CF4/O2 gas 플라즈마를 이용한 폴리이미드 박막의 식각

Abstract

Polyimide (PI) films have been studied widely as the interlayer dielectric materials due to a low dielectric constant, low water absorption, high gap-fill and planarization capability. The polyimide film was etched using inductively coupled plasma system. The etching characteristics such as etch rate and selectivity were evaluated at different CF4/(CF4+O2) chemistry. The maximum etch rate was 8300 Å/min and the selectivity of polyimide to SiO2 was 5.9 at CF4/(CF4+O2) of 0.2. Etch profile of polyimide film with an aluminum pattern was measured by a scanning electron microscopy. The vertical profile was approximately 90o at CF4/(CF4+O2) of 0.2. As 20% CF4 were added into O2 plasma from the results of the optical emission spectroscopy, the radical densities of fluorine and oxygen increased with increasing CF4 concentration in CF4/O2 from 0 to 20%, resulting in the increased etch rate. The surface reaction of etched PI films was investigated using x-ray photoelectron spectroscopy.