Measurement and Simulation of a VHF Remote Plasma Source

Abstract

Remote plasma sources are commonly used for chamber cleaning, blanket stripping, downstream abatement, and ashing processes. Most of the current remote sources are designed to operate at very high plasma densities using microwave or inductively-coupled RF energy. Often, these systems are highly tailored for specific applications, and due to the coupling mechanism or chemical incompatibility, the operating ranges are limited. This paper describes a new remote source technology using capacitively coupled, VHF energy to produce a flexible and unique remote plasma generator. The electrode design and internal construction are compatible with most processing chemistries, and allow generation of very low to very high plasma densities across extensive flow and pressure regimes. Due to the expansive operating range and chemical compatibility of the new, VHF RPS, characterization of the device becomes challenging. Engineering simulation methods are being used to supplement laboratory experimentation. Mechanical simulation has been employed to model and optimize aspects of the VHF RPS design, including: process gas flow, thermal performance, and structural reliability. Currently, plasma simulation is also being investigated as a method to augment and enhance characterization of the VHF RPS. Preliminary plasma simulation results are presented and compared to empirical data for a benchmark operating condition. Future work as well as long-term goals for plasma simulation are discussed. bAckgRound The term “remote plasma source” (RPS) describes a plasmagenerating device (source) which is installed remotely from the process chamber. By separating the higher energy plasma discharge (and the externally applied electric field) from the processing chamber, a remote plasma source can introduce a desirable stream of radicals to the substrate surface while minimizing bombardment of the substrate – and the associated damage – from higher energy ions and photons which