Electron beam lithography is widely used to fabricate densely packed devices such as high-frequency transistors, since optical lithography is unable to write the small patterns required for such devices. One major problem with micropattern writing with an electron beam exposure system, however, is slow writing speed; since the system has to write an extremely large number of patterns on low-sensitivity resist with a highly focused beam, exposure times are quite long. To speed up the writing process, we have attached a thermal field emission gun to our electron beam exposure system. This gun is designed to increase the electron source brightness and probe current density. In order to determine this new probe current density, we conducted an extensive evaluation on a complete lithography system which uses a thermal field emission gun. We have measured a current density of ~ 1000 A/cm2 at an accelerating voltage of 25 kV and conclude that this lithography system can be put to practical use in production areas requiring high throughput and submicron exposures.