the present embodiment, after removing the mask 31 formed in the impurity region forming step S1, a mask 33 is formed on the surface of the sacrificial layer 20 formed in the region 23 having a high N-type impurity concentration. After removing the mask 31, a hole 32 for exposing the silicon substrate 3 is formed in the sacrificial layer 20.

FIG. 5D shows a MEMS structure etc. forming step S3.
In the present embodiment, the movable portion 11, the base portion 12 (fixed portion 13) and the wiring 16 shown in FIG. 4A of the MEMS structure 1 shown in FIG. 4B are formed. The base portion 12 also serves as the fixing portion 13 in the first embodiment.
A polysilicon film is formed in the sacrificial layer 20 and the hole 32 by low pressure CVD.
By removing the mask 33 after forming the polysilicon film, the polysilicon film formed on the mask can also be removed.

FIG. 5E shows a sacrificial layer removal step S4.
In the sacrificial layer removal step S4, the sacrificial layer 20 is etched and removed by wet etching. The MEMS structure 1 is in contact with the silicon substrate 3 through the base 12.
The MEMS element 30 is obtained by a manufacturing method including the above manufacturing steps.
The operation of this embodiment is the same as that of the first embodiment shown in FIG.

Hereinafter, effects of the present embodiment will be described.
(3) In addition to the effects of the first embodiment, since the base portion 12 also serves as the fixing portion 13 in the first embodiment, the MEMS element 30 having a simpler structure and a simpler manufacturing method can be obtained.

(Third embodiment)
FIG. 6 is a schematic configuration diagram showing an embodiment of the MEMS element 40 according to the present invention. FIG. 6A is a schematic partial plan view of the MEMS element 40, and FIG. 6B is a schematic partial cross-sectional view taken along the line CC in FIG.
This embodiment has a double-supported beam structure in which two MEMS elements 30 in the second embodiment are coupled with the maximum movable portion 15 facing each other. As the manufacturing method, the same method as in the second embodiment can be used.

The operation of the MEMS element 40 will be described with reference to FIG.
In FIG. 6B, the state when the movable part 11 is displaced in the direction of the silicon substrate 3 is indicated by a dotted line. When the movable part 11 is formed with d1 = d2, the case where the movable part 11 is displaced is indicated by a two-dot chain line.
If the movable part 11 is displaced when d2 <d1 in the present embodiment, the boundary 17 between the intermediate movable part 14 and the maximum movable part 15 comes into contact with the silicon substrate 3. Therefore, it becomes a contact at a point or a line.
On the other hand, when the movable portion 11 in the case of d1 = d2 is displaced, the central portion 41 of the movable portion 11 contacts over a large area of the silicon substrate 3.

Hereinafter, effects of the present embodiment will be described.
(4) The same effects as those of the first and second embodiments can be obtained also in the MEMS element 40 having the double-supported beam structure.

(Modification)
FIG. 7 is a schematic configuration diagram showing an embodiment of the MEMS element 50 according to the present invention. FIG. 7A is a schematic partial plan view of the MEMS element 50, and FIG. 7B is a schematic partial cross-sectional view taken along the line DD in FIG.
In the modification, the shape of the region 21 having a high N-type impurity concentration and the region 22 having a low N-type impurity concentration in the second embodiment are different in plan view. In a plan view, the region 22 having a low N-type impurity concentration has a shape protruding in a tongue shape from the region 21 having a high N-type impurity concentration.
According to the method for manufacturing the MEMS element 50 of the present invention, the shape of the sacrificial layer 20 formed by thermal oxidation is reflected on the surface of the movable part 11 of the MEMS structure 1 facing the silicon substrate 3. The step shape of the surface facing the silicon substrate 3 can be changed without any special process.

It should be noted that the present invention is not limited to the above-described embodiments and modifications, and includes modifications and improvements as long as the object of the present invention can be achieved.
For example, a MEMS layer may be formed by forming a silicon layer on an insulator substrate as a substrate and forming regions 21, 22, and 23 as impurity diffusion regions 2 on the silicon layer.

(A) is a schematic fragmentary top view of the MEMS element concerning 1st Embodiment of this invention, (b) is a schematic fragmentary sectional view which follows the AA disconnection of the figure (a). The flowchart figure which shows the manufacturing method of the MEMS element concerning 1st Embodiment of this invention. The schematic sectional drawing in each process of the manufacturing method of the MEMS element concerning embodiment of this invention. (A) is a schematic fragmentary top view of the MEMS element concerning 2nd Embodiment of this invention, (b) is a schematic fragmentary sectional view which follows the BB disconnection of the figure (a). The schematic sectional drawing in each process of the manufacturing method of the MEMS element concerning 2nd Embodiment of this invention. (A) is a schematic fragmentary top view of the MEMS element concerning 3rd Embodiment of this invention, (b) is a schematic fragmentary sectional view in alignment with the CC disconnection of the figure (a). (A) is a schematic fragmentary top view of the MEMS element concerning the modification of this invention, (b) is a schematic fragmentary sectional view which follows the DD disconnection of the figure (a).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... MEMS structure, 3 ... Silicon substrate as a semiconductor substrate 10, 30, 40, 50 ... MEMS element, 11 ... Movable part, 12 ... Base part, 14 ... Intermediate movable part, 15 ... Maximum movable part, 18 ... Displacement An edge having the maximum amount, 20 ... a sacrificial layer, 21 ... a region with a high N-type impurity concentration, 22 ... a region with a low N-type impurity concentration.

Claims (2)

A MEMS element in which a movable part of a MEMS structure is movable by removing a sacrificial layer formed by oxidizing a semiconductor substrate,
The MEMS structure has the movable part and a base fixed to the semiconductor substrate,
The movable portion includes a maximum movable portion including a portion having a maximum amount of displacement in the semiconductor substrate direction,
An intermediate movable part at an intermediate position between the base and the maximum movable part;
The N-type impurity concentration in the region of the semiconductor substrate facing the maximum movable portion is higher than the N-type impurity concentration in the region of the semiconductor substrate facing the intermediate movable portion,
The distance between the maximum movable part and the semiconductor substrate is d1,
When the distance between the intermediate movable portion and the semiconductor substrate is d2,
d1 and d2 have the following relationship: d2 <d1
The MEMS element characterized by the above-mentioned. A method for manufacturing a MEMS device comprising a MEMS structure having a base on a semiconductor substrate,
By introducing N-type impurities into the semiconductor substrate,
An N-type impurity concentration in a region of the semiconductor substrate facing a maximum movable portion including a portion having a maximum amount of displacement in the semiconductor substrate direction of the MEMS structure,
An impurity region forming step for increasing the N-type impurity concentration in the region of the semiconductor substrate facing the intermediate movable portion at an intermediate position between the base and the maximum movable portion;
A sacrificial layer forming step of forming a sacrificial layer on the semiconductor substrate by thermal oxidation;
Forming the MEMS structure on the sacrificial layer;
And a step of removing the sacrificial layer by a wet etching method.

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