Study of SiO2/4H-SiC interface nitridation by post-oxidation annealing in pure nitrogen gas

Abstract

An alternative and effective method to perform interface nitridation for 4H-SiC metal-oxide-semiconductor (MOS) devices was developed. We found that the high-temperature post-oxidation annealing (POA) in N2 ambient was beneficial to incorporate a sufficient amount of nitrogen atoms directly into thermal SiO2/SiC interfaces. Although N2-POA was ineffective for samples with thick thermal oxide layers, interface nitridation using N2-POA was achieved under certain conditions, i.e., thin SiO2 layers (< 15 nm) and high annealing temperatures (>1350°C). Electrical characterizations of SiC-MOS capacitors treated with high-temperature N2-POA revealed the same evidence of slow trap passivation and fast trap generation that occurred in NO-treated devices fabricated with the optimized nitridation conditions.

Nitrogen‐Induced Changes in the Electronic and Structural Properties of 4H‐SiC (0001)/SiO2 Interfaces

“…The nitrogen reference is chosen because nitridation is produced through N 2 or NO during POA processes. [1,2,20,21] Additionally, other reference chemical potential choices (e.g., N and O) that could impact our results are discussed in the Supplementary Material. [41]…”

“…[1,2] Easily grown interfaces with the SiC native oxide, SiO 2 , can present a high density of interface states that largely degrade the performance of power devices by reducing carrier mobility and changing the threshold voltage. [3][4][5][6] The improved carrier mobilities after post-oxidation annealing (POA) of 4H-SiC/SiO 2 interfaces in N-rich conditions (N 2 , NO, or N 2 O) [1,2,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] or combined oxidation/annealing [22,23] have led to the adoption of the nitridation process in the production of SiC power electronics applications. The underlying mechanism of this process, however, is still elusive despite the considerable efforts made to date in modeling these interfaces, [24][25][26][27][28][29] with suggested mechanisms ranging from the healing of dangling bonds to the removal of interstitial C atoms.…”

“…The underlying mechanism of this process, however, is still elusive despite the considerable efforts made to date in modeling these interfaces, [24][25][26][27][28][29] with suggested mechanisms ranging from the healing of dangling bonds to the removal of interstitial C atoms. [1,27,[30][31][32][33][34][35][36][37] Owing to the large number of silica polymorphs and amorphous structures attained experimentally, describing silica interfaces to SiC with adequate atomic configurations is challenging. Previous studies on the effects of nitrogen in SiC grown under ultra-high vacuum conditions were based on thin epitaxial silicon-oxynitride (SiON) layers.…”

Growth and Characterization of Ternary HfxTayOz Films via Nitrogen-Infused Wet Oxidation

“…Depending on the oxidation temperature, the interface nitridation was likely to be enhanced. 25 A modification was employed in this work by introducing nitrogen as a carrier gas during the wet oxidation process, which has not been reported thus far to minimize the interfacial layer formation.…”

“…In addition, this study would also make use of the advantage of nitrogen, following the reported studies pertaining to interface nitridation method for 4H-SiC-based MOS devices during postoxidation annealing in pure nitrogen gas, in which the presence of a sufficient amount of nitrogen at the SiO 2 /4H-SiC interface could passivate slow traps at the interface. Depending on the oxidation temperature, the interface nitridation was likely to be enhanced . A modification was employed in this work by introducing nitrogen as a carrier gas during the wet oxidation process, which has not been reported thus far to minimize the interfacial layer formation.…”