KR101484520B1 - Mems driving unit, mems switch, and fabrication method thereof - Google Patents

Abstract

A MEMS driver is disclosed. The MEMS actuator includes a fixed electrode portion having a plurality of stepped fixed protrusions and a movable electrode portion that is displaceable so as to change a distance from the fixed electrode portion and changes the distance between the fixed electrode portion and the fixed electrode portion And a moving electrode portion having a moving projection. Thereby, driving with a low driving voltage is possible, and insertion loss characteristics are improved.

MEMS actuator, MEMS switch

Description

[0001] MEMS DRIVING UNIT, MEMS SWITCH, AND FABRICATION METHOD THEREOF [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MEMS driver, a MEMS switch, and a manufacturing method thereof, and more particularly, to a MEMS actuator, a MEMS switch, and a method of manufacturing the same.

MEMS (Micro ElectroMechanical System) refers to the field of processing microswitches, mirrors, sensors, and precision machine parts using semiconductor processing technology. Therefore, the precision processability, uniformity between products, and excellent productivity possessed by the semiconductor technology are applied to improve the performance and lower the price.

Among the devices using the MEMS technology as described above, MEMS switches are currently most widely manufactured. The MEMS switch is widely used in selective transmission of signals and impedance matching circuits in microwave or millimeter wave band wireless communication terminals and systems.

However, recently, in manufacturing a micro MEMS switch, the contact force is not increased as the size of the electrode provided in the MEMS switch is reduced. In addition, a problem arises that a high driving voltage is required to maintain the same contact force .

In order to increase the contact force using a low driving voltage, the gap between the opposing electrodes must be narrow. However, there is a problem in that it is very difficult to form facing electrodes at a narrow interval in a conventional electroplating process.

An object of the present invention is to provide a MEMS driver, a MEMS switch, and a method of manufacturing the MEMS actuator, which can be driven at a low driving voltage by including an electrode composed of a plurality of stages.

According to an aspect of the present invention, there is provided a MEMS actuator comprising: a fixed electrode part having a plurality of stepped fixed protrusions; And a moving protruding portion having a gap with the fixed protruding portion according to a distance from the fixed electrode portion.

In this case, it is preferable that the moving protrusions have a plurality of different shapes and are arranged in sequence in accordance with an area.

The moving electrode unit may include a moving electrode body having a plurality of moving protrusions, and each of the plurality of moving protrusions preferably has a gradually decreasing sectional area as the moving electrode body moves away from the moving electrode body.

The movable protrusions are formed in a plurality of stages arranged in sequence according to the areas having different areas, and a part of the lowermost end of the plurality of stages constituting the movable protrusions is fixed to each fixed It is preferable to be able to enter the space between the lowermost ends of the projections.

On the other hand, it is preferable that the moving protrusions have three different areas and are sequentially arranged in accordance with the area.

According to another aspect of the present invention, there is provided a MEMS switch including: a switch contact; a fixed electrode portion having a plurality of unitary fixed protrusions; a movable electrode portion that is displaceable with a distance from the fixed electrode portion; And a switch unit interlocking with the displacement of the movable electrode unit to be in contact with the switch contact, wherein the movable electrode unit has a plurality of stages arranged in sequence according to an area, And a moving protrusion that changes the gap with the fixed protrusion according to the distance, and a moving electrode body having a plurality of the moving protrusions.

In this case, it is preferable that the moving protrusion is composed of three stages having a larger area as it moves away from the moving electrode body.

According to another aspect of the present invention, there is provided a method of fabricating a MEMS switch comprising: patterning a surface of a first substrate to form a fixed electrode pattern and a moving electrode pattern that are opposed to each other; A step of bonding the movable electrode part and the fixed electrode part pattern to the first substrate, and a step of deep etching the area where the moving electrode part and the fixed electrode part pattern are not formed on the other surface of the first substrate, etching the substrate to form a movable electrode part having a fixed electrode part having a plurality of stepped fixed protrusions and a movable protrusion part disposed opposite to the fixed electrode part and having a plurality of stepped shapes.

In this case, it is preferable that the present MEMS switching fabricating method further includes a step of reducing the thickness of the first substrate after the combining step.

The first substrate may be a single crystal silicon.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a schematic diagram illustrating a configuration of a MEMS switch according to an embodiment of the present invention. Referring to FIG. 1, a MEMS switch according to a preferred embodiment of the present invention includes a MEMS driver 150, a switch contact 111, and a switch unit 110.

The switch unit 110 interlocks with the displacement drive of the MEMS driver 150 and is contactable with the switch contact 111. Specifically, the switch unit 110 may be connected to the MEMS driver 150 through the movable beam 151. [ Therefore, when the MEMS driver 150 is driven to displace, the switch unit 110 receives the displacement drive through the connected movable beam 151 and can be brought into contact with or separated from the switch contact 111 by the transmitted displacement drive have.

The MEMS driver 150 includes a fixed electrode unit 120 and a movable electrode unit 130, and is displaced according to a driving signal. Specifically, the MEMS driver 150 generates electrostatic force between the fixed electrode unit 120 and the movable electrode unit 130 according to an external control signal. The movable electrode unit 130 moves toward the fixed electrode unit 120 according to the generated static electricity and the displacement driving is performed to the switch unit 110 through the movable beam 151 connected to one side of the movable electrode unit 130 Lt; / RTI >

The fixed electrode unit 120 may include a plurality of fixed protrusions 121 and the movable electrode unit 130 may include a plurality of fixed protrusions 131. Although the fixed electrode unit 120 and the movable electrode unit 130 are rectangular in shape for convenience of description, the fixed electrode unit 120 and the movable electrode unit 130 in FIGS. .

The structure and operation of the fixed electrode portion 120 and the movable electrode portion 130 of the specific MEMS driver 150 will be described below with reference to FIGS. 2A and 2B.

2A and 2B are schematic diagrams of a MEMS driver 150 for explaining the operation of the MEMS driver 150 according to an embodiment of the present invention. 2A shows an initial state of the MEMS driver 150. Fig.

The fixed electrode unit 120 has a plurality of stepped fixed protrusions 121 and interacts with the movable electrode unit 130 to generate static electricity. The fixed electrode part 120 may be formed as a fixed electrode body having a plurality of fixed protruding parts 121. In this case, the fixed protruding part 121 may have a shape in which the sectional area gradually decreases as the distance from the fixed electrode body increases. For example, a cone, a quadrangular pyramid, or a triangular pyramid.

The movable electrode part 130 is displaceable so that the distance from the fixed electrode part changes and the movable protrusion part 131 changes according to the distance from the fixed electrode part to the fixed protrusion part 121. The moving protrusions 131 may have a plurality of different shapes and may have a plurality of unit shapes sequentially arranged according to the area. A plurality of the movable protrusions 131 may form the movable electrode body, and the fixed protrusions 121 may be formed in such a manner that the sectional area gradually decreases as the movable electrode body moves away from the movable electrode body.

 2A shows an initial state of the MEMS driver 150. Fig. Referring to FIG. 2A, the fixed electrode unit 120 and the movable electrode unit 130 have a plurality of fixed protrusions 121 and a movable protrusion 131, which are staggered from each other. The fixed protrusions 121 and the movable protrusions 131 in the present embodiment are implemented as rectangular three-step protrusions, and each of the protrusions 121 and 131 has a smaller area . Although the fixed protrusion 121 and the movable protrusion 131 embodied by the three-stage protrusion are shown in this embodiment, it is also possible to implement the fixed protrusion 121 and the movable protrusion 131 with four or more stages , Or a protruding shape such as a triangular shape.

When a drive signal is applied to the MEMS driver 150, an electrostatic force is generated between the fixed electrode part 120 and the movable electrode part 130. The movable electrode unit 130 gradually drives toward the fixed electrode unit 120 by the generated static electricity. Specifically, the electrostatic force between the electrodes is proportional to the area and inversely proportional to the distance. Accordingly, at the initial stage of driving, the surfaces facing each other between the stationary protrusions 121 and the moving protrusions 131 are narrow and the intervals 141 thereof are slightly distant from each other on the opposite surface, so that the initial static electricity is small . On the other hand, the gap between the fixed protrusion 121 and the movable protrusion 131 at the initial stage of driving has a gap 1 141 which is somewhat farther away, so that the design is facilitated in a semiconductor process in which the minimum line width exists.

FIG. 2B shows the ON state of the MEMS driver 150. FIG. Referring to FIG. 2B, the movable electrode unit 130 is moved to the fixed electrode unit 120 by the displacement drive according to the electrostatic force. The linear distance between the uppermost end of the movable protrusion 131 of the movable electrode portion where the initial static electricity is generated and the fixed protrusion 121 becomes smaller than the gap 2 143 in the gap 1 141, So that the electrostatic force becomes large. Further, as the movable electrode unit 130 moves, additional electrostatic force is generated also in a portion where the movable projection 131 and the fixed projection 121 face each other.

Meanwhile, in the present embodiment, the stationary protrusions 121 and the movable protrusions 131 are implemented in the form of a stepped shape. Accordingly, as the second and third stages of the fixed protrusions 121 and the movable protrusions 131 also gradually move, the bars 142 and 144 whose intervals are reduced can generate high electrostatic force.

Accordingly, the movable protrusion 131 of the movable electrode unit 130 and the fixed protrusion 121 of the fixed electrode unit 120 have a narrow gap in the process of driving the MEMS actuator 150 of the present invention, The opposing area between the movable protrusion 131 and the fixed protrusion 121 having a narrow gap is increased, so that a high contact force can be obtained. In particular, it has a high contact force, can be driven with a low driving voltage, and insertion loss characteristics can be improved.

3 is a schematic diagram showing a MEMS driver according to another embodiment of the present invention.

3, the fixed protrusions 121 are implemented as simple protrusions, and the movable protrusions 131 are formed in a plurality of stages arranged sequentially in accordance with areas and having different areas, and the movable protrusions 131 131 are formed so as to be able to enter between the lowermost ends of the fixed protrusions 121 provided in the fixed electrode unit. Accordingly, since the protrusion of the movable projection 131 can enter the lowermost end of the fixed projection, the driving displacement that the MEMS actuator can drive can be increased.

In FIG. 3, the movable projection 131 is composed of a plurality of stages. However, the movable projection 121 may be a simple projection type, and the fixed projection 121 may have a plurality of stages. Also, as shown in FIG. 2B, it is possible to embody both the fixed protrusion 121 and the movable protrusion 131 as a plurality of stages.

4 is a schematic diagram illustrating an SP4T MEMS switch according to another embodiment of the present invention. Referring to FIG. 4, four MEMS switches are formed on one substrate. Specifically, in the system requiring a plurality of switches such as a tunable filter, the SP4T MEMS switch of the present invention can be used. Although four MEMS switches are implemented in one substrate in this embodiment, four or more MEMS switches may be implemented in one substrate.

5A to 5F are schematic views showing a method of manufacturing a MEMS switch according to the present invention. 6A to 6F are cross-sectional views of the MEMS switch fabricating method of FIGS. 5A to 5F.

Referring to FIGS. 5A to 5F and FIGS. 6A to 6F, a predetermined region 211 is etched under the first substrate 210 (FIGS. 5A and 6A). Here, the predetermined region 211 under the first substrate can be designed in a proper shape in consideration of the displacement motion of the MEMS switch and the like. The substrate etch may be accomplished with conventional known etch techniques such as dry or wet etch. In this case, the first substrate 210 may be implemented using a single crystal silicon substrate to increase physical characteristics and structural stability.

Then, the first substrate 210 on which the insulating film 102 is formed and the second substrate 220 are bonded (Figs. 5B and 6B). In this case, the second substrate 220 may be formed using a glass sub-wafer in order to increase physical properties and structural stability.

When the bonding is performed, the first substrate 210 is etched by the thickness of the MEMS switch structure (FIGS. 5C and 6C). Then, the upper portion of the first substrate 210 may be etched to form the switch portion 110, the fixed electrode portion 120, and the moving electrode portion 130 (FIGS. 5D and 6D).

Then, a first planar waveguide (CPW) and a bias pad are fabricated by patterning the upper portion of the first substrate 210 (FIGS. 5E and 6E). Finally, a silicon deep etch is performed so that the fixed protrusions 121 and the movable protrusions 131 generate a HAR (high aspect ratio) structure to maintain a minimum gap and height (FIGS. 5F, 6F). The MEMS switch fabricated in this manner can have the structure shown in FIG.

Specifically, a strong capacitance is required for driving, and a capacitance is proportional to the area. Therefore, as described herein, the capacitance is proportional to the height of the facing surface. Thus, a structure having a HAR structure as described herein can have a high capacitance.

In this manufacturing method, the opposing surfaces of the fixed protrusions 121 and the movable protrusions 131 can be vertically formed by means of bulk micromachining, that is, the height between the electrodes is made higher than the Si substrate It is possible to form a structure having high contact force. In addition, since a high contact force is obtained, it is possible to drive with a low driving voltage.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

1 is a schematic diagram showing a configuration of a MEMS switch according to an embodiment of the present invention,

FIGS. 2A and 2B are schematic views of a MEMS actuator for explaining the operation of the MEMS driver according to an embodiment of the present invention;

3 is a schematic view showing a MEMS driver according to another embodiment of the present invention,

4 is a schematic diagram illustrating an SP4T MEMS switch according to another embodiment of the present invention.

5A to 5F are schematic views showing a method of manufacturing a MEMS switch according to the present invention,

Figs. 6A to 6F are cross-sectional views of the MEMS switch fabricating method of Figs. 5A to 5F.

Description of the Related Art [0002]

100: MEMS switch 150: MEMS driver

110: switch part 120: fixed electrode part

130:

Claims (10)

delete delete delete delete delete Switch contacts; A fixed electrode part having a plurality of stepped fixed protrusions; A movable electrode unit displaceable to change a distance from the fixed electrode unit; And And a switch unit interlocked with the displacement of the movable electrode unit to be in contact with the switch contact, The moving electrode unit includes: A movable protrusion having a plurality of stages arranged in sequence according to an area and having a different area, the gap being different from the fixed protrusion according to a distance from the fixed electrode; And And a moving electrode body having a plurality of moving protrusions formed thereon. The method according to claim 6, The moving projection And the third electrode has a larger area as it moves away from the moving electrode body. Patterning one surface of the first substrate to form a fixed electrode part pattern and a moving electrode part pattern which are disposed to face each other; Coupling a second substrate to the first substrate to a side where the moving electrode part and the fixed electrode part pattern are formed; And A fixed electrode portion having a plurality of stepped fixed projections on the other surface of the first substrate by deep etching a region where the moving electrode portion and the fixed electrode portion pattern are not formed, And forming a movable electrode part having a plurality of stepped movable protrusions arranged opposite to each other. 9. The method of claim 8, And reducing the thickness of the first substrate after the bonding. 9. The method of claim 8, Wherein the first substrate comprises: Wherein the substrate is a single crystal silicon.

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