Compact Modeling of Variability in Organic Thin-Film Transistors

Identifier:  TDX:4328

Handle: https://hdl.handle.net/20.500.11797/TDX4328

Authors:  Nikolaou, Aristeidis

Abstract:
In the current PhD thesis, a significant amount of research regarding topics that cover modeling aspects of variability of organic TFTs were presented. For verification reasons, seven flexible substrates containing organic TFTs and TFT-based circuits were fabricated and tested, accordingly. A physical charge-based drain-current variability model suitable for organic thin-film transistors was developed and verified, as the core of this research. Subsequently, an efficient alternative to the Monte Carlo statistical-analysis methodology that can be used for the variability study of integrated circuits has been presented. The proposed ''Noise-Based Variability Approach'' (NOVA) method has been tested on circuits based on organic TFTs and has been shown to be suitable for fast process and mismatch statistical circuit analyses. The principle advantage of NOVA over Monte Carlo is the significantly shorter processing time, which makes NOVA beneficial for circuit designers. Next, a semi-physical bias-dependent charge-based low-frequency noise model for organic thin-film transistors, a topic relevant to compact modeling of variability aspects, was implemented. The proposed model is based on charge carrier-number fluctuation-correlated mobility fluctuation (ΔΝ) and mobility-fluctuation (Hooge) (ΔΜ) effects, and it can be applied to TFTs fabricated in the inverted staggered device architecture. Using experimental data obtained from TFT-based current mirrors, the variability of the circuit characteristics were analyzed. For this purpose, a large number of nominally identical current mirrors were fabricated and characterized. Finally, the performance of organic TFTs changes when they are subjected to mechanical bending was investigated. The DC compact model utilized in the current manuscript is able to capture this effect by adjusting the value of the power-law exponent parameter β. In all cases, the results of the compact model utilized here are in good agreement with the measurement results.