Profile Control of SiO2 Trench Etching for Damascene Interconnection Process

The purpose of the present study is to reveal a microtrench generation mechanism in the damascene trench etch process for SiO2 film. Experiments are discussed for the CO gas flow and the pressure change, employing a C4F8/CO magnetron etch system. Increasing the CO gas flow or the pressure prevents the microtrench generation. Moreover, the microtrench ratio A/B that is defined by the depth at the edge of the trench bottom, A and the trench depth at the center of the trench bottom, B becomes higher in accordance with increasing larger space size. In previous reports, the main effect of CO gas and pressure increase is identified as decreasing CFx radical density by dilution of C4F8 or by increasing the residence time. The reduction of CFx radical flux may prevent microtrench generation by decreasing the formation of fluorocarbon film at the trench bottom. These results suggest that the microtrench generation is caused by thicker formation of fluorocarbon films at the center of the trench bottom which has a larger solid angle than at the edge of the trench bottom.