Particle Transport at Subatmospheric Pressures: Models and Verification

Periasamy, Ravindran; Yamamoto, Toshiaki; Donovan, R. P.; Clayton, Anthony

doi:10.1149/1.2220937

Cited by 3 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[4][5][6][7] Bare silicon wafers were exposed to 240 nm PSL particles using the ON/OFF protocol described in Sec. [4][5][6][7] Bare silicon wafers were exposed to 240 nm PSL particles using the ON/OFF protocol described in Sec.…”

Section: Resultsmentioning

confidence: 99%

“…The underlying physics of thermophoretic protection of heated surfaces has already been experimentally verified [4][5][6][7] at pressures from ϳ500 mTorr ͑ϳ70 Pa͒ up to atmospheric pressure. In this "high pressure" regime, experiments and theoretical models show conclusively that thermophoresis can effectively protect surfaces from particle deposition.…”

Section: Introductionmentioning

confidence: 94%

See 1 more Smart Citation

Verification studies of thermophoretic protection for extreme ultraviolet masks

Dedrick

Beyer

Rader

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

View full text Add to dashboard Cite

Cleaning of extreme ultraviolet lithography optics and masks using 13.5 nm and 172 nm radiation A "thermophoretic pellicle" has been proposed as an alternative to the traditional organic pellicle as a means of protecting extreme ultraviolet ͑EUV͒ lithographic photomasks from particle contamination. The thermophoretic pellicle protects a mask from particles by exploiting the thermophoretic force, which is exerted on a particle by a surrounding gas in which a temperature gradient exists. Two critical requirements of the thermophoretic pellicle are: ͑1͒ the mask is kept warmer than its surroundings and ͑2͒ the surrounding gas pressure is kept sufficiently high to enable thermophoretic protection. Experiments are presented which verify the viability of thermophoretic protection for EUV masks. In these experiments, wafers are exposed to a monodisperse, polystyrene-latex-sphere aerosol under carefully controlled experimental conditions. Robust thermophoretic protection is observed over a wide range of argon gas pressures ͑50-1600 mTorr or 6.66-213 Pa͒, particle sizes ͑65-300 nm͒, and temperature gradients ͑2-15 K/cm͒. Numerical simulations of the thermophoretic pellicle show good agreement with the data.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Verification studies of thermophoretic protection for extreme ultraviolet masks

Dedrick

Beyer

Rader

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

View full text Add to dashboard Cite

show abstract

“…Bowling and Larrabee (1989) recognized the increasing number of processes being carried out at low pressure, and reported analytic and experimental results for the gravitational deposiAerosol Science and Technology 28:2 February 1998 tion of particles in a vacuum chambcr. Periasamy et al (1993) looked at low-pressure particle deposition mechanisms including sedimentation, convective-diffusion, thermophoresis, and other phoretic forces. Periasamy et al (1993) also providcd qualitative experimental verification of their models in a custom-built vacuum chambcr.…”

Section: Introductionmentioning

confidence: 99%

“…Periasamy et al (1993) looked at low-pressure particle deposition mechanisms including sedimentation, convective-diffusion, thermophoresis, and other phoretic forces. Periasamy et al (1993) also providcd qualitative experimental verification of their models in a custom-built vacuum chambcr.…”

Section: Introductionmentioning

confidence: 99%

Showerhead-Enhanced Inertial Particle Deposition in Parallel-Plate Reactors

Rader¹,

Geller²

1998

Aerosol Science and Technology

View full text Add to dashboard Cite

ABSTRACT. Particle deposition is modeled in a parallel-plate reactor geometry characteristic of a wide range of semiconductor process tools: uniform downward flow exiting a perforated-plate showerhead separated by a small gap from a circular wafer resting on a parallel snsceptor. Because the area available to flow is constricted inside the showerhead, high gas velocities within showerhead holes can accelerate particles and lead to inertia-enhanced particle deposition on the wafer below. Numerical models are presented for determining the extent of inertia-enhanced deposition in a parallel-plate geometry for particles originating upstream of the showerhead. The problem is treated in two steps, for which particle and fluid transport are determined: 1) within a showerhead-hole, and 2) between the showerhead and susceptor. Analytic expressions are presented for the gas velocity in the showerhead holes. Particle transport analysis leads to an analytic expression for the dimensionless particle velocity at the exit of the showerhead as a function of the dimensionless showerhead thickness, the showerhead porosity, and the particle Stokes number. The fluid flow field in the inter-plate region is calculated by both an analytic 1-D creeping-flow approximation and by a numerical 2-D finite element method; for Reynolds numbers less than about four, the two methods are found to be in good agreement. To calc~~late the net effect of inertia-enhanced deposition, the analysis of particle acceleration in the showerhead is coupled with that for interplate transport. The final result is the particle collection efficiency (fraction of particles entering the reactor that deposit on the wafer) as a function of the dimensionless parameters characterizing: showerhead porosity, showerhead thickness, inter-plate Reynolds number, dimensionless particle drift velocity (a measure of the strength of applied external forces), and particle Stokes number. Conditions are found under which particle acceleration in the showerhead greatly enhances particle deposition on wafers. Numerical predictions are presented for the critical Stokes number, which is the nondimensional particle size at which inertial effects lead to substantial particle deposition even in the absence of external forces. Specific guidelines for reducing inertia-enhanced particle deposition include: increase the number of and/or enlarge the size of the showerhead holes, make the showerhead very thin, keep the inter-plate gap large, apply an external force that resists deposition, use low mass flow rates, avoid low pressure, or use a high molecular weight gas. For Reynolds numbers less than four, particle deposition efficiencies calculated with the analytic inter-plate flow field approximation are found to be in good agreement with numerical 2-D simulations. AEROSOL SCIENCE AND TECHNOLOGY 28:105-132 (1998) NOMENCLATURE radius of showcrhead holes (cm) showerhead hole area (cm2) showerhead area (cm2) gas mean molecular velocity = (8RTlvM) (cmls) diameter of showerhead holes (cm) par...

show abstract

“…A number of studies have appeared on particle deposition at subatmospheric pressures characteristic of process tools; both analysis and experimental veri cation have been presented (Bowling and Larrabee 1989;Schmidt et al 1992;Donovan et al 1993;Periasamy et al 1993). Because of industry trends toward smaller feature sizes on integrated circuits and low-pressure processing, the size of killer defects are now small enough that the role of particle Brownian motion in particle transport and deposition must be considered in addition to deposition resulting from external forces (Cooper 1986;Cooper et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Particle Deposition in Parallel-Plate Reactors: Simultaneous Diffusion and External Forces

Rader

Geller

Choi

2002

Aerosol Science and Technology

View full text Add to dashboard Cite

Particle deposition resulting from uniform external forces and Brownian motion is modeled in a parallel-plate reactor geometry characteristic of a wide range of semiconductor process tools: uniform, isothermal, downward ow exiting a perforated-plate showerhead separated by a small gap from a parallel, circular wafer. Particle transport is modeled using a Eulerian approach neglecting particle inertia and interception. Particles are assumed to originate in a planar trap located between the plates, such as would result for particles released from a plasma-induced particle trap after plasma extinction. Flow between in nite parallel plates is described by an analytic quasi-one-dimensional creeping ow approximation, where the showerhead is treated as a porous plate. An analytic, integral expression for particle collection ef ciency (fraction of particles that end up on the wafer) is derived as a function of four dimensionless parameters: the ow Reynolds number, a dimensionless trap height, a dimensionless particle drift velocity, and the particle Peclet number. Numerical quadrature is used to calculate particle collection ef ciency in terms of the controlling dimensionless parameters for external forces, which either enhance or inhibit particle deposition. Example calculations of collection ef ciency are also presented in dimensional terms for a representative set of process conditions. Strategies to reduce particle deposition include the use of a protective external force and manipulation of the trap to keep it as far from the wafer as possible.

show abstract

Particle Transport at Subatmospheric Pressures: Models and Verification

Cited by 3 publications

References 0 publications

Verification studies of thermophoretic protection for extreme ultraviolet masks

Verification studies of thermophoretic protection for extreme ultraviolet masks

Showerhead-Enhanced Inertial Particle Deposition in Parallel-Plate Reactors

Particle Deposition in Parallel-Plate Reactors: Simultaneous Diffusion and External Forces

Contact Info

Product

Resources

About