Quartz Window Research Articles

The CLYC-6 and CLYC-7 response to γ-rays, fast and thermal neutrons

The crystal Cs2LiYCl6:Ce (CLYC) is a very interesting scintillator material because of its good energy resolution and its capability to identify γ-rays and fast/thermal neutrons. The crystal Cs2LiYCl6:Ce contains 6Li and 35Cl isotopes, therefore, it is possible to detect thermal neutrons through the reaction 6Li(n, α)t while 35Cl ions allow to measure fast neutrons through the reactions 35Cl(n, p)35S and 35Cl(n, α)32P. In this work two CLYC 1″×1″ crystals were used: the first crystal, enriched with 6Li at 95% (CLYC-6) is ideal for thermal neutron measurements while the second one, enriched with 7Li at >99% (CLYC-7) is suitable for fast neutron measurements. The response of CLYC scintillators was measured with different PMT models: timing or spectroscopic, with borosilicate glass or quartz window. The energy resolution, the neutron-γ discrimination and the internal activity are discussed. The capability of CLYC scintillators to discriminate γ rays from neutrons was tested with both thermal and fast neutrons. The thermal neutrons were measured with both detectors, using an AmBe source. The measurements of fast neutrons were performed at the Frascati Neutron Generator facility (Italy) where a deuterium beam was accelerated on a deuterium or on a tritium target, providing neutrons of 2.5MeV or 14.1MeV, respectively. The different sensitivity to thermal and fast neutrons of a CLYC-6 and of a CLYC-7 was additionally studied.

Diving–Surfacing Smart Locomotion Driven by a CO2‐Forming Reaction, with Applications to Minigenerators

Harvesting energy from environment has attracted increasing attention for its potential applications in fabricating minigenerator. However, most studies in the fabrication of mini‐ or nanogenerators are based on the concept of piezoelectricity or triboelectrification while few of the reports paid attention to the classical theory of Faraday's law. Herein, a pH responsive smart surface is combined with the reaction between CaCO3 and HCl to develop a new minigenerator, which can convert mechanical energy generated from the chemical reaction into electrical energy through cutting magnetic lines with moving conductive lines. The conductive lines are connected with a smart device consisting of a pH‐responsive cube, a hydrophobic cube, and a quartz cell window; the device can perform diving‐surfacing cycled motions with an intelligent initiation through the adjustment of the solution. The device can surface through gathering CO2 bubbles from the reaction between CaCO3 and HCl and dive by releasing the bubbles on the water/air interface. Moreover, the results demonstrate that the inert CO2 was nonhazardous to the smart surfaces, which is meaningful for durable electricity generation.

Rapid Analysis of Textiles with Portable near Infrared Spectroscopy

counterfeit detection, such as in the textile and other industries, as well as rapid analysis of agricultural products in the field, having instrumentation that can be taken to the samples and has the ability to provide qualitative (identification) as well as quantitative measurements is important. Applications of portable NIR in agricultural applications were recently reviewed, highlighting how the growing demands around product quality and authentication are being met by advances in instrumentation that can be used by non-expert users in the field for evaluation of produce, milk, grain etc. 4 Portable instrumentation that provides actionable data can greatly reduce the time required to determine the fate of samples, and can increase productivity in many ways. When it comes to seizure of suspect items, on-the-spot analysis can reduce the influx of suspicious, potentially harmful products. In the current application on quantification of cotton content in textile fabrics, the BW a portable instrument that can be taken on-site for direct analysis, simplifying the process of combatting counterfeit textiles. Experimental Diffuse reflectance NIR spectra of fabric samples were collected with the i-Spec Plus portable NIR spectrometer over a wavelength range of 900–1700 nm at a resolution of 3.5 nm. Scans were taken using an integration time of 1200 µs with 32× averaging. Samples were placed over the integrating sphere and held in place with a press holder that provides a flat surface with intimate contact to the quartz measurement window. Samples used were blended fabrics of varying cotton and polyester content, with cotton content ranging from 0.031% to 0.856% (percentage by mass) and polyester fibre content from 0.144% to 0.969%. A total of 27 samples were measured, with three scans per sample.

Initiation of 2‐Hydroxyethyl Methacrylate Polymerization by Tert‐Butyl Peroxide in a Planar PECVD System

This article reports on the deposition conditions and characterization of poly(2‐hydroxyethyl methacrylate) thin films grown by initiated plasma enhanced chemical vapor deposition process. The plasma power is inductively coupled into the process chamber with a planar‐coil antenna through a quartz window, and the substrate is cooled to promote physical adsorption of monomers on its surface. The introduction of the initiator allowed for film deposition at very low plasma powers (1 W) and greatly improves the deposition rates. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) analyses confirmed that the chemical functionalities of the monomers are preserved to a good extent during the depositions that were carried out at low plasma powers. The deposition kinetics of PECVD‐produced films from HEMA can be tailored by varying the substrate temperature. The apparent activation energies observed from PHEMA deposition kinetics with varying substrate temperatures are observed to be negative, which supports the hypothesis of the free radical polymerization mechanism in the PECVD PHEMA deposition.

Parameters of the preproduction series SiPMs for the CMS HCAL phase I upgrade

In 2012 the HCAL SiPM photo sensor upgrade was approved for the increased luminosity (5*1034) of SLHC. The upgrade will replace the current hybrid photodiodes (HPDs) with multi-pixel Geiger-mode avalanche photodiodes, also known as silicon photomultipliers (SiPMs). A key aspect of the upgrade to SiPMs is to add longitudinal segmentation and improve signal to noise to compensate for scintillator radiation damage. After 5 years of R&D with multiple companies we developed custom large dynamic range SiPMs with large PDE and small ENC. To ensure good mechanical alignment and easy handling of the large number of production channels (>20,000) we have developed a custom ceramic package with a very thin 0.3mm quartz window with Kyocera. Each package holds 8 channels of SiPMs.Here we report on the final SiPM parameters of the 2014 preproduction run from Hamamatsu (HPK) who has produced a series of 175 arrays with a total of 1400 SiPMs. An overview of our QA results and measurements of the photon detection efficiency, spectral response, crosstalk and cell recovery time will be discussed.

Design and characterization of a W-band system for modulated DNP experiments

Magnetic-field and microwave-frequency modulated DNP experiments have been shown to yield improved enhancements over conventional DNP techniques, and even to shorten polarization build-up times. The resulting increase in signal-to-noise ratios can lead to significantly shorter acquisition times in signal-limited multi-dimensional NMR experiments and pave the way to the study of even smaller sample volumes. In this paper we describe the design and performance of a broadband system for microwave frequency- and amplitude-modulated DNP that has been engineered to minimize both microwave and thermal losses during operation at liquid helium temperatures. The system incorporates a flexible source that can generate arbitrary waveforms at 94GHz with a bandwidth greater than 1GHz, as well as a probe that efficiently transmits the millimeter waves from room temperature outside the magnet to a cryogenic environment inside the magnet. Using a thin-walled brass tube as an overmoded waveguide to transmit a hybrid HE11 mode, it is possible to limit the losses to 1dB across a 2GHz bandwidth. The loss is dominated by the presence of a quartz window used to isolate the waveguide pipe. This performance is comparable to systems with corrugated waveguide or quasi-optical components. The overall excitation bandwidth of the probe is seen to be primarily determined by the final antenna or resonator used to excite the sample and its coupling to the NMR RF coil. Understanding the instrumental limitations imposed on any modulation scheme is key to understanding the observed DNP results and potentially identifying the underlying mechanisms. We demonstrate the utility of our design with a set of triangular frequency-modulated DNP experiments.

Detection of early stage changes associated with adipogenesis using Raman spectroscopy under aseptic conditions.

There is growing interest in the development of methods capable of non‐invasive characterization of stem cells prior to their use in cell‐based therapies. Raman spectroscopy has previously been used to detect biochemical changes commensurate with the osteogenic, cardiogenic, and neurogenic differentiation of stem cells. The aim of this study was to characterize the adipogenic differentiation of live adipose derived stem cells (ASCs) under aseptic conditions. ASCs were cultured in adipogenic or basal culture medium for 14 days in customized culture flasks containing quartz windows. Raman spectra were acquired every 3 days. Principal component analysis (PCA) was used to identify spectral changes in the cultures over time. Adipogenic differentiation was confirmed using quantitative reverse transcription polymerase chain reaction for the marker genes PPARγ and ADIPOQ and Oil red O staining performed. PCA demonstrated that lipid associated spectral features varied throughout ASC differentiation with the earliest detection of the lipid associated peak at 1,438 cm−1 after 3 days of induction. After 7 days of culture there were clear differences between the spectra acquired from ASCs in adipogenic or basal culture medium. No changes were observed in the spectra acquired from undifferentiated ASCs. Significant up‐regulation in the expression of both PPARγ and ADIPOQ genes (P < 0.001) was observed after 14 days of differentiation as was prominent Oil red O staining. However, the Raman sampling process resulted in weaker gene expression compared with ASCs that had not undergone Raman analysis. This study demonstrated that Raman spectroscopy can be used to detect biochemical changes associated with adipogenic differentiation in a non‐invasive and aseptic manner and that this can be achieved as early as three days into the differentiation process. © 2015 The Authors. Published by Wiley Periodicals, Inc. on behalf of the International Society for Advancement of Cytometry.

4H-SiC Schottky photodiodes for ultraviolet flame detection

In the last few years silicon carbide (SiC) has emerged as an appropriate material for the detection of very low ultraviolet photon fluxes even at elevated temperatures. In this paper we report on the electro-optical characteristics of large area interdigit Ni2Si/4H-SiC photodiodes in TO metal can package with a suitable molded cap quartz window with high transmission in the ultraviolet wavelength range. The detectors have been tested for the detection of the ultraviolet component of the yellow flame emitted by a small candle, showing good sensitivity for very weak photon fluxes notwithstanding the linear operation condition of the photodiodes.

Direct Observation of the Current Distributions across SOFC by Measuring the Lateral Voltage Differences

Introduction In a realistic setting, each cell usually does not have a theoretical uniform distribution of the cell performance due to the cell design and manufacturing, especially for planar-type SOFCs. Electrochemical and mechanical thermal stress on the cells can affect the performances of the cell when the temperature and current gradients across the cell are not uniform. Therefore, direct observations are very important for the conformation of the SOFC reliability. This research evaluates the overall performances of the current distribution of planar-type SOFCs. With these distributions, clear understanding of the performances can be found of overall cell and at a certain location of the cell, which can help with improvements of the cell and the stacks. Experimental Procedures In this research, 5cm x 5cm anode-supported SOFC was used for conducting the experiment. The fuel for anode and the oxidant for cathode were 25 and 50% hydrogen and air. The operating temperature of the furnace was set at 800ºC. For the equipment, there is a quartz window on the cathode side with thirty-two 0.3mm diameter holes for the voltage probes. For current distribution, distributions of voltages on the cathode current collector, φ, were measured using a digital multimeter. Although the potential differences are theoretically uniform over the current collector, a slight gradient exists, which makes a lateral current flow towards the current lead. Using the charge conservation equation, the current across the cell can be calculated from the measured potential distribution of the cell. For the set-up of the potential probes, 0.2mm platinum wires were spot-welded onto the silver mesh at 32 different locations. Figure 1 shows the position of the probe on the silver mesh current collector. To measure the lateral voltages, voltages between the probe #1 and the rest of the probes were measured in respect to the overall current applied across cell. The lead-in current was located next to probe #1 and the lead out current was on the anode side at the lateral position next to probe #13. The current applied to the overall cell were at 0, 1, and 5A (0, 0.0625, and 0.3125 A/cm2). Results and Discussions The lateral potential for 0.0625, and 0.3125 A/cm2 for 50% hydrogen are shown in Figure 2. The overall voltages at 0, 0.0625, and 0.3125 A/cm2 were 1.079, 0.991, and 0.886 V. For the 0.0625 A/cm2, there was a uniform lateral potential except for a particular area (probe #8, 9, 10 area). This could be from a potential crack that was realized after the cell was completely cooled down and the equipment was opened. For the 0.3125 A/cm2, even with a slight depression of voltages at probe #8, 9, and 10, gradual distribution of lateral voltage difference was shown. Figure 3 shows the calculated current distribution for 50% hydrogen at 0.3125 A/cm2. There are negative current distributions at particular points, which could be due to the gas leakage. Also, at the current probe, there is a steep increase in the current. This is due to the possibility from Joule heating from applying a high overall current. Conclusion After measuring the potential across the cell and calculating the current, having only 32 points is not enough to calculate for the current distribution. Only 16 points in the middle of the cell can be calculated, which does not show the smooth transition of the distribution clearly. In addition, a simulation will be also done to compare the data with this experiment. Figure 1

Intensity Modulated Photocurrent Spectroscopy (IMPS) Used to Detect Photoactive Intermediates during Ni-W Electrodeposition

Intensity modulated photocurrent spectroscopy (IMPS) is a technique conventionally used to characterize the semiconductor/electrolyte interface. It is used here in a new way, to track the presence of adsorbed, photoactive intermediates during the electrodeposition process, using Ni-W alloy electrodeposition as an example. Interest in Ni-W alloys are related to their high corrosion resistance, ability to catalyze the hydrogen evolution reaction from water, and superior wear resistance. The Ni-W deposition behavior from aqueous solutions is described as a coupled reaction mechanism and better understanding of the mechanism can help to control the deposit composition, which in turn is related to the resulting properties. To this end, IMPS was used to examine codeposition using an ammonia free citrate-boric acid electrolyte. The IMPS spectra was generated for different applied potentials. A significant current response to the incident modulated UV light was detected where steady state Ni-W codeposition takes place. The results confirm the presence of photoactive intermediates during codeposition, and demonstrates the first use of this technique in the electrodeposition process of a metallic alloy. The attached figure shows a typical response during cathodic deposition of a Ni-W alloy at -1 V vs AglAgCl (42 wt % W) during IMPS compared to a potential where open circuit conditions are achieved and when clearly the alloy is treated anodically. A three electrode, single compartment cell with a flat quartz window was used with the following electrolyte: 0.375 M sodium citrate, 1.0 M boric acid, 0.075 M sodium tungstate, and 0.1 M nickel sulfate at a pH of 7. The response during deposition is significantly larger than that which occurs when a surface oxide is purposely generated; helping to valid that the deposition intermediate contributes to the observed impedance results. A simple model that includes the generated photocurrent contributing to an electrochemical reaction at the electrode/electrolyte interface or being lost to recombination was used to interpret the IMPS results. The dominate process occurring during IMPS is electron-hole pair recombination and thus, the modulated light does not significantly change the deposit composition, which was experimentally confirmed. Acknowledgments This material is based upon work supported by the U.S. National Science Foundation under Grant No.0957448. Figure 1

An original approach for Raman spectroscopy analysis of radioactive materials and its application to americium‐containing samples

An approach for Raman measurements of highly radioactive samples is presented here. The innovative part of this approach lies in the fact that no single part of the Raman equipment is in direct contact with the radioactive sample, as the sample is sealed in an alpha‐tight capsule. Raman analysis is effectively performed through the optical‐grade quartz window closing the capsule. This allows performing micro‐Raman measurements on radioactive samples with no limitations on the laser source wavelength, polarisation mode, spectrometer mode and microscope mode (provided the focal length of the microscope objective is greater than the thickness of the quartz window and with sub mg samples). Some example results are shown and discussed. In particular, some spectral features of americium‐containing oxide nuclear fuel specimens are presented. Raman spectra clearly reveal in these specimens the presence of abundant oxygen defects induced in the fcc fluorite lattice by trivalent americium. In order to complete the analysis the Raman spectrum of pure americium dioxide was also measured with a lower energy excitation source compared with previous research. The current results seem to be consistent with the possible occurrence of a photolysis process induced by the Raman laser, resulting in the formation of hyperstoichiometric americium sesquioxide Am2O3 + z. Such a photolytic process is deemed to be unavoidable when visible lasers are used as excitation sources for the Raman analysis of americium dioxide. © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley &amp; Sons, Ltd.

High Temperature Flow Visualization and Aerodynamic Window Protection of a 100-kWth Solar Thermochemical Receiver-reactor for ZnO Dissociation

Abstract A 100-kWth receiver-reactor designed for the thermal dissociation of ZnO into metallic Zn is separated from atmosphere by use of a transparent quartz window, through which concentrated solar radiation is admitted. Protection of such windows from reactant and product particle deposition is critical for successful reactor operation. Usingin-situ visualization techniques, the effectiveness of an auxiliary flow of inert gas in aerodynamically protecting a 600-mm-diameter quartz window mounted on the receiver-reactor has been directly assessed during high-temperature experimentation. This work has shown that: (i) high-temperature, in-situ flow visualization is possible and effective in assessing flow patterns developed inside the reactor;(ii) there exist three characteristic flow patterns inside the reactor that can be dynamically controlled by use of a set of tangential and radially oriented jets; and (iii) a region of stable protective flow, under a wide range of experimental and operational conditions, is capable of repeatedly and fully suppressing detrimental particle depositions on the quartz window.

Evidence of delayed light emission of tetraphenyl-butadiene excited by liquid-argon scintillation light

TetraPhenyl Butadiene is the wavelength shifter most widely used in combination with liquid Argon. The latter emits scintillation photons with a wavelength of 127 nm that need to be downshifted to be detected by photomultipliers with glass or quartz windows. TetraPhenyl Butadiene has been demonstrated to have an extremely high conversion efficiency, possibly higher than 100 % for 127 nm photons, while there is no precise information about the time dependence of its emission. It is usually assumed to be exponentially decaying with a characteristic time of the order of one ns, as an extrapolation from measurements with exciting radiation in the near UV. This work shows that TetraPhenyl Butadiene, when excited by 127 nm photons, reemits photons not only with a very short decay time, but also with slower ones due to triplet states de-excitations. This fact can strongly contribute to clarify the anomalies in liquid Argon scintillation light reported in literature since seventies, namely the inconsistency in the measured values of the long decay time constant and the appearance of an intermediate component. Similar effects should be also expected when the TPB is used in combination with Helium and Neon, that emit scintillation photons with wavelengths shorter than 127 nm.

Electron-Impact Excitation of Gas-Phase Sulfur

Herein we present results from a study of optical emission in the range 270–550 nm that was stimulated in collisions of low-energy electrons (2–50 eV) with gas-phase S. Experimental. Excitation of S was studied using an optical method with an MDR-2 high-aperture diffraction monochromator in the range 270–550 nm on an automated apparatus. The apparatus and procedures for measuring and calibrating the beam energy of exciting electrons were described in detail [7]. The beam diameter was 1.5 mm for electrons emitted by an oxide cathode. The beam was formed by a four-electrode electron gun, passed through a gas-fi lled cell 12 mm high and 10 mm in diameter, and was detected by a deep Faraday cup. The energy of electrons in the beam (full width at half-height of the distribution maximum of differentiated voltammetric characteristics) was ~0.5 eV at 20 ��A. Gas-phase S was fed into the collision cell from a separate resistance-heated reservoir loaded with S (~5 g) through a thin-walled tube 4 mm in diameter and 60 mm long. This enabled the temperatures of the collision cell, electron beam, and Faraday cup, which had their own independent resistance heaters, to be maintained 20–30 K above the temperature of the S reservoir. Thus, condensation of gas-phase S on the components of the aforementioned electron-optical system was avoided. The S reservoir temperature for all measurements was maintained within 335 ± 2 K. The vacuum chamber was evacuated using an oil pump at 500 L/s. The residual gas pressure in the vacuum chamber during the measurements was <10 –6 Torr. Emission resulting from collisions of electrons and gas-phase S passed through quartz windows of the collision cell and vacuum chamber, was focused using a dual-lens condenser onto the input slit of the MDR-2 diffraction monochromator (grating 1200 lines/mm, reverse dispersion 2 nm/mm), and was detected by an FEU-106 photoelectron multiplier. Single FEU photoelectron pulses were pre-amplifi ed, shaped by a broad-band amplifi er-discriminator, fed through an interface card into a pulse counter, and stored in a PC. The signal at each measurement point was accumulated for 10–60 s of exposure depending on the intensity of the emitted spectral lines or molecular bands in order to ensure that the measurement accuracy was better than 5–10% at the emission maximum.

Influence of the Window Thermal Diffusivity on the Silicon Wafer Temperature in a Rapid Thermal System

The heating of a silicon wafer in a rapid thermal process is studied by numerical simulation. In the model, the equations of conservation of mass and energy are solved with the finite-volume method and the determination of the solutions of the radiative transfer equation is based on the Monte-Carlo method. The results of numerical simulations, without optimization and in steady state, show a close relationship between the thermal profiles of the silicon wafer and the ones of the quartz window. By introducing a high thermal diffusivity value for the window, the homogeneity of the wafer temperature is improved by 54%. The effect of heat storage by the quartz window on the temperature profile of the silicon substrate is hence well appreciated. Finally, a selection of materials is proposed for the implementation of the high diffusivity infrared window.

The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the filters foreseen for the CaSSIS imager of the Exomars/TGO mission in order to prepare future science operations.

Development of a water load for a Ka-band 10 kW continuous-wave gyrotron in an ECR ion source system

A gyrotron is used as a microwave power source in an electron-cyclotron-resonance (ECR) ion source system. In order to test the gyrotron, which operates at a frequency of 28 GHz in the continuous-wave (CW) mode, the Korea Basic Science Institute (KBSI) developed a water load that absorbed up to 10 kW of power. The water load consists of an aluminum jacket, a quartz window, and a waveguide. A distilled water flow of 13 L/min, sealed with the quartz window, is used as the absorbent. At 28 GHz, the S11 parameter and the voltage standing-wave ratio (VSWR) of the water load design were calculated to be less than −30 dB and 1.05, respectively. In practical experiments, the increase in the water’s temperature was approximately 10 °C at the highest power.

Electron cyclotron resonance plasma source with belt-type magnet assembly and slit antennas

An electron cyclotron resonance plasma source with a belt-type magnet assembly and slit antennas was developed for generating high density plasmas at low operating pressures. To enhance plasma confinement and avoid the disadvantages of quartz windows, a continuous arrangement of magnets and direct microwave injection from the slit antennas without quartz windows was used. This plasma source operated at an argon gas pressure of 0.4–1 mTorr and microwave power of 300–800 W. Electron temperature and ion density are dependent on the radial and axial position.

Development of a Novel Cyclonic Flow Combustion Chamber for Achieving MILD/Flameless Combustion

The present study investigates the characteristics of MILD/Flameless Combustion in a prismatic (20x20x5 cm3) laboratory-scale burner. The main pre-heated flow rate composed by diluent and oxygen and the fuel (at environmental temperature) are fed inside the combustion chamber from one side. Diametrically opposed the feeding configuration is reproduced, thus realizing a cyclonic flow field inside the reactor. The outlet is located on the top of the chamber. The system is provided with a quartz window and some thermocouples to measure the temperature profiles inside the burner. The oxidation process of C3H8/O2 mixtures diluted in N2 was studied varying external parameters of the system, namely inlet temperatures (up to 1200K) and equivalence ratio (lean to reach mixtures) to identify the combustion regimes in a non-premixed facility. A numerical simulation of fluid dynamics in the chamber was performed to give proper indications concerning the design of the chamber.

Improvement of temperature homogeneity of a silicon wafer heated in a rapid thermal system (RTP: Rapid Thermal Process) by a filtering window

Rapid thermal processes are used in various key stages in the microelectronics industry. In this study, the heat transfer in a rapid thermal system is modelled with the finite volume method. The influence of the radiative properties of the quartz window on the thermal profile of the silicon wafer is first investigated. The obtained temperatures are interpreted by analyzing the radiative properties according to wavelength and temperature. The wafer temperature profile for a non-optimized heating in steady-state is explained by a four-phase scheme where the radiative heat fluxes are depicted. From this scheme, a filter on the underside of the quartz window is envisaged to achieve temperature uniformity for the wafer. Two configurations are tested, one where the filter covers the entire lower surface of the quartz window and another where it is placed in a ring close to the reactor wall to confine the infrared radiations with wavelengths beyond 2.6 μm in order to raise the temperature at the edge of the wafer. Simulations demonstrate that the latter modification enables a more significant improvement of the wafer temperature homogeneity with less than 1% dispersion. The implementation of the filtering window is also discussed.