High-throughput photomask fabrication using 50 kV variably shaped electron-beam lithography was examined for resist heating distortions. Effective absorbed energy changes in the resist due to heating were measured using beam current density and subfield time sequences as parameters. Absorbed energy changes due to short-range heating inside a subfield were also determined. Corresponding linewidth variations caused by resist heating were measured. This showed that the 1 mu m gaps had become completely broken. The sublimation of resist during exposure was investigated, and the subsequent reduction in resist thickness was measured as a function of exposure dose. The highly sensitive resist PBS [poly(butene-1 sulfone)], which is used widely for photomask manufacturing, was used for the heating measurements. It was concluded that high-throughput variably shaped electron-beam lithography with a high current density (20-80 A/cm(2)) may not be suitable for reticle fabrication without taking precautions for heating effects.