A study on the defects induced by ambient moisture and ammonia in the perhydropolysilazane spin on glass process

An insulation material for 20nm node memory devices requires superior gap fill characteristics to prevent void defects. Due to high flow-ability, atmospheric spin on glass (SOG) process rapidly replaced the classical chemical vapor deposition process especially for the trench isolation step. Perhydropolysilazane (PHPS), a representative SOG material, is vulnerable to environmental contamination because it is exposed to ambient air during the process. This paper describes the PHPS defects induced by the two most common airborne contaminants in semiconductor manufacturing environment. It was found that ammonia induces pattern leaning defects by forming an abnormal layer under the PHPS film and that moisture causes the electrical failure by the deterioration of silicon oxide integrity. Furthermore, based on the analysis of the environmental effects on mass production, the defect inhibiting concentration of ammonia and moisture were determined. This knowledge can be used to prevent environmental defects in the PHPS process.