Status of x-ray lithography

This paper will review some of the current approaches to x-ray lithography technology for device and circuit fabrication. Recent results in source, mask, process, and alignment research will be surveyed. A special emphasis will be placed on the differences in approach using full wafer, conventional source systems compared with those which are based on step and repeat and which may use a storage ring source. Systems which use a full wafer approach can compete with full wafer optical lithography at minimum circuit feature dimensions greater than about 1 1/2µm. Their resolution is also competitive with that of optical wafer steppers, but the overlay achievable with wafer steppers is potentially better. If the resolution achievable with x-rays (≪1µm) is combined with the local control over alignment obtainable with a step-and-repeat approach, then a lithographic technology compatible with dense submicron circuits is potentially obtainable. However, this case will need the increased exposure speed which is achieved most easily by use of a synchrotron radiation source.