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Chemical mechanical planarization(CMP) of amorphous Ge_2Sb_2Te_5(a-GST) is investigated using two typical soft pads(politex REG and AT) in acidic slurry.After CMP,it is found that the removal rate(RR) of a-GST increases with an increase of runs number for both pads.However,it achieves the higher RR and better surface quality of a-GST for an AT pad.The in-situ sheet resistance(R_s) measure shows the higher R_s of a-GST polishing can be gained after CMP using both pads and the high R_s is beneficial to lower the reset current for the PCM cells. In order to find the root cause of the different RR of a-GST polishing with different pads,the surface morphology and characteristics of both new and used pads are analyzed,it shows that the AT pad has smaller porosity size and more pore counts than that of the REG pad,and thus the AT pad can transport more fresh slurry to the reaction interface between the pad and a-GST,which results in the high RR of a-GST due to enhanced chemical reaction.
Chemical mechanical planarization (CMP) of amorphous Ge_2Sb_2Te_5 (a-GST) is investigated using two typical soft pads (politex REG and AT) in acidic slurry. After CMP, it was found that the removal rate (RR) of a- GST increases with an increase of runs number for both pads.However, it achieves the higher RR and better surface quality of a-GST for an AT pad.The in-situ sheet resistance (R_s) measure shows the higher R_s of a-GST polishing can be gained after CMP using both using pads and the high R_s are lower to the reset current for the PCM cells. In order to find the root cause of the different RR of a-GST polishing with different pads, the surface morphology and characteristics of both new and used pads are analyzed, it shows that the AT pad has smaller porosity size and more pore counts than that of the REG pad, and thus the AT pad can transport more fresh slurry to the reaction interface between the pad and a-GST, which results in the high RR of a-GST due to enhanced chemical reaction.