Kinetics of Thermal Oxidation of 6H Silicon Carbide in Oxygen Plus Trichloroethylene

Abstract

In this work, the behaviors of the trichloroethylene ͑TCE͒ thermal oxidation of 6H silicon carbide ͑SiC͒ are investigated. The oxide growth of 6H SiC under different TCE concentrations ͑ratios of TCE to O 2 ͒ follows the linear-parabolic oxidation law derived for silicon oxidation by Deal and Grove, J. Appl. Phys., 36 ͑1965͒. The oxidation rate with TCE is much higher than that without TCE and strongly depends on the TCE ratio in addition to oxidation temperature and oxidation time. The increase in oxidation rate induced by TCE is between 2.7 and 67% for a TCE ratio of 0.001-0.2 and a temperature of 1000-1150°C. Generally, the oxidation rate increases quickly with the TCE ratio for a TCE ratio less than 0.05 and then gradually saturates for a ratio larger than 0.05. The activation energy E B/A of the TCE oxidation for the TCE ratio range of 0.001-0.2 is 1.04-1.05 eV, which is a little larger than the 1.02 eV of dry oxidation. A two-step model for the TCE oxidation is also proposed to explain the experimental results. The model points out that in the SiC oxidation with TCE, the products ͑H 2 O and Cl 2 ͒ of the reaction between TCE and O 2 can speed up the oxidation, and hence, the oxidation rate is highly sensitive to the TCE ratio.In recent years, SiC has been an attractive wide-bandgap semiconductor material for high-temperature, high-frequency, and highpower applications. 1 SiC-based metal oxide semiconductor fieldeffect transistors ͑MOSFETs͒ and other MOS-related structures are promising devices for these purposes. 2 Because the high-quality gate insulator plays a critical role in MOSFETs, many researchers have studied the kinetics of SiC oxidation and the effects of oxidation method on the performance of SiC oxide films. 3-18 The methods of wet oxidation, dry oxidation, N 2 O oxidation, NO oxidation, and NH 3 nitridation, commonly used for silicon, have been investigated for SiC. However, trichloroethylene ͑TCE͒ oxidation is also a popular method for oxidizing silicon and has been shown to improve the performance and electrical properties of the oxide film. 19,20 Compared to HCl, TCE is much easier to handle, because it is far less corrosive. As a result, TCE is widely used for cleaning the quartz tubes of oxidation furnaces and fabricating gate-oxide films in the semiconductor industry. However, the TCE oxidation method is not yet fully studied for SiC, although preliminary work demonstrated that it can also enhance the quality of the SiO 2 /SiC interface and reduce the thermal budget. 21 Therefore, this work focuses on the behaviors and kinetics of SiC thermal oxidation in the presence of TCE. ExperimentalThe n-type ͑0001͒ Si-face 6H-SiC wafers used in this investigation were purchased from CREE Research, Inc. The wafers had a 5 m epitaxial layer grown on a heavily doped substrate. The doping concentration of the epitaxial layer was 4 ϫ 10 15 cm −3 . The wafers were cleaned using the conventional RCA method followed by a 1 min dip in 5% HF solution 22 and then loaded into an oxidation furnace. The samples ...

Mechanism of Low Temperature Oxidation of 4H-SiC by Nitric Acid Vapor Oxidation Method at 600°C

“…[2][3][4] Oxygen atoms generated by decomposition of HNO 3 molecules at the surface are the most probable oxidizing species:…”

“…Using the NAVOS method, oxidation of SiC proceeds at 600 • C, which is lower by more than 400 • C than the thermal oxidation temperature. [2][3][4] Oxygen atoms generated by decomposition of HNO 3 molecules at the surface are the most probable oxidizing species: 22…”

“…[2][3][4] For improvement of interfacial characteristics of SiO 2 /SiC structure, extensive studies have been performed so far, including heat treatments in N 2 O and NH 3 , 5,6 formation of oxynitride by heating in N 2 O or NO, 7,8 oxidation in oxygen-containing trichloroethylene, 9,10 hydrogen treatment at high temperatures in the range between 800 and 1000…”

“…On the other hand, SiC is much more chemically stable than Si, and consequently thermal oxidation of SiC for the formation of gate oxides in metal-oxide-semiconductor (MOS) devices requires more than 200 • C higher temperature (i.e., ∼1100 • C) than that of Si. [2][3][4] For improvement of interfacial characteristics of SiO 2 /SiC structure, extensive studies have been performed so far, including heat treatments in N 2 O and NH 3 , 5,6 formation of oxynitride by heating in N 2 O or NO, 7,8 oxidation in oxygen-containing trichloroethylene, 9,10 hydrogen treatment at high temperatures in the range between 800 and 1000 • C, 11,12 etc. In spite of these studies, interface state densities at SiO 2 /SiC interfaces are more than one order of magnitude higher than those for SiO 2 /Si interfaces.…”

Nitric Acid Oxidation of 3C-SiC to Fabricate MOS Diodes with a Low Leakage Current Density

“…Conventional thermal oxidation of SiC requires more than 200°C higher temperatures ͑i.e., ϳ1100°C͒ in comparison to those for Si thermal oxidation. [1][2][3][4] High-temperature thermal oxidation degrades characteristics of SiC-based metaloxide-semiconductor field effect transistors ͑MOSFETs͒, possibly due to the formation of high-density interface states. In fact, the interface-state density of SiC-based MOS devices is at least one order of magnitude higher than that of Si-based MOS devices even after treatments to decrease the interface state density, i.e., annealing of SiO 2 /SiC structure in N 2 O or NH 3 , [5][6][7] oxynitridation of SiC in N 2 O or NO, [8][9][10] oxidation in trichloroethylene-containing oxygen, 11,12 etc.…”