| With the improvement of the integration of integrated circuit and the reduction of critical dimension,new challenges are presented to semiconductor manufacturing technology.The requirement for wafer surface cleanliness is getting higher and higher,and the once allowed defects have become killer defects under the higher requirements.The unpatterned wafer inspection is beneficial to reduce the critical dimension of semiconductor manufacturing and improve the production yield.The dark field scattering technology can detect defects which are far smaller than the system resolution and spot size by detecting the scattered light generated by the defect under the illumination of the light source.It has the advantages of non-contact,non-destructive,high sensitivity and fast inspection speed,so it is widely used in the on-line inspection of unpatterned wafer.In response to the above problems,this thesis first elaborates the current research status of different technologies for inspection and its advantages,as well as disadvantages,and further analyzes the necessity of developing an unpatterned wafer inspection system based on dark field scattering,and finally completed the development and testing of this system.The main research contents and innovations of this paper are as follows:(1)The finite-difference time-domain method is used to establish the scattering field model of defects on unpatterned wafer.Through simulation analysis,the influence of incident angle,polarization state and defect diameter on the scattering field distribution is obtained.Due to the scattering field distribution and actual optical design constraints,two p-polarized light beams with normal and 70° oblique incidences are selected,and the scattered light with scattering angle of 7～40° is collected by the optical system.(2)According to the simulation results of the scattering field distribution,an unpatterned wafer inspection system based on dark field scattering is developed.The development contents include system scheme and optical design,component selection,mechanical structure design and control system construction.(3)The inspection capability of the system is evaluated by detecting the defects of five standard PSL(Polystyrene Latex)particles with a diameter of 125-1100 nm on the wafer surface,and the repeatability of the system is further evaluated by repeating the inspection of standard PSL particles with a diameter of 200 nm.The detection result shows that the detection limit of the system is 155 nm,and the standard deviation of repeatability is less than 5%,indicating that the system has a strong inspection capability.In this thesis,the scattering field distribution of defects on unpatterned wafer under different conditions is simulated by modeling.On this basis,an unpatterned wafer inspection system based on dark field scattering is developed.The inspection system developed in this thesis can realize the rapid,non-destructive and high-precision inspection of the surface defects on unpatterned wafer. |
