Fabrication of x-ray masks using evaporated electron sensitive layers for back patterning of membranes

Abstract

A process aimed at fabricating proximity x-ray lithography masks is presented. In this technique, the Ta absorber layer is deposited and patterned on the back side of the membrane and nonspin-coated electron sensitive layers were used in order to achieve high resolution patterning of this absorber. The advantages gained by this approach include a reduction of the membrane temperature during the plasma etching step of the absorber patterns without using any cooling gas. This temperature reduction results from the direct contact of the membrane with a cooling plate. This approach also allows increased protection of the absorber patterns from contamination during exposure of the mask. A third advantage is that the smooth surface of the mask exposed to the wafer in the x-ray lithography stepper may also make it possible to reduce the gap between wafer and mask, thus achieving increased resolution with the x-ray lithography process.

All evaporation submicron lift-off lithography process with negative e-beam QSR-5 resist

“…Another advantage is the very high resolution, permitting to define patterns as thin as sub-100 nm. Many more devices could be lithographed with QSR-5 resist such as optic fibers, non conventional flat surfaces, or three dimensions features such as MicroElectroMechanical Systems (MEMS) [15,16], and so on. It can be used as a mask for oxygen-free plasma or wet etching due to its high resistance with most common wet etch solutions.…”

Arrays of holes fabricated by electron-beam lithography combined with image reversal process using nickel pulse reversal plating

“…It is important to note that no dose correction or proximity pattern correction was used during exposure by the electron-beam lithography and that a uniform dose was used for all the dots. By combining a dry e-beam resist such as QSR-5 and electroplating, it is possible to invert the tonality of any pattern on any substrate such as back patterning of membranes, 20 flexible polymers or any relief structure. 21 This is not possible using conventional electron sensitive resists since spin-coating does not produce a uniform thickness layer on very high relief structures.…”