the masks for X-ray and e-litho are made on membranes, so that the beam is not absorbed or scaterred in the mask
the fabrication starts with a silicon wafer (green), which is oxidised (blue layer)
the oxide is etched on the backside and so is the total silicon wafer, except for the edges
the membrane is bonded at the edges, to insure stability
then the opaque regions are fabricated, as it is hown the next two pictures
the elements which are supposed to block the beams passing through the membrane, are made by additive (left) or substractive methods (right), as shown below
Substrate preparation
