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Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of these a-Si:C:H films. XPS revealed substantial Cu wetting of a-Si:C:H/OH and a-Si:C:H/OH/N films and some wetting of a-Si:C:H/N films, and similar Cu diffusion inhibition to 800 K by all of the a-:S:C:H films. These findings suggest the possible use of a-Si:C:H films as ILD and IMD materials, with the possibility of further tailoring a-Si:C:H films to meet future device requirements.

Ph.D. / The aim of this study was the development of a new technology for the manufacturing of amorphous silicon (a-Si:H) solar cells on flexible substrates. Kapton R , a commercially available polymer, was used as a substrate to this end. The use of such a polymer, as opposed to glass, results in dramatic savings and also affords the possibility for technological innovation. From the start the project was planned to develop and commission a medium-scale pilot plant manufacturing process. The project thus consisted of two sections: the design, fabrication and implementation of a large-area deposition system, as well as research and development of the materials and cells. A pilot plant was developed and successfully implemented. The optimization of the reactor resulted in very homogeneous materials with good electrical- and optical characteristics. The individual materials were optimized and incorporated into the standard cell configuration (on glass). This process was then transferred to kapton and the configuration was optimized. The use of kapton, as opposed to glass, implies the growth of silicon on a metal film on the kapton. This process leads to a number of phenomena occurring in cells on kapton which do not occur in standard cells on glass. The phenomena include the crystallization of a-Si:H at low temperatures, degradation of the material properties and unwanted microstructure. The origin of these phenomena can be linked to the high occurence of metal/Si-interdiffusion. It was found that this inter-diffusion can be decreased by the insert i on of a thin ZnO buffer layer between the back metal contact and the a-Si:H. The flexible cells were successfully developed and optimized for large areas. An operational manufacturing process was thus developed and the product of this study can now be applied successfully in practical applications.

by Lui Kai Man, Raymond. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 221-225). / Acknow1edgements / Abstract --- p.i / Table of Contents --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Sample Preparation --- p.12 / Chapter A. --- Introduction --- p.12 / Chapter B. --- The Working Systems --- p.12 / Chapter C. --- Sample Preparation --- p.14 / Chapter C.1 --- The Method Of Reactive Evaporation --- p.14 / Chapter C.2 --- The Method Of Posthydrogenation --- p.15 / Chapter D. --- The Substrates --- p.16 / Chapter Chapter 3 --- "Electrical Conductivities, Thermal and Optical Stability Experiments" --- p.21 / Chapter A. --- Introduction --- p.21 / Chapter B. --- Theory --- p.22 / Chapter B.1 --- Electronic Transport In Amorphous Semiconductor --- p.22 / Chapter B.2 --- dc Electrical Conductivity in Davis-Mott Model --- p.23 / Chapter B.3 --- Photoconductivity --- p.27 / Chapter B.4 --- Staebler-Wronski Effect --- p.28 / Chapter C. --- Experimental Method --- p.29 / Chapter C.1 --- Dark And Photo Conductivities Measurements --- p.29 / Chapter C.2 --- Optical Stability Measurement --- p.32 / Chapter C.3 --- Thermal Stability Measurement --- p.32 / Chapter D. --- Results --- p.34 / Chapter D.1 --- Reactively Evaporated Samples --- p.34 / Chapter D.2 --- Temperature Dependence Of Conductivities --- p.34 / Chapter D.3 --- Optical Stability Measurement --- p.35 / Chapter D.4 --- Thermal Stability Measurement --- p.36 / Chapter E. --- Discussions --- p.36 / Chapter E.1 --- Electrical Properties Of Reactively Evaporated a-Si:H --- p.36 / Chapter E.2 --- A Comparative Study Between Reactive Evaporated Samples With Those From Other Reactive Deposition Techniques And Glow-Discharge Process --- p.37 / Chapter F. --- Conclusions --- p.38 / Chapter Chapter 4 --- Infrared Absorption Experiment --- p.63 / Chapter A. --- Introduction --- p.63 / Chapter A.1 --- General Description --- p.63 / Chapter A.2 --- Types Of Atomic Vibrations --- p.64 / Chapter A.3 --- Infrared Spectroscopy Of a-Si:H --- p.64 / Chapter A.4 --- Effect Of Substrate Temperature On Bonding Configuration --- p.65 / Chapter B. --- Experimental Method --- p.66 / Chapter C. --- Results --- p.66 / Chapter D. --- Discussions --- p.67 / Chapter D.1 --- Identification Of The Two Absorption Bands --- p.67 / Chapter D.2 --- Effect Of Substrate Temperature --- p.68 / Chapter E. --- Conclusions --- p.70 / Chapter Chapter 5 --- Electron Spin Resonance Experiment --- p.82 / Chapter A. --- Introduction --- p.82 / Chapter B. --- Theory --- p.85 / Chapter B. 1 --- The Absorption Process --- p.85 / Chapter B. 2 --- The Relaxation Process --- p.86 / Chapter C. --- Experimental Method --- p.90 / Chapter D. --- Results --- p.92 / Chapter E. --- Discussions --- p.93 / Chapter F. --- Conclusions --- p.96 / Chapter Chapter 6 --- Optical Absorption Experiment --- p.114 / Chapter A. --- Introduction --- p.114 / Chapter B. --- Theory On Optical Transitions Within Amorphous Materials --- p.114 / Chapter B.1 --- General Descriptions --- p.114 / Chapter B.2 --- Band Models For Optical Absorptions In An Amorphous Semiconductor --- p.116 / Chapter C. --- Experimental Method --- p.121 / Chapter E. --- Analysis --- p.123 / Chapter E.1 --- Band Model --- p.123 / Chapter E.2 --- Deconvolution Of Absorption Spectrum --- p.124 / Chapter F. --- Discussions --- p.131 / Chapter G. --- Conclusions --- p.133 / Appendix A --- p.134 / Chapter A.1 --- An Outline On The Theoretical And Experimental Aspects Of PDS --- p.134 / Chapter Chapter 7 --- Recrystallization Of Amorphous Germanium By Rapid Thermal Annealing --- p.165 / Chapter A. --- Introduction --- p.165 / Chapter B. --- Theory --- p.166 / Chapter B.1 --- Recrystallization Of Amorphous Germanium --- p.166 / Chapter B.2 --- Nucleation And Growth - Isothermal Transformation --- p.167 / Chapter B.3 --- The Structure Of Polycrystalline Aggregates By X-ray Analysis --- p.170 / Chapter C. --- Experimental Set-ups --- p.172 / Chapter C. 1 --- The Rapid Thermal Processing Unit --- p.172 / Chapter C. 2 --- The Conventional Furnace --- p.175 / Chapter C. 3 --- The X-ray Diffractometer --- p.175 / Chapter C. 4 --- Electrical Conductivity Measurements --- p.176 / Chapter D. --- Experimental Method --- p.177 / Chapter D.1 --- The Samples --- p.177 / Chapter D.2 --- The Experiments --- p.177 / Chapter E. --- Results And Discussions --- p.178 / Chapter F. --- Conclusions --- p.185 / Appendix A --- p.216 / Chapter Chapter 8 --- Conclusions --- p.217 / Chapter A. --- Conclusions --- p.217 / Chapter B. --- Suggestions On Improvement And Further Development Of The Present Systems --- p.219 / References --- p.221

by Poon Sai Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1978. / Includes bibliographical references (leaves 92-94).

by Yeung Ching Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 69-71). / Text in English; abstract also in Chinese. / by Yeung Ching Chung. / Table of contents --- p.i / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- General overview --- p.1 / Chapter 1.2 --- The present study --- p.3 / Chapter Chapter 2 --- Sample preparation and characterization / Chapter 2.1 --- Sample preparation / Chapter A. --- General description --- p.5 / Chapter B. --- The thermal pulse furnace --- p.7 / Chapter C. --- The substrates --- p.9 / Chapter D. --- Sample preparation --- p.10 / Chapter 2.2 --- Sample characterization / Chapter A. --- Micro Raman system --- p.11 / Chapter B. --- Rutherford backscattering spectrometry (RBS) --- p.12 / Chapter C. --- X-ray powder diffraction --- p.13 / Chapter D. --- AFM. SEM and Surface Profiler --- p.13 / Chapter Chapter 3 --- Results and discussion / Chapter 3.1 --- The surface morphology / Chapter A. --- General description --- p.15 / Chapter B. --- The as-deposited amorphous film --- p.15 / Chapter C. --- The crystalline Ge film --- p.16 / Chapter D. --- The alloy film --- p.17 / Chapter E. --- The role of a-Si layer --- p.22 / Chapter 3.2 --- The depth profile (RBS) / Chapter A. --- General description --- p.24 / Chapter B. --- Peak temperature dependence --- p.27 / Chapter C. --- Heating rate dependence --- p.30 / Chapter 3.3 --- The near surface composition measured by Raman scattering / Chapter A. --- General description --- p.33 / Chapter B. --- Peak temperature dependence --- p.43 / Chapter C. --- Heating rate dependence --- p.45 / Chapter 3.4 --- Preferred growth direction / Chapter A. --- General description --- p.47 / Chapter B. --- Peak temperature dependence --- p.48 / Chapter C. --- Heating rate dependence --- p.51 / Chapter 3.5 --- Discussion / Chapter A. --- The particle size --- p.55 / Chapter B. --- The participation of Si substrate --- p.58 / Chapter C. --- The alloy formation --- p.58 / Chapter D. --- The abnormally fast interdiffusion --- p.63 / Chapter Chapter 4 --- Conclusion --- p.65 / Appendix --- p.67 / References --- p.69

Amorphous selenium (a-Se) and its alloys are important photoconductor materials used in direct conversion flat panel digital x-ray detectors. The performance of these detectors is determined, in part, by the electronic transport properties of the a-Se photoconductor layer namely, the charge carrier mobility m and the deep trapping lifetime t. The product of the mobility and the lifetime mt, referred to as the charge carrier range, determines the average distance that photo-generated charge will travel before being removed from the transport band by deep localized states in the mobility gap of the semiconductor. The loss of carriers to these deep states reduces the amount of charge collected per unit of x-ray exposure, and, hence, limits the x-ray sensitivity of the detector. Two experimental techniques that may be used to measure the transport properties of holes and electrons in high resistivity semiconductors are described in this thesis. The Time-of-Flight (TOF) transient photoconductivity technique is used to evaluate the charge carrier mobility by measuring the time required for the charge carriers to transit a fixed distance under the influence of an applied electric field. The Interrupted-Field Time-of-Flight (IFTOF) technique is used to determine the charge carrier deep trapping time; the drift of the injected carriers is temporarily interrupted at a position in the sample by removing the applied field. When the field is reapplied the number of charge carriers has decreased due to trapping events. The carrier lifetime is determined from the dependence of the fraction of recovered charge carriers before and after the interruption with the interruption time. <p> TOF and IFTOF measurements were carried out on a number of samples of vacuum deposited selenium alloy x-ray photoconductors. Device quality photoconductor films are fabricated by evaporating a-Se source material that has been alloyed with a small quantitiy of As (~0.3 at. %) and doped with a halogen (typically Cl) in the p.p.m. range. The dependence of the carrier range on the composition of the photoreceptor film was accurately measured using both TOF and IFTOF measurements. It was found that the transport properties of the film could be controlled by suitably adjusting the composition of the alloy. Combined IFTOF and TOF measurements were also performed on several samples to examine the effects of trapped electrons on the hole transport properties in a-Se films. It was found that drifting holes recombine with the trapped electrons, and that this process could be described by a Langevin recombination process. This finding is important for the correct modeling of amorphous selenium digital x-ray detector designs. Finally, the effects of x-ray exposure on a-Se films were examined. A temporary reduction in the effective hole lifetime was observed due to an increase in the number of hole capture centers following an x-ray exposure. The capture coefficient between free holes and the x-ray induced hole capture centers was measured using combined TOF and IFTOF measurements. It was shown that this capture process was governed by the Langevin recombination mechanism. From these observations it was concluded that trapped electrons from a previous x-ray exposure act as recombination centers for subsequently generated holes, thereby reducing the effective hole lifetime in the sample.

Amorphous selenium (a-Se) and its alloys are important photoconductor materials used in direct conversion flat panel digital x-ray detectors. The performance of these detectors is determined, in part, by the electronic transport properties of the a-Se photoconductor layer namely, the charge carrier mobility m and the deep trapping lifetime t. The product of the mobility and the lifetime mt, referred to as the charge carrier range, determines the average distance that photo-generated charge will travel before being removed from the transport band by deep localized states in the mobility gap of the semiconductor. The loss of carriers to these deep states reduces the amount of charge collected per unit of x-ray exposure, and, hence, limits the x-ray sensitivity of the detector. Two experimental techniques that may be used to measure the transport properties of holes and electrons in high resistivity semiconductors are described in this thesis. The Time-of-Flight (TOF) transient photoconductivity technique is used to evaluate the charge carrier mobility by measuring the time required for the charge carriers to transit a fixed distance under the influence of an applied electric field. The Interrupted-Field Time-of-Flight (IFTOF) technique is used to determine the charge carrier deep trapping time; the drift of the injected carriers is temporarily interrupted at a position in the sample by removing the applied field. When the field is reapplied the number of charge carriers has decreased due to trapping events. The carrier lifetime is determined from the dependence of the fraction of recovered charge carriers before and after the interruption with the interruption time. <p> TOF and IFTOF measurements were carried out on a number of samples of vacuum deposited selenium alloy x-ray photoconductors. Device quality photoconductor films are fabricated by evaporating a-Se source material that has been alloyed with a small quantitiy of As (~0.3 at. %) and doped with a halogen (typically Cl) in the p.p.m. range. The dependence of the carrier range on the composition of the photoreceptor film was accurately measured using both TOF and IFTOF measurements. It was found that the transport properties of the film could be controlled by suitably adjusting the composition of the alloy. Combined IFTOF and TOF measurements were also performed on several samples to examine the effects of trapped electrons on the hole transport properties in a-Se films. It was found that drifting holes recombine with the trapped electrons, and that this process could be described by a Langevin recombination process. This finding is important for the correct modeling of amorphous selenium digital x-ray detector designs. Finally, the effects of x-ray exposure on a-Se films were examined. A temporary reduction in the effective hole lifetime was observed due to an increase in the number of hole capture centers following an x-ray exposure. The capture coefficient between free holes and the x-ray induced hole capture centers was measured using combined TOF and IFTOF measurements. It was shown that this capture process was governed by the Langevin recombination mechanism. From these observations it was concluded that trapped electrons from a previous x-ray exposure act as recombination centers for subsequently generated holes, thereby reducing the effective hole lifetime in the sample.

Thesis (Ph. D. in Physics)--Vanderbilt University, 2003. / Title from PDF title screen. Includes bibliographical references.