Poly(methyl methacrylate) as masking material for microelectromechanical system (MEMS) fabrication

• Published in: Journal of applied polymer science Vol. 102; no. 3; pp. 2094 - 2098
• Main Authors: Bodas, Dhananjay S., Gangal, S. A.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05-11-2006; Wiley
• Subjects: Applied sciences; direct current (dc) sputtering; Exact sciences and technology; Forms of application and semi-finished materials; masking materials; poly(methyl methacrylate); Polymer industry, paints, wood; potassium hydroxide; Sheets and films; Technology of polymers; X-ray photoelectron spectroscopy; Coating material; poly(methyl methacrylate); Potassium hydroxide; Use; Methyl methacrylate polymer; Chemical base; Chemical etching; Experimental study; Thin film; Deposition process; Interface properties; masking materials; Chemical composition; Masking; Silicon; Radiofrequency sputtering; X-ray photoelectron spectroscopy; direct current (dc) sputtering
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.24091

In the present study direct current (dc) sputtered poly(methyl methacrylate) (PMMA) films deposited on silicon substrates were evaluated as masking materials for anisotropic etching of silicon in aqueous potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAH) solutions. Sputtered PMMA films were characterized by FTIR to ascertain the bonding, by X‐ray photoelectron spectroscopy (XPS) for the elemental composition, and by the contact angle for measuring the adhesion of the film with the substrate. FTIR and XPS data showed the presence of a poly(tetrafluoroethylene)‐like film on the silicon substrate. The interfacial tension was calculated from the contact angle value, which was 0.82 dyne/cm, confirming good adhesion of the film and the substrate. A pattern was lithographically transferred through the masking material on the silicon substrate, and the etch rate of the masking layer was calculated from the masking time data of the films. The etch rate value of 4 Å/min obtained for the masking material is low compared to the etch rate of the conventional masking materials (60 Å/min for SiO2 and 8 Å/min for Si3N4). © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2094–2098, 2006