X-RAY-LITHOGRAPHY, FROM 500 TO 30 NM - X-RAY NANOLITHOGRAPHY

Proximity X-ray lithography (XRL), using wavelengths between 0.8 and 1 .5 nm, provides a near-ideal match to the ''system problem'' of lithog raphy for feature sizes from 500 to 30 nm, by virtue of ''absorption w ithout scattering'' and recently developed mask technology. The effect s of photoelectrons, at one time thought to be problematic, are now un derstood not to limit resolution. With experiments and simulations via Maxwell's equations, we show that useful resolution is not limited by diffraction until linewidths are below 50 nm. It is critically import ant to optimize the source spatial incoherence to eliminate the delete rious effects of high spatial frequencies. Mask architecture and patte rning methods are presented which we believe are compatible with manuf acturing at linewidths from 500 to 30 nm. Distortion due to mask frame flexing and absorber stress can now be eliminated. Elimination of dis tortion at the pattern generation stage remains the problem of greates t concern. We discuss a proposed method of spatial-phase-locked electr on-beam lithography which could solve this problem. Our new interferom etric alignment scheme has achieved 18-nm alignment at 3sigma. We asse rt that projection XRL using multilayer mirrors at 13 nm can never mat ch the present performance of proximity XRL. Applications of sub-100-n m XRL, including MOS, quantum-effect, and optoelectronic devices are d iscussed which illustrate the benefits of high resolution, process rob ustness, low distortion, low damage, and high throughput.