Coherent Illumination Improves Step-And-Repeat Printing On Wafers

Michel Lacombat; Georges Michel Dubroeucq

doi:10.1117/12.957175

17 July 1979 Coherent Illumination Improves Step-And-Repeat Printing On Wafers

Michel Lacombat, Georges Michel Dubroeucq

Proceedings Volume 0174, Developments in Semiconductor Microlithography IV; (1979) https://doi.org/10.1117/12.957175
Event: Developments in Semiconductor Microlithography IV, 1979, San Jose, United States

Abstract

VLSI circuit fabrication will require new optical projection systems with micron resolution. If conventional incoherent illumination is used, large numerical aperture optics will be required, giving rise to smaller fields and reduced depth of focus. An attractive alternate approach is the use of nearly spatially coherent illumination which, for the same numerical aperture, gives higher resolution and better size control without sacrificing field size and depth of focus. Partially coherent illumination is defined and different designs for arc and laser sources are given. The effects on photoresist profile formation are analysed by using a resist behaviour model. It is shown that with partially coherent illumination, linewidths are less sensitive to variations of the energy absorbed in the resist and, consequently, are better controlled across oxide steps. A set of curves is given to determine the useful resolution and the linewidth variation amplitudes versus the coherence degree and the numerical aperture of the lenses. SEM micrographs confirm these results.

Citation Download Citation

Michel Lacombat and Georges Michel Dubroeucq "Coherent Illumination Improves Step-And-Repeat Printing On Wafers", Proc. SPIE 0174, Developments in Semiconductor Microlithography IV, (17 July 1979); https://doi.org/10.1117/12.957175

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