The smallest features produced by electron beam lithography have generally been isolated features, as nested features exacerbate the proximity effect, whereby electrons from exposure of an adjacent region spill over into the exposure of the currently written feature, effectively enlarging its image, and reducing its contrast, i.e., difference between maximum and minimum intensity. Hence, nested feature resolution is harder to control. For most resists, it is difficult to go below 25 nm lines and spaces, and a limit of 20 nm lines and spaces has been found. 

Proximity effects (due to electron scattering) can be reduced by solving the inverse problem and calculating the exposure function formula_17 that leads to a dose distribution as close as possible to the desired dose formula_18 when convolved by the scattering distribution point spread function formula_19

लेंस
Proximity effect
इलेक्ट्रॉन किरण अश्मलेखन तंत्र
See also