Impedance matching using independent capacitance and frequency control

• US 10,727,029 B2
• Filed: 07/29/2019
• Issued: 07/28/2020
• Est. Priority Date: 07/10/2017
• Status: Active Grant

• Current Assignee: ASM America Incorporated (ASM International NV)
• Original Assignee: Reno Technologies Inc.
• Inventors: Ulrich, Michael Gilliam, Bhutta, Imran Ahmed
• Primary Examiner(s): A, Minh D
• Application Number:
  US16/524,805
• Publication Number:
  US 20190355554A1
• Time in Patent Office: 365 Days
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching

Abstract

In one embodiment, the present disclosure is directed to an RF impedance matching network that includes an RF input coupled to an RF source, an RF output coupled to a plasma chamber, and an electronically variable capacitor (EVC). A first control circuit controls the EVC and is separate and distinct from a second control circuit controlling the RF source. To assist in causing an impedance match between the RF source and the plasma chamber, the first control circuit determines, using a match lookup table with a value based on a detected RF parameter, a new EVC configuration for providing a new EVC capacitance. To further cause the impedance match, the second control circuit alters the variable frequency of the RF source, but operates independently from the first control circuit.

Claims

1. A radio frequency (RF) impedance matching network comprising:

an RF input configured to operably couple to an RF source having a variable frequency;

an RF output configured to operably couple to a plasma chamber having a variable chamber impedance;

an electronically variable capacitor (EVC) having a variable capacitance;

a first control circuit operably coupled to the EVC and to a sensor configured to detect an RF parameter, the first control circuit controlling the EVC and being separate and distinct from a second control circuit controlling the RF source;

wherein, to assist in causing an impedance match between the RF source and the plasma chamber, the first control circuit is configured to;

determine, using a match lookup table with a value based on the detected RF parameter, a new EVC configuration for providing a new EVC capacitance; and

alter the EVC to the new EVC configuration; and

wherein the first control circuit does not provide instructions to the second control circuit for controlling the variable frequency of the RF source, such that, in further causing the impedance match between the RF source and the plasma chamber, the second control circuit alters the variable frequency of the RF source independently from the first control circuit.

2. The matching network of claim 1 wherein the second control circuit forms part of the RF source.

3. The matching network of claim 1 further comprising a frequency-sensitive circuit separate from the EVC, the frequency-sensitive circuit having an impedance that varies when the variable frequency of the RF source is altered.

4. A method of impedance matching comprising:

operably coupling an RF input of an impedance matching network to an RF source having a variable frequency;

operably coupling an RF output of the impedance matching network to a plasma chamber having a variable chamber impedance, wherein the impedance matching network further comprises an electronically variable capacitor (EVC) having a variable capacitance, and the impedance matching network is configured to cause an impedance match between the RF source and the plasma chamber;

operably coupling a first control circuit to the EVC and to a sensor, the first control circuit controlling the EVC and being separate and distinct from a second control circuit controlling the RF source;

detecting, by the sensor, an RF parameter;

determining, by the first control circuit, using a match lookup table with a value based on the detected RF parameter, a new EVC configuration for providing a new EVC capacitance,

altering, by the first control circuit, the EVC to the new EVC configuration; and

altering, by the second control circuit, the variable frequency of the RF source;

wherein the first control circuit does not provide instructions to the second control circuit for controlling the variable frequency of the RF source.

5. The method of claim 4 wherein the second control circuit forms part of the RF source.

6. The method of claim 4 wherein the matching network further comprises a frequency-sensitive circuit separate from the EVC, the frequency-sensitive circuit having an impedance that varies when the variable frequency of the RF source is altered.

7. The method of claim 6 wherein the frequency-sensitive circuit comprises an LC circuit.

8. The method of claim 7 wherein the variable chamber impedance provides an inductance or capacitance for the LC circuit.

9. The method of claim 4 wherein the determination of the new EVC configuration uses the match lookup table with an impedance at an output of the EVC, the EVC output impedance being the value based on the detected RF parameter.

10. The method of claim 9 wherein the EVC output impedance comprises the variable chamber impedance and the impedance of a frequency-sensitive circuit forming part of the impedance matching network, the impedance of the frequency-sensitive circuit varying when the variable frequency of the RF source is altered.

11. The method of claim 4:

wherein the EVC comprises discrete capacitors and has a first configuration defining ON and OFF states of the discrete capacitors; and

wherein the first control circuit;

determines, based on the detected RF parameter, an input impedance at the RF input of the matching network; and

determines an impedance at an output of the EVC from a parameter matrix lookup table using;

the determined input impedance of the impedance matching network; and

the first configuration of the EVC;

wherein the determination of the new EVC configuration uses the determined EVC output impedance with the match lookup table.

12. The method of claim 11 wherein the sensor is a voltage and current sensor positioned at the RF input of the matching network.

13. The method of claim 11 wherein the parameter matrix lookup table comprises two-port parameter matrices.

14. The method of claim 4 wherein the RF sensor is a phase or magnitude detector operably coupled to the RF input of the matching network, and the detected RF parameter used for the determination of the new EVC configuration is a phase error or a magnitude error.

15. The method of claim 4 wherein the RF sensor is operably coupled to the RF input of the matching network, and the detected RF parameter is at least one of a voltage, a current, or a phase at the RF input.

16. The method of claim 15 wherein the determination of the new EVC configuration uses the match lookup table with a reflection coefficient based on the at least one of the voltage, the current, or the phase, the reflection coefficient being the value based on the detected RF parameter.

17. The method of claim 4 wherein the RF sensor is operably coupled to an output of the EVC, and the determination of the new EVC configuration uses the match lookup table with an impedance at an output of the EVC, the EVC output impedance based on the RF parameter detected by the RF sensor at the RF output.

18. The method of claim 4:

wherein the EVC comprises discrete capacitors, each discrete capacitor having a corresponding switch to activate or deactivate the discrete capacitor; and

wherein the EVC is altered to the new EVC configuration by activating or deactivating at least one of the discrete capacitors of the EVC.

19. The method of claim 18 wherein the corresponding switch is in series with or parallel to the discrete capacitor.

20. 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, causing an impedance match between the RF source and the plasma chamber by;

operably coupling an RF input of an impedance matching network to the RF source, the RF source having a variable frequency;

operably coupling an RF output of the impedance matching network to the plasma chamber, the plasma chamber having a variable chamber impedance, wherein the impedance matching network further comprises an electronically variable capacitor (EVC) having a variable capacitance;

operably coupling a first control circuit to the EVC and to a sensor, the first control circuit controlling the EVC independently from a second control circuit controlling the RF source;

detecting, by the sensor, an RF parameter;

determining, by the first control circuit, using a match lookup table with a value based on the detected RF parameter, new EVC configuration for providing a new EVC capacitance; and

altering, by the first control circuit, the EVC to the new EVC configuration; and

altering by the second control circuit, the variable frequency of the RF source;

wherein the first control circuit does not provide instructions to the second control circuit for controlling the variable frequency of the RF source.

21. A semiconductor processing tool comprising:

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

an impedance matching network operably coupled to the plasma chamber, matching circuit comprising;

an RF input configured to operably couple to an RF source having a variable frequency;

an RF output configured to operably couple to the plasma chamber, the plasma chamber having a variable chamber impedance;

an electronically variable capacitor (EVC) having a variable capacitance;

a first control circuit operably coupled to the EVC and to a sensor configured to detect an RF parameter, the first control circuit controlling the EVC and being separate and distinct from a second control circuit controlling the RF source;

wherein, to assist in causing an impedance match between the RF source and the plasma chamber, the first control circuit is configured to;

determine, using a match lookup table with a value based on the detected RF parameter, a new EVC configuration for providing a new EVC capacitance; and

alter the EVC to the new EVC configuration; and

wherein the first control circuit does not provide instructions to the second control circuit for controlling the variable frequency of the RF source, such that, in further causing the impedance match between the RF source and the plasma chamber, the second control circuit alters the variable frequency of the RF source independently from the first control circuit.