Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction.
Abstract
A dry ex situ cleaning sequence, superior to conventional wet chemical processing, and based on UV/O3 oxidation and exposure to the vapor of a 10:1 buffered HF solution for removal of non-carbidic C and silicon oxide, respectively, has been demonstrated via XPS analysis for (0001)Si 6H-SiC surfaces. Exposure to UV/O3 resulted in a broad Si-O Si 2p peak at 102.4 eV and a shift in the non-carbidic Cls peak from 283.6 to 284.2 eV. The carbidic/non-carbidic C ratio increased from 0.8 to 2.7 after the UV/O3 treatment. Complete removal of the silicon oxide was demonstrated via the absence of the Si-O Si 2p peak at 102.4 eV. However, significant F was detected. A chemical vapor deposition system which incorporates a separate load lock from which growth and RHEED chambers are attached has been assembled for the growth of 4H- and 6H- SiC films. Numerous safety concerns and associated placement of the system are being resolved. As-deposited NiAl, Au, Ni, and Pt contacts were rectifying on p-type 6H-SiC with very low leakage current densities (^1x10(exp -8) A/sq cm at 10 V) and displayed a similar Schottky barrier trend as previously found for n-type 6H-SiC. Ni/NiAl contacts on p-type (1x10(exp 19) /cu cm) SiC were ohmic after annealing for 10-80s at 1000 deg C with a calculated specific contact resistivity of 2-3x10(exp -2)W sq cm. A three-step process and associated deposition system are being developed for oxide growth on 6H- and 4H-Si. The three stages of oxide formation, namely, (1) surface preparation, (2) initial insulator formation, and (3) oxide deposition will be integrated with in vacuo diagnostic capabilities to facilitate an understanding of the growth process and interface electrical characteristics.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1996
- Accession Number
- ADA320296
Entities
People
- Bayant Jayant Baliga
- M. O. Aboelfotoh
- Robert F Davis
- Robert J. Nemanich
- S. W. King
Organizations
- North Carolina State University