Development of High Selectivity Phosphoric Acid and Its Application to Flash STI Pattern

In a manufacturing semiconductor device, silicon nitride (Si3N4) and silicon oxide (SiO2) materials are typically and widely used as dielectric materials. In general, phosphoric acid is used for etch of silicon nitride film. The etch rate of phosphoric acid decreases as etch time increases and phosphoric acid has low selectivity against oxide layer. Therefore, phosphoric acid of high selectivity between silicon nitride and silicon oxide without particle generation is needed to remove silicon nitride film. Especially, high selectivity between nitride and oxide is important for flash device application since both nitride and oxide materials exist during nitride remove process in flash Shallow Trench Isolation (STI) pattern. Therefore, control of EFH through high selectivity nitride etching is important for improvement of device performance and we developed Phosphoric Acid with high selectivity between nitride and oxide without particle generation for further devices.