The invention provides a method for correcting thermally-induced field deformations of a lithographically exposed substrate. This device includes a generally cylindrically-shaped insulating sleeve, a substantially planar and disk-shaped metal insert with a rectangular aperture that pries off a bottle cap, and a ring-shaped structure that stabilizes the insert within the insulating sleeve. The process has the benefit of allowing continuous operation and providing an alternative to existing processes for hydrophobic coating. For those segments, it would be desirable to have the smallest segment size possible, namely, a single disk block. The pixel is isolated from radiation passing through the aperture.