Impact of post-nitridation annealing in CO₂ ambient on threshold voltage stability in 4H-SiC metal-oxide-semiconductor field-effect transistors

Abstract

The combination of NO annealing and subsequent post-nitridation annealing (PNA) in CO2 ambient for SiO2/SiC structures has been demonstrated to be effective in obtaining both high channel mobility and superior threshold voltage stability in SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs). N atoms on the SiO2 side of the SiO2/SiC interface incorporated by NO annealing, which are plausible cause of charge trapping sites, could be selectively removed by CO2-PNA at 1300°C without oxidizing the SiC. CO2-PNA was also effective in compensating oxygen vacancies in SiO2, resulting high immunity against both positive and negative bias-temperature stresses.

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

“…Additionally, a post-deposition annealing (PDA) in a CO 2 ambient was performed to compensate for the oxygen vacancy defects in the SiO 2 . 24) Although some nitrogen at the interface may be removed during the CO 2 annealing, 20) we show that this is not an issue because of the substantial initial nitrogen content at the interface resulting from the direct plasma nitridation of the SiC surface.…”

“…However, the signal intensity was approximately three times stronger for the Npla.-depo.-CO 2 than for ox.-NO. Note that while CO 2 -PDA reduces the amount of nitrogen at the interface, 20) the N 1s intensity remains higher in the case of the plasma-nitrided sample. This indicates that plasma nitridation is an effective method to introduce a significant amount of nitrogen at the SiC surface.…”

“…On the basis of this concept, a previous study attempted to remove nitrogen atoms from SiO 2 by subjecting it to post-nitridation annealing in a carbon dioxide (CO 2 ) ambient at high temperatures. 20) While this method effectively eliminates nitrogen atoms from SiO 2 , it also removes nitrogen from the interface. Hence, the process conditions must be carefully designed.…”