CN108471666B - Plasma generating method and device and semiconductor processing equipment - Google Patents
Plasma generating method and device and semiconductor processing equipment Download PDFInfo
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- CN108471666B CN108471666B CN201710100093.9A CN201710100093A CN108471666B CN 108471666 B CN108471666 B CN 108471666B CN 201710100093 A CN201710100093 A CN 201710100093A CN 108471666 B CN108471666 B CN 108471666B
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- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3402—Gas-filled discharge tubes operating with cathodic sputtering using supplementary magnetic fields
- H01J37/3405—Magnetron sputtering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3464—Operating strategies
- H01J37/3467—Pulsed operation, e.g. HIPIMS
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Abstract
The invention provides a plasma generating method and device and semiconductor processing equipment. The plasma generating method includes: the upper radio frequency source outputs a main pulse signal for exciting the process gas in the reaction chamber to form plasma, and in the closing stage of the main pulse signal, the upper radio frequency source outputs one or more auxiliary pulse signals which can maintain the plasma in the reaction chamber to be in a glow starting state in the closing stage of the main pulse signal. The plasma generating method maintains the plasma in the reaction chamber to be in the glow starting state in the closing stage of the main pulse signal through the auxiliary pulse signal, and can prevent the plasma in the closing stage of the main pulse signal from being extinguished due to insufficient loaded main pulse power in the reaction chamber, thereby realizing the stable generation of the plasma in the reaction chamber and the expansion of a process window, and enabling the plasma process to be stably carried out.
Description
Technical Field
The invention relates to the technical field of magnetron sputtering, in particular to a plasma generating method and device and semiconductor processing equipment.
Background
In semiconductor equipment, a plasma apparatus for a silicon etching process generally applies an Inductively Coupled Plasma (ICP) principle, and a radio frequency power supply supplies radio frequency energy to ionize a special gas (such as argon Ar, helium He, nitrogen N) in a high vacuum state in a chamber2Hydrogen gas H2Etc.), generating plasma containing a large amount of active particles such as electrons, ions, excited atoms, molecules, radicals, etc., which interact with the wafer disposed in the chamber and exposed to the plasma environment in a complex manner, causing various physical and chemical reactions to occur on the surface of the wafer material, thereby changing the surface properties of the material,and finishing the etching process of the wafer.
With the further development of integrated circuits, the original technical scheme can not meet the requirements of etching processes of 20nm and below, and the application of the new pulse plasma technology realizes breakthrough in the micronization process. The pulsed Plasma technology is used for reducing Plasma Induced Damage (PID) caused by continuous wave radio frequency energy, improving load effect (Loading effect) in an etching process, remarkably improving etching Selectivity (Selectivity), enlarging a process window and increasing an adjusting means, and therefore, is very critical to design of a pulsed Plasma source.
One prior art provides a typical dual coil inductively coupled plasma device. As shown in fig. 1, the apparatus is composed of a reaction chamber 3, an upper electrode system including an upper rf source 1, a first matcher 2, a current distribution unit 22, and an inductively coupled dual coil 19, a lower electrode system, and an electrostatic chuck 10. The inductive coupling type double coil 19 is composed of an inner coil 20 and an outer coil 21, both of which are located above the dielectric window 13. The upper rf source 1 is connected to the current distribution unit 22 through the first matcher 2 to output energy to the inner coil 20 and the outer coil 21, respectively, and the rf energy ionizes the gas input from the gas path nozzle 14, so as to generate plasma 23 to act on the wafer 17 for processing. The lower electrode system comprises a lower radio frequency source 15 and a third matcher 16, wherein the lower radio frequency source 15 and the third matcher 16 are connected to the electrostatic chuck 10, so that the radio frequency power feed of the lower electrode is realized. The upper radio frequency source 1 and the lower radio frequency source 15 are pulse radio frequency power supplies for outputting pulse radio frequency signals, and the two radio frequency power supplies are connected through a pulse synchronization cable 18.
The apparatus of fig. 1 uses a pulsing technique to deliver rf energy to the chamber to achieve reduced plasma damage and improved process performance. As shown in fig. 2, the pulse application mode is that the upper electrode system uses pulse wave rf energy, and the lower electrode system also uses pulse wave rf energy, and the rf energy frequencies loaded by the upper and lower electrodes are equal, the phases of the rf waveforms are synchronized, and the pulse frequency and the duty ratio of the rf energy are also equal (e.g., the pulse frequency is 100Hz or other pulse frequencies, and the duty ratio is 50% or other duty ratios). The particle speed and the particle temperature of the plasma are reduced to a greater extent through the synchronous pulse of the upper electrode system and the lower electrode system, so that the particle energy for bombarding the wafer is greatly reduced.
As shown in fig. 3, the synchronous pulse signals loaded by the upper electrode and the lower electrode are signals with the same frequency and duty ratio, and the actual loading signal in the chamber is the superposition of the two signals.
In the first prior art, when an upper electrode system and a lower electrode system load pulse signals and ignite simultaneously, the hardware window of the device is small because the power loading time in a pulse mode is short and plasma is difficult to ignite. In particular, when the duty ratio is relatively small, the time for applying the power is short, and thus the plasma may not be ignited or may not be maintained and extinguished after the ignition. As shown in fig. 4, when the pulse synchronization signal has a low duty ratio, matching is difficult, and it requires a plurality of pulse periods to achieve ignition and matching, and in fig. 4, ignition is achieved at time Ti, and at this time, a stable matching impedance Z and a stable plasma density ni are achieved, but the plasma temperature cannot be maintained very quickly because the energy for sustaining ignition is insufficient and the plasma is extinguished (for example, at time Tj). In the prior art, the starting of the plasma of the cavity in a pulse mode is unstable, so that the process repeatability is poor.
Disclosure of Invention
The present invention provides a plasma generating method and apparatus for solving the above-mentioned problems in the prior art. The plasma generating method maintains the plasma in the reaction chamber to be in the glow starting state in the closing stage of the main pulse signal through the auxiliary pulse signal, and can prevent the plasma in the closing stage of the main pulse signal from being extinguished due to insufficient loaded main pulse power in the reaction chamber, thereby realizing the stable generation of the plasma in the reaction chamber and the expansion of a process window, and enabling the plasma process to be stably carried out.
The present invention provides a plasma generating method, comprising: the upper radio frequency source outputs a main pulse signal for exciting a process gas in a reaction chamber to form a plasma, and in the closing stage of the main pulse signal, the upper radio frequency source outputs one or more auxiliary pulse signals which can maintain the plasma in the reaction chamber to be in an ignition state in the closing stage of the main pulse signal.
Preferably, a duty ratio of the auxiliary pulse signal is smaller than a duty ratio of the main pulse signal.
Preferably, the amplitude of the auxiliary pulse signal is smaller than the amplitude of the main pulse signal.
Preferably, the rising edge of the auxiliary pulse signal when turned on is delayed from the rising edge of the main pulse signal when turned on.
Preferably, the frequency of the auxiliary pulse signal is equal to the frequency of the main pulse signal, and the auxiliary pulse signal has the same radio frequency as the main pulse signal.
Preferably, the frequency of the main pulse signal comprises 100KHz or less, and the duty ratio of the main pulse signal comprises 90% or less.
The invention also provides a plasma generating device, which comprises an upper radio frequency source, wherein the upper radio frequency source can output a main pulse signal to excite the process gas in the reaction chamber to form plasma, and is characterized in that the upper radio frequency source can also output one or more auxiliary pulse signals in the closing stage of the main pulse signal, and the auxiliary pulse signals can maintain the plasma in the reaction chamber to be in an ignition state in the closing stage of the main pulse signal.
Preferably, the upper rf source includes a main rf source connected to a main coil at the top of the reaction chamber through a first matcher, and the main rf source is capable of outputting a main pulse signal and outputting one or more auxiliary pulse signals during a turn-off phase of the main pulse signal.
Preferably, the upper rf source includes a main rf source and an auxiliary rf source, wherein the main rf source can output the main pulse signal, and the main rf source is connected to the main coil at the top of the reaction chamber through a first matcher; the auxiliary radio frequency source is connected with the secondary coil at the top of the reaction chamber through a second matcher, and the auxiliary radio frequency source can output one or more auxiliary pulse signals at the closing stage of the main pulse signal.
Preferably, the main radio frequency source is connected with the auxiliary radio frequency source through a pulse trigger cable, and the pulse trigger cable can control the duty ratio of the auxiliary pulse signal to be smaller than that of the main pulse signal; and/or the amplitude of the auxiliary pulse signal is smaller than that of the main pulse signal; and/or the rising edge of the auxiliary pulse signal when being started is delayed from the rising edge of the main pulse signal when being started.
Preferably, the rf power amplifier further comprises a first control switch, wherein the first control switch is connected between an output end of the primary rf source and an input end of the first matcher, or the first control switch is connected between an output end of the first matcher and the primary coil; the first control switch is turned on or off to control the main radio frequency source to output the main pulse signal or stop outputting the auxiliary pulse signal to the main coil.
Preferably, the rf power amplifier further comprises a first control switch and a second control switch, wherein the first control switch is connected between the output end of the main rf source and the input end of the first matcher, or the first control switch is connected between the output end of the first matcher and the main coil; the first control switch is turned on or turned off to control the main radio frequency source to output or stop outputting the main pulse signal to the main coil;
the second control switch is connected between the output end of the auxiliary radio frequency source and the input end of the second matcher, or the second control switch is connected between the output end of the second matcher and the secondary coil; the second control switch is turned on or off to control the auxiliary radio frequency source to output or stop outputting the auxiliary pulse signal to the secondary coil.
Preferably, the main coil comprises an outer coil group and an inner coil group, the outer coil group and the inner coil group are arranged on the same or different planes perpendicular to a central axis of the reaction chamber, and the outer coil group is positioned on the outer side of the inner coil group far away from the central axis;
the secondary coil is arranged on a plane vertical to the central axis of the reaction chamber, and the projection of the secondary coil on the plane vertical to the central axis of the reaction chamber is positioned between the projections of the outer coil group and the inner coil group on the plane vertical to the central axis of the reaction chamber.
The invention also provides semiconductor processing equipment comprising the plasma generating device.
The invention has the beneficial effects that: according to the plasma generating method provided by the invention, the upper radio frequency source outputs one or more auxiliary pulse signals at the closing stage of the main pulse signal, and the plasma in the reaction chamber is maintained to be in the glow starting state at the closing stage of the main pulse signal through the auxiliary pulse signal, so that the plasma in the reaction chamber at the closing stage of the main pulse signal can be prevented from being extinguished due to insufficient power of the loaded main pulse signal, and therefore, the stable generation of the plasma in the reaction chamber and the expansion of a process window are realized, and a plasma process can be stably carried out.
The plasma generating device provided by the invention can load one or more auxiliary pulse signals into the reaction chamber at the closing stage of the main pulse signal by arranging the auxiliary radio frequency source or the main radio frequency source so as to maintain the plasma in the glow starting state at the closing stage of the main pulse signal, thereby preventing the plasma in the reaction chamber from being extinguished at the closing stage of the main pulse signal due to insufficient power of the main pulse loaded by the main radio frequency source, realizing the stable generation of the plasma in the reaction chamber and the expansion of a process window, and enabling the plasma process to be stably carried out.
By adopting the plasma generating device, the semiconductor processing equipment provided by the invention not only can reduce the plasma induced damage of the semiconductor processing equipment in the process, but also can prevent plasma glow discharge in the pulse closing stage caused by insufficient loaded radio frequency pulse power, thereby realizing the stable generation of the plasma and the expansion of the process window and improving the plasma process stability of the semiconductor processing equipment.
Drawings
FIG. 1 is a schematic structural diagram of an inductively coupled dual-coil plasma apparatus according to the prior art;
FIG. 2 is a schematic diagram of waveforms of upper and lower RF pulses loaded in a reaction chamber according to the prior art;
FIG. 3 is a schematic diagram of the waveforms of the upper and lower RF pulses loaded in the reaction chamber and their superimposed waveforms in the prior art;
FIG. 4 is a schematic diagram illustrating the ignition and extinction of a plasma in a reaction chamber during the RF pulse energy loading process in the prior art;
FIG. 5 is a schematic diagram of pulse waveforms of an upper RF source pulse signal and a lower RF source pulse signal and a reaction chamber superimposed on each other in example 1 of the present invention;
FIG. 6 is a schematic diagram of superposed RF pulse waveforms and corresponding plasma state curves in the reaction chamber in example 1 of the present invention;
FIG. 7 is a schematic structural view of a plasma generation apparatus according to embodiment 2 of the present invention;
FIG. 8 is a timing diagram illustrating the control of the control switches for controlling the output of the pulse signals from the main RF source and the auxiliary RF source of FIG. 7;
fig. 9 is a schematic structural diagram of a plasma generation apparatus in embodiment 3 of the present invention.
Wherein the reference numbers indicate:
1. an upper radio frequency source; 11. a primary radio frequency source; 12. an auxiliary radio frequency source; 2. a first matcher; 3. a reaction chamber; 4. a main coil; 41. an outer coil group; 42. an inner coil assembly; l. a central axis; 5. a second matcher; 6. a secondary coil; 7. a pulse trigger cable; 8. a first control switch; 9. a second control switch; 10. an electrostatic chuck; 13. a dielectric window; 14. a gas path nozzle; 15. a lower radio frequency source; 16. a third matcher; 17. a wafer; 18. a pulse synchronization cable; 19. an inductively coupled double coil; 20. an inner coil; 21. an outer coil; 22. a current distribution unit; 23. plasma; z, plasma impedance when impedance in the reaction chamber is matched; ni. reflect the plasma density at impedance matching within the chamber.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, a plasma generation method and apparatus and a semiconductor processing apparatus provided by the present invention are described in further detail below with reference to the accompanying drawings and the detailed description.
Example 1:
the present embodiment provides a plasma generating method, including: the upper radio frequency source outputs a main pulse signal for exciting the process gas in the reaction chamber to form plasma, and in the closing stage of the main pulse signal, the upper radio frequency source outputs one or more auxiliary pulse signals which can maintain the plasma in the reaction chamber to be in a glow starting state in the closing stage of the main pulse signal.
The upper radio frequency source outputs one or more auxiliary pulse signals at the closing stage of the main pulse signal, and the auxiliary pulse signals maintain the plasma in the reaction chamber to be in a glow starting state at the closing stage of the main pulse signal, so that the plasma in the reaction chamber at the closing stage of the main pulse signal can be prevented from being extinguished due to insufficient loaded main pulse power, stable generation of the plasma in the reaction chamber and expansion of a process window are realized, and a plasma process can be stably carried out.
It should be noted that, in the off phase of the main pulse signal, the upper rf source outputs one or more auxiliary pulse signals, which is determined according to specific process conditions and process requirements, as long as it can be ensured that the auxiliary pulse signal can maintain the plasma that has been ignited in the off phase of the main pulse signal in the ignition state, and does not extinguish the ignition when the on phase of the next main pulse signal comes.
In this embodiment, as shown in fig. 5, during the off-phase of the main pulse signal, the upper rf source outputs an auxiliary pulse signal. The duty ratio of the auxiliary pulse signal is smaller than that of the main pulse signal. The amplitude of the auxiliary pulse signal is smaller than the amplitude of the main pulse signal. With the arrangement, the auxiliary pulse signal can maintain the ignited plasma to be in an ignition state all the time in the closing stage of the main pulse signal, and the ignition is not needed to be extinguished when the starting stage of the next main pulse signal comes, so that the plasma in the reaction chamber is more stable in the process stage; meanwhile, the amplitude of the auxiliary pulse signal is smaller than that of the main pulse signal, and the condition that the plasma particle temperature is high due to the fact that the energy of the auxiliary pulse signal is large can be avoided, so that damage to the wafer is caused, namely, plasma induced damage is avoided.
It should be noted that the amplitude of the auxiliary pulse signal may be greater than or equal to the amplitude of the main pulse signal. Therefore, the plasma which is already ignited can be maintained to be always in an ignition state through the auxiliary pulse signal, and the plasma cannot be extinguished when the starting stage of the next main pulse signal arrives, so that the plasma in the reaction chamber is more stable in the process stage.
In this embodiment, the rising edge of the auxiliary pulse signal is delayed from the rising edge of the main pulse signal. The rising edge of the auxiliary pulse signal when being turned on refers to the loading time of the auxiliary pulse signal, the rising edge of the main pulse signal when being turned on refers to the loading time of the main pulse signal, and the loading time of the auxiliary pulse signal is later than the loading time of the main pulse signal, namely, the auxiliary pulse signal is always loaded at the main pulse signal turn-off stage between two adjacent main pulse signals. By the arrangement, in the closing stage of the main pulse signal, the plasma in the reaction chamber can not be extinguished by timely loading of the auxiliary pulse signal before the plasma energy in the reaction chamber is reduced to be extinguished.
It should be noted that the rising edge of the auxiliary pulse signal when turned on is delayed from the rising edge of the main pulse signal when turned on, and the specific delay time is determined according to the actual hardware condition and the process condition. Preferably, the frequency of the auxiliary pulse signal is equal to the frequency of the main pulse signal, and the auxiliary pulse signal has the same radio frequency as the main pulse signal. By the arrangement, the plasma in the reaction chamber can be more stable, and the plasma in the reaction chamber is not easy to extinguish in the closing stage of the main pulse signal; meanwhile, the generation of the main pulse signal and the auxiliary pulse signal is easier to control.
Of course, the frequency of the auxiliary pulse signal may be different from the frequency of the main pulse signal, and the rf frequencies of the auxiliary pulse signal and the main pulse signal may also be different.
In this embodiment, as shown in fig. 5, during the off-phase of the main pulse signal, the upper rf source outputs an auxiliary pulse signal. The frequency f of the main pulse signal is 1/(Tm + Tn), the pulse duty ratio D1 of the main pulse signal is Tm/(Tm + Tn), the frequency of the auxiliary pulse signal is equal to the frequency of the main pulse signal, the pulse duty ratio D2 of the auxiliary pulse signal is Ts/(Tm + Tn), the rising edge of the auxiliary pulse signal is delayed from the rising edge of the main pulse signal, and the delay time is Td. The frequency of the pulse signal formed by the superposition of the main pulse signal and the auxiliary pulse signal in the reaction chamber is equal to the frequency of the main pulse signal, and the pulse duty ratio of the pulse signal formed by the superposition is D3 ═ Tm + Ts)/(Tm + Tn.
In addition, in the present embodiment, the lower rf source also outputs an rf pulse signal for forming a negative bias on the electrostatic chuck for supporting the wafer. Preferably, the timing, pulse frequency and duty cycle of the radio frequency pulse signal and the main pulse signal are the same. The actually loaded pulse signal in the reaction chamber is the mutual superposition of the main pulse signal and the auxiliary pulse signal output by the upper radio frequency source and the radio frequency pulse signal output by the lower radio frequency source, so that the radio frequency pulse signal output by the lower radio frequency source is set, the particle speed and the particle temperature of plasma in the reaction chamber can be reduced to the maximum extent, the particle energy for bombarding the wafer is greatly reduced, and the induced damage of the plasma is avoided.
As shown in fig. 6, under the action of the electromagnetic field generated by the main pulse signal, the process gas in the reaction chamber is ionized to form plasma, and in the time period of the on period Tm of the main pulse signal, the process gas is rapidly ionized to form high-density plasma and reach stability, and then enters the off period of the main pulse signal; at the moment, the radio frequency pulse energy loaded to the reaction chamber is zero, so that the plasma impedance Z and the plasma density ni in the reaction chamber are rapidly reduced, meanwhile, the temperature of electrons and the temperature of ions in the plasma are reduced to be very small, and the damage of particles to the wafer after reaching the surface of the wafer is reduced to a very low level, so that the induced damage of the plasma can be reduced, and the process performance is improved; in the off period of the main pulse signal, the plasma impedance Z and the density ni are changed, the upper radio frequency source outputs an auxiliary pulse signal with a shorter duty ratio and lower power to the reaction chamber after delaying the time Td of the rising edge of the main pulse signal, so that the aim of maintaining the plasma glow state in the reaction chamber is fulfilled, thus the process that the process gas in the reaction chamber needs to be ionized again to form the plasma after the next main pulse signal is started is avoided, the plasma in the reaction chamber can be more stable and can be continuously maintained in the subsequent pulse period, and the process is circulated and repeated, so that the requirement of stabilizing the plasma processing process is met.
In this embodiment, the upper rf source outputs one or more auxiliary pulse signals at the off stage of the main pulse signal, so that the plasma in the reaction chamber can be stably maintained in the ignition state, thereby avoiding the situation that the main pulse signal needs to be restarted at the on stage again, and ensuring the stability of the plasma processing process. Preferably, the frequency of the main pulse signal comprises less than 100KHz, and the duty cycle of the main pulse signal comprises less than 90%. Since the lower the frequency and the duty ratio of the main pulse signal, the more easily the plasma is extinguished in the off stage of the main pulse signal, the plasma generation method in this embodiment can realize the application of the lower frequency and the lower duty ratio of the main pulse signal, thereby expanding the process application window.
In addition, in this embodiment, the radio frequency signal frequencies of the upper radio frequency source and the lower radio frequency source are both 13.56 MHz. Of course, the frequency of the rf signals of the upper rf source and the lower rf source may also be 400KHz, 2MHz, 27.12MHz, 40MHz, 60MHz, or 100 MHz. Meanwhile, the upper radio frequency source and the lower radio frequency source can also load radio frequency signals with different radio frequency frequencies respectively, for example, the frequency of the radio frequency signal loaded by the upper radio frequency source is 2MHz (namely, the radio frequency frequencies of the main pulse signal and the auxiliary pulse signal are both 2MHz), and the frequency of the radio frequency signal loaded by the lower radio frequency source is 13.56 MHz.
Beneficial effects of example 1: in the plasma generating method provided in embodiment 1, the upper rf source outputs one or more auxiliary pulse signals at the off stage of the main pulse signal, and the auxiliary pulse signal maintains the plasma in the reaction chamber to be in the ignition state at the off stage of the main pulse signal, so that plasma in the reaction chamber can be prevented from being extinguished at the off stage of the main pulse signal due to insufficient power of the loaded main pulse signal, and thus stable generation of the plasma in the reaction chamber and expansion of the process window can be achieved, and the plasma process can be stably performed.
Example 2:
based on the plasma generating method in embodiment 1, the present embodiment provides a plasma generating apparatus, as shown in fig. 7, including an upper rf source 1, where the upper rf source 1 can output a main pulse signal to excite a process gas in a reaction chamber 3 to form a plasma 23, and the upper rf source 1 can also output one or more auxiliary pulse signals during a turn-off phase of the main pulse signal, and the auxiliary pulse signals can maintain the plasma 23 in the reaction chamber 3 in an ignition state during the turn-off phase of the main pulse signal.
In this embodiment, the upper rf source 1 includes a main rf source 11, the main rf source 11 is connected to a main coil 4 at the top of the reaction chamber 3 through a first matcher 2, the main rf source 11 can output a main pulse signal, the upper rf source 1 further includes an auxiliary rf source 12, the auxiliary rf source 12 is connected to a sub-coil 6 at the top of the reaction chamber 3 through a second matcher 5, and the auxiliary rf source 12 can output one or more auxiliary pulse signals at the closing stage of the main pulse signal; the main pulse signal can excite the process gas in the reaction chamber 3 to form a plasma 23; the auxiliary pulse signal can maintain the plasma 23 in an ignition state during the off-phase of the main pulse signal.
By arranging the auxiliary radio frequency source 12, one or more auxiliary pulse signals can be loaded to the reaction chamber 3 in the closing stage of the main pulse signal to maintain the plasma 23 in the glow starting state in the closing stage of the main pulse signal, so that the plasma 23 in the closing stage of the main pulse signal is prevented from being extinguished due to insufficient main pulse power loaded by the main radio frequency source 11 in the reaction chamber 3, stable generation of the plasma 23 in the reaction chamber 3 and expansion of a process window are realized, and the process of the plasma 23 can be stably carried out.
In this embodiment, the main rf source 11 is connected to the auxiliary rf source 12 through the pulse trigger cable 7, and the pulse trigger cable 7 can control the duty ratio of the auxiliary pulse signal to be smaller than the duty ratio of the main pulse signal; the amplitude of the auxiliary pulse signal is larger than, smaller than or equal to that of the main pulse signal; and the rising edge of the auxiliary pulse signal when turned on is delayed from the rising edge of the main pulse signal when turned on. The control of the duty ratio and the amplitude of the auxiliary pulse signal by the pulse trigger cable 7 can ensure that the auxiliary pulse signal can maintain the ignited plasma 23 to be in an ignition state all the time in the closing stage of the main pulse signal, and the plasma 23 in the reaction chamber 3 is more stable in the process stage because the ignition stage of the next main pulse signal does not extinguish; meanwhile, the damage of the plasma 23 to the wafer caused by the high temperature of the plasma particles due to the large energy of the auxiliary pulse signal can be avoided, namely, the induced damage of the plasma 23 is avoided. In addition, the delay time of the auxiliary pulse signal relative to the main pulse signal is controlled by the pulse trigger cable 7, so that the plasma 23 in the reaction chamber 3 can not be extinguished by timely loading of the auxiliary pulse signal before the energy of the plasma 23 in the reaction chamber 3 is reduced to extinguish the plasma in the closing stage of the main pulse signal.
It should be noted that the pulse trigger cable 7 may also control only one of the parameters of the duty cycle, the amplitude and the delay time of the auxiliary pulse signal.
In this embodiment, the plasma generating apparatus further includes a first control switch 8, and the first control switch 8 is connected between the output end of the main rf source 11 and the input end of the first matcher 2. The first control switch 8 is turned on or off to control the main rf source 11 to output or stop outputting the main pulse signal to the main coil 4 (as shown in fig. 8); and, also include the second control switch 9, the second control switch 9 is connected between output end of the auxiliary radio frequency source 12 and input end of the second matcher 5. The second control switch 9 is turned on or off to control the auxiliary rf source 12 to output or stop outputting the auxiliary pulse signal to the secondary coil 6 (as shown in fig. 8). The first control switch 8 and the second control switch 9 are arranged to prevent mutual interference of the radio frequency pulse signals between the main radio frequency source 11 and the auxiliary radio frequency source 12 in the upper radio frequency source 1, so that influence of interference signals on the work of the main radio frequency source 11, the auxiliary radio frequency source 12, the first matcher 2 and the second matcher 5 is avoided, and damage to devices is avoided.
The first control switch 8 may be connected between the output terminal of the first matching unit 2 and the main coil 4. The second control switch 9 may be connected between the output terminal of the second matching unit 5 and the sub-coil 6. The arrangement of the first control switch 8 and the second control switch 9 also serves the above-mentioned function. In addition, only one of the first control switch 8 and the second control switch 9 may be provided.
In this embodiment, the main coil 4 includes an outer coil group 41 and an inner coil group 42, the outer coil group 41 and the inner coil group 42 are disposed on the same plane perpendicular to the central axis L of the reaction chamber 3, and the outer coil group 41 is located outside the inner coil group 42 away from the central axis L; the sub-coil 6 is disposed on a plane perpendicular to the central axis L of the reaction chamber 3, and a projection of the sub-coil 6 on the plane perpendicular to the central axis L of the reaction chamber 3 is located between projections of the outer coil group 41 and the inner coil group 42 on the plane perpendicular to the central axis L of the reaction chamber 3. This arrangement centers the secondary coil 6 in a plane perpendicular to the central axis L of the reaction chamber 3, thus reducing the effect of the secondary coil 6 on the uniformity of the plasma 23 in the reaction chamber 3 and also facilitating ignition of the plasma 23 in the reaction chamber 3. Because, if the position of the secondary coil 6 on the plane perpendicular to the central axis L of the reaction chamber 3 is close to the center of the central axis L, the density of the middle region of the plasma 23 in the reaction chamber 3 is high, and the uniformity of the plasma 23 is not good; if the secondary coil 6 is located at the outer circle far from the central axis L on the plane perpendicular to the central axis L of the reaction chamber 3, a higher voltage is applied to the secondary coil 6 to ionize the process gas, so that the plasma 23 in the reaction chamber 3 is less likely to ignite.
In this embodiment, the first matcher 2 for connecting the main coil 4 at the top of the reaction chamber 3 adopts a matcher with a current distribution function, the magnitudes of the currents loaded by the matcher with the current distribution function on the outer coil group 41 and the inner coil group 42 may be the same or different, and the magnitudes of the currents are the same or different, so that the magnitudes of the electric fields generated on the outer coil group 41 and the inner coil group 42 are the same or different, and thus, the uniformity of the plasma 23 generated in the reaction chamber 3 can be better according to specific process conditions and process requirements.
In addition, in the present embodiment, an electrostatic chuck 10 is further disposed at a lower portion in the reaction chamber 3, and the wafer 17 is placed directly above the electrostatic chuck 10. The medium window 13 is positioned at the upper part of the reaction chamber 3, the primary coil 4 and the secondary coil 6 are both positioned above the medium window 13, the center of the medium window 13 is provided with a gas path nozzle 14, and the process gas is introduced into the reaction chamber 3 through the gas path nozzle 14. The rf energy from the upper rf source 1 ionizes the process gas fed from the gas path nozzle 14 to generate a plasma 23 that acts on the wafer 17 for processing. The plasma generating device further comprises a lower radio frequency source 15, the lower radio frequency source 15 is connected with the electrostatic chuck 10 through a third matcher 16, the lower radio frequency source 15 also outputs a radio frequency pulse signal, and the pulse frequency and the duty ratio of the pulse signal output by the upper radio frequency source 1 and the pulse signal output by the lower radio frequency source 15 are the same. A pulse synchronization cable 18 is connected between the lower rf source 15 and the upper rf source 1, and the pulse synchronization cable 18 is used to control the timing of the output pulse signals of the upper rf source 1 and the lower rf source 15, for example, in this embodiment, the pulse synchronization cable 18 controls the timing of the output pulse signals of the upper rf source 1 and the lower rf source 15 to be the same. Because the actually loaded pulse signal in the reaction chamber 3 is the mutual superposition of the main pulse signal and the auxiliary pulse signal output by the upper radio frequency source 1 and the radio frequency pulse signal output by the lower radio frequency source 15, the particle velocity and the particle temperature of the plasma 23 can be reduced to a greater extent by the arrangement, so that the particle energy for bombarding the wafer 17 is greatly reduced, and the induced damage of the plasma 23 is further avoided.
The plasma generation device in the present embodiment may be an inductively coupled plasma generation device or a capacitively coupled plasma generation device.
Beneficial effects of example 2: the plasma generating apparatus provided in embodiment 2, by providing the auxiliary rf source, can load one or more auxiliary pulse signals into the reaction chamber at the off stage of the main pulse signal to maintain the plasma in the ignition state at the off stage of the main pulse signal, so as to prevent the plasma in the reaction chamber from being extinguished at the off stage of the main pulse signal due to insufficient power of the main pulse loaded by the main rf source, thereby achieving stable generation of the plasma in the reaction chamber and expansion of the process window, and enabling the plasma process to be stably performed.
Example 3:
based on the plasma generating method provided in embodiment 1, this embodiment provides a plasma generating apparatus, and unlike in embodiment 2, as shown in fig. 9, the upper rf source 1 includes only the main rf source 11, i.e., the plasma generating apparatus in this embodiment is provided with only the main rf source 11 and is not provided with the auxiliary rf source. The main rf source 11 is capable of outputting a main pulse signal and outputting one or more auxiliary pulse signals during the off-phase of the main pulse signal.
Correspondingly, the plasma generating device also comprises a first control switch 8, wherein the first control switch 8 is connected between the output end of the main radio frequency source 11 and the input end of the first matcher 2; the first control switch 8 is turned on or off to control the main rf source 11 to output or stop outputting the main pulse signal or the auxiliary pulse signal to the main coil 4. That is, in the present embodiment, both the main pulse signal and the auxiliary pulse signal are output to the main coil 4.
Other structures of the plasma generating apparatus in this embodiment are the same as those in embodiment 2, and are not described herein again.
Beneficial effects of example 3: the plasma generating apparatus provided in embodiment 3, by providing the main rf source, can load one or more auxiliary pulse signals into the reaction chamber at the off stage of the main pulse signal to maintain the plasma in the ignition state at the off stage of the main pulse signal, so as to prevent the plasma in the reaction chamber from being extinguished at the off stage of the main pulse signal due to insufficient power of the main pulse loaded by the main rf source, thereby achieving stable generation of the plasma in the reaction chamber and expansion of the process window, and enabling the plasma process to be stably performed.
Example 4:
this embodiment provides a semiconductor processing apparatus including the plasma generating device according to any one of embodiments 2 to 3.
By using the plasma generating apparatus in any one of embodiments 2 to 3, not only plasma-induced damage of the semiconductor processing apparatus during a process can be reduced, but also plasma extinction at a pulse off stage due to insufficient power of a loaded radio frequency pulse can be prevented, thereby achieving stable generation of plasma and expansion of a process window, and improving plasma process stability of the semiconductor processing apparatus.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (14)
1. A plasma generation method, comprising: the upper radio frequency source outputs a main pulse signal for exciting a process gas in a reaction chamber to form a plasma, and is characterized in that the upper radio frequency source outputs one or more auxiliary pulse signals in a part of the off-phase of the main pulse signal, and the auxiliary pulse signals can maintain the plasma in the reaction chamber in an ignition state in the off-phase of the main pulse signal.
2. The plasma generating method according to claim 1, wherein a duty ratio of the auxiliary pulse signal is smaller than a duty ratio of the main pulse signal.
3. The plasma generating method according to claim 1, wherein an amplitude of the auxiliary pulse signal is smaller than an amplitude of the main pulse signal.
4. The method of claim 1, wherein a rising edge of the auxiliary pulse signal when turned on is delayed from a rising edge of the main pulse signal when turned on.
5. The plasma generating method according to claim 1, wherein a frequency of the auxiliary pulse signal is equal to a frequency of the main pulse signal, and the auxiliary pulse signal is the same as a radio frequency of the main pulse signal.
6. The plasma generation method of claim 1, wherein the frequency of the main pulse signal comprises 100KHz or less and the duty cycle of the main pulse signal comprises 90% or less.
7. A plasma generating apparatus comprising an upper rf source capable of outputting a main pulse signal to excite a process gas in a reaction chamber to form a plasma, wherein the upper rf source is further capable of outputting one or more auxiliary pulse signals during a portion of an off phase of the main pulse signal, the auxiliary pulse signals being capable of maintaining the plasma in the reaction chamber in an ignition state during the off phase of the main pulse signal.
8. The plasma generating apparatus as claimed in claim 7, wherein the upper rf source comprises a main rf source connected to the main coil at the top of the reaction chamber through a first matcher, the main rf source being capable of outputting a main pulse signal and outputting one or more of the auxiliary pulse signals during a turn-off period of the main pulse signal.
9. The plasma generating apparatus as claimed in claim 7, wherein the upper rf source comprises a main rf source and an auxiliary rf source, wherein the main rf source is capable of outputting the main pulse signal, and the main rf source is connected to the main coil at the top of the reaction chamber through a first matcher; the auxiliary radio frequency source is connected with the secondary coil at the top of the reaction chamber through a second matcher, and the auxiliary radio frequency source can output one or more auxiliary pulse signals at the closing stage of the main pulse signal.
10. The plasma generating apparatus according to claim 9, wherein the main rf source and the auxiliary rf source are connected by a pulse trigger cable, and the pulse trigger cable can control a duty ratio of the auxiliary pulse signal to be smaller than a duty ratio of the main pulse signal; and/or the amplitude of the auxiliary pulse signal is smaller than that of the main pulse signal; and/or the rising edge of the auxiliary pulse signal when being started is delayed from the rising edge of the main pulse signal when being started.
11. The plasma generation apparatus of claim 8, further comprising a first control switch connected between an output terminal of the primary radio frequency source and an input terminal of the first matcher, or between an output terminal of the first matcher and the primary coil; the first control switch is turned on or off to control the main radio frequency source to output the main pulse signal or stop outputting the auxiliary pulse signal to the main coil.
12. The plasma generating apparatus as claimed in claim 9, further comprising a first control switch and a second control switch, the first control switch being connected between an output terminal of the primary rf source and an input terminal of the first matcher, or the first control switch being connected between an output terminal of the first matcher and the primary coil; the first control switch is turned on or turned off to control the main radio frequency source to output or stop outputting the main pulse signal to the main coil; the second control switch is connected between the output end of the auxiliary radio frequency source and the input end of the second matcher, or the second control switch is connected between the output end of the second matcher and the secondary coil; the second control switch is turned on or off to control the auxiliary radio frequency source to output or stop outputting the auxiliary pulse signal to the secondary coil.
13. The plasma generation apparatus of claim 9, wherein the main coil comprises an outer coil set and an inner coil set, the outer coil set and the inner coil set being disposed on the same or different planes perpendicular to a central axis of the reaction chamber, and the outer coil set being located outside of the inner coil set away from the central axis; the secondary coil is arranged on a plane vertical to the central axis of the reaction chamber, and the projection of the secondary coil on the plane vertical to the central axis of the reaction chamber is positioned between the projections of the outer coil group and the inner coil group on the plane vertical to the central axis of the reaction chamber.
14. A semiconductor processing apparatus, characterized by comprising the plasma generating device according to any one of claims 7 to 13.
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| CN111328174A (en) * | 2018-12-17 | 2020-06-23 | 北京北方华创微电子装备有限公司 | Reaction chamber and plasma generating method |
| CN111341636B (en) * | 2018-12-19 | 2023-07-11 | 北京北方华创微电子装备有限公司 | Semiconductor device and radio frequency loading method thereof |
| CN116779407A (en) * | 2020-10-13 | 2023-09-19 | 北京北方华创微电子装备有限公司 | Acquisition method, impedance matcher method and semiconductor process equipment |
| CN113394091A (en) * | 2021-05-10 | 2021-09-14 | 上海华力集成电路制造有限公司 | Dry etching radio frequency discharge enhancement method and dry etching equipment |
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