Effect of source/drain overlap region on device performance in a-IGZO thin-film transistors

In this paper, the effect of source/drain overlap length on the amorphous indium gallium zinc oxide (a-IGZO) TFT performance has been investigated. Results of this paper show that as source/drain overlap length decreases to a negative value forming S/D offset, the threshold voltage and S parameters of a-IGZO TFTs increased and the field-effect mobility decreased. The V(T) variation increases sharply as the channel length decreases because of the large resistance R(offset) when it is formed at a-IGZO source/drain. In the experiment, R(offset) of each 1 mu m, evaluated from the transfer length method (TLM), shows approximately 54-66 k Omega. This means that the source/drain overlap length is a very important control parameter for uniform device characteristics of a-IGZO TFTs.