Effects Of Bias Voltage On Structure And Dielectric Constant Of CN_x Films

The rapid development of microelectronic devices will lead to the continuous improvement of device performance and the increase of device integrated on a chip.In order to reduce the RC sign delay,dissipation and cross-talk between metal interconnects caused by size shrinking continuously,people are searching new dielectric materials to replace the Al/SiO2 structure,the low dielectric constant(low-k) materials have received intense attention since ninties of last century.Researches found that CNx film is one of prospecting low-k materials,which completely meets the requirements of integrated circuit in mechanics performance and chemical stability. We choose p-type doping crystal silicon substrate,with high-purity graphite for the target, high-purity nitrogen and argon gas for work gas.We prepare CNx films by microwave electron cyclotron resonance plasma enhanced unbalance magnetic sputtering with different deposition parameters.We studied the chemical composition,structure,dielectric properties of the films.Fourier transform infrared spectroscopy(FT-IR) and x-ray photoelectron spectroscopy(XPS) were used to study the composition and the bonding structure of the films. The dielectric constant is measured by C-V techniques with Al/CNx/Si (metal-insulate-semiconductor) multilayer structure..The refractive indexes of CNx films are measured with ellipsometry.The results showed that N content increased the sp~2 C-N content and decrease the sp~3 C-N while no bias was applied to the substrate.The refractive indexes decreased with the N/C ratio increasing.The bias voltage triggered by 13.5MHz AC increase sp~3 C-N which could increase the hardness and decrease the dielectric constant.The hardness is about 24GPa and the dielectric constant is about 2.3.