Virtual metrology for plasma particle in plasma etching equipment

Virtual metrology for a plasma particle in plasma etching equipment is described in this paper for the first time. No direct measurement of plasma particles is carried out by an inspection tool but the generation of plasma particles can be predicted by detecting plasma density change indirectly measured using an equipment monitoring tool. It is found that the plasma density change can be detected by several equipment parameters like self-bias voltage using PLS analysis. The correlation coefficient of 0.75 is obtained between measured number of particles and predicted number of particles by a virtual parameter. It is demonstrated that the virtual parameter generated several parameters is useful as virtual metrology for a plasma particle.