Method and apparatus for optically determining defects in a semiconductor material

A method of detecting individual defects in or near the surface of a semiconductor material, comprising the steps of:

• directing an infrared beam of monochromatic light, having an energy level below the bandgap energy of the semiconductor material, towards a first area of the semiconductor surface;
• simultaneously directing a time-modulated beam of monochromatic light, having an energy level above the bandgap energy of the semiconductor material, towards the surface of the semiconductor;
• focusing the time-modulated light beam to a second area, substantially smaller than, and within, the first area, the energy of the beam being substantially absorbed by said surface to excite electrons and holes in or near said material surface to alter the reflectivity of said surface;
• detecting the intensity of the infrared light beam reflected from the semiconductor surface;
• and
• processing only that portion of the detected infrared beam intensity that is modulated at the frequency of the time-modulated light beam to locate defects in or near the semiconductor surface.