Schottky Properties of Tungsten Compounds Refractory Contacts on n-GaAs Fabricated by Ion Beam Assisted Deposition
- PDF / 2,726,735 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 96 Downloads / 227 Views
SCHOTT'KY PROPERTIES OF TUNGSTEN COMPOUNDS REFRACTORY CONTACTS ON n-GaAs FABRICATED BY ION BEAM ASSISTED DEPOSITION C.s. Park, J.S. Lee, J.W. Lee, J.Y. Kang, and J.Y. Lee* Electronics and Telecommunications Research Institute P.O.Box 8 Daeduk Danji, Daejon 305-350, Korea KAIST, 373-1 Kusong-Dong, Daejon 305-701, Korea
ABSTRACT A low energy ion beam assisted deposition (IBAD) technique has been developed to fabricate refractory W-Si-N films for the application to gate electrode of GaAs metal-semiconductor field effect transistors( MESFETs ). Thermal stability of the IBAD refractory metal/n-GaAs interface was investigated by examining the microstructure and Schottky diode characteristics. The Schottky barrier heights of 0.71, 0.84, and 0.76 eV were obtained after thermal annealing at 850°C for the W/, WNo.27 /, and WSiozN 0./GaAs diodes, respectively, and these values are comparable to those of the best results published with conventional reactive sputtering. While some crystalization of the deposit and reaction between film and substrate at the interface were observed with TEM for the WI/and WN/GaAs contacts annealed at 800°C, the WSiN film remained amorphous and showed clear interface with the GaAs substrate without significant morphological change. The WS 03. N0./GaAs diode showed good thermal stability of Schottky barrier heights with only 20 meV vartiation in the temperature range between 700 and 850°C, and that is proposed to be due to the stable microstructure. INTRODUCTION Refractory metals and their low resistivity compounds play an important role as gate materials in the self-aligned GaAs metal-semiconductor field effect transistor(MESFET) technologylil]. The self-aligned gate, acting as a mask during the subsequent source/drain implantation step, should be stable without any degradation through the subsequent high temperature activation stage. High Schottky barrier height and its good thermal stability are also required for the integrated device application. The implementation of self-aligned gate technology to GaAs MESFET has drawn significant success in GaAs digital integrated circuit because this technology has several process advantages of simplicity, uniformity, and reproducibility. A key research issue in this technology involves the choice of refractory gate material and the deposition method. Tungsten being known as the refractory element which does not react with arsenic at 10000 C or below[2], many tungsten-based materials have been developed for this purpose including W[3], WN[4], WSi[5], and TiW[6] by sputter deposition. However, the major disadvantage, particularly for the application to MMIC, is the high gate resistance, which is inherent to refractory metal compounds. Recently, new types of self-aligned gate MESFET were proposed by adding Au or Ti/Au overlayer onto the refractory gate to reduce the gate resistance[7]. Still the major drawback is the complexity of the process to pattern the noble metal overlayer. In order to pattern the noble metal one needs ion milling for etching. But with
Data Loading...
