Browsing by Author "Deng, Hao"
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Item Comparison of Run-to-Run Control Methods in Semiconductor Manufacturing Processes(2000) Zhang, Chang; Deng, Hao; Baras, John S.; Baras, John S.; ISRRun-to Run (RtR) control plays an important role in semiconductor manufacturing.In this paper, RtR control methods are generalized. The set-valued RtR controllers with ellipsoidapproximation are compared with other RtR controllers bysimulation according to the following criteria: A good RtR controller should be able to compensate for variousdisturbances, such as process drifts, process shifts (step disturbance)and model errors; moreover, it should beable to deal with limitations, bounds, cost requirement, multipletargets and time delays that are often encountered in realprocesses.
Preliminary results show the good performance of the set-valued RtRcontroller. Furthermore, this paper shows that it is insufficient to uselinear models to approximate nonlinear processes and it is necessary to developnonlinear model based RtR controllers.
Item Run by Run Control for Semiconductor Manufacturing(1999) Deng, Hao; Baras, John S.; ISRA new type of Run-by-Run controller based on the DHOBE (Dasgupta-Huang Optimal Bounding Ellipsoid) algorithm is designed and simulated for semiconductor manufacturing process. One approach is to use the algorithm to implement online model identification which leads to a model-reference controller. The other approach utilizes the worst case idea, to implement the set-valued controller.Both kinds of controllers are applied to linear and quadratic models which are derived from experiments. The controllers are simulated for cases when processes satisfy slow drifting, abrupt shift, bad data and model errors. The controllers are tuned according to the requirements of the algorithm and process and the simulation data is analyzed according to the performance benchmark.
All the simulation results are compared to either the Exponentiallly Weighted Moving Average (EWMA) or Optimal Adaptive Quality Controller (OAQC) control method.
Item Run-to-Run Control Methods Based on the DHOBE Algorithm(1999) Deng, Hao; Zhang, Chang; Baras, John S.; ISR; CSHCNMany run-to-run (RtR) control methods have been developed in recentyears. Two particular set-valued RtR control schemes based on the Dasgupta-Huang OptimalBounded Ellipsoid (DHOBE) algorithm are introduced. Compared to other RtR control schemes, the methods in this paper only need to know the bound of the noises, and are easyto implement.The DHOBE algorithm, for eachrecursion, returns an outer bounding ellipsoid of the estimated parameters. If the center of the ellipsoid each time istaken as the model coefficients, the explicit model update isimplemented which leads to a model-reference method. If we choose theworst-case point which maximizes the cost function in the set, then wecan apply the set-valued worst case approach. These two methods were compared with two other main RtRcontrol schemes: the Exponentially Weighted Moving Average (EWMA) methodand the Optimizing Adaptive Quality Controller (OAQC) method. Simulation results showed the superior performance of the RtRcontrollers based on the DHOBE algorithm. Furthermore this paper showedthat it is necessary to applynonlinear models to compensate for severe nonlinear processes.