Yield improvement and queue time relaxation at contact process

As dimension shrinks in advanced technology nodes, the critical dimension (CD) plays a critical role and so does QTime. Front Opening Unified Pod (FOUP) door closure, delaying FOUP door opening, introducing N2 Purge and creating vacuum at optimum steps and for optimized duration has shown promising results in extending QTime and improving yield. Etch is often performed by reactive ion etching (RIE) process which generally has a physical and a chemical component to it. Etch residues, sometimes polymeric with metallic contaminants embedded inside, have to be removed in timely manner. If post etch residue (PER) is not removed soon enough, this gas/polymer then interacts with moisture inside the FOUP, leading to footing at the Nitride Stress layer and crystal growth on patterned wafers — thereby degrading yield. In this paper, we will discuss various approaches taken to improve the footing at bottom of contacts and increase the Queue Time (QTime) between Etch and Cleans processes.