X-ray nanolithography: Extension to the limits of the lithographic process

Abstract

The unique aspects of x-ray lithography that make it attractive for the sub-100nm domain include: a highly localized, sharply peaked point-spread function, leading to minimal proximity effects; absence of spurious scattering; an intrinsic resolution below 30 nm; compatibility with all pattern geometries; and parallel exposure (i.e., compatibility with volume production). The major problem areas are: the mask-sample gap (less than 5 μm for linewidths below 70 nm), and absorber stress, which must be near zero to avoid mask distortion. Nanometer-level pattern placement and alignment are considered achievable by means of spatial-phase-locked e-beam lithography and interferometric-broad-band imaging, respectively. The efficacy of x-ray nanolithography has been demonstrated via the fabrication of a variety of sub-100 nm-featured quantum-effect devices, Si MOSFETs, and grating-based optoelectronic devices. In the event that the small gaps required of proximity x-ray nanolithography prove unacceptable in manufacturing, x-ray projection using arrays of zone plates appears to be the only approach that can employ the optimal wavelengths (i.e., ~1 nm or 4.5 nm) and achieve deep sub-100 nm resolution. A scheme is proposed that employs an array of zone plates in a pattern generator mode.