Membrane mask aero and thermoelastic control for proximity lithography

Proximity lithography using thin membrane window structures to carry masking patterns during radiation exposure steps is reaching levels of such high precision that the process can benefit from active elastic control of membrane deformations. This paper discusses two methods of actively controlling membrane mask deformation. The first is the mitigation of unwanted out-of-plane aeroelastic effects caused by rapidly stepping between wafer exposure fields while maintaining a sub [email protected] gap. The second is an in-plane thermoelastic active deformation to improve overlay accuracy.