Integrated CMOS-MEMS technology for wired implantable sensors

• US 20070158769A1
• Filed: 10/12/2006
• Published: 07/12/2007
• Est. Priority Date: 10/14/2005
• Status: Abandoned Application

• Current Assignee: CardioMEMS Incorporated
• Original Assignee: CardioMEMS Incorporated
• Inventors: You, Liang
• Application Number:
  US11/546,852
• Publication Number:
  US 20070158769A1
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 29/41733 for thin film transistors with insulated gate

Abstract

Disclosed are wired implantable integrated CMOS-MEMS sensors and fabrication methods. A first ceramic substrate comprising a biocompatible material such as fused silica is provided. A polysilicon layer is formed on the first substrate. An integrated circuit is fabricated adjacent to the surface of the first substrate. A passivation layer is formed on the integrated circuit. A conductive area is formed on the passivation layer that provides electrical communication with the integrated circuit. A feedthrough is formed through the first substrate that contacts the conductive area and provides for external electrical communication to the integrated circuit. A second ceramic substrate or cap comprising a biocompatible material is fused to the first substrate so as to form a cavity that encases the integrated circuit and form a sensor. The cavity is preferably a pressure cavity which cooperates to form a pressure sensor

Claims

1. Apparatus comprising:

a first substrate comprising a ceramic material;

an integrated circuit formed on the first substrate;

at least one conductive feedthrough formed through the first substrate that is in electrical communication with the integrated circuit; and

a second substrate comprising a ceramic material that is hermetically sealed to the first substrate to define an cavity that encloses the integrated circuit, which cavity and integrated circuit cooperate to provide a sensing apparatus.

2. The apparatus recited in claim 1 further comprising:

a pair of lower capacitor electrodes formed on the first substrate that are respectively coupled to the integrated circuit;

wherein the second substrate is configured to have a deflective region that changes position in response to pressure; and

an upper capacitor electrode formed on the deflective region.

3. The apparatus recited in claim 1 wherein the first and second substrates are comprised of glass, fused silica, sapphire, quartz or silicon.

4. The apparatus recited in claim 3 wherein the integrated circuit is passivated using silicon nitride.

5. Apparatus comprising:

a first fused silica substrate;

an integrated circuit formed on the first fused silica substrate;

a feedthrough formed through the first fused silica substrate that in electrical communication with the integrated circuit; and

a second fused silica substrate sealed to the first fused silica substrate to define a cavity that encloses the integrated circuit, which cavity and integrated circuit cooperate to provide a sensing apparatus.

6. The apparatus recited in claim 5 further comprising:

at least one lower capacitor electrode formed on the first fused silica substrate;

a deflective region that changes position in response to pressure formed in the cavity; and

an upper capacitor electrode formed on the deflective region.

7. A method of fabricating implantable pressure sensing apparatus comprising:

providing a first substrate comprising a ceramic material;

forming a polysilicon layer on the first substrate;

fabricating an integrated circuit adjacent to a surface of the first substrate;

forming a passivation layer on the integrated circuit;

forming a conductive area on the passivation layer that provides electrical communication to the integrated circuit;

forming a feedthrough through the first substrate that contacts the conductive area that provides for external electrical communication to the integrated circuit; and

fusing a second substrate comprising a ceramic material to the first substrate to form a hermetic cavity that encases the integrated circuit.

8. The method recited in claim 7 wherein the first and second substrates comprise fused silica.

9. The method recited in claim 7 further comprising annealing the polysilicon layer to provide stress relief.

10. The method recited in claim 7 wherein the integrated circuit fabricated by:

forming an active area in the polysilicon layer;

forming source and drain electrodes in the active area;

growing gate oxide on the substrate; and

forming a gate on the gate oxide.

11. The method recited in claim 7 wherein the active area in the polysilicon layer and the source and drain electrodes are formed using photolithography and ion implantation.

12. The method recited in claim 7 wherein the gate comprises metal or polysilicon.

13. The method recited in claim 7 where the integrated circuit is passivated using silicon nitride.