A novel bilayer resist approach using radiation sensitive organometalics precursors

摘要

A novel negative-tone bilayer scheme has been developed using organometallic imaging materials in conjunction with organic planarizing layers. Precursor films containing the radiation sensitive organometallics are spin coated and converted to a metal oxide through electron beam exposure to form an etch mask for pattern transfer. After exposure, the unexposed regions are washed away using an appropriate developer solution and the etch mask pattern is transferred through the organic planarizing layer by an oxygen reactive ion etch (RIE). In this work, a multicomponent organometallic precursor Ba(Sr,Ti) [Ba(2-ethylhexanote), Sr(2-ethylhexanote), Ti(IV)(diisopropoxide) (bisacetylacetonate)] is evaluated as a possible imaging material for bilayer lithography applications. The sensitivity of the 1:1:2 (molar ratio of metals) Ba(Sr,Ti) precursor was found to be 56.5 μC/cm~2 with a contrast of 16.1 at 10keV accelerating potential. In order to enhance the sensitivity, partial conversion of the precursor to the metal oxide prior to electron beam exposure through thermal baking was investigated. It was found that a 30 second thermal bake at 150°C enhanced the sensivity to 23.3 μC/cm~2 but decreased the contrast to 4.2. Also, blanket etch studies on exposed samples found that the remaining organic ligands in the precursor are further converted to the metal oxide upon exposure to the O_2 plasma causing shrinkage of the etch mask. After shrinkage, the precursor offers excellent etch selectivity as compared to hard baked novolac. This bilayer process is demonstrated by printing 200 nm line and space patterns using electron beam patterning.