Particle Defect Reduction Through YF3 Coated Remote Plasma Source for High Throughput Dry Cleaning Process

We present the reduction in number of post process particles by use of YF
₃
coatings on an alumina plasma reactor for fluorine chemistry based dry cleaning. With the introduction of highly reactive gases such as fluorine in semiconductor dry cleaning processes, especially within highly energetic plasmas, physical and chemical reactions between equipment parts and process gases continues to become an issue. Unaccounted for compounds and microstructures on tools leads to increasing particle defects on product wafers. The plasma density and ion energy is especially high at the dielectric walls of the remote plasma source (RPS). By utilizing a 150 micron YF
₃
layer to coat the plasma dielectric walls of our high selectivity oxide removal tool, we were able to eliminate the formation of AlO
_x
F
_y
microstructures on the ceramic reactor surface, which in turn led to a greater than 85% reduction of “spark”-like particle contaminants near the centers of product wafer surface. Meanwhile electrical properties, etch rates, and selectivity were largely unaffected when compared to uncoated reactors. Surface profiler measurements showed an increase in surface roughness after coating, however a large reduction in reactor surface etch depth was shown after several hundred hours of processing. Furthermore, AlO
_x
F
_y
particles were not detected by Energy Dispersive X-Ray Spectroscopy (EDS) on wafers processed with the YF
₃
coated RPS, in contrast to results from uncoated sources.