Dissertations / Theses on the topic 'Scanning capacitance Microscopy - SCM'

Ce travail de thèse porte sur l'application des techniques Scanning Capacitance Microscopy (SCM) et Scanning Spreading Resistance Microscopy (SSRM) pour la caractérisation électrique de nanofils de ZnO avec l'objectif d'en déterminer le dopage par profilage des porteurs libres suite à des essais de dopage de type p. Afin de pouvoir utiliser un référentiel planaire nécessaire à ces mesures par sonde locale, un procédé de remplissage par dip-coating et de polissage a été spécialement développé sur des champs de nanofils quasi-verticaux. De plus, dans le but de parvenir à un étalonnage des mesures SCM et SSRM, nous avons conçu et fait fabriquer des échantillons étalons de dopage de type n, contenant des niveaux de Ga en escalier de densité variable de 2×10^17 à 3×10^20 cm^-3. Les mesures sur des coupes transversales de ces deux de structures multicouches ont permis, pour la première fois sur ZnO d'établir un étalonnage des mesures SCM et SSRM et de déterminer le dopage intrinsèque électriquement actif de couches 2D nanométriques, résultat difficilement atteignable par d'autres techniques d'analyse. Des résultats inattendus de concentration résiduelle de porteur de l'ordre de 2×10^18 et 3×10^18 cm^-3 ont été trouvés sur les nanofils de ZnO crus par MOCVD et par CBD respectivement. Outre la caractérisation électrique microscopique des nanofils par SCM et SSRM, des techniques macroscopiques classiques ont été utilisées pour caractériser des assemblées importantes de nanofils de ZnO. L'origine de la difference entre les résultats de deux genres de technique a été discutée. Nous avons aussi étudié les effets des dopages ex-situ par diffusion du phosphore (procédé SOD) et des dopages in situ par incorporation d'antimoine (Sb) pendant la croissance MOCVD. Les résultats majeurs sont obtenus pour l'antimoine, en utilisant des couches ZnO: Sb 2D et des nanofils cœur-coquille ZnO/ZnO: Sb, ou l'hypothèse d'une compensation partielle du dopage n résiduel par un centre accepteur créé par le dopage Sb semble pouvoir être établie raisonnablement
Based on atomic force microscope (AFM), scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) have demonstrated high efficiency for two dimensional (2D) electrical characterizations of Si semiconductors at nanoscale and then have been extensively employed in Si-based structures/devices before being extended to the study of some other semiconductor materials. However, ZnO, a representative of the third generation semiconductor material, being considered a promising candidate for future devices in many areas, especially in opto-electronic area, has rarely been addressed. Recently, extensive research interests have been attracted by ZnO NWs for future devices such as LED, UV laser and sensor. Therefore, a good understanding of electrical properties of the NWs is in need. In this context, this thesis work is dedicated to the 2D electrical characterization of ZnO NWs with the focus of carrier profiling on this kind of nanostructure in the effort of their p-type doping. For this purpose, a planarization process has been developed for the NWs structure in order to obtain an appropriate sample surface and perform SCM/SSRM measurements on the top of the NWs. For quantitative analysis, Ga doped ZnO multilayer staircase structures were developed serving as calibration samples. Finally, residual carrier concentrations inside the CBD and MOCVD grown ZnO NWs are determined to be around 3×10^18 cm^-3 and 2×10^18 cm^-3, respectively. The results from SCM/SSRM characterization have been compared with that from macroscopic C-V measurements on collective ZnO NWs and the differences are discussed. In addition to carrier profiling on NWs structure, applications of SCM/SSRM on some other ZnO-based nanostructures are also investigated including ZnO:Sb films, ZnO/ZnO:Sb core-shell NWs structure, ZnO/ZnMgO core-multishell coaxial heterostructures

La miniaturisation continue et la complexité des dispositifs poussent les techniques existantes de nano-caractérisation à leurs limites. De ce fait, la combinaison de ces techniques apparait être une solution attrayante pour continuer à fournir une caractérisation précise et exacte. Dans le but de dépasser les verrous existants pour l’imagerie chimique 3D haute résolution à l’échelle nanométrique, nous avons concentré nos recherches sur la création d’un protocole combinant la spectrométrie de masse à ions secondaires de temps de vol (ToF-SIMS) avec la microscopie à force atomique (AFM). Ceci permet entre autre de corréler la composition et la visualisation en 3 dimensions avec des cartographies de topographie ou d’autres propriétés locales fournies par l’AFM. Trois principaux résultats sont obtenus grâce à cette méthodologie : la correction d’un ensemble de données ToF-SIMS pour une visualisation 3D sans artefacts, la cartographie du taux de pulvérisation locale permettant de mettre en évidence les effets liés à la rugosité et la présence d’interfaces verticales et la superposition des informations avancées ToF-SIMS et AFM. Quatre applications de la méthodologie combinée ToF-SIMS et AFM sont abordées dans cette thèse. La procédure de correction des données ToF-SIMS en 3D a été appliquée sur une structure hétérogène GaAs / SiO2. Les artefacts liés à la pulvérisation, notamment l’effet d’ombrage, ont été étudiés par le biais des cartographies de taux de pulvérisation sur des échantillons avec nano-motifs structurés et non structuré. Enfin, nous avons exploré la combinaison de l’analyse ToF-SIMS avec trois modes avancées de microscopie AFM : piézoélectrique (PFM), capacité (SCM) et conducteur (SSRM). Une première étude a notamment permis d’observer l’évolution et la modification chimique suite à l’application d’une contrainte électrique sur deux film mince piézoélectriques. Une deuxième étude s’est focalisée sur l’impact de l’implantation Ga lors de la préparation d’échantillons par FIB pour voir comment limiter l’effet de l’amorphisation sur la mesure électrique. Les aspects techniques de la méthodologie seront abordés pour chacune de ces applications et les perspectives de cette combinaison seront discutés
The continuous miniaturization and complexity of devices have pushed existing nano-characterization techniques to their limits. The correlation of techniques has then become an attractive solution to keep providing precise and accurate characterization. With the aim of overcoming the existing barriers for the 3D high-resolution imaging at the nanoscale, we have focused our research on creating a protocol to combine time-of-flight secondary ion mass spectrometry (ToF-SIMS) with atomic force microscopy (AFM). This combination permits the correlation of the composition in 3-dimensions with the maps of topography and other local properties provided by the AFM. Three main results are achieved through this methodology: a topography-corrected 3D ToF-SIMS data set, maps of local sputter rate where the effect of roughness and vertical interfaces are seen and overlays of the ToF-SIMS and AFM advanced information. The application fields of the ToF-SIMS and AFM combined methodology can be larger than expected. Indeed, four different applications are discussed in this thesis. The procedure to obtain the topography-corrected 3D data sets was applied on a GaAs / SiO2 patterned structure whose initial topography and composition with materials of different sputter rates create a distortion in the classical 3D chemical visualization. The protocol to generate sputter rate maps was used on samples with structured and non-structured nano-areas in order to study the possible ToF-SIMS sputtering artefacts, especially the geometric shadowing effect. Finally, we have explored the combination of ToF-SIMS analysis with three AFM advanced modes: piezoresponse force microcopy (PFM), scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM). Specifically, two main applications were studied: the chemical modification during electrical stress of a piezoelectic thin film and the recovery of initial electrical characteristics of a sample subjected to Ga implantation during FIB preparation. Technical aspects of the methodology will be discussed for each application and the perspectives of this combination will be given

This thesis discusses the development of a novel scanning capacitance microscope (SCM) that enables the investigation of the local capacitance and conductivity of surfaces and near-surface nanostructures at cryogenic temperatures and high magnetic fields. Simultaneous atomic force microscopy (AFM) and SCM measurements can be made at a temperature of 1.5K and a magnetic field of 12T. The AFM/SCM sensor is based on a quartz-tuning fork with an etched metal tip. SCM measurements are made using an RF tuned filter design which allows changes in capacitance to be measured with sub-attofarad resolution and a bandwidth of 200Hz. Test measurements were made over an evaporated gold film. The capacitance distance curve was recovered from the measured quantities using a deconvolution scheme normally used for force-distance curves. Measurements have been made of a two-dimensional electron gas in the quantum Hall effect (QHE) regime. Highly conductive stripes form near the edge of the sample at integer Landau level filling factors in agreement with theoretical predictions. These measurements are the first direct imaging of the compressible stripes at the physical edge of a Hall bar device. Measurements were also made by point spectroscopy in a region that was locally depleted. Around this region a ring-shaped stripe of considerably larger width than at the sample edge is observed. The increased width was explained in terms of a shallower potential gradient compared to the physical edge of the sample. Preliminary measurements have demonstrated that the microscope is capable of imaging edge states whilst passing current through the device.

Ce travail a été dédié à l'étude expérimentale des mesures capacitives avec le microscope à force atomique (AFM) pour la caractérisation des profils des dopants dans des structures semiconductrices et pour la caractérisation des oxydes minces. La SCM est une méthode de caractérisation très utile pour les mesures de défaillance des profils des dopants, par exemple pour vérifier si des différentes étapes technologique s comme l'implantation des dopants dans des substrats semiconducteurs a été correctement effectuée. Nous avons démontré le potentiel de la SCM pour la caractérisation des profils des dopants en utilisant des échantillons de test qui couvrent à peu prés toutes les structures semiconductrices rencontrées dans l'industrie de la microélectronique: des profils des dopants, de type escalier, des puits quantiques, des jonctions p-n. Des images qualitatives ont été obtenues sur des échantillons contenant des profils des dopants des concentrations entre 2. E+15 at. Cm-3 et 5. E+19cm-3. Nous avons montré que la SCM est capable de détecter des puits quantiques avec une épaisseur d'environ 7 nm. La SCM est capable de faire la différence entre les dopants de type n et les dopants de type p. Tous ces résultats confirment l'utilité de la SCM comme méthode de caractérisation qualitative des profils des dopants à nano-échelle. Nous avons aussi étudié les paramètres expérimentaux qui jouent un rôle dans l'interprétation et la reproductibilité du signal capacitif: la lumière laser parasite provenant du système de détection de l'AFM, des couplage capacitifs parasites, les problèmes de contact entre la sonde AFM et l'échantillon, l'influence des champs électriques forts générés par la sonde AFM, la topographie des échantillons, la qualité et les propriétés de l'oxyde de grille. Nous avons proposé des solutions pour l'élimination de tous ces facteurs parasites et pour l'avancement de la SCM vers des mesures reproductibles et quantifiables
This work was devoted to the experimental study of the scanning capacitance microscopy (SCM) and spectroscopy (SCS) for the mapping of the dopants in the semiconductor structures and for the characterization of thin oxides. SCM has appeared to be a very powerful technique for doping mapping as long as qualitative images are needed, for example in order to check whether fabrication steps like implantations have been correctly operated during the fabrication of devices (presence or absence of doping of a given type in a region where it should be present). When quantitativity is needed, the only way of performing a calibration of SCM images for dopant mapping seems to grow exactly the same oxide on two different samples, one being a calibration sample from which a semi-calibration curve associating doping levels and SCM signal levels will be measured and applied to the unknown sample (semi-calibration). We have shown the capabilities of SCM for dopant mapping using a series of experimental situations and test samples covering almost all frequently encountered structures in the industry of silicon microelectronics : doping staircases of p-type and n-type structures, quantum wells and p-n junctions. Qualitative images have been obtained for a wide range of doping levels between 2. E+15 at. Cm-3 to 5. E+19 at. Cm-3. SCM is able to detect quantum wells of ~ 7 nm width. SCM is also able to differentiate between dopants of different type (p-type or n-type). All these results confirm the usefulness of SCM as a qualitative imaging technique. We have studied the experimental parameters playing a role in the interpretation and reproducibility of SCM signal: stray light, stray capacitance, the tip-sample contact, the influence of strong electrical fields, the sample’s topography, the quality and the properties of the top oxide. We have proposed solutions for eliminating all these parasitic factors and for rendering the SCM measurements reproducible and quantitative

Conselho Nacional de Desenvolvimento Científico e Tecnológico
Hybrid nanostructures which integrate two or more technologically interesting physical properties are fundamental for developing new generations of electronic devices. Exhibiting at least two coupled ferroic orders, multiferroics are an outstanding class of multifunctional materials. Compounds which present coupling between ferromagnetism and ferroelectricity are specially interesting. Although natural multiferroics are rarely found, the possibility of obtaining strain-mediated magnetoelectric coupling in composite structures, by integrating magnetostrictive and piezoelectric layers, paves the way to control electric properties by applying magnetic field or to the electric control of magnetism. Nevertheless, most scientific efforts have been on monophasic compounds or bulk composites. Considering the incorporation of magnetoelectric nanostructures in devices, expanding the scope of the magnetoelectric effect and targetting it to different kinds of applications is needed. Besides new characterization techniques, seeking new alternative materials to the lead-based piezoelectrics or oxide-based magnetostrictives is necessary. Recently, a few works using semiconductors such as ZnO and AlN, or amorphous magnetic alloys such as those based on Co, Fe and Ni, have been reported. In spite of not presenting remarkable piezoelectric and magnetostrictive effects, the features of such materials are promising for high frequency applications, for instance. Considering these issues, four independent surveys are presented. Firstly, the origin of the coupling, latest advances and current scenario of the field are reviewed. Then magnetostriction measurements in thin films are addressed by employing a direct technique based on the cantilever-capacitance method. The goals are to study magnetoelastic properties of some materials whose magnetostriction are not found very often in literature, and to check the reliability of this technique for investigating thin films. In this sense, measurements of some amorphous magnetic alloys mainly based on Co, Fe and Ni are performed. Most samples presents larger magnetoelastic response for magnetic field applied along the magnetization easy axis, as opposed to the theoretically expected. Two investigations on aluminum nitride thin films are reported. Firstly, the growth of AlN films onto several different substrates and buffer layers is studied. Films grown onto glass and polyimide show excellent structural properties for eletromechanical systems and flexible electronics applications. Samples with low residual stress on silicon substrates, suitable for incorporating in existing technologies, are obtained. Secondly, bilayers composed by AlN and ferromagnetic films are investigated. In addition to the structural and morphological properties of the AlN films which are checked, the magnetic characterization of the structures also contributes to design multilayers for exploring the magnetoelectric effect. Finally, problems involving electric fields in scanning probe microscopies are adressed. Surface images of AlN piezoelectric films are systematically acquired. Among other major observations, the possibility of getting reliable piezoresponse images of strongly polarized areas as well as of visualizing ferroelastic domains, is demonstrated. Furthermore, a new microscopy for investigating a sample s ferro and piezoelectric properties is proposed, exploring the direct piezoelectric effect. By utilizing acoustic excitation and electrical detection, the potency of this technique is illustrated with measurements on quartz and AlN surfaces.
Nanoestruturas híbridas, integrando duas ou mais propriedades físicas de grande interesse tecnológico, são fundamentais para o desenvolvimento de novas gerações de dispositivos eletrônicos. Uma classe interessante de materiais multifuncionais são os multiferróicos, que exibem pelo menos duas ordens ferróicas acopladas. Dentre eles, os que apresentam acoplamento entre ferromagnetismo e ferroeletricidade despertam interesse especial. Apesar de serem raros de ocorrer naturalmente, a possibilidade de gerar efeito magnetoelétrico em estruturas compósitas, intermediado pela deformação elástica entre camadas magnetostrictivas e piezoelétricas, abre caminho para que seja possível controlar propriedades elétricas aplicando-se campo magnético, ou propriedades magnéticas aplicando-se campo elétrico. Todavia, a maior parte das pesquisas atuais ainda envolve compostos monofásicos ou compósitos em forma massiva. Tendo em vista a incorporação de nanoestruturas magnetoelétricas em dispositivos, é fundamental ampliar a abrangência do efeito magnetoelétrico e direcioná-lo para diferentes tipos de aplicações. Para isto, além de novas técnicas de caracterização, é necessário buscar-se materiais alternativos aos tradicionais piezoelétricos baseados em chumbo e magnetostrictivos baseados em óxidos. Recentemente tem-se encontrado trabalhos pontuais onde são utilizados piezoelétricos semicondutores como ZnO e AlN, e ligas magnéticas amorfas como as baseadas em Co, Fe e Ni. Mesmo sem apresentar efeitos piezoelétrico e magnetostrictivo com magnitudes notáveis, as características destes materiais são promissoras para aplicações envolvendo altas frequências, por exemplo. Neste necessário, são apresentados quatro estudos independentes entre si. Primeiramente, é realizada uma revisão sobre a origem do acoplamento, os últimos avanços e o panorama atual das pesquisas na área. Em seguida, através de uma técnica direta baseada no método do cantiléver-capacitância, aborda-se o problema das medidas de magnetostricção em amostras na forma de filmes finos. Os objetivos são estudar as propriedades magnetoelásticas em alguns materiais que não são frequentemente abordados pela literatura, e avaliar a potencialidade da técnica para a análise de filmes finos. Para isto, são realizadas medidas principalmente em ligas ferromagnéticas amorfas baseadas em Co, Fe e Ni. Para a maioria das amostras analisadas, a resposta magnetoelástica é maior quando o campo magnético é aplicado na direção do eixo de fácil magnetização, de forma contrária à esperada teoricamente. São apresentadas duas investigações envolvendo filmes finos de nitreto de alumínio. Primeiro é estudado o crescimento de filmes de AlN sobre vários substratos e camadas semente. Filmes crescidos sobre vidro e poliimida apresentam excelentes propriedades estruturais para aplicações em sistemas eletromecânicos e eletrônica flexível. Amostras obtidas com baixos valores de tensão residual, sobre substratos de silício, são interessantes para incorporação em tecnologias existentes. Segundo, são investigadas bicamadas de AlN com filmes ferromagnéticos. Além das propriedades estruturais e morfológicas dos filmes de AlN, a análise das características magnéticas das estruturas contribui para o design de multicamadas que exploram o efeito magnetoelétrico. Finalmente, são abordados problemas em medidas de microscopias de varredura por sonda envolvendo campos elétricos. Imagens da superfície de filmes piezoelétricos de AlN foram coletadas sistematicamente. Entre outras observações importantes, demonstra-se que é possível adquirir imagens confiáveis de piezo-resposta em regiões fortemente polarizadas, e visualizar a formação de domínios ferroelásticos. Também é proposta uma nova técnica de microscopia, para investigar as propriedades ferro e piezoelétricas de uma amostra, explorando o efeito piezoelétrico direto. Utilizando excitação acústica e detecção elétrica, o potencial da nova técnica é demonstrado com imagens de superfícies cristalinas de quartzo e AlN.

Magister Scientiae - MSc (Chemistry)
Blending polymers together offers researchers the ability to create novel materials that have a combination of desired properties of the individual polymers for a variety of functions as well as improving specific properties. The behaviour of the resulting blended polymer or blend is determined by the interactions between the two polymers. The resultant synergy from blending an intrinsically conducting polymer like polyaniline (PANI), is that it possesses the electrical, electronic, magnetic and optical properties of a metal while retaining the poor mechanical properties, solubility and processibility commonly associated with a conventional polymer. Aromatic polyamic acid has outstanding thermal, mechanical, electrical, and solvent resistance properties that can overcome the poor mechanical properties and instability of the conventional conducting polymers, such as polyaniline.

碩士
國立中興大學
奈米科學研究所
107
Higher requirements of semiconductor characterization technology increase with the development of semiconductor processes. Among these requirements, scanning capacitance microscopy (SCM) has been one of the well-established and commercial techniques in recent years. SCM was mainly applied to analyze carrier polarity and concentration distribution in semiconductors. Furthermore, SCM is also a powerful tool for directly observing the p-n junctions in semiconductors. However, SCM still has some disadvantages. For instance, SCM specimen preparation including the surface oxidation and the back-contact of the sample electrode obviously alters SCM signals. Therefore, an impedance model has been developed in this study in order to understand how the specimen preparation alters SCM signals. Basing on the impedance components of the SCM setup, I established two models for predicting oxide thickness and carrier concentration, respectively. The line-width is only few tens nanometers for present semiconductor device processes. In the processes, an ultra-thin oxide was used for gate oxide layer. It is difficult to measure the equivalent oxide thickness (EOT) of an ultra-thin oxide. Using the model established in this study, one can estimate the unknown EOT by standard samples with a known EOT and SCM signals. In addition, a model for predicting carrier concentration was also established in this study in order to estimate unknown carrier concentration by standard samples with a known carrier concentration and SCM signals.

碩士
長庚大學
電子工程研究所
93
With the shrinkage of MOSFETs, accurately controlling doping concentrations becomes more important. SCM has been developed as a tool for analyzing doping profiles. The SCM samples are similar to MOS capacitors. The behavior of carriers can be monitored by analyzing the difference in capacitance. Majority carriers and minority carriers affect the capacitance between the depletion region. The evident change of capacitance can be observed due to minority carriers will flow from the other side of the pn junction when the tip is located at the depletion boundaries. By scanning the sample with a strong inversion bias, depletion boundaries can be clearly identified. Besides, with selected biases for scanning the sample, boundaries of the depletion region can be clearly demonstrated for memory array devices. Our study includes using HfO2 insulator used for SCM measurements. Effects from fringing field and shift of C-V curves were observed.

碩士
國立中興大學
奈米科學研究所
105
For studying the properties of materials, many materials analyses used modulation technology, which periodically perturbs the studied materials and detects the small responses, to obtain the characteristics of material properties. Scanning capacitance microscopy (SCM) is an electrical scanning probe microscopy combining with voltage modulation for nano-electrical analyses on electronic materials and devices, such as two-dimensional carrier distributions and p-n junctions in semiconductors. For analysis reliability, it is important to know how high the modulation voltage is applied to the analyzed areas, that is, how high the modulation efficiency (ME) is. Furthermore, it is also essential to develop a method controlling the modulation voltages in SCM. In this thesis, the conductive probe, the surface oxide layer, depletion regions in the SCM specimen, the sample substrate, the back contact electrode, and the SCM system were considered the series impedance components of SCM measurements. By this way, the influence of the surface oxide layer and the back contact electrode of SCM specimens on the ME will be discussed. Experimental results revealed that UV-assisted oxidation significantly improves the ME in comparison with the typical way. Moreover, the back contact electrode with low contact impedance, e.g., silver silicide electrode for n-type silicon, can also obviously enhanced the ME. High ME allows SCM to provide high image contrast for mapping carrier concentration distribution and to use low modulation voltage for high resolution. In addition to high ME, the metallic silicidation processes developed in this study obviously improve the relative standard deviation (RSD) of SCM measurements. In summary, this thesis clarified the significance of ME in SCM and emphasized the importance of specimen preparation to SCM.

碩士
國立中興大學
物理學系所
103
Scanning capacitance microscopy (SCM) observes carrier concentration distributions of semiconductors. The SCM signal is highly sensitive to the variation of the active dopant concentration in semiconductor. SCM can be applied to local scanning and analysis as well as providing two-dimensional electrical images. With the above advantages, SCM has been widely used in the researches of semiconductor materials, such as carrier concentration distribution, the position of electrical junction, the width of depletion region and channel length. In semiconductor industry, it is very general to employ ion implantation combined with proper annealing processes to form p-n junctions. The properties of p-n junctions may be affected by the distribution of dopant concentration, activation and deactivation mechanisms in a local area. Especially, the area near the neutral region of a p-n junction is significantly different from that of an ideal p-n junction. In this thesis, I employed SCM to investigate the property of the neutral region in depth. I first clarify the proper setup of the sample electrode in SCM. After that, the influence of photo-illumination on a p-n junction was studied by SCM. The specimen contained a p+-n junction used in this thesis were prepared by ion implantation. Experimental results indicated that dC/dV signal phase inversion was observed at a p-n junction under the external photo-illumination, implying that the neutral area exhibits electron and hole distribution close to the p- and n-sides respectively when external photo-illumination is applied. I also examined the samples with different annealing conditions and found that the low thermal budget of microwave annealing (MWA) leads to obvious dopant deactivation induced by post-MWA low temperature annealing.

碩士
逢甲大學
電子工程所
98
When the dimension of silicon devices is continuously scaling down, the channel length will be relatively reduced. Ultra-shallow junction is a main trend in nano-electronic devices. In ultra-shallow process, we use low energy ion implantation to control shallow doping profile and various annealing processes to active dopant. In this study, we investigated the dopant activation and electrical uniformity in implanted regions, including the influence of annealing time on dopant activation and the side-wall effect on dopant activation. We use scanning capacitance microscopy (SCM) and secondary ion mass spectrometer (SIMS) to investigate dopant activation and the distribution of free carrier concentration. The electrical uniformly of implanted regions with different hardmask material and thicknesses is also discussed. We have observed that the carrier concentration of the BF implanted sample decreases with annealing time. On the other hand, boron activation around surface region was further enhanced during post-SA FA treatment. We also found that hardmask material and thickness could affect the dopant activation uniformly of the implanted region. And the formation of indirectly ion implanted region affected the dopant activation in the boundary area of the implanted region.

Here we present a technique, the Schottky Scanning Capacitance Microscopy (SSCM) developed by the University of Manitoba SPM lab, for measuring carrier profiles on semiconductor device cross-sections. SSCM utilizes a sharp conducting probe tip that is raster scanned in contact with the sample surface. As a result of the work function difference between the two materials, a space charge depletion region and therefore a capacitor is formed at the interface. By applying a small ac voltage, the voltage derivative of the contact capacitance can be measured with a capacitance sensor and a lock-in amplifier. These voltage derivative measurements are used to delineate regions of different doping levels and dopant type with high spatial resolution. In this thesis we also present experimental results obtained from imaging cross-sections of a wide variety of semiconductor devices. A newly designed capacitance sensor is presented. A conversion algorithm was written to convert the measured data to carrier concentration.(Abstract shortened by UMI.)

碩士
國立中興大學
物理學系所
102
Sample preparation for scanning capacitance microscopy (SCM) significantly influences the accuracy of SCM measurements. Especially, the quality of the oxide layer on sample surface including surface roughness of the oxide layer, interface traps, and charges in the oxide layer is decided by sample preparation. These factors influencing the oxide qualities induce capacitor-voltage curve distortion and shift, and hence lead to exceptional differential capacitor (dC/dV) signal intensity. In this article, a short-wavelength semiconductor laser was employed to investigate the improvements of irradiation treatment on the surface oxide layer of a silicon substrate. The specimens were treated by laser illumination with different power and duration. With scanning capacitance spectroscopy (SCS), one can observe the changes in the stability of the surface oxide layers. Experimental results indicated that increasing the illumination power improves the quality of the surface oxide layer, resulting in dC/dV curves with a small flat-band voltage shift and higher signal intensities. Changing the illumination duration leads to changes in the full width at half maximum (FWHM) of SCS curves, but flat-band voltage shift. The main influence of illumination duration is to reduce the trapped charges in the surface oxide layer. For the sample preparation without illumination treatment, the SCS curves of the samples exhibited a high flat-band shift, implying that there are more oxide defects, i.e., low oxide quality. This results in low dC/dV signal intensities. The experimental approach provides a reference for enhancing the dC/dV signal intensities and the stability of SCM measurements on the micro-analysis of electronic materials and surface/interface analysis.

碩士
長庚大學
半導體科技研究所
91
Scanning capacitance microscopy (SCM) has been developed as a powerful dopant profile analysis tool for semiconductor devices. We quantitatively investigated the properties of SCM. Two parts of study for SCM are included in the thesis. The first one is to verify the method developed by Bell Lab for extracting electrical junction position. We use simulation and a metal-oxide-semiconductor capacitor as the major structure. We formed a p-n junction and made three n-type dopings to create “abrupt”、“general” and “smooth” junction profiles. From the simulation results, surface electrical junction rather than bulk electrical junction is obtained by SCM. This indicates that surface electrical property has great influence on SCM measurement. When we applied a bias to measure a p-n junction, surface carrier distribution is changed. Therefore, SCM measurement is sensitive to surface conditions. The second one is to perform an experiment and to compare the differences between experimental data and simulation results. We prepared samples with different dopant concentrations and different oxide thicknesses. In the process, good quality of oxide layer is obtained by thermal oxidation. Annealing at high temperatures for long time is to achieve uniform doping samples. Finally a commercial (Digital Instruments, D5000) SCM is used to obtain the images. We test the stability of SCM. Based on the characteristics of stability, we changed several measurement factors to analyze n- and p-type semiconductors with different dopant concentrations. The measured data show same tendencies as the simulation. From the comparison between simulation results and experimental data, we found light radiation effect and probe size effect. The former one is due to the laser beam used in the SCM system. Electron-hole pairs were generated when laser beam illuminated on the silicon surface. Simulation and experiment both show similar abnormal peaks of dC/dV curves in the inversion region. Radiation effect cannot be ignored in SCM. The latter one is that tip condition affects dC/dV curves. We changed the contact width between the sample and tip to simulate this effect. The result is that smaller tip widths lead to broader dC/dV curves. We believe that probe shape might be one of the factors causing the discrepancy between simulation and measured results. We speculate that the contact on the sample is not uniform.

碩士
逢甲大學
電子工程所
97
In order to enhance the performance of semiconductor devices, the fabrication of ultra-shallow junctions is one of the important processes for the transistor size scaling. In this study, we used low-energy BF ion implantation in silicon wafer to produce P-N junction with different thermal annealing treatments, comparing with the sample of implanted by B ions. We employed scanning capacitance microscope (SCM)、secondary ion mass spectrometer (SIMS) and transmission electron microscope (TEM) to investigate boron activation and distribution of free carrier concentration in surface region shallower than 100 nm in depth. We have observed that free carrier concentration of BF implanted sample increases with implanted region width after SA at temperature 1050°C. Due to the existence of fluorine, the result is opposite to it from the B implanted samples. On the other hand, boron activation around surface region was further enhanced during post-SA FA treatment. Moreover, we also found that hard mask thickness could affect the B deactivation of the side implanted region. The experimental results indicated that electrical instability induced by lattice defects could result in the electrical junction narrowing.

碩士
國立中央大學
物理研究所
99
Current microelectronics chip can be composed of thousands of microarrays that contain up to millions of physically identical transistors layout in vastly different micro-environment. Systematic threshold voltage (Vth) variation due to the detailed difference in the microenvironment has been shown in many electrical assessments. In this work, we have designed an experimental platform for investigating the dependence of dimensionality in two dimensional boron diffusion lengths (Ldi f f ). We systematically vary the ion implantation window length scales in both length (l) and width (w) directions using photolithography process. The two dimensional Ldi f f are measured with plane view scanning capacitance microscopy (SCM). The Ldi f f in width shrunk patterns exhibit stronger diffusion, especially in ion implantation windows with larger l, namely, boron transient diffusion roll-off. This observation suggest there is effectively more interstitial (Is) sources within the proximity of B-Is interaction range during annealing and lead to more significant transient enhanced diffusion (TED) at larger confinements. The normalized Ldi f f for ion implantation boundaries length scales ranging from 0.3 micron to 5 micron shows five folds difference. The normalized curves for both categories of patterns overlap, indicating similar physical mechanism in play for the two cases. We have developed a non-linear logistics model. We can successfully fit the experimental data with the above model by considering only the difference in dimensionality. In particular, we found a 3/5 ratio for the linear growth coefficients of effective Is supersaturation with respect to the ion implantation boundary dimensions between the two patterns. We relate this coefficient ratio to number of interstitial injection boundaries available within B-Is interaction range.

碩士
國立中興大學
物理學系所
100
Scanning capacitance microscopy (SCM) is a powerful technique for the electrical measurements of semiconductors and can qualitatively provides important information on device structures, such as carrier concentration profiles, junction depths, depletion region, and channel lengths. It has been reported in prior researches that photoperturbations induced by the AFM laser beam may lead to distortions on SCM images, such as junction narrowing and lower differential capacitance signals. Due to this, a dark-mode SCM was employed to remove the photoperturbations factor in this work. With dark-mode SCM, the influence of modulation voltage in SCM has been studied for the observation on electrical junction regions. In addition, solid Pt-probes provided higher signal intensities and sensitivity than commercial metal-coated probes, improving SCM measurements. Experimental results indicated that higher modulation voltages may reduce the observed junction width in SCM images. It is suggested that dark-mode SCM combined with a solid-Pt probe operated at a low modulation voltage is an advanced setup for more accurate SCM measurements. With this advanced setup, one can study the stability of electrical junctions formed by ion implantation and microwave annealing. For a patterned silicon wafer after BF2+ implantation, the SCM image of an implanted area upon thermal annealing exhibited a fan-shaped depletion region. This is quite different from that treated by spike annealing. Experimental evidences indicated that the fan-shaped depletion region is carried out from the hole concentration distribution in the BF2+-implanted area.

碩士
國立中興大學
物理學系所
105
Scanning capacitance microscopy (SCM) is an important technique measuring two-dimensional carrier distribution in semiconductors. SCM is very suitable for characterizing semiconducting materials because SCM is able to analyze a local area on sample surfaces and highly sensitive to capacitance changes. For instance, one can employed SCM to measure electrical junction depths (EJD), depletion widths, and the effective channel lengths. Microwave annealing (MWA) is an annealing method with a low thermal budget, effectively suppressing dopant diffusion and activating dopant. In this thesis, I used dark-mode SCM to investigate the influence of MWA time on carrier concentration distribution. With MWA time increasing, experimental results indicated that boron and phosphorus in shallow implanted regions have different electrical activation and deactivation behavior. For boron, deactivation occurred prior to activation when the MWA time is longer than 200 seconds. While for phosphorus, significant activation and deactivation were not observed for MWA time longer than 100 seconds. Prior studies indicated that low energy annealing is hard to eliminate the residual lattice defects induced by boron implantation, leading to instability of the boron-active region. However, the energy of MWA is much lower than that of typical thermal annealing. Therefore, the residual lattice defects might affect electrically active boron atoms. In this study, I performed post-annealing MWA to treat boron-implanted n-type silicon substrates and observed instability of the PN junctions formed by MWA. In addition, the influence of MWA sequence on phosphorus activation was also investigated since phosphorus is easy to activate in a short MWA time and exhibits good electrical stability. Experimental results indicated that the post-annealing MWA increased the EJD and the EJD was also closely related to the prior annealing processes.

碩士
國立成功大學
奈米科技暨微系統工程研究所
95
This research studies the capacitor between tip coated metallic films and metallic sample. We consider that the tip capacitance can composed of apex sphere and lateral surface capacitance. The charge inducing on the tip is considered as concentrated on the metal surface of the tip, so the concept of surface charge density is applied establish the capacitor model of cone and pyramid. The equation of surface charge density was proposed to explain the charge distribution on apex and lateral surface of tip, the difference of charge distribution on lateral surface of cone and pyramid was discussed. Therefore, the influence of radius and half cone angle for capacitor models and the electrostatic force. According to the present models the electrostatic force is dominated by the apex capacitor as the distance small than 10nm, whereas forces determined by lateral surface capacitor when the distance large than 100nm. This behavior is quite the same as that reported in the study of Belidi et al.

碩士
國立中興大學
物理學系所
106
With voltage modulation technology, scanning capacitance microscopy (SCM) is a metrology method analyzing electrical properties of semiconductor materials. SCM is extremely sensitive to capacitance variation and capable of electrical analyses of electronic devices and materials, such as observing p-n junctions and two-dimensional carrier distributions in semiconductors, as well as measuring the junction depth and effective channel length in electronic devices. Modulation efficiency (ME) is an important indicator of the signal detection in SCM. Combining the ME with the principle of signal balance at p-n junctions, one can establish the relation between the ME and the change in total capacitance, being helpful for discussing the influence of the ME on the observation of p-n junction depths. In this thesis, I discussed the influence of the carrier concentration distribution, the preparation processes of the surface oxide layer and the specimen contact electrode on the ME by increasing the modulation area. The modulation-voltage-induced junction shifts were also studied. Experimental results showed that the ME varied with carrier concentration in modulated area due to the non-monotonic behavior of the SCM signals. Therefore, the junction depth increased with the modulated area and hence shifted toward the area with a lower ME. With the same oxidation process, the surface oxide layer resulted in different oxidation rates for p-type and n-type specimens, leading to different ME values in p-type and n-type regions. For different electrodes contacting with a silicon substrate, the work function difference between the contact electrode and the silicon substrate leaded to different ME for p-type and n-type regions. According to the discussion on the factors influencing the ME, the importance of the ME to the observations and the measurements of p-n junctions was revealed.

碩士
國立中興大學
奈米科學研究所
107
S Scanning capacitance microscopy (SCM) is a characterization method that uses modulation voltage to measure the change in capacitance of semiconductor materials. SCM is also for reliability and failure analyses of semiconductor processes and can be used to observe two-dimensional carrier concentration distributions, effective channel lengths, and p-n junctions of semiconductor devices and materials. Basing on the relation between the modulation efficiency and the signal balance rule at a p-n junction, the factors affecting the depth of a p-n junction were discussed in depth in this article in order to find a contact electrode more suitable for observing p-n junctions and improving the reliability of SCM analysis. By studying the influence of the surface oxide layer, the back-contact electrode, the electrode material, and the conductive probe, on observing a p-n junction, I investigated the factors leading to observed junction-depth shift induced by the modulated voltage. With increasing the modulated voltage in SCM, the observed junction-depth shifted toward the region with low modulation efficiency. Experimental results showed that the surface oxide quality alters junction depth measurements. The back-contact electrode setup also affected the observed junction depth. In addition, the electrode materials for the back-contact electrode and the conductive probe were another dominant factors influencing the observation of p-n junctions and junction depth measurements. Eliminating the above factors affecting the SCM analyses of p-n junctions, the reliability of SCM measurements on p-n junctions can be enhanced.

碩士
國立東華大學
應用物理研究所
94
Using atomic force microscopy (AFM) and scanning capacitance force microscopy (SCFM), the study is first to get the surface morphology and surface capacitance profiles of n-type and p-type silicon wafers which are doped in different concentrations. Then, the capacitance force spectra are acquired at a local surface point of each silicon wafer by using capacitance force spectroscopy (CFS) that is based on SCFM. There are two modes in CFS: one is to detect the force change in decreasing the distance between the tip and the sample, and the other one is detect the force change with varying the dc bias on the sample. We find that the capacitance force increases with the decrease of the distance between tip and sample. This is because the spatial capacitance between tip and sample and the value of increase with the decrease of the distance. According to the capacitance force spectra, we can estimate the magnitudes of the surface capacitances that are about 10-11 F by the numerical simulation and calculation. In addition, the smaller the resistivity of the sample is, the larger the surface capacitance gets. When the dc voltage is applied to the sample, the capacitance force decreases. This is because the electric field force produced suppresses the capacitance force. The maximum capacitance force affected by the applied dc voltage is strongly related to the concentration of the n-type and p-type silicon wafers.