Research On The Evolution Mechanism And Control Method Of EUV-induced Plasma

The optical performance stability and service life of extreme ultraviolet(EUV)multilayer mirrors(MLMs)have become important factors restricting the development of EUV lithography machines.Therefore,in the EUV lithography machine,it is particularly important to clean the carbon deposition on the surface of the optical element of the MLM in a timely and effective manner.At present,a kind of plasma generated by EUV irradiation of low-pressure gas,EUV-induced plasma,has great application potential in in situ and online cleaning of carbon on the surface of MLMs and has attracted the attention of researchers.The study of this plasma is currently in the exploratory stage,and its formation mechanism and interaction with carbon deposition on the surface of MLMs are still unclear.In this paper,the mechanism of this new type of plasma and its flow control scheme is studied.Firstly,this paper deeply analyses the complex physical phenomena in the process of EUV-induced plasma from generation to decay.It includes physical phenomena such as photoionization,photoelectric effect emission from the surface of metals,collisions between plasma species,and secondary electron emission from the surface of solid.From the mechanism level,the complex process of EUV-induced plasma from generation to decay and disappearance is completed,which provides a theoretical basis for the subsequent proposal of a EUV-induced plasma control scheme and the establishment of mathematical models.Secondly,this paper constructs a scheme to control the EUV-induced plasma flow behavior.The scheme consists of the EUV light source and focusing system,the vacuum control system,sample support and adjustment mechanism,circuit control system,and heat exchange control system.An external electric field is formed through the bias potential difference between the peripheral structure cavity and the sample holder.The energy of the ions increases under the transfer in the electric field and bombards the surface of the MLM sample to achieve the purpose of cleaning the carbon layer.Thirdly,a mathematical model of the EUV-induced plasma evolution process in this control scheme is established based on the PIC-MCC method.Calculate the exact electric field distribution by discretizing the Poisson equation.The evolution mechanism of EUV-induced plasma under the action of an applied electric field is deeply studied by counting the energy flow of the plasmon bombardment on the surface of the cavity and the surface of the MLM sample and tracking the trajectory of the particle.The simulation found that the cavity structure and surface secondary electron yield are important factors affecting the EUV-induced plasma energy flux density.Finally,this paper optimizes the control scheme based on the effect of secondary electrons emission on EUV-induced plasma.The structure of the cavity was changed to a reasonable ellipsoid,the surface treatment material of the dynode of the photomultiplier tube was used as the inner surface material of the cavity,and the bombardment of ions on the surface of MLM was controlled by the bias voltage of the sample holder.Thus,achieves more stable and efficient control of EUV-induced plasma bombardment on the surface of MLM.In this paper,the evolution mechanism of EUV-induced plasma was studied,the conditions and factors affecting the mobility and energy of charged particles in the plasma were analyzed by numerical simulation,and the feasibility of the cleaning control scheme was analyzed.It provides a theoretical basis for EUV-induced plasma cleaning of carbon pollution on the surface of MLMs and is of great significance and reference value for the future online cleaning of carbon pollution on the surface of EUV MLMs.