High density plasma etching of low k dielectric polymers in oxygen-based chemistries

Abstract

We have studied the etching of low dielectric constant polymers in halogen-and sulfur-free chemistries under various plasma operating conditions. The polymer graphitization phenomenon, which corresponds to the transformation of the aromatic hydrocarbon network into an amorphous carbon backbone, has been fully investigated under several plasma conditions by in situ mass spectrometry and quasi-in situ x-ray photoelectron spectroscopy ͑XPS͒. Profile control in high aspect ratio contact holes is obtained thanks to the formation of a passivation layer on the polymer sidewalls preventing the spontaneous chemical attacks by the oxygen reactive species of the plasma. XPS studies show that the passivation layer only forms under conditions where the plasma induces a polymer graphitization. Strong correlations are observed between plasma conditions leading to the polymer graphitization, the presence of heavy carbon byproducts detected in the plasma gas phase, and the passivation layer formation.

Characterization of resist-trimming processes by quasi in situ x-ray photoelectron spectroscopy

“…This hypotheses will be confirmed in a future paper thanks to mass spectrometry analyses, but re-deposition of heavy carbon etch byproducts has already been observed when etching low-k dielectric polymers. 24,25 C. Influence of the pressure Figure 10 shows the lateral ͓Fig. 10͑a͔͒ and the vertical ͓Fig.…”

Via-Shape-Control for Copper Dual-Damascene Interconnects With Low-k Organic Film

“…The gas chemistry is 0894-6507/$25.00 © 2008 IEEE known as etching gas for organic low-k as well as [8]. The total gas pressure was controlled during discharge by variable orifice.…”

Anisotropic high aspect ratio etch for perfluorcyclobutyl polymers with stress relief technique

“…To reduce or eliminate this lateral etching, a gas can be added to the plasma to create a protective passivation layer on the sidewalls. 11,13,14,16 In this article we report the successful development of a PFCB etch using a CO/O 2 etch chemistry in an ICP RIE. We achieve deep ͑ϳ14 m͒, narrow ͑800 nm͒ trenches with vertical sidewalls for an etch aspect ratio of 18:1.…”

“…For example, a high aspect ratio etch of features as narrow as 150 nm has been developed for SiLK™ using a high density plasma source and in which anisotropy is a result of passivation with polymer graphitization. 11 The maximum achieved aspect ratio is ϳ6:1 in N 2 /O 2 and N 2 /H 2 plasmas. A deep reactive ion etch ͑RIE͒ with vertical sidewalls has likewise been achieved in polymethylmethacrylate ͑PMMA͒ using Ar and O 2 .…”