TABLE OF CONTENTS Variability in manufacturing processes can lead to deformations or nonconformities in finished products. Such process disturbances often result in faults, or unintentional changes in the performance or conformance of electronic products. The presence of such faults is quantified by the manufacturing yield. Yield is defined as the percentage of devices that meet a nominal performance specification.
Yield can be categorized as either functional or parametric. Functional yield is determined by the proportion of fully functional products. Often referred to as hard yield, the functional yield of microelectronic products is usually characterized by open circuits or short circuits caused by physical defects, such as particles. In some cases, however, a fully functional product still fails to meet performance specifications for one or more parameters, such as speed, noise level, or power consumption. These situations are described by parametric yield or soft yield.
The development of models to estimate the functional yield of microelectronic circuits and packages is fundamental to manufacturing. A model that provides accurate estimates of manufacturing yield can help predict product cost, determine optimum equipment utilization, or be used as a metric against which actual measured manufacturing yields can be evaluated. Yield models are also critical to support decisions involving new technologies and the identification of problematic products or processes.
As previously mentioned, functional yield is significantly impacted by the presence of defects. Defects can result from many random sources, including contamination from equipment, processes or handling, mask imperfections,...
