Chemical Mechanical Polishing And Mechanism Of Phase Change Materials Chromium Doped Antimony Telluride

Chromium doped antimony telluride?Cr-SbTe?,with high thermochemical stability and low power consumption,has the potential of replacing traditional phase change material Germanium-Antimony-Telluride?GST?as the functional layer of phase change memory?PCM?.Chemical mechanical polishing?CMP?is the key technology to form the confined cell structure of PCM.However,reports on CMP research of Cr-SbTe materials are almost blank.Therefore,this dissertation mainly explores and studies the CMP process of Cr-SbTe and the polishing mechanism of hydrogen peroxide as an oxide,which is of great significance for scientific research and practical application.First,the paper adopts the Design of Experimental method to study and optimize the polishing effect with the evaluation criteria of material removal rate?MRR?and root mean square?RMS?surface roughness.The parameter object is slurry including pH value,the concentration of oxidant and abrasive and process parameters including down force and platen rotation rate.Found that the acidic condition is in favor of Cr-SbTe polishing,and the MRR with abrasive concentration and hydrogen peroxide concentration keep rising before saturation,adding a small amount of hydrogen peroxide can reach a high selectivity to SiO₂;the MRR of Cr-SbTe increases with the increase of down force or platen rotation rate;combining MRR and RMS surface rough effect,in pH=2,with the 80.3nm colloidal silica abrasive in concentration of 10wt%and 0.5wt%hydrogen peroxide,under down force of 3psi and platen rotation rate of80rpm/min,have experiment on Cr-SbTe,MRR of 150.13nm/min and RMS surface roughness of 0.418nm were obtained.In addition,the dishing study of Cr-SbTe CMP under different via sizes shows that the severity of dishing increases with the increase of via size,but the dispersion of dishing distribution with different sizes has no obvious change.Then based on the studied slurry,the mechanism of hydrogen peroxide in the process of Cr-SbTe polishing was analyzed.On the one hand,fitting the Cr-SbTe removal rate with the down force of P and platen rotation rate of V,a negative intercept of MRR was gained,indicating that Cr-SbTe surface was passivated by oxidation layer;on the other hand,by electrochemical experiments,calculating of Eh-pH diagram and X ray photoelectron spectrum test,interpretation of polishing from the perspective of chemical mechanism.All the results show that a passivation layer is formed by oxidation on the surface of Cr-SbTe during the polishing process.Therefore,it is concluded that the process of Cr-SbTe film polishing follows the cyclic reaction polishing mechanism,and the equation of Cr-SbTe reaction with hydrogen peroxide during polishing is also proposed.The polishing process does not affect the phase transformation performance of the Cr-SbTe film.This paper provides a more sufficient theoretical basis and experimental basis for the application of the CMP process of phase change material Cr-SbTe to the fabrication of PCM.