US-12620555-B2 - Systems and methods for plasma process

Abstract

A method of performing a plasma process includes generating, at an output of a signal generator, a first RF signal at a first frequency. The signal generator is coupled to a plasma chamber through a matching circuit. Based on a feedback from the first RF signal, variable components of the matching circuit are moved to fixed positions. A second RF signal is generated at a second frequency at the output of the signal generator to ignite a plasma within the plasma chamber. In response to detecting the plasma, the signal generator switches to output a third RF signal at the first frequency to sustain the plasma, which is configured to process a substrate loaded into the plasma chamber while holding the matching circuit at the fixed positions.

Inventors

• Charles Schlechte
• Jianping Zhao
• John Carroll
• Peter Lowell George Ventzek

Assignees

• TOKYO ELECTRON LIMITED

Dates

Publication Date

20260505

Application Date

20220527

Claims (20)

1. 1 . A method of performing a plasma process, the method comprising: generating, at an output of a signal generator, a first RF signal at a first frequency, the signal generator being coupled to a plasma chamber through a matching circuit; based on a feedback from the first RF signal, the feedback comprising a signal from an optical sensor coupled with the plasma chamber, moving variable components of the matching circuit to fixed positions; generating, at the output of the signal generator, a second RF signal at a second frequency to ignite a plasma within the plasma chamber; and in response to detecting the plasma, switching the signal generator to output a third RF signal at the first frequency, the third RF signal sustaining the plasma, the plasma being configured to process a substrate loaded into the plasma chamber while holding the matching circuit at the fixed positions.
2. 2 . The method of claim 1 , further comprising holding the matching circuit at the fixed positions while generating the second RF signal to ignite the plasma.
3. 3 . The method of claim 1 , wherein the feedback from the first RF signal further comprises a feedback from a voltage-current (V-I) sensor on a radio-frequency (RF) signal pipe to the plasma.
4. 4 . The method of claim 1 , wherein the fixed positions are determined by a controller based on the feedback, the fixed positions being positions of constant delivered power to the plasma chamber.
5. 5 . The method of claim 4 , wherein the controller is configured to execute a program comprising a machine learning model stored in a memory, the machine learning model comprising instructions to generate the second RF signal at the second frequency.
6. 6 . The method of claim 5 , wherein the machine learning model further comprises a database of recordings of previous plasma processes.
7. 7 . The method of claim 1 , wherein generating the second RF signal at the second frequency is performed after moving variable components of the matching circuit to fixed positions.
8. 8 . A method of performing a plasma process, the method comprising: holding variable components of a matching circuit to fixed positions; determining an ignition frequency for igniting a plasma in a plasma chamber with a controller programmed with a machine learning model stored in a memory of the controller, the machine learning model including saved accumulated data from previous plasma processes; generating, at an output of a signal generator, a first signal at the ignition frequency to ignite the plasma within the plasma chamber; and in response to detecting the plasma using a photodiode coupled with the plasma chamber, switching the signal generator to output a second signal at a process frequency, the second signal sustaining the plasma while holding the variable components of the matching circuit to the fixed positions, the plasma being configured to process a substrate loaded into the plasma chamber.
9. 9 . The method of claim 8 , wherein the fixed positions of the variable components are determined prior to determining the ignition frequency.
10. 10 . The method of claim 8 , wherein switching the signal generator to output the second signal comprises performing frequency stepping.
11. 11 . The method of claim 8 , wherein switching the signal generator to output the second signal comprises performing a frequency sweep.
12. 12 . The method of claim 11 , wherein determining the ignition frequency comprises performing a pendulum search method.
13. 13 . The method of claim 11 , wherein determining the ignition frequency comprises performing a sweep up method.
14. 14 . The method of claim 11 , wherein determining the ignition frequency comprises performing a sweep down method.
15. 15 . The method of claim 11 , wherein determining the ignition frequency comprises holding the variable components of the matching circuit to the fixed positions.
16. 16 . A method of performing a plasma process, the method comprising: powering a plasma chamber at a process frequency based on an output of a signal generator, the signal generator being coupled to the plasma chamber through a matching circuit; determining a delivered power from the signal generator to the plasma chamber; determining a configuration of the matching circuit based on the delivered power; determining, for the determined configuration of the matching circuit, an ignition frequency for igniting a plasma in the plasma chamber; igniting the plasma at the ignition frequency within the plasma chamber; receiving feedback on ignition of the plasma from an optical emission spectrometer coupled with the plasma chamber; and after the igniting, powering the plasma in the plasma chamber at the process frequency, the plasma being configured to process a substrate loaded into the plasma chamber.
17. 17 . The method of claim 16 , further comprising exposing the substrate loaded into the plasma chamber to the plasma while holding the matching circuit at the determined configuration.
18. 18 . The method of claim 16 , wherein powering the plasma in the plasma chamber further comprises regulating the delivered power from the signal generator with feedback from a VI probe.
19. 19 . The method of claim 16 , wherein, prior to determining the ignition frequency, power from the signal generator is turned off after determining the configuration of the matching circuit.
20. 20 . The method of claim 8 , wherein the machine learning model is generated to be specific to the plasma chamber.

Description

TECHNICAL FIELD The present invention relates generally to plasma processing systems and methods, and, in particular embodiments, to a systems and methods for setting and adjusting process parameters prior to and during plasma processing. BACKGROUND Generally, advancements in semiconductor integrated circuits (IC's) are driven by a demand for higher functionality at reduced cost. Higher functionality at lower cost is provided primarily by increasing component packing density through miniaturization. An IC is a network of electronic components (e.g., transistor, resistor, and capacitor) interconnected by a multilevel system of conductive lines, contacts, and vias. Elements of the network are integrated together by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials over a semiconductor substrate using a fabrication flow comprising process steps such as chemical vapor deposition (CVD), photolithography, and etch. The packing density of circuit elements have been increased by periodically reducing minimum feature sizes with innovations such as immersion lithography and multiple patterning. Further miniaturization is achieved by reducing the device footprint with three-dimensional (3D) device structures (e.g., FinFET and stacked capacitor memory cell). Plasma processes such as reactive ion etching (RIE), plasma-enhanced CVD (PECVD), plasma-enhanced atomic layer etch and deposition (PEALE and PEALD), and cyclic plasma process (e.g., cycles of alternating deposition and etch) are routinely used in the deposition and patterning steps used in semiconductor IC fabrication. The challenge of providing manufacturable plasma technology for advanced IC designs, however, has intensified with the advent of feature sizes scaled down to a few nanometers with structural features controlled at atomic scale dimensions. A manufacturable plasma process is expected to provide structures with precise dimensions (e.g., linewidths, etch depth, and film thicknesses) along with precisely controlled features for both plasma etch (e.g., sidewall angle, anisotropy, and selectivity to etch-stop layers) and plasma deposition (e.g., conformality, aspect-ratio selectivity, and area selectivity for bottom-up patterning), and uniformity across a wide (e.g., 300 mm) wafer. In many of the plasma processes used in IC manufacturing, the plasma is sustained by RF power. Fast and repeatable plasma ignition and power delivery are desirable for achieving precise control of plasma processes. SUMMARY In accordance with an embodiment, a method of performing a plasma process includes: generating, at an output of a signal generator, a first RF signal at a first frequency, the signal generator being coupled to a plasma chamber through a matching circuit; based on a feedback from the first RF signal, moving variable components of the matching circuit to fixed positions; generating, at the output of the signal generator, a second RF signal at a second frequency to ignite a plasma within the plasma chamber, and in response to detecting the plasma, switching the signal generator to output a third RF signal at the first frequency, the third RF signal sustaining the plasma, the plasma being configured to process a substrate loaded into the plasma chamber while holding the matching circuit at the fixed positions. In accordance with another embodiment, a method of performing a plasma process includes: holding variable components of a matching circuit to fixed positions; determining an ignition frequency for igniting a plasma in a plasma chamber; generating, at an output of a signal generator, a first signal at the ignition frequency to ignite the plasma within the plasma chamber; and in response to detecting the plasma, switching the signal generator to output a second signal at a process frequency, the second signal sustaining the plasma while holding the variable components of the matching circuit to the fixed positions, the plasma being configured to process a substrate loaded into the plasma chamber. In accordance with yet another embodiment, a method of performing a plasma process includes: powering a plasma chamber at a process frequency based on an output of a signal generator, the signal generator being coupled to the plasma chamber through a matching circuit; determining a delivered power from the signal generator to the plasma chamber; determining a configuration of the matching circuit based on the delivered power; determining, for the determined configuration of the matching circuit, an ignition frequency for igniting a plasma in the plasma chamber; igniting the plasma at the ignition frequency within the plasma chamber; and after the igniting, powering the plasma in the plasma chamber at the process frequency, the plasma being configured to process a substrate loaded into the plasma chamber. It is to be understood that both the foregoing general description and the following detailed description are exemp