FMECA For Dual-stage System Of Lithography Machine

Lithography machine is a kind of equipment for semiconductor manufacturing. Itscore sub-systems include alignment system, exposure system and the wafer stagesystem. The technology blockade of foreign companies and impercipient importance ofdeveloping lithography technology in China has great impedes the development ofChinese lithography technology. It is very urgent to develop the lithography industrydue to the importance of semiconductor. As an important support technology in theproduction process, reliability technology plays an important role in developing thelithography, especially in the design phase.The research object of this paper is dual wafer system, which is composed of waferstage and reticle stage subsystem. Both subsystems are using the combination structureof macro platform with micro platform. The movement of macro platform is longdistant movement, and the movement of micro stage is micro distant in six degree offreedom. The dual wafer system is a complex and ultra-precision motion system. Thereliability requires of such system is very high, and the reliability analysis work ofcomplex equipment is also very difficult. There are some problems in the reliabilitywork of dual wafer stage.(1) During the design phase, equipment parameters are insufficient.(2) The system has a high reliability index and it hard to get failure data.(3) The system is too complex to do some experiments.(4) Few reliability analysis has been done with dual wafer stage. These problemscan lead a difficult task in analyzing dual wafer stage with reliability method.According to the above problem, some works have been done in this paper:(1) FTA models of wafer stage subsystem and reticle stage subsystem areestablished. And the qualitative and quantitative analyses are used to find the weaknessof both subsystems.(2) Because of the complex and unpractical of constructing FTA model of controlsubsystem, GO method is used to model the control subsystem and to analyze thecontrol subsystem. The reliability of control subsystem can be estimated. (3) According to the shortage of failure data, FMECA is used to analyze thereliability of wafer stage and reticle stage, and evaluate the reliability of the twosubsystems by expert scoring.(4) According to evidence conflict problem of experts scoring, a method based oninformation fusion method of evidence theory is proposed for reassign permissions. Andthe reassign permissions of each expert are used to calculate the new RPN value. Thenthe comparison of the two methods is given.