Abstract
Tetramethyl ammonium hydroxide (TMAH) has wide applications in semiconductor industry, including photoresist development, silica etching (especially Sigma etching), and wafer cleaning, etc. One of the critical areas of the photolithography process is the development of unexposed (negative) or exposed (positive) photoresists without pattern distortion. As a metal free, basic aqueous solution, TMAH is the most common positive photoresist developer providing no metal contaminations. The bath composition, especially the concentration of TMAH, is strictly controlled within the process specifications (~2.2 to 2.4 % (w/w)), since it greatly affects the developing rate and contrast [1]. Traditional monitoring of TMAH concentration does not suffice for the modern needs of a sub-20 nm IC fabrication process. Additional critical parameters include dissolved carbonate and proprietary surfactants.
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