Metal Etch Process Improvement based on Methodical Defect Reduction

摘要

Automatic wafer inspection tools were utilized to perform process development for metal etch chamber applications. A series of process studies were instigated with patterned wafers to examine the defect nature and extent after the standard etch process. Comprehensive defectivity studies must involve patterned wafers since many of the process have defects and issues unique to patterned wafers which are not reflected by blanket wafer analysis. A dome cleaning study was performed to evaluate the optimal cleaning conditions. Clean patterned wafers were obtained and processed, and inspected with the wafer inspection system the WF736. Duo to capture the defects. The standard sequence consisted of the following steps: etch, strip, wet dip, and baking. The wafer inspection results determined that there was significant side wall contamination that apparently resulted from the wet dip step. A new sequence was defined which consisted of: etch, and strip only. With this sequence the side wall contamination defects were essentially eliminated. This reduced process was qualified as viable, and provided wafers with sufficiently low defect count that process variables could then be evaluated. The dome cleaning study then provided the BKM based on the wafer inspection and additional analysis. In addition, a golden tool marathon was performed which showed that the new sequence was good to 3000 wafers. No sidewall contamination and no corrosion type defects were observed. One conclusion is that the wet dip may cause problems in fabs which have been incorrectly thought to be due to the etch step. The details of the inspection and examples of the results will be presented.