Characterization of SiC Materials and Devices by SIMS
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0911-B05-20
Characterization of SiC Materials and Devices by SIMS Yupu Li, and Yumin Gao Applied Microanalysis Labs, 2990 Scott Boulevard, Santa Clara, CA, 95054 ABSTRACT Based on the various implanted standards, we have used SIMS (Secondary Ion Mass Spectrometry) to characterize SiC materials and devices. For major dopants of N, Al, and B in SiC, the depth profiles measured by SIMS are compared with the simulated profiles obtained by the program of the Stopping and Range of Ions in Matter (SRIM) [1]. The agreements are found to be very good for N and B in SiC, and good for Al in SiC. The critical dpa (displacements per atom) level for amorphizing the SiC under keV range ion irradiations is expected to be similar to that for Si, which has been estimated as 0.29 [2]. We have found that the best detection limit for nitrogen in SiC was obtained using Cs+ primary beam bombardment and detection of negative molecular ions of (12C+14N)- at mass 26, about 2e15 atoms/cm3 under the normal depth profiling conditions and about 3e14 atoms/cm3 level for bulk analysis. For the multi-layer samples like Al/SiC, Cu/SiC, or GaN/SiC, using the Cs-attachment mode [3,4], nitrogen concentration are detected by following positive molecular ions of (Cs2N)+. INTRODUCTION Silicon carbide, with its wide band gap and high breakdown electric field, has long been recognized as an important semiconductor for use in high temperature and high power applications [5,6]. It can be seen that the ability to correctly measure dopant and impurity levels either in whole SiC wafers or tiny SiC dies are very important issues. Some various methods for SIMS analysis of a number of selected elements in SiC and some RSFs (Relative Sensitivity Factor) have been reported [7]. In this paper, based on the various implanted standards, we have optimized the methods to analyze the major dopants (i.e. N, B, and Al) in SiC. The comparison between the measured depth profiles by SIMS and the simulated profiles by the SRIM code are discussed. We report that developing of SIMS analysis on 2'' and 3'' SiC wafers using our customized sample load chamber at a Cameca 4f magnetic sector SIMS tool. We also report the two special mounting skills for small SiC dies. By using these skills, SIMS analysis on small patterned areas (say 50 microns x 50 microns or larger) on the tiny SiC dies were performed. EXPERIMENTAL A Cameca 5f magnetic sector SIMS tool and a Cameca 4f tool with customized sample load chamber (for 2” and 3” full SiC wafers) at Applied Microanalysis Labs in Santa Clara, California, were used to analyze the implanted standards and SiC samples for this work. Table I lists the used primary beams, the requested mass resolution power, and detection limits under normal depth profiling conditions for analyzing specific elements in SiC samples. These selections are based on a combination of general knowledge on SIMS analysis [8,9], prior practical experience and actual data from test samples. In general, we used Cs+ primary beam to analyze N, O, and P etc elements, and used O
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