Structure-Designable Formation-Method of Super Low-k SiOC Film (k=2.2) by Neutral-Beam-Enhanced-CVD
Ar neutral beam enhanced chemical vapor deposition can control the dielectric constant and film modulus of low-k SiOC deposited on Si substrates precisely because it avoids precursor dissociation due to electron collisions and UV photons in plasma. Optimizing the ratio between Si-O and Si-(CH3)x as well as the proportions of linear, network, and cage Si-O structures by changing the precursor, we obtained a k of 2.2 and a reasonable modulus by using either dimethyl diethoxy silane or dimethyl dimethoxy silane as a precursor.
Low dielectric constant insulator formed by downstream plasma CVD at room temperature using TMS/O2
We present an insulator with a dielectric constant lower than 3.0, thermal stability up to 500° C and good gap-filling characteristics. This insulator was formed by downstream plasma chemical vapor deposition (CVD) at room temperature using tetra-methylsilane (TMS)/O2 gases. It contained a large amount of water in the as-deposited state. Annealing at 350° C resulted in a decrease in the water content of the insulator, and the insulator did not absorb water after the annealing. The film is constructed from Si–O and Si–CH3 bonds, which produce a low dielectric constant and high thermal stability.
Coulomb-staircase observed in silicon-nanodisk structures fabricated by low-energy chlorine neutral beams
A silicon-nanodisk structure, a nanometer-scale silicon disk on extremely thin SiO2 film, was fabricated by etching a 3.5–4-nm-thick polycrystalline silicon (poly-Si) thin film/1.4–3-nm-thick underlying oxide layer/Si substrate structure with a 7-nm-diameter ferritin iron-core mask and Cl neutral beam etching (NBE). The degree of etching was precisely controlled by detecting its depth using x-ray photoelectron spectroscopy. Cross-sectional scanning transmission electron microscopy (STEM) with elemental mapping by electron energy-loss spectroscopy (EELS) revealed that the underlying oxide layer remained while the Si layer was accurately etched. The STEM-EELS observation also revealed that there was an Si layer about 1–2-nm thick even in the nanodisk, while the nanodisk’s surface region was covered by native oxide. Removing the surface oxide layer prior to the NBE process could decrease the nanodisk diameter. Irradiation by Cl NB of the underlying 1.4-nm-thick SiO2 film increased the thickness of the SiO2 f...