RF Inductive Heating Research Articles

Formation of D-Center in p-Type 4H-SiC Epi-Layers during High Temperature Treatments

The current work is devoted to studying the evolution of deep level defects in the lower half of the 4H-SiC bandgap after high temperature processing and ion implantation. Two as-grown and pre-oxidized 4H-SiC sets of samples have been thermally treated at temperatures up to 1950 °C for 10 min duration using RF inductive heating. Another set of as grown samples was implanted by 4.2 MeV Si ions at room temperature (RT) with different doses (1-4×108 cm-2). The so-called “D-center” at EV+0.6 eV dominates and forms after the elevated heat treatments, while it shows no change after the ion implantations (EV denotes the valence band edge). In contrast, the concentration of the so-called HK4 level at EV+1.44 eV increases with the implantation dose, whereas it anneals out after heat treatment at ≥ 1700 °C.

Electrical Properties of N Ion Implanted Layer in 3C-SiC(100) Grown on Self-Standing 3C-SiC Substrate

The electrical properties of N ion implanted 3C-SiC(100) have been investigated by means of Hall effect measurement. The p-type epitaxial layer grown on n+ substrate is multiply implanted with N ions with energy ranging from 15 to 120 keV at a total dose of 2.4×1015 cm-2 at room temperature, which corresponds to the doping layer with a N concentration of 1×1020 cm-3 and a thickness of 250 nm. The implanted sample is annealed by RF inductive heating annealer at temperature ranging from 1000 to 1500 oC for 10 min in Ar gas flow. The sample annealed at 1000 oC shows the sheet resistance of 1 k./sq. The sheet resistance of the implanted sample is decreased with the increase of annealing temperature. The sample annealed at 1500 oC shows the sheet resistance of 81 ./sq. and the sheet carrier concentration of 1.6×1015 cm-2. The electrical activity of implanted N impurity is estimated to be 68 %, which is much larger than that of N ion implanted 4H-SiC (about 0.9 %). The higher electrical activity of implanted N impurity is attributed to the shallower donor level than that in 4H-SiC.

Effect of Source Supply Methods on Low-Temperature Preparation of Lead Zirconate Titanate Thin Films Using SrTiO<sub>3</sub> Seed Layers by Metallorganic Chemical Vapor Deposition

Pb(Zr, Ti)O3 thin films were successfully prepared on (111)Pt/IrO2/SiO2/(100)Si substrates using SrTiO3 seeds at 290 oC by RF inductive heating type and 350 oC by resistive heating type metalorganic chemical vapor deposition method (MOCVD), respectively. The SrTiO3 was chosen as seed layers and prepared by pulsed laser deposition method. The crystal structures and orientations of SrTiO3 seeds were changed by deposition temperature. In the case of preparation with RF inductive heating MOCVD, the remanent polarization (2Pr) and coercive field (2Ec) were 42 μC/cm2 and 256 kV/cm, respectively.

SiC HTCVD Simulation Modified by Sublimation Etching

High temperature chemical vapor deposition (HTCVD) simulations of silicon carbide (SiC) were demonstrated with experimental results. A vertical cylindrical reactor was used in an RF inductive heating furnace and the temperature was more than 2200. SiH4 and C3H8 were used as source gases and H2 as carrier gas. A gas phase reaction model from the literature was used on the condition that the gas phase reaction is a quasi-equilibrium state. It was found that the major species were Si, Si2C, SiC2 and C2H2 in the gas phase reaction model as well as in the thermodynamic equilibrium calculation. Sublimation etching was considered in the surface reaction rates by modifying partial pressures of species with equilibrium vapor pressures. CFD-ACE+ and MALT2 software packages were used in the present calculation. The sticking coefficients were determined by fitting the calculated growth rates to the experimental ones. The simulated growth rate in a different reactor is in good agreement with the experimental value, using the same sticking coefficients. The present simulation could be useful to design a new reactor and to find optimum conditions.

Catalyst excitation by radio frequency for improved carbon nanotubes synthesis

Multiwall carbon nanotubes were grown on Fe:Co:CaCO 3 catalysts by catalytic chemical vapor deposition (CCVD) method using two heating methods, external oven and RF inductive heating. Comparative analysis of the nanotubes obtained by the two methods showed that inductive heating generates nanotubes with smaller external diameters, smaller number of walls, an aspect ratio in the range of hundreds, and with a ratio of the outside to the inside diameter ranging between 2 and 2.5. RF heating CCVD is an attractive method for growing carbon nanotubes because of the advantages it presents relative to the enhanced control ability of the growth process.

Development of RF and microwave heating equipment and clinical applications to cancer treatment in Japan

Development of RF and microwave (MW) heating equipment for hyperthermia and their clinical applications to various cancers undertaken in Japan have been reviewed in this paper. Originally developed heating devices include an RF capacitive and RF inductive heating device, an MW heating device with a lens applicator, an RF intraluminal heating device, an RF current interstitial heating device, and a ferromagnetic implant heating device. The concept and characteristics of those devices are described herein. Nonrandomized and randomized trials undertaken for superficial and deep-seated tumors demonstrated improved local response with the combined use of hyperthermia. Furthermore, the complications associated with treatment were not generally serious, except for chronic bowel damages suggested in a trial for colorectal cancers. These clinical results indicate the benefit of combined treatment of hyperthermia and radiotherapy. With the advancement of heating and thermometry technologies, hyperthermia will be more widely and safely used in the treatment of cancers.

Hyperthermic treatment of canine tibia through RF inductive heating of an intramedullary nail: a new experimental approach to hyperthermia for metastatic bone tumours.

Although the incidence of metastatic bone tumours is recently increasing, the local control rate of conventional treatment modalities is not satisfactory. If an intramedullary nail for the fixation of a weakened bone with metastatic lesions can be used as a heat-generating material for hyperthermia, the treatment result is expected to improve. This new approach to hyperthermic treatment of bone tumours has been investigated in a canine tibia. An intramedullary nail made of stainless steel was put into a medullary canal of a canine tibia. The leg was exposed to an alternating magnetic field of 100 kHz in the frequency and 100 Oe in the maximum intensity. The nail was inductively heated for 60 min. The temperature of the nail > 50 degrees C and the cancellous bone 5 mm from the nail was heated to a therapeutic temperature, 42.5 degrees C. After a bone labelling with tetracycline and calcein, the dogs were killed 2, 4 and 12 weeks after the heating. The area of osteonecrosis was evaluated by fluorescence microscopy analysis. The heated cancellous bone around the nail showed osteonecrosis in 2 weeks after the treatment, but it recovered completely in 12 weeks. This experiment has demonstrated the heating capability of the new hyperthermic technique and minimal toxicity to the bone, and suggests the clinical application to metastatic bone tumours.

Synthesis of diamond films in a rf induction thermal plasma

Microcrystals and microcrystalline films of diamond were prepared on molybdenum substrates in a thermal plasma which was produced by rf inductive heating in an argon-hydrogen-methane mixture gas under 1 atm pressure. The deposition rate amounted to 1 μm/min.

Doping effects in reactive plasma etching of heavily doped silicon

Etch rates of heavily doped silicon films (n and p type) and undoped polycrystalline silicon film were studied during plasma etching and also during reaction ion etching in a CF4/O2 plasma. The etch rate of undoped Si was lower than the n+-Si etch rate, but higher than the p+-Si etch rate, when the rf inductive heating by the eddy current was minimized by using thermal backing to the water-cooled electrode. This doping effect may be explained by the opposite polarity of the space charge present in the depletion layer of n+-Si and p+-Si during reactive plasma etching.

Heating Effects in Reactive Etching of Nb and Nb2 O 5

The reactive etching mechanism of Nb and in RF plasma has been studied in a flexible diode reactor, with special emphasis on a thin film heating effect. Etch rates of both materials during reactive ion etching are determined by a combination of the ion bombardment enhanced etching mechanism and the chemical etching mechanism. In niobium, the chemical etching always dominates over the ion enhanced etching. Etch rates in the plasma etching mode are primarily due to the chemical etching mechanism. The activation energy in the chemical etching is estimated to be 0.22 and 0.11 eV for Nb and , respectively. The Nb chemical reactivity (etch rate divided by a number density of the fluorine atoms) shows a substantial increase proportional to RF power and, surprisingly, to Nb film thickness. The thicker the film, the higher the etching rate observed during plasma etching. We argue that this is due to a temperature rise in a Nb film caused by the eddy current generated by the RF magnetic field (i.e., the RF inductive heating).

Silicon Etching Mechanisms - Doping Effect

AbstractEtch rates of heavily doped silicon films (n- and p-type) and undoped polysilicon film were studied during plasma etching and also during reactive ion etching in a CF4/O2 plasma. The etch rate of undoped Si was lower than the n+ Si etch rate, but higher than the p+ Si etch rate, when the RF inductive heating by the eddy current was minimized by using thermal backing to the water-cooled electrode. The thermal activation energy for spontaneous chemical etching was measured to be 0.10 eV, independent of the doping characteristics. This doping effect may be explained by the opposite polarity of the space charge present in the depletion layer of n+ Si and p+ Si during reactive plasma etching.

Thermal energy deposition from a single-loop rf whole-body applicator.

Whole-body hyperthermia at moderate temperatures (40.0 +/- 0.5 degrees C) is currently being investigated to assess its effectiveness as an adjuvant to other cancer therapies. At our institution, the whole-body heating is achieved by a combination of hot air circulation and rf inductive heating at 27.1 MHz. This paper reports the results of a study of the thermal energy deposition pattern associated with the rf applicator. The applicator consists of a single loop of nearly elliptical shape with dimensions 20 x 46 cm. The loop is embedded in a mattress and is fed by lead wires entering the side of the mattress. Temperature mapping in a heated gelatin phantom placed just above the rf loop showed maximum heating near the lead wires and a cool region above the center of the loop. Calculations of the magnetically induced and capacitive contributions to the electric field near the applicator indicate that the heating near the lead wires is largely capacitive in nature. This feature of the rf heating is of interest because capacitive fields result in preferential heating of fatty tissues. Further calculations showed that the capacitive heating contribution falls away much more rapidly than the induced field contribution with increasing distance from the plane of the rf loop.