Implementation of laser beam sensitive cells: A new approach for integrated circuits testing

Abstract

The use of library cells, specially designed for their sensitivity to a laser beam, is a potential solution for both 'observability' and 'controllability' problems encountered by the test engineers. The basic principle relies on the photo-induced current generated in the laser beam-silicon interaction. The 'observation' cells, when probed by the beam, are used to read directly a logic level inside the circuit, whereas the 'control' cells are used to force a particular node of the circuit. A test structure including a 16 bits counter with 16 'observation' cells and 1 'control' cell has been fabricated in BiCMOS technology in order to illustrate this new testing method.