The incoming clean of raw silicon wafers: challenges, root causes and possible solutions

An investigation of the cleaning efficiency of different raw wafer materials from different vendors is presented using a standard clean 1 and standard clean 2 incoming cleaning procedure. It will be discussed whether the observed material and vendor dependency is caused by the incoming clean, the used manufacturing tools or by the wafer material itself. By using particle and contact angle measurements, QCEPT, REM and EDX, significant variations of the raw wafer surface were found before and after the incoming clean. Thus, an analysis of the entire raw wafer supply chain was performed including production, packaging, transport and unpackaging of the wafers. A determination of the root cause of the observed cleaning inefficiencies was possible and solutions to overcome the apparent cleaning inefficiency could be derived.