TRANSISTOR WITH FLOATING GATE AND ELECTRET

• US 20080094074A1
• Filed: 09/27/2007
• Published: 04/24/2008
• Est. Priority Date: 09/27/2006
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Shen, Nick, Kan, Edwin, Lee, Chungho, Kim, Myongseob
• Granted Patent: US 7,960,776 B2
• Time in Patent Office: Days
• US Class Current: 324/658
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
• CPC Class Codes: H01L 29/66825 with a floating gate H01L29/6684 takes precedence
• CPC Class Codes: H01L 29/7885 Hot carrier injection from the channel

Abstract

A sensor includes a field effect transistor having a source, drain, a control gate and floating gate, wherein the floating gate has an extended portion extending away from the control gate. A sensing gate is capacitively coupled to the extended portion of the floating gate. A polymer electret sensing coating is electrically coupled to the sensing gate.

Claims

1. A sensor comprising:

a field effect transistor having a source, drain, a control gate and floating gate, wherein the floating gate has an extended portion extending away from the control gate;

a sensing gate capacitively coupled to the extended portion of the floating gate; and

a polymer electret sensing coating electrically coupled to the sensing gate.

2. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to selected chemical species.

3. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to chemical concentration.

4. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to pressure.

5. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to light.

6. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to proteins.

7. The sensor of claim 1 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to temperature.

8. The sensor of claim 1 wherein the floating gate is charged.

9. The sensor of claim 1 wherein the extended floating gate has an area of at least approximately 28,800 μ

m².

10. The sensor of claim 1 wherein the extended floating gate has an area of approximately 28,800 μ

m² or less.

11. The sensor of claim 1 wherein the polymer electret sensing coating is selected from the group consisting of polytetrafluoroethylene amorphous fluoropolymer, PZT, P3HT, and PVDF.

12. The sensor of claim 1 and further comprising multiple sensors formed in or supported by the substrate, wherein such sensors sense at least one of pressure, temperature, light, chemicals or proteins.

13. A sensor comprising:

a field effect transistor having a source and drain formed in or supported by a substrate with a tunnel oxide separating the source and drain, a control gate formed substantially over the tunnel oxide and partially over the source and drain, and a floating gate formed between the tunnel oxide and control gate, wherein the floating gate has an extended portion extending away from the control gate;

a sensing gate capacitively coupled to the extended portion of the floating gate; and

a polymer electret sensing coating electrically coupled to the sensing gate.

14. The sensor of claim 13 and further comprising an insulator formed on top of the control gate, extended floating gate and sensing gate, and wherein the oxide has been removed over a portion of the sensing gate to allow contact with the polymer electret sensing coating.

15. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to selected chemical species.

16. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to chemical concentration.

17. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to pressure.

18. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to light.

19. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to proteins.

20. The sensor of claim 13 wherein the polymer electret sensing coating changes charge conditions on the floating gate responsive to temperature.

21. The sensor of claim 13 wherein the floating gate is charged.

22. The sensor of claim 13 wherein the extended floating gate has an area of at least approximately 28,800 μ

m².

23. The sensor of claim 13 wherein the polymer electret sensing coating is selected from the group consisting of polytetrafluoroethylene amorphous fluoropolymer, PZT, P3HT, and PVDF.

24. The sensor of claim 13 and further comprising multiple sensors formed in or supported by the substrate, wherein such sensors sense at least one of pressure, temperature, light, chemicals or proteins.

25. A method comprising:

exposing an electret sensing coating to a medium to be sensed, such that the medium causes a change in charge density in the electret sensing coating;

capacitively coupling the electret sensing coating to an extended portion of a floating gate; and

changing a potential on a floating gate of an EEPROM device such that a threshold voltage of the EEPROM device is correlated to the electret charge density.