Patent Application
20080009687
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 (<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
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.
A coiling layer 104, such as, but not limited to, a stressed or compressive silicon nitride (Si3N4), 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.
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.
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.
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.
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.
As shown in
As shown in
As shown in
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.]
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.
In one embodiment, to create coiled circuits and devices, the MOS circuit device region should be encapsulated by material that is not sensitive to XeF2 etching, for example. The underlying substrate structure, on which the CMOS circuit device is configured, may ensure rapid lateral undercutting during the XeF2 etch. Metal to be used in the circuitry should be flexible, low resistance and resistant to XeF2 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.
The invention is not limited to the exclusive use of XeF2 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.
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.
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.
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.
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.
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.
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).
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 60476200 | Jun 2003 | US | |
| 60532175 | Dec 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11653964 | Jan 2007 | US |
| Child | 11802806 | May 2007 | US |
| Parent | 10861885 | Jun 2004 | US |
| Child | 11653964 | Jan 2007 | US |
