Image quality is one of the most important specifications of optical lithography tool and is affected notably by temperature, vibration, and contamination of projection lens（PL）. Traditional method of local temperat...Image quality is one of the most important specifications of optical lithography tool and is affected notably by temperature, vibration, and contamination of projection lens（PL）. Traditional method of local temperature control is easier to introduce vibration and contamination, so temperature control system with multi-closed loops is developed to control the temperature inside the PL, and to isolate the influence of vibration and contamination. A new remote indirect-temperature-control（RITC） method is proposed in which cooling water is circulated to perform indirect-temperature-control of the PL. Heater and cooler embedded temperature control unit（TCU） is used to condition the temperature of the cooling water, and the TCU must be kept away from the PL so that the influence of vibration and contamination can be avoided. A new multi-closed loops control structure incorporating an internal cascade control structure（CCS） and an external parallel cascade control structure（PCCS） is designed to prevent large inertia, multi-delay, and multi-disturbance of the RITC system. A nonlinear proportional-integral（PI） algorithm is applied to further enhance the convergence rate and precision of the control process. Contrast experiments of different control loops and algorithms were implemented to verify the impact on the control performance. It is shown that the temperature control system with multi-closed loops reaches a precision specification at ±0.006 ℃ with fast convergence rate, strong robustness, and self-adaptability. This method has been successfully used in an optical lithography tool which produces a pattern of 100 nm critical dimension（CD）, and its performances are satisfactory.展开更多
Polarization aberration caused by material birefringence can be partially compensated by lens clocking.In this Letter,we propose a fast and efficient clocking optimization method.First,the material birefringence distr...Polarization aberration caused by material birefringence can be partially compensated by lens clocking.In this Letter,we propose a fast and efficient clocking optimization method.First,the material birefringence distribution is fitted by the orientation Zernike polynomials.On this basis,the birefringence sensitivity matrix of each lens element can be calculated.Then we derive the rotation matrix of the orientation Zernike polynomials and establish a mathematical model for clocking optimization.Finally,an optimization example is given to illustrate the efficiency of the new method.The result shows that the maximum RMS of retardation is reduced by 64%using only 48.99 s.展开更多
Analysis of glass homogeneity using the attaching interferometric data model neglects body distribution.To improve analysis accuracy,we establish the three-dimensional gradient index(GRIN) model of glass index by anal...Analysis of glass homogeneity using the attaching interferometric data model neglects body distribution.To improve analysis accuracy,we establish the three-dimensional gradient index(GRIN) model of glass index by analyzing fused silica homogeneity distribution in two perpendicular measurement directions.Using the GRIN model,a lithography projection lens with a numerical aperture of 0.75 is analyzed.Root mean square wavefront aberration deteriorates from 0.9 to 9.65 nm and then improves to 5.9 nm after clocking.展开更多
基金supported by National Hi-tech Research and Development Program of China(863 Program, Grant No. 2002AA4Z300)National Basic Research Program of China (973 Program, Grant No. 2009CB724205)
文摘Image quality is one of the most important specifications of optical lithography tool and is affected notably by temperature, vibration, and contamination of projection lens（PL）. Traditional method of local temperature control is easier to introduce vibration and contamination, so temperature control system with multi-closed loops is developed to control the temperature inside the PL, and to isolate the influence of vibration and contamination. A new remote indirect-temperature-control（RITC） method is proposed in which cooling water is circulated to perform indirect-temperature-control of the PL. Heater and cooler embedded temperature control unit（TCU） is used to condition the temperature of the cooling water, and the TCU must be kept away from the PL so that the influence of vibration and contamination can be avoided. A new multi-closed loops control structure incorporating an internal cascade control structure（CCS） and an external parallel cascade control structure（PCCS） is designed to prevent large inertia, multi-delay, and multi-disturbance of the RITC system. A nonlinear proportional-integral（PI） algorithm is applied to further enhance the convergence rate and precision of the control process. Contrast experiments of different control loops and algorithms were implemented to verify the impact on the control performance. It is shown that the temperature control system with multi-closed loops reaches a precision specification at ±0.006 ℃ with fast convergence rate, strong robustness, and self-adaptability. This method has been successfully used in an optical lithography tool which produces a pattern of 100 nm critical dimension（CD）, and its performances are satisfactory.
基金This work was supported by the National Science and Technology Major Project(No.2016ZX02201)the State Key Laboratory of Laser Interaction with Matter(No.SKLLIM1804)the Jilin Scientific and Technological Development Program(No.20190302050GX).
文摘Polarization aberration caused by material birefringence can be partially compensated by lens clocking.In this Letter,we propose a fast and efficient clocking optimization method.First,the material birefringence distribution is fitted by the orientation Zernike polynomials.On this basis,the birefringence sensitivity matrix of each lens element can be calculated.Then we derive the rotation matrix of the orientation Zernike polynomials and establish a mathematical model for clocking optimization.Finally,an optimization example is given to illustrate the efficiency of the new method.The result shows that the maximum RMS of retardation is reduced by 64%using only 48.99 s.
基金supported by the Major National Science and Technology Project of China(No.2009ZX02205)
文摘Analysis of glass homogeneity using the attaching interferometric data model neglects body distribution.To improve analysis accuracy,we establish the three-dimensional gradient index(GRIN) model of glass index by analyzing fused silica homogeneity distribution in two perpendicular measurement directions.Using the GRIN model,a lithography projection lens with a numerical aperture of 0.75 is analyzed.Root mean square wavefront aberration deteriorates from 0.9 to 9.65 nm and then improves to 5.9 nm after clocking.
