| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThM |
| Session: | Plasma Modeling |
| Presenter: | N. Nakazaki, Kyoto University, Japan |
| Authors: | N. Nakazaki, Kyoto University, Japan Y. Takao, Kyoto University, Japan K. Eriguchi, Kyoto University, Japan K. Ono, Kyoto University, Japan |
| Correspondent: | Click to Email |
Profile anomalies and surface roughness are now critical issues to be resolved in the plasma etching of nanometer-scale microelectronics devices, which in turn requires a better understanding of the effects of the ion incident energy and angle on surface reaction kinetics. For example, the line edge and line width roughness on feature sidewalls and the roughness on bottom surfaces of the feature are assumed to be caused by the angular distribution of incident ions onto feature surfaces. In addition, incident neutral radicals also affect the surface reaction kinetics and thus etching characteristics achieved. This paper presents a classical molecular dynamics (MD) simulation of Si etching in HBr-based plasmas with different ion incident energies and angles, by using an improved Stillinger-Weber interatomic potential model for Si/H/Br system interactions. Emphasis is placed on the surface structure and the yield and stoichiometry of products depending on the ion incident energy, angle, and neutral radical-to-ion flux ratio.
In the MD simulation, a target substrate Si(100) was placed in the simulation cell, which was a square 32.58 Å on a side and initially contained 1440 Si atoms (6.78 × 1014 atom/cm2) in a depth of 26 Å. Energetic ions and low-energy neutral radicals were injected toward the surface from randomly selected horizontal locations above the target. We assumed that the plasma of interest consisted of HBr+ ions and H and Br neutrals. The ion incident energy was in the range Ei = 20–300 eV and the incident angle was in the range θi = 0–90˚. The neutral radical-to-ion flux ratio was Γn/Γi = 0 and 100. In addition, we sometimes added a layer of Si atoms at the bottom of the simulation cell, to maintain the number of target atoms during etching. The yield and stoichiometry of products, and the surface structures were analyzed by averaging more than 1000 impacts after the surface and etching characteristics had become statistically stable.
Numerical results indicated that the thickness of the surface reaction layer (SiHxBry layer) decreases with increasing θi, because of decreased penetration depth of incident ions at large θi, which is less significant for Γn/Γi = 100 than for Γn/Γi = 0 at each Ei incidence, owing to increased desorption of reaction products therefrom at increased Γn/Γi as a result of enhanced etching reactions. Moreover, the Si yield is larger for Γn/Γi = 100 than for Γn/Γi = 0, and correspondingly, the amount of volatile etch products containing H atoms is larger for Γn/Γi = 100 than for Γn/Γi = 0.