WO2008044665A1

WO2008044665A1 - Contact-less micro relay

Info

Publication number: WO2008044665A1
Application number: PCT/JP2007/069634
Authority: WO
Inventors: Seisuke Nigo; Seiichi Kato; Hideaki Kitazawa; Yoshio Uno
Original assignee: National Institute For Materials Science
Priority date: 2006-10-03
Filing date: 2007-10-02
Publication date: 2008-04-17
Also published as: JP5266472B2; JPWO2008044665A1

Abstract

It is possible to eliminate necessity of a relay contact micro processing which has been one of bottlenecks of MEMS. A contact-less micro relay turns ON/OFF power from an output terminal by ON/OFF of a relay terminal caused by a voltage change in an input terminal. The relay terminal is a relay element (1) formed by an insulating film (3) having a vertical nano structure formed on a conductive substrate (4) by an insulating material and an electrode (2) formed on the surface of the insulating film (3).

Description

Description Contactless Micro Relay Technical Field

The present invention relates to a contactless microrelay that can be used in an electric circuit in which a current of several milliamperes or more flows. Background art

Solid-state devices are used in electronic circuit relays that carry minute currents of several microamperes or less, making it possible to integrate electronic circuits. However, mechanical contact relays are used in electrical circuits. The reason for this is that mechanical contact relays are used because it is necessary to pass a current of several milliamperes or more through the electrical circuit, and that no leakage current flows when the relay is off.

In order to meet the recent miniaturization needs of devices, MEMS (Micro E 1 ectro Mechanical System) is used to integrate machine element parts, sensors, actuators, and electronic circuits on a single silicon substrate. Devices are being developed. In that case, it is necessary to make the mechanical contact relay as small as possible. Device for flexure of contact by micro processing technology using semiconductor manufacturing technology (for example, Japanese Patent Application Laid-Open No. 2003-203549) and device for increasing sensitivity by incorporating solid elements in parallel (for example, Japanese Patent Application Laid-Open No. 2003-21 7423, Japanese Patent Application Laid-open No. 2006) — 2 2871 7) and others, for example, developed a 2.5 mm 4. 0 x 1. 3 mm MEMS relay, which enabled the miniaturization of mobile phones. However, the increase in manufacturing costs due to microfabrication and the elimination of the basic weaknesses (contact flapping and life) of mechanical contacts have reached their limits. Disclosure of the invention

Problems to be solved by the invention ''

The present invention meets that need. One of the issues is to eliminate the need for relay contactlessness and microfabrication. Means for solving the problem

The present inventor has found that switching characteristics comparable to a mechanical contact relay can be obtained by a solid-state element, and has developed a contactless microrelay shown below using this. The contactless microrelay of the first aspect of the invention is a microphone port relay that turns on and off power from the output terminal by turning on and off the relay terminal caused by a voltage change at the input terminal, and the relay terminal is a conductive substrate. The relay element is composed of an insulating film having a vertical nanostructure formed on an insulating material and an electrode formed on the surface of the insulating film. The contactless microrelay of the invention 2 is the contactless microrelay of the invention 1, wherein the relay element is made of aluminum as a conductive substrate, and an insulating film having a vertical nanostructure of aluminum oxide is formed on the surface thereof. A vapor deposition electrode is provided on the surface of the insulating film. The invention's effect

For example, since a device with a size of 1 X 1 X 1 mm and a conventional semiconductor uses electrical conduction by a small number of carriers, the on-state current is small, and the generation of leakage current due to doped impurities is inevitable. there were. The element of the present invention is not a semiconductor device but a strongly correlated electron device. In other words, it is not the conduction by a minority carrier generated by thermal excitation like a semiconductor, but the metal conduction by the majority carrier electrons injected from the electrode. The off state is an insulating state with an insulating film to which no impurity is added. For this reason, the on / off resistance ratio is 6 digits or more, and switching characteristics comparable to mechanical contact relays can be obtained.

Also, vertical nanostructures are obtained by chemical treatment, so MEM s Microfabrication like relays is completely unnecessary, and the productivity is much higher than these. Furthermore, by using aluminum as the material, productivity can be expected to be 100 times that of MEMS relays. Brief Description of Drawings

Fig. 1 is a cross-sectional photograph (transmission electron micrograph) of the aluminum anodized film used in the relay element.

Figure 2 is a surface photograph (scanning electron micrograph) of the aluminum anodized film used in the relay element.

Fig. 3 is a schematic cross-sectional view of a relay element.

Fig. 4 is a photograph showing the appearance of the relay element.

FIG. 5 is a graph showing the current-voltage characteristics of the relay element.

FIG. 6 is a circuit diagram showing a circuit for measuring current-voltage characteristics.

Figure 7 is a circuit diagram of a self-holding electromagnetic relay.

FIG. 8 is a circuit diagram showing an example of an element relay.

Figure 9 is a graph showing the relationship between the aluminum oxide film thickness and the on-voltage.

FIG. 10 is a graph showing the current-voltage characteristics of Comparative Example 1.

FIG. 11 is a graph showing the current-voltage characteristics of Comparative Example 2.

Fig. 12 is a schematic cross-sectional view (off state) of the relay element.

Figure 13 is a plane slice transmission electron micrograph of a porous aluminum oxide film.

FIG. 14 is a schematic cross-sectional view (on state) of the relay element.

Figure 15 shows the surface of the aluminum oxide film (scanning electron micrograph) in a charged state.

FIG. 16 is a system diagram showing a two-step anodizing method. Explanation of symbols

(1) Relay element (2) Upper vapor deposition electrode (3) Anodized film

(4) Metal (5) Vapor deposition lead wire (6) Metal lead wire (31) Nanohole (32) Bulkhead

(32 A) Bulkhead inner layer (32B) Bulkhead outer layer

(40) Element relay (41 A) Input terminal A (41 B) Input terminal B

(42) Output terminal

(50) Electromagnetic relay (51) ON coil (52) Relay contact

(53 A) Input terminal A (53 B) Input terminal B (53C) Input terminal C (54) Off 'Coil (55) Output terminal

(H) Anodized film thickness

(L) Nanohole pitch

(G) Boundary layer with high-density oxygen coordination defects formed

(E) Electron (CH) conduction channel trapped in oxygen coordination defect

(F 1) Off potential (F 2) Off range

(N 1) ON potential (N2) ON range

(RV) Relay operating voltage range BEST MODE FOR CARRYING OUT THE INVENTION

Figure 9 shows the relationship between the oxide film thickness and the ON voltage switching to the ON state. The general range of the oxide film thickness is 1 to 0.1 μπι, preferably 0.8 to 0. l zm, more preferably 0.6 to 0.15 Aim. If the pitch of nanoholes perpendicular to the aluminum substrate is in the range of 20 to 200 nm, the switching characteristics are not affected.

The material conditions are as follows: (1) The oxide film is insulative, (2) The substrate is conductive, and (3) Metals other than aluminum are used if the nanoholes formed by anodization are perpendicular to the substrate Is possible. For example, tin and indium can not be used because the oxide is not insulative, but titanium satisfies the conditions ①, ②, and ③ and can be used.

The means for making the oxide film have the above preferred thickness can be controlled by the anodic oxidation treatment time and the electrolyte temperature. Table 1 shows examples.

The electrolyte used for anodic oxidation is 0.2 to 0. Sulfuric acid or phosphoric acid may be used at a concentration of 5 mol%.

In this example, the evaluation was made based on whether or not switching characteristics of an on-current of 25 milliamperes and an off-current (leakage current) of 4 nanoamperes can be obtained. However, the present invention is not limited to this. The point is that the contactless microrelay of the present invention that exhibits characteristics that can only be achieved with conventional mechanical contact relays is also included in the scope of the present invention. Example

As shown in Fig. 16, a board for the relay element (1) was created by the following procedure. (ST 1): Ammonium (A 1) with a thickness of 1 mm and a purity of 99.99% was used as the anode for the electrolyte of 0.3 mol% oxalic acid (13.6 g of oxalic acid dissolved in 500 ml of pure water). The anodization is performed while stirring with a stirrer at a constant temperature and constant voltage of 20 ° C and 40V, using a single-bonded electrode as the cathode. Immediately after the start, a tunnel current flows uniformly over the entire surface of the aluminum, and an oxide film is uniformly formed. However, when the film thickness increases to about 30 nm or more, the tunnel current becomes difficult to flow, the current flows locally, the temperature of the oxide film in that portion rises, and the surface is dissolved and recessed by oxalic acid. After that, since the oxide film in the recess is thin, a current selectively flows through the recess, and the oxidation of aluminum and the dissolution of aluminum oxide proceed simultaneously to deepen the recess. The first dents appear in random, but as time goes on, the dents disappear, and when the voltage is 40 V, the pitch of the dents is almost 100 nm after about 30 minutes.

(S T 2): In this state (20 ° C, constant temperature of 40, constant voltage) for 6 hours, anodizing while stirring with a stirrer to form an anodic oxide film (A l 1) on the surface.

(ST3): The above-mentioned anodized aluminum in a mixed solution of chromic acid and phosphoric acid (dissolved solution in which 7.8 g of chromium oxide was dissolved in 50 Om 1 of pure water and 17.5 ml of phosphoric acid was mixed). Immerse the plate and stir with a stirrer for 1 hour, and keep the liquid temperature at 60 ° C for dissolution. This treatment completely dissolves and removes the anodic oxide film (A l 1), and the remaining aluminum surface is in a state in which concaves with a depth of 20 nm are regularly arranged at an equal pitch of approximately 100 nm. (ST 4): After this aluminum plate was ultrasonically cleaned in pure water, it was again anodized for 60 seconds under the same conditions as the first, and an aluminum oxide film (A

1 2) was obtained. Fig. 1 shows a transmission electron micrograph of this oxide film cross section, and Fig. 2 shows a scanning electron micrograph of the oxide film surface. The aluminum oxide film (A 1 2) has a vertical 40 nm diameter nanohole (31) perpendicular to the aluminum bullion (4) and a 60 nm wide partition wall (32) arranged in 100 nm pitch. This anodized aluminum plate is found to be nanostructured, cut to 1 Omm square, and 50 nm thick gold is deposited on the surface of the oxide film (3) to form the upper electrode (2). A two-electrode element with a three-layer structure was made using gold as the lower electrode. Fig. 3 shows the cross-sectional structure and Fig. 4 shows the appearance. As shown in FIG. 12, the partition wall (32) is composed of an inner layer (32A) and an outer layer (32B), the inner layer (32 A) is composed of A 10 ₄ + A 10 ₅ , and the outer layer (32 B) is composed of A It consists of 1 o ₆ . This element (1) exhibits the current-voltage characteristics of FIG. 5, and can be switched between an on state and an off state by an applied voltage using a circuit as shown in FIG. For example, if a voltage of 5.5 V, which is the on-voltage (N 1), is applied, the connection at the point A is established, and if a voltage of 2 V, which is the off-voltage (F 1), is applied, the point B is not conducting It becomes a state. When the circuit voltage of the relay element (1) is 3 V, 25 mA (point C) flows when conducting, and the non-conducting leakage current is 4 nA (point D), and the on / off current ratio (25 mA / 4 nA 6 X 10 ⁶ ). By setting the range showing such an on / off current ratio to the relay operating voltage range (RV), it can be used as a switch of an electric circuit. The range that changes to the off state is the off range (F 2), and the range that changes to the on state is the on range (N2). The embodiment (Fig. 8) of the relay (40) using this relay element (1) is compared with the conventional device. The relay operation is explained in contrast to the self-retained electromagnetic relay (50) (Fig. 7). In the electromagnetic relay (50) in Fig. 7, when 6 V is applied between the AC terminals (53 A) and (53 C), the on-coil (52) is excited and the relay contact (52) comes into contact between the output terminals. Becomes conductive. When 6 V is applied between the BC terminals (53 B) and (53 C), the off coil (54) is excited, the relay contact (52) is cut, and the output terminals (55) are shut off. In the element relay (40) in Fig. 8, when a 5.5V pulse voltage is applied between the AB terminals (41A) (41B), the relay element (1) becomes conductive and the output terminal (42) is not connected. It becomes conductive. Also, if a 12V pulse voltage is applied between the AB terminals (41 A) and (41 B), the relay element (1) is cut off and the output terminals (42) are cut off. The output terminal (55) of the conventional self-holding electromagnetic relay (50) can be applied with a voltage (eg ± 12V) determined by the withstand voltage of the relay contact, but the output of the element relay (40) It is necessary to limit the terminal (42) within the range of the relay operating voltage (1 to 4V in the embodiment) shown in the current-voltage characteristic of FIG. When a voltage exceeding this range is applied to the output terminal, it is necessary to design a circuit that takes into account the switching characteristics of the element relay (40). With the miniaturization of electrical circuits, the use of lower voltages is advancing. For example, if the drive voltage of 1.5 V becomes the standard specification, this problem will disappear. The method of switching the element relay (40) with the pulse voltage requires control to generate the pulse voltage in the conventional DC circuit, but there is no problem with the digitized electric circuit. The on-voltage (N 1) can be adjusted by the thickness (H) of the aluminum oxide film (3). For example, Fig. 9 shows the on-voltage (N 1) of an element using a sample in which the thickness (H) of the aluminum oxide film (3) is changed by changing the anodic oxidation time. This relational expression is for the case where the upper electrode (2) is formed by vapor deposition of gold, and it varies depending on the type of electrode and the deposition method, but the influence of the oxide film thickness (H) is overwhelmingly large. The on-state voltage (N1) can be substantially controlled by the oxide film thickness (H). (Table 1) Oxide film thickness implementation and comparative example

Oxide thickness Anodizing condition On ¾ £ E in m) Liquid temperature Voltage Time (V) Comparative example 1 1. 9 20 ° C 40 V 4 min 3 X 10 ³ Example 0. 15 20 ° C 40V 60 seconds 4 Comparison Example 2 0. 08 20 ° C 40V 30 seconds No threshold Operation Evaluation Comparative example 1 Switching only at very high pulse voltage (Fig. 9) X

Example Good (Fig. 4) 〇 Comparative Example 2 Hysteresis phenomenon but no switching action (Fig. 10) X

Fig. 12 is a schematic diagram of an electron micrograph (Fig. 1), which is a schematic cross-sectional view of the entire relay element (1) including the upper electrode (2). When the film thickness is 80 nm or less, as shown in Comparative Example 2, the current value shows hysteresis depending on the voltage, but a clear switching phenomenon does not occur. On the other hand, if it is 1.9 microns, an on-voltage of 3000V or more is required, making it impractical. The diameter of the nanohole (31) is preferably 30 ηπιψ or more and 6 ηηπιφ or less. Outside this range, the shape of the nanohole deforms and becomes no longer vertical, and the off-operation becomes unstable. In addition, the pitch (L) of the nanohole (31) does not affect the switching characteristics as long as it is in the range of 20 to 200 nm. Fig. 13 is a transmission electron micrograph of an oxide film showing the state of the inner layer (32A) and outer layer (32 B) in the schematic diagram of the oxide film partition wall in Fig. 12. The inner layer (dark part) and outer layer A dense oxygen coordination defect (G) is formed at the boundary of the (bright part). Electrons (E) injected from the electrodes by the application of the on-voltage (N1) are trapped (captured) by the above-mentioned coordination defects, and the potential potential at the center of the partition (32) is lowered to form a conduction channel (CH). A schematic diagram is shown in FIG. Fig. 15 shows a scanning electron micrograph of the surface corresponding to a state close to the actual state of the schematic diagram in Fig. 14. Fig. 2 is a scanning electron micrograph of the surface corresponding to the off state. Compared to Fig. 15, it is clear that the electronic state of the surface differs between the on state and the off state. The reason why the anodized aluminum film (3) shown in Fig. 1 exhibits unique functionality is the presence of a two-dimensional layered electron level with a vertical nanostructure. The method for manufacturing such an aluminum anodic oxide film is different from the usual anodizing (anodizing) used for building materials and the like. Details are described at the beginning of the example with reference to FIG. That's right. Industrial applicability

The present invention is a new relay that has no moving parts, and is an indispensable part for the manufacture of micromachines.

Claims

The scope of the claims

1. A micro relay that turns on and off power from an output terminal by turning on and off of a relay terminal caused by a voltage change at an input terminal, wherein the relay terminal is formed of an insulating material on a conductive substrate. A contactless microrelay characterized in that it is a relay element composed of an insulating film having a vertical nanostructure and an electrode formed on the surface of the insulating film.

2. The contactless micro relay according to claim 1, wherein the relay element has aluminum as a conductive substrate, and an insulating film having a vertical nanostructure of aluminum oxide is formed on the surface thereof. A contactless microrelay characterized in that a vapor deposition electrode is provided on the surface of the insulating film.