Optimizing Atomic Layer Deposition Processes with Nanowire-Assisted TEM Analysis

Atomic layer deposition (ALD) is one of the premier methods to synthesize ultra-thin materials on complex surfaces. The technique allows for precise control of the thickness down to single atomic layers, while at the same time providing uniform coverage even for structures with extreme aspect ratios such as deep trenches or wires. While many materials can be readily deposited using ALD there is still a lot of research going on to make other materials more accessible. When establishing a new process or adapting an existing process to a new reactor, precise optimization of the deposition parameters is necessary. However, characterizing the parameters of deposition rate, uniformity, composition, and structure is a challenging and time-consuming task. Here a method is presented to optimize these process parameters during ALD deposition using high-aspect ratio nanowires and transmission electron microscopy (TEM). Nanowire samples are prepared directly on TEM grids that are put into the ALD reactor during deposition. Within min of the process the coated nanowires can be analyzed by TEM to obtain the thickness of the layers, chemical composition, crystallinity, and conformality of the coating. This allows for a high testing throughput and subsequently a rapid optimization of deposition parameters. This work introduces a fast and comprehensive method for process optimization of atomic layer deposition. Nanowires are used as substrates during a deposition process which enables the rapid assessment of deposition parameters using transmission electron microscopy within min after processing. The method is demonstrated in an in-depth analysis of aluminum oxide coatings. image