Fabrication of Carbon Membrane X-Ray Mask for X-Ray Lithography

Abstract

X-ray radiographic imaging techniques have been applied in many fields. Previously we proposed a method for X-ray phase imaging using X-ray Talbot interferometry which requires the use of X-ray gratings. In this work, we fabricated the X-ray gratings needed for X-ray Talbot interferometry using an X-ray lithography technique. For X-ray lithography the accuracy of the fabricated structure depends largely on the accuracy of the X-ray mask. Conventionally a resin material is used for the support membrane for large area X-ray masks. However, resin membranes have the disadvantage that they can sag after several cycles of X-ray exposure due to the heat generated by the X-rays. For our new proposal we used thin carbon wafers for the membrane material because carbon has an extremely small thermal expansion coefficient. This new type of X-ray mask is very easy to process, and it is expected that it will lead to more precise X-ray masks. We fabricated carbon membrane X-ray masks on 6 inch wafers with a 1:1 line-to-space ratio and a pitch of 5.3 μm, covering a large effective area of 100 × 100 mm2.