Hideshi Miyajima

Water absorption properties of fluorine-doped SiO2 films using plasma-enhanced chemical vapor deposition

The water absorption properties of a PE-CVD (plasma-enhanced chemical vapor deposition) fluorine-doped SiO2 film with a low dielectric constant were studied. It was concluded that highly stable F-doped SiO2 film was obtained at F contents from 2.0% to 4.2% (3.2≤k≤3.6) using high-density plasma CVD. However, at F contents higher than 4.2% (k<3.2), the amount of water absorption was markedly increased due to the presence of Si–F bonds, such as Si(–F)2 bonds, which are highly reactive with water. On the other hand, water absorption was observed at every F content for conventional plasma CVD films. Through gas phase component analysis and investigation of the incident ion energy distribution using a quadrupole mass spectrometer, it was confirmed that a high efficiency of gas dissociation and high-energy ion bombardment are the keys to obtaining high-quality films with a high resistance to water absorption.

Properties of high-performance porous SiOC low-k film fabricated using electron-beam curing

In this paper, we describe the effect of electron-beam (EB) curing on ultra-low-k dielectric porous SiOC material (k=2.2) and the application of this technology to the 90-nm-node Cu/low-k multilevel damascene process. A significant improvement of dielectric porous SiOC films with EB curing has been demonstrated. The mechanical and adhesion strength of these films were increased by a factor of 1.5–1.6 without degrading the films k. This result can be explained by the reconstruction of a Si–O random network structure from cage Si–O bonds and Si–CH3 bonds through EB curing. Additionally, the EB curing of spin-on dielectric (SOD) porous low-k films contributes to a decrease in their curing temperature and a decrease in their curing time. Under optimum EB curing conditions, no degradation of transistor performance was revealed. The excellent adhesion strength obtained by EB curing, has contributed to the success of multilevel damascene integration. On the basis of our findings, this EB curing technology can be applied in devices of 65-nm-node and higher.

Effect of Plasma Treatment and Dielectric Diffusion Barrier on Electromigration Performance of Copper Damascene Interconnects

The effect of plasma treatment and a dielectric diffusion barrier on electromigration (EM) performance was examined. The characteristics and adhesion properties at the interface between copper (Cu) and the dielectric diffusion barrier were also investigated by scanning transmission electron microscopy–electron energy loss spectrometry (STEM–EELS). The existence of oxygen at the interface after hydrogen (H2) plasma treatment, which has a large pre-exponential factor, causes a large EM drift velocity. Ammonium (NH3) plasma treatment can reduce the Cu oxide completely, resulting in an improvement in EM performance. On the other hand, the dielectric diffusion barrier of SiCxNy, which has a better adhesion property then SiCx, reduces EM drift velocity and provides a larger activation energy. The reduction of CuOx completely by plasma treatment is essential and the selection of dielectric diffusion barrier is important to improve the EM performance of Cu damascene interconnects.

A manufacturable copper/low-k SiOC/SiCN process technology for 90 nm-node high performance eDRAM

In this paper, we describe the Cu/low-k (k < 3) dual-damascene process integration targeting for 90 nm-node (0.28 /spl mu/m pitch) high performance embedded DRAM devices. A stable and well-controlled dual-damascene structure was realized both by using newly developed stacked mask process (S-MAP) and a low-damage resist ashing process. Problems and solutions for resist poisoning due to the stopper-SiCN layer and capping-SiO/sub 2/ layer are investigated. We also demonstrated a notable via chain yield (with 2.9 M vias) by applying low-k PE-CVD SiOC/SiCN dielectrics.

Structural Studies of High-Performance Low-k Dielectric Materials Improved by Electron-Beam Curing

With the use of a newly developed electron beam (EB) curing process, an advanced methylsilsesquioxane (MSQ) low-k dielectric (LKD) film of k=2.9 was developed. It is noteworthy that the EB curing process can drastically improve the mechanical strength of LKD film and reduces the thermal budget without increasing the k value. The X-ray absorption fine structure (XAFS) study on the LKD was conducted to clarify the structural change upon EB curing. The structure of the film was compared with those of two different types of other MSQ films, the ladder-network structure and the random-network structure, and a chemical vapor deposition (CVD) film. The Si–O–Si bond angle and Si–O (Si–C) bond length were determined by fitting the Fourier transformed extended X-ray absorption fine structure (EXAFS) spectra. Si–O–Si bond angle of LKD film was found to be between those of the ladder and the random structure, which are 135° and 147°, respectively. The X-ray absorption near-edge structure (XANES) spectra of LKD film revealed two broad features corresponding to a mixture of the two structures. In contrast, Si–O–Si angles of the EB-cured LKD film and the CVD film were similar, and the XANES features of both films were almost identical with those of the random structure. The electronic structure as determined from XANES spectra was also discussed by comparing three-dimensional-linkage models obtained by ab initio calculations. We confirmed that the EB curing process of LKD film causes a drastic structural change. The change from the mixture of ladder and random structures to the completely random structure was caused by C–H bond breaking followed by the formation of new polymer-like clusters with C–C bonds.

The application of simultaneous ebeam cure methods for 65 nm node Cu/low-k technology with hybrid (PAE/MSX) structure

High performance low-k hybrid-DD structure (poly-arylene-ether (PAE)/ poly-methylsiloxane (MSX)) is realized by simultaneous electron beam (ebeam) curing technique, and applied to a 65 nm node Cu/low-k multilevel damascene process. By eBeam curing for MSX, while maintaining a k value, both mechanical strength and adhesion strength of the bottom interface have been improved. In addition, since the introduction of the ebeam cure technique reduces cure temperature and time of spin on dielectric formation, the thermal budget is dramatically reduced. The simultaneous ebeam curing of PAE/MSX hybrid structure realizes low-cost and high reliability Cu/low-k interconnects. It is also considered that this ebeam cure technology will be very effective in 65 nm node devices and beyond.

High-Performance SiOF Film Fabricated Using a Dual-Frequency-Plasma Chemical Vapor Deposition system

With the use of a newly developed dual-frequency-plasma chemical vapor deposition (DFP-CVD) system, an advanced SiOF film of k = 3.4, which exhibits excellent resistance for moisture absorption, was developed. The physical and chemical properties of the SiOF film were compared to those of typical SiOF films deposited by both conventional high-density-plasma CVD (HDP-CVD) and plasma-enhanced CVD (PE-CVD) systems, with the same k value. The DFP-CVD SiOF film appears to be significantly superior to the HDP-CVD SiOF film, as revealed by the following results. The moisture absorption rate measured by thermal desorption spectroscopy (TDS) (after 4 days of air exposure) is about 5 times lower, the hardness was 1.8 times higher, and the hygroscopicity (after 1 hour of boiling) was 2.6 times lower. These results confirm that the DFP-CVD SiOF film is applicable to Al and Cu interconnect structures for devices of the 130 nm scale and beyond.

BEOL process integration technology for 45 nm node porous low-k/copper interconnects

Highly reliable BEOL integration technology with porous low-k (k=2.3) was realized by development focusing on plasma damage control and moisture control. A hybrid dielectric scheme with damage resistant porous low-k films and buffer film was applied in view of its inherent advantages for realizing reliable porous low-k integration. A metallization process was developed from the viewpoint of suppressing morphology and adhesion degradation of barrier metal by oxidation. A dummy wiring pattern was also adopted to remove moisture absorbed in porous low-k films. Stress-migration and electromigration satisfying practical reliability were obtained with via size of 75 nm for the first time by utilizing all possible measures for reducing the damage and the moisture.

Notable improvement in porous low-k film properties using electron-beam cure method

High performance Low-k dielectric with porous structure (k=2.2) is realized by Electron-Beam (EB) cure technique, and applied to a 90 nm node Cu/Low-k multilevel damascene process. By EB curing, while maintaining a low k value, both mechanical strength and adhesion strength of lower interface have been improved 1.5 times respectively. This strengthening effect was actually confirmed as avoiding peeling by CMP process. In addition, introduction of EB cure technique reduced spin on dielectric (SOD) cure temperature and time, therefore the thermal budget was reduced drastically. It was also considered that this EB cure technology will be very effective in future 65 nm node devices.

A plasma damage resistant ultra low-k hybrid dielectric structure for 45nm node copper dual-damascene interconnects

A plasma damage resistant hybrid (polyarylene ether (PAR)/SiOC) dielectric structure using the ultra low-k (ULK) films with k value of 2.2 was demonstrated for Cu dual-damascene (DD) interconnects. The reliability issues attributed to plasma process induced damage to ULK films were clarified and resolved. As well as ULK film selection with plasma damage resistance, insertion of a low-k buffer layer with k value of 3.0 between SiOC and PAE and damage restoration process using hydrophobic treatment were found to be most important factors for robust ULK process integration.