Etching characteristics of phase change material GeTe in inductively coupled BCl3/Ar plasma for phase change memory

• The GeTe were etched in inductively coupled BCl3/Ar plasma with various parameters: gas mixture, substrate bias, ICP power and gas pressure.
• The etch rate increased with increasing BCl3 fraction and bias power. It reached a maximum value and then decreases as the gas pressure and ICP power increase. The surface roughness increased with both the bias and ICP powers but decreased with the gas pressure.
• The etch damage is little, and the Ge/Te ration is stable after tens of seconds Ar ion sputtering.

The dry etching characteristics of phase change material GeTe were investigated in inductively coupled BCl3/Ar plasma. By changing gas ratio, gas pressure, substrate bias power, and inductively coupled plasma (ICP) source power, respectively, various characteristics of GeTe films were investigated about surface roughness, etch rate and profiles. Etching damage was studied by analyzing the X-ray photoelectron spectroscopy results of etched blank GeTe films. We found that the etch rate increases with the increase of BCl3 content and substrate bias power. However, it first increases then decreases with the increase of gas pressure and ICP power. Surface becomes smooth with the increase of gas pressure, but the higher power and substrate bias power lead rougher surface. Little C contamination, oxidation and halogenated layer were remained on the surface during etching process, which can be removed easily by Ar+ sputtering. The stoichiometric ratio of GeTe is stable after being sputtered in tens of seconds on the etched surface, indicating the etching damage is low.

The work we did was used to investigate the etching characteristics of GeTe films in inductively coupled BCl3/Ar plasma with various parameters, such as: substrate bias power, gas-mixing ratio, gas pressure and ICP power. By optimizing the etching parameters, we can achieve high etch rate, smooth surface, vertical sidewalls, highly anisotropic profiles. The Ge/Te ratio is unstable on the surface, and it will be stable after tens of seconds Ar+ sputtering by XPS results. The etching profile and depth were measured by field-emission scanning electron microscopy (SEM) as shown in the graphical. The surface roughness was measured by atomic force microscopy (AFM). It can be found the surface roughness increases with both the bias and ICP powers but to decrease with the gas pressure. The X-ray photoelectron spectroscopy (XPS) was applied to measure the etching damage, which is little by analyzing XPS spectra of C1s, O1s and Cl2p.Figure optionsDownload as PowerPoint slide