AVS 45th International Symposium
    Electronic Materials and Processing Division Tuesday Sessions
       Session EM+SE-TuM

Paper EM+SE-TuM6
Deposition of AlN Gate Dielectrics

Tuesday, November 3, 1998, 10:00 am, Room 316

Session: Critical Issues in Widebandgap Semiconductors
Presenter: B. Gila, University of Florida, Gainesville
Authors: B. Gila, University of Florida, Gainesville
S.M. Donovan, University of Florida, Gainesville
C.R. Abernathy, University of Florida, Gainesville
K.N. Lee, University of Florida, Gainesville
J.D. MacKenzie, University of Florida, Gainesville
F. Ren, University of Florida, Gainesville
S.J. Pearton, University of Florida, Gainesville
S.N.G. Chu, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
The development of a suitable insulator for GaN is a critical step in developing a GaN MOSFET technology. Conventional dielectrics such as SiO@sub 2@ and Si@sub 3@N@sub 4@ have generally failed on III-V materials because of high interface state densities. AlN is an attractive alternative because of its large bandgap, high thermal conductivity and excellent thermal stability. Also, a high relative dielectric constant (8-9) alleviates the problem of high fields in the dielectric in high voltage applications. AlN has also been proposed as a potential replacement for silicon dioxide in high temperature MIS based silicon carbide device applications. In this study, 375Å AlN films were deposited in ultrahigh vacuum (UHV) using an RF nitrogen plasma and dimethylethylamine alane (DMEAA) on Si, SiC and GaN/Sapphire at temperatures ranging from 325° to 525°C. Prior to deposition various surface cleans were employed including hydrogen plasma exposure, BOE (Si) high temperature exposure to ammonia and nitrogen plasma (GaN and SiC). Cross-sectional TEM (XTEM), Auger electron spectroscopy (AES), reflection high energy electron diffraction (RHEED), C-V and I-V analysis were used to characterize the films as functions of deposition temperature and surface preparation. In spite of the low deposition temperatures, none of the films were found to contain oxygen or carbon within the detection limit of AES. Consequently, the reverse breakdown characteristics of the layers were found to be excellent. By contrast, the interface state density as measured by C-V was found to depend strongly on the nature of the initial substrate surface. Optimization of the initial starting surface via mass spectrometry and RHEED during in-situ chemical cleaning produced substantial reduction in the interfacial leakage current. As a result, initial GaN HIGFET devices show promising performance with improved breakdown and C-V behavior relative to conventional MESFET structures.