Winfried Sabisch

Hybrid model for the calculation of ion distribution functions behind a direct current or radio frequency driven plasma boundary sheath

A hybrid fluid dynamic/kinetic model is presented which describes the sheath and the presheath regions of dc or rf driven low pressure gas discharges in a realistic and self-consistent way. The model assumes an infinite extended sheath parallel to the electrode, allowing a one-dimensional spatial description. It provides for the presence of multiple positive ion species and their collisional interactions with the neutral background, and takes into account the possibility of a nonharmonic modulation of the sheath potential and the application of an external dc bias; in this work, the model is applied to a two-species capacitively coupled argon and oxygen plasma. The input required by the model consists of the fluxes of the incoming ions, of the modulating current, and of the pressure, the composition, and the temperature of the background gas. On output, the model provides the values of the electric field and of the particle densities within the sheath and the presheath, the total voltage drop across the s...

Improvement of chrome CDU by optimizing focus ring design

Uniform radical distribution in the etching plasma is essential to meet chrome critical dimension (CD) uniformity for future technology nodes on chrome masks. The Etec Systems Tetra photomask etch chamber utilizes an alumina focus ring in order to optimize the etch uniformity of the chrome mask by minimizing gas flow effects and shaping the radial distribution of the etching radicals over the mask surface. This paper describes a systematic investigation to optimize the current focus ring, in order to improve etch critical dimension uniformity. The focus ring (FR) optimization work was made possible by manufacturing a modular focus ring that allowed the geometry to be varied at different heights and diameters. The circular shape of the modular focus ring, along with the height and diameter combinations, has a large influence on the etch performance at the mask corners and edges. The underlying mechanism was investigated by modeling and simulation. Based on simulation results the focus ring geometry was varied and the optimum FR configuration was found. The critical dimension uniformity could be adjusted on uniformly patterned masks with different pattern loads to meet production specifications.

Energetic neutral fluxes towards surfaces in a magnetically enhanced reactive ion etch-like reactor

In very large scale integrated microelectronics fabrication magnetically enhanced reactive ion etch (MERIE) reactors are established for many dry etch processes of conducting or dielectric materials. Angularly and energetically resolved distributions of the surfaces incident particles (ions and neutrals) as well as the fluxes of ions and neutrals play an essential role for feature scale profile evolution. The focus of this work is set on the calculation of the neutral to ion fluxes ratio. Therefore the MERIE reactor’s boundary sheath is simulated by the technology-oriented computer aided design simulation tool hybrid plasma sheath model (HPSM). HPSM consists of a self-consistent coupling of a fluid dynamical part to a Monte Carlo part. The sheath and presheath regions are described in one unified model. Energetic neutrals impinging the surface can be monitored in addition to the positive ion species. Simulations with parameters in the range of about 100 mTorr, rf voltages of a few 100 V, magnetic fields o...