SUB-PULSING DURING A STATE

• US 20150048740A1
• Filed: 08/22/2014
• Published: 02/19/2015
• Est. Priority Date: 02/22/2012
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, John C. Jr., Singh, Harmeet, Lyndaker, Bradford J.
• Granted Patent: US 9,390,893 B2
• Time in Patent Office: Days
• US Class Current: 315/111.21
• CPC Class Codes: H01J 2237/327 Arrangements for generating the plasma
• 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 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01J 37/3255 Material
• CPC Class Codes: H03K 3/01 Details
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H05H 2242/26 Matching networks

Abstract

A method for achieving sub-pulsing during a state is described. The method includes receiving a clock signal from a clock source, the clock signal having two states and generating a pulsed signal from the clock signal. The pulsed signal has sub-states within one of the states. The sub-states alternate with respect to each other at a frequency greater than a frequency of the states. The method includes providing the pulsed signal to control power of a radio frequency (RF) signal that is generated by an RF generator. The power is controlled to be synchronous with the pulsed signal.

Claims

1. A method comprising:

receiving a clock signal from a clock source, the clock signal having two states;

generating a pulsed signal from the clock signal, the pulsed signal having sub-states within one of the states, the sub-states alternating with respect to each other at a frequency greater than a frequency of the states; and

providing the pulsed signal to control power of a radio frequency (RF) signal that is generated by an RF generator, the power controlled to be synchronous with the pulsed signal.

2. The method of claim 1, wherein the power controlled to be synchronous with the pulsed signal has the same frequency as that of the pulsed signal.

3. The method of claim 1, wherein the clock source includes a crystal oscillator or a crystal oscillator coupled with a phase-locked loop.

4. The method of claim 1, wherein the RF generator is a 2 megahertz RF generator or a 60 megahertz generator.

5. The method of claim 1, wherein the two states include a high state and a low state, the high state having a higher logic level than the low state.

6. The method of claim 1, wherein the pulsed signal transitions from one of the two states to a first one of the two sub-states, then transitions from the first sub-state to a second one of the two sub-states, then transitions from the second sub-state to the first sub-state, then transitions from the first sub-state to the second sub-state, and then transitions from the second sub-state to the one of the two states.

7. The method of claim 6, wherein the power of the RF signal includes multiple power levels, wherein one of the power levels during a low one of the sub-states is the same as or higher than another one of the power levels during a low one of the states.

8. The method of claim 1, further comprising:

providing the clock signal to an additional RF generator for generating an additional RF signal that is synchronous with the clock signal.

9. The method of claim 8, wherein the RF signal that is generated by the RF generator and the additional RF signal that is generated by the additional RF generator are provided to an impedance matching circuit,

the impedance matching circuit generated a modified RF signal based on the RF signal and the additional RF signal and by matching an impedance of a plasma chamber and an RF transmission line with an impedance of the RF generator, the additional RF generator, an RF cable, and an additional RF cable,

the RF transmission line coupling the plasma chamber to the impedance matching circuit,

the RF cable coupling the RF generator to the impedance matching circuit, and

the additional RF cable coupling the additional RF generator to the impedance matching circuit.

10. The method of claim 1, wherein the RF signal has four sub-states including a first sub-state, a second sub-state, a third sub-state, and a fourth sub-state, the power of the RF signal having multiple power levels, a first one of the power levels transitioning from the first sub-state to a second one of the power levels in the second sub-state, the second power level then transitioning to the first power level in the first sub-state, the first power level then transitioning to the second power level in the second sub-state, the second power level then transitioning to a third one of the power levels in the third sub-state, the third power level then transitioning to a fourth one of the power levels to achieve the fourth sub-state, the fourth power level then transitioning to the third power level to achieve the third sub-state, the third power level then transitioning to the fourth power level.

11. The method of claim 10, wherein the second power level is the same as, or lower than, or greater than the fourth power level, wherein the first power level is lower than the third power level.

12. The method of claim 10, wherein the second power level is the same as, or lower than, or greater than the fourth power level, wherein the first power level is greater than the third power level.

13. The method of claim 10, wherein the clock source is located within a digital signal processor of the RF generator.

14. The method of claim 10, wherein the clock source is located outside the RF generator.

15. A radio frequency (RF) generator comprising:

a processor for;

receiving a clock signal from a clock source, the clock signal having two states;

generating a pulsed signal from the clock signal, the pulsed signal having sub-states within one of the states, the sub-states having a frequency greater than a frequency of the states; and

providing the pulsed signal to control power of an RF signal, the power controlled to be synchronous with the pulsed signal; and

an RF power supply coupled to the processor, the RF power supply for generating the RF signal having the power for providing the RF signal to a plasma chamber via an impedance matching circuit.

16. The RF generator of claim 15, further comprising:

a power controller coupled to the processor, the power controller for identifying a power level based on a mapping between the states and multiple power levels and based on a mapping between the sub-states and multiple power levels; and

a frequency tuner coupled to the processor, the frequency tuner for identifying a frequency level based on a mapping between the states and multiple frequency levels and based on a mapping between the sub-states and multiple frequency levels.

17. The RF generator of claim 15, wherein the plasma chamber includes an upper electrode and a chuck, the chuck facing the upper electrode, the power of the RF signal having multiple power levels, each power level mapped to an etch rate or a deposition rate.

18. A system comprising:

a processor for;

receiving a clock signal from a clock source, the clock signal having two states;

generating a pulsed signal from the clock signal, the pulsed signal having sub-states within one of the states, the sub-states having a frequency greater than a frequency of the states; and

providing the pulsed signal to control power of a radio frequency (RF) signal, the power controlled to be synchronous with the pulsed signal; and

an RF power supply for generating the RF signal having the power;

an RF cable coupled to the RF power supply;

an impedance matching circuit coupled to the RF power supply for receiving the RF signal via the RF cable, the impedance matching circuit for matching an impedance of a load coupled to the impedance matching circuit with that of a source coupled to the impedance matching circuit to generate a modified RF signal from the RF signal; and

a plasma chamber coupled to the impedance matching circuit for receiving the modified RF signal for changing an impedance of plasma.

19. The system of claim 18, further comprising an RF transmission line coupling the plasma chamber to the impedance matching circuit, wherein the load includes the plasma chamber and the RF transmission line, wherein the source includes the RF cable and the RF generator.

20. The system of claim 18, wherein the pulsed signal transitions from one of the two states to a first one of the two sub-states, then transitions from the first sub-state to a second one of the two sub-states, then transitions from the second sub-state to the first sub-state, then transitions from the first sub-state to the second sub-state, and then transitions from the second sub-state to the one of the two states.