Impact of oxidation of channel polysilicon on the trap-density of submicron bottom-gate TFT's
Abstract
Oxidation of channel polysilicon improves characteristics of narrow channel TFT's, especially in leakage current. Small leakage current of less than -20 fA/micron and high on/off ratio of about 7 orders of magnitude at a drain voltage of -3.3 V have been achieved by this method. By the analysis of trap densities, leakage current reduction in the oxidized TFT is attributed to the oxidation encroachment under the channel polysilicon which results in decrease of interface-state density from 5 x 10(exp 11)/sq cm to about 10(exp 10)/sq cm at both gate side and back side of the channel polysilicon. It is pointed out that interface state is in some cases more responsible to device degradation than bulk traps and that the reduction of interface state is indispensable to improve device characteristics. This new ingenious method is directly applicable to TFT load SRAM's in which TFT width is less than 0.5 micron.
- Publication:
-
IEEE Electron Device Letters
- Pub Date:
- January 1994
- DOI:
- 10.1109/55.289481
- Bibcode:
- 1994IEDL...15....1S
- Keywords:
-
- Gates (Circuits);
- Oxidation;
- Semiconductor Devices;
- Silicon Polymers;
- Transistor Circuits;
- Crystallization;
- Grain Size;
- Leakage;
- Electronics and Electrical Engineering