Research On Run-to-Run Control For Semiconductor Process

Run-to-Run is a control method which originated from the process ofsemiconductor production,On the basis of combining with the control method ofEPC(Engineering Process Control) and SPC(Statistical Process Control),Run-to-Run control is to eliminate the shift and drift in production process.InRun-to-Run control,the most widely used is the EWMA and double EWMAcontroller.The discount factor of traditiona l EWMA controller usually choose a fixedconstant,which can not reduce the initia l offset and output variance in the processof production at the same time.This paper is basis for Tseng’s relevantresearch,using the variable discount factor to adjust the production process. Thispaper presents an improved variable discount factor, called single EWMA(Exponentially Weighted Moving Average, EWMA) controller. This methodmakes controller without the constraint of the interference model.Analyticexpression of the variable discount factor is given that inference is in both case ofstationary time series model and non-stationary time series model. The deficiencyof great excursion and low speed of approaching the target value during the earlyproduction process were improved.The paper verified the effectiveness of thealgorithm and discuss the factors that influence effic iency of algorithmimplementation.On the basis of single EWMA controller to change the discountfactor,presents the variable discount factor Double EWMA controller,and analyticexpression of the variable discount factor is given that inference is in both case ofstationary time series model and non-stationary time series model.And the thesimulation was made under two situation.and controller meets the designrequirements.