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CMP (Chemical Mechanical Planarization) removes material from uneven topography on a wafer surface until a flat (planarized) surface is created. This allows subsequent photolithography to take place with greater accuracy, and enables film layers to be built up with minimal height variations. CMP combines the chemical removal effect of an acidic or basic fluid solution with the "mechanical" effect provided by polishing with an abrasive material. The CMP system usually has a polishing "head" that presses the rotating wafer against a flexible pad. A wet chemical slurry containing a micro-abrasive is placed between the wafer and pad.
CMP is performed primarily in the interconnect structure of the chip, where it is used multiple times. CMP is especially critical to fabricating copper-based semiconductors, where it is used to define the copper wiring structures. This advanced planarization capability enables chipmakers to continue shrinking circuits and extends the performance of lithographic tools. |
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