In order to further study the performance of laser illumination systems, a Monte Carlo simulation system is established for the return photons when laser illuminating the target. The physical process of photons from the emission to reception is simulated. The laser illumination system involves vacuum laser transmitting, atmospheric turbulence and return photons processing. Based on the simulation system, the quality of the laser far field spot is verified and the character of return photons is analyzed. The simulation results demonstrate that the simulation system performs well and satisfy requirements for research of laser illumination system with atmospheric turbulence.
Quality of exposures in step and scan lithographic equipment highly depends on the synchronization of wafer and reticle stage. In order to increase the synchronization between the two stages, a high precision synchronization control method for scanning movement of reticle and wafer stage based on phase compensation of tracking error with the same frequency is presented. This method is quite different from the traditional ones, which just focus on designing the synchronization control systems of wafer and reticle stage. In this paper, with the analysis of relationship between MA, MSD and correlation of tracking errors, the estimation of tracking error and the phase compensation with same frequency, the performance of synchronization control for reticle and wafer stage is improved notably. Compared with the traditional ones, this method has advantage of higher precision, lower cost and greater portability.
Lithographic equipments are highly complex machines used to manufacture integrated circuits (ICs). To make larger ICs, a larger lens is required, which, however, is prohibitively expensive. The solution to this problem is to expose a chip not in one flash but in a scanning fashion. For step-and-scan lithographic equipment (wafer scanner), the image quality is decided by many factors, in which synchronization of reticle stage and wafer stage during exposure is a key one. In this paper, the principle of reticle stage and wafer stage was analyzed through investigating the structure of scanners, firstly. While scanning, the reticle stage and wafer stage should scan simultaneously at a high speed and the speed ratio is 1:4. Secondly, an iterative learning controller (ILC) for synchronization of reticle stage and wafer stage is presented. In the controller, a master-slave structure is used, with the wafer stage acting as the master, and the reticle stage as the slave. Since the scanning process of scanner is repetitive, ILC is used to improve tracking performance. A simple design procedure is presented which allows design of the ILC system for the reticle stage and wafer stage independently. Finally, performance of the algorithm is illustrated by simulated on the virtual stages (the reticle stage and wafer stage).The results of simulation experiments and theory analyzing demonstrate that using the proposed controller better synchronization performance can be obtained for the reticle stage and wafer stage in scanner. Theory analysis and experiment shows the method is reasonable and efficient.
Lithography is one of the most important and complicated key equipments for the Integrated Circuit (IC) manufacture.
The ultra-precision stage is the important subsystem of lithography and its motion performance impacts directly on the
resolution and throughput of lithography. In this paper, a robust and high response speed control strategy for dual-stage
manipulator is presented. The coarse/fine dual-stage uses the linear motor driven coarse (macro) positioning stage and
the Lorenz plane motor driven fine (micro) positioning stage. By adopting merits of both coarse and fine actuator, a
desirable system having the capacity of large workspace with high resolution of motion is enabled. The feedback
controller is constructed so that the fine stage tracks the coarse stage errors. The controller is robustly designed as the
master-slave control strategy. In addition, the position decoupling which translates fine stage’s machine position
command into its actual position command are discussed and, as a result, the overall coarse/fine dual-stage servo system
exhibits robust and high response speed performance. Simulation shows that master-slave controller can much decrease
positioning error and improve response speed of the coarse/fine dual-stage system.
For step and scan lithography systems, the synchronization of reticle stage and wafer stage during exposure is one of the most important factors that decides the image quality. In this paper, their principle is analyzed through investigating the structure of step and scan lithography systems. And the coarse and fine laminated model is built. Based on this model, three different kinds of synchronous control structures containing parallel, series and cross-coupled are proposed. Then, the reticle stage is used to compensate the error of the synchronous control system of wafer and reticle stage. Simulation results demonstrate that this control strategy has good synchronization performance, and the synchronous error of wafer stage and reticle stage is less than 0.5nm without disturbance.
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