Direct Fine Powder Spraying Yttria Coatings Using Axial Plasma Technology

High-purity oxide ceramics such as yttria (Y2O3) are popular coating materials against plasma erosion in semiconductor equipment industries. Traditionally the yttria coatings have been sprayed with air plasma using agglomerated-and-sintered powders and are widely used on inner walls of dry etching chambers. The size of semiconductor and flat-panel-display (FPD) production equipment for dry etching has been increasing due to the increased size of Si wafer and the FPD. This trend presents higher requirements on the plasma erosion resistant coatings. Suspension plasma sprayed (SPS) yttria coatings were developed over last 15 years. SPS technology produces highly dense yttria coatings with better properties for erosion resistance and retention of smooth surface against plasma erosion, compared to APS coatings. In SPS process a liquid feedstock is used, which increase the process complex, thus presents more challenges for industrial applications. In this study, direct fine powder spraying using axial plasma technology will be presented. Direct fine powder spraying could produce dense yttria coatings with almost equal coating properties compared to SPS coatings. The effects of the powder types and spraying processes on the coating structures and properties will be discussed.