Source: http://www.google.com/patents/US6889565?dq=552685
Timestamp: 2013-12-12 02:41:47
Document Index: 215422508

Matched Legal Cases: ['art 86', 'art 86', 'art 90', 'art 86', 'art 90', 'art 86']

Patent US6889565 - Fingerprint sensors using membrane switch arrays - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Advanced Patent Search | Sign inAdvanced Patent SearchPatentsA sensor for identifying fingerprints or other skin textures includes an array of cells each including a membrane switch. Each switch includes a fixed lower electrode disposed on a chip substrate, and a flexible membrane disposed over the lower electrode and capable of flexing downward to establish electrical...http://www.google.com/patents/US6889565?utm_source=gb-gplus-sharePatent US6889565 - Fingerprint sensors using membrane switch arraysPublication numberUS6889565 B2Publication typeGrantApplication numberUS 10/038,505Publication dateMay 10, 2005Filing dateDec 20, 2001Priority dateMay 16, 2000Fee statusPaidAlso published asUS6578436, US6829950, US7638350, US20020121145, US20020166388, US20050229380, WO2001088837A1, WO2001088837A9Publication number038505, 10038505, US 6889565 B2, US 6889565B2, US-B2-6889565, US6889565 B2, US6889565B2InventorsKeith T. Deconde, Srinivasan K. Ganapathi, Randolph S. Gluck, Steve H. Hovey, Shiva Prakash, Christopher StoesselOriginal AssigneeFidelica Microsystems, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (46), Referenced by (16), Classifications (13), Legal Events (11) External Links: USPTO, USPTO Assignment, EspacenetFingerprint sensors using membrane switch arraysUS 6889565 B2Abstract A sensor for identifying fingerprints or other skin textures includes an array of cells each including a membrane switch. Each switch includes a fixed lower electrode disposed on a chip substrate, and a flexible membrane disposed over the lower electrode and capable of flexing downward to establish electrical contact between the lower electrode and an upper electrode. The upper electrode can form the membrane itself or a layer of the membrane, or can be attached to other membrane layers. Switches situated underneath skin ridges change state (e.g. are closed) by the applied pressure, while switches underneath skin valleys remain in their quiescent state (e.g. open). Adjacent switch chambers are connected by fluid tunnels which allow the passage of air between the chambers. Each chamber is substantially closed to the exterior of the sensor, such that particles from the environment cannot contaminate the switch contact surface defined between the switch electrodes. The cells are preferably not hermetically sealed, such that the pressure within the chamber interiors can stay equal to the external (atmospheric) pressure in varying environmental conditions. The membrane design of the cells according to the preferred embodiment allows improved sensor robustness, enhanced resistance to impact forces, decreased vulnerability to particle contamination, and reduced inter-cell crosstalk.
a) a base; b) a plurality of conductive row lines disposed on the base; c) a plurality of conductive column lines disposed on the base and insulated from the row lines; and d) an array of membrane switches disposed on the base such that a spacing between adjacent switches in the array is less than one half of a spacing between adjacent ridges, each membrane switch corresponding to a pair of one of the row lines and one of the column lines, said each membrane switch comprising: a lower electrode disposed on the base and electrically connected to said one of the row lines, and a flexible upper membrane structure disposed over and spaced apart from the lower electrode when in a quiescent state, the membrane structure comprising an upper electrode disposed facing the lower electrode and connected to said one of the column lines, wherein applying a ridge of the texture to said each membrane switch causes a flexure of the membrane resulting in a contact between the lower electrode and the upper electrode, the contact establishing an electrical communication between said one of the row lines and said one of the column lines, and wherein disposing a valley of the texture over said each membrane switch does not result in the contact between the lower electrode and the upper electrode. 2. The sensor of claim 1 wherein the upper electrode comprises a conductive membrane anchored to the base around an edge of the conductive membrane.
an array of membrane switches disposed on a base such that a spacing between adjacent switches in the array is less than one half of a spacing between adjacent ridges, each membrane switch comprising: a) a lower electrode disposed on the base; and b) a flexible upper membrane structure disposed over the lower electrode and comprising an upper electrode disposed facing the lower electrode, wherein applying a ridge of the texture to said each membrane switch causes a flexure of the membrane resulting in a contact between the lower electrode and the upper electrode, and wherein disposing a valley of the texture over said each membrane switch does not result in the contact between the lower electrode and the upper electrode. 24. The sensor of claim 23 wherein the upper electrode comprises a conductive membrane anchored to the base around an edge of the conductive membrane.
an array of membrane switches disposed on a base, each membrane switch comprising: a) a lower electrode disposed on the base; and b) a flexible upper membrane structure disposed over the lower electrode and spaced apart from the lower electrode when in a quiescent state, the upper membrane structure comprising an upper electrode disposed facing the lower electrode, wherein disposing a protrusion of the texture over said each membrane switch causes a flexure of the membrane resulting in a contact between the lower electrode and the upper electrode, and wherein disposing a valley of the texture over said each membrane switch does not result in the contact between the lower electrode and the upper electrode. 31. The sensor of claim 30 wherein the upper electrode comprises a conductive membrane anchored to the base around an edge of the conductive membrane.
a) a substrate; b) a plurality of row lines; c) a plurality of column lines; and d) a plurality of membrane switches disposed on the substrate in an array such that each row line and each column line is connected to a plurality of membrane switches, each switch including: a lower electrode electrically connected to one of the row lines; and a flexible membrane comprising an upper electrode spaced apart from said lower electrode when in a quiescent state and electrically connected to one of the column lines; wherein a ridge of the texture causes flexure of the membrane and thereby results in movement of the upper electrode and a change in a state of electrical contact between the upper electrode and the lower electrode, and wherein a valley of the texture disposed over another of the switches does not result in flexure of the membrane and the change in state of electrical contact between the upper electrode and the lower electrode associated with said another switch. 41. The sensor of claim 40, wherein the membrane structure further comprises an insulative diaphragm stacked over the upper electrode.
a) a fixed electrode rigidly coupled to the base; and b) a flexible upper membrane structure disposed over the base such that a cavity separates a central region of the membrane structure and the base when the fixed electrode and the movable electrode are not in contact, the membrane structure comprising a movable electrode disposed facing the fixed electrode, wherein disposing a protrusion of the texture over said each membrane switch causes a flexure of the membrane resulting in a change in contact state between the fixed electrode and the movable electrode, and wherein disposing a valley of the texture over said each membrane switch does not result in the change in contact state between the fixed electrode and the movable electrode. 49. The sensor of claim 48, wherein the fixed electrode is disposed underneath the movable electrode, and wherein the change in contact state is a change from an open quiescent state to a closed state.
a) depressing the texture over a sensor comprising an array of membrane switches, each membrane switch comprising a fixed lower electrode and a flexible upper membrane structure including an upper electrode disposed over the lower electrode; b) identifying a plurality of closed membrane switches, wherein a ridge of the texture disposed over each of the closed switches causes a flexure of a membrane structure of said each of the closed switches and an electrical contact between a lower electrode and an upper electrode of said each of the closed switches; and c) identifying a plurality of open membrane switches, wherein a valley of the texture disposed over each of the open switches does not cause an electrical contact between a lower electrode and an upper electrode of said each of the open switches. 52. The method of claim 51, wherein the texture is a skin texture.
RELATED APPLICATION DATA This application is a continuation-in-part of U.S. patent application Ser. No. 09/571,765, filed May 16, 2000, entitled �Method and Apparatus for Pressure Sensing,� which is herein incorporated by reference.
DETAILED DESCRIPTION OF THE INVENTION In the following description, it is understood that each recited element or structure can be formed by or be part of a monolithic structure, or be formed from multiple distinct structures. Unless otherwise specifically stated, the statement that a first layer or structure is disposed or deposited on a second layer or structure is understood to allow for the presence of parts of the first or second layer or structure that are not so disposed or deposited, and further allow for the presence of intermediate layers or structures between the first and second layers or structures. The terms �chip base� and �chip substrate� are understood to encompass monolithic substrates as well as structures containing multiple layers or parts. The terms �upper� and �lower� are used to describe relative positions, and s do not necessarily refer to the direction of gravity during operation of the sensor. A set of elements is understood to include one or more elements. A plurality of elements is understood to include two or more elements. Any recitation of an element is understood to refer to at least one element.
FIGS. 1-A and 1-B are schematic diagrams illustrating the electrical connections of a fingerprint or texture sensor 20 according to the preferred embodiment of the present invention. Sensor 20 comprises an array of switches (cells) spaced from each other by an appropriate distance that is a fraction of the inter-ridge spacing of the fingerprint or skin texture to be sensed. The preferable range of this fraction is � to {fraction (1/20)}. Typical spacings between fingerprint ridges are 400-500 μm. Each switch corresponds to an intersection of a row line and a column line illustrated in FIGS. 1-A and 1-B. Closed switches are denoted by their associated resistances Rs. The 8�8 switch array illustrated in FIGS. 1-A and 1-B is part of a larger m�n array.
A plurality of metallic leads arranged in an m�n orthogonal grid and electrically isolated from each other serve as the electrical input and output lines for each switch. The orthogonal grid of metallic leads comprises conductive rows 22 and columns 24, which lead into and out of each switch. Each row/column combination of conducting leads corresponds uniquely to a specific switch in the array. Each switch is addressed by applying a voltage and sensing a current between the row and column leads corresponding to the switch.
I closed /I open=1+NX/n(1−X), [1] wherein X=(Rsw/n+Rsw/n2+Rpd/n2)/(Rpd+Rsw/n+Rsw/n2+Rpd/n2), Rsw=Resistance in series with each switch, Rpd=Pull-down resistance at inputs to the row multiplexer, N=Total number of switches in any given row or column, n=Average number of closed switches on any given row or column. Some typical values for the parameters in the above equations are:
Rsw=100,000 Ω Rpd=100 Ω N=256 Switches n=128 Switches X=0.887
An order-of-magnitude estimate of the dependence of the central deflection of a circular membrane on the properties of the membrane can be calculated by considering an ideal, flat disk-shaped monolithic membrane anchored around its circular edge. The central deflection of such a membrane is on the order of y = Pha 4 EA p ⁢ h 4 [ 2 ] where P is applied pressure, h is the membrane thickness, a is the membrane radius, E is Young's Modulus for the membrane material, and Ap is a dimensionless stiffness coefficient.
A first sacrificial layer 82 is formed over the contact surface of lower electrode 50, and over part of insulator layer 80 and column lead 46. Sacrificial layer 82 includes a generally circular central part 86 extending over the entire extent of the contact surface of lower electrode 50 and over a part of insulator layer 80 surrounding the contact surface. Central part 86 of sacrificial layer 82 will form part of the air chamber of switch 40, between lower electrode 50 and the upper electrode. Sacrificial layer 82 also includes a tunnel part 90 a-b, which extends away from central part 86 in a direction parallel to row lead 44. Tunnel part 90 a-b will form an inter-cell air tunnel for facilitating the equalization of pressure between different switch chambers. Sacrificial layer 82 further includes a set of four vent extensions 88 extending away from central part 86, at 45� relative to row lead 44 and column lead 46. Vent extensions 88 serve to provide access to sacrificial layer 82 during a subsequent step in which sacrificial layer 82 is removed. In general, one or more (e.g. more than four) vent extensions may be used.
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