Method of hot switching a plasma tuner

• US 6,677,828 B1
• Filed: 08/17/2000
• Issued: 01/13/2004
• Est. Priority Date: 08/17/2000
• Status: Expired due to Term

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: ENI Technology, Inc.
• Inventors: Harnett, Sean O., Church, Richard E., Brounley, Richard W.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Jones, Stephen E.
• Application Number:
  US09/640,426
• Time in Patent Office: 1,244 Days
• Field of Search: 333/17.3, 333/18, 333/253, 333/32, 257/656, 315/111.21
• US Class Current: 333/17.3
• 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 37/32183 Matching circuits

Abstract

The present hot switching method and impedance matching circuit extends the tuning range of matching circuits to include increased power levels. The hot switching method and circuit includes coupling a controlled impedance network between an RF generator output and a plasma chamber input for matching impedances. The controlled impedance network includes an RF switch for switching a predetermined impedance. A device performance characteristic of the RF switch is determined. RF power is applied from the RF generator through the controlled impedance network to the plasma chamber. A signal characteristic of the impedance match is measured. The RF switch is controlled based upon the measured signal characteristic such that the impedance match is driven towards a predetermined matching range. The RF switch is switched any speed based upon the device performance characteristic.

Claims

1. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a coupled transformer having a primary winding and a secondary winding, the primary winding having an effective reactance and being coupled between the generator output and the plasma chamber;

an RF switch network having an BF switch being operable to selectively couple at least one reactive element to the transformer secondary winding such that the effective reactance of the primary winding is varied; and

a driver circuit coupled to the RF switch network for applying a forward bias voltage and a reverse bias voltage to the RF switch, thereby switching the RF switch network between a conduction state and a non-conduction state, the driver circuit including a reverse bias switch controlled by an isolate series cascode switch for applying the reverse bias voltage.

2. The controlled impedance network of claim 1 wherein the driver circuit further comprises a forward bias switch for applying the forward bias voltage, wherein the forward bias switch is driven by a bootstrap circuit.

3. The controlled impedance network of claim 2 further comprising a controller coupled to the driver circuit for generating a drive signal to operate the driver circuit.

4. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a coupled transformer having a primary winding and a secondary winding, the primary winding having an effective reactance and being coupled between the generator output and the plasma chamber;

an RF switch network having an RF switch being operable to selectively couple at least one reactive element to the transformer secondary winding such that the effective reactance of the primary winding is varied; and

a driver circuit coupled to the RF switch network for applying a forward bias voltage and a reverse bias voltage to the RF switch, thereby switching the RF switch network between a conduction state and a non-conduction state, the driver circuit including a reverse bias switch controlled by an isolated series cascode switch for applying the reverse bias voltage, wherein the driver circuit further comprises a feedback network for decreasing the turn-off time of the forward bias switch.

5. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a coupled transformer having a primary winding and a secondary winding, the primary winding having an effective reactance and being coupled between the generator output and the plasma chamber;

an RF switch network having an RF switch being operable to selectively couple at least one reactive element to the transformer secondary winding such that the effective reactance of the primary winding is varied; and

a driver circuit coupled to the RF switch network for applying a forward bias voltage and a reverse bias voltage to the RF switch, thereby switching the RF switch network between a conduction state and a non-conduction state, the driver circuit including a reverse bias switch controlled by a series cascode switch for applying the reverse bias voltage;

wherein the series cascode switch is an isolated cascode switch.

6. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a coupled transformer having a primary winding and a secondary winding, the primary winding having an effective reactance and being coupled between the generator output and the plasma chamber;

an RF switch network having an RIF switch being operable to selectively couple at least one reactive element to the transformer secondary winding such that the effective reactance of the primary winding is varied; and

a driver circuit coupled to the RF switch network for applying a forward bias voltage and a reverse bias voltage to the RF switch, thereby switching the RF switch network between a conduction state and a non-conduction state, the driver circuit including a reverse bias switch controlled by a series cascode switch for applying the reverse bias voltage;

wherein the driver circuit further comprises a forward bias switch for applying the forward bias voltage, wherein the forward bias switch is driven by a bootstrap circuit.

7. The controlled impedance network of claim 6 further comprising a controller coupled to the driver circuit for generating a drive signal to operate the driver circuit.

8. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a coupled transformer having a primary winding and a secondary winding, the primary winding having an effective reactance and being coupled between the generator output and the plasma chamber;

an RF switch network having an RF switch being operable to selectively couple at least one reactive element to the transformer secondary winding such that the effective reactance of the primary winding is varied; and

a driver circuit coupled to the RF switch network for applying a forward bias voltage and a reverse bias voltage to the RF switch, thereby switching the RF switch network between a conduction state and a non-conduction state, the driver circuit including a reverse bias switch controlled by a series cascode switch for applying the reverse bias voltage;

wherein the driver circuit further comprises a feedback network for decreasing the turn-off time of the forward bias switch.

9. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber; and

a driver circuit configured to switch a bias voltage to the RF switch using a driver input signal floated from ground, wherein the driver circuit comprises an isolated cascode switch configured to provide voltage level translation from the driver input signal.

10. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber; and

a driver circuit configured to switch a bias voltage to the RF switch using a driver input signal floated from ground, wherein the driver circuit further comprises;

forward and reverse bias switches configured to switch the bias voltage; and

a clamp network coupled between the bias switches and configured to decrease a switching time of the forward bias switch.

11. The controlled impedance network of claim 10 wherein the driver circuit further comprises a bootstrap circuit configured to increase a switching speed of the forward bias switch.

12. The controlled impedance network of claim 10 wherein the driver circuit forward and reverse bias switches are further configured to switch the bias voltage in less time than a carrier lifetime of the RF switch.

13. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber; and

a driver circuit configured to switch a bias voltage to the RF switch using a driver input signal floated from ground, wherein the driver circuit comprises first and second optocouplers connected in series with the driver input signal.

14. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber; and

a driver circuit configured to switch a bias voltage to the RF switch using a driver input signal floated from ground, wherein the driver circuit further comprises a reverse bias switch and an isolated cascode switch configured to control the reverse bias switch.

15. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber; and

a driver circuit configured to switch a bias voltage to the RF switch using a driver input signal floated from ground, wherein the driver circuit further comprises a forward bias power supply, a forward bias switch and a current regulator connected in series between the forward bias power supply and the forward bias switch.

16. The controlled impedance network of claim 15 wherein the driver circuit further comprises a feedback network for decreasing the turn-off time of the forward bias switch.

17. A controlled impedance network coupled between a generator output and a plasma chamber for controlling an impedance match characteristic, comprising:

a transformer having a primary winding connected between the generator output and the plasma chamber;

at least one RF switch configured to selectively couple at least one reactive element to the transformer such that an effective reactance of the primary winding is varied based on a measurement of the impedance match characteristic while RF power is applied to the plasma chamber, wherein the at least one RF switch comprises a plurality of RF switches configured to selectively couple a plurality of binary weighted reactive elements with the transformer; and

a driver circuit configured to switch a blas voltage to the RF switch using a driver input signal floated from ground.