Hardmask metrology for real-time process feedback
As the number of layers in 3D NAND increases, hardmasks are used for etching deep, high aspect ratio (HAR) features that conventional photoresists cannot withstand. Monitoring hard mask thickness is critical to the 3D NAND process as it goes through an iterative etch process. Film thickness and repeatability affects the active area of cell and consistency of the litho/etch performance.
The ability to accurately measure these layers and understand the correlation to the deposition and etch processes is critical to device performance and yield.