If an electron beam with high energy is channeled onto a resist layer (5- 100 keV), forward scattering (< 90° in direction of arrival) occurs as well as backward scattering (> 90° in direction of arrival). The deflection causes the electron beam to widen, thus reducing resolution. The backward scattered primary electrons, given a sufficient dose, cause a complete exposure of a resist volume which is significantly bigger than the original beamwidth. This effect can be systematically put to use in order to generate undercut resist structures. The electrons are scattered backward on the substrate and cause an increased exposure of the lower resist areas (proximity effect). The forming of the undercut can be specifically controlled by adjusting a suitable dose.
Overview E-beam Other Resists