The atomic layer etching (ALE) of silicon nitride (SiN) via a hydrogen plasma followed by exposure to fluorine radicals was investigated by using in situ spectroscopic ellipsometry and attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy to examine the surface reactions and etching mechanism. FTIR spectra of the surface following exposure to the hydrogen plasma showed an increase in the concentration of Si−H and N−H bonds, although the N−H bond concentration plateaued more quickly. In contrast, during fluorine radical exposure, the Si−H bond concentration decreased more rapidly. Secondary ion mass spectrometry demonstrated that the nitrogen atom concentration was decreased to a depth of 4 nm from the surface after the hydrogen plasma treatment and indicated a structure consisting of N−H rich, Si−H rich, and mixed layers. This indicated that Si−H bonds were primarily present near the surface, while N−H bonds were mainly located deeper into the film. The formations of the N−H and Si−H rich layers are important phenomena associated with modification by hydrogen plasma and fluorine radical etching, respectively.

No abstract

No abstract

No abstract

Interface defects in state-of-the-art semiconductors have a strong impact on device performance. These defects are often generated during device fabrication, in which a variety of plasma processing is used for deposition, etching and implantation. Here, we present the ion-induced defects in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) heterojunction. The experiments of argon ion (Ar+) irradiation over an a-Si:H/c-Si stack are systematically performed. The results suggest that the defects are generated not only by the impact of Ar+ (i.e. well-known effects), but also by another unique effect associated with “hot” mobile hydrogens (H). The mobile H atoms generated near the a-Si:H surface by the impact of Ar+ diffuse deeper, and they generate the a-Si:H/c-Si interface defects such as dangling bonds. The diffusion length of mobile H is determined to be 2.7 ± 0.3 nm, which indicates efficient reactions of mobile H with weak bonds in an a-Si:H network structure.

In this work, atomic layer etching (ALE) of Si compounds using H 2 or N 2 plasma modification followed by fluorine radical exposure is discussed. It is shown that the H 2 plasma modification process promotes the selective etching of SiN, SiC, and SiCO versus SiO 2 . The N 2 plasma modification, on the other hand, enables the selective etching of SiC and SiCO versus SiN and SiO 2 . The origin of the etching selectivity between different Si compounds is investigated using a combination of in situ SE and FTIR supported by several ex situ analysis techniques. It is shown that the formation of a hydrogen-rich layer after plasma modification is essential to enable the ALE process. The hydrogen-rich layer can be formed due to ion and radicals of the modification plasma (H 2 plasma modification) or be a result of the reconfiguration of hydrogen that is already present in the film (N 2 plasma modification). The obtained insights are expected to further enhance the etching selectivity of Si compound ALE processes. Furthermore, it is anticipated that the process can be extended to many other compound materials such as Ti and Hf, as well as enable selective etching between their oxides, carbides, and nitrides.

In this study, a linearization method is used to develop an implicit integration scheme for a class of high-temperature inelastic constitutive models based on non-linear kinematic hardening. A non-unified model is first considered in which the inelastic strain rate is divided into transient and steady parts driven, respectively, by effective stress and applied stress. By discretizing the constitutive relations using the backward Euler method, and by linearizing the resulting discretized relations, a tensor equation is derived to iteratively achieve the implicit integration of constitutive variables. The implicit integration scheme developed is shown to be applicable to a unified constitutive model in which back stress evolves due to static and dynamic recoveries in addition to strain hardening. The integration scheme is then programmed for a subroutine in a finite element code and applied to a lead-free solder joint analysis. It is demonstrated that the integration scheme affords quadratic convergence in the iterations even for considerably large increments, and that the non-unified and unified models give almost the same results in the solder joint analysis.

We consider corona model and local thermal equilibrium approximations of a real plasma to present measurements of electron temperature (Te) and density (ne), respectively, using optical emission spectroscopy (OES) method...