SAMCO is presenting a paper at PacSurf 2016, titled “Selectivity of Plasma Treatment Effects on Wettability Modulation between Silicon, Glass, Polyimide and PMMA, Using Several O₂, CF₄ and CHF₃ Gas Ratios“.

Date: December 14
Session: Afternoon Poster Session
Poster Number: TF-TuP17

Abstract

Surface wettability of materials is influenced by surface energy as well as surface roughness, and the surface energy can be modulated by changing surface chemistries. Plasma treatment is one of the techniques to control the surface chemistries, and is used for the surface wettability modulation of materials in device fabrication. However, few papers have investigated the selectivity of plasma treatment effects on the wettability modulation between two or more materials in a batch process [1], [2]. In this research, the roles of reactive species of oxygen- and fluorine-based plasma chemistries were investigated for selective surface wettability modulation of materials. Using a reactive ion etching system (RIE-10NR, SAMCO Inc.), various plasma chemistries with several gas flow ratios of O₂, CF₄ and CHF₃ were formed over inorganic (silicon and glass) and organic (polyimide and PMMA) materials. Static contact angle and XPS were utilized to study the surface wettability and surface chemical bonding structure before and after plasma treatment. The contact angle was also investigated over the course of 20+ days storage in a N₂-purged desiccator in order to examine the stability of the wettability modulation effects.
With a gas flow ratio adjustment, a large contact angle contrast was observed between the materials. In pure CF₄ plasma treatment, the inorganic materials showed contact angle reduction after the plasma treatment, while the organic materials showed significant contact angle increase. XPS analysis revealed that the silicon surface retained 9.5 at.% fluorine, while 35.4 at.% fluorine was observed on PMMA surface after the pure CF₄ plasma treatment. This indicates that the PMMA wettability modulation was caused by the fluorine-containing chemical functional groups at the outermost surface layers.
After ageing the samples in storage, the contact angle contrast was gradually decreased due to a contact angle increase of the inorganic materials after pure O₂ or CF₄ plasma treatment. On the other hand, samples processed in a plasma using a gas mixture of CF₄ and CHF₃ showed stable contact angles. This difference is attributed to the existence of a thin fluorocarbon layer deposited during the CHF₃ based plasma treatment.
These results indicate that the reaction of oxygen and fluorine-containing active species on substrate surfaces influences wettability modulation effects of materials and also the stability of these effects.
[1] P. Svarnas, L. Yang, M. Munz, A.J. Edward, A.G. Shard, and J. W. Bradley., J. Appl. Phys. 107, 103313 (2010)
[2] H. Inui, K. Takeda, K. Ishikawa, T. Yara, T. Uehara, M. Sekine, and M. Hori., J. Appl. Phys. 109, 013310 (2011)