An introduction to process visualization capabilities and considerations in the environmental scanning electron microscope (ESEM)

Process visualization can be a very powerful tool for understanding dynamic processes. Process visualization requires a non‐destructive technique that can be monitored in real time. In this paper various methods of non‐destructive inspection will be described and compared. The applicability of these non‐destructive inspection methods to process visualization will be compared and contrasted. Particular attention will be paid to a recent development in this area, the environmental scanning electron microscope (ESEM) which is inherently a non‐destructive inspection technique with the advantages of electron microscopy for superior magnification and depth of field capability. The ESEM offers a unique platform for process visualization studies. The majority of process visualization is currently done using optical microscopes with hot stages for observing morphological effects top down (optical microscopes) or from the side (contact angle). Major limitations of these optical methods include lack of magnification, poor depth of field, and clouding of optics. Process visualization is best carried out utilizing a non‐destructive technique, such as the ESEM, since invasive sample preparation techniques such as conductive coatings alter the sample and make interpretation more difficult. Common process variables such as thermal profiling and the effect of ambient conditions have been examined using the ESEM. Other process variables that could be of interest in the future will be discussed. There are limitations in the ability of the ESEM to reproduce actual process conditions, such as pressure and mass flow rate trade‐offs. The ESEM can also be combined directly and indirectly with other analytical techniques to determine the composition of the sample and/or byproducts of a reaction that is being monitored. This paper will serve as an overview and introduction for several papers which deal in depth with specific process visualization applications which utilize the ESEM. A series of illustrative examples of previous work will be referenced and briefly discussed. The examples will emphasize the importance of non‐destructive testing techniques in material science and semiconductor applications. The application window of the ESEM for process visualization will be explored, including trade‐offs in process conditions that can be examined. Observation of dynamic processes include examples such as corrosion studies of various materials such as stainless steel and thermal studies of industrially relevant processes such as ceramic processing, soldering, and sealing. Morphological and compositional process visualization applications will be presented. An example of morphological applications observed is solder reflow and intermetallic formation as a function of the materials used and the atmosphere during processing. Morphological coupled with compositional applications include monitoring outgassing products from solder paste and Ag/glass die attach material. © 1993 Wiley‐Liss, Inc.