PMD (preferential metal deposition) aluminum process for 16 giga-bit DRAM and beyond

The scale-down of ULSI devices has been increasing the importance of CMP process not only in logic but also in DRAM back-end processes. The utilization of CMP process in DRAM integration resulted in same depths of contact and via holes, and their actual depths ended up being deeper in comparison to the conventional planarizations. Although there are various techniques to fill these deep contacts, the need for the preceding barrier layer as a diffusion barrier and metal reliability enhancement in Si to metal contact and via application has delayed the implementation of the selective CVD-Al process. The present work reports a novel integration technique, named Al-PMD (preferential metal deposition), for complete filling of deep and small contacts and via holes by selective CVD-Al process.