Measuring the heat evolved from individual reaction steps in atomic layer deposition

Abstract

A thermopile has been constructed for detecting heat of reaction during the individual steps taking place in the growth cycles of atomic layer deposition (ALD). The thermopile sensor consists of 64 junctions of thermocouple type K. It has successfully been applied to characterize ALD growth of Al2O3 from Al(CH3)3 (TMA) and H2O, and has furthermore been applied to explore energetics of ALD growth for the following combinations of precursors: TMA + O3, TMA + O2, TMA + hydroquinone, TiCl4 + H2O, and Zn(CH3CH2)2 + H2O. The thermopile clearly identifies exo/endothermal reaction steps, the effect of surface temperature on exposure to precursors from cold sources as well as variation in the flow of gases, and allows setting up of experiments where variations in precursors and pulsing parameters may provide mechanistic insight into the ALD growth. The sensor represents a new and complementary tool for in situ characterization of thin film growth by ALD.