A Multi-scale Study On Quasi-atomic Layer Etching Of Silicon-oxide In CF₄/Ar Inductively Coupled Plasma

Plasma etching is an important step in the manufacturing process of Integrated Circuit?IC?.In recent years,with the continuous improvement of IC integration,the feature size has been shrinking,in addition,the application of 3D transistor,Fin field-effect transistor and other complex structures,the requirements of Aspect Ratio?AR?and etching groove morphology control were further improved.Especially with the development of less than 10 nm technology,the deviation of atomic scale may also affect the device performance.Traditional etching is obviously difficult to meet the requirements in some key steps,and the control ability of atomic accuracy becomes the key to further reduce the characteristic scale.In addition,the progress of atomic layer etching?ALE?technology has enabled plasma atomic layer etching with atomic precision controlling to gradually enter the stage from research to industrial application.ALE realizes the atomic-level accuracy etching by self-limiting removal of the outermost atoms of the surface.A complete ALE will go through two purification chambers,which takes a lot of time,making the yield too low.In order to solve this problem,in recent years,a large number of studies have been conducted on the atomic layer precision etching by controlling the pulse bias waveform and discharge parameters of the plate and so on,without changing the gas.This method can increase efficiency by several times.It is called plasma enhanced"quasi-ALE".In this paper,a multi-scale etching evolution model including plasma discharge chamber model,sheath model and trench model is established to study the effects of different discharge pressure,power,bias waveform etc.on the morphology of the plasma enhanced quasi-atomic layer etching SiO₂ under CF₄/Ar in inductively coupled plasma?ICP?discharge.Firstly,commercial software CFD-ACE+simulation plasma generation process was used to obtain the density and flux of ions and neutral particles under different discharge parameters.Secondly,the obtained particle density is used as the boundary condition of the sheath model,the IEDs and the IADs?IEADs?bombardment on the plate are calculated in a self-consistent manner.Finally,the particle flux,IEADs were used as the initial conditions of the trench model to simulate the evolution process of the trench under different conditions.This paper also compares the trench morphology of traditional ALE,quasi-ALE and reactive ion etching?RIE?,and studies the aspect ratio dependence effect?ARDE?of quasi-ALE.The results show that different external conditions have a great influence on the IEDs and IADs,and then the morphology of the trench;quasi-ALE can still increase the etching rate under the conditions of maintaining the desired etching topography,and to a certain extent,can inhibit the ARDE.