With the downscaling of silicon transistors into sub 5 nm size, quantum effects in conductivity start to play a major role, making the transistors increasingly unreliable. Emerging technologies in this field rely on crystalline oxides such as LiNbO3 or BaTiO3.
However, to date their processing and deposition are not under CMOS compatible conditions. Thus, there is a strong demand for developing manufacturing processes to enable epitaxial growth under CMOS compatible conditions, either allowing for integrating ferroelectric perovskites (such as BaTiO3) on silicon or for epitaxial growth of hafnia-based ferroelectrics. These are the two key materials in this proposal.
Atomic layer deposition (ALD) is potentially a key enabler for the deposition of epitaxial crystalline ferroelectrics. In the literature, ALD was successfully used for replacing SiO2 in the MOSFET gate by amorphous high-k HfO2. However, ALD growth of epitaxial crystalline oxides is still hugely challenging, and requires a fundamental understanding of surface and precursor chemistry. The core contribution of this work is to use first principles simulations to develop ALD processes for direct epitaxial crystalline ferroelectric deposition. The epitaxial ferroelectrics studied are: BaTiO3 (BTO) and Hf0.5Zr0.5O2(HZO), while other epitaxial semiconductors, including (Ba,Sr)SnO3 (BSO), and WO3 are of interest.
The challenge addressed requires the use of high performance computing (HPC) infrastructure to predict suitable deposition process chemistries.
Tyndall National Institute, Ireland.