JP3893636B2 - Manufacturing method of micromachine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a micromachine having a microstructure.ofMore specifically regarding the manufacturing method, even if the movable microstructure is in contact with the opposing member, the micromachine is less likely to break or stick.ofIt relates to a manufacturing method.
[0002]
[Prior art]
A conventional micromachine and its manufacturing method will be described with reference to FIG. This figure is shown in the literature (Theresa A. Core, WK Tsang, Steven.
J. et al. Sherman, “Fabrication Technology for an Integrated Surface-Micromachined Sensor”, Solid State Technology, October 1993, 39-47), and only the part according to the present invention.
[0003]
As shown in FIG. 11A, a conventional micromachine and its manufacturing method are as follows. First, an oxide film 101 is formed on a main surface of a silicon substrate 100 by thermal oxidation, and silicon nitridation is performed by LP-CVD (low pressure-chemical vapor deposition). A film 102 and an LTO (low temperature oxide) film 103 are sequentially formed in layers by CVD.
[0004]
Thereafter, as shown in FIG. 11B, etching is performed to the extent that it does not penetrate the LTO film 103 to form the dimple 104, and etching that penetrates the LTO film 103, the silicon nitride film 102, and the oxide film 101 is performed. An opening 105 is formed.
[0005]
Next, as shown in FIG. 11C, a polysilicon film 106 is formed by LP-CVD and patterned by photolithography and etching.
[0006]
Then, as shown in FIG. 11D, the LTO film 103 is sacrifice-etched with hydrofluoric acid or the like to obtain a self-supporting microstructure 107.
[0007]
The microstructure 107 includes a movable portion 108 and an anchor portion 109 that fixes the movable portion 108 to the silicon substrate 100 that is a support base. Corresponding to the position of the dimple 104 of the LTO film 103, a bump 110 is formed on the bottom surface of the movable portion 108, and a dimple 111 is formed on the surface of the movable portion 108. When the bottom surface of the movable portion 108 comes into contact with the surface of the silicon substrate 100, the bump 110 has an effect of reducing the contact area and thereby reducing the possibility of adhesion. The silicon nitride film 102 acts as an etching stopper when the LTO film 103 is sacrificially etched, but reduces the frictional force when the bottom surface of the movable part 108 rubs against the surface of the silicon substrate 100 and reduces wear. In addition, the bottom surface of the movable portion 108 is in contact with the surface of the silicon substrate 100 to reduce the possibility of adhesion.
[0008]
Now, a case where various external forces such as vibration and drop impact are applied to the micromachine obtained in this way will be described with reference to FIG.
[0009]
As shown in FIG. 12A, when an acceleration motion is performed in the downward direction in the figure, the movable portion 108 is bent downward.
[0010]
As shown in FIG. 12B, in the case of dropping or colliding in the downward direction in the figure, the movable portion 108 is hit against the surface of the silicon substrate 100, and the movable portion 108 receives a downward convex bending.
[0011]
As shown in FIG. 12C, when an acceleration motion is performed in the upward direction in the figure, the movable portion 108 receives an upward convex bending.
[0012]
As shown in FIG. 12D, in the case of falling or colliding in the upward direction in the figure, the movable portion 108 is hit against the back surface of the cover 202, and the movable portion 108 receives upward convex bending.
[0013]
As shown in FIGS. 12A and 12B, when the movable portion 108 is bent downward, tensile stress is concentrated on the root 200 of the bump 110 indicated by a circle in FIG. However, it is not desirable because it tends to be destroyed from here. When the movable portion 108 is bent upward as shown in FIGS. 12C and 12D, the tensile stress is concentrated on the bottom 201 of the dimple 111 indicated by a circle in FIG. However, it is not desirable because it tends to be destroyed from here.
[0014]
[Problems to be solved by the invention]
However, in such a conventional example, when the bottom surface of the movable portion 108 comes into contact with the surface of the silicon substrate 100, the bump 110 acting to reduce the contact area and thus reduce the possibility of adhesion is provided. Since the structure is provided in the portion 108 and the manufacturing method thereof, there is a problem that a structure for concentrating stress on the movable portion 108 that receives bending by an external force is simultaneously formed.
[0015]
In this conventional example, the structure constituting the movable part is made of polysilicon, and external force is also applied to the molecular structure such as the innumerable grain boundaries and dislocations inherent in the material called polycrystalline. In this structure, stress is concentrated, and there is a tendency to brittle fracture from here. Furthermore, the grain boundary also has a unique phenomenon such as grain boundary erosion or grain boundary cracking, which increases the tendency of brittle fracture.
[0016]
Furthermore, polysilicon has a strong compressive stress, and it is difficult to control the stress. For this reason, the deposition rate is slow and it is difficult to obtain a thick structure.
[0017]
In addition, it is difficult to stably form, for example, a piezoresistor, which is an element for detecting stress, using polysilicon, and therefore, the displacement amount of the movable part of the micromachine has to rely on a low-sensitive electrostatic type. In addition, semiconductor elements made of polysilicon have significantly poorer performance than semiconductor elements made of single crystal silicon, such as large variations in characteristics, low breakdown voltage, and large reverse saturation current. Therefore, it has been necessary to form a single crystal silicon substrate which is a support substrate in an external region of the micromachine.
[0018]
  The present invention has been made in view of such conventional problems, and in a micromachine having a movable part and a fixed part facing the movable part, the tendency of adhesion when the movable part comes into contact with the fixed part is reduced. Reduced tendency to break when the moving part is bent, and further, the micro machine is free from phenomena such as intergranular corrosion and intergranular cracking when the moving part is treated with chemicals or gasofThe object is to provide a manufacturing method.
[0019]
[Means for Solving the Problems]
  A method of manufacturing a micromachine according to a first aspect of the present invention is a micromachine having a movable part and a fixed part facing the movable part, wherein the movable part is single crystal silicon, and the movable part is A method of manufacturing a micromachine having a convex portion on the fixing portion that reduces a contact area when contacting the fixing portion, the supporting substrate, an embedded insulating film formed on the supporting substrate, and the embedded A so-called SOI substrate composed of a single crystal silicon layer formed on a buried insulating film, wherein an interface between the single crystal silicon layer and the buried insulating film is flat, and the buried insulating film and the A first step of forming an SOI substrate having a convex portion at the interface with the support substrate, etching through the single crystal silicon layer of the SOI substrate is performed, and an opening reaching the buried insulating film is formed in the single crystal silicon layer 2nd process to form A third step of obtaining a self-supporting structure made of the single crystal silicon layer by etching the buried insulating film using the opening as an etching hole, and the first step includes: Forming a recess in the main surface; forming an insulating film on the main surface of the structure; and planarizing the main surface of the insulating film; and bonding a silicon substrate to the structure; And a step of thinning the film.
[0020]
  A method of manufacturing a micromachine according to a second aspect of the present invention is a micromachine having a movable part and a fixed part facing the movable part, wherein the movable part is single crystal silicon, and the movable part is A method of manufacturing a micromachine having a convex portion on the fixing portion that reduces a contact area when contacting the fixing portion, the supporting substrate, an embedded insulating film formed on the supporting substrate, and the embedded A so-called SOI substrate composed of a single crystal silicon layer formed on a buried insulating film, wherein an interface between the single crystal silicon layer and the buried insulating film is flat, and the buried insulating film and the A first step of forming an SOI substrate having a convex portion at the interface with the support substrate, etching through the single crystal silicon layer of the SOI substrate is performed, and an opening reaching the buried insulating film is formed in the single crystal silicon layer 2nd process to form A third step of obtaining a self-supporting structure made of the single crystal silicon layer by etching the buried insulating film using the opening as an etching hole, and the first step includes the step of: Forming an insulating film on the main surface and forming a recess on the main surface of the insulating film; forming an intermediate film on the main surface of the structure; and planarizing the main surface of the intermediate film; Bonding the structure to a support substrate via the intermediate film, and thinning the silicon substrate.
[0021]
  A manufacturing method of a micromachine according to a third aspect of the present invention is a micromachine having a movable part and a fixed part facing the movable part, wherein the movable part is single crystal silicon, and the movable part is A method of manufacturing a micromachine having a convex portion on the fixed portion that reduces a contact area when contacting the fixed portion, wherein a support substrate and a single crystal silicon substrate are prepared, and the support substrate or the single crystal is prepared. A step of forming a spacer on any main surface of the silicon substrate, a step of forming a convex portion on the main surface of the support substrate, and the support substrate and the single crystal silicon substrate are bonded via the spacer. Forming a cavity; thinning the single crystal silicon substrate to obtain a single crystal silicon layer; and etching through the single crystal silicon layer to open the cavity. Part is formed, and having a step of obtaining the single crystal made of silicon layer freestanding structure.
[0022]
  A method of manufacturing a micromachine according to a fourth aspect of the present invention is a micromachine having a movable part and a fixed part facing the movable part, wherein the movable part is single crystal silicon, and the movable part is A method of manufacturing a micromachine having a convex portion on the fixing portion that reduces a contact area when contacting the fixing portion, the supporting substrate, an embedded insulating film formed on the supporting substrate, and the embedded Etching that penetrates the single crystal silicon layer of a so-called SOI substrate composed of a single crystal silicon layer formed on the buried insulating film, and forms an opening reaching the buried insulating film in the single crystal silicon layer Etching the buried insulating film to obtain a self-supporting structure made of the single crystal silicon layer, and etching the buried insulating film of the support substrate. Areas to perform an electrochemical process, characterized by a step of non-planar with the treatment part of the electrochemical treatment.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the micromachine of the present inventionofEmbodiments of the manufacturing method will be described in detail with reference to the drawings.
[0035]
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
[0036]
As shown in FIG. 1A, a recess 301 is formed on the main surface of the first silicon substrate 300 by a trench etching technique.
[0037]
Thereafter, as shown in FIG. 1B), an oxide film 302 and a silicon nitride film 303 are formed on the structure by thermal oxidation and LP-CVD (low pressure chemical vapor deposition).
[0038]
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 thereof is flattened by a polishing method.
[0039]
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 a single crystal silicon layer 305.
[0040]
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, and the thinned single crystal silicon layer 305 is used as an SOI (silicon on insulator) layer. An SOI substrate 306 is formed. An interface 309 between the oxide film 304 which is a buried oxide film and the single crystal silicon layer 305 which is an SOI layer is formed of a flat surface without unevenness, and the oxide film 304 which is a buried oxide film and the first silicon An interface 310 with the support substrate made of the substrate 300 has a convex portion 307 and a concave portion 308.
[0041]
FIG. 2A) shows the configuration of the main surface of the SOI substrate 306. When the structure is rewritten, 300 is a first silicon substrate, 302 is an oxide film, 303 is a silicon nitride film, 304 is a buried oxide film, 305 is a single crystal silicon layer, and 310 is an oxide film 304 which is a buried oxide film. And the first silicon substrate 300 which is the support substrate, 308 is a concave portion of the interface 310, and 307 is a convex portion of the interface 310.
[0042]
As shown in FIG. 2B), etching through the single crystal silicon layer 305 is performed to form an opening 316 reaching the oxide film 304.
[0043]
As shown in FIG. 2C), the oxide film 304 is etched from the opening 316 with an etchant containing hydrofluoric acid to obtain a microstructure 340 made of self-supporting single crystal silicon. Reference numeral 311 denotes a movable portion, and reference numeral 312 denotes an anchor portion that fixes the movable portion 311 to the silicon substrate 300 that is a support base.
[0044]
Through the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon, and the convex portion that reduces the contact area when the movable portion contacts the fixed portion. A micromachine characterized in that it is provided in the fixed part is obtained.
[0045]
Note that in the microstructure 340 made of single crystal silicon, whether it becomes a movable portion or an anchor depends on the pattern of the opening portion 316 in the process step 2B). FIG. 2D) shows a plan view of a pattern example. Shown is the patterned single crystal silicon layer 317 of FIG. 2B). 313 is a large pattern portion, for example, 200 μm square, 314 and 319 are line pattern portions, for example, 10 μm wide, 315 is a worm-eaten pattern portion, for example, 200 μm square, and 10 μm square holes 318 are opened innumerably at a pitch of 20 μm. Suppose that The thickness of the oxide film 304 is 1 μm.
[0046]
The structure is immersed in an etching solution containing hydrofluoric acid, and an etching process is performed 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 etched away, and the amount of under-etching proceeding under the single crystal silicon layer 317 is 10 μm. At this time, the oxide film directly under the large pattern portion 313 is under-etched by 10 μm in the front, rear, left, and right directions, and remains in a size of 180 μm square. Accordingly, the large pattern portion 313 becomes an anchor portion 312 connected to the support substrate by the remaining oxide film 304.
[0047]
The oxide film 304 immediately below the line pattern portions 314 and 319 is under-etched by 10 μm before and after, and this under-etching overlaps and no longer remains, and the line pattern portions 314 and 319 are suspended. float. In FIG. 2, the ends of the line pattern portions 314 and 319 are connected to the anchor portion 312, thereby forming 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 immediately below the worm-eaten pattern portion 315 is not only under-etched by 10 μm at the front, rear, left and right, but also isotropically under-etched from countless holes 318, and these countless under-etching is over. -No longer remains after wrapping, and the worm-eaten pattern portion 315 floats in the air. In FIG. 2, it is connected to the anchor portion 312 via the line / pattern portion 314 to form a self-supporting structure. Therefore, the LL sectional view and the MM sectional view of FIG. 2D) become FIG. 2C), and the NN sectional view of FIG. 2D) becomes FIG. 2E).
[0048]
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 like the worm-eaten pattern portion 315 is designed as a weight.
[0049]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0050]
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 a CVD method, and a recess that does not penetrate the oxide film 404 is formed on the main surface of the oxide film 404. 401 is formed using an etchant containing hydrofluoric acid.
[0051]
Next, in FIG. 3B), a silicon nitride film 403 is formed on the structure by the LP-CVD method, a polycrystalline silicon film 402 is formed by the CVD method, and the main surface of the polycrystalline silicon film 402 is polished. Flatten by technique.
[0052]
Thereafter, in FIG. 3C), a 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 technique to obtain a single crystal silicon layer 405.
[0053]
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 single crystal silicon layer 405 obtained by thinning the first single crystal silicon substrate 400 is formed into an SOI ( A so-called SOI substrate 406 serving as a silicon-on-insulator layer is formed.
[0054]
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 formed of a flat surface without unevenness, and the oxide film 304 which is a buried oxide film and the second single crystal silicon layer 405. The interface 410 with the support substrate made of the crystalline silicon substrate 420 has a convex portion 407 and a concave portion 408.
[0055]
FIG. 4A) shows the configuration of the main surface of the SOI substrate 406. When the structure is rewritten, 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, 405 is a single crystal silicon layer, and 410 is a buried layer. The interface between the oxide film 304 that is the embedded oxide film and the second single crystal silicon substrate 420 that is the support substrate, 408 is a concave portion of the interface 410, and 407 is a convex portion of the interface 410.
[0056]
In FIG. 4B), etching through the single crystal silicon layer 405 is performed to form an opening 416 reaching the oxide film 404.
[0057]
In FIG. 4C), the oxide film 404 is etched from the opening 416 with an etchant containing hydrofluoric acid to obtain a microstructure 440 made of self-supporting single crystal silicon. Reference numeral 411 denotes a movable portion, and reference numeral 412 denotes an anchor portion that fixes the movable portion 411 to the single crystal silicon substrate 420 that is a support base.
[0058]
In the microstructure 440 made of single crystal silicon, whether it becomes a movable part or an anchor depends on the pattern of the opening 416 in the process step 4B) as in the first embodiment.
[0059]
By the manufacturing method including the above steps, as in the first embodiment, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon and the movable portion is fixed. Thus, a micromachine characterized in that a convex portion that reduces a contact area when contacting the portion is provided on the fixed portion.
[0060]
4D) shows a structure obtained when an oxide film 421 is formed on the main surface of the planarized polycrystalline silicon film 402 in FIG. 3B) by the CVD method, and the same process is performed thereafter. .
[0061]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.
[0062]
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, and is patterned with an etchant containing hydrofluoric acid.
[0063]
As shown in FIG. 5B, an oxide film 504 is formed on the structure by a CVD method, and a silicon nitride film 503 is formed by a CVD method.
[0064]
As shown in FIG. 5C), a polycrystalline silicon film 502 is formed on the structure by a CVD method, and the main surface of the polycrystalline silicon film 502 is flattened by a 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.
[0065]
Through the above steps, the oxide films 501 and 504 are used as buried oxide films, the second single crystal silicon substrate 520 is used as a support substrate, the first single crystal silicon substrate 500 is thinned, and the obtained single crystal silicon layer 505 is obtained. Thus, a so-called SOI substrate 506 is formed in which is used as an SOI (silicon on insulator) layer. An interface 509 between the oxide films 501 and 504 which are buried oxide films and the single crystal silicon layer 505 which is an SOI layer is formed of a flat surface without unevenness, and the oxide films 501 and 504 which are buried oxide films An interface 510 between the second single crystal silicon substrate 520 and the supporting substrate has a convex portion 507 and a concave portion 508.
[0066]
FIG. 6A) shows the configuration of the main surface of the SOI substrate 506. When the structure is rewritten, 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 Denotes an interface between the oxide film 504 which is a buried oxide film and the support substrate made of the second single crystal silicon substrate 520, 508 is a concave portion of the interface 510, and 507 is a convex portion of the interface 510.
[0067]
In FIG. 6B, etching is performed through the single crystal silicon layer 505 to form openings 516 reaching the oxide films 501 and 504.
[0068]
In FIG. 6C), the oxide film 504 is etched from the opening 516 with an etching solution containing hydrofluoric acid to obtain a microstructure 540 made of self-supporting single crystal silicon. Reference numeral 511 denotes a movable portion, and reference numeral 512 denotes an anchor portion that fixes the movable portion 511 to a single crystal silicon substrate 520 that is a support base.
[0069]
In the microstructure 540 made of single crystal silicon, whether it becomes a movable part or an anchor depends on the pattern of the opening 516 in the above-described process FIG. 6B), as in the first embodiment.
[0070]
By the manufacturing method including the above steps, as in the first embodiment, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon and the movable portion is fixed. Thus, a micromachine characterized in that a convex portion that reduces a contact area when contacting the portion is provided on the fixed portion.
[0071]
FIG. 6D) shows a structure obtained when an oxide film 530 is formed on the main surface of the planarized polycrystalline silicon film 502 in FIG. 5C) by the CVD method and the same process is performed thereafter. .
[0072]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
[0073]
As shown in FIG. 7A), first, a recess 601 is patterned on the main surface of a single crystal silicon substrate 600, and an oxide film 602 is sequentially formed by a thermal oxidation method, and a silicon nitride film 603 is sequentially formed by an LP-CVD method. To do.
[0074]
Next, in FIG. 7B), an oxide film 604 is formed on the structure by a CVD method, and the main surface of the oxide film 604 is planarized by a polishing method, and an opening 630 reaching the single crystal silicon substrate 600 and silicon nitride are formed. An opening 631 reaching the film 603 is formed.
[0075]
Thereafter, in FIG. 7C), a polycrystalline silicon film is formed on the main surface of the structure by a CVD method, and the single crystal silicon substrate 600 in the opening 630 is used as a seed, and the polycrystalline silicon film is scanned by laser scanning. A single crystal silicon layer 605 is obtained by directional crystal growth.
[0076]
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 support substrate, and the single crystal silicon layer 605 obtained by lateral crystal growth of the polycrystalline silicon film is converted into SOI (silicon-on-silicon). A so-called SOI substrate 606 serving as an insulator layer is formed. 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 formed from a flat surface without unevenness, and the oxide film 604 which is a buried oxide film and a single crystal silicon substrate. An interface 610 with the support substrate 420 includes a convex portion 607 and a concave portion 608.
[0077]
FIG. 8A) shows the configuration of the main surface of the SOI substrate 606. When the structure is described again, 600 is a single crystal silicon substrate as a support substrate, 602 is an oxide film, 603 is a silicon nitride film, 604 is a buried oxide film, 605 is a single crystal silicon layer, and 610 is a buried oxide film. The interface between the oxide film 604 and the single crystal silicon substrate 600 is a support substrate, 608 is a recess of the interface 610, and 607 is a protrusion of the interface 610.
[0078]
Thereafter, in FIG. 8B), etching is performed through the single crystal silicon layer 605 to form an opening 616 that reaches the oxide film 604.
[0079]
8C), the oxide film 604 is etched from the opening 616 with an etchant containing hydrofluoric acid to obtain a microstructure 640 made of self-supporting single crystal silicon. Reference numeral 611 denotes a movable portion, and reference numeral 612 denotes an anchor portion that fixes the movable portion 611 to the single crystal silicon substrate 600 that is a support base.
[0080]
In the microstructure 640 made of single crystal silicon, whether it becomes a movable part or an anchor depends on the pattern of the opening 616 in the process step 8B) as in the first embodiment.
[0081]
By the manufacturing method including the above steps, as in the first embodiment, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon and the movable portion is fixed. Thus, a micromachine characterized in that a convex portion that reduces a contact area when contacting the portion is provided on the fixed portion.
[0082]
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG.
[0083]
As shown in FIG. 9A), first, a single crystal silicon layer 705 is formed on the main surface of a high impurity concentration single crystal silicon substrate 700 by an epitaxial growth technique, and etching is performed so as not to penetrate the single crystal silicon layer 705. A recess 730 is formed in line. As a result, a region that is not etched protrudes relatively to become a convex portion 731.
[0084]
Next, as shown in FIG. 9B), a recess 708 is formed on the main surface of the glass substrate 732 by etching. As a result, a region that is not etched protrudes relatively to become a convex portion 707.
[0085]
Thereafter, as shown in FIG. 9C), the main surface of the structure of FIG. 9A) and the main surface of the structure of FIG. 9B) are joined, and a high impurity concentration having a composition of hydrofluoric acid: nitric acid: acetic acid = 1: 3: 8. Only the single crystal silicon substrate 700 having a high impurity concentration is etched using a selective etching solution that selectively dissolves only the silicon. 9A) and the main surface of the structure of FIG. 9B) are joined via the convex portion 731, and thus a cavity 733 is formed.
[0086]
9D), an opening 716 that penetrates the single crystal silicon layer 705 of the structure and reaches the cavity 733 is formed by a dry etching technique, and a microstructure 740 made of self-supporting single crystal silicon is obtained. . Reference numeral 711 denotes a movable portion, and reference numeral 712 denotes an anchor portion that fixes the movable portion 711 to a glass substrate 732 that is a support base.
[0087]
By the manufacturing method including the above steps, as in the first embodiment, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon and the movable portion is fixed. Thus, a micromachine characterized in that a convex portion that reduces a contact area when contacting the portion is provided on the fixed portion.
[0088]
(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG.
[0089]
As shown in FIG. 10A), the structure of the main surface of a standard SOI substrate is shown. The structure is explained. A single crystal silicon layer 805 is an SOI layer, a buried oxide film 804 is a buried insulating film, and a silicon substrate 800 is a support substrate.
[0090]
In FIG. 10B), etching through the single crystal silicon layer 805 is performed to form an opening 816 reaching the oxide film 804.
[0091]
In FIG. 10C, the oxide film 804 is etched from the opening 816 with an etchant containing hydrofluoric acid to obtain a microstructure 840 made of self-supporting single crystal silicon. Reference numeral 811 denotes a movable portion, and 812 denotes an anchor portion that fixes the movable portion 811 to the silicon substrate 800 that is a support base.
[0092]
In FIG. 10D), the structure is immersed in an etching solution containing hydrofluoric acid, and electrolytic etching is performed while applying voltage to the silicon substrate 800 to form a porous silicon layer 830. The porous silicon layer 830 is formed by self-alignment only in the region where the buried oxide film 804 of the silicon substrate 800 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.
[0093]
Through the above steps, in the micromachine having the movable portion and the fixed portion facing the movable portion, the movable portion is single crystal silicon, and the convex portion that reduces the contact area when the movable portion contacts the fixed portion. A micromachine characterized in that it is provided in the fixed part is obtained.
[0094]
Similarly, the structure shown in FIG. 10C) may be immersed in an electrolytic plating solution as shown in FIG. 10E), and electroplated while applying a voltage to the silicon substrate 800 to form a plating layer 831. The plating layer 831 is formed by self-alignment only in the region where the buried oxide film 804 of the silicon substrate 800 is removed. The microstructure 840 is not electrically connected to the silicon substrate 800 and is not subjected to electrolytic plating, and thus a plating layer is not formed.
[0095]
In the above description of the first to sixth embodiments, specific examples have been described, but the present invention is not limited to these terms and drawings. An example will be described below.
[0096]
For example, in the first, second, third and fourth embodiments, the silicon nitride films 303, 403, 503 and 603 have been described as examples. However, the present invention is not limited to this, and other members may be used. In some cases, it may be omitted. Further, although LP-CVD has been described as an example of a method for forming the silicon nitride films 303, 403, and 503, the present invention is not limited to this, and other methods such as plasma-CVD or direct silicon nitridation may be used. .
[0097]
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. May be.
[0098]
In the first, second, third, and fifth embodiments, the direct bonding of two substrates has been described as an example. However, the present invention is not limited to this and may be a eutectic alloy bonding. However, other bonding methods such as anodic bonding may be used.
[0099]
In the second and third embodiments, the polycrystalline silicon films 402 and 502 have been described as intermediate layers for bonding to the support substrate. However, the present invention is not limited to this, and the polycrystalline silicon film is not limited thereto. You may use 402,502 as a lower electrode facing a movable part. At this time, as shown in FIGS. 4D) and 6D), oxide films 421 and 530 may be formed as insulating films between the polycrystalline silicon films 402 and 502 and the silicon substrates 420 and 520, respectively.
[0100]
Further, although the sixth embodiment has been described by taking electrolytic etching and electrolytic plating as examples, it is not limited to this, and self-alignment is performed only in the region where the buried oxide film 804 of the silicon substrate 800 is removed. As long as it is electrochemically provided with unevenness, for example, other members may be deposited by electrolytic polymerization.
[0101]
In the first, second, third, and fourth embodiments, the planarization of the oxide film 304, the polycrystalline silicon films 402 and 502, and the oxide film 604 has been described as an example of polishing. However, the present invention is not limited to this. However, other planarization methods such as etch back may be used.
[0102]
In the first, second, and third embodiments, the thinning of the silicon substrate when obtaining the single crystal silicon layers 305, 405, and 505 has been described as an example of polishing. However, the present invention is not limited to this. Alternatively, other thinning methods, for example, selective etching as in the fifth embodiment may be used, etching by time control, or etching of only the n-type silicon layer is stopped electrochemically, and p-type is performed. So-called electrochemical etching may be used in which only the silicon substrate is etched. Of course, in the fifth embodiment as well, the thinning technique is not limited.
[0103]
In the first, second, and third embodiments, the SOI substrate structure in which the oxide films 304, 404, and 504 are formed on the entire surface has been described as an example. However, the present invention is not limited to this. Alternatively, a partial SOI substrate structure in which a buried insulating film is formed only in a region for forming the semiconductor layer may be used. The same applies to the oxide films 302, 402, and 502 and the silicon nitride films 303, 403, and 503.
[0104]
In the fourth embodiment, an example in which the anchor portion 612 is provided in the opening 631 and the micromachine 640 is insulated from the silicon substrate 600 has been described as an example. However, the present invention is not limited to this. For example, an anchor portion may be provided in the opening 630 and directly connected to the silicon substrate.
[0105]
In the fifth embodiment, the spacer for forming the cavidy 733, that is, the convex portion 731 is provided in the single crystal silicon layer 705, but may be provided in the glass substrate 732. A spacer made of single crystal silicon may be provided by another member.
[0106]
In the first, second, and third embodiments, the convex portion at the interface between the buried insulating film and the support substrate is formed on the entire surface of the substrate. However, the convex portion may be provided only on the portion facing the movable portion.
[0107]
In the first, second, third, fourth, fifth and sixth embodiments, the micromachines 340, 440, 540, 640, 740 and 840 have been described as examples. However, the present invention is not limited to this. For example, a semiconductor element or a circuit for driving a micromachine may be formed. The region where the semiconductor element or the circuit is formed may be a region where no micromachine is formed, or may be an anchor portion of the region where the micromachine is formed. In addition, a region where a semiconductor element or a circuit is formed may be a region of an SOI structure portion or a region that is not an SOI structure portion.
[0108]
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. However, the present invention is not limited to this, and other substrates, For example, a glass substrate may be used. Of course, 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, for example, a sapphire substrate.
[0109]
In the first, second, third, fourth, and fifth embodiments, the shape of the convex portions 307, 407, 507, 607, and 707 is not particularly mentioned, but techniques such as taper etching and reflow are used. It may be used to round the corners of the convex portion, or to have a trapezoidal shape or a droplet shape. In this case, it is possible to reduce the tendency of the convex portion or the movable portion to be damaged when the movable portion collides with the convex portion due to a strong external force.
[0110]
In all the embodiments, single crystal silicon has been described as an example of the structural material of the micromachine. However, applying the present invention to other single crystal materials such as gallium arsenide, crystal, or single crystal metal is the same. It is possible if it is a trader.
[0111]
According to the first, second, third, and fourth embodiments described above, the interface between the buried oxide film and the SOI layer is formed of a flat surface without unevenness, and the interface between the buried oxide film and the support substrate. In addition, it is common to form a micromachine after forming an SOI substrate characterized by having a convex part. Therefore, a highly integrated circuit and micromachine are integrally formed by trench isolation. Therefore, sophistication (intelligent) and miniaturization of the micromachine are realized.
[0112]
In addition, the silicon nitride films 303, 403, 503, and 603 reduce the frictional force when the bottom surfaces of the movable parts 311, 411, 511, and 611 are rubbed against the outermost surface of the support substrate, thereby reducing wear. It is possible to reduce the tendency that the bottom surface of the movable part contacts and adheres to the outermost surface of the support substrate.
[0113]
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 can be realized. Can do. Therefore, the mass of the weight portion of the micromachine can be increased and the capacitance of the comb electrode electrode can be increased, so that the sensitivity of the micromachine, for example, the mechanical quantity sensor unit, and the increase of the power of, for example, the electrostatic actuator can be realized.
[0114]
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 two silicon substrates, a low-stress structural material is obtained. Obtained, and no process for stress control is required.
[0115]
According to the first embodiment, the interface between the buried oxide film and the SOI layer is constituted by a flat surface without irregularities, and has a convex part at the interface between the buried oxide film and the support substrate. In the first, second, third, and fourth embodiments for forming a featured SOI substrate, the process for forming the SOI substrate is relatively short, and particularly when the silicon nitride film is formed by a direct nitridation technique. Is short.
[0116]
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 formed from a flat surface without unevenness. Since the SOI substrate having a convex portion is formed at the interface between the buried oxide film and the support substrate, the oxide film and the single crystal silicon layer according to the first embodiment are formed. The effect that the bonding strength is higher than that of an SOI substrate formed by bonding 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 the abnormal etching rate increase phenomenon that occurs at the interface between the oxide film and the single crystal silicon layer does not occur. Is obtained.
[0117]
In addition, since it is not necessary to perform patterning on the substrate that becomes the support substrate for bonding (the substrate that is not subject to thinning by polishing), disturbance is given to the substrate that becomes a support substrate with strict standards for flatness, parallelism, and warpage. Therefore, the yield of the joining process can be improved.
[0118]
In addition, the polycrystalline silicon that becomes compressive stress is provided on the bonding surface side of the substrate to be thinned, and the bonding surface of the substrate has an action of being convex upward, so that the yield of the bonding process can be improved. .
[0119]
Polycrystalline silicon layers 402 and 502 can be used as a lower electrode facing the movable portion.
[0120]
According to the sixth embodiment, a standard SOI substrate can be used as SIMOX or bonded SOI, and an electrochemical process performed by self-alignment is performed in one step without adding any mask. Since it only needs to be added, the increase in cost can be kept low. When electrolytic plating is used, the plating layer can be used as a low-resistance lower electrode facing the movable part.
[0121]
【The invention's effect】
By the manufacturing method including the steps described above, in a micromachine having a movable part and a fixed part facing the movable part, the movable part is single crystal silicon, and the contact area when the movable part comes into contact with the fixed part is reduced. The effect that the micromachine characterized by having the convex part to reduce in the fixed part is realizable is acquired.
[0122]
In the micromachine of the present invention, when the bottom surface of the movable portion contacts the outermost surface of the support substrate, the convex portion provided on the fixed portion has an action of reducing the contact area, and therefore tends to adhere. There is a reduction effect. The bottom surface and the top surface of the movable part have an effect of being formed from a flat surface having no irregularities, and therefore there is an effect of reducing the tendency of breakage due to stress concentration when the movable part is subjected to bending. In addition, there is an effect that there is no grain boundary in the movable part, and there is an action formed from single crystal silicon with few dislocations and defects, and therefore the effect of reducing the tendency of breakage due to stress concentration when the movable part is bent by external force, It has the effect of avoiding the phenomenon of intergranular corrosion and intergranular cracking when the moving part is treated with chemicals or gas.
[0123]
Furthermore, in the present invention, since the micromachine is constituted by a material having a stable physical property of single crystal silicon, for example, a piezoresistor, which is an element for detecting stress, can be stably formed in the micromachine, and is therefore movable. The sensitivity of the displacement detection of the part can be increased, and for example, the sensitivity of the mechanical quantity sensor part can be increased. Furthermore, the semiconductor element can be built in, for example, an anchor portion inside the micromachine, and the effect of realizing the sophistication (intelligent) and miniaturization of the micromachine can be obtained.
[0124]
The above various excellent effects can be enjoyed simultaneously.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating the steps up to formation of an SOI substrate according to a first embodiment of the present invention.
FIGS. 2A to 2C are views for explaining the formation from the SOI substrate formation to the micromachine formation in the first embodiment of the present invention, wherein A) to C) and E are cross-sectional views, and D) is a plan view.
FIG. 3 is a cross-sectional view illustrating the process up to the formation of an SOI substrate according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating from SOI substrate formation to micromachine formation in a second embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating the process up to formation of an SOI substrate according to a third embodiment of the present invention.
FIG. 6 is a cross-sectional view illustrating from SOI substrate formation to micromachine formation in a third embodiment of the present invention.
FIG. 7 is a cross-sectional view illustrating the process up to formation of an SOI substrate in a fourth embodiment of the present invention.
FIG. 8 is a cross-sectional view illustrating from SOI substrate formation to micromachine formation according to the fourth embodiment of the present invention.
FIG. 9 is a cross-sectional view illustrating from SOI substrate formation to micromachine formation in a fifth embodiment of the present invention.
FIG. 10 is a cross-sectional view for explaining from SOI substrate formation to micromachine formation in 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 cross-sectional view showing a problem of a conventional micromachine.
[Explanation of symbols]
300, 400, 420, 500, 520, 600, 800 Silicon substrate
301,308,401,408,508,601,608,708,730,731 Recess
302,304,404,421,504,530,602,604,804 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 Projection
309, 310, 409, 410, 590, 510, 609, 610
interface
311, 411, 511, 711, 811 Movable part
312, 412, 512, 712, 812 Anchor part
313 Large pattern
314,319 Line pattern part
315 worm-eaten pattern part
316, 416, 516, 616, 630, 631, 716 opening
317 patterned single crystal silicon layer
318 holes
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 (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 convex portion that reduces a contact area when the movable portion contacts the fixed portion. A manufacturing method of a micromachine provided in the fixing part,
A so-called SOI substrate comprising a supporting substrate, a buried insulating film formed on the supporting substrate, and a single crystal silicon layer formed on the buried insulating film, wherein the single crystal silicon layer and the buried substrate are formed. A first step of forming an SOI substrate having a flat interface with the embedded insulating film and having a convex portion at the interface between the buried insulating film and the support substrate;
A second step of performing an etching through the single crystal silicon layer of the SOI substrate and forming an opening reaching the buried insulating film in the single crystal silicon layer;
A third step in which the opening is an etching hole, the buried insulating film is etched, and a self-supporting structure made of the single crystal silicon layer is obtained;
The first step includes a step of forming a recess in the main surface of the support substrate, a step of forming an insulating film on the main surface of the structure, and a step of flattening the main surface of the insulating film; And a step of bonding the silicon substrate to a thin film. 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 that reduces a contact area when the movable portion contacts the fixed portion. A manufacturing method of a micromachine provided in the fixing part,
A so-called SOI substrate comprising a supporting substrate, a buried insulating film formed on the supporting substrate, and a single crystal silicon layer formed on the buried insulating film, wherein the single crystal silicon layer and the buried substrate are formed. A first step of forming an SOI substrate having a flat interface with the embedded insulating film and having a convex portion at the interface between the buried insulating film and the support substrate;
A second step of performing an etching through the single crystal silicon layer of the SOI substrate and forming an opening reaching the buried insulating film in the single crystal silicon layer;
A third step in which the opening is an etching hole, the buried insulating film is etched, and a self-supporting structure made of the single crystal silicon layer is obtained;
In the first step, an insulating film is formed on the main surface of the silicon substrate, a recess is formed on the main surface of the insulating film, and an intermediate film is formed on the main surface of the structure. A method of manufacturing a micromachine, comprising: a step of flattening a main surface of a film; and a step of bonding the structure to a support substrate through the intermediate film and thinning the silicon substrate. 3. The micromachine manufacturing method according to claim 1, wherein a friction coefficient between the first substrate and the second substrate on the outermost surface of the convex portion is larger than that of the support substrate between the first step and the second step. A method of manufacturing a micromachine, comprising a step of forming a small film. 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 that reduces a contact area when the movable portion contacts the fixed portion. A manufacturing method of a micromachine provided in the fixing part,
Preparing a support substrate and a single crystal silicon substrate, forming a spacer on the main surface of the support substrate or the single crystal silicon substrate; and
Forming a protrusion on the main surface of the support substrate;
Bonding the support substrate and the single crystal silicon substrate via the spacer, and forming a cavity;
Thinning the single crystal silicon substrate to obtain a single crystal silicon layer;
Etching through the single crystal silicon layer, forming an opening reaching the cavity, and obtaining a self-supporting structure comprising the single crystal silicon layer;
A method for manufacturing a micromachine, comprising: 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 that reduces a contact area when the movable portion contacts the fixed portion. A manufacturing method of a micromachine provided in the fixing part,
A supporting substrate, a buried insulating film formed on the supporting substrate, and a buried insulating film formed on the buried insulating film; Etching so as to penetrate the single crystal silicon layer of the so-called SOI substrate composed of the single crystal silicon layer, and forming an opening reaching the buried insulating film in the single crystal silicon layer;
Forming the opening as an etching hole, etching the buried insulating film, and obtaining a self-supporting structure made of the single crystal silicon layer; and
Performing an electrochemical process on a region of the support substrate where the buried insulating film has been etched, so that a portion to be processed of the electrochemical process is not flat;
A method for manufacturing a micromachine, comprising: 6. The method of manufacturing a micromachine according to claim 5, wherein the electrochemical treatment is an anodic oxidation etching process. 6. The method of manufacturing a micromachine according to claim 5, wherein the electrochemical treatment is an electrolytic deposition treatment.

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