The lithography process for 0.8um almost certainly uses UV wavelength of 365nm. The optical wavelength is used to pattern a photoresist masking layer between 1.0um and 3.0um thick on the surface of the wafer. This resist is patterned then developed using a weak alkali to leave the photoresist in the pattern of the mask. Photoresist is normally positive resist. This resist is resistant to the etches that are used to make the final patterns on the wafer. They are typically novolak resins that can withstand wet acids, alkalis and plasmas. They are removed using either Sulphuric acid doped with hydrogen peroxide which will strip off any organic material, or using an oxygen plasma (creatining ozone radicals which will strip off organic materials).
For 0.35um and smaller, the wavelenth of the UV light was pushed lower for higher resolution (Deep UV) then for 0.1um and smaller pushed even lower into the 195nm range. So using various optical tricks, 195nm can produces features of 65nm. One trick is to pattern the minimum dimension possible with the light source (say 90nm) then lightly etch away the resist in an oxygen plasma. So if you deposit 1.2um of resist and pattern it to produce a cross section of 1200x90nm, then etch away 0.2um of resist in a plamsa, you get 1000x70nm producing a minimum linewidth of 0.07um.
The plasma etch systems are set up to reproduce the photoresist linewidth into whatever material you are etching, so the minimum linewidth is dominated by the photoresist pattern just prior to etching.