Amorphous silicon‐silicon nitride thin‐film transistors

ABSTRACTAmorphous silicon thin film transistors have been fabricated with a number of different structures and materials. To date, the best performance is obtained with amorphous silicon - silicon nitride thin film transistors in the inverted staggered electrode structure, where the gate insulator and semiconductor are deposited sequentially by plasma enhanced chemical vapour deposition in the same growth apparatus.Localised electron states in the amorphous silicon are crucial in determining transistor performance. Conduction band states (Si-Si antibonding σ*) are broadened and localised in the amorphous network, and their energy distribution determines the field effect mobility. The silicon dangling bond defect is the most important deep localised state and their density determines the prethreshold current and hence the threshold voltage. The density of states is influenced by the gate insulator interface and there is probably a decreasing density of states away from this interface. The silicon dangling bond defect in the bulk amorphous silicon nitride also leads to a localised gap state, which is responsible for the observed threshold voltage instability.Other key material properties include the fixed charge densities associated with primary passivating layers placed on top of the amorphous silicon. The low value of the bulk density of states in the amorphous silicon layer increases the sensitivity of device characteristics to charge at the top interface.

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Thin-Film Transistors based on Hot-Wire Amorphous Silicon on Silicon Nitride

MRS Proceedings ◽

10.1557/proc-557-659 ◽

1999 ◽

Vol 557 ◽

Cited By ~ 8

Author(s):

B. Stannowski ◽

H. Meiling ◽

A. M. Brockhoff ◽

R. E. I. Schropp

Keyword(s):

Thin Film ◽

Chemical Vapor Deposition ◽

Silicon Nitride ◽

Glow Discharge ◽

Silicon Dioxide ◽

Amorphous Silicon ◽

Vapor Deposition ◽

Thin Film Transistors ◽

Chemical Vapor ◽

Hot Wire

AbstractWe present state-of-the-art thin-film transistors (TFTs) incorporating amorphous silicon i-layers deposited by hot-wire chemical vapor deposition. The TFTs are deposited on glow-discharge silicon nitride as well as on thermally-grown silicon dioxide. The devices on silicon nitride have a field-effect mobility above 0.7 cm2/Vs, a threshold voltage around 2 V and a sub-threshold slope as low as 0.5 V/dec. As commonly observed, the TFTs on silicon-dioxide have higher values for the threshold voltage and the sub-threshold slope. In the annealed state the hot-wire TFTs show almost the same properties as TFTs deposited by conventional plasma-enhanced chemical vapor deposition. Nevertheless, the stress-time dependent behavior under prolonged gate-voltage stress at elevated temperature is different from that of the glow-discharge devices. The hot-wire TFTs are clearly more stable than their glow-discharge counterparts. Furthermore, we found differences in the stress behavior of the hot-wire TFTs deposited on silicon nitride and silicon dioxide.

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Plasma enhanced chemical vapor deposited silicon nitride as a gate dielectric film for amorphous silicon thin film transistors—a critical review

Vacuum ◽

10.1016/s0042-207x(98)00282-6 ◽

1998 ◽

Vol 51 (4) ◽

pp. 741-745 ◽

Cited By ~ 29

Author(s):

Yue Kuo

Keyword(s):

Thin Film ◽

Silicon Nitride ◽

Amorphous Silicon ◽

Critical Review ◽

Thin Film Transistors ◽

Gate Dielectric ◽

Dielectric Film ◽

Chemical Vapor ◽

Silicon Thin Film ◽

Chemical Vapor Deposited

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