| AVS 60th International Symposium and Exhibition | |
| Transparent Conductors and Printable Electronics Focus Topic | Wednesday Sessions |
| Session TC+EM+TF-WeM |
| Session: | Oxide and Flexible Electronics |
| Presenter: | G.S. Herman, Oregon State University |
| Authors: | B. Flynn, Oregon State University S.A. Thevuthasan, Pacific Northwest National Laboratory H. Bluhm, Lawrence Berkeley National Laboratory G.S. Herman, Oregon State University |
| Correspondent: | Click to Email |
Thin film transistors (TFT) utilizing amorphous InGaZnO4 (a-IGZO) have multiple applications in high performance electronic devices, from flat-panel displays and integrated circuits to non-volatile memories. A-IGZO enables low processing temperatures, while retaining large electron mobilities, and low operation voltages and off currents. These stable carrier transport and electrical characteristics are crucial for many applications, and can be strongly affected by backchannel surface chemistry of a-IGZO TFTs. Understanding the chemistry of absorbed species and their effect on the electronic structure of a-IGZO is critical to improve the stability of these TFTs, while reactions at the metal/a-IGZO interface strongly influences switching characteristics of resistive random access memories. In this study we have characterized sputter-deposited thin films of a-IGZO using in-situ x-ray photoelectron spectroscopy (XPS). Both standard Al Ka and synchrotron-based radiation were used to investigate chemical changes at the a-IGZO surface. We have observed surface segregation and desorption of oxygen containing impurities for anneals up to 300 °C in ultra-high vacuum (UHV). The O 1s spectra were very sensitive to the local chemistries at the surface, and we used these spectra to characterize the interaction of molecular oxygen and water with well-defined a-IGZO surfaces for a wide range of temperatures and exposures. It was found that water adsorbs both molecularly and dissociatively at temperatures below 200 K, with corresponding downward band bending of ~0.15 eV for >20 Langmuir exposures. Oxygen did not appreciably affect the XPS spectra for the temperatures and exposures studied. We have also characterized the initial growth of platinum metal films on a-IGZO. The XPS characterization of chemical state differences of the elements and band bending due to surface effects will be discussed along with the film processing conditions.