Specific CMP process requirements

In the early days of CMP, when the process engineers had recognized that the planarization technology developed for very large-scale integration devices could also be of benefit for their MEMS structures, they transferred the processes almost one-to-one to their applications. But it showed very quickly that they had to adjust these processes to the specific manufacturing requirements of their structures. 

While the roughness of the polished surface is of very high importance for More Moore because of the further decreasing layer and stracture dimensions, optically flat, that is, mirror-like, surfaces are especially required for MOEMS devices. For mirror stmctures using poly-Si surface micromachining, processes based on those developed for atomically flat surfaces for Si wafer fabrication can be employed successfully. 

Otherwise, micro-scratches and other defects can be less critical. Also, post-CMP cleaning and surface contamination play a minor role. Small scratches can be tolerated 

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The advancements of microelectronics with its increasing device performance and decreasing structure dimensions, which recently fell below the 100-nm mark, follow the path given by Moore s law. In contrast, microfabrication deals with a broad range of structure dimensions between submicrometers and millimeters [7]. The main developments in CMP are traditionally connected to those in advanced IC manufacturing. In recent years, however, the CMP equipment and consumable communities have also paid close attention to microfabrication. It is recognized that MEMS-specific CMP processes require dedicated consumables [8] and optimized tool sets [9] due to their diversity in structure dimension and materials to be processed. 

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