AVS 58th Annual International Symposium and Exhibition
    Transparent Conductors and Printable Electronics Focus Topic Thursday Sessions
       Session TC-ThP

Paper TC-ThP1
A Combinatorial Thin Film Sputtering Approach of the Synthesis and Characterization of Al2O3-TiO2 High-k Dielectrics for Oxide TFT Application

Thursday, November 3, 2011, 6:00 pm, Room East Exhibit Hall

Session: Transparent Conductors and Printable Electronics Poster Session
Presenter: JooHyon Noh, The University of Tennessee
Authors: J.H. Noh, The University of Tennessee
J. Noh, The University of Tennessee
P.D. Rack, The University of Tennessee
Correspondent: Click to Email
For the last decade, oxide based thin-film transistors (TFTs) have been extensively investigated because of their transparency, high mobility, low process temperature which are expected to serve as the basis for new optoelectronic and flexible devices. However, most of the work on oxide TFTs still rely on conventional dielectrics from Si technology, such as plasma-enhanced chemical vapor deposited (PECVD) SiO2 or SiNx with process temperature of 250–300°C. For high performance, low-cost and flexible electronics, high-k dielectrics at low process temperatures are needed. rf sputtering is alternative process for low temperature dielectrics. Usually, the deposition rate with oxide target is very low, so it is not compatible for mass production. In order to overcome this problem, reactive sputtering is adapted in this study. Although oxide TFTs with low-temperature sputtered materials such as Al2O3, HfO2, Y2O3, Ta2O5 have already been reported in the literature, TFTs performance are worse than standard higher temperature dielectrics because of high interface trap density due to low temperature. In order to improve the TFT performance, high-k materials are preferable. However, most of the high-k materials show a polycrystalline structure and small bandgap, hence the leakage current is high and breakdown voltage is low. These problems can be overcome through a combination of high-k but low bandgap and low-k but large bandgap materials. In this study, TiO2 is chosen as a high-k material because of very high dielectric constant of ~ 80, and Al­2O3 is chosen as a low-k material because of large bandgap of 8.7 eV. For optimization of high dielectric constant and low leakage current, a combinatorial thin film sputtering approach is used for the synthesis and characterization of Al2O3-TiO2 high-k dielectrics because a combinatorial thin film sputtering approach can yield a wide range of compositions via a single co-sputter deposition process. The composition ranges of the films are simulated using a co-sputtering simulation and compared favorably to compositions measured by the wavelength dispersive spectrometer (WDS). The TFTs are fabricated with a bottom-gate staggered structure using amorphous indium gallium zinc oxide (a-IGZO) and In2O3 as the semiconducting active layer. Standard I-V and C-V data on the dielectric multilayers will be compared as a function of composition and finally, the TFTs’ performance will be presented according to the relative contents of TiO2 and Al2O3.