Penumbral blurring

In addition to penumbral blur, there is also a small magnification factor (A) at the edge of the mask. This is termed run-off distortion and results from the separation of source and mask as shown in the following equation ... 

For integrated circuit applications, the significant factor to be observed from Figure 6 is that a gap in excess of 100 can be tolerated for 1 resolution. With conventional sources, penumbral blurring due to the finite source size is more likely to limit resolution. X-ray lithography is perhaps the most promising method for large production of sub-0.75 devices because it... 

There are, however, some major limitations of x-ray lithography, and these include the difficulty of fabricating 1 x masks, the high cost of generating the x rays at sufficient power, penumbral and diffraction blurs that limit resolution (in the case of point sources), and overlay control. ... 

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