Patent ID: 7355143

Claim:
A circuit board producing method in executing, inside a processing chamber, a treatment of forming a thin-film on a to-be-processed target or a treatment of processing said thin-film formed on said to-be-processed target, comprising the steps of: performing an irradiation with a laser light into said processing chamber through an observing window, said laser light having a desired polarization and a desired wavelength and being intensity-modulated with a desired frequency, wavelength-separating and light-receiving a light of a wavelength component of said frequency out of backward scattered-lights that have been scattered by particles inside said processing chamber through said irradiation and that have passed through said observing window, detecting said frequency component out of said light-received signal obtained by being light-received, obtaining, using said detected signal, information about number and size of said particles existing in a region irradiated with said laser light inside said processing chamber, and outputting said obtained information about said number and said size of said particles.