Process for fabricating thin film transistors

• US 7,365,394 B2
• Filed: 08/17/2004
• Issued: 04/29/2008
• Est. Priority Date: 04/18/2000
• Status: Expired due to Fees

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Inventors: Chen, Yu, Jacobson, Joseph M, Kazlas, Peter T, Denis, Kevin L, Drzaic, Paul S
• Primary Examiner(s): Smith; Matthew
• Assistant Examiner(s): Nguyen; Khiem D
• Application Number:
  US10/919,657
• Publication Number:
  US 20050067656A1
• Time in Patent Office: 1,351 Days
• Field of Search: 438/149, 438/151, 438/146, 438/155, 438/158, 257/347, 257/E29.117, 257/40, 257/59, 257/E51.005, 257/E51.027, 257/E29.151, 359/296, 359/606, 204/600, 345/107
• US Class Current: 257/347
• CPC Class Codes: H01L 29/66765 Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate
• CPC Class Codes: H01L 29/78603 characterised by the insulating substrate or support H01L29/78657 takes precedence

Abstract

Transistors are formed by depositing at least one layer of semiconductor material on a substrate comprising a polyphenylene polyimide. The substrate permits the use of processing temperatures in excess of 300° C. during the processes used to form the transistors, thus allowing the formation of high quality silicon semiconductor layers. The substrate also has a low coefficient of thermal expansion, which closely matches that of silicon, thus reducing any tendency for a silicon layer to crack or delaminate.

Claims

1. An electrophoretic display comprising, in order:

a metal layer;

a polyimide substrate;

at least one transistor on the polyimide substrate; and

an electrophoretic medium having a plurality of electrophoretic particles dispersed in a suspending fluid and capable of moving therethrough on application of an electric field to the medium.

2. An electrophoretic display according to claim 1 wherein the metal layer comprises stainless steel.

3. An electrophoretic display according to claim 1 wherein the electrophoretic particles and the suspending fluid are encapsulated within a plurality of capsules.

4. An electrophoretic display comprising, in order:

a metal layer;

a polyimide substrate;

at least one transistor on the polyimide substrate; and

an electrophoretic medium having a plurality of electrophoretic particles dispersed in a suspending fluid and capable of moving therethrough on application of an electric field to the medium, wherein the polyimide is a polyphenylene polyimide.

5. An electrophoretic display according to claim 4 wherein the polyphenylene polyimide is a derivative of biphenyl-3,3′

,4,4′

-tetracarboxylic acid.

6. An electrophoretic display according to claim 5 wherein the polyimide is a derivative of biphenyl-3,3′

,4,4′

-tetracarboxylic acid and an a,ω

-alkanediamine.

7. An electrophoretic display comprising, in order:

a metal layer;

a polyimide substrate;

at least one transistor on the polyimide substrate; and

an electrophoretic medium having a plurality of electrophoretic particles dispersed in a suspending fluid and capable of moving therethrough on application of an electric field to the medium, the display further comprising a passivating layer between the polyimide substrate and the at least one transistor.

8. An electrophoretic display according to claim 7 wherein the passivating layer comprises silicon dioxide or aluminum nitride.

9. An electrophoretic display according to claim 7 wherein the passivating layer has a thickness in the range of about 20 to about 100 nm.

10. An electrophoretic display according to claim 7 wherein the passivating layer is deposited on both surfaces of the substrate.

11. An electrophoretic display comprising, in order:

a metal layer having walls defining apertures extending through the metal layer;

a polyimide substrate;

at least one transistor on the polyimide substrate; and

an electrophoretic medium having a plurality of electrophoretic particles dispersed in a suspending fluid and capable of moving therethrough on application of an electric field to the medium.

12. An electrophoretic display comprising, in order:

a metal layer;

a polyimide substrate;

at least one transistor on the polyimide substrate; and

an electrophoretic medium having a plurality of electrophoretic particles dispersed in a suspending fluid and capable of moving therethrough on application of an electric field to the medium, wherein the transistor comprises at least one amorphous silicon layer.

13. An electrophoretic display according to claim 12 wherein the polyimide substrate bears at least two transistors, each of the transistors comprising at least one amorphous silicon layer and the silicon layer extending continuously between the two transistors.

14. An electrophoretic display according to claim 12 wherein the transistor further comprises at least one n-type silicon layer in contact with the amorphous silicon layer.