| 摘要 |
PURPOSE:To achieve stable and quick detection of foreign matter regardless of direction thereof by use of an S deflected laser respectively for the laser beams irradiated in the X and Y axes. CONSTITUTION:A pair of S deflected laser oscillators 30 of a wavelength lambda1 is arranged in the X-axis irradiation system and a pair of S deflected laser oscillator 31 of a wavelength lambda2 in the X-axis irradiation system. When irradiated at the detection point 43 on the wafer 32 from the S deflected laser oscillators 30 and 31, laser beam is spattered on the wafer depending on the pattern and foreign matters. The beam thus scattered is collected through the lens 33, the slit 34 and the realy lens 35 and then, the laser beam component of the wavelength lambda1 is made to transmit with a dichromic mirror 36 while the laser beam component of the wavelength lambda2 is reflected. Then, only the P deflected laser beam component 37 and the S deflected laser beam component 38 are extracted with the S deflected cut filters 39 and 40 to be detected with photoelectric elements 41 and 42. Addition of the two detection outputs enables one to determine whether there is foreign matter or not regardless of the direction thereof. |
