Improvements of CMP characteristics using slurry filter and high-spray bar of de-ionized water

As the integrated circuit device size shrinks to smaller dimensions, a chemical mechanical polishing (CMP) process was required for the global planarization of inter-metal dielectric (IMD) layer free of defects. However, as the IMD layer gets thinner, micro-scratches are becoming a major concern. Micro-scratches are generated by agglomerated slurry, solidified and attached slurry in the pipe-lines of the slurry supply system. In order to prevent the agglomerated slurry particles from slurry inflow, we installed a 0.5-m point-of-use (POU) filter, which is a depth-type filter and has 80% filtering efficiency for the 1.0-m size particles. Also, a high-spray bar of de-ionized water with high pressure was installed in the CMP equipment. In this paper, we studied the relationship between defect generation and pad counts to understand the exact efficiency of the slurry filter, and to determine the appropriate pad usage. Our experimental results showed that it is impossible to prevent defect-causing particles completely through the depth-type filter. Thus, we suggest that it is necessary to optimize the slurry flow rate and to install a high-spray bar of de-ionized water (DIW) with high pressure, in order to overcome weak points of the POU depth-type filter.     

Linear and non-linear dynamic response of sandwich panels to blast loading

The problem of the dynamic response of sandwich flat panels exposed to blast loadings is addressed. The sandwich model includes a number of non-classical effects such as the anisotropy and heterogeneity of face sheets, transverse orthotropy of the core layer, the geometrical non-linearities considered in the von Kármán sense, as well as the initial geometric imperfections. As concerns the blast pulses considered in this analysis, these are due to either an underwater/in-air explosion, or are due to a pressure wave traveling across the panel span. Implications of the explosive charge, stand-off distance, directionality property of face sheets material, damping ratio, geometric non-linearity, initial geometric imperfection, and of the characteristics of the blast, on dynamic response and dynamic magnification factor are put into evidence via a parametric study, and pertinent conclusions are outlined.     

An optimization of tungsten plug chemical mechanical polishing (CMP) using different consumables

The continuous shrinkage of integrated circuit devices provides the advantage of having more electrical functions on the smaller chips. However, it has posed severe challenges to the manufacturing of these products. In patterning steps, the depth of focus becomes small, due to the nature of patterning small features and is aggravated by the presence of step height differences in the exposure field. When the aspect ratio of holes increases, aluminum, which has been the choice of metal to fill holes, no longer effectively fills small holes. On some occasions, discontinuous aluminum exists in the holes, resulting from poor step coverage. Tungsten (W), on the other hand, can satisfactorily fill small holes by chemical vapor deposition and thus fills a need to replace aluminum as an electrical connector plug for layers separated by this plug. Chemical mechanical polish (CMP) has been used recently to planarize substrates and improve the depth of focus, as in the case of hole patterning. It is also used to prepare the metal plug effectively. CMP processing involves various parameters, such as machine configuration, slurry chemistry and formulation, polishing pad configuration, pad hardness, etc. Although the mechanism is not fully understood, these parameters are known to significantly influence the degree of planarization, contamination, defects, etc. In this paper we explore the effects of consumables used in the W-CMP process on the control of several problems, such as recessed plug, dishing and oxide erosion, etc. Based on our findings, we implement a two-step W-CMP process to improve the qualities of the polished wafers. The first step involves a proper combination of slurry and pad to polish most of the bulk tungsten with a high polish rate. The second step uses the same pad, slurry and a proprietary additive to slowly polish the remaining tungsten. In this way, we are able to obtain a workable W-CMP process. © 2001 Kluwer Academic Publishers     

One-pot fabrication of hollow SiO2 nanowires via an electrospinning technique

Hollow SiO₂ nanowires (NWs) were one-pot fabricated via an electrospinning method. Their morphologies, structures, and chemical compositions were investigated by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In order to fabricate optimum hollow SiO₂ NWs, the relative volume ratio of tetraethyl orthosilicate (TEOS, an alkoxide precursor) to ethanol (solvent) was systematically controlled from 0.02 to 0.36. SEM, HRTEM, XRD, and XPS results indicate that amorphous SiO₂ hollow NWs can be one-pot synthesized by using the volume ratio of 0.18 under a constant voltage of 8.0 kV.     

Correlation analysis between pattern and non-pattern wafer for characterization of shallow trench isolation–chemical–mechanical polishing (STI–CMP) process

This study is about control of oxide removal amounts on the shallow trench isolation (STI) patterned wafers using removal rate and thickness of blanket (non-patterned) wafers. At first, the removal properties of plasma enhanced tetra-ethyl ortho-silicate (PETEOS) blanket wafers was investigated, and then it was compared with the removal properties and the planarization (step height) as a function of polishing time of the specific STI patterned wafers. We found that there is a relationship between the amount of oxide removal by blanket and patterned wafers. We analyzed this relationship, and the post-CMP thickness of patterned wafers could be controlled by removal rate and removal target thickness of blanket wafers. As the result of correlation analysis, we confirmed that there was the strong correlation between patterned and blanket wafers (correlation factor: 0.7109). So, we could confirm the repeatability as applying to STI CMP process from the linear formula obtained.     

Semi-abrasive free slurry with acid colloidal silica for copper chemical mechanical planarization

New semi-abrasive free slurry for copper chemical mechanical planarization (CMP) was investigated through the addition of below 0.5 wt% acid colloidal silica, hydrogen peroxide and other additives. The additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP were also evaluated. This semi-abrasive free slurry provides good hydrogen peroxide stability, excellent colloidal silica dispersion ability and easiness of post-CMP cleaning. The extent of enhancement in tantalum nitride CMP was verified through an electrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.     

Effect of dietary patterns on the blood/urine concentration of the selected toxic metals (Cd,Hg, Pb) in Korean children

Food Science and Biotechnology - This study was aimed to examine the association the blood/urinary concentration of toxic metal (Hg, Pb, and Cd) with children’s dietary patterns. This...     

Sulfonated poly(arylene ether sulfone)/Laponite-SO3H composite membrane for direct methanol fuel cell

Polymer nanocomposite membranes based on sulfonated poly(arylene ether sulfonate) (SPAES) containing a flake filler (Laponite) with varying degrees of sulfonation, were prepared and characterized for application in direct methanol fuel cells (DMFCs). Unlike most other clays, Laponite crystals are very small in size with a very low aspect ratio (diameter to thickness ratio) of 25–30. They improve the mechanical, thermal properties and decreased the fuel permeability. However, polymer composite membranes containing non-proton conducting inorganic particles tend to show low proton conductivity, as compared with pristine polymer membranes. To resolve this problem, prior to the preparation of the composite membranes, Laponite-Na+(NLa) was sulfonated with various amounts of organo silanes (3-Mercaptopropyl trimethoxysilane (SH-silane)) via an ion exchange method. Functionalized Laponite with the organic silane compound showed higher ion exchange capacity and ion conductivity, respectively. In order to minimize the loss of proton conductivity while reducing the methanol permeability, various amounts (0.5–2.0 wt%) of the organically sulfonated Laponite (SLa) were introduced into the SPAES matrices. The performances of hybrid membranes for DMFCs in terms of mechanical properties, behavior of water in membranes, proton conductivity and methanol permeability were investigated.     

Reduction of loading effects with the sufficient vertical profile for deep trench silicon etching by using decoupled plasma sources

This study presents the features of profile evolution in deep trench silicon etching, which is crucial for commercial wafer-processing applications. Experiments to minimize the macroscopic and microscopic loading effects were performed with anisotropic deep trench etching in high-density decoupled HBr/CF₄/Cl₂/O₂ and SF₆/CF₄/O₂ plasmas. The process parameters, including gas chemistry, pressure, source power, bias power, and dual electrostatic chuck system, were also optimized for these applications. Notching and trenching phenomena were effectively improved during the deep trench etching process. The optimized deep trench silicon process resulted in vertical profiles (87–90°) with a loading effect of <1% by using the SF₆-based chemistry, which was more effective than the HBr-based process. The bias constant verified the linear-etching parameter system, depending on the pattern density of the device, in order to commercialize deep trench silicon etching for mass production.     

An investigation of transition boiling mechanisms of subcooled water under forced convective conditions

A mechanistic model for forced convective transition boiling has been developed to investigate transition boiling mechanisms and to predict transition boiling heat flux realistically. This model is based on a postulated multi-stage boiling process occurring during the passage time of the elongated vapor blanket specified at a critical heat flux (CHF) condition. Between the departure from nucleate boiling (DNB) and the departure from film boiling (DFB) points, the boiling heat transfer is established through three boiling stages, namely, the macrolayer evaporation and dryout governed by nucleate boiling in a thin liquid film and the unstable film boiling characterized by the frequent touches of the interface and the heated wall. The total heat transfer rates after the DNB is weighted by the time fractions of each stage, which are defined as the ratio of each stage duration to the vapor blanket passage time. The model predictions are compared with some available experimental transition boiling data. The parametric effects of pressure, mass flux, inlet subcooling on the transition boiling heat transfer are also investigated. From these comparisons, it can be seen that this model can identify the crucial mechanisms of forced convective transition boiling, and that the transition boiling heat fluxes including the maximum heat flux and the minimum film boiling heat flux are well predicted at low qualities/high pressures near 10 bar. In future, this model will be improved in the unstable film boiling stage and generalized for high quality and low pressure situations.