Accelerated Screening
Process of applying electrical and thermal stress to all semiconductor devices on a single silicon slice before they are separated into individual chips defines the test. Wafer level burn in identifies early life failures by forcing latent defects to appear. Screening occurs early in the manufacturing sequence to save the cost of packaging faulty silicon.
Defect Acceleration
High temperatures and elevated voltages are applied to the circuitry to simulate years of operation in just a few hours. Weak gate oxides or thinning metal traces fail under these conditions, allowing the manufacturer to discard them. Reliability of the final product delivered to the customer is improved through this method.
Equipment Capacity
Specialized probe cards with thousands of tiny needles are used to contact the pads on every die simultaneously. The complexity of these interfaces makes the setup expensive to design and maintain. Large-scale production requires multiple burn-in chambers to handle the volume of wafers coming off the line.
Yield Impact
Removing the infant mortality portion of the population reduces the number of field returns and warranty claims. Although this process lowers the initial yield of the wafer, it ensures that the surviving parts have a much higher probability of reaching their full service life. Tracking the failure patterns across the wafer surface provides valuable feedback to the fabrication team for improving the manufacturing process.
Statistical analysis of these results helps to refine the stress parameters for future product generations. Final test results are used to update the process control charts for the lithography and etching stages.
