Determination of wall boundary conditions for high-speed-ratio direct simulation Monte Carlo calculations

1994 ◽  
Vol 31 (6) ◽  
pp. 965-970 ◽  
Author(s):  
Frank G. Collins ◽  
E. C. Knox
Keyword(s):  
Monte Carlo ◽  
Boundary Conditions ◽  
High Speed ◽  
Direct Simulation Monte Carlo ◽  
Speed Ratio ◽  
Direct Simulation ◽  
Monte Carlo Calculations ◽  
Wall Boundary Conditions ◽  
Simulation Monte Carlo

Study on the Deposition Profile Characteristics in the Micron-Scale Trench Using Direct Simulation Monte Carlo Method

1998 ◽  
Vol 120 (2) ◽  
pp. 296-302 ◽  
Author(s):  
Masato Ikegawa ◽  
Jun’ichi Kobayashi ◽  
Morihisa Maruko
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Boundary Conditions ◽  
Gas Flow ◽  
Direct Simulation Monte Carlo ◽  
Low Pressure ◽  
Sputter Deposition ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Profile Characteristics

As integrated circuits are advancing toward smaller device features, step-coverage in submicron trenches and holes in thin film deposition are becoming of concern. Deposition consists of gas flow in the vapor phase and film growth in the solid phase. A deposition profile simulator using the direct simulation Monte Carlo method has been developed to investigate deposition profile characteristics on small trenches which have nearly the same dimension as the mean free path of molecules. This simulator can be applied to several deposition processes such as sputter deposition, and atmospheric- or low-pressure chemical vapor deposition. In the case of low-pressure processes such as sputter deposition, upstream boundary conditions of the trenches can be calculated by means of rarefied gas flow analysis in the reactor. The effects of upstream boundary conditions, molecular collisions, sticking coefficients, and surface migration on deposition profiles in the trenches were clarified.

Numerical Simulation of 3D Flow in Turbomolecular Pump by Direct Simulation Monte Carlo Method

2005 ◽  
Author(s):  
S. Wang ◽  
H. Ninokata
Keyword(s):  
Monte Carlo ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Direct Simulation Monte Carlo ◽  
Speed Ratio ◽  
Maximum Pressure ◽  
3D Analysis ◽  
Direct Simulation ◽  
Turbomolecular Pump ◽  
Simulation Monte Carlo

A Turbomolecular pump (TMP) is one of the key apparatus to produce high and ultrahigh vacuum. It works mainly in the conditions of free molecular and transitional regimes, where the Navier-Stokes equations of continuum gas dynamics can not be correctly applied. In this study, the flow field in single blade row of one stage TMP is investigated by direct simulation Monte Carlo (DSMC) method with a 3D analysis in a rotating reference frame. Considering the Coriolis and centrifugal accelerations, the equations about the molecular velocities and position are deduced on this frame. The VSS model and NTC collision schemes are used to calculate the intermolecular collisions. The diffuse reflection is employed on the molecular reflection from the surfaces of boundary. The transmission probabilities are calculated and applied to analyze the relationship between the outlet pressure and the maximum pressure ratio. The pumping performances between H2 and N2 on the same blade speed and same blade speed ratio are compared and analyzed carefully. The maximum pumping efficiencies on the different blade angles are also calculated. Numerical results show good quantitative agreement with existing experiment data.

Direct Simulation Monte Carlo Solution of Subsonic Flow Through Micro/Nanoscale Channels

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Ehsan Roohi ◽  
Masoud Darbandi ◽  
Vahid Mirjalili
Keyword(s):  
Monte Carlo ◽  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Analytical Solutions ◽  
Direct Simulation Monte Carlo ◽  
Direct Simulation ◽  
Channel Outlet ◽  
Simulation Monte Carlo

We use a direct simulation Monte Carlo (DSMC) method to simulate gas heating/cooling and choked subsonic flows in micro/nanoscale channels subject to either constant wall temperature or constant/variable heat flux boundary conditions. We show the effects of applying various boundary conditions on the mass flow rate and the flow parameters. We also show that it is necessary to add a buffer zone at the end of the channel if we wish to simulate more realistic conditions at the channel outlet. We also discuss why applying equilibrium-based Maxwellian distribution on molecules coming from the channel outlet, where the flow is nonequilibrium, will not disturb the DSMC solution. The current velocity, pressure, and mass flow rate results are compared with different analytical solutions of the Navier–Stokes equations. Although there are good agreements between the DSMC results and the analytical solutions in low compressible flow, the analytical solutions yield incorrect velocity and mass flow rate values in short micro/nanochannel flows with high compressibility and/or choked flow conditions.

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