Wafer zone based yield analysis

The wafer fabrication process can produce both global problems that uniformly reduce the wafer probe yields and regionally distinct problems that reduce the yield of specific regions of the wafer. This paper discusses the methods used to develop simple programs capable of finding and reporting severity of low yielding wafer regions. Wafer regional yield trend graphs are explained and the comparative interpretation of yield trend changes is discussed. Finally, the methods used to correlate the regional yield changes to specific units of process equipment at specific process steps are briefly explained