Surface modification of SU-8 for metal/SU-8 adhesion using RF plasma treatment for application in thermopile detectors. (19th August 2015)

• Record Type: Journal Article
• Authors: Ashraf, Shakeel; Mattsson, Claes G; Fondell, Mattis; Lindblad, Andreas; Thungström, Göran
• Is Part Of: Materials research express. Volume 2:Number 8(2015)
• Publication Date: 2015-08-19
• Subjects: SU-8 -- contact angle -- plasma treatment -- surface modification -- adhesion -- tape test -- theromocouples; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/2/8/086501
• Languages: English
• ISSNs: 2053-1591

Abstract

Abstract: This article reports on plasma treatment of SU-8 epoxy in order to enhance adhesive strength for metals. Its samples were fabricated on standard silicon wafers and treated with (O2 and Ar) RF plasma at a power of 25 W at a low pressure of (3 × 10 −3 Torr) for different time spans (10–70 s). The sample surfaces were characterized in terms of contact angle, surface (roughness and chemistry) and using a tape test. During the contact angle measurement, it was observed that the contact angle was reduced from 73° to 5° (almost wet) and 23° for (O2 and Ar) treated samples, respectively. The root mean square surface roughness was significantly increased by 21.5% and 37.2% for (O2 and Ar) treatment, respectively. A pattern of metal squares was formed on the samples using photolithography for a tape test. An adhesive tape was applied to the samples and peeled off at 180°. The maximum adhesion results, more than 90%, were achieved for the O2 -treated samples, whereas the Ar-treated samples showed no change. The XPS study shows the formation of new species in the O2 -treated sample compared to the Ar-treated samples. The high adhesive results were due to the formation of hydrophilic groups and new O2 species in the O2 -treated samples, which were absent in Ar-treated samples.