Water-Processable Resists Casting and Development

Attempts have been made to design chemical amplification resists that can be cast from and/or developed with pure water, although casting from a solvent with a high surface tension (such as water) might not produce high quality thin films needed for microlithography. [Pg.166]

Commercially available water soluble copolymers of maleic anhydride with ethylene and methyl vinyl ether (presumably partially hydrolyzed to vicinal carboxylic acids) and triphenylsulfonium triflate were dissolved in water as a casting solvent. Spin-cast films were baked at 130 °C for 10 s, exposed to 254 nm radiation, and postexposure-baked at 130 °C for 40 s. Development with pure water provided negative tone images, presumably due to acid-catalyzed dehydration between vicinal carboxylic acids to form less polar anhydride, as was demonstrated for polarity reversal (4.3.1). However, a copolymer of maleic acid with methyl vinyl ether failed to provide any negative images, [Pg.166]

2-Isopropenyl-2-oxazoline was homo- and copolymerized with styrene via radical mechanism to prepare two-component negative resists (Fig. 140) [403]. Polymers containing at least 80 mol% oxazoline afforded casting from and developing with water. However, higher quality imaging was achieved when the resist was cast from 2-methoxyethanol, presumably because side reactions such [Pg.168]

To address these shortcomings the carboxylic acid was replaced with weaker phenol for a better shelf life and dry etch stability and the vinyl ether functionality was separated from the acidic functionality employing a three component design. A water soluble phenolic copolymer was prepared by radical copolymerization of 4-acetoxystyrene and sodium styrenesulfonate, followed by deacetylation with ammonium hydroxide. A water soluble bis(vinyl ether) [Pg.170]

However, no aqueous resist system has been reported that has both high resolution and dry etch resistance. In order to design an aqueous processable positive resists with more practical performance, pure water was replaced with [Pg.171]