Floating gate field effect transistors for chemical and/or biological sensing

• US 7,462,512 B2
• Filed: 01/11/2005
• Issued: 12/09/2008
• Est. Priority Date: 01/12/2004
• Status: Active Grant

• Current Assignee: Polytechnic Institute Of New York University (New York University)
• Original Assignee: Polytechnic University (New York University)
• Inventors: Rahman, Arifur, Levon, Kalle, Zhao, Ben, Sai, Tsunehiro
• Primary Examiner(s): Whitehead, Jr.; Carl
• Assistant Examiner(s): MCCALL SHEPARD, SONYA D
• Application Number:
  US11/033,046
• Publication Number:
  US 20050230271A1
• Time in Patent Office: 1,428 Days
• Field of Search: 438/48, 438/49, 438/56, 438/257, 257/253, 257/414
• US Class Current: 438/123
• CPC Class Codes: G01N 27/4145 specially adapted for biomolecules, e.g. gate electrode with immobilised receptors
• CPC Class Codes: G01N 27/4148 Integrated circuits therefor, e.g. fabricated by CMOS processing CMOS processing per se H01L21/82

Abstract

Specific ionic interactions with a sensing material that is electrically coupled with the floating gate of a floating gate-based ion sensitive field effect transistor (FGISFET) may be used to sense a target material. For example, an FGISFET can use (e.g., previously demonstrated) ionic interaction-based sensing techniques with the floating gate of floating gate field effect transistors. The floating gate can serves as a probe and an interface to convert chemical and/or biological signals to electrical signals, which can be measured by monitoring the change in the device'"'"'s threshold voltage, V_T.

Claims

1. A method for fabricating a floating gate field effect transistor, the method comprising:

a) fabricating a floating gate field effect transistor using a 2-polysilicon and 2-metal layer 1.2 μ

m (or micron) process technology, wherein a floating gate is electrically coupled with a receptor on a second metal layer;

b) encapsulating the second metal layer in glass;

c) removing some of the glass to

i) expose bonding pads on the second metal layer to create bond wire connections for packaging, and

ii) expose at least a portion of the second metal layer; and

d) immobilizing a ligand to the exposed portion of the second metal layer, wherein the act of immobilizing includes spin coating the exposed portion of the second metal layer with ion-sensitive material.

2. The method of claim 1 wherein the ion-sensitive material has a charge that changes in the presence of the target substance.

3. The method of claim 2 wherein the target substance is one of (A) a specific chemical and (B) a specific class of chemicals.

4. The method of claim 2 wherein the target substance is one of (A) a specific biological material and (B) a specific class of biological materials.

5. The method of claim 1 further comprising:

e) electrically coupling the floating gate of the floating gate field effect transistor to a substrate of the floating gate field effect transistor, thereby providing a discharge path for any accumulated charges on the floating gate; and

f) making the electrical coupling non-conducting after fabrication steps involving plasma.

6. The method of claim 1 further comprising:

e) electrically coupling the floating gate of the floating gate field effect transistor to a substrate of the floating gate field effect transistor using a second metal layer interconnect; and

f) making the second metal layer interconnect non-functional after fabrication steps of the 2-polysilicon and 2metal layer 1.2 μ

m (or micron) process technology involving plasma.

7. The method of claim 6 wherein the act of making the second metal layer interconnect non-functional includes cutting the second metal layer interconnect with a focused laser beam.