Invited Paper TF-MoM1
New Heteroleptic Precursors Enabling Industrial Scale ALD of Next Generation Metal Oxides and Metal Films

Monday, November 7, 2016, 8:20 am, Room 105A

Thermal and Plasma Enhanced Atomic Layer Deposition (ALD & PEALD) have been major enablers to access new film systems in complex 3D architectures such as sub-14nm logics, sub 20nm DRAM architectures as well as new memory concepts. For example, new oxides film systems could be deposited in a conformal way. Similarly, Ni, Co, Ru metal (PE)ALD drew tremendous attention, with recent efforts towards selective deposition. Chemical functionalization requirements of ALD precursors have been more and more challenging, requiring creative approaches to overcome limitations of previous processes.

Leading groups in 2005-2006 opened the path to the use of “combinatorial” heteroleptic chemicals as ALD precursors. This approach consists in multi-functionalizing the molecule by combining the advantages of several ligand systems, and therefore empirically tailoring its physical and chemical properties (for instance melting point, volatility, thermal stability) - a traditional example being Air Liquide’s ZyALD™ precursor, ZrCp(NMe₂)₃. This concept has been extended to multiple ligands and elements. Beyond expected outcome (e.g. physical properties tuning), surprising effects have been observed such as synthesis yield improvement, deposited film crystallinity/stability impact, or even selective deposition.

In this work, achievements using this methodology with new ligand systems and elements will be presented. Specific emphasis will be put on necessary requirements for an industrially viable new precursor, and benchmark with standard molecules.

First, a new set of rare-earth/lanthanide (La, Lu, Sc, Y) precursors will be presented and characterized by various techniques, from a physical & chemical point of view (TGA, DSC, VP), and from deposition behavior point of view (growth rate, film composition). Those novel precursors, for instance combining amidinate (-(R¹NC(R²)NR³) and alkylcyclopentadienyl (C₅R₅) ligands, present unique properties which enable access to new material systems via ALD, not only ternary oxides in semiconductor field but also in other areas such as hydrophobic surfaces. This concept will be illustrated with new elements and for example new viable high yield liquid Scandium and lanthanum Oxide precursors will be introduced.

Second, recent improvements in Co, Ni metal ALD/PEALD processes will be presented, especially with the introduction of alkylsilyl ligands for Co precursors chemistry and allyl/amidinate ligands for Ni precursors chemistry. Applicability of those new precursors for advanced logics metal PEALD/ALD/CVD and their comparison with standard molecules (like dicobalt haxacarbonyl tert-butylacetylene - CCTBA) will be presented.