Paper PS-TuP18
Effect of Superimposed Multi-frequency on Plasma Characteristics of an Inductively Coupled Plasma Source

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

To achieve reduced production cost and improved productivity for nanoscale semiconductor devices, the specifications of dry etchers have become more stringent. One of the important specifications for next generation plasma systems is the extremely high uniformity from center to edge of the substrate. Especially for inductively coupled plasma (ICP) sources, as the power to the ICP sources is increased for increased plasma density, non-uniform power deposition resulting in non-uniformity of the plasma has increased further. Recently, numerous theoretical and experimental studies have been performed to improve the plasma uniformity such as separate dual frequency excitation, very high frequency mixing, etc. However, controllability of a plasma uniformity over a large area substrate still remains as one of the major challenges.

In this study, as one of the methods in controlling the plasma uniformity, superimposed multi-frequency operation on an ICP source has been investigated. On the ICP source, dual frequency power selected from 2~ 40 MHz was applied and, on the substrate, a single frequency was applied, and the effect of power ratio of multi-frequency power on the plasma characteristics including the etch uniformity was investigated for a 300 mm diameter ICP etch system. The variation of multi-frequency power at a same total power changed the electron energy distribution profiles and plasma uniformity. When SiO₂ wafer was etched using Ar/CF₄, an improved etch uniformity by using a multi-frequency operation of the ICP source could be observed.