Supercritical drying for water-rinsed resist systems

Two methods of supercritical resist drying (SRD) using CO2 have been developed for water-rinsed resist patterns. The key to their effectiveness is the use of a surfactant. In indirect SRD, a solution of n-hexane, a CO2-philic liquid, and a surfactant, sorbitan fatty acid ether, first replaces the water, and is in turn replaced with liquid CO? before SRD is performed. The addition of a compound with a high hydrophilic-lipophilic balance to the surfactant compensates for the poor miscibility of water in a solution of n-hexane and sorbitan fatty acid ether. In direct SRD, which does not require a CO2-philic liquid, the water is replaced directly with liquid CO2 containing a surfactant, fluoroether carboxylate, which makes water miscible in CO2; and then SRD is performed. The excellent results Obtained by both methods demonstrate that there is no inherent barrier to the use of SRD on water-rinsed resist patterns. (C) 2000 American Vacuum Society. [S0734-211X(00)01406-2].