Surface studies on benzophenone doped PDMS microstructures fabricated using KrF excimer laser direct write lithography

• Published in: Applied surface science Vol. 314; pp. 292 - 300
• Main Authors: Kant, Madhushree Bute, Shinde, Shashikant D., Bodas, Dhananjay, Patil, K.R., Sathe, V.G., Adhi, K.P., Gosavi, S.W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30-09-2014; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Direct laser writing; Direct write laser lithography; Exact sciences and technology; Excimer lasers; Exposure; Fourier transforms; Infrared spectroscopy; Lasers; Microfabrication, micropatterning; Physics; Poly(dimethylsiloxane) (PDMS); Scanning electron microscopy; Silicone resins; Microfabrication, micropatterning; Poly(dimethylsiloxane) (PDMS); Direct write laser lithography; Lithography; Doped materials; Excimer lasers; Microstructure
• DOI: 10.1016/j.apsusc.2014.06.054
• EISSN: 1873-5584
• ISSN: 0169-4332

•Use of KrF Laser micromachining for Lab-On-Chip applications at lower fluence.•Addition of Benzophenone in PDMS enhances its self development sensitivity.•Benzophenone helps efficient energy transfer for equal density of bond scissioning.•Correlation of chemical composition with laser dose and microstructure.•Microstructures with well defined clean sidewalls.
This paper discusses microfabrication process for benzophenone doped polydimethylsiloxane (PDMS) using laser lithography. KrF excimer laser of 248nm with 20ns pulse width at repetition rate of 1Hz was used for microfabrication of undoped and benzophenone doped PDMS. The doped-PDMS shows sensitivity below 365nm, permitting processing under ambient light. The analysis of etch depth revealed that doped PDMS shows self developable sensitivity at lower fluence of ∼250mJ/cm2. The unexposed and exposed surface was studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Scanning electron microscopy (SEM). Spectrocopic analysis indicated increase in CO, CO, SiO3 and SiO4 bonding at the expense of SiC and SiO2 bonds of PDMS. In case of laser exposed doped-PDMS, removal of benzophenone from probe depth of spectroscopy was observed. Whereas the surface morphology of exposed and unexposed doped-PDMS was observed to be same, indicating clean development of PDMS micropatterns. The present study indicates that addition of 3.0wt.% benzophenone in PDMS enhance self development sensitivity of PDMS. The self developable results on doped-PDMS are quite encouraging for its potential use in point of care Lab-On-Chip applications, for fabricating micropatterns using direct write laser lithography technology.