Preparation Of N-type SiCN Thin Film And Investigation Of Its Ohmic Contact

As one of wide bandgap semiconductor materials,SiCN is considered as a promising material for micro-electro-mechanical systems(MEMS) operated at high temperature due to its excellent physical and chemical properties such as adjustable band-gap 2.86～5.0ev,high thermal conductivity,high electron drift velocity,and high breakdown voltage ant-radiation including its better adhesion with many materials like Si,SiO₂ and good compatibility with silicon-based device technologies.To realize SiCN MEMS devices for high temperature,one of the most important problem is to obtain thermal dynamically stable ohmic contact with low contact resistance between SiCN and electrode.The thesis contains two parts:one part is the preparation of the phosphorus-doped n-type SiCN film;another part is the research of contact characteristics of Ti / WSi / Ni-SiCN structure.The main results are made as follows,1,In the dissertation,using CH₄,N₂ and H₂,and SiH₄ as source gases,SiCN films with different phosphorus content were deposited by traditional plasma-enhanced chemical vapor deposition method.Results show that:all samples prepared were a new type of 6H-SiCN phase combined as atomic-scale structure, meanwhile,phosphorus was doped,and its structure can be expressed as[Si_x+C_1-x]₃[N]₄:2,With increasing of phosphorus content,the morphologies and structures of the films had no significant changes,while the carrier density and drift velocity increased, both stand at 5×10¹⁷cm^-3-8×10¹⁸cm^-3 and 200-280cm²/V respectively.3,Circular transmission line model(CTLM) was used to measure the current-voltage curve under different annealing temperature.The results show that: the sample showed a Schottky rectifier characteristics at low annealing temperature (300～600℃);When the temperature was increased to 1000℃and above,the sample showed ohmic contact characteristics,besides,contact resistance significantly reduced with the increase of annealing temperature.4,The interface structure and composition of the contact were analyzed before and after annealing at 1000℃.The results showed that the elements next to interface had diffused after annealing and compounds TiN,WC,Ni₂Si and Ni₃Si₅ were formed which was considered to the reason for the low resistance ohmic contact.