Si3N4 Etching with Carboxylic-Acid-Containing Superheated Water

A selective Si3N4 etching is required in the semiconductor manufacturing process. In general, Si3N4 was selectively etched to SiO2 in hot H3PO4. However, since the existing Si3N4 etching process used a high-temperature and high-concentration acid solution, environment, health, and safety issues may occur. In this study, a new Si3N4 etching process based on superheated water was studied. In superheated water, Si3N4 was etched, but also Si and SiO2 were etched, making it difficult to apply to actual Si3N4 etching process. By adding carboxylic acid to superheated water, Si3N4 was selectively etched without material loss of Si and SiO2 in a Si3N4/SiO2 repeated stack structure. The Si3N4 etching process using superheated water with addition of carboxylic acid is an eco-friendly, safe and new etching process that can solve various problems that may occur in the existing H3PO4 process.