Alpha Carbon Hardmask in 3D-NAND Device Manufacturing Characterization by Multiple Metrology Methods for In-Line Control of High Aspect Ratio Etching

A-Carbon films are critical in the 3D NAND process. Thickness and elastic modulus are important to define channel hole and to tune etch profile, respectively. Multiple metrology tools are used to comprehensively characterize this complex system:

• PULSE acoustic metrology provides thickness and velocity. Velocity is directly correlated to elastic modulus.
• In combination with optical metrology, it enables tuning of etch process for high aspect ratio structures.
• FTIR has found adoption as a complementary technique to provide information on the bonding structure of the films.