This project will develop the science and technology for etching metallic films one atomic later at a time. This know-how is most important in the field of memory devices, specifically based on magnetic principles used in computers, digital cameras, mobile phones and other similar devices. These devices based on the technology developed should demonstrate lower power consumption, smaller sizes, and lower cost of production compared to the other modern alternatives. However, to achieve this goal, very high level of control over making very thin metallic layers is necessary. The thickness of these layers must be highly reproducible to ensure reliable memory performance. For the metal components required, it is difficult to deposit them by traditional methods; however, it is possible to deposit relatively thick layers of these materials and then partially etch them away with the atomic layer precision. In addition to the obvious advantages of capabilities to make simpler, cheaper, faster, and more reliable memory devices this work can affect a wide variety of the systems that are at the core of national interests, including aerospace and military systems, image storage and analysis, data logging and many other applications. The combination of university and industrial research in this grant will offer special educational and training opportunities to the students and facilitate this development to reach the marketplace more quickly.
This GOALI project will target new approaches for removal of deposited metals in a layer-by-layer manner through atomic layer etching (ALEt). One of the prime targets for potential application of ALEt is in the field of Magnetic Random Access Memory (MRAM). Atomic Layer Etching (ALEt) requires reacting a metallic surface with a precursor molecule that saturates the surface and reduces the binding of the first layer of atoms to the bulk. A second input, be it chemical, energetic, or some combination of the two, will cause the first layer of metal atoms (with their associated ligands) to desorb. The second layer of atoms will now be exposed to the saturating precursor, followed by the desorption steps. As the process proceeds, the atoms will be removed from the surface layer by layer. Fe, Co, Ni, and Pt thin films deposited on a Si substrate will be used as the initial targets. The experimental approach will take two tracks. First, model systems will be designed, modeled, and tested. This approach will build on the understanding obtained through studying atomic layer deposition (ALD). A suite of surface characterization techniques will be coupled with high-resolution microscopies to understand these processes at the atomic level. In the second approach, work with American Air Liquide will study the ALEt process in manufacturing systems including temperature controlled wafer chucks, mass flow controllers for the reactants, and plasma sources. These systems will also be equipped so that the ALEt process can be monitored in operando. A model processing system will be constructed at the University of Delaware so that the composition and chemistry of the surface can be studied at any point in the process, in-situ studies. At the end of the proposal, working processes for various materials, including those of importance in MRAM application, will be developed. A deeper understanding of the physical components of the ALEt process will also be achieved.