Development of SiN ESL for Cu BEOL of Advanced Flash Memory Devices

The effect of hydrogen in a PECVD SiN film used as a copper cap in Flash memory devices was studied. The SiN film is known to have a significant effect on electromigration; however, the SiN can also have a significant effect on the electrical performance of the memory cell. Silicon nitride films with low Si-H bonding were developed and tested in 90 nm and 65 nm Spansion Flash memory devices These films were analyzed for copper adhesion, diffusion barrier quality, hillock growth, electromigration and data retention. Results show improved data retention for low Si-H SiN; however, film properties and electromigration are degraded. Therefore, a composite SiN film was developed and tested to determine if the best properties of the low Si-H bonded and conventional SiN films could be combined.