JP2006062053A - Method for manufacturing micromachine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To selectively form an organic film in a desired region of a micromachine. <P>SOLUTION: A substrate 101 formed with a movable part electrode 104, a supporting part 107 and a movable part 108 and a counter electrode made of platinum are immersed in electrodeposition solution containing sulfonium ions to be cationic species (INSULEED of Nippon Paint Co., Ltd, for instance), negative voltage is impressed on the movable part electrode 104, the supporting part 107 and the movable part 108, and positive voltage is impressed on the counter electrode. Namely, the movable part electrode 104, the supporting part 107 and the movable part 108 are made as negative electrode, the counter electrode is made as positive electrode to be immersed in electrodeposition solution, voltage is impressed by using a constant voltage source, and cationic electrodeposition is performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a micromachine in which the surface of an electrode or the like is covered with a resin film.

  In a MEMS (MicroElectro Mechanical System) device, a micromachine configured by three-dimensionally arranging fine movable parts and control electrodes is used (see Non-Patent Document 1). Such a movable part made of a silicon or metal structure of a micromachine is driven by an electrostatic force generated by an electrode disposed opposite thereto. For example, as shown in FIG. 6A, the movable portion 604 supported by the support portion 603 on the substrate 601 made of silicon or the like on which the insulating film 602 is formed is on the substrate 601 below the distal end portion of the movable portion 604. It is made to drive by the static electricity which the electrode 605 provided in the.

  In such a configuration, it is not easy to draw the movable portion 604 toward the electrode 605 by static electricity generated from the electrode 605 and to keep it at an arbitrary distance from the underlying electrode 605. This is because the balance between the attractive force attracted by the electrode 605 and the elastic force that the movable portion 604 tries to return to is original and unstable. If these balances are lost, for example, if the attractive force is better, the tip of the movable portion 604 comes into contact with the surface of the electrode 605.

  When a conductive material or a semiconductor material is used for the movable portion 604, and the electrode 605 and the movable portion 604 are electrically connected when they come into contact with each other, the contact portion 606 reacts and joins as shown in FIG. In other words, the rebound caused by the elastic force of the movable part 604 may not be restored. This phenomenon is called sticking or sticking and is a problem when driving a movable part in a micromachine. Further, the movable portion 604 has a problem that the electrode 605 is damaged due to friction caused by contact.

In order to avoid the problem caused by the contact between the tip of the movable part and the electrode, it is sufficient that at least one contact surface is covered with a protective film such as an organic resin. In order to realize this, for example, an organic thin film may be formed only on the surface of the electrode. If an organic film is unnecessarily formed in a portion other than the contacted portion, for example, it may cause the operation of the movable portion to be hindered.
As a technique for forming such an organic film, a vapor deposition method, a sputtering method, a spin coating method, and the like have been proposed (see Non-Patent Document 2).

However, since the above-described conventional technique is a two-dimensional film formation method applied to the planar process, in a three-dimensional complex structure such as a micromachine, an organic thin film is formed on a desired region such as only the electrode surface. It is difficult to form a nonconductor such as.
On the other hand, an electrodeposition method has been proposed as a technique for forming a nonconductive film such as an organic resin on a three-dimensional structure. The electrodeposition method is a technique in which a thin film forming material dispersed (dissolved) in a solvent is electrophoresed, and is deposited and adhered to a conductor surface such as a metal (see Non-Patent Document 3).

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
James A. Knapp and Maarten P. de Boer, "Mechanics of Microcantilever Beams Subject to Combined Electrostatic and Adhesive Forces", Journal of microelectromechanical System, Vol. 11, No. 6, (2002). Satoshi Kanehara, Hideo Fujiwara, “Thin Film”, Hanafusa Hagi, 1979 Midoru Kawauchi, Hiroshi Okaho, Yukihiro Nemoto, “Uniformity Improvement Technology in Electrodeposition Coating”, Paint Research, No. 136, Apr. 2001.

However, the formation of the organic film by the above-described electrodeposition method is a technique for coating an automobile casing or the like, and a technique for forming a thin film to be applied to a fine structure of a micromachine used with a semiconductor device has been proposed. Absent.
The present invention has been made to solve the above-described problems, and an object thereof is to enable an organic film to be selectively formed in a desired region of a micromachine.

In the micromachine manufacturing method according to the present invention, for example, a first step in which a first structure having conductivity is formed on a substrate made of a semiconductor, and a second structure having conductivity is the first A second step in which the structure is insulated and separated from the structure and formed on the substrate; and the first structure and the second structure are immersed in an electrodeposition solution containing a cation species; A voltage is applied to at least one of the structure and the second structure, and an organic thin film composed of cationic species is formed on at least one of the surface of the first structure and the surface of the second structure by electrodeposition And a third step for achieving the above state.
Therefore, an organic thin film is selectively formed on the structure formed on the substrate.

In the micromachine manufacturing method, the second structure is a movable structure including a movable part that is spaced apart from the surface of the substrate and extends in a predetermined direction, and the first structure controls the operation of the movable part. Control electrode.
In the micromachine manufacturing method, the cation species may be a sulfonium ion.

  In the method for manufacturing the micromachine, the maximum thickness of the organic thin film to be formed is limited by performing the third step in which the temperature of the electrodeposition liquid is set to a predetermined temperature or lower. In the third step, the maximum film thickness of the formed organic thin film can be controlled (variable) by applying a voltage of a predetermined value or less.

  As described above, according to the present invention, an organic thin film is formed on at least one of the surface of the first structure and the surface of the second structure by electrodeposition using an electrodeposition liquid containing a cationic species. Since the organic thin film is selectively formed on the structure formed on the substrate, the organic film can be selectively formed in a desired region of the micromachine. Excellent effect is obtained.

Hereinafter, the simplest embodiment constituting the gist of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing an example of a method of manufacturing a micromachine according to an embodiment of the present invention.
First, as shown in FIG. 1A, the insulating layer 102 is formed on the semiconductor substrate 101 made of silicon by, for example, a thermal oxidation CVD (Chemical Vapor Deposition) method. Next, a gold / chromium or gold / titanium film is sequentially formed by a vapor deposition method or the like, and these metal films are processed by a known photolithography technique and wet etching so that a movable part electrode having a desired shape is obtained. 104 and the control electrode (first structure) 105 are formed on the insulating layer 102.

Next, a deposited film of silicon oxide is formed on the insulating layer 102 including the movable part electrode 104 and the control electrode 105 by a CVD method, and this film is patterned to obtain the movable part as shown in FIG. A sacrificial film 106 having an opening 106a from which a part of the electrode 104 is exposed is formed.
Next, polysilicon is deposited on the sacrificial film 106 by a CVD method, a polysilicon film is formed in a state in which the opening 106a is filled, and then this polysilicon film is processed by a known photolithography technique and wet etching. Then, as shown in FIG. 1C, the support portion 107 and the movable portion (second structure) 108 supported by the support portion 107 are formed.

  Next, the sacrificial film 106 made of silicon oxide is selectively removed by wet etching with a hydrofluoric acid solution, and a movable part having a movable part extending on the control electrode 105 as shown in FIG. It is assumed that 108 is formed in a state where it is supported by the support portion 107. The movable part 108 is arranged such that the movable part is spaced apart from the control electrode 105 by a predetermined distance. By applying an electric signal to the control electrode 105, the movable part is actuated (displaced) in a predetermined direction by the action of an electric field. ) As described above, the operation of the movable part is controlled by the control electrode 105.

  Next, a semiconductor substrate in which the movable part electrode 104, the support part 107, and the movable part 108 described above are formed in an electrodeposition liquid (for example, Nippon Paint Co., Ltd., INSULED) containing sulfonium ions that are cationic species. 101 and a counter electrode made of platinum are immersed, and a negative voltage is applied to the movable part electrode 104, the support part 107, and the movable part 108, and a positive voltage is applied to the counter electrode. That is, the movable part electrode 104, the support part 107, and the movable part 108 are used as negative electrodes, the counter electrode is used as a positive electrode and immersed in an electrodeposition solution, and a voltage is applied using a constant voltage source to perform cationic electrodeposition.

  Through the above operation, the organic thin film forming material dispersed (dissolved) in the electrodeposition liquid is deposited on the surfaces of the movable part electrode 104, the support part 107, and the movable part 108 to which a negative voltage is applied, and is deposited on these surfaces. A state is obtained in which an organic thin film 109 having a film thickness of about several tens of nm to 5 μm is formed (FIG. 1E). The material dispersed (dissolved) in the electrodeposition liquid does not adhere to the surfaces of the insulating layer 102 and the control electrode 105 to which a negative voltage is not applied, but selectively deposits on the portion to which a negative voltage is applied. Thus, the organic thin film 109 is formed.

  In this embodiment, the support part 107 and the movable part 108 are made of polysilicon, and the movable part electrode 104 and the control electrode 105 are made of gold / chromium or gold / titanium. Any conductor that can form the thin film 109 may be used. As the above-mentioned conductor, for example, copper / chromium or copper / titanium, SUS, iron or other metals, high-concentration n-type silicon, high-concentration p-type silicon, or polyacetylene , Hydrocarbon-based conductive polymers such as polyazulene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene, or heteroatom-containing conductive polymers such as polypyrrole, polyaniline, polythiophene, polythienylene vinylene, or The charge transfer complex can also be constructed.

  In the above description, the organic thin film 109 is formed only on the movable portion electrode 104, the support portion 107, and the movable portion 108. However, the present invention is not limited to this. For example, the organic thin film 109 can be formed only on the control electrode 105 by selectively applying a negative voltage to the control electrode 105. Further, by applying a negative voltage to both the movable portion 108 (including the movable portion electrode 104 and the support portion 107) and the control electrode 105, the movable portion 108 (including the movable portion electrode 104 and the support portion 107). It is also possible to form the organic thin film 109 on both the control electrode 105 and the control electrode 105.

  In the above description, a liquid containing sulfonium ions is used as the electrodeposition liquid. However, the liquid is not limited to this as long as it is a liquid containing cationic species.

Next, another example of the manufacturing method of the micromachine in the embodiment of the present invention will be described. FIG. 2 is a process diagram showing a method of manufacturing a micromachine in the embodiment of the present invention.
First, as shown in FIG. 2A, for example, a silicon layer 210 having a thickness of about 2 μm doped with an n-type impurity at a high concentration, a buried insulating layer 202 having a thickness of about 4 μm, and a silicon substrate portion 201 are formed. An SOI (Silicon on Insulator) substrate is prepared. Next, the silicon layer 210 is processed by a known photolithography technique and etching technique, and a support part 207 and a movable part 208 having desired shapes are formed on the buried insulating layer 202 as shown in FIG. State.

  Next, as shown in FIG. 2C, a lower seed layer 203a made of titanium, for example, having a thickness of about 0.1 μm is formed on the buried insulating layer 202 including the support portion 207 and the movable portion 208. Subsequently, an upper seed layer 203b made of, for example, gold and having a thickness of about 0.3 μm is formed on the lower seed layer 203a. Next, a resist film formed by applying a resist thereon is patterned to form a resist film 206 having an opening 206a from which a part of the upper seed layer 203b is exposed.

  Next, a metal pattern 205 made of gold is formed on the upper seed layer 203b exposed in the opening 206a of the resist film 206 by electrolytic plating. The metal pattern 205 has a top surface formed at the same height as the support part 207 and the movable part 208, and the metal pattern 205, the support part 207, and the surface of the movable part 208 are formed on the same plane. State. The formed metal pattern 205 is integrated with the lower upper seed layer 203b made of the same material of gold. Moreover, each opposing surface of the metal pattern 205 and the movable part 208 is spaced apart by about 2 to 4 μm, for example.

  Next, after removing the resist film 206, the upper seed layer 203b made of gold is selectively removed by wet etching using an iodine / ammonium iodide solution using the metal pattern 205 as a mask. The lower seed layer 203a made of titanium is selectively dissolved and removed by wet etching with an acid solution, so that the control electrode 215 is formed as shown in FIG. The control electrode 215 includes a part of the lower seed layer 203 a, a part of the upper seed layer 203 b, and the metal pattern 205.

  Further, a resist film is formed on these by applying a resist, and the resist film is patterned to form a resist pattern having an opening through which a part of the support portion 207 is exposed. As shown in FIG. 2E, the movable part electrode 204 made of gold is formed on the support part 207 by plating with gold.

  Next, the substrate on which the control electrode 215 described above is formed and the counter electrode made of platinum are immersed in an electrodeposition solution containing sulfonium ions that are cationic species (for example, Nippon Paint Co., Ltd., INSULED). A negative voltage is applied to the control electrode 215 and a positive voltage is applied to the counter electrode. That is, the control electrode 215 is used as a negative electrode, the counter electrode is used as a positive electrode and immersed in an electrodeposition solution, and a voltage is applied using a constant voltage source to perform cation electrodeposition.

  Through the above operation, the organic thin film forming material dispersed (dissolved) in the electrodeposition liquid is deposited on the surface of the control electrode 215 to which a negative voltage is applied, and as shown in FIG. An organic thin film 209 having a film thickness of about 0.2 μm is formed on the exposed surface. The material dispersed (dissolved) in the electrodeposition liquid does not adhere to the surfaces of the buried insulating layer 202, the movable part electrode 204, the support part 207, and the movable part 208 to which no negative voltage is applied, and the negative voltage is applied. The organic thin film 209 is formed by selectively precipitating on the portion to which is applied.

  In this embodiment, the movable portion 208 is made of n-type silicon doped at a high concentration, and the control electrode 215 is made of gold / chromium or gold / titanium. However, the organic thin film 209 is formed by electrodeposition. Any conductor that can be formed may be used. As the above-mentioned conductor, for example, metal such as copper / chromium or copper / titanium, SUS, iron, highly doped p-type silicon or polysilicon, or polyacetylene, polyazulene, polyphenylene, polyphenylene vinylene, It can also be composed of a hydrocarbon conductive polymer such as polyacene, polyphenylacetylene, polydiacetylene, a heteroatom-containing conductive polymer such as polypyrrole, polyaniline, polythiophene, polythienylene vinylene, or a charge transfer complex.

  In the above description, the organic thin film 209 is formed only on the control electrode 215. However, the present invention is not limited to this. For example, the organic thin film 209 can be selectively formed on the support portion 207 and the movable portion 208 by applying a negative voltage only to the support portion 207 and the movable portion 208 before forming the movable portion electrode 204.

  Further, before forming the movable part electrode 204, a negative voltage is applied to the movable part 208 (including the support part 207), and after forming the movable part electrode 204, a negative voltage is applied to the control electrode 215. The organic thin film 209 can also be formed on both 208 (including the support portion 207) and the control electrode 215.

Note that the organic thin film 209 may be formed on the surface of the control electrode 215 by electrodeposition after the buried insulating layer 202 is selectively dissolved and removed by wet etching with a hydrofluoric acid solution.
In the above description, a liquid containing sulfonium ions is used as the electrodeposition liquid. However, the liquid is not limited to this as long as it is a liquid containing cationic species.

  Finally, the buried insulating layer 202 is selectively dissolved and removed by wet etching with a hydrofluoric acid solution, so that the support portion 207 shown in FIG. 2G is formed on the silicon substrate portion 201 via the insulating layer 211. Thus, the control electrode 215 that is fixed to the organic thin film 209 and whose surface is protected by the organic thin film 209 is fixed on the silicon substrate portion 201 via the insulating layer 212. As shown in the perspective view of FIG. 3, the movable portion 208 is a rod-like structure extending from one corner of the support portion 207, and the movable portion 208 applies an electric signal to the control electrode 215, thereby It operates in a predetermined direction by the action of.

  Next, the formation of the organic thin film 109 in the micromachine shown in FIG. 1 will be described in more detail. In the electrodeposition process, cation electrodeposition is performed by changing the temperature of the electrodeposition liquid (Nippon Paint Co., Ltd., INSULED) in the range of 22.5 ° C to 35 ° C under an applied voltage of 7V. The film thickness of the organic thin film is measured. The organic thin film deposited on the negative electrode surface is washed with water for 10 minutes and then annealed at 230 ° C. for 40 minutes. The film thickness is measured with a stylus type step gauge.

FIG. 4 is a characteristic diagram showing the relationship between temperature and electrodeposition film thickness as a result of measuring the film thickness described above.
As shown in FIG. 4, when the temperature (liquid temperature) of the electrodeposition liquid is less than 30 ° C., the organic thin film is formed to a maximum thickness of about 2 μm and is thicker than this regardless of the electrodeposition time. There is nothing. As described above, according to the present embodiment, by setting the temperature of the electrodeposition liquid to less than 30 ° C., it becomes possible to automatically stop the formation of the organic thin film, and it is necessary to control the electrodeposition time. Absent. Therefore, by setting the temperature of the electrodeposition liquid during the electrodeposition process to a predetermined temperature or less, the process margin with respect to the processing time can be increased, and a margin can be given to the manufacturing process.

  Next, the relationship between the applied voltage and the formed electrodeposition film will be described. First, in the electrodeposition step, the electrodeposition liquid is fixed at a temperature of 22.5 ° C., and the applied voltage is changed from 6V to 30V to perform cationic electrodeposition. Measure. Similarly to the above, the organic thin film deposited on the negative electrode surface is washed with water for 10 minutes and then annealed at 230 ° C. for 40 minutes. The film thickness is measured with a stylus type step gauge.

FIG. 5 is a characteristic diagram showing the relationship between the applied voltage and the electrodeposition film thickness as a result of measuring the film thickness described above. As shown in FIG. 5, the maximum thickness of the electrodeposition film can be controlled by controlling the applied voltage under the condition that the temperature of the electrodeposition liquid is 25.5 ° C. For example, when the applied voltage is 30 V or less, the maximum film thickness of the organic film formed by electrodeposition can be 5 μm or less.
Accordingly, it is possible to form a nonconductor such as an organic thin film having a constant (saturated) film thickness of 5 μm or less with respect to a minute and complicated three-dimensional structure such as a MEMS device.

  As described above, by setting the temperature of the electrodeposition liquid to a predetermined temperature or lower and applying the applied voltage to a predetermined voltage or lower, an organic thin film as thin as 5 μm or less can be obtained regardless of the electrodeposition processing time. It becomes possible to form in a location. For example, when “Nippon Paint Co., Ltd., INSULED” is used as the electrodeposition liquid, the organic thin film having a thickness of 2 μm or less is obtained by setting the temperature of the electrodeposition liquid to 25.5 ° C. or less and the applied voltage to 6 V or less. Can be formed on the surface of a desired electrode of the micromachine.

It is process drawing which shows an example of the manufacturing method of the micromachine in embodiment of this invention. It is process drawing explaining the example of the manufacturing method of the other micromachine in embodiment of this invention. It is a perspective view which shows the structural example of a micromachine. It is a characteristic view which shows the relationship between temperature and an electrodeposition film thickness as a measurement result of a film thickness. It is a characteristic view which shows the relationship between an applied voltage and an electrodeposition film thickness as a measurement result of a film thickness. It is explanatory drawing explaining the drive of the movable part in a micromachine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Semiconductor substrate, 102 ... Insulating layer, 104 ... Movable part electrode, 105 ... Control electrode, 106 ... Sacrificial film, 106a ... Opening part, 107 ... Support part, 108 ... Movable part, 109 ... Organic thin film.

Claims (5)

A first step in which a first structure having conductivity is formed on a substrate;
A second step in which a second structure having conductivity is formed on the substrate by being insulated from the first structure;
The first structure and the second structure are immersed in an electrodeposition solution containing a cationic species, a voltage is applied to at least one of the first structure and the second structure, and the first structure And a third step of forming an organic thin film composed of the cationic species by electrodeposition on at least one of the surface of one structure and the surface of the second structure. Manufacturing method. In the manufacturing method of the micromachine of Claim 1,
The second structure is a movable structure including a movable part that is spaced apart from the surface of the substrate and extends in a predetermined direction.
The first structure is a control electrode that controls an operation of the movable part. In the manufacturing method of the micromachine of Claim 1 or 2,
The method for producing a micromachine, wherein the cationic species is sulfonium ion. In the manufacturing method of the micromachine of any one of Claims 1-3,
The third step is performed by setting the temperature of the electrodeposition liquid to a predetermined temperature or lower. In the manufacturing method of the micromachine of Claim 4,
In the third step, the voltage less than or equal to a predetermined value is applied.

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