Work-induced stress and long-term stability in optically polished silicon

A matrix of experiments was used to diagnose the presence and effect of surface stress in single crystal silicon as a result of various optical fabrication processes. These experiments employed a series of prepolished silicon samples, 4.5 inches in diameter, one surface of which was then subjected to fabrication procedure(s) typical to the refinement of a silicon optical component. The unaltered face was preserved in its originally-polished condition and interferometrically measured to detect changes of contour resulting from changes in stress characteristics imposed on the opposite, altered face. Samples representing specific process histories were periodically removed from the matrix and retained for long-term observation and assessment of any transient behavior. For comparison, a series of unaltered samples were retained for observation in the originally-polished condition, and a series of disks were also processed through the matrix from a rough blank state. the data collected during this effort are presented and discussed.