Phosphorus Concentration Profiles Research Articles

Estimation of Phosphorus Concentration in Silicon Thin Film on Glass Using ToF-SIMS

Evaluating the impurity concentrations in semiconductor thin films using time of flight secondary ion mass spectrometry (ToF-SIMS) is an effective technique. The mass interference between isotopes and matrix element in data interpretation makes the process complex. In this study, we have investigated the doping concentration of phosphorus in, phosphorus doped silicon thin film on glass using ToF-SIMS in the dynamic mode of operation. To overcome the mass interference between phosphorus and silicon isotopes, the quantitative analysis of counts to concentration conversion was done following two routes, standard relative sensitivity factor (RSF) and SIMetric software estimation. Phosphorus doped silicon thin film of 180 nm was grown on glass substrate using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using ToF-SIMS, the phosphorus-31 isotopes were detected in the range of 101~104 counts. The silicon isotopes matrix element was measured from p-type silicon wafer from a separate measurement to avoid mass interference. For the both procedures, the phosphorus concentration versus depth profiles were plotted which agree with a percent difference of about 3% at 100 nm depth. The concentration of phosphorus in silicon was determined in the range of 1019~1021 atoms/cm3. The technique will be useful for estimating distributions of various dopants in the silicon thin film grown on glass using ToF-SIMS overcoming the mass interference between isotopes.

Diffusion of Phosphorus and Boron from Atomic Layer Deposition Oxides into Silicon

Oxides containing group III or group V elements (B2O3/Sb2O5 and P2O5/Sb2O5) are grown by plasma‐assisted atomic layer deposition (ALD) on single‐crystalline silicon and serve as dopant sources for conformal and shallow doping. Transport phenomena in ALD‐oxide–Si structures during rapid thermal annealing (RTA) are investigated subsequently by X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS). The XPS and TEM analyses of the annealed ALD‐oxide–Si structures demonstrate that the ALD oxide converts to a silicon oxide and partially evaporates during annealing. In addition, dopant‐containing, spherical, and partially crystalline particles form in the oxide, and Si‐P precipitates at the oxide–Si interface. After diffusion annealing at 1000 °C, the SIMS analyses reveal phosphorus and boron concentration profiles in the silicon substrate with maximum concentrations exceeding their solid solubility limits by roughly one order of magnitude. Experimental doping profiles of phosphorus and boron in silicon are compared with simulation results, considering a slight injection of self‐interstitials and dynamical defect clustering.

Model of phosphorus diffusion in silicon for highly doped solar cell emitter layer

Purpose The purpose of this paper was the development of a model enabling precise determination of phosphorus concentration profile in the emitter layer of a silicon solar cell on the basis of diffusion doping process duration and temperature. Fick’s second law, which is fundamental for describing the diffusion process, was assumed as the basis for the model. Design/methodology/approach To establish a theoretical model of the process of phosphorus diffusion in silicon, real concentration profiles measured using the secondary ion mass spectrometry (SIMS) method were used. Samples with the phosphorus dopant source applied onto monocrystalline silicon surface were placed in the heat zone of the open quartz tube furnace, where the diffusion process took place in the temperature of 880°C-940°C. The measured real concentration profiles of these samples became template profiles for the model in development. Findings The model was developed based on phenomena described in the literature, such as the influence of the electric field of dopant ionized atoms and the influence of dopant atom concentration nearing the maximum concentration on the value of diffusion coefficient. It was proposed to divide the diffusion area into low and high dopant concentration region. Originality/value A model has been established which enabled obtaining a high level of consistency between the phosphorus concentration profile developed theoretically and the real profile measured using the SIMS method. A coefficient of diffusion of phosphorus in silicon dependent on dopant concentration was calculated. Additionally, a function describing the boundary between the low and high dopant concentration regions was determined.

Redistribution of phosphorus during NiPtSi formation on in-situ doped Si

This study focuses on silicide formation on phosphorus in-situ doped samples, the phosphorus diffusion and its distribution during the solid-state reaction. The silicidation is achieved with a 16 nm thin film of Ni0.9Pt0.1 followed by a two steps annealing process using rapid thermal annealing, selective etching and dynamic surface annealing. Silicide formation is investigated thanks to in-situ X-ray diffraction and X-ray reflectivity, while the phosphorus concentration profiles after silicidation are obtained by Time-of-Flight Secondary Ion Mass Spectroscopy. Based on these profiles, simulation of the phosphorus redistribution is achieved. The latter is linked to a fast diffusion in the silicide and at its grain boundaries. This feature is put forward to explain how doping may influence the phase sequence of silicide formation.

Redistribution of phosphorus during Ni0.9Pt0.1-based silicide formation on phosphorus implanted Si substrates

Phosphorus diffusion and its distribution during the solid-state reactions between Ni0.9Pt0.1 and implanted Si substrates are studied. Silicidation is achieved through a first rapid thermal annealing followed by a selective etching and a direct surface annealing. The redistribution of phosphorus in silicide layers is investigated after the first annealing for different temperatures and after the second annealing. Phosphorus concentration profiles obtained thanks to time of flight secondary ion mass spectrometry and atom probe tomography characterizations for partial and total reactions of the deposited 7 nm thick Ni0.9Pt0.1 film are presented. Phosphorus segregation is observed at the Ni0.9Pt0.1 surface and at Ni2Si interfaces during Ni2Si formation and at the NiSi surface and the NiSi/Si interface after NiSi formation. The phosphorus is evidenced in low concentrations in the Ni2Si and NiSi layers. Once NiSi is formed, a bump in the phosphorus concentration is highlighted in the NiSi layer before the NiSi/Si interface. Based on these profiles, a model for the phosphorus redistribution is proposed to match this bump to the former Ni2Si/Si interface. It also aims to bind the phosphorus segregation and its low concentration in different silicides to a low solubility of phosphorus in Ni2Si and in NiSi and a fast diffusion of phosphorus at their grain boundaries. This model is also substantiated by a simulation using a finite difference method in one dimension.

Formation of shallow front emitters for solar cells by rapid thermal processing

AbstractIn this work we report on formation of shallow front emitters by phosphorus in‐diffusion during rapid thermal processing (RTP). Both Filmtronics P509 diffusant and concentrated phosphoric acid were deposited on 1 Ωcm p‐type mono crystalline silicon samples. Diffused shallow emitters were realized by annealing at 900 °C and 950 °C in the range of 10 – 40 s using an Annealsys AS‐Micro furnace. The chemical concentration versus depth profiles of phosphorus were measured by secondary ion mass spectrometry (SIMS) and the sheet resistance was measured by four‐point probing. It is found that emitters with depths in the range 100 – 275 nm and the maximum doping concentrations in the range 2 × 1020 – 1 × 1021 cm–3 can be formed after RTP.By varying the RTP‐conditions, a sheet resistance of 314 – 40 Ω/sq for diffusant‐treated samples and of 175 – 40 Ω/sq for phosphoric acid treated samples are obtained. The P509 diffusant and concentrated phosphoric acid gave similar emitter profiles. High solubility of phosphorus in silicon at elevated temperatures ensured a low sheet resistance even for short annealing times. It is shown that phosphorus in‐diffusion during RTP is a viable method in formation of shallow front emitters for solar cells. In particular, the highest phosphorus peak concentration and the shallowest diffusion profile were achieved by in‐diffusion from dehydrated phosphoric acid (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Liquid-Phase Diffusion of Phosphorus Atoms in Laser-Doped Crystalline Silicon Solar Cells

In this paper, a nonlinear numerical model of laser melting of crystalline silicon solar cells and phosphorus diffusion has been established by finite difference method implemented in MATLAB. Based on the features of liquid-phase diffusion of phosphorus atoms in melting silicon, theoretical simulation for phosphorus concentration profiles and explanation for the mechanism of laser doping are achieved. The theoretical phosphorus concentration profile is in good agreement with the experimental SIMS data.

Phosphorus release from sediments in a treatment wetland: Contrast between DET and EPC 0 methodologies

Wetlands are capable of reducing nutrient loadings to receiving water bodies, and hence many artificial wetlands have been constructed for wastewater nutrient removal. In this study, diffusive equilibrium in thin films (DETs) and equilibrium phosphorus concentration (EPC 0) analysis were used to examine the role of sediment as a nutrient source or sink in a constructed treatment wetland in summer. The effect of dredging on sediment-water nutrient exchange was also studied. Soluble reactive phosphorus (SRP), ammonium (NH 4 +) and sulphate (SO 4 2−) concentration profiles were measured by DET across the sediment-water interface (SWI) in both a settling pond and iris reed bed within the wetland. The SRP concentrations in the sediment pore-waters of the settling pond were extremely high (up to 29,500 μg l −1) near the SWI. This is over an order of magnitude higher than the levels found in the water column, which in turn are over an order of magnitude higher than environmental levels proposed to limit eutrophication in rivers. The profiles demonstrated an average net release of SRP and NH 4 + from the settling pond sediment to the overlying water of 58 mg m −2 d −1 (±32 mg m −2 d −1 (1 sd)) and 16 mg m −2 d −1 (±25 mg m −2 d −1 (1 sd)), respectively. The DET SO 4 2− concentration profiles revealed that the sediment was anoxic within 2 cm of the SWI. Dredging of the reed bed made no significant difference to the P release characteristics across the SWI. The EPC 0s were much lower than the SRP concentration of the overlying water, indicating that the sediment had the potential to act as a phosphate sink. The apparent contradiction of the DET and EPC 0 results is attributed to the fact that DET measurements are made in situ, where as EPC 0 measurements are ex situ. These results show that substantial releases of P can occur from wetland sediments, and also highlight the need for caution when interpreting ex situ EPC 0 analytical results.

Measurement of soluble reactive phosphorus concentration profiles and fluxes in river-bed sediments using DET gel probes

DET (diffusive equilibrium in thin films) gel probes were used for sampling river-bed sediment porewaters, to characterise in situ soluble reactive phosphorus (SRP) concentration profiles and fluxes. DET probes were deployed in three contrasting rural streams: (1) a headwater ‘pristine’ stream, with minimal P inputs from low intensity grassland and no point sources, (2) an intensively cultivated arable catchment, and (3) a stream subject to high P loadings from sewage effluent and intensive arable farming. The DET results showed highly enriched porewater SRP concentrations of between ca. 400 and 5000 ug-P/1 in the sewage-impacted stream. In contrast, the arable and pristine streams had porewater SRP concentrations <70 ug-P/1 and <20 ug-P/1, respectively. Porewater SRP concentration profiles in both the sewage-impacted and arable-impacted streams showed well-defined vertical structure, indicating internal sources and sinks of SRP within the sediment. However, there was little variability in porewater SRP concentrations in the pristine stream. The DET porewater profiles indicated net diffusion of SRP (a) from the overlying river water into the surface sediment and (b) from subsurface sediment upwards towards the sediment–water interface. A mass balance for the sewage-impacted site showed that the influx of SRP into the surface sediments from the overlying river water was small (ca. 1% of the daily river SRP load). The DET results indicated that, in the arable and sewage-impacted streams, the surface ‘cap’ of fine sediment may play an important role in inhibiting upward movement of SRP from subsurface porewaters into the overlying river water, under steady-state, low-flow conditions.

Phosphorus speciation, burial and regeneration in coastal lagoon sediments of the Gippsland Lakes (Victoria, Australia)

Environmental context. Eutrophication can lead to the production of harmful algal blooms and is one of the world’s most serious water quality issues. Phosphorus is potentially the limiting macro-nutrient in fresh, estuarine and some marine waters. Consequently, it plays a crucial role in determining the ecological status of many aquatic ecosystems. Considerable effort has been invested in monitoring dissolved reactive phosphorus and total phosphorus in the water column, but less is known about the speciation of phosphorus, particularly in the sediment. This compartment is an important and dynamic reservoir of phosphorus and a potential long-term source of phosphorus release to the water column by the sediment–water interface. This paper investigates the solid-phase speciation and reorganisation of phosphorus within the sediments of a shallow lake system in south-east Australia (the Gippsland Lakes) which suffers from recurring harmful algae blooms. Various strategies are proposed to determine the minimum realistic timescale required to deplete the sediment of labile and reactive phosphorus species. Abstract. Solid-phase phosphorus pools in the sediments of two shallow lakes (Wellington and Victoria) in the Gippsland Lakes coastal lagoon system of south-east Australia are discussed. Cores (20-cm depth) were taken in summer and winter in both lakes and a sequential extraction scheme (SEDEX) was used to profile the exchangeable P (Pex), iron oxide/hydroxide bound P (PFe), authigenic P (Pauth), detrital P (Pdet) and organic P (Porg). Pore-water (Ppw) dissolved reactive phosphorus concentration profiles were also measured. The dominant forms of P were PFe (up to 53%) and Porg (35–55%), with the PFe fraction playing a key role in the short-term retention of P in the sediment. Benthic phosphorus fluxes at the sediment–water interface (μmol m–2 d–1) were determined from the sequential extraction data. The results were compared with flux measurements from the complementary approaches of benthic chamber experiments and Fickian diffusion calculations, to allow an insight into the nature and seasonal variations of the fluxes. The burial flux of phosphorus was also estimated from excess 210Pb profiles in the sediment of the lakes. All of these data were used to produce a phosphorus budget for the Gippsland Lakes which suggested that the sediment represents a substantial source of phosphorus within the lakes and thus clearly highlights the importance of the sedimentary compartment in shallow eutrophic ecosystems. Minimum realistic timescales for complete labile phosphorus depletion from the sediment (assuming no resupply from the sediment–water interface) were calculated and ranged from 8 to 22 years.

Two-dimensional small-scale variability of pore water phosphate in freshwater lakes: results from a novel dialysis sampler.

Vertical concentration profiles of soluble reactive phosphorus (SRP) in the upper sedimentary zone of freshwater lakes are an important means for studying internal phosphorus (P) loading and to gain insight into early diagenetic processes. The interpretation of such pore water profiles generally neglects the occurrence of horizontal variability at a specific sampling site. To further examine this variability, we have designed a novel two-dimensional sampler (2D peeper) consisting of 2280 chambers at a spatial resolution of 9 mm providing a sampling area of 43 x 44 cm. This new device was deployed in three eutrophic lakes in north-eastern Germany. The resulting 2D images of the SRP concentrations, diffusive fluxes, and turnover rates revealed systematic vertical and horizontal structures with local niches of increased phosphorus release. Thus, the extrapolation of P flux calculations based on one-dimensional pore water profiles may lead to a considerable error. The observed small-scale horizontal heterogeneity, probably mainly caused by organisms, was larger in the biologically more active Lake Müllrose and Süsser See than in the deeper Arendsee where meio- and macrozoobenthos were missing. In all cases, the variability was highest at the sediment-water interface and diminished with sediment depth.

Redistribution of phosphorus implanted into silicon doped heavily with boron

The special features of redistribution of phosphorus implanted into silicon wafers with a high concentration of boron (NB=2.5×1020 cm−3) were studied. It is shown that, in silicon initially doped heavily with boron, the broadening of concentration profiles of phosphorus as a result of postimplantation annealing for 1 h in the temperature range of 900–1150°C is significantly less than in the case of lightly doped silicon. The results are interpreted in terms of the impurity-impurity interaction with the formation of stationary boron-phosphorus pairs. The binding energy of boron-phosphorus complexes in silicon was estimated at 0.6–0.8 eV.

Phosphorus concentration profile in silicon produced by means of the nuclear reaction [formula omitted

A possibility to introduce phosphorus in silicon, different from direct phosphorus ion implantation, is discussed. The method is based on the nuclear reaction 30 Si( p,γ) 31 P that occurs when a silicon sample is bombarded with energetic protons. It is shown that the pattern of the phosphorus concentration profile can be accurately controlled through an appropiate choice of the energetic characteristics of the proton beam.

Electronic and vibrational spectra of InP quantum dots formed by sequential ion implantation

Sequential ion implantation of indium and phosphorus into silica combined with controlled thermal annealing has proven to be a novel and effective technique to fabricate InP quantum dots in dielectric hosts. This technique has been applied to synthesize other III–V and II–VI quantum dots. Due to the unique bimodal distribution of the indium in a silica host and a stoichiometric mismatch between the indium and phosphorus concentration profiles, it is believed that two different-sized InP quantum dots were fabricated. More importantly, we have shown that the infrared reflectance technique is a very effective method to identify the species in the dielectric host and is also a powerful tool to investigate surface phonon modes.

Studies on the concentration profiles and growth rate of GaP by liquid-phase epitaxy

The concentration profiles of phosphorus at successive equally spaced layers in front of a GaP crystal growing under normal conditions of liquid phase epitaxy (LPE) have been simulated using the appropriate boundary conditions and hence the growth rate of GaP has been calculated. The concentration gradient at the interface has been used to calculate the growth rate and hence the amount etched or grown as a function of time has been investigated. Our theoretical predictions have been compared with the reported experimental values and the results are discussed in detail.

Dopant and Strain Dependence of Extended Defect Generation in Silicon by 1-MeV Electron Irradiation

ABSTRACTResults are presented of an in-situ study of 1-MeV electron irradiation induced {113}-defect generation in silicon with boron, phosphorus or arsenic doped surface layers. By 1-MeV electron irradiation in a high voltage transmission electron microscope, {113}-defects are dorni-nandy formed in areas with a well defined dopant concentration range which depends on the tjpe of dopant atom, the irradiation temperature and fluence and the sample thickness. The observations for samples with boron and phosphorus concentration profiles are compared with published data on electron irradiation induced ( 113}-defect formation in uniformly doped silicon. In the present paper first results on heavily arsenic doped silicon are presented. It is shown that ihe observed dopant dependence of the {113}-defect generation can be understood on the basis of known point defect reactions. A few irradiation experiments are also performed on a local isolation structure illustrating for the first time the influence of localised tensile and compressive strain fields on {113} -defect nucleation.

Macro-mineral concentrations in milk of two goat breeds at different stages of lactation

First-year freshened French-Alpine and Anglo-Nubian does, ten each, were randomly selected from the University milking herd to study concentration profiles of calcium, phosphorus, sodium, potassium, magnesium and sulphur for 0 h, 6 h, 12 h, 24 h, and 2, 3, 10, 30, 60, 90, 120 and 150 days postpartum and to evaluate differences in levels of teh six major minerals between breeds, stages of lactation and their interactions. Overall mean contents (mg/100ml) for Alpines and Nubians were: calcium: 138.6, 139.3; phosphorus: 129.2, 142.8; sodium: 55.4, 66.1; potassium: 110.8, 87.0; magnesium: 17.6, 19.2; sulphur: 2.97, 2.81, respectively. For pooled breed data, there were no differences in mean contents of calcium, phosphorus and sodium among lactation periods, but a few variations occurred in separate breed cases. The magnesium and sulphur levels revealed typical lactation trends, where colostrum contained significantly ( P<0.05) greater levels than normal milk. The potassium levels fluctuated greatly by periods, and potassium and sodium levels were significantly ( P<0.01) different between breeds. Interactions between breeds and lactation periods had no influence on the levels of any minerals. There were significant ( P<0.01), positive correlations between calcium and phosphorus and negative correlations between sodium and potassium or calcium in the milk.

Two-dimensional phosphorus diffusion for soft drains in silicon MOS transistors

Phosphorus has a considerably less steep concentration profile than arsenic. Therefore phosphorus is considered as an alternative dopand for soft drain concepts in future MOS devices. In-diffusion of phosphorus starting from a high surface concentration generatesexcess point defects which diffuse into the depth of the crystal and lead to a tail in the phosphorus concentration profile by considerably enhancing the phosphorus diffusion in this region. It is also well known that the interface between silicon and a non growing oxide acts as a sink for excess point defects. Since source/drain areas of MOS transistors are surrounded by gate and isolation oxides, the question arises how the resulting excess point defect distribution may influence the lateral and vertical diffusion profile of phosphorus and hence the channel length and the junction depth of the source/drain region in a MOS device. We extended the one-dimensional Fair-Tsai model of phosphorus diffusion into two dimensions and incorporated that the interface between silicon and a gate oxide acts as a sink for excess point defects and modifies their distribution. The appropriate code was implemented in the two-dimensional process simulation program LADIS. Based on this extended model two-dimensional simulations of phosphorus drains have been performed and compared to experimental results and to results from other numerical models. It turns out that the presence of the gate oxide reduces the tail in the phosphorus concentration profile, considerably in lateral direction and less pronounced in vertical direction. Limitations of the model will be discussed in detail.

Theoretical estimates of phosphorus concentration profiles across grain boundaries in Fe-P and Fe Ni-P systems

The equilibrium “intergranular segregation extent (ISE)” of P in the above two alloy systems has been calculated on the basis of a model presented here. The ISE of P is defined as the monolayer thickness of a P-enriched bulk region adjacent to the grain boundary, where a normalized concentration of P is greater than one-tenth of that of the grain boundary. The model is in principle analogous to Ono's discrete lattice approach based on a simple regular solution model under the assumption of the nearest neighbor interaction of atoms. The ISE of P thus calculated is. irrespective of the Ni-concentration of the alloys, ~ one monolayer thick at most whatever magnitudes are chosen for the various parameters adopted within their limited ranges in the present model. This suggests that the equilibrium intergranular segregation of P occurs exclusively at grain boundaries per se in ferrous alloys.

Phosphorus distribution in TaSi2 films by diffusion from a polycrystalline silicon layer

Secondary ion mass spectroscopy was used to measure phosphorus concentration profiles in TaSi2 thin films deposited on P doped polycrystalline Si/SiO2/Si wafers by cosputtering. Fast redistribution of P in TaSi2 takes place by its up-diffusion from the polycrystalline Si layer. Radioactive assay of 32P obtained by neutron activation confirmed the fast-diffusion character of P in TaSi2. From preliminary results the temperature dependence of the diffusion coefficients over the temperature range of 664 °C-913 °C can be expressed by the following relations: Dc=6.44×10−10 exp[−0.61/(kT)] and Da=2.0×10−8 exp[−0.76/(kT)], where Dc and Da represent diffusion in the silicide film near and away from the surface, respectively.