Effect of H atoms and UV wideband radiation on cured low-k OSG films

Abstract

Effects of hydrogen atoms and UV radiation (λ > 210 nm) on nanoporous organosilicate glass (OSG) low-k films are studied in the temperature range from 20°C to 300°C. The purpose of the study is to understand the mechanisms of low-k films modification that can happen during the cleaning from carbon containing residues formed from sacrificial porogen and accumulated during the air storage. It is shown that exposure of low-k films to hydrogen atoms at low temperature leads to slight modification of hydrocarbon bonds in hydrocarbon residues not bonded to Si. At high temperature (T≥300°C), the relative concentration of -CHx bonds changes in a complex way and depends on the amount and structure of the carbon-containing compounds. The general trend is relatively rapid decrease of –CH2 bonds concentration, while the terminal –CH3 groups are more stable. Temperature also initiates the reaction of hydrogen atoms with low-k with partial modification of low-k matrix breaking Si-O bonds. The destruction of Si-O and Si-CH2 groups leads to the formation of oxygen-deficient centers, followed by the formation of Si-(CH3)2 groups due to their interaction with methyl groups. At 300°C, the total number of Si-CH3 + Si-(CH3)2 groups starts to decrease indicating on partial removal of the methyl groups bonded to silicon. Besides with increasing temperature a slight modification of the structure of matrix under exposure to H atoms is also observed. UV radiation has almost no effect on these processes in the studied conditions. Thus, there exist the “optimal” conditions for H atom impact on OSG low-k films which allows improving film performance by removing porogen residue without damage.