Cu Pad Size and Linewidth Affect Dishing

Although the exposed Cu can immediately react with oxygen to form an oxide film, the film is porous and not of a self-protective nature. Therefore, a capping material, such as SiN, is necessary to prevent the corrosion of Cu. Unfortunately, the Cu corrosion depends on the delay time from the CMP polish of Cu to deposition of the protective layer. On the production line, the manufacture available time and efficiency are very hard to reach 

After ECP Plating After Cu ECP Polish 30nm IMP TaN Capping Cu CMP TaN Re-polish 

FIGURE 4.27 TaN capping process procedure. 30 tun TaN was capped after Cu CMP, and after TaN repolishing there remains a very thin TaN layer on the Cu surface. 

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