Projection objective system for microlithography uses set of lenses and mirrors and beam divider with tilting control and aspherical top, front and rear surfaces

摘要

The projection system (1) incorporates a lighting system (2) with a laser and a pattern for the microstructure in the objective plane (3). There is a lens (17) and a quarter-wave plate (14) between the objective plane and the aspherical top surface (26) of the beam splitter (20). The semireflecting splitter surface (29) is inclined at an angle of 45 degrees plus or minus 10 degrees. Reflected light passes through a second quarter-wave plate (15) and two lenses (5) before being reflected back on its path by a concave mirror (6). Light passes back through the aspherical front surface (27) and part of the beam passes through the aspherical rear surface (28) of the beam splitter. The light is reflected from a plane mirror (11), passes through a lens group (13) and a third quarter-wave plate and is focused on the wafer or chip (4) being prepared for etching.