Study On The Optical Design And Aberration Compensation Of Immersion Lithography Lens

Since the invention of the first transistor in 1947,the rapid development of semiconductor technology represented by integrated circuits has promoted the digitization and informationization of human society and brought us an efficient and comfortable modern life.The hardware foundation of the integrated circuit manufacturing industry is various types of special-purpose integrated circuit manufacturing equipment.The core equipment is the lithography tool.The core component of the lithography tool is the projection lens.The difficulty in research and development of projection lens is the pinnacle of ultra-precision optics.The prominent features of current mainstream projection lens are high NA(1.35),large field of view(26mm × 5.5mm),and extremely high imaging quality requirements(including scalar aberration and polarization aberration).This places extremely high requirements on the design,processing,and image quality compensation of projection lens.The research work of this thesis is based on the above background.The main research contents are summarized as follows:First,the current research status at home and abroad is investigated,including the development history of projection lens and the methods of aberration compensation.Based on this,the first part of the thesis carried out the design optimization of immersion projection lens.The immersion lithography tool uses polarized light illumination,and it is necessary to consider the impact of the polarization aberration of the projection lens on imaging.Therefore,this paper first expands the scalar imaging theory of the projection lens and establishes a theory system of polarization aberration.For the scalar aberration requirements,the difficulties and methods of aberration correction of the immersion projection lens are analyzed.Under the condition of reasonable system complexity,in order to correct the field curvature,a catadioptric structure must be adopted.The characteristics of different catadioptric structures are analyzed and the coaxial reflex structure using two mirrors is selected to complete the optical design.For the requirements of the polarization aberration,the influence of the coating on the polarization aberration is analyzed.Then according to the incidence angle of different surfaces of the projection lens,the coating is optimized using low index material.The second part of the paper analyzes the compensation method of scalar aberration of immersion projection lens.In order to more effectively analyze the effect of tolerance on the system and guide the assembly and other compensation analysis,this paper uses Legendre polynomial to fit the aberrations of different field points,and systematically analyzes the aberrations caused by one-dimensional and twodimensional tolerances.Different aberrations are compensated by different compensators.In particular,when analyzing the influence of glass homogeneity,a more accurate gradient refractive index model is established considering the 3D volume distribution of homogeneity.The third part of the paper analyzes the compensation method of polarization aberration of immersion projection lens.Material stress birefringence is an important factor that causes polarization aberrations of projection lens.First,the intrinsic birefringence and stress birefringence of the material are introduced,and the measurement methods and ray tracing method of birefringence are analyzed.According to the distribution characteristics of material birefringence,two optimization compensation methods are proposed.The first compensation method using particle swarm optimization is called PSO;the second compensation method is based on birefringence sensitivity and is called NLS.This NLS method first uses the orientation Zernike polynomial(OZP)to fit the birefringence distribution,and based on this,the system birefringence sensitivity matrix is calculated,then the rotation matrixd of OZP is derived.Finally,the NLS mathematical model was established.At the end,the two optimization methods are compared.The sensitivity-based optimization method is more efficient and the optimization result is much better.Finally,the whole paper is summarized,and the future development of projection lens is prospected,and its future development direction and development trend are analyzed.