Characterization and chemical recovery of plasma damaged porous low-k SiOCH dielectric for the semiconductor industry
In recent years, in ultra large-scale integrated electronic circuits novel dielectrics have become necessary as the pattern size is reduced more and more of the metallization system. These dielectrics have two main properties. Firstly, in conjunction with silicon and oxygen, the dielectric consists of carbon, and secondly they are porous. Both properties provide an enhanced potential in damaging the material, especially during plasma-based patterning processes. As no filly proven damage-free plasma process has yet come into existence, alternative methods to restore the dielectric properties are needed. The silylation reaction is therefore, discussed in this work as a method to improve the properties of plasma damaged electronic circuit, with an emphasis on production. One requirement for an effective silylation process is an open pore system. Hence, a downstream process is always preferable over a reactive ion etch-based plasma process. Independent of the plasma chemistry used, a downstream process avoids pore sealing. Another requirement is an adequate diffusion behavior. As a consequence of reduced pore-size due to plasma damage and the formation of adsorption sides In the damage zone, a simple diffusion is inhibited. Therefore, a vapor-phase process, at elevated temperatures of > 300 °C is at all times better than any liquid-based process at room temperature. Most promising chemistries are those which have two methyl and two reactive groups. These chemicals reduce the influence of steric influence and show, generally a higher amount of silylation. Specifically, bis(dimethylamino)dimethylsilans (DMADMS) warrants a mention. DMADMS influences improvement in the electrical properties of a damaged test structures related to the 45 nm technology node. An improvement in the dielectric capacitance to resistance behavior of up to ~ 10 % was achieved. At the same time the leakage current was reduced and an adequate defect level was provided.