CHARGING EFFECTS ON TRILEVEL RESIST AND METAL LAYER IN ELECTRON-BEAM LITHOGRAPHY

Charging effects of trilevel resist on a W layer have been investigated with an electron beam lithography system. The tungsten layer was deposited before the resist and the charge-induced beam deflections were measured for several thick W layers. A test pattern was employed consisting of an array 21 x 21 cross marks in a 3 mm field. The charging effects show different dependencies on W thickness between 20 and 30 keV because of the W backscattering. To evaluate the correlation between the charging and the backscattering process in W and trilevel resist, reflected electron signals were detected from the developed resist marks. The resist mark signal has a double sloped inverse peak characteristic due to backscattering from the W layer and absorption by the resist mark. As a result, the charge-induced beam deflections and the intensity of backscattered electrons are increased in proportion to W thickness. The authors will discuss the electron distribution caused by the electron beam and sample material interacting using these experimental approaches and numerical simulations of electron beam scattering.