High-temperature CO₂ treatment for improving electrical characteristics of 4H-SiC(0001) metal-oxide-semiconductor devices

Abstract

High-temperature CO2 treatments for 4H-SiC(0001) surfaces and SiO2/SiC structures were investigated. A stoichiometric SiO2 insulating layer was found to be grown on SiC by thermal oxidation in atmospheric CO2 ambient with an activation energy of 7.5 eV. Post-oxidation annealing (POA) in CO2 at a temperature of 1200 °C or more was effective in reducing interface fixed charges, oxide traps, and defect precursors, which are intrinsically involved in SiO2/SiC system grown with O2 oxidant. Furthermore, modification of the SiO2/SiC interface promoted by oxidizing SiC with CO2 at 1400 °C or more reduced the amount of interface states, thus the SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) treated with CO2 at 1400 °C exhibited improved channel mobility with a stable threshold voltage.

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

“…The D it value for the 1400 °C CO 2 -PNA sample was close to that for a SiO 2 /SiC interface formed by CO 2 oxidation. 29) This suggests that most of the N atoms incorporated into the SiO 2 /SiC interface by the NO-POA were removed by the CO 2 -PNA at 1400 °C, which is consistent with the interface SiC oxidation leading to the SiO 2 growth observed in Fig. 1(a).…”

“…However, the peak μ FE of the device with CO 2 -PNA at 1400 °C is 15 cm 2 V −1 s −1 , which is higher than that of the device with CO 2 -POA at temperatures above 1400 °C (11 cm 2 V −1 s −1 ). 29) Furthermore, it should be noted that μ FE remained at 24 cm 2 V −1 s −1 even after CO 2 -PNA at 1300 °C, which is about 80% of the device without CO 2 -PNA (NOonly).…”

“…[24][25][26][27][28] We have recently reported that CO 2 annealing of as-oxidized SiO 2 /4H-SiC(0001) structures at temperatures below 1400 °C is effective in improving their immunity against charge trapping and improving the SiO 2 /SiC interface properties of SiC MOS devices without causing SiO 2 film growth. 29) Thus, we expect that CO 2 annealing of NO-treated SiO 2 /SiC structures would selectively remove N atoms on the SiO 2 side and compensate for oxygen vacancies. In this study, we systematically investigated the effect of post-nitridation annealing (PNA) in a CO 2 atmosphere on SiO 2 /4H-SiC(0001) MOS devices, by means of electrical characterization and X-ray photoelectron spectroscopy (XPS).…”

“…Then, samples were subjected to CO 2 -PNA in pure atmospheric CO 2 at temperatures ranging from 1200 to 1400 °C for 30 min by using coldwall rapid thermal annealing apparatus. 29,30) Finally, an Al gate electrode and a back contact were deposited by vacuum evaporation to obtain the MOS capacitors.…”

Working principle and characteristic analysis of SiC MOSFET

“…The threshold voltage drift can be controlled by controlling the gas atmosphere in the hightemperature oxidation annealing. The number of interfaces fixed charges Q f , oxide traps, and defect precursors can be reduced by high-temperature annealing in the atmosphere of hydrogen or some inert gas [12]. The movable ion Q m is generally a positive ion that hardly migrates at low or room temperatures.…”