The question “are there any bubbles trapped” has been asked many times of step-and-flash nanoimprinting. ASML was granted a U.S. patent on Tuesday, 6 April, with the title “Imprint lithography” [US7692771] The invention envisions a visible wavelength illumination and a scattering detector focussed on the template/resist interface. By watching the amount of light scattered from the interface, one can determine whether bubbles are present. The feedback loop permits real-time control of the delay between the template positioning and resist hardening steps, for example.
This patent has a sibling [US2007-0018360] which is ready to issue. Its allowed claims are more explicit, stating
the output providing an indication of whether or not the imprintable material has substantially fully flowed into a recess of the imprint template.