Soft-polymer based microparticles are currently being applied in many biomedical applications, ranging from bioimaging and bioassays to drug delivery carriers. As one class of soft-polymers, hydrogels are materials, which can be used for delivering drug cargoes and can be fabricated in controlled sizes. Among the various hydrogel-forming polymers, poly(ethylene glycol) (PEG) based hydrogel systems are widely used due to their negligible toxicity and limited immunogenic recognition. Physical and chemical properties of particles (i.e., particle size, shape, surface charge, and hydrophobicity) are known to play an important role in cell-particle recognition and response. To understand the role of physicochemical properties of PEG-based hydrogel structures on cells, it is important to have geometrically precise and uniform hydrogel structures. To fabricate geometrically uniform structures, we have employed electron beam lithography (EBL) and ultraviolet optical lithography (UVL) using PEG or PEG diacrylate polymers. These hydrogel structures have been characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy, and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) confirming control of chemistry, size, and shape.
Nickel silicide is a most up-to-date self-aligned silicide ͑salicide͒ technology for nanoscale complementary metal-oxidesemiconductor field-effect transistors. However, an unintended oxidation of nickel silicide happened only on As-doped substrate. This abnormal oxidation phenomenon occurred only when the annealing temperature was higher than 613°C ͑sublimation point of As͒. The main reason for the oxidation is believed to the thermal energy that induces the diffusion of Ni from the nickel silicide to the substrate direction. Due to the oxidation, nickel silicide on As-doped substrate showed poor thermal stability contrasted to BF 2 -doped substrate.Salicide ͑Self-aligned silicide͒ technologies have been widely used in high-speed metal-oxide semiconductor field-effect transistors ͑MOSFETs͒ to increase the drive current by reducing the sheet and contact resistance of source/drain ͑S/D͒ and gate. Titanium silicide (TiSi 2 ) and cobalt silicide (CoSi 2 ) have been used sequentially for salicide technology. TiSi 2 replaced CoSi 2 mainly due to its strong linewidth dependency below 0.25 m complementary ͑C͒MOS technology. 1 CoSi 2 has also revealed some problems such as oxide contamination, large silicon consumption, and drastic increase of sheet resistance in nanoscale MOSFETs. 2,3 Therefore, new salicide technology is needed for nanoscale CMOSFETs and nickel silicide is a strong candidate for the replacement of CoSi 2 . 4,5 Using NiSi technology, low resistivity ͑ϳ14 ⍀-cm͒ can be obtained with reduced silicon consumption. It also has a very thin layer after the formation of silicide. Therefore, NiSi is adequate for deep submicrometer integrated circuits that need ultrashallow junctions. 6 However, despite these advantages, poor thermal stability hinders the application of NiSi to nano CMOS technologies which need hightemperature postsilicidation processes. Therefore improvement in thermal stability is a key issue for developing NiSi technology suitable for nanoscale CMOSFETs. In this article, the thermal stability of NiSi was studied with different dopant types, i.e., BF 2 and As, and especially abnormal oxidation of As was characterized in depth before and after postsilicidation annealing. ExperimentalBF 2 and As-doped substrates were used for this experiment and the key processes are as follows. BF 2 ͑20 keV, 4 ϫ 10 15 cm Ϫ2 ) and As ͑50 keV, 5 ϫ 10 15 cm Ϫ2 ) ion implantation for p ϩ /n and n ϩ /p junctions was followed by rapid thermal annealing ͑RTA͒ activation for 10 s at 1050°C. Then, Ni ͑200 Å͒ was deposited using ion beam sputter ͑IBS͒ at a base pressure about 7 ϫ 10 Ϫ7 Torr after a dilute HF dip to remove the native oxide. Next, rapid thermal process ͑RTP͒ was applied to form NiSi at 500°C, 30 s. Unreacted Ni was etched selectively in a chemical solution of HCl ϩ H 2 O 2 ϩ H 2 O ͑4:1:1͒ at room temperature. To test the thermal stability of NiSi, the samples were furnace annealed between 600 and 800°C for 30 min with N 2 ambient after the formation of NiSi.X-ray photoelectron spectroscopy ͑XPS͒ analysis was ...
A novel boron-diffusion process is described for the fabrication of high-efficiency P+/N silicon solar cells. Over the range of diffusion parameters investigated this diffusion process results in a boron-rich surface layer and shallow junctions (0.15–0.4 μm) having two properties important to the formation of high-efficiency solar cells—relatively low values of sheet resistance (35–140 Ω/⧠) which facilitates the front-surface grid-metal design and large resultant lifetimes approaching 60 μs. The characteristics of P+/N solar cells, fabricated using this diffusion process in single-crystal (CZ) silicon wafers, having AM1 efficiencies ranging from 14 to 17% are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.