Isobutyl Silane Precursors for SiCH Low-k Cap Layer beyond the 22 nm Node: Analysis of Film Structure for Compatibility of Lower k-value and High Barrier Properties

Abstract

To form SiCH films with a high carbon content using plasma-enhanced chemical vapor deposition (CVD), isobutyl trimethylsilane (iBTMS) and diisobutyl dimethylsilane (DiBDMS) were examined as precursors for a low-k cap layer and Cu diffusion barrier at the top of Cu lines. We elucidated the relationship between the structure of low-k SiCH films made from these newly developed precursors and their barrier properties against copper and oxygen diffusion. We also studied the relationship between the structure of SiCH and the deposition process under various RF plasma powers. A Monte Carlo simulation was employed to estimate the deposition profile in an overhang test structure. Fourier transform infrared spectroscopy (FT-IR) was used to analyze molecular structures. Our studies indicate that deposition conditions cannot dictate carbon content, but can control porosity/density. Precursor selection is thus an important factor in forming SiCH with a high carbon content that achieves both lower k and good barrier properties. #

Material design of plasma-enhanced chemical vapour deposition SiCH films for low-kcap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects

“…Newly designed organic silanes, iBTMS, DiBDMS, SSN and DVScP, were confirmed to be favorable for forming SiCH with a high C content. The high C content in SiCH films prepared using iBTMS or DiBDMS was thought to be derived from the iso-butyl fragment, as reported previously [15]. …”

“…Therefore, we developed precursors iBTMS and DiBDMS for a Si–CH 2 –Si network and C-rich SiCH films [14, 15], and SSN and DVScP for a Si–C 2 H 4 –Si network and C-rich SiCH films [14, 16]. These precursors were designed based on their reactions in plasma estimated by quantum-chemical calculations.…”

“…In the cap layer, however, good diffusion barrier properties and a low k have a tradeoff relation [13–15]. Most dielectrics with a low k are obtained by decreasing the density of the films, mostly by introducing multiple pores, which in turn results in inferior barrier properties.…”

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…[402][403][404][405] Shimizu's results using precursors such as 1,1-divinyl silacyclopentane (DVScP) and 5-silaspiro- [4,4]-nonane (SSN) have shown that a-SiC:H films with a significant improvement in mass density can be achieved for a given dielectric constant relative to a-SiC:H films deposited using traditional tetramethylsilane (4MS) precursors. 403 Using similar precursors, 100 nm a-SiC:H films with k values as low as 3.1 that show Cu diffusion barrier performance equivalent to higher k = 5.0 a-SiCN:H have also been demonstrated. 402,404 Matsuda has also shown that similar a-SiC:H films can exhibit increased fracture strength due to increased crack tip plasticity arising from the more ductile -(CH 2 ) x -bonding.…”

Advanced Interconnects: Materials, Processing, and Reliability

“…Carbon and hydrogen rich SiCN films with relatively low dielectric constants (k ≈ 3.5-4) have been considered and reported as promising candidates. 16 In addition, materials with relatively high k values (k ≈ 8-9) such as AlN have been proposed because they can provide good barrier properties at relatively low thicknesses. The selection of cap layers is also an important issue to reduce Cu electromigration.…”