JPH07220994A - Microstructure and forming method for the same - Google Patents

Abstract

PURPOSE:To electrically connect a board without restriction of a structure material by adhering a first board to a second board via an adhesive layer made of a resin thin film, forming a thin film structure of the second board formed in a thin film from a rear surface, mechanically connecting the first board to the structure via a supporting layer, and removing the adhesive layer. CONSTITUTION:A beam pattern 5 is formed on an Si board 4 by an RIE with a photoresist 101 formed on the board 4 by a photolithography method as a mask, and the resist 101 is then peeled as a second board. Then, after an adhesive layer 6 made of a PMMA resin thin film is formed on the glass board 1 of the first board, the second board is adhered to the first board by applying a pressure from the rear surfaces of the boards. Thereafter, after the second board is wet etched to a thin film, it is further etched by an RIE to form an Si beam 2. Then, the PMMA is etched by the RIE, the formed Al thin film is patterned to form a support, and the PMMA is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a microstructure manufactured by using a micromechanics technique, particularly a microstructure manufactured by using a sacrificial layer.

[0002]

2. Description of the Related Art In recent years, micromachines having a small movable mechanism have been studied by micromechanics technology. In particular, a microstructure formed by using a semiconductor integrated circuit formation technique (semiconductor photolithography process) can form a plurality of small mechanical parts with high production reproducibility on a substrate. Therefore, it is relatively easy to form an array and reduce the cost, and due to the miniaturization, high-speed response can be expected as compared with the conventional mechanical structure.

[0003]

There are the following four typical methods for producing a microstructure on a substrate. As a first method, a wobbled micromotor (M. Mehregany et al., “Operatio” composed of a polysilicon film is used.
n of microfabricated harmonic and oridinary side-d
rive motors ”. Proceedings IEEE Micro Electro Mec
hanical Systems Workshop 1990. p.1-8) and linear microactuator (P. Cheung et al., “Modeling
and position-detection of a polysilicon linear mic
roactuator ”, Micromechanical Sensors, Actuators,
and Systems ASME 1991, DS C-Vol.32, p.269-278) and the like, which is a method for forming a sacrificial silicon oxide film on a Si substrate and a thin film poly structure for forming a microstructure. Silicon, SOI (Sion Insulator) or SIM
OX (Separation by ion implantation of oxygen, B.
Diem et al., “SOI (SIMOX) as a Substrate for Surfa
ce Micromachining of Single Crystalline Silicon Se
nsors and Actuators ”, The 7th International Confe
rence on Solid-State Sensors and Actuators, Transd
ucers '93, June 7-10, 1993. p.233-236), which is a method of using a silicon oxide film as a sacrificial layer after removing the silicon oxide film with a hydrofluoric acid solution after patterning the silicon film into a desired shape. .

In the first method, however, it is necessary to use a hydrofluoric acid corrosion resistant material which is not etched by hydrofluoric acid as a structure in order to remove the silicon oxide film by etching with an aqueous solution of hydrofluoric acid. It is not possible to wire electrodes such as electrodes. Furthermore, when polysilicon is used as a microstructure, it is necessary to control the film stress of polysilicon so that warpage due to film stress does not occur. When the SOI substrate is used, the silicon oxide film under the bulk Si thin film is removed, so that the silicon oxide film supporting the structure is etched back and the structure becomes a beam shape, which makes electrical connection between the substrate and the structure difficult. Becomes

The second method is a spatial light modulator (LJ Hornbec) consisting of an aluminum (Al) thin film micromirror.
k, Japanese Unexamined Patent Publication (Kokai) No. 2-8812), in which a photoresist serving as a sacrificial layer is coated on a substrate, an Al thin film is formed into a thin film, and patterned into a desired shape, followed by dry etching using oxygen plasma. In this method, the resist is removed to form a microstructure composed of an Al thin film.

In this method, by using a photoresist as a sacrificial layer, it is possible to form microstructures on various kinds of substrates without depending on the surface roughness of the substrate. As a result, the sacrificial layer can be removed by dry etching by reactive ion etching (RIE), and the microstructure and the substrate that are attached when the sacrificial layer is removed by wet etching (St
icking) can be avoided. However, it is necessary to form the structure thin film at a low temperature at which the photoresist does not cause thermal damage during the manufacturing process, and the structure material is largely restricted.
Furthermore, in order to form a thin film of the microstructure by a thin film forming process such as vacuum deposition and sputtering, it is necessary to control the stress of the film so that the manufactured microstructure does not warp due to the film stress.

A third method is to form a microstructure pattern on a bulk Si substrate, then bond a part of the pattern to a glass substrate by an anodic bonding method, and etch the bonded Si substrate from the back surface. In this method, only the microstructure is left on the glass substrate.
A linear actuator (Y. Gianchandani et al., Consisting of a bulk Si thin film obtained by thinning a Si substrate by using this method)
“Micron-Size, HighAspect Ratio Bulk Silicon mic
romechanical Devices ”, Proceedings IEEE Electro M
echanical Systems Workshop. 1992. p.208-213) and AFM (Atomic Force Microscop) made of silicon nitride film.
e) Cantilevers (TR Albrecht et al., United S
tates Patent Number 5,221,415) and the like can be formed.

In this method, it is not necessary to use a sacrificial layer, and it is possible to form the microstructure with a material having no hydrofluoric acid resistance. However, since it is necessary to perform anodic bonding with glass, the material is conductive Si, Al, Ti, Ni or the like that forms an oxide, or a material such as a silicon nitride film or a silicon oxide film that can be anodically bonded only in a thin film. Limited. Also, the bonding temperature during anodic bonding is 300
The glass must have a coefficient of thermal expansion almost equal to that of the Si substrate in order to avoid the damage of the substrate due to the distortion of thermal stress. The glass that can be used for this purpose is limited to Pyrex glass, and the trade name is # 7740 Corning glass. Furthermore, it is not possible to wire the pattern of the electrodes on the microstructure formed so as to previously form the voids in the microstructure. Further, since it is necessary to use glass containing mobile ions as the substrate, it is not possible to use a substrate such as Si or GaAs on which circuits can be integrated. Furthermore, when the glass and the conductive material are bonded by anodic bonding, the surface roughness of the glass and the conductive material is 50.
It is necessary to keep it below 0A. SP5,221,415
Then, when anodic bonding the silicon nitride film and the glass 4
Since the electrodes are bonded to each other at a temperature of 75 ° C., the electrodes are vacuum-deposited on the entire surface of the substrate after forming the microstructure, so that the pattern cannot be formed on the cantilever.

In view of the above problems, it is an object of the present invention to provide a method of forming a microstructure capable of realizing the following and a microstructure using the same. (1) The materials for the microstructure and the substrate are not limited, and (2) an electrode pattern is formed on the microstructure so that the microstructure can be electrically connected to the substrate, and the microstructure. .

[0010]

That is, the present invention, which has been made to achieve the above object, comprises a step of forming an adhesive layer on a first substrate and / or a second substrate, and a first step through the adhesive layer.
Bonding the substrate and the second substrate, forming a thin film structure composed of the second substrate, removing a part of the adhesive layer, the thin film structure and the first substrate A method for forming a microstructure, comprising: a step of forming a support layer for connecting to each other; and a step of removing the adhesive layer, wherein the adhesive layer is made of a resin thin film, and the first substrate and / or Alternatively, a groove may be formed on the second substrate.

Further, the microstructure manufactured by the above-mentioned forming method comprises a first substrate, a support portion composed of a support layer, and
A second part supported by the supporting part via the gap and the substrate;
And a beam formed by thinning the substrate, wherein the supporting portion connects and supports the first substrate and the upper surface of the beam when supporting the beam through a gap.

As the step of forming the adhesive layer, a usual method used as an adhesive method can be used. For example, a method in which a solution obtained by diluting resin molecules with an organic solvent is applied by a spinner method, a dipping method, a spray method, or the like, Alternatively, a resin thin film forming method such as a method of forming a film by the Langmuir-Brogit (LB) method is used. With the coating method, the resin thin film can be coated with good flatness even if there are surface irregularities on the substrate, and this makes it possible to achieve good results without depending on the substrate surface roughness in the step of adhering to the second substrate. Surface bonding becomes possible. As the resin material, a photoresist containing few impurities such as Na ions is preferable when forming an adhesive layer on a Si substrate on which circuits are integrated. More preferably, it is a rubber-based photoresist containing a rubber excellent in adhesion and mechanical strength. Particularly preferred is a rubber photoresist containing a rubber having particularly excellent adhesion and mechanical strength.

The rubber usable in the present invention is, for example, "Microfabrication and Resist" (Saburo Nonogaki, edited by The Polymer Society of Japan, published by Kyoritsu Shuppan, 1991), page 11, lines 13 to 12.
The cyclized rubber described on page 3, line 3 is preferred, and OMR is used as a high-resolution negative photoresist manufactured by Tokyo Ohka Kogyo Co., Ltd.
A photoresist containing rubber such as −83 can be preferably used.

When the Langmuir-Brogit method is used, a monomolecular cumulative film, that is, an LB film (Langmuir-Brogit film) composed of a hydrophobic group or a hydrophilic device is cumulatively formed on the surface of the first substrate by a single layer or more. , Hydrophobic groups,
Alternatively, film formation is performed with the adhesive surfaces composed of hydrophilic groups facing each other. In the LB method, it is possible to control the film thickness of the resin film with a precision of nanometer, and thereby it is possible to control the interval of the voids formed by removing the resin thin film with a precision of nanometer.

In the step of adhering the first substrate and the second substrate, the first substrate and the second substrate are pressed against each other from the back side with pressure through a thin film-coated adhesive layer, and then heat-treated to adhere them. The organic solvent contained in the layer film is evaporated,
A method is preferable in which the resin is cured and the adhesive strength to each substrate is strengthened. By forming a groove in the first and / or second substrate, the vapor of the organic solvent generated during the heat treatment can escape through the groove. If the first substrate and the second substrate are conductors, it is also possible to apply a voltage between the substrates and apply a pressure using the generated electrostatic force to bond them.

When the first substrate and the second substrate are bonded using the LB cumulative film, the bonding surface of the LB film formed on the first substrate and / or the second substrate and the bonding surface of the second substrate are overlapped. At the same time, a voltage is applied to the first and second substrates and they are bonded by the generated electrostatic force. When gluing, first and second
When the LB film is formed on both substrates, the adhesive surfaces are hydrophobic groups or hydrophilic groups, and when the LB film is formed on either the first substrate or the second substrate, the LB film is adhered. If the surface is a hydrophobic group (or hydrophilic group), the adhesive surface of the other substrate will be hydrophobic (or hydrophilic). By applying a voltage and performing bonding while heating at a temperature at which the LB cumulative film is not thermally decomposed, stronger bonding can be achieved.

The second substrate is formed into a thin film in order to form the thin film structure after the second substrate is bonded to the adhesive layer. To make a thin film, wet etching using an etching solution suitable for the substrate material, dry etching using a reactive gas,
Alternatively, the back surface may be shaved by a method of lapping with abrasive grains. When Si is used as the second substrate,
As an etching solution, potassium hydroxide solution (KOH),
An alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH) or a mixed aqueous solution of hydrofluoric acid and nitric acid is used, and a plasma gas such as CF ₄ , SF ₅ and NF ₃ is used as the reactive gas. If a bulk substrate such as Si is used as the second substrate, the microstructure does not warp, and the problem of warpage due to film stress is a problem when a thin film is formed on the sacrificial layer to fabricate the microstructure. Can be avoided.

In the step of forming the thin film structure, the thinned second substrate is patterned by a semiconductor photolithography process, or a pattern of the structure is formed on the bonding surface of the second substrate in advance. It is formed by removing it from the back surface. It is also possible to use the stepped portion of the pattern of the previously formed structure as the groove.

The supporting layer is for mechanically connecting the first substrate and the thin film structure, and is formed on the upper surface of the thin film structure and the surface of the first substrate by being formed before removing the adhesive layer. The structure is such that the thin film structure is suspended from above.
By using a metal thin film (such as Al) as the support layer,
The thin film structure and the first substrate can be electrically connected.

In the step of removing the adhesive layer, a commonly used method can be used, for example, a method of removing by wet etching by immersing the resin thin film in a solution that dissolves it, a dry etching by ashing using oxygen plasma and oxygen radicals. Or when the LB film is used as the adhesive layer, the LB film is heated to decompose and evaporate and remove the LB film. As another heating method, thermal decomposition may be performed by laser cross irradiation such as CO ₂ laser. Since the adhesive layer is made of resin, dry etching is possible, and sticking, which is a problem when removing the sacrificial layer by wet etching, is avoided.

[0021]

In the method of forming a microstructure of the present invention having the above-described structure, the first substrate and the second substrate are adhered by the adhesive layer made of the resin thin film formed on the first and / or the second substrate. After that, a thin film structure is formed on the second substrate which is thinned from the back surface, the first substrate and the thin film structure are mechanically connected by a supporting layer, and the adhesive layer is removed. By adhering with a resin thin film and making the second substrate a thin film from the back surface, the material of the thin film structure formed on the first substrate, the second substrate, and the second substrate is not limited, and the adhesive layer is removed. Electrodes and the like can be formed on the thin film structure in the preceding step.
Since the adhesive layer is made of a resin thin film, it can be removed by solvent, ashing, heating, etc., and the electrode is not etched. Then, sticking can be avoided by removing the adhesive layer by dry etching or by thermally decomposing it by heating.

Examples of the microstructure which can be manufactured by the method of the present invention include an electrostatic actuator, A
Cantilevers used in microscope systems that detect tunnel currents such as FM and STM (Sanning Tunneling Microscope), van der Waals force, magnetic force, electrostatic force, etc., and air bridge structure type wiring, etc. can be manufactured with high precision. According to the method of the present invention, a substrate, a fixed electrode and a drive electrode formed on the substrate, a beam supported through a gap by a support made of a metal thin film above the drive electrode, and a movable beam formed on the beam. In an electrostatic actuator including an electrode, the supporting portion electrically connects the movable electrode and the fixed electrode, mechanically supports the beam from the upper surface of the beam, and applies a voltage to the drive electrode and the movable electrode. By doing so, it is possible to manufacture a microstructure such as an electrostatic actuator characterized in that the beam is displaced.

[0023]

EXAMPLE An example of a method of forming a microstructure according to the present invention will be described in detail with reference to the drawings of FIGS. The microstructure of the present invention will also be described.

First Embodiment FIGS. 1 and 2 are manufacturing process diagrams for explaining a first embodiment of the method for forming a microstructure of the present invention, and FIG. 3 is a microstructure manufactured by using the same. It is a perspective view of a body. The microstructure of the present invention has the following structure from FIG. 1
Is a glass substrate serving as a first substrate, 2 is a beam made of Si formed by thinning the second substrate, and 3 is a support portion made of an Al thin film. The beam 2 has a structure in which it is suspended from the upper surface of the beam by a supporting part 3 through a gap, and the supporting part 3 mechanically connects the beam 2 and the substrate 1 by an air bridge structure. .

The forming method of the present invention in the AA sectional view of the microstructure shown in FIG. 3 will be described with reference to FIGS. The Si substrate 4 made of bulk Si is used as the second substrate, and the photoresist 101 is applied to the substrate, and the photoresist is patterned by a photolithography process of exposing and developing (FIG. 1A). Using the photoresist as a mask, the Si substrate 4 is SF ₆ and CC
A beam pattern 5 is formed on the Si substrate 4 by etching by reactive ion etching (RIE) using a mixed gas of l ₂ F ₂ . The photoresist 101 is peeled off using a resist peeling liquid to manufacture a second substrate shown in FIG. The step difference of the beam pattern 5 was 5 μm.

Next, a solution of polymethylmethacrylate (PMMA) dissolved in methyl ethyl ketone (MEK) on the glass substrate 1 (trade name, # 7059 Corning) which is the first substrate is one of the organic thin film coating methods. It is applied by a spinner method to form an adhesive layer 6 made of a resin thin film of PMMA (FIG. 1 (C)). The glass substrate has a thermal expansion coefficient about 1.4 times larger than that of Si. The second substrate of FIG. 2B and FIG.
The first substrate on which the adhesive layer 6 of (C) is formed is bonded by applying pressure from the back surface of each substrate as shown in FIG. 1 (D). Adhesive pressure was applied while observing from the glass surface side of the second substrate so that the beam pattern 5 was sufficiently adhered to the adhesive layer. After adhering the first substrate and the second substrate via the adhesive layer, the adhesive layer was cured by heating to 150 ° C. The film thickness of the adhesive layer after curing was set to 2 μm.

After that, the Si substrate 4 was wet-etched with a 30 wt% KOH aqueous solution heated to 100 ° C. to make the second substrate into a thin film as shown in FIG. 1 (E). Then S
The second substrate was further etched by RIE using F ₆ gas to form a Si beam 2 having a film thickness of 1 μm (FIG. 1).
(F)). Subsequently, PMM is performed by RIE using oxygen gas.
A was etched in the same pattern as the beam (Fig. 1
(G)). An Al thin film 7 serving as a support layer was formed on the Si beam formed as described above to a thickness of 1 μm by a sputtering method using an Al target, which is one of vacuum deposition methods. A photoresist is applied on the Al film by a photolithography process, exposed, and developed (FIG. 2 (I)),
The Al film 7 was patterned using an Al etchant composed of phosphoric acid, nitric acid, and acetic acid to form the pattern of the supporting portion 3 in FIG. 2 (J). Finally, PMMA was immersed in OMR stripping solution-502 (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd. for removal to remove the Si beam having a film thickness of 1 μm having a void 8 of 2 μm in FIG. 2 (K). The microstructure shown in FIG. 3 supported by an Al thin film was formed. The stripper is an organic solution and does not etch the Al electrode.

In the forming method of the present invention, the bulk Si substrate 4 is used.
As shown in FIG. 1B, a beam-shaped thin film structure pattern is first formed. By making the bulk Si into a thin film, it was possible to produce a warp-free beam having essentially no internal stress. Further, a groove is formed on the Si substrate 4 by the pattern of the beam, and the vapor of the solvent generated when the resin thin film is heat-treated and cured in the step of FIG. 1D can escape through the groove. . When there is no groove, when the content of the solvent contained in the resin-dissolved solution at the time of coating is not adjusted, the bubbles between the adhesive layer and the second substrate remain due to the solvent vapor during the heat treatment. There is. Forming the groove has an effect of preventing the generation of bubbles. Further, by using the resin thin film as the adhesive layer, it becomes possible to use, as the first substrate, a material having a coefficient of thermal expansion different from that of the second substrate. As shown in the present invention, the resin thin film serves as an adhesive layer for adhering the first substrate and the second substrate together with a role of a sacrificial layer for forming a microstructure.

Although a metal thin film made of an Al thin film is used for the supporting portion, an electrically insulating microstructure can be formed on the substrate by the same process if an insulating film such as a silicon oxide film is used. Needless to say.

Second Embodiment FIGS. 4 and 5 are manufacturing process diagrams for explaining a second embodiment of the method for forming a microstructure according to the present invention, and FIG. 6 is a microstructure manufactured using the same. It is a perspective view of a body. The microstructure of the present invention has the following structure from FIG. 1
0 is a Si substrate, 14 is an insulating layer made of a silicon oxide film,
Reference numerals 15 and 16 denote driving electrodes and fixed electrodes formed in a thin film on the insulating layer 14, and the beam 12 has a torsion bar and is supported by the supporting portions 13 and 13 ′ from the upper surface of the beam through a gap. The movable electrode 17 is formed. The support portion 13 is made of an electric conductor and electrically connects the movable electrode 17 and the fixed electrode 16. The microstructure of the present invention can be displaced as an electrostatic actuator by applying a voltage to the fixed electrode 16 electrically connected to the drive electrode 15 and the movable electrode on the beam 12.

As a result, the electrostatic actuator has a structure in which the beam 12 is suspended from the upper surface of the beam by the supporting portions 13 and 13 'through the gap, and the supporting portions 13 and 13' are provided.
Air between the beam 12, the insulating layer 14 and the fixed electrode 16.
A bridge (Air Bridge) structure is used to connect mechanically and electrically. By applying a voltage to the drive electrode and the movable electrode, the torsion bar twists and rotates, and the beam is displaced.

A second embodiment of the forming method of the present invention in the BB sectional view of the microstructure shown in FIG. 6 will be described with reference to FIGS. As the second substrate, the silicon nitride film 19 which will eventually become the structural material of the beam is formed by low pressure CVD (LPCV).
According to D), the Si substrate 18 is used, which is formed into a film of 1 μm at 850 ° C. with a mixed gas of dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) (FIG. 4A). An adhesive layer 20 of photoresist is applied on the silicon nitride film 19 by a spinner method (FIG. 4 (B)). For the photoresist, OMR83 which is a rubber type resist manufactured by Tokyo Ohka Co., Ltd.
(Trade name) was used. An insulating layer 14, a fixed electrode 16 (not shown), and a drive electrode 15 are provided on the other first substrate to be bonded.
The Si substrate 10 having The insulating layer 14 is a silicon oxide film having a thickness of 1 μm obtained by thermally oxidizing the Si substrate 10 using an oxidizing gas, and the drive electrode 15 and the fixed electrode 16 have Cr of 5 nm and Au by an electron beam evaporation method on the insulating layer.
Is continuously formed into a film having a thickness of 200 nm and is patterned into an electrode pattern shown in FIG. 6 by a photolithography process. The same adhesive layer 21 of photoresist as the second substrate is applied to the first substrate (FIG. 4C). After applying the photoresist, the first substrate and the second substrate are pre-treated at 50 ° C. for 10 minutes to adjust the content of the solvent contained in the photoresist, and the solvent vapor at the time of adhesion is used to remove the photoresist. Prevented from leaving bubbles in the. Figure 4 (B)
The second substrate of 1) and the first substrate of FIG. 4 (C) are bonded as shown in FIG. 4 (D). At the time of adhesion, a voltage of 100 V was applied to the Si substrate 18 and the Si substrate 10, and pressure was applied by the electrostatic force generated at this time (not shown). A voltage was applied to bond the first substrate and the second substrate through the adhesive layer made of photoresist, and then heated to 120 ° C. to cure the photoresist. After curing, the adhesive layers 20 and 21 were integrated, and the thickness of the adhesive layer 22 was 2 μm.

Next, the Si substrate 18 was wet-etched with a 30 wt% KOH aqueous solution heated to 100 ° C., leaving only the silicon nitride film 19 as shown in FIG. 4 (E). The silicon nitride film 19 has an extremely slow etching rate as compared with Si and is hardly etched. Then, a metal film 100 of Cr and Au is formed in the same manner as the fixed electrode 15 is formed, a photoresist 102 is applied, and patterning is performed by a photolithography process (FIG. 4).
(F)). The metal film 100 was etched with an aqueous solution of iodine and potassium iodide using the photoresist 102 as a mask to form the movable electrode 17. Next, the photoresist 103 is patterned in the same manner as in FIG.
(G)), using the photoresist 103 as a mask, the silicon nitride film 19 is etched by RIE using CF ₄ gas, then the etching gas is changed to oxygen gas, and the photoresist 103 is ashed by RIE using oxygen gas. Was formed (FIG. 4 (H)). An Al thin film 25 serving as a support layer was formed on the beam of the silicon nitride film formed as described above and the movable electrode 17 to a thickness of 1 μm. A photoresist 104 is applied, exposed, and developed on the Al film by a photolithography process (see FIG. 2).
(I)), and the Al film 25 was patterned by RIE using a mixed etching gas of BCl ₃ and Cl ₂ to form the supporting portions 13 and 13 ′ (FIG. 4 (K)).

By using RIE, the photoresist 104 and the photoresist under the beam pattern 24 were removed by etching with oxygen plasma to form a gap 26. The etching conditions at this time were 50 ccm of oxygen or more and a gas pressure of 20 Pa or more at the time of etching, and the conditions for taking a large side etch were adopted. FIG. 4 using the above forming method.
The microstructure shown in FIG. 6 in which the beam 12 of the silicon nitride film having the film thickness of 1 μm and having the void 26 of 2 μm of (I) was supported by the Al thin film was formed. Sticking, which is a problem when removing the sacrificial layer by wet etching, could be avoided without dry etching of each electrode.

According to the forming method of the present invention, the beam can be formed by thinning the silicon nitride film formed on the Si substrate 10 by removing bulk Si. Further, the drive electrode can be formed on the beam, and the fixed electrode formed on the first substrate can be electrically connected through the supporting portion. Further, by applying a voltage between the movable electrode and the driving electrode, the free end of the beam was displaced in the direction of the first substrate in accordance with the torsional rotation of the torsion bar.

By applying the resin thin film on the first substrate, it is possible to apply the resin thin film evenly to the irregularities on the substrate caused by the drive electrodes, the fixed electrodes, etc., and it is possible to maintain the flatness of the adhesive surface and to obtain a good result. It became possible to bond substrates to each other.
Further, by using the photoresist as the adhesive layer, it goes without saying that the microstructure can be similarly formed even if the substrate in which the integrated circuit is formed on the Si substrate 10 which is the first substrate is used. Since the photoresist has a very low content of mobile ions, it does not cause a malfunction due to the mobile ions entering an electronic device such as a MOS transistor.

Since the substrate is made of Si, which is a conductor, a voltage can be applied to bond the first and second substrates, and the applied pressure required for bonding can be easily controlled. It was

As described above, according to the method for forming a microstructure of the present invention, an Al electrode is formed on an insulator made of a silicon nitride film formed at a high temperature of 850 ° C., and an Al electrode is formed on the substrate without sticking. It became possible to make an electrical connection through the void.

Here, a silicon nitride film is used as an insulator.
Although used, Si with a silicon oxide film formed on the second substrate
If a substrate is used, the same manufacturing process as shown in FIGS.
A beam made of silicon oxide film can be formed
Is. Al as the insulator ₂ O₃ , AlN, etc.
It is possible to use materials, and it is not limited to insulators.
It can be replaced with a thin metal film of Ni, Cr, Au, etc.
Is. Thin film used as beam material formed on the second substrate
The thickness of is not important, for example glue and remove the second substrate
After that, it is thinned by etching to obtain the desired film thickness
It is also possible. Although the Si substrate was used as the second substrate,
A glass substrate such as fused quartz may be used. In this case,
In the manufacturing process of FIG. 4, LPCV is used instead of the silicon nitride film.
Hydrofluoric acid aqueous solution by using polysilicon by D
Through the same steps except that the glass substrate is removed by
Beam of polysilicon can be formed
Is. That is, according to the forming method of the present invention, an insulator, a gold
Microstructures made of various materials such as metals and semiconductors
Can be formed avoiding icking.

Similar to the first embodiment, the resin thin film serves as an adhesive layer for adhering the first substrate and the second substrate together with the role of a sacrificial layer for forming a microstructure.

Third Embodiment A third embodiment of the method for forming a microstructure of the present invention using an LB film as an adhesive layer will be described with reference to FIG. In the figure, 31 is a Si substrate which is a first substrate, 32 is a Si substrate which is a second substrate for adhering to the Si substrate 31, and 33 is an LB film formed on the surface of the Si substrate 31 by the LB method. ,
Reference numerals 34, 35, and 36 are LB films accumulated in layers. Similarly, multiple LB films are accumulated between the LB film 35 and the LB film 36, and are omitted in the drawing (broken line portion in the drawing). L
The B film is laminated so that the total thickness of the B film is 80 nm. 41, 43, 45, 47 are hydrophobic groups of the LB film, 40,
42, 44, and 46 are hydrophilic groups of the LB film, and the films were formed with the adhesive surfaces of the hydrophobic groups or the hydrophilic groups facing each other. Reference numeral 53 is a power source for applying a voltage between the Si substrate 31 and the Si substrate 32, and the lead wires 54, 5
5 electrically connects to the needle-shaped electrodes 51 and 52.
50 is a platen having electrical conductivity.

Stearic acid was used for the LB films 33, 34, 35 and 36. The Si substrate 32 is superposed on the adhesive surface of the LB film formed on the Si substrate 31. Then power 53
By applying a voltage of 6 V between the Si substrate 31 and the Si substrate 32 for 30 minutes, the Si substrate 32 and the LB film 36 are brought close to each other by the electrostatic force generated by the voltage, and the Si substrate 32
And the hydrophobic group 47 of the LB film adhered.

Next, the substrate thus bonded is similarly composed of a support portion made of an Al film and a Si beam by using the steps of FIGS. 1 (E) to 2 (J) of the first embodiment. A microstructure pattern was formed. Unlike the first embodiment, a Si substrate having no beam pattern is used as the first substrate, and an LB cumulative film is used as the adhesive layer.

The step of removing the adhesive layer has the same shape except that the LB film is used as the adhesive layer.
The substrate shown in (J) was heated to decompose and evaporate the LB cumulative film. By this decomposition and evaporation, the adhesive layer composed of the LB cumulative film disappears and is removed. After heating for 1 hour at a heating temperature of 350 ° C., the LB cumulative film was removed, and the Si beam could be formed by being supported by the support part of the Al film. The space between the voids was 80 nm, which was the same as the film thickness of the LB cumulative film.

In the method of the third embodiment of the present invention, by using the LB film, it was possible to form a microstructure in which the distance between the voids formed by removing the resin thin film was controlled with nanometer accuracy. Moreover, by removing the adhesive layer by heating, sticking, which is a problem when removing the sacrificial layer by wet etching, could be avoided.

Although the LB cumulative film is formed only on the first substrate in this embodiment, the LB film may be formed on both the first and second substrates. In this case, the LB film surface has a hydrophobic group. Or hydrophilic groups. As another method of removing the adhesive layer, thermal decomposition by irradiation with a laser beam such as a CO ₂ laser is also possible. By using the method of the present invention, it is possible to manufacture a microstructure having an extremely narrow void spacing of about several tens of nm because the void spacing is controlled by the film thickness of the LB cumulative film and removed by heating. became.

Although stearic acid was used as the LB cumulative film, arachidic acid, a ferroelectric LB film (for example, a diacetylene-based or benzene derivative-based), or another LB film such as a polyimide LB film may be used. Needless to say, the intention of the present invention is not changed. Further, although Si is used as the substrate, it goes without saying that other substrates such as glass, metal, and a glass substrate having a metal film formed thereon can be used.

[0048]

As described above, according to the method for forming a microstructure of the present invention, the first substrate and the second substrate are adhered by the adhesive layer made of the resin thin film, and the back surface is made into a thin film. By forming a thin film structure with two substrates, mechanically connecting the first substrate and the thin film structure with a support layer, and removing the adhesive layer, a micro-layer made of various materials such as an insulator, a metal, and a semiconductor. The structure could be formed, the electrode pattern was formed on the microstructure, and the microstructure capable of electrical connection with the substrate was formed.

Further, it is possible to use a bulk material as the beam, and it is possible to form a beam having no warp.

Further, since the resin thin film is an adhesive layer for adhering the first substrate and the second substrate and also plays a role of a sacrifice layer for forming the microstructure, oxygen is used as a method for removing the resin thin film. It became possible to use dry etching with gas or evaporation method by thermal decomposition, and it was possible to avoid sticking, which is a problem when removing the sacrificial layer.

Further, the resin thin film can form a flat surface without being affected by the unevenness due to the electrode pattern or the like formed on the substrate, and the good adhesion can be achieved without depending on the surface roughness of the substrate.

Further, according to the method of the present invention, the microstructure can be formed in a relatively low temperature process, and the microstructure can be formed even if substrates having different thermal expansion coefficients are used.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a first embodiment of a method for forming a microstructure of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the first embodiment of the method for forming a microstructure of the present invention.

FIG. 3 is a perspective view illustrating a microstructure manufactured by using the method for forming a microstructure according to the first embodiment.

FIG. 4 is a diagram showing a manufacturing process of a second embodiment of the method for forming a microstructure of the present invention.

FIG. 5 is a diagram showing a manufacturing process of a second embodiment of the method for forming a microstructure of the present invention.

FIG. 6 is a perspective view illustrating an electrostatic actuator that is a microstructure manufactured by using the method for forming a microstructure according to the second embodiment.

FIG. 7 is an LB of a third embodiment of the method for forming a structure of the present invention.
It is a figure explaining the process of adhering with a film.

[Explanation of symbols]

 1 Glass Substrate 2,12 Beam 3,13,13 'Support 4 Si Substrate 5,24 Beam Pattern 6,20,21,22 Adhesive Layer 7 Al Layer 8,26 Void 10 Si Substrate 11 Torsion Bar 14 Insulation Layer 15 Drive electrode 16 Fixed electrode 17 Movable electrode 18 Si substrate 19 Silicon nitride film 25 Al film 31, 32 Si substrate 33, 34, 35, 36 LB film 41, 43, 45, 47 LB film hydrophobic group 40, 42, 44, 46 LB film hydrophilic group 50 Platen 51, 52 Needle electrode 53 Power supply 54, 55 Lead part 100 Metal film 101, 102, 103, 104 Photoresist

Claims (18)

[Claims] 1. A first substrate, and a support portion composed of a support layer,
The substrate is supported by the supporting portion via a gap, and
A microstructure including a beam formed by thinning a substrate, wherein the supporting unit connects and supports the first substrate and an upper surface of the beam when supporting the beam through an air gap. body. 2. The microstructure according to claim 1, wherein the supporting part is made of a metal thin film. 3. The microstructure according to claim 2, wherein the metal thin film is made of aluminum. 4. The microstructure according to claim 1, wherein the beam is made of Si. 5. The microstructure according to claim 1, wherein the beam is made of an insulating thin film. 6. The method for forming a microstructure according to claim 1,
A step of forming an adhesive layer made of a resin film on the substrate and / or the second substrate, a step of adhering the first substrate and the second substrate via the adhesive layer, and a thin film structure comprising the second substrate. A method for forming a microstructure, comprising: a step of forming, a step of forming a support layer for connecting the thin film structure and the first substrate, and a step of removing the adhesive layer. 7. The method for forming a microstructure according to claim 6, wherein the step of forming the adhesive layer is performed by applying a thin film of a solution in which resin molecules are diluted with a solvent. 8. The method of forming the adhesive layer is formed by a Langmuir-Brogit method.
The method for forming a microstructure according to 1. 9. The method for forming a microstructure according to claim 6, wherein the resin film is made of photoresist. 10. The method for forming a microstructure according to claim 9, wherein the photoresist contains a cyclized rubber. 11. The method for forming a microstructure according to claim 6, wherein a groove is formed on the first substrate and / or the second substrate. 12. The bonding step includes the step of applying pressure to the first and second substrates.
The method for forming a microstructure according to 1. 13. The method for forming a microstructure according to claim 12, wherein the step of applying the pressure is performed by applying a voltage to the first substrate and the second substrate. 14. The method for forming a microstructure according to claim 6, wherein the supporting layer is made of a metal thin film. 15. The method for forming a microstructure according to claim 6, wherein the step of removing the adhesive layer is performed by dry etching using oxygen. 16. The method for forming a microstructure according to claim 15, wherein the dry etching is performed by plasma etching. 17. The method of forming a microstructure according to claim 8, wherein the step of removing the adhesive layer comprises heating. 18. A substrate, a fixed electrode and a drive electrode formed on the substrate, which are formed by using the method for forming a microstructure according to claim 6, and a support made of a metal thin film above the drive electrode. An electrostatic actuator comprising a beam supported through a gap by a section and a movable electrode formed on the beam, the supporting section electrically connects the movable electrode and the fixed electrode, and mechanically An electrostatic actuator characterized in that a beam is supported from an upper surface of the beam, and the beam is displaced by applying a voltage to the drive electrode and the movable electrode.