A Comprehensive Overview of Plasma Surface Interactions with RFEA Measurements

Abstract  

The understanding of plasma-surface interactions is key to solving the challenges in modern nanofabrication. Typically, recipes are designed with particular powers, pressures, gases and run times in a specific plasma tool, with those parameters varied until the desired features are achieved. But, the fundamental surface interaction parameters of ion energy, ion flux, ion/neutral ratio and ion angular distributions are rarely reported or known for those conditions. Without this information, transferring or scaling a process is not possible without starting from scratch.  

 

In this talk we will demonstrate the role of energetic ions in plasmas and how they affect the properties of materials etched or deposited in plasma processing. We will show how to use measured ion flux, ion energies and ion-neutral fractions to optimize industrial plasma-assisted processes. For example, sputtering modifies the surface morphology and can also alter the compositional structural properties of the surface. Potentially leading to changes in its physical and chemical behavior. We will present ion data which will give insights into common issues such as high aspect ratio profile errors, RIE-lag and why quasi-ALE happens instead of true ALE. We will also give the general trends of how ions behave under different tool conditions, to give an intuition of why raising ICP power or lowering bias is needed to achieve the right final substrate features. [1-4] 

 

The data presented will be from ion energy analysers. Etch data will be from the Semion RFEA, which measures the ion energies, the ion flux, negative ions, and bias voltage hitting surfaces inside a plasma chamber. Deposition data will be from a Quantum RFEA, which is an energy resolving gridded quartz crystal microbalance (QCM), used to measure the ion-neutral fraction hitting a surface inside a plasma reactor. This instrument also measures the etching/deposition rate, ion energy, ion flux and bias voltage [1]. 

 

References  

[1] Impedans Ltd, Dublin, Ireland [www.impedans.com]  

[2] H. B. Profijt et al., J. Vac. Sci. Technol. A 31, 1 (2013) 

[3] M. H Heyne et al., 2D Mater. 6, 035030 (2019) 

[4] S. Karwal et al., Plasma Chemistry and Plasma Processing 40, 697–712 (2020)