Abstract

Since 1970, advances in lithography have allowed the minimum dimensions of commercially produced microelectronic integrated circuit elements to be reduced by a factor of two every six years. If this industry trend is to be sustained, a lithographic technology must be commercially available within 10 years for the manufacture of memory and logic circuits having minimum feature sizes ≤0.13 μm. The strategy to decrease the printed linewidth in optical projection lithography has been to decrease the exposure wavelength, increase the numerical aperture (NA), or both. The relatively new method of Extreme Ultraviolet Lithography (EUVL) employs short-wavelength 11-14 nm EUV radiation in combination with all-reflective, low-NA reduction imaging cameras to simultaneously achieve 0.1 μm resolution and ±1 μm depth-of-focus. Fig. 1 shows a schematic representation of the method. A multilayer-coated EUV reflective condenser collects EUV from a laser plasma source to illuminate a reflective object mask. An image of the mask is projected with demagnification by an all-reflective imaging objective to a resist-coated wafer where the lithographic pattern is produced. Fig. 2 shows a scanning electron micrograph of representative test gratings patterned in resist with EUVL. The grating have equal lines and spaces with the dimensions shown. The current status and future prospects of using EUVL for the fabrication integrated circuits with dimensions ≤0.13 μm will be reviewed in this presentation.

© 1995 IEEE