Paper SS1-MoA11
Nanobonding between 2-nm β-crystobalite SiO₂ on OH(1x1)Si(100) and SiO_x for Monolithic Electronics by Surface Smoothing via Wet Chemical and Spin Processing: TMAFM Study and Modelling of Interphases

Monday, October 31, 2011, 5:20 pm, Room 109

β-crystobalite nanofilms, 2-nm thick, are nucleated on OH(1x1)Si(100) via the Herbots-Atluri (H-A) method [1,2] and form ultra-smooth, ordered, interphases that desorb at low temperatures (T </~ 200 °C) [3] These ordered oxide nanophases on OH (1x1)-Si(100) promote oxidation at low temperatures in ambient, when in contact with oxygen-deficient phases of SiO₂ used in electronics. They can nucleate and grow a cross-bonding interphase between two substrates and achieve “nanobonding” [4] between various combinations Si and silica.

Nanobonding means forming cross-bonding molecules which condense into a continuous macroscopic bonding interphase between 2 smooth surfaces put into mechanical contact. For this to occur, the surfaces need to exhibit wide flat atomic terraces (width >/10 nm), low atomic step density (< 500 steps/µm across atomic terraces direction) and very low particulate density (less than 1/100 µm2). This contrasts with the typical density of surface steps ( ~ 500 steps/µm a.a.t.d.) and particulate density >/~0.1 -1 µm^-2 in as received wafers or post-processing. A surface step density ≥ 500 step/µm a.a.t.d, typically found on Si(100) with miscuts < 0.025° and particulates densities ≥ 0.1 µm-2 particulates results in 3-dimensional isolated bonding points of contacts as opposed to more uniform, 2-dimensional interphases that grow laterally as well as across is shown to occur in nanobonding. Wet chemical processing and SEZ spin technology are compared and combined to smmoth susbtrates via the H-A chemistry [1,2] via Tapping Mode Atomic Force Microscopy, before and after nanobonding. Our results show nanobonding can result in bonding strength larger than 10 MPa/cm2 as measured by mechanical bond pull tests. Wafers fracture within the bulk of both Si and silicate substrates rather than interfacial delamination.

[1] US Patent 6,613,677, issued 9/2/03 "Long range ordered semiconductor interface phase and oxides." 6,613,677, Herbots, N; Atluri, V. P.; Bradley J.D.; Swati, Banerjee; Hurst, Q.B.; Xiang, J.

[2] US patent 7,851,365 issued 12/14/10, "Methods for preparing semiconductor substrates & interfacial oxides there on” Herbots N., Bradley J.D. , Shaw J.M. , Culbertson and Atluri V.P.

[3] Patent Filed: 4/30/09, “Low Temperature Wafer Bonding and for Nucleating Bonding Nanophases. N. Herbots, R. J. Culbertson, J.D. Bradley, M. A. Hart, D. A. Sell and S. D. Whaley

[4] N. Herbots, Q. Xing, M. Hart, J. D. Bradley, D. A. Sell, R. J. Culbertson, Barry J. Wilkens; "IBMM of OH Adsorbates and Interphases on Si-based Materials". Nucl. Instr. and Meth. in Phys. Res., B. IBMM 17^th International Conference Proceeds (Aug, 2010), accepted