CN1151954C

CN1151954C - Radio frequency microelectronic mechanical single knife commutator and its producing method

Info

Publication number: CN1151954C
Application number: CNB011057831A
Authority: CN
Inventors: 孙晓玮; 李小卫; 程知群; 王嘉宽; 郝幼申; 姚文澜
Original assignee: Shanghai Institute of Metallurgy of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS; Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2001-03-23
Filing date: 2001-03-23
Publication date: 2004-06-02
Anticipated expiration: 2021-03-23
Also published as: CN1311158A

Abstract

The present invention relates to a radio frequency microelectronic mechanical single-pole double-throw (SPDT) switch and a producing method thereof, which belongs to the field of a microelectronic mechanical system. Each SPDT switch has a one-divided-into-two branch structure formed from three coplanar wave guides, wherein one wave guide is used as a signal input end, and the other two wave guides are connected with a signal input end. Each branch line is provided with a capacitor and an external voltage end, two planar wave guides on the branch lines respectively form a microelectronic mechanical switch (MEMS), and the function of the SPDT switch is realized by the alternate voltage application of the external voltage ends on the branch lines; thus, the purposes of high isolation degree, low insertion loss, small volume and low cost are realized.

Description

A kind of radio frequency microelectronic mechanical single knife commutator and manufacture method thereof

The present invention relates to a kind of radio frequency microelectronic mechanical single knife commutator and manufacture method thereof, more precisely about single-pole double throw (SPDT) switch and the manufacture method of a kind of control radio frequency (RF) signal break-make, it can be widely used in various types of communication system and the radar, belongs to microelectromechanical systems (MEMS) field.

RF switch commonly used at present all is as switch element by semiconductor devices, field-effect transistor or PIN diode etc. are wherein arranged, though these switches have the advantage that conversion speed is fast between open and closed, operating voltage is low, have following shortcoming: 1. the resistance that forms after the alloying between metal and semiconductor makes switch insertion loss big; 2. because the existence of p-n junction, thereby the non-linear and harmonic wave or the crossover modulation of I-V curve have been produced; 3. the bigger operating current of the need of work of these devices makes power attenuation bigger, and the isolation of this switch is not high in addition.These shortcomings are intrinsic deficiencies of semiconductor devices, in order to overcome these shortcomings, people are devoted to make switch with passive device, as the intrinsic formula of RF (RF-intrinsic) switch by the exploitation of U.S. Raytheon system house, be generally bridge architecture, can form parallel metal one insulator one Metal Contact that is provided with of a SPST (single-pole single-throw(SPST).Switching circuit is produced on and has deposited the thick SiO of one deck 1 μ m ₂High impedance (＞10km) on the silicon substrate, switch is undertaken by the electrostatic force between the upper/lower electrode, insertion loss when " opening " 1GHZ under the attitude is 0.1dB (Liu Zewen etc. " the ME MS device that is used for the communications field " the 7th phase electronics technology Leader " ME MS special column " in 1999), is 0.3dB when 40GHZ; During " pass " attitude, inserting loss loss when 20-40GHZ is 20-25dB.But should the isolation height, insert the little volume again of loss switch little, that cost is low and fail to realize always.Along with the progressively raising of microelectronic process engineering, design and processing microelectronic mechanical switch have become possibility.

The objective of the invention is to design that a kind of insertion loss with the processing of microelectron-mechanical manufacturing process is little, isolation is high, power attenuation is bordering on zero integrated RF single-pole double-throw switch (SPDT).

Implementation method of the present invention: on the substrate of GaAs (GaAs), carry out processes such as photoetching, metal coating, dried wet etching, air bridges and finish with microelectronic manufacturing technology.At first form co-plane waveguide (CPW) with the photoetching evaporation technology, each bar co-plane waveguide has three lines, a middle transmission line as the transmission signal, and two as earth connection in addition.Have three co-plane waveguides (CPW) in single-pole double-throw switch (SPDT), one as signal input part, in addition two a kind of branched structures that are divided into two of formation that link to each other with signal input part.An electric capacity and an applied voltage end (seeing accompanying drawing 2 for details) are respectively arranged on each branch line, and two slab guides respectively constitute a micro-machinery switch on the branch line.Applied voltage end on two branch lines alternately applies voltage, realizes the single-pole double-throw switch (SPDT) function.On two branch's co-plane waveguide intermediate conveyor lines, set up air bridges, the two ends of bridge link to each other respectively with two earth plates of co-plane waveguide, the mid portion of bridge exceeds the certain distance of co-plane waveguide intermediate conveyor line, partly has width to be slightly larger than the dielectric material of air bridges width over against air bridges on co-plane waveguide intermediate conveyor line.Under normal conditions, be air between bridge and dielectric material, signal is by the transmission of intermediate conveyor line.When the needs signal ends, just on the transmission line of centre, add suitable DC voltage, because electrostatic induction will produce electrically opposite electric charge on transmission line and air bridges, electrostatic attraction between the charges of different polarity makes the air bridges mid portion move down, up to contacting with insulating materials below the bridge.At this moment, bridge, dielectric material and co-plane waveguide intermediate conveyor line three form an electric capacity, and signal will be by this capacity earth, thereby have realized the closed condition of high-frequency signal.When needing out again, just voltage to be removed, air bridges will return to original position under the effect of elastic force, and signal will transmit in the past this moment.Single-pole double-throw switch (SPDT) is to realize by the lifting of controlling two bridges on the co-plane waveguide: signal enters from input, control two bridges and be in the state that rises and fall respectively, signal is in the end output of the state of liter from bridge, when needs when the other end is exported, the bridge of the other end is risen and the bridge of this end fallen to get final product.Each micro-machinery switch is made up of underlay substrate 11, earth plate 12, transmission line 13, dielectric material 15 and air bridges 14.Specifically, it is by underlay substrate 11, form with earth plate 12 and metal transmission line 13, the dielectric material 15 between air bridges 14 and transmission line 13 and the air bridges 14 that links to each other with two earth plates that substrate closely links to each other.

The manufacture method of the micro-machinery switch in each branch is to adopt photoetching evaporation technology evaporated gold Au or Ti/Au, Cr/Au alloy on substrate 11, its thickness is 2000 -2 μ m, middle one as transmission line, two earth plates in both sides, on a middle transmission line, deposit the dielectric material then, as Si ₃N ₄, PI (polyamide) etc., thickness is 2000 -5000 , the width of dielectric layer is than co-planar waveguide intermediate conveyor live width 2-10 μ m.Then, set up air bridges on co-planar waveguide (CPW), air bridges is used in the metals such as Au, Ni or Al a kind of, and bridge exceeds coplanar waveguide transmission line 1-10 μ m.Air bridges length is 100-150 μ m, and width is 30-70 μ m, and thickness is 1-1.5 μ m, and rectangle or circular aperture are arranged on the air bridges, is used as the material of sacrifice layer below this helps the making of air bridges and can conveniently remove when making air bridges.

Owing to adopt the structure of this micromechanics (MEMS), there are not the p-n junction of conventional radio frequency switch and the Ohmic contact between metal and semiconductor, thereby the insertion loss is little, the isolation height, and owing to adopt the Kai Heguan of Electrostatic Control switch, basically do not have electrostatic current, the power interface of its consumption is bordering on zero.

Radio frequency single-pole double-throw switch (SPDT) structure of the present invention is very simple, externally under the control of driving voltage, and one road signal conduction, another road is then closed.

Further illustrate invention characteristics of the present invention and substantive progressive below in conjunction with drawings and Examples, but the present invention absolutely not only is confined to embodiment.

Fig. 1 has provided the principle schematic of micro-machinery switch.

Cross-sectional view when (d) not adding static

Plan structure schematic diagram when (e) not adding static

(f), (d) applied the decline process of air bridges behind the static.

Fig. 2 is the structured flowchart of single-pole double-throw switch (SPDT)

11 is underlay substrate among the figure; 12 is earth plate; 13 is transmission line; 14 is air bridges; 15 is dielectric material, and 21 is input, 22 and 22 ' be two identical MIM electric capacity, 23 and 23 ' be the applied voltage end, 24 and 24 ' be two identical mems switches, 25 and 25 ' be output.

As shown in Figure 1,12 and 13 consist of co-plane waveguide (CPW), and the centre is transmission line, and both sides are Earth connection, shown in figure (a), under normal conditions, it is certain that air bridges 14 exceeds intermediate conveyor line 13 Height, at this moment, the state that micro-machinery switch is in out, signal transmits from transmission line, when the needs letter In number when cut-off, just add suitable electrostatic pressure 13, owing to electrostatic induction, will produce on 14 and 13 Electrical opposite electric charge, the mutual attraction between electrostatic charge so that air bridges 14 move down, until with Jie Matter layer 15 contact is to prevent 14 with after 13 contact in 13 purposes that add dielectric layer, and both will be with Upper identical electric charge, electrostatic repulsion can go back 14 bounce-backs. At this moment, signal is by 14,13,15 three's shapes The electric capacity that becomes is led ground, realizes the function that switch closes.

As shown in Figure 2,22 and 22 ' electric capacity be metal-insulator medium-metal (MIM) electric capacity, its Effect has two: the one, and the signal that enters branch is passed through, link to each other with micro-machinery switch; Another effect To make direct current pressure side and the input isolation that adds. The selection of the capacitance of electric capacity should be two with whole hilted broadsword Throw switch uses frequency range relevant, external dc voltage end 23,23 ' be by electric capacity 22,22 ' with import Signal end 21 isolation. Signal is divided into two branch branch roads then from 21 inputs, and first branch arrives through 22 24, from 25 outputs, second branch through 22 ' to 24 ', from 25 ' output. 23 and 23 ' be outer powering up Pressure side, its effect be control respectively micro-machinery switch 24 and 24 ' Kai Heguan. Namely by 23 and 23 ' alternately Apply voltage and realize the function of single-pole double-throw switch (SPDT). The added-time of 23 making alives 23 ' not, through 22,24, Another branch of a branch leading of 25 outputs closes. With reason, 23 ' making alive, 23 added-time not are through 22 ', 24 ', 25 ' output a branch leading, another branch closes.

Embodiment 1: on substrate 11, constitute co-plane waveguide with photoetching process, and its evaporating materials Ti/Au alloy, thickness is about 2000 , and two earth plates 12 and transmission line 13 constitute co-plane waveguides, and the dielectric thin-film material on a middle transmission line is Si ₃N ₄Its thickness is 2000 , air bridges length is 100 μ m, and width is 40 μ m, and thickness is 1 μ m, the rectangle aperture is arranged on the air bridges, air layer thickness between dielectric film and bridge is 2 μ m, forms single micro-machinery switch therefrom, is formed the branched structure of one-to-two by the co-plane waveguide transmission line, a micro-machinery switch is arranged on every branch line, two switches alternately drive and close the realization single-pole double-throw switch (SPDT).

Embodiment 2: the material that forms co-plane waveguide is the Cr/Au alloy, thickness is 1 μ m, described dielectric material is PI (polyamide), thickness is 4000 , and air bridges length is 150 μ m, and width is 60 μ m, thickness is 1.5 μ m, aperture is circular on the air bridges, and the height of air is 5 μ m between dielectric film and bridge, and all the other are with embodiment 1.

Claims

1, a kind of radio frequency microelectronic mechanical single knife commutator is characterized in that:

(a) have three co-plane waveguides in the single-pole double-throw switch (SPDT), one as signal input part, in addition two branched structures that the formation that links to each other with signal input part is divided into two;

(b) electric capacity and an applied voltage end are respectively arranged on each branch line, the slab guide of two branch lines respectively constitutes a micro-machinery switch;

(c) the applied voltage end on two branch lines alternately applies voltage, realizes the single-pole double-throw switch (SPDT) function;

(d) micro-machinery switch is made up of underlay substrate, the earth plate that links to each other with underlay substrate and metal transmission line, the insulating medium layer between air bridges and transmission line and the air bridges that links to each other with two earth plates.

2. by the described radio frequency microelectronic mechanical single knife commutator of claim 1, it is characterized in that its capacitance of described electric capacity is relevant with the single-pole double-throw switch (SPDT) frequency of utilization.

3. by the described radio frequency microelectronic mechanical single knife commutator of claim 1, it is characterized in that the applied voltage end in the described branch is to isolate by MIM electric capacity in the branch and input end signal.

4. the manufacture method of a radio frequency microelectronic mechanical single knife commutator, comprise the photoetching that forms co-planar waveguide, metal coating, removal sacrifice layer wet etching and the air bridges making of thickening air bridges thickness, it is characterized in that forming co-plane waveguide with the photoetching evaporation technology earlier, each bar co-plane waveguide has three lines, middle one as the transmission signal, two as earth connection in addition; A single-pole double-throw switch (SPDT) has three co-plane waveguides, and one as signal input part, and two link to each other with signal output part in addition, are two branches; On two branch's co-plane waveguide intermediate conveyor lines, set up air bridges, the two ends of bridge link to each other respectively with two earth plates of co-plane waveguide, the mid portion of bridge exceeds the certain distance of co-plane waveguide intermediate conveyor line, on co-plane waveguide intermediate conveyor line, partly there is width to be slightly larger than the dielectric material of air bridges width over against air bridges, each constitutes a micro-machinery switch, and it is made up of underlay substrate, earth plate, transmission line, dielectric material and air bridges.

5. press the manufacture method of the described radio frequency microelectronic mechanical single knife commutator of claim 4, it is characterized in that micro-machinery switch in each branch is to adopt photoetching process evaporated gold Au or Ti/Au, Cr/Au alloy, deposition dielectric material Si on the middle transmission line on substrate ₃N ₄Or polyamide, the width of dielectric layer then, is set up air bridges than co-planar waveguide intermediate conveyor live width 2-10 μ m on co-planar waveguide, and bridge exceeds coplanar waveguide transmission line 1-10 μ m; It between dielectric film and air bridges air.

6. by the manufacture method of the described radio frequency microelectronic mechanical single knife commutator of claim 5, it is characterized in that the Au that evaporates on the substrate or Ti/Au, Cr/Au alloy, thickness is 2000 -2 μ m; Thickness of insulating layer 2000-5000 ; Air bridges is used among Au, Ni or the Al a kind of, and rectangle or circular aperture are arranged on the bridge.