Electronic – Evaluating the quality of photomasks


Photolithography would be new in our instituion and i could not ask any experts there about it, thats why i turned here.

I have created a photomask using an electrolithograpy proccess and am now stuck on how to QUANTITATIVELY evaluate the physical quality of the mask. I have googled that i can check the size consistency of the paterns (digital size to printed size on mask), thats it all i know, what else should i check for? Any help would be appeciated.


We will be using the mask in contack uv photolithography to create stuctures in silicon substrate within the micrometer range. By far, google have shown results on evaluating masks based on how good is it for producing stuctures. but few result show how to evaluate a photomask before creating the structures.

Best Answer

The simplest way to evaluate the mask is just to inspect it visually, as you say you have already done. Be sure to take a look at the critical (ie smallest) features to ensure the mask looks how you expect. With a good light microscope with high NA objective, you can get sub-micron resolution on optical images.

Another things you can check if you really want to dive deep into evaluating the quality of the mask is to measure the consistency of the height of your features. If the features on the mask do not press against the resist evenly across the whole wafer, some areas on the wafer might get exposed unevenly. You could look at this with a profilometer or even SEM if you want to really get into the weeds.

That being said, testing it out in the actual process is the best way to examine the quality. In my experience, I usually have to expose a couple test wafers to optimize the exposure time anyway, so this provides a built-in test of the mask. Having an exposure grid with different sized features can make this process a little easier.