KR101385398B1 - MEMS switch and drive method thereof - Google Patents

Abstract

The present invention relates to a MEMS switch and a driving method thereof, wherein a voltage is applied to a piezoelectric capacitor to bend the cantilever portion, and the conductive contact portion is close to the signal line by bending the cantilever portion, and then a voltage is applied to the first and second electrodes. The contact force between the conductive contact portion and the signal line can be improved by bringing the first and second electrodes into contact with the electric power and contacting the conductive contact portion with the signal line at the same time.

In addition, the present invention can improve the contact force between the conductive contact portion and the signal line even at a low operating voltage by contacting the conductive contact portion with the signal line by the cantilever deflection and electrostatic force.

MEMs, switch, contact, electrostatic force, deflection, equipotential, release, voltage

Description

MEMS switch and drive method

The present invention relates to a MEMS switch capable of improving the contact force between the conductive contact portion and the signal line.

Recently, with the development of information and communication technology, research for miniaturization, light weight, and high performance of devices has been actively conducted.

In particular, the RF switch is a key component that has a wide range of applications as a component for signal control and variable element implementation of information and communication devices, and has a very important effect on the miniaturization and performance of the device.

Currently, much effort has been focused on the development of RF switches to meet the specifications required by satellite communication antennas, signal control systems and mobile communication terminals.

Next-generation mobile communication terminals will evolve into multi-band integrated phones incorporating PCS, CDMA, GSM, WCDMA phones, etc., and at the same time, demand for multifunctional phones such as the Internet, TV, and GPS will be greatly expanded.

Therefore, an RF switch is required to match the impedances of RF components such as antennas, power amplifiers, and filters in a wide frequency band. As described above, the multi-band and multi-band of mobile communication terminals are in progress. It is expected that the importance will increase even more.

In the future, if the bandwidth is increased to 6 or more bands, the cost and size can be greatly increased by using existing RF components. However, by applying the RF MEMS switch, the increase in cost and size can be limited.

Therefore, many studies have been made to implement such a technology, and in particular, there is an urgent need for miniaturization and performance improvement of an RF switch as a variable core component for a high frequency band and a multi band application.

Conventional RF switches mainly use electrical switches using FETs or PIN diodes.

Electrical switches have a high frequency band, which leads to a large insertion loss, and at the same time, has limitations in signal isolation characteristics.

In addition, the power loss for driving the switch is increased, the nonlinearity of the device and the signal distortion phenomenon has become a factor that makes it difficult to implement the performance of the entire system.

As a viable alternative for solving the problems of the conventional electrical switch, research on the RF MEMS switch has attracted much attention.

RF MEMS switches replace electrical switch elements with mechanical switches to improve insertion loss in high frequency bands and provide good signal isolation.

In addition, according to the driving method of the switch, not only can the power loss be reduced, but also the linearity is improved, and the signal has the advantage of reducing the distortion and interference.

Conventional driving methods such as electrostatic, electromagnetic, and thermal methods are used to drive conventional RF MEMS switches. In the case of a switch using electromagnetic force and thermal drive, the switch has a disadvantage in that the driving speed of the switch is slow and power consumption is large due to the current required for driving.

In the case of using the constant power as the driving method of the switch, the most research has been made due to the advantages that the drive time of the switch is fast, the power consumption is small, and the device manufacturing method is easy.

In general, when the electrostatic power is used, the size of the device can be reduced, the contact force is large, and there is no power loss. However, the driving voltage for the performance of the switch is increased, and thus the structure for low voltage design and reliability is secured. The disadvantages are difficult to implement.

In the case of the RF MEMS switch driven by the constant power, the driving unit and the bottom electrode are required to drive the switch, and therefore, the upper substrate having the cavity structure is required for the packaging of the switch structure.

On the other hand, the piezoelectric RF MemZ switch has a drive voltage of about 5 V or less and is excellent in insertion loss, isolation, switching speed, power consumption, and the like.

In addition, the entire switch element is packaged by eutectic substrate bonding at the same time as the fabrication of the switch, thereby enabling wafer-level packaging with excellent RF characteristics and mechanical properties of the packaging. It is possible to manufacture a device.

However, the major disadvantage of the piezoelectric structured switch is that it is a contact force.

Since the contact is caused by bending due to the low voltage piezoelectric drive, the contact force is about tens of uN, which is lower than about several hundred uN of the constant power switch.

This low contact force has a problem in that the contact resistance value directly related to insertion loss becomes large.

FIG. 1 is a perspective view showing a schematic structure of a conventional MEMS switch. The MEMS switch of the related art includes a cantilever 11 having one side fixed to a support portion 10 and a hinge 12 provided on the cantilever 11, And the signal transmission lines 21 and 22 connected to the contact electrode 13 in a conductive manner.

At this time, when the cantilever 11 is bent by the driving force of the driving unit, the contact electrode receives the force of the cantilever 11 from the hinge 12 and comes into contact with the signal transmission lines 21 and 22.

Therefore, the MEMS switch is disconnected from the signal transmission lines 21 and 22.

The driving part of the MEMS switch is operated by electrostatic force, electromagnetic force, heat and piezoelectric force.

When the driver does not operate, the signal transmission lines 21 and 22 are in an open state.

The present invention is to solve the problem that the contact force is low to deteriorate the characteristics of the MEMS switch.

Preferred embodiments of the present invention are,

A first substrate having a piezoelectric capacitor, a first electrode, and a cantilever portion having conductive contacts formed thereon;

MEMS switch comprising a second substrate facing the first electrode and a signal line which is turned on or off by contact with the conductive contact portion and is spaced apart from an upper portion of the first substrate Is provided.

According to another preferred embodiment of the present invention,

On or off by contacting the first substrate having a piezoelectric capacitor, a first electrode and a cantilever portion having a conductive contact portion formed thereon, and a second electrode facing the first electrode and the conductive contact portion. Preparing a MEMS switch including a second substrate having a signal line formed thereon and spaced apart from an upper portion of the first substrate;

Applying a voltage to the piezoelectric capacitor to bend the cantilever portion to the second substrate to bring the conductive contact portion closer to the signal line;

There is provided a method of driving a MEMS switch, comprising applying a voltage to the first and second electrodes to contact the first and second electrodes to contact the conductive contact portion with the signal line.

According to the present invention, a voltage is applied to a piezoelectric capacitor to bend the cantilever portion, the cantilever portion is bent to bring the conductive contact portion closer to the signal line, and then a voltage is applied to the first and second electrodes to contact the first and second electrodes by electrostatic power. By simultaneously contacting the conductive contact portion with the signal line, the contact force between the conductive contact portion and the signal line can be improved.

In addition, the present invention has an effect of improving the contact force between the conductive contact portion and the signal line even at a low operating voltage by contacting the conductive contact portion and the signal line by the cantilever deflection and electrostatic force.

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

FIG. 2 is a schematic cross-sectional view for describing a MEMs switch according to the present invention. The MEMs switch of the present invention has a piezoelectric capacitor 120, a first electrode 140, and a conductive contact portion 130 formed thereon. A first substrate 100 having a); A signal line 250 that is turned on or off is formed by contact between the second electrode 240 facing the first electrode 140 and the conductive contact 130, and the first substrate is formed. The second substrate 200 is spaced apart from the upper portion of the 100.

Therefore, according to the present invention, the cantilever unit 110 is bent by applying a voltage to the piezoelectric capacitor 120, and the conductive contact 130 is close to or close to the signal line 250 by the bent of the cantilever unit 110. After the contact, a voltage is applied to the first and second electrodes 140 and 240 to contact the first and second electrodes 140 and 240 by electrostatic power to improve the contact force between the conductive contact 130 and the signal line 250. You will be implementing a MEMs switch.

Therefore, the MEMS switch of the present invention can increase the contact force of the conductive contact portion and the signal line by the electrostatic power even when the voltage applied to the piezoelectric capacitor is low, so that the contact force between the conductive contact portion and the signal line can be improved even at a low operating voltage. have.

3A to 3C are schematic cross-sectional views illustrating a method of driving a MEMS switch according to the present invention, in which the first substrate 100 and the second substrate 200 in the MEMS switch of the present invention are spaced apart from each other.

That is, the first electrode 140 of the first substrate 100 and the second electrode 240 of the second substrate 200 are spaced apart by a 'd1' interval, as shown in FIG. 3A.

In this case, when a voltage is applied to the piezoelectric capacitor 120 of the first substrate 100, the piezoelectric element expands in the thickness direction in the longitudinal direction due to a potential difference between the upper electrode and the lower electrode of the piezoelectric capacitor 120. Will contract.

Here, since the piezoelectric capacitor 120 is formed on the cantilever portion 110, when the piezoelectric body of the piezoelectric capacitor 120 contracts, the cantilever portion 110 receives a bending force, and the bending force is applied to the bending force. As a result, the cantilever part 110 is bent to the second substrate 200.

Therefore, the first electrode 140 of the first substrate 100 is close to the second electrode 240 of the second substrate 200, and the first electrode 140 and the second electrode 240 are close to each other. The interval between them becomes 'd2', so that the interval becomes narrower than before the voltage is applied to the piezoelectric capacitor 120 (where d1> d2).

In addition, the conductive contact portion 130 in the cantilever portion 110 also partially contacts or comes close to the signal line 250 of the second substrate 200.

In this case, the conductive contact portion 130 is not completely in contact with the signal line 250, so that the contact force between the conductive contact portion 130 and the signal line 250 is small and thus the switching characteristic is low.

The piezoelectric capacitor 120 has a structure in which a lower electrode, a piezoelectric body, and an upper electrode are stacked.

In the piezoelectric body, PZT, which is a material having a large piezoelectric coefficient, is preferably used. When the PZT is used as a piezoelectric material, the cantilever can be moved in the vertical direction even at a low voltage. Can reduce the insertion loss.

Thereafter, when a voltage is applied to the first electrode 140 and the second electrode 240, the first electrode 140 is driven by the electrostatic force between the first electrode 140 and the second electrode 240. And the second electrode 240 are in contact.

By the contact between the first electrode 140 and the second electrode 240, the conductive contact 130 comes into contact with the signal line 250 of the second substrate 200, thereby turning on the signal line 250. On or Off.

As a result, the MEMS switch of the present invention bends the cantilever portion by the piezoelectric force, thereby bringing the conductive contact portion 130 into close proximity or contact with the signal line 250, and the conductive contact portion 130 by the electrostatic force to the signal line 250. Since it can make perfect contact, the switching characteristic of an element can be made excellent.

In addition, the MEMS switch of the present invention may simultaneously apply piezoelectric power and electrostatic power.

Various methods are used to release the state in which the conductive contact portion 130 is in contact with the signal line 250.

First, when the voltage applied to the piezoelectric capacitor 120 and the first and second electrodes 140 and 240 in the first substrate 100 is released, the cantilever is restored to its original state in a bent state. The electrostatic force between the first and second electrodes 140 and 240 is also removed.

In another method, the upper electrode and the lower electrode of the piezoelectric capacitor 120 are made into an equipotential, and the first and second electrodes 140 and 240 are also made into an equipotential.

Here, the equipotential is to apply the same voltage or ground voltage, and to apply the same voltage to the upper electrode and the lower electrode of the piezoelectric capacitor 120 or to apply the ground voltage to the upper electrode and the lower electrode.

When the same voltage is applied to the first and second electrodes 140 and 240 or the ground voltage is applied, the contacted state is released.

In another method, in order to contact the conductive contact 130 with the signal line 250, a voltage having a polarity opposite to that applied to the upper and lower electrodes of the piezoelectric capacitor 120 may be applied to the piezoelectric capacitor 120. The first and second electrodes 140 and 240 are applied to the upper electrode and the lower electrode of the upper and lower electrodes, and a voltage having a polarity opposite to that applied to the first and second electrodes 140 and 240 is applied to the first and second electrodes. The contact state is released by applying to the two electrodes 140 and 240.

4A and 4B are schematic cross-sectional views for describing the MEMS switch according to the present invention. In the MEMS switch according to the present invention, the signal line is turned on or off by the contact of the conductive contact.

Therefore, the signal line which is turned on by the contact of the conductive contact portion is composed of a pair of signal lines 251 and 252 spaced apart from each other, as shown in FIG. 4A, and is connected to the pair of signal lines 251 and 252. The conductive contacts 130 are in contact with each other to be turned on.

That is, when the conductive contact portion 130 is not in contact with the pair of preference lines 251 and 252, the RF signal input through the '251' signal line does not flow through the '252' signal line and is turned off, and the conductive contact portion 130 ) Contacts the pair of signal lines 251 and 252, the RF signal flows from the '251' signal line to the '252' signal line, thereby switching on.

The signal line that is turned off by the contact of the conductive contact portion is a single signal line 253 through which an RF signal flows, as shown in FIG. 4B.

The conductive contact portion 130 is connected to the ground.

In this case, when the conductive contact portion 130 contacts the single signal line 253, the RF signal flowing through the single signal line 253 exits to the ground through the conductive contact portion 130.

Therefore, in the MEMS switch including the single signal line 253 and the conductive contact portion 130 connected to the ground, when the conductive contact portion 130 is in contact with the single signal line 253, no signal is transmitted, and the conductive contact portion ( If 130 is not in contact with the single signal line 253, since the signal is transmitted, the operation of the shunt switch is performed.

5 is a cross-sectional view showing a state in which the first and second electrodes of the MEMS switch according to the present invention are bonded to the electrostatic power, and the MEMS switch according to the present invention is the first and second electrodes with the electrostatic power generated by the applied voltage. In order to further improve electrostatic power, as shown in FIG. 5, a dielectric film 270 is formed on the first electrode 140 or the second electrode 240, and the first electrode and the second electrode ( When the 240 contacts, the dielectric layer 270 is configured to be positioned between the first electrode 140 and the second electrode 240.

FIG. 6 is a schematic cross-sectional view for describing a first embodiment of the MEMS switch according to the present invention. The first substrate 100 and the second substrate 200 described above are bonded to each other, and the first substrate 100 and the first substrate 100 are bonded to each other. The second substrate 200 is spaced apart from each other at a predetermined interval d3.

Therefore, in order to maintain the distance d3 between the first substrate 100 and the second substrate 200, the structure 300 is positioned between the first substrate 100 and the second substrate 200. The structure 300 is bonded to each of the first substrate 100 and the second substrate 200 to form a MEMs switch.

Thus, the structure 300 is adhered to the upper portion of the first substrate 100, and the second substrate 200 is adhered to the upper portion of the structure 300.

FIG. 7 is a schematic cross-sectional view for describing a second embodiment of a MEMs switch according to the present invention, wherein the MEMS switch of the present invention has a cantilever part by a voltage applied to the piezoelectric capacitor 120 on the first substrate 100. In order to prevent the piezoelectric capacitor 120 from contacting the second substrate 200 when the 110 is bent, it is preferable that the receiving groove 290 is formed in the second substrate 200.

Therefore, the movement of the piezoelectric capacitor 120 is freed by the receiving groove 290.

FIG. 8 is a schematic cross-sectional view for describing a third embodiment of the MEMS switch according to the present invention. The piezoelectric capacitor 120 includes a lower electrode 121, a piezoelectric body 122, and an upper electrode 123.

Here, the first and second electrodes 140 and 240 for electrostatic power are connected to the lower electrode 121 or the upper electrode 123 of the piezoelectric capacitor 120.

That is, the first electrode 140 formed on the cantilever part 110 is connected to the lower electrode 121 of the piezoelectric capacitor 120 and the second electrode 240 formed on the second substrate 200. The first electrode 140 is connected to the upper electrode 123 of the piezoelectric capacitor 120, or the second substrate 200 is connected to the upper electrode 123 of the piezoelectric capacitor 120. The formed second electrode 240 is connected to the lower electrode 121 of the piezoelectric capacitor 120.

Therefore, as shown in FIG. 8, a structure in which a conductive line 320 connected to the second electrode 240 is formed in the second substrate 200, and a conductive via hole connected to the conductive line 320 is embedded. The MEMS switch may be configured by connecting to the upper electrode 123 of the piezoelectric capacitor 120.

Meanwhile, as shown in FIG. 9, a first conductive via hole 281 connected to the second electrode 240 is formed in the second substrate 200 and an electrode line 282 connected to the first conductive via hole 281. A second conductive via hole 283 formed in the second substrate 200 and connected to the electrode line 282 is formed in the second substrate 200, and is formed in the second conductive via hole 283. A structure 310 having a built-in conductive via hole connected thereto may be connected to the upper electrode 123 of the piezoelectric capacitor 120 to form a MEMs switch.

The structure having the above-described conductive via hole may be replaced with a conductive structure having overall conductivity.

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 invention as defined by the appended claims.

1 is a perspective view showing a schematic configuration of a conventional MEMS switch,

Figure 2 is a schematic cross-sectional view for explaining the MEMs switch according to the present invention

3A to 3C are schematic cross-sectional views illustrating a method of driving a MEMs switch according to the present invention.

4a and 4b is a schematic cross-sectional view for explaining the MEMs switch according to the present invention

5 is a cross-sectional view showing a state in which the first and second electrodes of the MEMS switch according to the present invention bonded to the electrostatic force

6 is a schematic cross-sectional view for explaining a first embodiment of the MEMs switch according to the present invention;

7 is a schematic cross-sectional view for explaining a second embodiment of the MEMS switch according to the present invention;

8 is a schematic cross-sectional view for explaining a third embodiment of the MEMS switch according to the present invention;

9 is a schematic cross-sectional view for explaining a fourth embodiment of the MEMs switch according to the present invention.

Claims (12)

A first substrate having a piezoelectric capacitor, a first electrode, and a cantilever portion having conductive contacts formed thereon; And And a second substrate having a signal line turned on or off by contact with the second electrode facing the first electrode and the conductive contact portion, and spaced apart from an upper portion of the first substrate. , The piezoelectric capacitor, It consists of a lower electrode, a piezoelectric body and an upper electrode, And the first electrode is connected to the lower electrode of the piezoelectric capacitor, and the second electrode is connected to the upper electrode of the piezoelectric capacitor. The method according to claim 1, The conductive contact portion and the signal line, And the cantilever portion is bent and contacted with the voltage applied to the piezoelectric capacitor. The method according to claim 1, The first and second electrodes, The MEMS switch, characterized in that configured to be in contact with the constant power by the applied voltage. The method according to claim 1, The signal line, A pair of signal lines spaced apart from each other and turned on by the contact of the conductive contact portion. The method according to claim 1, The signal line, RF signal is flowing and is a single signal line that is turned off by the contact of the conductive contact, MEMS switch, characterized in that the conductive contact is connected to the ground. The method according to claim 1, In the second substrate, And a receiving groove for preventing the piezoelectric capacitor from contacting the second substrate when the cantilever portion is bent by the voltage applied to the piezoelectric capacitor. delete A first substrate having a piezoelectric capacitor, a first electrode, and a cantilever portion having conductive contacts formed thereon; And And a second substrate having a signal line turned on or off by contact with the second electrode facing the first electrode and the conductive contact portion, and spaced apart from an upper portion of the first substrate. , The piezoelectric capacitor, It consists of a lower electrode, a piezoelectric body and an upper electrode, And the first electrode is connected to an upper electrode of the piezoelectric capacitor, and the second electrode is connected to a lower electrode of the piezoelectric capacitor. The method according to claim 1, A dielectric film is further formed on the first electrode or the second electrode, And the dielectric layer is configured to be positioned between the first electrode and the second electrode when the first electrode and the second electrode contact each other. delete delete delete

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