Damage of porous SiCOH low-k dielectrics by O, N and F atoms at lowered temperaturesстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 7 июля 2020 г.
Аннотация:Information on porous organosilicate glasses (OSG) degradation by active radicals and atoms is of a high importance for their integration as low-k dielectrics in the next generation of ULSI production. The films degradation is caused by depletion of the pore surface methyl coverage. OSG samples with different porosity and pore size have been treated by O, N and F atoms under the lowered temperatures (down to - 45° С) in downstream of O2, N2 and SF6 ICP discharges respectively. It has been shown that temperature lowering reduces the films degradation. In case of O atoms this reduction is insignificant while the effect is much more noticeable for F atoms. In addition, there is F atoms accumulation in fluorocarbon layer forming during F atom treatment. The accumulated fluorine can interact with surface Si atoms giving rise to film etching. The film degradation under O and F atoms increases with pore size and porosity due to deeper atoms penetration. In case of N atoms even a small temperature reduction essentially decreases OSG degradation while –CH3 modification is not so clear as in O and F cases. DFT and ab initio MD simulations of reaction mechanisms show that atom reactions with surface Si-CH3 groups are the initial stages of OSG degradation. Subsequent mechanisms include branched reaction pathways with formation, modification and destruction of different surface groups. In case of O and F atoms these reactions lead to formation of HxCО and CFx bonds. For the direct reaction of N(4S) atoms with –СН3 groups significant activation energy is required. In downstream plasma conditions, –СН3 groups are destructed in reactions with metastable particles, first of all, metastable atoms N(2D), N(2P) and molecules N2(A3Σu +) which are also produced inside the pores in surface recombination of nitrogen atoms.