Novolak

Novolaks (incorrectly often novolaks ) are phenolic resins with a formaldehyde - phenol ratio of less than 1: 1, which are obtained by acidic condensation of the starting materials. Novolaks are thermoplastic and can be obtained by adding formaldehyde donors such as B. hexamethylenetetramine are cured. This then results in infusible phenoplasts .

Structural formula of a novolak

Combined with photosensitive substances such as, for example, diazonaphthoquinone , are novolaks in the microelectronics and micromechanics to photolithography as a photoresist used. After exposure and development, a structured lacquer surface remains, which protects the substrate from the next process step (e.g. ion implantation , galvanic growth of metal, thermal oxidation , etching, etc.).

Novolaks are usually spun onto a substrate using a spin coater and resist thicknesses of up to a few 10 µm can be achieved per coating step. For larger layer thickness is recommended PMMA .

Web links

• Douglas R. Robello: The Chemistry of Photoresists ( Memento of March 26, 2014 in the Internet Archive ). In: Chem 421: Introduction to Polymer Chemistry. 2002, accessed May 21, 2010.
• Heinrich Kirchauer: Composition of DQN Resist . Institute for Microelectronics, TU Vienna, April 17, 1997, accessed on May 21, 2010.

Individual evidence

1. ↑ Peter Kurzweil: Chemistry . 10th edition. Springer Fachmedien, Wiesbaden 2015, ISBN 978-3-658-08660-2 , p. 254 , doi : 10.1007 / 978-3-658-08660-2 .