Image transfer for photolithographic mfr. of integrated circuits - uses constant duration pulse type laser and cumulative measurement of radiant energy transport and comparator to control laser output

摘要

The radiating energy source is used to transfer composite patterns, so that the image of a non diffusing object whose transparency is not uniform is reproduced with a predetermined enlargement on a substrate covered with a material sensitive to the emitted radiations. The source is a pulsed laser which emits pulses whose duration is constant. The energy emitted by the laser is controlled and verified by a system which takes cumulative measurements of the amounts of energy transported by the pulses and which compares these amounts with the reference value. The rate of lithographic transfers is much increased whilst maintaining or improving the resolution. The laser is of the krypton-fluorine type with an emission band centred at 248 nm.