Effect of Crystal Orientation Upon the Surface Energy of Native Oxides on Si(100) and Si(111) as Measured by Three Liquid Contact Angle Analysis (3LCAA)

The surface energy $\gamma^{\mathrm{T}}$ of native oxides on Si(100) and (111) is measured via Three Liquid Contact Angle Analysis (3LCAA) to detect crystal orientation effects. Low surface roughness of Si wafers lowers $\gamma^{\mathrm{T}}$ via low density of dangling bonds, so $\gamma ^{\mathrm{T}}$ scales with chemical reactivity freely from topography [1]. 3LCAA based on the Van Oss theory measures $\gamma^{\mathrm{T}}$ via surface interactions with molecular dipoles (Lifshitz-Van der Waals), labeled $\gamma^{\mathrm{LW}}$, with electron donors, $\gamma ^{\mathrm{+}}$, and acceptors, $\gamma^{\mathrm{-}}$. Surface energy components $\gamma^{\mathrm{LW}}$, $\gamma^{\mathrm{+}}$, and $\gamma ^{\mathrm{-}}$ give insights into optimizing $\gamma^{\mathrm{T}}$ for hermetic NanoBonding\texttrademark in sensors [1], to extend lifetime and reliability in saline environments from days to years via matching electronegativity in cross-bonding pairs.$^{\mathrm{\thinspace }}$3LCAA with 18 M$\Omega $ Deionized water, glycerine, and $\alpha $-bromonaphthalene in a Class 100 hood and the Sessile Drop method yield for native SiO2/Si(111) $\gamma^{\mathrm{T}} \quad =$ 56.7$+$/-2 mJ/m$^{\mathrm{2}}$, and $\gamma ^{\mathrm{T}} \quad =$ 49.7$+$/-2 mJ/m$^{\mathrm{2}}$ on Si(100), a 13{\%} difference. Since Si(111) surface atomic density is 12{\%} larger than Si(100), 3LCAA finds that $\gamma^{\mathrm{T}}$ scales with surface atomic density. [1] US9018077, granted 2015, \textit{Herbots et al}