Rapid Thermal Processing Method Research Articles

Thermal Load Influence during the Formation of Al-Al Contacts on the Electrical Parameters of the Integrated Circuits with Aluminum-Polysilicon Contacts

This work is devoted to establishing the effect of using rapid thermal processing (RTP) method (450 °C, 7 s) to form an ohmic contact between two layers of aluminum metallization on the electrical parameters and reliability of integrated circuits. The resistance values of contact chains aluminum-silicon, aluminum-polysilicon, polysilicon-silicon n+, aluminum-silicon n+, current-voltage characteristics of the tested bipolar transistors, as well as the results of the reliability analyses by conducting thermal field tests were chosen as the analyzed parameters of this microcircuit. Comparison of these parameters was carried out with respect to the microcircuits manufactured using standard RTP method (450 °C, 20 min) to form this contact. An analysis of the results of the resistance value of various contact chains showed that, regardless of the type of thermal treatment, all contact chains, with the exception of the aluminum-polysilicon contact chain, have almost the same resistance. By analyzing the elemental composition of the cleavage in the area of this contact by scanning electron microscopy, it was found that during rapid heat treatment, the depth of penetration of aluminum into polysilicon is 2 times less than during its standard formation due to a 2-fold reduction in the time of exposure to high temperature compared to the standard process. This leads to a lower concentration of the aluminum in the silicon and as a result to a higher contact resistance between the aluminum and polysilicon. An analysis of the currentvoltage characteristics showed that they are all identical, except for the course of the direct branch of the base current value from the emitter-base voltage. The deviation of the linear nature of this dependence in the region of their low voltage values (£ 200 mV) in the case of the formation of ohmic Al-Si and Al-Al contacts with the use of long-term heat treatments is due to the predominance of the generation-recombination current in this region associated with an increased density of traps in the depleted region and on the surface of the semiconductor. The ideal behavior of the base current versus the emitter-based voltage is maintained by applying rapid RTP method to form an Al-Al contact by eliminating traps both in the depletion layer and on the surface of the semiconductor. The tests carried out on the reliability of these products showed that it does not depend on the type of formation of ohmic contacts between the metallization layers.

Research of Electrophysical Properties of Thin Gate Dielectrics Obtained by Rapid Thermal Processing Method

Researches of the electrophysical characteristics of gate dielectrics obtained by the rapid thermal processing (RTP) method by two-stage and three-stage processes have been carried out. Each photonic processing (stage) was carried out for 12 s at a constant power of halogen lamps and heating the wafers to a maximum temperature of 1250 °C. The first two stages of the process were carried out in an oxygen atmosphere, the third - in nitrogen or a forming gas. It was found that for dielectrics obtained by the process with final processing in a nitrogen atmosphere, the absolute value of the voltage of flat zones is 0.42 V less, than for insulators, formed by a two-stage process. This is the consequence of the elimination of a significant part of the defects, responsible for the presence of Coulomb centers in the dielectric layer. Carrying out photonic processing in anitrogen atmosphere at high temperatures of procedures for proceeding of the restructuring of the structure of the dielectric layer. For insulators obtained by a three-stage process with final processing in N2, an increase in dielectric strength and breakdown voltage by 1 V and 3.3 MV/cm, respectively, is observed in comparison with dielectrics, obtained by a two-stage process. An increase in dielectric strength indicates relaxation of elastic stresses of deformed bonds and compensation for dangling bonds both in the dielectric and at its interface with Si during high-temperature photonic treatment. Passivation by nitrogen atoms of deformations at the dielectric/semiconductor interface will also have a positive effect on the strength of the insulator.

PREPARATION OF CZTS THIN FILM EMPLOYING RAPID THERMAL PROCESSING METHOD

CZTS thin film was fabricated by sulfurization process of deposited thin films on Mo coated glass substrates. Cu, Zn, and Sn thin film layers were deposited sequentially to form Glass/Mo/CuSn/Zn/Cu. The CuSn layer in the stacked structure was formed by annealing process in the sputtering chamber after sequential deposition of Cu and Sn, respectively. The sulfurization process was performed by rapid thermal processing method (RTP) so as to obtain kesterite CZTS structure. The obtained CZTS thin film was analyzed using several characterization methods such as EDX, XRD, Raman spectroscopy, SEM and PL measurements. The EDX measurements showed that elemental loss was not observed after the annealing process in sulfur atmosphere. The fabricated CZTS thin film showed Cu stoichiometric and Zn rich composition. The XRD pattern of annealed sample revealed formation of kesterite CZTS structure. The Raman spectra of the sample proved formation of kesterite CZTS structure. In addition, some CTS phases were detected in the structure by Raman spectroscopy. Polycrystalline surface microstructure was seen in SEM surface measurement. The room temperature PL measurement exhibited a transition around at 1.39 eV that is very close to band gap of kesterite CZTS structure. Overall, with this study, it has been shown that the CZTS thin film structure can be easily produced using the RTP method with very high heating rate.

Long-Term Performance and Stability of Interlayer-Free Mesoporous Silica Membranes for Wetland Saline Water Pervaporation.

Wetland water is an alternative water resource around wetland areas. However, it is typically saline due to seawater intrusion and contains high natural organic matter (NOM) that is challenging to treat. This study evaluated the stability of interlayer-free mesoporous silica matrix membranes employing a dual acid–base catalyzed sol–gel process for treatment of saline wetland water. The silica sols were prepared under a low silanol concentration, dip-coated in 4 layers, and calcined using the rapid thermal processing method. The membrane performance was initially evaluated through pervaporation under various temperatures (25–60 °C) using various feeds. Next, the long-term stability (up to 400 h) of wetland saline water desalination was evaluated. Results show that the water flux increased at higher temperatures up to 6.9 and 6.5 kg·m−2·h−1 at the highest temperature of 60 °C for the seawater and the wetland saline water feeds, respectively. The long-term stability demonstrated a stable performance without flux and rejection decline up to 170 h operation, beyond which slow declines in water flux and rejection were observed due to fouling by NOM and membrane wetting. The overall findings suggest that an interlayer-free mesoporous silica membrane offers excellent performance and high salt rejection (80–99%) for wetland saline water treatments.

Charging properties of thin gate dielectrics, obtained by the method of rapid thermal processing

The charge properties of thin dielectrics, obtained by rapid thermal processing (RTP), and their interfaces with silicon for MOS transistors are investigated. The production of insulator layers was carried out by a two- or three-stage RTP with photon processing regimes similar for each stage (duration – 12 s, maximum temperature – 1250 °C). After the third stage of RTP in a nitrogen atmosphere of the gate oxides, obtained by a two-stage process in oxygen atmosphere, the defects responsible for local charge centers are partially eliminated. There is also an increase in the relative value of the surface potential by an average of 100 relative units. The elimination of defects is a consequence of the rearrangement of the structure of the dielectric, its interface with silicon, and the diffusion of oxygen and silicon atoms along the interface of the insulator layer. For samples obtained by a two-stage RTP in an oxygen atmosphere and subjected to the third stage of processing in a forming gas, there is an almost complete elimination of local charge centers and an increase in the relative value of the surface potential by an average of 300 relative units. In this case, in addition to the processes occurring during the treatment of SiO2 by the RTP method in an nitrogen atmosphere, the liquidation of charge centers is a consequence of the passivation of defects by hydrogen atoms.

Formation of a gate dielectric of nanometer thickness by rapid thermal treatment

Investigations of the thickness and optical characteristics of thin SiO2 films obtained by one-, two-, or three-stage rapid thermal processing (RTP) at atmospheric pressure, pulses of 6, 12, and 20 s duration have been carried out. To obtain thin SiO2 films by the RTP method, N-type:Ph 4.5 Оhm/□ (100) silicon wafers were used as initial samples. The samples were preliminarily oxidized at 1000 °C of the obtained wet oxygen (SiO2 d = 100 nm), then the silicon oxide was completely removed in a solution of hydrofluoric acid, after which the wafers were subjected to chemical cleaning using the Radio Corporation of America (RCA) technology. Oxidation in a stationary oxygen atmosphere was carried out in one or two stages by heating the plates with a light pulse of different power up to maximum temperatures of 1035 – 1250 °C, as well as a three-stage process, where the final stage was annealing in a nitrogen atmosphere or in a forming gas (N2 97% + H2 3%). The characteristics of SiO2-Si barrier structures nitrided in N2, obtained by the RTP process by light fluxes with pulses of a second duration, were studied to improve the electrophysical parameters of gate oxides by the RTP method. It is of interest for integrated circuits (ICS) with a high density of the active regions of devices.

Development of Hybrid and Templated Silica-P123 Membranes for Brackish Water Desalination.

Water scarcity is still a pressing issue in many regions. The application of membrane technology through water desalination to convert brackish to potable water is a promising technology to solve this issue. This study compared the performance of templated TEOS-P123 and ES40-P123 hybrid membranes for brackish water desalination. The membranes were prepared by the sol–gel method by employing tetraethyl orthosilicate (TEOS) for the carbon-templated silica (soft template) and ethyl silicate (ES40) for the hybrid organo-silica. Both sols were templated by adding 35 wt.% of pluronic triblock copolymer (P123) as the carbon source. The silica-templated sols were dip-coated onto alumina support (four layers) and were calcined by using the RTP (rapid thermal processing) method. The prepared membranes were tested using pervaporation set up at room temperature (~25 °C) using brackish water (0.3 and 1 wt.%) as the feed. It was found that the hybrid membrane exhibited the highest specific surface area (6.72 m2·g−1), pore size (3.67 nm), and pore volume (0.45 cm3·g−1). The hybrid ES40-P123 was twice thicker (2 μm) than TEOS-P123-templated membranes (1 μm). Lastly, the hybrid ES40-P123 displayed highest water flux of 6.2 kg·m−2·h−1. Both membranes showed excellent robustness and salt rejections of >99%.

Rapid Thermal Processing and Long Term Stability of Interlayer-free Silica-P123 Membranes for Wetland Saline Water Desalination

The intrusion of sea water through to wetland areas creates wetland water became saline and very poor quality of water. For that, the interlayer-free silica-P123 (Si-P123) membranes calcined via rapid thermal processing (RTP) method was successfully investigated for desalination of wetland saline water. RTP method is a fast and low costs method to fabricate Si-P123 membranes compare to conventional thermal processing (CTP) method. The aims of this works are to improve the stability of silica base membranes by templating triblock copolymer P123 as carbon sources into silica matrices, and also to investigate the performance and long-term stability of Si-P123 membranes calcined under RTP method. Desalination through pervaporation process have been applied to produce potable water. Results shows the highest water flux of Si-P123 membrane calcined at 350 °C was 2.6 - 4.5 kg m-2 h-1. It was also found that this membrane was offering high surface area of 572 m2 g-1 and give mesopore structures (2.2 nm). For that, the performance of salt rejection was excellent (>98%). Furthermore, long-term stability appeared very stable for water fluxes and salt rejections measurement (over 400 h). Moreover, the permeate salt concentration was excellent (99% still under WHO limit standard (600 ppm) of potable water. It can be concluded that the stability of Si-P123 membrane was very robust for wetland saline water desalination for over 400 h of long-term stability.

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.

Liquid assisted grain growth in solution processed Cu(In,Ga)(S,Se)2

Many solution based methods of fabricating thin film Cu(In,Ga)Se2 solar cell absorbers can be described as a two step process, consisting of initial precursor deposition followed by high temperature post processing. This post processing step is termed “selenization” when the sample is treated in a selenium-rich environment, and is responsible for transforming the nanocrystalline or amorphous precursor layer into the large crystal grains that are necessary for high efficiency solar cells. Here we study the selenization of nanoparticle Cu(In,Ga)S2 precursor layers by a rapid thermal processing method, and develop a liquid assisted growth model to explain how large grain Cu(In,Ga)(S,Se)2 crystals nucleate and grow. We find that processing with saturated selenium, achieved by maintaining a higher temperature for the selenium source than the sample, is a necessary but not sufficient condition for grain growth of a 1–2 μm thick Cu(In,Ga)(S,Se)2 film. An additional necessary condition is an external supply of Na, without which grain growth of films on soda-lime glass stagnates at about 400 nm thickness, with the remainder of the film consisting of a bottom layer of fine grains. This stagnation of grain growth is hypothesized to be caused by diffusion limitations of Cu, In and Ga containing species from the coarsened selenized particles in the fine grain layer as well as accumulation of carbon left behind by the solution processing method which is rejected during grain growth. We find that deposition of a NaF layer on the nanoparticle precursor film followed by selenization at temperatures greater than 534 °C under a saturated selenium atmosphere results in large surface grains that span the thickness of the film, with only a thin bottom small grain layer primarily composed of carbon and selenium. Grain growth prior to stagnation is well described by a normal grain growth model, and our kinetic study yielded an estimated rate constant activation energy of 126.1 kJ/mol. Attempting to grow grains beyond the stagnation point results in abnormal grain growth. We develop a liquid assisted grain growth model to explain these observations.

Desalination Process via Pervaporation of Wetland Saline Water

Water is a very important resource for life on earth. Nowadays, water scarcity is a big issue around the world. Especially people who live in wetland areas, river is an important water source for their daily life. Unfortunately, the water becomes salty due to seawater intrusion into the river. The objective of this work is to apply desalination via pervaporation process of wetland saline water using pure silica membranes employ TEOS (tetraethyl orthosilicate) as a precursor. A two-step acid-base catalysed method has been applied to produce silica sols. The pure silica membranes were calcined under RTP (Rapid Thermal Process) method at 600°C for 1 hour. The various temperatures (20, 40 & 60 °C have been set in pervaporation set up in order to investigate the performance of silica membranes. It was found that at high temperature, silica membranes start to densify and give the lowest rejection compare to lower temperatures (84.9 %). In contrary, there was 100% of water flux increases when the feed temperature increases (from 0.61 to 1.19 kg m-2 h-1)

Rapid thermally processed hierarchical titania-based hollow fibres with tunable physicochemical and photocatalytic properties

A series of photocatalytic TiO2–carbon composite hollow fibres (HFs) was prepared in this study by a wet-dry phase inversion spinning method followed by a rapid thermal processing (RTP). The RTP method consists of two stages: (1) calcination at 800 °C for 15 min encased in a quartz tube followed by (2) a short open heating exposure at 800 °C for 0 to 7.5 min in air. The innovative two-stage RTP method led to a time saving of more than 90%. Results revealed that the pyrolysis conditions during the second stage of HF fabrication were essential to the final physical and chemical properties of resultant TiO2-carbon HFs, such as TiO2 crystallinity and carbon content, mechanical, textural and electronic properties, as well as photocatalytic reactivity. The best results show that HFs pyrolysed for a short duration (< 2 min) in the second stage produced a high microporous surface area of 217.8 m2·g−1, a good mechanical strength of 11 MPa and a TiO2 anatase-to-rutile (A/R) ratio of 1.534 on the HF surface. The HFs also achieved a 68% degradation of acid orange 7 dye with a kapp of 0.0147 min−1 based on a Langmuir-Hinshelwood model during the photocatalysis under UV light. Thus, this work provides a new synthesis protocol with significant time and cost savings to produce high-quality HFs for wastewater treatment.

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.

Intermediate band materials obtained by rapid thermal process of Co-implanted silicon

The intermediate band solar cell (IBSC) is a kind of novel photovoltaic device with very high efficiency limit. The intermediate band (IB) material is a key factor for fabricating high-performance IBSC. We explore to prepare IB material by Co implantation in silicon followed by a rapid thermal process (RTP). The results show that an IB is successfully formed in Si layer. The IB is located at about 0.3eV above the valence band edge. Moreover, no impurity phase is formed in the samples. Our results indicated that it is effective to form IB materials with the combination of ion implantation and RTP method. This approach is attractive since the RTP technique is beneficial to fabricate IB materials with thick impurity layers and convenient to use for mass production.

Structural and electroluminescent characteristics of sputtered SrS:Ce thin films by rapid thermal process

Thin film electroluminescent (EL) structure of Y 2O 3/SrS:Ce/BaTiO 3 has been deposited by rf-magnetron reactive sputtering and subsequently submitted to various thermal treatments. The effects of rapid thermal process (RTP) on the structural and EL characteristics of SrS:Ce thin films have been investigated, and compared with the results obtained by the conventional furnace. After the post-deposition annealing, the SrS film has the tendency to recrystallize preferentially in the (200) plane. The higher RTP temperature also results in the larger grain size of SrS. Auger measurements show that the RTP method can overcome the nonstoichiometry and interdiffusion problems encountered in the furnace-treated sample. It was found that the EL peaks gradually recovered to the band transitions of Ce 3+ ions (475 and 530 nm) in the SrS crystal field as the RTP temperature increased from 650 to 850°C. The threshold voltage can be further reduced to 150 V and the brightness increases eight times as much as the optimum furnace-treated device. The improvements in EL performance are due to the facts that the RTP can enhance the crystallinity of SrS, alleviate oxygen-induced defect centers from interdiffusion, activate Ce 3+ ions in phosphor, and yield a blue shift in emission colors.

The effects of rapid thermal process on the properties of sputtered SrS:CeF3 thin films

A Y2O3/SrS:Ce/BaTiO3 electroluminescent (EL) structure has been deposited by rf-magnetron reactive sputtering and, subsequently, submitted to various thermal treatments. The effects of the rapid thermal process (RTP) on the properties of SrS:Ce thin films have been investigated, and compared with the results obtained by the conventional furnace. After postdeposition annealing, the SrS film has the tendency to recrystallize preferentially in the (200) plane. The higher RTP temperature also results in the larger grain size of SrS. Auger measurements show that the RTP method can overcome the nonstoichiometry and interdiffusion problems encountered in the furnace-treated sample. It was found that the EL peaks gradually recovered to the band transitions of Ce3+ ions (475 and 530 nm) in the SrS crystal field as the RTP temperature increased from 650 to 850 °C. The threshold voltage can be further reduced to 150 V, and the brightness increases to eight times, as compared with that of the optimum furnace-treated device. The improvements in EL performance are owing to the facts that the RTP can enhance the crystallinity of SrS, alleviate oxygen-induced defect centers from interdiffusion, activate Ce3+ ions in phosphor, and yield a blueshift in emission colors.

Variations of electron traps in bulk n-GaAs by rapid thermal processing

Rapid thermal processing (RTP) using halogen lamps for liquid encapsulated Czochralski grown GaAs doped with Si has been studied by deep-level transient spectroscopy, capacitance-voltage, and photoluminescence measurements. RTP is performed at 700, 800, and 900 °C for 6 s with and without SiO2 encapsulation. Three electron traps ED1(Ec −0.26 eV), ED2(Ec −0.49 eV), and ED3(Ec −0.55 eV) are produced depending on RTP conditions. The trap ED1 is observed in all RTP samples, and its depth profiles vary with RTP conditions. The decrease of the shallow donor concentration occurs for RTP samples above 800 °C, especially for those without encapsulation. It is thought that these results, which are peculiar to the RTP method, are related to the production of As interstitials and As vacancies by the large thermal stress induced by the rapid heating for RTP. The decrease of the concentration of trap EL2(Ec −0.81 eV) is not observed with RTP as reported in the furnace processing. This is due to the effect of the short-time processing of RTP.