Study On Evolutions Of Plasma Etching Profiles Using Tailored Bias Voltage Waveforms In RF ICP

Plasma etching technology,in combination with film deposition,photo lithography and other processes steps,forms the microstructure of micro-electronic devices on the substrate material through fine graphic transfer,which is an indispensable technology in semiconductor manufacturing.In plasma etching,ion sheath transport plays a vital role in etching profile evolution.Specifically,ion energy distribution reaching the surface of the material is the key physical quantity,because it drives the surface reaction,determines the reaction rate,influences polymer formation and etching selectivity.In order to meet the current requirements for etching profile accuracy at the atomic/molecular level,it is extremely important to accurately control the ion energy distributions（IEDs）and the ion angular distributions（IEDs）reaching the material surface.In this thesis,a multi-scale model is used to further study the influence of IEDs and IADs on etching profile evolution by applying tailored bias voltage waveforms to accurately regulate the etching profile evolution,which provides theoretical support for process optimization and equipment development in the industry and reduces the cost of trial and error.In the first chapter of this thesis,the background,development,current situation and challenges of plasma etching technology are given,as well as the research progress of IEDs and IADs.In the second chapter of this thesis,a multiscale etching simulation evolution model is established,which is composed of a global model,a sheath model and a trench model,according to the multi-level and cross-scale characteristics of plasma etching.In the third chapter of this thesis,the global model is applied to simulate the inductively coupled plasma discharge of Ar/Cl₂ to reveal the influence of discharge parameters on the plasma state parameters in the reaction chamber.The results show that the flux ratio of neutral to charged particles depends on the dilution of argon.With the increase of argon content,the dissociation rate of chlorine increases and the electronegativity decreases.With the increase of discharge power,the ion collision intensifies,which leads to the increase of ionization rate and the decrease of electronegativity.As the pressure increases,the density of charged particles increases slightly and then continues to decrease.In the fourth chapter of this thesis,the sheath model is used to reveal the effects of the discharge parameters and the tailored bias voltage waveforms to IEDs and IADs on the material surface.The results show that IEDs with one or two peaks can be generated by applying tailored bias voltage waveforms,and they have the ability to select the ion energy and relative flux from each peak value.With the increase of discharge pressure,the high energy peak moves to the low energy region,and the number of ions distributed at small angles decreases.With the increase of discharge power,the number of ions in the high energy region increases and the ion angle distribution becomes more concentrated.In the fifth chapter of this thesis,we use the trench model to reveal the influence of the tailored bias voltage waveforms on the etching profile evolution by using the particle flux obtained from the global model and IEDs and IADs obtained from the sheath model under different discharge parameters as the input parameters of the trench model.The results show that the bottom of the trench is relatively flat,but the etching rate is small,and the sidewall etch is more serious when only low-energy ions are controlled.When there are only high-energy ions,the etching rate is high,but the microtrenchs at the bottom of the trench is obvious.The results of etching profile evolution not only depend on the average energy of the ions,but also obviously depend on the shape of detailed IEDs.