The use of ALD in industry and academic research requires specific processes to optimise the properties of deposited layers, production yields, costs, etc.
There is currently a wide variety of ALD processes available; each day bringing new innovations. Innovations can come from a :
- Modification of precursor injection systems
- Modification of the ALD sequence: temporal to spatial (SALD)
- Modification of the number of substrates that can be processed at one time (e.g. single plate to multi plate system)
- Modification of the process to have a mix of CVD and ALD to improve deposition speed while maintaining excellent compliance
- Adaptation of the process not to deposit a layer atom by atom, but to remove a layer atom by atom: Atomic Layer Etching (ALE or ALEt) process
- Modification of the plasma source and its design for a PEALD process
Within the framework of the GDR, this working group proposes to monitor (technology watch) and actively participate in the development of innovative ALD processes. Three innovations are currently being studied: the use of a direct liquid injection (DLI) system for precursors with low vapour pressures; the development of an atmospheric space process with or without plasma assistance; and the development of Atomic Layer Etching processes, which can only be used in conjunction with ALD to produce future transistors, as illustrated in the TEM figure below of a 5 nm GAAFETs transistor by IMB and Samsung. The trenches between the Fin's were made using an ALE process, whereas the high k /Metal Gate stacking required the use of ALD to have ultra conformal deposits.
TEM cross-section : 5nm GAAFETs - IBM, Samsung and Globalfoundries (Source IBM)
C. VALLEE, SunyPoly