Dana A. Gronbeck

Methacrylate resists and antireflective coatings for 193-nm lithography

Methacrylates were the first class of resist to be examined for use in 193nm lithography. They are still useful today, but have a very different molecular structure because of the requirements for development in 0.262N tetramethyl ammonium hydroxide and high etching resistance. A major driving force for their continued use is the availability of a wide variety of methacrylate monomers and the use of free racial polymerization which imparts a wide range of properties to the polymers and makes them very cost effective.

Planarizing AR for DUV lithography

A systematic approach was taken in order to improve the planarity of a DUV anti reflectant (AR) utilized for various lithographic steps, particularly those involving a patterned transparent layer. These layers can occur in both front and back end processing. Two approaches were pursued to accomplish this. The first approach was to minimize the molecular weight of the AR polymer. Polymers with weight average molecular weights from 45,000 daltons to as low as 2,300 daltons were evaluated. The planarity of the AR improved significantly for polymers with Mws below 20,000 daltons. The second approach was to add plasticizers in order to reduce the glass transition temperature of the precrosslinked film. The addition of plasticizers to the AR was effective in increasing the planarity. One of the plasticizers contained a DUV chromophore used to maintain the required optical density of the AR. It was proven possible to make these changes while maintaining lithographic performance in both resist profiles and reflection control.