Plasma and Free Radical Interactions with Surfaces

Collaborations:

Prof. David Graves (UC Berkeley)

Dr. G. A. Antonelli (Novellus Systems)

Prof. Jincheng Du (UNT)

Prof. G. Verbeck (UNT)

 

Introduction

    Plasmas are complex environments involving exciting neutrals, ions, photons, and electrons.  The separate and synergistic interactions of these species with surfaces are in general poorly understood.  Major applications involve microelectronics processing, particularly the oxygen plasma-induced stripping of photoresists and consequent damage to ultralow-k dielectric materials.  Other applications involve surface modifications for biocompatibility, and fundamental studies of surface oxidation and related properties.  Although currently focused on conventional plasma and free radical applications in microelectronics and II-VI surface chemistry, future efforts will include the application of low temperature atmospheric plasmas to surface modification and etching.  We can generate millitorr plasmas in our plasma/XPS system.  Generation of thermal free radicals is by a catalytic cracker capable of operating under UHV conditions (fig. 1).  An atmospheric plasma jet source (in collaboration with Prof. G. Verbeck) is planned for the near future.  Evolving interactions involving Profs. Verbeck, Du, Cooke and Kelber (all at UNT) have led to the formation of the Physical Electronics Working Group.

 

Recent Accomplishments:

Fundamental Damage Mechanisms for Oxygen Plasma Etching of Organosilicate (SiCOH) Films

 

    In collaboration with Profs. Grave, Du, and Dr. Antonelli, we have recently demonstrated that:

  • Thermal oxygen in the electronic ground state (O(3P), <E kin>, < ~0.1 eV) is a principal reactive agent for methyl abstraction and silanol formation in organosilicate films
  • The kinetics of methyl abstraction are dominated by the diffusion of low energy O radicals through nanopores in ultra-low k organosilicate films.
  • Methyl abstraction and related damage processes are inhibited by He plasma pretreatment, or by minimizing pore interconnectedness (diffusivity) while maximizing pore volume. (fig. 2)