Preparation of thin windows in silicon masks for x-ray lithography

Soft x-ray lithography requires the fabrication of thin windows in a material which is relatively transparent at the wavelength of the x rays used. A system under evaluation employs Al Kα radiation, thin window silicon masks, and pattern written in gold on the thin silicon membrane. Windows of uniform 1–5 μ thicknesses up to ∼4 cm in diameter have been made. A description is given of the procedures we now use for producing the complete masks. The etching itself takes 15–45 min. The procedures are uncritical and lend themselves to semiautomated operation. The yield for the etching procedure alone is close to 100%.