Performance Comparisons of Abrasive Containing and Abrasive Free Slurries for Copper Low-k CMP

The commercially available abrasive containing slurries for copper CMP have shown some advantages in high removal rates, low friction at low down force, and minimal to no copper residues, regardless of the polisher architecture, either rotary, orbital, or linear polishing. However, the abrasive containing slurries have some disadvantages such as high dishing and erosion with more micro-scratches due to the presence of abrasives. In contrast, the abrasive free polishing slurry has lower removal rate, and seems to be sensitive to polishing architecture, but it has good planarization, low topography, less micro-scratches, and most importantly is insensitive to over-polish.At this stage, the best results for copper CMP are being achieved by the use of the multi-step and multi-slurry process in which copper is polished first, and barrier layers are polished with a different set of consumables. The intent of this paper is to focus on the first step, the copper removal step, and to compare different approaches for this first step; namely, the use of slurries containing abrasives with slurries that are free of abrasives on the orbital polisher. The combined process with low percent solid and small-sized abrasives for the bulk copper removal step and abrasive free polishing (AFP) slurry for the residual copper removal step on an orbital polisher has produced a very robust process window with excellent results including low topography, low erosion, insensitivity to over-polish and low cost of ownership.

RESULT OF ANTERIOR DEBRIDEMENT AND FUSION IN PYOGENIC VERTEBRAL OSTEOMYELITIS: ANALYSIS OF 20 CASES

Twenty cases of pyogenic vertebral osteomyelitis treated by anterior debridement and fusion from January 1989 to January 1999 were analyzed. Thirteen were males, seven females. Age ranged from 16 to 76 years (median, 52 years). The most common location was L4–L5 level (12 patients). The mean duration of symptoms was 3.5 months (range, 3 days to 12 months). Gram-positive cocci infection was the most frequent causative organism. Fever was found in only two patients (10%). Misdiagnoses frequently occurred, especially at L4–L5 involvement (9 patients). Anterior debridement and fusion using iliac crest graft was chosen when the patient was neurologically compromised or had spinal instability or doubtful diagnosis. The result was rated as good in 75 percent. Solid fusion occurred in 18 cases within one year. Complications occurred in five cases, most of them related to the surgical approach.

Effects of Clarithromycin on Rheological Properties of Nasal Mucus in Patients with Chronic Sinusitis

Macrolide antibiotics have a variety of actions along with antimicrobial action. To determine the effects of oral administration of clarithromycin (CAM) on rheological properties, we measured the spinability, dynamic viscoelasticity, and solid composition of human nasal mucus from 18 patients with chronic sinusitis before and after administration of CAM for 4 weeks. After administration of CAM, the spinability and percent solid composition of nasal mucus increased from 26.5 ± 12.2 mm to 40.2 ± 18.7 mm and 7.86% ± 3.47% to 13.90% ± 3.67% (p < .05), respectively, whereas the ratio of the viscosity to the elasticity (η′/G′) of nasal mucus after the administration of CAM decreased in all of the mucus samples. These results suggest that treatment with CAM may modulate the rheological properties of nasal mucus in patients with chronic sinusitis.

Mucus-depleted frog palate as a model for the study of mucociliary clearance

To better understand the frog palate model of mucociliary transport, we measured the transport rate of mucus (MTR) from the leopard frog, Rana pipiens, and from the bullfrog, R. catesbeiana, recorded the stability of the MTR over a period of hours and days and over the course of 1 yr, and measured the viscoelasticity, percent solid composition, and spinnability (filance) of mucus from both species. Bullfrog mucus was less rigid than leopard frog mucus (log G* at 1 rad/s 2.09 vs. 2.61; P less than 0.01) and had a higher viscosity-to-elasticity ratio (tan delta at 1 rad/s 0.36 vs. 0.26; P less than 0.05). It also had a lower solids content (8.71 vs. 13.72%; P = 0.02), and there was a trend to lower spinnability for bullfrog mucus (filance 26.7 vs. 33.5 mm). These data suggest that bullfrog mucus has viscoelastic properties similar to normal mammalian respiratory mucus and leopard frog mucus has viscoelasticity similar to sputum samples. MTR was significantly slower in the winter than in the summer months (17 vs. 30 mm/min; P less than 0.0001). Although the leopard frog palate could be used for at least 7 consecutive days without exhaustion, bullfrog palates could be used for only 5 days. Palates of either species could generally be tested for 6 h/day without a significant decrease in MTR. These data clarify some of the sources of variability in the use of this system and suggest methods of standardization.

Physical and Chemical Characteristics of Cenospheres From the Combustion of Heavy Fuel Oil

Characterization of an existing sample of cenospheres produced during residual-oil-fired steam power plant combustion included: scanning electron microscopy of surface structure; photomicrography of particle cross sections; measurement of porosity, surface area, and density; and measurement of chemical composition. The studies showed that typical large (100–200 μm) and small (20–40 μm) cenospheres were spheroidal and hollow and had at least one blowhole. The sizes of the blowholes range from 10 to 50 percent of the diameters of the cenospheres. The ratio of outer to inner diameter of the shell was of the order of 1.3–1.4. The shells are porous, the larger ones appearing spongelike, the smaller ones appearing smoother but containing many pores a few micrometers in diameter. The solid portions of the shell appear flaky and layered. A typical cenosphere contained only about 18 percent solid material on a volumetric basis. A relatively concentrated percentage content of elements S, Fe, Na, and V was indicative of the potential contribution to high-temperature corrosion from cenosphere deposition on heat exchanger surfaces.

Measurements of Turbulence Generated by 60 Percent Solid Perforated Plates

Combustion experiments simulating spark-ignition engine conditions require generation and measurement of high intensity, rapidly decaying turbulence in a combustion test cell. Turbulence is generated by drawing various perforated plates across the test cell and is measured by hot-wire anemometry in the test cell and behind the same perforated plates in a steadily flowing wind tunnel. To correlate test cell and wind tunnel turbulence measurements, a simple statistical model of hot-wire anemometer response in turbulence with negligible mean flow is used. Good agreement between the two measurements tends to confirm the model for this case and demonstrates the value of perforated plate turbulence generators in producing controllable, measurable turbulence for confined combustion research.