International Business Machines Corporation

Roger W Fleury

Jon A Patrick

A method of dynamically switching the voltage screen test parameters without falsely rejecting over stressing short channel length devices. Protection to more vulnerable devices is provided by determining the speed of the die prior to the voltage test screen, segregating the devices based on operational speed performance. A lower voltage is effectively applied during wafer probe test to the faster devices, which directly correspond to the population of short channel devices. Device speed is acquired by measuring the drain-to-source current of each FET, and dividing the resultant sum by the device gate channel width. The device with the higher values represent the faster devices. Alternatively, since faster devices draw more current, the supply current specification may be adjusted based on operational speed measurements.

Method of dynamically switching voltage screen test levels based on initial device parameter measurements

This invention teaches an apparatus and method for determining a more efficient quality assurance or reliability test screen without falsely rejecting, i.e., over stressing, short channel length devices during voltage stress test screening. Short channel lengths devices fabricated on a semiconductor wafer have a higher tendency to fail at voltage levels that would otherwise not harm long channel length devices. The failures, however, are not related to device defects. Protection to the more vulnerable devices is provided by determining the speed of the die prior to the voltage test screen, thus, segregating the devices based on operational speed performance. Next, a lower voltage is effectively applied during wafer probe test to the faster devices, which directly correspond to the population of short channel devices. A preferred measurement for device speed entails measuring the drain-to-source current of each FET, and dividing the resultant sum by the device gate channel width. The devices with the higher values represent the faster devices. Alternatively, since faster devices draw more current, the supply current specification may be adjusted based on operational speed measurements, for fast and slow devices accordingly.

Dynamically switched voltage screen

Method for determining a more efficient quality assurance or reliability test screen without falsely rejecting, i.e., over stressing, short channel length devices during voltage stress test screening. Short channel lengths devices fabricated on a semiconductor wafer have a higher tendency to fail at voltage levels that would otherwise not harm long channel length devices. The failures, however, are not related to device defects. Protection to the more vulnerable devices is provided by determining the speed of the die prior to the voltage test screen, thus, segregating the devices based on operational speed performance. Next, a lower voltage is effetively applied during wafer probe test to the faster devices, which directly correspond to the population of short channel devices.

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Jericho, VT, United States of America

Roger W Fleury