Effect of NH3/N2 ratio in plasma treatment on porous low dielectric constant SiCOH materials

This study investigates the effect of the NH3/N2 ratio in plasma treatment on the physical and electrical properties as well as the reliability characteristics of porous low-k films. All of the plasma treatments resulted in the formation of a thin and modified layer on the surface of porous low-k films, and the properties of this modified layer were influenced by the NH3/N2 ratio in the plasma. Experimental results indicated that pure N2 gas plasma treatment formed an amide-like/ nitride-like layer on the surface, which apparently leads to a higher increase in the dielectric constant. Plasma treatment with a mixture of NH3/N2 gas induced more moisture uptake on the surface of the low-k dielectric, degrading the electrical performance and reliability. Among all plasma treatment with NH3/N2 mixed gas, that with pure NH3 gas yielded low-k dielectrics with the worse electrical and reliability characteristics.