New application of laser beam to failure analysis of LSI with multi-metal layers

A new technique for failure analysis of LSI with multi metal layers is described. There is a fabrication technique to form a big and optional window on upper layers using Nd-YAG laser without destroying any electrical function, and to approach the failure point through this window. The failure analysis procedure based on logical flow is presented. Fabrication technique is located in part of this procedure which consists of four steps. Two difficult reasons for approaching the failure point without fabrication technique are described. This difficulty results from line composition and line width. The fabrication procedure using Nd-YAG laser is reported. This procedure is to cover the chip surface with photo resist, and form a big and optional size window on upper layer with laser beam, and finally expose the purposed layer. Three failure analysis examples using this technique are introduced: unformed contact falure mode, Si-noduled failure mode, and isolation destroying failure mode.