In-situ monitoring for CVD processes

Aiming towards process control of industrial high yield/high volume CVD reactors, the potential of optical sensors as a monitoring tool has been explored. The sensors selected are based on both Fourier transform infrared spectroscopy (FTIR) and tunable diode laser spectroscopy (NIR-DLS). The former has the advantage of wide spectral capability, and well established databases. NIR-DLS spectroscopy has potentially high sensitivity, laser spatial resolution, and the benefits of comparatively easier integration capabilities-including optical fibre compatibility. The proposed technical approach for process control is characterised by a 'chemistry based' feedback system with in-situ optical data as input information. The selected optical sensors continuously analyze the gas phase near the surface of the growing layer. The spectroscopic data has been correlated with process performance and layer properties which, in turn establish data basis for process control. The new process control approach is currently being verified on different industrialised CVD coaters. One of the selected applications deals with the deposition of SnO2 layers on glass based on the oxidation of (CH3)2SnCl2, which is used in high volume production for low-E glazing

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Ruptura de aneurisma da aorta toracoabdominal em cavidade pleural direita Ruptured thoracoabdominal aortic aneurysm in the right pleural space

É relatado um caso de ruptura de aneurisma aórtico toracoabdominal em cavidade pleural direita, em paciente de 76 anos, com insuficiência renal crônica. Serão discutidas as possibilidades terapêuticas, salientando a importância do diagnóstico e tratamento precoces.<br>The case of a thoracoabdominal aortic aneurysm rupture in the right pleural space of a 76-year-old patient with chronic renal insufficiency is reported. Possible therapeutic measures are discussed

FTIR monitoring of industrial scale CVD processes

Chemical vapour deposition (CVD) as well as infiltration (CVI) processes are key technologies in many industrial sectors, including extensive use in micro electronics, surface protection of components, for energy efficient optical coatings on glass for buildings and for manufacturing fibre reinforced ceramic composite materials. Gaseous precursors containing the elements to be deposited are pyrolysed at the heated substrate or, alternatively, by exciting the molecules with laser photons or by a plasma. Although the techniques are used on a technological scale, the underlying chemistry is not completely understood. The goal of the presentation is to improve CVD process control by a multipurpose, knowledge based feedback system for monitoring the CVD/CVI process with in-situ FTIR spectroscopic data as input information. In the presentation, three commonly used, and distinctly different, types of industrial CVD/CVI processes are taken as test cases: (i) a thermal high capacity CVI batch p rocess for manufacturing carbon fibre reinforced SiC composites for high temperature applications, (ii) a continuously driven CVD thermal process for coating float glass for energy protection, and (iii) a laser stimulated CVD process for continuously coating bundles of thin ceramic fibres (i) The CVI process operates near 1000oC, in the low pressure region and with CH3SiCl3 (MTS) as a SiC precursor. Using FTIR emission spectroscopy, several gaseous species have been detected including MTS, SiCl2, (SiCl3)n=1,2, SiCl4, HSiCl3, CH4, CH3Cl and HCl which, consequently, can be monitored simultaneously. (ii) The CVD process operates at atmospheric pressure. A model reactor has been developed for studying the concentration dependence of FTIR emission spectra. The measured spectra are compared with calculated spectra which have been derived by optical modelling of a multilayer based optical model. (iii) Based on an industrial 6kW cw-CO2- laser, a laser driven process currently runs in a prototy pe coater. Layers of graphitisised carbon and several ceramic materials (SiC, TiCxNy, TiB2, BN, etc.) have been deposited on carbon fibres and on SiC fibres. Depending on the selected precursor, the chemistry of the laser driven CVD process is characterised by photothermal reaction paths, typically in the temperature region 1300oC -2500oC and photolytical paths. The FTIR measurements have been carried out by rapid extraction of the gaseous reaction products and measurements in an optimised volume gas cell. As an example, the deposition of SiC layers from MTS results in the detection of HCl, HSiCl3, H2SiCl2, SiCl2, CH4, CO and C2H2

Deposition of thin film SnO2:F onto aluminium foil for use in flexible tandem solar cells

Atmospheric pressure Chemical Vapour Deposition has been used to deposit polycrystalline thin films of SnO2:F on aluminium foil. This foil is used commercially as a temporary substrate in the production of flexible solar cells. The resulting thin films were characterised and fabricated into a-Si:H/mc-Si:H tandem solar cells. These devices gave promising initial energy conversion efficiencies up to 7.5% and high current densities. Spectral response measurements showed good blue response indicating sufficient transparent conducting oxide/p-interface and excellent current values for the bottom cell as a result of the high quality of the SnO2:F

NIR diode laser based process control for industrial CVD reactors

The proposed new technical approach for CVD process control is characterised by a "chemistry based" feedback system with in-situ optical data as input information. The selected optical sensors continuously analyse the gas phase near the surface of the growing layer. The spectroscopic data has been correlated with process performance and layer properties, which in turn establish a data basis for process control. Diode laser spectroscopy in the near infra red (NIR-DLS) has been successfully applied for monitoring industrial CVD reactors. This technology has some notable potential advantages for production process applications. For example, the technology is robust and simple to operate, interference between species detection can be reduced, and simultaneous multi-point monitoring is readily achieved. The new process control approach is currently being verified on different industrialised CVD coaters. The paper will present some results of recent process monitoring studies on deposition of SnO2 layers on glass, based on the oxidation of (CH3)2SnCl2, which is used in high volume production for low-E glazings. Kinetic investigations support the empirically determined stiff correlation between gas phase composition and deposition rate

NIR diode laser based process control for industrial CVD reactors

The proposed new technical approach for CVD process control is characterised by a "chemistry based" feedback system with in-situ optical data as input information. The selected optical sensors continuously analyse the gas phase near the surface of the growing layer. The spectroscopic data has been correlated with process performance and layer properties, which in turn establish a data basis for process control. Diode laser spectroscopy in the near infra red (NIR-DLS) has been successfully applied for monitoring industrial CVD reactors. This technology has some notable potential advantages for production process applications. For example, the technology is robust and simple to operate, interference between species detection can be reduced, and simultaneous multi-point monitoring is readily achieved. The new process control approach is currently being verified on different industrialised CVD coaters. The paper will present some results of recent process monitoring studies on deposition of SnO2 layers on glass, based on the oxidation of (CH3)2SnCl2, which is used in high volume production for low-E glazings. Kinetic investigations support the empirically determined stiff correlation between gas phase composition and deposition rate

NIR Diode Laser Based Process Control for Industrial CVD Reactors

The proposed new technical approach for CVD process control is characterised by a chemistry based feedback system with in-situ optical data as input information. The selected optical sensors continuously analyse the gas phase near the surface of the growing layer. The spectroscopic data has been correlated with process performance and layer properties, which in turn establish a data basis for process control. Diode laser spectroscopy in the near infra red (NIR-DLS) has been successfully applied for monitoring industrial CVD reactors. This technology has some notable potential advantages for production process applications. For example, the technology is robust and simple to operate, interference between species detection can be reduced, and simultaneous multi-point monitoring is readily achieved . The new process control approach is currently being verified on different industrialised CVD coaters. The paper will present some results of recent process monitoring studies on dep osition of SnO2 layers on glass, based on the oxidation of (CH3)2SnCl2, which is used in high volume production for low-E glazings. Kinetic investigations support the empirically determined stiff correlation between gas phase composition and deposition rate

The influence of F-doping in SnO2 thin films

Transparent conductive oxide (TCO) films are widely used in many consumer products. The properties of the TCO can critically affect the efficiency of the application. With this in mind the surface morphological, optical and electrical properties have been targeted by systematic exploration of the Atmospheric Pressure Chemical Vapour Deposition (APCVD) growth parameters and in this work particularly the effect of dopant concentrations. APCVD processes are particularly suited to use in industry due to the high volume, continuous growth processes and fast growth rates achievable. Using the APCVD process, F-doped SnO2 has been deposited on glass using monobutyl tin trichloride with trifluoro-acetic acid as the dopant source. The deposited films were characterised for crystallinity, morphology, optical haze and electrical properties. Additionally, the stability of the films to post growth annealing were studied, as this is an important factor as most TCO’s will need further processing for the production of consumer products. It has been shown that increasing the dopant levels led to a decrease in surface roughness along with a reduction in feature size. The surface features also showed a decrease in the average angle, although with a broader distribution. As expected increased doping gave increased carrier concentration and mobility, with a non-linear decrease in resistivity. The polycrystalline structure became less selective in orientation on doping, but no further change was seen on increasing the dopant level. The samples tested showed only marginal changes in electrical and optical properties at elevated temperatures, confirming their thermal stability