Wafer fab yield is a driving force for many FA activities and can originate from fab process interactions, fab defects, design issues, reliability fails and customer returns. This presentation will provide an overview of various types of yield issues and sources of yield loss. The difference between systematic and and random yield loss mechanisms will be described. Common terminology and general approaches to yield analysis and yield improvement will be discussed. Several case studies that involved failure analyis to help resolve yield issues will be given.