A COMPACT, LOW-COST SYSTEM FOR SUB-100 NM X-RAY-LITHOGRAPHY

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 Cu(L) electron bombardment x-ray source (lambda = 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-mu-m-thick SiN(x). The exposure chamber contains a pin chuck to keep the wafer flat, a mask holder, and piezoelectrically driven X, Y, and theta stages. In this initial design, mask-to-wafer alignment is performed using a high NA (0.95), 1000x 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 approximately 5-mu-m to avoid the deleterious consequences of diffraction at the Cu(L) 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.