Damage to porous SiCOH low-k dielectrics by O, N and F atoms at lowered temperatures

Abstract

Information on the degradation of porous organosilicate glasses (OSGs) by active radicals and atoms is of high importance for their integration as low-k dielectrics in the next generation of ultra large scale integration (ULSI) production. The films’ degradation is caused by depletion of coverage of the pore surface methyl. OSG samples with differing porosities and pore sizes were treated by O, N, and F atoms at lowered temperatures (down to −45 °С) downstream of O2, N2, and SF6 inductively coupled plasma discharges, respectively. It has been shown that lowering the temperature reduces film degradation. In the case of O atoms, this reduction is insignificant, while the effect is much more noticeable for F atoms. In addition, an accumulation of F atoms forms a fluorocarbon layer 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 atom penetration. In the case of N atoms, even a small temperature reduction essentially decreases OSG degradation, while –CH3 modification is less clear in the cases of O and F atoms. Density functional theory and ab initio molecular dynamics 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 the formation, modification, and destruction of different surface groups. In the cases of O and F atoms, these reactions lead to the formation of HxCО and CFx bonds. For the direct reaction of N(4S) atoms with –СН3 groups, significant activation energy is required. Under downstream plasma conditions, –СН3 groups are destroyed in reactions with metastable particles, and first of all, with metastable atoms N(2D), N(2P) and molecules , which are also produced inside the pores in the surface recombination of nitrogen atoms.

Nanoporous SiOx plasma polymer films as carrier for liquid‐infused surfaces

“…[ 20,58 ] The porosity in SiOx can further be enhanced by plasma postoxidation yielding hydrocarbon removal by etching and further formation of Si–OH, while the Si–O–Si network is largely maintained. In a simplified way, the following reactions are mainly responsible for etching and oxidation [ 59–61 ] : $$$\text{Si}\mbox{--}{\text{CH}}_{3}+{\rm{O}}\to \text{Si}\mbox{--}{{\text{CH}}_{2}}^{\bullet }+\text{OH},$$$ $$$\text{Si}\mbox{--}{\text{CH}}_{3}+\text{OH}\to \text{Si}\mbox{--}{{\text{CH}}_{2}}^{\bullet }+{{\rm{H}}}_{2}{\rm{O}},$$$ $$$\text{Si}\mbox{--}{{\text{CH}}_{2}}^{\bullet }+{\rm{O}}\to {\text{Si}}^{\bullet }+{{\rm{H}}}_{2}\text{CO},$$$ $$${\text{Si}}^{\bullet }+{\rm{O}}\to \text{Si}\mbox{--}{\rm{O}},$$$ $$${\text{Si}}^{\bullet }+{{\rm{H}}}_{2}{\rm{O}}\to \text{Si}\mbox{--}\text{OH}+{\rm{H}},$$$ …”

“…In a simplified way, the following reactions are mainly responsible for etching and oxidation [59][60][61] :…”

Modification of Porous Ultralow-k Film by Vacuum Ultraviolet Emission

“…Methyl groups can be removed from the pore surface, leaving the active surface sites for water adsorption once the film is exposed to the atmosphere. The induced damage associated with exposure to active plasma species such as ions, radicals ,,,− and vacuum ultraviolet (VUV) light with λ ≤ 190–200 nm. ,,− …”

Surface Analysis of TMCTS-Based SiOC(H) Low-k Dielectrics in Post-Etch Strip of ACL Hardmask

“…Plasma-induced damage to porous SiOC(H) low-k dielectrics following the etching process has been reported. The application of hard SiON/TiN/SiON masks and pulsed plasma etching have been reported to reduce damage to porous SiOC(H) thin films [6,7]. Etches introduced during the BEOL process are extremely narrow (<45 nm), so if continuous wave plasma is used for etching, ultraviolet (UV), vacuum ultraviolet (VUV), and high-energy ion irradiation seriously damage the Materials 2021, 14, 1144 2 of 12 sidewalls.…”