## 4 Conclusions
Moreover, the addition of corrosion inhibitors with protonated amine groups (i.e., NH\({}_{2}\)\({}^{+}\) and NH\({}_{3}\)\({}^{+}\)) effectively coated the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface by forming an organic passivation layer on the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface to suppress corrosion. In particular, the protonated amine groups (i.e., NH\({}_{2}\)\({}^{+}\) and NH\({}_{3}\)\({}^{+}\)) were preferentially highly negatively charged on the Si\({}_{3}\)N\({}_{4}\) film surface rather than the negatively charged Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface, so that the CMP was stopped and could achieve minimum recess of the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface. Because the Fenton reaction between the ferric-ionic catalyst and H\({}_{2}\)O\({}_{2}\) is a strong exothermic reaction, after H\({}_{2}\)O\({}_{2}\) was mixed with a CMP slurry, the remaining H\({}_{2}\)O\({}_{2}\) decreased remarkably with time. Thus, research on the addition of a scavenger to suppress the Fenton reaction is essential for achieving stability of the CMP slurry. Figure 10: Schematic Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP mechanism using Fenton reaction and corrosion inhibitor. (**a**) Fenton reaction between ferric-ionic catalyst and H\({}_{2}\)O\({}_{2}\) on as sputtered Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film followed by laser annealing, (**b**) diffusion and adsorption of dissolved O\({}_{2}\), OH\({}^{\star}\), HO\({}_{2}\)\({}^{\star}\), and corrosion inhibitor (i.e., PEI) with protonated amine groups, (**c**) chemical oxidation via chemical reaction between Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface, dissolved O\({}_{2}\), OH\({}^{\star}\), and HO\({}_{2}\)\({}^{\star}\), (**d**) mechanical rubbing between colloidal silica abrasives and chemically oxidized Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface and passivation of corrosion inhibitor polymer, and (**e**) adsorption of corrosion inhibitor polymer on stopping layer (i.e., Si\({}_{3}\)N\({}_{4}\) film) and Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface after self-stopping of CMP. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/article/10.3390/app112210872/s1](https://www.mdpi.com/article/10.3390/app112210872/s1)]([https://www.mdpi.com/article/10.3390/app112210872/s1](https://www.mdpi.com/article/10.3390/app112210872/s1)), Figure S1: Material properties of Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film subjected to sputtering followed by laser annealing, Figure S2: Pourbaix diagram for Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface, Figure S3: Dependency of CMP performance on ferric ionic catalyst types and catalyst concentration for Fenton reaction of Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP slurry, Figure S4: Zeta potential of Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface against pH, Figure S5: Dependency of relative surface roughness (i.e., pixel intensity) on the concentration of the corrosion inhibitor (i.e., PEI) determined using SEM images of the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface after CMP, Figure S6: Surface roughness (Rq) of the polished Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface using Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP slurry including the PDTA-Fe of 0.05 wt% and PEI 0.09 wt%, measured by AFM in the scanning area 5 \(\times\) 5 \(\upmu\)m, Table S1: Chemical structure of ferric-ionic-catalysts. Conceptualization, G.-P.J. and J.-G.P. ; methodology, G.-P.J. ; investigation, Y.-H.S., P.-S.K., M.-H.H. and S.-W.H. ; data curation, G.-P.J., J.-S.P. ; writing--original draft preparation, G.-P.J. ; writing--review and editing, J.-G.P. ; validation, J.-H.P., H.C., B.-U.Y. ; supervision, J.-G.P. All authors have read and agreed to the published version of the manuscript. This research was funded by the MOTIE (Ministry of Trade, Industry and Energy), KSRC (Korea Semiconductor Research Consortium) and the Brain Korea 21 PLUS Program and Samsung Electronic Co., Ltd.  
Not applicable.