JP2004207466A - Plasma film forming equipment and its cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an amount of use and an amount of discharge of PFC gas used for cleaning a chamber in plasma film forming equipment. <P>SOLUTION: A reaction condition or an exclusion condition is modified by monitoring reactive gas or exhaust gas during the cleaning of the chamber to detect a completed point of cleaning and performing the feedback of the point to a flow rate control device or an exclusion device. Thus, the amount of the use and the amount of the discharge of the PFC gas are reduced and the cleaning in the chamber can be efficiently and surely performed without excessively operating the exclusion device. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma film forming apparatus for manufacturing a semiconductor device and a method of cleaning the same, and more particularly, to reducing the amount of PFC gas used and discharged without lowering the cleaning performance in a chamber cleaning step of the plasma film forming apparatus. The present invention relates to a plasma film forming apparatus and a cleaning method thereof.
[0002]
[Prior art]
In recent years, pollution of the global environment has become a problem. Worldwide measures are being taken against environmental pollution, and various efforts are being made in the semiconductor industry.
[0003]
One of the pollutions of the global environment is global warming caused by greenhouse gases. In the process of manufacturing semiconductor devices, a large amount of PFC (perfluoro compound) gas (CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , NF ₃ , SF _6, etc.) is used in particular as a greenhouse gas. are doing. Since these PFC gases have a high global warming potential, it is necessary to reduce the amount of PFC gas used and its emission.
[0004]
As a conventional cleaning method of a plasma apparatus for the purpose of reducing the emission amount of PFC gas, a reaction gas in a chamber is analyzed after detoxification, and when the emission amount of PFC gas exceeds a certain value, the plasma apparatus is cleaned. Some include a step of stopping the chemical treatment or a step of increasing the abatement efficiency (for example, see Patent Document 1).
[0005]
FIG. 9 shows a conventional plasma apparatus. In the plasma device shown in FIG. 9, various chemical treatments are performed on the surface of the semiconductor substrate disposed on the stage in the chamber 1. An induction coil 2 connected to a high frequency power supply 12 is provided on the outer periphery of the chamber 1, and plasma is formed in the chamber 1 by the high frequency power applied to the induction coil 2. The stage is supplied with power for substrate bias from another high frequency power supply 11. The reaction gas stored in the gas cylinder 14 is introduced into the chamber 1 via the flow control device 13.
[0006]
The chamber 1 is connected to an exhaust pump 6 through a pipe 4. A pressure control valve 5 is inserted between the chamber 1 and the exhaust pump 6, and an abatement device 7 for decomposing gas exhausted from the exhaust pump 6 is provided downstream of the exhaust pump 6. I have. The reaction gas in the chamber 1 is exhausted to the outside via the abatement device 7, but a part of the gas exhausted from the abatement device 7 is collected by the mass spectrometer 19 and analyzed by mass spectrometry. The amount of PFC gas is calculated. The exhaust gas collected by the mass spectrometer 19 is exhausted to the outside by the second exhaust pump 20.
[0007]
On the other hand, an induction coil 18 connected to a high frequency power supply 17 is also provided on the outer periphery of the abatement apparatus 7. Decomposition gas is supplied from the gas cylinder 10 to the abatement apparatus 7 via the flow rate control device 9, and is converted into plasma by high-frequency power supplied to the induction coil 18. This plasma decomposes PFC gas and the like in the exhaust gas.
[0008]
The pressure control valve 5, the flow controllers 9 and 13, and the high-frequency power supplies 11, 12 and 17 are controlled by the controller 15. The control device 15 is connected to another control device 8 via an electric circuit 16.
[0009]
In the conventional example, the controller 8 compares the analysis result of the PFC gas in the exhaust gas by the mass spectrometer 19 with a preset reference value. When the PFC gas in the exhaust gas is larger than the reference value, the information is transmitted to the control devices 8 to 15 and a command to stop the process or increase the high-frequency power of the abatement device 7 is output from the control device 15. I do. In this way, the emission amount of the PFC gas is suppressed to a certain value or less.
[0010]
[Patent Document 1]
JP 2001-23969 A
[Problems to be solved by the invention]
However, in the conventional cleaning method of a plasma apparatus, only the amount of PFC gas emission is measured, and when the amount exceeds a certain value, it is detected as an abnormality and a response is taken. Therefore, the process conditions cannot be flexibly changed depending on the process state. In particular, in the cleaning process of the plasma film forming apparatus, it is necessary to perform extra cleaning after the cleaning end point in order to completely remove the products in the chamber.
[0012]
However, during the cleaning process of the plasma film forming apparatus, the amount of by-produced PFC gas (particularly, CF ₄ gas) increases rapidly after the end point of cleaning, and the amount of PFC gas discharged increases. Further, there is a problem that if the abatement apparatus is operated excessively for the purpose of removing the by-products, the abatement apparatus is deteriorated and the cost is increased.
[0013]
The present invention has been made in view of the above problems, and performs cleaning without excessively operating the abatement apparatus and without increasing the amount of PFC gas generated as a by-product after the end of cleaning. An object of the present invention is to provide a plasma film forming apparatus and a cleaning method thereof.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a plasma film forming apparatus according to the present invention is a plasma film forming apparatus that performs a film forming process using plasma, and includes a chamber for performing the process, and a PFC (perfluoro) inside the chamber. Flow rate control means for supplying the reaction gas containing the compound, a pump for exhausting the reaction gas in the chamber, abatement means for decomposing the exhaust gas exhausted from the chamber, and a PFC concentration contained in the reaction gas or the exhaust gas And a control means for controlling the flow rate control means or the abatement means based on the measurement result of the PFC concentration.
[0015]
With this configuration, the amount of use and discharge of the PFC gas can be reduced, and the inside of the chamber can be efficiently and reliably cleaned without operating the abatement apparatus excessively.
[0016]
In the above-described plasma film forming apparatus, the control unit changes the setting condition of the flow rate control unit or the detoxification unit from the calculation result of the first calculation unit and the calculation result of the first calculation unit. It is preferable to include a second operation unit that performs the operation.
[0017]
In the above-described plasma film forming apparatus, it is preferable that the abatement unit decomposes the exhaust gas by using combustion or thermal decomposition.
[0018]
Further, the method for cleaning a plasma film forming apparatus according to the present invention is a method for cleaning a plasma film forming apparatus that performs a film forming process using plasma, and supplies a reaction gas containing PFC (perfluoro compound) into a chamber. A step of exhausting a reaction gas in the chamber, a step of removing the exhaust gas exhausted from the chamber using combustion or thermal decomposition, and a step of measuring a PFC concentration contained in the reaction gas or the exhaust gas. And controlling the supply flow rate of the reaction gas or the operating condition of the exhaust gas based on the measurement result of the PFC concentration.
[0019]
With this configuration, the amount of use and discharge of the PFC gas can be reduced, and the inside of the chamber can be efficiently and reliably cleaned without operating the abatement apparatus excessively.
[0020]
In the above method for cleaning a plasma film forming apparatus, the step of controlling the supply flow rate of the reaction gas preferably reduces the supply flow rate of PFC contained in the reaction gas.
[0021]
In the above-described method for cleaning a plasma film forming apparatus, the step of controlling the supply flow rate of the reaction gas preferably changes the flow rate ratio of the reaction gas.
[0022]
In the above-described cleaning method for a plasma film forming apparatus, the step of controlling the supply flow rate of the reaction gas preferably reduces the total flow rate of the reaction gas.
[0023]
In the above-described method for cleaning a plasma film forming apparatus, it is preferable that the step of controlling the operating conditions of the exhaust gas enhances the abatement efficiency (combustion efficiency or decomposition efficiency) of the exhaust gas.
[0024]
In the above method for cleaning a plasma film forming apparatus, the step of controlling the operating conditions of the exhaust gas preferably includes increasing the combustion temperature or the thermal decomposition temperature of the exhaust gas.
[0025]
In the above-described method for cleaning a plasma film forming apparatus, the step of controlling the operating conditions of the exhaust gas preferably includes increasing the supply flow rate of the decomposition gas mixed with the exhaust gas.
[0026]
In the above-described method for cleaning a plasma film forming apparatus, the decomposition gas is a city gas (CH ₄ gas, C ₂ H ₆ gas, C ₃ H ₈ gas, C ₄ H ₁₀ gas), H ₂ gas, O ₂ gas or Preferably, it is Air.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
(Embodiment 1)
FIG. 1 is a configuration diagram showing a first embodiment of a plasma film forming apparatus according to the present invention.
[0029]
The illustrated apparatus is a plasma film forming apparatus that performs a film forming process using plasma, includes a chamber 1 for performing the process, and forms a film on a surface of a semiconductor substrate disposed on a stage in the chamber 1. On the other hand, a desired film forming process is performed.
[0030]
An induction coil 2 connected to a high frequency power supply 12 is provided on the outer periphery of the chamber 1, and plasma is formed in the chamber 1 by the high frequency power applied to the induction coil 2. Power for substrate bias is supplied to the stage in the chamber 1 from another high frequency power supply 11. The reaction gas stored in the gas cylinder 14 is introduced into the chamber 1 via the flow control device 13. Although a single gas cylinder 14 is shown in FIG. 1, a predetermined reaction gas is actually introduced into the chamber 1 from each of the plurality of gas cylinders at a predetermined flow rate.
[0031]
The chamber 1 is provided with an analyzer 3 for analyzing the reaction gas in the chamber 1, and further controls the chamber 1, the detoxifier 7, and the analyzer 3 based on the analysis result of the analyzer 3. And a control device 8. As the analyzer 3, for example, an EPD (End Point Detector) for detecting the intensity of the plasma emission spectrum is used.
[0032]
The chamber 1 is connected to an exhaust pump 6 through a pipe 4. A pressure control valve 5 is inserted between the chamber 1 and the exhaust pump 6, and an abatement device 7 for decomposing gas exhausted from the exhaust pump 6 is provided downstream of the exhaust pump 6. I have. The reaction gas in the chamber 1 is exhausted to the outside through the harm removal device 7.
[0033]
On the other hand, gas such as city gas (CH ₄ gas, C ₂ H ₆ gas, C ₃ H ₈ gas, C ₄ H ₁₀ gas), H ₂ gas, O ₂ gas, Air and the like are supplied from the gas cylinder 10 to the abatement apparatus 7. The PFC gas and the like in the exhaust gas are supplied through the flow control device 9 and are burned by these gases.
[0034]
The operation of the pressure control valve 5, the flow control devices 9 and 13, the high-frequency power supplies 11 and 12, and the abatement device 7 are controlled by the control device 15. The control device 15 is connected to another control device 8 via an electric circuit 16. In the control devices 8 and 15, one computer may serve as both control devices. In the example of FIG. 1, in addition to the control device 15 used for controlling the plasma film forming apparatus main body and the abatement device 7, a control device 8 for controlling the plasma film forming device, the abatement device 7, and the analysis device 3. Is provided.
[0035]
The analysis result by the analyzer 3 is subjected to various arithmetic processing by the controller 8. A signal based on the result of the arithmetic processing is transmitted to the control device 15 via the electric circuit 16, and adjusts the operations of the plasma film forming apparatus main body, the abatement apparatus 7, and the analyzer 3. This makes it possible to reduce the amount of PFC gas used and the amount of PFC gas in exhaust gas.
[0036]
FIG. 2 shows a combustion type abatement apparatus. In order to decompose gas exhausted from a plasma film forming apparatus (not shown) by combustion, a combustion furnace 31 that burns exhaust gas by a burner 32 and a combustion furnace 31 are used. A cooling chamber 33 for cooling the exhaust gas passing therethrough and a scrubber 34 are provided. The decomposition gas supplied to the burner 32 is supplied from a gas cylinder (not shown). The temperature control device 36 supplies city gas (CH ₄ gas, C ₂ H ₆ gas, C ₃ H ₈₎ supplied from a gas cylinder (not shown) based on the output of the temperature sensor 35 for detecting the temperature of the combustion furnace 31. Gas, C ₄ H ₁₀ gas), H ₂ gas, O ₂ gas, Air and the like are adjusted to control the temperature. In addition, as such an abatement device 7, a thermal decomposition type abatement device may be used, or an abatement device having a known configuration may be used.
[0037]
(Embodiment 2)
Next, a second embodiment of the plasma film forming apparatus according to the present invention will be described with reference to FIG.
[0038]
In the first embodiment, the reaction gas in the chamber 1 is monitored and analyzed. In the present embodiment, a part of the gas exhausted from the exhaust pump 6 to the abatement apparatus 7 is collected and analyzed. The exhaust gas after the analysis is sent to the abatement apparatus 7.
[0039]
That is, the exhaust gas taken into the analyzer 3 is sampled from the pipe connecting the exhaust pump 6 and the abatement apparatus 7 and analyzed, and then is again sent to the pipe connecting the exhaust pump 6 and the abatement apparatus 7. It is exhausted and sent to the abatement device 7. As the analyzer 3, for example, FT-IR is used.
[0040]
(Embodiment 3)
An embodiment of a first cleaning method using the plasma deposition apparatus of the first embodiment will be described.
[0041]
First, a normal cleaning condition (hereinafter referred to as cleaning condition 1) and a cleaning condition (hereinafter referred to as cleaning condition 2) for reducing the emission amount of PFC gas are input to the control device 15 of the plasma film forming apparatus. . After the completion of the film forming process, the analyzer 3 starts the analysis at the same time as the cleaning under the cleaning condition 1 is started. When the analyzer 3 detects the end point of the cleaning, the cleaning condition is changed from the cleaning condition 1 to the cleaning condition 2.
[0042]
The reason why it is necessary to change process conditions such as cleaning conditions and detoxification conditions after the end point of cleaning will be described with reference to an example using C ₃ F ₈ gas. FIG. 4 shows the result of monitoring the PFC concentration of exhaust gas during chamber cleaning. This indicates that the concentration of the CF ₄ gas by-produced from the C ₃ F ₈ gas sharply increased after the end point of the cleaning. This is because fluorine radicals remain after the end point of cleaning.
[0043]
However, if the cleaning is stopped at the end point, the inside of the chamber cannot be reliably cleaned. Therefore, it is important to reduce by-produced PFC gas (particularly CF ₄ gas) after the end point of cleaning.
[0044]
FIG. 5 is a graph of the cumulative discharge amount of SiF ₄ generated by cleaning according to the cleaning time. The cleaning amount of the product in the chamber was compared with the flow rate ratio of PFC gas / O ₂ gas being 0.3 and 0.5. From this, it can be seen that even if the flow rate ratio of the PFC gas / O ₂ gas is changed, there is no difference in the cleaning amount of the product in the chamber at the end of the cleaning, and the cleaning performance is not affected.
[0045]
FIG. 6 shows the CF ₄ gas generation rate when the PFC gas / O ₂ gas flow ratio was changed. From this, it can be seen that when the flow rate ratio of PFC gas / O ₂ gas is reduced, the generation rate of CF ₄ gas is reduced.
[0046]
From these results, when the flow rate ratio of PFC gas / O ₂ gas is reduced, the amount of PFC gas used can be reduced, and the emission amount of PFC gas can be reduced. Further, since the generation rate of CF ₄ gas is also reduced, the emission amount of PFC gas can be further reduced. Therefore, the first cleaning condition under which the discharge amount of PFC gas can be reduced is a condition in which the flow ratio of PFC gas / O ₂ gas is reduced.
[0047]
FIG. 7 is a graph showing the variation of the cleaning end point depending on the total gas flow rate of the PFC gas and the O ₂ gas at the time of cleaning. This indicates that the cleaning performance is not affected even if the total gas flow rate is reduced. Since the total gas flow rate is reduced, the amount of PFC gas used can be reduced, and the amount of PFC gas emission can be reduced. Therefore, the second cleaning condition that can reduce the emission amount of the PFC gas is a condition in which the total gas flow rate is reduced.
[0048]
The above-described cleaning conditions can reduce the amount of PFC gas used, which leads to cost reduction.
[0049]
(Embodiment 4)
An embodiment of a second cleaning method using the plasma deposition apparatus of the first embodiment will be described.
[0050]
First, the control device 15 for controlling the abatement apparatus 7 is provided with a normal abatement condition (hereinafter referred to as abatement condition 1) and an abatement condition with an increased abatement efficiency (hereinafter referred to as an abatement condition 2). Input. After the completion of the film forming process, the cleaning is started under the detoxification condition 1 and at the same time, the analysis is started by the analyzer 3. When the analyzer 3 detects the end point of the cleaning, the removal condition is changed from the removal condition 1 to the removal condition 2.
[0051]
FIG. 8 is a graph of the decomposition efficiency of CF ₄ gas and C ₃ F ₈ gas depending on temperature. While C ₃ F ₈ gas has a decomposition efficiency of about 100% at 1050 ° C. or more, CF ₄ gas has a decomposition efficiency of about 95% at 1200 ° C. or more, and the decomposition efficiency differs depending on the temperature.
[0052]
Before the end point of the cleaning, since the generation rate of CF ₄ gas is low, the detoxification condition 1 is that the decomposition efficiency of C ₃ F ₈ gas is sufficiently high and the combustion temperature is about 1050 ° C. After the end point of the cleaning, the generation rate of the CF ₄ gas becomes high. Therefore, the detoxification condition 2 is set to a combustion temperature of about 1200 ° C. where the decomposition efficiency of the CF ₄ gas is sufficiently high. As a result, even if the generation rate of CF ₄ gas is increased, it is possible to reliably perform the harm removal, which leads to a reduction in PFC gas emission.
[0053]
Further, since the removal conditions are changed after the CF ₄ gas generation rate is increased, it leads to cost reduction and prevention of deterioration of the removal device.
[0054]
(Embodiment 5)
An embodiment of a first cleaning method using the plasma film forming apparatus according to the second embodiment will be described.
[0055]
In the case of the plasma film forming apparatus according to the second embodiment, first, a normal cleaning condition (hereinafter, referred to as a cleaning condition 1) and a cleaning condition (hereinafter, referred to as a cleaning condition 1) for reducing the discharge amount of PFC gas are provided to the control device 15 of the plasma film forming apparatus. Cleaning condition 2) and the set value of the CF ₄ gas concentration in the exhaust gas are input. When the film forming process is started, background data is acquired to improve the analysis accuracy of the analyzer 3. After completion of the film forming process, the cleaning by the cleaning condition 1 is started, and at the same time, the analysis by the analyzer 3 is started.
[0056]
From the analysis of the exhaust gas, when the CF ₄ gas concentration in the exhaust gas exceeds the set value, the cleaning condition is changed from the cleaning condition 1 to the cleaning condition 2. In the vicinity of the end point of cleaning, fluorine radicals are left over, so that the generation of CF ₄ gas increases. From this, it can be said that the place where the amount of generated CF ₄ gas is increasing is the end point of the cleaning.
[0057]
(Embodiment 6)
An embodiment of the second cleaning method using the plasma deposition apparatus of Embodiment 2 will be described.
[0058]
In the case of the plasma film forming apparatus according to the second embodiment, first, the control device 15 for controlling the abatement apparatus 7 is provided with a normal abatement condition (hereinafter referred to as abatement condition 1) and an abatement with high abatement efficiency. A condition (hereinafter referred to as abatement condition 2) and a set value of the CF ₄ gas concentration in the exhaust gas are input. When the film forming process is started, background data is acquired to improve the analysis accuracy of the analyzer 3. After the completion of the film forming process, the cleaning by the removal condition 1 is started, and at the same time, the analysis by the analyzer 3 is started. According to the analysis of the exhaust gas, when the CF ₄ gas concentration in the exhaust gas exceeds the set value, the harm removal condition is changed from the harm removal condition 1 to the harm removal condition 2.
[0059]
In the above embodiment, EPD or FT-IR is used as the analyzer. However, the analyzer is not limited to EPD and FT-IR, but may be any device that can analyze the condition in the chamber and detect the end point of cleaning. Good.
[0060]
Further, in the above embodiment, the thermal decomposition type abatement system is used, but the abatement device is not limited to the thermal abolition type, but may be a combustion type.
[0061]
【The invention's effect】
As described above, according to the plasma film forming apparatus and the cleaning method of the present invention, the reaction gas or the exhaust gas is monitored at the time of cleaning the chamber, the end point of the cleaning is detected, and the end point of the cleaning is fed back to the flow control apparatus or the detoxification apparatus. By doing so, the reaction conditions or detoxification conditions are changed. Therefore, the amount of use and discharge of the PFC gas can be reduced, and the inside of the chamber can be efficiently and reliably cleaned without operating the abatement apparatus excessively.
[Brief description of the drawings]
1 is a configuration diagram showing a first embodiment of a plasma device according to the present invention; FIG. 2 is a configuration diagram of a combustion type abatement device; FIG. 3 is a configuration diagram showing a second embodiment of a plasma device according to the present invention; Figure 4 shows the PFC concentration in the exhaust gas in the chamber cleaning Figure 5 is a view 6 showing the amount of chamber product by the flow rate ratio of the PFC gas / O ₂ gas PFC gas / O ₂ gas Figure 7 PFC gas showing the generation rate of the CF ₄ gas by flow rate ratio, with temperature of FIG. 8 CF ₄ gas and C ₃ F ₈ gas, which shows the variation of the cleaning end point by the total gas flow rate of O ₂ gas FIG. 9 is a diagram showing decomposition efficiency. FIG. 9 is a configuration diagram of a conventional plasma apparatus.
DESCRIPTION OF SYMBOLS 1 Chamber 2 Induction coil 3 Analysis device 4 Pipe 5 Pressure control valve 6 Exhaust pump 7 Absorbing device 8 Control device 9 Flow control device 10 Gas cylinder 11 High frequency power supply 12 High frequency power supply 13 Flow control device 14 Gas cylinder 15 Control device 16 Electric circuit

Claims (11)

A plasma film forming apparatus that performs a film forming process using plasma,
A chamber for performing the treatment,
Flow rate control means for supplying a reaction gas containing PFC (perfluoro compound) into the chamber;
A pump for exhausting the reaction gas in the chamber,
Abatement means for decomposing exhaust gas exhausted from the chamber,
Analysis means for measuring a PFC concentration contained in the reaction gas or the exhaust gas;
A plasma film forming apparatus comprising: a control unit that controls the flow rate control unit or the abatement unit based on the measurement result of the PFC concentration. A control unit configured to calculate an end point of the cleaning from a measurement result of the PFC concentration;
2. The plasma deposition apparatus according to claim 1, further comprising a second operation unit configured to change a setting condition of the flow rate control unit or the abatement unit based on a calculation result of the first operation unit. 3. The plasma deposition apparatus according to claim 1, wherein the abatement unit decomposes the exhaust gas using combustion or thermal decomposition. A method for cleaning a plasma film forming apparatus that performs a film forming process using plasma,
Supplying a reaction gas containing PFC (perfluoro compound) into the chamber;
Exhausting the reaction gas in the chamber;
Removing the exhaust gas exhausted from the chamber using combustion or thermal decomposition,
Measuring a PFC concentration contained in the reaction gas or the exhaust gas;
Controlling the supply flow rate of the reaction gas or the operating condition of the exhaust gas based on the measurement result of the PFC concentration. 5. The method according to claim 4, wherein the step of controlling the supply flow rate of the reaction gas reduces the supply flow rate of the PFC contained in the reaction gas. 6. The method according to claim 5, wherein the step of controlling the supply flow rate of the reaction gas changes a flow rate ratio of the reaction gas. 6. The method according to claim 5, wherein the step of controlling the supply flow rate of the reaction gas reduces a total flow rate of the reaction gas. The method for cleaning a plasma film forming apparatus according to claim 4, wherein the step of controlling the operating condition of the exhaust gas increases a removal efficiency (combustion efficiency or decomposition efficiency) of the exhaust gas. 9. The method according to claim 8, wherein the step of controlling the operating conditions of the exhaust gas includes increasing a combustion temperature or a thermal decomposition temperature of the exhaust gas. 9. The method according to claim 8, wherein the step of controlling the operating condition of the exhaust gas includes increasing a supply flow rate of a decomposition gas mixed with the exhaust gas. The cracking gas claims, characterized in that the city gas (CH ₄ gas, C ₂ H ₆ gas, C ₃ H ₈ gas, C ₄ H ₁₀ gas), H ₂ gas, O ₂ gas or Air A method for cleaning a plasma film forming apparatus according to claim 10.

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