Ionic Conductivity of Elevated Pressure TMAHCO_3/MeOH/CO_2 Mixtures

摘要

Carbon-dioxide-based elevated pressure cleaning mixtures for photoresist and plasma etch residue removal are being considered as alternative environmentally benign approaches for back end of line microelectronic device manufacture. Despite many attractive features, CO_2 has little solvating power for photoresist or inorganic materials. Addition of a basic modifier such as tetra-methylammonium bicarbonate (TMAHCO_3) to CO_2, can yield a mixture suitable for residue removal. In this work, characterization of the TMAHCO_3 /methanol-modified fluids was performed by measuring the ionic conductivity as a function of concentration and mole fraction of CO_2 at room temperature and various pressures. The conductivity displays a strong dependence on the dielectric properties of the fluid medium.