Zinc Oxide And Cobalt Oxide In An Atomic Layer Deposition And Material Characterization

With the development of semiconductor technology, the feature size of Integrated Circuit is becoming smaller and smaller. Therefore, the preparation of nanoscale materials is becoming increasingly important. Recently, as one of the key technologies for the future IC processing. Atomic Layer Deposition is attracting more and more attention and considered as the key deposition process for 45 nm node and beyond. The ALD is a self-limiting process, which can offer low deposition temperature, excellent conformalitv. precise thickness control and high-quality thin films over a large area. Therefore, in this thesis, the ALD growth of ZnO thin films/nanocrystals and CoOx thin film has been explored, and the corresponding material properties have also been characterized and analysed. The content can be divided into three parts as follows.1. The ALD growth of ZnO thin film using DEZn and H2O2 solution as precursors has been explored. The surface morphology. optical and electrical properties, and chemical composition of the ZnO films have also been investigated. Lots of experiments indicate that ZnO films offer good thickness uniformity when the pulse time of DEZn and H2O2 is 0.5 s and 2 s. respectively. Under a substrate temperature of 200℃, the ZnO sample shows the most stable growth rate and the best surface morphology. Besides, when the substrate temperature is increased form 180℃to 220℃, the ZnO samples exhibits the best photoluminescence and UV absorption properties, and a high crystallinity. Furthermore, when the substrate temperature is increased above 180℃. ALD ZnO thin films have higher carrier mobility and a relative low resistivity. It can be also found that more zinc and oxygen atoms bind together with incrasing the reaction temperature according to the XPS spectrum of the samples.2. On the base of ALD ZnO thin films, ZnO nanocrystals directly grown on different substrates (SiO2, Si etc) using N2-diluted DEZn and H2O2 solution has been explored and characterized. The experimental results indicate that when the deposition temperature is 200℃, the surface roughness of the resulting samples increases gradually with increasing the deposition cycles, revealing nonuniformity of nanoparticles-like sizes and distribution on the their surface. The cross-section TEM image shows that the aforementioned nano-particles are composed of the corrugated surfaces of the film that are formed by the accumulation of ZnO nanocrystals. Secondly. ZnO samples on SiO2 substrate were annealed under different temperatures for 30 s. It is found that higher annealing temperature is preferred for ZnO samples with more reaction cycles. As each ZnO sample is annealed under even higher temperature, the size and density of the nanocrystals will decrease. accompanied with the emergence of very few large ZnO particles. Then, according to the process window of ALD technique, well separated and distributed ZnO nanocrvstals are achieved when the substrate temperature is elevated to 300℃. which successfully avoid the high thermal budget in annealing process. In the end. XPS analysis has been performed to investigate the chemical composition of ZnO under 300℃. A small amount Carbon contamination is found in the surface of the ZnO sample. and there are also few Zn-OH bonds found under the surface of ZnO sample.3. The ALD growth of CoOx using CoCp2 and H2O2 solution as precursors has been explored. The surface morphology and chemical composition of the CoOx smples have also been investigated. According to the experiments, the best process condition of ALD CoOx is as follows:the CoCp2 precursor is kept at 80℃:the substrate temperature is 200℃. The precursor pulse/purge time is 2,15,2 and 5 s. respectively. N2 is used as carrier gas, with a flow rate of 100 seem. According to the surface morphology and chemical composition of formed CoOx samples, the roughness is relative high, and there are a large amount of carbon contaminations in the CoOx samples.