I don't know about production chips with such things integrated, but it's certainly been tried. The below article is from 2008. https://www.eetimes.com/ibm-git

I don't know about production chips with such things integrated, but it's certainly been tried. The below article is from 2008. https://www.eetimes.com/ibm-git-demo-3d-die-with-microchannel-cooling/ https://www.eetimes.com/ibm-git-demo-3d-die-with-microchanne...