Meaning
Percentage of manufactured units that fail to meet specification and are discarded during the production cycle. Calculating yield loss provides a metric for assessing the stability of a fabrication process. High rejection rates often stem from contamination or equipment misalignment.
Monitoring these statistics allows for the identification of systemic errors in the manufacturing chain.
Defect Distribution
Particle contamination on a wafer surface causes localized circuit failures. This yield loss is often concentrated in specific areas where the cleanroom environment has been compromised.
Process Variation
Inconsistency in the etching or deposition stages leads to devices that operate outside of the required electrical tolerances. Fluctuations in the thickness of the gate oxide contribute to this yield loss by altering the transistor threshold voltage. Regular calibration of the production machinery is required to keep these variations within acceptable limits.
Financial Consequence
Reduced output of functional chips increases the effective cost of each individual unit sold to the customer. When yield loss is high, the manufacturer must process more wafers to meet the target volume for an order. This inefficiency wastes raw materials and energy while occupying valuable time on the production line.
Large scale operations rely on high yields to maintain a competitive price point in the market. Accurate tracking of these losses identifies specific stages in the production line that require optimization.
