Formation of Recessed Hole by NF_3/O_2 Etching for Phase Change Memory

摘要

In this work, we discuss about the formation of recessed hole in the manufacturing process of phase change memory (PCM). Three recessed holes with different slope angle and depth were obtained by changing the NF_3/O_2 gas mixing ratio. The recessed holes upon bottom electrode contact (BEC) were achieved by etch back process after the formation of BEC. The etching process takes advantage of the etch rate of TiN which is faster than that of SiN. With increasing content of O_2 gas, the decrease in the etch rate of SiN was larger than that of TiN, and this increases the selectivity of TiN to SiN. Oxidation layer can be found upon the SiN layer in the energy dispersive X-ray (EDX) elemental mapping profile after the recessed etching step. It is the existence of oxidation layer that suppressed the etching of SiN.