Measurement head for monitoring development of photoresist

摘要

The head comprises a collecting lens (4) and an annular detector (3) located in the focal plane of the lens. Lens and detector are positioned centrally about a common optical axis which is at 90 deg to the photoresist surface (5). The light beam projected from the light source can be distributed centrally about the optical axis, can be monochromatic and be focussed in the centre of the ring detector by a lens. By providing several annular detectors arranged around a common axis the reflected light can be detected over suitably divided solid angle areas.