RF impedance matching network

• US 9,584,090 B2
• Filed: 03/04/2016
• Issued: 02/28/2017
• Est. Priority Date: 02/20/2015
• Status: Active Grant

• Current Assignee: ASM America Incorporated (ASM International NV)
• Original Assignee: Reno Technologies Inc.
• Inventors: Mavretic, Anton
• Primary Examiner(s): Jones, Stephen E
• Application Number:
  US15/061,068
• Publication Number:
  US 20160248396A1
• Time in Patent Office: 361 Days
• Field of Search: 333/17.3
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 27/28 Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in line transmission systems H04B3/46
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/28556 by chemical means, e.g. CVD, LPCVD, PECVD, laser CVD H01L21/28518 - H01L21/28537 and H01L21/28568 take precedence
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/67115 mainly by radiation
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

An RF impedance matching network includes a transformation circuit coupled to an RF input and configured to provide a transformed impedance that is less than a fixed source impedance; a first shunt circuit in parallel to the RF input, the first shunt circuit including a first shunt variable component providing a first variable capacitance or inductance; and a first virtual ground coupled to the first shunt variable component and a ground; and a second shunt circuit in parallel to the RF input and, the second shunt circuit including a second shunt variable component providing a second variable capacitance or inductance; and a second virtual ground coupled to the second shunt variable component and the ground.

Claims

1. An RF impedance matching network comprising:

an RF input configured to couple to an RF source, the RF source having a fixed RF source impedance;

an RF output configured to couple to a load, the load having a variable load impedance;

a transformation circuit coupled to the RF input and configured to provide a transformed impedance that is less than the fixed source impedance;

a first shunt circuit in parallel to the RF input, the first shunt circuit comprising;

a first shunt variable component providing a first variable capacitance or inductance; and

a first virtual ground coupled to the first shunt variable component and a ground; and

a second shunt circuit in parallel to the RF input and, the second shunt circuit comprising;

a second shunt variable component providing a second variable capacitance or inductance; and

a second virtual ground coupled to the second shunt variable component and the ground.

2. The matching network of claim 1 wherein the transformation circuit comprises:

a transformation capacitor in series with the RF input; and

a transformation inductor in parallel to the RF input and coupled to a ground.

3. The matching network of claim 2 wherein the first shunt variable component is a first shunt variable capacitance component comprising (a) a plurality of first shunt capacitors coupled in parallel, and (b) a plurality of first shunt switches coupled to the plurality of first shunt capacitors and configured to connect and disconnect each of the plurality of first shunt capacitors to the first virtual ground.

4. The matching network of claim 3 wherein the second shunt variable component is a second shunt variable capacitance component comprising (a) a plurality of second shunt capacitors coupled in parallel, and (b) a plurality of second shunt switches coupled to the plurality of second shunt capacitors and configured to connect and disconnect each of the plurality of second shunt capacitors to the second virtual ground.

5. The matching network of claim 4 wherein the first shunt circuit further comprises:

a first shunt padding capacitor coupled in parallel to at least one of the plurality of first shunt capacitors, the first shunt padding capacitor coupled to the first virtual ground;

a first shunt ground capacitor coupled between the first virtual ground and the ground; and

a first shunt resistor coupled between the first virtual ground and the ground.

6. The matching network of claim 5 wherein the second shunt circuit further comprises:

a second shunt padding capacitor coupled in parallel to at least one of the plurality of second shunt capacitors, the second shunt padding capacitor coupled to the second virtual ground;

a second shunt ground capacitor coupled between the second virtual ground and the ground; and

a second shunt resistor coupled between the second virtual ground and the ground.

7. The matching network of claim 6 further comprising a series inductor in series with the RF input and coupled between the transformation capacitor and the RF output.

8. The matching network of claim 1 wherein the transformation circuit comprises:

a transformation inductor in series with the RF input; and

a transformation capacitor in parallel to the RF input and coupled to a ground.

9. The matching network of claim 8 wherein the first shunt variable component is a first shunt variable inductive component comprising (a) a plurality of first shunt inductors coupled in parallel to a first shunt padding inductor, and (b) a plurality of first shunt switches coupled to the plurality of first shunt inductors and configured to connect and disconnect each of the plurality of first shunt inductors to a first virtual ground.

10. The matching network of claim 9 wherein the second shunt variable component is a second shunt variable capacitance component comprising (a) a plurality of second shunt capacitors coupled in parallel, and (b) a plurality of second shunt switches coupled to the plurality of second shunt capacitors and configured to connect and disconnect each of the plurality of second shunt capacitors to a second virtual ground.

11. The matching network of claim 10 wherein the first shunt circuit further comprises:

a first shunt ground capacitor coupled between the second virtual ground and the ground; and

a first shunt resistor coupled between the first virtual ground and the ground.

12. The matching network of claim 11 wherein the second shunt circuit further comprises:

a padding capacitor coupled in parallel to at least one of the plurality of second shunt capacitors, the padding capacitor coupled to the second virtual ground;

a second shunt ground capacitor coupled between the second virtual ground and the ground; and

a second shunt resistor coupled between the second virtual ground and the ground.

13. The impedance matching network of claim 1 wherein the at least one RF input parameter is a voltage, a current, and a phase at the RF input.

14. The impedance matching network of claim 13 further comprising a control unit configured to receive a signal from the sensor indicative of the at least one RF input parameter, the control unit further configured to determine the variable load impedance based on the RF input parameter.

15. The impedance matching network of claim 14 wherein the control unit is further configured to determine a first shunt capacitance value for the first shunt variable capacitance component and a second shunt capacitance value for the second shunt variable capacitance component to create an impedance match at the RF input.

16. The impedance matching network of claim 15 further comprising at least one driver circuit configured to:

alter a first shunt variable capacitance of the first shunt variable capacitance component based on a first control signal received from the control unit; and

alter a second shunt variable capacitance of the second shunt variable capacitance component based on a second control signal received from the control unit.

17. The RF impedance matching network of claim 16 wherein the impedance match results in 10% or less RF power reflected back to the RF source.

18. A method of matching an impedance, the method comprising:

determining a variable load impedance of a load, with an impedance matching network coupled between the load and an RF source, wherein the RF source has a fixed RF source impedance, and the impedance matching network comprises;

an RF input configured to couple to an RF source;

an RF output configured to couple to a load;

a transformation circuit coupled to the RF input and configured to provide a transformed impedance that is less than the fixed source impedance;

a first shunt circuit in parallel to the RF input, the first shunt circuit comprising;

a first shunt variable component providing a first variable capacitance or inductance; and

a first virtual ground coupled to the first shunt variable component and a ground; and

a second shunt circuit in parallel to the RF input and, the second shunt circuit comprising;

a second shunt variable component providing a second variable capacitance or inductance; and

a second virtual ground coupled to the second shunt variable component and the ground;

determining a first shunt capacitance value for the first shunt variable capacitance component and a second shunt capacitance value for the second shunt variable capacitance component for creating an impedance match at an RF input of the impedance matching network; and

generating a control signal to cause the first shunt variable capacitance component to provide the first shunt capacitance value, or to cause the second shunt variable capacitance component to provide the second shunt capacitance value.

19. A method of manufacturing a semiconductor comprising:

placing a substrate in a plasma chamber configured to deposit a material layer onto the substrate or etch a material layer from the substrate; and

energizing plasma within the plasma chamber by coupling RF power from an RF source into the plasma chamber to perform a deposition or etching, and while energizing the plasma;

determining a variable load impedance of the plasma chamber, with an impedance matching network coupled between the load and the RF source, wherein the RF source has a fixed RF source impedance, and the impedance matching network comprises;

an RF input configured to couple to an RF source;

an RF output configured to couple to a load;

a transformation circuit coupled to the RF input and configured to provide a transformed impedance that is less than the fixed source impedance;

a first shunt circuit in parallel to the RF input, the first shunt circuit comprising;

a first shunt variable component providing a first variable capacitance or inductance; and

a first virtual ground coupled to the first shunt variable component and a ground; and

a second shunt circuit in parallel to the RF input and, the second shunt circuit comprising;

a second shunt variable component providing a second variable capacitance or inductance; and

a second virtual ground coupled to the second shunt variable component and the ground;

determining a first shunt capacitance value for the first shunt variable capacitance component and a second shunt capacitance value for the second shunt variable capacitance component for creating an impedance match at an RF input of the impedance matching network; and

generating a control signal to cause the first shunt variable capacitance component to provide the first shunt capacitance value, or to cause the second shunt variable capacitance component to provide the second shunt capacitance value.