Rapid Thermal Processing Treatment Research Articles

Improved Endurance of Ferroelectric HfxZr1–xO2 Integrated on InAs Using Millisecond Annealing

AbstractFerroelectric HfxZr1–xO2 (HZO) is typically achieved by crystallization of an amorphous thin film via rapid thermal processing (RTP) at time scales of seconds to minutes. For integration on III–V semiconductors, this approach can severely degrade the sensitive HZO/III–V interface. To evaluate whether a reduced thermal budget can improve the interface quality, millisecond duration thermal anneals are utilized using a flash lamp annealer (FLA) on HZO/InAs capacitors. Through thorough electrical characterization such as polarization hysteresis, endurance, and capacitance‐voltage measurements, as well as synchrotron‐based chemical interface characterization, the FLA and RTP treatments are compared and the FLA results are found in lower interface defect density and higher endurance, but also have generally lower remanent polarization (Pr) compared to RTP. Additionally, ways to achieve high Pr and low interface defect density using multiple lower energy flashes, as well as by pre‐crystallization during the ALD growth step are investigated. Using FLA, Pr exceeding 20 µC cm−2 is achieved, with extended endurance properties compared to RTP treatment and a considerably decreased defect density, indicative of a higher quality HZO/InAs interface. This work presents valuable insight into the successful integration of ferroelectric HZO on low thermal budget III–V semiconductors.

Point-defect engineering of nanoporous CuBi2O4 photocathode via rapid thermal processing for enhanced photoelectrochemical activity

Engineering point defects such as metal and oxygen vacancies play a crucial role in manipulating the electrical, optical, and catalytic properties of oxide semiconductors for solar water splitting. Herein, we synthesized nanoporous CuBi2O4 (np-CBO) photocathodes and engineered their surface point defects via rapid thermal processing (RTP) in controlled atmospheres (O2, N2, and vacuum). We found that the O2-RTP treatment of np-CBO increased the charge carrier density effectively without hampering the nanoporous morphology, which was attributed to the formation of copper vacancies (VCu). Further analyses revealed that the amounts of oxygen vacancies (Vo) and Cu1+ were reduced simultaneously, and the relative electrochemical active surface area increased after the O2-RTP treatment. Notably, the point defects (VCu, Cu1+, and Vo) regulated np-CBO achieved a superb water-splitting photocurrent density of −1.81 mA cm−2 under simulated sunlight illumination, which is attributed to the enhanced charge transport and transfer properties resulting from the regulated surface point defects. Finally, the reversibility of the formation of the point defects was checked by sequential RTP treatments (O2-N2-O2-N2), demonstrating the strong dependence of photocurrent response on the RTP cycles. Conclusively, the surface point defect engineering via RTP treatment in a controlled atmosphere is a rapid and facile strategy to promote charge transport and transfer properties of photoelectrodes for efficient solar water-splitting.

Shining a Hot Light on Emerging Photoabsorber Materials: The Power of Rapid Radiative Heating in Developing Oxide Thin-Film Photoelectrodes

The unique possibilities of rapid thermal processing (RTP) for overcoming two significant challenges in the development of oxide thin-film photoelectrodes are demonstrated. The first is the need to exceed normal temperature limits for glass-based F:SnO2 substrates (FTO, ∼550 °C) to achieve the desired density, crystallinity, and low defect concentrations in metal oxides. Flash-heating of Ta2O5, TiO2, and WO3 photoelectrodes to 850 °C is possible without damaging the FTO. RTP heating-rate dependencies suggest that the emission spectrum of the RTP lamp, which blue-shifts with increasing heating power, can significantly influence the crystallization behavior of wide-bandgap photoelectrodes (≥1.8 eV). The second challenge is avoiding the formation of structural defects, trap states, grain boundaries, and phase impurities, which can be particularly difficult in multinary metal oxides. RTP treatment of α-SnWO4, a promising photoanode material, resulted in an increase in grain size and favorable crystallographic reorientation, culminating in a new performance record.

Effects of temperature gradients on magnetic anisotropy of SmCo based films

The magnetic anisotropy of SmCo-based permanent magnetic thin films are generally controlled by introducing buffer layer or heating substrate. However, the design for the multi-layer thin film system is complicated and the thickness of SmCo is limited due to a short range of interfacial stress/strain between the buffer layer and SmCo layer. In this work, the effects of temperature gradients, generated by RTP (rapid thermal process), on the magnetic anisotropy of the SmCo-based films were systematically investigated. The results show that the as-deposited films exhibit amorphous state. The out-of-plane coercivity of RTP-treated films is strongly correlated with the heating rate, and its optimum value (2810 Oe) is larger than that of the CTA (conventional thermal annealing) treated films (1670 Oe). For the RTP-treated films, the intensity of characteristic diffraction peaks for in-plane oriented SmCo5 (200) and Sm2Co17 (300) decreases, together with reducing the roughness. Besides, the grain size is finer and the contrast of magnetic domains becomes stronger for the RTP-treated films due to that the easy axis of SmCo5/Sm2Co17 phase gradually changes from in-plane to out-of-plane direction. It is suggested that the RTP treatment with a shorter annealing time has beneficial effects on obtaining finer microstructure and improving the out-of-plane magnetic anisotropy of the SmCo-based films. This work provides a novel way to control the magnetic anisotropy via annealing temperature gradients for permanent magnetic thin films, compared with conventional methods, to induce the magnetic anisotropy.

Preparation of Al-Containing ZSM-58 Zeolite Membranes Using Rapid Thermal Processing for CO2/CH4 Mixture Separation.

The synthesis of DDR-type zeolite membranes faces the problem of cracks that occur on the zeolite membrane due to differences in the thermal expansion coefficient between zeolite and the porous substrate during the detemplating process. In this study, Al-containing ZSM-58 zeolite membranes with DDR topology were prepared by rapid thermal processing (RTP), with the aim of developing a reproducible method for preparing DDR zeolite membrane without cracks. Moreover, we verified the influence of RTP before performing conventional thermal calcination (CTC) on ZSM-58 membranes with various silica-to-aluminum (Si/Al) molar ratios. Using the developed method, an Al-containing ZSM-58 membrane without cracks was obtained, along with complete template removal by RTP, and it had higher CO2/CH4 selectivity. An all-silica ZSM-58 membrane without cracks was obtained by only using the ozone detemplating method. ZSM-58 crystals and membranes with various Si/Al molar ratios were analyzed by using Fourier-transform infrared (FTIR) spectroscopy to confirm the effects of RTP treatment. Al-containing ZSM-58 zeolites had higher silanol concentrations than all-silica zeolites, confirming many silanol condensations by RTP. The condensation of silanol forms results in the formation of siloxane bonds and stronger resistance to thermal stress; therefore, RTP caused crack suppression in Al-containing ZSM-58 membranes. The results demonstrate that Al-containing ZSM-58 zeolite membranes with high CO2 permeance and CO2/CH4 selectivity and minimal cracking can be produced by using RTP.

Light and elevated temperature induced degradation in B–Ga co-doped cast mono Si PERC solar cells

The utilization of boron-doped Si solar cells based on the structure of a passivated emitter and rear cell (PERC) in the solar industry has increased recently. However, this type of high efficiency solar cell is exposed to a so-called light and elevated temperature induced degradation (LeTID). A suppressing of mc-Si LeTID has been studied through a regeneration treatment at high temperature under illumination or in the dark, but most was about the lifetime samples. In this work, to evaluate the applicability of regeneration and annealing at industrial relevant conditions, industrially made B–Ga co-doped cast-mono Si PERC solar cells were treated in a light soaking tool in which the intensity of light and substrate temperature could be adjusted separately and a rapid thermal process (RTP) system. This treatment was evaluated during a subsequent intentional degradation under conditions of 75 °C with an LED white light source at an intensity of 1 kW/m2. The results showed that properly regenerated samples by high intensity illumination at elevated temperatures suffered from the least degradation, while untreated solar cells had most severe degradation. The RTP method could improve the performance of the solar cells but the RTP-treated samples were less stable than the regenerated samples. It demonstrates the application of a fast (around 20 min) regeneration method could be coupled in mass production. Further, RTP treatment combining with an accelerated regeneration step may be a potential method to provide both the improved performance and high anti-LeTID properties in Si PERC solar cells.

Passivating and low-resistive poly-Si tunneling junction enabling high-efficiency monolithic perovskite/silicon tandem solar cells

We present a p+/n+ poly-Si tunneling junction (TJ) based on a tunnel oxide passivated contact (TOPCon) that enables both low contact resistivity ρc and high implied open-circuit voltages iVoc. It will be shown that the charge carrier profile of the TJ and the junction resistance are strongly affected by the applied thermal budget, consisting of a furnace anneal and/or a rapid thermal processing treatment, and the deposition parameters of the a-Si layers. A minimum combined junction resistance of the p+/n+ poly-Si/SiOx stack of less than 10 mΩ cm2 and iVoc of up to 726 mV at 1 sun illumination is reported. This work aims for incorporation of our p+/n+ poly-Si TJ into an industrially feasible tandem solar cell featuring a Si bottom cell with a TOPCon front emitter and the industrial standard technology of a passivated emitter and rear cell rear structure.

Highly oriented CuSbS2 thin films by rapid thermal processing of pre-annealed Sb2S3-Cu layers for PV applications

Copper antimony sulfide (CuSbS2) is an emerging absorber material in solar cells due to its nearly ideal optoelectronic properties, earth abundancy and environmentally benign composed elements. In the present work, highly oriented CuSbS2 thin films have been prepared by annealing layered structures of chemical bath deposited Sb2S3 and thermal evaporated Cu, followed by rapid thermal processing (RTP). A systematic study was performed by varying the processing time. Crystalline structure, morphology, elemental composition, chemical state, optical and electrical properties of the films formed at different conditions were analyzed using various techniques. X-Ray diffraction analysis showed that the post RTP treatment resulted CuSbS2 thin films with preferential orientation along (301) planes perpendicular to the substrate surface, on glass as well as Mo coated glass substrates. Optical properties showed that CuSbS2 has a direct bandgap of 1.6 eV supported by photo-current sensitivity at different wavelengths, which is nearly the ideal bandgap for an absorber layer in solar cell.

Preparation and characterization of the Si:Co layer for intermediate band solar cell applications

Abstracts The Co-implanted silicon layers with rapid thermal process (RTP) have been prepared for intermediate band materials. The characterization of the Si:Co layer has been analyzed and discussed. The results show that the Co concentrations in effective implanted region of the Si layers exceed the Mott limit, satisfying the requirement for the formation of intermediate band in silicon. The Co-implanted samples are well crystallized by RTP treatment. The effective lifetime of the carriers in the samples increases with the Co dose implanted. This indicates that the non-radiative recombination has been suppressed in the post-annealed samples. Furthermore, the optical absorptance of the samples is much enhanced in the wavelength range of above 1100 nm. It can be concluded that the Si:Co layer can be prepared by Co implantation in Si followed by RTP method, and it is a promising material that can be used for intermediate band solar cells.

Optimized rapid thermal processing for the template removal of SAPO-34 zeolite membranes

The synthesis of defect-free zeolite membrane remains a big challenge due to the fact that thermal expansion mismatch between the zeolite film and the porous support can generate thermal stress and cracks during template removal process. Rapid thermal processing (RTP) for the template removal of SAPO-34 zeolite membrane was systematically studied and an optimized procedure was provided. A short RTP at 973 K led to substantially increased selectivity and permeance. The higher selectivity is the result of bonding between zeolite crystals generated during the rapid heating, which reduced cracking during the flowing slow calcinations. Moreover, RTP also facilitated the decomposition of template molecules which resulted into higher permeance. Long exposure at high temperature and thermal cycling may lead to the formation of defects in SAPO-34 membranes. The integration of RTP and conventional calcination, using a 1 min RTP at 973 K, fast cooling to 673 K, then 4 h calcination and slow cooling to room temperature, led to significantly improved selectivity and permeance. This optimized template removal procedure inherited the advantage of RTP treatment and also reduced the exposure time at high temperature, thus led to membranes with both high permeance and selectivity. Permporometry analysis confirmed the reduced defect size and area caused by RTP treatment. The best membrane exhibited CO2 permeance of 6.1 × 10−7 mol/(m2 s Pa) and CO2/CH4 selectivity of 88 at 4.0 MPa pressure drop, which were improved by 49% and 80% respectively, compared with membranes calcined by conventional template removal procedure.

Control of Cu doping and CdTe/Te interface modification for CdTe solar cells

Copper doping in polycrystalline CdTe thin films and optimal band alignment at the CdTe/back-contact interface are critical for obtaining high performance devices. A CuCl2 solution treatment was used in this work to enhance the p-doping of CdTe. The carrier density of CdTe was increased from 4.72 × 1013 to 1.11 × 1014cm−3 and the open circuit voltage of the device was obviously improved more than ~50mV from 728 to 783mV. In order to further improve device performance, Te/Cu bilayer using rapid thermal processing was implemented to reduce barrier at the back contact. The short time-high temperature process efficiently activated the Te/Cu bilayer back contact and precisely controlled the Cu diffusion. The proper dose of Cu diffusion can further increase the p-doping of CdTe (~2.22 × 1014cm−3), resulting in the apparent increase in response from the CdS spectral region. The chemical reaction occurred between Te and Cu after rapid thermal processing treatments causing the formation of the CuxTe phases, which can form a barrier in the conduction band to reflect electrons and reduce recombination at the back contact. With the increase of the temperature, the open circuit voltage of the device increased. However, the device with excessive Cu contacted at higher temperature showed the reduction in response in the long-wavelength region and decrease in fill factor due to the formation of much more Cu-related recombination states. Finally, open circuit voltage of > 820mV, and fill factor of > 72% for CdTe solar cells with an area of 0.24cm2 were achieved.

Single-phase control of CuTe thin films for CdTe solar cells

Phase control is important to obtain high-performance CdTe solar cells when copper telluride is used as a back-contact for CdTe solar cells. In this paper single-phase CuTe was mainly controlled by the Cu/Te ratio via a co-evaporation method in combination with rapid thermal processing treatments. The alloy thin films as-deposited were mainly amorphous. After thermal treatments, the films experienced the phase transformation from mixed phases of CuTe and Cu1.4Te to single phase CuTe and then to coexisting phases. Single phase CuTe thin films were p-type semiconductor compounds and had a high carrier concentration, ∼1021 cm−3. With the copper telluride buffer layer, device performance than those without the buffer layer has been obtained. Moreover, single-phase orthorhombic CuTe contact buffer layer obviously improved diode characteristics and enhanced the device performance.

Oxidation and crystallization behavior of calcium europium silicon nitride thin films during rapid thermal processing

Luminescent thin films were fabricated on silicon wafers using reactive magnetron sputtering of Ca, Si and Eu in Ar/N2 atmosphere. In order to activate the luminescence, the as-deposited nitride films were heated to 1100°C by a rapid thermal processing treatment. X-ray diffraction measurements reveal the crystal phases that form during thermal treatment. By recording scanning electron microscopy images of the surface and the cross-section of the film at different radial locations, the formation of different layers with a thickness depending on the radial position is revealed. Energy dispersive x-ray spectroscopy analysis of these cross-sections reveals the formation of an oxide top layer and a nitride bottom layer. The thickness of the top layer increases as a function of radial position on the substrate and the thickness of the bottom layer decreases accordingly. The observation of different 4f65d1→4f7 Eu2+ luminescence emission bands at different radial positions correspond to divalent Eu doped Ca3Si2O4N2, Ca2SiO4 and CaSiO3, which is in agreement with the phases identified by X-ray diffraction analysis. A mechanism for the observed oxidation process of the nitride films is proposed that consists of a stepwise oxidation from the as-deposited amorphous nitride state to crystalline Ca3Si2O4N2, to Ca2SiO4 and finally CaSiO3. The oxidation rate and final state of oxidation show a strong temperature–time dependency during anneal treatment.

Suppression of void nucleation in Sn3.0Ag0.5Cu/CU solder joint by rapid thermal processing

Electrodeposited (ED) Cu was prepared and exhibited a strong voiding propensity at the Cu3Sn/Cu interface in the subsequent Sn3.0Ag0.5Cu/Cu solder joint. However, we found that the rapid thermal processing treatment could significantly reduce the voiding propensity of ED Cu. After rapid annealing, the grain size of Cu was obviously increased, which was found to reduce the amount of effective vacancies and lower the driving force of void formation. Meanwhile, the ED Cu before and after rapid annealing was analyzed using X-ray photoelectron spectroscopy, and it can be found that there did exist additives remained in the Cu layer during electroplating process. However, after rapid annealing treatment, some residuals would evaporate, and the others would decompose and react with Cu, which would change the residuals from the free state to the “deactivated” state and make them lose their acting as the precipitate for the heterogeneous nucleation. Thus, the Cu3Sn/Cu interface with few voids was finally formed.

Effect of Rapid Thermal Processing on the structural and device properties of (Ag,Cu)(In,Ga)Se2 thin film solar cells

(AgwCu1−w)(In1−xGax)Se2 alloy absorber layers with w≈0.8 and x≈0.78 ratios were deposited using multi-source elemental evaporation and analyzed by glancing incidence X-ray diffraction, scanning electron microscopy combined with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The effect of Rapid Thermal Processing (RTP) on the structure and composition of the near-surface layers was investigated. It was found that the RTP doesn't have a noticeable effect on the grain size and roughness of the film surface. On the other hand, additional reflections of the films with 0.5≤Ga/(Ga+In)<1 and Ag/(Ag+Cu)>0.5, due to an ordered defect phase which is confined to the near-surface region of the film, are completely diminished after RTP with excess Se present. X-ray photoelectron spectroscopy results show that RTP with excess Se present altered the distribution of elements, rendering the film surface less group I deficient after that process. Consequently, atomic ratios were changed from the composition of I1III5VI8 compound to the composition close to that of I1III3VI5 ordered defect phase. Additionally, the RTP treatment, especially with excess Se, significantly enhanced solar cell efficiency performance due to an improvement in the open circuit voltage.

Modulation of atomic-layer-deposited Al2O3 film passivation of silicon surface by rapid thermal processing

We have investigated the effect of a thin interfacial silicon oxide on the atomic-layer-deposited Al2O3 film passivating the silicon surface based on rapid thermal process (RTP). It is found that the effective carrier lifetime of samples strongly depends on the RTP temperature and reaches the maximum value at 550 °C. Both capacitance-voltage measurements and theoretical simulation have revealed that the RTP treatment cannot only modulate the charges in the Al2O3 film but also reduce the density of interface states responsible for the surface recombination. These results are interesting for the fabrication of high efficiency silicon solar cells in photovoltaics.

Boron activation and diffusion in silicon and strained silicon-on-insulator by rapid thermal and flash lamp annealings

We present experimental results on the activation and diffusion behaviors of boron in silicon-on-insulator and strained silicon-on-insulator using standard rapid thermal processing treatments as well as flash lamp annealing. After boron implantation at different doses and at a low energy of 1 keV, samples were annealed to activate the dopants, and secondary ion mass spectrometry and Hall measurements were carried out to determine boron diffusion and the amount of activated dopants, respectively. In contrast to rapid thermal annealing, flash lamp annealing enables the activation without significant diffusion of dopants. In addition, we investigated the effect of coating the samples with antireflection layers to increase the absorbed energy during flash annealing. As a result, the activation was increased significantly to values comparable with the activation obtained with standard annealing. Furthermore, the relation between the observed boron diffusion and activation as a function of the implantation and annealing parameters is discussed in terms of the kinetics of the defects involved in these processes.

Amorphous SiOx nanowires grown on silicon (100) substrates via rapid thermal process of nanodiamond films

Rapid thermal process (RTP) has been carried out on the deposited nanocrystalline diamond (NCD) films. The RTP treatments performed at 800 and 1200 °C have been shown to exert prominent influence on the morphology and structure of the NCD films. The loss of material at grain boundaries has been observed at both 800 and 1200 °C RTP treatments. Large-scale amorphous SiOx nanowires with diameters of 30–50 nm and length up to 10 μm were synthesized after RTP treatment at 1200 °C for 60 s. The synthesized nanowires were characterized in detail by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and energy-dispersed X-ray spectrometry analysis. A possible growth mechanism has been proposed to explain the observed phenomenon.

Electrical Characterization of 13 A In Situ Steam-Generated Oxynitride Gate Dielectrics

Ultrathin oxynitride gate dielectrics of similar thickness (∼1.3 nm) processed by an in situ steam-generated (ISSG), an ISSG with NO rapid thermal processing (RTP) treatment (ISSG-NO), and an ISSG with O 2 RTP treatment (ISSG-O 2 ) are investigated. The results demonstrate that ISSG-NO gate dielectrics exhibit superior interface properties, reduced leakage current, and improved reliability compared to other gate dielectrics. The ISSG-NO oxynitride film is an attractive candidate as the gate dielectrics in 90 nm and possibly beyond for complementary metal oxide semiconductor technologies.

Effect of rapid thermal processing on high temperature oxygen precipitation behaviour inCzochralski silicon wafer

The effect of rapid thermal processing (RTP) on the oxygen precipitation occurring at1050 °C in a Czochralski (CZ) silicon wafer has been investigated. It has been proved thatthe RTP-induced vacancies only enhance the early stage oxygen precipitation at1050 °C in terms of the precipitation rate. Furthermore, it is somewhat unexpected that after a lengthy1050 °C anneal the oxygen precipitates generated in the CZ silicon wafer with prior RTP treatmenthad considerably lower density and larger sizes in comparison with those generated in theCZ silicon wafer without prior RTP treatment. The reason for this is that the prior RTPtreatment will dissolve some of the grown-in oxygen precipitates, thus making the RTP-treatedwafer possess fewer nuclei contributing to oxygen precipitation in the subsequent1050 °C anneal. Moreover, the numbers of resulting precipitated oxygen atoms due to a lengthy1050 °C anneal were nearly the same in the CZ silicon wafers with and without prior RTPtreatment. Additionally, it has been illustrated that the high temperature RTP hassuperior capability to dissolve the existing oxygen precipitates. It is worthwhile to point outthat, when addressing the effect of RTP on the oxygen precipitation behaviour duringthe subsequent anneal, two functions arising from the RTP treatment, that is,the injection of vacancies into the silicon wafer and the dissolution of grown-inoxygen precipitates existing in the silicon wafer, should be taken into account.