Abstract:
A coiled bio-medical device has a base layer coiled to form a plurality of concentric cylinders. The base layer comprises an inner surface. The coiled bio-medical includes a bio-sensor arranged on the inner surface of the base layer. The bio-sensor is adapted to collect bio-medical data from an organism. A transmitter is arranged on the inner surface of the base layer and is adapted to transmit the collected bio-medical data.

Description:
REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part (CIP), under 35 U.S.C. § 120, of U.S. application Ser. No. 11/653,964 entitled “Coiled Circuit Device with Active Circuitry and Methods for Making the Same,” filed Jan. 17, 2007, which is a CIP of U.S. application Ser. No. 10/861,885, entitled “Coiled Circuit Device and Method of Making the Same,” filed Jun. 7, 2004, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional application No. 60/476,200, filed on Jun. 6, 2003, and to U.S. Provisional application No. 60/532,175, filed on Dec. 24, 2003, all of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention is generally directed to integrated circuits. More particularly, the present invention is directed to a coiled bio-medical device and methods for making the same.  
       BACKGROUND OF THE INVENTION  
       [0003]     The information age has significantly increased the need for miniature electronic devices. Tremendous demand exists for portable electronic devices, such as digital cameras, digital camcorders, laptops and other similar products. Devices that are small and fully functional with processing, power, information gathering and storing capabilities built in are desirable.  
         [0004]     Using current semiconductor process technology, an incredible amount of functionality can be integrated onto a single, large silicon die. This single die can now contain an entire system on a chip, such as an entire computer or, a cell phone. However, one of constraints affecting further miniaturization is the thickness of the silicon substitute that the integrated circuit is manufactured on.  
         [0005]     Applications for miniature devices are countless including commercial applications, such as cameras, communication devices, computers, and miniature bio-sensing devices that are implantable within, for example, a human body. There exist a variety of sensors for detecting almost any physical property related to an organism, including optical, chemical, and electrochemical properties.  
         [0006]     Conventional semiconductor processing technologies limit the miniaturization of a bio-sensing device. In addition it is desirable to have a fully functional bio-sensor that is as small as possible.  
       SUMMARY OF THE INVENTION  
       [0007]     A coiled biomedical device has a base layer coiled to form a plurality of concentric cylinders. The base layer comprises an inner surface. The coiled bio-medical includes a bio-sensor arranged on the inner surface of the base layer. The bio-sensor is adapted to collect bio-medical data from an organism. A transmitter is arranged on the inner surface of the base layer and is adapted to transmit the collected bio-medical data. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is shows a side view of a device which may be coiled according to an embodiment of the invention.  
         [0009]      FIG. 2  is a perspective view of a coiled active circuit device in accordance with an embodiment.  
         [0010]      FIGS. 3-5  illustrate a method for fabricating a base for a coiled active circuit device in accordance with an embodiment.  
         [0011]      FIGS. 6-7  illustrate a method for fabricating a base for a coiled active circuit device in accordance with an embodiment.  
         [0012]      FIG. 8  illustrates a base for a coiled active circuit device.  
         [0013]      FIG. 9  illustrates a base for a coiled active circuit device.  
         [0014]      FIGS. 10A and 10B  illustrate a method for integrated circuit formation for a coiled active circuit device in accordance with an embodiment.  
         [0015]      FIGS. 11A and 11B  illustrate a method for integrated circuit formation for a coiled active circuit device in accordance with an embodiment.  
         [0016]      FIGS. 12-19  illustrate methods for forming a coiled active circuit device in accordance with an embodiment.  
         [0017]      FIGS. 20A and 20B  illustrate dielectric buttons that may be used in a coiled active circuit device.  
         [0018]      FIG. 21  is a diagrammatic representation of a circuit device before and after coiling, in accordance with an embodiment.  
         [0019]      FIG. 22  shows electronic images of various nanocoils, in accordance with an embodiment.  
         [0020]      FIG. 23  is a block diagram of a coiled active circuit device, in accordance with an embodiment.  
         [0021]      FIG. 24  shows a coiled active circuit device in accordance with an embodiment.  
         [0022]      FIG. 25  is a flowchart illustrating a method for fabricating a coiled circuit device in accordance with an embodiment.  
         [0023]      FIG. 26  illustrates an implanted coiled bio-medical device, in accordance with an embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0024]     As disclosed herein, nanocoil Micro-Electro-Mechanical System (MEMS) based technologies can be employed to produce a nanocoil bio-medical device compacted into an extremely small cylinder. The nanocoil bio-medical device may be implanted (e.g., subcutaneously) in an organism. In an embodiment, the nanocoil bio-medical device may be used to measure a physical property or perform a treatment function. For example, the nanocoil biomedical devices may monitor temperature, blood pressure, blood flow, intra-ocular pressure, and glucose levels, for example. In addition, the nanocoil biomedical device can be used in treatment functions, such as laser ablation, micro-drug delivery, or razor edged semiconductor thin films for surgery.  
         [0025]     In accordance with an embodiment, the coiled bio-medical device provides a medical system-on-a-chip with full functionality (e.g., medical diagnostic, telemetry, and treatment functions) without the inherent miniaturization limitations of conventional microelectronic technologies. In one embodiment, the entire functionality of a miniature wireless medical platform may be compacted into an extremely small nanocoil bio-medical device (e.g., with a cylinder shape) with a sub-100 μm diameter, with an approximately 100 times to 1000 times reduction in system volume for a given medical function compared to conventional semiconductor processing technologies. The nanocoil bio-medical device, described herein, may provide the smallest surface and volume per medical function of existing electronics implanted into an organism.  
         [0026]     In standard planar semiconductor processing techniques, information density is achieved by scaling down the transistor gate lengths and therefore the device foot print. Thus allowing the devices to be packed in to active area/volume (surface-to-volume ratio) device densities of at most 100 cm −1 . However, the active area of the device is typically only a few thousand angstroms in depth, and therefore, the substrate thickness of approximately 100 μm needed for mechanical support, is largely wasted volume. In other words, only a thin layer on the surface of each silicon die is electrically active.  
         [0027]     An embodiment of the present invention is a silicon die layered with active circuitry formed into a coiled (or nanocoil) bio-medical device. The coiled bio-medical device may provide a self contained bio-medical system or device that, while extremely small, may offer many features, such as data collecting or data sensing, storing, processing, and data transmission or reception, or both. The coiled bio-medical device may include various other components and features. The coiled device may include, for example, memory, processor(s), communication devices, power generation and storage, camera(s), battery systems, bio-sensors or other sensors, transmitters, logic gates, analog or digital circuits, antennas, microphones, speakers, or other devices and components.  
         [0028]     In an embodiment, an underlying base or die including a device layer is formed. Active circuitry (e.g., including a bio-sensor) is fabricated on the base device layer. The active portion of the base including the active circuitry is “skimmed off” or released, and the device is coiled or curled into an extremely compact small tightly wound coil. The coiled biomedical device may be of any size. In one embodiment, the coiled bio-medical device diameter is approximately equal to the diameter of a human hair. The biomedical device layer of the base used for fabricating the active circuitry may be, for example, a single crystal silicon or poly-silicon, or a combination of both, which maintains the electrical properties of the underlying base or die. In other words, the single crystal silicon skimmed off has the same electrical properties as the larger silicon base, and can be used to deposit active circuitry. The single crystal silicon layer with active circuitry may be released from the underlying substrate material and curled into a compact coil. Also, polycrystalline silicon thin films, released from the underlying substrate, may be used for the active portion of the die used for fabricating the active circuitry.  
         [0029]     The coiled biomedical device configuration described herein may achieve on the order of 1,000 to 10,000 times increase in the surface/volume ratio as compared with conventional top planar technology. The resulting coiled circuit may provide a bio-medical device or system-on-a-chip, an application specific bio-sensor, or other device which can be so small that it is virtually imperceptible.  
         [0030]     The technology and methods as described in U.S. patent application Ser. Nos. 10/861,885 and 11/653,964, incorporated herein by reference in its entirety, provide additional techniques and details that may be applicable to the coiled circuit configuration as described herein.  
         [0031]      FIG. 1  shows a side view of a device which may be coiled according to an embodiment. The device  100  includes a circuit layer  102 , a coiling layer  104 , and outer electrical insulation and metal interconnect layers  106 . The circuit layer  102  may include active circuitry for the bio-medical device. The active circuitry may include, for example, one or more sensors (e.g., a bio-sensor), storage memory, processor(s), communication devices, power systems, logic gates and circuits, analog or digital circuitry, antennas, speakers or the like.  
         [0032]     The circuit layer  102  may include thin silicon on insulator metal oxide semiconductor (SOI MOS) technology or other technologies. In an embodiment, a very thin layer (&lt;100 nm), on the surface of the underlying base, may be used for the microelectronic fabrication. For example, extremely thin silicon metal oxide semiconductor (MOS) technology, such as complementary metal oxide semiconductor (CMOS) technology, which uses less than 10 nm of silicon may be used. As shown in  FIG. 1 , the total device thickness using extremely thin MOS memory cell technology is only approximately 50 nm (500 Å). Removal of this thin layer from the substrate and coiling it into a cylinder, containing only the active portions of the circuit, may provide an approximate 1000 times improvement (reduction) in the volume of the circuitry. The improvement in surface area/volume can be leveraged to incorporate a correspondingly higher amount of energy storage (described below), while producing a device that may be similar in size, shape, and diameter to a human hair.  
         [0033]     The circuit layer  102  may also include other material, such as silicon, silicon geranium, polysilicon, thermal and deposited oxides, and selective doping material to form integrated circuitry.  
         [0034]     A coiling layer  104 , such as, but not limited to, a stressed or compressive silicon nitride (Si 3 N 4 ), may be included in the device to facilitate coiling of the device  100 . The atoms of the coiling layer are in constant tension, causing the coiling layer  104 , the circuit layer  102  and the interconnect layers, for example, to coil around the coiling layer, when released from the underlying substrate. The interconnect layers  106  may be a conductor, containing materials such as copper, gold or aluminum, or any combination thereof. Further, nitride is known to capture charge and therefore, an alternative insulator may be used in reducing the effects a nitride layer may have on the circuit layer. For example, thermally activated bimetallic layers can be deposited on the surface of active device circuitry to induce coiling. When heated, the bi-metallic layers will contract and force the planar circuit into a cylindrical shape.  
         [0035]     Thin MOS memory circuit technology is described in co-owned U.S. Pat. No. 5,969,385 entitled, “Ultra-low Power-Delay Product NNN/PPP Logic Devices,” the complete contents of which are incorporated herein by reference. Some non-limiting features of thin MOS technology can include: 100+Å Si, SOI for minimum sub-threshold current and maximum transconductance; an accumulation mode for predictable, low thresholds and minimum gate tunneling; 10-15 Å gate oxide for maximum transconductance; and SiGe amorphization ohmics for minimum source-drain resistance.  
         [0036]      FIG. 1  only shows a portion of device  100 , however, as described below, circuitry can be fabricated onto wafers in sheets or strips (see, e.g.,  FIG. 2 ), and then coiled using different curling processes. Therefore, reference may also be made to device  100  as a “sheet” throughout this document. Thin MOS technology allows a workable geometry for the present invention and the creation of suitable sheets of active circuitry; however, other technologies, such as Gallium Arsenic (GaAs), Gallium Nitride (GaN), Silicon Germanium (SiGe), or Silicon bipolar devices, may be used to create the active circuitry the substrate, which may be coiled as described herein.  
         [0037]     In one example, each of the layers of the sheet  100  may be fabricated such that the total thickness of the sheet  100  is approximately between 1000 and 1500 Å. Of course, the coiled memory device can be made larger or smaller in size in order to achieve the desired volume, speed, capacity, capabilities, etc.  
         [0038]      FIG. 2  shows a perspective view of a coiled active circuit device  100  according to an embodiment. Device  100 , including the coiling layer  104  and the circuit layer  102 , is fabricated onto a wafer or substrate  200 , and on top of a sacrificial layer  202 . As shown, the sacrificial layer  202  is gradually removed, during which the coiling layer  104  forces the device  100  to coil. Coiling layer  104  may be in compression while the circuit layer  102  may be in tension. Circuit layer  102  contracts at a different rate than the coiling layer  104 , from the original coiling layer forcing the device  100  to coil as the sacrificial layer is removed. The sacrificial layer  202  can be gradually removed until device  100  is completely coiled into a substantially cylindrical shape. Optionally, the equivalent of a miniature spindle can be bonded to the thinned active silicon layer and then rotated to wind up the active silicon layer into an equivalent tight and extremely small coil. As will be discussed in further detail below, the device  100  may be fabricated to adjust the radius of the coil.  
         [0039]     As described above, the coiled active circuit device (e.g., a bio-medical device) process uses the electronic circuit layer that lies within a thin layer on top of a much thicker substrate, for example. The 1000× times increase in the surface/volume ratio may be achieved as a result of the coiling of the top active layer. In addition, a corresponding reduction in the parasitic capacitive coupling between the coiled circuit area and the substrate may result.  
         [0040]      FIGS. 3-5  illustrate a method for fabricating a base for a coiled biomedical device in accordance with an embodiment.  FIG. 3  shows a silicon on insulator (SOI) wafer  305 , which includes silicon layer  300 , silicon dioxide layer  310  and substrate layer  350 . The silicon layer  300  may be a single crystal silicon layer or polycrystalline silicon thin film. In this example, silicon layer  300  may be approximately 1000 angstroms (Å) thick and maintains its electrical properties. Silicon dioxide  310  deposited between silicon  300  and substrate  350  may be approximately 500 Å thick, while the substrate  350  may be approximately 700 μm thick. The measurements provided herein are given by way of example only, and these measurements may be varied as desirable.  
         [0041]      FIG. 4  illustrates a second SOI wafer  405  deposited on the SOI wafer  305 . The second SOI wafer  405  includes substrate layer  450 , silicon dioxide layer  410  and silicon device layer  400 . The SOI wafer  405  may also include a second silicon dioxide layer  420 . As shown, SOI  405  is bonded with SOI  305 . The substrate  450  is removed by lapping or etching at the buried silicon oxide  410  (at the dotted lines shown in  FIG. 4 ). After the buried silicon oxide  410  is removed, a double silicon on insulator (DSOI) wafer  505  is formed, as shown in  FIG. 5 .  
         [0042]     In accordance with an embodiment, the SOI  305  or DSOI wafer  505 , or both, may be used as the underlying base, for the coiled circuit device, on which active circuitry may be fabricated. The active circuitry may be fabricated on the device layer  300  or  400  in accordance with an embodiment of the invention.  
         [0043]      FIGS. 6-7  illustrate an alternative method for fabricating a base for a coiled active circuit device in accordance with an embodiment. As shown, SOI wafer  605  includes silicon device layer  600 , silicon dioxide layer  610 , and substrate layer  650 . SOI wafer  605  is bonded with wafer  615  which includes substrate layer  660 , silicon dioxide layer  670 , poly-silicon layer  680  and silicon dioxide layer  690 . After wafer  615  is bonded with SOI wafer  605 , substrate  650  is removed by lapping or etching at the buried silicon oxide  610 . After the buried silicon oxide  610  is removed, a wafer  705  with a poly-silicon layer  680  and a silicon layer  600  is formed, as shown in  FIG. 7 . In accordance with an embodiment, the silicon on poly-silicon wafer  705  may be used as the base, for the coiled circuit device, on which active circuitry may be fabricated. The active circuitry may be fabricated on the device layer  600  in accordance with an embodiment of the invention.  
         [0044]      FIG. 8  illustrates a base  805  for a coiled active circuit device. Base  805  is a double SOI wafer which includes an underlying substrate  850 , a first buried silicon oxide layer  810 , a sacrificial silicon or poly-silicon layer  820 , a second buried oxide layer  830  and a silicon device layer  800 . The wafer  805  may be fabricated in accordance with the methods described herein. In accordance with an embodiment, wafer  805  may be used as the base, for the coiled circuit device, on which active circuitry may be fabricated on device layer  800 .  
         [0045]      FIG. 9  illustrates an alternative base for a coiled active circuit device. Base  900  is a single SOI wafer in accordance with an embodiment. Wafer  900  includes an underlying substrate  950 , a first buried silicon oxide layer  910  and a silicon device layer  920 . The wafer  900  may be fabricated in accordance with methods described herein. In accordance with an embodiment, single SOI wafer  900  described herein may be used as the base, for the coiled circuit device, on which active circuitry may be fabricated on device layer  920 .  
         [0046]      FIG. 10  illustrates a method for integrated circuit formation (e.g., forming the active circuitry) for a coiled bio-medical device, in accordance with an embodiment. Specifically,  FIGS. 10A and 10B  show an elevated doping isolation technique that may be used for transistor isolation to form the active circuitry for the coiled bio-medical device.  FIG. 10A  shows device  1000  that includes a silicon substrate  1050 , buried oxide  1010  and a silicon device layer  1020 . A photoresist layer  1025  is deposited on the device layer  1020  as shown. The device layer  1020  is positively (P+) doped creating positive (P+) regions  1026  and  1027 , as shown in  FIGS. 10A and 10B . The photo resist layer  1025  is stripped leaving a P+ regions  1026  and  1027  separating the NMOS (negative-channel metal oxide semiconductor) device region  1020 .  
         [0047]      FIG. 11  illustrates an alternative method for integrated circuit formation (e.g., forming the active circuitry) for a coiled biomedical device isolation, in accordance with an embodiment.  FIGS. 11A and 11B  show a trench or LOCOS oxide isolation technique that may be used for transistor isolation to form the active circuitry for the coiled biomedical device.  FIG. 11A  shows device  1180  that includes a silicon substrate  1181 , buried oxide  1182  and a silicon device layer  1185 . A photoresist layer  1186  is deposited on the device layer  1185  as shown. Silicon isolation trench etching is used to remove portions of the device layer  1185 . The etched trenches  1183  are filled with oxide, and planarized using oxide Chemical-Mechanical Polishing (CMP) to isolate (separate) NMOS device region  1185 . The photoresist layer  1186  is stripped leaving a oxide regions  1183  separating the NMOS device region  1185 .  
         [0048]      FIGS. 12-19  illustrate methods for forming a coiled bio-medical device in accordance with an embodiment.  FIG. 12  illustrates further processing of device  1180  using the trench oxide isolation technique. As shown, photoresist layer  1280  is deposited on the silicon device layer  1285 , region  1287  and portions of region  1290 . NMOS channel doping is applied to the silicon device layer  1185  to create NMOS device channel regions to set a first threshold voltage for the device  1180 . The photoresist layer  1280  is subsequently stripped.  
         [0049]     As shown in  FIG. 13 , a photoresist layer  1381  is deposited on the silicon device layer  1185 , oxide region  1183  and portions of region  1290 . PMOS channel doping is applied to the silicon device layer  1285  to create PMOS device channel regions to set a second threshold voltage for the device  1180 . In  FIG. 14 , gate oxide layers  1460  and  1450  are grown on PMOS silicon device layer  1285  and NMOS silicon device layer  1185 , respectively. Gate poly-silicon  1465  and  1455  is deposited and etched on gate oxide layers  1460  and  1450 , respectively, to form PMOS and NMOS transistor gates.  
         [0050]     As shown in  FIG. 15 , NMOS lightly doped drain (NLDD)  1550  and PMOS lightly doped drain (PLDD)  1555  are implanted in PMOS silicon device layer  1285  and NMOS silicon device layer  1185 , respectively. Spacers  1580  and  1585  are formed, and P+ regions  1285  and N+ regions  1185  are implanted and activated. In  FIG. 16 , a stress inducing layer  1650  is deposited over the CMOS transistor structure  1610 . The stress inducing layer  1650  provides dielectric isolation between metal layers (described below) and device regions  1285  and  1185 . Contacts are etched and metal one layers  1760 ,  1762  and  1765  are deposited, as shown in  FIG. 17 . In  FIG. 18 , photoresist  1850  is deposited over the entire CMOS structure  1180 . Openings  1860  and  1865  are etched for XeF 2  (Xenon Difluoride) to under cut the CMOS structure  1180 , after the photoresist  1850  is removed, as shown in  FIG. 19 . As an alternate to photoresist other insulating materials that are not attacked by XeF 2 —such as silicon dioxide—can be employed to encapsulate the active circuitry prior to XeF 2  release and coiling. Alternatively or additionally, the stress coiling layer can be provided by heavy implantation or diffusion of impurity layers at levels from 0.1% to 10% concentration of the Silicon Host Lattice. The layers can be controlled to provide either compressive or tension stress to coil the silicon circuit to the required outside radius. As shown, the XeF 2  etch is used to selectively etch the silicon substrate  1181  without etching the CMOS device circuitry region  1610 . In this example, as the CMOS device circuitry is etched, the thin (e.g., approximately several microns) CMOS device circuitry region  1610  begins to coil in the direction shown by arrow  1900  due to the compression caused by the deposited stress inducing layer  1650 . The device circuitry region  1610 , once completely etched from the silicon substrate  1181  results in a coiled CMOS circuit  1950 , as shown in  FIG. 19 .  
         [0051]     As shown in  FIGS. 20A and 20B , dielectric buttons  2050  may be used to isolate, for example, contacts or other metal conductors metal  1   2045  from metal  2   2080 . The dielectric buttons  2050  may be employed to limit the amount of overall material that needs to be coiled. In other words, as opposed to depositing a layer of dielectric over the entire device, the dielectric material is selectively deposited as dielectric buttons  2050  to keep the thickness of the device circuitry and thus the resulting coiled CMOS circuit device to a minimum, while maintaining isolation between metals. Dielectric buttons  2050  may be used to isolate, for example, metal X-Y address conductors, which may be used to maintain memory writing and reading speeds. By fabricating the thin X-Y address conductors out of metal (e.g., aluminum or gold), the X-Y line resistance can be kept acceptably low.  
         [0052]     In order to achieve small device volume, a tight coil is desirable. Thus, very thin insulator layers may be used to achieve tight curling, which compounds the need for low resistance. Thin oxides and thin metal lines give RC read/write time-constants that are not much different than conventional fast memory, and yet allow the ability to wind the memory device into a tight coil.] 
         [0053]     The above techniques, such as techniques for the CMOS integrated circuit formation, may be employed to create all types of active circuitry that can be included in the coiled CMOS circuit device. Although the above techniques with respect to creating CMOS integrated circuits only show creation of a single transistor region  1610 , it is understood that the techniques described herein can be applied to create any number of transistors, circuits and/or devices. Moreover, all known and future circuit techniques as well as techniques for releasing the circuitry from the base substrate may be employed to create the coiled circuits and devices as described herein.  
         [0054]     In one embodiment, to create coiled circuits and devices, the MOS circuit device region should be encapsulated by material that is not sensitive to XeF 2  etching, for example. The underlying substrate structure, on which the CMOS circuit device is configured, may ensure rapid lateral undercutting during the XeF 2  etch. Metal to be used in the circuitry should be flexible, low resistance and resistant to XeF 2  etching. For example, metals such as Chrome-Gold (Cr—Au) may be utilized along with titanium-Tungsten (Ti—W) or platinum (Pt) barrier material in the contact. The overall MOS device structure should be flexible for reliable cooling and the device layers should be as thin as possible so that a virtually imperceptible circuit device is formed.  
         [0055]     The invention is not limited to the exclusive use of XeF 2  to remove the sacrificial layer supporting the CMOS active circuitry. Other techniques may be used for releasing or coiling. For example, after coating the front-side of the wafer with a protective layer, the wafer backside can be thinned to remove all of the silicon substrate material beneath the buried oxide layer. The individual circuits can then be individually etched out followed by the removal of the front-side protective layer. The stress-inducing layer will then force each of the individual die into a tight cylindrical coil. Alternatively, an external mechanical force can be applied to wind the individual circuits into separate tight cylindrical coils.  
         [0056]      FIG. 21  shows a circuit device  2100  before and after coiling. As shown, the device may include, for example, memory  2100 , central processing unit (CPU)  2120 , input/output (I/O) device interface  2130  and external contacts  2140 . The device  2100  may also include a bio-sensor and/or a treatment module, in accordance with an embodiment. The device  2100  may include additional components such as a power supply  2170 , and/or additional memory or memory controller  2160 , for example. The device  2100  may include additional components as described herein. The circuits and/or components of device  2100  may be created using any method including, but not limited to, the methods as described herein. In this example, the size of the device  2100  may be 1 cm in width, approximately 0.5 cm in length and several microns (μm) in thickness. As the circuitry  2100  is coiled, the resulting coiled CMOS circuit  2140 , as shown in  FIG. 21 , may be formed. In this example, the coiled CMOS device  2140  is approximately 75 μm thick. Of course, the size of the CMOS device may vary depending on various parameters, such as the size and the number of components located on the device, the capabilities of the CMOS device and/or the methods used to create the active circuitry.  
         [0057]      FIG. 22  shows electronic images of nanocoils in accordance with an embodiment of the invention. Image  2210  shows a single coil on which circuit devices may be formed. Image  2220  shows a corrugated  13  coil, 1000 μm long poly-crystalline coil, that may form a plurality of concentric circles, formed in accordance with an embodiment of the invention. Image  2230  shows a side view of a 13 turn coil. Image  2240  shows a coil having an inside diameter of approximately 65.7 μm and an outside diameter of approximately 75.8 μm.  
         [0058]      FIG. 23  is a block diagram of a coiled bio-medical device  2310  in accordance with an embodiment. The device  2310  may include, for example, a central processing unit or signal processing unit  2325 , memory unit  2335  (e.g., storage memory, OS code memory, etc.), internal power supply  2350  (or energy storage), sensor and sensor circuitry  2370  (e.g., a bio-sensor), radio frequency input/output interface  2360  (e.g., transmitter and/or receiver) and antenna  2370 . The coiled bio-medical device  2310  may include a treatment module (omitted) and/or other component. The sensor circuitry may be any appropriate circuitry to interface the sensor with the CPU/signal processor  2325 . In an embodiment, the antenna  2370  may be used to transmit or receive signals, or both. Components of system  2310  may be fabricated on a substrate and coiled into coiled bio-medical device, as described herein.  
         [0059]      FIG. 24  shows a coiled bio-medical device  2400  in accordance with an embodiment of the invention, before coiling. Also shown is the coiled biomedical device after coiling  2450 . The coiled bio-medical device  2400  may include, for example, a battery  2405  (e.g., a thin film battery), one or more integrated antennas  2410  (e.g., a dipole antenna), a capacitive power storage device  2415 , a radio frequency receiver/transmitter  2420 , processing unit  2425 , memory  2430 , coding/decoding signal processing circuitry  2435  and one or more bio-sensor modules  2440 . In an embodiment, the nanocoil circuit device  2400  is fabricated and released from a substrate in accordance with methods and systems as described herein and related applications.  
         [0060]     In the bio-medical device, the one or more bio-sensors  2440  may include, but are not limited to, temperature sensors, strain sensors, pressure sensors, magnetic sensors, acceleration sensors, ionizing radiation sensors, acoustic wave sensors, chemical sensors, and photo-sensors including imagers and integrated spectrophotometers. The coiled bio-sensor architecture, described herein, allows for the employment of any other sensors that can be realized using monolithic microelectronics or MEMS wafer processing.  
         [0061]     Other types of sensors included in the coiled bio-medical device  2400  may be, for example, an optical sensor, radiation sensor, thermal sensor, electromagnetic sensor, mechanical sensor (e.g., pressure sensor), chemical sensor, motion sensor, orientation or location sensor, distance sensor or any other type of sensor. Some of the sensors may employ MEMS technology.  
         [0062]     In accordance with an embodiment, the coiled bio-medical device  2400  may monitor temperature, blood pressure, blood flow, intra-ocular pressure, and glucose levels, for example. This information or data may be collected or sensed by one or more bio-sensors  2440 . The transmitter/receiver  2420  may transmit the collected data to an external device using antenna  2410 . The external device may be, for example, a portable device or the like that collects and or processes the information collected by the bio-sensors. The information collected by the bio-sensors  2440  may be stored in memory  2430  and/or processed by components of the coiled bio-medical device  2400  (e.g., processing unit  2425  and/or coding/decoding signal processing circuitry  2435 ). The processed information may also be transmitted to any external device if appropriate.  
         [0063]     In an embodiment, the receiver/transmitter  2420  receives signals using antenna  2410 . These received signals may include instructions to the bio-medical device, such as instructions to take a measurement or reading, or to perform a treatment function (described below). The received signals may also be signals used to charge the capacitive power storage device  2415  and/or thin film battery  2405 , using techniques commonly employed in RFID circuits such as a Dickson charge pump.  
         [0064]     In addition, the coiled biomedical device  2400  can be used in treatment functions, such as laser ablation, micro-drug delivery, or razor edged semiconductor thin films for surgery. In an embodiment, the coiled medical device  2400  may also include a treatment module (omitted). The treatment module may be part of the sensor module  2440  or may be a separate module. The treatment module may include, for example, a laser, a drug delivery system, and/or a razor edge (e.g., for performing surgery). The treatment module may employ any type of MEMS technology to provide appropriate treatment functions. The treatment module may be remotely controlled by an external device. The instructions for the treatment module may be received by antenna  2410  and transmitter/receiver  2420 , and processed by other components of the coiled bio-medical device, as appropriate.  
         [0065]     The coiled bio-medical device may be implanted in any number of locations in an organism to, for example, measure any physical property or perform a treatment function. For example, the coiled bio-medical device may be implanted subcutaneously or on a surface (e.g., skin surface to measure temperature).  
         [0066]     In accordance with an embodiment, the coiled bio-medical device provides a medical system-on-a-chip with full functionality (e.g., medical diagnostic, telemetry, and treatment functions). In one embodiment, the entire functionality of a miniature wireless medical platform may be compacted into an extremely small coiled bio-medical device (e.g., with a cylinder shape). In an embodiment, as shown in  FIG. 24 , the coiled bio-medical device may have a length (L) that may range from 1 μm to 1 cm. The coiled bio-medical device may have a width (W) prior to coiling that ranges from 50 μm to several centimeters (2 to 5 centimeters), for example. The coiled bio-medical device may have a coiled diameter (D) that ranges from 25 μm to 250 μm. Of course, the coiled bio-medical devices can be made smaller or larger, as desired.  
         [0067]     In an embodiment, the battery  2405  may be a re-chargeable battery that is re-charged by, for example, an RF signal received by transmitter/receiver  2420  via antenna(s)  2410 . The capacitive power storage device  2410  may also be charged using signals received by the receiver  2420 . The power storage device  2515  may receive and rectify pulsed RF energy. The processing unit  2425  and/or coding/decoding address chip  2435  may process data or signals received by transmitter/receiver  2520  via antenna(s)  2410 . The memory may be any type of memory such as SRAM or Integrated non-volatile memory. The size of the memory may range from a few bytes to several megabytes or gigabytes or more.  
         [0068]     With the coiling of microelectronic circuitry, as described herein, many types of bio-sensors may be deployed, with the least complex being designed, for example, to detect certain chemicals in a body, for example. A simple sensor fabricated using the coiled circuit technology, as described herein, may return a single bit of data when externally queried or polled, or on its own initiative, or both.  
         [0069]     As described above, the increased surface area/volume ratio achieved by the coiled bio-medical device provides increased area for the bio-sensor components, device power supply, treatment components, or other components. However, when coiled, bio-medical device provides an extremely small device that can be implanted virtually anywhere on or inside a body.  
         [0070]     As described above, the device power could be supplied from thin film batteries or high energy density thin film capacitors. The power source could be rechargeable, for example, deriving some of its power from ambient RF energy available from the surrounding environment. Operating the sensors at frequencies populated by commercial wireless signals (e.g., in the several hundred MHz range) also offers the opportunity to scavenge RF energy to re-charge the on-board energy source. In an embodiment, RF energy may be purposefully directed at the coiled bio-medical device as a way to recharge the onboard energy storage system. The collected RF input signal may be converted into DC supply voltage to power the coiled bio-medical device.  
         [0071]     Since the human body tends to attenuate high frequency signals (e.g., in the GHz range), lower frequency RF signals in the several hundred MHz range, for example, are desirable for both communication and/or device power purposes. Optionally or additionally, inductive coupling may also be used to communicate with an implanted coiled bio-medical device, where the transmitter/receiver may be the coiled structure of the biomedical device. The coiled structure may create a very small inductor with multiple turns (coils) of metal interconnect making up the metal winding on the nanocoil. An external device may be placed near (e.g., on the outside of the body) the implanted coiled bio-medical device to communicate with the implanted coiled bio-medical device.  
         [0072]     Device power requirements will determine how often the device power supply will require charging or the type of power supply required, or both. For example, if the coiled bio-medical device is employed as a sensor, the duty cycle for when the device is sensing (actively collecting information) and when the sensor is charging and/or transmitting, will determine the power requirements. For example, the sensor might capture (and store) data in a few microseconds. The next hour or so (depending on other parameters, such as the proximity of the receiver) may be spent charging an internal storage capacitor, located on the device, to enable a short burst RF transmission to the receiver, followed by another charge to provide enough energy for another round of data collection.  
         [0073]     Coiled bio-medical device communications may be tied to the power requirements and power availability for the device. For example, the available power will determine how far data can be transmitted as well as how much data, and how often data can be transmitted to a remote receiver. Also, the long, cylindrical shape of the coiled biomedical device may form a natural dipole antenna, that facilitates the transmit and receive functions of the coiled bio-medical device. The small size of the coiled circuit antenna may limit its gain, thereby limiting its transmit and receive distance, which is acceptable for such bio-medical devices.  
         [0074]      FIG. 25  is a flowchart illustrating a method for fabricating a coiled bio-medical device in accordance with an embodiment. As shown in  3310 , a silicon oxide layer is deposited on a silicon substrate. A device layer is deposited over the silicon oxide layer, as shown in  3320 . Active circuitry including a bio-sensor is formed on the device layer, as in  3330 . A stress inducing layer is deposited on the active circuitry including the bio-sensor, as shown in  3340 . The device layer having the active circuitry deposited with the stress inducing layer is released by selectively etching the sacrificial layer from the silicon substrate, as shown in  3350 . The device layer having the active circuitry is coiled as the device layer is released from the silicon substrate forming the coiled bio-medical device. The internal stresses in the stress inducing layer cause the coiling as the device layer is released either at room temperature or as an external heat source is applied. Optionally, an external mechanical force can be applied to wind the thinned active layer into a tight cylindrical coil.  
         [0075]      FIG. 26  illustrates a coiled bio-medical device  2620  implanted into a human body, in accordance with an embodiment. The coiled bio-medical device  2620  may contain blood chemistry silicon-germanium sensor and transmitter package. The coiled bio-medical device may include an antenna cap  2610  that may be used to transmit or receive signals. In an embodiment, the coiled bio-medical device may be approximately 4 to 6 mm in length and may have a diameter ranging from 50 μm to 100 μm, for example.  FIG. 26  also shows a conventional SOA #33 gauge BD Ultra-Fine™ Lancet 2690, used to deliver fluids to the human body. In comparison, a conventional #33 gauge Ultra-Fine Hypodermic needle  2690  is 200 μm in diameter, making it approximately 2.5 times larger in diameter than the coiled bio-medical device  2620  shown in  FIG. 26 .  
         [0076]     Coiling or curling of an active circuit device is shown and described herein as resulting in a coiled device, which may be in a cylindrical form, forming a plurality of essentially concentric circles. However, the invention is not intended to be restricted to cylinder or circular type shapes. One will understand that other geometries can result form the coiling process, such as square or octagonal geometries, for example. Therefore, reference to “coiling” or “coiled” throughout this document is intended to cover other geometries than cylindrical or circular.  
         [0077]     In an embodiment, the circuit device layer may have an approximate thickness of approximately 1000 angstroms. As a result, a complete coiled bio-medical device (as described herein) can be coiled into, e.g., a approximately 0.00005 cubic cm coil. The coiled device of this size may be virtually imperceptible but has the capacity to hold a large amount of circuitry and related hardware to, for example, capture, process, store and/or send and receive information. Various configurations and techniques may be employed to combine a plurality of coiled devices into a single device to create a super-dense integrated circuit device.  
         [0078]     A number of techniques are contemplated for undercutting the sacrificial layer to achieve a tight coil. One embodiment of a process of removing the sacrificial layer and coiling the circuit includes a step of adding a temporary or permanent tapered etch shield to encourage progressive sacrificial etching from one end. As the sacrificial layer is undercut, the etch shield controls the rolling up of the sheet, causing coiling from the narrow end (e.g., right end) to the thicker end (e.g., left end), and prevents the corners of circuit sheet from curling. Etching may be, e.g., wet etching or dry etching. As described herein, multiple devices may be fabricated on a single wafer.  
         [0079]     The etching shield may be adjusted in size and shape to achieve the desired effect. For example, the etching shield may be designed to prevent curling entirely at a certain point, in order to hold the coiled memory device to the wafer.  
         [0080]     For example, the coiling layer could be selected from other materials whose characteristics could effect coiling while the sacrificial layer is removed. Additionally, although the invention has been described in terms of memory devices, the present invention is certainly adaptable to coil many other types or circuits. Furthermore, although silicon (MOS) circuits were described, other types of coiled circuits are contemplated, such as radio frequency (RF) devices, GaAs and GaAs circuitry, silicon microprocessors and other analog and digital circuitry.  
         [0081]     Several embodiments of the present invention are specifically illustrated and/or described herein. However, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.