X-Ray Wafer Probe for Total Dose Testing

An x-ray source has been developed for total-dose irradiation testing of semiconductor electronic devices at the wafer stage of fabrication. This Semiconductor X-ray Test Source, as it is designated, was designed to provide an intense, uniform exposure to the device under test. The dose-rate range of 50 to 2×105 rad(Si) per minute allows test flexibility, high throughput, and facilitates standardization with fixed dose-rate sources. Bias to the die being irradiated is applied by the wafer prober; and a collimator mounted on the probe card permits the irradiation of discrete areas of the wafer or individual die. An electronic shutter system permits manual or automatic operation. A silicon detector provides a direct measurement of the dose-rate delivered to the device under test. Good correlation between doses administered by a cobalt-60 source and the test source has been demonstrated. Routine probe testing sequences can be accomplished automatically through a computer interface. Safety features include an enclosure that is both radiation-safe and light-tight; a vital shutter system; interlocks; and a warning light.