Source: http://patents.com/us-8120229.html
Timestamp: 2019-01-21 16:06:38
Document Index: 614939040

Matched Legal Cases: ['Application No. 06744966', 'Application No. 200680017137', 'art 1924', 'arts 1924', 'art 1922', 'art 1922', 'art 1922', 'arts 1922', 'arts 1922', 'art 1922', 'art 1922', 'art 1922', 'art 1922', 'arts 1922']

US Patent # 8,120,229. Middle spring supported micro-electro-mechanical transducers - Patents.com
United States Patent 8,120,229
Huang February 21, 2012
Appl. No.: 11/914,608
PCT No.: PCT/IB2006/051569
PCT Pub. No.: WO2006/123301
Current U.S. Class: 310/309 ; 367/181; 381/191; 600/459; 73/514.32
Current International Class: H02N 1/00 (20060101); H04R 19/00 (20060101); A61B 8/00 (20060101)
Field of Search: 310/309 381/174,191 600/459,437 367/163,181 73/514.32
1306901 (A2) May., 2003 EP
Hwang et al, "Design and Fabrication of the Thin-Film Micromirror Array-actuated for Large Projection Displays," Journal of the Korean Physical Society, vol. 33, Nov. 1998, pp. S467-8470. cited by other .
Extended Europoean Search Report mailed on Feb. 18, 2011 for European Patent Application No. 06744966.0, a counterpart foreign application for U.S. Appl. No. 11/914,584, 16 pgs. cited by other .
Translated the Chinese Office Action mailed Mar. 23, 2011 for Chinese Patent Application No. 200680017137.1, a counterpart foreign application of U.S. Appl. No. 11/914,597. cited by other .
Final Office Action for U.S. Appl. No. 11/917,666 mailed Apr. 25, 2011, Yongli Huang, "Micro-Electro-Mechanical Transducer Having an Insulation Extension". cited by other .
This application further incorporates herein by reference in entirety the following: International Application (PCT) PCT/IB2006/051566, entitled THROUGH-WAFER INTERCONNECTION, filed on May 18, 2006; International Application (PCT), PCT/IB2006/051567, entitled METHODS FOR FABRICATING MICRO-ELECTRO-MECHANICAL DEVICES, filed on May 18, 2006; and International Application (PCT), PCT/IB2006/051568, entitled MICRO-ELECTRO-MECHANICAL TRANSDUCERS, filed on May 18, 2006.
It is noted that the terms "transducer" and "transducing member" are used in a broad sense in the present description to not only include devices that perform both actuation and sensing functions but also include devices that perform either an actuation function or an sensing function. It is also noted that the term "cantilever" is used in this description in a broad sense to describe a structure that has an anchored end, a resilient portion extending from the anchored, and to an exerting end to activate or move the resilient portion. A cantilever thus does not necessarily suggest a literal one-dimensional bema-like cantilever, but also includes similar structures have multibeams extending in different directions such as a bridge, or a crossbar, and most definitely also includes area or plane springs (two-dimensional "cantilevers") in which the anchored end is an extended line which may be a closed perimeter of an area or a portion thereof, the resilient portion is an extended area, and the exerting end may be a single point, a small area, or an extended line (close ended, open-ended, or segmented). In addition, the words "circular" and "annular" only suggest in the broadest sense that a shape has a looped form, a curved shape that is nearly looped, or an arrangement that is generally shaped like a ring, and do not suggest a rounded shape or any other shape in particular, nor does it suggest that the loop or ring is entirely complete or unbroken.
The cMUT portion 510 is built on a substrate 501, on top of which there is a standing feature (referred to as "sidewall anchor" hereinafter) 503 having two sidewalls on two opposing sides bordering cavities 502 and 502a, respectively. The standing feature (sidewall anchor) 503 may be an integrated part of the substrate 501 formed as a result of forming the cavities 502 and 502a, but may also be an additional structure added onto a separate substrate. In one embodiment, for example, the sidewall anchor 503 is part of the middle spring layer 520. The substrate of 501 may be made of either a nonconductive material or a conductive material such as silicon or polysilicon. In a configuration where the sidewall anchor 503 is a separate structure, conductivity of the sidewall anchor 503 may be the same as or different from that of the substrate 501. For example, the substrate 501 may be made of a nonconductive material while the sidewall anchor 503 a conductive material such as metal, silicon or polysilicon.
The connector 1430 stands out from the middle spring layer 1420 to define a transducing space 1460 below the top plate layer 1440. In this particular embodiment, the actual height D.sub.a of the transducing space 1460 is reduced by the thicknesses of the bottom electrode 1425 and the middle spring layer 1420 in the configuration shown in FIG. 14. The connector 1430 is horizontally distanced from the sidewall anchor 1403 by a sufficient length to define a cantilever anchored at the sidewall anchor 1403. The cantilever and the cavity 1402 enable a vertical displacement of the connector 1430, which transports the top plate 1440 substantially vertically with a piston-like motion, thus changing the transducing space 1460. When the both halves of the cMUT structure 1410 move in the same phase, the vertical piston-like motion is further assured.
As shown in FIG. 14, the maximum vertical displacement D.sub.m of the connector 1430 is limited by a motion stopper 1490 disposed in the cavity 1402. When D.sub.m is designed to be no greater than (preferably smaller than) D.sub.a, the vertical displacement of the connector 1430 (and thus the maximum vertical transportation distance of the top plate layer 1440) is limited to be less than the height D.sub.a of the transducing space. This effectively prevents the top plate layer 1440 from touching the bottom electrode 1425 to cause a short, thus eliminating the need for an insulation layer under the top plate layer 1440. In one preferred embodiment, D.sub.m is at least one third less than D.sub.a.
FIGS. 15A-15C show three exemplary configurations of a top plate layer of the present invention. FIG. 15D shows a graph of the corresponding ratio of 1st resonant frequency over the total mass of the top plate as the function of the diameter of the etched holes in the three configurations. In the first configuration shown in FIG. 15A, an array of holes 1544A of a diameter of 8 .mu.m is formed on the top plate 1540A. There is a separation distance of 10 .mu.m between the neighboring holes. In the second configuration shown in FIG. 15B, an array of holes 1544B of a diameter of 4 .mu.m is formed on the top plate 1540B. There is a separation distance of 10 .mu.m between the neighboring holes. In the third configuration shown in FIG. 15C, a solid top plate 1540C without holes formed therein is used.
In a capacitance micromachined ultrasonic transducer (cMUT), the bottom electrode may be either on the middle spring layer or on the substrate wafer. In the present description, the term "on" does not necessarily suggest that a separate material or layer is placed on another layer. The bottom electrode may be a part of the middle spring layer or the substrate wafer. For example, the middle spring layer may comprise a conductive material to effectuate the bottom electrode.
In contrast to the cMUT structures shown in FIGS. 5A-5C, the cMUT structure 1911 features self-aligned cantilevers. To achieve this, a thick middle spring layer 1920 is used. Cantilever lengths L.sub.a and L.sub.b are defined by a respective thinner part 1924a or 1924b of the spring membrane layer 1920. In the example shown, the two thinner parts 1924a and 1924b are separated by a thicker part 1922 in the middle of the bridge formed by the spring membrane layer 1920. In the bridge configuration shown here, the thicker part 1922 functions as a cantilever divider. In other configurations, the thicker part 1922 may be a cantilever terminator forming an end of a cantilever on one side only. The two anchoring thicker parts 1922a and 1922b are on top of the two sidewall anchors 1903 and 1903m, respectively. In some embodiments, the two anchoring thicker parts 1922a and 1922b form at least a part of the two sidewall anchors 1903 and 1903m, or even the entire sidewall anchors 1903 and 1903m.
The plate-spring connector 1930 is located on the thicker part 1922. In this configuration, the cantilever length L.sub.a is defined by the distance between the edge 1906 of the thicker part 1922 and the edge 1904 of the thicker part 1922a. The cantilever length L.sub.b is defined similarly. The cantilever lengths L.sub.a and L.sub.b can therefore be predetermined and self-aligned during the fabrication. Any misalignment of the connector 1931 relative to the middle spring layer 1920 (or the thicker part 1922 to be exact), or misalignment of the middle spring layer 1920 (or the thicker parts 1922a and 1922b) relative to the sidewall anchors 1903 or 1903m will have a minimum impact on the effect of cantilever lengths and the corresponding spring strengths of the cantilevers. The cantilever lengths L.sub.a and L.sub.b in the cMUT structure 1911 and the corresponding spring lengths the cantilevers therefore have little or none dependence on any discrepancies among individual fabrication steps.
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