Etching of Silicon Nitride in 3D NAND Structures

We present results of experimental measurements, simulations, and models to better understand etching of SiN with H3PO4 in 3D NAND structures. SiN and SiO2 etch rates were measured on blanket wafers, and those etch rates were used to simulate etching of 3D NAND structures. Results show that the etching is reaction limited, and that diffusion and acid flow rate has no effect on the local etch rate, but temperature and concentration do affect the etch rate.