Abstract
Roughness on silicon wafers is becoming a critical surface parameter with the advent of improved semiconductor processes. Roughness levels in the order of 1 angstrom are routinely manufactured, challenging the limits of some micro-roughness measurement technologies. Additionally, measurement is moving from R&D and Q.A. areas into the manufacturing line placing more emphasis on speed of analysis, robustness, correlation and repeatability of the various techniques. This paper attempts to identify, review, and correlate suitable techniques for measurement at such low levels of micro- roughness. The strengths and weakness of each technique from a production viewpoint are also touched upon. Wafer roughness measurements were used to characterize a set of semiconductor wafers with a varying dopant and process characteristics. One hundred, 8' bare wafer samples with various dopants were prepared for measurements in the order of 1 angstrom to 2 angstrom. The samples were then measured with different methods using total integrated scatter (TIS), atomic force microscopy (AFM), interferometry (IF) and optical profilometers (OP). These techniques differ in many ways in their assessment of surface roughness and the results from each technique are presented and a discussion of the correlation issues between the different measurement systems is given.
