X-RAY NANOLITHOGRAPHY - EXTENSION TO THE LIMITS OF THE LITHOGRAPHIC PROCESS

The unique aspects of x-ray lithography that make it attractive for th e sub-100 nm domain include: a highly localized, sharply peaked point- spread function, leading to minimal proximity effects, absence of spur ious scattering; an intrinsic resolution below 30 nm; compatibility wi th all pattern geometries; and parallel exposure (i.e., compatibility with volume production). The major problem areas are: the mask-sample gap (less than 5 mu m for linewidths below 70 nm), and absorber stress , which must be near zero to avoid mask distortion. Nanometer-level pa ttern placement and alignment are considered achievable by means of sp atial-phase-locked e-beam lithography and interferometric-broad-band i maging, respectively. The efficacy of x-ray nanolithography has been d emonstrated via the fabrication of a variety of sub-100 nm-featured qu antum-effect devices, Si MOSFETs, and grating-based optoelectronic dev ices. In the event that the small gaps required of proximity x-ray nan olithography prove unacceptable in manufacturing, x-ray projection usi ng arrays of zone plates appears to be the only approach that can empl oy the optimal wavelengths (i.e., similar to 1 nm or 4.5 nm) and achie ve deep sub-100 nm resolution. A scheme is proposed that employs an ar ray of zone plates in a pattern generator mode.