This past summer, I had the opportunity to work in the Microscopy Image and Spectroscopy Tech Lab on the UMSL campus on a project jointly funded by MEMC Electronic Materials and the NASA Missouri Space Grant Consortium. Using transmission electron microscopy, I worked to accurately and precisely determine the thickness of buried silicon oxide layers in a new class of silicon wafers being marketed by MEMC.
I learned a great deal about the world of the exceedingly small during my work. A large part of my summer was spent mastering sample preparation for the TEM. The cross sectional samples of the silicon wafers, being only microns thick, were very fragile and required extreme care and patience to handle. There were times when even a badly timed breath could destroy a day’s worth of work! Once we were ready to take data, I used the Philips EM430 300KV high resolution TEM to take images of the samples at 110k to 240k times magnification to be able to “see” the buried oxide layer. In the images we were able to see the silicon-silicon oxide interfaces and columns of atoms in the silicon crystal. Using the silicon crystal spacings as internal standards in the images, we were able to measure the thickness of the oxide layers to angstrom level accuracy.
In the process of developing the method to measure the thickness of the oxide layer, we also did work on characterizing that “sharpness” and “roughness” of buried interfaces on the atomic level. We also explored the limits of calibrating magnifications of TEM images. Furthermore, I developed a new protocol for preparing cross section samples that I will be posting for future members of the MIST lab to use.
I had a lot of fun this summer. At the beginning of the project I was able to tour the manufacturing facility at MEMC. I was excited to use the TEM, and by the end of the summer, I was allowed to use it pretty much by myself. It was a wonderful experience to be able to use such an advanced and exclusive piece of equipment. I am planning to apply to graduate programs in materials science this winter so I can continue into the world of the incredibly small.
~DANISH ALI, UNIVERSITY OF MISSOURI—ST. LOUIS