Interfacial characteristics of N2O and NO nitrided SiO2 grown on SiC by rapid thermal processing

Abstract

Interfacial characteristics of Al/SiO2/n-type 6H–SiC metal–oxide–semiconductor capacitors fabricated by rapid thermal processing (RTP) with N2O and NO annealing are investigated. Interface state density was measured by a conductance technique at room temperature. RTP oxidation in pure O2 leads to an excellent SiO2/n-type 6H–SiC interface with interface state density in the order of 1010–1011 eV−1 cm−2. NO annealing improves the SiO2/n-type 6H–SiC interface, while N2O annealing increases the interface state density.

Nitrogen Passivation of the Interface States Near the Conduction Band Edge in 4H-Silicon Carbide

“…We have observed that, for dry oxides, wet oxides, thin oxides (~ 40nm) and thick oxides (80nm), our optimized NO passivation process results in an interface state density of around 2x10 12 cm -2 eV -1 for n-4H-SiC at E c -E = 0.1eV. This interface state density may be compared to a trap density of approximately 10 10 cm -2 eV -1 for passivated Si/SiO 2 .…”

“…Li et al [12] reported improvements in the interface characteristics of 6H-SiC MOS capacitors following high temperature anneals in nitric oxide (NO). We have applied similar techniques to 4H-SiC to develop a passivation process that reduces the interface state density near the conduction band edge by more than one order of magnitude for n-4H-SiC MOS capacitors [13].…”

“…The reduction in the interface state density is associated with the passivation of carbon cluster states that have energies near the conduction band edge. However, attempts to optimize the the passivation process for both dry and wet thermal oxides do not appear to reduce D it (E c ) below about 2x10 12 cm -2 eV -1 (compared to approximately 10 10 cm -2 eV -1 for passivated Si/SiO 2 ). This may be an indication that two types of interface states exist in the upper half of the SiC band gap -one type that is amenable to passivation by nitrogen and one that is not.…”

“…The nitrogen passivation process that is described herein is based on post-oxidation, high temperature anneals in nitric oxide. An NO anneal at atmospheric pressure, 1175 o C and 200-400sccm for 2hr reduces the interface state density at E c -E ≅ 0.1eV in n-4H-SiC by more than one order of magnitude -from > 3x10 13 to approximately 2x10 12 cm -2 eV -1 . Measurements for passivated MOSFETs yield effective channel mobilities of approximately 30-35cm 2 /V-s and low field mobilities of around 100cm 2 /V-s.…”

Nanoscale transport properties at silicon carbide interfaces

“…The first experiments on nitridation of oxides on SiC were presented by Li et al [126], who observed a reduction of the interface state density at SiO 2 /6H-SiC interfaces after an annealing in NO, with respect to a rapid thermal oxidation process in O 2 . The beneficial impact of the NO process on the interface state density was generically attributed to a reaction of nitrogen with the silicon dangling bonds during the oxidation.…”