Cycloolefin copolymer containing hindered hydroxyl group for 193nm Photoresist

The basic requirements for polymer design rule in photoresist are as following. The performances of the photoresist relate to transmittance, adhesion on BARC material, dry etch resistance and process margin as a function of the exposure tool. However, It is very difficult for us to find the polymer that has good performance for 193nm ArF photoreist, because it has many limitations as target feature size of photoresist become smaller. One of the most important properties in it is adhesion. Researchers usually introduce functional group, as an adhesion promoter, such as carboxylic acid group, hydroxyl group and lactone group at the side chain of the polymer. Carboxylic acid group represents the highest adhesive property, but it has poor dark erosion because of affinity with developer, 2.38wt% TMAH solution. Lactone group has a limit for introduction as a functional group because it can cause low dry etch resistance and pattern slope. On the other hand, in case of primary alcohol, the hydroxyl group occurs cross-link with carbonyl unit of a neighboring unit. We have recently synthesized cycloolefin copolymer, which has a secondary hindered alcohol in its side chain. And they showed good performances in adhesion, resolution, PED stability, processing window, dry etch resistance, and good pattern profile in both US and C/H pattern profile. In this paper we will discuss the properties and the evaluation results.