between areas 10 and 14 needs to be minimized since area 10 is receiving heat from the euv radiation from the lithography process the other areas of the euv reticle designated by 14 are the proposed areas for the additional heat source as illustrated the section of the mask exposed to radiation 10 and the areas 14 that are not exposed vary as a function of time as the reticle is moved across the euv exposure field 0019 fig2 illustrates schematically how the invention is intended to solve the problem of thermal gradients on euv reticle by supplying an additional heat source 20 to the areas of the mask that aren 39 t exposed to euv radiation a constant heat flux can be supplied to the mask surface minimizing any temperature gradients across the mask surface this is done through one or more filters illustrated as filter a and filter b in fig2 0020 fig3 illustrates an example system how the invention would operate in an euv lithography environment as the euvl reticle 12 is scanned across the euv exposure field additional heat through heating source 20 will be supplied to the non euv exposed areas 14 in fig1 through optics 34 and filters a and b in such a manner to maintain the surface of the mask at a constant temperature control device 32 both measures temperatures and controls cooling chuck 31 and heating source 21 it also synchronizes filters a and b with the movement of the euvl reticle 12 on reticle stage 33 calculations in table 1 below indicate that a 200w heating source is adequate to maintain the reticle at a constant temperature the calculations are based on crystalline and elemental.