Methods to predict and correct resist heating during lithography

Abstract

The present invention relates to methods of predicting proximity heating in real-time as the writing proceeds enabling beam compensation to be performed in real-time. Particular attention is given to vector scanning in which the pattern of writing does not follow prescribed kinematics, but the writing tends to cluster into cells. A library of standard cells is constructed. As writing of the pattern proceeds, the individual flashes are agglomerated into cells that are compared with standard cells to determine proximity heating in the resist as a function of the distance of the previously written cells from the point of present writing, and the elapsed time since writing a previously written cell. Present writing snaps to a sufficiently coarse space-time grid to limit the computational burden but fine enough the represent variations in temperature over space and time. Further agglomeration of cells into super-cells, super-super-cells, etc. are also described. An advantage of the present technique is its applicability to vector scanning and to stenciling techniques for writing patterns on the wafer surface, not dependent on foreknowledge of a particular pattern of writing, as is the case for raster or serpentine scanning.