Nano-scale gap filling and mechanism of deposit–etch–deposit process for phase-change material

Ge₂Sb₂Te₅ gap filling is one of the key processes for phase-change random access memory manufacture. Physical vapor deposition is the mainstream method of Ge₂Sb₂Te₅ film deposition due to its advantages of film quality, purity, and accurate composition control. However, conventional physical vapor deposition process cannot meet the gap-filling requirement with device critical dimension scaling down to 90 nm or below. In this study, we find that the deposit-etch-deposit process shows better gap-filling capability and scalability than single-step deposition process, especially at the nano-scale critical dimension. The gap-filling mechanism of the deposit-etch-deposit process was briefly discussed. We also find that re-deposition of phase-change material from via sidewall to via bottom by argon ion bombardment during etch step was a key ingredient for the final good gap filling. We achieve void-free gap filling of phase-change material on the 45-nm via by two-cycle deposit-etch-deposit process. We gain a rather comprehensive insight into the mechanism of deposit-etch-deposit process and propose a potential gap-filling solution for over 45-nm technology nodes for phase-change random access memory.