Addressing Mobility Overestimation in Short-Channel IGZO TFTs Using the Gated Van der Pauw Method

Abstract

The determination of field-effect mobility in indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) is pivotal for advancing high-performance electronic devices. However, accurately evaluating the field-effect mobility in IGZO-TFTs with short channel lengths of less than a few micrometers poses a formidable challenge. This difficulty arises due to the increasing significance of contact resistance in the total resistance as the channel length decreases. Consequently, increasing contact resistance can lead to inaccurate sheet resistance values, resulting in overestimating critical parameters, such as mobility and contact resistance, during device evaluations. Therefore, a precise method for extracting sheet resistance, an intrinsic channel characteristic, is imperative for short-channel IGZO TFTs. Herein, a gated van der Pauw (gVDP) method was employed to extract sheet resistance precisely and independently of contact resistance. This contact-resistance-independent approach mitigates the risk of overestimating charge behaviors in IGZO TFTs. Furthermore, it facilitates precise evaluations of intrinsic channel mobility, enabling accurate predictions of the maximum performance of devices with short channels.