AVS 56th International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF2-TuM

Paper TF2-TuM5
CVD of Three Aminosilanes on Silicon Oxide: Effect of Silane Concentration, Surface Characterization and Stability, and Cyanine Dye Adsorption

Tuesday, November 10, 2009, 9:20 am, Room B4

Session: ALD/CVD: Basics, Organics, Electronics
Presenter: M.R. Linford, Brigham Young University
Authors: M.R. Linford, Brigham Young University
F. Zhang, Brigham Young University
H. Samha, Southern Utah University
K. Sautter, Yield Engineering Systems
R.C. Davis, Brigham Young University
Correspondent: Click to Email
Amino silanes are among the most frequently deposited reagents for surface modification to prepare biosensors and other biologically active materials. Of the various ways to deposit silanes, it is becoming increasingly recognized that CVD is the most reproducible and reliable. However, CVD of these important reagents is also much less studied than the less reproducible and much more widely practiced deposition from solution. We also stress the environmentally friendly and industrially viable nature of CVD silane deposition. Our work differs from that of most academic researchers because of the tool we use for silane deposition, which is a commercially available CVD system (the 1224P) from Yield Engineering Systems. This tool gives complete control of oven temperature, pressure, and reagent delivery, in addition to offering plasma pretreatment of the substrates at a range of powers and conditions. In our work we have explored the CVD at 150°C of 3-aminopropyltriethoxysilane (APTES), which is arguably the most widely used and important silane. We show that surface saturation leading to the same level of surface functionalization occurs over a very wide range of gas phase concentrations. This important result indicates that there is a wide process window for APTES deposition. We further compare CVD of APTES to the gas phase deposition of two of its aminosilane analogs – one with two methyl groups (3-aminopropyldimethylethoxysilane), and the other with two isopropyl groups (3-aminopropyldiisopropylethoxysilane). X-ray photoelectron spectroscopy (XPS) shows a decrease in nitrogen concentration for these two molecules compared to APTES. All of these films are extremely flat by atomic force microscopy, and spectroscopic ellipsometry indicates the expected monolayer coverages of our silanes. Of particular significance is the stability against base of the diisopropyl aminosilane, which should make it valuable in a number of applications. The interactions of our different amino surfaces with a cyanine dye are also probed, and the structure/adsorption of the dye seems to be well correlated to the amine density determined by XPS.