Introduction

Low-temperature polycrystalline silicon (LTPS) thin-film transistors have been widely applied to AMOLED (Active Matrix Organic Light Emitting Diode) as the most suit­able means for high mobility, high switching speed and high resolution [1-2].

A Laser Annealing Process such as Excimer Laser Annealing (ELA) is used to manufacture by converting Amorphous Silicon (a-Si) to Polycrystalline Silicon (poly-Si) at low temperature. The poly-Si structure (produced through ELA) shows the laser wavelength, pulse width and spatial beam dependencies.

Organic thin-film transistors (OTFTs) are promising devices for future low-cost electronics[1][2]. However, to enable the development of this technology, circuit design simulation is needed. TCAD with MixedMode approach provides a suitable route for the physics based simulation of these transistors within simple circuits. As circuits become more complicated, more devices are needed and the computing time increases significantly. Compact models describe the behavior of the device with only a few equations and thus the computing time is reduced to a viable magnitude. Such equations are written down in a Verilog-A format which can be used by most SPICE simulators.

Introduction

As MOS field-effect transistors are scaled down to a nanometer regime, quantum effects in both transverse and transport directions start playing a major role in determining device characteristics. In order to address a new challenge, SILVACO has started a deployment of new quantum mechanical models based on Non Equilibrium Green’s Function (NEGF) approach. This is a fully quantum mechanical approach which treats such effects as source-to-drain tunneling, ballistic transport, and quantum confinement on equal footing. The new NEGF solver is suitable to model ballistic quantum transport in such devices as Double Gate or Surround Gate MOSFET, using rectangular or cylindrical geometries in ATLAS. The method used is based on references [1] and [2].

Introduction

In recent years, the investigation of Organic Light Emitting Diodes (OLEDs) and photovoltaic devices based on small organic molecules and polymers has attracted significant interest due to their potential for inexpensively generated electricity. ATLAS has been used already to investigate OLEDs [1] and compound material GaInP[2][3] devices.

Abstract

This paper is focused on the stability of n-channel laser-crystallized polysilicon thin-film transistors (TFTs) submitted to a hydrogenation process during the fabrication and with small grains dimension. With the aid of numerical simulations, we investigate the effects of static stress using two types of procedures: the on stress and the hot carrier stress. Results show that the variations of trap state density into the whole polysilicon layer and not only near the drain junction are responsible for the degradation of TFTs performances in both the two types of stress and that the interface trap states play a negligible role compared to the bulk trap states.