Meaning
The percentage of manufactured microchips that meet all specific electrical and performance criteria, such as speed and power limits, defines the quality of a wafer batch. If a chip is functional but consumes too much power or runs too slowly, it fails the parametric yield limits. This metric is different from functional yield, which only checks if the chip works at all.
Performance Sorting
Measuring the performance of chips requires testing them under extreme voltage and temperature conditions. Those that fall outside the limits are either discarded or sold at a lower price. This process helps manufacturers recover some of their costs.
Contractual Guarantee
Supply contracts for high-performance servers often specify a minimum parametric yield for the delivered batches. If too many chips are slow, the buyer can reject the lot or demand a price reduction. This contract clause forces the foundry to maintain tight control over their manufacturing processes.
Foundry Optimization
Adjusting manufacturing parameters, such as the thickness of the gate oxide or the concentration of dopants, allows the foundry to optimize the performance of the chips. The foundry monitors these changes continuously to ensure that the process does not drift over time. This continuous adjustment prevents the parametric yield from dropping, which protects the profitability of both the foundry and the customer by ensuring a steady flow of high-margin products.
