JP2005012197A - Method and apparatus of aerosol cleaning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate fine aerosol by increasing pressure within an aerosol nozzle with relatively small refrigerating capacity. <P>SOLUTION: When a gas fed into an aerosol 20 is cooled using a heat exchanger 38, a low flow of gas is fed into the heat exchanger and then a high flow of the gas is fed, thereby pressure within the aerosol 20 is temporarily increased, and thus the mean particle diameter of the aerosol is reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aerosol cleaning method and apparatus, and more particularly to a semiconductor wafer, an optical exposure mask or reticle, an X-ray mask or reticle, an electron beam (EB) mask or reticle, an ion beam (IB) mask or reticle, and a lithography mask. Or, to-be-cleaned objects suitable for cleaning various substrates such as reticles, flat panel substrates, magnetic disk substrates, flying head substrates, and the surfaces of magnetic heads, micromachines and MEMS (Micro Electro Mechanical Systems). The present invention relates to an aerosol cleaning method and apparatus capable of cleaning without damaging the fine structure and the like.

  Since the fine particles (particles) and dirt on the surface of a semiconductor wafer in a semiconductor manufacturing process such as LSI and on the surface of a liquid crystal (LCD) or a solar cell greatly reduce the yield of the final product, the surface of the wafer or the like is cleaned. Is extremely important. Wafer cleaning in the semiconductor manufacturing process, in particular, is accelerating the high integration due to the miniaturization of elements, and the important manufacturing process for maintaining the manufacturing yield is said to be about 30% of the total number of cleaning processes. It is a process. Also, photo exposure mask or reticle, X-ray mask or reticle, EB mask or reticle, IB mask or reticle, lithography mask or reticle, flat panel substrate, magnetic disk substrate, flying head substrate, magnetic head, micromachine and MEMS It is extremely important to clean the fine particles without damaging the object to be cleaned because it has a fine structure.

  As cleaning apparatuses, wet cleaning using pure water is the mainstream, and single-wafer cleaning apparatuses such as wet bath type batch cleaning, brush cleaning, jet spin cleaning, and ultrasonic cleaning are frequently used.

Further, in recent years, as a dry cleaning method that replaces wet cleaning, a reaction system product cleaning / removal apparatus using laser light, UV light, and various plasmas, carbon dioxide (CO ₂ ), argon (Ar) gas, nitrogen ( An aerosol cleaning type cleaning apparatus using N ₂ ) gas, which is a mixture of liquid, solid, and gas, has been developed, and various types of use have begun depending on the semiconductor device process. Patent Document 1 describes a surface cleaning method using nitrogen aerosol.

Among them, in the conventional cleaning by aerosol spraying, as shown in FIG. 1 (overall view) and FIG. 2 (detailed view of essential parts), argon (Ar) gas, nitrogen (N ₂ ) gas, or a mixed gas of each gas is used. For example, after cooling with a heat exchanger 38 using a helium (He) cryocooler 36, a vacuum cleaning chamber (also referred to as a process chamber) 42 from a nozzle hole 20 </ b> A of an aerosol generation nozzle (hereinafter also simply referred to as an aerosol nozzle) 20. The fine aerosol 22 is formed by being further cooled by adiabatic expansion during ejection, and the aerosol 22 is made to collide with the surface of the object to be cleaned 10 such as a wafer for cleaning.

  In FIG. 1, an argon gas, a nitrogen gas or a mixed gas thereof whose flow rate is controlled by the mass flow controllers 30 and 32, for example, after passing through a ceramic filter 34, is cooled in a heat exchanger 38, and then the aerosol nozzle 20 From a large number of fine nozzle holes 20 </ b> A opened, the aerosol 22 is ejected into a cleaning chamber 42 for cleaning a wafer that is evacuated by an exhaust pump 40. In FIG. 1, reference numeral 44 denotes an exhaust control valve.

  The wafer to be cleaned is placed on a process hand (XY scanning stage) 46 that is scanned in the X-axis direction and the Y-axis direction by a wafer scanning mechanism (not shown), and the entire surface of the wafer can be cleaned. .

  Further, for the purpose of preventing the reattachment of particles to the wafer surface, the purge gas (for example, nitrogen gas) 66 flowing from one end (the left end in the figure) of the cleaning chamber 42 through the mass flow controller 62 and the ceramic filter 64 is cleaned. The liquid is supplied into the chamber 42.

  Furthermore, in the case of cleaning only by aerosol spraying, the physical spraying force is insufficient when applied to particles that adhere strongly, and therefore, as a method for improving cleaning performance, aerosol acceleration is provided separately from the aerosol nozzle 20. The acceleration nozzle 24 is used (Patent Documents 2 to 4). Then, a high-speed acceleration gas (for example, nitrogen gas) 26 supplied to the acceleration nozzle 24 through the mass flow controller 52 and the ceramic filter 54 and blown out from the nozzle hole 24A is sprayed on the aerosol 22 as shown in FIG. By accelerating the aerosol 22 and colliding with the wafer surface, the removal performance is greatly improved against contaminants such as particles firmly adhering to the wafer surface, which is the object to be cleaned.

Japanese Patent No. 2567341 Japanese Patent Laid-Open No. 6-252114 JP-A-6-295895 JP-A-8-298252

  In wet cleaning, the amount of pure water used, the amount of chemicals (inorganic and organic), drainage or drainage treatment, shape deformation due to over-etching with fine pattern chemicals, development of chemicals for new materials, various There are problems such as dealing with various chemicals and damage to fine patterns.

  Similarly, aerosol cleaning using carbon dioxide gas or argon gas has a problem of damage to fine patterns.

  In particular, it is a very important issue to establish a cleaning method that does not damage a pattern in a semiconductor device manufacturing process where pattern miniaturization is accelerated in the future. Also, optical exposure masks or reticles, X-ray masks or reticles, EB masks or reticles, IB masks or reticles, lithography masks or reticles, flat panel substrates, magnetic disk substrates, flying head substrates, magnetic heads, micromachines and MEMS However, these have a fine structure, and cleaning without damage is a very important issue.

  In Patent Document 1, as in the present invention, the pressure of the nitrogen aerosol is increased to about 20 psig to 690 psig (137.8 to 4754.1 kPa), preferably about 20 psig to 100 psig (137.8 to 689 kPa). Although described, if the gas flow rate is simply increased to increase the gas pressure, the temperature of the gas will rise, so the refrigerator 36 is required to have a high refrigeration capacity, and the apparatus becomes larger and expensive. In addition, there is a problem that the amount of gas consumption increases.

  The present invention has been made to solve the above-described conventional problems, and damages to the fine structure of an object to be cleaned while maintaining a relatively low refrigeration capacity and a relatively small amount of gas consumption. It is an object of the present invention to realize a low temperature (cryogenic) aerosol cleaning that can be performed without giving water.

  In the present invention, a cleaning gas or liquid cooled by a heat exchanger or a mixture of gas and liquid is blown out from an injection nozzle having a fine nozzle hole to generate a fine aerosol, and the fine droplet, fine solid or gas, or those In an aerosol cleaning method in which a mixture of two or more of the above is sprayed on the surface to be cleaned, a low flow rate gas is flowed through the heat exchanger, and then a high flow rate gas is flowed to temporarily increase the pressure in the aerosol generation nozzle. However, the problem is solved by reducing the average particle size of the aerosol.

The cleaning gas or liquid or a mixture of gas and liquid may be Ar, N ₂ , He, Ne, O ₂ , CO ₂ , N ₂ O, H ₂ O, Kr, SF ₆ , Xe, or H ₂ alone. Gas or mixed gas.

Further, when the cleaning gas or liquid or a mixture of gas and liquid is N ₂ single gas, the pressure in the aerosol generating nozzle is controlled in the range of 100 kPa to 1500 kPa.

  In addition, when the object to be cleaned is moved in the direction of the central axis of the aerosol generating nozzle and in the direction perpendicular to the axis, the speed in the direction perpendicular to the central axis of the nozzle is set to 200 mm / second to 400 mm / second. By controlling to the range of seconds, it is possible to quickly clean at a low damage rate.

  Further, by attaching a heat insulating material to the aerosol generating nozzle, it is possible to prevent a temperature increase of the aerosol generating nozzle and to spray a stable aerosol.

  Also, purge gas or the like flows around the aerosol generating nozzle by eliminating the space around the aerosol generating nozzle or by attaching a shield plate that prevents the gas from flowing around the aerosol generating nozzle. Thus, the temperature is prevented from rising and a stable aerosol can be sprayed.

  In addition, the pressure of the cleaning chamber in which fine droplets, fine solids, gas, or a mixture of two or more thereof is blown out from the spray nozzle is controlled in the range of 0.1 kPa to 20 kPa. A lower pressure in the cleaning chamber is desirable because it has a higher cleaning ability and less reattachment of particles.

  The present invention further enhances the cleaning power by spraying an acceleration gas onto the fine aerosol blown from the spray nozzle so as to collide with the surface to be cleaned.

  In addition, an object to be cleaned is a semiconductor wafer, a light exposure mask or reticle, an X-ray mask or reticle, an EB mask or reticle, an IB mask or reticle, a lithography mask or reticle, a flat panel substrate, a magnetic disk substrate, or a flying head substrate. , Magnetic head, micromachine, or MEMS.

  The present invention also generates a fine aerosol by blowing out a cleaning gas or liquid cooled by a heat exchanger or a mixture of gas and liquid from an injection nozzle having fine nozzle holes, and the fine droplets, fine solid or gas Alternatively, in an aerosol cleaning apparatus that sprays a mixture of two or more of them onto the surface to be cleaned, a low flow rate upstream of the heat exchanger is used to flow a high flow rate gas after flowing a low flow rate gas through the heat exchanger. A bypass pipe and a valve are provided in parallel with the flow pipe, and the pressure in the aerosol generation nozzle is temporarily increased by a high flow rate gas flowing through the bypass pipe, thereby reducing the average particle diameter of the aerosol, thereby solving the above problem. It is a thing.

Also provided with a pressure regulating valve and a pressure gauge for controlling the pressure in the aerosol generating nozzle in the range of 100 kPa to 1500 kPa when the cleaning gas or liquid or a mixture of gas and liquid is N ₂ single gas. It is.

  Further, the object to be cleaned is moved in the direction of the central axis of the aerosol generating nozzle and in the direction perpendicular to the axis so that the speed in the direction perpendicular to the nozzle central axis is 200 mm / second to 400 mm / second. An XY scanning means controlled in the second range is provided.

  In order to eliminate dust generation from the apparatus, the driving and operating parts of the XY scanning means are installed outside the cleaning chamber.

  Further, by attaching a heat insulating material to the aerosol generating nozzle, it is possible to prevent a temperature increase of the aerosol generating nozzle and to spray a stable aerosol.

  In addition, by providing a block for eliminating the space around the aerosol generating nozzle or by providing a shield plate for preventing gas from flowing around the aerosol generating nozzle, the air flows around the aerosol generating nozzle. The temperature rise due to the purge gas or the like is prevented, and stable aerosol can be sprayed.

  The hole diameter of the injection nozzle is in the range of 0.05 mm to 0.3 mm, and the number of holes is 1 to 100. If the hole diameter is too large, the gas flow rate increases, a large refrigerating capacity is required, and the gas consumption increases. Conversely, the lower limit of the hole diameter is determined by the processing limit. On the other hand, a larger number of holes is preferable because the arrangement pitch of the holes becomes smaller and the cleaning time can be shortened. However, conventionally, the gas flow rate has increased so much that it could not be increased from more than ten. Since it is now possible to drill fine holes, the number of holes can be increased.

  The present invention also provides an exhaust pump and an exhaust control for controlling the pressure of a cleaning chamber in which fine droplets, fine solids, gas, or a mixture of two or more thereof are blown out from the injection nozzle in a range of 0.1 kPa to 20 kPa. A valve is provided.

  Furthermore, an acceleration nozzle is provided for spraying an acceleration gas on the fine aerosol blown out from the spray nozzle to collide with the surface to be cleaned.

As described in Patent Document 1, if the gas pressure is increased, the aerosol can be made finer and the cleaning ability can be increased. However, when the pressure is constantly increased, the flow rate of the gas increases, the refrigerator is required to have a large refrigeration capacity, and the gas consumption also increases. Therefore, in the present invention, in order to enable a high pressure with a small refrigerating capacity, a low flow rate (for example, 45 SLM) is provided in a section T ₁ (for example, 1 to 20 minutes) from time t1 to t2 as shown by a solid line in FIG. Gas (for example, N ₂ ) and the temperature of the gas and nozzle is lowered as shown in FIG. 3B (for example, 83 K on the heat exchanger outlet side and 97 to 101 K on the aerosol generating nozzle), and time t 2 Then, a gas having a high flow rate (for example, 150 SLM) is made to flow at a high pressure (for example, 800 kPa), and the aerosol is refined and cleaned in a section T ₂ (for example, 0.5 to 8 minutes) until time t3. After completion of the cleaning, the gas flow rate is returned to a low flow rate again, and the heat exchanger or the aerosol generating nozzle is waited for sufficiently cooling. By repeating this operation, cleaning can be performed intermittently.

  The inventors further investigated the relationship between the nozzle pressure and the scanning speed of the object to be cleaned. That is, a sample of a semiconductor material in which a large number of linear protrusions having a line width of 130 nm and an aspect ratio of 3 are arranged is cleaned by changing the nozzle pressure and the scanning speed in the X direction, and observed with a microscope. If there was damage even at one place, the damage rate was evaluated assuming that the sample was damaged, and the results shown in Table 1 were obtained.

  The cleaning conditions are 100% nitrogen cleaning, acceleration is 20 SLM, purge is 150 SLM, the number of scans in the Y direction is 17 times, and the cleaning time is about 60 seconds when the scanning speed is 130 mm / second, and about 30 when the scanning speed is 250 mm / second. Seconds.

  As is apparent from Table 1, when the nozzle pressure is 200 kPa, the damage rate is 100% regardless of the scanning speed. This seems to be because the aerosol particle size is too large. On the other hand, as the nozzle pressure is increased to 600 kPa and 800 kPa, the damage rate decreases, and at both 600 kPa and 800 kPa, the damage rate is reduced by half when the scanning speed is increased from the conventional 130 mm / second to 250 mm / second. It was confirmed that The detergency was the same as in the case of argon, and there was no problem.

  Therefore, the scanning speed is preferably controlled in the range of about 200 mm / second to 400 mm / second.

  According to the present invention, it is possible to generate a fine aerosol by a high gas pressure with a relatively small refrigerating capacity, and it is possible to clean without damaging the fine structure of the surface of the object to be cleaned.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 4, the first embodiment of the present invention bypasses the mass flow controllers 30 and 32 in the same configuration as in FIG. 1 and, for example, maintains a high pressure (for example, 150 SLM) while maintaining the original pressure. In addition to providing bypass pipes 70 and 72 for flowing air, open / close valves 74, 76, 78 and 80 for turning on / off the mass flow controllers 30 and 32 and bypass pipes 70 and 72, respectively, are further provided. Pressure regulating valves 82 and 84 and a pressure gauge 86 for controlling the internal pressure in the range of 100 to 1500 kPa are provided in front of the filter 34. Pressure control valves 86 and 90 and open / close valves 88 and 92 are also provided before and after the mass flow controller 52 for acceleration gas and the mass flow controller 62 for purge gas, respectively.

  Further, a speed control device 94 for controlling the X-direction scanning speed of the process hand 46 in the range of 200 to 400 mm / second is also provided.

  In the present embodiment, as shown in detail in FIG. 5, the periphery of the aerosol nozzle 20 is covered with a heat insulating material 100 to prevent a temperature rise of the aerosol nozzle particularly at a high flow rate, and stable aerosol spraying is possible. It is said.

  In FIG. 5, reference numeral 102 denotes a buffer chamber for exchanging with the next object to be cleaned, and 104 denotes a shield plate for preventing the purge gas 66 from directly hitting the aerosol nozzle 20.

  In this embodiment, since the heat insulating material 100 is only provided around the aerosol nozzle 20, the configuration is simple. In addition, the method of thermally insulating an aerosol nozzle is not limited to this, A double pipe can be used, or the aerosol nozzle itself can be made of a heat insulating material.

  Next, the second embodiment in which the temperature rise of the aerosol nozzle is prevented by another method will be described in detail.

  In the present embodiment, as shown in FIG. 6, the space around the aerosol nozzle 20 and the acceleration nozzle 24 is made of, for example, aluminum so as not to generate a gas flow due to the purge gas 66 or the like around the aerosol nozzle 20 and the acceleration nozzle 24. It is filled with block 110.

  According to the present embodiment, it is possible to reliably prevent the purge gas 66 and the like from entering the periphery of the aerosol nozzle 20 and the acceleration nozzle 24 and to spray the aerosol with high stability.

  The material of the block 110 is not limited to aluminum, and may be other metals or resins.

  Next, the third embodiment in which the temperature rise of the aerosol nozzle is prevented by another method will be described in detail.

  In this embodiment, as shown in FIG. 7, in addition to the shield plate 104, for example, shield plates 112 and 114 made of metal plates are used to prevent purge gas and the like from flowing around the aerosol nozzle 20 and the acceleration nozzle 24. Is provided.

  According to the present embodiment, it is possible to prevent the purge gas 66 and the like from flowing around the aerosol nozzle 20 and the acceleration nozzle 24 with a relatively simple configuration.

  The material of the shield plates 112 and 114 is not limited to metal, and may be resin.

  In any of the above-described embodiments, the acceleration nozzle 24 is provided and the acceleration gas 26 is injected, so that the aerosol 22 can be accelerated and the control of the collision speed with the object to be cleaned 10 is easy. Note that the acceleration nozzle 24 may be omitted.

Also, the type of cleaning fluid is not limited to Ar or N ₂ , and other cleaning fluids such as He, Ne, O ₂ or CO ₂ , N ₂ O, H ₂ O can be used. In addition, Kr, SF ₆ , Xe, H ₂ or the like can be used.

  In the above-described embodiment, the present invention is applied to a semiconductor wafer cleaning apparatus. However, the application target of the present invention is not limited to this, and an optical exposure mask or reticle, an X-ray mask or reticle, and an EB. It is apparent that the present invention can be similarly applied to cleaning apparatuses such as masks or reticles, IB masks or reticles, lithography masks or reticles, flat panel substrates, magnetic disk substrates, flying head substrates, magnetic heads, micromachines, and MEMS.

Pipeline diagram showing the overall configuration of an example of a conventional low-temperature aerosol cleaning device Similarly, an enlarged cross-sectional view showing the area around the aerosol nozzle Time chart showing the principle of aerosol cleaning according to the present invention 1 is a conduit diagram showing the overall configuration of a first embodiment of a low-temperature aerosol cleaning apparatus according to the present invention; Similarly, an enlarged cross-sectional view showing the area around the aerosol nozzle The expanded sectional view which shows the aerosol nozzle periphery in 2nd Embodiment of this invention Similarly expanded sectional view showing the aerosol nozzle periphery in the third embodiment

Explanation of symbols

10 ... object to be cleaned (wafer)
DESCRIPTION OF SYMBOLS 20 ... Aerosol nozzle 22 ... Aerosol 24 ... Acceleration nozzle 26 ... Acceleration gas 42 ... Cleaning chamber 70, 72 ... Bypass piping 74, 76, 78, 80, 88, 92 ... Open / close valve 82, 84, 86, 90 ... Pressure adjustment valve 86 ... Pressure gauge 94 ... Speed control device 100 ... Insulating material 104, 112, 114 ... Shield plate 110 ... Block

Claims (20)

A cleaning gas or liquid cooled with a heat exchanger or a mixture of gas and liquid is blown out of an injection nozzle having a fine nozzle hole to produce a fine aerosol, and its fine droplets or fine solid or gas or two or more thereof In the aerosol cleaning method of spraying the mixture onto the surface to be cleaned,
An aerosol characterized by temporarily increasing the pressure in the aerosol generating nozzle and decreasing the average particle size of the aerosol by flowing a high flow rate gas after flowing a low flow rate gas through the heat exchanger. Cleaning method. The cleaning gas or liquid or a mixture of gas and liquid may be Ar, N ₂ , He, Ne, O ₂ , CO ₂ , N ₂ O, H ₂ O, Kr, SF ₆ , Xe, H ₂ each single gas or The aerosol cleaning method according to claim 1, wherein the aerosol cleaning method is a mixed gas. _2. The aerosol cleaning method according to claim 1, wherein when the cleaning gas or the liquid or a mixture of the gas and the liquid is an N ₂ single gas, the pressure in the aerosol generation nozzle is controlled in a range of 100 kPa to 1500 kPa. .   When the object to be cleaned is moved in the direction of the central axis of the aerosol generating nozzle and in the direction perpendicular to the axis, the speed in the direction perpendicular to the central axis of the nozzle is set to 200 mm / second to 400 mm / second. The aerosol cleaning method according to claim 1, wherein the aerosol cleaning method is controlled within a range.   The aerosol cleaning method according to any one of claims 1 to 4, wherein a stable aerosol is sprayed by attaching a heat insulating material to the aerosol generating nozzle.   The aerosol cleaning method according to claim 1, wherein a stable aerosol is sprayed by eliminating a space around the aerosol generation nozzle.   The aerosol cleaning method according to any one of claims 1 to 5, wherein a stable aerosol is sprayed by attaching a shield plate for preventing gas from flowing around the aerosol generating nozzle.   The pressure in the cleaning chamber in which fine droplets, fine solids, gas, or a mixture of two or more thereof is blown out from the spray nozzle is controlled in a range of 0.1 kPa to 20 kPa. The aerosol cleaning method according to 1.   The aerosol cleaning method according to any one of claims 1 to 8, wherein an acceleration gas is blown to the fine aerosol blown from the injection nozzle to collide with a surface to be cleaned.   Objects to be cleaned are semiconductor wafers, light exposure masks or reticles, X-ray masks or reticles, electron beam masks or reticles, ion beam masks or reticles, lithography masks or reticles, flat panel substrates, magnetic disk substrates, flying head substrates The aerosol cleaning method according to claim 1, wherein the aerosol cleaning method is any one of a magnetic head, a micromachine, and a MEMS. A cleaning gas or liquid cooled with a heat exchanger or a mixture of gas and liquid is blown out of an injection nozzle having a fine nozzle hole to produce a fine aerosol, and its fine droplets or fine solid or gas or two or more thereof In an aerosol cleaning device that sprays the mixture onto the surface to be cleaned,
After flowing a low flow rate gas through the heat exchanger, in order to flow a high flow rate gas, a bypass pipe and a valve are provided in parallel with the pipe through which the low flow rate upstream of the heat exchanger flows. An aerosol cleaning apparatus, wherein the pressure in the aerosol generation nozzle is temporarily increased by a gas at a flow rate to reduce the average particle diameter of the aerosol. A pressure regulating valve and a pressure gauge are provided for controlling the pressure in the aerosol generating nozzle in a range of 100 kPa to 1500 kPa when the cleaning gas or liquid or a mixture of gas and liquid is N ₂ single gas. The aerosol cleaning apparatus according to claim 11.   The object to be cleaned is moved in the direction of the central axis of the aerosol generating nozzle and in the direction perpendicular to the axis, and the speed in the direction perpendicular to the central axis of the nozzle is 200 mm / second to 400 mm / second for cleaning the object to be cleaned. The aerosol cleaning apparatus according to claim 11, wherein an XY scanning unit controlled in a range is provided.   14. The aerosol cleaning apparatus according to claim 13, wherein the driving and operating parts of the XY scanning means are installed outside the cleaning chamber in order to eliminate dust generation from the apparatus.   The aerosol cleaning apparatus according to claim 11, wherein a heat insulating material is attached to the aerosol generation nozzle.   The aerosol cleaning apparatus according to claim 11, wherein a block for eliminating a space around the aerosol generating nozzle is provided.   16. The aerosol cleaning apparatus according to claim 11, further comprising a shield plate that prevents gas from flowing around the aerosol generation nozzle.   18. The aerosol cleaning apparatus according to claim 11, wherein a hole diameter of the spray nozzle is in a range of 0.05 mm to 0.3 mm and a number of holes is 1 to 100. .   An exhaust pump and an exhaust control valve are provided for controlling the pressure of the cleaning chamber in which fine droplets, fine solids, gas, or a mixture of two or more thereof are blown out from the injection nozzle in a range of 0.1 kPa to 20 kPa. The aerosol cleaning apparatus according to any one of claims 11 to 18, wherein   The aerosol cleaning apparatus according to any one of claims 11 to 19, further comprising an acceleration nozzle for spraying an acceleration gas to the fine aerosol blown from the injection nozzle to collide with a surface to be cleaned. .

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