Aluminum is one of the main materials used in semiconductor manufacturing. It provides conductive interconnection lines for the device so that signals can be transmitted throughout the device. Any defects existing in this layer can cause interruption of the signal. Reducing the number of these defects is crucial for device yield improvement and circuit performance. With the INSPEX pattern wafer inspection system, a killer defect was located in our aluminum sputter process. Through a systematic approach, it was confirmed that the transfer of wafers from the production cassette to/from the sputter cassette produced aluminum contaminants on the wafer. These contaminants originated from the silicon wafer scraping the aluminum cassette groove and produced various sizes of aluminum particulates on the wafer surface. These contaminants were carried to the following patterning process and causes bridging and/or broken aluminum lines. After the defect source had been isolated, an automatic wafer transfer system was recommended for proper wafer handling. Now this defect has been eliminated. This study shows that in process development it is important to consider all possible contamination sources for total defect reduction.
"Defect reduction on the metal sputter cassette transfer system", Proc. SPIE 1802, Microelectronics Manufacturing and Reliability, (14 January 1993); doi: 10.1117/12.139363; https://doi.org/10.1117/12.139363