Uniformity enhancement of a microwave surface-wave plasma by a field agitation

Abstract

Microwave surface-wave plasma (SWP) provides relatively higher ion density and radical species density than RF plasma, making it a promising plasma source for semiconductor fabrication. However, its plasma uniformity is compromised due to the non-uniform field distribution as the microwave wavelength is typically shorter than chamber dimensions. This could be a bottleneck as the practical application of SWP in semiconductor fabrication demands a large-area plasma with a high uniformity. In this work, we propose field agitation by applying the phase difference of 0° and 180° between the two input microwaves in the chamber to enhance the plasma uniformity. The chamber, optimized for the TM130 mode at 2.458 GHz, successfully produces a large-area SWP with a diameter of 450 mm under 800 W absorption power and 200 mTorr argon pressure. The measurement results show that the system is capable of yielding enhanced uniformity of large-area SWP while maintaining high ion density.