Field inversion in CMOS double metal circuits due to carbon based SOGs

The authors have shown that under certain conditions carbon-based spin-on-glasses (SOGs) can cause field inversion leading to failure of devices. The authors formulate a model that explains the leakage. On the basis of this model it is possible to use the carbon-based SOGs in double-metal circuits without field inversion by restricting the amount of SOG by doing an etchback and using a passivation that does not liberate H, such as oxynitride or oxide. Some of the recent dielectric deposition systems can deposit nitride films that evolve little to no H on annealing. It is possible to use inorganic SOGs such as phosphorus-doped silicates and not have the problem at all. However, the issue of cracking with these SOGs is always of concern for reliability. The model raises concerns about the presence of organic compounds in the intermetal dielectric either through the use of organic reactants such as TEOS or inadvertently through the incomplete removal of photoresist during some of the masking steps.<>