The development step is critical to the fabrication of nanostructures in chemically amplified photoresist technology. With critical dimensions (CD) shrinking to sub-100 nm and the concurrent reduction in exposure radiation wavelength, line-edge roughness (LER) is becoming more important to control. One method is to identify the contributions to LER from the development step, which requires an improved framework. The aqueous base tetramethylammonium hydroxide (TMAH) is typically used to selectively dissolve radiation-exposed photoresist by shifting the chemical equilibrium from the un-ionized to ionized form. This ionization is responsible for both observed thin film swelling and dissolution. The mechanism of dissolution and correlation to the final surface roughness remains a technical challenge.We present a method to measure the aqueous base profile and resulting thin film swelling by zero-average contrast immersion neutron reflectivity. This method quantifies the total film swelling, complemented by a quartz crystal microbalance technique, but also provides the base profile and dependence on TMAH concentration within sub-100 nm films. These experiments provide data that can be incorporated into future models for dissolution and LER.
Proceedings Title: Proceedings of SPIE
Conference Dates: February 28-March 4, 2005
Conference Location: San Jose, CA
Conference Title: SPIE Advanced Lithography
Pub Type: Conferences
dissolution, interface, line-edge roughness, lithography, neutron reflectivity, photoresist, swelling