Kiyohiro Matsushita

Depth dependence of ultraviolet curing of organosilicate low-k thin films

UV radiation curing has emerged as a promising postdeposition curing treatment to strengthen organosilicate interlayer dielectric thin films. We provide the evidence of film depth dependent UV curing which has important effects on through thickness mechanical and fracture properties. Force modulation atomic force microscopy measurements of the elastic modulus through the thickness of the films revealed evidence of periodic modulations of the glass stiffness which increased in magnitude with UV curing time. Furthermore, while significant increases in fracture energy were observed with UV curing time at the top of the organosilicate film, much lower increases were observed at the bottom. The increase in fracture energy with UV curing was film thickness dependent. The cohesive fracture resistance was less sensitive to UV curing. Possible explanations for the stiffness modulations through the film thickness involving UV light interference or phase separation by spinodal decomposition during the cure process a...

Tuning depth profiles of organosilicate films with ultraviolet curing

This study demonstrates that ultraviolet (UV) radiation curing can control depth profiles of organosilicate films. Striking differences between the effects of monochromatic and broadband UV irradiation were observed. For the same as-deposited organosilicate film and cure duration, monochromatic radiation has a greater impact on film structure, elastic modulus, and fracture resistance, but also results in a greater degree of depth dependent properties. Oscillating elastic modulus through the film thickness was observed with force modulation atomic force microscopy. We present a new standing wave model that accurately predicts the resulting depth dependent stiffness variations considering changes in film shrinkage and refractive index in terms of curing time, and can further be used to account for initial film thickness dependence of UV curing and film absorption. Promising applications of the depth dependent UV curing to produce multifunctional ultralow-k layers with a single postdeposition curing process ...

Impacts of UV cure for reliable porous PECVD SiOC integration [IC interconnect applications]

An ultra violet (UV) cure was investigated to improve the mechanical and electrical properties of porous carbon-doped PECVD (plasma enhanced chemical vapor deposition) oxide film (k<2.4) for the 45 nm node technology and beyond. Drastic improvement in the film modulus and leakage current between Cu interconnects was observed. The formation of Si-O chemical bonds by breaking Si-CH/sub 3/ bonds after UV irradiation is thought to be an origin for the results of Si-O-C-H networks in p-SIOC films.

Plasma enhanced ALD pore sealing for highly porous SiOCH films with k = 2.0

In order to implement highly porous PECVD SiOCH films with k = 2.0 in ILD integration, the UV-assisted restoration to remove plasma damages related with dry etch and pore sealing by plasma enhanced ALD (PEALD)-SiN formation to prevent the metal penetration into the film during subsequent metallization process was investigated. Sequential application of the restoration and pore sealing processes was proved to be the best solution enabling successful sealing capability with preserving pristine k-value of the porous SiOCH films.

Impact of Hydrocarbon Control in Ultraviolet-Assisted Restoration Process for Extremely Porous Plasma Enhanced Chemical Vapor Deposition SiOCH Films with k = 2.0

We investigated the effects of UV-assisted restoration on porous plasma-enhanced chemical vapor deposition (PECVD) SiOCH films with k = 2.0 and 2.3 having high porosities. By applying the UV-assisted restoration to O2-plasma-damaged films with k = 2.0 and 2.3, the recovery of the k-value was observed on the k = 2.3 film in proportion to –OH group reduction. However, the k = 2.0 film did not show recovery in spite of –OH group reduction. We found that hydrocarbon content in the k = 2.0 film was significantly increased by the UV-assisted restoration compared with the k = 2.3 film. According to these findings, we optimized the UV-assisted restoration to achieve improved controllability of the hydrocarbon uptake in the k = 2.0 film and confirmed the recovery of the k-value for O2-plasma-damaged film. Thus, adjusting the hydrocarbon uptake was crucial for restoring extremely porous SiOCH film.

Robust Low-k Diffusion Barrier (k=3.5) for 45-nm Node Low-k (k=2.3)/Cu Integration

A robust low-k diffusion barrier, i.e., advanced SiC(O) (A-SiC(O), k = 3.5), was developed to attain a keff of less than 2.7 for reliable ultra-low-k/Cu integration for 45-nm node technology and beyond. A new precursor that requires that requires no oxidizing agent was introduced for deposition to obtain higher film density while maintaining the k-value. The A-SiC(O) film has a low leakage current because of its low defect density and a comparable barrier property with conventional SiC. Drastic improvement in the keff and TDDB lifetime were obtained by adopting A-SiC(O) without using underlying SiCN and oxidizing agent in the deposition, Reliable ultra-low-k/Cu integration was accomplished by combining A-SiC(O) and Aurora-ELK (k=2.3), which has a high modulus of 7.2 GPa, with a UV cure

Pore-sealing process initiated by self-assembled layer for extreme low-k SiOCH (k=2.0)

A pore sealing process by Plasma-enhanced ALD (PEALD) with an amino-silane precursor has been developed, which enabled simultaneous restoration and pore-sealing film formation on damaged low-k film with k = 2.0. The precursor adsorbed preferentially at OR termination on the low-k surface to form self-assembled (SA) SiOC layer, which simultaneously recovered low-k damage. It is suggested that the SA-SiOC layer narrowed the pore opening at the low-k surface, and was followed by hermetic SiCN layer formation by PEALD. Sealing of pores against wet chemical was confirmed by forming 1.3 nm SiCN. Leakage current after pore-sealing formation was reduced by more than one magnitude compared to the pristine low-k. The current process will pave the way for enabling extremely thin diffusion barrier <;2nm at IX nm node Cu interconnect.

Plasma-Enhanced Atomic Layer Deposition Sealing Property on Extreme Low-k Film with k = 2.0 Quantified by Mass Metrology

We have investigated plasma-enhanced atomic layer deposition (PEALD) SiN pore-sealing film formation and diffusion behavior on highly porous SiOCH films. Mass measurement revealed the diffusion of the precursor used in PEALD into pores of SiOCH films, which was enhanced for higher-porosity SiOCH films. The diffusion of the precursor into the pores was reduced by applying UV-assisted restoration treatment before the pore-sealing process, which helped the formation of hermetic pore-sealing films. The results indicated that a 1-nm-thick SiN film was sufficient to seal the surface of the restored SiOCH film with k = 2.0. It was found that the decrease in k due to the pore-sealing deposition was as small as 0.02. The results indicated that the sequential application of UV-assisted restoration and PEALD-SiN pore sealing is a promising method of introducing the use of highly porous SiOCH films with k = 2.0 into interconnect integration.

Plasma-enhanced CVD low-k process enabling global planarity by controlling flowability

Plasma-enhanced CVD (PECVD) flowable low-k process compatible with the conventional UV cure process has been developed. Reduction of shrinkage by the UV cure was critical to ensure gap-filling capability with planarity, which was achieved by deposition condition tuning to reduce hydro-carbon constituent in the film and enhancement of dehydration by applying post-deposition treatment. Complete filling of 45-nm-space trench was achieved with excellent global planarity. The present results suggest applicability of the process for future pre-metal dielectric (PMD) or inter-layer dielectric (ILD) for aggressively scaled devices.

Integration of Porogen-Based Low-k Films: Influence of Capping Layer Thickness and Long Thermal Anneals on Low-k Damage and Reliability

This paper discusses integration aspects of a porous low-k film (k ~2.45) cured with a broadband UV lamp. Different process splits are discussed which could contribute to avoid integration induced damage and improve reliability. The main factor contributing to a successful integration is the presence of a thick (protecting) cap layer partially remaining after chemical mechanical polishing (CMP), which leads to yielding structures with a keff of ~2.6, a breakdown voltage of ~6.9 MV/cm and time dependent dielectric breakdown (TDDB) lifetimes in the excess of 100 years. Long thermal anneals restore the k-value but degrade lifetime.