Atomic Layer Deposition And Physical Vapor Deposition On Silicon Pt Thin Film Technology Research

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 (ALD) is attracting more and more attention and considered as the key deposition process for45nm node and beyond. The ALD is a self-limiting process, which can offer low deposition temperature, excellent conformality, precise thickness control and high-quality thin films over a large area.Several ALD processes for different noble metals, such as Pt, Ru, Rh, Pd, and Ir, have been investigated in recent years. Those noble metals, especially Pt, are candidate materials in the applications such as capacitor electrodes in dynamic random access memories and in ferroelectric random access memories. Platinum growth by ALD is also well known for its attractive properties for potential use in many applications concerning nanoscale structures. For instance, Pt nano-particles grown by ALD are being studied for the purpose of nano-crystal nonvolatile memory applications. Because of its large work function, Pt by ALD is also appropriate to be used as a band edge metal gate with high-k dielectrics in metal oxide semiconductor field effect transistors (MOSFET). Platinum is also widely used in fuel cells owing to its high catalytic activity. Additionally, Pt can easily form Pt-silicide in the presence of Si and therefore Pt by ALD could be suitable for potential use in the source/drain region of future nano-scale MOS transistors in which ultra-shallow junctions are required.Historically the trend in the application area of silicide formation moved form furnace annealing to Rapid Thermal Processing, Spike Annealing, and various versions of Laser Annealing. Although all these methods demonstrated a successful application to the Source/Drain anneal, they are all accompanied by some problems that make the cost of the processing steps more expensive. One of the perspective techniques is microwave annealing. The volumetric absorption of the microwave power by dielectric materials is used in many applications. Microwave processing is quite common in thermal processing of ceramic materials, however, the application to semiconductor are rather new.The content can be divided into several parts as follows:Atomic layer deposition of Pt by ALD can be successfully grown by using 3and O2as precursor gases. The surface morphology, section structure and chemical composition of Pt films have been investigated. Experimental results indicate that Pt growth by ALD will reach a stable and quick deposition rate if the pulse time of CH3C5H4Pt(CH3)3and O2are set as Is and160ms respectively. Silicon substrates with both HF-last and Oxide-last surface treatments are employed to investigate the influence of surface preparation on Pt-ALD. Significantly longer incubation time and less homogeneity are observed for Pt growth on the HF-last substrate as compared to the Oxide-last substrate. For the HF-last sample, after the HF-last process step, the Si surface is terminated with chemically stable Si-H bonds which are very difficult to break up to yield Si dangling bonds. For the Oxide-last samples, the surface is terminated with-O or-OH which can be easily broken off the surface. The intensity of the Pt4f peaks increases with increasing cycle count, indicating an increase of Pt density or thickness, and hence the particle size. The peaks of Si2p and O Is suggest that platinum deposited on HF-last substrate have not turned into silicide and element oxygen exists only in the presence of SiO2not in the presence of PtOx.An interfacial oxide layer about2.5nm in thickness is clearly observed on the HF-last substrate, while it is roughly5nm for the Oxide-last substrate. The latter is identical to the thickness of the originally grown oxide layer. The former2.5nm thick oxide layer is most likely formed during the ALD process at300℃, since after HF treatment the regrown native oxide is measured to be around1.5nm after exposure for a few hours under ambient conditions. Furthermore, the presence of Pt could enhance Si oxidation, since it is known that noble metals can act as a catalyzer during the metal-promoted oxidation and oxygen can easily diffuse through a Pt film and reach the underlying Si surface forming an oxide layer at the Pt-Si interface.We have compared the MWA and RTP methods in the formation of Pt silicide which was achieved by MWA at lower temperature compared with RTP. Only parts of Pt2Si are turned into PtSi when the annealing temperature at550℃using rapid thermal processing. However, the annealing temperature is lower than rapid thermal processing by250℃when using microwave annealing.