Area-Selective Atomic Layer Deposition of ZnO on Si\SiO₂ Modified with Tris(dimethylamino)methylsilane

Delayed atomic layer deposition (ALD) of ZnO, i.e., area selective (AS)-ALD, was successfully achieved on silicon wafers (Si\SiO₂) terminated with tris(dimethylamino)methylsilane (TDMAMS). This resist molecule was deposited in a home-built, near-atmospheric pressure, flow-through, gas-phase reactor. TDMAMS had previously been shown to react with Si\SiO₂ in a single cycle/reaction and to drastically reduce the number of silanols that remain at the surface. ZnO was deposited in a commercial ALD system using dimethylzinc (DMZ) as the zinc precursor and H₂O as the coreactant. Deposition of TDMAMS was confirmed by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and wetting. ALD of ZnO, including its selectivity on TDMAMS-terminated Si\SiO₂ (Si\SiO₂\TDMAMS), was confirmed by in situ multi-wavelength ellipsometry, ex situ SE, XPS, and/or high-sensitivity/low-energy ion scattering (HS-LEIS). The thermal stability of the TDMAMS resist layer, which is an important parameter for AS-ALD, was investigated by heating Si\SiO₂\TDMAMS in air and nitrogen at 330 °C. ALD of ZnO takes place more readily on Si\SiO₂\TDMAMS heated in the air than in N₂, suggesting greater damage to the surface heated in the air. To better understand the in situ ALD of ZnO on Si\SiO₂\TDMAMS and modified (thermally stressed) forms of it, the ellipsometry results were plotted as the normalized growth per cycle. Even one short pulse of TDMAMS effectively passivates Si\SiO₂. TDMAMS can be a useful, small-molecule inhibitor of ALD of ZnO on Si\SiO₂ surfaces.