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What is Wafer Testing? How to perform wafer testing?

wafer testingWafer testing is a pin test of each die on a wafer to check its electrical characteristics.wafer tester During the test, the wafer is held on a vacuum suction chuck and aligned with a probe galvanometer while the probe makes contact with each solder pad on the chip. The galvanometer is driven by a power supply to test the circuit and record the results. The number, sequence and type of tests are controlled by a computer program.

The objectives of wafer testing include:

1. Identification of Qualified Chips: Tests to determine which chips are qualified before the wafers are sent to the packaging facility.

2. Characterization: Characterize the electrical parameters of the device/circuit and monitor the distribution of the parameters to maintain the quality level of the process.

3. Accounting for Passes and Defects: Counting the number of passes and defects on a chip provides feedback to wafer production personnel on overall performance.

As the area of the chip increases and the density increases,wafer probe testing the cost of wafer testing is getting bigger and bigger. As a result, longer test times and more sophisticated and complex power supplies, mechanical devices, and computer systems are required to perform test work and monitor test results. Visual inspection systems have also become more sophisticated and expensive. To simplify the test process and increase efficiency,vibration isolation table designers introduce memory arrays for testing and use simplified test procedures after the chip parameters have been evaluated and qualified. Alternatively, chips on a wafer can be tested in interlaced rows or multiple chips can be tested at the same time.