A compact, low-cost system for sub-100 nm x-ray lithography

Abstract

We have developed a compact, low-cost system for sub-100-nm x-ray lithography. This system, which provides mask alignment and exposure at atmospheric pressure, was designed for sub-100-nm electronics research where the process latitude and high throughput of x-ray nanolithography have proven to be especially valuable. The system includes a CuL electron bombardment x-ray source (λ=1.34 nm) and an exposure chamber. The exposure chamber is filled with 1 atm of helium and is separated from the vacuum chamber housing the electron bombardment source by a 2-cm-diam window of 1–2-μm-thick SiNx. The exposure chamber contains a pin chuck to keep the wafer flat, a mask holder, and piezoelectrically driven X, Y, and θ stages. In this initial design, mask-to-wafer alignment is performed using a high NA (0.95), 1000× optical microscope. Future designs will incorporate computer-controlled interferometric alignment, which is compatible with sub-10-nm precision. For sub-100-nm lithography, the mask and substrate are separated by less than ∼5 μm to avoid the deleterious consequences of diffraction at the CuL wavelength. The mask-to-wafer gap is adjusted using a piezoelectrically controlled mask holder. The system is modular, easily reproduced, and suitable for low-budget nanolithography.