| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF2-ThM |
| Session: | Area-selective Deposition and Sequential Infiltration Synthesis |
| Presenter: | John Ekerdt, University of Texas at Austin |
| Authors: | J.G. Ekerdt, University of Texas at Austin H. Nallan, University of Texas at Austin Z. Zhang, University of Texas at Austin S. Chopra, University of Texas at Austin |
| Correspondent: | Click to Email |
In this work, we demonstrate the selective atomic layer deposition of Co onto MgO/Si and HfO2/Si substrates. Magnetic materials such as Ni and Co are used in a wide variety of devices ranging from microelectronics to RF technology to energy. Recently, Co films have been explored as the magnetic material for a magnetic tunnel junction structure of an STT-RAM heterostack. Previous efforts to deposit Co metals using ALD precursors bis(N-tert butyl, N’ethylpropionamidnato) cobalt (II) and H2 have suffered from carbon and nitrogen incorporation into the film. Furthermore, etching ferromagnetic films typically relies on plasma processes that can generate side products and are detrimental to device performance.
Here we offer an alternative to this deposition and patterning approach through a sequence of area-selective atomic layer deposition (A-SALD) followed by an oxide reduction. A-SALD is a process by which the energy of a surface can be manipulated such that there is preferential wetting and nucleation of ALD precursors only in desired regions. It is shown that CoO ALD is successfully blocked on MgO or HfO2 surfaces that have been treated with a self-assembled monolayer such as n-octadecyltrichlorosilane or a diblock polymer such as poly(trimethyl)silystyrene/polystyrene. Once patterned, these organic blocking layers are used to prevent CoO deposition in particular areas of the substrate. The CoO deposition is performed at a temperature of ~180o using cobalt bis(diisopropylacetamidinate) and water as co-reactants. Following deposition, it is shown that the CoO can be reduced to form Co metal using a reducing gas such as H2 or CO at elevated temperature and/or by capping the CoO film with an oxygen-scavening layer of Al that reacts to Al2O3. With this approach, we are able to deposit Co metal in only desired regions of the substrate. X-ray photoelectron spectroscopy is used to determine the oxidation state of cobalt and film stoichiometry. Film crystallinity and structure of the films are analyzed with X-ray diffraction and reflection high-energy electron diffraction. Using a scanning superconducting quantum interference device, we explore how the magnetic properties of the Co films can be manipulated using different CoO thickness and capping metals.