Production lithography is undergoing a technology shift, and the requirements of beam delivery system (BDS) are increasing which also raises the precision requirements of the beam steering units (BSU) in BDS. In essence, the BSU is a two rotational degree of freedom platform. In this paper, a BSU based on 3-RPS flexure parallel mechanism is proposed. By analyzing the relationship between the unit’s dimensions and mechanics, a mathematical model is built. Then the BSU with a balance between lower stress of the flexure hinges and higher accuracy of the unit can be got by optimizing the dimensions with the mathematical model. Finally a simulation is conducted to verify the design.
Immersion lithography is one of the main technologies used to manufacture integrated circuits with the shortest feature size. In immersion lithography, temperature of immersion liquid is strictly constrained and its allowable range is less than ±0.01°C at 22°C. To meet this requirement, a temperature control algorithm adopted by the test rig which controls the temperature of the immersion liquid with process cooling water (PCW) via heat exchangers is proposed. By adjusting the flow rate of PCW through the heat exchangers, the control system varies the amount of heat exchanged, and the temperature of the immersion liquid can be properly controlled. The temperature control rig is a multi-disturbed, timevariant, non-linear and time-delayed system and its transfer function varies with the inlet temperature and flow rates of the streams through the heat exchangers. Considering the characteristics of the system, a cascade-connected fuzzy PID feedback algorithm is designed.
The position and tilt between the image plane of projection lens and wafer surface must be accurately measured and
corrected as much as possible. Defocus always occurs when the imaging plane does not consist with the best focus plane.
And it reduces the clarity of optical image. It has been reported that proper focusing is a critical factor in the lithography.
An automatic focusing and leveling measurement system (FLMS) presented in the reference and widely used in high
resolution lithography has been studied. We reveal a detailed principle of the signal processing of the FLMS and evaluate
its performance by simulation. The simulation results show that measurement accuracy of the FLMS can be less than
10nm. And this FLMS meets the requirement of high resolution photolithography.
Image quality is the most important performance of optical lithography tool and it is influenced by many factors.
Temperature stability of projection lens is one of the main factors. It is difficult to control temperature stability of the
projection lens because of its features of big inertia, multi-time-delay and multi-perturbation. Temperature control unit
(TCU), which is used to control the projection lens temperature, is required to operate far away from projection lens,
otherwise it will increase COO of lithography tool and its vibration will affect the performance of projection lens. So a
remote temperature control method is proposed. A two-input and two-output intelligent algorithm is presented to
improve convergent rate and steady-state accuracy of the temperature control system for projection lens. Control process
is divided into five phases according to the ideal dynamic response curve. A nonlinear PI algorithm is recommended to
precisely adjust temperature and an intelligent decision decides the switch of five multi-phases. The experiment results
show that ±0.006°C temperature stability can be realized and the algorithm has advantage of quick convergent rate,
strong robustness and self-adaptability. This algorithm has been used in optical lithography tool with 100nm CD and has
achieved good temperature stability.
Nanostructural vanadium dioxide thin films are investigated as intelligent window coatings. The films are fabricated using reactive sputtering and post annealing. A reversible semiconductor to metal phase transition for as-deposited VO2 nanostructure films with grain size of ~8nm takes place at a temperature of 35°C, which lowers about 33°C in comparison with a phase transition temperature of 68°C in conventional VO2 films with a grain size of 1-2 μm. The results indicate that the nanostructural VO2 films are more suitable to the application for smart thermochromic glazing of windows than that of conventional VO2 films.
In this paper, delicacy gene formula was presented to describe the transmittance error which varied with thickness change of the given layer, the transmittance error bred by every layer thickness error was calculated on the basis of the narrow interference bandpass filters that we designed to use in WDM system. The affected properties of the transmittance curves was compared and analyzed, and according to the results the conclusions were attained that can be extremely useful for practical film coating processes.
The relations between the precision of the transmittance turning point monitoring system and the thickness error of the monitored thin film layer are analyzed in this paper. The functions are derived under different conditions. This paper has developed a program to simulate the structures of deposited coatings and the real-time variation of the transmittance through the thin film stake and substrate assembly in deposition process that take the transmission turning point monitoring approach. The simulated value of the thickness of each layer after deposition is composed of the thickness correspond to the transmittance extreme found by 1D search algorithm and random thickness error calculated by the relations mentioned above. The computer simulation accord with the experiment results.