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Thin Film Transistor

A thin film transistor (TFT) is an insulated-gate field effect transistor that is fabricated using thin film techniques on an insulating substrate rather than a semiconductor. Integrated circuits (IC) built using polysilicon thin film transistors at low temperatures have attracted much attention in various large area applications such as flat panel displays and page width optical scanners. In conventional TFTs, the drain is offset from the channel region in order to achieve low leakage current. However, this offset causes a severe current pinching problem which in turn results in high on-resistance. This problem is even more severe in high voltage TFT devices since a longer offset region is required.

The invention relates to a novel high voltage conductivity modulated TFT. The new thin film transistor comprises a channel region and a drain, each being formed of a doped polysilicon material on an insulating substrate, said channel region and said drain being spaced apart by an offset region of undoped polysilicon material. The new design of the transistor provides much lower on-resistance compared to that of the conventional offset drain TFT. Since the density of traps in polysilicon is very high, minority carrier life-time is very short and so the TFT does not experience any latch-up and there is no degredation of switching speed.
Technology Benefits
1. Low leakage current
2. High on-state current
3. Easy to operate
4. Simple to make
Technology Application
- Electronic devices such as flat panel display, page width optical scanners, page width printer heads, etc.
Supplementary Information
Patent Number: US5869847A
Application Number: US1997959074A
Inventor: Sin, Johnny Kin On | Kottarath Parambil, Anish Kumar | Wong, Man
Priority Date: 19 Jul 1995
Priority Number: US5869847A
Application Date: 28 Oct 1997
Publication Date: 9 Feb 1999
IPC Current: H01L0029739
US Class: 257066 | 257059 | 257345 | 257346 | 257347 | 257E29195 | 438156 | 438158 | 438163
Assignee Applicant: The Hong Kong University of Science & Technology
Title: Thin film transistor
Usefulness: Thin film transistor
Novelty: Thin film transistor having lower on-resistance in which conductivity of offset region is modulated by injection of holes from drain
Sub Category
Application Date
28 Oct 1997
Application No.
US 08/959074
Patent Information
US 5869847
ID No.
Hong Kong

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