Plasma processing apparatus and method for controlling source frequency of source radio-frequency power
A plasma processing apparatus includes a chamber, a substrate support, a radio-frequency power supply, and a bias power supply. The radio-frequency power supply generates source radio-frequency power to generate plasma in the chamber. The bias power supply provides a pulse of bias energy to a bias electrode in each of a plurality of pulse periods. The radio-frequency power supply sets, based on a change in a degree of reflection of the source radio-frequency power, a source frequency of the source radio-frequency power in each of a plurality of phase periods in each of a plurality of overlap periods. Each of the plurality of overlap periods overlaps a corresponding pulse period of the plurality of pulse periods. The degree of reflection is identified with the source frequency being set differently in identical phase periods in two or more preceding overlap periods.
1. A plasma processing apparatus, comprising:
a chamber;
a substrate support located in the chamber and including a bias electrode;
a radio-frequency power supply configured to generate source radio-frequency power to generate plasma in the chamber; and
a bias power supply configured to provide a pulse of bias energy to the bias electrode in each of a plurality of pulse periods,
wherein the bias power supply is configured to periodically provide the bias energy having a waveform cycle to the bias electrode in each of the plurality of pulse periods,
the radio-frequency power supply is configured to set a source frequency of the source radio-frequency power in each of a plurality of phase periods in each of a plurality of waveform cycles of the bias energy included in each of a plurality of overlap periods, and each of the plurality of overlap periods being an overlap in time with a corresponding pulse period of the plurality of pulse periods, and
the radio-frequency power supply is configured to perform interpulse feedback to adjust the source frequency in an n-th phase period of the plurality of phase periods in an m-th waveform cycle of the plurality of waveform cycles of the bias energy in a k-th overlap period of the plurality of overlap periods based on a change in a degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in the m-th waveform cycle in each of two or more overlap periods of the plurality of overlap periods preceding the k-th overlap period.
2. The plasma processing apparatus according to claim 1 , wherein
the two or more overlap periods include a (k−K 1 )th overlap period and a (k−K 2 )th overlap period, and K 1 and K 2 are natural numbers satisfying K 1 >K 2 , and
the radio-frequency power supply is configured to have the interpulse feedback set, in response to the degree of reflection decreasing with the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 )th overlap period being set to a frequency resulting from a frequency shift in a first direction being one of a decrease or an increase from the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 1 )th overlap period, the source frequency in the n-th phase period in the m-th waveform cycle in the k-th overlap period to a frequency resulting from the frequency shift in the first direction from the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 ) overlap period.
3. The plasma processing apparatus according to claim 2 , wherein
the radio-frequency power supply is further configured to have the interpulse feedback set, in response to the degree of reflection increasing with the source frequency in the n-th phase period in the m-th waveform cycle in the k-th overlap period being set to the frequency resulting from the frequency shift in the first direction from the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 )th overlap period, the source frequency in the n-th phase period in the m-th waveform cycle in a (k+K 3 )th overlap period of the plurality of overlap periods subsequent to the k-th overlap period to an intermediate frequency between the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 ) overlap period and the source frequency in the n-th phase period in the m-th waveform cycle in the k-th overlap period.
4. The plasma processing apparatus according to claim 3 , wherein
the radio-frequency power supply is further configured to have the interpose feedback set, in response to the degree of reflection exceeding a threshold when the intermediate frequency is set in the n-th phase period in the m-th waveform cycle in the (k+K 3 )th overlap period, the source frequency in the n-th phase period in the m-th waveform cycle in an overlap period of the plurality of overlap periods subsequent to the (k+K 3 )th overlap period to a frequency resulting from a frequency shift in a second direction being the other of the decrease or the increase from the intermediate frequency, and an amount of the frequency shift in the second direction has a greater absolute value than an amount of the frequency shift in the first direction.
5. The plasma processing apparatus according to claim 2 , wherein
an amount of the frequency shift in the first direction has a greater absolute value for the source frequency in the n-th phase period in the m-th waveform cycle in the k-th overlap period than for the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 )th overlap period.
6. The plasma processing apparatus according to claim 1 , wherein
the two or more overlap periods include a (k−K 1 )th overlap period and a (k−K 2 )th overlap period, and K 1 and K 2 are natural numbers satisfying K 1 >K 2 , and
the radio-frequency power supply is further configure to have the interpulse feedback set, in response to the degree of reflection increasing with the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 )th overlap period being set to a frequency resulting from a frequency shift in a first direction being one of a decrease or an increase from the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 1 )th overlap period, the source frequency in the n-th phase period in the m-th waveform cycle in the k-th overlap period to a frequency resulting from a frequency shift in a second direction being the other of the decrease or the increase from the source frequency in the n-th phase period in the m-th waveform cycle in the (k−K 2 )th overlap period.
7. The plasma processing apparatus according to claim 1 , wherein
the bias energy is bias radio-frequency power having a bias frequency that is an inverse of a time length of the waveform cycle or includes a pulse of a voltage provided to the bias electrode in each of the plurality of waveform cycles, and each of the plurality of waveform cycles has a time length being the inverse of the bias frequency.
8. The plasma processing apparatus according to claim 2 , wherein
the bias energy is bias radio-frequency power having a bias frequency that is an inverse of a time length of the waveform cycle or includes a pulse of a voltage provided to the bias electrode in each of the plurality of waveform cycles, and each of the plurality of waveform cycles has a time length being the inverse of the bias frequency.
9. The plasma processing apparatus according to claim 3 , wherein
the bias energy is bias radio-frequency power having a bias frequency that is an inverse of a time length of the waveform cycle or includes a pulse of a voltage provided to the bias electrode in each of the plurality of waveform cycles, and each of the plurality of waveform cycles has a time length being the inverse of the bias frequency.
10. The plasma processing apparatus according to claim 1 , wherein
the plurality of overlap periods include first to K a -th overlap periods, and K a is a natural number greater than or equal to 2, and
the radio-frequency power supply is configured to perform, in each of first to M a -th waveform cycles of the plurality of waveform cycles included in each of the first to K a -th overlap periods, an initial process to set source frequencies in the plurality of phase periods to a plurality of frequencies included in a predefined frequency group, and
perform, after the M a -th waveform cycle of the plurality of waveform cycles in each of the first to K a -th overlap periods, intrapulse feedback to adjust the source frequency in the n-th phase period in the m-th waveform cycle based on a change in the degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in each of two or more waveform cycles of the plurality of waveform cycles preceding the m-th waveform cycle.
11. The plasma processing apparatus according to claim 2 , wherein
the plurality of overlap periods include first to K a -th overlap periods, and K a is a natural number greater than or equal to 2, and
the radio-frequency power supply is configured to perform, in each of first to M a -th waveform cycles of the plurality of waveform cycles included in each of the first to K a -th overlap periods, an initial process to set source frequencies in the plurality of phase periods to a plurality of frequencies included in a predefined frequency group, and
perform, after the M a -th waveform cycle of the plurality of waveform cycles in each of the first to K a -th overlap periods, intrapulse feedback to adjust the source frequency in the n-th phase period in the m-th waveform cycle based on a change in the degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in each of two or more waveform cycles of the plurality of waveform cycles preceding the m-th waveform cycle.
12. The plasma processing apparatus according to claim 3 , wherein
the plurality of overlap periods include first to K a -th overlap periods, and K a is a natural number greater than or equal to 2, and
the radio-frequency power supply is configured to perform, in each of first to M a -th waveform cycles of the plurality of waveform cycles included in each of the first to K a -th overlap periods, an initial process to set source frequencies in the plurality of phase periods to a plurality of frequencies included in a predefined frequency group, and
perform, after the M a -th waveform cycle of the plurality of waveform cycles in each of the first to K a -th overlap periods, intrapulse feedback to adjust the source frequency in the n-th phase period in the m-th waveform cycle based on a change in the degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in each of two or more waveform cycles of the plurality of waveform cycles preceding the m-th waveform cycle.
13. The plasma processing apparatus according to claim 4 , wherein
the plurality of overlap periods include first to K a -th overlap periods, and K a is a natural number greater than or equal to 2, and
the radio-frequency power supply is configured to perform, in each of first to M a -th waveform cycles of the plurality of waveform cycles included in each of the first to K a -th overlap periods, an initial process to set source frequencies in the plurality of phase periods to a plurality of frequencies included in a predefined frequency group, and
perform, after the waveform cycle of the plurality of waveform cycles in each of the first to K a -th overlap periods, intrapulse feedback to adjust the source frequency in the n-th phase period in the m-th waveform cycle based on a change in the degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in each of two or more waveform cycles of the plurality of waveform cycles preceding the m-th waveform cycle.
14. The plasma processing apparatus according to claim 12 , wherein
the plurality of overlap periods further include (K a +1)th to K b -th overlap periods, and K b is a natural number greater than or equal to (K a +1), and
the radio-frequency power supply is configured to perform the initial process in each of first to M b1 -th waveform cycles of the plurality of waveform cycles included in each of the (K a +1)th to K b -th overlap periods,
perform the interpulse feedback in (M b1 +1)th to M b2 -th waveform cycles of the plurality of waveform cycles included in each of the (K a +1)th to K b -th overlap periods, and
perform the intrapulse feedback after the M b2 -th waveform cycle in each of the (K a +1)th to K b -th overlap periods, and M b1 and M a satisfy M b1 <M a .
15. The plasma processing apparatus according to claim 14 , wherein
the radio-frequency power supply is configured to perform the interpulse feedback in first to M c -th waveform cycles of the plurality of waveform cycles included in each of (K b +1)th to last overlap periods of the plurality of overlap periods, and
perform the intrapulse feedback after the M c -th waveform cycle in each of the (K b +1)th to last overlap periods.
16. The plasma processing apparatus according to claim 12 , wherein
in at least one overlap period of second to last overlap periods of the plurality of overlap periods, the radio-frequency power supply is configured to set the source frequency in the n-th phase period in an earliest waveform cycle of the plurality of waveform cycles in which the intrapulse feedback is performed to the source frequency in the n-th phase period in a last waveform cycle of the plurality of waveform cycles included in an overlap period of the plurality of overlap periods immediately preceding the at least one overlap period, or to an average of source frequencies in n-th phase periods in two or more waveform cycles of the plurality of waveform cycles including the last waveform cycle.
17. The plasma processing apparatus according to claim 15 , wherein
in at least one overlap period of second to last overlap periods of the plurality of overlap periods, the radio-frequency power supply is configured to set the source frequency in the n-th phase period in an earliest waveform cycle of the plurality of waveform cycles in which the intrapulse feedback is performed to the source frequency in the n-th phase period in a last waveform cycle f the plurality of waveform cycles included in an overlap period the plurality of overlap periods immediately preceding the at least one overlap period, or to an average of source frequencies in n-th phase periods in two or more waveform cycles of the plurality of waveform cycles including the last waveform cycle.
18. The plasma processing apparatus according to claim 12 , wherein
the radio-frequency power supply is configured to end the initial process under a condition a monitor value reflecting the degree of reflection falls within a specified range during the initial process.
19. The plasma processing apparatus according to claim 16 , wherein
the radio-frequency power supply is configured to end the initial process under a condition a monitor value reflecting the degree of reflection falls within a specified range during the initial process.
20. A method for controlling a source frequency of source radio-frequency power, the method comprising:
periodically providing a pulse of bias energy having a waveform cycle to a bias electrode in each of a plurality of pulse periods, the bias electrode being located on a substrate support in a chamber in a plasma processing apparatus;
providing the source radio-frequency power from a radio-frequency power supply to generate plasma in the chamber; and
setting a source frequency the source radio-frequency power in each of a plurality of phase periods in each of a plurality of waveform cycles of the bias energy included in each of a plurality of overlap periods, each of the plurality of overlap periods being an overlap in time with a corresponding pulse period of the plurality of pulse periods,
wherein the source frequency in an n-th phase period of the plurality of phase periods in an m-th waveform cycle of the plurality of waveform cycles of the bias energy in a k-th overlap period of the plurality of overlap periods is adjusted based on a change in a degree of reflection of the source radio-frequency power occurring when the source frequency is set differently in the n-th phase period in the m-th waveform cycle in each of two or more overlap periods of the plurality of overlap periods preceding the k-th overlap period.