Substrate sensor

• US 20030078484A1
• Filed: 11/04/2002
• Published: 04/24/2003
• Est. Priority Date: 09/12/1997
• Status: Active Grant

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Shah, Rajiv, Schulman, Joseph H., Byers, Charles L., Gord, John C., Canfield, Lyle Dean
• Granted Patent: US 7,079,881 B2
• Time in Patent Office: Days
• US Class Current: 600/373
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61M 5/1723 using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/372 Arrangements in connection with the implantation of stimulators
• CPC Class Codes: A61N 1/3754 Feedthroughs
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 29/0657 characterised by the shape of the body
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/19041 being a capacitor

Abstract

An implantable substrate sensor has electronic circuitry and electrodes formed on opposite sides of a substrate. A protective coating covers the substrate, effectively hermetically sealing the electronic circuitry under the coating. Exposed areas of the electrodes are selectively left uncovered by the protective coating, thereby allowing such electrodes to be exposed to body tissue and fluids when the sensor is implanted in living tissue. The substrate on which the electronic circuitry and electrodes are formed is the same substrate or “chip” on which an integrated circuit (IC) is formed, which integrated circuit contains the desired electronic circuitry. Such approach eliminates the need for an hermetically sealed lid or cover to cover hybrid electronic circuitry, and allows the sensor to be made much thinner than would otherwise be possible. In one embodiment, two such substrate sensors may be placed back-to-back, with the electrodes facing outward. As required, capacitors that form part of the sensor'"'"'s electronic circuits are formed on the substrate by placing metalization layers and a dielectric in vacant areas of the substrate surface.

Claims

1. An implantable sensor for sensing a specified parameter or substance to which the sensor is exposed, comprising:

an integrated circuit (IC), said IC comprising a semiconductor substrate having an active surface on which electronic circuitry is formed and a non-active surface where electronic circuitry is not formed;

sensor electrodes formed on the non-active surface of the semiconductor substrate;

means for electrically connecting the sensor electrodes with the electronic circuitry formed on the active surface of the IC;

a protective coating that covers all areas of the surface of the semiconductor substrate except for selected portions of the sensor electrodes; and

means for making electrical connection with and providing operating power to the electronic circuitry formed on the semiconductor substrate.

2. The implantable sensor of claim 1 wherein the means for electrically connecting the sensor electrodes with the electronic circuitry formed on the active surface of the IC comprises vias that pass through the body of the semiconductor substrate.

3. The implantable sensor of claim 2 wherein the vias that electrically connect the sensor electrodes with the electronic circuitry through the body of the semiconductor substrate comprise stair-stepped vias.

4. The implantable sensor of claim 1 wherein the protective coating comprises at least one layer of a biocompatible encapsulation material selected from the group comprising alumina, zirconia, or alloys of alumina and/or zirconia.

5. The implantable sensor of claim 1 wherein the means for making electrical connection with and providing operating power to the electronic circuitry comprises:

a plurality of conductive pads formed on the semiconductor substrate which are not covered by the protective coating; and

a plurality of non-straight vias that respectively electrically connect each of the plurality of pads with the electronic circuitry formed on the active surface of the semiconductor substrate.

6. The implantable sensor of claim 5 wherein each end of the substrate includes a pair of said conductive pads.

7. The implantable sensor of claim 1 wherein the electronic circuitry formed on the active surface of the semiconductor substrate includes at least one built-in capacitor, said at least one built-in capacitor comprising a first conductive layer formed on the substrate, a dielectric layer deposited over the first conductive layer, a second conductive layer deposited over the dielectric layer, and conductive means for making electrical connection with the first and second conductive layers.

8. The implantable sensor of claim 7 wherein a plurality of built-in capacitors are formed on the surface of the substrate at locations where electronic circuitry and electrodes and not present.

9. The implantable sensor of claim 1 wherein said electrodes and electronic circuitry include means for operating said sensor as an electrochemical sensor.

10. The implantable sensor of claim 9 wherein said electrodes formed on the non-active surface of the substrate include first and second working electrodes, each of the first and second working electrodes having an exposed surface area which is not covered by the protective coating.

11. The implantable sensor of claim 10 further including:

a first membrane covering said substrate and electrodes,

a saline solution held within said first membrane, said saline solution being in contact with the exposed surface areas of said electrodes,

a second membrane covering the first membrane, said second membrane having a window pocket formed therein above the exposed surface area of the first working electrode, and

a prescribed enzyme placed within the window pocket of the second membrane;

whereby said implantable sensor comprises an enzyme electrode sensor.

12. An implantable sensor assembly comprising:

a first substrate sensor having an electrode surface and a circuit surface;

a second substrate sensor also having an electrode surface and a circuit surface, the circuit surface of the second substrate sensor being placed against the circuit surface of the first substrate sensor, whereby the electrode surfaces of both the first and second substrate sensors face out from the sensor assembly;

each of the first and second substrate sensors comprising;

an integrated circuit (IC), said IC comprising a semiconductor substrate having an active surface on which electronic circuitry is formed and a non-active surface where electronic circuitry is not formed, the active surface of the substrate comprising the circuit surface of the sensor,

sensor electrodes formed on the non-active surface of the semiconductor substrate, the non-active surface comprising the electrode surface of the sensor,

means for electrically connecting the sensor electrodes with the electronic circuitry formed on the active surface of the IC,

a protective coating that covers all areas of the surface of the semiconductor substrate except for selected portions of the sensor electrodes; and

means for making electrical connection with and providing operating power to the electronic circuitry formed on-the semiconductor substrate from a location outside of the implantable sensor.

13. A substrate sensor for immersion or implantation in a saline solution comprising:

a semiconductor substrate having front and back surfaces;

at least one working electrode formed on the front side of the semiconductor substrate;

electronic circuitry formed on the back side of the semiconductor substrate;

a via that passes through the semiconductor substrate and electrically connects the at least one working electrode with the electronic circuitry;

a coating that covers the semiconductor substrate with a biocompatible protective layer except for an exposed area of the at least one working electrode; and

means for coupling operating signals with the electronic circuitry.

14. The substrate sensor of claim 13 wherein electronic circuitry comprises a CMOS integrated circuit, and wherein the semiconductor substrate comprises a portion of a semiconductor wafer on which the CMOS integrated circuit is formed.

15. The substrate sensor of claim 14 wherein said protective coating comprises at least one layer of a biocompatible encapsulation material selected from the group comprising alumina, zirconia, or alloys of alumina and/or zirconia.

16. The substrate sensor of claim 15 wherein the means for coupling operating signals with the electronic circuitry comprises:

a plurality of conductive pads formed on the semiconductor substrate which are not covered by the protective coating; and

a plurality of non-straight vias that respectively electrically connect each of the plurality of pads with the electronic circuitry formed on the back surface of the semiconductor substrate.

17. The substrate sensor of claim 16 wherein the electronic circuitry formed on the back surface of the semiconductor substrate includes at least one built-in capacitor, said at least one built-in capacitor comprising a first conductive layer formed on the substrate, a dielectric layer deposited over the first conductive layer, a second conductive layer deposited over the dielectric layer, and conductive means for making electrical connection with the first and second conductive layers.

18. A method of making an implantable sensor, said implantable sensor including a substrate, electrodes formed on one side of the substrate, and electrical circuitry formed on the other side of the substrate, said method comprising:

forming the electrical circuitry on an active surface of a semiconductor substrate

forming electrodes on a non-active surface of the semiconductor substrate;

electrically interconnecting the electrodes with the electrical circuitry through the use of stair-stepped conductive vias that pass through the body of the semiconductor substrate; and

depositing a protective layer of a biocompatible material over the entire surface area of the substrate except for an exposed area of the electrodes, whereby all but the exposed area of the electrodes is sealed and protected.

19. The method of claim 18 wherein the step of, depositing a protective layer over the entire surface area of the substrate except for an exposed area of the electrodes comprises

plating the electrodes with a biocompatible metal;

masking the area of the electrodes to be exposed with a suitable masking material;

sputtering a layer of a biocompatible encapsulation material over the entire surface area of the substrate and masking material, the biocompatible encapsulation material being selected from the group comprising alumina, zirconia, or alloys of alumina and/or zirconia; and

removing the masking material to expose the plated electrodes.

20. The method of claim 19 wherein the plating step comprises plating the electrodes with a metal selected from the group comprising platinum, iridium or alloys thereof.