A MULTILEVEL APPROACH TO THE CONTROL OF A CHEMICAL-MECHANICAL PLANARIZATION PROCESS

A multilevel hierarchical control system has been designed and is bein g applied to chemical-mechanical planarization (CMP) process control, The current implementation of the control system incorporates closed-l oop run-to-run (R2R) control and open-loop real-time monitoring, and c an accommodate inter-cell control. The R2R control element is enabled via a generic cell controller (GCC) implementation that provides flexi ble automated control of the process and equipment, multiple control a lgorithm branches and fuzzy logic decision capability among the branch es, simulation capabilities, hardware and software independence, and e xtensive GUI support for control and data analysis. The R2R element ut ilizes a linear approximation multivariate control algorithm (branch) that supports individual exponential weighted moving average (EWMA) mo deling of advices (outputs), weighting of inputs, granularity, and inp ut bounding. The real-time element of the control system utilizes a pa rtial least squares (PLS) algorithm to identify real-time equipment in put trace patterns and relate these patterns to alarming conditions. T he entire control system is designed to provide multivariate control o f CMP process removal rate and uniformity. As a result of extensive de sign of experiments and testing, the R2R control level has been demons trated to achieve good control of removal rate and fair control of uni formity. The addition of the real-time element is expected to improve process control and reduce R2R process noise, thus leading to a more e ffective R2R control element. (C) 1996 American Vacuum Society.