Stability of nanocrystalline silicon bottom-gate thin film transistors with silicon nitride gate dielectric

We report on the stability of nanocrystalline silicon (nc-Si) bottom-gate (BG) thin film transistors (TFTs) with various compositions of hydrogenated amorphous silicon nitride (a-SiNx:H) gate dielectric. TFTs with nitrogen-rich nitride exhibit higher output transconductance, threshold voltage stability, and effective field effect mobility (μFE) than the devices with silicon-rich gate dielectric. For example, μFE drops from 0.75to0.2cm2∕Vs when the gate dielectric composition [N]∕[Si] changes from 1.3 to 1. The corresponding threshold voltages (VT) are 4 and −2V. Following 5h electrical stress tests, the shift in threshold voltage (ΔVT) is larger for dielectrics with lower [N]∕[Si] content, regardless of the operating regime. Indeed, ΔVT in the saturation regime is considerably less and correlates with the charge concentration in the channel, i.e., ΔVT in saturation is about 2∕3 of that in the linear regime. Relaxation tests on the stressed TFTs show that the charge trapping is the instability mechanism in...

[1]  S. Wagner,et al.  Evolution of nanocrystalline silicon thin film transistor channel layers , 2004 .

[2]  Arokia Nathan,et al.  Amorphous silicon nitride deposited at 120 °C for organic light emitting display-thin film transistor arrays on plastic substrates , 2002 .

[3]  G. Parsons,et al.  Bulk and interface charge in low temperature silicon nitride for thin film transistors on plastic substrates , 2004 .

[4]  Jerzy Kanicki,et al.  Electrical Instability of Hydrogenated Amorphous Silicon Thin-Film Transistors for Active-Matrix Liquid-Crystal Displays , 1998 .

[5]  G. Kamarinos,et al.  Study of the Drain Leakage Current in Bottom-Gated Nanocrystalline Silicon Thin-Film Transistors by Conduction and Low-Frequency Noise Measurements , 2007, IEEE Transactions on Electron Devices.

[6]  A. Nathan,et al.  Drain-bias dependence of threshold voltage stability of amorphous silicon TFTs , 2004, IEEE Electron Device Letters.

[7]  D. Greve.  Field Effect Devices and Applications: Devices for Portable Low Power, and Imaging Systems , 1998 .

[8]  Arokia Nathan,et al.  Low-Temperature Materials and Thin Film Transistors for Flexible Electronics , 2005, Proceedings of the IEEE.

[9]  Regis Vanderhaghen,et al.  Stable microcrystalline silicon thin-film transistors produced by the layer-by-layer technique , 1999 .

[10]  R. Schropp,et al.  Thin-film transistors deposited by hot-wire chemical vapor deposition , 2003 .

[11]  Y. Bonnassieux,et al.  Effects of grain size and plasma-induced modification of the dielectric on the mobility and stability of bottom gate microcrystalline silicon TFTs , 2004 .

[12]  N. Lustig,et al.  Gate dielectric and contact effects in hydrogenated amorphous silicon‐silicon nitride thin‐film transistors , 1989 .

[13]  R. Street,et al.  Hydrogenated amorphous silicon: Index , 1991 .

[14]  Jerzy Kanicki,et al.  Stability of electrical properties of nitrogen-rich, silicon-rich, and stoichiometric silicon nitride films , 1989 .

[15]  J. R. Hughes,et al.  Time and temperature dependence of instability mechanisms in amorphous silicon thin-film transistors , 1989 .

[16]  M. Powell,et al.  Charge trapping instabilities in amorphous silicon‐silicon nitride thin‐film transistors , 1983 .

[17]  Jackson,et al.  Stretched-exponential relaxation arising from dispersive diffusion of hydrogen in amorphous silicon. , 1987, Physical review letters.

[18]  A. Nathan,et al.  Amorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic , 2004, IEEE Journal of Solid-State Circuits.

[19]  A. Nathan,et al.  Highly conductive n+ hydrogenated microcrystalline silicon and its application in thin film transistors , 2004 .

[20]  Takatoshi Tsujimura,et al.  Amorphous/Microcrystalline Silicon Thin Film Transistor Characteristics for Large Size Oled Television Driving , 2004 .

[21]  J. Andreu,et al.  Stability of hydrogenated nanocrystalline silicon thin-film transistors , 2001 .