Industrial Applications and Devices Using Block Copolymers

6 Industrial Applications and Devices Using Block Copolymers 

One of the first journal articles about block copolymer lithography, introduced by Park and coworkers from Princeton University in 1997, opened the door for future application of block copolymers in lithography (Park et al, 2008). In this pioneering work, a monolayer of poly (styrene-Z /6 cA -butadiene) (PS-Z -PB) was used in two different approaches to create positive-tone holes and negative-tone nanopillars on a silicon nitride substrate depending on the processing technique used on the PB block. 

In the first approach, the PB block was degraded upon exposure to ozone gas. The highly reactive ozone molecules attack carbon-carbon double bonds in the diene backbone, cutting the linkages and converting the polymer into butadiene monomer, which can easily be dispersed in water. The resulting nanostructure consisted of a periodic array of 1.3 x 10 holes per square centimeter in a PS matrix that could then be used as an etch mask for an underlying silicon nitride substrate. 

The second approach demonstrated the ability to switch the durability of the PB block under RIE conditions. In the inverse process, the reactive double bonds in PB can be stained with a heavy metal vapor of osmium tetroxide, dramatically increasing the polymer s CF4/O2 etch resistance relative to the PS matrix ( 2 1 etch ratio of PS osmium-stained PB). This enabled the creation of silicon nanopillars, which foresaw later industrial applications of BCs, as described below. 

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