CMP Pad Surface Analysis and the Components of Pad Surface Texture
Andrew S. Lawing, Rohm and Haas Electronic Materials CMP Technologies, 451 Bellevue Road, Bldg 6, Newark, DE 19711
Pad surface analysis is a powerful tool to help understand the impact of pad texture on CMP process performance as well as the implications of pad texture on process and consumable design. Pad surface data can be obtained from any number of surface analytical techniques. The most effective are non-contact optical methods such as confocal microscopy or vertical scanning interferometry. These optical techniques can provide accurate 3-dimensional representations of the pad surface. Three dimensional pad surface textural data can be interpreted in the form of pad height probability distribution functions, which provide a statistical representation of how the pad surface is distributed in space. The pad height probability distribution function can be deconvolved into three components arising from: 1) the native porosity of the pad material, 2) the surface texturing process applied to the pad material and 3) polishing process effects on the pad near surface. These data can be used to help drive pad design, pad manufacturing process improvements and CMP process improvements and consumable design. In this talk we will discuss examples of the respective textural components including the characterization of two different pad types illustrating the effect of conditioning on pad materials with differing native porosity and an example illustrating the competing effects of textural restoration from pad conditioning, and pad asperity wear.