In X-ray lithography, if S is the size of the X-ray source, g is the gap between wafer and mask, and D is the distance between the source and the mask, then the blur is

-Ray lithography

• In X-ray lithography, an X-ray source illuminates a mask, which casts shadows on to a resist-covered wafer.
• The mask and resist material for X-ray lithography are mainly determined by the absorption spectra of these materials in the X-ray region.

Proximity printing

Since the wavelength of X-ray is small, diffraction effects can be ignored and simple geometrical considerations can be used in relating the image to the pattern on the mask.

• The opaque parts of the mask cast shadows onto the wafer below.
• The edge of the shadow is not sharp because of the finite diameter of the focal spot of the electrons on the anode [X-ray source] at a finite distance from the mask.

The blurring of shadow can be evaded by the following equation.

\(\partial = \frac{{Sg}}{D}\) 

∂: Blur

g: the gap between the mask and the wafer

D: Distance of source from the mask