| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS1-WeA |
| Session: | Plasma Diagnostics, Sensors and Control 2 |
| Presenter: | M. Funk, Tokyo Electron America |
| Authors: | M. Funk, Tokyo Electron America B.G. Lane, Tokyo Electron America L. Chen, Tokyo Electron America J. Zhao, Tokyo Electron America R. Sundararajan, Tokyo Electron America Y. Yamazawa, Tokyo Electron Limited, Japan |
| Correspondent: | Click to Email |
The measurement of ion energy at the wafer surface at conditions that are realistic for commercial equipment and process development without extensive modification of the reactor geometry has been an industry challenge. High energy, wide frequency range, process gases tolerant, minimally perturbing, contamination free and accurate ion energy measurements are the base requirements. In this work we will report on the complete system developed to achieve the base requirements, including the safe and easy use by engineers. The system includes: a reusable silicon ion energy analyzer (IEA) wafer, signal feed through, RF confinement, and high voltage measurement and control.
The commercial manufacturing of an IEA system at a reasonable cost involves many disciplines, but can be achieved through the use of commercial methods and suppliers. Design aspects will be presented, including MEMs silicon etch technology that enables features in the sensor design that overcomes challenges in high voltage RF potentials while minimizing ion neutralization. The IEA wafer detail design required careful understanding of the relationships between the plasma Debye length, the number of grids, intergrid charge exchange (spacing), capacitive coupling, materials, and dielectric flash over constraints. RF confinement with measurement transparency was addressed so as not to disturb the chamber plasma, wafer sheath and DC self-bias as well as to achieve spectral accuracy. For commercial plasma etch reactors the wafer is floating at several kV relative to the outside ground and often the plasma wetted DC ground area is small and not well defined. To overcome the difference between the wafer surface and the outside environment a non-perturbing measurement system was developed that can be isolated and floated by several thousands of volts, while making accurate ion energy current and voltage measurements.The experimental results reported were collected using a commercial parallel plate etcher powered by a dual frequency (VHF + LF) bottom electrode; with various power combinations. Various process gases were tested and variations by pressure were tested to confirm the robustness and sensitivity of the physical design and measurement circuit and methods.