Photosensitive glass

[2][3][4] When the glass is exposed to UV light with wavelengths between 280–320 nm, a latent image is formed.

The glass remains transparent at this stage, but its ability to absorb UV light increases.

This increased absorption is only detectable using UV transmission spectroscopy and is caused by an oxidation reduction reaction that occurs inside the glass during exposure.

[6] The lithium metasilicate in the exposed regions of the glass can be etched by hydrofluoric acid (HF).

This forms glass microstructures with a roughness in the range of 5 μm, resulting in a three-dimensional image of the mask to be produced.