Design and characterization of a microreactor for spatially confined atomic layer deposition and in situ UHV surface analysis

Abstract

The authors report the design and characterization of a microreactor probe that enables gas-phase reactions such as atomic layer deposition (ALD) at low-to-medium vacuum, which is coupled directly to an ultrahigh vacuum (UHV) analysis chamber for subsequent in situ surface characterization without an air break. Avoiding this air break is critical to developing a complete understanding of the growth of ultrathin films, particularly in the early stages of growth. Making use of a precisely defined gap between the microreactor probe and the substrate surface, the reactants are well confined in the reaction zone (total volume ∼1 cm3) by the use of “curtain gas” flow. Computational fluid dynamics was used to simulate both the steady-state and transient operations of the microreactor and the surrounding UHV chamber in which fluid flow, heat transport, and mass transport were considered. The authors provide two examples of the efficacy of the design by considering exposure of a Cu substrate to I2(g) vapor, and conducting the ALD of ZrO2 using Zr[N(C2H5)(CH3)]4 and H2O as reactants, the latter at a total pressure of 18 Torr. In both cases, the authors achieved excellent confinement of the reactants to the central reaction zone, as confirmed by in situ spatially resolved x-ray photoelectron spectroscopy.