Effect of Time-varying Axial Magnetic Field on High Aspect Ratio SiO2 Etching in an Inductively Coupled Plasma

초록

낮은 주파수를 갖는 축방향 약자장을 유도결합형 C4F8/Ar 플라즈마에 적용하였다. 높은 종횡비를 갖는 미세구조의 식각특성과 플라즈마내에 존재하는 각종 이온과 라디칼의 농도변화에 자화 주파수가 미치는 영향을 살펴보았다. AMS(Appearance Mass Spectroscopy)와 XPS(X-ray Photoelectron Spectroscopy)를 이용하여 플라즈마내에 존재하는 폴리머 전구체의 변화와 그에 따른 식각특성을 고찰하였으며, 이를 통하여 0.2m의 직경과 종횡비 10을 갖는 contact hole을 성공적으로 형성할 수 있었다. Low frequency weak magnetic field is applied axially to an inductively coupled plasma (ICP). Efficient power transfer from RF source to plasma is enhanced by the axial magnetic field. High aspect ratio deep-sub-micron contact holes in BPSG have been etched by C4F8/Ar plasma. The role of deposition of polymeric precursors in the etching process is monitored. By means of appearance mass spectroscopy (AMS), the distributions of fluorocarbon ions (CFx+; x=1-3) and CFx radicals are measured as a function of magnetization frequency. The axial magnetic field is found to influence the densities of CFx+ ions and F and CFx radicals. X-ray photoelectron spectroscopy (XPS) shows that fluorocarbon polymer on BPSG layer strongly varies with the magnetization frequency. Contact holes of 0.2m diameter with aspect ratio of 10 are successfully fabricated in this system.