Method of deep trench formation with improved profile control and surface area

摘要

A method for etching trenches includes providing a patterned mask stack on a substrate. A trench is etched in the substrate by forming a tapered-shaped trench portion of the trench, which narrows with depth in the substrate by employing a first plasma chemistry mixture including O2, HBr and NF3. An extended portion of the trench is formed by etching a second profile deeper and wider than the tapered-shaped trench portion in the substrate by employing a second plasma chemistry mixture including O2, HBr and SF6 or F2.