Degradation of NO-nitrided SiC MOS interfaces by excimer ultraviolet light irradiation

Abstract

The impact of excimer ultraviolet (UV) light irradiation on SiO2/SiC(0001) and (1120) interfaces was examined to get insight into the effect of NO nitridation. While NO nitridation appears to be effective in passivating the electron traps at the SiO2/SiC interfaces, we found that the nitridation induces additional traps that are not active until UV light is irradiated. The traps include those causing hysteresis and frequency dispersion in the C–V characteristics and those affecting the long-term reliability of MOS devices. A non-nitrided SiO2/SiC interface was less sensitive to the UV light, indicating the instability of the nitrided SiC MOS structure.

Improvement of interface properties in SiC(0001) MOS structures by plasma nitridation of SiC surface followed by SiO2 deposition and CO2 annealing

“…We then investigated the stability of MOS structures by irradiating the SiO 2 /SiC interface with excimer UV light. 17) Figure 5 shows a comparison of the bidirectional C-V characteristics of the samples with and without excimer UV irradiation. Here, the UV light was irradiated prior to the gate electrode formation.…”

“…[14][15][16] They also contain traps that are activated by excimer ultraviolet (UV) light irradiation. 17) These degradations are likely caused by the incorporation of nitrogen atoms into the SiO 2 dielectric. [17][18][19] In fact, a correlation was found between the amount of nitrogen in SiO 2 and the density of electron traps activated by UV irradiation.…”

“…17) These degradations are likely caused by the incorporation of nitrogen atoms into the SiO 2 dielectric. [17][18][19] In fact, a correlation was found between the amount of nitrogen in SiO 2 and the density of electron traps activated by UV irradiation. 17) Thus, the ideal approach is to design the SiO 2 /SiC structure such that nitrogen atoms are incorporated only at the SiC-side of the interface and not in SiO 2 .…”

“…sample. A reference sample was also created by oxidation of SiC at 1200 °C, followed by Ar annealing at 1200 °C and NO nitridation at 1250 °C for 60 min 17) (sample: "ox.-NO"). Then, several samples were subjected to excimer UV light irradiation (λ = 172 nm) at room temperature in a vacuum for 10 min to assess stability.…”

“…The low-frequency capacitance was evaluated by quasi-static measurements. Figure 4 17) samples evaluated by XPS. SiO 2 was completely removed with 10%-HF before the measurement.…”