Ion energy control by RF pulse shape

• US 9,536,749 B2
• Filed: 12/15/2014
• Issued: 01/03/2017
• Est. Priority Date: 12/15/2014
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Marakhtanov, Alexei, Chen, Zhigang, Holland, John Patrick
• Primary Examiner(s): Lu, Jiong-Ping
• Application Number:
  US14/570,859
• Publication Number:
  US 20160172216A1
• Time in Patent Office: 750 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01J 2237/334 Etching
• 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: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

A method for slope control of ion energy is described. The method includes receiving a setting indicating that an etch operation is to be performed using a radio frequency (RF) pulse signal. The RF pulse signal includes a first state and a second state. The first state has a higher power level than the second state. The method further includes receiving a pulse slope associated with the RF pulse signal. The pulse slope provides a transition between the first state and the second state. Also, the pulse slope is other than substantially infinite for reducing an amount of ion energy during the etch operation. The method includes determining power levels and timings for achieving the pulse slope and sending the power levels and the timings to an RF generator to generate the RF pulse signal.

Claims

1. A method for setting operational parameters of a plasma processing system used for etching a substrate layer when placed on an electrode of the plasma processing system, comprising:

receiving measured ion energy of ions within a plasma chamber;

setting a pulsing frequency of a radio frequency (RF) generator, the RF generator producing an RF pulse signal having the pulsing frequency, the pulsing frequency switching between a low power level and a high power level, wherein the high power level is defined between an envelope having a rise transition and a fall transition;

setting a slope parameter for modifying the RF pulse signal based on the measured ion energy, the slope parameter being set for each of the rise transition and fall transition of the envelope, the slope parameter defining a reduction in a rate of rise for the rise transition and a reduction in a rate of fall for the fall transition, wherein the reduction of the rate of rise and rate of fall shapes a reduced pulse width of the envelope at the high power level, wherein the high power level has a shorter duration than the low power level during the pulsing frequency; and

supplying the RF pulse signal modified by the slope parameter to the electrode of the plasma processing system, wherein an increase in low energy ions occurs during the rise transition and the fall transition when the RF pulse signal is modified by the slope parameter, and high ion energy is produced during the reduced pulse width of the envelope, wherein the low energy ions have a lower energy than high energy ions having the high ion energy.

2. The method of claim 1, further comprising setting a shape of the RF pulse signal, the shape associated with the rise transition or the fall transition.

3. The method of claim 1, wherein the pulsing frequency is a frequency at which the envelope is pulsed between the high power level and the low power level.

4. The method of claim 1, wherein the RF pulse signal has a radio frequency and the radio frequency is different from the pulsing frequency.

5. The method of claim 1, wherein the low power level has power amounts that are lower than power amounts of the high power level.

6. The method of claim 1, wherein the envelope is an amplitude of the RF pulse signal.

7. The method of claim 1, wherein the rise transition is a transition from the low power level to the high power level.

8. The method of claim 1, wherein the fall transition is a transition from the high power level to the low power level.

9. The method of claim 1, wherein the slope parameter provides an angle of the RF pulse signal during the rise time.

10. The method of claim 1, wherein the slope parameter provides an angle of the RF pulse signal during the fall time.

11. The method of claim 1, wherein the RF pulse signal is modified to be other than a square-shaped pulse signal.

12. The method of claim 1, wherein the reduction in the rate of rise increases a rise time for the rise transition, the rise time being for transitioning from the low power level to the high power level.

13. The method of claim 1, wherein the reduction in the rate of fall decreases a fall time for the rise transition, the fall time being for transitioning from the high power level to the low power level.

14. The method of claim 1, wherein the reduced pulse width of the envelope is reduced compared to a pulse width of a square-shaped pulse signal.

15. The method of claim 1, wherein the shorter duration is shorter than a pulse width duration of a square-shaped pulse signal.

16. The method of claim 1, wherein supplying the RF pulse signal modified by the slope parameter includes supplying via an RF cable, an impedance matching circuit, and an RF transmission line the RF pulse signal that is modified to the electrode, wherein the RF generator is coupled to the impedance matching circuit via the RF cable, wherein the plasma chamber is connected to the impedance matching circuit via the RF transmission line.

17. The method of claim 1, further comprising optimizing a duty cycle of the RF pulse signal to increase an amount of the low-energy ions.

18. The method of claim 1, wherein the slope parameter and the reduced pulse width increases a selectivity associated with an oxide layer of the substrate layer compared to a selectivity associated with a square RF pulse, wherein the slope parameter and the reduced pulse width increases an etch rate uniformity associated with a selective etch compared to an etch rate uniformity associated with the square RF pulse.

19. A method for setting operational parameters of a plasma processing system used for etching a substrate layer when placed on an electrode of the plasma processing system, comprising:

receiving measured ion energy of ions within a plasma chamber;

setting a pulsing frequency of a radio frequency (RF) generator, the RF generator producing an RF pulse signal having the pulsing frequency, the pulsing frequency switching among a low power level, a medium power level, and a high power level, wherein the high power level is defined between an envelope having a rise transition and a first fall transition, wherein the medium power level is defined between an envelope that starts from an edge of the first fall transition until an edge of a second fall transition;

setting a slope parameter for modifying the RF pulse signal based on the measured ion energy, the slope parameter being set for each of the rise transition, the first fall transition, and the second fall transition, the slope parameter defining a reduction in a rate of rise for the rise transition, a reduction in a rate of fall for the first fall transition, and a reduction in a rate of fall for the second fall transition, wherein the reduction of the rate of rise and the rate of fall for the first transition shapes a reduced pulse width of the envelope at the high power level, wherein the reduction of the rate of fall for the second transition shapes a reduced pulse width of the envelope at the medium power level, wherein each of the high power level and the medium power level has a shorter duration than the low power level during the pulsing frequency; and

supplying the RF pulse signal modified by the slope parameter to the electrode of the plasma processing system, wherein an increase in low energy ions occurs during the rise transition, the first fall transition, and the second fall transition when the RF pulse signal is modified by the slope parameter, and high ion energy is produced during the reduced pulse width of the envelopes at the high and medium power levels, wherein the low energy ions have a lower energy than high energy ions having the high ion energy.

20. The method of claim 19, further comprising controlling a direct current (DC) power supply to supply power during the low power level to generate ions having a charge opposite to a charge associated with the etching of the substrate layer, the ions generated to reduce the charge associated with the etching of the substrate layer.

21. The method of claim 19, wherein the medium power level is between the high power level and the low power level.