Influences of atomic hydrogen on porous low-k dielectric for 45-nm node

Atomic hydrogen generated by a heated tungsten catalyzer has been investigated in terms of the damage-less ash and restoration of damaged low-k dielectric. No difference of damaged thickness of low-k dielectric between before and after the ash by HF dip using patterned porous methyl silsesquioxane (MSQ) film was found. Moreover atomic hydrogen exposure slightly reduced capacitance of the micro-structured capacitor with the Cu wire and the CVD porous low-k dielectric.     

Extraction of effective dielectric constants and the effect of process damage of low-k dielectrics for advanced interconnects

In this paper, the line-to-line parasitic capacitance of an advanced interconnects with a low-k dielectric (k < 3.0) was extracted by electrical measurement on comb-serpentine structures with various spacing. The empirical values are higher than the prediction from the filed solver, especially in the small geometries. A model was derived based on the damage of low-k dielectric during processing, which causes the increase of the dielectric constant. Then, the effective dielectric constant was evaluated by both simulation and theoretical models. The k value of damage zone was determined from blanket wafer by mercury probe after oxygen plasma treatment. Good agreement was obtained after we modified the simulation structure to include the damage zone. Especially, the concept of low-k damage due to plasma treatment was characterized for the first time. Thus, it is possible to use this model in the future study, such as the porous low-k in 65 nm or even 45 nm generations.     

Porogen residues detection in optical properties of low-k dielectrics cured by ultraviolet radiation

The optical properties of low dielectric constant (low-k) films have been determined by variable angle spectroscopic ellipsometry in the range from 2 eV to 9 eV to characterize the process of porogen removal during the UV-cure. The studied carbon doped oxide (SiCOH) porous dielectric films have been prepared by plasma enhanced chemical vapor deposition. The films have been deposited as a composition of a matrix precursor and an organic porogen. After deposition, the films have been cured by thermal annealing and UV irradiation (λ = 172 nm) to remove the porogen and create a porosity of 33%, reaching a dielectric constant of 2.3. The process of porogen decomposition and removal has been studied on series of low-k samples, UV-cured for various times. Additional samples have been prepared by the deposition and curing of the porogen film, without SiCOH matrix, and the matrix material itself, without porogen. The analysis of the optical response of the porous dielectric as a mixture of matrix material, porogen and voids, together with Fourier transform infrared analysis, allows the sensitive detection of the volume of the porogen and indicates the existence of decomposed porogen residues inside the pores, even for long curing time. The variation of the deposition and curing conditions can control the amount of the porogen residues and the final porosity.     

Low-resistivity Cu film electrodeposited with 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonate for the application to the interconnection of electronic devices

In this study, we analyzed the properties of Cu films electrodeposited with 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonate (DPS) as an organic additive in damascene Cu electrodeposition, in comparison with bis(sulfopropyl) disulfide (SPS). It was observed that the resistivity of Cu film electrodeposited with DPS was lower than that with SPS. Spectroscopic analyses showed that the impurity level and crystallinity of Cu films are almost the same, but the difference was found in the film roughness. Low roughness of Cu film electrodeposited with DPS led to the low resistivity, and it was speculated that the low roughness is related to the strong adsorption through the nitrogen atom in the DPS molecule.     

Characterization and integration of new porous low-k dielectric (k < 2.3) for 65 nm technology and beyond

In this paper, new porous spin-on dielectric (HL02™, trademark of the LG Ltd.) was studied. The characterizations, such as thermal stability, chemical structure, dielectric constant (k) and mechanical properties (hardness and modulus), of methylsilsesquioxane (MSQ)-based dielectrics were evaluated. An optimized material (k = 2.25), characterized by a hardness and a modulus of 1.0 GPa and 6.5 GPa each in association with a porosity of 30% and a mean pore radius of 2.2 nm, was successfully integrated in damascene process with 10 levels of Cu/low-k film for 65 nm technology and beyond. Good electrical results were obtained in metal line resistance and leakage current.     

A comparison of various dielectric/metal sidewall diffusion barriers for Cu/porous ultra-low-K interconnect technology in terms of leakage current and breakdown voltage

A very thin dielectric flash layer (DFL) was used in addition to Ta for Cu/ultra-low-K (porous SiLK™) back-end technology. Atomic force microscopy showed that SiC DFL is superior to Si₃N₄ or SiO₂ DFL in terms of smaller surface roughness. It appears to the authors that the key point to get a very smooth DFL is to avoid the use of nitrogen-containing gases like NH₃, N₂ or N₂O during the DFL deposition process. An alternative explanation is that trimethylsilane is the better Si source compared to silane. Electrical testing showed that SiC DFL is superior to Si₃N₄ or SiO₂ DFL in terms of higher breakdown voltage.