Electron-Enhanced Atomic Layer Deposition (EE-ALD) of Boron Nitride Thin Films at Room Temperature and 100°C
Alexana Roshko, Jaclyn Springer, Steven M. George, Andrew S. Cavanagh, Huaxing Sun, Paul T. Blanchard
Electron-enhanced atomic layer deposition (EE-ALD) was used to deposit boron nitride (BN) thin films at room temperature and 100 °C using sequential exposures of borazine (B3N3H6) and electrons. Electron stimulated desorption (ESD) of hydrogen surface species and the corresponding creation of reactive dangling bonds is believed to facilitate borazine adsorption and reduce the temperature required for BN film deposition. In situ ellipsometry measurements showed that the BN films grew linearly versus the number of EE-ALD cycles at room temperature. Maximum growth rates of ~3.2 Å/cycle were measured at electron energies of 80-160 eV. BN film growth was self-limiting versus borazine and electron exposures as expected for an ALD process. The calculated hydrogen ESD cross section was σ = 3.9 x 10-14 cm2. Ex situ spectroscopic ellipsometry measurements across the ~1 cm2 area of the BN film defined by the electron beam displayed good uniformity in thickness. Ex situ x-ray photoelectron spectroscopy (XPS) and in situ Auger spectroscopy revealed high purity boronrich BN films with C and O impurity levels <3 at.%. Ex situ grazing incidence x-ray diffraction (GIXRD) measurements observed peaks consistent with textured, hexagonal BN. High-resolution transmission electron microscopy (HR-TEM) imaging revealed hexagonal and turbostratic BN with the c-axis aligned nearly perpendicular to the substrate surface. The BN EE-ALD growth rate of ~3.2 Å/cycle is close to the distance of 3.3 Å between BN planes in hexagonal BN. The growth rate and HR-TEM images suggest that approximately one monolayer of BN is deposited for every BN EE-ALD cycle. TEM and scanning TEM/electron energy loss spectroscopy (STEM/EELS) measurements of BN EE-ALD on trenched wafers also observed preferential BN EE-ALD on the horizontal surfaces and little deposition on the more vertical sidewalls of the trenches. This selective deposition on the horizontal surfaces suggests that EEALD may enable bottom-up fill of via
, Springer, J.
, , S.
, Cavanagh, A.
, Sun, H.
and Blanchard, P.
Electron-Enhanced Atomic Layer Deposition (EE-ALD) of Boron Nitride Thin Films at Room Temperature and 100°C, Journal of Physical Chemistry C, [online], https://doi.org/10.1021/acs.jpcc.8b00796
(Accessed March 1, 2024)