Effect of Other Additives on Cleaning

Citric acid + BTA Citric acid + BTA+NH,OH Citric acid + BTA+TMAH (pH 2) (pH 6) (pH 6) 

FIGURE 16.24 The adhesion forces between Cu wafers and spherical silica particles in different solutions. 

FIGURE 16.25 FESEM images of the Cu surfaces (a) before and (b) after dipping in slurry cleaned with (c) DI water, (d) citric acid solution with BTA, (e) citric acid and BTA solution with NH4OH, and (Q citric acid and BTA solution with TMAH (from Ref. 43). 

5 ADHESION FORCE, FRICTION FORCE, AND DEFECTS DURING Cu CMP 

As described in the last section, the adhesion forces between the particles and the polished surface can provide insight into post-CMP cleaning mechanism and efficiency. As a matter of fact, measurements of adhesion force and alike can directly help in the understanding of CMP and post-CMP cleaning processes. In this section, some basic principles and applications of adhesion and friction force measurements in copper CMP will be presented. The discussion is certainly applicable to post-CMP cleaning processes when similar systems are involved. 

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