Optimizing CMP for Ultra-Low-k Dielectrics

摘要

Optimization of chemical mechanical planarization (CMP) is crucial for reliable integration of ultra-low-k (ULK) materials for the next technology nodes. We present a quantitative road map for optimized CMP of ULK in which critical factors such as defect evolution, CMP damage, diffusion, effective k increase, and CMP removal rates are for the first time all correlated. Additions of common nonionic surfactants are shown to have dramatic effects on defect evolution. In addition, the surfactant melts and their aqueous solutions can readily diffuse in even strongly hydrophobic nanoporous ULK films affecting k values. Finally, the same solution chemistries and surfactants are shown to have an important effect on CMP removal rates. Measured defect growth rates, solution diffusion coefficients, and removal rates varied markedly depending on molecular weight, hydrophilic-lipophilic balance (HLB), and molecular structure of the surfactants. A roadmap is provided in which all of these variables are quantitatively correlated.