US5491603A
Expired / Lapsed
US
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Method of determining a dechucking voltage which nullifies a residual electrostatic force between an electrostatic chuck and a wafer
Assignee: Applied Materials Inc
•
Filing: 1994-04-28
•
Granted: 1996-02-13
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Expires: 2014-04-28
Abstract
Abstract The invention is embodied in a method of determining an optimum de-chucking voltage for nullifying residual electrostatic forces on a wafer in an electrostatic chuck for removal of the wafer from the chuck, including holding the wafer on the electrostatic chuck by applying an electrostatic potential to the chuck, introducing a gas between the wafer and the chuck, reducing the electrostatic potential of the chuck while observing a rate of leakage of the gas from between the wafer and the chuck, and recording as the optimum dechucking voltage the value of the electrostatic potential obtaining when the rate of leakage exceeds a predetermined threshold.
Inventors
- 👤 Manoocher Birang
- 👤 Jian Ding
- 👤 Hyman J. Levinstein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:51
CPC Classifications
H; H10; H10P; H10P72/00; H10P72/70; H10P72/72; H10P72/722; H02; H02N; H02N13/00
Claims Analysis
Total Claims: 66
Claim 1
Independent Claim
99 words
A method of determining an optimum de-chucking voltage for nullifying residual electrostatic forces on a wafer in an electrostatic chuck for removal of the wafer from the chuck, comprising: holding said wafer on said electrostatic chuck by applying an electrostatic potential to said chuck; introducing a gas between said wafer and said chuck; reducing said electrostatic potential of said chuck while observing a rate of leakage of said gas from between said wafer and said chuck; and recording as said optimum dechucking voltage the value of said electrostatic potential obtaining when said rate of leakage exceeds a predetermined threshold.
Claim 2
Independent Claim
99 words
A method of determining an optimum de-chucking voltage for nullifying residual electrostatic forces on a wafer in an electrostatic chuck for removal of the wafer from the chuck, comprising: holding said wafer on said electrostatic chuck by applying an electrostatic potential to said chuck; introducing a gas between said wafer and said chuck; reducing said electrostatic potential of said chuck while observing a rate of leakage of said gas from between said wafer and said chuck; and recording as said optimum dechucking voltage the value of said electrostatic potential obtaining when said rate of leakage exceeds a predetermined threshold.
Claim 3
Dependent Claim
46 words
The method of claim 1 wherein the step of observing said rate of leakage comprises comparing a current value of a flow rate of said gas with a value of a flow rate of said gas measured prior to the step of reducing said electrostatic potential.
Claim 4
Dependent Claim
33 words
The method of claim 1 wherein the step of reducing said electrostatic potential is performed in discrete steps, and wherein the step of observing a rate of leakage is repeated at each step.
Claim 5
Dependent Claim
24 words
The method of claim 1 wherein said predetermined threshold corresponds to a point at which said wafer begins to float on said electrostatic chuck.
Claim 6
Dependent Claim
15 words
The method of claim 1 wherein said threshold is on the order of approximately 25%.
Claim 7
Dependent Claim
24 words
The method of claim 1 further comprising maintaining said gas between said wafer and said chuck at a pressure suited for said determining method.
Claim 8
Dependent Claim
16 words
The method of claim 6 wherein said pressure is on the order of approximately 4 Torr.
Claim 9
Dependent Claim
16 words
The method of claim 7 wherein said predetermined threshold is on the order of approximately 25%.
Claim 10
Dependent Claim
24 words
The method of claim 3 wherein said steps are each a decrease in said electrostatic potential of on the order of approximately 50 volts.
Claim 11
Dependent Claim
31 words
The method of claim 9 wherein prior to the step of reducing, said electrostatic potential has an initial value in the range of between about one thousand and several thousand volts.
Claim 12
Dependent Claim
12 words
The method of claim 1 wherein said gas comprises an inert gas.
Claim 13
Dependent Claim
85 words
The method of claim 2 further comprising measuring said flow rate prior to pressurizing the gas between said wafer and said chuck, and wherein the step of observing is performed in accordance with the following formula: (F.sub.new -F.sub.initial)/(F.sub.initial -F.sub.0) where F initial is the initial flow rate observed prior to the reducing step, F new is a flow rate measured during the step of reduction and F 0 is the flow rate measured prior to pressurization of the gas between said wafer and said chuck.
Claim 14
Dependent Claim
48 words
The method of claim 1 wherein said chuck comprises a chuck electrode to which said electrostatic potential is applied and an insulating layer between said chuck electrode and said wafer, and wherein said residual electrostatic force arises from electric charge from said wafer trapped in said insulating layer.
Claim 15
Independent Claim
102 words
A method of de-chucking a wafer from an electrostatic chuck, comprising: holding said wafer on said electrostatic chuck by applying an electrostatic potential to said chuck; introducing a gas between said wafer and said chuck; reducing said electrostatic potential of said chuck while observing a rate of leakage of said gas from between said wafer and said chuck; recording as said optimum dechucking voltage the value of said electrostatic potential obtaining when said rate of leakage exceeds a predetermined threshold; and returning said electrostatic potential to the value thereof recorded during said recording step and mechanically lifting said wafer from said chuck.
Claim 16
Independent Claim
102 words
A method of de-chucking a wafer from an electrostatic chuck, comprising: holding said wafer on said electrostatic chuck by applying an electrostatic potential to said chuck; introducing a gas between said wafer and said chuck; reducing said electrostatic potential of said chuck while observing a rate of leakage of said gas from between said wafer and said chuck; recording as said optimum dechucking voltage the value of said electrostatic potential obtaining when said rate of leakage exceeds a predetermined threshold; and returning said electrostatic potential to the value thereof recorded during said recording step and mechanically lifting said wafer from said chuck.
Claim 17
Dependent Claim
27 words
The method of claim 14 wherein said recording step is followed by performing plasma-enhanced processing of said wafer while said wafer is held on said electrostatic chuck.
Claim 18
Dependent Claim
46 words
The method of claim 14 wherein the step of observing said rate of leakage comprises comparing a current value of a flow rate of said gas with a value of a flow rate of said gas measured prior to the step of reducing said electrostatic potential.
Claim 19
Dependent Claim
33 words
The method of claim 14 wherein the step of reducing said electrostatic potential is performed in discrete steps, and wherein the step of observing a rate of leakage is repeated at each step.
Claim 20
Dependent Claim
24 words
The method of claim 14 wherein said predetermined threshold corresponds to a point at which said wafer begins to float on said electrostatic chuck.
Claim 21
Dependent Claim
15 words
The method of claim 14 wherein said threshold is on the order of approximately 25%.
Claim 22
Dependent Claim
24 words
The method of claim 14 further comprising maintaining said gas between said wafer and said chuck at a pressure suited for said de-chucking method.
Claim 23
Dependent Claim
16 words
The method of claim 20 wherein said pressure is on the order of approximately 4 Torr.
Claim 24
Dependent Claim
16 words
The method of claim 21 wherein said predetermined threshold is on the order of approximately 25%.
Claim 25
Dependent Claim
24 words
The method of claim 16 wherein said steps are each a decrease in said electrostatic potential of on the order of approximately 50 volts.
Claim 26
Dependent Claim
31 words
The method of claim 23 wherein prior to the step of reducing, said electrostatic potential has an initial value in the range of between about one thousand and several thousand volts.
Claim 27
Dependent Claim
12 words
The method of claim 14 wherein said gas comprises an inert gas.
Claim 28
Dependent Claim
85 words
The method of claim 16 further comprising measuring said flow rate prior to pressurizing the gas between said wafer and said chuck, and wherein the step of observing is performed in accordance with the following formula: (F.sub.new -F.sub.initial)/(F.sub.initial -F.sub.0) where F initial is the initial flow rate observed prior to the reducing step, F new is a flow rate measured during the step of reduction and F 0 is the flow rate measured prior to pressurization of the gas between said wafer and said chuck.
Claim 29
Dependent Claim
153 words
Apparatus for determining an optimum de-chucking voltage for nullifying residual electrostatic forces on a wafer in an electrostatic chuck for removal of the wafer from the chuck, comprising: a variable power supply for applying an electrostatic potential to said chuck of an initial value sufficient to hold said wafer to said chuck; a mass flow controller for regulating the pressure of gas between said wafer and said chuck and indicating a rate of leakage of said gas from between said wafer and said chuck; a chuck controller for reducing said electrostatic potential of said chuck while observing said rate of leakage of said gas from between said wafer and said chuck and determining when said rate of leakage exceeds a predetermined threshold; and a memory responsive to said chuck controller for recording as said optimum dechucking voltage the value of said electrostatic potential obtained when said rate of leakage exceeds a predetermined threshold.
Claim 30
Dependent Claim
153 words
Apparatus for determining an optimum de-chucking voltage for nullifying residual electrostatic forces on a wafer in an electrostatic chuck for removal of the wafer from the chuck, comprising: a variable power supply for applying an electrostatic potential to said chuck of an initial value sufficient to hold said wafer to said chuck; a mass flow controller for regulating the pressure of gas between said wafer and said chuck and indicating a rate of leakage of said gas from between said wafer and said chuck; a chuck controller for reducing said electrostatic potential of said chuck while observing said rate of leakage of said gas from between said wafer and said chuck and determining when said rate of leakage exceeds a predetermined threshold; and a memory responsive to said chuck controller for recording as said optimum dechucking voltage the value of said electrostatic potential obtained when said rate of leakage exceeds a predetermined threshold.
Claim 31
Dependent Claim
51 words
The apparatus of claim 27 wherein said chuck controller determines when said rate of leakage exceeds said predetermined threshold by comparing a current value of a flow rate of said gas with a value of a flow rate of said gas measured prior to the step of reducing said electrostatic potential.
Claim 32
Dependent Claim
29 words
The apparatus of claim 27 wherein said chuck controller reduces said electrostatic potential in discrete steps, and wherein said chuck controller observes said rate of leakage at each step.
Claim 33
Dependent Claim
24 words
The apparatus of claim 27 wherein said predetermined threshold corresponds to a point at which said wafer begins to float on said electrostatic chuck.
Claim 34
Dependent Claim
15 words
The apparatus of claim 27 wherein said threshold is on the order of approximately 25%.
Claim 35
Dependent Claim
27 words
The apparatus of claim 27 wherein said mass flow controller maintains said gas between said wafer and said chuck at a pressure suited for said determining apparatus.
Claim 36
Dependent Claim
16 words
The apparatus of claim 32 wherein said pressure is on the order of approximately 4 Torr.
Claim 37
Dependent Claim
16 words
The apparatus of claim 33 wherein said predetermined threshold is on the order of approximately 25%.
Claim 38
Dependent Claim
24 words
The apparatus of claim 28 wherein said steps are each a decrease in said electrostatic potential of on the order of approximately 50 volts.
Claim 39
Dependent Claim
25 words
The apparatus of claim 35 wherein said electrostatic potential has an initial value in the range of between about one thousand and several thousand volts.
Claim 40
Dependent Claim
12 words
The apparatus of claim 27 wherein said gas comprises an inert gas.
Claim 41
Dependent Claim
48 words
The apparatus of claim 27 wherein said chuck comprises a chuck electrode to which said electrostatic potential is applied and an insulating layer between said chuck electrode and said wafer, and wherein said residual electrostatic force arises from electric charge from said wafer trapped in said insulating layer.
Claim 42
Dependent Claim
143 words
In a vacuum processing environment, a method of releasing a workpiece from an electrostatic chuck, wherein the chuck includes dielectric elements and at least one electrode energized with a first voltage to electrostatically attract the workpiece to the chuck with a first electrostatic force, and wherein the chuck further includes a gas passageway therethrough, the method comprising the steps of: supplying a heat transmission gas via the gas passageway between the workpiece and chuck while the workpiece is held to the chuck by electrostatic attraction; while reducing the supply of heat transmission gas to the passageway, energizing the electrode with a second voltage of the same polarity as said first voltage, of a magnitude smaller than the first voltage, and which would result in a second electrostatic attractive force smaller than said first force; and thereafter physically removing the workpiece from the chuck.
Claim 43
Dependent Claim
143 words
In a vacuum processing environment, a method of releasing a workpiece from an electrostatic chuck, wherein the chuck includes dielectric elements and at least one electrode energized with a first voltage to electrostatically attract the workpiece to the chuck with a first electrostatic force, and wherein the chuck further includes a gas passageway therethrough, the method comprising the steps of: supplying a heat transmission gas via the gas passageway between the workpiece and chuck while the workpiece is held to the chuck by electrostatic attraction; while reducing the supply of heat transmission gas to the passageway, energizing the electrode with a second voltage of the same polarity as said first voltage, of a magnitude smaller than the first voltage, and which would result in a second electrostatic attractive force smaller than said first force; and thereafter physically removing the workpiece from the chuck.
Claim 44
Dependent Claim
37 words
The method of claim 39, which further includes the steps of monitoring the rate of leakage of the gas from between the wafer and the chuck and comparing same to one or more predetermined levels of leakage.
Claim 45
Dependent Claim
41 words
The method of claim 40, in which said level of leakage corresponds to said smaller electrostatic attraction force of a reduced magnitude to permit the wafer to begin to float on the pedestal under the influence of the heat transmission gas.
Claim 46
Dependent Claim
20 words
The method of claim 41, in which the second voltage is of a magnitude to produce said smaller electrostatic force.
Claim 47
Dependent Claim
36 words
The method of claim 40, which further includes the step of selecting the second voltage to produce a second electrostatic force of reduced magnitude which would permit the wafer to begin to float on the pedestal.
Claim 48
Dependent Claim
46 words
The method of claim 43, in which a trial workpiece is processed using said steps of monitoring, comparing and selecting to determine a value for said second voltage, and in which subsequent workpieces are processed without one or more of said monitoring, comparing and selecting steps.
Claim 49
Dependent Claim
35 words
The method of claim 44, which further includes the step of storing the value of the second voltage obtained using the trial workpiece, and utilizing said stored value as said second voltage for subsequent workpieces.
Claim 50
Dependent Claim
23 words
The method of claim 39, in which the workpiece is removed from the chuck while the electrode is energized at said second voltage.
Claim 51
Dependent Claim
17 words
The method of claim 39, in which the heat transmission gas is supplied at a preselected pressure.
Claim 52
Dependent Claim
38 words
The method of claim 39, which further includes the steps of: selecting said second voltage of a magnitude which permits the wafer to begin to float on the pedestal; and fixing the value of such selected second voltage.
Claim 53
Dependent Claim
46 words
The method of claim 39, in which said selecting step is performed for a first workpiece of a plurality to be processed, and the value of said second voltage which is thereby selected is thereafter utilized as said second voltage for the remainder of said plurality.
Claim 54
Dependent Claim
147 words
In a vacuum processing environment, a method of releasing a workpiece from an electrostatic chuck, wherein the chuck includes dielectric elements and at least one electrode energized with a first voltage to electrostatically attract the workpiece to the chuck with a first electrostatic force, and wherein the chuck further includes a gas passageway therethrough, the method comprising the steps of: supplying a heat transmission gas via the gas passageway between the workpiece and chuck while the workpiece is held to the chuck by electrostatic attraction; while reducing the supply of heat transmission gas to the passageway, energizing the electrode with a second voltage, of a magnitude smaller than said first voltage, and which would result in a reduced electrostatic attraction permitting a leakage rate of the heat transmission gas into the vacuum processing environment exceeding a predetermined level; and thereafter physically removing the wafer from the chuck.
Claim 55
Dependent Claim
147 words
In a vacuum processing environment, a method of releasing a workpiece from an electrostatic chuck, wherein the chuck includes dielectric elements and at least one electrode energized with a first voltage to electrostatically attract the workpiece to the chuck with a first electrostatic force, and wherein the chuck further includes a gas passageway therethrough, the method comprising the steps of: supplying a heat transmission gas via the gas passageway between the workpiece and chuck while the workpiece is held to the chuck by electrostatic attraction; while reducing the supply of heat transmission gas to the passageway, energizing the electrode with a second voltage, of a magnitude smaller than said first voltage, and which would result in a reduced electrostatic attraction permitting a leakage rate of the heat transmission gas into the vacuum processing environment exceeding a predetermined level; and thereafter physically removing the wafer from the chuck.
Claim 56
Dependent Claim
18 words
The method of claim 50 wherein the step of supplying comprises supplying said gas at a preselected pressure.
Claim 57
Dependent Claim
18 words
The method of claim 50 wherein said second voltage is of the same polarity as said first voltage.
Claim 58
Dependent Claim
37 words
The method of claim 50, which further includes the steps of monitoring the rate of leakage of the gas from between the wafer and the chuck and comparing same to one or more predetermined levels of leakage.
Claim 59
Dependent Claim
41 words
The method of claim 53, in which said level of leakage corresponds to said reduced electrostatic attraction force of a reduced magnitude to permit the wafer to begin to float on the pedestal under the influence of the heat transmission gas.
Claim 60
Dependent Claim
20 words
The method of claim 54, in which the second voltage is of a magnitude to produce said reduced electrostatic force.
Claim 61
Dependent Claim
36 words
The method of claim 53, which further includes the step of selecting the second voltage to produce a second electrostatic force of reduced magnitude which would permit the wafer to begin to float on the pedestal.
Claim 62
Dependent Claim
46 words
The method of claim 56, in which a trial workpiece is processed using said steps of monitoring, comparing and selecting to determine a value for said second voltage, and in which subsequent workpieces are processed without one or more of said monitoring, comparing and selecting steps.
Claim 63
Dependent Claim
35 words
The method of claim 57, which further includes the step of storing the value of the second voltage obtained using the trial workpiece, and utilizing said stored value as said second voltage for subsequent workpieces.
Claim 64
Dependent Claim
23 words
The method of claim 50, in which the workpiece is removed from the chuck while the electrode is energized at said second voltage.
Claim 65
Dependent Claim
38 words
The method of claim 50, which further includes the steps of: selecting a second voltage of a magnitude which permits the wafer to begin to float on the pedestal; and fixing the value of such selected second voltage.
Claim 66
Dependent Claim
45 words
The method of claim 50, in which said selecting step is performed for a first workpiece of a plurality to be processed, and the value of second voltage which is thereby selected is thereafter utilized as said second voltage for the remainder of said plurality.
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