| Due to the excellent electrical properties,stable temperature characteristics and the richness of the material system of ferroelectric thin film materials,in recent years,ferroelectric devices based on silicon have wide range of micro-electro-mechanical systems(MEMS),new energy photovoltaic,especially nonvolatile memory application.Graphic process to produce a certain pattern of ferroelectric thin film is the basis for its integrated application.With the continuous development of microelectronics technology,the production of smaller size ferroelectric thin film is conducive to improve the storage density of ferroelectrics,reduce the cost of production.However,the ferroelectric performance damage caused by the graphic process has become more and more serious,which has become one of the important reasons for restricting the development of ferroelectric devices.Lead zirconate titanate(PZT)is the most representative ferroelectric material,which has the advantages of large remnant polarization,small coercive field value and low crystallization temperature.It has become a hotspot in ferroelectric thin film materials.In this paper,the micro-patterning process of PZT thin films prepared by sol-gel method was studied by ion beam etching(IBE).The effect of etching parameters on the quality of pattern and ferroelectric properties were investigated,and the improvement of the etching process was studied.The main contents of this thesis are as follows:(1)Pb1.1(Zr0.52,Ti0.48)O3 thin films were prepared by sol-gel method.The effect of annealing temperature on the ferroelectric properties of PZT thin films was studied,and PZT ferroelectric thin film with remnant polarization value of about 25 ?C/cm2 and coercive field value of about 100 kV/cm was prepared at an optimum annealing temperature of 650 °C.(2)The preparation parameters of PZT ferroelectric thin film etching protection layer(ILR-1050 type photoresist)were optimized.The effect of exposure energy,prebake temperature,development time and postbake temperature on the surface quality and sidewall of the etched protection layer were studied.The best photolithographic parameters were obtained by optimizing the process,such as 4500 rpm,prebake temperature of 90 °C,exposure time of 12 s,development time of 60 s,postbake temperature of 120 °C,and the image of photoresist with smooth surface,straight edges,clean development and integrated graphic was gained(3)The effect of ion beam incident angle,screen voltage and argon flow rate on the etching rate and surface roughness of PZT ferroelectric thin films were investigated.It is found that when the argon flow rate is 7 sccm,the screen voltage is600 V and the angle of the argon ion beam is about 45°,the optimum process parameters were obtained.At the same time,the etching rate reaches the maximum value of 25 nm/min,Rq and Ra were respectively 0.976 nm and 0.776 nm,and their declines were 65.2% and 65.9%,respectively.(4)The etching performance of PZT ferroelectric thin films was studied by calculating the thickness ratio and the pattern size of PZT ferroelectric thin films.It was found that the coercive field of the sample decreased with the increase of the initial film thickness when the same thickness ratio was etched.With the increase of the size of the PZT ferroelectric capacitance,due to the clamping effect of the substrate on the ferroelectric thin film,a larger interface potential well is formed,resulting in an increase in the coercive field.The results show that after the amorphous etching process,compared to the un-etched PZT film,there is no or very little degradation on coercive field value,leakage current,and fatigue performance and so on.When the PZT film is in the amorphous state,the two-step etching method,its ferroelectric performance will be a greater degree of improvement. |
PDF Full Text Request