A control strategy for dry etch processing

The article describes a control strategy for a dry etching process. The basis for this control methodology is that a dry etching stage may be described by one or more response surfaces or parametric models in a multidimensional space. The process trajectory is defined in relation to response functions (parametric models) and is maintained by the use of adaptive control algorithms. The control factors are not confined to external machine variables, such as gas flow rate or operating pressure. Rather, it is recognised that dry etching performance is dependent on fundamental plasma parameters, such as ion flux, ion energy and the concentration of reactive species in the discharge. The process chosen is the dry etching of polymeric layers in oxygen plasmas generated under reactive ion etching (RIE) conditions. This process finds important application in schemes involving plasma-developable resists or in multilevel resist structures