Preparation And Study Of SbTe Based Thin Films For Phase Change Memory

As is known to all,with the advent of the era of big data and AI,people have higher and higher requirements for data processing.Phase change memory(PCRAM)has attracted wide attention due to its excellent performance in reading and writing speed,capacity,and anti-radiation.As the core material of PCRAM structure,phase change film determines the performance of PCRAM.At present,the commercial Ge2Sb2Te5(GST)phase change material has excellent electrical properties,but its crystallization temperature and thermal stability need to be further improved.In view of the above shortcomings,the SbTe-based phase change materials-Sb2Te3(ST)and GST were doped and modified by double target magnetron co-sputtering in this paper.Three nanocomposite film materials were studied.The performance of phase change materials was improved by limiting the grain size in the phase change films.The main research contents and results are as follows:1.Preparation and study of(SiC)x(ST)1-x phase change memory films:When a small amount of SiC(11 at%)was doped,amorphous Si-C,Si-Sb and C-Te phases were formed at the grain boundary,which reduced the grain size of the film(27 nm),and increased the crystallization temperature(Tc)and crystallization activation energy(Ea)of the film to 203? and 4.11 eV,respectively.Moreover,the change of surface roughness of(SiC)11(ST)89 film before and after annealing is small,improving the contact quality between thin film and electrode.With the increase of SiC doping content,Sb and Si crystal phases are precipitated in the film,resulting in heat loss,reducing Tc and Ea,and weakening its performance.2.Preparation and study of(ZnO)x(ST)1-x phase change memory films:Through the analysis of structure and bonding,the introduction of ZnO did not bond with the elements in the substrate Sb2Te3,but directly dispersed in the grain boundary of the composite film in the form of amorphous state.After doping,small nano-regions were formed,which improved the electrical properties and optical band gap(Eopt)of the film.Moreover,the Tc and Ea of the films increase with the increase of ZnO content.(ZnO)21(ST)79 thin films have higher Tc(216?),larger Ea(3.44 eV),and smaller grain size(16 nm).It not only has high thermal stability,but also has large Eopt(0.36 eV),which is conducive to reducing the power consumption and threshold current of the device.In addition,the surface roughness of(ZnO)21(ST)79 film is only 1.005 nm,which makes the film more reliable for PCRAM.3.Preparation and study of(ZnO)x(GST)1-x phase change memory films:With the increase of ZnO doping content in Sb2Te3 substrate,the grain size is greatly reduced,and the Tc,Ea and Eopt of the film are gradually increased,indicating that ZnO is an excellent doping material and can be used for doping modification of GST phase change films.(ZnO)13(GST)87 thin film material has higher crystallization temperature(211?),larger optical band gap(0.45 eV)and smaller surface roughness(0.626 nm)after annealing.This is because ZnO inhibits grain growth in the form of amorphous state and obtains smaller grain size(9 nm).In addition,the addition of ZnO inhibits the secondary crystallization of GST,directly forms FCC phase,hinders the formation of HEX phase,and changes the crystallization mode(from nucleation type to growth type)of the film,which is of great significance for improving the phase transition rate.It is worth noting that the Ea of(ZnO)13(GST)87 film reaches 4.15 eV,and the thermal stability is relatively outstanding,which can be used as a candidate material for PCRAM application in high temperature environment.