Novel application of ultrasonic decapsulation and etching in failure analysis

Abstract

Ultrasonic cleaner is a workhorse in all failure analysis labs for residue removal after decapsulation or etching. In this paper, we present a novel method of ultrasonic decapsulation, where acid mixture was used in conjunction with ultrasonic agitation and was discovered to provide exceptionally high quality preservation of the surface of the copper bond wires which exceeds the quality of laser decap which induces thermal damage to the surface of the wire, while highly accelerating the mold compound etching process at room temperature. High quality preservation of the wire surface is sometimes needed to investigate the root cause of the failure. The paper also describes a few case studies of where ultrasonic etching using acids were used for accelerated selective etching of materials and improvement in delineation.