ZnO Thin Film Transistors Fabricated by Atomic Layer Deposition Method
- PDF / 1,184,430 Bytes
- 5 Pages / 595.28 x 841.89 pts (A4) Page_size
- 10 Downloads / 239 Views
1201-H10-27
ZnO Thin Film Transistors Fabricated by Atomic Layer Deposition Method Yumi Kawamura1, Nozomu Hattori2, Naomasa Miyatake2, Kazutoshi Murata2, and Yukiharu Uraoka 1,3 1
Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan 2 Mitsui Engineering & shipbuilding Co., Ltd., 3-16-1 Tamahara, Tamano, Okayama 706-0014, Japan 3 CREST, Japan Science and Technology Agency, 4-1 Honcho, Kawaguchi, Saitama 332-0012, Japan
ABSTRACT In this study, we deposited zinc oxide (ZnO) thin films by atomic layer deposition (ALD) as an active channel layer in thin film transistor (TFT) using two different oxidizers, water (H2OALD) and oxygen radical (PA-ALD). The fabricated TFTs were annealed at various temperatures, in oxygen ambient gas. The electrical properties of TFTs with PA-ALD ZnO film annealed at the temperature up to 400 oC improved without any degradation of the subthreshold swing or any large shift of the threshold voltage. Through this study, we found that the high performance ZnO TFTs is possible to obtain by using PA-ALD at low temperature, and the electrical properties are dependent on the annealing temperature. I TRODUCTIO The most commonly used materials as an active channel layer in thin film transistors (TFTs) have been amorphous (a-Si:H) and polycrystalline silicon (poly-Si).[1] However, there are a number of drawbacks for these materials, such as issue of uniformity, their high temperature fabrication process, and it is difficult to fabricate on large substrates.[1-3] In recent years, the application of zinc oxide (ZnO) thin films as an active channel layer in TFTs has become of great interest owing to their specific characteristics. ZnO is transparent to visible wavelengths because of its wide band gap (~3.37eV), and the ability to fabricate good quality films over large areas at low temperature suggests the compatibility of these films with plastic or flexible substrates [4-6]. Higher field-effect mobility of ZnO-TFTs than a-Si:H TFTs has recently been demonstrated.[4-10] However, there is still critical issue that has to be solved. Reliability for electrical stress is serious problem in their mass production. An atomic layer deposition (ALD) method is a thin film preparation technology that attracts much attention in the LSI industry. ALD thin films are deposited with alternating exposures of a source gas and an oxidant. ALD films have additional features of accurate thickness control, high conformity, and uniformity over large areas, because of their layer-bylayer growth. [11] Further, it is reported that TFTs with ALD thin film as the channel layer demonstrate high mobility. [12-14] In this study, we fabricated TFTs using ZnO thin film as the channel layer deposited by ALD (ALD-ZnO), and the electrical properties were measured. The dependences of TFT
characteristics on annealing conditions are evaluated, and the dependence of their electrical properties on the composition of the ZnO films was characterized. EXPERIME T A schemat
Data Loading...
