Gerhard Ittner

Future Possibilities Of Dioptric Lenses In Microelectronics

After a survey of the present state of optics in microelectronics future possibilities especially of dioptric lenses are discussed. Those lenses are marked mainly by the numerical aperture providing the resolution, and the diameter of image field. The numerical aper-ture seems to have a usefull limit between 0.4 and 0.5, providing minimum line widths of 0.4 to 0.7 microns. A future limit of field sizes cannot be given today. The possibility to develop new lenses is not only given by the capability of the optical designer, but also by other parameters, such as mechanical size limitations and lens manufactoring problems.

Reduction lens and illumination system for deep-UV aligners

The optical equipment for DUV-Aligners consisting of an all-quartz lens and an illumination system for a 248 nm narrowband excimer laser has been developed. First the concept of the illumination system is discussed. It was possible to achieve good illumination homogeneity in reticle and pupil planes combined with a reasonable efficiency. Data on illumination intensity and homogeneity is reported. An all-quartz lens which cannot be chromatically corrected has been designed and tested. The 5 : 1 reduction lens has a NA of 0. 42 and can print 0. 5 iim lines and spaces over a field diameter of 21. 2 mm. To obtain diffraction limited resolution a spectral bandwidth of 3 pm is required. Experimental data on optical performance is presented. Changes in environmental conditions can be compensated and do not influence the imaging quality. 1.