A Low-Temperature Batch Process for the Deposition of High-Quality Conformal Alumina Thin Films for Electronic Applications

High-quality, alumina thin films are extensively used as dielectrics, passivation layers, and barrier layers in electronics and many other applications. However, to achieve optimum stoichiometry and thus performance, the layers are often grown at elevated temperatures (>200 degrees C) using techniques such as atomic layer deposition (ALD). This is problematic for substrates or structures with low thermal budgets. Herein, alumina thin films are grown on 200 mm silicon substrates employing a versatile deposition method known as MVD at low deposition temperatures (35-150 degrees C). The chemical composition of the resulting films is investigated postdeposition using X-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry, with fully stoichiometric Al2O3 achieved at deposition temperatures as low as 100 degrees C. Dielectric measurements confirm outstanding dielectric properties compared to typical thermal ALD layers deposited at much higher temperatures. This low-temperature deposition performance by considering the MVD reactor design and the "pump-type" regime of precursor delivery versus the "flow-type" regime of ALD is rationalized and understood. The results clearly demonstrate that alumina thin films grown with MVD are highly versatile for electronic applications and are of particular relevance and interest for the high-volume processing of dielectric, passivation, and barrier layers at low temperatures.