Impedance-based adjustment of power and frequency

• US 9,607,810 B2
• Filed: 09/10/2015
• Issued: 03/28/2017
• Est. Priority Date: 02/22/2012
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, John C. Jr., Lyndaker, Bradford J.
• Primary Examiner(s): King, Monica C
• Application Number:
  US14/850,851
• Publication Number:
  US 20160005573A1
• Time in Patent Office: 565 Days
• US Class Current: 1/1
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32981 Gas analysis
• CPC Class Codes: H01J 37/3299 Feedback systems

Abstract

Systems and methods for impedance-based adjustment of power and frequency are described. A system includes a plasma chamber for containing plasma. The plasma chamber includes an electrode. The system includes a driver and amplifier coupled to the plasma chamber for providing a radio frequency (RF) signal to the electrode. The driver and amplifier is coupled to the plasma chamber via a transmission line. The system further includes a selector coupled to the driver and amplifier, a first auto frequency control (AFC) coupled to the selector, and a second AFC coupled to the selector. The selector is configured to select the first AFC or the second AFC based on values of current and voltage sensed on the transmission line.

Claims

1. A system comprising:

a digital pulsing source for generating a pulsed signal;

a primary generator including;

a primary driver and amplifier coupled to an electrode for generating a primary radio frequency (RF) signal to be transferred to the electrode;

one or more primary processors coupled to the digital pulsing source for receiving the pulsed signal,

the one or more primary processors configured to;

identify a first one of two states of the pulsed signal and a second one of the two states;

determine to provide a first primary power value to the primary driver and amplifier upon identifying that the pulsed signal is in the first state; and

determine to provide a second primary power value to the primary driver and amplifier upon identifying that the pulsed signal is in the second state;

a secondary generator including;

a secondary driver and amplifier coupled to the electrode for generating a secondary RF signal to be transferred to the electrode;

the one or more secondary processors configured to;

determine whether a parameter associated with plasma exceeds a first boundary when the pulsed signal is in the first state;

determine whether the parameter exceeds a second boundary when the pulsed signal is in the second state;

determine to provide a first secondary power value to the secondary driver and amplifier in response to determining that the parameter exceeds the first boundary;

determine to provide a second secondary power value to the secondary driver and amplifier in response to determining that the parameter exceeds the second boundary.

2. The system of claim 1, further comprising a selector coupled to the one or more secondary processors for selecting the first secondary power value or the second secondary power value, the selector for selecting the first secondary power value in response to receiving a signal from the one or more secondary processors indicating that the parameter exceeds the first boundary, the selector for selecting the second secondary power value in response to receiving a signal from the one or more secondary processors indicating that the parameter exceeds the second boundary.

3. The system of claim 1, wherein the parameter includes a gamma value or an impedance difference value.

4. The system of claim 1, wherein the electrode includes a lower electrode of a plasma chamber.

5. The system of claim 1, wherein during the first state, the primary driver and amplifier is configured to generate the primary RF signal having a lower frequency than that of the secondary RF signal, wherein the primary RF signal has a higher amount of power than the secondary RF signal.

6. The system of claim 1, wherein each of the primary and secondary frequency values are tuned.

7. The system of claim 1, wherein the one or more primary processors determine whether the pulsed signal is in the first or the second state based on a magnitude of the pulsed signal.

8. A method comprising:

receiving current and voltage values;

calculating parameters associated with plasma impedance from the current and voltage values;

determining during a first state of a digital pulsing signal whether a first one of the parameters exceeds a first boundary;

providing a first power value to a radio frequency (RF) driver and amplifier upon determining that the first parameter exceeds the first boundary;

determining during a second state of the digital pulsing signal whether a second one of the parameters exceeds a second boundary; and

providing a second power value to the RF driver and amplifier upon determining that the second parameter exceeds the second boundary.

9. The method of claim 8, wherein the method is used to process semiconductor wafers to make integrated circuits.

10. The method of claim 8, wherein the parameters include gamma values or impedance difference values.

11. The method of claim 8, further comprising selecting between providing the first power value or the second power value.