Photo-assisted atomic layer deposition in real time

The project is concerned with the operando study of photo-assisted atomic layer deposition (photo-ALD) and corresponding thermal ALD processes.

ALD is an important thin film growth method in modern semiconductor technology, based on the cyclic exposure of a support to two alternating gas phase precursors. Thickness control is excellent in ALD, but lateral size control without sample masking is much more challenging.

Photo-ALD, in which UV light is used to provide the energy necessary for growth initiation, is capable of lateral control of the film growth in the absence of masking if patterned supports are chosen with areas on which photo-ALD occurs and such on which photo-ALD is suppressed.

The physical and chemical reasons for this selectivity are, however, unknown, in the same way as much of the surface physics and chemistry of thermal ALD remain to be determined.We will make use of ambient pressure x-ray photoelectron spectroscopy (APXPS) to investigate photo-ALD and corresponding thermal ALD processes.

APXPS will be used to monitor the surface reactions during the exposure of the support to the precursors and UV light, i.e. in an operando fashion. We will improve the time resolution of APXPS ALD experiments down to the ms timescale. Reaction mechanisms and the role of the UV light will be investigated.

The experiments, together with post mortem characterisation and DFT calculations, will provide unique insight into photo-ALD and thermal ALD processes.