Thin film transistor and method of fabricating the same

• US 6,215,154 B1
• Filed: 02/13/1998
• Issued: 04/10/2001
• Est. Priority Date: 02/17/1997
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation), Sony Corporation (Sony Group Corp.), Submar.Inc.
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation), Sony Corporation (Sony Group Corp.)
• Inventors: Kuriyama, Hiroyuki, Nakahara, Yasuo, Shimogaichi, Yasushi, Ishida, Satoshi, Yamada, Tsutomu, Yoneda, Kiyoshi
• Primary Examiner(s): Abraham, Fetsum
• Application Number:
  US09/024,855
• Time in Patent Office: 1,152 Days
• Field of Search: 349/54-59, 349/72, 349/60, 349/66, 349/347
• US Class Current: 257/347
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: H01L 21/02107 Forming insulating materials on a substrate
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 21/316 composed of oxides or glassy oxides or oxide based glass
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• 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 29/78636 with supplementary region or layer for improving the flatness of the device
• CPC Class Codes: H01L 29/78678 with inverted-type structure, e.g. with bottom gate

Abstract

A thin film transistor (TFT) which may be used as a pixel drive element in an active matrix LCD display includes a pair of side wall spacers adjacent to the opposing side walls of its gate electrode. The side wall spacers provide the gate electrode with a substantially rectangular cross section, such that the gate electrode has a substantially constant thermal conductivity over its area. The TFT has a uniform device characteristic.

Claims

1. A bottom gate thin film transistor structure comprising:

an insulator substrate;

a gate electrode having a pair of opposing side walls and located on the insulator substrate, wherein the gate electrode has a substantially rectangular cross section;

a pair of side wall spacers formed adjacent to both of the side walls of the gate electrode, on the insulator substrate but not on the gate electrode;

a gate insulator film located above the insulator substrate, the gate electrode and the pair of side wall spacers; and

a polycrystalline silicon film located on the gate insulator film.

2. The thin film transistor according to claim 1, wherein the pair of side wall spacers comprise an SOG film.

3. The thin film transistor according to claim 2, wherein the SOG film comprises a solution of silicon dioxide in which a silicon compound is dissolved in an organic solvent.

4. The thin film transistor according to claim 2, wherein the SOG film comprises an inorganic SOG film.

5. The thin film transistor according to claim 4, wherein the inorganic SOG film has a hygroscopicity.

6. The thin film transistor according to claim 4, wherein the inorganic SOG film contains large amounts of water and hydroxyl groups.

7. The thin film transistor according to claim 2, wherein the SOG film comprises an organic SOG film which contains an organic component in a silicon compound.

8. The thin film transistor according to claim 2, wherein the gate electrode has a substantially constant thermal conductivity over its area.

9. A bottom gate thin film transistor structure comprising:

an insulator substrate;

a gate electrode having a pair of opposing side walls and located on the insulator substrate, wherein the gate electrode has a substantially rectangular cross section;

a flattening insulator film provided adjacent to each of the side walls of the gate electrode, on the insulator substrate but not on the gate electrode, the flattening insulator film being substantially equal in thickness to the gate electrode;

a gate insulator film provided above the gate electrode and the flattening insulator film, wherein the gate insulator film is flattened; and

a polycrystalline silicon film located on the gate insulator film, wherein the polycrystalline silicon film is flattened.

10. A bottom gate thin film transistor structure comprising:

an insulator substrate;

a gate electrode having a pair of opposing side walls formed on the insulator substrate, wherein the gate electrode has a substantially rectangular cross section;

a pair of side wall spacers formed adjacent to the gate electrode side walls but not on the gate electrode, wherein the side wall spacers prevent the gate electrode side walls from tapering such that the gate electrode has a substantially constant thermal conductivity over its area;

a gate insulator film formed above the insulator substrate, the gate electrode and the side wall spacers; and

a polycrystalline silicon film formed on the gate insulator film.