Fundamentals of laser photoemission for testing high speed devices and circuits

Abstract

Photoelectron emission has been widely exploited for the understanding of the electronic structure of materials. This knowledge base, both the underlying physics and the instrumention, may provide a valuable basis for recent interest in applying photoemission to the voltage testing of high speed semiconductor devices and circuits. By coupling photoemission measurements to advanced laser systems, it appears that rapid measurements can be made with picosecond time resolution to determine ac switching transient waveforms as well as dynamic logic states. Laser photoemission testing also provides the possibility of truly damage-free contactless testing (laser photon energy below insulator band gap), parallel (simultaneous) measurement at an array of points on the chip, and measurement at wiring nodes which lie beneath passivation (insulator) layers. This paper reviews the physics of photoemission and current ideas for exploiting laser photoemission for high speed contactless voltage measurements.