Mechanism of inhibitor action in novolak film

摘要

In the original percolation model of novolak resists, dissolution inhibition was through to occur through the blocking of hydrophilic (phenolic) percolation sites by the inhibitor. Closer analysis revealed that mere site blocking cannot account for the size of the inhibition effect observed in practical systems; a more profound reorganization of resin structure is needed. In this communication it is suggested that hydrogen bonding between OH-groups leads to the formation of phenolic clusters in concentrated novolak solutions, and these clusters are preserved in the solid films. The introduction of the strong acceptor groups of inhibitors reinforces the cohesion in the clusters and concentrates the OH-groups. In this way the inhibitor creates a deficit of hydrophilic sites in other areas of the percolation field, thereby lowering the dissolution rate.