First the photoresist is applied to the substrate to be etched. Photoresist can be applied by the following methods:
- Lamination
- Spin coating
![](http://toolnotes.com/wp-content/uploads/2021/02/photoresist.png)
A photo tool or mask is created.
Masks can be
- Positive development
- Maskant (photoresist) becomes more soluble after exposure
- The unexposed areas are not dissolved in the development process.
- Negative development
- Maskant become less soluble after exposure
![](http://toolnotes.com/wp-content/uploads/2021/02/Phototool.png)
Photoresist is exposed to UV light.
![](http://toolnotes.com/wp-content/uploads/2021/02/exposure.png)
A latent image is created. In this case, the exposed area will become more soluble when developed.
![](http://toolnotes.com/wp-content/uploads/2021/02/Latent-image.png)
The resist is developed and the undeveloped resist is washed away.
![](http://toolnotes.com/wp-content/uploads/2021/02/Development.png)
The developed resist is now ready for etching.
![](http://toolnotes.com/wp-content/uploads/2021/02/Developed.png)
The exposed areas are etched away by the etchant solution and the mask is washed away.
![](http://toolnotes.com/wp-content/uploads/2021/02/Etching1.png)
The workpiece is then ready for other processes.
![](http://toolnotes.com/wp-content/uploads/2021/02/Etched-Workpiece.png)
Example application: Signage. Etched areas can be filled with paint.
![](http://toolnotes.com/wp-content/uploads/2021/02/Paint-filled-etching.png)
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