Semiconductor Production 101

Photolithography

EUV lights with a wave length of 13.5 nm are used to expose the photoresist and transfer images from masks to the silicon wafer.

The exposure time and focus are very important to reach the desired results. An inadequate focus will result in leftover photoresist particles as some holes aren't exposed properly. You get similar results with underexposure. The photoresist webs can easily be too wide and holes aren't exposed sufficiently. Overexposure creates holes that are too large or photoresist webs that are too thin. It's tricky and time-consuming to adjust and optimize this process, and inappropriate holes will hamper the interconnects.

So called steppers are used to move the wafer to the exact position. A row or a different section, typically a single die, can then be exposed properly. So-called micro steppers or micro exposure tools can then be used to make additional changes. This is used to debug existing technology and optimize the production process. Micro steppers usually work at areas of less than 1 mm, while regular steppers cover much larger areas.

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