Investigation of ion-induced etch damages on trench surface of Ge2Sb2Te5 in high density Ar/SF6 plasma

Abstract

Ion-induced etch damage on trench surfaces of Ge2Sb2Te5 (GST) by reactive ion etching (RIE) is investigated with Ar/SF6 capacitively coupled plasma (CCP). Etch damage on the sidewall increases with higher plasma density and decreases with the bias power. The roughness of the bottom decreases with the bias power due to the ion sputtering. It is demonstrated that the optimum process condition to minimize the ion-induced damage can be obtained from the feature analysis of the virtual metrology, which was developed with plasma information parameters named PI-VM, and it predicted the GST etch rate and surface roughness. It reveals that the energetic ions play a crucial role in removing the halogenated surfaces by high-energy ion sputtering. In addition, the sidewall damage by the lower F radicals is significant because the collisional diffused F radicals are enhanced in the high-density plasma. It explains the control of bias power required to achieve the profiling etch in the high-density plasma.