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Monolithic integrated pressure sensor systems are realized by the combination of two different technologies: CMOS-technology for the electrical part and MEMS-technology for the pressure sensor part. The paper describes the modification of such pressure sensor systems to extend their original nominal pressure range from 600 mbar to the low pressure range of 40 mbar by keeping a sufficient signal to noise ratio and without changing the original mask set. The general methodology is described, and a comparison between theoretical signal evaluation and measurement is given. The study concentrates on the aspect of the different piezocoefficients for various Boron doping concentrations of the piezoresistors

In recent years the relevance of passivated emitter and rear contact solar cells for industrial application increased due to significantly higher cell efficiencies compared to full area back surface field solar cells. However, the formation of local Al contacts is particularly sensitive to the manufacturing process parameters. Under non-optimized conditions, the eutectic in local Al contacts is missing and so-called voids are formed. So far, their impact onto the electrical parameters of the solar cells is not fully understood, mainly because of their difficult spatially resolved detection. Within this work the application of scanning acoustic microscopy circumvents this difficulty and allows a classification of local contacts in terms of “voids” or “filled contacts” on large cell area. The passivation quality of the BSF in the local contacts is investigated in detail through the local internal quantum efficiency (IQE) measured by light beam induced current (LBIC). It is found that there is a large spreading for the IQE values, attributed to a variation in BSF layer thickness. In addition, LBIC measurements of voids are fitted by 2D simulations, according to a detailed modelling of the surface recombination velocities (SRV) in local contacts. The final model is based on a non-uniform SRV in the void's vicinity, attributed to laser damage close to the interface. It is demonstrated that the electrical parameters of the solar cell are affected by voids only when their surface is not sufficiently passivated by a local BSF.

Amorphous silicon (a-Si) is common in the production of technical devices and can be deposited by several techniques. In this study intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370 degrees C. Secondary ion mass spectrometry of a boron doped (p) a-Si layer shows that the concentration of dopants in the sputtered layer becomes the same as present in the sputter-target. Improved surface passivation of phosphorous doped 5 Omega cm, FZ, (n) c-Si can be achieved by post-hydrogenation yielding a minority carrier lifetime of similar to 360 mu s finding an optimum for similar to 40 nm thin films, deposited at 325 degrees C. This relatively low minority carrier lifetime indicates high disorder of the hydrogen-less sputter deposited amorphous network. Post-hydrogenation leads to a decrease of the number of localized states within the band gap. Optical band gaps (Taucs gab as well as E-04) can be determined to similar to 1.88 eV after post-hydrogenation. High resolution transmission electron microscopy and optical Raman investigations show that the sputtered layers are amorphous and stay like this during post-hydrogenation. As a consequence of the missing hydrogen during deposition, sputtered a-Si forms a rough surface compared to CVD a-Si. Atomic force microscopy points out that the roughness decreases by up to 25% during post-hydrogenation. Nuclear resonant reaction analysis permits the investigation of hydrogen depth profiles and allows determining the diffusion coefficients of several post-hydrogenated samples from of a model developed within this work. A dependency of diffusion coefficients on the duration of post-hydrogenation indicates trapping diffusion as the main diffusion mechanism. Additional Fourier transform infrared spectroscopy measurements show that hardly any interstitial hydrogen exists in the post-hydrogenated a-Si layers. The results of this study open the way for further hydrogen diffusion experiments which require an initially unhydrogenated drain layer.

Ideally formed local Al-contacts of passivated emitter and rear contact solar (PERC) cells feature an eutectic and an uniform local back surface field (LBSF). Under certain conditions the eutectic is missing after the co-firing process, referring to the well-known voids. So far light beam induced current (LBIC) measurements are used to obtain information concerning the passivation quality of the LBSF in local contacts in general. In addition, the destructive technique of scanning electron microscopy (SEM) is established for distinguishing whether a void features a sufficiently thick BSF-layer or a very thin/no BSF-layer. However, both methods are very time consuming.This paper shows a non-destructive and fast characterization of solar cells by applying electroluminescence (EL) and photoluminescence (PL) measurements to investigate the effect on the electrical parameters after locating the voids by scanning acoustic microscopy (SAM). For filled contacts EL and PL measurements correlate well with the resulting values for series resistance (RS) and dark saturation current density (j0): the formed LBSF leads to a good surface passivation (high PL signal intensity, low value for j0) and the eutectic layer ensures a good electrical contact (high EL signal intensity, low value for RS). Voids with a sufficiently thick LBSF show a high PL signal intensity whereas the intensity is significantly reduced for a very thin or completely missing LBSF. Increased values for RS can be explained by the missing eutectic layer. In addition, the electrical connection of the LBSF to the paste can be derived from the value of RS. published

Two metastable defects with energy levels at Ec-0.28eV and Ec-0.37eV, which previously have been reported in proton implanted- and in proton implanted and annealed crystalline silicon are discussed. Recent results on the peculiar behavior of these defects upon periodical application of two different bias conditions during DLTS measurement are reviewed. Two specifically designed DLTS measurement sequences are proposed in order to further reveal the defects transformation rates and respective activation energies.

Deep-level defects remaining in the upper half of the band-gap of silicon implanted with protons at fluences and annealing temperatures typically used for proton-implantation doping are investigated. For proton fluences in the range of several 1013 cm−2 to several 1014 cm−2, a multitude of deep-level defects remain active in comparatively high concentrations of up to 1013 cm−3 even after anneals at temperatures up to 500 °C. The detected deep-levels are assigned to known lattice defects on the basis of their electrical characteristics obtained by Fourier-transform DLTS measurements. Despite the low oxygen content of the float-zone silicon used, a large number of the detected defects are ascribed to (non-)hydrogenated vacancy-oxygen defects. The annealing temperature ranges, in which the deep-level defects were detected, are shown. Furthermore, the dependencies of the deep-level defects on the proton fluence and their depth distributions in the implantation profile are investigated.

The impact of the thermal budget on hydrogen-related donor profiles in high purity silicon implanted with protons in the MeV energy range is investigated. The appearance of donor profiles is limited to the annealing temperature between 350 {degree sign}C and 500 {degree sign}C. The activation of doping profiles is limited by the diffusion of implanted hydrogen from the end-of-range region throughout the radiation-induced damage. This formation process of profiles is described by a diffusion model with an effective activation energy of 1.2 eV. The hydrogen-related donors are radiation-induced defect complexes decorated by hydrogen. The thermal stability of these donors is limited by dissociation. The deactivation of the doping is modeled by two hydrogen-related donor species with effective dissociation energies of 2.5 eV and 3 eV. The described formation and dissociation mechanisms define upper and lower limits of the post-implantation thermal budget, respectively, for sensible use of proton implantation doping in crystalline Silicon.

Electron beam induced current (EBIC) measurements were used to determine the doping type and to extract the diffusion length in proton implanted silicon wafers. This method makes it possible to distinguish between n-type and p-type at low carrier concentrations. Because of the defects caused by the implantation, the diffusion length is much smaller in the implanted than in the non-implanted regions.

Capacitance-voltage (CV) spectroscopy of classic metal-insulator-semiconductors (MIS) using insulating oxides as well as highly passivating intrinsic and hydrogenated amorphous silicon ((i) a-Si:H) has been discussed extensively in literature, particularly with regard to photovoltaic applications. Imperfectly passivating as well as thermal or light-induced degraded (i) a-Si:H exhibits a reduced passivation quality and an increased defect-based shunt conductivity. These properties cannot be accounted for by classical CV spectroscopy as described in literature for insulating oxides or highly passivating (i) a-Si:H. To characterize such imperfectly passivating or degraded (i) a-Si:H thin films by CV spectroscopy, the required MIS samples have to be prepared following special design rules. Design rules were defined on the base of electric field FEM investigations and empirically validated. In combination with an adapted approach to calculate the number of defects (ND) CV spectrometry becomes a more reliable analytic tool to describe imperfectly passivating as well as degraded (i) a-Si:H. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The reduction of void formation in local Al contact structures is of high interest in studies dealing with passivated emitter and rear contact (PERC) solar cells. So far, several processing parameters and their impact on local contact formation were investigated in detail. However, up to now density variation of Al in dependence on temperature and Si content in the melt were not taken into account as a principal reason for void formation. In this context the current assumption of a constant volume of the Al paste particles is discussed in more detail. Based on the results of energy dispersive X-ray spectroscopy, void formation implies either an expansion of paste particles or their burst during contact formation. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

The diffusion of hydrogen within an hydrogenated amorphous silicon (a-Si:H) layer is based on a trap limited process. Therefore, the diffusion becomes a self-limiting process with a decreasing diffusion velocity for increasing hydrogen content. In consequence, there is a strong demand for accurate experimental determination of the hydrogen distribution. Nuclear resonant reaction analysis (NRRA) offers the possibility of a non-destructive measurement of the hydrogen distribution in condensed matter like a-Si:H thin films. However, the availability of a particle accelerator for NRR-analysis is limited and the related costs are high. In comparison, Fourier transform infrared spectroscopy (FTIR) is also a common method to determine the total hydrogen content of an a-Si:H layer. FTIR spectrometers are practical table-top units but lack spatial resolution. In this study, an approach is discussed that greatly reduces the need for complex and expensive NRR-analysis. A model based prediction of hydrogen depth profiles based on a single NRRA measurement and further FTIR measurements enables to investigate the trap limited hydrogen diffusion within a-Si:H. The model is validated by hydrogen diffusion experiments during the post-hydrogenation of hydrogen-free sputtered a-Si. The model based prediction of hydrogen depth profiles in a-Si:H allows more precise design of experiments, prevents misinterpretations, avoids unnecessary NRRA measurements and thus saves time and expense. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Electron beam induced current (EBIC) measurements were used to produce cross sectional images of superjunctions in CoolMOS™ power transistors. The positions of the pn-junctions were determined by EBIC measurements. Knowing the exact locations of the pn-junctions is important for CoolMOS™ since it relies on the principle of charge compensation. For charge compensation, the donors in the n-doped regions must be compensated by an equal amount of acceptors in the p-doped regions. We show that EBIC can provide valuable input for process tuning and process simulations. This will enable the use of smaller dimensions and higher doping levels resulting in a lower on-state resistance.

Monolithic integrated pressure sensor systems are realized by the combination of two different technologies: CMOS-technology for the electrical part and MEMS-technology for the pressure sensor part. The paper describes the modification of such pressure sensor systems to extend their original nominal pressure range from 600 mbar to the low pressure range of 40 mbar by keeping a sufficient signal to noise ratio and without changing the original mask set. The general methodology is described, and a comparison between theoretical signal evaluation and measurement is given. The study concentrates on the aspect of the different piezocoefficients for various Boron doping concentrations of the piezoresistors.

Radiation-induced defects are a common tool in the manufacturing of modern power semiconductor devices. Hydrogen-related doping is a feasible method to introduce deep doping profiles with a low thermal budget. The hydrogen-related donors (HDs) require radiation damage and hydrogen, which can be induced by different methods, e.g., proton implantation, helium and proton co-implantation, or an implantation followed by a hydrogen-plasma step. The choice of these methods significantly affects the introduction efficiency of the donors and the necessary post-implantation thermal budget. By controlling the hydrogen-to-damage ratio, the manufacturing process of the HD profiles may be moved on a trade-off between the activation efficiency and the necessary thermal budget. A low hydrogen-to-damage ratio leads to an increased activation of the HDs, whereas a high hydrogen-to-damage ratio reduces the necessary diffusion time of the hydrogen during the post-implantation anneal. For the technical usage of hydrogen-related doping, knowledge of an efficient process window is desirable. In this paper, we consider proton implantation, helium and proton co-implantation, and a proton implantation followed by a hydrogen-plasma step as different introduction methods of HD profiles with regard to the activation efficiency of the HDs and the necessary thermal budget.

We discuss the consequent application of the theory of piezoresis-tivity with regard to the optimization of monolithic integrated pres-sure sensor family designs, based on CMOS technology. The achievement of a sufficient signal for the given signal conditioning, as well as mechanical stability of the membrane, were the primary goal of the investigation. A rigorous systematic approach is essential since limiting boundary conditions for certain parameters of the sensor design occur. Based on structural analysis of the sensor model, and self written MATLAB signal extraction scripts, the design of the new pressure sensor product family was investigated. Main focus was the achievable sensitivity under the constraint of the feasible mechanical fracture limit - mechanical overload - of crystalline silicon of below 700MPa. Hence, the allowed range of the thickness deviation per pressure range of the silicon mem-brane was deduced. Experimental verification shows a very good matching between measurements and simulations results.

Doping profiles in proton and helium co-implanted and annealed n-type float zone silicon wafers are analyzed by means of spreading resistance measurements. After annealing at sufficiently high temperatures and/or long-enough duration, the hydrogen-related donor profiles known from proton implantations are significantly enhanced by the helium irradiation. The resulting profile shape exhibits a strong resemblance to the radiation damage distribution of the co-implantation. By increasing the ultimately introduced num-ber of hydrogen related donors without varying the available amount of hydrogen, it is shown that the donor profile resulting from proton implantation and annealing is limited by the defect species and the implanted hydrogen is supplied in surplus. The maximum of the additionally induced donor distribution by the he-lium implantation shows a different dependency on the fluence compared to the donor maximum induced by mere proton irradia-tion. The diffusion of protons through the irradiated layer during annealing is impacted by the He-irradiation.

A well-known method for the determination of vacancy distributions in silicon is based on the decoration of vacancies with in-diffused platinum and subsequent profiling of the Pt-distribution with DLTS analysis. The vacancy profile can then be correlated with the substitutional Pt profile. However, there are significant drawbacks of this method: The in-diffusion of platinum is a high-temperature step, which already can alter the vacancy profile; moreover, DLTS measurements with a suitable depth resolution are time-consuming and difficult. Therefore, it is proposed in this paper to decorate the vacancies with hydrogen by processes finally resulting in the formation of vacancy- and hydrogen-related donor and acceptor states. The determination of such doping profiles and by this the detection of vacancy distributions can be easily enabled by depth-resolved spreading resistance measurements with a very good spatial resolution. Hydrogen atoms for the decoration of vacancies can be incorporated by plasma exposure or ion implantation.

Indium-tin-oxide (ITO) films deposited on crystalline silicon wafer and Corning glass are prepared by direct-current magnetron sputtering method at room temperature with various thicknesses. The thickness dependences of structure, resistance and optical reflectance of ITO films are characterized. The results show that when the film thickness is less than 40 nm, the resistivity and optical reflectance of the ITO film changes remarkably with thickness. The optoelectrical properties trend to stabilize when the thickness is over 55 nm. The GXRD result implies that the ITO film begins to crystallize if only the thickness is large enough.

Hydrogenated intrinsic amorphous silicon ((i)°a-Si:H) can be grown by plasma-enhanced chemical vapor deposition with a non-columnar or columnar morphology. Nuclear resonant reaction analysis and corresponding effective stopping cross section analysis indicate a dependency of hydrogen effusion on the morphology of the (i)°a-Si:H layer as well as the doping type and concentration of the c-Si wafer. The doping type of the c-Si wafer also affects the growth of the amorphous network. It is found that for moderately doped p-type c-Si a non-columnar (i)°a-Si:H layer yields a significantly better and more stable passivation already during thermal anneal and illumination, while for passivating n-type c-Si a columnar layer is recommended. Passivating lowly doped c-Si by (i)°a-Si:H is not dependent on morphology. Combining different (i)°a-Si:H morphologies to a multi-layer stack improves the quality of surface passivation. Hydrogen embedded in a well passivating but hydrogen-permeable columnar layer supports good surface passivation when covered by a non-columnar layer, featuring a fast growing layer acting as a hydrogen barrier and enhancing surface passivation quality.

Nuclear Resonant Reaction Analysis (NRRA) is a common method detecting the nearsurface hydrogen distribution of a sample in a depth of up to a few microns. The mass density and related stopping power of a hydrogenated amorphous silicon (a-Si:H) layer depends on the hydrogen content. Correct hydrogen depth profiles are calculated considering the effective ion beam stopping crosssection as well as the related stopping power of the investigated film. The consideration of the local hydrogen concentration is important to avoid misinterpretations of the hydrogen distribution regarding profile depth. Therefore, stopping powers have to be considered carefully when interpreting hydrogen depth profiles especially of films that exhibit variations in hydrogen concentration. Moreover, further investigations like morphology dependent changes of the effective stoppingcross section are not possible without correctly calculated hydrogen depth profiles. Here the correct way is presented how to consider the embedded hydrogen of an a-Si:H layer when calculating absolute depth information of a NRRA measured hydrogen depth profile.

Boron-oxygen related lifetime degradation is a severe problem for high-efficiency solar cells as the applied concepts like PERC suffer strongly from the observed lifetime degradation. However, these efficiency losses can be avoided via the Regeneration process eliminating the harmful defects. Within this contribution the effect of device structure on Regeneration kinetics is investigated. It is found that PERC-type cells regenerate faster than full area Al-BSF-type cells. It is pointed out why PERC-type cells benefit from an injection level effect. But this effect is not the only reason for the accelerated Regeneration. By means of especially adapted PERC cells, which do not benefit from the injection level advantage, it is shown that a second hydrogen containing layer on the rear has a positive influence, too, probably due to an increased hydrogenation of the silicon bulk.

The trapping of hydrogen in crystalline silicon at a buried defect layer has been investigated by Raman scattering spectroscopy. The defect concentration of the trap layer was created by various implantation doses of hydrogen ions. Hydrogen was additionally inserted by subsequent plasma exposure at various temperatures. The basic platelet formation and hydrogen trapping mechanisms are investigated with regard to the use for hydrogen induced silicon layer exfoliation. The analyzed results exhibit that the platelet formation mechanism highly depends on the hydrogenation temperature and on the vacancy concentration.

Boron doped [100]-oriented Cz Si wafers are hydrogenated with a plasma enhanced chemical vapor deposition setup at a substrate temperature of about 260 °C. In-situ Raman spectroscopy is applied on samples under thermal and laser annealing. It is found that different Si-H species have different stabilities. The most stable one is the Si-H bond at the inner surfaces of the platelets. The dissociated energy of Si-H bonds is deduced based on the first order kinetics. It is found that the hydrogen atoms which are released during annealing are trapped again by the platelets and passivate the silicon dangling bonds at the inner surfaces of the platelets or form H2 molecules in the open platelet volume, possibly relating to the basic mechanism of the hydrogen-induced exfoliation of the silicon wafer and the socalled “smart-cut” process.

µ-Raman measurements were carried out on hydrogen implanted, plasma hydrogenated and subsequently annealed Cz Silicon samples, respectively. In comparison to as-implanted or asplasma treated samples, in consideration of the thermal evolution, the effects of the implanted and subsequently plasma treated samples were analyzed. An enhanced trapping of molecular hydrogen in multivacancies has been observed after hydrogen implantation and subsequent plasma hydrogenation. In comparison to as-implanted samples, the intensity of the local vibrational modes (LVM) of vacancy-hydrogen complexes and silicon-hydrogen bonds are increasing.

P-n junctions are created in p-type Czochralski silicon after a low temperature (270°C) hydrogen plasma exposure. This is attributed to the formation of hydrogen-related shallow donors. A deep level (E1) with an activation energy of about EC-0.12 eV is observed by DLTS measurement and assigned to a metastable state of the hydrogen-related shallow donors. At an annealing temperature of 340°C, the E1 centres disappear and oxygen thermal donors appear. The concentrations of the oxygen thermal donors are found typically to be 2-3 decades lower than that required for over-compensating the initial p-type doping and for contributing the excess free carriers.

High-quality indium-tin-oxide (ITO) films are deposited on p-type Czochralski silicon and 7059 Corning glass by direct-current magnetron sputtering at various temperatures. The structural, electrical and optical properties of the ITO films are investigated as functions of the substrate temperature. A comparison between the characteristics of the ITO films on silicon and Corning glass is presented. The results show that for the ITO film on silicon, the nucleation begins from room temperature; the resistivity reaches a maximum value at 75°C; the reflectivity increases with increasing temperature; when temperature is above 125°C, the ITO grows in a three-dimensional manner and forms a granular structure. However, for the ITO film on glass, it is still in an amorphous state at 75°C. Moreover, both the resistivity and the reflectivity decrease with increasing temperature. Above 125°C, the ITO grows in a two-dimensional manner and forms a domain structure.

In plasma-hydrogenated p-type Czochralski silicon, rapid thermal donor (TD) formation is achieved, resulting from the catalytic support of hydrogen. The n-type counter doping by TD leads to a p-n junction formation. A simple method for the indirect determination of the diffusivity of hydrogen via applying the spreading resistance probe measurements is presented. Hydrogen diffusion in silicon during both plasma hydrogenation and post-hydrogenation annealing is investigated. The impact of the hydrogenation duration, annealing temperature, and resistivity of the silicon wafers on the hydrogen diffusion is discussed. Diffusivities of hydrogen are determined in the temperature range 270–450°C. The activation energy for the hydrogen diffusion is deduced to be 1.23eV. The diffusion of hydrogen is interpreted within the framework of a trap-limited diffusion mechanism. Oxygen and hydrogen are found to be the main traps.

We investigated the ultrastructure of the secondary layer of the calcite shell of the terebratulide brachiopod Megerlia truncata with SEM and electron beam backscattering diffraction. The material of the secondary layer is an inorganic/organic fibre composite. Each individual cell of the outer epithelium secrets a single crystal confined in a protein sheath. The morphological fibre axes of the single crystals are almost parallel to the shell surface. The fibrous growth occurs in arbitrary directions perpendicular to the triad symmetry direction of calcite. Accordingly, the fibres form a cylindrical \"fibre\" texture, with the texture axis perpendicular to the shell surface. The curvature of the fibres is caused by lateral displacements or rearrangements of the secreting cell array during growth. In these events the existing crystal lattice is not distorted - it is the substrate for continued crystal growth from the cell, irrespective of direction.

The effect of electron irradiation on n-type Cz- and oxygen-doped FZ-Si containing oxygen-related thermal donors (OTDs) due to a plasma hydrogenation and a subsequent thermal donor formation step at 450°C is investigated by capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements. In order to explain the electron irradiation induced reduction of the carrier concentration, DLTS measurements were performed. They revealed the presence of thermal donors (TDs) and radiation-induced complexes. It is shown that the peak at E C -0.09 eV related to OTDs in CZ-Si diode is not changed by the electron irradiation.

In this paper, an overview will be given about analytical techniques which are suitable for the study of oxygen and oxygen precipitation in highly- and lowly-doped silicon. It will be shown that in the case of highly-doped silicon, the application of Fourier Transform Infrared (FT-IR) absorption spectroscopy requires the use of ultra-thinned or high-fluence irradiated samples and a dedicated data analysis. This sample preparation is necessary to reduce the free carrier absorption in the mid-IR region. It is shown that besides the interstitial oxygen concentration [O i ] and the amount of precipitated oxygen, it is possible to determine the stoichiometry of oxygen precipitates from the study of the corresponding absorption bands. Oxygen precipitation in p + silicon can also be investigated by the D1–D2 lines in photoluminescence (PL) on as-grown or heat–treated material without special sample preparation. In oxygen-doped high-resistivity float-zone silicon, standard FT-IR analysis can be applied to determine [O i ]. The presence of oxygen-related shallow donors can be probed by a combination of electrical (spreading resistance probe, SRP; capacitance–voltage, C – V ) and (quasi-)spectroscopic techniques (deep-level transient spectroscopy, DLTS).

Depth resolved μ-Raman measurements were carried out on plasma hydrogenated and annealed silicon samples. The plasma exposure was done at 260 270 °C, and subsequent annealing at 450 °C or 550 °C. A thin structured plasma damage layer up to 100 150 nm depth and a subsurface layer up to a depth of ∼ 1 μm were observed by cross-sectional transmission electron and atomic force microscopy. In the subsurface region (111)and (100)-oriented platelets are located. Si-H Raman modes attributed to the plasma damage at the wafer surface exhibit a significant higher intensity than those attributed to platelets in the subsurface region. H2 molecules are located in the platelets, as was clearly seen by the fact that the H2 Raman signal exhibits a maximum in the intermediate subsurface region, where the platelets are located. After annealing hydrogen is released from the surface damage layer, while at the platelets it is still trapped.

The role of hydrogen in a recently developed one-step method for the formation and separation of a thin porous Si film from the initial Si substrate is investigated by means of Raman spectroscopy and detailed morphological analysis. It is shown that hydrogen plays a crucial role in the formation and separation of the porous Si film. Micro-Raman spectroscopy reveals that hydrogen in molecular form is accumulated in the micropores and creates hydrodynamic pressure which could be strong enough to break the thin pore walls in a high-porosity layer. As a result the upper porous Si film is separated from the original substrate. The kinetics of the process is confirmed by transmission and scanning electron microscopy.

Standard [001]-oriented p - (12–20 Ω cm) and n -type (1.8–2.6 Ω cm) Czochralski (Cz) silicon wafers were treated by a RF (13.56 MHz) hydrogen plasma at a substrate temperature of 250 °C. After the plasma hydrogenation subsequent annealing was applied up to 600 °C in air. The formation of H 2 molecules in voids/platelets was investigated by Raman spectroscopy. The Raman intensities of the H 2 vibration modes at ~4150 cm −1 exhibited significant intensity modulations in dependence on the annealing temperature. The intensities of the H 2 Raman lines indirectly monitor the evolution of the voids/platelets upon annealing. This assumption was verified by cross-sectional transmission electron microscopy (XTEM), which was applied for comparison. The intensity modulations of the H 2 Raman signal can be explained by the evolution of and platelets. At lower annealing temperatures ( 500 °C) platelets laying in planes are dominant, while at elevated temperatures ( ≥ 500 °C) [001]-oriented platelets become more and more important. platelets were also observed using XTEM measurements in p -type material. In case of p -type substrates the Raman intensities were significant higher than for n -type material. The higher H 2 Raman intensities in p -type Cz Si can be explained by the amphoteric character of hydrogen in silicon.

This paper presents a way to design a finite-element computer model of cooling system with a complicated geometry. The computer model is developed on the basis of a commercial software package ABAQUS. The steady state forced-convective fluid cooling of a pin-fin heat converter for power (∼1 kW heat power) semiconductor module has been investigated on the basis of computer simulation. A phenomenological equation has been used for calculation of the local value of the heat transfer coefficient for the liquid-solid interface. The impacts of the thermal conductivity of the pin-fin sink material, volume flow rate of the cooling liquid and geometrical design of the pin-fin sink on the thermal resistance of the converter are shown. Copyright © 2003 John Wiley & Sons, Ltd.

The modifications of the surface and subsurface properties of p-type multicrystalline silicon (mc-Si) after wet chemical etching and hydrogen plasma treatment were investigated. A simple heterojunction (HJ) solar cell structure consisting of front grids/ITO/(n)a-Si:H/(p)mc-Si/Al was used for investigating the conversion efficiency. It is found that the optimized wet chemical etching and cleaning processes as a last technological step before the deposition of the a-Si:H emitter are more favorable to HJ solar cells fabrication than the hydrogenation. Solar cells on p-type mc-Si were prepared without high-efficiency features (point contacts, back surface field). They exhibited efficiencies up to 13% for a cell area of 1 cm 2 and 12% for a cell area of 39 cm 2 .

Free-standing microwave plasma enhanced chemical vapor deposited (CVD) diamond films of thickness between 250 and 350 μm are thermochemically beveled at elevated temperatures (≤800 °C) in an argon–hydrogen (96%–4%) gas mixture. Beveling is done on both sides of the films at angles of ≤20°. The radii of curvature of the cutting edges are estimated to be approximately 50 nm using a scanning electron microscope (SEM). These cutting edges can be used as knives for microsurgical applications and as styli for surface roughness measuring equipment such as the stylus profilometer.

The low-temperature photoluminescence (PL) measurements (down to 4.2 K) were employed for the investigations of the defects and impurities in multicrystalline silicon (mc-Si) samples grown by block-casting method. The optical properties of as-grown, irradiated by gamma-rays, heat and hydrogen plasma treated samples were studied. It was found that carbon and oxygen as the residual impurity atoms are responsible for the formation of the zero-phonon PL lines with 0.9355 eV (T line) and 0.9652 eV (I line) after heat treatments at about 350–550°C. The appearance of PL lines with the energies of 0.9697 eV (A line) and 0.7894 eV (C line) after a gamma-rays irradiation can be attributed to the formation of carbon- and oxygen-related centers, respectively. The comparison of the PL properties of the mc-Si samples with the mono-crystalline one is performed. It is shown that the main peculiarities of the low-temperature PL spectra of mc-Si can be explained both by the influence of residual impurities and the residual strains in this material.

Some crucial limiting process steps of ITO/(n)a-Si:H/(p)c-Si solar cell manufacturing were investigated. The influence of amorphous silicon deposition temperature on the efficiency of heterojunction (HJ) solar cells as well as ITO deposition on the properties of ITO/a-Si:H/c-Si interfaces were studied. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and SIMS measurements were employed for the investigations. It was observed that the decrease in a-Si:H deposition temperature from 230 down to 100°C leads to a reduction in solar cell efficiencies to only 1%. It was found that the ITO deposition process itself can significantly modify the ITO/a-Si:H/c-Si interfaces due to the interaction of oxygen, and In and Sn atoms with silicon at the initial stage. It was concluded that this modification has a more significant impact on the quality of the HJ solar cells than on that of the a-Si:H layer.

Hydrogensupportedthermaldonor(TD)formationwasobservedinoxygenenrichedhighresistivefloatzone(FZ)siliconbeingusedassubstratesfordetectorsintheLargeHadronCollider(CERN).TDformationwasprovidedbya‘‘2-step-process’’,consistingofaplasmahydrogenationat250 C(60min)andsubsequentannealingat450 Cinair(typicallyfor20–30min).Thesampleswereanalyzedbyspreadingresistanceprobe(SRP),CðVÞ andDLTSmea-surements.DopingbyTDsintheoxygenenrichedlayersofFZSisamplesmightbeapromisingmethodforthecreationofverydeep( 100lmÞ electricalfieldgradientsforanimprovedperformanceofSiradiationdetectors. 2002ElsevierScienceB.V.Allrightsreserved. Keywords: Float-zonesilicon;Oxygen;Hydrogen;Thermaldonors;Radiationdetectors 1. IntroductionSinceseveralyearsoxidizedhighlyresistivefloat-zone(FZ)siliconfacesstrongscientificre-searchinterest,sinceitwillbethebasicsubstratematerialfornuclearradiationdetectorsinfuturehighenergyphysicsexperimentsatthe‘LargeHadronCollider’atCERNinGeneva[1–3].Suchradiationhardsilicondetectorshavetosurvivehighenergyphysicsexperimentsrunningforperi-odsupto10years.Duringsuchlongoperationtimesthedetectorsareexposedtohighfluxesofparticles,andthereforetheysustainahighradia-tiondamage.Sinceapartoftheradiationinduceddefectsexhibitselectricalactivity,thedetectorscanbesignificantlyalteredduringlongtimeoperation.AcandidateforanelectricalactivedefectcenterinFZSidetectorsubstrates,whichmightbere-sponsibleforanegativespacechargeformationunder applied bias, is the di-vacancy-oxygen(V

Positron beam annihilation Doppler-broadening (PADB) and Raman studies were carried out on H-plasma treated and annealed p-type Cz-Si. Samples were treated by a 13.56 MHz H-plasma for 2 h at RT (∼30 °C) and 250 °C, respectively. Annealing was done in air between 100 and 600 °C for annealing times between 10 and 480 min. The Raman spectra of the RT treated samples show no (or only very weak) H 2 -molecule signals, in contrast to the samples H-plasma treated at 250 °C. Raman intensity changes as a function of temperature are observed, which are attributed to the evolution of voids or platelets. The positron annihilation data correlate with these results, since annealing of the RT plasma treated samples reduces the Doppler-broadening S -values with increasing temperature and/or annealing time. Together with an increasing positron diffusion length this suggests that defects acting as positron trapping centers are (partially) annealed out. For the sample plasma treated at 250 °C the following depth dependent behavior of the Doppler parameters is found. Below 100 nm depth the Doppler parameters follow the same trend as those of the RT treated samples. In a zone between 100 and 200 nm depth the S parameter strongly increases after annealing at 600 °C. This is attributed to the formation of positronium (Ps), indicative for the presence of nano-cavities capable of trapping molecular hydrogen in this region.

In this paper we present an experimental study on light emitting layers, which were formed by hydrogen plasma treatments of standard Czochralski silicon wafers and subsequent oxidation. The plasma hydrogenation was done at 250 °C. Annealing was done in air up to 600 °C. The layers were analyzed by Raman/photoluminescence (PL) spectroscopy. The surface morphology of the treated samples was investigated by scanning electron microscopy (SEM). Due to the hydrogen plasma exposure, thin layers are created at the silicon wafer surface, which are structured on the sub-100 nm scale. After appropriate oxidization and hydrogenation, these layers exhibit a broad light emission (LE) in the visible spectral range. The appearance and efficiency of the LE depends on the initial structuring caused by the hydrogen plasma. It is assumed that LE originates from the formation of Si–O–H complexes in the surface/subsurface layers.

The incorporation of hydrogen into the p-type Czhochralski (Cz) silicon by a plasma results in an enhanced thermal donor (TD) formation at temperatures around 400°C. Counter doping by the TDs and a rapid p–n junction formation occur in the p-type Cz Si. It is shown that the controlled TDs formation can be used for the low-temperature production of device structures: p–n junctions, p–n–p structures and structures with gradient doping. The characterization of the samples was done by the depth resolved spreading resistance probe (SRP) analysis. A kinetic model for the analysis of the hydrogen-enhanced TDs formation in the as-grown as well as in the Cz Si samples with denuded zone is developed. It can be concluded, that the controlled hydrogen enhanced TDs formation can be used as an alternative low-cost, low-temperature doping method, which might be favorable for active defect-engineering in the Cz Si.

The limits of sensors in harsh environments are discussed. Failures of sensor materials, interconnects, and cables are shown. Remote measurements can be solutions to overcome material problems. Sensor material and measurement systems are presented for cases such as high temperature, high pressure, toxicity, explosiveness, nuclear radiation, and high electromagnetic pulse (EMP) levels.

Parameters controlling the removal rate of chemical vapor deposition (CVD) diamond films thermochemically polished on transition metals in a mixed argon-hydrogen atmosphere were investigated. The ambient temperature, the pressure exerted on the diamond film, the angular velocity of the polishing plate, the frequency and the amplitude of the transverse vibrations were among the parameters used in the experiments. Temperature measurements showed that the removal rate was increased exponentially with increasing magnitude of the parameter. An exponential increase in the removal rate was also observed with increasing pressure and hence with increasing contact between the diamond film and the polishing plate. However, an exponential decrease in the removal rate was observed with increasing angular velocity of the polishing plate. The removal rate obtained with the application of transverse vibrations was more than three times that obtained without transverse vibrations. Moreover, the removal rate was seen to be higher at resonant frequencies. An increase in the removal rate with increasing amplitude of the transverse vibrations was also observed. Raman measurements carried out on the films to determine the presence of the non-diamond carbon layer after thermochemical polishing revealed non-diamond Raman lines only for films polished at 1000 °C and 1050 °C for the temperature range 750–1050 °C.