X-ray lithography at ˜100 A linewidths using X-ray masks fabricated by shadowing techniques

Abstract

Abstract A new technique for fabricating high contrast X-ray masks with precisely controlled linewidths of less than 100 A is described. The technique is based on the deposition at an oblique angle ("shadowing") of X-ray absorber material onto relief structures of triangular or square cross-section in a polyimide plastic membrane. Precise linewidth control is possible because shadowing angle, absorber thickness and relief structure can be precisely determined. The smooth and well-controlled triangular cross-section structures required are produced in silicon by anisotropic chemical etching and then transferred to polyimide by molding. The square structures are made by reactive-ion-etching SiO 2 with CHF 3 and are transferred to polyimide by molding. Results of a numerical model of carbon K (45 A) X-ray exposures in PMMA of shadowed triangular profile masks are presented which indicate that linewidth control of ±50 A should be possible for submicrometer period gratings. Scanning electron micrographs of PMMA gratings of 1 μm, 3200 A and 1968 A period with linewidths as small as 400 A are shown. The successful replication of <200 A linewidth patterns in PMMA using the carbon K X-ray and shadowed square cross-section masks is reported.

Inventors

• 👤 Dale C. Flanders

Bibliographic Details