KR20040099808A - MEMS RF switch - Google Patents

Abstract

PURPOSE: An MEMS(Micro Electro Mechanical System) RF(Radio Frequency) switch is provided to induce a high power by using low voltage. CONSTITUTION: An MEMS RF switch includes input and output electrodes(110,120), a pair of anchors(131a,131b), a pair of first structures(132a,132b), a second structure(133), a third structure, a pair of fourth structures(135a,135b), an armature(130), and piezoelectric drivers(151,152). The input and output electrodes are spaced from each other on one side of a substrate. The anchors are spaced from each of the input and output electrodes and are formed to be spaced from each other on the substrate. The first structures are extended on one side of the anchors and are formed to be floating above the substrate. The structure includes two ends coupled with longitudinal ends of the first structures. The third structure is extended between the first structure from a central portion of the second structure and to a position above the input and output electrodes. The fourth structures are extended to the third structure. The armature is formed on a lower portion of the third structure and is made of a conductive material. The piezoelectric drivers are formed on each of the first structures.

Description

MEMS RF switch {MEMS RF switch}

The present invention relates to a MEMS RF switch, and more particularly, it is possible to implement an active RF switch capable of actively generating and maintaining a switched-on state by inducing a large force even at a low voltage, and according to an adjustment of an applied voltage. The present invention relates to a MEMS RF switch capable of easily adjusting a contact force in which a contactor contacts an input / output electrode.

In general, RF (radio frequency) switch is an indispensable component with a high power low noise amplifier in a system using microwave, that is, a microwave having a wavelength of 1mm to 1m, and performs the function of passing or not passing the RF signal. do.

Among the RF switches, MEMS (Micro Electro Mechanical System) RF switch is an application device widely used in signal routing or impedance matching circuit in a wireless communication system using microwave or millimeter wave.

Recently, researches on various MEMS RF switches have been actively conducted, and the importance of MEMS RF switches is increasing with the explosion of the mobile communication terminal market. Accordingly, various types of MEMS RF switches have been proposed.

FIG. 1 is a schematic plan view showing a state in which basic components of a MEMS RF switch according to the related art are formed on a substrate, and an upper electrode pad 11 is formed on one side of the substrate 20. Input and output electrodes 31a and 31b spaced apart from each other on the other side of the substrate 20 are formed, and are disposed on the substrate 20 between the upper electrode pad 11 and the input and output electrodes 31a and 31b. The lower electrode 14 is formed.

FIG. 2 is a cross-sectional view illustrating a state in which a MEMS RF switch according to the related art is turned off. The upper electrode 12 is electrically contacted with the upper electrode pad 11 of FIG. 1, and the lower electrode ( 14, an elastic support 18 formed by covering the upper and lower surfaces of the upper electrode 12 with the insulating film 13 is formed.

The elastic support 18 extends to an upper side spaced apart from the input and output electrodes 31a and 31b, and a contactor 15 is formed at the lower end of the elastic support 18.

The operation principle of the conventional MEMS RF switch formed as described above will be described. First, the RF switch illustrated in FIG. 2 is in an OFF state.

That is, in order to keep the RF switch off, it is not necessary to apply a voltage to the upper and lower electrodes 12 and 14.

In this case, the electrostatic attraction is not induced between both electrodes, so that the contactor 15 is spaced apart from the lower input electrode 31a and the output electrode by a predetermined distance, and the input electrode 31a and the output electrode are disconnected. The switch is turned off, which is inactive.

3 is a cross-sectional view illustrating a state in which a MEMS RF switch is turned on according to the related art. In the RF switch on state, when a voltage difference is applied between the upper electrode 12 and the lower electrode 14, the upper electrode ( 12 and the lower electrode 14 generate an electrostatic attraction that is attracted to each other, the elastic support 18 in the region of the upper electrode 12 is in contact with the lower electrode (14).

Therefore, the pole 15 at the end of the elastic support 18 also sags downward, and as shown in FIG. 4, the pole 15 is connected to the input electrode 31a and the output electrode 31b. The two electrodes 31a and 31b are electrically connected to each other.

This state is switched on.

Here, the process of restoring from the switch-on state to the off state is a process of changing from the state of FIG. 3 to the state of FIG. 2, and removes an applied voltage difference between the upper and lower electrodes 12 and 14 opposed to switch off. The electrostatic force caused by the application will also disappear.

Therefore, the elastic support is returned to the state as shown in FIG. 2 by the spring restoring force of the elastic support to return to the initial equilibrium state due to the loss of the electrostatic force that is pulling the elastic support downward.

As such, the MEMS RF switch of the prior art shown in FIGS. 1 to 3 described above is described in US Patent US6046659, and the elastic force is elastic enough to overcome the spring resistance of the elastic support so that the contactor contacts the input / output electrodes. The support beam is moved to exert its function as a switch. The electrostatic attraction is proportional to the reciprocal of the distance between the counter electrodes, so that the distance becomes small even if the distance is small.

Thus, the driving voltage of the electrostatically pulled MEMS RF switch has been very large, several tens of volts.

Therefore, it is difficult to use in a field where only a few volts of voltage in a low voltage state is allowed.

On the other hand, the conventional RF switch because the electrostatic force is weak compared to the other driving method, in order to move the elastic support by the weak electrostatic attraction, the spring coefficient must be made small.

Here, the small spring coefficient means that the elastic support is soft enough to easily move even with a small force.

Therefore, the biggest problem caused by the soft elastic support is that, due to the disappearance of the electrostatic force holding the elastic support down when switching from the switched on state to the off state, the elastic support to try to return to the original state by the spring restoring force do.

However, the spring restoring force also becomes small due to the small spring coefficient, so that the force that separates the electrode and the input / output electrode is small.

Therefore, when the conventional RF switch is repeatedly used for a long time, the contact surface between the pole and the input / output electrode is worn, or the spring restoring force is smaller than the naturally occurring electrostatic force, which causes problems that do not stick together. It has a fatal flaw that can no longer function as a switch.

In addition, since the electrostatic attraction is proportional to the inverse of the distance between the opposite electrodes, when the distance between the electrode and the input / output electrode is increased, the electrostatic attraction becomes weak so that the elastic support cannot be pulled downward.

If the distance between the counter electrodes is increased, the electrostatic attraction can be increased, while the closer the distance is, the lower the electrical insulation of the electrode and the input / output electrode when the switch is off.

As a result, the conventional electrostatic attraction RF switch has a disadvantage in that it has a basic limitation that the distance between the counter electrode plates must be below a certain level.

Accordingly, the present invention has been made to solve the above problems, it is possible to implement an active RF switch that can actively generate and maintain the switch-on state by inducing a large force even at a low voltage, the poles in accordance with the control of the applied voltage It is an object of the present invention to provide a MEMS RF switch that can easily adjust the contact force in contact with the self input and output electrodes.

Another object of the present invention is to provide a MEMS RF switch capable of making the distance between the poles longer than that of the conventional electrostatic attraction type structure, thereby increasing the insulation between the poles and the input / output electrodes.

According to a preferred aspect of the present invention, there is provided an input electrode and an output electrode spaced apart from one another on an upper surface of a substrate;

A pair of anchors spaced apart from each of the input electrode and output electrode and spaced apart from each other by a predetermined distance;

A pair of first structures each extending on one side of the pair of anchors and floating from the top of the substrate;

A second structure having one side and the other side connected to ends of the pair of first structures, respectively;

A third structure extending between the first structures from a central side of the second structure to a position spaced above the input electrode and the output electrode;

A pair of fourth structures extending from said mutually opposite side of said pair of anchors to said third structure;

An armature formed on a lower surface of the third structure and made of a conductive material;

There is provided a MEMS RF switch formed in each of the first structures, the piezoelectric drive unit of which deformation occurs according to the applied voltage.

Another preferred aspect for achieving the above object of the present invention is an input electrode and an output electrode formed spaced apart from each other on one side of the substrate;

A spacer spaced upward from each of the input electrode and the output electrode and contacting and electrically connecting the input and output electrodes during driving;

An end structure connected to the electrode;

A lever formed in the middle of the end structure;

According to the voltage, the MEMS RF switch comprising a driving unit which moves the terminal structure upward and downward with respect to the lever to contact or non-contact with the input and output electrodes is provided.

1 is a schematic plan view showing a state in which the basic components of a MEMS RF switch according to the prior art are formed on a substrate;

2 is a cross-sectional view showing a state in which the MEMS RF switch is off according to the prior art;

Figure 3 is a cross-sectional view showing a state in which the MEMS RF switch according to the prior art Figure 4 is a schematic plan view showing a state in which the MEMS RF switch according to the prior art (On)

5 is a perspective view of a MEMS RF switch according to the present invention;

6 is a side view of a non-operating, off state of a MEMS RF switch according to the present invention;

Figure 7 is a side view of the MEMS RF switch in operation, On (On) state in accordance with the present invention

8 is a view illustrating a state in which a structure is deformed by operating and turning on a MEMS RF switch according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: substrate 110, 120: input and output electrode

130: polarizer 131a, 131b: anchor

132a, 132b: first structure 133: second structure

134: third structure 135a, 135b: fourth structure

151,152: piezoelectric drive part

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 5 is a perspective view of a MEMS RF switch according to the present invention, the input electrode and the output electrode (110, 120) formed spaced apart from each other on one side of the substrate 100; A pair of anchors 131a and 131b spaced apart from each of the input and output electrodes 110 and 120 and spaced apart from each other by a predetermined distance; A pair of first structures (132a, 132b) extending on one side of the pair of anchors (131a, 131b), respectively, and floating from the top of the substrate (100); A second structure 133 having one side and the other side connected to ends of the pair of first structures 132a and 132b, respectively; A third structure 134 extending between the first structures 132a and 132b from a central side of the second structure 133 to an upper position spaced apart from the input and output electrodes 110 and 120; A pair of fourth structures (135a, 135b) extending from said mutually opposite sides of said pair of anchors (131a, 131b) to said third structure (134); An armature 130 formed on a lower surface of the third structure 134 and made of a conductive material; The first structures 132a and 132b are formed on the first structures 132a and 132b, respectively, and are composed of piezoelectric driving parts 151 and 152 that are deformed according to an applied voltage.

The piezoelectric driving parts 151 and 152 are in the form of a piezoelectric capacitor composed of a lower electrode / piezoelectric film / upper electrode.

FIG. 6 is a side view of the MEMS RF switch according to the present invention in a non-operational and off state. When no voltage is applied to the piezoelectric actuators, the MEMS RF switch of the present invention is turned off.

In this off state, the piezoelectric actuators 152 are not operated so that the electrode 130 is in a floating state at a predetermined distance from the input electrode and the output electrode 120.

Therefore, the input electrode and the output electrode 120 are disconnected to the off state in which the switch is in an inoperative state.

FIG. 7 is a side view of the MEMS RF switch according to the present invention operating and being on. When a voltage is applied to the upper and lower electrodes of the piezoelectric actuators, the MEMS RF switch is turned on. do.

That is, the upper electrode applies a low voltage and the lower electrode applies a high voltage. For example, when the upper electrode is in a ground voltage state and a voltage of about 5 V is applied to the lower electrode, as shown in FIG. 7, the upper electrode and the lower electrode of the piezoelectric actuators 152 are connected to the upper electrode. Due to the difference, mechanical deformation occurs in the piezoelectric film positioned in the middle thereof, such that the first structures 132a and 132b supporting the piezoelectric driving parts are bent in an upward direction.

As a result, the third structure region connected with the second structures moves in the upward direction (+ Z axis), while the third structure region in the direction of the input / output electrode is moved by the fourth structure connected to the third structure and the angler. It moves in the downward direction (-Z axis).

Thus, the contactor of the lower surface of the third structure contacts the input electrode and the output electrode, thereby electrically connecting the input / output electrode.

This state is switched on.

In addition, the process of restoring from the switched on state to the off state is a process of changing from FIG. 7 to FIG. 6. When the voltage difference applied between the piezoelectric drivers for switching off disappears, the induced piezoelectric driving force also disappears.

At this time, since the first structure is lifted upward, the piezoelectric driving force holding down the contactor is lost, and thus, the spring restoring force of the first structure to return to the initial equilibrium state is acted on, and the state of FIG. It will return to the same state as 6.

8 is a view showing a state in which the structure of the MEMS RF switch according to the present invention is operated and turned on, the piezoelectric drive unit in the MEMS RF switch of the present invention, when the pair of opposing pair With respect to the pair of fourth structures extending from each side of the anchors to the third structure, the structures connected to the piezoelectric drive portion move upwards, and the opposite side moves downward.

That is, as shown in FIG. 8, the state is changed from the initial 'A' state to the 'B' state.

Therefore, the present invention and the input electrode and the output electrode formed spaced apart from each other on one side of the upper substrate; A spacer spaced upward from each of the input electrode and the output electrode and contacting and electrically connecting the input and output electrodes during driving; An end structure connected to the electrode; A lever formed in the middle of the end structure; It is composed of a drive unit for moving the terminal structure in the upper and lower directions based on the lever in accordance with the voltage, the contactor is in contact or non-contact with the input and output electrodes.

Here, the end structure is shaped like the third structure shown in FIG. 2, and the lever extends to the third structure 134 at each side of each of the pair of anchors 131a and 131b facing each other. It is preferably composed of a pair of fourth structures 135a and 135b.

In addition, as described above, the driving unit includes a pair of anchors 131a and 131b spaced apart from the input electrode and the output electrode 110 and 120 and spaced apart from each other by a predetermined distance; A pair of first structures (132a, 132b) extending on one side of the pair of anchors (131a, 131b), respectively, and floating from the top of the substrate (100); A second structure 133 having one side and the other side connected to ends of the pair of first structures 132a and 132b, respectively; A third structure 134 extending between the first structures 132a and 132b from a central side of the second structure 133 to a position spaced apart from the upper side of the input and output electrodes 110 and 120; The piezoelectric driving units 151 and 152 may be formed on each of the first structures 132a and 132b and may be deformed according to an applied voltage.

As described above, the present invention employs a structure (the above-mentioned 'fourth structure') that leverages the lever acting to move the movement driven upward of the piezoelectric drive unit using the piezoelectric film to the lower layer without going through a complicated multilayer manufacturing process of several layers. Accordingly, there is an advantage that an active RF switch that can generate and maintain a switched-on state by inducing a large force even at a low voltage can be implemented.

In addition, by adjusting the voltage difference applied to the piezoelectric drive unit, there is an advantage that the contactor can easily adjust the contact force in contact with the input and output electrodes in accordance with the control of the applied voltage.

In the conventional electrostatic attraction type structure, when the distance between the pole and the input / output electrode increases, the attraction force is proportional to the inverse of the distance according to the basic physical law of the electrostatic attraction, so that the distance between the pole and the input / output electrode is 1 to 2 microns. In the present invention using a piezoelectric drive unit, the distance between these poles can be made longer than that of the conventional electrostatic attraction structure, and the insulation between the poles and the input / output electrode can be improved when the electrode is turned off. There is an advantage.

On the other hand, in order to implement a reliable switch-off state, the spring restoring force should be large. When the spring restoring force is formed in the conventional structure, a larger force is required to implement the switch-on state, but in the structure of the present invention, the spring Even if the width of the piezoelectric driving unit is increased to increase the restoring force, it is not necessary to use a larger force for the switched-on state, and the switch-on state is further facilitated.

As described above, the present invention can implement an active RF switch capable of actively generating and maintaining a switched-on state by inducing a large force even at a low voltage, and in accordance with the control of the applied voltage, the contact force of the contactor to the input / output electrode. There is an effect that can be easily adjusted.

In addition, in the present invention, the distance between the poles can be made longer than that of the conventional electrostatic attraction structure, so that the insulation between the poles and the input / output electrode can be improved when off.

In addition, in the structure of the present invention, even if the width of the piezoelectric drive unit is increased to increase the spring restoring force, a larger force is not required for the switched-on state, and the switched-on state becomes easier.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (4)

An input electrode and an output electrode formed spaced apart from each other on one side of the substrate; A pair of anchors spaced apart from each of the input electrode and output electrode and spaced apart from each other by a predetermined distance; A pair of first structures each extending on one side of the pair of anchors and floating from the top of the substrate; A second structure having one side and the other side connected to ends of the pair of first structures, respectively; A third structure extending between the first structures from a central side of the second structure to a position spaced above the input electrode and the output electrode; A pair of fourth structures extending from said mutually opposite side of said pair of anchors to said third structure; An armature formed on a lower surface of the third structure and made of a conductive material; MEMS RF switch formed in each of the first structures, consisting of a piezoelectric drive unit that deformation occurs in accordance with the applied voltage. The method of claim 1, The piezoelectric drive unit MEMS RF switch, characterized in that consisting of the lower electrode / piezoelectric film / upper electrode. An input electrode and an output electrode formed spaced apart from each other on one side of the substrate; A spacer spaced upward from each of the input electrode and the output electrode and contacting and electrically connecting the input and output electrodes during driving; An end structure connected to the electrode; A lever formed in the middle of the end structure; MEMS RF switch comprising a driving unit for moving the terminal structure in the upper and lower directions based on the lever to contact or non-contact the input and output electrodes according to the voltage. The method of claim 3, wherein The driving unit, A pair of anchors formed on the substrate spaced apart from each other by a predetermined distance; A pair of first structures each extending on one side of the pair of anchors and floating from the top of the substrate; A second structure having one side and the other side connected to each of the ends of the pair of first structures; A third structure extending between the first structures from a central side of the second structure to a spaced position above the input and output electrodes; MEMS RF switch is formed on each of the first structure, characterized in that consisting of piezoelectric drive parts that deformation occurs in accordance with the applied voltage.