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 Mw's 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.
This paper focuses on all aspects of acid quantification in DUV resists using novel acid sensitive dyes. The design criteria for creating acid sensitive dyes are discussed and several new classes of dyes are described. Upon protonation, these molecules undergo a large bathochromic shift in the absorption maximum. This change in the UV absorption spectrum can readily be used to quantify acid generation spectrophotometrically. The utility of these new acid sensitive dyes will be demonstrated by quantifying the acid generating efficiency of different PAG classes. In this paper, the relationship between resist performance and PAG structure is studied for a series of DUV PAGs in which the structure of both the chromophore and the acid are varied. In addition, the sensitivity of these dyes is sufficiently high that trace amounts of acid lost from chemically amplified resists during exposure may be measured. Preliminary results of acid loss experiments on assorted DUV PAGs will also be presented.
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