US5061444A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Systems for reducing deposition of fluid-borne particles
Assignee: California Institute of Technology
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Filing: 1991-03-22
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Granted: 1991-10-29
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Expires: 2011-03-22
Abstract
Abstract Objects are protected against deposition of fluid-borne particles in a diameter range of from one-hundredth of a micron to several microns from a convection boundary layer flow, by establishing a temperature difference between surfaces of these objects and fluid adjacent thereto such that the temperature of these surfaces is higher by not more than 10K than that of the adjacent fluid, to such an extent that the thermophoretic effect dominates the combined effects of Brownian motion and gravitational deposition of the particles in the boundary layer flow. Highly advanced articles of manufacture are produced when those surfaces are changed structurally, such as during manufacture of integrated circuits, while the thermophoretic effect dominates the latter combined effects.
Inventors
- 👤 William W. Nazaroff
- 👤 Glen R. Cass
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:47
CPC Classifications
B; B01; B01J; B01J19/00; B01J19/0006; B01J19/002; B08; B08B; B08B17/00; B08B17/02; B01J2219/00; B01J2219/00049; B01J2219/00245; B01J2219/00252; Y; Y10; Y10S; Y10S438/00; Y10S438/909
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
97 words
A method of reducing deposition of fluid-borne particles in a diameter range of from one-hundredth of a micron to several microns from a convection boundary layer flow onto a surface of an object to be protected, comprising the step of: causing thermophoretic effect to dominate the combined effects of Brownian motion and gravitational sedimentation of said particles in said boundary layer flow by establishing a temperature difference between said surface of the object and adjacent fluid such that the temperature of said surface is higher than that of said adjacent fluid by not more than 10° K.
Claim 2
Independent Claim
97 words
A method of reducing deposition of fluid-borne particles in a diameter range of from one-hundredth of a micron to several microns from a convection boundary layer flow onto a surface of an object to be protected, comprising the step of: causing thermophoretic effect to dominate the combined effects of Brownian motion and gravitational sedimentation of said particles in said boundary layer flow by establishing a temperature difference between said surface of the object and adjacent fluid such that the temperature of said surface is higher than that of said adjacent fluid by not more than 10° K.
Claim 3
Dependent Claim
29 words
A method as claimed in claim 1, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 4
Dependent Claim
20 words
A method as claimed in claim 1, wherein: said object is heated at said surface relative to said adjacent fluid.
Claim 5
Dependent Claim
20 words
A method as claimed in claim 1, wherein: said adjacent fluid is cooled relative to said surface of the object.
Claim 6
Dependent Claim
15 words
A method as claimed in claim 1, including the step of: enclosing said surface laterally.
Claim 7
Dependent Claim
49 words
A method as claimed in claim 1, including the step of: reducing deposition by gravitational sedimentation of said particles by arranging said object such that said surface is located within a range including and extending from a substantially vertical to and including a downwardfacing horizontal orientation of said surface.
Claim 8
Dependent Claim
38 words
A method as claimed in claim 6, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects, and while said surface is located within said range.
Claim 9
Dependent Claim
63 words
A method as claimed in claim 1, wherein: said surface of the object extends substantially vertically; and the following temperature relationship is established: ##EQU30## wherein: surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Le is the particle Lewis number, Pr is the Prandtl number of the fluid, and >> means several times higher than.
Claim 10
Dependent Claim
29 words
A method as claimed in claim 8, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 11
Dependent Claim
126 words
A method as claimed in claim 1, wherein: said surface of the object faces downwardly; and the following temperature relationship is established: ##EQU31## wherein: ΔT is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid, L is the characteristic length of said surface, given by the ratio of surface area to surface perimeter, and Ra L Rayleigh number of the flow, defined by ##EQU32## wherein: g is the acceleration of gravity, α is the thermal diffusivity of the fluid, and β is the coefficient of thermal expansion of the fluid.
Claim 12
Dependent Claim
34 words
A method as claimed in claim 10, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects and said surface faces downwardly.
Claim 13
Dependent Claim
17 words
A method as claimed in claim 1, said surface is open to fluid flow at its perimeter.
Claim 14
Dependent Claim
99 words
A method as claimed in claim 1, wherein: said surface of the object faces downwardly and is provided with either a full enclosure of height H, or a peripheral enclosure of height H' (corresponding to half a height H of a full enclosure); and the following temperature relationship is established: ##EQU33## wherein: T is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid.
Claim 15
Dependent Claim
29 words
A method as claimed in claim 13, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects
Claim 16
Dependent Claim
128 words
A method as claimed in claim 1, wherein: said surface of the object faces upwardly; and the following temperature relationship is established: ##EQU34## wherein: ΔT is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid, L is the characteristic length of said surface, given by the ratio of surface area to surface perimeter, and Ra L is the Rayleigh number of the flow, defined by ##EQU35## where: g is the acceleration of gravity, α is the thermal diffusivity of the fluid, and β is the coefficient of thermal expansion of the fluid.
Claim 17
Dependent Claim
29 words
A method as claimed in claim 15, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 18
Dependent Claim
128 words
A method as claimed in claim 1, wherein: said surface of the object faces upwardly; and the following temperature relationship is established: ##EQU36## wherein: ΔT is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid, L is the characteristic length of said surface, given by the ratio of surface area to surface perimeter, and Ra L is the Rayleigh number of the flow, defined by ##EQU37## wherein: g is the acceleration of gravity, α is the thermal diffusivity of the fluid, and β is the coefficient of thermal expansion of the fluid.
Claim 19
Dependent Claim
29 words
A method as claimed in claim 17, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 20
Dependent Claim
138 words
A method as claimed in claim 1, wherein: said surface of the object faces upwardly and is provided with a full enclosure; and the following temperature relationship is established: ##EQU38## wherein: ΔT is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient of the particles, Le is the particle Lewis number, Pr is the Prandtl number of the fluid, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid, and Ra H is the Rayleigh number of the flow, defined by ##EQU39## wherein: g is the acceleration of gravity, α is the thermal diffusivity of the fluid, β is the coefficient of thermal expansion of the fluid, and H is the height of said enclosure.
Claim 21
Dependent Claim
29 words
A method as claimed in claim 19, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 22
Dependent Claim
105 words
A method as claimed in claim 1, wherein: said surface of the object faces upwardly and is provided with either a full enclosure of height H, or a peripheral enclosure of height H' (corresponding to half a height H of a full enclosure); and the following temperature relationship is established for Ra H <10 3 : ##EQU40## wherein: ΔT is the temperature of the object at said surface minus the temperature of said adjacent fluid, T.sub.∞, K is the thermophoresis coefficient or one particles, Sc is the particle Schmidt number, v g is gravitational particle settling velocity, ν is the kinematic viscosity of the fluid.
Claim 23
Dependent Claim
29 words
A method as claimed in claim 21, including the step of: performing work on said object to change said surface structurally while said thermophoretic effect dominates said combined effects.
Claim 24
Dependent Claim
60 words
A method as claimed in claim 1, wherein: a flux to said surface of gas-borne particles of diameters listed in FIG. 9 is reduced by establishing a temperature difference (ΔT) between said surface of the object (T s ) and adjacent fluid (T.sub.∞) pursuant to the curves shown in said FIG. 9 for particle diameters of 0.1 micrometer and larger.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-10-28 | 1995-04-29 | 1995-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-10-28 | 1999-04-29 | 1999-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-10-28 | 2003-04-29 | 2003-10-29 | $7700.00 | Window Closed / Lapsed |