Is it possible to use Photolithography for telescope image sensor? The current largest digital CCD camera is the Vera C. Rubin Observatory, which has a whopping 3.2 gigapixels with a pixel size of 10 micrometers. In contrast, Agfa 10E56 holographic film has a resolution of over 4,000 lines/mm—equivalent to a pixel size of 0.125 micrometers.
It makes me think. Will it be possible to use a chemical image sensor to achieve a nanometer pixel size?
Between 1983 and 2006 the Digitized Sky Survey(DSS2) produced 1.1-gigabyte images (23,040 x 23,040) of 15 micrometers corresponding to 1.0 arcseconds using Photographic-plates. One of their challenges was storage space. They were forced to use a lossy adaptive algorithm to shrink the output size, during which data was lost.
But since 2018, we can produce 7 nanometers chips via the Photolithography process.
Can the same technology be used for image sensors? What can we do in 2021?
The pixel size is not a major constraint on the imaging capabilities of an astronomical telescope. The angular resolution of the image is limited by diffraction at the aperture of the telescope. For a reasonable pixel size, the telescope geometry can then be designed so that each pixel corresponds to a region of sky smaller than that angular resolution, so that making the pixels smaller would gain you very little.
Responding to a comment. A diffraction limited telescope with an aperture of $d$  observing at a wavelength of $\lambda$ has (at best) an angular resolution of $\lambda/d$ radians. So if it has an effective focal length of $l$, the smallest useful pixel size will be around $l\lambda/d$. The effective focal length depends on the whole optical setup and will usually be designed to make this size big enough.