WO2022264829A1

WO2022264829A1 - Cleaning method and plasma processing device

Info

Publication number: WO2022264829A1
Application number: PCT/JP2022/022512
Authority: WO
Inventors: 保原田; 稔本多; 隆文野上
Original assignee: 東京エレクトロン株式会社
Priority date: 2021-06-16
Filing date: 2022-06-02
Publication date: 2022-12-22
Also published as: JP2022191960A

Abstract

A method for cleaning a plasma processing device for performing processing on a substrate by introducing microwaves into a chamber through a transmission window and using a plasma of a processing gas, the cleaning method comprising a step for performing cleaning using a plasma of a fluorine-containing gas, and a step for performing, after the cleaning is performed, seasoning using a plasma of a rare gas and H2 gas. The step for performing the seasoning comprises a first step in which the concentration of the H2 gas to the rare gas is a first concentration, and a second step in which the concentration of the H2 gas to the rare gas is a second concentration different from the first concentration. A series of steps comprising the first step and the second step is performed a plurality of times.

Description

Cleaning method and plasma processing apparatus

The present disclosure relates to a cleaning method and a plasma processing apparatus.

For example, Patent Document 1 proposes a cleaning method for a chamber that processes substrates with microwave plasma. Patent Document 1 has a step of introducing a cleaning gas containing a fluorine-containing gas, an argon gas, and a helium gas, and a step of supplying microwave power. The gas flow rate ratio is set within the range of 2/3-9.

JP 2021-34515 A

The present disclosure provides technology that can reduce particles.

According to one aspect of the present disclosure, there is provided a cleaning method for a plasma processing apparatus in which microwaves are introduced into a chamber through a transmission window and a substrate is processed by plasma of a processing gas, the cleaning method comprising: a step of performing cleaning with plasma of a fluorine _- containing gas; and a step of performing seasoning with plasma of a rare gas and H2 gas after performing the cleaning, wherein the step of performing the seasoning is performed by removing the a first step in which the concentration of the H2 gas is a first concentration; and a _second step in which the concentration of the H2 gas with respect to the rare gas is a _second concentration different from the first concentration; A cleaning method is provided in which a series of steps including the step and the second step are repeated multiple times.

According to one aspect, particles can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The cross-sectional schematic diagram which shows an example of the plasma processing apparatus which concerns on embodiment. FIG. 4 is a diagram schematically showing an AlF compound to be seasoned according to the embodiment; FIG. 4 is a diagram showing an example composition of deposits on the chamber side wall; 4 is a flowchart showing a cleaning method according to the embodiment; 4 is a flowchart showing a seasoning method according to an embodiment; 4 is a timing chart of gases and microwaves during seasoning according to the embodiment; A graph of experimental results showing an example of the correlation between the number of cycles and the number of particles in FIG. 5 is a graph showing an example of the modification result of deposits by the seasoning method according to the embodiment; 5 is a graph showing an example of film formation results after execution of the seasoning method according to the embodiment; 7 is a graph of experimental results showing an example of the correlation between the number of cycles and the number of particles according to the embodiment and the reference example;

Embodiments for carrying out the present disclosure will be described below with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description may be omitted.

[Plasma processing equipment]
A plasma processing apparatus according to an embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus. A microwave plasma processing apparatus 100 will be described below as an example of a plasma processing apparatus that executes the film forming method and the cleaning method according to the embodiment. The microwave plasma processing apparatus 100 of the present disclosure is an RLSA (registered trademark) microwave plasma processing apparatus. A microwave plasma processing apparatus forms a silicon-containing film such as a silicon nitride film (SiN) on a substrate W such as a semiconductor wafer by plasma CVD (Chemical Vapor Deposition).

The microwave plasma processing apparatus 100 has a cylindrical chamber 1 that is hermetically configured and grounded. A circular opening 10 is formed in a substantially central portion of the bottom wall 1a of the chamber 1, and the bottom wall 1a is provided with an exhaust chamber 11 that communicates with the opening 10 and protrudes downward.

The inner wall of the chamber 1 is made of a metallic material such as aluminum and is thermally sprayed with alumina (Al ₂ O ₃ ) or yttria (Y ₂ O ₃ ), for example. A stage 2 made of ceramics such as AlN is provided in the chamber 1 for supporting the substrate W horizontally. The stage 2 is supported by a cylindrical support member 3 made of ceramic such as AlN and extending upward from the center of the bottom of the exhaust chamber 11 . A resistance heating type heater 5 is embedded in the stage 2 . The heater 5 heats the stage 2 and controls the temperature of the substrate W by being supplied with power from the heater power source 6 . An electrode 7 is embedded in the stage 2 , and a high-frequency power source 9 for bias application is connected to the electrode 7 through a matching box 8 . The stage 2 may be provided with an electrostatic chuck for electrostatically attracting the substrate W, a temperature control mechanism, a gas flow path for supplying a heat transfer gas to the rear surface of the substrate W, and the like.

The stage 2 is provided with wafer support pins (not shown) for supporting and lifting the substrate W so as to protrude from the surface of the stage 2 . Annular

gas introduction portions

15 and 16 are provided on the side wall of the chamber 1, and

gas emission holes

15a and 16a are equally formed in the

gas introduction portions

15 and 16 in the circumferential direction. A gas supply unit 17 is connected to the

gas introduction units

15 and 16 . The gas supply unit 17 supplies a processing gas for film formation during film formation. The gas supply unit 17 may introduce a cleaning gas during cleaning.

The top plate of the chamber 1 is made of a dielectric such as alumina (Al ₂ O ₃ ) and serves as a transmission window 28 that transmits microwaves. A microwave power introduction portion 42 is provided in the center of the transmission window 28 . A processing gas for film formation or a cleaning gas may be introduced from the gas introduction portion 18 provided around the introduction portion 42 through the gas emission holes 18a.

An exhaust pipe 23 is connected to the side of the exhaust chamber 11, and an exhaust device 24 including a vacuum pump, an automatic pressure control valve, etc. is connected to the exhaust pipe 23. By operating the vacuum pump of the exhaust device 24 , the gas in the chamber 1 is uniformly exhausted into the space 11 a of the exhaust chamber 11 and exhausted through the exhaust pipe 23 . An automatic pressure control valve can control the inside of the chamber 1 to a predetermined degree of vacuum.

On the side wall of the chamber 1, a loading/unloading port 25 for loading/unloading the substrate W to/from a transfer chamber (not shown) adjacent to the microwave plasma processing apparatus 100 and a gate valve 26 for opening/closing the loading/unloading port 25 are provided. and are provided.

The upper part of the chamber 1 is an opening, and the peripheral edge of the opening is a ring-shaped support part 27 . A disc-shaped transmission window 28 is provided in the support portion 27 via a seal member 29 . Thereby, the inside of the chamber 1 is kept airtight. A disk-shaped planar antenna 31 corresponding to the transmission window 28 is provided on the upper surface of the transmission window 28 . A planar antenna 31 is locked to the upper end of the side wall of the chamber 1 .

The planar antenna 31 is composed of a disc made of a conductive material, and has a plurality of slots 32 passing through it for radiating microwaves. As an example of the pattern of the slots 32, a plurality of pairs of slots 32 are arranged concentrically, with two slots 32 arranged in a T shape forming a pair. The length and arrangement intervals of the slots 32 are determined according to the wavelength (λg) of the microwave, and the slots 32 are arranged so that the intervals between them are λg/4, λg/2 or λg, for example. Note that the slots 32 may have other shapes such as a circular shape and an arc shape. Further, the arrangement form of the slots 32 is not particularly limited, and they can be arranged concentrically, spirally, or radially, for example.

On the upper surface of the planar antenna 31, a plate-like member 33 made of a dielectric material having a dielectric constant greater than that of vacuum, such as resin such as quartz, polytetrafluoroethylene, or polyimide, is provided. The plate-shaped member 33 has a function of making the wavelength of the microwave shorter than that in a vacuum and reducing the dimensions of the planar antenna 31 .

The flat antenna 31 and the transmission window 28 are in close contact with each other, and the plate member 33 and the flat antenna 31 are also in close contact. Further, the thicknesses of the transmission window 28 and the plate member 33 are adjusted so that an equivalent circuit formed by the plate member 33, the planar antenna 31, the transmission window 28, and the plasma satisfies the resonance condition. By adjusting the thickness of the plate-shaped member 33, the phase of the microwave can be adjusted. is minimized and the microwave radiation energy is maximized. Further, by using the same material for the plate member 33 and the transmissive window 28, it is possible to prevent interface reflection of microwaves.

A space may be provided between the planar antenna 31 and the transmission window 28 and between the plate-like member 33 and the planar antenna 31 . A shield lid 34 made of a metal material such as aluminum, stainless steel, or copper is provided on the upper surface of the chamber 1 so as to cover the planar antenna 31 and the plate member 33 . The upper surface of the chamber 1 and the shield lid 34 are sealed by a sealing member 35 . A cooling water flow path 34a is formed in the shield lid 34, and the shield lid 34, the plate member 33, the planar antenna 31, and the transmission window 28 are cooled by flowing cooling water through the cooling water flow path 34a. do. The shield lid 34 is grounded.

An opening 36 is formed in the center of the upper wall of the shield lid 34 , and a waveguide 37 is connected to the opening 36 . A microwave output section 39 is connected to the end of the waveguide 37 via a matching circuit 38 . As a result, microwaves having a frequency of 2.45 GHz, for example, generated by the microwave output section 39 are propagated to the planar antenna 31 via the waveguide 37 . As the frequency of the microwave, for example, frequencies in the range of 100 MHz to 2450 MHz can be used.

The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 36 of the shield lid 34 and the upper end of the coaxial waveguide 37a via a mode converter 40. and a rectangular waveguide 37b extending in the horizontal direction. The mode converter 40 has a function of converting the microwave propagating in the TE mode in the rectangular waveguide 37b into the TEM mode. An internal conductor 41 extends through the center of the coaxial waveguide 37 a , and a lower end portion (introduction portion 42 ) of the internal conductor 41 is connected and fixed to the center of the planar antenna 31 . Thereby, the microwaves are uniformly propagated to the planar antenna 31 through the inner conductor 41 of the coaxial waveguide 37a.

The microwave plasma processing apparatus 100 has a control section 50. The control unit 50 is a CPU that controls each component of the microwave plasma processing apparatus 100, such as the microwave output unit 39, the heater power source 6, the high-frequency power source 9, the exhaust device 24, the valves and flow rate controllers of the gas supply unit 17, and the like. (computer). The control unit 50 also has an input device (keyboard, mouse, etc.), an output device (printer, etc.), a display device (display, etc.), and a storage device (storage medium). The control unit 50 causes the microwave plasma processing apparatus 100 to perform the following film formation method based on a processing recipe stored in a storage medium built in a storage device or a storage medium set in the storage device, for example. Let

An embodiment of a film forming method using the microwave plasma processing apparatus 100 having such a configuration will be described. First, the gate valve 26 is opened, and the substrate W is loaded into the chamber 1 through the loading/unloading port 25 and placed on the stage 2 . Next, the gate valve 26 is closed, the inside of the chamber 1 is adjusted to a predetermined pressure, and the processing gas is introduced into the chamber 1 from the gas supply section 17 through the

gas introduction sections

15 , 16 and 18 . Then, a microwave having a predetermined power is introduced into the chamber 1 from the microwave output unit 39 to generate plasma, and a SiN film as an example of a Si-containing film is formed on the substrate W by plasma CVD.

A microwave with a predetermined power from the microwave output section 39 is guided to the waveguide 37 through the matching circuit 38 . The microwave guided to the waveguide 37 propagates in the rectangular waveguide 37b in TE mode. The TE mode microwave is mode-converted to the TEM mode by the mode converter 40, and the TEM mode microwave propagates in the TEM mode through the coaxial waveguide 37a. The TEM mode microwave is transmitted through the plate member 33 , the slot 32 of the planar antenna 31 and the transmission window 28 and radiated into the chamber 1 .

The surface wave of the microwave spreads in the area directly below the transmission window 28, thereby generating a surface wave plasma that has a high electron density and a low electron temperature. As a result, active species dissociated from the film forming gas react on the substrate W to form a predetermined film.

When the film forming process described above is performed on a plurality of substrates W one by one, the components of the film formed on the inner walls and parts of the chamber 1 gradually adhere. When the deposits are deposited and peeled off, they become particles. Since a predetermined number of particles or more causes a decrease in yield, the inside of the chamber 1 is cleaned at predetermined intervals.

When forming a SiN film, silane gas (SiH ₄ ) and N ₂ gas, or silane gas and NH ₃ gas are supplied as an example of processing gas. Microwaves are introduced into the chamber 1 through a transmissive window 28 made of alumina.

When cleaning the inside of the chamber 1 at predetermined intervals, plasma of NF ₃ gas, for example, is used. Therefore, an AlF compound containing fluorine contained in the NF ₃ gas and aluminum contained in the alumina forming the transmission window 28 adheres to the side walls of the chamber 1 after cleaning. The AlF compound is AlF mixed with Si, N, and H, and adheres to the side walls of the chamber 1, etc., as shown in FIG. 2A, and can be represented by AlFx (Si/N/H).

A chemical reaction between fluorine radicals in the plasma generated from the NF ₃ gas used as the cleaning gas and alumina (Al ₂ O ₃ ) forming the transmission window 28 of the chamber 1 causes the inner surface of the transmission window 28 and the chamber An AlF compound (AlFx) adheres to the inner side surface of 1 . Si and N mixed in the AlF compound are Si and N in the SiN film, Si substrate or silane gas (SiH ₄ ) and N ₂ (or NH ₃ ) gas. The H mixed in the AlF compound is the H in the _SiH4 used as the process gas.

In particular, in the microwave surface wave plasma, as shown in FIG. 2A, a large amount of AlF compound adheres to the surface of the transmission window 28 and the upper side wall in the chamber 1 where the plasma is strong. AlF compounds contain Si and N impurities and are not chemically stable. FIG. 2B is a diagram showing an example of the composition of deposits on the side walls of the chamber 1, showing an example of the results of analyzing the deposits on the side walls of the chamber 1 by X-ray Photoelectron Spectroscopy (XPS). From this result, the deposit in chamber 1 contains 23.4% Al and 51.8% F, accounting for about 75% of the AlF compound. The remaining components of the AlF compound include 11.2% N, 8% O, 4.7% C, 0.6% Si and 0.4% Y. It is considered that the Y component in the AlF compound was detected in the coating film coating the inner wall of the chamber 1 with yttria (Y ₂ O ₃ ). It is considered that the O component in the AlF compound is due to the oxidation of AlF or the detection of O in yttria. As for the C component, since a carbon tape was used during the XPS analysis, it is considered that C was detected in the tape. Although it is difficult to detect the H component by XPS analysis, it is considered that H is also contained based on past experience.

Thus, the AlF compound is in an unstable state containing Si, N, and H components compared to the chemically stable state of AlF. For this reason, when argon ions in plasma generated from argon gas, which is a rare gas, collide with the AlF compound, the AlF compound is easily peeled off from the inner wall of the chamber 1, which is considered to be a cause of particle generation.

Therefore, as a method for stabilizing the AlF compound adhering to the side wall of the chamber 1 after cleaning, in the seasoning according to the present embodiment, plasma of argon gas and hydrogen (H ₂ ) gas, which are examples of rare gases, is generated. , thereby generating hydrogen radicals. Then, the AlF compound is reduced by hydrogen radicals (H ^* ) in the plasma. Specifically, the chemically unstable AlF compound (Si/N/H) state is reformed into a stable AlF state by the following chemical reaction (1), and the Si, N, and H components are NH ^* and SiH ^* are volatilized and exhausted.
AlFx(Si/N/H)+Ar ^* +H ^* →AlF+Al+NH ^* +SiH ^* (1)

As a result, in the seasoning according to the present embodiment, the unstable state of AlFx (Si/N/H), which is the cause of particle generation, is changed to the stable state of AlF. can be reduced. As a result, maintenance intervals can be lengthened, the operating rate of the plasma processing apparatus can be increased, and productivity can be improved. In the present specification, modifying an AlF compound means removing Si, N, and H from the AlF compound to form AlF. However, the modification of the AlF compound includes reducing the Si, N and H components in the AlF compound, and some Si, N and H may be mixed in the AlF compound.

[Cleaning method]
Next, a film formation and cleaning method performed by the microwave plasma processing apparatus 100 will be described with reference to FIGS. 3 to 5. FIG. The cleaning method MT includes a fluorine-containing gas plasma cleaning process and a rare gas and H ₂ gas plasma seasoning process, which are performed after SiN films are formed on a predetermined number of substrates W in the film formation process. A film forming process, a plasma cleaning process, and a plasma seasoning process are controlled by the controller 50 . In the following, NF3 gas is used as an example of fluorine-containing gas in the plasma cleaning process, but the fluorine _- containing gas is not limited to this and may be _ClF3 gas _, CF4 gas, or the like. Also, although Ar gas is used as an example of the rare gas in the plasma seasoning process, the rare gas is not limited to this and may be He gas. In addition, although a SiN film is formed as an example of a Si-containing film in the film forming process, the SiCN film, SiO ₂ film, and SiC film may be formed.

FIG. 3 is a flow chart showing the film formation and cleaning method MT according to the embodiment. In the film formation and cleaning method MT shown in FIG. 3, first, in step S1, the substrate W is loaded into the chamber 1 and placed on the stage 2 for preparation. Next, in step S3, silane (SiH ₄ ) gas and nitrogen (N ₂ ) gas as processing gases are supplied into the chamber 1, and microwaves are introduced. For example, nitrogen gas is supplied into the chamber 1 through the gas emission holes 18a, and silane gas is supplied into the chamber 1 through the

gas emission holes

15a and 16a. Microwaves are introduced into chamber 1 through transmissive window 28 .

Next, a SiN film is formed on the substrate W by plasma of silane gas and nitrogen gas generated in step S5. Next, in step S6, the substrate W after film formation is unloaded from the chamber 1. Next, as shown in FIG.

Next, in step S7, it is determined whether cleaning is to be performed. Whether or not cleaning is to be performed may be determined to be performed, for example, when the cumulative time of the film formation process or the cumulative time of applying microwaves reaches a predetermined time or longer. The thickness of deposits on the inner wall of the chamber 1 may be measured, and when the thickness reaches a predetermined thickness or more, it may be determined that cleaning should be performed.

If it is determined in step S7 that cleaning is not to be performed, the process returns to step S1, and film formation processing for the next substrate W is performed. Steps S1 to S7 are repeated to form a SiN film on each substrate W until it is determined in step S7 that cleaning is to be performed.

If it is determined in step S7 that cleaning is to be performed, plasma of NF ₃ gas is generated by microwaves in step S11, and the inside of the chamber 1 is cleaned by the plasma. Next, the seasoning method is executed in step S15. Details of the seasoning method will be described later with reference to FIG.

After executing the seasoning in step S15, it is determined in step S17 whether to end the processing of the substrate W. If it is determined not to end the processing of the substrate W, the process returns to step S1, and the film formation processing of the next substrate W is performed. to resume. If it is determined to end the processing of the substrate W, this processing ends. Note that the seasoning in step S15 may be performed immediately after the plasma cleaning in step S11 as in the above flow, or may be performed at an arbitrary timing such as when an increase in particles is confirmed after the film formation process is restarted. you can go

[Seasoning method]
Details of the seasoning method in step S15 of FIG. 3 will be described with reference to FIGS. 4 and 5. FIG. The seasoning method MT2 shown in FIG. 4 is called from step S15 in FIG. 3 and executed. FIG. 4 shows the flow of the seasoning method MT2 according to the embodiment. FIG. 5 shows supply timings of Ar gas, H ₂ gas and microwave in the seasoning method MT2 shown in FIG.

As shown in FIG. 4, in the seasoning method MT2, first, in step S20, 1 is set to the number of executions n of the "series of steps". A series of steps shows one cycle of performing seasoning by changing the concentration of H ₂ gas with respect to Ar gas to a first concentration, a second concentration, and a third concentration, which are all different concentrations.

Specifically, in step S 21 , the flow rate of Ar gas or H ₂ gas is controlled so that the concentration of H ₂ gas with respect to Ar gas becomes the first concentration, and supplied into the chamber 1 . Next, in step S23, microwaves are introduced into the chamber 1, and the AlF compound adhering to the inner wall of the chamber 1 is reformed by the plasma of the _first concentration Ar gas and H2 gas generated by the microwaves. As an example of the supply timing of Ar gas, H2 gas, and microwaves, as shown in _FIG . , T2 ₍ T2>T1). The first concentration is B/A1.

Returning to _FIG . 4, next, in step S24, the supply of Ar gas, H2 gas and microwaves is stopped after a predetermined time has elapsed. That is, as shown in _FIG . 5, the supply of Ar gas, H2 gas and microwaves is stopped at time T3.

Next, in step S25, it is determined whether or not the number of execution times n is 3 or more. Since n is 1 at this point, it is determined to be "No", and 1 is added to the execution count n in step S26, and in step S27 the concentration of H ₂ gas with respect to Ar gas becomes the n-th concentration (n=2 at this point). ), the flow rate of Ar gas or H ₂ gas is controlled. Next, returning to step S23, the second concentration of H ₂ gas and Ar gas is supplied into the chamber 1, and the plasma of the second concentration of Ar gas and H ₂ gas generated by microwaves is applied to the inner wall of the chamber 1 and the like. Modifies the attached AlF compound. For example, as shown in FIG. 5, Ar gas with a flow rate of A2 (A2>A1) is supplied at time T4, microwaves are introduced at time T5 (T5>T4), and flow rate B is introduced at time T6 (T6>T5). _H2 gas is supplied. The second density is B/A2, and the first density>second density holds.

Returning to _FIG . 4, next, in step S24, the supply of Ar gas, H2 gas and microwaves is stopped after a predetermined time has elapsed. That is, as shown in _FIG . 5, the supply of Ar gas, H2 gas and microwaves is stopped at time T7.

Next, in step S25, it is determined whether or not the number of execution times n is 3 or more. Since n is 2 at this point, it is determined to be "No", and 1 is added to the execution count n in step S26, and in step S27 the concentration of H ₂ gas with respect to Ar gas becomes the n-th concentration (n=3 at this point). ), the flow rate of Ar gas or H ₂ gas is controlled. Next, returning to step S23, the third concentration H ₂ gas and Ar gas are supplied into the chamber 1, and the plasma of the third concentration Ar gas and H ₂ gas generated by the microwaves is applied to the inner wall of the chamber 1 and the like. Modifies the attached AlF compound. For example, as shown in FIG. 5, Ar gas with a flow rate of A3 (A3>A2) is supplied at time T8, microwaves are introduced at time T9 (T9>T8), and flow rate B is introduced at time T10 (T10>T9). _H2 gas is supplied. The third density is B/A3, and the relationship of first density>second density>third density is established.

Returning to _FIG . 4, next, in step S24, the supply of Ar gas, H2 gas and microwaves is stopped after a predetermined time has elapsed. That is, as shown in _FIG . 5, the supply of Ar gas, H2 gas and microwaves is stopped at time T11.

Next, in step S25, it is determined whether the number of executions n is 3 or more. Since n is 3 at this point, it is determined as "Yes", and it is determined in step S28 whether the cycle has been repeated a preset number of times. Returning to step S20, the "series of steps" shown in steps S20 to S27 are repeated until it is determined that the number of cycles has been repeated. If it is determined in step S28 that the process has been repeated for the number of cycles, the seasoning process ends.

[Number of cycles in seasoning method]
In step S28 of FIG. 4, the seasoning of the first density to the third density is repeated for the number of cycles. An experiment was conducted on the optimum value of the number of cycles. FIG. 6 is a graph of experimental results showing an example of the correlation between the number of cycles in S28 of FIG. 4 and the number of particles. The experimental conditions are as follows.
<Experimental conditions>
1. First concentration 5.6 H2 gas ₂₈₀ sccm, Ar gas 50 sccm, pressure 4 Pa,
Microwave power 4500W, seasoning time 60s
2. _Second concentration 2.8 H2 gas 280 sccm, Ar gas 100 sccm, pressure 4 Pa,
Microwave power 4500W, seasoning time 60s
3. third concentration 1.4 H2 gas ₂₈₀ sccm, Ar gas 200 sccm, pressure 4 Pa,
Microwave power 4500W, seasoning time 60s
4 Pa is the pressure inside the chamber 1, and the damage to the chamber 1 can be reduced by lowering the pressure. 60 s is the seasoning time for each concentration, which is the time from the first supply of Ar gas until the supply of each gas is stopped.

The horizontal axis in FIG. 6 indicates the number of seasoning cycles, and the vertical axis indicates the number of particles. From the experimental results shown in FIG. 6, it was found that the total number of particles, which is the sum of SiN and AlF particles, decreased to about 100 when the number of cycles was about 5. Even if the number of cycles is 6 or more, the total number of particles is at least about 100, which is not much different from 5 times. For this reason, the number of cycles may be five or more, but the longer the number of cycles, the longer the cleaning time including seasoning, and the lower the throughput. Therefore, it was found that it is preferable to set the number of cycles to 5 so that the seasoning time is the shortest and the effect of reducing the number of particles to about 100 can be obtained.

[Effect of seasoning]
Next, the effects of the seasoning method MT2 of the present disclosure will be described with reference to FIG. FIG. 7 is a graph showing an example of the modification result of deposits by the seasoning method MT2 according to the embodiment. FIG. 7(a) shows an example of the result of analyzing deposits on the side wall of the chamber 1 by X-ray photoelectron spectroscopy before executing the seasoning method MT2. The horizontal axis of FIG. 7A indicates the names of the elements constituting the AlF compound, and the vertical axis indicates the ratio thereof. From this result, the deposit in the chamber 1 before executing the seasoning method MT2 was in the state of an AlF compound containing Si and N in AlF.

FIG. 7(b) shows an example of the result of analyzing deposits on the side wall of the chamber 1 after executing the seasoning method MT2 by X-ray photoelectron spectroscopy. The horizontal axis of FIG. 7(b) indicates the names of the elements constituting the AlF compound, and the vertical axis indicates the ratio thereof. From this result, the deposits on the inner wall of the chamber 1 after execution of the seasoning method MT2, as shown in the chemical reaction (1) above, the AlF compound is reduced by hydrogen radicals in the H ₂ gas plasma, and the AlF compound is It was reformed and Si, N and H components were volatilized to form stable AlF. As a result, the deposit on the inner wall of the chamber 1 after seasoning is chemically stable AlF, which is less likely to come off than the AlF compound. As a result, particles can be reduced by executing the seasoning method MT2.

The seasoning method MT2 is not limited to changing the concentration of H ₂ gas with respect to Ar gas by fixing the flow rate of H ₂ gas and changing the flow rate of Ar gas. _In seasoning method MT2, the flow rate of Ar gas may be fixed and the flow rate of H2 gas may be changed to change the concentration of H2 gas relative to Ar gas, or the concentration may be changed by changing the flow rates of _both gases. You may let By changing the concentration of H2 gas with respect to Ar gas, it is possible to perform reforming suitable for various AlF compounds with different amounts of Si, _N , and H mixed in, and various AlF compounds with different adhesion locations (top plate, stage, side wall, etc.). be possible. In other words, hydrogen plasma in a state suitable for various AlF compounds with different amounts of Si, N, and H adhering to them can be generated by changing the H2 concentration, and various AlF compounds can be stabilized to AlF. be able to. As a result, the AlF compound can be reformed into AlF even if Si, N, and H adhere to different locations and are mixed in different amounts.

The cleaning method MT according to the present embodiment has been described above. The cleaning method MT includes a step of performing cleaning with plasma of fluorine-containing gas, and a step of performing seasoning with plasma of noble gas and H ₂ gas after cleaning.

As shown in the seasoning method MT2 of FIG. 4, the step of performing seasoning includes a first step in which the concentration of H2 gas with respect to the rare gas is the _first concentration, and a step in which the concentration of H2 gas with respect to the rare gas is different from the _first concentration. A second step with a second concentration and a third step with a third concentration different from the first and second concentrations are provided, and a series of steps including the first to third steps are repeated multiple times. The number of times may be 5 times or more, but 5 times is preferable. The first density, the second density, and the third density may all be different, and the density may be decreased stepwise, the density may be increased stepwise, or the density may be increased or decreased. You may

In the seasoning method MT2 of the present disclosure, the concentration of H ₂ gas with respect to Ar gas is controlled in three stages from the first concentration to the third concentration, but the present invention is not limited to this. The concentration of H2 gas with respect to Ar gas may be controlled in _two stages or four stages or more. For example, the step of performing seasoning includes a first step in which the concentration of H ₂ gas with respect to the rare gas is the first concentration, and a second step in which the concentration of H ₂ gas with respect to the rare gas is a second concentration different from the first concentration. and a series of steps including the first step and the second step may be repeated multiple times.

Also, in one experiment of the seasoning method MT2, the first to third concentrations were 1.4 to 5.6, but the present invention is not limited to this. _The concentration of H2 gas with respect to Ar gas may be 0.1 or more and 10 or less.

[Effect of seasoning on film formation]
Next, the result of examining the influence of execution of the seasoning method MT2 on the film formation characteristics will be described with reference to FIG. FIG. 8 is a graph showing an example of the result of film formation performed after executing the seasoning method MT2.

FIG. 8(a) shows an example of the measurement result of the film thickness of the film formed after executing the seasoning method MT2. FIG. 8B shows an example of measurement results of RI (refractive index) of film formed after execution of the seasoning method MT2.

The film thickness of the SiN film shown in FIG. 8(a) indicates an average value obtained by measuring the film thickness at 49 points within the wafer surface. R/A [%] indicates a value obtained by dividing the difference between the maximum value and the minimum value of the film thickness at 49 points in the plane of the wafer by the average value. That is, R/A indicates the film thickness distribution. The film thickness on the left vertical axis and the film thickness distribution (R/A) on the right vertical axis did not change with the number of cycles of seasoning on the horizontal axis of FIG. It was also found that there is no adverse effect on the film formation process.

The RI of the SiN film shown in FIG. 8(b) indicates the average value of the RI measured at 49 points in the plane of the wafer. Range indicates the difference between the maximum value and the minimum value of RI at 49 points in the plane of the wafer. Range indicates the RI distribution. With respect to the number of seasoning cycles on the horizontal axis of FIG. 8B, there is no change in the RI distribution (Range) on the left vertical axis and the RI distribution (Range) on the right vertical axis. was found to have no adverse effect on

[Comparison of seasoning according to the embodiment and reference example]
Finally, a comparison of seasonings according to the embodiment and the reference example will be described with reference to FIG. FIG. 9 is a graph of experimental results showing an example of the correlation between the number of cycles and the number of particles according to the embodiment and the reference example.

A line g indicates the number of particles on the vertical axis with respect to the number of

cycles

1, 5, and 10 on the horizontal axis when the seasoning method MT2 of the present embodiment is executed under the <experimental conditions> when the experiment in FIG. 6 was performed. Lines e and f show the number of particles for

cycles

1, 5 and 10 when the flow rates of Ar gas and H2 gas are fixed as shown in Reference Examples 1 and 2. FIG. In the case of Reference Example 1, the flow rates of Ar gas and H2 gas were fixed at 50 sccm and 280 sccm, respectively, and this was defined as one cycle. In the case of Reference Example 2, the flow rates of Ar gas and H2 gas were fixed at 200 sccm and 280 sccm, respectively, and this was defined as one cycle. In the seasoning method MT2 of the present embodiment, as shown in <Experimental conditions>, the flow rates of Ar gas and H2 gas are set to three concentrations of (1) 50 sccm, 280 sccm, (2) 100 sccm, 280 sccm, and (3) 200 sccm, 280 sccm. This was regarded as one cycle.

In the seasoning method MT2 of the present embodiment, by changing the concentration of H2 gas to Ar gas in _three stages, hydrogen plasma in a state suitable for various AlF compounds having different amounts of Si, N, and H mixed and adhesion locations is generated. , could be generated by varying the _H2 concentration, and various AlF compounds could be modified to AlF. As a result, as indicated by line g, the number of particles counted could be reduced when the number of cycles was 5 or more.

On the other hand, in Reference Examples 1 and 2, the concentration of H ₂ gas relative to Ar gas was fixed as shown by lines e and f. As a result, in both Reference Examples 1 and 2, the particle count increased as the number of cycles increased. The reason for this is that when seasoning is performed without changing the concentration of H ₂ gas relative to Ar gas, various AlF compounds with different amounts of Si, N, and H mixed and where they adhere cannot be reformed into stable AlF. This is probably because the AlF compound in an unstable state remained on the deposits on the inner wall or the like. As a result of hitting the unstable AlF compound such as the inner wall of the chamber 1 with Ar radicals, Ar ions, etc., the number of particles increased.

As described above, according to the seasoning method MT2 according to the embodiment, the concentration of H ₂ gas with respect to Ar gas is changed in two or more stages. As a result, various AlF compounds with different amounts of Si, N, and H mixed and where they adhere can be reformed into stable AlF. As a result, particles can be reduced, and productivity can be improved by lengthening the maintenance cycle.

The cleaning method and plasma processing apparatus according to the embodiments disclosed this time should be considered as examples and not restrictive in all respects. Embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The items described in the above multiple embodiments can take other configurations within a consistent range, and can be combined within a consistent range.

The plasma processing apparatus of the present disclosure can be applied to any type of apparatus as long as it introduces microwaves into the chamber through a transmissive window made of alumina and processes a substrate with plasma of a processing gas.

This application claims priority from Basic Application No. 2021-100503 filed on June 16, 2021 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

1 chamber 2

stage

15, 16, 18 gas introduction part 17 gas supply part 28 transmission window 39 microwave output part 50 control part 100 microwave plasma processing apparatus

Claims

A cleaning method for a plasma processing apparatus in which microwaves are introduced into a chamber through a transmission window and a substrate is processed by plasma of a processing gas, comprising:
The cleaning method is
a step of cleaning with plasma of a fluorine-containing gas;
and a step of performing seasoning with plasma of a rare gas and H gas after performing the cleaning,
The step of performing the seasoning includes:
a first step, wherein the concentration of the H2 gas relative to the noble gas is a first concentration;
a second step in which the concentration of the H2 gas relative to the noble gas is a second concentration different from the first concentration;
A cleaning method in which a series of steps including the first step and the second step are repeated multiple times.
The step of performing the seasoning includes:
further comprising a third step of a third concentration different from the first concentration and the second concentration;
repeating a series of steps including the first step, the second step and the third step a plurality of times;
A cleaning method according to claim 1 .
The step of performing the seasoning stabilizes the AlF compound containing Si and N deposited in the chamber.
The cleaning method according to claim 1 or 2.
In the step of performing the seasoning, the AlF compound is modified into AlF.
The cleaning method according to claim 3.
Repeating the series of steps 5 or more times,
The cleaning method according to claim 1 or 2.
A step of forming a silicon-containing film by plasma of the processing gas before the step of cleaning,
The cleaning method according to claim 1 or 2.
The silicon-containing film is a silicon nitride film,
The cleaning method according to claim 6.
The concentration of the H2 gas with respect to the noble gas is 0.1 or more and 10 or less.
The cleaning method according to claim 1 or 2.
A plasma processing apparatus having a chamber, a transmission window, and a controller,
The control unit
introducing microwaves into the chamber through the transmissive window to form a silicon-containing film on the substrate by plasma of a processing gas;
a step of cleaning with plasma of a fluorine-containing gas;
and performing seasoning with plasma of noble gas and H2 gas after performing the cleaning,
In the step of performing the seasoning,
a first step, wherein the concentration of the H2 gas relative to the noble gas is a first concentration;
and a second step in which the concentration of the H 2 gas with respect to the rare gas is a second concentration different from the first concentration.