The Price Curve between Accuracy Grades in One Product Family
Sensor accuracy price curves scale exponentially because higher tiers demand longer thermal chuck dwell times, lower silicon yields, and guard-banded calibration.
Process Variability
Deviation Factor
Inherent fluctuations in the chemical and physical processes used to manufacture semiconductors lead to differences in the performance of chips from the same wafer. Managing process variability requires designers to create circuits that can function correctly even when the transistor speed or the resistance of the interconnects varies. These differences are a fundamental property of high volume manufacturing.
Wafer Variation
Measurements taken at the center of a silicon disc often differ from those taken at the edge due to the way gases flow in the reaction chamber. Process variability shows up as a distribution of parameters like threshold voltage or leakage current across the entire lot. Engineers use statistical process control to monitor these distributions and ensure they stay within the allowed limits.
Design Margin
Safety factors are built into the timing and power calculations to account for the worst case corners of the manufacturing process. A design that does not account for process variability will fail to yield functional parts when the manufacturing conditions shift slightly.
Quality Control
Final testing at the end of the production line filters out the units that fall outside of the specified performance window. This ensures that only parts meeting the datasheet requirements reach the customer.