Offset-gate chemical-sensitive field-effect transistors (OG-CHEMFETS) with electrolytically-programmable selectivity

• US 4,437,969 A
• Filed: 04/08/1982
• Issued: 03/20/1984
• Est. Priority Date: 04/09/1981
• Status: Expired due to Fees

• Current Assignee: CIBA Vision Corporation (Novartis Ag)
• Original Assignee: Corning Glass Works (Corning Incorporated)
• Inventors: Sibbald, Alastair, Covington, Arthur K.
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US06/366,721
• Time in Patent Office: 712 Days
• Field of Search: 357/25, 204/195 R, 204/195 M, 204/195 B, 204/416, 204/420, 204/403, 204/415, 128/635, 324/71 SN, 324/71.5, 324/71.6, 435/817
• US Class Current: 257/253
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
• CPC Class Codes: H01L 2224/4847 the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
• CPC Class Codes: H01L 23/5256 comprising fuses, i.e. connections having their state changed from conductive to non-conductive
• CPC Class Codes: H01L 29/4238 characterised by the surface lay-out
• 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 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: Y10S 435/817 Enzyme or microbe electrode

Abstract

A selective chemosensitive microelectronic transducer is provided for the detection and measurement of chemical properties, by engineering a field-effect transistor such that source 6 and drain 7 regions are connected to bonding pads 2 and 4, and the semiconductor bulk connected to pad 1. The metal gate 8 is extended laterally to a remote area 9, and also to bonding pad 3 via a narrow metallization track 5 designed to support only a limited, predetermined electrical current in the manner of a fusible link. External electrical access to the device is achieved with wirebonding 14, and the device is selectively sealed with an inert, impervious encapsulation material 10 such that only gate area 9 remains exposed. Electroactive materials are deposited over the offset-gate area 9, or electrodeposited using connection through 8, 5 and 3. Subsequently, link 5 is open-circuited by pulsed electrical overload, creating a floating chemosensitive gate.

Claims

1. A field-effect device comprising a semiconductor substrate, a source region located in a first surface of said substrate, a drain region located in said first surface and spaced apart from said source region, a layer of electrical insulator material overlying at least a portion of said source and drain regions and the surface of the substrate lying between said regions, a gate conductor disposed over said insulator material between said source and drain regions, a planar, offset gate comprising a conductive layer disposed on said first surface in a region remote from said source and drain regions, conductive means for electrically connecting said conductive layer to said gate conductor, an electrical conductor connected to said conductive layer, and a fusible link connected in series with said electrical conductor.

2. A field-effect device according to claim 1 wherein said conductive means comprises a layer of conductive material disposed on the surface of said substrate.

3. A field-effect device according to claim 2 wherein said conductive means and said conductive layer are extensions of said gate conductor.

4. A field-effect device according to claim 1 further comprising a layer of electroactive material suitable for the detection and measurement of chemical properties disposed over at least a portion of the surface of said conductive layer.

5. A field-effect device according to claim 1 wherein said conductive means and said conductive layer are extensions of said gate conductor, said device further comprising a layer of electroactive material suitable for the detection and measurement of chemical properties disposed over at least a portion of the surface of said conductive layer.

6. A field-effect device according to claim 5 further comprising a coating of inert encapsulating material extending over that portion of said substrate including said source and drain regions to an area of said substrate between said source and drain regions and said conductive layer, whereby said electroactive material is exposed.

7. A field-effect device comprising a semiconductor substrate, a source region located in a first surface of said substrate, a drain region located in said first surface and spaced apart from said source region, an electrical insulator material overlying at least a portion of said source and drain regions and the surface of the substrate lying between said regions, a gate conductor disposed over said insulator material between said source and drain regions, said gate conductor extending laterally along said first surface to a region remote from said source and drain regions, the width of that portion of said gate conductor in said remote region being greater than the width of said gate conductor in the region of said source and drain regions, at least a portion of said lateral extension of said gate conductor being covered by at least one electroactive material suitable for the detection and measurement of chemical properties to which the device is exposed, an electrical conductor connected to said conductive layer, and a fusible link connected in series with said electrical conductor.

8. A field-effect device according to claim 7 further comprising a coating of inert encapsulating material extending over that portion of said substrate including said source and drain regions to an area of said substrate between said electroactive material and said source and drain regions whereby said electroactive material is exposed.