Width Walk Control in 3D NAND Staircase Structure Etching

As the number of 3D NAND layers rises, the need to precisely control the lateral shift, called width walk, during the staircase etching process becomes crucial. In this study, we reveal that the width walk of staircase formation is controllable by three specific tuning parameters in the etching recipe. The improved control of the width walk reduces the shift of 4.9 nm per ON layer etching to 0.81nm, and it can be as low as −1.4 nm per ON layer etching when low power is applied. For 51-layer ON etching, the overall width walk of staircase formation only shifts around 7.5nm after optimization in a cost-effective staircase process.