The Challenges

As chips become more complex, wafer probing in the product environment becomes increasingly difficult. Greater chip functionality increases the number of bond pads, or pin-count on a chip. The pin-count of a chip is typically several hundred and can be as high as 3,000.

As feature sizes decrease, bond pads become smaller and the distance between the centers of adjacent pads or pitch decreases. In addition, all probe touch-downs deform the bond pad metal and can cause damage to the material surrounding the bond pad if the probe tip is misaligned. Damage to material surrounding bond pads results in diminished yields. Excessive bond pad damage can cause unreliable electrical connections to the pads when the chip is packaged. Smaller pads make the chip more susceptible to such damage.

Market pressures to produce more complex and less costly chips are driving chip suppliers to seek new wafer probing technologies capable of meeting the test requirements of increasingly complex chips while reducing the effective test cost per chip. Compounding these pressures, production engineers are expected to decrease time to yield or the time required to achieve acceptable yields for a new chip or manufacturing process to reach productive levels in increasingly expensive fabrication facilities.