Rozprawy doktorskie na temat „Silicon Nano-structured Thin Films”

Magister Scientiae - MSc (Physics)
An increasing energy demand and growing environmental concerns regarding the use of fossil fuels in South Africa has led to the challenge to explore cheap, alternative sources of energy. The generation of electricity from Photovoltaic (PV) devices such as solar cells is currently seen as a viable alternative source of clean energy. As such, crystalline, amorphous and nanocrystalline silicon thin films are expected to play increasingly important roles as economically viable materials for PV development. Despite the growing interest shown in these materials, challenges such as the partial understanding of standardized measurement protocols, and the relationship between the structure and optoelectronic properties still need to be overcome.

It has been debated that among all the renewable energy alternatives, only solar energy offers sufficient resources to meet energy demands. Silicon thin film solar cells are at the frontier of commercial solar technology. Hot wire chemical vapour deposition (HWCVD) is the technique of choice for silicon thin film deposition due to the absence of ion bombardment and its independence toward geometry or electromagnetic properties of the substrate, as seen by plasma enhanced chemical vapour deposition (PECVD). With the implementation of nanostructures in a multi-band gap tandem solar cell, considerable improvement has been achieved over the single junction solar cells. Defect assisted tunnelling processes at the junctions between individual solar cells in a tandem structure solar cell largely affect the efficiency of these solar cells. In this contribution, the investigation toward the improvement of silicon thin films for tandem solar cell application is initiated. This study reports on the effects of hydrogen dilution and deposition time on six silicon thin films deposited at six specific deposition regimes. The thin film properties are investigated via X-Ray diffraction analysis, Raman spectroscopy, Fourier transform infra-red spectroscopy, elastic recoil detection analysis, scanning and transmission electron microscopy and UV-visible spectroscopy. This investigation revealed the dominating etching effect of atomic hydrogen with the increase in hydrogen dilution and a bonded hydrogen content (CH) exceeding 10 at.% for each of the six thin films. The optically determined void volume fraction and static refractive index remain constant, for each thin film, with the change in CH. A new deposition procedure, utilising the deposition conditions of the previously investigated thin films, is performed by HWCVD to deposit two silicon thin films. This deposition procedure involved either increasing (protocol 1) or decreasing (protocol 2) hydrogen dilution during deposition. Structural and optical variation with depth was observed for the dynamically deposited silicon thin films, with nano-voids existing across the entire cross section and bond angle variations which are indicative of good structural order. The optical absorption curves differ for the two silicon thin films whereas the optical density remains constant for both.
>Magister Scientiae - MSc

La nano-impression est une technique de lithographie qui consiste à reproduire les motifs contenus dans un moule, par pressage de celui-ci sur un film de résine. Cette technologie – rapide et peu coûteuse à mettre en oeuvre – est prometteuse mais son utilisation à l’échelle industrielle nécessite encore des améliorations notamment en termes de limitation de la défectivité des motifs reproduits. Des solutions existent pour pallier cette limitation, à travers notamment l’utilisation de traitements antiadhésifs qui se greffent en surface des moules et permettent de favoriser les étapes de démoulage. Cependant, ces traitements de moules ont une durée de vie limitée, ce qui limite la rentabilité globale du procédé de nano-impression.Ce projet de thèse s’intéresse à la question de la durabilité des moules et propose des matériaux alternatifs pour la fabrication de moules de nano-impression.Pour répondre aux exigences des acteurs de la nano-impressions, quatre matériaux (le Diamond-like carbon, le carbure de silicium et leurs versions dopées en fluor) ont été développés pour une utilisation en tant que matériaux de moules alternatifs au silicium et au quartz. La caractérisation des propriétés physiques et physico-chimiques a été réalisée de sorte à sélectionner les matériaux les plus prometteurs qui ont ensuite été structurés pour une utilisation en tant que moules fonctionnels.Les propriétés d’adhérence de ces matériaux ont ensuite été caractérisées tant en nano-impression assistée par ultraviolets qu’en nano-impression thermique. Ces essais ont permis de montrer que les matériaux développés, malgré une grande énergie de surface, présentent intrinsèquement un caractère antiadhésif lié à leur inertie chimique
Nanoimprint is a lithography technology which consists in structuring a polymer film by pressing a structured mold into it. This promising method is low-cost and has a high throughput, but its implementation in industry still requires improvements, particularly regarding the defectivity of imprinted structures. To circumvent this defectivity, the use of antiadhesive treatments, grafted to the mold surface has been developed to facilitate the demolding step. However, these treatments have a limited lifespan, thereby empeding the global nanoimprint cost-effectiveness.This thesis focuses on mold durability and suggests alternative materials for the fabrication of nanoimprint molds.To match nanoimprint requirements, four materials (Diamond-like carbon, Silicon carbide and their fluorine-doped versions) were developed to be used as alternatives to silicon and quartz. Physical and physico-chemical characterization were carried out, so as to determine the best candidates that were then patterned, leading to usable molds.Adhesion properties of these materials were then characterized both in UV-nanoimprint and thermal-nanoimprint procedures. These investigations showed that despite their high surface energies, the developed materials exhibit intrinsically antiadhesive properties, thanks to their chemical inertness

Thesis advisor: Michael J. Naughton
Geometrically generalized analytical expressions for device transport are derived from first principles for a photovoltaic junction. Subsequently, conventional planar and unconventional coaxial and hemispherical photovoltaic architectures are applied to detail the device physics of the junction based on their respective geometry. For the conventional planar cell, the one-dimensional transport equations governing carrier dynamics are recovered. For the unconventional coaxial and hemispherical junction designs, new multi-dimensional transport equations are revealed. Physical effects such as carrier generation and recombination are compared for each cell architecture, providing insight as to how non-planar junctions may potentially enable greater energy conversion efficiencies. Numerical simulations are performed for arrays of vertically aligned, nanostructured coaxial and hemispherical amorphous silicon solar cells and results are compared to those from simulations performed for the standard planar junction. Results indicate that fundamental physical changes in the spatial dependence of the energy band profile across the intrinsic region of an amorphous silicon p-i-n junction manifest as an increase in recombination current for non-planar photovoltaic architectures. Despite an increase in recombination current, however, the coaxial architecture still appears to be able to surpass the efficiency predicted for the planar geometry, due to the geometry of the junction leading to a decoupling of optics and electronics
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

In this century some of our main issues are energy shortage and pollution. This work will briefly describe these problems, proposing a plan of action combining energy saving and different sustainable energy sources. Within different types of renewable energy sources, solar energy is the most abundant one. To make solar energy a more sustainable and cost effective technology we focus on enhancing the optical characteristics of thin film solar cells. In this category, organic solar cells are good options for their exiguous amount of material and the low energy needed for the fabrication process. This technology can be lightweight, transparent, flexible and conformal in order to be applied to and integrated in various architectural solutions and consumer electronics. After a study of the physics of such devices and on how to optically enhance their performances, we will show some examples where we theoretically and experimentally collect the solar radiation with optical antennas. We report, for the first time in literature, a nanogap antenna that efficiently couples the light in our active material thin film. Finally, we elaborate on the concept of building integrated photovoltaics introducing some examples of solar façades. Based on our research, we are able to design and fabricate an organic transparent solar cell with a visible transparency above 20% and an optically enhanced photon-electron conversion efficiency remarkably similar to its opaque equivalent.
En el presente siglo, algunas de las prioridades son la escasez de la energía y la contaminación. Este trabajo describirá brevemente estos problemas y propondrá un plan de acción que combina el ahorro energético con diferentes fuentes sostenibles de energía. Dentro de estas fuentes de energía renovables, la energía solar es la más abundante. Con el objetivo de hacer la tecnología solar más sostenible y eficiente económicamente nos concentramos en aumentar las características ópticas en celdas solares de película delgada. Dentro de esta categoría, las celdas solares orgánicas son una buena opción porque su desarrollo requiere bajas cantidades de materiales y su fabricación es de baja energía embebida. Adicionalmente, esta tecnología puede ser liviana, transparente, flexible mecánicamente y modular para ser aplicada e integrada en varias soluciones arquitectónicas y de electrónica de consumo. Luego de estudiar los procesos físicos en tales dispositivos y de determinar las metodologías para aumentar ópticamente sus desempeños, mostraremos algunos ejemplos donde teórica y experimentalmente se colecta la radiación solar mediante antenas ópticas. Se reporta por primera vez, una antena de nanogap que acopla eficientemente la luz en la capa activa de la celda solar. Finalmente, se desarrolla el concepto de tecnología fotovoltaica integrada en edificaciones tras introducir algunos ejemplos de fachadas solares. Basados en nuestra investigación, fue posible diseñar y fabricar una celda solar orgánica transparente cuya transparencia en el rango visible estuvo por encima del 20% y una eficiencia de conversión foton-electron aumentada ópticamente que resulto notoriamente similar a la celda solar orgánica opaca equivalente.
La rareté grandissante des ressources en énergie associée à une augmentation de la pollution font partie des enjeux plus importants de ce siècle. Cette thèse décrira brièvement ces deux problématiques et proposera un plan d’action combinant économie d’énergie et diversité des sources d’énergies renouvelables. Parmi les formes d’énergies renouvelables disponibles, l’énergie solaire est la plus abondante. Pour faire de l’énergie solaire une ressource plus durable et plus rentable économiquement, nous proposons d’amplifier les propriétés optiques de cellules solaires en couches minces. Dans cette catégorie, les cellules solaires organiques représentent un choix pertinent de part la faible quantité de matériau nécessaire ainsi que la faible énergie nécessaire au procédé de fabrication. Cette technologie peut être légère, transparente et flexible de sorte qu’elle peut être utilisée dans différentes solutions architecturales s’adaptant à des produits électroniques pour le grand publique. Suivra la théorie sous jacente à ces dispositifs et l’explication de la manière dont leurs performances sont améliorées. Nous présenterons quelques exemples où l’on collecte la radiation solaire avec une antenne optique. Ainsi, nous faisons la toute première démonstration d’une antenne auto-assemblée qui couple efficacement la lumière dans le matériau constituant la couche mince que nous utilisons. Finalement, nous développons le concept de cellules photovoltaïques intégrées en présentant différents cas de façades solaires. Ces travaux nous ont permis de concevoir et de fabriquer une cellule solaire organique transparente avec une transparence dans le visible de 20% et une efficacité de conversion photon-électron améliorée, similaire à une cellule équivalente opaque.
La difficile reperibilità di risorse energetiche e l’inquinamento sono alcuni dei problemi più importanti di questo secolo. In questo lavoro saranno presentati brevemente questi temi proponendo un piano d’azione che abbini il risparmio energetico alle differenti fonti di energia rinnovabili. Nell’insieme delle fonti energetiche rinnovabili l’energia solare è senz’altro la più abbondante. Con l’obbiettivo di rendere lo sfruttamento di tale energia più sostenibile ed economicamente vantaggioso, ci premuriamo di migliorare le caratteristiche ottiche di celle fotovoltaiche a film sottile. In questa categoria utilizziamo, tra le diverse opzioni, le celle solari organiche in quanto la loro fabbricazione richiede una quantità di materiale minimo e un basso consumo energetico. Inoltre questi tipi di dispositivi possono essere leggeri, trasparenti, flessibili e conformabili alle superfici su cui sono applicati. Questa è una tecnologia che potrebbe essere implementata e integrata in varie soluzioni architettoniche o nell’ elettronica di consumo. Dopo aver presentato i principi fisici di tali dispositivi e determinato le metodologie ottiche per aumentarne le prestazioni, vengono illustrati alcuni esempi dove, teoricamente e sperimentalmente, riusciamo a intercettare la radiazione solare con antenne ottiche. Riportiamo, per la prima volta in letteratura, un’antenna ottica con nano-gap che accoppia efficacemente la luce solare nel nostro materiale attivo a film sottile. Nell’ultima parte sviluppiamo il concetto di tecnologia solare integrata negli edifici, introducendo alcuni esempi di facciate solari. Basando il design sulla nostra ricerca, è possibile realizzare una cella solare fotovoltaica organica trasparente, con una trasparenza superiore del 20% e un’ efficienza di conversione fotone-elettrone migliorata grazie all’ottica, che risulta molto vicina all’ equivalente cella fotovoltaica organica non trasparente.

碩士
南台科技大學
光電工程系
98
There had been few published literatures of porous-silicon (PS) on ultra-violet (UV) photodetectors, because the optical absorption of this material ranged from visible to infrared light. Although as a wide-bandgap semiconductor due to the quantum-size effect, nano-porous-Si (NPS) also can hardly absorb UV energy due to its insufficiently large bandgap (< 2ev). In this thesis, oxidized nano-porous-Si (ONPS) that prepared by rapid-thermally oxidizing NPS thin-films was proposed for UV sensing applications. NPS thin-films with uniformly distributed Si nano-crystallites (3nm~10nm) were firstly prepared on heavily doped p+-type (100) Si wafers by anodic etching processes with low etching current density (10mA/cm2 ). Then ONPS films were obtained from rapid-thermal-oxidation (RTO) treatment of NPS at 850℃ for 90 sec. Photo-sensing diodes were made with ONPS films as the light-absorption layers, after depositing inter-digitated aluminum (Al) electrodes on the front sides of the devices. The optical bandgap of a NPS film was measured about 1.6ev, whereas it was raised to 3.5ev for the as-formed ONPS film after RTO processes. The photo-response spectra of a NPS film located within wavelengths from 500nm to 900nm. However, an ONPS film exhibited high photoresponsivity for incident wavelengths between 300nm and 400nm, showing it was very suitable for UV sensing applications. Furthermore, an ONPS photodiode can achieve a high photo-to-dark current ratio up to about 2000 under an incident light wavelength of 350nm while obtained quite low dark current down to 7.3A/cm2. Experimental results indicated that ONPS photodetectors had high UV sensitivity. Finally, a tentative carrier transport mechanism was proposed to illustrate the UV photoresponse processes in an ONPS structure.

碩士
國立聯合大學
材料科學工程學系碩士班
105
In this study, the molybdenum nitride, MoN, multilayer coatings modulated by single layer molybdenum nitride with distinguished structure was proposed. The microstructures with crystalline, preferred orientation and featureless structure, respectively, are fabricated by magnetization sputtering with the input power and gas inlet control. Three kinds of multilayer coatings were successfully prepared by stacking of MoN single layer coating of above mentioned three structural features. The structure of the multilayer coatings were controlled at a total of 20 layers and 1 um, while each building layer was 50 nm. Sample M1-2, which is formed by alternately stacking of the crystalline and the preferred orientation structure, exhibits a strong suppression on formation of the preferred orientation, and the columnar crystalline structure is confined to each of the building layers. On the other hand, the continuous columnar crystalline structure are observed in the microstructure of M1-7and M2-7 which are made of crystalline/amorphous, and preferred orientation/amorphous structures, respectively. The atoms in the amorphous layer are easily to grow along the grain in the previous layer. In particular, the continuous columnar crystalline structure with (111) preferred orientation grown through several layers is observed in the M2-7 coating. The multilayers showed excellent adhesion as compared to the single layer coatings. M1-7 exhibited the superior adhesion, strength with almost no peeled coating fragments around the edges of the pit. The tribological behavior of multilayer and single layer was also discussed.

碩士
國立成功大學
材料科學及工程學系碩博士班
100
In this research, TaN is used as a metal gate due to its excellent conductivity, thermal stability, and tunable work function. A reactive magnetron sputtering system is used to deposit TaN thin films with various deposition parameters, such as the working pressures and deposition powers. The film thickness is measured by a profilometer. The sheet resistance is characterized by a four-point probe. The surface morphology and structures are characterized by scanning electron microscopy and X-ray diffraction, respectively. The electrical results are characterized by a probe station equipped with a LCR meter. The effects of different working pressures and working powers on sheet resistance, deposition rate, crystallinity, grain size, particle size and work functions are investigated in this research. We found the TaN thin films made at higher working power (〉 85W) and lower deposition pressures (〈 7 mTorr) are with reasonable good conductivity and nanocrystallinity. The work function of TaN made at 100W and 5 mTorr is 5.07 eV which is promising for P-MOS application.

碩士
國立臺灣科技大學
化學工程系
102
The discotic liquid-crystals (DLCs) systems are appealing in organic electronics because of their solution-processibility and controllable inter-molecular ordering. Generally, these orderings are induced by the strong inter-planar π-π interactions and result in columnar self-assembly with hexagonal arrangement. These systems are expected to gives rise to better semiconducting properties with the charges hopping along stacks of π-conjugated planes. Therefore, to control the orientation of the column stakes between two electrodes would be an important issue in designing semiconducting devices, such as field-effect transistors. In the first part of this study, the orientations and structures of several discotic liquid crystals on surface were characterized using reflection-absorption infrared spectroscopy (RAIRS), powder X-ray diffractometer, polarizing microscope (POM) and atomic force microscope (AFM) to investigate the film structure. In the second part, in order to understand the semiconducting properties and packing behaviors of DLCs in different environments, the film structure on planar substrate and nanopillar-templated substrate were examined. Less morphological imperfections were observed when DLC films were formed on nanopillar-templated surfaces, compared to that on a planar surface. The sidewalls of nanopillars appear to assist the growth of DLCs into columnar alignment with their long-axis parallel to the nanopillar and against the substrate. FET devices are also fabricated for these materials. The mobility was measured in TC4TBC based lateral transistor devices and reached 7.59E-4 cm2V-1s-1. Field effect mobilities were measured for all four materials in vertical transistor configuration.

碩士
國立中央大學
光電科學研究所
100
Recently, the effect of few kinds of texturing structures on solar cell has been received intense attention and plenty of researches. In this thesis, we use Sentaurus TCAD and Lumerical FDTD to study the effect of intrinsic layer thickness and different microstructure on amorphous silicon thin film solar cell. First of all, we establish the plane type a-Si solar cells (Glass/ TCO/ a-Si:H(p)/ a-Si:H(i)/ a-Si:H(n)/ TCO/ EVA) in the two programs. By the utilization in Sentaurus TCAD, we find the short circuit current in the thinner intrinsic layer (100nm) model achieves 5.55mA/cm2, while the external quantum efficiency achieves 14%. Additionally, if the high-defected intrinsic layer gets thicker, there are more photogenerated carriers but higher defect density of state but more serious light degradation. Replacing that by thinner intrinsic layer and modulating the microstructure of the solar cell in Lumerical FDTD are the ways to compensate for the lack of short circuit current brought from the thinner thickness. Reflection peak of textured glass (microstructure and glass film) gets reduced by the increasing structure height. For being the superior anti-reflection, sub-wavelength microstructure would be a good choice as choosing small structure height. For the muti-layer textured solar cell, how to get balanced between superior AR and low scatter dispersion at the back contact is a crucial topic. The solar cell with 300nm intrinsic layer has its short circuit current achieving 18.67mA/cm2 and enhancement 49% with P=0.8μm and H=0.8μm. Whereas the solar cell with 100nm intrinsic layer has its short circuit current 18.39mA/cm2 and enhancement 73% with P=0.2μm and H=0.5μm. From the result of external quantum efficiency, it is found that the thinner intrinsic layer performs the more obvious enhancement effect.

碩士
長庚大學
光電工程研究所
106
We want to reduce using toxic solvent on the preparation of perovskite solar cell, so we try to change the toxic solvent(DMF or DMSO) to DI water and the lead precursor from PbI2 to Lead acetate. Through two-step preparation, we dipped in MAI solution then transform Perovskite crystallization. But the PCE% compared with using lead nitrate precursor solution to prepared Perovskite solar cell is much lower. Therefore we try to observe surface and electrical through the following instrument: Contact Angle Measure, SEM, EDS, PV Characterization System etc., hope can learn more about water-soluble lead acetate precursor. At the end, the short current, open circuit voltage and fill factor have all been increased it’s because of enhancing surface crystallization flatness and coverage. And the Power conversion efficiency increased from 1.784% to 3.723%.

碩士
國立雲林科技大學
工業化學與災害防治研究所
93
In the thesis, the silica colloid solution was synthesized by sol-gel method, humidity sensors of silica aerogel thin films were obtained via supercritical drying of wet silica films of alcohol gel that coated on alumina substrate by spin and dip coating technique. The activation energy of polymerization of silica colloid solution was 17.2 kJ/mole. Microstructure analysis revealed silica aerogel thin film that was built-up by nanoparticles, particle size around 30 nm. Surface chemical structure analysis revealed silica aerogel that possesses Si-OH groups and easily bounded with water molecule or polar species. The humidity sensing characteristics of silica aerogel thin films were studied by impedance response. Silica aerogel thin films encompass better humidity sensitivity than xerogel thin films, the microstructure was directly related to the sensors performance. Silica aerogel thin films fabricated with different colloid viscosity results in different structures. Silica aerogel films S-AG15 obtained from sping coating technique showed the best humidity sensitivity, and D-AG15 showed the obvious humidity response, pore structure and films thickness were the main factors. Frequency 1 kHz of voltage was suitable to the sensors performance of humidity response. Silica aerogel thin films fabricated with lower viscosity showed the bigger hysteresis response, and on the other hand, with higher viscosity of silica aerogel films showed the wider range of hysteresis response. The response time directly related to the film thickness structure, the thinner of film layer showed the fast response time.

博士
國立中正大學
物理所
98
In this thesis, we focus on the fabrication and research of periodic nano- and micro- optical application structures by self-assembly process. The scales of self-assembly in this thesis were classified as three parts. First, in sub- micro scale, the capillary fore play an important role in the self-assembly process. For example, the spheres in solutions, called colloids, are easily aggregated by capillary force in drying process at room temperature. The spheres always self-assemble into close-packed structures, e.g. face-centered cubic crystals. In our experiments, the colloid SiO2 particles are self-assembled into f.c.c. crystals by capillary force. Such crystals are called “artificial opal”, similar the “opal” in nature can be applied as photonic crystals (PCs). Furthermore, due to the more wide open photonic band gap, the inverse opal is fabricated based on opal templates for more useful applications. In molecular (nano-) scale, the self-assembly can be classified with two types, intra- and inter- molecular self-assembly. In intra- molecular self-assembly, such as protein folding, the structures become stable and regular architectures from random coil polymers. In inter- molecular, such as block copolymers (BCPs) self-assembled with nano- morphologies by phase-separation effect, form a supramolecular from micelle molecules in solution. In micro- scale, the moistures condense on the solution surface of mixing polystyrene and solvent by evaporation-cooling effect which forms to hexagonal porous, called “Breath Figures” (BFs). The advanced applications in microlens and optical diffuser films from BFs will be discussed

碩士
大同大學
光電工程研究所
97
Nano-crystalline silicon has been deposited on glass and plastic substrates by direct vacuum arc system at room to cryogenic temperature(77 K). Solid silicon wafer source were amount on both anode and cathode to be the electrodes which were highly doped single crystal silicon wafer(0.005 Ω/cm). It is suitable for deposited thin films on flexible substrate due to low deposition temperature. Silicon films were characterized by Raman spectroscopy、x-ray diffraction (XRD)、tunneling electron microscope (TEM) and scanning electron microscope (SEM). The result revealed that the crystalline structure embedded in amorphous matrix. High-resolution transmission electron microscopy (HRTEM) was used for direct analyzing the particle where the fully crystallized structure were inert the particles and these particles were random distributed over the substrate. The crystalline volume fraction were calculated from Raman spectrum and it showed the values between 0~92 ％. The impurity concentration was measured by SIMS, that the P-type and N-type impurity was permeated simultaneously into the film during the deposition without additional doping process, thus P-N junction could be achieved. Nano-crystalline silicon has higher electron mobility and more stability against prolong light exposure than amorphous silicon. According to our research, the opto-electronic effect were not obviously, we assume that a large number of defects existed in the films. Compared to CVD process, arc discharge system has the advantages of low cost, less environment pollution and non-dangerous of processing. Such research has not yet been observed. Low temperature deposited nano-crystalline silicon thin film has attracted much attention due to applicable on low-cost substrates, like glass and flexible plastic substrate. Key words: Direct vacuum arc, Flexible substrate, crystalline volume fraction.

碩士
國立清華大學
電子工程研究所
92
In recent years, particularly, metal–insulator–semiconductor (MIS) structures based on nano-dots are widely studied for their new physical phenomena as well as their potential applications in single-electron memory devices of the next generation. Transmission electron microscopy (TEM) showed that Si NDs embedded in the silicon nitride (SiNx) thin film have been fabricated by plasma enhanced chemical vapor deposition technique, and the sheet density is the order of 1011–1012 cm-2. Charge trapping and storage in nc-Si were exhibited in capacitance–voltage (C–V) measurements at room temperature through the hysteresis and shift of the flat-band voltage (ΔVFB) of the nc-Si samples. In the nitride memory, we know there are many deep energy-level of defect traps in this sample, and the carriers transport at low electric-field with hopping trapping named Poole-Frenkle emission. In the silicon oxide thin film, the carriers transport at high electrical–field names Fowler-Norhdiem effect tunneling, as is known to all. Differ from the storage media containing two kinds of discrete charge storage centers: nitride traps in the case of SONOS and isolated Si nanocrystals in the flash memory, the Si NDs embedded in the (SiNx) thin film grown by plasma enhanced chemical vapor deposition has a larger window size of hysteresis in C-V curve. In this study, we observed the two different hysteresis phenomenon measured with the same repeated sweep voltage in the same device. We try to analyze the relationship between memory effect and the ratio of SiH4 and N2, and the different memory phenomenon from the traps and the silicon nano-dots. The Other thing is to investigate the carrier transport mechanism in the SiNx thin film.

碩士
元智大學
先進能源研究所
99
In this study, the silicon nano-crystals were embedded into amorphous silicon thin films, leading to an increase in optical band gap due to the quantum confinement effect. A nc-Si:H film with the band gap of 1.95 eV was obtained by VHF (27.12 MHz) PECVD system and was used as a window layer for p-i-n a-Si:H thin film solar cells. The hetero-junction, p-layer nc-Si:H/i-layer a-Si:H, solar cell demonstrated an open-circuit voltage (Voc) of 0.88 V and a conversion efficiency of greater than 9%. This kind of cell structure has great potential for the development of the a-Si/uc-Si tandem cell and the conversion efficiency is expected to be 11%. In addition, ECR-CVD (microwave frequency: 2.45 GHz) technique is powerful for the deposition of silicon films with high deposition rate. In this study, we attempted to use the system to deposit silicon films. The PECVD process experiences were helpful to give reasonable deposition parameters for ECR-CVD. Finally, we give some suggestions base on the measurement results of the film deposited by ECR-CVD.

碩士
崑山科技大學
機械工程研究所
96
In this paper, we fabricated polycrystalline silicon films with very large grains by the method of nanometer thick aluminum induced crystallization (nano-AIC) on the a-Si:H film deposited by plasma enhanced chemical vapor deposition (PECVD) and analyzed the best function by using different aluminum induced crystallization. One part of this paper, the effect of annealing ramp-up time of the nano-AIC process on the crystalline volume fraction is discussed. Four different annealing ramp-up time periods, 1, 5, 10, 20 hours, respectively; are fabricated and tested. The results show that crystalline volume fraction calculated is about 50~60% and the average crystalline size grows from 20 to 100 μm under four different annealing ramp-up time. The mobility of the poly-Si film increases with the increase of annealing ramp-up time. The maximum mobility obtained in this paper is about 1.5 cm2/Vs in the case of 20 hours of annealing ramp-up time. The leak current density is between 10-4~10-6 A/cm2, The other part of this paper , we fabricated AIC specimens with in this five different aluminum thicknesses of 10, 20, 40,80 and 160 nm, respectively. The results show that crystalline volume fraction calculated is about 42~90%. In our analysis, we can see when deposited aluminum thickness varies from 10 to 20 nm, it is not possible to induce poly silicon thin film from the results of, Raman and XRD analyses. Therefore, we can confirm poly silicon will be induced only when aluminum thickness deposition is over 30 nm.

碩士
國立交通大學
材料科學與工程系所
97
The structure-property relationship of nano-clustering silica (NCS) porous low-k films (k ~2.8 to 2.0) was investigated by controlling silica matrix TEOS/MTMS ratio and structure directing agent or also acted as pore generator TPAOH concentration. Emphasize had been laid on structure parameters such as the chemical and molecular bonding, porosity, pore size, pore shape and pore size distribution and the influence on ultimate electrical, mechanical, thermal stress properties. NCS2 to NCS5 porous low-k film have κ-value ranging from κ =2.3 to κ =2.8. The silica matrix was composed by the addition of MTMS (Si-CH3) in balance with TEOS (Si-O-Si). Therefore high modulus porous low-k film was obtained (E~10GPa). NCS2 through NCS5 film possessed spherical pore shape. The accommodation of Si-CH3 was equilibrated by the addition of Si-O precursor, in the agreement that the Si-O-Si linkage of NCS low-k film still preserved in the present of Si-CH3 groups. By adding more TPAOH, the porosity increased from NCS5 to NCS2 (ρ<27%) without causing much deterioration on mechanical modulus. Pore size was well controlled in the order of d<10nm with most population in the d=0.5nm. In order to push κ-value <2.3, NCS1 porous low-k film was proposed with κ=2.0, that was obtained from less cross-link structure and higher porosity. The silica matrix was composed by higher content of MTMS (Si-CH3) instead of TEOS. Moreover, the incorporation of high methyl content and high porosity (ρ=38%) to NCS1 significantly reduced the κ value. But the modulus substantially dropped to E=2.76GPa. Nevertheless, its Si-O-Si cross-linking was not rigid enough and also the higher porosity cause matrix could not sustain the thermal stress, therefore collapsed to form more stable structure, and formed elliptic cylindrical pore shape (din-plane=3.3nm dout-of-plane=1.9nm). Overall, the degree of Si-O-Si cross-link (TEOS/MTMS ratio) and porosity (TPAOH ratio) must be controlled in order to obtain high mechanical modulus NCS film with low dielectric constant. Among these NCS films, NCS2 with k=2.3 and E=9.2 GPa, which possessed optimal ratio of Q [(SiO)4Si] to T [(SiO)3Si(CH3)] group, would be the best ILD candidate materials meeting the requirements of device integration.

碩士
國防大學中正理工學院
應用化學研究所
96
This study fabricates the nano-thin-film of cobalt-molybdenum-phosphorous (Co-Mo-P) alloy by non-isothermal deposition (NITD) method. The higher deposition temperature in the NITD method provides higher driving force to directly reduce the electrolyte to the Co-Mo-P nano-particles in acidic bath. These nano-particles finally grew to form a nano-scale thin film, which can act as a barrier layer in the copper interconnects. The study of the effect of cobalt-based nano-thin-film deposited in NITD is investigated from different operating parameters, such as the concentration of cobalt sulfate, the pH value of the solution, the deposition time and the concentration of sodium molybdate. The result of the study indicates that the granule size of the surface of the thin-film refines and the thickness of the thin-film reduces with decreasing the concentration of cobalt sulfate and the pH value of the electrolyte . After adding the sodium molybdate , it can inhibit the deposition rate to reduce the thickness of thin- film, and it can increase the thermal stable of the thin- film. In experimental result realize that the nano-thin-film of cobalt-molybdenum-phosphorous alloy deposited in the pH value of the electrolyte is 4, the concentration of cobalt sulfate is 1.28×10-2M, the concentration of sodium molybdate is 8.26×10-3M, the deposition temperature is 400℃ and the deposition time is 360 sec, it has unapparent crystal structure and good surface roughness, moreover, the thickness of thin- film is 15 nm. By the analysis of heat stability , the nano-thin-film of cobalt-molybdenum-phosphorous alloy loses the efficiency of the barrier layer, when the thermal anneal at 700℃. So the barrier layer of cobalt-molybdenum-phosphorous alloy is fabricated by non-isothermal deposition method, it has good potential energy in the copper interconnects.

碩士
國防大學中正理工學院
應用化學研究所
94
This thesis aims to study the deposition of Ni-Mo-P nano-thin-film on silicone wafer using non-isothermal deposition (NITD) method. The higher deposition temperature in the NITD method provides higher driving force to directly reduce the electrolyte to the Ni-Mo-P nano-particles without using of any noble metal as catalyst. These nano-particles finally grew to form a nano-scale thin film, which can act as a barrier layer in the copper Damascene process of IC semiconductor industry. The effects of operating parameters, such as the composition of electrolyte, the PH value of electrolyte、the deposition temperature、the concentration of NiSO4 and Na2MoO4, and the deposition time, on the morphology of deposited particles, the surface toughness, microstructure and sheet resistivity of deposited films were studied. The Cyclic Voltammetry was also used to analyze the effect of MoO42- on the deposition current. The result shows that there was a great quantity of nano particles forming in the NITD process. The higher deposition temperature resulted in a greater amount of Ni-Mo-P nano-particles and smaller mean size of these particles, which eventually grew to a thinner deposition film. On the contrary, the lower deposition temperature resulted in a lesser amount of Ni-Mo-P particles and larger mean size of these particles, which eventually grew to a thicker deposition film. The adding of Na2MoO4 can increase the thermal stable of the deposition film, reduce the residual stress of Ni films and alloy and inhibit the coarsening of Ni-Mo-P nucleus to reduce the thickness of deposition film to nano-scale.

碩士
國立交通大學
材料科學與工程系所
95
While the semiconductor industry continues to scale down device sizes for better performance, lower power consumption and higher packing density, the interconnect delay and cross-talk between adjacent metal lines must be reduced. The performance of an IC chip can be degraded by interconnect RC delay and power consumption. In order to alleviate the problems, low dielectric constant (k) materials are used to replace the conventional intermetal dielectric (IMD), SiO2. In this research, low-k nanoporous silica dielectrics was selected as the ultra-low k IMD material for nanoscaled integrated circuit technology. However, integration of the porous ultralow-k dielectric into Cu interconnect processes is subjected to impurity diffusion through pore channels and moisture uptake on the pore surface due to high porosity. Because of the very low mass density and enormously large and active surface area, low-k nanoporous silica dielectrics are extremely susceptible to plasma damage during etch and CVD processes. Without appropriate pore-sealing treatment, these materials are not suitable for application for Cu interconnect technology. In the study, plasma treatments were implemented to seal open pores of porous ILDs by forming a thin dense layer on the dielectric surface. Ion bombardment on the dielectric surface during the plasma treatment will result in the collapse of the pore structure near the surface region, thereby forming a dense surface layer while making the porous bulk intact. In the surface layer, chemical and microstructure properties were dramatic different from that of the bulk. The changes in the film chemistry, mechanical properties, and resistance to metal diffusion were studied by various spectroscopies and microscopies, such as x-ray diffractometry, electron nicroscopies, and x-ray photoelectron spectroscopy.

碩士
國立交通大學
電子工程系所
98
In this thesis, we utilize planar and nano-wire poly-silicon thin film transistors for gas sensing measurements. We investigate their electrical characteristics under various environments, such as normal ambient, nitrogen ambient, and vacuum, and study the effects of adding moisture and ammonia on device performance. The sensitivity of the devices to the variation of environment is also found to be very strongly dependent on the channel thickness. A model considering the interaction of H-related species in the air with the poly-Si is proposed to explain the observed results.