Study of the Electron Beam Effect on Critical Sizes of Photoresistive Mask Elements in SEM Measurements

In the present paper, we study the effect of photoresist line shrinkage used in KrF lithography processes while measuring the lateral dimensions of a photoresist mask by scanning electron microscopy. It is shown that the highest change in critical sizes is observed after the first two or three measurements, while sunsequent measurements have a smaller effect on the line shrinkage The influence of various parameters (time of exposure by electron beam, accelerating voltage, geometrical parameters of photomask) on the decreases of critical sizes is shown. An exponential character of the dependence of line shrinkage on the electron beam exposure dose is shown. The parameters of the maximum shrinkage and saturation time are determined and compared with previous researches. An assessment of influence of the initial photoresist viscosity on the the line shrinkage is made. In conclusion, some methods are proposed to minimize or avoid the shrinkage effect on the studied samples and are applicable as in-line systems for lithography process control in the production cycle.