Search

Understanding and characterizing very low-energy (∼ eV) background sources is a must in rare-event searches. Oscura, an experiment aiming to probe electron recoils from sub-GeV dark matter using a 10 kg skipper-CCD detector, has recently fabricated its first two batches of sensors. In this work, we present the characterization of defects/contaminants identified in the buried-channel region of these newly fabricated skipper-CCDs. These defects/contaminants produce deferred charge from trap emission in the images next to particle tracks, which can be spatially resolved due to the sub-electron resolution achieved with these sensors. Using the trap-pumping technique, we measured the energy and cross section associated with these traps in three Oscura prototype sensors from different fabrication batches which underwent different gettering methods during fabrication. Results suggest that the type of defects/contaminants is more closely linked to the fabrication batch rather than to the gettering method used. The exposure-dependent single-electron rate (SER) of one of these sensors was measured ∼ 100 m underground, yielding (1.8 ± 0.3) × 10 − 3 e − /pix/day at 131 K. The impact of the identified traps on the measured exposure-dependent SER is evaluated via a Monte Carlo simulation. Results suggest that the exposure-dependent SER of Oscura prototype sensors would be lower in lower background environments as expected. [ABSTRACT FROM AUTHOR]

Metallic impurities in the silicon wafer bulk are one of the major efficiency-limiting factors in silicon solar cells. Gettering can be used to significantly lower the bulk metal concentrations. Aluminum oxide thin films from plasma-enhanced atomic layer deposition (PE-ALD) have been reported to getter iron from silicon wafers. However, its gettering mechanism and kinetics remain unclear. In this study, by experimentally monitoring the kinetics of iron reduction in the silicon wafer bulk, aluminum oxide gettering of iron is shown to be caused by a segregation mechanism. Fitting the experimental iron reduction kinetics by the simulation of a segregation gettering process based on various diffusion scenarios suggests that the gettering kinetics is limited by both the diffusivities of iron in the silicon wafer bulk and in the aluminum oxide film. The activation energy of the segregation gettering process (negative meaning exothermic reaction) is estimated to be −0.47 ± 0.16 eV for the investigated as-deposited PE-ALD aluminum oxide film at 550–900 °C, and −0.35 ± 0.06 eV at 400–900 °C for the same film after a 400 °C forming gas anneal (FGA), i.e., after activating the passivation effect of the film. Capacitance–voltage measurements of the films indicate a higher surface defect density in the as-deposited films as compared to the FGA-activated films, which suggests a possible correlation between the surface defect density and gettering. [ABSTRACT FROM AUTHOR]

The paper studies the gettering properties of nickel clusters in the silicon lattice. The gettering properties of nickel clusters were studied in various states, i.e., in original (reference) samples, as well as in samples with additionally doped interstitial and lattice site impurity atoms of sulfur and manganese. The electrophysical and photoelectric parameters were studied using modern instrumentation: INFRAM-I-type infrared microscope, IKS-21 and scanning electron microscope SEM (Oxford Instruments ZEISS EVOMA10), IKS-21. A new technology has also been proposed that makes it possible to getter harmful impurities; it is recommended for widespread use in the electronics industry and scientific research institutes for the production of materials with stable parameters and the development of fundamentally new devices. [ABSTRACT FROM AUTHOR]

In this study, we developed a shallow defect layer formation process using moderate-pressure H2 plasma at 3.3 kPa for an extrinsic gettering layer of ultra-thin Si chips aimed at three-dimensional integrated circuits. This process can be conducted in the presence of trivial amounts of air impurities (∼0.01 vol. %), thereby avoiding the use of high-vacuum equipment. We investigated the dependence of defect formation behavior on various processing parameters such as H2 flow rate, processing time, substrate temperature, and input power. It was determined that the absence of H2 gas flow was favorable for the defect layer formation because Si etching by hydrogen atoms was suppressed. A low Si temperature and high input power are desirable for a high defect density in the shallow surface region of the extrinsic gettering layer. When pulse-modulated plasma irradiation was attempted, the defect layer that formed became thinner and had a higher defect density than that obtained by continuous plasma, demonstrating good Cu gettering performance. Without using harmless chemicals, or high-cost equipment, a shallow gettering layer can be formed using inexpensive H2 gas. [ABSTRACT FROM AUTHOR]

Titanium zirconium vanadium (TiZrV) is a widely used non-evaporable getter (NEG) material with the characteristics of a low activation temperature and a large gas absorption capacity. At present, the research on TiZrV getters mainly focuses on the thin-film state, with little research on the bulk state. In this paper, a TiZrV getter was optimized by adding Al, and the phase structure, activation properties, and gettering performance were studied. With the addition of Al, the α-Zr phase and Ti2Zr phase changed into the Ti-Zr phase and Al-Zr, Al-Ti phase. The newly generated phase promoted the diffusion of hydrogen and oxygen atoms. The activation temperature decreased significantly, as shown in the in situ XPS results. The H2 and CO gettering performance of TiZrVAl samples was promoted to 2073 cm3·s−1 and 1912.8 cm3·s−1, increased by 40.7% and 40.3%. This paper provides valuable ideas for optimizing the properties of bulk TiZrV getters. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The research results present the influence of nickel impurities introduced by diffusion into monocrystalline silicon on the characteristics of solar cells (SCs). It is established that doping with nickel atoms makes it possible to increase the lifetime of the MCCs in the material by up to a factor of two and the efficiency of SCs by 20–25%. It is shown that the distribution of nickel clusters in the volume of the material is almost uniform, and their size does not exceed 0.5 μm. The concentration of clusters in the volume is ~1011–1013 cm–3; and in the near-surface layer, ~1013–1015 cm–3. The physical mechanisms of the influence of the bulk and near-surface clusters of nickel atoms on the efficiency of silicon SCs are revealed. It is experimentally established that the decisive role in increasing their efficiency is played by the processes of gettering of recombination-active technological impurities by nickel clusters, occurring in the nickel-enriched front surface region of the SCs. [ABSTRACT FROM AUTHOR]

This study focuses on the enhanced passivation and gettering of boron‐doped p‐type solar grade silicon wafers by incorporating carrier‐selective and passivating tunnel oxide contact (TOPCon). A symmetrical stack of aluminum oxide (Al2O3)/p‐doped n‐type polysilicon (n‐poly‐Si)/ ultrathin silicon oxide (SiOx) in conjunction with long cycles of forming gas annealing is used for enhancing the silicon wafer quality with a novel approach. Multilayer of n‐poly‐Si/SiOx on p‐type crystalline silicon wafer exhibits an implied open‐circuit voltage (iVoc) of 726 mV, effective carrier lifetime (τeff) of 857 μs, and a low recombination current density (Jo) of 1.9 fA cm−2 when subjected to a postdeposition annealing (PDA) of phosphorus‐doped hydrogenated amorphous silicon (n‐a‐Si:H) at 820 °C. To boost passivation and gettering quality, 10 nm‐thick Al2O3 layers on both sides of n‐poly‐Si/SiOx samples are added. This leads to improved τeff (962 μs), reduced Jo (1.1 fA cm−2), and higher iVoc (728 mV). Herein, a thinner 50 nm n‐poly‐Si layer for improved properties is applied. The experiments show improved passivation and gettering. A Quokka‐3 simulation examines the potential of high‐efficiency p‐type TOPCon cells. A novel solar‐grade p‐type wafer quality enhancement approach is introduced, amalgamated with Quokka‐3 results, which could be a milestone in high‐efficiency p‐type TOPCon solar cell production. [ABSTRACT FROM AUTHOR]

An assessment of the bulk material quality of industrial Czochralski (Cz) grown phosphorus‐doped n‐type silicon (Si) wafers along an ingot is reported. The minority charge carrier lifetimes of the Cz‐Si wafer bulk before and after phosphorous (POCl3) diffusion gettering are assessed, by applying room‐temperature superacid surface passivation to avoid any additional gettering or hydrogenation effect. A substantial increase in the bulk lifetime of all of the n‐type Cz‐Si wafers along the ingot is observed, indicating the effectiveness of a gettering step for such wafers and the presence of getterable metallic impurities in these wafers. By experimentally monitoring the lifetime changes upon a gettering anneal and simulating the gettering kinetics based on different metal diffusivities, iron is identified to be a limiting defect, at least for the wafers from the tail part of the ingot. A dissolved iron concentration of (8±2) ×1011 cm−3$\left(\right. 8 \pm 2 \left.\right) \textrm{ } \times \left(10\right)^{11} \left(\text{ cm}\right)^{- 3}$ is estimated from the bulk lifetimes of the tail wafers. This lifetime kinetics approach is also a demonstration of a new method to identify iron, or other getterable metals with moderate diffusivities such as chromium, in n‐type silicon wafers. [ABSTRACT FROM AUTHOR]

Conventional silicon (Si) wafers are produced by energy‐intensive ingot crystallization which is responsible for a major share of a solar cell's carbon footprint. This work explores Si epitaxially grown silicon wafers (EpiWafers) that are produced by direct epitaxial deposition of trichlorosilane on a reusable substrate. This approach requires less energy and material and hence offers a potential for reduced cost and carbon footprint. Solar cells made from EpiWafers usually suffer from efficiency losses due to recombination at structural crystal defects associated with epitaxial growth. The nature of these defects is investigated and defects at the EpiWafer's back surface are critical. Most of these defects are highly recombination‐active, pairwise‐connected misfit dislocations in the <110> direction. They originate from a lattice mismatch between the highly doped substrate and the less‐doped epitaxially grown layer. In this contribution, the detrimental impact of these defects can be mitigated using typical manufacturing processes of high‐efficiency solar cells, such as KOH etching, gettering, and oxidation. Local minority charge carrier lifetimes as high as 2.2 ms after industrially feasible processes are reported. Simulations using efficiency‐limiting bulk recombination analysis implies that the material would allow conversion efficiencies of up to 25.6% considering tunnel oxide‐passivated contact acting as rear emitter solar cell design. [ABSTRACT FROM AUTHOR]

This study demonstrates that the concentration of nickel atoms near the surface of solar cells is 2-3 orders of magnitude higher than in the bulk material, significantly enhancing the gettering rate at the surface. Using IR-microscopy, SEM, and SIMS, we found that the surface density of nickel clusters is approximately 106-107 cm-2, with an average cluster diameter of 20-100 nm and a cluster concentration of 1011±1015 cm-3 Experimental results revealed that nickel clusters on the surface of silicon samples contain a substantial amount of oxygen and recombination impurities (Cu, Fe, Cr), indicating excellent gettering properties. We identified the physical mechanisms underlying the effects of nickel impurity atom diffusion and additional thermal annealing on the state of nickel atoms near the surface and base of the solar cells. Physical models were developed for the structure of nickel atom clusters in silicon and for the gettering process of fast-diffusing impurities by these clusters. The binding energy of fast-diffusing impurity atoms with a nickel cluster was estimated to be approximately 1.39 eV. Calculations indicated that nickel doping can increase the lifetime of minority charge carriers by a. factor of 2-4, and experimental results confirmed an increase in the lifetime of minority charge carriers by up to a. factor of 2. These findings highlight the potential of nickel doping to enhance the performance and efficiency of silicon-based solar cells, offering a promising avenue for future research and development in photovoltaic technology. [ABSTRACT FROM AUTHOR]

The mechanism of structure transformation in Cr/4H–SiC UV photo detectors, which is responsi-ble for the cyclic gettering of radiation defects, under repeated proton irradiation, is proposed in this work. [ABSTRACT FROM AUTHOR]

The paper presents the results of study of the electrophysical properties of metal-semiconductor junctions, where the influence of the structuralimpurity state of the semiconductor substrate and deposited film is significant. The influence of different preparing modes for the silicon substrate, including the thermal gettering treatment, on minority charge-carrier lifetime and on the concentration of electrically active impurity defects in the surface layer of n-Si is considered. The calculation results of the I-V characteristics of Fe/n-Si and (Fe + C)/n-Si junctions are presented with the proposed method for the quantification of their rectifying capabilities. The influence of the Fe film surface oxide and its alloying with carbon on the rectifying capability of the Fe/n-Si junctions is shown. The decreasing of the rectifying capability of the (Fe + C)/n-Si junction is established using the unique method for measuring the electrophysical properties of thin-film junction under conditions of an increase in external mechanical load. [ABSTRACT FROM AUTHOR]

It was demonstrated that the concentration of nickel atoms near the surface of solar cells (SCs) is higher by 2–3 orders of magnitude in comparison with the bulk material, resulting in a significantly increased gettering rate in the former case. Experiments determined the optimal gettering conditions for nickel clusters (nickel diffusion temperature 800–850°C and additional thermal annealing temperature 750–800°C) and the structure of a silicon SC that enhances its efficiency by 25–30% in comparison with the reference structure. Physical mechanisms were identified for the effect of the diffusion of nickel impurity atoms and additional thermal annealing on the state of nickel atoms near the surface and the SC base and, consequently, on SC parameters. Physical models were developed for the structure of a cluster of nickel atoms in silicon and for the gettering process of fast-diffusing impurities by clusters of nickel atoms. The binding energy of fast-diffusing impurity atoms with a nickel cluster was estimated to be approximately 1.39 eV. Calculations showed that nickel doping can increase the minority carrier lifetime and the collection coefficient by factors of 2–4 and 1.4–2, respectively. Experiments demonstrated a twofold increase in minority carrier lifetime and a 25–30% improvement in the efficiency of SCs. [ABSTRACT FROM AUTHOR]

Ionizing radiation has the potential to cause operational disruptions and destroy microelectronic devices. This paper introduces and demonstrates a method of hardening microelectronic devices for sustained use in applications where exposure to ionizing radiation exists. By incorporating quantum structures below active regions of devices, gettering of charges created by ionizing radiation becomes possible. The gettering of electrons and holes forces recombination of carriers, thus eliminating photocurrent surges and trap filling which would otherwise disrupt device operation. Experimental results discussed here show a reduction in photocurrent of over two orders of magnitude when utilizing energy band engineering to create quantum structures for charge gettering. In this work, a nitride-based high electron mobility two-dimensional electron gas demonstrates the method. However, the theory utilized pertains not only to nitride-based devices, but transfers to other materials as well. [ABSTRACT FROM AUTHOR]

Herein, a systematic study of the electronic quality of gallium‐doped p‐type silicon wafers from Czochralski‐grown ingots with melt recharging is presented. It is found that in the as‐grown state, the ingots contain interstitial iron concentrations in the range of 3 × 109–2 × 1010 cm−3, with a trend of slightly higher concentrations toward the tail end of each ingot, and in subsequently grown ingots. However, analysis of the effective lifetimes indicates that iron–gallium pairs are not the dominant recombination centers in the as‐grown state. Moreover, when these wafers are subjected to a tabula rasa step, an increase in the iron concentration is observed in the range of 1 × 1010–6 × 1010 cm−3, with iron–gallium pairs becoming the dominant recombination centers. This is possibly caused by the dissolution of pre‐existing precipitated iron in the wafers. Nevertheless, the negative impact of iron contamination can be dramatically reduced by subjecting the wafers to a phosphorus diffusion gettering step, as is commonly incorporated in the fabrication of p‐type passivated emitter and rear cells. Therefore, it is concluded that the quality of the ingots is not limited by iron contamination, even after multiple ingots are pulled from the recharged melt. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In addition to excellent surface passivation and carrier selectivity, the structure based on the heavily doped polysilicon layer on an ultrathin silicon oxide interlayer also demonstrates strong impurity gettering effects. Herein, the gettering strength of a range of phosphorus‐ or boron‐doped polysilicon films from different fabrication techniques is assessed and compared. Iron, one of the most common metallic impurities in silicon, is used as a tracer impurity to quantify the gettering strength (segregation coefficient). A comparison of the experimental results to the literature, combined with measurements of the electrically active and inactive dopant concentrations, enables us to suggest the main gettering mechanisms in different polysilicon films. The differences in the segregation coefficients of the phosphorus‐doped polysilicon films for iron are within one order of magnitude, in spite of their different combinations of gettering mechanisms. On the other hand, boron‐doped polysilicon films show a large variation in their gettering effects, although the predominant gettering mechanisms are all attributed to electrically inactive boron, according to the current understanding of the gettering mechanisms from the literature. Finally, the impact of different polysilicon gettering effects on the efficiency of tunnel oxide‐passivated contact (TOPCon) cells is simulated and discussed. [ABSTRACT FROM AUTHOR]

High-performance multicrystalline silicon (HP mc-Si) from directional solidification has become the mainstream industrial material for fabricating mc-Si based solar cells for photovoltaic applications. Transition metal impurities are inherently contained in HP mc-Si during ingot growth, and they are one of the major efficiency-limiting drawbacks. In this work, we investigate the gettering of transition metals (Cu, Ni, Fe, and Cr) in HP mc-Si wafers along an industrial-standard p-type HP mc-Si ingot, via examining the metal concentration and distribution in the near-surface gettering layers using secondary ion mass spectrometry. We applied both conventional phosphorus diffusion gettering and the recently developed silicon nitride (from plasma-enhanced chemical vapour deposition) gettering techniques. Both techniques are shown to remove significant quantities of metals from the silicon wafer bulk to the surface gettering layers. Improvements in the bulk minority carrier lifetimes throughout the ingot height are also observed by lifetime measurements and spatially-resolved photoluminescence imaging. The gettered Cu and Ni concentrations, as well as the as-grown dissolved Fe concentrations in the silicon wafer bulk, along the HP mc-Si ingot height are shown to follow a similar concentration profile as the metals in conventional mc-Si ingots. [ABSTRACT FROM AUTHOR]

Black silicon (b‐Si) has many attractive properties and is currently being adopted in various fields of semiconductor technology. It is shown here that b‐Si during thermal activation may serve as an external gettering layer to remove metallic impurities and associated defects from bulk Si. The gettering efficiency by b‐Si is estimated according to the results of studying the resistivity, defect density, interstitial iron concentration, and effective minority carrier lifetime on gettered test and ungettered reference Si samples. It is shown that in the thermal oxidation process, the b‐Si layer serves as an effective drain for excess iron atoms and other fast‐diffusing impurities, thereby significantly reducing the density of oxidation‐induced stacking faults in Si. In addition, the resistivity of the substrates decreases, and the bulk carrier lifetime increases significantly. Finally, gettering by b‐Si is introduced into the solar cells fabrication process and its effect on solar cell current–voltage characteristics is investigated. It has been shown that all electronic parameters of the solar cells are improved. The conversion efficiency of ungettered solar cells is 16.8%, and for gettered solar cells, depending on the oxidation temperature, it increases by 1.36–1.96%. [ABSTRACT FROM AUTHOR]

the results of a study of the galvanomagnetic properties of indium arsenide grown by liquid-phase epitaxy are presented. It is shown that the use of the rare earth element holmium in the growth of InAs epitaxial layers makes it possible to reduce the electron concentration by two orders of magnitude to n = 2.1 × 1015 cm–3 at T = 77 K. This effect is due to the gettering of shallow background impurities with the formation of their compounds in the melt. With an increase in the holmium content of more than 0.12 mol % the concentration of current carriers in the material begins to increase, while mobility decreases due to the influence of VAs–Ho donor centers. This method of gettering is promising for obtaining A3B5 materials with a low concentration of current carriers, which are in demand in the optoelectronic industry. [ABSTRACT FROM AUTHOR]

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures. [ABSTRACT FROM AUTHOR]

The formation of clusters of impurity atoms in the crystal lattice of semiconductor materials is of great interest. The formation of nanoclusters with controlled parameters in the lattice of semiconductor materials can serve as the basis for the technology of creating and obtaining bulk nanostructured semiconductor material. This paper shows the experimental results obtained, as well as the proposed physical model of the structure of nickel atomic clusters. It is shown that the clusters move and migrate in the crystal lattice of monosilicon with an anomalously high diffusion coefficient of about c (D ~ 10-9 cm2/s at T = 800°C). The structural composition of clusters of impurity atoms is determined, its structure and the mechanism of migration in the crystal lattice are proposed. Thus, it was found that it is possible to control the state of impurity atom clusters in the silicon crystal lattice, obtaining a new type of semiconductor materials with unique functional and properties using the cluster migration process. This makes it possible to create a new class of photonic materials with bulk superlattices based on semiconductors with ordered clusters, which has unique functionality for creating optoelectronic, nanoelectronic, photoelectric devices and sensors of physical quantities of a new generation. [ABSTRACT FROM AUTHOR]

• Two-step annealing enhances oxygen precipitation, and thus reduce the recovery of minority carrier lifetime during phosphorus gettering. • The effectiveness of phosphorus gettering is influenced by the size and quantity of oxygen precipitates. This study investigates the effects of single-step and two-step annealing processes on the formation of oxygen precipitates and their impact on metal impurity gettering in gallium-doped monocrystalline silicon. The research focuses on the competitive relationship between internal gettering by oxygen precipitates and external gettering through phosphorus diffusion. Experimental results show that two-step annealing generates larger and more abundant oxygen precipitates, enhancing the internal gettering effect and reducing the recovery of minority carrier lifetime after phosphorus gettering. Despite this, phosphorus diffusion gettering remains effective in improving minority carrier lifetime, although the degree of improvement depends on the size and quantity of oxygen precipitates. These findings offer valuable insights for optimizing the fabrication process of silicon-based solar cells. [ABSTRACT FROM AUTHOR]

Phosphorus gettering using tubular diffusion furnaces was performed on n-type cast monocrystalline silicon wafers to assess its impact on wafer quality and the conversion efficiency of heterojunction solar cells. A comprehensive analysis of temperature, duration, and cooling rate in the diffusion process was conducted. The optimal parameters were identified at a temperature of 850 °C for 30 min, with a cooling rate of 5 °C/min down to 500 °C. This gettering process effectively reduced interstitial iron concentration, improved minority carrier lifetime, and increased the average efficiency of HJT cells by an absolute 0.4 %, with a 1.1 % increase for those made from bottom wafers with high metal concentration. [ABSTRACT FROM AUTHOR]

This study reports on the electronic properties of industrial phosphorus-doped n-type silicon ingots for photovoltaic applications grown using the Recharged Czochralski method. The electronic quality is assessed via carrier lifetime measurements, both directly on the ingots and on passivated wafers, and via implied open-circuit (i V O C), and implied maximum power point (i V M P P) voltages. The wafers are studied in the as-grown state, and after various high temperature steps, including Tabula Rasa , phosphorus diffusion gettering, and boron diffusion. The material exhibited very high bulk quality, with bulk lifetimes up to 8 ms at an injection level of 5 × 10 14 cm − 3 , and with i V O C (1-sun) values up to 750 mV , prior to any high temperature processing. A Tabula Rasa step did not significantly improve the wafer quality, indicating a low presence of oxygen-related defects in this material, consistent with the low interstitial oxygen content of below 5 × 10 17 cm − 3 . However, phosphorus diffusion gettering improved the wafer quality, especially towards the tail end of each ingot, and at lower injection levels near maximum power point. Phosphorus diffusion gettering increased the i V O C (1-sun) of the wafers by around 5 mV , approaching the Auger limit. Additionally, a boron diffusion step had minimal impact on the bulk lifetimes. Overall, our findings suggest that these RCz-grown n-type wafers exhibit very high quality, approaching the Auger limit near open-circuit, and are well-suited for high-efficiency solar cells without the need for additional high-temperature processing. • Assessing the material quality of n-type RCz industrial ingots, both directly on the ingot and on passivated wafers. • Bulk lifetimes of up to 8 ms and i V O C (1-sun) values up to 750 mV. • Low interstitial oxygen content of below 5 × 10 17 cm − 3 , low presence of oxygen-related defects. • Improvement of the wafer quality after gettering, particularly towards the bottom of each ingot, nearing the Auger limit. • No significant degradation after boron diffusion. [ABSTRACT FROM AUTHOR]

We have developed silicon epitaxial wafers with high gettering capability using hydrocarbon molecular ion implantation for advanced Complementary Metal-Oxide-Semiconductor (CMOS) image sensors. These wafers have three unique silicon wafer characteristics for improvement of CMOS device electrical parameter such as high metallic impurity gettering, oxygen out-diffusion barrier effects from Czochralski silicon (CZ) substrate and hydrogen passivation effect for interface state defect at Si/SiO2. We demonstrate that double epitaxial growth silicon wafers have an extremely high gettering capability during CMOS device fabrication process. We also found that gettering capability strongly dependence on oxygen impurity amount in hydrocarbon molecular ion implantation projection range. We believe that this novel silicon wafer can drastically contribute to the improvement of CMOS image sensor device performance such as white spot defect and dark current.

Interdiffusion in gold/titanium films with titanium evaporated on silicon at different oblique angles (0°, 30°, 50°, and 70°) and gold evaporated under normal incidence is investigated using a scanning electron microscope and in-situ sheet resistance measurements for the optimization of the films' effective gettering ability during and after a low-temperature thermal activation. Films have a tilted columnar structure and a porosity increasing with the deposition angle in agreement with calculated values. The oxygen effective gettering ability, characterized by energy-dispersive X-ray spectroscopy, increases with the deposition angle. It is shown that the gold/titanium film with titanium deposited with an oblique angle of 50° is an optimized condition to obtain the largest sorption capacity after 1 h thermal activation at temperatures lower or equal to 300 °C. This film has a low initial residual stress that becomes highly tensile if thermal activation is performed above 300 °C. [ABSTRACT FROM AUTHOR]

Using a new implantation technique with multielement molecular ions consisting of carbon, hydrogen, and phosphorus, namely, CH2P molecular ions, we developed an epitaxial silicon wafer with proximity gettering sinks under the epitaxial silicon layer to improve the gettering capability for metallic impurities. A complementary metal-oxide-semiconductor (CMOS) image sensor fabricated with this novel epitaxial silicon wafer has a markedly reduced number of white spot defects, as determined by dark current spectroscopy (DCS). In addition, the amount of nickel impurities gettered in the CH2P-molecular-ion-implanted region of this CMOS image sensor is higher than that gettered in the C3H5-molecular-ion-implanted region; and this implanted region is formed by high-density black pointed defects and deactivated phosphorus after epitaxial growth. From the obtained results, the CH2P-molecular-ion-implanted region has two types of complexes acting as gettering sinks. One includes carbon-related complexes such as aggregated C–I, and the other includes phosphorus-related complexes such as P4–V. These complexes have a high binding energy to metallic impurities. Therefore, CH2P-molecular-ion-implanted epitaxial silicon wafers have a high gettering capability for metallic impurities and contribute to improving the device performance of CMOS image sensors. (This manuscript is an extension from a paper presented at the 6th IEEE Electron Devices Technology & Manufacturing Conference (EDTM 2022)). [ABSTRACT FROM AUTHOR]

We discuss the needs and challenges of deployable security research by sharing our experience designing CryptoGuard, a high-precision tool for detecting cryptographic application programming interface misuses. Our project has produced multiple benchmarks as well as measurement results on state-of-the-art solutions. [ABSTRACT FROM AUTHOR]

The operating temperature has a critical impact on the electrical performance of solar cells. It has been shown that the temperature coefficient is not uniform across devices and often varies between different regions due to the inhomogeneous distributions of defects. In this study, temperature‐dependent photoluminescence imaging measurements are used to assess the influence of different processes such as gettering, firing and advanced hydrogenation on the temperature‐dependent electrical performance of cast‐mono silicon wafers. It is found that the height of the wafer within the ingot impacts the response of the temperature coefficient to different fabrication processes. Advanced hydrogenation is found to reduce the temperature sensitivity, more than expected solely from the improvement in implied open‐circuit voltage. Crystallographic defects are found to be the least temperature sensitive regions, indicating that their detrimental impact is reduced at higher operating temperatures. The interesting low temperature sensitivity in the defective regions is further investigated using hyperspectral photoluminescence imaging measurements and atom probe tomography. It is suggested that the reduced sensitivity is due to impurities decorating crystallographic defects. [ABSTRACT FROM AUTHOR]

Pulse diodes are widely used as part of high-frequency pulse circuits. However, it should be noted that the cost of pulsed diodes remains relatively high, due to the low yield of suitable devices when they are sorted according to the criteria of reverse current and rated capacitance. This is largely caused by the significant dependence of their electrical parameters on the density of structural defects and impurities in the active regions of the diodes. The study is devoted to identifying the causes and mechanisms of the low yield of diodes when they are sorted according to the criteria of reverse current and rated capacitance, as well as determining the possibility of using gettering operations to increase the yield of suitable devices. It is found that the low yield of the diodes is caused by the structural defects that are formed in the active areas of the diodes during high-temperature technological operations. The paper describes the mechanisms in which the structural defects affect the electrical parameters of diodes. The proposed technology for manufacturing diode structures using gettering of structural impurity defects by means of high-temperature annealing in an inert medium before the thermal oxidation operation is considered. It is shown that high-temperature annealing of silicon structures before thermal oxidation eliminates packing defects formed during epitaxy, cleans the active areas of the diodes from nuclei of defects and unwanted impurities, and prevents the formation of structural defects in them during the subsequent high-temperature thermal operations. The use of the proposed technology allows increasing the yield of suitable diode structures by 8.9% when sorted according to rated capacitance and by 9.4% when sorted according to reverse current, the level of reverse currents reducing by 2—9 times.

This work models competitive gettering of metals (Cu, Ni, Fe, Mo, and W) by boron, phosphorus, and dislocation loops, and connects those results directly to device performance. Density functional theory calculations were first performed to determine the binding energies of metals to the gettering sites, and based on that, continuum models were developed to model the redistribution and trapping of the metals. Our models found that Fe is most strongly trapped by the dislocation loops while Cu and Ni are most strongly trapped by the P4V clusters formed in high phosphorus concentrations. In addition, it is found that none of the mentioned gettering sites are effective in gettering Mo and W. The calculated metal redistribution along with the associated capture cross sections and trap energy levels are passed to device simulation via the recombination models to calculate carrier lifetime and the resulting device performance. Thereby, a comprehensive and predictive TCAD framework is developed to optimize the processing conditions to maximize performance of lifetime sensitive devices. [ABSTRACT FROM AUTHOR]

Chemical composition around diamond/silicon heterointerfaces fabricated by surface activated bonding (SAB) at room temperature is examined by energy-dispersive X-ray spectroscopy under scanning transmission electron microscopy. Iron impurities segregate just on the bonding interfaces, while oxygen impurities segregate off the bonding interfaces in the silicon side by 3–4 nm. Oxygen atoms would segregate so as to avoid the amorphous compound with silicon and carbon atoms, self-organized at the bonding interfaces in the SAB process. When the bonding interfaces are annealed at 1000 °C, the amorphous compound converts into cubic silicon carbide (c-SiC), and nano-voids 5–15 nm in size are formed at the region between silicon and c-SiC, at which the oxygen density is high before annealing. The nano-voids can act as the gettering sites in which metal impurities are preferentially agglomerated, and the impurity gettering would help to improve the electronic properties of the bonding interfaces by annealing. [ABSTRACT FROM AUTHOR]

Polycrystalline‐silicon/oxide (poly‐Si/SiOx) passivating contacts for high efficiency solar cells exhibit excellent surface passivation, carrier selectivity, and impurity gettering effects. However, the ultrathin SiOx interlayer can act as a diffusion barrier for metal impurities and this potentially slows down the overall gettering rate of the poly‐Si/SiOx structures. Herein, the factors that determine the blocking effects of the SiOx interlayers are identified and investigated by examining two general types of the SiOx interlayers: 1.3 nm ultrathin tunneling SiOx with negligible pinholes and 2.5 nm SiOx with thermally created pinholes. Iron is used as tracer impurity in silicon to quantify the gettering rate. By fitting the experimental gettering kinetics by a diffusion‐limited segregation gettering model, the blocking effects of the SiOx interlayers are quantified by a transport parameter. Both the oxide stoichiometry and pinhole density affect the effective transport of iron through SiOx interlayers. The oxide stoichiometry depends strongly on the oxidation method, while the pinhole density is affected by the activation temperature, doping concentration, doping technique, and possibly the dopant type as well. To enable a fast gettering process during typical high‐temperature formation of the poly‐Si/SiOx structures, a SiOx interlayer that is less stoichiometric or with a higher pinhole density is preferred. [ABSTRACT FROM AUTHOR]

The effects of germanium (Ge)‐codoping at 1018, 1019, or 1020 cm−3 level on the grown‐in oxide precipitates in 1014 cm−3 level nitrogen (N)‐doped Czochralski (NCZ) silicon have been investigated. It is found that Ge‐codoping enhances the formation of relatively larger grown‐in oxide precipitates. However, such enhancement effect weakens with the increasing Ge‐codoping concentration. On this basis, the effect of 1018 cm−3 level Ge‐codoping on the near‐surface denuded zone (DZ) and bulk microdefects (BMDs) associated with oxygen precipitation in NCZ silicon subjected to an anneal at 1100 °C for 4 h (1100 °C/4 h) has been paid close attention. Moreover, the sustainability of the DZ in the 1100 °C/4 h ‐annealed NCZ silicon subjected to a "copper decoration" or a rigorous oxygen precipitation anneal featuring a prolonged nucleation anneal has been addressed. Thus, it is technologically significant to learn that for the 1100 °C/4 h ‐annealed NCZ silicon, the 1018 cm−3 level Ge‐codoping can remarkably increase the BMD density to better satisfy the requirement of internal gettering (IG) and also ensure the existence of a well‐defined DZ. Finally, the mechanism underlying the effect of Ge‐codoping on the formation of grown‐in oxide precipitates in NCZ silicon has been tentatively elucidated. [ABSTRACT FROM AUTHOR]

In silicon power semiconductors, platinum is used to improve the switching characteristics of the devices by adjusting the lifetime of the minority charge carriers. Platinum diffusion in silicon has been a research topic for many scientists over the past decades. Herein, the current state of knowledge is presented together with the concepts developed for its use in silicon power devices. The relevant processes include diffusion from a platinum silicide, postimplantation annealing, and phosphorus‐diffusion gettering. The evaluation of corresponding experiments and the calibration of the models have not only resulted in more narrow limits for the equilibrium concentrations of vacancies and self‐interstitials in silicon and the transport capacity of interstitial platinum, but also in improved devices. [ABSTRACT FROM AUTHOR]

The study considers the reasons and mechanisms of degradation of reverse characteristics of varicaps with aluminum-based ohmic contacts. The authors present and analyze the experimental results on how gettering affects the reverse current of varicaps, as well as possible mechanisms of such effect. Gettering was performed with a getter site created on the back side of the substrate before the epitaxial layer is deposited on the working side of the substrate. The article demonstrates that the proposed technology using gettering is rather effective in reducing the level of reverse currents and in increasing the yield of devices.

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures.

It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 ° C to 900 ° C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 ° C. The gettering process is found to become reaction-limited at higher temperatures. [ABSTRACT FROM AUTHOR]

We report a systematic study into the effects of long low temperature (≤500 °C) annealing on the lifetime and interstitial iron distributions in as-grown multicrystalline silicon (mc-Si) from different ingot height positions. Samples are characterised in terms of dislocation density, and lifetime and interstitial iron concentration measurements are made at every stage using a temporary room temperature iodine-ethanol surface passivation scheme. Our measurement procedure allows these properties to be monitored during processing in a pseudo in situ way. Sufficient annealing at 300 °C and 400 °C increases lifetime in all cases studied, and annealing at 500 °C was only found to improve relatively poor wafers from the top and bottom of the block. We demonstrate that lifetime in poor as-grown wafers can be improved substantially by a low cost process in the absence of any bulk passivation which might result from a dielectric surface film. Substantial improvements are found in bottom wafers, for which annealing at 400 °C for 35 h increases lifetime from 5.5 μs to 38.7 μs. The lifetime of top wafers is improved from 12.1 μs to 23.8 μs under the same conditions. A correlation between interstitial iron concentration reduction and lifetime improvement is found in these cases. Surprisingly, although the interstitial iron concentration exceeds the expected solubility values, low temperature annealing seems to result in an initial increase in interstitial iron concentration, and any subsequent decay is a complex process driven not only by diffusion of interstitial iron. [ABSTRACT FROM AUTHOR]

The fundamental understanding of molecule-surface reactions is of great importance to heterogeneous catalysis, motivating many theoretical and experimental studies. Even though much attention has been dedicated to the dissociative chemisorption of N2 on tungsten surfaces, none of the existing theoretical models has been able to quantitatively reproduce experimental reaction probabilities for the sticking of N2 to W(110). In this work, the dissociative chemisorption of N2 on W(110) has been studied with both static electronic structure and ab initio molecular dynamics (AIMD) calculations including the surface temperature effects through surface atom motion. Calculations have been performed using density functional theory, testing functionals that account for the long range van der Waals (vdW) interactions, which were previously only considered in dynamical calculations within the static surface approximation. The vdW-DF2 functional improves the description of the potential energy surface for N2 on W(110), returning less deep molecular adsorption wells and a better ratio between the barriers for the indirect dissociation and the desorption, as suggested by previous theoretical work and experimental evidence. Using the vdW-DF2 functional less trapping-mediated dissociation is obtained compared to results obtained with standard semi-local functionals such as PBE and RPBE, improving agreement with experimental data at Ei = 0.9 eV. However, at Ei = 2.287 and off-normal incidence, the vdW-DF2 AIMD underestimates the experimental reaction probabilities, showing that also with the vdW-DF2 functional the N2 on W(110) interaction is not yet described with quantitative accuracy. [ABSTRACT FROM AUTHOR]

The bulk minority-carrier lifetime in p- and n-type kerfless epitaxial (epi) crystalline silicon wafers is shown to increase >500x during phosphorus gettering. We employ kinetic defect simulations and microstructural characterization techniques to elucidate the root cause of this exceptional gettering response. Simulations and deep-level transient spectroscopy (DLTS) indicate that a high concentration of point defects (likely Pt) is "locked in" during fast (60 °C/min) cooling during epi wafer growth. The fine dispersion of moderately fast-diffusing recombination-active point defects limits as-grown lifetime but can also be removed during gettering, confirmed by DLTS measurements. Synchrotron-based X-ray fluorescence microscopy indicates metal agglomerates at structural defects, yet the structural defect density is sufficiently low to enable high lifetimes. Consequently, after phosphorus diffusion gettering, epi silicon exhibits a higher lifetime than materials with similar bulk impurity contents but higher densities of structural defects, including multicrystalline ingot and ribbon silicon materials. Device simulations suggest a solar-cell efficiency potential of this material >23%. [ABSTRACT FROM AUTHOR]

Substrate gettering and the contribution to the contamination reduction of backside layers are evaluated after high‐temperature annealing, following intentional iron contamination at the backside in silicon epitaxial wafers typical of power technologies. Iron is detected at the frontside by deep‐level transient spectroscopy within a depth corresponding to the actual devices. Herein, contamination occurring at the beginning of the semiconductor process flow is simulated and the role of the different gettering mechanisms is isolated. Substrate boron in epitaxial p over p+ wafers is effective in more than halving iron contamination at the front compared with a p‐only substrate, especially at high contamination doses. In the absence of a specific thermal cycle for oxygen precipitation and growth in the bulk, long thermal treatment at 1200 °C induces a significant precipitate growth even in the beginning of the process, greatly contributing to iron gettering in the bulk. However, this effect is found to strongly depend on the silicon condition after crystal growth. No significant contribution to iron gettering from a backside polycrystalline silicon layer is found after high‐temperature annealing, whereas a backoxide acts as diffusion barrier, effectively screening the substrate from contamination only for short thermal treatments or annealing temperature below 1000 °C. [ABSTRACT FROM AUTHOR]

The effects of germanium (Ge)-doping with concentrations in the range of 1018–1020 cm−3 on oxygen precipitation (OP) in Czochralski (CZ) silicon wafers subjected to the low (800 °C)–high (1000 °C) two-step anneal following the rapid thermal anneal (RTA) at 1250 °C, which is actually the RTA-based internal gettering (IG) process, have been comprehensively investigated. It is found that whether the Ge-doping enhances or suppresses OP in the CZ silicon wafers with the aforementioned three-step anneal is quite dependent on the Ge-doping concentration and on the nucleation time at 800 °C. On the one hand, the Ge-doping is experimentally and theoretically revealed to facilitate the formation of vacancy-oxygen (VOm, m ≥ 1) complexes in the CZ silicon wafer during the prior RTA at 1250 °C. In this sense, the Ge-doping enhances the nucleation of oxide precipitates thus being beneficial for OP. On the other hand, the considerably high concentration of Ge-doping introduces compressive stress into silicon lattice in a manner due to the slightly larger covalent radius of Ge atom. Such introduced compressive stress not only increases the critical size required for the onset growth of oxide precipitate nuclei at 1000 °C but also suppresses the growth of oxide precipitates in the course of 1000 °C anneal. Thus, the Ge-doping is unfavorable for the growth of oxide precipitates. Based on the advantageous and disadvantageous effects of Ge-doping on the nucleation and growth of oxide precipitates, respectively, which have been definitely revealed in this work, the above finding has been essentially understood. Of practical significance, this work offers technological guideline to improve the IG capability of CZ silicon wafer through adopting appropriate Ge-doping and RTA-based annealing scheme. [ABSTRACT FROM AUTHOR]