INFLUENCE OF OXIDE THICKNESS VARIATION ON ANALOG AND RF PERFORMANCES OF SOI FINFET

This paper focuses on the impact of variation in the thickness of the oxide (SiO2) layer on the performance parameters of a FinFET analysed by varying the oxide layer thickness in the range of 0.8nm to 3nm. While varying the oxide layer thickness, the overall width of the FinFET is fixed at a value 30nm, and the FinFET parameters are analysed for structures with different oxide layer thickness. The parameters like drain current, transconductance, transconductance generation factor, parasitic capacitances, output conductance, cut-off frequency, maximum frequency, GBW, energy and power consumption are calculated to study the influence of FinFET oxide (SiO2) layer thickness variation. It is detected from the result and analysis that the drain current, transconductance, transconductance generation factor, gain bandwidth and output conductance improve with decrement in oxide layer thickness whereas, the parasitic capacitances, cut-off frequency and maximum frequency degrade when there is a reduction in oxide (SiO2) layer thickness. The parameters like energy and consumed power of FinFET get better when the oxide (SiO2) layer thickness increases

Multigate MOSFETs for digital performance and high linearity, and their fabrication techniques

The aggressive downscaling of complementary metal–oxide–semiconductor (CMOS) technology is facing great challenges to overcome severe short-channel effects. Multigate MOSFETs are one of the most promising candidates for scaling beyond Si CMOS, due to better electrostatic control as compared to conventional planar MOSFETs. Conventional dry etching-induced surface damage is one of the main sources of performance degradation for multigate transistors, especially for III-V high mobility materials. It is also challenging to increase the fin aspect ratio by dry etching because of the non-ideal anisotropic etching profile. Here, we report a novel method, inverse metal-assisted chemical etching (i-MacEtch), in lieu of conventional RIE etching, for 3D fin channel formation. InP junctionless FinFETs with record high-aspect-ratio (~ 50:1) fins are demonstrated by this method for the first time. The i-MacEtch process flow eliminates dry-etching-induced plasma damage, high energy ion implantation damage, and high temperature annealing, allowing for the fabrication of InP fin channels with atomically smooth sidewalls. The sidewall features resulting from this unique and simplified process ensure high interface quality between high-k dielectric layer and InP fin channel. Experimental and theoretical analyses show that high-aspect-ratio FinFETs, which could deliver more current per area under much relaxed horizontal geometry requirements, are promising in pushing the technology node ahead where conventional scaling has met its physical limits. The performance of the FinFET was further investigated through numerical simulation. A new kind of FinFET with asymmetric gate and source/drain contacts has been proposed and simulated. By benchmarking with conventional symmetric FinFET, better short-channel behavior with much higher current density is confirmed. The design guidelines are provided. The overall circuit delay can be minimized by optimizing gate lengths according to different local parasites among circuits in interconnection-delay-dominated SoC applications. Continued transistor scaling requires even stronger gate electrostatic control over the channel. The ultimate scaling structure would be gate-all-around nanowire MOSFETs. We demonstrate III-V junctionless gate-all-around (GAA) nanowire (NW) MOSFETs for the first time. For the first time, source/drain (S/D) resistance and thermal budget are minimized by regrowth using metalorganic chemical vapor deposition (MOCVD) in III-V MOSFETs. The fabricated short-channel (Lg=80 nm) GaAs GAA NWFETs with extremely narrow nanowire width (WNW= 9 nm) show excellent transconductance (gm) linearity at biases (300 mV), characterized by the high third intercept point (2.6 dBm). The high linearity is especially important for low power applications because it is insensitive to bias conditions

Performance analysis of ultrathin junctionless double gate vertical MOSFETs

The main challenge in MOSFET minituarization is to form an ultra-shallow source/drain (S/D) junction with high doping concentration gradient, which requires an intricate S/D and channel engineering. Junctionless MOSFET configuration is an alternative solution for this issue as the junction and doping gradients is totally eliminated. A process simulation has been developed to investigate the impact of junctionless configuration on the double-gate vertical MOSFET. The result proves that the performance of junctionless double-gate vertical MOSFETs (JLDGVM) are superior to the conventional junctioned double-gate vertical MOSFETs (JDGVM). The results reveal that the drain current (ID) of the n-JLVDGM and p-JLVDGM could be tremendously enhanced by 57% and 60% respectively as the junctionless configuration was applied to the double-gate vertical MOSFET. In addition, junctionless devices also exhibit larger ION/IOFF ratio and smaller subthreshold slope compared to the junction devices, implying that the junctionless devices have better power consumption and faster switching capability

Multi-gate Si nanowire MOSFETs:fabrication, strain engineering and transport analysis

Multi-gate devices e.g. gate-all-around (GAA) Si nanowires and FinFETs are promising can- didates for aggressive CMOS downscaling. Optimum subthreshold slope, immunity against short channel effect and optimized power consumption are the major benefits of such archi- tectures due to higher electrostatic control of the channel. On the other hand, Si nanowires show excellent mechanical properties e.g. yield and fracture strengths of 10±2% and 30±1% in comparison to 3.7% and 4.0% for bulk Si, respectively, a strong motivation to be used as exclusive platforms for innovative nanoelectronic applications e.g. novel strain engineering techniques for carrier transport enhancement in multi-gate 3D suspended channels or lo- cal band-gap modulation using > 4 GPa uniaxial tensile stress in suspended Si channels to enhance the band-to-band tunneling current in multi-gate Tunnel-FETs, all without plastic deformation and therefore, no carrier mobility degradation in deeply scaled channels. In this thesis and as a first step, a precise built-in stress analysis during local thermal oxidation of suspended Si NWs in the presence of a Si3N4 tensile hard mask was done. Accumulation of up to 2.6 GPa uniaxial tensile stress in the buckled NWs is reported. The contribution of hard mask/spacer engineering on the stress level and the NW formation was studied and buckled self-aligned dual NW MOSFETs on bulk Si with two sub-100 nm cross-sectional Si cores including ∼0.8 uniaxial tensile stress are reported. Micro-Raman spectroscopy was widely used in this thesis to measure stress in the buckled NWs on both bulk and SOI substrates. A process flow was designed to make dense array of GAA sub-5 nm cross-sectional Si NWs using a SOI substrate including a high level of stress. The NW stress level can be engineered simply using e.g. metal-gate thin film stress suitable for both NMOS and PMOS devices. Lately, highly and heavily doped architectures with a single-type doping profile from source to drain, called junctionless and accumulation-mode devices, are proposed to significantly simplify the fabrication process, address a few technical limitations e.g. ultra-abrupt junctions in order to fabricate shorter channel length devices. Therefore, in this process flow, a highly doped accumulation-mode was targeted as the operation mechanism. Finally, extensive TCAD device simulation was done on GAA Si NW JL MOSFETs to study the corner effects on the device characteristics, from subthreshold to strong accumulation, report the concept of local volume accumulation/depletion, quantum flat-band voltage, significant bias-dependent series resistance in junctionless MOSFETs and finally, support the experimental data to extract precisely the carrier mobility in sub-5 nm Si NW MOSFETs

Geometric and process design of ultra-thin junctionless double gate vertical MOSFETs

The junctionless MOSFET architectures appear to be attractive in realizing the Moore’s law prediction. In this paper, a comprehensive 2-D simulation on junctionless vertical double-gate MOSFET (JLDGVM) under geometric and process consideration was introduced in order to obtain excellent electrical characteristics. Geometrical designs such as channel length (Lch) and pillar thickness (Tp) were considered and the impact on the electrical performance was analyzed. The influence of doping concentration and metal gate work function (WF) were further investigated for achieving better performance. The results show that the shorter Lch can boost the drain current (ID) of n-JLDGVM and p-JLDGVM by approximately 68% and 70% respectively. The ID of the n-JLVDGM and p-JLVDGM could possibly boost up to 42% and 78% respectively as the Tp is scaled down from 11nm to 8nm. The channel doping (Nch) is also a critical parameter, affecting the electrical performance of both n-JLDGVM and p-JLDGVM in which 15% and 39% improvements are observed in their respective ID as the concentration level is increased from 1E18 to 9E18 atom/cm3. In addition, the adjustment of threshold voltage can be realized by varying the metal WF

Caractérisation électrique et modélisation du transport dans matériaux et dispositifs SOI avancés

This thesis is dedicated to the electrical characterization and transport modeling in advanced SOImaterials and devices for ultimate micro-nano-electronics. SOI technology is an efficient solution tothe technical challenges facing further downscaling and integration. Our goal was to developappropriate characterization methods and determine the key parameters. Firstly, the conventionalpseudo-MOSFET characterization was extended to heavily-doped SOI wafers and an adapted modelfor parameters extraction was proposed. We developed a nondestructive electrical method to estimatethe quality of bonding interface in metal-bonded wafers for 3D integration. In ultra-thin fully-depletedSOI MOSFETs, we evidenced the parasitic bipolar effect induced by band-to-band tunneling, andproposed new methods to extract the bipolar gain. We investigated multiple-gate transistors byfocusing on the coupling effect in inversion-mode vertical double-gate SOI FinFETs. An analyticalmodel was proposed and subsequently adapted to the full depletion region of junctionless SOI FinFETs.We also proposed a compact model of carrier profile and adequate parameter extraction techniques forjunctionless nanowires.Cette thèse est consacrée à la caractérisation et la modélisation du transport électronique dans des matériaux et dispositifs SOI avancés pour la microélectronique. Tous les matériaux innovants étudiés(ex: SOI fortement dopé, plaques obtenues par collage etc.) et les dispositifs SOI sont des solutions possibles aux défis technologiques liés à la réduction de taille et à l'intégration. Dans ce contexte,l'extraction des paramètres électriques clés, comme la mobilité, la tension de seuil et les courants de fuite est importante. Tout d'abord, la caractérisation classique pseudo-MOSFET a été étendue aux plaques SOI fortement dopées et un modèle adapté pour l'extraction de paramètres a été proposé. Nous avons également développé une méthode électrique pour estimer la qualité de l'interface de collage pour des plaquettes métalliques. Nous avons montré l'effet bipolaire parasite dans des MOSFET SOI totalement désertés. Il est induit par l’effet tunnel bande-à-bande et peut être entièrement supprimé par une polarisation arrière. Sur cette base, une nouvelle méthode a été développée pour extraire le gain bipolaire. Enfin, nous avons étudié l'effet de couplage dans le FinFET SOI double grille, en mode d’inversion. Un modèle analytique a été proposé et a été ensuite adapté aux FinFETs sans jonction(junctionless). Nous avons mis au point un modèle compact pour le profil des porteurs et des techniques d’extraction de paramètres

Electrical characterization and modeling of low dimensional nanostructure FET

At the beginning of this thesis, basic and advanced device fabrication process which I haveexperienced during study such as top-down and bottom-up approach for the nanoscale devicefabrication technique have been described. Especially, lithography technology has beenfocused because it is base of the modern device fabrication. For the advanced device structure,etching technique has been investigated in detail.The characterization of FET has been introduced. For the practical consideration in theadvanced FET, several parameter extraction techniques have been introduced such as Yfunction,split C-V etc.FinFET is one of promising alternatives against conventional planar devices. Problem ofFinFET is surface roughness. During the fabrication, the etching process induces surfaceroughness on the sidewall surfaces. Surface roughness of channel decreases the effectivemobility by surface roughness scattering. With the low temperature measurement andmobility analysis, drain current through sidewall and top surface was separated. From theseparated currents, effective mobilities were extracted in each temperature conditions. Astemperature lowering, mobility behaviors from the transport on each surface have differenttemperature dependence. Especially, in n-type FinFET, the sidewall mobility has strongerdegradation in high gate electric field compare to top surface. Quantification of surfaceroughness was also compared between sidewall and top surface. Low temperaturemeasurement is nondestructive characterization method. Therefore this study can be a propersurface roughness measurement technique for the performance optimization of FinFET.As another quasi-1 D nanowire structure device, 3D stacked SiGe nanowire has beenintroduced. Important of strain engineering has been known for the effective mobility booster.The limitation of dopant diffusion by strain has been shown. Without strain, SiGe nanowireFET showed huge short channel effect. Subthreshold current was bigger than strained SiGechannel. Temperature dependent mobility behavior in short channel unstrained device wascompletely different from the other cases. Impurity scattering was dominant in short channelunstrained SiGe nanowire FET. Thus, it could be concluded that the strain engineering is notnecessary only for the mobility booster but also short channel effect immunity.Junctionless FET is very recently developed device compare to the others. Like as JFET,junctionless FET has volume conduction. Thus, it is less affected by interface states.Junctionless FET also has good short channel effect immunity because off-state ofjunctionless FET is dominated pinch-off of channel depletion. For this, junctionless FETshould have thin body thickness. Therefore, multi gate nanowire structure is proper to makejunctionless FET.Because of the surface area to volume ratio, quasi-1D nanowire structure is good for thesensor application. Nanowire structure has been investigated as a sensor. Using numericalsimulation, generation-recombination noise property was considered in nanowire sensor.Even though the surface area to volume ration is enhanced in the nanowire channel, devicehas sensing limitation by noise. The generation-recombination noise depended on the channelgeometry. As a design tool of nanowire sensor, noise simulation should be carried out toescape from the noise limitation in advance.The basic principles of device simulation have been discussed. Finite difference method andMonte Carlo simulation technique have been introduced for the comprehension of devicesimulation. Practical device simulation data have been shown for examples such as FinFET,strongly disordered 1D channel, OLED and E-paper.At the beginning of this thesis, basic and advanced device fabrication process which I haveexperienced during study such as top-down and bottom-up approach for the nanoscale devicefabrication technique have been described. Especially, lithography technology has beenfocused because it is base of the modern device fabrication. For the advanced device structure,etching technique has been investigated in detail.The characterization of FET has been introduced. For the practical consideration in theadvanced FET, several parameter extraction techniques have been introduced such as Yfunction,split C-V etc.FinFET is one of promising alternatives against conventional planar devices. Problem ofFinFET is surface roughness. During the fabrication, the etching process induces surfaceroughness on the sidewall surfaces. Surface roughness of channel decreases the effectivemobility by surface roughness scattering. With the low temperature measurement andmobility analysis, drain current through sidewall and top surface was separated. From theseparated currents, effective mobilities were extracted in each temperature conditions. Astemperature lowering, mobility behaviors from the transport on each surface have differenttemperature dependence. Especially, in n-type FinFET, the sidewall mobility has strongerdegradation in high gate electric field compare to top surface. Quantification of surfaceroughness was also compared between sidewall and top surface. Low temperaturemeasurement is nondestructive characterization method. Therefore this study can be a propersurface roughness measurement technique for the performance optimization of FinFET.As another quasi-1 D nanowire structure device, 3D stacked SiGe nanowire has beenintroduced. Important of strain engineering has been known for the effective mobility booster.The limitation of dopant diffusion by strain has been shown. Without strain, SiGe nanowireFET showed huge short channel effect. Subthreshold current was bigger than strained SiGechannel. Temperature dependent mobility behavior in short channel unstrained device wascompletely different from the other cases. Impurity scattering was dominant in short channelunstrained SiGe nanowire FET. Thus, it could be concluded that the strain engineering is notnecessary only for the mobility booster but also short channel effect immunity.Junctionless FET is very recently developed device compare to the others. Like as JFET,junctionless FET has volume conduction. Thus, it is less affected by interface states.Junctionless FET also has good short channel effect immunity because off-state ofjunctionless FET is dominated pinch-off of channel depletion. For this, junctionless FETshould have thin body thickness. Therefore, multi gate nanowire structure is proper to makejunctionless FET.Because of the surface area to volume ratio, quasi-1D nanowire structure is good for thesensor application. Nanowire structure has been investigated as a sensor. Using numericalsimulation, generation-recombination noise property was considered in nanowire sensor.Even though the surface area to volume ration is enhanced in the nanowire channel, devicehas sensing limitation by noise. The generation-recombination noise depended on the channelgeometry. As a design tool of nanowire sensor, noise simulation should be carried out toescape from the noise limitation in advance.The basic principles of device simulation have been discussed. Finite difference method andMonte Carlo simulation technique have been introduced for the comprehension of devicesimulation. Practical device simulation data have been shown for examples such as FinFET,strongly disordered 1D channel, OLED and E-paper.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Effect Of Channel Length Variation On Analog And RF Performance Of Junctionless Double Gate Vertical Mosfet

This paper investigates the effect of channel length (Lch) variation upon analogue and radio frequency (RF) performance of Junctionless Double Gate Vertical MOSFET (JLDGVM). The study has been performed under the fixed level of process parameters by considering the dependence of analogue and RF properties on the channel length. Furthermore, this paper aims to give a comprehensive insight on possible improvement in the performance of analogue and RF of the JLDGVM device. The structure and characteristics of the device are developed and extracted respectively via 2D TCAD simulation. The results show that both transconductance generation factor (TGF) and transconductance (gm) of the JLDGVM device are tremendously increased by 83% and 74% respectively as the scale of channel length is reduced from 12 nm to 9 nm. On the other hand, the unity gain cut-off frequency (fT) and the gain-band-width product (GBW) tremendously improved by ~93% and ~74% respectively as the channel length of the device is scaled from 12 nm to 9 nm

Transport properties and low-frequency noise in low-dimensional structures

Les propriétés électriques et physiques de structures à faible dimensionalité ont été étudiées pour des applications dans des domaines divers comme l électronique, les capteurs. La mesure du bruit bruit à basse fréquence est un outil très utile pour obtenir des informations relatives à la dynamique des porteurs, au piègeage des charges ou aux mécanismes de collision. Dans cette thèse, le transport électronique et le bruit basse fréquence mesurés dans des structures à faible dimensionnalité comme les dispositifs multi-grilles (FinFET, JLT ), les nanofils 3D en Si/SiGe, les nanotubes de carbone ou à base de graphène sont présentés. Pour les approches top-down et bottom-up , l impact du bruit est analysé en fonction de la dimensionalité, du type de conduction (volume vs surface), de la contrainte mécanique et de la présence de jonction metal-semiconducteur.Electrical and physical properties of low-dimensional structures have been studied for the various applications such as electronics, sensors, and etc. Low-frequency noise measurement is also a useful technique to give more information for the carrier dynamics correlated to the oxide traps, channel defects, and scattering. In this thesis, the electrical transport and low-frequency noise of low-dimensional structure devices such as multi-gate structures (e.g. FinFETs and Junctionless FETs), 3-D stacked Si/SiGe nanowire FETs, carbon nanotubes, and graphene are presented. From the view point of top-down and bottom-up approaches, the impacts of LF noise are investigated according to the dimensionality, conduction mechanism (surface or volume conduction), strain technique, and metal-semiconductor junctions.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

FABRICATION AND CHARACTERIZATION OF ACTIVE NANOSTRUCTURES

Three different nanostructure active devices have been designed, fabricated and characterized. Junctionless transistors based on highly-doped silicon nanowires fabricated using a bottom-up fabrication approach are first discussed. The fabrication avoids the ion implantation step since silicon nanowires are doped in-situ during growth. Germanium junctionless transistors fabricated with a top down approach starting from a germanium on insulator substrate and using a gate stack of high-k dielectrics and GeO2 are also presented. The levels and origin of low-frequency noise in junctionless transistor devices fabricated from silicon nanowires and also from GeOI devices are reported. Low-frequency noise is an indicator of the quality of the material, hence its characterization can reveal the quality and perhaps reliability of fabricated transistors. A novel method based on low-frequency noise measurement to envisage trap density in the semiconductor bandgap near the semiconductor/oxide interface of nanoscale silicon junctionless transistors (JLTs) is presented. Low-frequency noise characterization of JLTs biased in saturation is conducted at different gate biases. The noise spectrum indicates either a Lorentzian or 1/f. A simple analysis of the low-frequency noise data leads to the density of traps and their energy within the semiconductor bandgap. The level of noise in silicon JLT devices is lower than reported values on transistors fabricated using a top-down approach. This noise level can be significantly improved by improving the quality of dielectric and the channel interface