Optimized BARC films and etch byproduct removal for wafer edge defectivity reduction

In semiconductor manufacturing, wafer edge defects such as films cracking, delaminating, surface damage, and particles have been reported. They are a major source for yield fallout. Inadequate edge bead removal (EBR) has a significant contribution to this class of defects. One method of EBR and wafer bevel cleaning is to dispense solvent on the back side of the wafer as the wafer is spinning. By controlling the speed, one can control how far the solvent can reach the outer edge and top side. In via and contact modules the etched holes are filled with tungsten (W). Any organic residue on the edge of the wafer will prevent good adhesion of W to the substrate and eventually cause metal delamination. In this paper we focus on delamination defects that are caused by poor metal adhesion due to organic residue. A designed experiment that includes contact photolithography, wafer spinning speed during solvent back side cleaning, etch and post etch organic films striping and byproduct removal steps has been used to modulate edge defectivity. The amount of edge defects has been quantified by counting the number of metal peeling sites at the edge of the wafer post contact hole filling. By optimizing the dry plasma process that is used for post etch organic films removal, the organic residue that is left from the photolithography step can be effectively removed. In this novel method, the removal of the organic residue from the EBR step has been integrated with the post etch photoresist and organic bottom antireflective (BARC) films strip. No solvent or acid use is required. The etch byproduct and residue are converted to a volatile byproduct that is pumped out from the plasma chamber and non volatile residue is converted to a water soluble compound. The plasma step is followed by a DI water rinse.