> For the complete documentation index, see [llms.txt](https://docs.hackerfabiitb.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hackerfabiitb.org/fab-basics/litho-performance.md).

# Litho performance

## Resolution test patterns

Pitch: the spacing between corresponding points of an array. Known in math as the period:

$$
T: f(x+T=f(x)
$$

A line array with 50% duty cycle is a pattern with linewidth=x, spacewidth=x, and period=x+x=2x

Isolated lines take spacewidth>>linewidth giving enough room for underexposed tails to extend

## Characterization Techniques

### Visual inspection: Optical Microscope

Gives inexpensive and immediate visual feedback: interference colours show resist thickness variation.

### Cross-section and 3D mapping: Profilometry, AFM


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