Role of Surface Energy, Hydroaffinity, and Topography in Nano-bonding™ of Si(100) with Silica Polymorphs Using a ß-Cristobalite Precursor Phase: A Quantitative Analysis and Atomistic Model

Dry and steam nano-bonding™ are conceived and researched to bond Si-based surfaces, via nucleation and growth of a two-dimensional SiOxHy, or hydrated SiOxHy interphase connecting surfaces at the nano-scale across macroscopic domains. The motivation is to create strong, long lasting, hermetically bonded sensors with their electronics for the development of an artificial pancreas and to bond solar cells to glass panels for robust photovoltaic technology. The first step in Nano-bonding is to synthesize 20 nm smooth surfaces with a precursor phase, ß-cSiO2 on Si(100)and oxygen-deficient SiOx in the silica by means of the Herbots-Atluri process and  using the Entrepix spin etching as opposed to the industry standard 2 nm smooth Si surfaces. The use of smooth precursor phases as geometric and chemical template allows for nucleation and growth of macroscopic contacting domains where cross bridging occurs via arrays of molecular strands in the hydrated SiOxHy interphase . Steam pressurization is found to catalyze Nano-bonding™ consistently, eliminating the need for direct mechanical compression that limits the size and shape of wafers to be bonded in turn, reducing the cost of processing. Total surface energy measurements via three liquid contact angle analysis correlate well with Tapping Mode Atomic Force Microscopy (TMAFM) analysis and provide an example of strong quantitative representation of the surface energy. Analysis at all steps in the process shows a drop in surface energy to 42.43 ±  .572 mJ/m2 from 57.52 ± 1.41 mJ/m2 after the Herbots-Atluri clean of an As Received standard wafer. Coupled with TMAFM data, this demonstrates a smooth and ordered surface. Further contact angle analysis after steam pressurization Nano-bonding™ shows almost complete elimination from 13.8 mJ/m2 ± 1.0 to 0.002 ± .0002 mJ/m2 in the contribution of donors to the free surface energy, and an increase from 0.2 ± .03 to 23.8 ± 1.6 mJ/m2 in the contribution of acceptors. This is likely due to the saturation of the surface termination with OH ions establishing a consistent precursor phase for cross bridging. This is consistent with an increase in hydroxylation of the ß-cSiO2 surface establishing a consistent precursor phase for cross-bridging. This research optimizes the use of glycerin, water, and alpha-Bromonaphtalene in the use of three liquid contact angle measurements to effectively quantify the components of total free surface energy, which helps to better understand the most consistent method of Nano-bonding™.