JPH09260745A - Micro machine and method of manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro machine of which movable part is hard to be damaged from treatment with chemicals or gases and by use with repeated strain by external stress, and operates stable for long period of time in the micro machine that comprises the small movable part, a part of which is joined to a fixed part. SOLUTION: A single crystal Si 317 (B) is formed with patterning by etching an SOI substrate (A) that is formed by laminating an oxide film 302, an Si nitride film 303 and a flattened Si oxide film 304 in sequence on an Si substrate 300 with a recessed part on the surface, and a single crystal Si plate 305 is joined on the substrate 300. The micro machine of (C) is formed by etching the Si oxide film 304 with the etching liquid that includes hydrofluoric acid. The nitride film 303 works as a stopper for the etching process. A movable part 311 does not stick to the fixed part, when it is deformed due to existence of the protrusion 307 of the fixed part. Both the movable part 311 and the substrate 300 of the fixed part are tough and hard to be damaged by such deformation, since they are made of single crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromachine having a microstructure and a method for manufacturing the same, and more specifically, even if a movable microstructure contacts an opposing member, breakage or sticking hardly occurs. The present invention relates to a micromachine and its manufacturing method.

[0002]

2. Description of the Related Art A conventional micromachine and its manufacturing method are
This will be described with reference to FIG. This figure is based on the literature (Ther
esa A. Core, W.C. K. Tsang, Steve
enJ. Sherman, “Fabrication
Technology for an Integra
ted Surface-Micromachined
"Sensor", Solid State Tech
noology, October 1993, 39-4
7) is simplified and only the part according to the present invention is described.

FIG. 11 shows a conventional micromachine and its manufacturing method.
As shown in (A), first, on the main surface of the silicon substrate 100, an oxide film 101, LP-CVD (low pressure-) is formed by thermal oxidation.
Silicon nitride film 102, CVD by chemical vapor deposition)
Then, the LTO (low temperature oxide) film 103 is sequentially formed in layers.

After this, as shown in FIG. 11B, the LTO
The dimples 104 are formed by etching so as not to penetrate the film 103, and the openings 105 for the anchors are formed by etching the LTO film 103, the silicon nitride film 102 and the oxide film 101.

Then, as shown in FIG. 11 (C), LP-
A polysilicon film 106 is formed by CVD and patterned by photolithography and etching.

Then, as shown in FIG.
The film 103 is sacrificial-etched with hydrofluoric acid or the like to obtain a free-standing microstructure 107.

The microstructure 107 has a movable portion 108.
And the silicon substrate 100 as a supporting base
And an anchor portion 109 fixed to the anchor. LTO
The movable part 1 corresponding to the position of the dimple 104 of the film 103
The bumps 110 on the bottom surface of 08 and the movable portion 10
Dimples 111 are formed on the surface of No. 8. The bump 110 has an effect of reducing the contact area when the bottom surface of the movable portion 108 comes into contact with the surface of the silicon substrate 100, thereby reducing the possibility of attachment.
The silicon nitride film 102 acts as an etching stopper when the LTO film 103 is sacrificial-etched, but reduces the frictional force when the bottom surface of the movable portion 108 rubs against the surface of the silicon substrate 100, and reduces wear. , And has the effect of reducing the possibility that the bottom surface of the movable portion 108 contacts and adheres to the surface of the silicon substrate 100.

Now, the case where various external forces such as vibration and drop impact act on the thus obtained micromachine will be described with reference to FIG.

As shown in FIG. 12 (A), when an accelerating motion is made in the downward direction in the figure, the movable portion 108 is bent downward.

As shown in FIG. 12 (B), when the movable part 108 falls and collides with the lower part of the figure, the movable part 108 has a silicon substrate 100.
The movable part 108 is bent downward and is convex.

As shown in FIG. 12 (C), when an acceleration motion is performed in the upward direction in the figure, the movable portion 108 is subjected to upward bending.

As shown in FIG. 12 (D), when the movable portion 108 falls and collides with the upper side in the figure, the movable portion 108 is struck on the back surface of the cover 202, and the movable portion 108 is subjected to upward convex bending.

As shown in FIGS. 12 (A) and 12 (B), when the movable portion 108 is bent downwardly, it is pulled to the root 200 of the bump 110, which is marked with a circle in FIG. This is undesirable because stress tends to concentrate and tend to break from here. Further, when the movable part 108 is subjected to upward convex bending as in the case of FIGS. 12C and 12D, the tensile stress concentrates on the bottom 201 of the dimple 111 marked with a circle in the figure. However, it has a tendency to be destroyed from here, which is not desirable.

[0014]

However, in such a conventional example, when the bottom surface of the movable portion 108 contacts the surface of the silicon substrate 100, the contact area is reduced,
Therefore, since the bump 110 that acts to reduce the possibility of adhesion is provided in the movable portion 108 and the manufacturing method thereof, a structure that concentrates stress in the movable portion 108 that is bent by an external force is also created. There was a problem that it would come out.

Further, in this conventional example, the structure forming the movable portion is formed of polysilicon, and the molecular structure such as the infinite number of grain boundaries and dislocations which the material called polycrystalline essentially has external force. It is a structure in which stress is concentrated when applied, and has a tendency of brittle fracture from here. Furthermore, grain boundaries also have peculiar phenomena such as grain boundary erosion or grain boundary cracking, which increases the tendency of brittle fracture.

Further, since polysilicon has a strong compressive stress, it is difficult to control the stress, and therefore the film formation rate is slow and it is difficult to obtain a thick structure.

Further, it is difficult to stably form, for example, a piezoresistor, which is an element for detecting stress, by using polysilicon. Therefore, the displacement amount of the movable portion of the micromachine has to rely on a low sensitivity electrostatic type. I don't get it. In addition, the performance of a semiconductor element formed of polysilicon is significantly inferior to that of a semiconductor element formed of single crystal silicon, such as a large variation in characteristics, a low withstand voltage, and a large reverse saturation current. In addition, it is necessary to form the substrate on a single crystal silicon substrate which is a support substrate for an external region of the micromachine.

The present invention has been made in view of the above conventional problems, and in a micromachine having a movable portion and a fixed portion facing the movable portion, the movable portion adheres when the movable portion contacts the fixed portion. Reduced tendency, reduced tendency to break when moving parts undergo bending, and escape from phenomena such as intergranular corrosion and intergranular cracking when moving parts are treated with chemicals or gas Another object of the present invention is to provide a micromachine and a manufacturing method thereof.

[0019]

To achieve the above object, the present invention provides a micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon and the movable portion is The fixed portion is provided with a convex portion that reduces a contact area when the fixed portion is contacted.

A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and the convex portion reduces the contact area when the movable portion contacts the fixed portion. In the method for manufacturing a micromachine in which is provided in the fixed portion, the method is formed including the following steps.

1) A so-called SOI substrate composed of a supporting substrate, a buried insulating film and a single crystal silicon layer, wherein the interface between the SOI layer and the buried insulating film is flat, and the buried insulating film and the support are supported. A step of forming an SOI substrate having a convex portion at an interface with the substrate.

2) A step of etching the SOI layer of the SOI substrate to form an opening reaching the buried insulating film.

3) A step of etching the buried insulating film using the opening as an etching hole to obtain a free-standing structure made of a single crystal silicon layer.

A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and a convex portion for reducing a contact area when the movable portion contacts the fixed portion is provided. In the method for manufacturing the micromachine provided in the fixed part, the micromachine is formed including the following steps.

1) A step of preparing a support substrate and a single crystal silicon substrate, and forming a spacer on the main surface of either the support substrate or the single crystal silicon substrate.

2) A step of forming a convex portion on the main surface of the supporting substrate.

3) A step of joining the supporting substrate and the single crystal silicon substrate through a spacer to form a cavity.

4) A step of thinning a single crystal silicon substrate to obtain a single crystal silicon layer.

5) A step of etching the single crystal silicon layer to form an opening reaching the cavity to obtain a self-standing structure made of the single crystal silicon layer.

A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and a convex portion for reducing a contact area when the movable portion contacts the fixed portion is provided. The method for manufacturing the micromachine provided in the fixed part includes the following steps.

1) SO of a so-called SOI substrate composed of a supporting substrate, a buried insulating film and a single crystal silicon layer
A step of performing etching through the I layer to form an opening reaching the buried insulating film.

2) A step of etching the buried insulating film using the opening as an etching hole to obtain a free-standing structure made of a single crystal silicon layer.

3) A step of subjecting the region of the supporting substrate where the buried insulating film is etched to an electrochemical treatment so that the portion to be treated by the electrochemical treatment is not flat.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a micromachine and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1A, a recess 301 is formed on the main surface of the first silicon substrate 300 by a trench etching method.

Thereafter, as shown in FIG. 1B), an oxide film 302 is formed on the above structure by thermal oxidation, and a silicon nitride film 303 is formed by LP-CVD (low pressure chemical vapor deposition).
To form a film.

Next, as shown in FIG. 1C), an oxide film 304 is formed on the main surface of the structure by a CVD (chemical vapor deposition) method, and the surface is flattened by a polishing method. .

Then, as shown in FIG. 1D), a second silicon substrate is bonded to the main surface of the structure, and the second silicon substrate is thinned by a polishing method to obtain the single crystal silicon layer 3
05 is obtained.

Through the above steps, the oxide film 304 is used as a buried oxide film, the first silicon substrate 300 is used as a support substrate,
A so-called SOI in which the thinned single crystal silicon layer 305 is used as an SOI (silicon on insulator) layer
A substrate 306 is formed. Oxide film 30 which is a buried oxide film
4 and the interface 3 with the single crystal silicon layer 305 which is the SOI layer
Reference numeral 09 denotes a flat surface having no unevenness, and an interface 310 between the oxide film 304 which is a buried oxide film and the supporting substrate made of the first silicon substrate 300 has a convex portion 307 and a concave portion 30.
8

FIG. 2A) shows the structure of the main surface of the SOI substrate 306. Rewriting the configuration, 300 is the first silicon substrate, 302 is an oxide film, 303 is a silicon nitride film, 3
04 is a buried oxide film, 305 is a single crystal silicon layer, 310
Is an interface between the oxide film 304 which is a buried oxide film and the first silicon substrate 300 which is a supporting substrate, 308 is a concave portion of the interface 310, and 307 is a convex portion of the interface 310.

As shown in FIG. 2B), etching is performed through the single crystal silicon layer 305 to form an oxide film 304.
Forming an opening 316 reaching

As shown in FIG. 2C), the oxide film 304 is etched through the opening 316 with an etching solution containing hydrofluoric acid to obtain a freestanding microstructure 340 made of single crystal silicon. Reference numeral 311 denotes a movable portion, and reference numeral 312 denotes an anchor portion for fixing the movable portion 311 to the silicon substrate 300 as a support base.

Through the above steps, in a micromachine having a movable portion and a fixed portion facing the movable portion, the movable portion is made of single crystal silicon, and the contact area when the movable portion contacts the fixed portion can be reduced. A micromachine characterized in that the convex portion is provided on the fixed portion can be obtained.

In the microstructure 340 made of single crystal silicon, whether it is a movable part or an anchor depends on
It depends on the pattern of the openings 316 in the above process drawing 2B). FIG. 2D) shows a plan view of an example pattern. Shown is the patterned single crystal silicon layer 317 of FIG. 2B). 313 is a large pattern portion, for example, 2
It is assumed that it is 00 μm square, 314 and 319 are line pattern parts, for example, 10 μm in width, and 315 is a worm-eaten pattern part, for example, 200 μm square, and innumerable holes 318 of 10 μm square are opened in 20 μm pitch. The thickness of oxide film 304 is 1 μm.

The above structure is immersed in an etching solution containing hydrofluoric acid, and is subjected to etching treatment for a time corresponding to etching the oxide film 304 by 10 μm. Then, using the patterned single crystal silicon layer 317 as a mask, the oxide film 304 is isotropically removed by etching, and the amount of under-etching that proceeds under the single crystal silicon layer 317 is 10 μm. At this time, the oxide film immediately below the large pattern portion 313 is under-etched by 10 μm before, after, right and left, and remains in a 180 μm square size. Therefore, the large pattern portion 313 becomes an anchor portion 312 connected to the support substrate by the remaining oxide film 304.

The oxide film 304 immediately below the line pattern portions 314 and 319 is under-etched by 10 μm each before and after, and the under-etching overlaps and no longer remains. Floats in the air. In FIG. 2, the ends of the line pattern portions 314 and 319 are connected to the anchor portion 312,
This results in a self-supporting structure. In this case, if there is no connection to the anchor portion, so-called lift-off is performed. In addition, the oxide film 304 directly below the worm-eating pattern portion 315 is not only under-etched by 10 μm in front, rear, left-right directions, but also isotropically under-etched from the innumerable holes 318, and these innumerable under-etches are formed.
The etching overlaps and no longer remains, and the worm-eaten pattern portion 315 floats in the air. In FIG. 2, it is connected to the anchor part 312 via the line pattern part 314, and becomes a self-standing structure. Therefore, FIG.
2D) is an LL sectional view and an MM sectional view of D).
A sectional view taken along line N-N in FIG. 2D) is shown in FIG. 2E).

In the micromachine, a thin portion such as the line pattern portion 314 is designed as a beam or a spring, and a large floating portion such as the worm-eating pattern portion 315 is designed as a weight.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 3A), first, an oxide film 404 is formed on the main surface of the first single crystal silicon substrate 400 by the CVD method, and the oxide film 404 is formed on the main surface of the oxide film 404.
A recess 401 that does not penetrate through is formed with an etching solution containing hydrofluoric acid.

Next, in FIG. 3B), L is added to the structure.
The silicon nitride film 403 is formed by the P-CVD method, the polycrystalline silicon film 402 is formed by the CVD method, and the main surface of the polycrystalline silicon film 402 is planarized by the polishing method.

Thereafter, in FIG. 3C), the second single crystal silicon substrate 420 is bonded to the main surface of the structure, and the single crystal silicon substrate 400 is thinned by a polishing method to obtain a single crystal silicon layer 405.

Through the above steps, the oxide film 404 is used as a buried oxide film, the second single crystal silicon substrate 420 is used as a supporting substrate, and the first single crystal silicon substrate 400 is thinned to obtain a single crystal silicon layer 405. Is an SOI (silicon on insulator) layer, so-called SOI substrate 40
6 are formed.

An interface 409 between the oxide film 404 which is a buried oxide film and the single crystal silicon layer 405 which is an SOI layer is composed of a flat surface having no unevenness, and the oxide film 304 which is a buried oxide film and the An interface 410 with the supporting substrate formed of the second single crystal silicon substrate 420 has a convex portion 407 and a concave portion 408.

FIG. 4A) shows the structure of the main surface of the SOI substrate 406. When the structure is re-described, 400 is a second single crystal silicon substrate which is a supporting substrate, 402 is a polycrystalline silicon film, 403 is a silicon nitride film, 404 is a buried oxide film, 4
Reference numeral 05 is a single crystal silicon layer, 410 is an interface between the oxide film 304 that is a buried oxide film and the second single crystal silicon substrate 420 that is a supporting substrate, 408 is a concave portion of the interface 410, and 407 is a convex portion of the interface 410. .

In FIG. 4B), the single crystal silicon layer 4 is formed.
Etching is performed through 05 to form an opening 416 reaching the oxide film 404.

In FIG. 4C), from the opening 416,
The oxide film 404 is etched with an etching solution containing hydrofluoric acid, and the microstructure 4 is made of single crystal silicon that is free-standing.
Get 40. 411 is a movable part, and 412 is a movable part 4.
11 is an anchor portion for fixing 11 to a single crystal silicon substrate 420 which is a supporting base.

Microstructure 440 made of single crystal silicon
In the same manner as in the first embodiment, whether to be the movable portion or the anchor depends on the pattern of the opening 416 in the above-mentioned process drawing 4B).

By the manufacturing method including the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, as in the first embodiment, the movable portion is made of single crystal silicon and is movable. It is possible to obtain a micromachine characterized in that the fixing portion is provided with a convex portion that reduces the contact area when the portion contacts the fixing portion.

Further, FIG. 4D) is obtained when an oxide film 421 is formed on the main surface of the polycrystalline silicon film 402 flattened in FIG. 3B) by a CVD method and the same steps are performed thereafter. It is a structure.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 5A), an oxide film 501 is formed on the main surface of the first single crystal silicon substrate 500 by a thermal oxidation method.
Is formed and patterned with an etching solution containing hydrofluoric acid.

CVD is applied to the structure as shown in FIG. 5B).
The oxide film 504 is formed by the above method, and the silicon nitride film 503 is formed by the CVD method.

As shown in FIG. 5C), CV was added to the above structure.
The polycrystalline silicon film 502 is formed by the method D, and the main surface of the polycrystalline silicon film 502 is flattened by the polishing method. As shown in FIG. 5D), a second single crystal silicon substrate 520 is bonded to the main surface of the structure, and the single crystal silicon substrate 500 is thinned by a polishing method to obtain a single crystal silicon layer 505.

Through the above steps, the oxide films 501 and 504
As a buried oxide film, the second single crystal silicon substrate 520 as a support substrate, the first single crystal silicon substrate 500 is thinned, and the obtained single crystal silicon layer 505 is SOI (silicon on insulator). Layer, so-called SO
The I substrate 506 is formed. Oxide film 5 which is a buried oxide film
01, 504 and a single crystal silicon layer 505 which is an SOI layer
The interface 509 with and is composed of a flat surface without unevenness,
Interface 510 between oxide films 501 and 504, which are buried oxide films, and a supporting substrate made of second single crystal silicon substrate 520.
Has a convex portion 507 and a concave portion 508.

FIG. 6A) shows the structure of the main surface of the SOI substrate 506. Rewriting the configuration, 520 is a second single crystal silicon substrate which is a supporting substrate, 502 is a polycrystalline silicon film, 503 is a silicon nitride film, 501 and 504 are buried oxide films, 505 is a single crystal silicon layer, 510. Is an oxide film 504 which is a buried oxide film and a second single crystal silicon substrate 520.
An interface with the support substrate, 508 is a concave portion of the interface 510, and 507 is a convex portion of the interface 510.

In FIG. 6B), the single crystal silicon layer 5 is formed.
Etching through the oxide film 501, 5
An opening 516 reaching 04 is formed.

In FIG. 6C), through the opening 516,
The oxide film 504 is etched with an etching solution containing hydrofluoric acid, and the microstructure 54 made of single crystal silicon that is free-standing.
Get 0. 511 is a movable part, and 512 is a movable part 51.
1 is an anchor portion for fixing 1 to a single crystal silicon substrate 520 which is a supporting base.

Microstructure 540 made of single crystal silicon
In the same manner as in the first embodiment, depending on the pattern of the opening 516 in the above-mentioned process drawing 6B), whether it becomes a movable part or an anchor.

By the manufacturing method including the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, as in the first embodiment, the movable portion is made of single crystal silicon and is movable. It is possible to obtain a micromachine characterized in that the fixing portion is provided with a convex portion that reduces the contact area when the portion contacts the fixing portion.

Further, FIG. 6D) is obtained when an oxide film 530 is formed on the main surface of the polycrystalline silicon film 502 which is flattened in FIG. 5C) by a CVD method and the same steps are performed thereafter. It is a structure.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 7A), first, a concave portion 601 is patterned on the main surface of the single crystal silicon substrate 600, and an oxide film 602 is formed by LP-CVD by a thermal oxidation method.
The silicon nitride film 603 is sequentially formed by the above method.

Then, in FIG. 7B),
The oxide film 604 is formed by the CVD method, and the oxide film 60 is formed.
The main surface of No. 4 is flattened by a polishing method, and the opening 630 reaching the single crystal silicon substrate 600 and the silicon nitride film 60 are formed.
An opening 631 reaching 3 is formed.

Then, in FIG. 7C), a polycrystalline silicon film is formed on the main surface of the structure by a CVD method,
A single crystal silicon layer 605 is obtained by lateral crystal growth of the polycrystalline silicon film by laser scanning using the single crystal silicon substrate 600 of the opening 630 as a seed.

Through the above steps, the oxide film 604 is used as a buried oxide film, the single crystal silicon substrate 600 is used as a supporting substrate,
A so-called SOI substrate 606 is formed in which the single crystal silicon layer 605 obtained by lateral crystal growth of a polycrystalline silicon film is used as an SOI (silicon on insulator) layer. An interface 609 between the oxide film 604 which is a buried oxide film and the single crystal silicon layer 605 which is an SOI layer is composed of a flat surface without unevenness, and the oxide film 60 which is a buried oxide film.
An interface 610 between the No. 4 and the supporting substrate made of the single crystal silicon substrate 420 has a convex portion 607 and a concave portion 608.

In FIG. 8A), the SOI substrate 606 is formed.
The structure of the main surface of FIG. When the structure is re-described, 600 is a single crystal silicon substrate which is a supporting substrate, 602 is an oxide film, and 60
3 is a silicon nitride film, 604 is a buried oxide film, 605 is a single crystal silicon layer, and 610 is an oxide film 60 which is a buried oxide film.
4 is an interface between the support substrate composed of the single crystal silicon substrate 600 and the substrate 4, 608 is a concave portion of the interface 610, and 607 is a convex portion of the interface 610.

After that, etching is performed through the single crystal silicon layer 605 in FIG.
An opening 616 reaching 04 is formed.

Then, in FIG. 8C), the opening 61 is formed.
6, the oxide film 604 is etched with an etching solution containing hydrofluoric acid to obtain a freestanding microstructure 640 made of single crystal silicon. Reference numeral 611 is a movable portion, and 612 is an anchor portion for fixing the movable portion 611 to the single crystal silicon substrate 600 which is a supporting base.

Microstructure 640 made of single crystal silicon
In the same manner as in the first embodiment, depending on the pattern of the opening 616 in the above-mentioned process drawing 8B), whether it becomes a movable part or an anchor.

By the manufacturing method including the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, as in the first embodiment, the movable portion is made of single crystal silicon and is movable. It is possible to obtain a micromachine characterized in that the fixing portion is provided with a convex portion that reduces the contact area when the portion contacts the fixing portion.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 9A), first, the single crystal silicon layer 705 is formed on the main surface of the high impurity concentration single crystal silicon substrate 700 by the epitaxial growth method, and the single crystal silicon layer 705 is not penetrated. Is etched to form the recess 730. This allows
The non-etched area is relatively protruded and the convex portion 73
It becomes 1.

Next, as shown in FIG. 9B), a recess 708 is formed in the main surface of the glass substrate 732 by etching. As a result, a region that is not etched relatively protrudes to become a convex portion 707.

Thereafter, as shown in FIG. 9C), FIG. 9A)
9B) and the main surface of the structure of FIG. 9B) are joined, and hydrofluoric acid:
Only the single crystal silicon substrate 700 having a high impurity concentration is etched by using a selective etching solution having a composition of nitric acid: acetic acid = 1: 3: 8 and selectively dissolving only a high impurity concentration of silicon. This allows the structure of FIG. 9A) and the structure of FIG.
The bonding of the main surfaces of the structure of B) is performed via the convex portion 731, and thus the cavity 733 is formed.

Then, in FIG. 9D), the single crystal silicon layer 7 of the above structure is formed by the dry etching technique.
A microstructure 7 formed of free-standing single crystal silicon which forms an opening 716 that penetrates 05 to reach the cavity 733.
Get 40. 711 is a movable part, and 712 is a movable part 7.
11 is an anchor portion for fixing 11 to the glass substrate 732 which is a supporting base.

By the manufacturing method including the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, as in the first embodiment, the movable portion is made of single crystal silicon and is movable. It is possible to obtain a micromachine characterized in that the fixing portion is provided with a convex portion that reduces the contact area when the portion contacts the fixing portion.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 10A), a standard SOI
2 shows the structure of the main surface of the substrate. To explain the configuration, reference numeral 805 denotes a single crystal silicon layer as an SOI layer, 804 a buried oxide film as a buried insulating film, and 800 a silicon substrate as a support substrate.

In FIG. 10B), etching is performed through the single crystal silicon layer 805 to form an oxide film 804.
Is formed.

In FIG. 10C), the oxide film 804 is etched through the opening 816 with an etching solution containing hydrofluoric acid to obtain a microstructure 840 made of free-standing single crystal silicon. Reference numeral 811 denotes a movable portion, and 812 denotes an anchor portion for fixing the movable portion 811 to a silicon substrate 800 as a support base.

In FIG. 10D), the above structure is immersed in an etching solution containing hydrofluoric acid and electrolytically etched while applying a voltage to the silicon substrate 800 to form a porous silicon layer 830. Porous silicon layer 830
Are self-aligned only in the region of the silicon substrate 800 where the buried oxide film 804 is removed. The microstructure 840 is not electrically connected to the silicon substrate 800 and is not subjected to electrolytic etching, so that no porous silicon layer is formed.

Through the above steps, in a micromachine having a movable portion and a fixed portion facing the movable portion, the movable portion is made of single crystal silicon, and the contact area when the movable portion contacts the fixed portion can be reduced. A micromachine characterized in that the convex portion is provided on the fixed portion can be obtained.

Similarly, the structure of FIG.
As shown in E), the plating layer 8 is immersed in an electrolytic plating solution and electrolytically plated while applying a voltage to the silicon substrate 800.
31 may be formed. Plating layer 831 is formed in a self-aligned manner only in the region of silicon substrate 800 from which buried oxide film 804 has been removed. The microstructure 840 is not electrically connected to the silicon substrate 800 and is not subjected to electrolytic plating, so that no plating layer is formed.

In the above description of the first to sixth embodiments, specific examples have been used for explanation, but the present invention is not limited to these words and drawings. An example will be described below.

For example, in the first, second, third and fourth embodiments, the silicon nitride films 303, 403, 50 are respectively formed.
Although 3 and 603 have been described as an example, the present invention is not limited to this, and other members may be used or may be omitted in some cases. Further, although LP-CVD has been described as an example of the method for forming the silicon nitride films 303, 403, and 503, the method is not limited to this, and other methods such as plasma-CVD or direct nitriding of silicon may be used. .

In the first and fourth embodiments, the oxide films 302 and 602 are provided as stress buffer films for the silicon nitride films 303 and 603 formed by LP-CVD, respectively. It may be omitted depending on the situation.

In the first, second, third and fifth embodiments, direct bonding of two substrates has been described as an example, but the invention is not limited to this and eutectic alloy bonding is used. Alternatively, another joining method such as anodic joining may be used.

Although the polycrystalline silicon films 402 and 502 have been described as the intermediate layers for bonding to the supporting substrate in each of the second and third embodiments, the present invention is not limited to this and is not limited thereto. The crystalline silicon films 402 and 502 may be used as the lower electrode facing the movable part. At this time, as shown in FIGS. 4D) and 6D), the polycrystalline silicon films 402 and 502 and the silicon substrates 420 and 520 are formed.
The oxide films 421 and 530 may be formed as an insulating film between and.

In the sixth embodiment, the electrolytic etching and the electrolytic plating have been described as an example. However, the present invention is not limited to this, and the region where the buried oxide film 804 of the silicon substrate 800 is removed is not limited thereto. It is only necessary that the unevenness is provided electrochemically by self-alignment, and other members may be deposited by electrolytic polymerization, for example.

In the first, second, third and fourth embodiments, the oxide film 304 and the polycrystalline silicon film 40 are respectively provided.
Although polishing has been described as an example in the planarization of 2, 502 and the oxide film 604, the present invention is not limited to this.
Other planarization methods such as etch back may be used.

In the first, second and third embodiments, the thinning of the silicon substrate for obtaining the single crystal silicon layers 305, 405, 505 has been described by using polishing as an example, but the present invention is not limited to this. But not by other thinning methods,
For example, selective etching may be performed as in the fifth embodiment, etching by time control, or n
The so-called electro-chemical etching in which only the p-type silicon substrate is etched by electrochemically stopping only the p-type silicon layer may be used. Of course, the fifth embodiment does not limit the method of thinning.

Further, in the first, second, and third embodiments, the SOI substrate structure in which the oxide films 304, 404, and 504 are entirely formed has been described as an example, but the present invention is not limited to this. For example, it may be a partial SOI substrate structure in which a buried insulating film is formed only in a region where a micromachine is formed. The same applies to the oxide films 302, 402 and 502 and the silicon nitride films 303, 403 and 503.

In the fourth embodiment, the structure in which the anchor 612 is provided in the opening 631 and the micromachine 640 is insulated from the silicon substrate 600 has been described as an example, but the present invention is not limited to this. Instead, for example, an anchor portion may be provided in the opening 630 and directly connected to the silicon substrate.

In addition, in the fifth embodiment, the spacers for forming the cavities 733, that is, the convex portions 7 are formed.
Although 31 is provided in the single crystal silicon layer 705, it may be provided in the glass substrate 732. A spacer made of single crystal silicon may be provided by another member.

Further, in the first, second and third embodiments, the convex portion at the interface between the embedded insulating film and the supporting substrate is formed on the entire surface of the substrate, but it may be provided only at the portion facing the movable portion. good.

Further, in the first, second, third, fourth, fifth and sixth embodiments, the micromachines 340, 440 and 54 are respectively provided.
Although 0, 640, 740, and 840 have been described as an example, the present invention is not limited to this, and for example, a semiconductor element or a circuit for driving a micromachine may be formed. A region where a semiconductor element or a circuit is formed may be a region where a micromachine is not formed, or may be, for example, an anchor portion of a region where a micromachine is formed. In addition, a region where a semiconductor element or a circuit is formed may be a region of the SOI structure portion or a region which is not the SOI structure portion.

Further, in the first, second, third and sixth embodiments, the silicon substrates 300, 420, 520 and 800 have been described as examples of the supporting substrate, but the present invention is not limited to this and other embodiments are possible. Substrate, for example, a glass substrate may be used. Of course, also in the fifth embodiment, the support substrate is not limited. The support substrate in the fourth embodiment may be a substrate on which silicon can be epitaxially grown, and may be, for example, a sapphire substrate.

In the first, second, third, fourth and fifth embodiments, the convex portions 307, 407, 507 and 60 are respectively provided.
Although the shapes of Nos. 7 and 707 have not been mentioned in particular, the corners of the convex portions may be rounded by using a technique such as taper etching or reflow, and may have a trapezoidal shape or a droplet shape.
In this case, the tendency of the protrusion or the movable portion to be damaged when the movable portion collides with the protrusion due to a strong external force can be reduced.

In all the embodiments, single crystal silicon has been described as an example of a structural material for micromachines, but the present invention can be applied to other single crystal materials such as gallium arsenide, quartz or single crystal metal. Are possible for those skilled in the art.

According to the above-described first, second, third and fourth embodiments, the interface between the buried oxide film and the SOI layer is formed of a flat surface without unevenness, and the buried oxide film and the support substrate are formed. It is common that an SOI substrate having a convex portion is formed at an interface between the micromachine and the micromachine. Therefore, a circuit densely integrated by the trench isolation and the micromachine are formed. Since they can be formed integrally, sophistication (intelligence) and miniaturization of micromachines can be realized.

Further, the silicon nitride films 303, 403, 5
03 and 603, movable parts 311, 411, 51
The effect of reducing the frictional force when the bottom surfaces of 1 and 611 rub against the outermost surface of the support substrate and reducing the abrasion, and reducing the tendency of the bottom surface of the movable portion to contact and adhere to the outermost surface of the support substrate Can be done.

According to the first, second, third, fifth and sixth embodiments, since the single crystal silicon layers 305, 405, 505, 705 and 805 are obtained by thinning the silicon substrate, a thick structure is formed. Can be realized. Accordingly, it is possible to increase the mass of the weight portion of the micromachine and increase the capacitance of the comb-teeth electrode, thereby realizing high sensitivity of the micromachine, for example, a dynamic quantity sensor unit, and high power of, for example, an electrostatic actuator.

According to the first, second, third, fourth and sixth embodiments, since the single crystal silicon layers 305, 405, 505, 605 and 805 are obtained by joining the two silicon substrates, the stress is low. A structural material is obtained, and no special stress control step is required.

According to the first embodiment, the interface between the buried oxide film and the SOI layer is composed of a flat surface having no unevenness, and a convex portion is formed at the interface between the buried oxide film and the supporting substrate. In the first, second, third and fourth embodiments for forming an SOI substrate characterized by having a case where the step of forming the SOI substrate is relatively short and the silicon nitride film is formed by a direct nitriding method. , Especially the process is short.

According to the second and third embodiments, by bonding the polished polycrystalline silicon layer and the single crystal silicon layer, the interface between the buried oxide film and the SOI layer is flat without any unevenness. Since the SOI substrate having a convex surface is formed at the interface between the buried oxide film and the supporting substrate, the oxide film and the single crystal silicon according to the first embodiment are formed. An effect that the bonding strength is higher than that of an SOI substrate formed by bonding with a layer is obtained. The upper and lower interfaces of the buried oxide film to be sacrificial etched are obtained by sequential film formation, and the effect that abnormal phenomenon of increase in etching rate that occurs at the junction interface between the oxide film and the single crystal silicon layer does not occur. Is obtained.

Further, since it is not necessary to perform patterning on the substrate that becomes the supporting substrate (the substrate that is not thinned by polishing) at the time of bonding, it is possible to use the substrate that becomes a supporting substrate with strict standards of flatness, parallelism and warpage. No disturbance is given, and therefore the yield of the joining process can be improved.

Further, the polycrystalline silicon, which is a compressive stress, is provided on the bonding surface side of the substrate to be thinned, and the bonding surface of the substrate has a function of projecting upward, thus improving the yield of the bonding process. be able to.

In addition, polycrystalline silicon layers 402 and 502
Can be used as the lower electrode facing the movable portion.

According to the sixth embodiment, a standard SOI substrate can be used as the SIMOX or the bonded SOI, and the electrochemical process performed by self-alignment without adding any mask. Since it is only necessary to add one step, the cost increase can be suppressed to a low level. When electrolytic plating is used, the plated layer can be used as a low-resistance lower electrode facing the movable part.

[0121]

According to the manufacturing method including the steps described above, in a micromachine having a movable portion and a fixed portion facing the movable portion, the movable portion is single crystal silicon and the movable portion contacts the fixed portion. In this case, it is possible to realize a micromachine characterized in that the convex portion that reduces the contact area at the time is provided on the fixed portion.

In the micromachine of the present invention, the convex portion provided on the fixed portion has an action of reducing the contact area when the bottom surface of the movable portion comes into contact with the outermost surface of the supporting substrate, and therefore the adhesion is reduced. The effect of reducing the tendency to There is an effect that the bottom surface and the top surface of the movable portion are formed from flat surfaces without irregularities, and therefore, there is an effect of reducing the tendency of breakage due to stress concentration when the movable portion undergoes bending. In addition, there is no grain boundary in the movable portion, and there is an action of being formed from single crystal silicon with few dislocations and defects, and therefore the effect of reducing the tendency of damage due to stress concentration when the movable portion is bent by an external force, It has the effect of avoiding the phenomenon of intergranular corrosion and intergranular cracking when the movable part is treated with chemicals or gas.

Furthermore, in the present invention, since the micromachine is made of a material having stable physical properties such as single crystal silicon, it is possible to stably form a piezoresistor which is an element for detecting stress on the micromachine. Therefore, it is possible to improve the sensitivity of the displacement detection of the movable part, and thus the sensitivity of the mechanical quantity sensor part, for example. Further, the semiconductor element can be built in, for example, an anchor portion inside the micromachine, and the effect of achieving sophistication (intelligentization) and miniaturization of the micromachine can be obtained.

The various excellent effects described above can be simultaneously enjoyed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining formation of an SOI substrate according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining from SOI substrate formation to micromechanical formation in the first embodiment of the present invention, A) to
C) and E are sectional views, and D) is a plan view.

FIG. 3 is a cross-sectional view for explaining formation of an SOI substrate according to the second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a process from forming an SOI substrate to forming a micromachine according to the second embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining formation of an SOI substrate according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view explaining from SOI substrate formation to micromechanical formation in the third embodiment of the invention.

FIG. 7 is a cross-sectional view for explaining formation of an SOI substrate according to a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating an SOI substrate formation to micromechanical formation according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating an SOI substrate formation to micromechanical formation according to a fifth embodiment of the present invention.

FIG. 10 is a cross-sectional view for explaining from SOI substrate formation to micromechanical formation according to a sixth embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a structure of a conventional micromachine and a manufacturing method thereof.

FIG. 12 is a sectional view showing a problem of a conventional micromachine.

[Explanation of symbols]

300, 400, 420, 500, 520, 600, 8
00 Silicon substrate 301, 308, 401, 408, 508, 601, 6
08,708,730,731 Recesses 302,304,404,421,504,530,6
02,604,804 oxide film 303,403,503,603 silicon nitride film 305,405,505,605,705,805
Single crystal silicon layer 306,606 SOI substrate 307,407,507,607,707 Convex part 309,310,409,410,590,510,6
09,610 Interface 311, 411, 511, 711, 811 Movable part 312, 412, 512, 712, 812 Anchor part 313 Large pattern part 314, 319 Line pattern part 315 Worm eating pattern part 316, 416, 516, 616, 630, 631,7
16 Opening 317 Patterned single crystal silicon layer 318 Hole 340, 440, 540, 640, 740, 840
Micromachine 402,502 Polycrystalline silicon layer 406,506 SOI layer 700 High concentration silicon substrate 732 Glass substrate 733 Cavity 830 Porous silicon layer 831 Plating layer

Claims (10)

[Claims] 1. A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and the movable portion contacts the fixed portion. A micromachine characterized in that a convex portion is provided to reduce the contact area at the time. 2. The micromachine according to claim 1, wherein a film having a small friction coefficient is provided on the outermost surface of the convex portion provided on the fixed portion. 3. A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and a contact area when the movable portion contacts the fixed portion is set. A method of manufacturing a micromachine, comprising the following steps, in a method of manufacturing a micromachine in which a convex portion to be reduced is provided on the fixed portion. 1) A so-called SOI substrate including a supporting substrate, a buried insulating film, and a single crystal silicon layer, wherein the SOI substrate
Forming an SOI substrate having a flat interface between a layer and the buried insulating film and having a convex portion at the interface between the buried insulating film and the support substrate. 2) A step of etching through the SOI layer of the SOI substrate to form an opening reaching the buried insulating film. 3) A step of etching the buried insulating film using the opening as an etching hole to obtain a self-standing structure made of the single crystal silicon layer. 4. The method for manufacturing a micromachine according to claim 3, wherein the interface between the SOI layer and the embedded insulating film is flat, and the convex portion is provided at the interface between the embedded insulating film and the supporting substrate. A method of manufacturing a micromachine, wherein the step of forming an SOI substrate includes the following steps. 1) A step of forming a recess on the main surface of the supporting substrate. 2) A step of forming an insulating film on the main surface of the structure and planarizing the main surface of the insulating film. 3) A step of bonding a silicon substrate to the structure and thinning the silicon substrate. 5. The method for manufacturing a micromachine according to claim 3, wherein the interface between the SOI layer and the buried insulating film is flat, and
The SO having a convex portion at the interface between the embedded insulating film and the supporting substrate
A method of manufacturing a micromachine, wherein the step of forming the I substrate includes the following steps. 1) A step of forming an insulating film on the main surface of the silicon substrate and forming a recess on the main surface of the insulating film. 2) A step of forming an intermediate film on the main surface of the structure and flattening the main surface of the intermediate film. 3) A step of thinning the silicon substrate by bonding the structure to a support substrate via the intermediate film. 6. The method for manufacturing a micromachine according to claim 4 or 5, wherein a step of forming a film having a small friction coefficient with silicon is formed between step 1) and step 2). A method for manufacturing a micromachine characterized by the above. 7. A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and a contact area when the movable portion contacts the fixed portion is set. A method of manufacturing a micromachine, wherein the method of manufacturing a micromachine in which a convex portion to be reduced is provided on the fixed portion includes the following steps. 1) A step of preparing a support substrate and a single crystal silicon substrate, and forming a spacer on a main surface of either the support substrate or the single crystal silicon substrate. 2) A step of forming a convex portion on the main surface of the support substrate. 3) A step of joining the support substrate and the single crystal silicon substrate through the spacer to form a cavity. 4) A step of thinning the single crystal silicon substrate to obtain a single crystal silicon layer. 5) A step of etching through the single crystal silicon layer to form an opening reaching the cavity to obtain a self-supporting structure made of the single crystal silicon layer. 8. A micromachine having a movable portion and a fixed portion facing the movable portion, wherein the movable portion is single crystal silicon, and a contact area when the movable portion contacts the fixed portion is reduced. A method of manufacturing a micromachine, wherein a method of manufacturing a micromachine in which a prominent convex portion is provided on the fixed portion is formed by including the following steps. 1) A step of etching a so-called SOI substrate formed of a support substrate, a buried insulating film and a single crystal silicon layer to penetrate the SOI layer to form an opening reaching the buried insulating film. 2) A step of etching the buried insulating film using the opening as an etching hole to obtain a self-standing structure made of the single crystal silicon layer. 3) A step of performing an electrochemical treatment on a region of the supporting substrate where the buried insulating film is etched so that a portion to be treated by the electrochemical treatment is not flat. 9. The method of manufacturing a micromachine according to claim 8, wherein the electrochemical treatment is an etching treatment by anodic oxidation. 10. The method for manufacturing a micromachine according to claim 8, wherein the electrochemical treatment is electrolytic deposition treatment.