Ti/Ni/Au/Diamond MIS Field Effect Transistors With TiO 2 Gate Dielectric

  • PDF / 123,659 Bytes
  • 6 Pages / 612 x 792 pts (letter) Page_size
  • 45 Downloads / 178 Views

DOWNLOAD

REPORT


M8.8.1

Ti/Ni/Au/Diamond MIS Field Effect Transistors With TiO2 Gate Dielectric Yuhong Cai, Aris Christou Department of Material Science and Engineering, University of Maryland, College Park, MD 20770, U.S.A. ABSTRACT Ti/Ni/Au/diamond metal-insulator-semiconductor field effect transistors with TiO2 gate dielectric have been successfully fabricated. In this work, multi-layer metallization on the semiconducting diamond surface was investigated. Post-metallization annealing was performed and EDS analysis was conducted both before annealing and after annealing. Elevated temperature annealing accelerates the diffusion between multi-layer metal and lowers the ohmic contact resistance of the interface. Current-voltage characteristics of the transistor are reported.

INTRODUCTION Diamond, an insulating material, if appropriately doped, is an excellent wide bandgap semiconductor (Eg = 5.5ev). A unique combination of extreme properties, such as high breakdown voltage, high thermal conductivity, small dielectric constant, as well as the good optical properties, make diamond well suited for high speed, high power, and high temperature applications [1]. Recent investigations on metallizing diamond have focused on the study of different combinations of multi-layers thin metals for ohmic contacts. Adhesion to the substrate, low stress, good electrical conductivity and minimal reactions at subsequent processing temperatures are the best desired characteristics for a metallization system [2]. Since gold has good electrical conductivity, it is usually selected as the metal for the conductive layer. As reported, carbideforming refractory metals such as Ti, Mo, Ta and their combinations have been used by several groups [3-5]. Based on the above considerations, we selected Ti/Ni/Au as the ohmic contact materials. Rapid thermal annealing at elevated temperatures after metal deposition will enhance diffusion between metals and will also enhance the carbide formation at the interface between diamond and metal. The method of deposition has been found to affect diamond contacts. It has been reported that sputtering resulted in degradation of the electrical characteristics of the rectifying contacts on diamond. Ion beam assisted deposition (IBAD) is a unique process that combines ion bombardment/implantation with vacuum deposition. An improvement in adhesion was founded for the metal films deposited on diamond with IBAD [6]. After a series of experiments, we have selected electron beam vapor deposition as the method for depositing the thin films.

EXPERIMENTS The size of diamond substrates used in our investigations is 24mm x 24mm. Since the interface between metal and diamond is very critical for the electrical properties of the metal

M8.8.2

contact, surface preparation was carried out prior to device fabrication. The diamond specimen was cleaned by using a cascade rinse of trichloroethane (TCE), acetone, methanol, H2SO4, H2O2. The wafer was then rinsed in deionized water for 2 minutes and dried with flowing nitrogen gas. Finally, the waf