Virtual metrology for plasma etch using tool variables

This paper presents work carried out with data from an industrial plasma etch process. Etch tool parameters, available during wafer processing time, are used to predict wafer etch rate. These parameters include variables such as power, pressure, temperature, and RF measurement. A number of variable selection techniques are examined, and a novel piecewise modelling effort is discussed. The achievable accuracy and complexity trade-offs of plasma etch modelling are discussed in detail.