Effects of SF6 addition to O-2 plasma on polyimide etching

For further scaling down of silicon devices, the application of low-k inter layer dielectrics instead of silicon oxide has been considered to reduce po wer consumption, crosstalk and interconnection delay. In this paper, the ef fect of SF6/O-2 plasma chemistry on the etching characteristics of polyimid e has been studied using a electron cyclotron resonance (ECR) plasma etchin g system. Addition of SF6 gas results in a very smooth etched surface even though this causes a reduced etch rate due to the formation of nonvolatile fluorine compounds inhibiting the reaction between oxygen and hydrocarbon p olymers. However, the etch rate can be compensated by applying a substrate bias or increasing the microwave power. As a result, 1-2 mum line and space patterns were successfully obtained using a SiO2 hard mask.