Pulsed direct current power supply configurations for generating plasmas

• US 5,917,286 A
• Filed: 05/08/1996
• Issued: 06/29/1999
• Est. Priority Date: 05/08/1996
• Status: Expired due to Term

• Current Assignee: Advanced Energy Industries Incorporated
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Christie, David J., Scholl, Richard A.
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Philogene, Haissa
• Application Number:
  US08/646,616
• Time in Patent Office: 1,147 Days
• Field of Search: 315/111.21, 315/164, 315/168, 315/209 R, 363/63, 363/98, 219/121.43, 219/121.54
• US Class Current: 315/111.21
• CPC Class Codes: H01J 37/32045 Circuits specially adapted for controlling the glow discharge
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

Various embodiments of a power supply are disclosed for generating plasmas. Current controlled power sources are disclosed that are capable of generating currents in low resistance, high temperature plasmas that are regulated to prevent the generation of excessive currents in the plasma. Current reversing switches are provided that control the flow of a direct current in a plasma chamber between various electrodes. A single current controlled power source capable of providing a substantially constant direct current can be utilized with various switch configurations to provide current that is delivered through three or more electrodes in a plasma chamber. Multiple power sources are also provided in association with shunt switches for delivering a plurality of sources of direct current in various directions between electrodes in a plasma chamber. In another embodiment of the present invention, inductive impedance can be provided in switch paths to cause a source of direct current to flow through a plasma chamber in various directions between electrodes. The use of multiple electrodes in association with a single voltage controlled power source is also disclosed.

Claims

1. A power supply for generating a pulsed direct current having alternating polarities to be applied to a plasma chamber to generate plasmas comprising:

a power source that generates a substantially constant supply of said direct current;

current connections for delivering said pulsed direct current to said plasma chamber;

current reversing switches having at least two predetermined positions, said current reversing switches coupled to said power source and said current connections that cause said substantially constant supply of said direct current to flow in a first direction through said current connections whenever said current reversing switches are set in a first predetermined position, and in a second direction through said current connections whenever said current reversing switches are set in a second predetermined position;

wherein said current reversing switches comprise a first pair of switches connected in series across said power source and connected to a first current connection at a point where said first pair of switches are connected in series, and a second pair of switches connected in series across said power source and connected to a second current connection at a point where said second pair of switches are connected in series; and

at least one additional pair of switches connected in series across said power source and connected to an additional current connection at a point where said additional pair of switches are connected in series.

2. A method of generating both positive and negative polarity current pulses in a plasma comprising:

generating a substantially constant supply of current using a current controlled power source;

reversing flow direction of said substantially constant supply of current through said plasma that produces said current pulses in said plasma having both positive and negative polarities; and

preventing the generation of excessive currents in said plasma by shunting the flow of said substantially constant supply of current using said flow reversing switches so that said substantially constant supply of current does not pass through said plasma.

3. The method of claim 2 further comprising:

reducing capacitively stored energy in said power source to allow said power source to function substantially as a current supply.

4. A circuit that causes at least two substantially constant currents to flow to at least two electrodes in a plasma chamber, comprising:

a first power source that generates a substantially constant supply of a first direct current, said first power source having a lead coupled to a first electrode;

a second power source that generates a substantially constant supply of a second direct current said second power source having a lead coupled to a second electrode;

a circuit common;

a first switch coupled between said first electrode and said circuit common that, when closed, causes current to flow from said second power source through said plasma chamber and shunts current from said first power source to said circuit common;

a second switch coupled between said second electrode and said circuit common that, when closed, causes current to flow from said first power source in a second direction through said plasma chamber and shunts current from said second power source to said circuit common;

at least one additional power source that generates a substantially constant supply of an additional direct current for each additional power source, said additional power source having lead coupled to an additional electrode for each additional power source; and

an additional switch for each additional power source coupled between said additional electrode and said circuit common that, when closed, causes current to flow from other power sources in said circuit through said plasma chamber, and shunts current from said additional power source.

5. A method for causing two substantially constant direct currents to flow in a plasma chamber comprising:

generating a first substantially constant direct current using a first current controlled power source;

generating a second substantially constant direct current using a second current controlled power source;

connecting said first current controlled power source to said plasma chamber to cause said first substantially constant direct current to flow through said plasma chamber in a first direction during a first state of operation;

connecting said second current controlled power source to said plasma chamber to cause said second substantially constant direct current to flow through said plasma chamber in a second direction during a second state of operation; and

shunting said first and second substantially constant direct currents from said first and second current controlled power sources to a common return during a third state of operation so that no current passes through said plasma chamber during said third state of operation to increase the duty cycle of said first and second substantially constant direct currents delivered to said plasma chamber.

6. A method of directing a substantially constant supply of direct current to at least two different electrodes in a plasma chamber comprising the steps of:

generating a substantially constant supply of current from a current controlled power source;

directing current from said current controlled power source to a first electrode and through said plasma chamber to cause current to continue to flow in a first inductor coupled to said first electrode while simultaneously causing current to increase in a second inductor;

directing current from said current controlled power source to a second electrode and through said plasma chamber to cause current to continue to flow in a second inductor coupled to a second electrode, while simultaneously causing current to increase in said first inductor.

7. The method of claim 6 further comprising the steps of:

directing current from said current controlled power source through said plasma chamber to at least one additional electrode to cause current to continue to flow in at least one additional inductor.

8. A power supply for generating voltage pulses to be applied to a plasma chamber to generate plasmas comprising:

a power source that generates a substantially constant supply of DC voltage;

at least three electrodes coupled to said substantially constant supply of DC voltage;

current reversing switches connected to said electrodes having at least three predetermined positions that produce at least three predetermined states of operation wherein each of said three electrodes can function as an anode.

9. The power supply of claim 8 wherein said current reversing switches comprise:

a first pair of switches connected in series across said power source, and a first electrode of said at least three electrodes connected at a point between said first pair of switches;

a second pair of switches connected in series across said power source, and a second electrode of said at least three electrodes connected at a point between said second pair of switches;

a third pair of switches connected in series across said power source, and a third electrode of said at least three electrodes connected at a point between said third pair of switches.

10. The power supply of claim 9 further comprising:

at least one additional pair of switches connected in series across said power source, and an additional electrode for each of said at least one additional pair of switches, that is connected at a point between each of said at least one additional pair of switches.

11. A method of generating voltage pulses that are applied to at least three electrodes in a plasma chamber to generate a plasma comprising the steps of:

generating a substantially constant supply of voltage using a voltage controlled power source;

applying said substantially constant supply of voltage to more than one of said at least three electrodes using current revering switches so that more than one of said electrodes functions as an anode.

12. The method of claim 11 wherein said step of applying said substantially constant supply of voltage to more than one of said at least three electrodes comprises applying said substantially constant supply of voltage to more than one of said at least three electrodes during different time intervals.

13. The method of claim 11 wherein said step of applying said substantially constant supply of voltage to more than one of said at least three electrodes comprises applying said substantially constant supply of voltage to more than one of said at least three electrodes using said current reversing switches during the same time period.