Fabrication of Silicon Carbide PIN Diodes by Laser Doping and Planar Edge Termination by Laser Metallization
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Fabrication of Silicon Carbide PIN Diodes by Laser Doping and Planar Edge Termination by Laser Metallization Z. Tian, N.R. Quick1 and A. Kar Laser-Aided Manufacturing, Materials and Micro-Processing Laboratory (LAMMP) College of Optics and Photonics/CREOL, University of Central Florida Orlando, FL 32816-2700, USA 1 AppliCote Associates, LLC, 3259 Progress Drive A, Orlando, FL 32826, USA ABSTRACT Silicon carbide PIN diodes have been fabricated using a direct write laser doping and metallization technique. Trimethyaluminum (TMA) and nitrogen are precursors used to laser dope p-type and n-type regions, respectively, and a 4.3 µm p-type doped junction and 4 µm ntype doped junction are fabricated in semi-insulating 6H-SiC wafers. Rutherford backscattering studies show that no amorphization occurred during the laser doping process. A planar edge termination is fabricated by laser metallization in argon ambient to form a high resistivity layer. With this termination, the leakage current of the PIN diodes can be suppressed effectively compared to that of diodes without edge termination. The performance of the diodes can also be tailored by shrinking the active area of the diode and by conventional annealing. INTRODUCTION Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. However, there are still some technology barriers for silicon carbide device fabrication such as dielectric deposition, etching, oxidation, etc. Metallization and doping are also challenges in silicon carbide processing. The drawbacks of metal conductors lie in the generation of strains due to thermal expansion coefficient mismatch and oxidation and reaction with chemical species in hostile environments, all of which can decrease the device efficiency. [1] Ion implantation, the most common doping technique used for fabricating SiC devices, generates implantation-induced defect centers in the wafer and high annealing temperatures are required to remove these defects and to electrically activate the dopants. Some of these defects centers can be repaired at high annealing temperatures (~1700 °C); however, remaining defects may eventually degrade the performance of the devices. In addition, annealing at these high temperatures can cause severe surface damage due to Si sublimation and redistribution [2]. A laser conversion technology, first reported by Quick [3] was investigated [1, 4-9] to laser direct metallize without metal deposition and laser dope in SiC without high temperature annealing, as an alternative to the conventional ion implantation, and fabricate Schottky diodes and PIN diodes on 4H- and 6H-SiC wafers. This paper presents experimental results on the improved performance of PIN diodes fabricated by laser doping using three methods; reducing the active area of the diode, annealing and edge termination by laser metallization. EXPER
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