Electrical Test and QML Test

Electrical Wafer Testing

Table showing post wafer fabrication testing at the Microcircuit Emulation Center
Test Description
Wafer Acceptance Testing (WAT) Post-wafer fabrication testing of dedicated test structures to ensure the wafer processing was executed correctly
Wafer Level Reliability (WLR) Wafer level lifetime testing of dedicated test structures to ensure reliable performance
Wafer Sort Wafer level functional testing to determine yield of each circuit die within a wafer

ELECTRICAL TESTING TO VALIDATE WAFER FABRICATION

  • Wafer level testing and reliability screening are performed in compliance with MIL-PRF-38535 procedures after wafer fabrication and before assembly and packaging of the die
  • Wafer Acceptance Testing (WAT), also known as Process Control Monitoring or the Parametric Monitor, measure and verifies:
    • Wafer processing has been executed correctly
    • Electrical measurements are uniform and within the specification limits across the wafer
  • Each test site includes 100 to 500 parametric measurements (including, but not limited to):
    • Threshold voltage
    • Sheet resistance
    • Contact resistance
    • Transistor gain
    • Breakdown voltage
  • Wafer Level Reliability (WLR) testing performed on the Technology Characterization Vehicle (TCV)
    • Provides lifetime expectations based on intrinsic failure or wear-out mechanisms
    • Ensures that all wafer processing produces acceptable levels of reliability
    • Measurements are taken to analyze structures for:
      • Metal electromigration
      • Hot carrier degradation
      • Oxide integrity
      • Other indicators for performance overtime
  • WAT and WLR tests are performed in a climate controlled micro-chamber to perform parametric testing over the full Mil-Spec operating temperature range (-55 °C to +125 °C)

WAFER SORT (FUNCTIONAL) ELECTRICAL TESTING

  • After wafer manufacturing, wafer sort testing is performed to verify functional performance of each microcircuit on the wafer
  • Automated Test Equipment (ATE) systems perform both digital and analog testing with customized test programs and dedicated test fixture hardware

Once wafer level testing is successfully completed wafers are diced and sent for assembly and packaging.