Improvement of Plasma Homogeneity - Homogenization through modulated electrode arrangement

In the semiconductor industry, radial inhomogeneities in capacitively coupled radio frequency (RF) low-temperature plasmas are a major problem. They lead to uneven etching and coating results, which reduces production yield and increases manufacturing costs. Conventional approaches to homogenization – such as dielectric lenses, structured or segmented electrodes – are technically complex, expensive and often require costly modifications to the plasma chamber. In addition, these solutions are not very flexible, as they are strongly tied to specific process conditions.

The invention presented here pursues a fundamentally new approach for the first time: instead of laboriously changing the geometry of the main components, an additional ring-shaped electrode is integrated near the reactor wall, which is operated with an individually controlled RF alternating voltage. The frequency and amplitude can be controlled independently of the main voltage of the sample plate. This allows high-energy electrons to be generated specifically in the edge area of the plasma and directed to areas with insufficient plasma density, where they locally increase the plasma density by ionizing the background gas.

The wall electrode features variable geometry: both its dimensions and its tilt angle can be adjusted. This allows dynamic fine-tuning of the plasma profiles without any structural changes to the process chamber.