JP2017027995A - Etching end point detection method and control apparatus for plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect an end point of etching from the emission intensity of a predetermined wavelength in plasma.SOLUTION: In an etching end point detection method of a plasma processing apparatus, plasma is generated from a processing gas in a processing chamber by high frequency power, and a predetermined etching treatment is performed on the substrate by the plasma. The etching end point detection method is provided in which in synchronization with a synchronization signal output according to a procedure set in a process recipe, at least one of a high frequency power for plasma generation, a high frequency power for pulling ions and a processing gas is supplied in a pulse wave form, the emission intensity of the predetermined wavelength in the plasma is sampled according to the output of the synchronization signal, and the end point of the etching is detected on the basis of the emission intensity data of the predetermined wavelength sampled for each output of the synchronization signal.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an etching end point detection method and a plasma processing apparatus control apparatus.

  A plasma process is known in which two kinds of gases, a deposition gas and an etching gas, are alternately supplied to alternately perform a step of forming a protective film on the etching target film and a step of etching the etching target film (for example, patents). Reference 1).

  In addition, a plasma process is known in which high-frequency power for plasma generation and high-frequency power for ion attraction are synchronously applied in a pulse wave shape (see, for example, Patent Document 2).

  It is also known to detect the emission intensity of an active species that emits light at a specific wavelength in plasma and detect the end point of the etching process from the fluctuation of the emission intensity (see, for example, Patent Document 3).

JP 2006-523030 A JP2015-43470A Japanese Patent Application Laid-Open No. 09-115883

  However, in the plasma process, the gas, the high frequency power for plasma generation, and the high frequency power for ion attraction are switched in, for example, several seconds or less. The software that controls the switching operation performs the switching operation according to the procedure set in the recipe, for example, with a resolution of 100 msec. Therefore, a delay of 100 msec at the maximum occurs in the switching operation. When this delay occurs, variations occur in the generation of plasma. As a result, the emission intensity of the predetermined wavelength in the plasma varies, making it difficult to accurately detect the end point of etching.

  In view of the above problem, in one aspect, an object of the present invention is to accurately detect an end point of etching from emission intensity of a predetermined wavelength in plasma.

  In order to solve the above-described problem, according to one aspect, there is provided an etching end point detection method for a plasma processing apparatus that generates a plasma from a processing gas in a processing container using high-frequency power and performs a predetermined etching process on the substrate using the plasma. In synchronism with a synchronization signal output according to the procedure set in the process recipe, at least one of high-frequency power for plasma generation, high-frequency power for ion attraction, and processing gas is supplied in a pulse waveform, An etching end point detection method that samples the emission intensity of a predetermined wavelength in plasma according to the output of the synchronization signal, and detects the end point of etching based on the data of the emission intensity of the predetermined wavelength sampled for each output of the synchronization signal. Provided.

  According to one aspect, it is possible to accurately detect the end point of etching from the emission intensity of a predetermined wavelength in plasma.

The longitudinal section which shows an example of the whole structure of the plasma processing apparatus concerning one Embodiment. The figure which shows an example of the etching process concerning one Embodiment. The figure which shows the comparative example of the light emission intensity of the predetermined wavelength in plasma, and the end point detection of an etching. The figure which shows the comparative example of the light emission intensity of the predetermined wavelength in plasma, and the end point detection of an etching. The figure which shows an example of the laminated film of the etching object concerning one Embodiment. The figure which shows an example of the emitted light intensity of the predetermined wavelength in the case of switching the gas concerning one Embodiment, and smoothing. The flowchart which shows an example of the end point detection process of the etching concerning one Embodiment. The figure which shows an example of the emitted light intensity of the predetermined wavelength in the case of switching RF concerning one Embodiment, and smoothing.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Overall configuration of plasma processing apparatus]
First, an overall configuration of a plasma processing apparatus 1 according to an embodiment of the present invention will be described with reference to an example of a longitudinal section of the plasma processing apparatus in FIG. In the present embodiment, as an example of the plasma processing apparatus 1, a capacitively coupled plasma etching apparatus is exemplified.

  The plasma processing apparatus 1 according to the present embodiment is not particularly limited, but the semiconductor wafer W (hereinafter also referred to as “wafer W”) is subjected to atomic layer etching (ALE) processing and reactive ion etching (RIE). Reactive Ion Etching) and plasma processing such as ashing can be performed.

  The plasma processing apparatus 1 includes a processing container (chamber) 10 made of a conductive material such as aluminum, and a gas supply source 15 that supplies gas into the processing container 10. The gas supply source 15 alternately supplies a deposition gas for forming a protective film (hereinafter also referred to as “deposition gas”) and an etching gas for promoting etching.

  The processing container 10 is electrically grounded, and a lower electrode 20 and an upper electrode 25 disposed in parallel to face the lower electrode 20 are provided in the processing container 10. The lower electrode 20 also functions as a mounting table on which the wafer W is mounted. A power supply device 30 is connected to at least one of the lower electrode 20 and the upper electrode 25, in FIG. 1, the lower electrode 20. The power supply device 30 includes a first high-frequency power source 32 that supplies a first high-frequency power (high-frequency power HF for plasma generation) at a first frequency, and a second high-frequency power (ion attraction) that has a second frequency lower than the first frequency And a second high frequency power supply 34 for supplying a high frequency power LF). The first high frequency power supply 32 is connected to the lower electrode 20 via the first matching unit 33. The second high frequency power supply 34 is connected to the lower electrode 20 via the second matching unit 35. The first matching unit 33 and the second matching unit 35 are for matching the load impedance to the internal (or output) impedance of the first high frequency power source 32 and the second high frequency power source 34, respectively. When plasma is generated in the processing container 10, the first high frequency power supply 32 and the second high frequency power supply 34 function so that the internal impedance and the load impedance seem to coincide with each other.

  The upper electrode 25 is attached to the ceiling portion of the processing container 10 via a shield ring 40 that covers the peripheral edge portion thereof. The upper electrode 25 is provided with a diffusion chamber 50 for diffusing the gas introduced from the gas supply source 15. A gas introduction port 45 is formed in the diffusion chamber 50, and various gases can be introduced into the diffusion chamber 50 from the gas supply source 15 through the gas introduction port 45. The upper electrode 25 is formed with a number of gas flow paths 55 for supplying the gas from the diffusion chamber 50 into the processing container 10.

  The gas from the gas supply source 15 is first distributed and supplied to the diffusion chamber 50 via the gas inlet 45 shown in FIG. The gas supplied to the diffusion chamber 50 is supplied into the processing container 10 through the gas flow path 55. From the above, the upper electrode 25 having such a configuration also functions as a gas shower head that supplies gas.

  An exhaust port 60 is formed in the bottom surface of the processing container 10, and the inside of the processing container 10 is exhausted by an exhaust device 65 connected to the exhaust port 60. Thereby, the inside of the processing container 10 can be maintained at a predetermined degree of vacuum.

  A gate valve G is provided on the side wall of the processing vessel 10. The gate valve G opens and closes the loading / unloading port when loading and unloading the wafer W from the processing container 10.

  The plasma processing apparatus 1 is provided with a control unit 100 that controls the operation of the entire apparatus. The control unit 100 includes a CPU (Central Processing Unit) 105, a ROM (Read Only Memory) 110, and a RAM (Random Access Memory) 115. The RAM 115 stores process recipes. Control information of the plasma processing apparatus 1 for process conditions (etching conditions) is set in the process recipe. The control information includes process time, switching time, pressure (gas exhaust), high frequency power and voltage, various gas flow rates, chamber temperature (for example, upper electrode temperature, chamber side wall temperature, ESC temperature) and the like. The process recipe may be stored in a hard disk or a semiconductor memory. Further, the process recipe may be set at a predetermined position in the storage area while being stored in a storage medium readable by a portable computer such as a CD-ROM or DVD.

  The CPU 105 alternately supplies two kinds of gases, a deposition gas and an etching gas, according to the procedure of the process recipe stored in the RAM 115, and performs a process of forming a protective film on the etching target film and a process of etching the etching target film. The etching process performed alternately is controlled.

  In the plasma processing 1, a light emission sensor 108 capable of measuring the light emission intensity of each wavelength in the plasma in the processing container 10 through the quartz window 109 is attached. The detected value of the emission intensity of each wavelength in the plasma detected by the light emission sensor 108 is accumulated in a storage unit such as the RAM 115. The control unit 100 measures the emission spectrum of a specific wavelength based on the detected value (data) of the emission intensity accumulated in the RAM 115, and detects the etching end point.

[Etching process]
Next, an example of the etching process performed in the plasma processing apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. In this embodiment, atomic layer etching (ALE) is performed. However, the etching process to which the etching end point detection method according to this embodiment can be applied is not limited to atomic layer etching.

In the etching process according to the present embodiment, the deposition gas and the etching gas are alternately switched cyclically at several Hz. While the deposition gas is supplied, the deposition step of FIG. 2 is performed, and a protective film is formed in the etched hole or the like. While the etching gas is supplied, the etching step shown in FIG. 2 is performed to etch holes and the like. Etching is completed when an end point (EP) is detected.
-Etching conditions are as follows.

Depot steps:
Gas containing deposition gas C ₄ F ₆ (hexafluoro1,3 butadiene) gas, O ₂ (oxygen) gas, Ar (argon) gas Processing time 3 seconds Etch step:
Etching gas Ar (argon) gas processing time 4.5 seconds Under the above etching conditions, the deposition step and the etching step are set as one cycle, and the silicon oxide (SiO ₂ ) film is etched while switching the gas by repeating a plurality of cycles to several tens of cycles. An example of the emission intensity at the time is shown in FIG. FIG. 3A shows the light emission intensity of CO having a wavelength of 226 nm among the detection values detected by the light emission sensor 108 in the etching process under the etching conditions.

  As shown in FIG. 3B, the control unit 100 detects an etching end point (EP) based on sampling data extracted from the emission intensity of CO having a wavelength of 226 nm. When the control unit 100 detects the end point of etching, the control unit 100 ends the etching process.

  FIG. 4 shows a method of sampling from the emission intensity of CO having a wavelength of 226 nm shown in FIG. 3A and extracting sampling data shown in FIG. A dotted line A in FIG. 4 shows the emission intensity of CO of 226 nm detected in the depot step. A broken line B in FIG. 4 shows the emission intensity of 226 nm CO detected in the etch step. In this method, filtering is performed in which a high-frequency component of CO emission intensity included in the mask time T provided at the rising and falling edges of the dotted lines A and B is cut by a low-pass filter. As a result, plasma fluctuations corresponding to variations in the switching operation between the deposition step and the etch step can be removed from the sampling data. The average value FCA of the solid lines FC1 and FC2 indicating the sampling data after filtering becomes a part of the line shown in FIG. 3B for detecting the etching end point.

  However, in the software control that performs the switching operation, the switching of the deposition step and the etch step is performed with a resolution of, for example, 100 msec. The time accuracy may cause a delay of up to 100 msec. Due to this delay, the transient response time of the plasma changes, and it is difficult to obtain accurate sampling data until the plasma is stabilized. As a result, it is difficult to accurately detect the end point of etching with the sampling data extracted by the above method.

[Overall configuration of plasma processing apparatus]
Therefore, the control unit 100 according to the present embodiment uses a synchronization signal used when supplying at least one of the high-frequency power HF for plasma generation, the high-frequency power LF for ion attraction, and the processing gas in a pulse waveform. Extract sampling data. In other words, as illustrated in FIG. 1, the control unit 100 outputs the synchronization signal S according to the procedure set in the process recipe. When supplying high-frequency power for plasma generation in a pulse wave shape, the first high-frequency power supply 32 supplies high-frequency power for plasma generation in a pulse wave shape in synchronization with the synchronization signal S. When supplying high frequency power for ion attraction in the form of pulse waves, the second high frequency power supply 34 supplies high frequency power for ion attraction in the form of pulse waves in synchronization with the synchronization signal S. When supplying the processing gas in the form of a pulse wave, the gas supply source 15 alternately supplies the deposition gas and the etching gas in synchronization with the synchronization signal S.

  The control unit 100 samples the emission intensity of a predetermined wavelength in the plasma according to the output of the synchronization signal S. The control unit 100 detects the end point of etching based on the emission intensity data of a predetermined wavelength sampled every time the synchronization signal S is output.

  Based on the etching conditions described above, the deposition gas and the etching gas are alternately supplied in a pulse wave shape to be processed. FIG. 6A shows an example of measurement results of the emission intensity of the substance having the first wavelength in the etch step and the emission intensity of the substance having the second wavelength in the deposition step in this process.

  The horizontal axis of the graph in FIG. 6A represents time, the vertical axis (left side) represents the emission intensity of the substance having the first wavelength, and the vertical axis (right side) represents the emission intensity of the substance having the second wavelength. .

  Line D shows the emission intensity of the second wavelength material of the deposition step. Line E shows the emission intensity of the first wavelength material of the etch step. Switching between the deposition gas and the etching gas shown in FIG. 6A is performed in accordance with the output of the synchronization signal S in FIG. When the synchronization signal S is turned on, the supply of the deposition gas is stopped and the supply of the etching gas is started. Thereby, the supply of the deposition gas into the processing container 10 is gradually reduced, and the supply of the etching gas into the processing container 10 is gradually increased. Thereby, the line D decreases and the line E increases. The etching gas is stably supplied after the second mask time DT has elapsed since the synchronization signal S was turned on.

  When the synchronization signal S is turned off, the etching gas rapidly decreases and the supply of deposition gas increases. In this embodiment, the emission intensity of the first wavelength substance detected in the etch step is a sampling target, and the emission intensity of the second wavelength substance detected in the depot step is out of the sampling target.

  In the etch step, the supply of the etching gas is started in accordance with the rising (on) timing of the synchronization signal S, and the amount of the etching gas in the processing chamber 10 gradually increases. Thereby, the emission intensity of the substance having the first wavelength gradually increases. The time from the rising edge of the synchronization signal S until the supply of the etching gas is gradually stabilized and the light emission intensity of the substance having the first wavelength is stabilized is determined as the second mask time DT in advance. Alternatively, it is stored in the RAM 115. The controller 100 starts sampling the emission intensity of the substance having the first wavelength in the plasma after the second mask time DT has elapsed since the synchronization signal S was turned on. The control unit 100 stops sampling the emission intensity of the substance having the first wavelength according to the timing when the synchronization signal S is turned off. In FIG. 6, the data C1 of the emission intensity of the substance having the first wavelength detected at the sampling time FT is sampled.

  In this way, every time the synchronization signal S is turned on, the emission intensity of the substance having the first wavelength in the plasma is sampled and stored in the RAM 115. As a result, sampling data C 1, C 2, C 3, C 4, C 5... Of the emission intensity of the substance having the first wavelength is accumulated in the RAM 115. As shown in FIG. 6B, the control unit 100 determines the end point of etching based on data obtained by connecting sampling data C1, C2, C3, C4, C5... Of emission intensity of the substance having the first wavelength. Perform detection.

[Etching end point detection process]
The etching end point detection process performed by the control unit 100 described above will be described with reference to the flowchart of FIG. When the etching end point detection process shown in FIG. 7 is started, the control unit 100 determines whether or not the synchronization signal S is turned on (step S10). The control unit 100 repeats step S10 until the synchronization signal S is turned on. When it is determined that the synchronization signal S is turned on, the control unit 100 determines whether the second mask time DT has elapsed since the synchronization signal S was turned on. (Step S12).

  The control unit 100 repeats Step S12 until the second mask time DT elapses, and when it is determined that the second mask time DT has elapsed, the data of the emission intensity of the substance having the first wavelength is sampled (Step S12). S14). An example of the emission intensity of the first wavelength substance sampled at this time is the emission wavelength of CO at a wavelength of 226 nm in the etch step.

  Next, the control unit 100 determines whether or not the synchronization signal S is turned off (step S16), and samples the emission intensity data of the substance having the first wavelength until the synchronization signal S is turned off. Sampling data is stored in the RAM 115.

  When the control unit 100 determines that the synchronization signal S is turned off, the control unit 100 combines the data of the emission intensity of the first wavelength material sampled last time stored in the RAM 115 (step S18). Next, the control unit 100 determines whether or not the etching end point EP has been detected based on the joined sampling data (step S20). For example, the control unit 100 may detect the etching end point EP based on the slope of the sampled data. The controller 100 may detect the etching end point EP by another known method based on the sampling data.

  When it is determined that the etching end point EP has been detected, the control unit 100 controls the end of etching (step S22), and ends this process. When it is determined that the etching end point EP has not been detected, the control unit 100 ends the present process without ending the etching.

  The above-described etching end point detection processing is executed every time the synchronization signal S is output, whereby the sampling data C1, C2, C3... Are connected in time series as shown in FIG. .

  As described above, according to the etching end point detection method according to the present embodiment, the emission intensity of the substance having the first wavelength triggered by the synchronization signal S output by the control unit 100 according to the process recipe setting procedure. Control the timing of sampling. Then, the end point of etching is detected based on the data sampled every time the synchronization signal S is output. According to this, by sampling the emission intensity data of the first wavelength substance after a predetermined mask time has elapsed after the synchronization signal S, which is unlikely to cause delay or variation, is sampled, An accurate etching end point can be detected from the emission intensity.

  In addition, according to the etching end point detection method according to the present embodiment, in consideration of the time required from when the gas is switched to when the gas after switching is supplied into the processing container 10, the rising edge of the synchronization signal S is started. Only the data of the emission intensity of the substance having the first wavelength after the elapse of the second mask time DT is sampled. Thereby, it is possible to sample the emission intensity data of the substance having the first wavelength when the supply of the etching gas to the processing container 10 is stabilized, and as a result, it is possible to detect an accurate etching end point.

  However, all the data of the emission intensity of the substance having the first wavelength from the rising edge to the falling edge of the synchronization signal S may be sampled without providing the second mask time DT.

[RF pulse wave]
In the above description, an example in which the deposition gas and the etching gas are alternately supplied in a pulse waveform has been described. However, the etching end point detection method according to the present embodiment is not limited to this. For example, at least one of the high-frequency power HF for plasma generation and the high-frequency power LF for ion attraction may be supplied in a pulse waveform.

  When the high frequency power HF for generating plasma is supplied in a pulse waveform, the control unit 100 emits light with a predetermined wavelength in the plasma according to the timing at which the synchronization signal S is output based on the procedure set in the process recipe. Is sampled. Similarly, when the high frequency power LF for ion attraction is supplied in the form of a pulse wave, the emission intensity of a predetermined wavelength is sampled according to the timing at which the synchronization signal S is output. Then, the control unit 100 detects the etching end point based on the emission intensity data of a predetermined wavelength sampled every time the synchronization signal S is output.

  However, as the sampling data, all data of emission intensity of a predetermined wavelength from the rising edge to the falling edge of the synchronization signal S may be sampled. Out of the data of the emission intensity of the predetermined wavelength from the rising edge to the falling edge of the synchronization signal S, the emission intensity data of the predetermined wavelength excluding the data from the rising edge of the synchronization signal S until the first mask time elapses is sampled. Also good.

An example in which high-frequency power LF for ion attraction is supplied in the form of a pulse wave will be described below.
As shown in FIG. 5, the sample structure of the wafer W according to the present embodiment has a SiN (silicon nitride) film 103, an ODL (organic) film 102, and a Si-ARC (antireflection) film 101 on a silicon substrate 104. Are formed in order, and the pattern of the ArF mask 106 is formed immediately above the Si-ARC film 101. FIG. 8A shows light emission data when the high-frequency power LF for ion attraction is supplied in the form of a pulse wave when the ODL (organic) film 102 is etched.

  For example, FIG. 8A shows the light emission intensity of CN having a wavelength of 387 nm detected by the light emission sensor 108.

  The control unit 100 acquires sampling data of the emission intensity of the wavelength from the rising edge of the synchronization signal S and accumulates it in a storage unit such as the RAM 115. FIG. 8B shows a combination of the sampling data C10, C11, C12, C13, C14... Acquired and accumulated every time the synchronization signal S is output. The control unit 100 detects the etching end point EP based on the sampling data shown in FIG. Thereby, a more accurate end point of etching can be detected.

  The second mask time is preferably set to be longer than the first mask time. This is because the time until the application of the high-frequency power is stabilized is instantaneous, whereas the time required until the gas supply into the processing container 10 is stabilized is longer. Therefore, it is preferable to provide the second mask time. The first mask time may or may not be present.

  Further, when all of the high frequency power HF for plasma generation, the high frequency power LF for ion attraction, and the processing gas are supplied in a pulse wave shape, after the second mask time has elapsed since the synchronization signal S was turned on, a predetermined wavelength The sampling of the emission intensity of is started. In this way, when all of the high frequency power HF for plasma generation, the high frequency power LF for ion attraction, and the processing gas are supplied in a pulse waveform, the timing of starting the emission intensity sampling is the latest after the synchronization signal S is turned on. By using the timing, a more accurate end point of etching can be detected.

  As described above, the etching end point detection method and the plasma processing apparatus control apparatus have been described in the above embodiment. However, the etching end point detection method and the plasma processing apparatus control apparatus according to the present invention are not limited to the above embodiment. Various modifications and improvements are possible within the scope of the invention. The matters described in the above embodiments can be combined within a consistent range.

  For example, the etching end point detection method according to the present invention is applicable not only to a capacitively coupled plasma (CCP) apparatus but also to other plasma processing apparatuses. Other plasma processing apparatuses include inductively coupled plasma (ICP), a plasma processing apparatus using a radial line slot antenna, a helicon wave excited plasma (HWP) apparatus, an electron cyclotron resonance plasma ( An ECR (Electron Cyclotron Resonance Plasma) apparatus or the like may be used.

  In this specification, the semiconductor wafer W has been described as an object to be etched, but various substrates used for LCD (Liquid Crystal Display), FPD (Flat Panel Display), etc., photomasks, CD substrates, printed boards, etc. good.

1: Plasma processing apparatus 10: Processing container 15: Gas supply source 20: Lower electrode (mounting table)
25: Upper electrode (shower head)
32: First high frequency power supply 34: Second high frequency power supply 45: Gas inlet 45
50: Diffusion chamber 55: Gas flow path 100: Control unit 108: Light emission sensor

Claims (6)

An etching end point detection method for a plasma processing apparatus that generates plasma from a processing gas in a processing container with high-frequency power and performs a predetermined etching process on the substrate with the plasma,
In synchronization with a synchronization signal output in accordance with the procedure set in the process recipe, at least one of high-frequency power for plasma generation, high-frequency power for ion attraction and processing gas is supplied in a pulse waveform,
According to the output of the synchronization signal, the emission intensity of a predetermined wavelength in the plasma is sampled,
Etching end point detection is performed by data of emission intensity of a predetermined wavelength sampled for each output of the synchronization signal.
Etching end point detection method. The timing to start sampling the emission intensity of the predetermined wavelength is when the synchronization signal is turned on or when a predetermined mask time has elapsed since the synchronization signal was turned on.
The etching end point detection method according to claim 1. When at least one of the high-frequency power for plasma generation and the high-frequency power for ion attraction is supplied in the form of a pulse wave, the time for sampling the emission intensity of the predetermined wavelength is after the synchronization signal is turned on. After the elapse of the first mask time and until the synchronization signal is turned off.
The etching end point detection method according to claim 2. When the processing gas is supplied in a pulse waveform, the time for sampling the emission intensity of the predetermined wavelength is after the elapse of a second mask time longer than the first mask time after the synchronization signal is turned on. Until the sync signal is turned off.
The etching end point detection method according to claim 3. The etching process repeatedly executes a step of forming a protective film by plasma of a deposition gas of the processing gas and a step of etching by plasma of an etching gas of the processing gas,
The emission intensity of the predetermined wavelength to be sampled is the emission intensity of the predetermined wavelength in the plasma of the etching gas.
The etching end point detection method as described in any one of Claims 1-4. A control device for a plasma processing apparatus that generates plasma from a processing gas in a processing container with high-frequency power and performs a predetermined etching process on the substrate with the plasma,
A synchronization signal is output according to the procedure set in the process recipe, and in synchronization with the synchronization signal, at least one of high-frequency power for plasma generation, high-frequency power for ion attraction, and processing gas is supplied in a pulse waveform,
According to the output of the synchronization signal, the emission intensity of a predetermined wavelength in the plasma is sampled,
Accumulated data of emission intensity of a predetermined wavelength sampled for each output of the synchronization signal in the storage unit,
Etching end point detection is performed based on the data stored in the storage unit.
Control device for plasma processing apparatus.

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