Methods and apparatus for controlling a plasma processing system
First Claim
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1. A method comprising:
- obtaining a radio frequency (RF) voltage signal from an RF sensing mechanism via a high impedance path, the RF voltage signal having multiple RF frequencies associated with multiple RF generators, the multiple frequencies including a first frequency and a second frequency, said RF sensing mechanism is an RF rod, wherein said RF rod is proximate to a component of an electrostatic chuck (ESC) subsystem, wherein the component is outside a region having plasma when formed in a plasma chamber, wherein the RF rod is used for sensing said RF voltage signal, said RF rod providing said RF voltage signal to a capacitor divider network;
processing said RF voltage signal to generate a plurality of signals, one of the signals in said plurality of signals having the first frequency and another one of the signals in said plurality of signals having the second frequency;
applying a transfer function to the signal having the first frequency and the other signal having the second frequency to derive a wafer potential; and
providing the wafer potential as a control signal to control at least a subsystem of said plasma processing system.
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Abstract
A method and apparatus for compensating a bias voltage at the wafer by measuring RF voltage signals in RF driven plasma including at least an electrostatic, chuck (ESC), a capacitive divider, a signal processing and signal conditioning network is disclosed. The bias compensation device includes a capacitive divider to detect the RF voltage at the ESC, a signal conditioning network for the purpose of filtering specific RF signals of interests, and a signal processing unit for computing the DC wafer potential from the filtered RF signals.
34 Citations
19 Claims
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1. A method comprising:
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obtaining a radio frequency (RF) voltage signal from an RF sensing mechanism via a high impedance path, the RF voltage signal having multiple RF frequencies associated with multiple RF generators, the multiple frequencies including a first frequency and a second frequency, said RF sensing mechanism is an RF rod, wherein said RF rod is proximate to a component of an electrostatic chuck (ESC) subsystem, wherein the component is outside a region having plasma when formed in a plasma chamber, wherein the RF rod is used for sensing said RF voltage signal, said RF rod providing said RF voltage signal to a capacitor divider network; processing said RF voltage signal to generate a plurality of signals, one of the signals in said plurality of signals having the first frequency and another one of the signals in said plurality of signals having the second frequency; applying a transfer function to the signal having the first frequency and the other signal having the second frequency to derive a wafer potential; and providing the wafer potential as a control signal to control at least a subsystem of said plasma processing system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A plasma processing system configured for processing at least one wafer disposed on an electrostatic chuck (ESC), the plasma processing system comprising:
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a radio frequency (RF) sensing mechanism, said RF sensing mechanism is proximate to a component of said ESC to obtain an RF voltage signal, wherein the component is outside a region having plasma when formed in a plasma chamber, the RF voltage signal having multiple frequencies associated with multiple RF generators, the multiple frequencies including a first frequency and a second frequency, said RF sensing mechanism is an RF rod and said component is a base plate; a high impedance voltage probe arrangement coupled to said RF rod, wherein said high impedance voltage probe arrangement is implemented at least by a capacitor divider network to facilitate acquisition of said RF voltage signal from said RF rod while reducing perturbation of RF power driving the plasma in said plasma processing system; a signal processing arrangement configured to receive said RF voltage signal, the signal processing arrangement for generating a plurality of signals from said RF voltage signal, one of the signals in the plurality of signals having the first frequency and another one of the signals in the plurality of signals having the second frequency, the signal processing arrangement for applying one of a digital and analog version of the signal having the first frequency and the other signal having the second frequency to a transfer function to obtain a wafer bias; and an ESC power supply subsystem configured to receive said wafer bias as a feedback signal to control said plasma processing system during processing of said at least one wafer. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification