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- Forsgren, Katarina, et al.
(author)
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Deposition of HfO2 thin films in HfI4-based processes
- 2002
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 149:10, s. F139-F144
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Journal article (peer-reviewed)abstract
- This study describes deposition of HfO2 thin films by chemical vapor deposition (CVD) and atomic layer deposition (ALD) using HfI4 as the metal precursor. The layer-by-layer growth was also studied in real time with a quartz crystal microbalance. In ALD, the deposition rate was independent of the growth temperature, whereas in CVD, an exponential rate increase was observed. Monoclinic HfO2 was deposited on MgO and poly-Si substrates in a wide temperature range, and the choice of substrate had a strong influence on the orientation of the films. Epitaxial growth of HfO2 was observed on MgO(001) substrates at 400-500°C in the ALD process and at 500-600°C in the CVD process. The electrical characterization showed that the crystallinity of the films had a stronger influence on the dielectric constant than did the film thickness.
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- Forsgren, Katarina, et al.
(author)
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Iodide-Based Atomic Layer Deposition of ZrO2 : Aspects of Phase Stability and Dielectric Properties
- 2002
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In: Chemical Vapor Deposition. - 0948-1907 .- 1521-3862. ; 8:3, s. 105-109
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Journal article (peer-reviewed)abstract
- This study is an investigation into the influence of temperature, substrate, and thickness on the properties of ZrO2 thin films grown by atomic layer deposition (ALD). ZrI4 and H2O2 were used as source materials, and films deposited at temperatures between 250 °C and 500 °C consisted of mixed tetragonal and monoclinic ZrO2. The phase content and electrical properties of films of 3–30 nm thickness were studied for different temperatures and substrates. The films crystallized at smaller thicknesses on the Pt/Ti/SiO2/Si (denoted Pt in the following text) substrate than on polycrystalline Si (poly-Si) and MgO(001). It was also found that the film thickness had a stronger effect on the dielectric constant than either the growth temperature or the substrate.
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- Gjirja, Savo, 1945, et al.
(author)
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Fischer- Tropsch-Synthesis Fuels as Diesel Engine Fuel-Fuel of the Future
- 2000
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Reports (other academic/artistic)abstract
- The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feed-stocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with regular diesel fuel if produced in large volumes.The aim of this investigation is to reveal and analyze the effects of F- T fuels on a research diesel engine performance. Previous engine laboratory tests indicate that F-T fuels are promising alternative fuels because they can be used in unmodified diesel engines, and substantial quantitative exhaust emission reductions can be reached. Also substantial qualitative reductions, e.g. reduction of the number of hazardous chemicals and reduction of the concentration of hazardous chemicals in the exhausts may be realized. Since the engine performance is close1y related to in-cylinder processes, a detailed thermodynamic analysis has been performed revealing the real thermo-chemistry history. The experimental results have shown that F-T fuels have a beneficial effect not only on the emissions levels, but also on other energetic parameters of the engine. Heat release analysis has shown that ignition delay, cylinder peak pressure, heat release gradient and indicated efficiency are affected as well.Two different mixtures of FT-fuels with variation in carbon chain branching and, to a certain extent variation in chain 1ength were tested and their results were compared with those obtained from conventional fuel (MK 1). The selected optimized F-T fuels mixture were further tested according to the 13 mode ECE R49 test cycle and were found as good competitive alternative diesel fuels.
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| 9. |
- Westlinder, Jörgen, 1973-
(author)
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Investigation of Novel Metal Gate and High-κ Dielectric Materials for CMOS Technologies
- 2004
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Doctoral thesis (other academic/artistic)abstract
- The demands for faster, smaller, and less expensive electronic equipments are basically the driving forces for improving the speed and increasing the packing density of microelectronic components. Down-scaling of the devices is the principal method to realize these requests. For future CMOS devices, new materials are required in the transistor structure to enable further scaling and improve the transistor performance.This thesis focuses on novel metal gate and high-κ dielectric materials for future CMOS technologies. Specifically, TiN and ZrN gate electrode materials were studied with respect to work function and thermal stability. High work function, suitable for pMOS transistors, was extracted from both C-V and I-V measurements for PVD and ALD TiN in TiN/SiO2/Si MOS capacitor structures. ZrNx/SiO2/Si MOS capacitors exhibited n-type work function when the low-resistivity ZrNx was deposited at low nitrogen gas flow. Further, variable work function by 0.6 eV was achieved by reactive sputter depositing TiNx or ZrNx at various nitrogen gas flow. Both metal-nitride systems demonstrate a shift in work function after RTP annealing, which is discussed in terms of Fermi level pinning due to extrinsic interface states. Still, the materials are promising in a gate last process as well as show potential as complementary gate electrodes.The dielectric constant of as-deposited (Ta2O5)1-x(TiO2)x thin films is around 22, whereas that of AlN is about 10. The latter is not dependent on the degree of crystallinity or on the measurement frequency up to 10 GHz. Both dielectrics exhibit characteristics appropriate for integrated capacitors. Finally, utilization of novel materials were demonstrated in strained SiGe surface-channel pMOSFETs with an ALD TiN/Al2O3 gate stack. The transistors were characterized with standard I-V, charge pumping, and low-frequency noise measurements. Correlation between the mobility and the oxide charge was found. Improved transistor performance was achieved by conducting low-temperature water vapor annealing, which reduced the negative charge in the Al2O3.
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