Electron Radiation as an Indicator of Gold Nodule Defect during E-beam Evaporation

Kezia Cheng
Skyworks Solutions, Inc. 20 Sylvan Road, Woburn, MA. kezia.cheng@skyworksinc.com (781) 241-2821

Keywords: … Back scattered electron, E-beam evaporation, Gold nodules, Gold spitting

Abstract

Gold (Au) nodule defects are a common problem during metal deposition by evaporation. Small Au spheres, often referred to as spits in the semiconductor industry, can be ejected from the molten source under certain conditions. If the nodules land on the bottom electrode of a metal-insulator-metal (MIM) structure, the capacitor can fail under operating stress and is a reliability concern. Larger particles can cause electrical short circuits and even damage expensive test probes. Although rarely published, there are several known causes for this problem. We have identified several factors that directly influence Au nodule defect density and different mechanisms that lead to spitting. This paper will focus on the material aspect of the spitting phenomenon. The mechanism by which the carbon in the Au source promotes spitting will be explained. We will provide results from our experiments that confirm carbon level in the source material is directly proportional to the spit count on an evaporated film. We will also show that by fabricating an electrode in the evaporator chamber, we are able to determine the cleanliness of the source by the measured electrical potential and therefore prompting us when a melt needs to be replaced before spitting occurs.

Paper 13.10.pdf