US-12626887-B2 - Systems and methods for radiofrequency signal generator-based control of impedance matching system

Abstract

An RF signal supply system for plasma generation includes an RF signal generator, an impedance matching system, and a control module. The RF signal generator includes a control system. The impedance matching system has an input connected to an output of the RF signal generator, an output connected to a plasma processing system, a gamma control capacitor, and a frequency control capacitor. The control module is connected in data communication with each of the RF signal generator and the impedance matching system. The control module is programmed to transmit control signals to the impedance matching system based on corresponding data received from the control system of the RF signal generator, where the control signals direct control of the gamma control capacitor and the frequency control capacitor. The control module is also programmed to transmit data received from the impedance matching system to the control system of the RF signal generator.

Inventors

• Bradford J. Lyndaker
• Alexei Marakhtanov
• Felix Leib Kozakevich
• David Hopkins

Assignees

• LAM RESEARCH CORPORATION

Dates

Publication Date

20260512

Application Date

20211109

Claims (17)

1. 1 . A radiofrequency signal supply system for plasma generation, comprising: a radiofrequency signal generator configured to generate radiofrequency signals and transmit the radiofrequency signals through an output of the radiofrequency signal generator, the radiofrequency signal generator including a control system configured to determine a real-time value of an indicator parameter indicative of an efficacy of transmission of radiofrequency power to a plasma processing system, wherein the indicator parameter is one or more of a radiofrequency signal reflection coefficient, a negative-to-positive reflected power ratio, and a negative-to-positive delivered power ratio; an impedance matching system having an input connected to the output of the radiofrequency signal generator, an output connected to a radiofrequency feed structure of a plasma processing system, a first control capacitor connected between the input of the impedance matching system and a reference potential, and a second control capacitor connected between a first terminal of a first inductor and the reference potential, the first inductor having a second terminal connected to the output of the impedance matching system; and a control module connected in data communication with each of the radiofrequency signal generator and the impedance matching system, the control module configured to generate control signals for the impedance matching system based on the real-time value of the indicator parameter determined by the control system of the radiofrequency signal generator, the control signals directing control of the first control capacitor and the second control capacitor to cause movement of the real-time value of the indicator parameter toward a corresponding target value, the control module programmed to transmit the control signals to the control system of the radiofrequency signal generator.
2. 2 . The radiofrequency signal supply system for plasma generation as recited in claim 1 , wherein the first control capacitor is a first variable capacitor, the impedance matching system including a gamma capacitor control system configured to control the first control capacitor in accordance with control signals received from the control module, and wherein the second control capacitor is a second variable capacitor, the impedance matching system including a frequency capacitor control system configured to control the second control capacitor in accordance with control signals received from the control module.
3. 3 . The radiofrequency signal supply system for plasma generation as recited in claim 2 , wherein each of the gamma capacitor control system and the frequency capacitor control system is connected in data communication with a network interface controller within the impedance matching system.
4. 4 . The radiofrequency signal supply system for plasma generation as recited in claim 2 , wherein the impedance matching system further includes a capacitor and a second inductor connected in series between the input and the output of the impedance matching system.
5. 5 . The radiofrequency signal supply system for plasma generation as recited in claim 2 , wherein the radiofrequency signal generator includes a voltage/current sensor connected to the output of the radiofrequency signal generator, the control system of the radiofrequency signal generator connected to receive voltage measurement data from the voltage/current sensor.
6. 6 . The radiofrequency signal supply system for plasma generation as recited in claim 5 , wherein the control system of the radiofrequency signal generator is programmed to use the voltage measurement data received from the voltage/current sensor to determine a real-time reflection coefficient at the output of the radiofrequency signal generator, and wherein the control system of the radiofrequency signal generator is programmed to determine an adjustment of the first control capacitor within the impedance matching system to minimize the real-time reflection coefficient at the output of the radiofrequency signal generator, the control system of the radiofrequency signal generator programmed to transmit data to the control module that directs execution of the determined adjustment of the first control capacitor, the control module programmed to direct the gamma capacitor control system to execute the determined adjustment of the first control capacitor.
7. 7 . The radiofrequency signal supply system for plasma generation as recited in claim 2 , wherein the control system of the radiofrequency signal generator is programmed to determine an actual frequency of signals generated by the radiofrequency signal generator, determine an adjustment of the second control capacitor within the impedance matching system to minimize a difference between the actual frequency and a target frequency, and transmit data to the control module that directs execution of the determined adjustment of the second control capacitor, the control module programmed to direct the frequency capacitor control system to execute the determined adjustment of the second control capacitor.
8. 8 . The radiofrequency signal supply system for plasma generation as recited in claim 1 , wherein the first control capacitor is a first variable capacitor, the impedance matching system including a gamma/power ratio capacitor control system connected and configured to control the first control capacitor in accordance with control signals received from the control module, wherein the second control capacitor is a second variable capacitor, the impedance matching system including a frequency capacitor control system connected and configured to control the second control capacitor in accordance with control signals received from the control module, wherein the control system of the radiofrequency signal generator is programmed to determine a real-time value of a negative-to-positive reflected power ratio, determine an adjustment of the first control capacitor within the impedance matching system to minimize a difference between the real-time value of the negative-to-positive reflected power ratio and a corresponding target value, and transmit data to the control module that directs execution of the determined adjustment of the first control capacitor, the control module programmed to direct the gamma/power ratio capacitor control system to execute the determined adjustment of the first control capacitor.
9. 9 . The radiofrequency signal supply system for plasma generation as recited in claim 1 , wherein the first control capacitor is a first variable capacitor, the impedance matching system including a gamma/power ratio capacitor control system connected and configured to control the first control capacitor in accordance with control signals received from the control module, wherein the second control capacitor is a second variable capacitor, the impedance matching system including a frequency capacitor control system connected and configured to control the second control capacitor in accordance with control signals received from the control module, wherein the control system of the radiofrequency signal generator is programmed to determine a real-time value of a negative-to-positive delivered power ratio, determine an adjustment of the first control capacitor within the impedance matching system to minimize a difference between the real-time value of the negative-to-positive delivered power ratio and a corresponding target value, and transmit data to the control module that directs execution of the determined adjustment of the first control capacitor, the control module programmed to direct the gamma/power ratio capacitor control system to execute the determined adjustment of the first control capacitor.
10. 10 . A method for optimizing transmission of radiofrequency power to a plasma, comprising: (a) transmitting radiofrequency signals from a radiofrequency signal generator through an impedance matching system to a plasma processing system; (b) determining a real-time value of an indicator parameter indicative of an efficacy of transmission of radiofrequency power to the plasma processing system, wherein the indicator parameter is one or more of a radiofrequency signal reflection coefficient, a negative-to-positive reflected power ratio, and a negative-to-positive delivered power ratio; (c) determining an adjustment of a gamma control capacitor within the impedance matching system to adjust the real-time value of the indicator parameter with respect to a corresponding target value; and (d) transmitting gamma control data to effect execution of the determined adjustment of the gamma control capacitor.
11. 11 . The method as recited in claim 10 , further comprising: (e) repeating operations (b), (c), and (d) until a difference between the real-time value of the indicator parameter and the corresponding target value has reached a minimum achievable value.
12. 12 . The method as recited in claim 11 , wherein the gamma control capacitor is connected between an input of the impedance matching system and a reference potential.
13. 13 . The method as recited in claim 11 , further comprising: adjusting a capacitance setting of the gamma control capacitor in accordance with the gamma control data.
14. 14 . The method as recited in claim 11 , further comprising: measuring a time-varying voltage at the output of the radiofrequency signal generator; and determining the real-time reflection coefficient at the output of the radiofrequency signal generator based on the measured time-varying voltage.
15. 15 . The method as recited in claim 11 , further comprising: (f) determining a frequency difference value, where the frequency difference value is an absolute value of a difference between an actual frequency of radiofrequency signals generated by the radiofrequency signal generator and a target frequency; (g) determining an adjustment of a frequency control capacitor within the impedance matching system that adjusts the frequency difference value toward a minimum value; and (h) transmitting frequency control data to effect execution of the determined adjustment of the frequency control capacitor.
16. 16 . The method as recited in claim 15 , further comprising: (i) repeating operations (f), (g), and (h) until the frequency difference value has reached a minimum achievable value.
17. 17 . The method as recited in claim 16 , further comprising: receiving frequency control signals configured to direct execution of the determined adjustment of the frequency control capacitor; and adjusting a capacitance setting of the frequency control capacitor in accordance with the frequency control signals.

Description

This application is a national stage filing of and claims priority, under 35 U.S.C. § 371, to PCT/US2021/058649, filed on Nov. 9, 2021, which claims the benefit of U.S. Provisional Application No. 63/113,818, filed on Nov. 13, 2020. The entire disclosure of each application referenced above is incorporated herein by reference. BACKGROUND 1. Field of the Disclosure The present disclosure relates to semiconductor device fabrication. 2. Description of the Related Art In the fabrication of semiconductor devices such as integrated circuits, memory cells, and the like, a series of manufacturing operations are performed to define features on a semiconductor wafer (“wafers” hereafter). The wafer includes integrated circuit devices in the form of multi-level structures defined on a silicon substrate. At a substrate level, transistor devices with diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define a desired integrated circuit device. Also, patterned conductive layers are insulated from other conductive layers by dielectric materials. Many modern semiconductor chip fabrication processes include generation of a plasma from which ions and/or radical constituents are derived for use in either directly or indirectly effecting a change on a surface of a substrate exposed to the plasma. For example, various plasma-based processes can be used to etch material from a substrate surface, deposit material onto a substrate surface, or modify a material already present on a substrate surface. The plasma is often generated by applying radiofrequency (RF) power to a process gas in a controlled environment, such that the process gas becomes energized and transforms into the desired plasma. The characteristics of the plasma are affected by many process parameters including, but not limited to, material composition of the process gas, flow rate of the process gas, geometric features of the plasma generation region and surrounding structures, temperatures of the process gas and surrounding materials, frequency of the RF power applied, magnitude of the RF power applied, and temporal manner in which the RF power is applied, among others. Therefore, it is of interest to understand, monitor, and/or control some of the process parameters that may affect the characteristics of the generated plasma, particularly with regard to generation and delivery of the RF power to the plasma generation region. It is within this context that the present disclosure arises. SUMMARY In an example embodiment, an RF signal supply system for plasma generation is disclosed. The RF signal supply system includes an RF signal generator configured to generate RF signals and transmit the RF signals through an output of the RF signal generator. The RF signal generator includes a control system. The RF signal supply system also includes an impedance matching system that has an input connected to the output of the RF signal generator. The impedance matching system has an output connected to an RF feed structure of a plasma processing system. The impedance matching system includes a first control capacitor connected between the input of the impedance matching system and a reference potential. The impedance matching system also includes a second control capacitor connected between a first terminal of a first inductor and the reference potential. The first inductor has a second terminal connected to the output of the impedance matching system. The RF signal supply system also includes a control module connected in data communication with each of the RF signal generator and the impedance matching system. The control module is programmed to transmit control signals to the impedance matching system based on corresponding data received from the control system of the RF signal generator. The control signals direct control of the first control capacitor and the second control capacitor. The control module is also programmed to transmit data to the control system of the RF signal generator based on corresponding data or signals received from the impedance matching system. In another example embodiment, a method is disclosed for optimizing transmission of RF power to a plasma. The method includes transmitting RF signals from an RF signal generator through an impedance matching system to a plasma processing system. The method also includes determining a real-time value of an indicator parameter indicative of an efficacy of transmission of radiofrequency power to the plasma processing system. In some embodiments, the indicator parameter is a reflection coefficient, or a voltage standing wave ratio, or a negative-to-positive reflected power ratio, or a negative-to-positive delivered power ratio. The method also includes determining an adjustment of a first control capacitor within the impedance matching system to adjust the real-time value of the indicator parameter with respe