Impedance matching network and method

• US 10,714,314 B1
• Filed: 02/28/2020
• Issued: 07/14/2020
• Est. Priority Date: 07/10/2017
• Status: Active Grant

• Current Assignee: ASM America Incorporated (ASM International NV)
• Original Assignee: Reno Technologies Inc.
• Inventors: Bhutta, Imran, Lozic, Tomislav, Decker, Ronald, Kandampalayam, Bala
• Primary Examiner(s): Jones, Stephen E.
• Application Number:
  US16/804,324
• Publication Number:
  US 20200203130A1
• Time in Patent Office: 137 Days
• Field of Search: 333 173, 333 32, 333 33, 333 99 PL
• CPC Class Codes: H01J 2237/332 Coating
• CPC Class Codes: H01J 2237/334 Etching
• 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 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

In one embodiment, the present disclosure is directed to a method for impedance matching including a) positioning a matching network between a radio frequency (RF) source and a plasma chamber; b) determining, from among the plurality of match configurations, a new match configuration to be used when there is an expected pulse level change from a first of the pulse levels to a second of the pulse levels; and c) sending a control signal to alter the at least one EVC to provide the new match configuration. The control signal is sent a predetermined time period before a time for the expected pulse level change, the predetermined time period being substantially similar to a time period for the EVC to switch between two match configurations of the plurality of match configurations.

Claims

1. An impedance matching network comprising:

an RF input configured to operably couple to a radio frequency (RF) source, the RF source configured to provide at least two repeating, non-zero pulse levels, the at least two pulse levels comprising a first pulse level and a second pulse level;

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

at least one electronically variable capacitor (EVC) configured to switch between a plurality of match configurations for reducing a reflected power at an output of the RF source as the variable impedance of the plasma chamber changes; and

a control circuit configured to carry out the operations of;

determining, from among the plurality of match configurations, a new match configuration to be used when there is an expected pulse level change from a first of the pulse levels to a second of the pulse levels; and

sending a control signal to alter the at least one EVC to provide the new match configuration, wherein the control signal is sent a predetermined time period before a time for the expected pulse level change, the predetermined time period being substantially similar to a time period for the EVC to switch between two match configurations of the plurality of match configurations.

2. The matching network of claim 1 wherein the control circuit is further configured to repeat its operations for a subsequent expected pulse level change.

3. The matching network of claim 1 wherein the control circuit is further configured to determine the time for the expected pulse level change based on measured durations for each of the pulse levels.

4. The matching network of claim 1 wherein the control circuit is further configured to perform the operations of:

receiving from the RF source or from a semiconductor processing tool (a) the durations of each of the at least two pulse levels and (b) a start time for one of the at least two pulse levels; and

determining the time for the expected pulse level change based on the received durations;

wherein the matching network and the plasma chamber form part of the semiconductor processing tool.

5. The matching network of claim 1 wherein the determination of the new match configuration is based on a value of the second pulse level and a measured parameter related to the plasma chamber.

6. The matching network of claim 5 wherein the measured parameter value is at least one of a voltage, a current, or a phase at an input of the matching network.

7. The matching network of claim 6 wherein the determination of the new match configuration is based on a parameter-related value and a previously-determined parameter-related value.

8. A semiconductor processing tool comprising:

a plasma chamber having a variable impedance and configured to deposit a material onto a substrate or etch a material from a substrate; and

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

an RF input configured to operably couple to a radio frequency (RF) source, the RF source configured to provide at least two repeating, non-zero pulse levels, the at least two pulse levels comprising a first pulse level and a second pulse level;

an RF output configured to operably couple to the plasma chamber;

at least one electronically variable capacitor (EVC) configured to switch between a plurality of match configurations for reducing a reflected power at an output of the RF source as the variable impedance of the plasma chamber changes; and

a control circuit configured to carry out the operations of;

determining, from among the plurality of match configurations, a new match configuration to be used when there is an expected pulse level change from a first of the pulse levels to a second of the pulse levels; and

sending a control signal to alter the at least one EVC to provide the new match configuration, wherein the control signal is sent a predetermined time period before a time for the expected pulse level change, the predetermined time period being substantially similar to a time period for the EVC to switch between two match configurations of the plurality of match configurations.

9. A method for impedance matching comprising:

a) positioning a matching network between a radio frequency (RF) source and a plasma chamber, wherein;

the RF source is configured to provide at least two repeating, non-zero pulse levels, the at least two pulse levels comprising a first pulse level and a second pulse level;

the plasma chamber has a variable impedance; and

the matching network comprises at least one electronically variable capacitor (EVC) configured to switch between a plurality of match configurations for reducing a reflected power at an output of the RF source as the variable impedance of the plasma chamber changes;

b) determining, from among the plurality of match configurations, a new match configuration to be used when there is an expected pulse level change from a first of the pulse levels to a second of the pulse levels; and

c) sending a control signal to alter the at least one EVC to provide the new match configuration, wherein the control signal is sent a predetermined time period before a time for the expected pulse level change, the predetermined time period being substantially similar to a time period for the EVC to switch between two match configurations of the plurality of match configurations.

10. The method of claim 9 further comprising repeating steps b) and c) for a subsequent expected pulse level change.

11. The method of claim 9 further comprising measuring a duration for each of the pulse levels, and determining the time for the expected pulse level change based on the measured durations for each of the pulse levels.

12. The method of claim 9 further comprising:

receiving from the RF source or from a semiconductor processing tool (a) the durations of each of the at least two pulse levels and (b) a start time for one of the at least two pulse levels; and

determining the time for the expected pulse level change based on the received durations;

wherein the matching network and the plasma chamber form part of the semiconductor processing tool.

13. The method of claim 9 wherein each EVC of the at least one EVC comprises discrete capacitors configured to switch in and out to vary a capacitance of the EVC and thereby provide the plurality of match configurations.

14. The method of claim 9 wherein the at least two pulse levels comprise a third pulse level.

15. The method of claim 9 wherein the determination of the new match configuration is based on a value of the second pulse level and a measured parameter related to the plasma chamber.

16. The method of claim 15 wherein the measured parameter value is at least one of a voltage, a current, or a phase at an input of the matching network.

17. The method of claim 16 wherein the determination of the new match configuration is based on a parameter-related value and a previously-determined parameter-related value.

18. The method of claim 9 wherein the determination of the new match configuration is based on a load impedance value, which is determined based on an input impedance value at the input of the matching network or a reflection coefficient, which is determined based on the measured parameter value.

19. The method of claim 18 wherein the load impedance value is determined using a parameter matrix.

20. A method of manufacturing a semiconductor, the method 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;

coupling an impedance matching network between an RF source and the plasma chamber, wherein;

the RF source is configured to provide at least two repeating, non-zero pulse levels, the at least two pulse levels comprising a first pulse level and a second pulse level;

the plasma chamber has a variable impedance; and

the matching network comprises at least one electronically variable capacitor (EVC) configured to switch between a plurality of match configurations for reducing a reflected power at an output of the RF source as the variable impedance of the plasma chamber changes; and

performing impedance matching by;

determining, from among the plurality of match configurations, a new match configuration to be used when there is an expected pulse level change from a first of the pulse levels to a second of the pulse levels; and

sending a control signal to alter the at least one EVC to provide the new match configuration, wherein the control signal is sent a predetermined time period before a time for the expected pulse level change, the predetermined time period being substantially similar to a time period for the EVC to switch between two match configurations of the plurality of match configurations.