AVS 60th International Symposium and Exhibition
    Thin Film Thursday Sessions
       Session TF+PS-ThM

Paper TF+PS-ThM1
Non-destructive Spectroscopic Analysis of Gradient Hydrocarbon/Fluorocarbon Thin Films to Demonstrate the Formation of a Stable Gradient Structure during PECVD Film Growth

Thursday, October 31, 2013, 8:00 am, Room 102 C

Session: Advanced CVD Methods
Presenter: B.D. Tompkins, Colorado State University
Authors: B.D. Tompkins, Colorado State University
E.R. Fisher, Colorado State University
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Thin films that have a continuous change in composition in one or more dimensions have a wide variety of potential applications, including biomimetic materials, barrier films, adhesion interlayers, and optical coatings. These gradient film structures are valuable for their ability to direct processes within a film or along a surface; the ability to tailor these materials allows for unprecedented control over such a process. We have developed a plasma enhanced chemical vapor deposition (PECVD) system capable of fabricating a range of arbitrary gradient film structures using dynamic mixing of C3F8 and H2. We used time resolved optical emission spectroscopy (TR-OES) to characterize the PECVD process and found that the relative gas-phase density of key radical species change reproducibly based on the C3F8/H2 ratio at any given time. Although the C3F8/H2 composition can be varied continuously, verifying that a stable continuous gradient composition has been fabricated presents a more complicated analysis problem. Recently, we have adapted standard non-destructive spectroscopic analysis techniques to elucidate the structure within a gradient film. A series of homogenous films and model gradient films were examined using x-ray photoelectron spectroscopy (XPS), variable angle spectroscopic ellipsometry (VASE), and infrared spectroscopy (FTIR). By examining the shift in CF2 binding energy from XPS, dielectric constant from VASE, and the shift in ν(CF2) from FTIR, we demonstrate that stable confined layers with high fluorocarbon content remain incorporated into the gradient material when fabrication is complete. The ability to tailor surface composition and properties through programed deposition will also be discussed.