The deposition and characterisation of CVD tungsten silicide for applications in microelectronics

Silicon rich WSix was deposited by CVD onto 100mm diameter 〈100〉 silicon substrates. It is reported that the anneal temperature and anneal time determines the properties of the final WSi2 layer. A comparison is presented between rapid thermal annealing (RTA) and furnace annealing, with regard to resistivity, stress and microstructure. Reflectance measurements were also carried out on the annealed samples. It was found that furnace annealed layers were less stressed than the RTA layers. It is proposed that this is due to less silicon incorporation into the final WSi2 layer during furnace annealing. The RT annealed substrates, consistently exhibited a lower resistivity over the furnace annealed substrates. It is proposed that this was due to the enhanced grain growth experienced by the RTA substrates. The post anneal microstructure was determined using AFM. The reflectance of the layers yielded by both types of anneal was measured. The RTA layers proved to be consistently poorer than furnace annealed layers, due to the surface roughness caused by the enhanced grain growth.