Eiichi Kondoh

Deposition of Cu and Ru Thin Films in Deep Nanotrenches/Holes Using Supercritical Carbon Dioxide

Supercritical CO2 behaves like both a gas and a liquid, and posseses unique features such as nanopenetration capability, high diffusivity, and solvent ability. The technique described in this paper uses the supercritical CO2 as a reaction medium for thin film growth and realizes filling or coating of nanofeatures with conducting metals. In this paper, we demonstrate the possibilities of this technique in Cu and Ru thin film deposition. A basic approach to achieving Cu metallization of deca-nanometer trenches or vias were studied. Ru, a promising material for capacitor electrodes and also a new candidate for the next-generation Cu barrier, was successfully deposited and its deposition characteristics were studied. Filling capability and the possibility of conformal deposition were also demonstrated as well as the fabrication of a Cu\Ru stack.

Conformal Deposition and Gap-Filling of Copper into Ultranarrow Patterns by Supercritical Fluid Deposition

Supercritical fluid deposition (SCFD) of Cu onto ultranarrow vias (50 to 220 nm and 1 µm depth) was studied with using angled polishing for future ultralarge scale integration metallization. SCFD conformally fabricated a smooth, continuous, and 10-nm-thick Cu film in ultranarrow vias. Excess H2 compared with the precursor as well as surface saturation of the precursor enabled uniform nucleation and conformal deposition. Highest H2 concentration in this study (0.39 mol/L) promoted the nucleation density, resulting in formation of a smooth and continuous film. In conclusion, SCFD successfully achieved complete filling without any voids onto via patterns.

Deposition of Ru Thin Films from Supercritical Carbon Dioxide Fluids

Ruthenium has been of interest for application in ULSI capacitor electrodes and more recently as a barrier metal against Cu diffusion. Thin-film deposition from supercritical CO2 has gained particular attention as a new deposition technique that provides nano-penetration capability and a possibility of developing new deposition chemistries. However, few papers have been published on this technique. In this article, first, the deposition characteristics of Ru thin films using H2 reduction chemistry were described. It was found that Ru films grow only on conductive surfaces when H2 reduction chemistry was employed. These films can be beneficial for some specific applications; however they are not very much favored for general deposition technology. Second, we report that Ru films, oxygen-containing Ru films in fact, grew on dielectric/non-conductive surfaces when oxidative chemistry was used. O3 was used as an oxidant for thin film deposition from supercritical fluids for the first time. The use of O3 promotes heterogenous nucleation and increases the amount of oxygen in the films. Oxygen-containing Ru was reduced by another reduction run using supercritical CO2.

Comparative Study of Pore Size of Low-Dielectric-Constant Porous Spin-on-Glass Films Using Different Methods of Nondestructive Instrumentation

The pore sizes of hydrogen-methyl-siloxane-based porous spin-on-glass (SOG) thin films having different k values (k=1.8–2.5) are comparatively studied using different nondestructive instrumental ways and also with reference to sorption porosimetry. The pore size and its spread are found to increase with increasing porosity, or with decreasing dielectric constant.

Wafer thermal desorption spectrometry in a rapid thermal processor using atmospheric pressure ionization mass spectrometry

This paper demonstrates the possibility of performing thermal desorption spectrometry (TDS) on wafers in an atmospheric pressure rapid thermal processor (RTP). A special gas sampling system is described, which allows the analysis of gas composition inside the RTP chamber with atmospheric pressure ionization mass spectrometry (APIMS). Sampling is controlled with no valve operation and high dilution of the sample gas flow can be achieved while maintaining a short sample transfer time. It is shown how gas flows can be optimized to improve the sensitivity and resolution of TDS spectra. The RTP-APIMS setup was used in a study of H/sub 2/O absorption by low dielectric constant fluorinated silica glass (FSG) films, helping to develop a cap that reduced H/sub 2/O absorption upon storage by a factor of 60. NH/sub 3/ is shown to desorb from FSG and SiO/sub 2/ films deposited by plasma-enhanced chemical vapor deposition (PECVD), which may be of concern for the reliability of integrated circuits.

Kinetics of Deposition of Cu Thin Films in Supercritical Carbon Dioxide Solutions from a F-Free Copper(II) β -Diketone Complex

Kinetics of deposition of Cu thin films in supercritical carbon dioxide solutions from copper bis(di-isobutyrylmethanate) {Cu[(CH 3 ) 2 CH(CO)CH(CO)CH(CH 3 ) 2 ] 2 }, Cu(dibm) 2 ), a F-free copper(II) complex, via hydrogen reduction were studied. A flow-type reaction system was employed to control each deposition parameter independently and at a constant value. Apparent activation energies for Cu growth were determined for a temperature range of 200―260°C as a function of hydrogen concentration. The determined values varied from 0.35 to 0.63 eV and decreased as hydrogen concentration increased. At a deposition temperature of 200°C, growth rate followed a Langmuir-type dependence against Cu(dibm) 2 and hydrogen concentrations, showing first-order dependence at lower concentrations and zero-order dependence at higher concentrations. At a higher deposition temperature of 240°C, no saturation in the growth rate was observed. A Langmuir―Hinshelwood-type growth mechanism was discussed, and a rate equation for growth was proposed, taking into account the temperature dependence of both the rate constant of the rate-determining reaction and adsorption equilibrium constants. The hydrogen concentration dependence of the apparent activation energy for Cu growth was discussed with this rate equation.

Step Coverage Quality of Cu Films by Supercritical Fluid Deposition Compared with Chemical Vapor Deposition

Feasibility of step coverage (SC) by supercritical fluid deposition (SCFD) of Cu was evaluated using a finite element method (FEM) simulation with experimentally estimated kinetics and transport properties of the precursor. This SC by Cu-SCFD was compared with that by chemical vapor deposition (CVD). SCFD showed superior SC, especially for ultra narrow features less than 1 µm wide, although CVD has a higher diffusion coefficient. This superior SC was due to the non-linear reaction kinetics of SCFD (CVD has linear reaction kinetics), where precursor concentration had negligible effect on growth rate when the precursor concentration was higher than about 1 mol/L.

Deposition of Zinc Oxide Thin Films in Supercritical Carbon Dioxide Solutions

This article reports the deposition of ZnO thin films in supercritical CO2 solutions likely for the first time. Zincacetylacetonate was dissolved in supercritical CO2, together with oxygen, and was processed at 8–13 MPa and 230–380 °C. Continuous crystalline films were obtained on Si and sapphire at temperatures higher than 280 °C. The-band-edge emission at 370 nm was confirmed in photoluminescence spectra.

Initial Cu Growth in Cu-Seeded and Ru-Lined Narrow Trenches for Supercritical Fluid Cu Chemical Deposition

The morphological stability of Cu films in narrow trenches during the initial growth of Cu was studied at temperatures of 140–280 °C for the chemical deposition of Cu in supercritical CO2. Cu seed layers agglomerated and the deposited Cu and the seed layer coalesced at elevated temperatures. This mechanism resulted in bottom-up like growth at lower temperatures of 160–180 °C. The seed agglomeration was suppressed by starting deposition before reaching the temperature at which agglomeration started of about 150 °C. When Ru-lined trenches were used instead of Cu-seeded trenches, no clear agglomeration or grain coarsening was observed and Cu grew with a conformal topography.

Measurements of trace gaseous ambient impurities on an atmospheric pressure rapid thermal processor

Gaseous impurities in nitrogen ambient in the chamber of an atmospheric pressure rapid thermal processor were quantitatively measured. We employed atmospheric ionization mass spectrometry (APIMS) for this purpose. APIMS is the most sensitive technique to detect trace impurities in a gas at atmospheric pressure. A wide dynamic range (0.1 ppb→10 ppm) measurement was successfully performed, which allowed real-time monitoring of impurities during rapid thermal annealing. This work reports fundamental behavior of the ambient impurities originating from different sources. The sources discussed in this article are fourfold: source gas, system background, air (wafer loading), and wafer itself. The contribution of the source gas was found to be negligible, whereas the air and the wafer were found to be most crucial. Ambient management requires a better understanding of the independent contribution of each source to processing. It is shown how in situ measurements help to define process recipe for different types o...