Abstract
Ultra-thin conformal silver films are the focus of development for applications such as anti-microbial surfaces, optical components and electronic devices. In this study, metallic silver films have been deposited using direct liquid injection thermal atomic layer deposition (ALD) using (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) as the metal source and tertiary butyl hydrazine (TBH) as a co-reactant. The process provides a 23°C wide ‘self-limiting’ ALD temperature window between 105 and 128°C, which is significantly wider than is achievable using alcohol as a co-reactant. A mass deposition rate of ∼20ng/cm2/cycle (∼0.18Å/cycle) is observed under self-limiting growth conditions. The resulting films are crystalline metallic silver with a near planar film-like morphology which are electrically conductive. By extending the temperature range of the ALD window by the use of TBH as a co-reactant, it is envisaged that the process will be exploitable in a range of new low temperature applications.
Highlights
Thermal atomic layer deposition (ALD) offers a highly desirable and perhaps even ‘unique’ combination of attributes that makes it highly attractive as a manufacturing process for applications where ultra-thin, conformal, pinhole-free coatings are required
We investigate the effect of using tertiary butyl hydrazine (TBH) as a reactive co-reagent for the thermal ALD of silver films
The effects of deposition temperature on the ALD growth rate using TBH as a co-reactant was investigated between 80 ◦C and 200 ◦C
Summary
Thermal atomic layer deposition (ALD) offers a highly desirable and perhaps even ‘unique’ combination of attributes that makes it highly attractive as a manufacturing process for applications where ultra-thin, conformal, pinhole-free coatings are required. The key advantages of ALD are, only realisable within a limited window of process parameters (temperatures, pressures, dose times, purge times etc) for each particular set of chemical reactants. In thermal ALD, temperature is a fundamentally important process parameter and the term ‘ALD window’ is widely used to define the range over which growth rate is independent of temperature. A wide ‘ALD window’ is advantageous as it means that larger spatial or temporal fluctuations in temperature can be tolerated, making the process intrinsically more stable, repeatable and easier to control. A reasonably wide ALD window is important for coat-
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