| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Innovative Chemistries for Advanced Etch Processes |
| Presenter: | R. Gupta, Air Liquide |
| Authors: | R. Gupta, Air Liquide C. Anderson, Air Liquide V. Surla, Air Liquide B. Lefevre, Air Liquide V. Pallem, Air Liquide N. Stafford, Air Liquide |
| Correspondent: | Click to Email |
In order to enable high aspect ratio etching capabilities in materials such as SiO and SiN, it is highly desirable to determine what role the plasma etch chemistry can play. Both saturated and unsaturated fluorocarbons have been introduced over the years, as well as simple hydrofluorocarbon molecules. Mixtures of the above are often employed to allow control of etching species in the plasma recipe. In this work we systematically study the role of the gas molecule structure on the etching behavior that can be achieved. The ultimate goal is to identify ideal candidate molecules that will allow achieving the future process requirements.
This study will provide a comparative study of fluorocarbon-based etch chemistries, wherein a 200mm dual-CCP tool has been employed to produce high aspect ratio structures. By studying the specific effects of H, C=C double bonds, F:C ratio, and molecule structure, we can identify relationships to the etching performance. The model chemistries for this work include both cyclic- and linear-type structures. The performance of each molecule is initially studied on blanket wafers, measuring etch rates of silicon oxide, silicon nitride, amorphous carbon, and undoped poly-Si. For selected conditions of optimized etch rate and mask selectivity, 100nm trench width patterns are also etched and examined in cross-section SEM.
In order to develop a strong correlation between etch performance and the molecule structure, we perform mass spec measurements of the gases by direct injection of the fluorocarbon gas, measuring the electron-impact fragmentation of each gas. Electron energies from 10-100 eV are recorded, and the relative abundance of each fragment species is plotted against the electron energy. By studying the dominant fragments, we observe that oxide etch rate and mask selectivity can be predicted based on the C:F ratio of majority species.