Defect Profiling of Oxide‐Semiconductor Interfaces Using Low‐Energy Muons

Abstract

Muon spin rotation with low‐energy muons (LE‐µSR) is a powerful nuclear method where electrical and magnetic properties of surface‐near regions and thin films can be studied on a length scale of ≈200 nm. This study shows the potential of utilizing low‐energy muons for a depth‐resolved characterization of oxide‐semiconductor interfaces, i.e., for silicon (Si) and silicon carbide (4H‐SiC). The performance of semiconductor devices relies heavily on the quality of the oxide‐semiconductor interface; thus, investigation of defects present in this region is crucial to improve the technology. Silicon dioxide (SiO2) deposited by plasma‐enhanced chemical vapor deposition (PECVD) and grown by thermal oxidation of the SiO2‐semiconductor interface are compared with respect to interface and defect formation. The nanometer depth resolution of LE‐µSR allows for a clear distinction between the oxide and semiconductor layers, while also quantifying the extension of structural changes caused by the oxidation of both Si and SiC. The results demonstrate that LE‐µSR can reveal unprecedented details on the structural and electronic properties of the thermally oxidized SiO2‐semiconductor interface.

Investigation of the SiO2 - SiC Interface Using Low-Energy Muon-Spin-Rotation Spectroscopy

“…The 1300× and 1300Ar1300 samples exhibit similar behavior while the contrast is stark to the case after NO annealing. For the NO-annealed samples almost no Mu 0 precession is observed, indicating that the fraction of the implanted muons forming Mu 0 quickly transforms to Mu − or quickly depolarizes due to the interaction with free charge carriers [3,35]. Additionally, for samples annealed in the NO environment we observe that in 4H-SiC, the A D reduces with depth, whereas the paramagnetic signal is close to zero.…”

“…It was shown in Ref. [35] that a high concentration of defects in SiO 2 could be responsible for the increase in the A * D signal. Further, a drop in the A * D signal is recorded as we transition from the SiO 2 to 4H-SiC but not to the bulk level as observed for the nonannealed (1300×) sample.…”

“…In thermally grown SiO 2 , Mu 0 formation is supported due to high structural order and therefore a typical A D signal [35] between 0.05 to 0.06 is observed across the samples. In 4H-SiC, at 10 K, a freeze out of carriers is expected.…”

“…The bulk level shown in Figs. 3 and 4(a) as reference is taken from the μSR data of an unprocessed, low-doped n-type 4H-SiC sample [35]. From the A D signal in SiO 2 , it can be observed that close to the interface the diamagnetic signal for both the NO-annealed samples is slightly higher than the nonannealed and the Ar-annealed samples.…”

“…In order to minimize the impact of the spread of the muon-depth profile on the muon response near the interface, we perform a deconvolution of the experimental data and the stopping depth profile of the muons using a multilayer fitting approach that was employed for interfaces in Ref. [35]. The diamagnetic signal extracted from this method is written as A * D in the rest of the paper to distinguish it from the measured diamagnetic signal, A D .…”