Formation Of Buried Layers Research Articles

Verification of a Fabless Device Model Using TCAD Tools: from Bipolar Transistor Formation to I-V Characteristics Extraction

This paper describes the analysis of processes used in microand nanoelectronic device manufacturing. It also presents an exemplary and novel laboratory exercise in which an epitaxial planar n + pn bipolar transistor with junction isolation is illustrated and analyzed stepbystep. Only seven photolithography steps are used to obtain this bipolar transistor structure: for buried layer formation, for junction transistor isolation and collectors regions formation, for base region formation, for emitter and collector n+ region formation, for contact windows, for first aluminum metallization, and, finally, for passivation. Silvaco TCAD software tools are used to implement all of these manufacturing processes and to simulate the resulting IV characteristics of all presented semiconductor structures. This type of laboratory work provides students with basic knowledge and a consistent understanding of bipolar transistor manufacturing, as well as facilitating theoretical understanding, analysis, and simulation of various semiconductor manufacturing processes without the need for costly and lengthy technological manufacturing experiments. This article also presents the conclusions and other benefits of such laboratory work, as well as possible recommendations for further improvement or expansion.

GISAXS Analysis of the In-Depth Morphology of Thick PS-b-PMMA Films.

The morphological evolution of cylinder-forming poly(styrene)-b-poly(methyl methacrylate) block copolymer (BCP) thick films treated at high temperatures in the rapid thermal processing (RTP) machine was monitored by means of in-depth grazing-incidence small-angle X-ray scattering (GISAXS). The use of this nondisruptive technique allowed one to reveal the formation of buried layers composed of both parallel- and perpendicular-oriented cylinders as a function of the film thickness (24 ≤ h ≤ 840 nm) and annealing time (0 ≤ t ≤ 900 s). Three distinct behaviors were observed depending on the film thickness. Up to h ≤ 160 nm, a homogeneous film consisting of perpendicular-oriented cylinders is observed. When h is between 160 and 700 nm, a decoupling process between both the air-BCP and substrate-BCP interfaces takes place, leading to the formation of mixed orientations (parallel and perpendicular) of the cylinders. Finally, for h > 700 nm, the two interfaces are completely decoupled, and the formation of a superficial layer of about 50 nm composed of perpendicular cylinders is observed. Furthermore, the through-film morphology affects the nanodomain long-range order, which substantially decreases in correspondence with the beginning of the decoupling process. When the thick samples are exposed to longer thermal treatments, an increase in the long-range order of the nanodomains occurs, without any sensible variation of the thickness of the superficial layer.

Formation and properties of the buried isolating silicon-dioxide layer in double-layer “porous silicon-on-insulator” structures

The oxidation of mesoporous silicon in a double-layer “macroporous silicon–mesoporous silicon” structure is studied. The morphology and dielectric properties of the buried insulating layer are investigated using electron microscopy, ellipsometry, and electrical measurements. Specific defects (so-called spikes) are revealed between the oxidized macropore walls in macroporous silicon and the oxidation crossing fronts in mesoporous silicon. It is found that, at an initial porosity of mesoporous silicon of 60%, three-stage thermal oxidation leads to the formation of buried silicon-dioxide layers with an electric-field breakdown strength of Ebr ~ 104–105 V/cm. Multilayered “porous silicon-on-insulator” structures are shown to be promising for integrated chemical micro- and nanosensors.

Comparison of SIMS and RBS for depth profiling of silica glasses implanted with metal ions

Ion implantation of metal ions, followed by annealing, can be used for the formation of buried layers of metal nanoparticles in glasses. Thus, photonic structures with nonlinear optical properties can be formed. In this study, three samples of silica glasses were implanted with Cu+, Ag+, or Au+ ions under the same conditions (energy 330 keV and fluence 1 × 1016 ions/cm2), and compared to three identical silica glass samples that were subsequently coimplanted with oxygen at the same depth. All the implanted glasses were annealed at 600 °C for 1 h, which leads to the formation of metal nanoparticles. The depth profiles of Cu, Ag, and Au were measured by Rutherford backscattering and by secondary ion mass spectrometry and the results are compared and discussed.

Lithium implantation at low temperature in silicon for sharp buried amorphous layer formation and defect engineering

The crystalline-to-amorphous transformation induced by lithium ion implantation at low temperature has been investigated. The resulting damage structure and its thermal evolution have been studied by a combination of Rutherford backscattering spectroscopy channelling (RBS/C) and cross sectional transmission electron microscopy (XTEM). Lithium low-fluence implantation at liquid nitrogen temperature is shown to produce a three layers structure: an amorphous layer surrounded by two highly damaged layers. A thermal treatment at 400 °C leads to the formation of a sharp amorphous/crystalline interfacial transition and defect annihilation of the front heavily damaged layer. After 600 °C annealing, complete recrystallization takes place and no extended defects are left. Anomalous recrystallization rate is observed with different motion velocities of the a/c interfaces and is ascribed to lithium acting as a surfactant. Moreover, the sharp buried amorphous layer is shown to be an efficient sink for interstitials impeding interstitial supersaturation and {311} defect formation in case of subsequent neon implantation. This study shows that lithium implantation at liquid nitrogen temperature can be suitable to form a sharp buried amorphous layer with a well-defined crystalline front layer, thus having potential applications for defects engineering in the improvement of post-implantation layers quality and for shallow junction formation.

Formation of silicon nanoclusters in buried ultra-thin oxide layers

The peculiarities of buried layer formation obtained by co-implantation of O2 ions with the energy of 130 keV and carbon ions within the energy range of 30-50 keV have been investigated. The corresponding ion doses for carbon and oxygen ions were equal to and , respectively. It has been observed that annealing at 1150 °C results in enhanced oxygen diffusion towards the region with a maximum carbon concentration. Analysis of X-ray diffraction patterns with a SIMS depth profiles inherent to annealed samples suggests formation of Si nanoclusters in the region with maximum concentrations of carbon and oxygen vacancies. The intensive luminescence has been observed with the maximum at 600 nm, which could be associated with silicon nano-inclusions in thin stoichiometric SiO 2 16 cm 10 2 − × 2 17 cm 10 8 . 1 − ×

Stimulated Creation of the SOI Structures with Si Nano-Clustersw by Low–Dose SIMOX Technology

The peculiarities of a buried layer formation obtained by a co-implantation of O2 ions with the energy of 130 keV and carbon ions within the energy range of 30-50 keV have been investigated. The corresponding ion doses for carbon and oxygen ions were equal to 2∙1016 cm-2 and 1.8∙1017 cm-2, respectively. It has been observed that annealing at 1150°C results in enhanced oxygen diffusion towards the region with a maximum carbon concentration. Analysis of x-ray diffraction patterns and TEM images confirm formation of Si nanoclusters in the SiO2 buried layer. The intensive luminescence with the maximum at 600 nm has been observed in the synthesized structures.

Effects of thermal and athermal processing on the formation of buried SiC layers

In the present study, systematic investigations on 100 keV C ion implanted Si (100) substrates annealed subsequently at a temperature of 1000 °C for 2 h or athermally processed using 110 MeV Ni8+ ion irradiation have been performed. A detailed analysis using the techniques of x-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy (TEM) at high resolutions is performed. The observations suggest the formation of cubic silicon carbide (β-SiC) crystallites surrounded by an amorphous background in the samples thermally annealed at 1000 °C. However, ion irradiation did not influence the as-implanted layers to any significant extent. Various defects formed after annealing inside C implanted Si such as missing planes, edge dislocations, and grain boundaries during thermal crystallization are visualized through high resolution TEM.

Buried Nano - Structured Layers in High Temperature – Pressure Treated Si:He

The effect of treatment at up to 1400 K (HT) under enhanced hydrostatic pressure (HP, up to 1.2 GPa) on helium implanted single crystalline silicon (Si:He, He ion dose up to 6x1017cm-2, energy up to 300 keV) has been investigated by transmission electron microscopy, secondary ion mass spectrometry, photoluminescence and X-Ray methods. The treatment of Si:He at ≤ 920 K - HP results in a formation of buried nano-structured layers containing helium filled cavities/bubbles and numerous extended defects; many less dislocations are created at ≥ 1270 K in Si:He treated under HP. HP affects the recrystallization of amorphous Si, diffusivity of implanted He and of implantation-induced defects and thus promotes the creation of more but smaller He-filled cavities/bubbles as well as other defects near the range of implanted He+.

Formation and study of buried SiC layers with a high content of radiation defects

Protons with energy E=100 keV were implanted with doses ranging from 2×1017 to 4×1017 cm−2 into 6H-and 4H-SiC n-type samples at room temperature. The samples were subjected to various types of postimplantation heat treatment in the temperature range 550–1500°C. The parameters of the samples were studied by measuring the capacitance-voltage and current-voltage characteristics and by analyzing the photoluminescence spectra. Blistering on the surface of the sample is observed after annealing the samples at a temperature of 800°C only after implantation of protons with a dose of ≤3×1017 cm−2. A decrease in the resistivity of the compensated layer sets in after annealing at a temperature of ∼1200°C and is completed after annealing at a temperature of ∼1500°C. A drastic decrease in the photoluminescence intensity is observed after implantation for all types of samples. Recovery of the photoluminescence intensity sets in after annealing at temperatures ≥800°C and is complete after annealing at a temperature of 1500°C.

Nanostructure formation by high temperature–pressure treatment of silicon implanted with hydrogen/helium

The effect of high temperature (HT, up to 1400 K)–hydrostatic pressure (HP, up to 1.2 GPa) on Czochralski silicon implanted with hydrogen (Si:H, H dose, D H = 5 × 1 0 16 cm − 2 ), helium (Si:He, D He = 5 × 1 0 16 cm − 2 ) or helium + hydrogen (Si:He, H, total D H + He = 1 × 1 0 17 cm − 2 ) has been investigated by TEM, SIMS and PL measurements. The treatment of Si:H, Si:He and Si:He, H at ≤1070 K–HP results in a formation of buried nanostructured layers composed of hydrogen/helium filled cavities/platelets and numerous point and extended defects; much fewer dislocations are created at ≥1270 K–HP. The microstructure of Si:He, H evidences specific interaction of implanted helium and hydrogen, affecting the creation of Si–H bonds.

Buried nanoscale damaged layers formed in Si and SiC crystals as a result of high-dose proton implantation

Buried nanoscale damaged layers formed in Si and SiC crystals via 50-and 100-keV proton implantation were studied. It is shown that the sensitivity of atomic-force microscopy is sufficiently high to detect the initial stages of the development of hydrogen-containing voids and microcracks in subsurface layers of irradiated crystals and to study exfoliation of the crystals in the plane of microcracks. As a result, quantitative criteria for the formation of buried damaged layers in the studied crystals were derived; also, the conditions for blistering and for implementation of the “Smart-Cut” technology were determined.

Influence of ion implantation induced defects on formation of buried CoSi 2 structures in Si(1 0 0)

The evolution of buried structures of cobalt disilicide formed in a Si(1 0 0) matrix by 400 keV Co + implantation at 875 K substrate temperature was studied by cross-sectional transmission electron microscopy. Varying the dose of implanted ions allowed a detailed study of the role of defects created by the Co + flux in nucleation and growth of CoSi 2 precipitates. Implantation induced defects create diffusive links that assist in anisotropic diffusion of Co in the bulk resulting in organized self-growth of long rectangular precipitates with alignment along the 〈1 1 1〉 direction toward the surface. The transport of the implanted material along these diffusive links eventually leads to the formation of a second CoSi 2 band between the main layer and the surface. This mechanism is considered to be the reason for the formation of several buried layers of disilicide.

Cathodoluminescence from BN buried layers by high-dose ion implantation

Boron, nitrogen, and carbon ions were co-implanted in silicon wafers, and subsequently annealed. Infrared spectra show the formation of BN-rich buried layers. The presence of a band at 1375 cm−1 characteristic of boron nitride in a hexagonal configuration has been observed. Traces of the cubic phase formation were detected in some cases. Implanted samples exhibit a broad emission band about 550 nm.

Role of ripening and defects in the formation of mesotaxial cobalt-disilicide layers

Previous studies of the formation of buried silicide layers through mesotaxy, i.e., the introduction of the metal component by ion implantation with subsequent annealing of the structure, have shown that high-quality films can be achieved, but at processing temperatures too high to be useful for integration with silicon device technology. Recently, we proposed a modified ripening model to describe the early stages of the formation of a buried film which intentionally excluded the role of defects. In the current study, the predictions of that model are tested by varying sample preparation conditions. We show that the shift of the silicide precipitate layer is correlated with the narrowing of the cobalt profile, thus requiring both processes to be described by the same mechanism. We also show in a TEM study that specific defect morphologies are correlated with specific properties of the forming buried film, requiring an extension of the previous model.

Synthesis of single-crystalline Al layers in sapphire

Single-crystalline, buried aluminium layers were synthesized by 180 keV high-dose Al + ion implantation into sapphire at 500°C. The approximately 70 nm thick Al layers exhibit in XTEM investigations locally abrupt interfaces to the single-crystalline Al 2O 3 top layer and bulk, while thickness and depth position are subjected to variations. The layers grow by a ripening process of oriented Al precipitates, which at low doses exist at two different orientations. With increasing dose, precipitates with one out of the two orientations are observed to exist preferentially, finally leading to the formation of a single-crystalline layer. Al outdiffusion to the surface and the formation of spherical Al clusters at the surface are found to be competing processes to buried layer formation. The formation of Al layers is described by Rutherford Backscattering Spectroscopy (RBS), Cross-section transmission electron microscopy (XTEM) and Scanning electron microscopy (SEM) studies as a function of dose, temperature and substrate orientation.

Influence of oxygen on the ion-beam synthesis of silicon carbide buried layers in silicon

The properties of silicon structures with silicon carbide (SiC) buried layers produced by high-dose carbon implantation followed by a high-temperature anneal are investigated by Raman and infrared spectroscopy. The influence of the coimplantation of oxygen on the features of SiC buried layer formation is also studied. It is shown that in identical implantation and post-implantation annealing regimes a SiC buried layer forms more efficiently in CZ Si wafers or in Si (CZ or FZ) subjected to the coimplantation of oxygen. Thus, oxygen promotes SiC layer formation as a result of the formation of SiOx precipitates and accommodation of the volume change in the region where the SiC phase forms. Carbon segregation and the formation of an amorphous carbon film on the SiC grain boundaries are also discovered.

Article

We present results on the formation of buried silicide layers at ion implantation doses in the range of 1-60% of the critical dose for formation of a uniform layer. We emphasize observations for the low-dose range of 1-5% where the precipitate density is quite dilute. The Co redistribution during post-implant annealing is measured using Rutherford backscattering techniques and secondary ion mass spectrometry. Experimental observations during post-implantation annealing at 1000°C involves (i) a contraction of the Co depth profile for all doses, (ii) shifting of the peak of the profile towards the bulk, and (iii) formation of a secondary Co peak near the surface. The secondary peak is only present in samples implanted to greater than 3% of the critical dose. The interpretation of the shift of the main peak and the occurrence of the secondary peak requires a model exceeding the standard ripening model used previously to describe mesotaxy. We suggest that more recent ripening-based concepts allow for a full description of these observations with a minimum of parameters, particularly not requiring interaction with the complex defect profiles formed initially during implantation. Essential for this model is a proper inclusion of precipitate-precipitate interactions and the role of diffusion screening.Key words: silicide, Co implantation, mesotaxy, precipitate, ripening, screening.

High-fluence ion implantation of In into Al crystals: formation and evolution of buried layers

High-fluence ion implantation of In into Al crystals: formation and evolution of buried layers

High-fluence ion implantation of In into Al crystals: Formation and evolution of buried layers

Abstract Al(110) single-crystal samples were implanted at T = 200°C with In+ ions of 250 keV energy with fluences ranging from 4×1020 to 3×1021 m−2. The implantation resulted in the formation of In precipitates growing with fluence in topotactical alignment with the host matrix. High-fluence implantation was used in an attempt to produce single-crystal buried layers of In embedded into Al. Rutherford back-scattering (RBS)-channelling analysis of the implanted samples and transmission electron microscopy studies of the incorporated In layer morphology were carried out. With increasing fluence the peak In concentration was observed to increase gradually until a maximum value of about 38 at.% was reached at an implantation dose of 1·5×1021 m−2. The buried layer thus formed was found to have fragmentary morphology consisting of large In precipitates. During further implantation the peak concentration decreased drastically to reach a steady state. In order to study a possible effect of sputtering on the In pro...