Systems and methods for reverse pulsing

• US 9,761,459 B2
• Filed: 09/23/2015
• Issued: 09/12/2017
• Est. Priority Date: 08/05/2015
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Long, Maolin, Tan, Zhongkui, Wu, Ying, Fu, Qian, Paterson, Alex, Drewery, John
• Primary Examiner(s): Ahmed, Shamim
• Application Number:
  US14/863,331
• Publication Number:
  US 20170040174A1
• Time in Patent Office: 720 Days
• Field of Search: None
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32128 using particular waveforms, e.g. polarised waves
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32577 Electrical connecting means
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

Systems and methods for reverse pulsing are described. One of the methods includes receiving a digital signal having a first state and a second state. The method further includes generating a transformer coupled plasma (TCP) radio frequency (RF) pulsed signal having a high state when the digital signal is in the first state and having a low state when the digital signal is in the second state. The method includes providing the TCP RF pulsed signal to one or more coils of a plasma chamber, generating a bias RF pulsed signal having a low state when the digital signal is in the first state and having a high state when the digital signal is in the second state, and providing the bias RF pulsed signal to a chuck of the plasma chamber.

Claims

1. A method for operating a plasma chamber during plasma processing, the method comprising:

receiving a digital signal, the digital signal having a first state and a second state;

generating a transformer coupled plasma (TCP) radio frequency (RF) pulsed signal having a high state when the digital signal is in the first state and having a low state when the digital signal is in the second state, wherein the high state of the TCP RF pulsed signal has a higher amount of power than an amount of power of the low state of the TCP RF pulsed signal;

providing the TCP RF pulsed signal to one or more coils of the plasma chamber;

generating a bias RF pulsed signal having a low state when the digital signal is in the first state and having a high state when the digital signal is in the second state, wherein the high state of the bias RF pulsed signal has a higher amount of power than an amount of power of the low state of the bias RF pulsed signal, wherein generating the bias RF pulsed signal includes;

transitioning the bias RF pulsed signal from the high state to the low state at a time of transition of the TCP RF pulsed signal from the low state to the high state; and

transitioning the bias RF pulsed signal from the low state to the high state at a time of transition of the TCP RF pulsed signal from the high state to the low state; and

providing the bias RF pulsed signal to a chuck of the plasma chamber, wherein providing the TCP RF pulsed signal occurs while providing the bias RF pulsed signal, wherein said transitioning of the bias RF signal from the low state to the high state at the time of transition of the TCP RF pulsed signal from the high state to the low state is performed to increase vertical directionality of ions generated in the plasma chamber towards the chuck to process an etch operation of high aspect ratio features.

2. The method of claim 1, wherein having the high state of the biased RF pulsed signal and the low state of the TCP RF pulsed signal during the second state acts to decrease a temperature of electrons in the plasma chamber, such that the decrease in temperature assists in enhancing the directionality of the ions.

3. The method of claim 1, wherein generating the TCP RF pulsed signal comprises:

transitioning the TCP RF pulsed signal from the low state to the high state within a predetermined amount of time from a transition of the digital signal from the second state to the first state; and

transitioning the TCP RF pulsed signal from the high state to the low state within a predetermined amount of time from a transition of the digital signal from the first state to the second state.

4. The method of claim 1, wherein generating the bias RF pulsed signal comprises:

transitioning the bias RF pulsed signal from the high state to the low state within a predetermined amount of time from a transition of the digital signal from the second state to the first state; and

transitioning the bias RF pulsed signal from the low state to the high state within a predetermined amount of time from a transition of the digital signal from the first state to the second state.

5. The method of claim 1, wherein generating the TCP RF pulsed signal comprises:

transitioning the TCP RF pulsed signal from the low state to the high state at a time of a transition of the digital signal from the second state to the first state; and

transitioning the TCP RF pulsed signal from the high state to the low state at a time of a transition of the digital signal from the first state to the second state.

6. The method of claim 1, wherein generating the bias RF pulsed signal comprises:

transitioning the bias RF pulsed signal from the high state to the low state at a time of a transition of the digital signal from the second state to the first state; and

transitioning the bias RF pulsed signal from the low state to the high state at a time of a transition of the digital signal from the first state to the second state.

7. The method of claim 1, wherein the TCP RF pulsed signal has zero power during the low state and a positive amount of power during the high state.

8. The method of claim 1, wherein the bias RF pulsed signal has zero power during the low state and a positive amount of power during the high state.

9. The method of claim 1, wherein the TCP RF pulsed signal has a high level of power during the high state and a low level of power during the low state, wherein the high level is greater than the low level, wherein the low level is greater than zero.

10. The method of claim 1, wherein the bias RF pulsed signal has a high level of power during the high state and a low level of power during the low state, wherein the high level is greater than the low level, wherein the low level is greater than zero.

11. The method of claim 1, wherein the digital signal is generated by a clock source, wherein the clock source is located within an RF generator, wherein generating the bias RF pulsed signal is performed by the RF generator.

12. The method of claim 1, wherein the digital signal is generated by a clock source, wherein the clock source is located within a host system coupled to an RF generator, wherein generating the bias RF pulsed signal is performed by the RF generator.

13. The method of claim 1, wherein the digital signal is a clock signal.

14. A method for operating a plasma chamber during processing, the method comprising:

receiving a digital signal periodically transitioning between a first state and a second state; and

providing a transformer coupled plasma (TCP) radio frequency (RF) pulsed signal to one or more TCP coils of the plasma chamber and a bias RF pulsed signal to a chuck of the plasma chamber, wherein said providing the TCP RF pulsed signal includes synchronizing based on the digital signal a high state of the TCP RF pulsed signal with a low state of the bias RF pulsed signal and a low state of the TCP RF pulsed signal with a high state of the bias RF pulsed signal, wherein the high state of the TCP RF pulsed signal has a higher amount of power than an amount of power of the low state of the TCP RF pulsed signal, wherein the high state of the bias RF pulsed signal has a higher amount of power than an amount of power of the low state of the bias RF pulsed signal,

wherein providing the TCP RF pulsed signal and the bias RF pulsed signal includes;

transitioning the bias RF pulsed signal from the high state to the low state at a time of transition of the TCP RF pulsed signal from the low state to the high state; and

transitioning the bias RF pulsed signal from the low state to the high state at a time of transition of the TCP RF pulsed signal from the high state to the low state,

wherein said transitioning of the bias RF signal from the low state to the high state at the time of transition of the TCP RF pulsed signal from the high state to the low state is performed such that ions generated in the plasma chamber are influenced to have increased vertical directionality towards the chuck to process an etch operation of high aspect ratio features.

15. The method of claim 14, wherein said synchronizing based on the digital signal comprises:

transitioning the TCP RF pulsed signal from the high state to the low state when the digital signal transitions from the first state to the second state;

transitioning the TCP RF pulsed signal from the low state to the high state when the digital signal transitions from the second state to the first state;

transitioning the bias RF pulsed signal from the high state to the low state when the digital signal transitions from the second state to the first state; and

transitioning the bias RF pulsed signal from the low state to the high state when the digital signal transitions from the first state to the second state.

16. The method of claim 14, wherein the TCP RF pulsed signal is in the high state when the bias RF pulsed signal is in the low state and the TCP RF pulse signal is in the low state when the bias RF pulsed signal is in the high state.

17. The method of claim 14, wherein the digital signal is a clock signal.