The addition of a surface conditioning agent to the de-ionized water rinse used to quench the photoresist development process is an attractive methodology that can afford a controlled decrease in resist line edge roughness (LER) or a reduction in defectivity levels, during lithographic patterning. The use of additive-containing rinses involves the interfacial adsorption of the surface-active material (e.g. ionic surfactants, neutral polymers, polyelectrolytes) and/or its penetration into the patterned resist structure, which can be held responsible for polymer chain relaxation and reorganization within the resist matrix, resulting in reduced LER. The non-specific adsorption process can also lead to the creation of repulsive (electrostatic or steric) forces between additive-coated surfaces, thus allowing for particulate stabilization in the rinse liquid and the minimization of defects. In this study, LER improvement (8 % to 16 %) induced by an organic salt and defectivity reduction (ca.= 100) created by a polyelectrolyte contained in the rinse liquid are demonstrated in 193 nm resist systems. Also, additive adsorption to a 193 nm resist surface is monitored using a quartz crystal microbalance (QCM), while the repulsive force created between additive-coated surfaces is detected using atomic force microscopy (AFM) and the presence of residual additive is quantified using total x-ray reflection fluorescence (TXRF), near edge x-ray absorption fine structure (NEXAFS) and contact angle measurements. The experimental evidence provided supports the proposed mechanisms leading to LER and defectivity improvement.
Citation: Journal of Microlithography Microfabrication and Microsystems
Pub Type: Journals
adsorption, LER, line edge roughness, resist defetivity, rinse additive, surface conditioning, surfactants