Murrae J. Bowden

Lithographic properties of novel acetal-derivatized hydroxy styrene polymers

Lithographic properties of a variety of acetal-derivatized styrene based polymers are reported. The structural modifications in the polymers involve varying the size of the pendent acetal moiety. the lithographic performances of the resists containing structurally modified acetals were found to be superior to the conventional acetals. In the cases where the acidolysis products of the modified acetals are non-volatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved.

Thermal properties of COMA materials

Glass transition measurements of cycloolefin/maleic anhydride (COMA) resist resins are complicated by the fact that their glass transitions and the thermal decomposition of their imaging groups often occur over the same temperature range. In order to gain insight into the Tg ranges of these materials, a series of model non-imaging COMA polymers was synthesized and evaluated by DSC. Among the materials thus examined were copolymers of substituted norbornenes with maleic anhydride, copolymers of nobornene with maleic anhydride and cyclohexyl acrylate, and copolymers of vinyl ethers with maleic anhydride. The effects of cholate additives on thermal properties of COMA polymers were also examined.

Optimizing a DUV positive resist for metal layers

Structurally modified acetal resist is designed for lithography on metal layers. The acetal-based polymer used in the resist has intrinsically low post-exposure volatilization and superior metal etch resistance. This resist is designed to have excellent substrate compatibility as indicated by a foot size of less than 10 nm for 250 nm feature size. Lithographic evaluations reveal that this resists is capable of resolving sub-200 nm features on TiN substrates with high photosensitivity, dose latitude and excellent process windows for line and post features. The reduced foot size and enhanced resolution could be achieved by optimizing the resist chemistry and the processing conditions.

ANTI-REFLECTIVE POLYMER COATINGS IN OPTICAL MICROLITHOGRAPHY

ABSTRACT Dedicated to the memory of Professor Sukant K. Tripathy The use of polymers based on biphenyl methacrylate as antireflective coatings (ARC) in lithographic applications is described. The optimum range of refractive index (n) and complex index (k) resulting in minimal reflectivity, as predicted by Prolith simulation, was 1.56 to 1.76 and 0.125 to 0.275, respectively, which corresponded to polymers containing 50 to 70 mol% of biphenyl methacrylate. ARCs from these polymers were formulated with a melamine crosslinker and a thermally activated catalyst. Optimal lithographic performance was obtained by baking the spin-coated films at 200°C for 90 seconds for crosslinker concentrations less than 7.5% as confirmed by lack of footing and scum at imaging layer/ARC interface.

Dissolution properties of cycloolefin-maleic-anhydride-based resist resins

Influence of different functional groups on dissolution behavior of resist resins based on charge-transfer polymerization of cycloolefins with maleic anhydride was studied. tertButyl carboxylate moiety was used in all materials as an imaging group. Two approaches were identified for increase in the dissolution rate of totally deprotected polymers (Rmax). First, the Rmax value can be modified by changing the total amount of tertbutyl-protected and unprotected carboxylate moieties in the polymer. On the other hand, Rmax can be improved by introducing the base- hydrolyzable functionalities, such as a formate esters, into the polymer chain. It was established that such polymers are stable to hydrolysis in hydrophobic matrix but undergo quick hydrolysis in hydrophilic film. For example, a polymer in which the cycloolefin moiety has a formate side group displayed dissolution rate of approximately 10,000 angstrom/sec while an analogous polymer in which the cycloolefin moiety does not have a formate group showed a dissolution rate of approximately 500 angstrom/sec.