ADJUSTABLE NON-DISSIPATIVE VOLTAGE BOOSTING SNUBBER NETWORK FOR ACHIEVING LARGE BOOST VOLTAGES

• US 20140232266A1
• Filed: 02/20/2014
• Published: 08/21/2014
• Est. Priority Date: 11/01/2012
• Status: Active Grant

• Current Assignee: AES Global Holdings Pte Ltd. (Advanced Energy Industries, Inc. (China))
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Finley, Kenneth W., Walde, Hendrik
• Granted Patent: US 9,224,579 B2
• Time in Patent Office: Days
• US Class Current: 315/111.21
• CPC Class Codes: H01J 37/32027 DC powered
• CPC Class Codes: H01J 37/32055 Arc discharge
• CPC Class Codes: H01J 37/32064 Circuits specially adapted for controlling the arc discharge for plasma torches H01H1/36
• CPC Class Codes: H01J 37/34 operating with cathodic sputtering H01J37/36 takes precedence ; methods of cathodic sputtering C23C14/34
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 2242/26 Matching networks

Abstract

This disclosure describes a non-dissipative snubber circuit configured to boost a voltage applied to a load after the load'"'"'s impedance rises rapidly. The voltage boost can thereby cause more rapid current ramping after a decrease in power delivery to the load which results from the load impedance rise. In particular, the snubber can comprise a combination of a unidirectional switch, a voltage multiplier, and a current limiter. In some cases, these components can be a diode, voltage doubler, and an inductor, respectively.

Claims

1. A pulsed DC power supply system that provides pulsed DC power to a plurality of anodeless electrodes sustaining a plasma in a plasma processing chamber, the pulsed DC power supply system comprising:

a DC power supply coupled to and providing a first DC power to a first and second rail, such that a rail voltage exists across the first and second rails;

a switching circuit coupled to the first and second rails and receiving the first DC power via the first and second rails and converting the first DC power to a first pulsed DC voltage configured for delivery to at least a first anodeless electrode of the plasma processing chamber; and

a voltage-boosting circuit coupled between the first and second rails, the voltage-boosting circuit comprising;

a first diode coupled between the first rail and a first electrical node and forward biased when a voltage measured from the first rail to the first electrical node is sufficiently positive to forward bias the first diode;

a capacitive element coupled between the first electrical node and the second rail;

a switch selectively coupling the first electrical node and a second electrical node;

a second diode coupled between the second rail and the second electrical node and forward biased when a voltage measured from the second rail to the second electrical node is sufficiently positive to forward bias the second electrical node; and

an inductive element coupled between the second electrical node and the first rail.

2. The pulsed DC power supply system of claim 1, wherein the capacitive element is charged via current passing through the first diode and is discharged through the switch and the inductive element.

3. The pulsed DC power supply system of claim 1 further comprising a third diode coupled between the first and second electrical nodes and forward biased when a voltage measured from the second electrical node to the first electrical node is sufficiently positive to forward bias the third diode.

4. The pulsed DC power supply system of claim 1, wherein the switch is selected from the group consisting of:

insulated-gate bipolar transistors (IGBTs), bipolar junction transistors, and field effect transistors.

5. The pulsed DC power supply system of claim 1, wherein the voltage-boosting circuit is part of the DC power supply.

6. The pulsed DC power supply system of claim 1, wherein the voltage-boosting circuit is part of the switching circuit.

7. A pulsed DC power supply system configured to provide pulsed DC power to a plurality of anodeless electrodes of a plasma processing chamber, the pulsed DC power supply comprising:

a pulsed DC power supply system coupled to and providing a DC current via a first and second rail;

a voltage-boosting circuit coupled between the first and second rail and comprising;

a first diode coupled between the first rail and a first electrical node, an anode of the first diode being at a voltage of the first rail;

a voltage multiplier coupled between the second rail and the first electrical node, the voltage multiplier having an output;

a first inductive element coupled between the first rail and a second electrical node;

a first switch coupled between the first and second electrical nodes and selectively discharging a portion of a voltage stored in the voltage multiplier through the first inductive element to the first rail;

a second diode coupled between the first rail and a third electrical node, an anode of the second diode being at a voltage of the third electrical node; and

a second inductive element being coupled between the output of the voltage multiplier and the third electrical node;

a switching circuit coupled to the first and second rails and receiving the DC current via the first and second rails and generating a pulsed DC voltage, the switching circuit having first and second outputs configured to provide the first pulsed DC voltage to at least first and second anodeless electrodes of the plasma processing chamber.

8. The pulsed DC power supply system of claim 7, wherein the voltage multiplier comprises two capacitive elements arranged to charge in series and discharge in parallel.

9. The pulsed DC power supply system of claim 8, wherein a first of the two capacitive elements is arranged so as to discharge through the first switch and the first inductor and the second of the two capacitive elements is arranged so as to discharge through the output of the voltage multiplier, the second inductive element, and the second diode.

10. The pulsed DC power supply system of claim 9, wherein the first switch is selected from the group consisting of:

insulated-gate bipolar transistors (IGBTs), bipolar junction transistors, and field effect transistors.

11. The pulsed DC power supply system of claim 8, wherein the voltage multiplier comprises the first and second capacitive elements arranged in parallel and at least a third and fourth diode, the third diode having an anode coupled to the first capacitive element and having a cathode coupled to the second capacitive element, the cathode of the third diode being at a same potential as the output of the voltage multiplier, wherein the fourth diode has a cathode at a same potential as the anode of the third diode and the fourth diode having an anode at the same potential as the second rail.

12. The pulsed DC power supply system of claim 7, wherein the voltage multiplier increases a rail voltage V_AB between the first and second rails by at least a factor of two when the plasma impedance load substantially decreases.

13. The pulsed DC power supply system of claim 7, further comprising a second switch selectively coupling the second rail and the third electrical node.

14. The pulsed DC power supply system of claim 7, wherein the first rail is positive and the second rail is negative.

15. A method of operating a voltage-boosting circuit arranged between a first and second rail carrying DC current to a switching circuit that converts DC current on the first and second rails to a pulsed DC voltage and provides the pulsed DC voltage across a plasma load of a plasma processing chamber, the method comprising:

providing a rail voltage V_AB between the first and second rails equal to a process voltage V₁;

absorbing some of the DC current in a capacitive element when an impedance of the plasma load increases sufficiently to forward bias a diode coupled between the first rail and a first electrical node, the capacitive element being coupled between the second rail and the first electrical node;

raising the rail voltage V_AB to greater than twice the process voltage V₁ as a result of the absorbing;

closing a switch coupled between the first electrical node and a second electrical node after the raising;

lowering the rail voltage V_AB to the process voltage V₁ as a result of the closing; and

discharging, during the lowering, at least a portion of charge stored in the capacitive element through the switch and an inductive element, the inductive element being coupled between the first rail and the second electrical node.

16. The method of claim 15, further comprising charging the capacitive element via the diode and discharging the capacitive element via the switch and the inductive element.

17. The method of claim 16, further comprising opening the switch after the diode becomes reverse biased but before a switching of the switching circuit.

18. A method of operating a voltage-boosting circuit arranged between a first and second rail carrying DC current to a switching circuit that converts DC current on the first and second rails to a pulsed DC voltage and provides the pulsed DC voltage across a plasma load of a plasma processing chamber, the method comprising:

absorbing in a voltage multiplier some of the DC current when an impedance of the plasma load substantially increases;

discharging to the switching circuit at least some energy stored in the voltage multiplier from the absorbed DC current, and thereby boosting a voltage of the DC current;

monitoring a voltage across a capacitive element of the voltage multiplier that absorbs some of the DC current;

closing the switch when the voltage exceeds a maximum voltage threshold;

reducing the voltage across the capacitive element as a result of the closing until the voltage falls below a minimum voltage threshold; and

then

opening the switch when the voltage falls below the minimum voltage threshold; and

increasing the voltage across the capacitive element as a result of the opening.

19. The method of claim 18, wherein discharge of the voltage-boosting circuit boosts a rail voltage V_AB between the first and second rail by a boost voltage V₂, wherein the boost voltage V₂ is greater than a process voltage V₁.

20. The method of claim 18, further comprising:

charging the capacitive element via a first diode coupled between the first rail and the voltage multiplier; and

discharging the capacitive element via a second inductive element and a second diode.

21. The method of claim 18, further comprising adjusting a duty cycle of a second switch to control the voltage across the capacitive element, the capacitive element arranged so as to charge in series with another capacitive element of the voltage multiplier and discharge in parallel therewith.

22. The method of claim 18, further comprising opening the first switch when one or more arcs in the plasma processing chamber are detected, thus preventing the another capacitive element from discharging through the arcs.

23. The method of claim 18, further comprising:

closing the second switch when a voltage across one of the two capacitive elements in the voltage multiplier exceeds the maximum voltage threshold; and

opening the second switch when the voltage across the one of the two capacitive elements in the voltage multiplier falls below the minimum voltage threshold.