US-20260128258-A1 - HYBRID FREQUENCY PLASMA SOURCE

Abstract

A plasma system includes a first matchless plasma source (MPS) that generates a first sinusoidal waveform having a first frequency. The plasma system includes a first filter coupled to the first MPS to filter a second frequency. The plasma system further includes a first capacitive circuit coupled to the first filter to balance reactances of the first filter and a radio frequency (RF) coil to further provide a first RF signal to a point. The plasma system includes a second MPS that generates a second sinusoidal waveform having the second frequency. The plasma system includes a second filter coupled to the second MPS to filter the first frequency. The plasma system includes a second capacitive circuit that is coupled to the second filter to balance a reactance of the second filter with the reactance of the RF coil to further provide a second RF signal to the point.

Inventors

• Yuhou WANG
• Alexander Miller Paterson
• John Stephen Drewery
• Ying Wu

Assignees

• LAM RESEARCH CORPORATION

Dates

Publication Date

20260507

Application Date

20220831

Claims (20)

1. 1 . A system comprising: a first matchless plasma source configured to generate a first sinusoidal waveform, wherein the first sinusoidal waveform is generated based on a first square waveform, wherein the first sinusoidal waveform has a first frequency; a first filter coupled to the first matchless plasma source, wherein the first filter is configured to filter a second frequency from interfering with the first sinusoidal waveform; a first capacitive circuit coupled to the first filter, wherein the first capacitive circuit is configured to balance a reactance of the first filter with a reactance of an RF coil of a plasma chamber to output a first radio frequency (RF) signal, wherein the first capacitive circuit is configured to provide the first RF signal to a point that is coupled to the RF coil; a second matchless plasma source configured to generate a second sinusoidal waveform, wherein the second sinusoidal waveform is generated based on a second square waveform, wherein the second sinusoidal waveform has the second frequency; a second filter coupled to the second matchless plasma source, wherein the second filter is configured to filter the first frequency from interfering with the second sinusoidal waveform; and a second capacitive circuit coupled to the second filter, wherein the second capacitive circuit is configured to balance a reactance of the second filter with the reactance of the RF coil to output a second RF signal, wherein the second capacitive circuit is configured to provide the second RF signal to the point.
2. 2 . The system of claim 1 , wherein the first RF signal is combined with the second RF signal at the point to provide a combined RF signal to the RF coil.
3. 3 . The system of claim 1 , wherein the second frequency is greater than the first frequency.
4. 4 . The system of claim 1 , further comprising the plasma chamber including the RF coil and a substrate support.
5. 5 . The system of claim 4 , further comprising: a first bias RF generator configured to generate a third RF signal; a match coupled to the first bias RF generator; a second bias RF generator coupled to the match, wherein the second bias RF generator is configured to generate a fourth RF signal, wherein the match is configured to receive the third and fourth RF signals and modify impedances of the third and fourth RF signals to output a combined RF signal, wherein the match is configured to provide the combined RF signal to the substrate support.
6. 6 . The system of claim 4 , wherein the substrate support is coupled to a ground potential.
7. 7 . The system of claim 1 , wherein the first capacitive circuit is configured to receive a reflected RF signal having RF power reflected from the plasma chamber, wherein the reflected RF signal has the second frequency.
8. 8 . The system of claim 1 , wherein the second capacitive circuit is configured to receive a reflected RF signal having RF power reflected from the plasma chamber, wherein the reflected RF signal has the first frequency.
9. 9 . The system of claim 1 , wherein there is a lack of a match between the first matchless plasma source and the RF coil and there is a lack of a match between the second matchless plasma source and the RF coil.
10. 10 . A system comprising: a matchless plasma source configured to generate a sinusoidal waveform, wherein the sinusoidal waveform is generated based on a square waveform, wherein the sinusoidal waveform has a first frequency; a first filter coupled to the matchless plasma source, wherein the first filter is configured to filter a second frequency from interfering within the sinusoidal waveform; a capacitive circuit coupled to the first filter, wherein the capacitive circuit is configured to balance a reactance of the first filter with a reactance of an RF coil of a plasma chamber to output a first radio frequency (RF) signal, wherein the capacitive circuit is configured to provide the first RF signal to a point that is coupled to the RF coil; a source RF generator configured to generate a second RF signal having the second frequency; and an impedance matching network coupled to the source RF generator, wherein the impedance matching network is configured to receive the second RF signal and modify an impedance of the second RF signal to output a modified RF signal, wherein the impedance matching network includes a second filter, wherein the second filter is configured to filter the first frequency from interfering with the second RF signal, wherein the impedance matching network is configured to provide the modified RF signal to the point.
11. 11 . The system of claim 10 , wherein the point is configured to combine the first RF signal with the modified RF signal to provide a combined RF signal to the RF coil.
12. 12 . The system of claim 10 , wherein the second frequency is greater than the first frequency or is equal to the first frequency or is less than the first frequency.
13. 13 . The system of claim 10 , further comprising the plasma chamber including the RF coil and a substrate support.
14. 14 . The system of claim 13 , further comprising: a first bias RF generator configured to generate a third RF signal; a match coupled to the first bias RF generator; a second bias RF generator coupled to the match, wherein the second bias RF generator is configured to generate a fourth RF signal, wherein the match is configured to receive the third and fourth RF signals and modify impedances of the third and fourth RF signals to output a combined RF signal, wherein the match is configured to provide the combined RF signal to the substrate support.
15. 15 . The system of claim 13 , wherein the substrate support is coupled to a ground potential.
16. 16 . The system of claim 10 , wherein the capacitive circuit is configured to receive a reflected RF signal having RF power reflected from the plasma chamber, wherein the reflected RF signal has the second frequency.
17. 17 . The system of claim 10 , wherein there is a lack of a match between the matchless plasma source and the RF coil, wherein the match includes a physical housing.
18. 18 . A system comprising: a first matchless plasma source configured to generate a first sinusoidal waveform, wherein the first sinusoidal waveform is generated based on a first square waveform, wherein the first sinusoidal waveform has a first frequency; a first filter coupled to the first matchless plasma source, wherein the first filter is configured to filter a second frequency from interfering with the first sinusoidal waveform; a first capacitive circuit coupled to the first filter, wherein the first capacitive circuit is configured to balance a reactance of the first filter with a reactance of a first radio frequency (RF) coil of a plasma chamber to output a first RF signal, wherein the first capacitive circuit is configured to provide the first RF signal to a point that is coupled to the first RF coil; a second matchless plasma source configured to generate a second sinusoidal waveform, wherein the second sinusoidal waveform is generated based on a second square waveform, wherein the second sinusoidal waveform has the second frequency; a second filter coupled to the second matchless plasma source, wherein the second filter is configured to filter the first frequency from interfering with the second sinusoidal waveform; a second capacitive circuit coupled to the second filter, wherein the second capacitive circuit is configured to balance a reactance of the second filter with a reactance of the first RF coil and a reactance of a second RF coil of the plasma chamber to output a second RF signal; and a signal splitter coupled to the second capacitive circuit, wherein the signal splitter is configured to split the second RF signal into a third RF signal and a fourth RF signal, wherein the signal splitter includes a third capacitive circuit and a fourth capacitive circuit, wherein the third capacitive circuit is configured to receive the third RF signal and balance the reactance of the first RF coil of the plasma chamber with the reactance of the second filter to provide a fifth RF signal to the point, wherein the fourth capacitive circuit is configured to receive the fourth RF signal and balance the reactance of the second RF coil with the reactance of the second filter to provide a sixth RF signal to the second RF coil.
19. 19 . The system of claim 18 , wherein the point is configured to combine the first RF signal with the fifth RF signal to provide a seventh RF signal to the first RF coil.
20. 20 . The system of claim 18 , wherein the second frequency is greater than the first frequency.

Description

FIELD The present embodiments relate to a hybrid frequency plasma source. BACKGROUND A plasma system is used to perform a variety of operations on wafers. The plasma system includes a radio frequency (RF) generator, an RF match, and a plasma chamber. The RF generator is coupled to the RF match via an RF cable and the RF match is coupled to the plasma chamber. An RF power is provided via the RF cable and the RF match to the plasma chamber in which a wafer is processed. Also, one or more gases are supplied to the plasma chamber and upon reception of the RF power, plasma is generated or maintained within the plasma chamber. When the RF power is provided, sometimes plasma is not stricken within the plasma chamber or arcing occurs within the plasma chamber. It is in this context that embodiments described in the present disclosure arise. SUMMARY Embodiments of the disclosure provide systems, apparatus, methods and computer programs for providing a hybrid frequency plasma source. It should be appreciated that the present embodiments can be implemented in numerous ways, e.g., a process, or an apparatus, or a system, or a piece of hardware, or a method, or a computer-readable medium. Several embodiments are described below. Each inductively coupled plasma (ICP) coil of a plasma chamber is driven by one radio frequency (RF) generator at one RF frequency at any instant. A choice of the RF frequency is limited by multiple factors. Coil voltage at the ICP coil increases with an increasing RF frequency, which can cause arcing on the ICP coil or sputtering on a dielectric window of the plasma chamber. The arcing or sputtering is caused by ions accelerated by capacitively coupled RF power from the coil. On the other hand, with lower radio frequencies, the coupling becomes less effective especially at lower plasma densities. It is also more difficult for the RF generator to breakdown neutral gas and strike plasma with a lower voltage at the ICP coil. In one embodiment, a dual-frequency ICP source operating at two radio frequencies is presented. For example, two independent RF sources, such as RF generators or matchless plasma sources (MPSs), tuned at two significantly separated RF frequencies are used to simultaneously power the ICP coil through a single feed. To illustrate, two MPSs, such as a low frequency MPS and a high frequency MPS, are used to drive the same ICP coil. The two MPSs operate at two separated frequencies, a low frequency and a high frequency. As an example, the low frequency is in a range of 1.8 megahertz (MHz) to 2.2 MHz and the high frequency is in the range of 12.35 MHz and 13.65 MHz. As another example, the low frequency is in the range of 400 kilohertz (kHz) to 2 MHz and the high frequency is in the range of 12 MHz to 27 MHz. A corresponding output of each of the MPSs is attached to a filter circuit for isolation. Also, each filter circuit is coupled to a corresponding capacitor to cancel any remaining reactance from the ICP coil and the filter circuit, such that series resonances at the low and high frequencies are presented to the low frequency MPS and the high frequency MPS respectively. Each capacitor can be either a fixed value or a variable value capacitor. For example, a network between each of the MPSs and ICP coil includes fixed elements, such as fixed capacitors and fixed inductors, without including any variable elements, so that active control of the network is not needed during operation. In an embodiment, a low pass filter and a high pass filter can be coupled to an output of the low frequency MPS and the high frequency MPS respectively. In one embodiment, a band pass filter can be coupled to an output of any of the two MPSs. For example, a series resonance circuit including a series circuit of a capacitor and an inductor can be used as the band pass filter to provide adequate isolation from the low frequency or the high frequency, In an embodiment, a first band pass filter is coupled to an output of the low frequency MPS and a second band pass filter is coupled to an output of the high frequency MPS. In an embodiment, two 50-ohm RF generators operate at separate RF frequencies to power the same ICP coil. The two RF generators employed are capable of outputting tuned RF in a low frequency band from 400 kHz to 2 MHz and in a high frequency band from 12 MHz to 27 MHz respectively. The two RF generators provide input to a dual-frequency impedance matching network, which transforms an impedance of the ICP coil at its output port to 50 ohms to present to the two RF generators. In one embodiment, the dual-frequency impedance matching network includes one or more isolation filter circuits. The dual-frequency impedance match network includes two sub-networks, one for a transfer of the low frequency and another one for a transfer of the high frequency. An isolation filter circuit can be placed either on an input side or an output side, or both the input and output sides, of each of the two sub-