Dana L. Durham

Lithographic performance of a dry-etch stable methacrylate resist at 193 nm

High resolution performance down to the 0.13 micrometers level is demonstrated in a methacrylate resist with pendent polycyclic side groups. The best performance is achieved with a bottom coat although interactions with the resist were still observed which led to the presence of scum in fine lines and to a large dose change relative to silicon. The demonstrated dry etch rate of the resist was found to be about 10% higher than APEX-E; predictions based on the ring parameter would have led us to expect a more favorable etch rate. The observed discrepancy has led us to speculate on possible exposure of the resist by the plasma environment and loss of the etch resistance polycyclic unit through evaporation.

Cycloolefin/maleic anhydride copolymers for 193 nm resist compositions

Cycloolefin/maleic anhydride systems are a favorable approach to dry etch resistant resists for 193 nm lithography. This paper reports on poly(BNC/HNC/NC/MA) tetrapolymers, from t- butylnorbornene carboxylate (BNC), hydroxyethyl-norbornene carboxylate (HNC), norbornene carboxylic acid (NC) and maleic anhydride (MA). It was found that moisture has to be excluded in the synthesis of these systems if reproducible results are to be obtained. Lithographic evaluation of an optimized, modified polymer has shown linear isolated line resolution down to 100 nm using conventional 193 nm illumination. Possible reactions of the alcohol and anhydride moieties are discussed, and the effect of the anhydride unit on polymer absorbance is discussed using succinnic anhydride as a model compound.

Low-polydispersity novolak resins for i-line resists

Low polydispersity novolak resins were prepared in a sequential process where low molecular weight (Mw) oligomers were first synthesized in a preliminary stp followed by a second condensation with preformed bis-hydroxymethyl derivatives of phenolic starting materials. Resins prepared in this way were found to have polydispersities comparable to that of fractionated resins made in the standard resin synthetic process. The sequential process afforded higher yields of usable resins since no low Mw fractions were isolated and discarded. In several instances, unique bis- hydroxymethyl phenol monomers or monomer/dimmer mixtures were prepared for use in making the low dispersity resins. These compounds were further condensed with the products of the initially prepared low Mw resins in a second acid catalyzed condensation.

Performance of 193-nm resists based on alicyclic methacrylate and cyclo-olefin systems

Among the chemistries/polymers reported for the 193nm photoresist applications, methacrylate copolymers consisting of 2-methyl-2-adamantane methacrylate and mevalonic lactone methacrylate and cycloolefin polymers derived from derivatives of norbornene have shown promising results. We have studied the lithographic properties of these two but different promising chemistries. Both system offer linear resolutions down to 0.13 micrometers using conventional 193 nm illumination and high sensitivity at standard developer conditions. While the methacrylate based system shows best performance on substrates with bottom coats, the cycloolefin-Maleic anhydride alternate copolymer based resists performs well on bare silicon as well as substrates with bottom coats. The etch rates of the methacrylate and cycloolefin based resists were found to be 1.4 and 1.3 times relative to that of KrF resist APEX-E. Further, new polymers consisting of isobornyl and alkyl ether chains on the ester groups of norbornene carboxylate were made in order to decrease the glass-transition temperatures of the norbornene-maleic anhydride type polymers. These results will be included and discussed in detail.