Various approaches can be used to interrogate a surface such as a surface of a layered semiconductor structure on a semiconductor wafer. Certain approaches employ Second Harmonic Generation while other utilize four wave-mixing or multi-wave mixing. Corona discharge may be applied to the sample to provide additional information. Some approaches involve determining current flow from a sample illuminated with radiation.

A electronic apparatus manufacturing apparatus includes at least two transporters transporting process products, a processor performing a manufacturing process on a process product transported by at least one of the at least two transporters, a processor measurer disposed on the processor to measure a processor vibration of the processor, and a controller calculating a processor frequency response of the processor based on the processor vibration and adjusting a velocity and a position of each transporter and/or a number of transporters arranged in one area among the at least two transporters based on the processor frequency response.