Achievement of Low Carrier Concentration of High-Uniformity SiC Films Grown by High Speed Wafer Rotation Vertical CVD Tool

2020 ◽  
Vol 1004 ◽  
pp. 84-90
Author(s):  
Yoshiaki Daigo ◽  
Akio Ishiguro ◽  
Shigeaki Ishii ◽  
Takehiko Kobayashi ◽  
Yoshikazu Moriyama
Keyword(s):  
Carrier Concentration ◽  
High Speed ◽  
Carrier Lifetime ◽  
Lower Sensitivity ◽  
Wafer Thickness ◽  
High Uniformity ◽  
The Mean ◽  
Sic Film ◽  
Sic Films ◽  
Effect Of Surface

N-type 4H-SiC homo-epitaxial films were grown by high speed wafer rotation vertical CVD tool, and effect of surface C/Si ratios on in-wafer uniformity and lower limit of carrier concentration of the SiC films on 150 mm diameter wafers was investigated. From analysis of in-wafer distribution by mapping of whole wafers, it was found that high in-wafer thickness uniformity was obtained for the films grown both at lower introduced C/Si ratio of about 1.35, which corresponds to surface C/Si ratio is lower than 1.0, and at higher introduced C/Si ratio of about 1.80, which corresponds to surface C/Si ratio is higher than 1.0. However, larger fluctuation of the carrier concentration at wafer edge was observed for the film grown at lower introduced C/Si ratio, compared with the film grown at higher introduced C/Si ratio. Lower fluctuation of the carrier concentration for the film grown at higher introduced C/Si ratio is thought to be due to lower sensitivity of carrier concentration on growth temperature, which is observed for the film grown at surface C/Si ratio higher than 1.0. Also, the film grown at higher introduced C/Si ratio showed longer carrier lifetime with higher uniformity, although the film grown at lower introduced C/Si ratio indicated shorter carrier lifetime with lower uniformity. The mean carrier concentration of the films grown at higher introduced C/Si ratio was reduced by two digits compared with those grown at lower introduced C/Si ratio, and low carrier concentration of 1.7 x 1014 cm-3 with high in-wafer uniformity for intentionally doped SiC film grown at higher introduced C/Si ratio was achieved. Based on the results mentioned above, fabrication of thick and low-doped epi layer on 150 mm diameter wafer with high in-wafer uniformity was demonstrated.

Improvement of Repeatability on N-Type 4H-SiC Epitaxial Growth by High Speed Wafer Rotation Vertical CVD Tool

2020 ◽  
Vol 1004 ◽  
pp. 78-83
Author(s):  
Yoshiaki Daigo ◽  
Akio Ishiguro ◽  
Shigeaki Ishii ◽  
Takehiko Kobayashi ◽  
Yoshikazu Moriyama
Keyword(s):  
Carrier Concentration ◽  
High Speed ◽  
Epitaxial Films ◽  
The Other ◽  
Short Term ◽  
Wafer Thickness ◽  
Sic Film ◽  
Sic Films ◽  
Effect Of Surface

N-type 4H-SiC homo-epitaxial films were grown on 150 mm diameter wafers by high speed wafer rotation vertical CVD tool, and effect of surface C/Si ratio on short-term and long-term repeatability of the SiC films was investigated. By tuning of growth condition, high uniform SiC film with in-wafer thickness uniformity of ±2.8 % (1.6 % σ/mean) and carrier concentration uniformity of ±3.1 % (1.9 % σ/mean) was successfully grown at higher introduced C/Si ratio of about 1.80, which corresponds to surface C/Si ratio higher than 1.0 on the whole wafer. This result was comparable to the film grown at lower introduced C/Si ratio of about 1.35, which corresponds to surface C/Si ratio lower than 1.0 on the whole wafer. On the other hand, the films on 13 wafers successively grown at higher introduced C/Si ratio indicated low fluctuation from 1.85 to 3.09 % (σ/mean), and the short-term repeatability of the in-wafer carrier concentration uniformity of the films grown at higher introduced C/Si ratio was improved compared with the films grown at lower introduced C/Si ratio. Additionally, in-wafer carrier concentration uniformity of the films on 171 wafers grown at higher introduced C/Si ratio showed 75 % quartile of 4.26 % (σ/mean), and this result was greatly superior to that of 8.21 % (σ/mean) for the films on 130 wafers grown at lower introduced C/Si ratio.

Effect of Transverse and Longitudinal Surface Waviness on the Operation of Journal Bearings

1972 ◽  
Vol 14 (3) ◽  
pp. 168-172 ◽  
Author(s):  
P. Shelly ◽  
C. Ettles
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Surface Waviness ◽  
Machining Processes ◽  
Finishing Process ◽  
Oil Flow ◽  
Method Of Solution ◽  
The Mean ◽  
Effect Of Surface ◽  
Bearing Friction

An analysis is made to evaluate the effect of surface finish produced by the two final machining processes of high speed aero boring and broaching. A finite difference method of solution is used in which the number of waves superimposed on the basic geometry is successively increased. A strong asymptotic trend was found for all bearing characteristics beyond a relatively small number of waves. It is found that the load capacity compared to a smooth bearing is reduced for both processes if the surface waviness is included as an addition to the film height. If the film thickness is assumed to extend to the mean wave height, the load capacity is increased. The effect of surface waviness becomes more pronounced at higher eccentricities or as the amplitude of the waviness is increased. The variation of bearing friction and oil flow is shown. It is concluded that neither finishing process would have a serious deleterious effect on journal bearing performance.

Repeatability of Epitaxial Growth of n-Type 4H-SiC Films by High Speed Wafer Rotation Vertical CVD Tool

2019 ◽  
Vol 963 ◽  
pp. 101-104 ◽  
Author(s):  
Yoshiaki Daigo ◽  
Akio Ishiguro ◽  
Shigeaki Ishii ◽  
Yoshikazu Moriyama ◽  
Kunihiko Suzuki ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Carrier Concentration ◽  
High Speed ◽  
Epitaxial Films ◽  
Short Term ◽  
Gas Nozzle ◽  
Sic Films ◽  
Growth Experiments ◽  
Nozzle Structure

N-type 4H-SiC homo-epitaxial films were grown by high speed wafer rotation vertical CVD tool, and both short term repeatability and long term repeatability of epitaxial growth were investigated. In the short term repeatability investigated by 6 epitaxial wafers chosen from successively grown 12 epitaxial wafers using same recipe, it was found that total variation of thickness and carrier concentration for all measurement points of 6 wafers is 1.44 and 4.64 % respectively, which indicates excellent repeatability as well as high uniform thickness and carrier concentration. In the long term repeatability investigated by a very large number of growth experiments, probability achieving target uniformity of thickness and carrier concentration of the SiC films was increased up to 1.32 times by optimizing gas nozzle structure in gas inlet compared with in the case of conventional gas nozzles. Moreover, adjustment range of C/Si ratio necessary to achieve target uniformity of thickness and carrier concentration of the films was considerably reduced to 22 % by optimized gas nozzles.

Articulatory Behavior Pre and Post Full-Mouth Tooth Extraction and Alveoloplasty

1980 ◽  
Vol 23 (3) ◽  
pp. 630-645 ◽  
Author(s):  
Gerald Zimmermann ◽  
J.A. Scott Kelso ◽  
Larry Lander
Keyword(s):  
Control Subject ◽  
High Speed ◽  
Tooth Extraction ◽  
Kinematic Parameters ◽  
Experimental Conditions ◽  
Mean Values ◽  
Articulatory Movements ◽  
The Mean ◽  
Experimental Subjects ◽  
Normal Speech

High speed cinefluorography was used to track articulatory movements preceding and following full-mouth tooth extraction and alveoloplasty in two subjects. Films also were made of a control subject on two separate days. The purpose of the study was to determine the effects of dramatically altering the structural dimensions of the oral cavity on the kinematic parameters of speech. The results showed that the experimental subjects performed differently pre and postoperatively though the changes were in different directions for the two subjects. Differences in both means and variabilities of kinematic parameters were larger between days for the experimental (operated) subjects than for the control subject. The results for the Control subject also showed significant differences in the mean values of kinematic variables between days though these day-to-day differences could not account for the effects found pre- and postoperatively. The results of the kinematic analysis, particularly the finding that transition time was most stable over the experimental conditions for the operated subjects, are used to speculate about the coordination of normal speech.

scholarly journals The influence of solar wind on extratropical cyclones – Part 1: Wilcox effect revisited

2009 ◽  
Vol 27 (1) ◽  
pp. 1-30 ◽  
Author(s):  
P. Prikryl ◽  
V. Rušin ◽  
M. Rybanský
Keyword(s):  
Time Series ◽  
Solar Wind ◽  
Northern Hemisphere ◽  
High Speed ◽  
Coronal Holes ◽  
Extratropical Cyclones ◽  
Sector Boundary ◽  
Speed Solar Wind ◽  
The Mean ◽  
High Speed Solar Wind

Abstract. A sun-weather correlation, namely the link between solar magnetic sector boundary passage (SBP) by the Earth and upper-level tropospheric vorticity area index (VAI), that was found by Wilcox et al. (1974) and shown to be statistically significant by Hines and Halevy (1977) is revisited. A minimum in the VAI one day after SBP followed by an increase a few days later was observed. Using the ECMWF ERA-40 re-analysis dataset for the original period from 1963 to 1973 and extending it to 2002, we have verified what has become known as the "Wilcox effect" for the Northern as well as the Southern Hemisphere winters. The effect persists through years of high and low volcanic aerosol loading except for the Northern Hemisphere at 500 mb, when the VAI minimum is weak during the low aerosol years after 1973, particularly for sector boundaries associated with south-to-north reversals of the interplanetary magnetic field (IMF) BZ component. The "disappearance" of the Wilcox effect was found previously by Tinsley et al. (1994) who suggested that enhanced stratospheric volcanic aerosols and changes in air-earth current density are necessary conditions for the effect. The present results indicate that the Wilcox effect does not require high aerosol loading to be detected. The results are corroborated by a correlation with coronal holes where the fast solar wind originates. Ground-based measurements of the green coronal emission line (Fe XIV, 530.3 nm) are used in the superposed epoch analysis keyed by the times of sector boundary passage to show a one-to-one correspondence between the mean VAI variations and coronal holes. The VAI is modulated by high-speed solar wind streams with a delay of 1–2 days. The Fourier spectra of VAI time series show peaks at periods similar to those found in the solar corona and solar wind time series. In the modulation of VAI by solar wind the IMF BZ seems to control the phase of the Wilcox effect and the depth of the VAI minimum. The mean VAI response to SBP associated with the north-to-south reversal of BZ is leading by up to 2 days the mean VAI response to SBP associated with the south-to-north reversal of BZ. For the latter, less geoeffective events, the VAI minimum deepens (with the above exception of the Northern Hemisphere low-aerosol 500-mb VAI) and the VAI maximum is delayed. The phase shift between the mean VAI responses obtained for these two subsets of SBP events may explain the reduced amplitude of the overall Wilcox effect. In a companion paper, Prikryl et al. (2009) propose a new mechanism to explain the Wilcox effect, namely that solar-wind-generated auroral atmospheric gravity waves (AGWs) influence the growth of extratropical cyclones. It is also observed that severe extratropical storms, explosive cyclogenesis and significant sea level pressure deepenings of extratropical storms tend to occur within a few days of the arrival of high-speed solar wind. These observations are discussed in the context of the proposed AGW mechanism as well as the previously suggested atmospheric electrical current (AEC) model (Tinsley et al., 1994), which requires the presence of stratospheric aerosols for a significant (Wilcox) effect.

scholarly journals Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 162 ◽  
Author(s):  
Thorben Helmers ◽  
Philip Kemper ◽  
Jorg Thöming ◽  
Ulrich Mießner
Keyword(s):  
High Speed ◽  
Process Intensification ◽  
Continuous Phase ◽  
Channel Cross Section ◽  
Optimization Approach ◽  
Mean Flow ◽  
Bypass Flow ◽  
Wall Film ◽  
Proposed Model ◽  
The Mean

Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data.

Highly Loaded Low-Pressure Turbine: Design, Numerical, and Experimental Analysis

2010 ◽  
Author(s):  
J. T. Schmitz ◽  
S. C. Morris ◽  
R. Ma ◽  
T. C. Corke ◽  
J. P. Clark ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine ◽  
The Mean ◽  
Highly Loaded

The performance and detailed flow physics of a highly loaded, transonic, low-pressure turbine stage has been investigated numerically and experimentally. The mean rotor Zweifel coefficient was 1.35, with dh/U2 = 2.8, and a total pressure ratio of 1.75. The aerodynamic design was based on recent developments in boundary layer transition modeling. Steady and unsteady numerical solutions were used to design the blade geometry as well as to predict the design and off-design performance. Measurements were acquired in a recently developed, high-speed, rotating turbine facility. The nozzle-vane only and full stage characteristics were measured with varied mass flow, Reynolds number, and free-stream turbulence. The efficiency calculated from torque at the design speed and pressure ratio of the turbine was found to be 90.6%. This compared favorably to the mean line target value of 90.5%. This paper will describe the measurements and numerical solutions in detail for both design and off-design conditions.

Friction and Wear Properties of Magnetron Sputtered DLC/SiC Films on Magnesium Alloy

2009 ◽  
Vol 610-613 ◽  
pp. 853-858 ◽  
Author(s):  
Xiao Jing Xu ◽  
Deng Fu Xia
Keyword(s):  
Friction And Wear ◽  
High Hardness ◽  
High Wear Resistance ◽  
Modulus Ratio ◽  
Wear Properties ◽  
Silicon Carbon ◽  
Alloy Az91d ◽  
The Mean ◽  
Friction And Wear Properties ◽  
Sic Films

The nano-indentation response and the friction/wear properties of DLC/SiC (diamond-like carbon/silicon carbon) double layer thin films deposited on Mg alloy (AZ91D) substrate using magnetron sputtering technique at room temperature were investigated. The results show that the DLC films displayed low nano-hardness (3.05 GPa), low Young's modulus (24.67 GPa) but high hardness-to-modulus ratio (0.124). The films-substrate system exhibited a good friction and wear properties with the mean friction coefficient of about 0.175, the special wear rate in the magnitude order of 10−6 mm3 m−1 N−1 together with little film-cracking and interface-delaminating, when sliding against Si3N4 (silicon nitride) ball using ball-on-disc wear tester under dry frictional condition. The high wear-resistance is in accordance with high ductility of the films, good modulus match in the films-substrate system, and high hardness-to-modulus ratio of the films. The underlying factors are discussed and are believed to be due to the substrate is Mg, a metal with high activity.

China's economy will struggle to halt secular slowdown

2021 ◽  
Keyword(s):  
High Speed ◽  
Regression To The Mean ◽  
Content Type ◽  
Strong Force ◽  
Global Demand ◽  
The Mean ◽  
Productivity Gains ◽  
Global Growth ◽  
China’S Economy

Significance Comparisons with two formerly fast-growing Asian neighbours, Japan and South Korea, suggest that China will continue to slow for another decade. Analysis of global growth trends over 50 years points to a strong force of ‘regression to the mean’, meaning that continued high-speed growth is statistically unlikely. Impacts Continued Chinese economic slowing will reduce global demand for resources such as iron ore and coal. Achieving productivity growth will require deepening reforms to increase the role of the market, the private sector and competition. World Bank economists emphasise that imposing stricter financial discipline is a key step to enhancing market-based productivity gains.

Extensive curettage using a high-speed burr versus dehydrated alcohol instillation for the treatment of enchondroma of the hand

2013 ◽  
Vol 40 (4) ◽  
pp. 384-391 ◽  
Author(s):  
S. M. Cha ◽  
H. D. Shin ◽  
K. C. Kim ◽  
I. Y. Park
Keyword(s):  
Analogue Scale ◽  
High Speed ◽  
Proximal Phalanx ◽  
Healing Time ◽  
Complete Healing ◽  
Pathological Fractures ◽  
Active Motion ◽  
The Mean ◽  
High Speed Burr

The purpose of this retrospective study was to compare the clinical and radiological outcomes of patients treated with different adjuvant methods after curettage for enchondromas of the hand. Sixty-two patients with enchondroma were treated with high-speed burring (29 patients) or alcohol instillation (33 patients) after curettage. The mean follow-up was 40.8 months. No significant differences in the visual analogue scale, Disabilities of the Arm, Shoulder, and Hand scores, total range of active motion, grip strength, and complete healing time were observed between the groups. The distribution of the results of the formula by Wilhelm and Feldmeier were not significantly different between the groups. No surgery-related complications, postoperative pathological fractures, or recurrence was found in either group. For the treatment of enchondroma in the metacarpal and proximal phalanx, alcohol instillation immediately after curettage was as effective as extensive curettage using a high-speed burr.

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