Articles you may be interested inMethods of producing plasma enhanced chemical vapor deposition silicon nitride thin films with high compressive and tensile stress J. Vac. Sci. Technol. A 26, 517 (2008); 10.1116/1.2906259 Silicon nanocrystal formation in annealed silicon-rich silicon oxide films prepared by plasma enhanced chemical vapor deposition A comparative study on inductively-coupled plasma high-density plasma, plasma-enhanced, and low pressure chemical vapor deposition silicon nitride filmsThe formation of nanosized Si crystals in dual-frequency plasma-enhanced chemical-vapor-deposited silicon oxides is identified in this study. As a higher SiH 4 N 2 O gas flow rate ratio is employed during the deposition process, the silicon-to-oxygen atomic ratio and the dangling bond density both increase. The resulting oxide films contain more Si-H bonds and less Si-O and Si-O-H bonds, as determined from the Fourier-transform infrared spectra. The main type of charge defects in these oxides change from "SiwO 3 bonds (EЈ centers͒ to "SiwSi 3 bonds, which eventually cluster together and precipitate out from the oxide network to form the Si nanocrystals. The size of these Si nanocrystals falls within the range of 30-50 nm, as observed by high-resolution transmission electron microscopy. The formation of these nanocrystals inside the silicon-rich oxides results in a lower film density, a tensile stress component, and a higher wet etching rate, even under the ion bombardment provided by the rf bias power during deposition. The underlying mechanisms for the formation of these Si nanocrystals from the silicon oxide will be proposed.

As the trend toward shrinking design rules for ultralarge scale integrated circuits (ULSI) continues, the requirements of the planarization process become more and more stringent due to concerns over narrowing lithographic process latitudes in the presence of ever-reducing depth of focus. Among the planarization technologies, chemical mechanical polishing (CMP) is the only technique that is capable of achieving global planarization across the lithographic field, and therefore becomes one of the most important ULSI process technologies for the 0.25 m generation and beyond. 1 Despite its popularity and widespread applications, the practice of CMP still remains at an empirical level owing to the numerous process parameters involved and the lack of a systematic methodology for characterizing and optimizing the process. For instance, for the planarization of intermetal dielectric (IMD) through CMP, process engineers are often confronted with the challenge of determining the thickness of deposited IMD layer that will be removed subsequently by the CMP step. This problem is further complicated when it comes to optimize the numerous CMP process parameters in order to broaden the process latitude, while maintaining a high enough planarization efficiency in the presence of varying pattern densities that would lead to over-or underpolishing of the dielectrics within a chip.To investigate the influence of each parameter over a wide range of variables and to reduce the sample size under such a complex variable experiments, this study utilized the standard L-25 orthogonal array experiments design 2,3 to derive the characteristic trends of removal rate and within-wafer nonuniformity (WIWNU) against various CMP process parameters. With the L-25 orthogonal array experimental setting, removal rate and WIWNU values may be biased if certain polishing parameters dominate the output results or there exists interaction between parameters. To correct this, parametric experiments based on the summary from orthogonal array results are performed afterward to eliminate the side effects. This also provides precise numerical data of each parameter for the decision of optimal value for subsequent experimental setting. The optimal polishing conditions derived above are then adopted to planarize the intermetal dielectric oxide films with various patterned metal pitches underneath to investigate the efficiency of planarization (%EOP). Based on the observation of the above experimental results, a rule including the integral nonuniformity, thickness of dielectric, efficiency of planarization, geometry of device, removal rate, and its variation for CMP polishing time estimation (INTEGRATE) is proposed to estimate the required dielectric thickness and polish time for the integration of IMD and CMP processes. Scanning electron microscopy (SEM) cross-sectional micrographs and chip level long scan profiles reveal the excellent global planarization achieved through the practice of the proposed INTEGRATE rule in this study. ExperimentalFirst, the plasma-e...

The chemical-mechanical polishing (CMP) process has been proven to be the most promising method for accomplishing global planarization. In this paper, results of chemical-mechanical polishing of fluorinated silicon dioxide (SiOF) thin films are presented. Nanohardness, elastic modulus, and bonding structure of fluorinated silicon dioxides are characterized in order to evaluate their correlations with CMP performance. The results show that under fixed chemistry and mechanical parameters, the CMP removal rate increases significantly with increasing fluorine content in the oxides due to the lower hardness and elastic modulus in the films. Higher CMP removal rate is observed for fluorinated oxides polished with slurry of pH 10 relative to pH 9. Compared with undoped oxides, SiOF films are more sentisitive to chemical and moisture attacks as reflected by the post-CMP increase in refractive index.

The cosmic background radiation is thermal radiation with a temperature of 2.75 K still present throughout the universe, a relic of its hot, big bang, initial phase. Detailed studies of this radiation, and particularly its angular variations, can provide information obtainable in no other way about the global geometry and expansion of the universe, about the distribution of mass near our Galaxy, and about the process of galaxy formation. This review treats searches for such angular variations and the consequences of the resulting measurements of, or upper limits on, variations in the cosmic background radiation.The only unambiguously detected angular variation is the dipole component of the radiation, believed to arise from a Doppler shift due to the motion of the Earth; the inferred velocity of the Earth relative to the background is -350 km s-'. Searches for a quadrupole component have found none, with upper limits on the fractional variation, A T / T , of a few times IO-'. The absence of a significant quadrupole moment allows us to reject many models for the universe which include anisotropic expansion or shear. These constraints are reinforced by upper limits on the linear polarisation of the cosmic background radiation.Searches for smaller scale variations, at angles from arcseconds to degrees, have thus far failed to find any. At some angular scales, upper limits on temperature fluctuations have now reached a level of a few times Reviewed here are both the observational methods employed in such searches and some of the sources of statistical and systematic errors encountered. Several consequences of the upper limits on fluctuations in the radiation are examined. Among these are constraints on models for the formation of large astronomical systems like galaxies, and the support these observations lend to models for the very early expansion of the universe which arise from new theories in particle physics.An outline of big bang cosmology is contained in an appendix for readers unfamiliar with the nomenclature of cosmology.

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