Methods and apparatus for controlling ion energy and plasma density in a plasma processing system
First Claim
1. A plasma processing system for processing a workpiece comprising:
- a plasma reactor coupled to a plasma chamber interior;
a workpiece holder in the plasma chamber interior;
a first power circuit configured to supply a first radio frequency (rf) energy within the plasma chamber, the first rf energy being suitable for creating a direct current bias on a workpiece on the workpiece holder within the plasma chamber;
a second power circuit configured to supply a second rf energy within the plasma chamber, the second rf energy being suitable for striking a plasma within the plasma chamber by ionizing particles within the plasma chamber for treating the workpiece;
a feedback circuit coupled to the first power circuit and configured to detect at least one rf parameter associated with the first rf energy and output a feedback control signal based thereon to the first power circuit, the first power circuit being connected to be responsive to the feedback control signal for supplying the first rf energy to the plasma chamber such that a level of energy of the ionized particles within the plasma chamber is substantially controlled via only the direct current bias.
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Accused Products
Abstract
A plasma processing system includes a plasma reactor, a first power circuit, a second power circuit and a feedback circuit. The first power circuit supplies a first radio frequency (rf) energy to the plasma reactor that is suitable for creating a direct current bias on a workpiece positioned within a plasma chamber. The second power circuit supplies a second rf energy to the plasma reactor that is suitable for striking a plasma within the plasma chamber. The feedback circuit is coupled to control the first power circuit by detecting at least one parameter associated with the first rf energy and providing a feedback control signal to the first power circuit. The first power circuit adjusts the first rf energy so that a level of energy of the ionized particles within the plasma chamber is substantially controlled via the direct current bias created by the first rf energy. A second feedback circuit can also be provided to control the second power circuit so that a level of plasma density within the plasma chamber is substantially controlled.
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Citations
54 Claims
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1. A plasma processing system for processing a workpiece comprising:
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a plasma reactor coupled to a plasma chamber interior;
a workpiece holder in the plasma chamber interior;
a first power circuit configured to supply a first radio frequency (rf) energy within the plasma chamber, the first rf energy being suitable for creating a direct current bias on a workpiece on the workpiece holder within the plasma chamber;
a second power circuit configured to supply a second rf energy within the plasma chamber, the second rf energy being suitable for striking a plasma within the plasma chamber by ionizing particles within the plasma chamber for treating the workpiece;
a feedback circuit coupled to the first power circuit and configured to detect at least one rf parameter associated with the first rf energy and output a feedback control signal based thereon to the first power circuit, the first power circuit being connected to be responsive to the feedback control signal for supplying the first rf energy to the plasma chamber such that a level of energy of the ionized particles within the plasma chamber is substantially controlled via only the direct current bias. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
a first rf power supply coupled to the feedback control circuit and responsive to the feedback control signal, the first rf power supply generating a first unmatched rf signal; and
a first match network coupled to the first rf power supply and configured to receive the first unmatched rf signal and output the first rf signal to the electrode.
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4. The plasma processing system as recited in claim 3 wherein the parameter of the first rf energy is selected from the group of a current, a voltage, a power, an impedance, and a phase angle associated with the first rf signal.
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5. The plasma processing system as recited in claim 4 wherein the feedback circuit includes:
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a sensor arranged between the match network and the electrode and configured to output at least one sensed parameter signal; and
a controller coupled to the sensor and the first rf power supply and configured to output the feedback control signal based on the sensed parameter signal and a desired parameter level.
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6. The plasma processing system as recited in claim 5 wherein the sensor is an rf probe.
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7. The plasma processing system as recited in claim 5 wherein the controller is a computer system.
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8. The plasma processing system as recited in claim 5 wherein the feedback circuit operates to maintain the first rf signal at a substantially constant root-mean-square voltage level.
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9. The plasma processing system as recited in claim 1 wherein the second power circuit includes a coil arranged in proximity to the plasma chamber and is configured to supply a second rf signal to the coil.
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10. The plasma processing system as recited in claim 9 wherein the second power circuit further includes:
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a second rf power supply coupled that generates a second unmatched rf signal; and
a second match network coupled to the second rf power supply and configured to receive the second unmatched rf signal and output the second rf signal to the coil.
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11. The plasma processing system as recited in claim 10 further comprising:
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a second feedback circuit coupled to the second power circuit and configured to detect at least one parameter of the second rf energy and output a second feedback control signal based thereon to the second power circuit, wherein the second power circuit is responsive to the second feedback control signal in supplying the second rf energy to the plasma chamber such that a level of plasma density within the plasma chamber is substantially controlled via only the second rf signal.
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12. The plasma processing system as recited in claim 1 wherein the second rf power supply is coupled to the second feedback control circuit and responsive to the second feedback control signal.
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13. The system of claim 1 wherein the detected rf parameter is rf voltage the first power circuit supplies to create the direct current bias.
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14. An apparatus for controlling a direct current (dc) bias in a plasma processing system for processing a workpiece, the apparatus comprising:
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a first power circuit arranged to supply a first rf power to a workpiece on a workpiece holder within the plasma processing system, the first power circuit including a control circuit for monitoring at least one rf parameter associated with the first rf power; and
a second power circuit arranged to supply a second rf power to the workpiece within the plasma processing system, wherein the first and second rf powers are substantially decoupled from one another by the control circuit such that the dc bias is controlled via the first rf power independently of the second rf power. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A method of using a control circuit so there is control of ion energy and plasma density on a workpiece in a plasma reactor responsive to a first power circuit that applies rf power to an electrode in the plasma reactor coupled to the workpiece and a second power circuit that applies rf power to plasma in the reactor, the method comprising:
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measuring at least one rf parameter associated with the rf power the first power circuit applies to the electrode coupled with the workpiece in the plasma reactor; and
adjusting a rf parameter associated with the rf power the first power circuit applies to the electrode in response to the measured parameter and a specified parameter level, the adjusting step being performed so the ion energy is controlled independently of the power the second power circuit applies to plasma in the reactor, the output of the first power circuit causing a direct current (dc) bias to be created at the electrode, and controlling the second power circuit so the plasma density is controlled independently of the power the first power circuit applies to the plasma. - View Dependent Claims (22, 23, 24, 25, 26)
providing a first radio frequency (rf) signal to the plasma reactor with the first power circuit;
creating the dc bias with the first rf signal on a workpiece located within a plasma chamber of the plasma reactor;
providing a second rf signal to the plasma reactor with the second power circuit;
striking a plasma within the plasma reactor with the second rf signal, the plasma including ionized particles;
detecting a parameter of the first rf signal with an rf sensor, the parameter being detected after the first rf signal has been generated and conditioned by a match network within the first power circuit;
comparing the parameter to a specified parameter level; and
modifying the first rf signal based on the comparison results such that the level of energy of the ionized particles contacting the workpiece is substantially controlled via only the magnitude of the direct current bias as established by the first rf signal.
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23. The method as recited in claim 22 wherein the parameter of the first rf signal is selected from the group of a current, a voltage, a power, an impedance, and a phase angle.
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24. The method as recited in claim 23 for further controlling plasma density, further comprising:
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detecting a second parameter of the second rf signal, the second parameter being detected after the second rf signal has been generated and conditioned by a second match network within the second power circuit;
comparing the second parameter to a second desired parameter level; and
modifying the second rf signal based on the second comparison results such that the density of the plasma within the reactor is substantially controlled via only the magnitude of the second rf signal.
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25. The method of claim 21 wherein the first power circuit applies rf power to the electrode, and a measured parameter associated with power the first power circuit applies to the electrode is an rf parameter in a line coupling power to the electrode.
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26. The method of claim 25 wherein the rf parameter is rf voltage.
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27. Apparatus for controlling an ac plasma for treating a workpiece in a plasma processing chamber including a workpiece holder having an electrode comprising a first ac source, a first match network connected between the first ac source and the electrode;
- the first ac source, first match network and electrode being constructed and arranged to cause ac to be coupled between the plasma and the workpiece via the electrode to cause application of a bias voltage to the workpiece, the plasma being included in a load for the first ac source;
a reactance coupled with the plasma processing chamber for exciting gas in the chamber into a plasma;
a second ac source;
a second match network connected between the reactance and the second ac source to cause the plasma to be a load for the second ac source;
a sensor arrangement for an electric parameter of the load; and
a controller arrangement responsive to the sensor arrangement for controlling ac the first ac source applies to the load via the electrode and for controlling ac the second ac source applies to the load via the reactance. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 41, 42)
- the first ac source, first match network and electrode being constructed and arranged to cause ac to be coupled between the plasma and the workpiece via the electrode to cause application of a bias voltage to the workpiece, the plasma being included in a load for the first ac source;
- 38. A method of processing a workpiece with an ac plasma in a plasma processing chamber having (a) a workpiece holder including an electrode and (b) a reactance coupled to gas in the gas, comprising applying ac from a first source to the workpiece via a first match network and the electrode so the plasma is included in a load for the first source, exciting gas in the chamber into a plasma by applying ac from a second source to the reactance via a second match network, sensing at least one electric parameter of the load, controlling an electric parameter the first source applies to the load via the first match network in response to one of the at least one sensed electric parameter of the load, and controlling an electric parameter the second source applies to the load via the second match network in response to one of the at least one sensed electric parameter of the load.
- 49. A method of processing a workpiece with an ac plasma in a plasma processing chamber having (a) a workpiece holder including an electrode and (b) a reactance coupled to gas in the gas, comprising applying ac from a first source to the workpiece via a first match network and the electrode so the plasma is included in a load for the first source, exciting gas in the chamber into a plasma by applying ac from a second source to the reactance via a second match network, sensing an ac electric parameter in a line between the first ac source and the electrode, and controlling an electric parameter the first source applies to the load via the first match network and the electrode in response to the sensed ac electric parameter.
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52. Apparatus for controlling an ac plasma for treating a workpiece in a plasma processing chamber including a workpiece holder having an electrode comprising a first ac source, a first match network connected between the first ac source and the electrode;
- the first ac source, first match network and the electrode being constructed and arranged to cause ac to be coupled between the plasma and the workpiece via the electrode to cause application of a bias voltage to the workpiece, the plasma being included in a load for the first ac source;
a reactance coupled with the plasma processing chamber for exciting gas in the chamber into a plasma;
a second ac source;
a second match network connected between the reactance and the second ac source to cause the plasma to be a load for the second ac source;
a sensor arrangement for an ac electric parameter, the sensor arrangement being coupled to a line between the first ac source and the electrode so as to be responsive to an ac parameter in the line; and
a controller arrangement responsive to the sensor arrangement for controlling ac the first ac source applies to the load via the electrode. - View Dependent Claims (53, 54)
- the first ac source, first match network and the electrode being constructed and arranged to cause ac to be coupled between the plasma and the workpiece via the electrode to cause application of a bias voltage to the workpiece, the plasma being included in a load for the first ac source;
Specification