On the impact of nanotopography of silicon wafers on post-CMP oxide layers

The impact of nanotopography of silicon wafers on the thickness homogeneity of oxide layers after deposition and chemical-mechanical polishing (CMP) is investigated. Comparison of nanotopographical height with post-CMP oxide thickness for the same position on a wafer may result in inconclusive data with no obvious correlation. However, a simple relation is obtained when (i) the root-mean-square roughness of nanotopographical height (sigma(NH)), (ii) the standard deviation of post-CMP oxide thickness (sigma(OTD)) and (iii) the standard deviation of post-CMP oxide thickness caused only by fluctuations of the combination of oxide deposition and CMP (sigma(CMP)) are considered: sigma(OTD)(2) approximate to sigma(CMP)(2) + alpha(lambda(P))(2).sigma(NH)(2) . alpha(lambda(P)) is a coefficient that is fairly independent of the nanotopography features of wafers, but which depends on the planarization length lambda(P) of the CMP process applied. Using data by Boning et al., the relation alpha(lambda(P)) = -(0.09 mm)lambda(P) + 0.12, 1.3 mm < λ(P) < 12.4 mm is obtained with an r(2) of 0.96. Otherwise, alpha(lambda(P)) approximate to 0 for lambda(P) < 1.3 mm and α(λ(P)) = -1 for λ(P) > 12.4 mm. (C) 2003 Elsevier Science Ltd. All rights reserved.