Pulsing RF coils of a plasma chamber in reverse synchronization
Systems and methods for pulsing radio frequency (RF) coils are described. One of the methods includes supplying a first RF signal to a first impedance matching circuit coupled to a first RF coil, supplying a second RF signal to a second impedance matching circuit coupled to a second RF coil, and pulsing the first RF signal between a first parameter level and a second parameter level. The method includes pulsing the second RF signal between a third parameter level and a fourth parameter level in reverse synchronization with the pulsing of the first RF signal.
1 . A method for pulsing radio frequency (RF) coils, comprising:
supplying, from a first RF generator, a first RF signal to a first impedance matching circuit coupled to a first RF coil;
supplying, from a second RF generator, a second RF signal to a second impedance matching circuit coupled to a second RF coil;
pulsing, by the first RF generator, the first RF signal between a first parameter level and a second parameter level; and
pulsing, by the second RF generator, the second RF signal between a third parameter level and a fourth parameter level in reverse synchronization with said pulsing of the first RF signal,
wherein the first parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the first RF signal, the second parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the first RF signal, the third parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the second RF signal, and the fourth parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the second RF signal.
2 . The method of claim 1 , wherein said pulsing the second RF signal in reverse synchronization with said pulsing of the first RF signal comprises:
transitioning the second RF signal from the third parameter level to the fourth parameter level during a time period in which the first RF signal transitions from the first parameter level to the second parameter level; and
transitioning the second RF signal from the fourth parameter level to the third parameter level during a time period in which the first RF signal transitions from the second parameter level to the first parameter level,
wherein the first parameter level is different from the third parameter level, and the second parameter level is different from the fourth parameter level.
3 . The method of claim 1 , further comprising:
maintaining, by the second RF generator, the second RF signal at the third parameter level during a time period in which the first RF signal is maintained at the first parameter level; and
maintaining, by the second RF generator, the second RF signal at the fourth parameter level during a time period in which the first RF signal is maintained at the second parameter level.
4 . The method of claim 1 , wherein the first RF coil and the second RF coil are located above a dielectric window of the plasma chamber.
5 . The method of claim 1 , wherein the first parameter level includes one or more values and the second parameter level includes one or more parameter values, wherein the one or more values of the first parameter level are exclusive of the one or more values of the second parameter level.
6 . The method of claim 1 , wherein the third parameter level includes one or more values and the fourth parameter level includes one or more values, wherein the one or more values of the third parameter level are exclusive of the one or more values of the fourth parameter level.
7 . The method of claim 1 , wherein the first RF signal has a substantially same frequency as the second RF signal.
8 . The method of claim 1 , wherein each of the first RF signal and the second RF signal has a frequency ranging between 10 kilohertz (kHz) and 100 kHz.
9 . The method of claim 1 , wherein the first parameter level of the first RF signal has a duty cycle, wherein the second parameter level has a duty cycle that is equal to a difference between 100 percent and the duty cycle of the first parameter level of the first RF signal, wherein the fourth parameter level has a duty cycle that is equal to the difference.
10 . The method of claim 1 , wherein the first parameter level and the second parameter level occur during a cycle of a synchronization signal, wherein the third parameter level and the fourth parameter level occur during the cycle.
11 . The method of claim 1 ,
wherein said pulsing the first RF signal includes:
transitioning the first RF signal from the first parameter level to the second parameter level during a cycle of a synchronization signal;
transitioning the first RF signal from the second parameter level to the first parameter level during the cycle of the synchronization signal,
wherein said pulsing the second RF signal includes:
transitioning the second RF signal from the third parameter level to the fourth parameter level during the cycle of the synchronization signal;
transitioning the second RF signal from the fourth parameter level to the third parameter level during the cycle of the synchronization signal.
12 . The method of claim 1 , further comprising:
supplying, from a third RF generator, a third RF signal to a third RF coil of the plasma chamber via a third impedance matching circuit;
pulsing, by the third RF generator, the third RF signal between a fifth parameter level and a sixth parameter level,
wherein the third RF signal is pulsed in reverse synchronization with the first RF signal and the second RF signal.
13 . The method of claim 1 , wherein the method is performed during a semiconductor wafer processing operation to minimize tilting of features.
14 . A controller for pulsing radio frequency (RF) coils, comprising:
a processor configured to:
control a first RF generator to supply a first RF signal to a first impedance matching circuit, wherein the first impedance circuit is configured to be coupled to a first RF coil; and
control a second RF generator to supply a second RF signal to a second impedance matching circuit, wherein the second impedance circuit is configured to be coupled to a second RF coil,
wherein the first RF generator is controlled to pulse the first RF signal between a first parameter level and a second parameter level,
wherein the second RF generator is controlled to pulse the second RF signal between a third parameter level and a fourth parameter level in reverse synchronization with the pulsing of the first RF signal,
wherein the first parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the first RF signal, the second parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the first RF signal, the third parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the second RF signal, and the fourth parameter level is a peak-to-peak amplitude or a zero-to-peak amplitude of the second RF signal; and
a memory device coupled to the processor.
15 . The controller of claim 14 , wherein to pulse the second RF signal in reverse synchronization with the pulsing of the first RF signal, the processor is configured to:
control the second RF generator to transition the second RF signal from the third parameter level to the fourth parameter level during a time period in which the first RF signal transitions from the first parameter level to the second parameter level; and
control the second RF generator to transition the second RF signal from the fourth parameter level to the third parameter level during a time period in which the first RF signal transitions from the second parameter level to the first parameter level,
wherein the first parameter level is different from the third parameter level, and the second parameter level is different from the fourth parameter level.
16 . The controller of claim 14 , wherein the processor is configured to:
control the second RF generator to maintain the second RF signal at the third parameter level during a time period in which the first RF signal is maintained at the first parameter level; and
control the second RF generator to maintain the second RF signal at the fourth parameter level during a time period in which the first RF signal is maintained at the second parameter level.
17 . The controller of claim 14 , wherein the first RF coil and the second RF coil are located above a dielectric window of the plasma chamber.
18 . The controller of claim 14 , wherein the first parameter level includes one or more values and the second parameter level includes one or more values, wherein the one or more values of the first parameter level are exclusive of the one or more values of the second parameter level.
19 . The controller of claim 14 , wherein the third parameter level includes one or more values and the fourth parameter level includes one or more values, wherein the one or more values of the third parameter level are exclusive of the one or more values of the fourth parameter level.
20 . The controller of claim 14 , wherein the first RF signal has a substantially same frequency as the second RF signal, wherein each of the first RF signal and the second RF signal has a frequency ranging between 10 kilohertz (kHz) and 100 kHz.