MECHANISM OF ENHANCED DIFFUSION OF ALUMINUM IN 6H-SiC IN THE PROCESS OF HIGH-TEMPERATURE ION IMPLANTATION Igor 0. USOV *, A.A. SUVOROVA*, V.V. SOKOLOV, Y.A. KUDRYAVTSEV* and A.V. SUVOROV** loffe Physical Technical Institute RAS, St. Petersburg, 194021, Russia Cree Research Inc., Durham, NC 27713, USA Abstract The diffusion of Al in 6H-SiC during high-temperature ion implantation was studied using secondary ion mass spectrometry. A 6H-SiC wafer was implanted with 50 keV Al ions to a dose of 1.4E16 cm 2 in the high temperature range 1300°- 1800TC and at room temperature. There are two diffusion regions that can be identified in the Al profiles. At high Al concentrations the gettering related peak and profile broadening are observed. At low Al concentrations, the profiles have a sharp kink and deep penetrating diffusion tails. In the first region, the diffusion coefficient is temperature independent, while in the second it exponentially increases as a function of temperature. The Al redistribution can be explained with the substitutional-interstitial diffusion mechanism. Introduction Silicon carbide is one of the most important semiconductors for electronic and optoelectronic device applications. Diffusion of Al implanted into SiC has been studied by several investigators [1-5]. In the previous studies, implants were mostly performed either at room temperature (RT) or at temperatures lower than 850TC. It was established that the 800TC implanted SiC has a broader Al distribution as compared with the RT implanted sample [1]. Only a slight Al in- diffusion of the RT implantation was observed for the annealing temperature up to 1800'C [2,3]. However, in our previous paper we have shown the anomalously high diffusion of Al implanted at 1800TC [5]. Experimental data on Al diffusion in SiC are few and the diffusion mechanism has not been well understood. In this work the implant temperature dependence of the enhanced Al difflusion is investigated. Experiment In this study we have used 3 litm thick n-type Si-faced 6H-SiC epitaxial layers with a carrier concentration of 5.5E 17 cm 3 grown on n-type 6H-SiC substrates from Cree Research Inc. Ion implantation was done with 50 keV Al' ions to a dose of 1.4E16 cm 2 and ion current density of 8.5 ptA/cm 2 (implantation time about 320 sec). The implants were performed at RT and at high temperatures (HT) ranging from 1300TC to 1800TC using a holder which could be resistevely heated. During implantation the samples were tilted 7' off the normal to minimize channeling. The secondary-ion mass spectrometry (SIMS) profiles of Al were determined using a CAMIECA IMS-4F spectrometer. Results and Discussion The concentration profiles of Al implanted at different temperatures are shown in Figure 1 and Figure 2. The Al profile of the RT implanted sample can be fit to a Gaussian distribution with a 141 Mat. Res. Soc. Symp. Proc. Vol. 504 © 1998 Materials Research Society