Frequency monitoring to detect plasma process abnormality
AssigneeApplied Materials, Inc.
InventorsBeom Soo Park, Soo Young Choi, John M. White, Hong Soon Kim, James Hoffman
Life of this patent
Estimating the term…
Abstract
Abnormal conditions within an RF-powered plasma process chamber are detected by detecting whether the frequency of a variable-frequency RF power supply moves outside established lower and upper limits. In a first aspect, a first pair of lower and upper limits are established as a function of the frequency of the power supply sampled after a new process step begins or after a sample control signal changes state. In a second aspect, a second pair of lower and upper limits are not adapted to the frequency of the power supply. Both aspects preferably are used together to detect different occurrences of abnormal conditions.
Claims15
Apparatus for signaling when a variable-frequency RF power supply is supplying RF power to an abnormal RF impedance within a plasma chamber, comprising:
- a controller circuit that produces a frequency control signal having a value that represents a frequency;
- a variable-frequency RF power supply having an output and a frequency control input, wherein:
- (i) the frequency control input is connected to receive the frequency control signal produced by the controller circuit, and
- (ii) the RF power supply, in response to the frequency control signal, produces RF power at its output having a frequency equal to the value represented by the frequency control signal;
- a comparator circuit connected to receive the frequency control signal from the controller circuit;
- wherein the comparator circuit produces an alert signal when the frequency represented by the frequency control signal is less than a lower frequency limit or greater than an upper frequency limit.
A method of signaling when a variable-frequency RF power supply is supplying RF power to an abnormal RF impedance within a plasma chamber, comprising the steps of:
- providing a frequency signal having a value that represents the frequency of RF power being supplied by an RF power supply;
- providing a sample control signal having at least a first state and a second state;
- sampling the value of the frequency signal at the most recent time when the sample control signal changes from the first state to the second state;
- establishing a first lower frequency limit and a first upper frequency limit as a function of said sampled value of the frequency signal;
- repeatedly comparing the frequency represented by the frequency signal to the first lower frequency limit and the first upper frequency limit so as to determine whether the frequency represented by the frequency signal is less than the first lower frequency limit or greater than the first upper frequency limit;
- and
- producing an alert signal when the comparing step determines that the frequency represented by the frequency signal is less than the first lower frequency limit or greater than the first upper frequency limit.
A method of signaling when a variable-frequency RF power supply is supplying RF power to an abnormal RF impedance within a plasma chamber, comprising the steps of:
- providing a variable-frequency RF power supply having an output;
- coupling to the RF power supply a frequency control signal having a value that represents a frequency;
- the RF power supply, in response to the frequency control signal, producing RF power at its output having a frequency equal to the value represented by the frequency control signal;
- establishing a lower frequency limit and an upper frequency limit;
- and
- producing an alert signal when the frequency represented by the frequency control signal is less than the lower frequency limit or greater than the upper frequency limit.
Dependencies are inferred from the claim text.