Precision, damage-free etching by electron-enhanced reactions: Results and simulations

Ion-enhanced dry etch methods inflict "etch process damage" through surface ion bombardment. These inherent limitations in conventional dry etch methods create potential roadblocks to achieving device properties necessary for scaling below 32 nm. We describe an alternative dry etch method in which electrons with energies below about 100 eV stimulate precision etching of features as small as 20 nm without damage. This Low Energy Electron Enhanced Etching (LE4) method also gives atomically smooth etched surfaces, very high selectivity between materials, and maintains stoichiometry of compound materials. LE4 etches low K dielectric materials with no loss of carbon, and gives Line Width Roughness (LWR) values dramatically smaller than achieved by ion-enhanced etching. We have developed the Electron Force Field (eFF) method to describe electron dynamics in highly excited electronic states, and use it to show preferential bond breaking and product desorption after electronic excitation of the sample surface.