Rapid Thermal Processing Furnace Research Articles

Synthesis of multi-walled carbon nanotubes on nichrome and nickel by using rapid thermal processing furnace

Synthesis of multi-walled carbon nanotubes on nichrome and nickel by using rapid thermal processing furnace

Novel and economical approach of sulfurizationof Bi-facial CIGSe layers on flexible substrate

The surface sulfurization is significant method to enhance the VOC of Copper Indium Gallium Diselenide (CIGSe) solar cells. However, a large amount of sulfur (S) in the layer deteriorates the FF and JSC owing to the lower absorption of photons with low energy and increased deep-level recombination. Since sulfurization is temperature-dependent, it is difficult to control the diffusion depth of S in the CIGSe layer. Herein, we report the band gap engineering of CIGSe by the addition of sulfur using a simple and rapid thermal processing (RTP) technique without involving toxic H2S or H2Se gasses, and the bifacial growth of CIGSe was reported using a non-aqueous electrochemical technique. The films were heat treated in an RTP furnace in ambient S at 450 °C using a two-step program. Sulfurization was performed with 2 mg and 20 mg of S powder, and the effect of the amount of S on the various properties of the CIGSe layers was investigated. A significant improvement in the properties of CIGSe was observed upon sulfurization. X-ray Diffraction, Spectroscopy and Raman spectroscopy indicated that the sulfurization process resulted in the formation of a Copper Indium Gallium Sulfoselenide (CIGSSe) absorber layer, which was highly crystalline and did not exhibit any secondary phase formation. The development of the CIGSSe layer at the surface of CIGSe in the sulfurized sample was confirmed by the existence of distinguished S 2p doublet peaks in the CIGSe layer sulfurized with 20 mg S powder as compared to 2 mg S powder, whereas it was completely absent in the as-prepared layer in the X-ray photoelectron spectroscopy (XPS) core level spectra. Rietveld refinement confirms the formation of CIGSSe along with CIGSe in layer upon sulfurization.

Temperature Gradient Image Analysis to Optimize an Ultrafast Regeneration of Boron–Oxygen-Related Defects

In this study, we introduce a temperature screening image analysis to investigate the temperature dependence of boron-oxygen-related defect regeneration achieved by using one sample. For that purpose, we induce a temperature gradient in a single sample over a broad temperature range in our laser-based rapid thermal processing furnace, while other influencing factors are kept constant. Spatially resolved measurements of the temperature during the regeneration process (thermographic images) and photoluminescence (PL) images at different boron-oxygen-related defect states are recorded. By a pixelwise assignment of the PL images to the temperature image, the effectiveness of the regeneration process in terms of regeneration completeness is evaluated for each pixel. In this experiment, we investigate the temperature dependence of a boron-oxygen-related defect regeneration in a temperature range of 100-500 °C for different treatment times of 2-30 s at an illumination intensity of 100 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Thereby, we determine the temperature regimes that allow for efficient regeneration for the respective regeneration parameter set with a single sample. The results can be used for industrial optimization of a boron-oxygen-related defect regeneration process. Furthermore, this technique can also be applied to other temperature-dependent process optimizations and even fundamental research.

Modulation of microstructural and electrical properties of rapid thermally synthesized MoS2 thin films by the flow of H2 gas

Two dimensional transition metal dichalcogenides (TMDC) have gained potential attention of the researchers, owing to their fascinating electronic and optoelectronic properties. Among the TMDC, the widely studied molybdenum disulphide (MoS2) stands out as a prototypical material. In this work, rapid thermal process (RTP) is adopted for the deposition of MoS2 thin film, using sputtered molybdenum (Mo) thin film and thermally evaporated sulphur (S) film. The microstructural and electrical characteristics of the MoS2 thin films were studied by varying the H2 flow rate in the rapid thermal processing furnace. Field Emission Scanning Electron Microscope images showed the improvement in the uniformity of the MoS2 thin films with the increase in the flow rate of H2 gas. The X-ray diffraction peak has been observed at 14.1°, corresponding to the (002) plane of the hexagonal MoS2 (2H). Raman spectra depict two peaks around 400 cm−1 for A1g and E2g1active modes, which a fingerprint of 2H MoS2. The FTIR studies also depicted the enhancement of MoS2 characteristics peaks with the increase in H2 flow rate. In order to study the effect of substrate, MoS2 films were grown on both Si and SiO2/Si substrates. Among the various H2 flow rates used during the RTP, MoS2 thin films grown with 20 sccm H2 gas at 800 °C has shown better microstructural properties. In order to study the semiconductor properties of MoS2 thin films, the carrier concentration has been calculated from the heterojunction capacitance and is found to be ~1016 cm−3. The comprehensive study on the effect of H2 flow rate on the properties of MoS2 thin films imparts the underlying role of hydrogen atoms in the deposition process, which paves a way for the controlled synthesis of low dimensional materials.

Thermal stress during RTP processes and its possible effect on the light induced degradation in Cz-Si wafers

In this study, the carrier lifetime variation of p-type boron-doped Czochralski silicon (Cz-Si) wafers was investigated after a direct rapid thermal processing (RTP). Two wafers were passivated by silicon nitride (SiNx:H) layers, deposited by a PECVD system on both surfaces. Then the wafers were subjected to an RTP cycle at a peak temperature of 620 °C. The first wafer was protected (PW) from the direct radiative heating of the RTP furnace by placing the wafer between two as-cut Cz-Si shield wafers during the heat processing. The second wafer was not protected (NPW) and followed the same RTP cycle procedure. The carrier lifetime τeff was measured using the QSSPC technique before and after illumination for 5 h duration at 0.5 suns. The immediate results of the measured lifetime (τRTP) after the RTP process have shown a regeneration in the lifetime of the two wafers with the PW wafer exhibiting an important enhancement in τRTP as compared to the NPW wafer. The QSSPC measurements have indicated a good stable lifetime (τd) and a weak degradation effect was observed in the case of the PW wafer as compared to their initial lifetime value. Interferometry technique analyses have shown an enhancement in the surface roughness for the NPW wafer as compared to the protected one. Additionally, to improve the correlation between the RTP heat radiation stress and the carrier lifetime behavior, a simulation of the thermal stress and temperature profile using the finite element method on the wafers surface at RTP peak temperature of 620 °C was performed. The results confirm the reduction of the thermal stress with less heat losses for the PW wafer. Finally, the proposed method can lead to improving the lifetime of wafers by an RTP process at minimum energy costs.

Structure and photoelectrochemistry of silver-copper-indium-diselenide ((AgCu)InSe2) thin film

In this work, silver (Ag) precursors with different thicknesses were sputtered on the surfaces of CuIn alloys, and (AgCu)InSe2 (ACIS) films were formed after selenization at 550 °C under nitrogen condition using a rapid thermal process furnace. The structure and electrical properties of the ACIS films were investigated. The result showed that the distribution of Ag+ ion was more uniform with increasing the thickness of Ag precursor, and the surface of the thin-film became more homogeneous and denser. When Ag/Cu ratio ≥0.249, the small grain particles disappeared. The band gap can be rationally controlled by adjusting Ag content. When (Ag + Cu)/In ratio ≥ 1.15, the surface of the ACIS thin-film mainly exhibited n-type semiconductor. Through the photoelectrochemistry measurement, it was observed that the incorporation of Ag+ ions could improve photocurrent by adjusting the band gap. With the Ag precursor thickness increased, the dark current decreased at the more negative potential.

Role of the post‐annealing conditions on the conductivity of niobium doped titanium dioxide electrodes prepared by sol–gel and their function in organic solar cells

In this work, we report the fabrication of indium tin oxide free organic solar cells and demonstrate the ability of niobium doped titanium dioxide (TNO) layers produced by sol–gel as feasible alternative electrode. The conductivity of the TNO was tailored by changing the layer thickness and the post-annealing conditions. Later, the crystal structure was revealed by X-ray diffraction. The post-annealing treatments were performed in a rapid thermal processing furnace under different gas atmospheres, temperatures and times. The conductivity of the samples was measured using a four-point set-up and the transparency through a UV–VIS spectrophotometer. A good sheet resistance of 181 Ω/□ is achieved when the electrode was heated in an N2/H2 atmosphere mixture at 1000 °C for 10 min. TNO based organic solar cells were manufactured and their performance was evaluated by current-voltage measurements. A power conversion efficiency of 0.71% was attained.

Effect of Post-Annealing Treatment on the Structure and Luminescence Properties of AIN:Tb&lt;sup&gt;3+&lt;/sup&gt; Thin Films Prepared by Radio Frequency Magnetron Sputtering

Terbium-doped aluminum nitride thin films have been deposited by radio frequency magnetron sputtering. The influence of annealing treatments on structural, morphological and luminescence properties of the films is examined with the aim to optimize post-deposition annealing conditions. Temperatures starting from 500 up to 1000°C using two annealing techniques were investigated: rapid thermal processing and quartz tube furnace. X-ray diffraction analysis revealed the formation of aluminum oxide and aluminum oxynitride phases at temperatures higher than 750°C. The oxygen content in the surface layer was measured with energy dispersive X-ray. The terbium emission was obtained after excitation either by photons or electrons. The films treated with rapid thermal processing at 750°C resulted in the highest emission.

Al-implanted on-axis 4H-SiC MOSFETs

In this paper, the impact of temperature and time stress on gate oxide stability of several multi-implanted and epitaxied 4H-SiC nMOSFET is presented. The oxide layer was processed under a rapid thermal process (RTP) furnace. The variation of the main electrical parameters is shown. We report the high quality and stability of such implanted MOSFETs, and point out the very low roughness effect of the on-axis-cut sample. Particularly, in the best case, effective channel mobility (μfe) overcomes 20 cm2.V−1.s−1 at 300 °C for a channel length of 12 μm, which is very encouraging for implantation technology. Starting from 200 °C, the apparent increase of the μfe peak of the MOSFET ceases and tends to saturate with further temperature increase. This is an indication of the potential of MOSFETs built on on-axis substrates. Thus, starting from the real case of an implanted MOSFET, the global purpose is to show that the electrical performance of such an on-axis-built device can tend to reach that of the ideal case, i.e. epitaxied MOSFET, and even overcome its electrical limitation, e.g. in terms of threshold voltage stability at high temperature.

Investigation of Contact Formation during Silicon Solar Cell Production

Abstract This article deals with the investigation of the influence of sintering conditions on the formation process of screen printed contacts on passivated boron doped P+ emitters. The experiment was focused on measuring of resistance changes of two thick film pastes during firing processes with different conditions. Two different temperature profiles were compared at an atmospheric concentration of O2. The influence of the O2 concentration on resistance was investigated for one profile. A rapid thermal processing furnace modified for in-situ resistance measurements was used. The change of resistance was measured simultaneously with the temperature.

Influence of Al Particle Size and Firing Profile on Void Formation in Rear Local Contacts of Silicon Solar Cells

In this paper, the influence of Al particle size and the applied firing profile on void formation in local rear contacts of wafer-based silicon solar cells is investigated. Samples with a passivated emitter and rear cell (PERC) rear, but without front metallization, were metalized with six different Al screen-printing pastes, i.e., both commercial and homemade, featuring different particle size distributions and fired in a rapid thermal processing furnace with different firing profiles. Voids were detected with scanning acoustic microscopy measurements, and the fraction of voids in rear local contacts was analyzed. It was shown that the heating phase of the firing process has the strongest influence on void formation. With slower heating, void formation could be reduced to a fraction lower than 5% of the local contact area. Furthermore, it was shown that Al pastes consisting of a mixture of small and large Al particle sizes have a positive effect on the formation of voids.

Fabrication of Cu2SnS3 thin-film solar cells with power conversion efficiency of over 4%

Cu2SnS3 (CTS) thin films were produced by the co-evaporation of Cu, Sn, and cracked sulfur, followed by annealing. The as-deposited films were then annealed at 570 °C for 5 min in the presence of 100 mg of sulfur lumps in a rapid thermal processing furnace filled with N2 gas at atmospheric pressure. Solar cells were then fabricated using the CTS films as absorber layers, and their efficiency was evaluated for different Cu/Sn compositional ratios. The largest grain size was found for films with a slightly Sn-rich composition. The highest performance was obtained for solar cells containing a CTS thin film with a Cu/Sn ratio of about 1.9. A cell with a Cu/Sn ratio of 1.87 exhibited an open-circuit voltage of 258 mV, a short-circuit current density of 35.6 mA/cm2, a fill factor of 0.467, and a power conversion efficiency of 4.29%.

Inkjet Printing of Microporous Silica Gas Separation Membranes

Inkjet printing was applied to manufacture silica‐based gas separation membranes, which were coated on a pore‐graduated alumina substrate with a mesoporous γ‐alumina interlayer. A silica sol diluted by 1‐propanol was used to print the membrane layer followed by thermal treatment in a rapid thermal processing furnace. The membrane thickness was varied between 30 and 110 nm by conducting one, two, and three coating steps. In the latter case, H2 permeance in the range of 2.0 × 10−8–3.3 × 10−8 mol/s·m2·Pa combined with H2/CO2 selectivities in the range of 15–25 were achieved, proving the concept that inorganic gas separation membranes can be successfully processed by inkjet printing.

A 5.1% efficient kesterite Cu2ZnSnS4 (CZTS) thin film solar cell prepared using modified sulfurization process

AbstractCu2ZnSnS4 (CZTS) absorber thin films are prepared by sulfurization of sputtered Cu/Sn/Zn (CZT) stacked metallic precursor. The modified sulfurization process is adapted to prepare photovoltaic quality CZTS films. Specifically, sputtered CZT precursor films are sulfurized in sulfur powder contained graphite box using rapid thermal processing furnace at 580 °C for 10 min, in N2(95%) + H2S (5%) atmosphere. The Cu‐poor CZTS films with various Cu/(Zn+Sn) ratio are prepared by varying Cu layer deposition time. The effect of Cu/(Zn+Sn) ratio on the properties of CZTS films is investigated. The CZTS thin film solar cells with Cu/(Zn+Sn)=0.76 shows best conversion efficiency of 5.1% (Voc: 573 mV, Jsc: 18.38 mA/cm2, FF: 0.48%, and active area: 0.31 cm2). (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Cu2 ZnSnSe4 thin film solar cells above 5% conversion efficiency from electrodeposited Cu Sn Zn precursors

Cu2ZnSnSe4 solar cells were synthesized by electrodeposition of metal stack precursors followed by selenization, a high potential process for industry, leading to conversion efficiencies above 5%. An additional selenium-capping layer deposited on the precursor before annealing showed improved uniformity and morphology of CZTSe layers compared to other selenization routes. Two different atmospheric annealing systems were used: a closed graphite box in a tubular furnace and a three-chamber dynamic rapid thermal processing furnace. The RTP system gave larger grains and more compact layers, whereas CZTSe selenized in tube furnace had smaller grains and a higher series resistance. Both annealing systems gave best cells power conversion efficiencies over 5%. We will discuss the device photoelectric properties and their relation to material structures and processing.

The component interaction network approach for modeling of complex thermal systems

A practical approach for the thermal modeling of complex thermal systems, called the component interaction network (CIN) is presented. Its stages are explained: description of the thermal system as a set of non-overlapping components and their interactions by heat and mass exchanges, modeling of components with different levels of precision using finite volumes and finite elements, modeling of interactions by conduction, convection, radiation and advection, time resolution scheme and simulation. Non-conventional notions of conditional existence of components or time events are introduced. The approach is illustrated with a simple example of an electric furnace. It is then applied to a rapid thermal processing (RTP) furnace and validated experimentally. The advantages of the CIN approach are demonstrated.

Formation mechanisms of Cu(In,Ga)Se2 solar cells prepared from electrodeposited precursors

The development of low cost industrial processes is one of the key issues to make Cu(In,Ga)Se2 based solar cells reach grid-parity. Such a process is found by using a two-step technology based on the sequential electro-deposition of a metallic precursor followed by a rapid annealing. Three types of metallic precursors (two-compound systems as copper–indium, copper–gallium and three-compound system as copper–indium–gallium) have been electrodeposited on a molybdenum sputtered soda lime glass and alloyed through a low annealing temperature. Then a selenium film has been evaporated and the stack has been annealed at high temperature in a rapid thermal processing furnace. A one-step heating profile has been used from room temperature to 550°C in less than 1min. Samples for which the heating was stopped after different annealing times have been characterized using several techniques: X-ray fluorescence spectrometry for elemental composition, X-ray diffraction and Raman spectroscopy for phase composition, scanning electron microscopy for structural analysis and glow discharge optical emission spectroscopy for diffusion study. Preferential formation reactions of the two-compound based metallic precursors have been studied and compared with the copper–indium–gallium metallic precursor used in a two step process. A gallium free system reacts faster than a gallium-based system and presents well-formed ternary compound after a standard selenization. However, the incorporation of gallium can be improved through a longer annealing time or a higher annealing temperature.

Validation of inverse boundary condition design in a thermometry test bed

This study presents validation of an inverse boundary condition design analysis used in the design of an axisymmetric vacuum chamber with characteristics of a semiconductor rapid thermal processing (RTP) furnace. The vacuum chamber with heater is a thermometry test bed and is equipped with thermocouples and an instrumented silicon wafer to map the temperature field in the system. In order to model the physical system accurately, precise characterization of the system is essential. In the absence of any medium, radiative heat transfer is the dominant heat transfer mode. The radiative properties of the system's important components are measured and a numerical sensitivity study is conducted to understand the effects of property and model-based uncertainty introduced to the solution. The required power input for the heaters is estimated directly using inverse design so that specified thermal conditions across the silicon wafer are achieved at steady state. Through application of the estimated power distribution in the system, the design is validated by comparing the design goal and measured temperature distribution along the silicon wafer accounting for the uncertainties of the solution.

Effect of pyrolysis temperature on the properties of Bi 3.5La 0.5Ti 3O 12 thin films deposited by aqueous chemical solution deposition

Bi 3.5La 0.5Ti 3O 12 thin films for ferroelectric random access memory application were fabricated by the aqueous chemical solution deposition method. The precursor films were deposited by spin coating and subsequently transformed into the oxide by thermal treatment on three hot plates and crystallizing in a rapid thermal processing furnace at a temperature as low as 650 °C. The temperature of the third hot plate step was varied, which affected the ferroelectric properties of the prepared films. The ferroelectric properties of the crystallized films as well as their crystallographic structure, texture and microstructure were characterized using various experimental techniques. The evolution of the precursor chemical structure of the thin films, containing organic compounds, was studied at different temperatures during the thermal treatment. In order to maximize the remanent polarization of the crystalline Bi 3.5La 0.5Ti 3O 12 thin films to approximately 6 μC cm −2 it is preferable to remove all the organic components of the thin-film precursor prior to the intermediate crystallization step in the rapid thermal processing furnace. A temperature of 370 °C has been shown to be the minimal temperature for achieving the complete decomposition of the organic constituents of the precursor thin film.

Combined in-depth scanning Auger microscopy and Raman scattering characterisation of CuInS2 polycrystalline films

In this work, the combination of in-depth scanning Auger microscopy with Raman microprobe spectroscopy is applied for the detailed microstructural characterisation of CuInS2 (CIS) thin films. CIS films are used for the fabrication of high efficiency solar cell devices. These films are obtained by sequential sputtering of Cu and In layers on a Mo-coated glass substrate, followed by a sulphurisation step at 500°C in a rapid thermal processing furnace. In order to study this process, samples obtained at intermediate steps are investigated. The obtained data show the formation of the CIS phase already at the first stages of the sulphurisation process, although with a highly disordered structure. Moreover, segregation of CuS towards the surface is observed before sulphurisation is completed. This fact is accompanied by a significant increase of the structural quality of the CIS film, which allows for the fabrication of high efficiency solar cell devices. The performed analysis corroborates the strong complementarity between the used techniques for the detailed microstructural analysis of complex multilayer systems.