Use a SEM on a Production Line?

The use of the scanning electron microscope (SEM) as an in-line, quality control tool to selectively sample-screen semiconductor devices for metallization anomalies is recommended in future procurements. Experiences with failed devices at GSFC have led to development of an inspection technique and a subsequent specification which are discussed in this report. Criteria (with typical demonstrative photographs) are proposed for distinguishing between acceptable and unacceptable units and the viewing parameters necessary to effect meaningful examination are given; viz., the angle of sample tilt relative to the primary beam, the proper sample rotation relative to contact windows, and the necessary magnification range. The proposed sampling and inspection procedure is designed to create minimum perturbation in the normal manufacturing process and to detect, at an early stage, those metallization anomalies which affect device reliability and which cannot be resolved by the optical microscope during preseal visual inspection. The procedure, as well as lot acceptance plan, is outlined pointing out both the advantages to the user and the manufacturer. Preliminary results and manufacturers´ acceptance of this plan will be discussed.