Source: http://www.google.com/patents/US20030116417?dq=6317900
Timestamp: 2017-08-20 06:29:24
Document Index: 31897972

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US20030116417 - MEMS device having contact and standoff bumps and related methods - Google Patents
MEMS Device Having Contact and Standoff Bumps and Related Methods. According to one embodiment, a movable MEMS component suspended over a substrate is provided. The component can include a structural layer having a movable electrode separated from a substrate by a gap. The component can also include...http://www.google.com/patents/US20030116417?utm_source=gb-gplus-sharePatent US20030116417 - MEMS device having contact and standoff bumps and related methods
Publication number US20030116417 A1
Application number US 10/291,107
Also published as CN1292447C, CN1613128A, CN1613154A, CN1695233A, CN100474519C, CN100550429C, DE60215045D1, DE60215045T2, DE60217924D1, DE60217924T2, DE60222468D1, DE60222468T2, DE60229675D1, DE60230341D1, DE60232471D1, DE60238956D1, EP1454333A1, EP1454333A4, EP1454333B1, EP1454349A2, EP1454349A4, EP1454349B1, EP1461816A2, EP1461816A4, EP1461816B1, EP1717193A1, EP1717193B1, EP1717194A1, EP1717194B1, EP1717195A1, EP1717195B1, EP1721866A1, EP1721866B1, EP1760036A1, EP1760036B1, EP1760746A2, EP1760746A3, EP1760746B1, US6746891, US6847114, US6876047, US6876482, US6882264, US6917086, US8264054, US8420427, US20030116848, US20030116851, US20030117257, US20030119221, US20040012298, US20040188785, US20040197960, US20070158775, WO2003040338A2, WO2003040338A3, WO2003041133A2, WO2003041133A3, WO2003042721A2, WO2003042721A3, WO2003043038A2, WO2003043038A3, WO2003043042A1, WO2003043044A1
Publication number 10291107, 291107, US 2003/0116417 A1, US 2003/116417 A1, US 20030116417 A1, US 20030116417A1, US 2003116417 A1, US 2003116417A1, US-A1-20030116417, US-A1-2003116417, US2003/0116417A1, US2003/116417A1, US20030116417 A1, US20030116417A1, US2003116417 A1, US2003116417A1
Inventors Dana DeReus
Referenced by (55), Classifications (54), Legal Events (11)
US 20030116417 A1
MEMS Device Having Contact and Standoff Bumps and Related Methods. According to one embodiment, a movable MEMS component suspended over a substrate is provided. The component can include a structural layer having a movable electrode separated from a substrate by a gap. The component can also include at least one standoff bump attached to the structural layer and extending into the gap for preventing contact of the movable electrode with conductive material when the component moves.
(a) a structural layer having a movable electrode separated from a substrate by a gap; and
(b) at least one standoff bump attached to the structural layer and extending into the gap for preventing contact of the movable electrode with conductive material when the component moves.
2. The MEMS component according to claim 1, wherein the structural layer comprises a nonconductive, resilient material.
(a) a substrate having a stationary electrode and a first stationary contact; and
(b) a movable component suspended above the substrate, the component comprising:
(i) a structural layer having a movable electrode and a movable contact, wherein the movable electrode is spaced from the stationary electrode by a first gap and the movable contact is spaced from the first stationary contact by a second gap; and
(ii) at least one standoff bump attached to the structural layer and extending into the first gap for preventing the contact of the movable electrode with the stationary electrode.
15. The MEMS device according to claim 14, wherein the structural layer comprises a nonconductive, resilient material.
(a) a substrate including a first and second stationary electrode and a stationary contact, wherein the stationary contact is positioned between the first and second stationary electrodes;
(b) a structural layer including a first and second end fixed with respect to the substrate and including first, second, and third portions having bottom surfaces, the bottom surfaces suspended over the substrate;
(c) a first movable electrode attached to the bottom surface of the first portion and spaced from the first stationary electrode by a first gap;
(d) a first standoff bump attached to the structural layer and extending into the first gap for preventing the contact of the first movable electrode with the first stationary electrode;
(e) a second movable electrode attached to the bottom surface of the second portion and spaced from the second stationary electrode by a second gap;
(f) a second standoff bump attached to the structural layer and extending into the second gap for preventing the contact of the second movable electrode with the second stationary electrode; and
(g) a movable contact attached to the bottom surface of the third portion and suspended over the stationary contact.
36. The switch according to claim 35, wherein the structural layer comprises a nonconductive, resilient material.
(a) a top surface opposing the bottom surface and including first, second, and third portions opposing the first, second, and third portions, respectively, of the structural layer; and
(b) a first and second electrode interconnect attached to the first and second portions, respectively, of the top surface of the structural layer.
38. The switch according to claim 35, wherein the first and second standoff bumps comprise a nonconductive material.
(a) a substrate having a stationary electrode and a stationary contact;
(b) a movable, folded component suspended above the substrate, the component comprising:
(i) a structural layer having a bottom surface and including a first and second folded beam and a cantilever attached to attachment ends of the first and second folded beams;
(ii) a movable electrode separated from the substrate by a first gap;
(iii) at least one standoff bump attached to the structural layer and extending into the first gap for preventing contact of the movable electrode with conductive material when the component moves toward the substrate;
(iv) a movable contact spaced from the stationary contact by a second gap; and
(v) at least one standoff bump attached to the structural layer and extending into the first gap for preventing the contact of the movable electrode with the stationary electrode.
42. The switch according to claim 41, wherein the at least one standoff bump is attached to the movable electrode.
43. The switch according to claim 41, wherein the at least one standoff bump is attached to the attachment ends of the first and second folded beams.
(a) providing a MEMS device having standoff bumps, the device comprising:
(i) a substrate having a stationary electrode;
(ii) a structural layer having a movable electrode spaced from the stationary electrode by a gap; and
(iii) at least one standoff bump attached to the structural layer and extending into the first gap for preventing the contact of the movable electrode with the stationary electrode when the structural layer moves towards the stationary electrode; and
(b) applying a voltage between the movable electrode and the stationary electrode to electrostatically couple the movable electrode with the stationary electrode across the gap, whereby the structural layer is moved toward the substrate and the at least one standoff bump contacts the stationary electrode.
45. A method for fabricating a movable, MEMS component having a standoff bump, comprising:
(a) depositing a sacrificial layer on a conductive component;
(b) forming a movable electrode on the sacrificial layer for spacing the movable electrode and the conductive material by a gap upon the removal of the sacrificial layer;
(c) forming a standoff bump in the sacrificial layer whereby the standoff bump extends into the gap between the movable electrode and the conductive component;
(d) depositing a structural layer on the movable electrode and the standoff bump; and
(e) removing the sacrificial layer to form a gap spacing the conductive component from the movable electrode whereby the standoff bump extends into the gap for preventing contact of the movable electrode with the conductive material when the component moves.
46. The method according to claim 1, wherein the movable electrode is composed of conductive material.
47. The method according to claim 1, wherein the movable electrode is composed of semiconductive material.
48. The method according to claim 1, wherein the standoff bump is composed of a nonconductive material.
(a) forming a stationary electrode on a substrate;
(b) depositing a sacrificial layer on the stationary electrode and the substrate;
(c) forming a movable electrode on the sacrificial layer for spacing the movable electrode and the stationary electrode by a gap upon the removal of the sacrificial layer;
(d) forming a standoff bump in the sacrificial layer whereby the standoff bump extends into the gap between the movable electrode and the stationary electrode formed by the removal of the sacrificial layer;
(e) depositing a structural layer on the movable electrode and the standoff bump; and
(f) removing the sacrificial layer to form a gap spacing the stationary electrode and the movable electrode whereby the standoff bump extends into the gap for preventing contact of the movable electrode with the conductive material when the structural layer moves towards the stationary electrode.
50. The method according to claim 49, wherein the movable electrode is composed of conductive material.
This nonprovisional application claims the benefit of U.S. Provisional Application No. 60/337,527, filed Nov. 9, 2001; U.S. Provisional Application No. 60/337,528, filed Nov. 9, 2001; U.S. Provisional Application No. 60/337,529, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,055, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,069, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,072, filed Nov. 9, 2001, the disclosures of which are incorporated by reference herein in their entirety. Additionally, the disclosures of the following U.S. patent applications, commonly assigned and simultaneously filed herewith, are all incorporated by reference herein in their entirety: U.S. patent applications entitled “MEMS Device Having a Trilayered Beam and Related Methods”; “Trilayered Beam MEMS Device and Related Methods”; “MEMS Switch Having Electrothermal Actuation and Release and Method for Fabricating”; and “Electrothermal Self-Latching MEMS Switch and Method”.
The present invention generally relates to micro-electro-mechanical systems (MEMS) devices and methods. More particularly, the present invention relates to the design and fabrication of a MEMS device having contact and standoff bumps and related methods.
Many current MEMS switch designs employ a cantilevered beam/plate, or multiple-supported beam/plate geometry. In the case of cantilevered beams, these MEMS switches include a movable, bimaterial beam comprising a structural layer of dielectric material and a layer of metal. Typically, the dielectric material is fixed at one end with respect to the substrate and provides structural support for the beam. The layer of metal is attached on the underside of the dielectric material and forms a movable electrode and a movable contact. The layer of metal can be part of the anchor. The movable beam is actuated in a direction toward the substrate by the application of a voltage difference across the electrode and another electrode attached to the surface of the substrate. The application of the voltage difference to the two electrodes creates an electrostatic field, which pulls the beam towards the substrate. The beam and substrate each have a contact which is separated by an air gap when no voltage is applied, wherein the switch is in the “open” position. When the voltage difference is applied, the beam is pulled to the substrate and the contacts make an electrical connection, wherein the switch is in the “closed” position.
One of the problems that faces current MEMS switches is unwanted contact of the electrode pair. The electrodes of a MEMS switch are ideally positioned very close together while in an “open” position. By placing the electrodes closely together, the power required to deflect the beam to the “closed” position is reduced. However, an unwanted contact of the electrodes can result from this design. The electrodes can also touch if the beam deforms in such a way that the electrodes touch when the beam is moved to the “closed” position. Other undesirable structural deflections usually result from intrinsic or extrinsic stresses in the structural materials. Structural deflections due to intrinsic material stresses occur as a result of a nominal material stress value in combination with the structure design and/or an unbalanced composite structure, or a result of a stress gradient through the thickness of the structural material. The state of nominal and gradient residual stresses is a function of many varied processing conditions and parameters. A common undesirable structural deflection due to extrinsic stress occurs over temperature in composite structures comprised of two or more materials with different Coefficients of Thermal Expansion (CTE). It is undesirable for the electrodes to touch because an electrical short between the electrodes can result.
According to one embodiment, a movable MEMS component suspended over a substrate is provided. The component can include a structural layer having a movable electrode separated from a substrate by a gap. The component can also include at least one standoff bump attached to the structural layer and extending into the gap for preventing contact of the movable electrode with conductive material when the component moves.
[0020]FIG. 1 illustrates a cross-sectional side view of a MEMS switch having standoff bumps in an “open” position in accordance with an embodiment of the present invention;
[0021]FIG. 2 illustrates a cross-sectional side view of a MEMS switch having standoff bumps in a “closed” position;
[0022]FIG. 3 illustrates a cross-sectional front view of a MEMS switch having standoff bumps;
[0023]FIG. 4 illustrates a top plan view of a MEMS switch having standoff bumps;
[0024]FIG. 5 illustrates a perspective top view of a MEMS switch having standoff and contact bumps in accordance with another embodiment of the present invention;
[0025]FIG. 6 illustrates a perspective bottom view of a MEMS switch having standoff and contact bumps;
[0026]FIG. 7 illustrates a perspective bottom view of another embodiment of a MEMS switch having standoff and contact bumps;
[0027]FIG. 8 illustrates a perspective top view of a MEMS switch having standoff and contact bumps operating in an “open” position;
[0028]FIG. 9 illustrates a perspective top view of a MEMS switch having standoff and contact bumps operating in a “closed” position;
[0029]FIG. 10 illustrates a perspective view of the top side of another embodiment of a MEMS switch;
[0030]FIG. 11 illustrates a perspective side view of a MEMS switch having standoff and contact bumps;
[0031]FIG. 12 illustrates a perspective top view of a MEMS switch having standoff and contact bumps in accordance with another embodiment of the present invention;
[0032]FIG. 13 illustrates a perspective bottom view of a MEMS switch having standoff and contact bumps;
[0033]FIG. 14 illustrates a perspective top view of a MEMS switch having standoff and contact bumps in accordance with another embodiment of the present invention;
[0034]FIG. 15 illustrates a perspective side view of a MEMS switch having standoff and contact bumps;
[0035]FIG. 16 illustrates a top plan view of a MEMS switch having a folded geometry and standoff and contact bumps in accordance with another embodiment of the present invention;
[0036]FIG. 17 illustrates a perspective top view of a MEMS switch having standoff and contact bumps in accordance with another embodiment of the present invention;
[0037]FIG. 18 illustrates a perspective view of the underside of the structural layer of a MEMS switch having standoff and contact bumps; and
For purposes of the description herein, it is understood that when a component such as a layer or substrate is referred to herein as being deposited or formed “on” another component, that component can be directly on the other component or, alternatively, intervening components (for example, one or more buffer or transition layers, interlayers, electrodes or contacts) can also be present. Furthermore, it is understood that the terms “disposed on” and “formed on” are used interchangeably to describe how a given component can be positioned or situated in relation to another component. Therefore, it will be understood that the terms “disposed on” and “formed on” do not introduce any limitations relating to particular methods of material transport, deposition, or fabrication.
Contacts, interconnects, conductive vias, and electrodes of various metals can be formed by sputtering, CVD, or evaporation. If gold, nickel or PERMALLOY™ (NixFey) is employed as the metal element, an electroplating process can be carried out to transport the material to a desired surface. The chemical solutions used in the electroplating of various metals are generally known. Some metals, such as gold, might require an appropriate intermediate adhesion layer to prevent peeling. Examples of adhesion material often used include chromium, titanium, or an alloy such as titanium-tungsten (TiW). Some metals combinations can require a diffusion barrier to prevent a chromium adhesion layer from diffusing through gold. Examples of diffusion barriers between gold and chromium include platinum or nickel.
As used herein, the term “device” is interpreted to have a meaning interchangeable with the term “component.” As used herein, the term “conductive” is generally taken to encompass both conducting and semiconducting materials.
Referring to FIGS. 1-4, different views of a MEMS switch, generally designated 100, having a trilayered beam are illustrated. Referring specifically to FIG. 1, a side cross-sectional view of MEMS switch 100 is illustrated in an “open” position. MEMS switch 100 includes a substrate 102. Non-limiting examples of materials which substrate 102 can comprise include silicon (in single-crystal, polycrystalline, or amorphous forms), silicon oxinitride, glass, quartz, sapphire, zinc oxide, alumina, silica, or one of the various Group III-V compounds in either binary, ternary or quaternary forms (e.g., GaAs, InP, GaN, AIN, AlGaN, InGaAs, and so on). If the composition of substrate 102 is chosen to be a conductive or semi-conductive material, a non-conductive, dielectric layer can be deposited on the top surface of substrate 102, or at least on portions of the top surface where electrical contacts or conductive regions are desired.
Substrate 102 includes a first stationary contact 104, a second stationary contact (not shown), and a stationary electrode 106 formed on a surface thereof. First stationary contact 104, second stationary contact, and stationary electrode 106 comprises a conductive material such as a metal. Alternatively, first stationary contact 104, second stationary contact, and stationary electrode 106 can comprise a polysilicon or any suitable conductive material known to those skilled in the art. The conductivity of stationary electrode 106 can be much lower than the conductivity of first stationary contact 104 and second stationary contact. Preferably, first stationary contact 104 and second stationary contact comprises a very high conductivity material such as copper, aluminum, gold, or their alloys or composites. Alternatively, first stationary contact 104, second stationary contact, and stationary electrode 106 can comprise different conductive materials such as gold-nickel alloy (AuNi5) and aluminum, respectively, and other suitable conductive materials known to those of skill in the art. The conductivity of stationary electrode 106 can be much lower than the conductivity of first stationary contact 104 and second stationary contact. Preferably, first stationary contact 104 and second stationary contact comprise a very high conductivity material such as copper. As an example, first stationary contact 104 and second stationary contact can have a width range 7 μm to 100 μm and a length range of 115 μm to 75 μm. Stationary electrode 106 can have a wide range of dimensions depending on the required actuation voltages, contact resistance, and other functional parameters. Preferably, the width range from 25 μm to 250 μm and the length ranges from 100 μm to 500 μm. However, the dimensions are only limited by manufacturability and the functional requirement.
MEMS switch 100 further comprises a movable, trilayered beam, generally designated 108, suspended over first stationary contact 104, second stationary contact, and stationary electrode 106. Beam 108 is fixedly attached at one end to a mount 110. Beam 108 extends substantially parallel to the top surface of substrate 102 when MEMS switch 100 is in an “open” position. Beam 108 generally comprises a structural dielectric layer 112 sandwiched between two electrically conductive layers. Structural layer 112 comprises a bendable material, preferably silicon oxide (SiO2, as it is sputtered, electroplated, spun-on, or otherwise deposited), to deflect towards substrate 102 for operating in a “closed” position. Structural layer 112 provides electrical isolation and desirable mechanical properties including resiliency properties. Alternatively, structural layer 112 can comprise silicon nitride (SixNy), silicon oxynitride, alumina or aluminum oxide (AlxOy), polymers, polyimide, high resistivity polysilicon, CVD diamond, their alloys, or any other suitable non-conductive, resilient material known to those of skill in the art.
Beam 108 further includes an electrically conductive movable electrode 114 attached to an underside surface 116 of structural layer 112. Movable electrode 114 forms a second layer of beam 108. Movable electrode 114 is positioned over stationary electrode 106 and displaced from stationary electrode 106 by an air gap when MEMS switch 100 is operating in the “open” position. Beam 108 is moved in a direction toward substrate 102 by the application of a voltage difference across stationary electrode 106 and movable electrode 114. The application of the voltage difference to stationary electrode 106 and movable electrode 114 creates an electrostatic field, which causes beam 108 to deflect towards substrate 102. The operation of MEMS switch 100 is described in further detail below. Movable electrode 114 is dimensioned substantially the same as stationary electrode 106. Movable electrode 114 can be dimensioned substantially the same as stationary electrode 106. Matching the dimensions of movable electrode 114 and stationary electrode 106 produces the maximum electrostatic coupling, thereby actuation force. This consideration ignores any contribution from fringing field effects at the edge of the respective electrodes. Matching the dimensions of movable electrode 114 and stationary electrode 106 has some disadvantages that can be overcome by mismatching their respective dimensions. By making stationary electrode 106 larger in extent than movable electrode 114, the manufacturing process tolerances and manufacturing alignment tolerances have a minimized effect on the actuation response. A second consideration is the intensification of the electric fields, in the space between movable electrode 114 and stationary electrode 106, which is increased by the closest proximity of the edges of these two electrodes. Because of dielectric or gas breakdown issues, it is desirable to move far apart the edges of these two electrodes. A third consideration is shielding, whereby stationary electrode 106 can shield movable electrode 114 from charge or other electric potentials on substrate 102. Movable electrode 114 and stationary electrode 106 can comprise similar materials, such as gold, such that the manufacturing process is simplified by the minimization of the number of different materials required for fabrication. Movable electrode 114 and stationary electrode 106 can comprise conductors (gold, platinum, aluminum, palladium, copper, tungsten, nickel, and other materials known to those of skill in the art), conductive oxides (indium tin oxide), and low resistivity semiconductors (silicon, polysilicon, and other materials known to those of skill in the art). Movable electrode 114 comprises a conductive material that includes adhesion layers (Cr, Ti, TiW, etc.) between movable electrode 114 and structural material 112. Movable electrode 114 comprises a conductive material and an adhesion layer that includes diffusion barriers for preventing diffusion of the adhesion layer through the electrode material, the conductor material through the adhesion layer or into the structural material.
Movable electrode 114 and stationary electrode 106 can comprise different materials for breakdown or arcing considerations, “stiction” considerations during wet chemical processing, or fabrication process compatibility issues.
Beam 108 further includes a first standoff bump 118 and a second standoff bump (shown in FIG. 3) attached to structural layer 112 and protruding through movable electrode 114 towards stationary electrode 106. First standoff bump 118 is positioned between movable electrode 114 and stationary electrode 106 for intercepting stationary electrode 106 prior to the surface of movable electrode 114 when MEMS switch 100 is moved to a “closed” position. First standoff bump 118 prevents movable electrode 114 from contacting stationary electrode 106. First standoff bump 118 preferably comprises a non-conductive material for preventing an unwanted electrical short between movable electrode 114 and stationary electrode 106. Preferably first standoff bump 118 and the second standoff bump are manufactured with the same non-conductive material as structural layer 112 since first standoff bump 118 and the second standoff bump can be formed when structural layer 112 is produced. Standoff bump 118 can comprise a non-conductive material such as alumina, aluminum oxide (AlxOy), silicon dioxide (SiO2), silicon nitride (SixNy), CVD diamond, polyimide, high resistivity polysilicon, or other suitable materials known to those of skill in the art. Standoff bump 118 can also comprise an electrically isolated material, such as gold or aluminum, or an electrically-isolated semiconductor material such as single crystal or polycrystalline silicon. Some examples of non-shorting combinations of standoff bump material and intercepting material include a nonconductive bump to conductive intercepting material, electrically-isolated conductive standoff bump to conductive intercepting material, conductive or nonconductive standoff bump to a non-conductive intercepting surface, and a conductive or non-conductive standoff bump to electrically isolated conductive surface. Preferably, first standoff bump 118 and the second standoff bump are positioned near the end of the movable electrode furthest from the anchor. Alternatively, first standoff bump 118 and the second standoff bump can be positioned near areas of movable electrode 114 that would contact stationary electrode 106 first during actuation.
Beam 108 further includes an electrically conductive, movable contact 120 attached to underside surface 116 of structural layer 112 and suspended over first stationary contact 104 and the second stationary contact. The movable contact 120 is positioned in this manner so that it will provide electrical connection between first stationary contact 104 and the second stationary contact when beam 108 is in the “closed” position. Movable contact 120 is positioned over first stationary contact 104 and the second stationary contact and displaced from the contacts by an air gap when MEMS switch 100 is operating in the “open” position. When MEMS switch 100 is moved to the “closed” position, movable contact 120 and first stationary contact 104 and the second stationary contact make an electrical connection. First standoff bump 118 and the second standoff bump can contact stationary electrode 106 simultaneously to prevent stationary electrode 106 from contacting movable electrode 118. Alternatively, first standoff bump 118 and the second standoff bump can contact stationary electrode 106 before or after movable contact 120 contacts stationary contact 104. Movable contact 120 is dimensioned smaller than first stationary contact 104 and second stationary contact to facilitate contact when process variability and alignment variability are taken into consideration. First stationary contact 104 and the second stationary contact is sized so that movable contact 120 always makes contact with first stationary contact 104 and the second stationary contact on actuation. A second consideration that determines the size of movable contact 120 and first stationary contact 104 and the second stationary contact is the parasitic response of the switch. The parasitic actuation response is generated by electric fields produced by potential differences between movable electrode 114 and stationary electrode 106, or by potential/charge differences between stationary electrode 106 and beam 108 that produce electric fields and a force on movable contact 120. The dimensions of movable contact 120 are connected to the dimensions of movable electrode 114 to achieve a specific ratio of the parasitic actuation to the actuation voltage.
MEMS switch 100 is operated by applying a potential voltage difference between movable electrode 114 and stationary electrode 106. The applied potential voltage causes beam 108 to deflect towards substrate 102 until movable contact 120 touches first stationary contact 104 and the second stationary contact, thus establishing an electrical connection between movable contact 120 and first stationary contact 104 and the second stationary contact. Referring to FIG. 2, a cross-sectional side view of MEMS switch 100 is illustrated in a “closed” position. As shown in the “closed” position, movable contact 120 is touching first stationary contact 104 and the second stationary contact. Furthermore, first standoff bump 118 is contacting stationary electrode 106. As described below, the components of MEMS switch 100 are dimensioned such that movable electrode 114 does not contact stationary electrode 106 in the “closed” position, thus preventing a short between components 106 and 114. Furthermore, the components of MEMS switch 100 are dimensioned such that first stationary contact 104 and the second stationary contact touch movable contact 120 in the “closed” position. MEMS switch 100 is returned to an “open” position by sufficiently reducing or removing the voltage difference applied across stationary electrode 106 and movable electrode 114. This in turn reduces the attractive force between movable electrode 114 and stationary electrode 106 such that the resiliency of structural layer 112 enables structural layer 124 to return to a position substantially parallel to the surface of substrate 102.
In the “open” position, movable contact 120 is separated from first stationary contact 104 and the second stationary contact by a gap distance a 138 as shown in FIG. 1. Movable electrode 114 is separated from stationary electrode 106 by a gap distance b 140. In this embodiment, distance a 138 is less distance b 140. If distance a 138 is less distance b 140, the operation of MEMS switch 100 is more reliable because potential for shorting between stationary electrode 106 and movable electrode 114 is reduced. The length of beam 108 is indicated by a distance c 142. The center of movable contact 120 is a distance d 144 from mount 110 and a distance e 146 from the end of beam 108 that is distal mount 110. The edge of electrode interconnect 122 distal mount 110 is a distance f 148 from mount 110. In this embodiment, distance a 138 is preferably nominally microns; distance b 140 is preferably 2 microns; distance c 142 is preferably 155 microns; distance d 144 is preferably 135 microns; distance e 146 is preferably 20 microns; distance f 148 is preferably 105 microns; and distance g 150 is preferably 10 microns. These dimensions are designated to provide certain functional performance, but other dimensions can be selected to optimize manufacturability and reliability for other functional requirements. For example, in this embodiment, standoff bump 118 is separated from stationary electrode 106 by distance a 138. Depending on requirements, the distance separating standoff bump 118 from stationary electrode 106 can be a different distance than or identical distance to the distance separating movable contact 120 from stationary contact 104.
Referring now to FIG. 6, a perspective bottom view of MEMS 500 switch is illustrated. MEMS switch 500 further includes a stationary electrode 516 and stationary contacts 518 and 520 attached to a surface 522 of a substrate 524 (shown in FIG. 5). Movable contact 514 touches contacts 518 and 520 when MEMS switch 500 is operating in a “closed” position. Thus, in a “closed” position, stationary contacts 518 and 520 are electrically connected via movable contact 514. Further, contacts 518 and 520 can be connected through movable contact 522 and contact interconnect 510. Movable contact 514 further includes a first and second set of contact bumps, generally designated 526 and 528, respectively. Contact bumps 526 and 528 comprise a conductive material for facilitating electrical communication between stationary contacts 518 and 520 in the “closed” position. Contact bumps 526 and 528 reduce the gap distance between movable contact 514 and stationary contacts 518 and 520, thus reducing the potential for shorting between stationary electrode 516 and movable electrode 512. Contact bumps 526 and 528 insure reliable contact with stationary contacts 518 and 520 because without contact bumps there is a potential for interference between movable contact 514 and surface 522 between stationary contact 518 and 520. Additionally, contact bumps 526 and 528 provide design flexibility to meet contact resistance and current capacity requirements. These requirements can be achieved by optimization of the following: contact bump geometry (e.g., circular, square, elliptical, rectangular hemispherical) and the geometric pattern of the contact bumps, such as a rectangular pattern (as shown with 1 bump leading 2 bumps), a triangular pattern (with 2 bumps leading 1 bump), an elliptical pattern, and a star pattern. In this embodiment, contact bumps 526 and 528 are shown cylindrical and in a triangular grouping of 3 bumps, wherein 1 bump leads 2 bumps. Furthermore, contact bumps 526 and 528 can be considered a macro definition of contact asperities, which are normally determined by the surface roughness of the contacting surfaces. The contact resistance and current capacity are determined by the number of microscopic asperities, so the macroscopic definition of asperities enhances the design space.
MEMS switch 500 further includes a first standoff bump 530 and a second standoff bump 530 attached to structural layer 504 and protruding through movable electrode 512 towards stationary electrode 516. Standoff bumps 530 and 532 are positioned between movable electrode 512 and stationary electrode 516 for intercepting stationary electrode 516 prior to the surface of movable electrode 512 when MEMS switch 500 is moved to a “closed” position.
MEMS switch 700 further includes a first stationary contact 716 and a second stationary contact 718 formed on the substrate. Movable contact 714 includes a first contact bump 720 and a second contact bump 722, which protrude from movable contact 714 for reducing the gap distance between movable contact 714 and stationary contacts 716 and 718. Contact bumps 720 and 722 comprise conductive material for providing electrical connection between stationary contacts 716 and 718 when MEMS switch 700 is in the “closed” position.
MEMS switch 700 includes a stationary electrode 724 formed on the substrate. Beam 702 further includes a first standoff bump 726 and a second standoff bump 728 attached to structural layer 706 and protruding through movable electrode 712 towards stationary electrode 724. Standoff bumps 726 and 724 prevent movable electrode 712 from contacting stationary electrode 728. Standoff bumps 726 and 728 can comprise a non-conductive material for preventing an unwanted electrical short between movable electrode 712 and stationary electrode 724 and can be positioned near the end of movable electrode 712 furthest from the anchor. The positioning of standoff bumps 726 and 728 relative to contact bumps 720 and 722 can be a critical aspect. The optimal position for standoff bumps 726 and 728 is such that a maximum overdrive actuation voltage can be supported without shorting electrodes 712 and 724 and maximizing the contact force between contacts 716 and 720 and contacts 718 and 722, respectively, thereby minimizing the contact resistance. Preferably, standoff bumps 726 and 728 are positioned closer to fixed end 704 than contact bumps 720 and 722. In this configuration, contact bumps 720 and 722 establish contact with stationary contacts 716 and 718, respectively, before standoff bumps 726 and 728 establish contact with stationary electrode 724. Once contact bumps 720 and 722 contact stationary contacts 716 and 718, respectively, the actuation voltage can be increased to increase the contact force and decrease the contact resistance. The contact resistance can continue to decrease with increased actuation voltage until standoff bumps 726 and 728 contact stationary electrode 724. When contact between standoff bumps 726 and 728 and stationary electrode 724 is established, the contact resistance and chance of shorting begins to increase with increased voltage, an undesirable condition. Standoff bumps 726 and 728 can be positioned across the width of beam 702 such that as the beam width increases, the number of standoff bumps can preferably increase to preserve isolation of electrodes 712 and 724. Further, it is preferable to minimize the total surface area of structural layer 706 occupied by standoff bumps because it will reduce the amount of surface available for movable electrode 712, thus reducing electrostatic force.
Referring now to FIG. 8, a top perspective view is provided of MEMS switch 700 operating in the “open” position. Upon the application of sufficient voltage across electrode interconnect 708 and stationary electrode 724, beam 702 deflects towards a substrate 800 for operation in a “closed” position Referring now to FIG. 9, a top perspective view of MEMS switch 700 is illustrated in the “closed” position.
MEMS switch 1000 further includes a stationary electrode 1016 and a contact electrode 1018 formed on a surface 1020 of a substrate 1022. Stationary electrode 1016 and stationary contact 1018 are in alignment with and can be dimensioned substantially the same as electrode interconnect 1008 and a contact interconnect 1010, respectively. End 1004 of beam 1002 is fixed with respect to substrate 1022. As shown, electrode interconnect 1008 partially surrounds contact interconnect 1010. In this embodiment, movable electrode 1012 substantially surrounds movable contact 1014. This arrangement of the electrode interconnect, movable electrode, and stationary electrode further from the anchor reduces the power necessary to move the MEMS switch to a “closed” position. Additionally, this configuration aides in preventing unwanted actuation resulting from parasitic voltages applied across stationary contact 1018 and movable contact 1014. As shown in this embodiment, electrode interconnect 1008, movable electrode 1012, and stationary electrode 1016 are wider in relation to the contact as compared with embodiments previously described herein.
Movable contact 1014 includes a contact bump 1028 which extends beyond standoff bumps 1024 and 1026 for contacting stationary contact 1018 before standoff bumps 1024 and 1026 during an operation to “close” MEMS switch 1000. In this embodiment, contact bump 1028 can have equal extension as the standoff bumps 1024 and 1026 for simplifying the process flow. The preferred positioning of standoff bumps 1024 and 1026 relative to contact bump 1028 is such that a maximum overdrive voltage can be supported without shorting electrodes 1012 and 1016 and wherein the contact force is maximized. Thus, standoff bumps 1024 and 1026 are positioned closer to fixed end 1004 than contact bump 1028. In this configuration, contact bump 1028 establishes contact with stationary contact 1018 before standoff bumps 1024 and 1026 establishes contact with stationary electrode 1016. Once contact bump 1028 contacts stationary contact 1018, the actuation voltage can be increased to increase the contact force and decrease the contact resistance. The contact resistance continues to decrease until standoff bumps 1024 and 1026 establish contact with stationary electrode 1016. When standoff bumps 1024 and 1026 contact stationary electrode 1016, the contact resistance and chance of shorting increases. Standoff bumps 1024 and 1026 are positioned across the width of beam 1002, such that the beam width increases, the number of standoff bumps can increase.
MEMS switch 1200 further includes a stationary electrode 1212 and a first and second stationary contact 1214 and 1216 attached to a surface 1218 of a substrate 1220. Stationary electrode 1212 is in alignment with and dimensioned substantially the same as electrode interconnect 1208 and a contact interconnect 1210, respectively. As shown, electrode interconnect 1208 partially surrounds contact interconnect 1210. Structural layer 1206 includes a narrowed anchor zone located at end 1204 for reducing the actuating force required to “close” MEMS switch 1200. The required actuating force is reduced because the local cross-sectional area of structural layer 1206 that must be bent in the direction of stationary electrode 1212 is reduced. Contact is improved by applying an overdrive voltage to electrode interconnect 1202 and the stationary electrode.
Referring to FIGS. 19F-19G, a process for producing a standoff bump 1918 and a structural layer 1920 is illustrated. Referring now to FIG. 3F, a standoff via 1922 is etched through movable electrode 1914 and into sacrificial layer 1910. Alternatively, grooves can be etched for forming standoff bumps through other layers and into sacrificial layer 1920 for forming a standoff bump to extend into a gap between the beam and substrate 1900. Referring to FIG. 3G, structural layer 1920 can be deposited on movable contact 312, movable electrode 314, sacrificial layer 310, and first dielectric layer 302. Structural layer 1920 can also be deposited in standoff via 1922 for forming standoff bump 1918. Standoff bumps can be manufactured to attach to the beam for extending into the gap between the beam and the substrate in any suitable process known to those of skill in the art. Structural layer 1920 comprises oxide in this embodiment. In the alternative, standoff bump 1918 can be formed in a different step than the processing of structural layer 1920 such as by etching grooves into sacrificial layer 1910 and forming contact bump 1918 prior to forming any subsequently formed components. This alternative can be beneficial when it is not desirable to etch through subsequently formed components for forming contact bump 1918.
The MEMS switch is illustrated in an “open” position. In a “closed” position, beam 1938 is deflected towards substrate 1900 and movable contact 1912 contacts stationary contact 1904. As described above, a voltage can be applied across electrode interconnect 1926 and stationary electrode 1906 for moving the MEMS switch into a “closed” position. Standoff bump 1918 extends into the gap between stationary electrode 1906 and movable electrode 1914 to prevent electrodes 1906 and 1914 from contacting.
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U.S. Classification 200/181, 257/E27.112, 361/207, 361/233
International Classification H01L23/522, H01L29/86, B81B7/00, H01L21/302, B81B3/00, H02N1/00, H01L23/373, H01H1/04, H01L27/12, H01H59/00, H02N10/00, H01H61/04, H01H1/50
Cooperative Classification Y10T29/49222, H01L2924/09701, B81C2201/0109, B81B3/0051, H01L27/1203, H01H61/04, B81B2207/07, B81B2201/018, H01H59/0009, B81B3/0024, H01H2001/0042, H01L2924/0002, H01H1/504, B81C2201/0107, H02N10/00, H01H2001/0063, H01H2059/0072, B81C2201/0108, H01H2061/006, H01H2001/0089, H02N1/006, B81C1/0015, B81B2203/0118, H01L23/522, H01H1/04, B81B2201/014, H01L23/3735, B81B2203/04
European Classification H02N1/00B2, H01L23/522, H01L23/373L, B81C1/00C4C, B81B3/00K6, B81B3/00H4, H01H59/00B, H02N10/00, H01H61/04
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TURNSTONE SYSTEMS, INC.;REEL/FRAME:016844/0295