Yoshiyuki Kikuchi

A new metallic complex reaction etching for transition metals by a low-temperature neutral beam process

We investigated a new oxidation reaction at a low temperature (−30 °C) as a result of O2 neutral beam bombardment at a low activation energy (<0.025 eV), which can efficiently form a thin oxide film of all transition metals, such as tantalum, ruthenium and platinum. Meanwhile, a new neutral beam enhanced chemical etching for the neutral beam oxidized transition metals that uses a new metallic complex reaction process and does not cause chemical or physical damage at low temperatures was also proposed. As a result, a highly anisotropic etching profile without re-deposition on the sidewall could be achieved with just the pure chemical reaction between ethanol and metallic oxide at a low kinetic energy using the neutral beam process.

Non-porous ultra-low-k SiOCH (k = 2.3) for damage-free integration and Cu diffusion barrier

Pores in ultra-low-k carbon-doped silicon oxide (SiOCH) film have been a serious problem because they produce fragile film strength, with the film incurring damage from integration and diffusion of Cu atoms in thermal annealing. To address this problem, we developed a practical large-radius neutral-beam-enhanced chemical vapour deposition process to precisely control the film structure so as to eliminate any pores in the film. We used the process with dimethoxy-tetramethyl-disiloxane (DMOTMDS) as a precursor to form a SiOCH film on an 8 inch Si wafer and obtained a non-porous film having an ultra-low k-value of 2.3 with sufficient modulus (>10 GPa). Analysing the film structure by experimental and theoretical techniques showed that symmetric linear Si–O molecular chains were grown and cross-linked to each other in the film. This particular film did not incur any damage from acid or alkali solution or oxygen plasma. Furthermore, the dense film almost completely resisted Cu diffusion into it during thermal annealing.

Extremely non-porous ultra-low-k SiOCH (k=2.3) with sufficient modulus (>10 GPa), high Cu diffusion barrier and high tolerance for integration process formed by large-radius neutral-beam enhanced CVD

We developed a practical large-radius neutral beam enhanced CVD with a dimethoxy tetramethy ldisiloxane (DMOTMDS) to form low-k SiOCH film on 8-inch Si wafers. We fabricated extremely non-porous film with an ultra-low k-value of 2.3 and a sufficient modulus (>10 GPa). This particular film did not show any damage from the oxygen plasma and acid or alkali solutions used in the fabrication process. Furthermore, the dense film almost completely resisted Cu diffusion into the film during thermal annealing.

Large-radius neutral beam enhanced chemical vapor deposition process for non-porous ultra-low-k SiOCH

Pores in ultra-low-k carbon-doped silicon oxide (SiOCH) film have been a serious problem because they produce fragile film strength, with the film incurring damage from integration and diffusion of Cu atoms in thermal annealing. To address this problem, we developed a practical large-radius neutral beam enhanced CVD process to precisely control the film structure so as to eliminate any pores in the film. We used the process with dimethoxy-tetramethyl-disiloxane (DMOTMDS) as a precursor to form a SiOCH film on an 8-inch Si wafer and obtained a non-porous film having an ultra-low k-value of 2.2 with sufficient modulus (>10 GPa). Analyzing the film structure by experimental and theoretical techniques showed that symmetric polymethylsilaxane (PMS) chains were grown and cross-linked to each other in the film. This particular film did not incur any damage from acid or alkali solution or oxygen plasma. Furthermore, the dense film almost completely resisted Cu diffusion into it during thermal annealing.

Robust Ultralow-k Dielectric (Fluorocarbon) Deposition by Microwave Plasma-Enhanced Chemical Vapor Deposition

A robust fluorocarbon film was successfully deposited on a substrate at a temperature above 400 °C by the new microwave plasma-enhanced chemical vapor deposition (MWPE-CVD) method using the linear C5F8 precursor instead of a conventional cyclic C5F8 one. The fluorocarbon performed keeping the dielectric constant low as a value of 2.25 by controlling the molecular structure forming cross-linked poly(tetrafluoroethylene) (PTFE) chains with configurational carbon atoms. The novel fluorocarbon demonstrates less fluorine degassing at an elevated temperature, with high mechanical strength and without degradation of adhesion of the fluorocarbon film to SiCN and SiOx stacked films after thermal stress at 400 °C and 1 atm N2 for 1 h. Consequently, this robust fluorocarbon film is considered a promising candidate for general porous silicon materials with applications to practical integration processes as an interlayer dielectric.