Abstract:
A miniature radio-frequency identification (RFID) transceiver and a method for making the same are provided. The RFID transceiver is small in size and physically rugged. The RFID transceiver includes an integrated circuit and a radio-frequency antenna that is fixed to the integrated circuit and electrically connected to the integrated circuit. The integrated circuit includes an RFID transceiver circuit. The antenna may be a single thin-film layer over the top surface of the integrated circuit or multiple layers that form a larger antenna in a compact, folded structure. Multiple antenna layers may also be used to form a three-dimensional structure for improved antenna operation or may be used to form separate, independent antennas.

Description:
BACKGROUND OF THE INVENTION 
     A radio-frequency identification (RFID) transceiver is a device that receives an electronic signal, generates a response signal, and then transmits the response signal. Uses for RFID transceivers include locating or identifying individual items within a large group, such as a single garment within a department store, a pet within a group, or an animal within a herd. 
     Some RFID transceivers include one or more antennae that are electrically connected to an accompanying electronic circuit. The electronic circuit portion of the RFID transceiver can be fabricated of discrete components on a printed circuit board or may be formed within an integrated circuit (i.e., a semiconductor chip). The antenna portion of the REID transceiver may be a three-dimensional structure such as a metal coil or may be a thin-film on a printed circuit board or other substrate. 
     One known RFID transceiver includes an electronic circuit and an antenna that are physically separate from each other, but that electrically communicate through capacitive or inductive coupling. Another RFID transceiver uses bond wires to electrically connect an integrated circuit to the antenna; the antenna and circuit are then encapsulated in a potting material, or in packaging such as a glass tube. Still another RFID transceiver uses no attendant circuitry but uses an antenna that resonates and retransmits at specific radio frequencies when stimulated by a radio signal. 
     SUMMARY OF THE INVENTION 
     The present invention provides a miniature radio-frequency identification (RFID) transceiver and a method for making the same. 
     One embodiment of an RFID transceiver within the present invention includes an integrated circuit that further includes at least an REID transceiver circuit. The REID transceiver also includes at least one radio-frequency antenna that is formed on the integrated circuit. The antenna and the integrated circuit are electrically connected. 
     The antenna may be made of one or more patterned, thin-film layers. Having multiple antenna layers can provide the benefit of a relatively large antenna in a compact, folded structure. Alternatively, having multiple antenna layers can provide multiple, independent antennas for use by the RFID transceiver. Implementation of the antenna on the integrated circuit provides an RFID transceiver that is small in size, physically rugged, and relatively inexpensive. 
     The forgoing and other objects, aspects, and advantages of the present invention will be better understood from the following drawings and the detailed description of various alternative embodiments of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  depicts a cross-sectional side view of radio-frequency identification (RFID) transceiver  1 . 
     FIG. 1 b  is an exploded top view of the RFID transceiver of FIG. 1 a.    
     FIG. 2 is an exploded top view of an alternative RFID transceiver. 
     FIG. 3 a  depicts a cross-sectional side view of a further alternative RFID transceiver having multiple antenna layers that are directly, electronically connected to each other. 
     FIG. 3 b  is an exploded top view of the RFID transceiver of FIG. 3 a.    
     FIG. 4 a  depicts a cross-sectional side view of an alternative RFID transceiver having multiple antenna layers that are not directly, electronically connected to each other. 
     FIG. 4 b  is an exploded top view of the RFID transceiver of FIG. 4 a.    
     FIG. 5 is a flow chart of an exemplary method  50  of making an RFID transceiver. 
     FIG. 6 is a flow chart of an exemplary method  60  of making an alternative RFID transceiver. 
    
    
     In the drawings, where the different embodiments have similar structures, the same reference numbers are usually used. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 a  depicts a cross-sectional side view of radio-frequency identification (RFID) transceiver  1  in accordance with one embodiment of the present invention. RFID transceiver  1  includes integrated circuit  10 . Integrated circuit  10  includes an RFID transceiver circuit and at least one contact area  12 , and may include accompanying control or processing circuitry. Insulating layer  20  is superimposed over the top surface of integrated circuit  10 , and antenna layer  30  is superimposed over the top surface of insulating layer  20 . 
     Insulating layer  20  provides electrical insulation between integrated circuit  10  and antenna layer  30 . Electrical conductor  34  electrically connects contact area  12  of integrated circuit  10  to antenna layer  30 , through insulating layer  20 . 
     Contact area  12  may be, for example, a metal input/output pad, a semiconductor area, or any other desired part of integrated circuit  10 . Contact area  12  provides either direct electrical connection to the RFID transceiver circuit or indirect electrical connection to the RFID transceiver circuit through an intervening connection to accompanying processing or control circuitry. The term “electrically connects” and variations thereof are used broadly herein to mean providing an electrically conductive path between the “electrically connected” structures, which may be due to a direct or indirect physical connection. 
     FIG. 1 b  is an exploded top view of RFID transceiver  1 , wherein integrated circuit  10 , insulating layer  20 , and antenna layer  30  are separated for illustration. Insulating layer  20  contains at least one contact via  24  through which electrical conductor  34  extends so as to electrically connect integrated circuit  10  to antenna layer  30 . Antenna layer  30  follows a pattern that conforms to a desired antenna design. FIG. 1 b  is an exemplary embodiment in which antenna layer  30  has a spiral pattern. 
     Antenna layer  30  acts as a radio-frequency antenna and receives an electrical stimulus signal that has been radio-transmitted to RFID transceiver  1  from external polling equipment. Typically, in an RFID application, an electrical stimulus signal is a radio-frequency tone (electronic sinewave-shaped signals having specific frequencies) or a simple modulation thereof. Antenna layer  30  passes the electrical stimulus signal to integrated circuit  10 . Integrated circuit  10  generates a desired electrical response signal, and passes the electrical response signal back to antenna layer  30 . Antenna layer  30  then radio-transmits the generated electrical response signal. Typically, in an RFID application an electrical response signal is a radio-frequency tone or a simple modulations thereof. A specific response signal indicates a particular RFID transceiver and thereby implicitly identifies the individual item, such as a piece of clothing or an individual animal, into which the particular RFID transceiver is installed. More complex stimulus and response signals may be used for more demanding applications, such as identification of individuals or equipment for military uses. 
     FIG. 2 is an exploded top view of an alternative embodiment of an RFID transceiver  2  within the present invention. Integrated circuit  10 , insulating layer  20 , and antenna layer  30  of RFID transceiver  2  are similar to those of RFID transceiver  1  of FIGS. 1 a ,  1   b , except that RFID transceiver  2  of FIG. 2 has two contact vias  24  extending through insulating layer  20 . An electrical conductor  34  extends through each of the contact vias  24  and respectively provides electrical connection between integrated circuit  10  and antenna layer  30 . In this embodiment, the pattern of antenna layer  30  is serpentine, and the respective ends of antenna layer  30  are electrically connected to a different contact area  12  of integrated circuit  10 . 
     Thus, antenna layer  30  and integrated circuit  10  can be electrically connected at a single point, as in RFID transceiver  1  of FIGS. 1 a ,  1   b , or at multiple points, as in RFID transceiver  2  of FIG.  2 . Exemplary of possible embodiments of the present invention, the design of antenna layer  30  may, among other possibilities, form either: (1) a single, physically continuous antenna, (2) multiple, separate antenna elements that work in concert, (3) multiple separate antennas that work independently, or (4) a part of a larger, multiple-layer antenna. The electrical operation of antenna layer  30  will depend on the layer design, the location of electrical connection with integrated circuit  10  and the operation of integrated circuit  10 . 
     FIG. 3 a  depicts a cross-sectional side view of another alternative embodiment of an RFID transceiver  3  within the present invention. RFID transceiver  3  includes an integrated circuit  10 , first insulating layer  20 , and first antenna layer  30  similar to those of RFID transceiver  1  of FIG. 1 a . However, RFID transceiver  3  also includes a second insulating layer  22  over first antenna layer  30 , and a second antenna layer  32  over second insulating layer  22 . Antenna layers  30  and  32  are electrically connected, thereby forming a two-layer antenna that is approximately twice as long as the single-layer antennas of RFID transceivers  1  and  2  of FIGS. 1 a ,  1   b  and  2 . 
     FIG. 3 b  provides an exploded top view of RFID transceiver  3  of FIG. 3 a  with the layers separated for illustration. As in RFID transceiver  1  of FIG. 1 a ,  1   b , a first contact via  24  extends through first insulating layer  20 . A first electrical conductor  34  extends through contact via  24  and provides electrical connection between integrated circuit  10  and first antenna layer  30 . However, in FIGS. 3 a ,  3   b , a second contact via  26  extends through second insulating layer  22 . Second electrical conductor  36  extends through second contact via  26  and provides electrical connection between second antenna layer  32  and first antenna layer  30 . Second electrical conductor  36  increases the length of the antenna of RFID transceiver  3  by adding the length of second antenna layer  32  to that of first antenna layer  30 . Thus, the present invention allows the use of multiple antenna layers, such as are found in FIGS. 3 a ,  3   b , to produce a final antenna of a desired length and design that will have a desired electrical resonance or operation at a desired radio-frequency. 
     FIG. 4 a  depicts a cross-sectional side view of a further alternative embodiment of an RFID transceiver  4  in accordance with the present invention. RFID transceiver  4  of FIG. 4 a  includes an integrated circuit  10 , first and second insulating layers  20  and  22 , and first and second antenna layers  30  and  32 , similar to those seen in FIGS. 3 a ,  3   b.    
     FIG. 4 b  is an exploded top view of RFID transceiver  4 . As in RFID transceiver  3  of FIGS. 3 a ,  3   b , a first contact via  24  and a first electrical conductor  34  extend through first insulating layer  20  and provide electrical connection between first antenna layer  30  and first contact area  12  of integrated circuit  10 . 
     However in FIGS. 4 a ,  4   b , a second contact via  26  and a second electrical conductor  36  extend through second insulating layer  22 , first antenna layer  30 , and first insulating layer  20 . Second electrical conductor  36  provides electrical connection between second antenna layer  32  and a second contact area  12  of integrated circuit  10 , without a direct electrical connection to first antenna layer  30 . This allows antenna layers  30  and  32  to be used, for example, as separate antenna structures, as seen in FIG. 4 b . Exemplary uses for the separate antennas of RFID transceiver  4  are to respond to two different stimulus signals or to transmit two different electrical response signals. As an alternative example (not shown), antenna layer  30  may be designed as a shielding layer held at a reference voltage (e.g., ground voltage) that electrically isolates second antenna layer  32  from the circuitry below. 
     FIG. 5 is a flow chart of an exemplary method  50  of making an RFID transceiver in accordance with the present invention. For the sake of example, assume that method  50  is used to make RFID transceiver  1  of FIGS. 1 a ,  1   b . The order of the steps may vary. 
     In step  51 , an integrated circuit  10  is provided that includes an RFID transceiver circuit. The active, top surface of integrated circuit  10  includes an exposed, contact area  12  with a top surface that serves as an input/output connector for creating electrical contact with integrated circuit  10 . 
     In step  52 , a first insulating layer  20  is applied onto the top surface of integrated circuit  10 . First insulating layer  20  may be formed of any insulating material that is compatible with a semiconductor chip, such as spin-on glass, polyimide, SiO 2 , or silicon nitride. This material may be spun-on, deposited, or grown using any convenient method, such as those commonly used in semiconductor chip manufacture or packaging. Typically, insulating layer  20  will be applied over the entire top surface of integrated circuit  10 , including over contact area  12 . Alternatively, insulating layer  20  may be applied around and not covering contact area  12 , obviating the need for step  53  which is discussed below. 
     In step  53 , assuming that contact area  12  is covered by insulating layer  20 , a first contact via  24  is formed through first insulating layer  20  so as to expose contact area  12  of integrated circuit  10 . First contact via  24  can be formed using any convenient method, such as photo-lithography including etching, e-beam lithography including etching, or contact molding. 
     In step  55 , first contact via  24  is filled with an electrically conductive material so as to form electrical conductor  34 . Conductor  34  makes electrical connection to the exposed surface of contact area  12 . The material used to fill first contact via  24  can be any electrically conductive material, such as metal, doped semiconductor, doped polymer, metal-filled epoxy, or electrically conductive ink. The material of electrical conductor  34  may be applied by a variety of convenient methods, such as chemical vapor deposition, sputtering, plating, screening, and spin-on, among other possibilities. 
     In step  57 , an electrically conductive layer is formed onto the top surface of first insulating layer  20 . The electrically conductive layer may be made of any electrically conductive material, such as metal, doped semiconductor, doped polymer, metal-filled epoxy, or electrically conductive ink. The material of the electrically conductive layer may be applied by a variety of convenient methods, such as chemical vapor deposition, sputtering, plating, screening, and spin-on, among other possibilities. In addition to being applied onto the top surface of first insulating layer  20 , the electrically conductive layer is also applied onto the exposed top surface of electrical conductor  34 , thereby forming an electrical connection between contact area  12  and the electrically conductive layer through electrical conductor  34 . Steps  55  and  57  may be done simultaneously by having the material of the conductive layer also fill first contact via  24 . 
     In step  59 , the electrically conductive layer is patterned to form a first antenna layer  30 . Patterning may be done using any convenient method, such as photo-lithography including etching, e-beam lithography including etching, or contact molding. 
     Alternatively, after step  55 , a patterned antenna layer  30  may be applied directly onto the first insulating layer  20  through contact printing, screening, or any other method for transferring a pattern of material onto a surface. As another alternative, a pre-patterned conductive antenna layer  30 , for example, a patterned metal foil, may be attached onto the top surface of insulating layer  20  and over electrical conductor  34 . 
     Artisans will appreciate that method  50  may be modified to form the other exemplary embodiments discussed herein. 
     FIG. 6 is a flow chart of an exemplary method  60  of making an alternative RFID transceiver in accordance with the present invention. For the sake of example, assume that method  60  is used to make RFID transceiver  3  of FIGS. 3 a ,  3   b . Steps  51  through  59  are followed as in method  50 . Then steps  52  through  59  of method  50  are repeated, as steps  62  through  69 , to form a second insulating layer  22  and a second antenna layer  32  onto the top surface of first antenna layer  30 . Also, a second contact via  26  and a second electrical conductor  36  are formed through second insulating layer  22  so as to electrically connect second antenna layer  32  to first antenna layer  30 . As an option, the location of second electrical conductor  36  can be chosen so that it is not directly over first electrical conductor  34 . Staggering the locations of electrical conductors  34  and  36  can improve the planarity of the RFID transceiver. 
     As an alternative example, method  60  may be used to make RFID transceiver  4  of FIGS. 4 a ,  4   b . However, second contact via  26  and second electrical conductor  36  are formed in steps  63  and  65  respectively to extend through second insulating layer  22 , first antenna layer  30 , and first insulating layer  20 . Second electrical conductor  36  electrically connects second antenna layer  32  and a second contact area  12  of integrated circuit  10 , without directly electrically connecting to first antenna layer  30 . This allows antenna layers  30  and  32  to be used, for example, as separate antenna structures, as seen in FIG. 4 b.    
     The embodiments of the RFID transceiver and assembly methods described above are merely examples of the present invention. Those skilled in the art will appreciate that variations are possible within the scope of the claims set forth below.