JP2010267708A - Device and method for vacuum processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for vacuum processing, capable of uniforming temperature of a sample within a surface of the sample. <P>SOLUTION: In the device and method for vacuum processing wherein a sample is sucked and held within a vacuum processing chamber and processed by controlling temperature of the sample, projecting parts for supporting a sample 1 are separately disposed in an outer periphery and inside of the periphery on a sample mounting surface, push-up pin holes 206 are disposed within the surface of one of the projecting parts, a heat transfer gas supply hole 205 is disposed in a portion excluding the projecting parts, and the sample 1 is processed while a heat transfer gas having a pressure higher than that of the heat transfer gas supplied to the portion excluding the projecting parts is supplied to the push-up pin holes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vacuum processing apparatus and a vacuum processing method, and more particularly to a vacuum processing apparatus and a vacuum processing method suitable for processing by holding a sample on a sample stage by adsorption.

  In recent semiconductor device manufacturing processes, for the purpose of improving throughput, it is required to continuously process etching of different kinds of films such as a photoresist layer, an antireflection film layer, a hard mask layer, a polysilicon layer, and a metal layer. It has been. In this multi-step continuous processing, the final film shape after processing is required to have processing accuracy equal to or higher than that in the conventional non-continuous processing. For this reason, the processing accuracy of each film in continuous processing needs to be stricter than the conventional method, that is, a technology that makes the sample surface a uniform temperature within the sample surface, such as a semiconductor substrate that is closely related to the processing accuracy. is required. As literature regarding conventional vacuum processing apparatuses and vacuum processing methods, there are, for example, Patent Documents 1 to 4.

JP 2001-160586 A JP 7-32185 A JP-A-11-330215 JP-A-8-274153

  Regarding the control of the sample temperature, Patent Document 1 discloses a vacuum processing apparatus including a heat transfer gas supply means for supplying a heat transfer gas between a sample such as a semiconductor substrate held by the electrostatic chuck and the electrostatic chuck. A technique is disclosed in which a convex portion for supporting a sample is provided on the sample mounting surface of the electrostatic chuck so as to be spaced apart from the outer peripheral portion and the inside thereof, and a push-up pin for conveying the sample is provided on the sample supporting portion. Yes.

  Patent Document 2 discloses a vacuum processing apparatus including a heat transfer gas supply unit that supplies a heat transfer gas between a sample such as a sample held by the electrostatic chuck and the electrostatic chuck. Has a gas supply hole, and the electrostatic chuck is provided with a push-up pin hole for storing a sample push-up pin. Heat transfer gas is supplied from this gas supply hole and the push-up pin hole. Is disclosed.

  Patent Document 3 discloses a vacuum processing apparatus including a heat transfer gas supply unit that supplies a heat transfer gas between a sample such as a semiconductor substrate held by an electrostatic chuck and the electrostatic chuck. Discloses a technique in which a gas supply hole is provided and the heat transfer gas is supplied from the gas supply hole.

  Patent Document 4 discloses a vacuum processing apparatus including a heat transfer gas supply unit that supplies a heat transfer gas between a sample such as a semiconductor substrate held by an electrostatic chuck and the electrostatic chuck. Discloses a technique for providing a push-up pin hole for storing a sample push-up pin, and supplying heat transfer gas from the push-up pin hole.

  However, in the above technique, sufficient consideration has not been given to the in-plane uniformity of the sample temperature. That is, the electrostatic chuck needs to be provided with a push-up pin as a transport mechanism for transporting and placing the sample. For this reason, a through hole is provided on the sample placement surface of the electrostatic chuck, and the inside of the through hole is provided. It is necessary to dispose the sample push-up pin. The heat transfer performance from the sample located directly above the through hole provided in this electrostatic chuck to the sample stage is lower than the heat transfer performance from the sample located around the through hole to the sample stage. When the sample is placed on and processed by plasma or the like, the sample temperature rises from the vicinity in the vicinity of the through hole and becomes non-uniform in the sample surface. Due to the in-plane non-uniformity of the sample temperature, there is a problem that the processed shape of the finally obtained sample is non-uniform within the sample surface.

  An object of the present invention is to provide a vacuum processing apparatus and a vacuum processing method capable of making a sample temperature uniform in a plane.

  As an aspect for achieving the above object, a processing chamber that is evacuated to a predetermined pressure, a sample stage that is provided in the processing chamber and has an electrostatic chuck, and a temperature of the electrostatic chuck are set. In a vacuum processing apparatus comprising: a variable temperature varying means; and a heat transfer gas supply means for supplying a heat transfer gas between a sample held by the electrostatic chuck and a sample arrangement surface of the electrostatic chuck. A heat transfer gas supply hole and a push-up pin hole for placing a push-up pin for the sample are provided through the sample placement surface of the electrostatic chuck, and the sample is supported on the sample placement surface of the electrostatic chuck. A convex part is provided apart from the outer peripheral part and the inside thereof, a push-up pin hole is provided in the surface of the convex part, and the heat transfer gas supply hole is provided other than the convex part, and the push-up pin hole part The heat transfer gas pressure of the heat transfer gas pressure other than the convex part The vacuum processing apparatus and providing a control means for remote high control.

  In addition, a convex portion that is arranged in the vacuum processing chamber and that supports the sample is provided on the sample mounting surface of the electrostatic chuck so as to be spaced apart from the outer peripheral portion and the inside thereof, and a push-up pin hole is provided in the surface of the convex portion. In the vacuum processing method in which the sample is processed by controlling the sample temperature while holding the sample electrostatically on a sample stage provided with a heat transfer gas supply hole other than the convex part, A vacuum processing method is characterized in that a heat transfer gas having a pressure higher than the heat transfer gas pressure supplied to other than the convex portions is supplied to process the sample.

  Further, in a vacuum processing apparatus having a sample stage provided with a mechanism for adsorbing a sample, a processing chamber in which the sample stage is arranged, and an exhaust means for exhausting the processing chamber, the sample stage has a ring-shaped convex portion. Region, a push-up pin hole provided in the ring-shaped convex region, a concave region provided inside the ring convex region, and a heat transfer gas supply hole provided in the concave region. The pressure of the heat transfer gas supplied to the push pin hole is set to a value exceeding the pressure of the heat transfer gas supplied to the heat transfer gas supply hole. A processing device is used.

  Vacuum processing apparatus and vacuum processing method capable of making the sample temperature uniform in the surface by controlling the heat transfer gas pressure in the push-up pin hole higher than the heat transfer gas pressure supplied to other than the convex portion Can be provided.

It is a longitudinal cross-sectional view which shows the outline of the vacuum processing apparatus which concerns on a 1st Example. It is a longitudinal cross-sectional view which shows the detail of the sample stand which concerns on a 1st Example. It is a cross-sectional view showing details of the sample stage according to the first embodiment. It is a figure which shows the heat transfer gas pressure of the sample back surface at the time of the sample holding | maintenance in the sample stand which concerns on a 1st Example. It is a time chart which shows the vacuum processing method using the new processing apparatus which concerns on a 1st Example. It is a longitudinal cross-sectional view which shows the detail of the sample stand which concerns on a 2nd Example.

  Hereinafter, the embodiment will be described in detail.

  A first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic view of a plasma vacuum processing apparatus. In this embodiment, a plasma etching apparatus is shown. The processing chamber 3 is configured by installing a quartz shower plate 103 and a quartz lid 101 on an upper part of a vacuum chamber 102 and connecting a vacuum pump 105 to a lower surface of the vacuum chamber via a valve 104. The gap between the members constituting the processing chamber 3 is hermetically sealed by an appropriate sealing means such as an O-ring (not shown), and the pressure in the processing chamber can be maintained at a high vacuum of 1 / 10,000 Pa.

  The upper space of the processing chamber 3 is a gas reservoir 109 constituted by the shower plate 103, the lid 101, the chamber 102, and the gas introduction hole 107. The gaps between the constituent members of the gas reservoir 109 are hermetically connected by a sealing means such as an O-ring (not shown). The processing gas is first introduced into the gas reservoir 109 from the processing gas supply device 108, and then introduced into the processing chamber 3 in a shower shape through a large number of through holes 110 provided in the shower plate 103.

As the processing gas, a single substance gas or a gas in which a plurality of substances are mixed at a predetermined ratio and at an optimum flow rate ratio is used for each process. For example, if the material to be etched is a Si-based material, an HBr / Cl ₂ / O ₂ gas system or a fluorine-based gas such as SF ₆ , CF ₄ , or CHF ₃ in combination with the left can be used.

  A disk-shaped antenna 111 is installed above the processing chamber 3. A microwave oscillator 112 is connected to the antenna 111, and an electromagnetic wave can be generated by applying a high frequency voltage to the antenna 111. Due to the interaction between the electromagnetic wave introduced into the processing chamber 3 and the magnetic field generated by the coil 113 installed around the vacuum chamber, high-density plasma can be generated in the processing chamber.

  A sample stage 2 on which a sample 1 such as a semiconductor substrate is arranged is provided below the processing chamber 3, and an electrostatic chuck 14 is attached to the surface on which the sample 1 is placed. The sample stage 2 has a high frequency power source 114 for applying a bias voltage to the sample 1 held by the electrostatic chuck 14, an electrostatic attraction power source 115 for sucking and holding the sample 1, and a gap between the sample and the electrostatic chuck. A heat transfer gas supply device 116 for supplying a heat transfer gas is connected. Reference numeral 106 denotes a focus ring, and reference numeral 117 denotes a control device.

  FIG. 2 shows details of the sample stage. In this case, the electrostatic chuck 14 on the top of the sample stage 2 is formed by laminating an electric insulating film 200, an electrostatic adsorption electrode 201, and a dielectric film 202. The attracting electrode 201 is a dipole type having two outer electrodes 201a and an inner electrode 201b, and each electrode is connected to the electrostatic attracting power source 115. In addition, the electrode described on the opposite side to the inner electrode 201b across the push-up pin 206 is integral with the inner electrode 201b. That is, the push-up pin 206 moves up and down in an opening provided through the inner electrode 201b.

  Ring-shaped convex portions 203 and 204 are formed at the outermost peripheral portion of the mounting surface of the sample 1 and at a position spaced inwardly therefrom. The heat transfer gas is supplied to the back surface of the sample through a gas supply hole 205 provided in a concave region other than the convex region and a push-up pin hole 206 provided in the convex region.

  The heat transfer gas supply line to the gas supply hole 205 is provided with a valve 208, and the heat transfer gas supply line to the push-up pin hole 206 is provided with a valve 207. The opening degree of the valves 207 and 208 can be adjusted independently, and the heat transfer gas supply amount and gas pressure can be adjusted independently in each line. The heat transfer gas from the heat transfer gas supply hole 205 is supplied to the space between the ring-shaped convex portions 203 and 204.

  Further, the sample stage 2 includes a heat radiating means and a temperature varying means (not shown). Reference numeral 209 denotes a seal, reference numeral 210 denotes a push-up pin, and reference numeral 211 denotes a push-up pin driving device. FIG. 3 is a cross-sectional view including the adsorption electrode 201 of the sample stage in FIG.

  In addition, as a material of the sample stand 2, any metal can be used as long as it has an appropriate strength. For example, stainless steel, aluminum, aluminum alloy, titanium, and the like can be preferably used. Or it may not be a metal.

The material of the electrical insulating film 200 and the dielectric film 202 may be any material as long as it can maintain insulation and has plasma resistance. For example, alumina (aluminum oxide, Al _2). O ₃ ) and yttria (yttrium oxide, Y ₂ O ₃ ) are preferably used. The material of the adsorption electrode 201 may be any metal, but for example, tungsten or nickel is preferably used.

  In the present embodiment, the adsorption electrode 201 is a dipole type having two outer electrodes 201a and 201b, but it is not necessarily a dipole type and may be a monopole type. Further, an adsorption method other than electrostatic adsorption may be used.

  2, the sample 1 is electrostatically adsorbed by the electrostatic chuck 4 and the heat transfer gas is supplied to the back surface of the sample through the gas supply hole 205 and the push-up pin hole 206. FIG. 4 shows the distribution of the heat transfer gas pressure on the back surface of the sample. By supplying the heat transfer gas while adjusting the valve 207 and the valve 208, it is possible to supply a heat transfer gas having a pressure higher than the heat transfer gas pressure supplied to the push-up pin hole other than the convex portion. it can. A wide range of pressure control is possible by attaching a compression means such as a compressor to the heat transfer gas supply line to the push-up pin hole. Further, since the heat transfer gas is discharged to the processing chamber 3, the flow rate is several orders of magnitude less than the reaction gas so as not to affect the reaction.

  The heat transfer gas supplied into the inside of the push-up pin hole 206 causes heat transfer via the heat transfer gas, that is, the sample back surface—the side wall surface of the push-up pin hole, between the sample back surface and the push-up pin, and the lift pin hole. The heat transfer occurs between the side wall surface and the push-up pin. By heat transfer through these heat transfer gases, heat input such as plasma to the sample is transferred from the back of the sample to the heat transfer gas, and there is some heat that passes through the inside of the push-up pin, but eventually the pin hole To the side surface of the sample and to the heat dissipating means (not shown) inside the sample stage.

  There are two types of paths through which the heat input of the sample directly above the push-up pin hole is transmitted to the sample stage. The first is a heat transfer path through the heat transfer gas inside the push-up pin hole as described above, that is, the heat transfer gas in the push-up pin from the back of the sample directly above the push-up pin, the side wall surface of the pin hole, This is a path through which heat is transferred in the order of cooling means (not shown) inside the sample. The second is that the heat transfer gas inside the push-up pin hole does not pass through, that is, heat input to the upper surface of the sample immediately above the push-up pin hole is first conducted by conducting heat transfer in the horizontal direction inside the push-up pin hole. To the electrostatic chuck via the heat transfer gas other than the contact surface with the electrostatic chuck on the convex part of the sample stage or the push pin hole, and further to the surface of the sample stage. This is a path that is transmitted to heat radiating means (not shown) by conductive heat transfer inside the sample stage.

  Of the two types of heat transfer paths as described above, the heat transfer path that does not pass through the heat transfer gas inside the push-up pin hole is accompanied by horizontal conduction heat transfer inside the sample. This will cause a temperature distribution. Therefore, in order to make the temperature in the sample surface uniform, it is necessary to transfer the heat input of the sample immediately above the push-up pin hole to the sample stage via the heat transfer gas inside the push-up pin hole.

  When the heat input of the sample immediately above the push-up pin hole is transferred to the sample stage, the distribution of the heat transfer amount to the two heat transfer paths as described above is performed inside the push-up pin hole in the sample stage shown in FIG. The heat transfer gas pressure can be adjusted. While increasing the heat transfer gas pressure in the push-up pin hole, and increasing the density of the heat transfer gas gas molecules, the heat transfer performance through the heat transfer gas in the push-up pin hole is improved. Among them, the amount of heat transfer increases in the path through the heat transfer gas in the push-up pin hole. In contrast, the amount of heat transfer in the heat transfer path that does not pass through the heat transfer gas in the push-up pin hole is reduced.

  FIG. 4 shows the heat transfer gas distribution during sample processing in this example. The heat transfer gas distribution in the present embodiment controls the heat transfer gas pressure at the push-up pin hole to be higher than the heat transfer gas pressure other than the convex part at the periphery of the push-up pin hole. FIG. 4 also shows the heat transfer gas distribution during sample processing as a comparative example. In the heat transfer gas distribution of the comparative example, the difference from the present embodiment is that the heat transfer gas pressure distribution inside the push-up pin hole is substantially the same as the heat transfer gas pressure other than the convex portion at the periphery of the push-up pin hole. It is that.

  Hereinafter, it will be described with reference to the embodiment shown in FIG. 4 and the comparative example that the temperature in the sample surface is made uniform by controlling the heat transfer gas pressure higher in the push-up pins than in the convex portions.

  First, in the comparative example shown in FIG. 4, when there is heat input to the sample from above the sample such as plasma, and this heat transfer is transmitted from the back of the sample to the sample stage or the electrostatic chuck, the heat transfer gas pressure is constant on the back of the sample. Therefore, the distribution of heat transfer performance in the sample surface is determined by the difference in heat transfer distance.

  The diameter of the push-up pin hole is on the order of several millimeters, and the distance between the back surface of the sample and the upper surface of the electrostatic chuck is one order or more smaller than this, so the heat transfer distance is just above the push-up pin hole and other parts. Too long. That is, the heat transfer performance is lower in the push-up pin hole than in other portions. Therefore, if there is heat input to the sample immediately above the push-up pin hole, the amount of heat transfer through the heat transfer gas in the push-up pin hole will decrease, and the heat transfer performance will be limited to those other than the push-up pin hole with relatively high heat transfer performance. The amount of heat transferred through increases. That is, conduction heat transfer is generated in the horizontal direction from the push-up pin hole portion to other portions inside the sample, and the sample temperature immediately above the push-up pin hole becomes higher than the surroundings. Therefore, when the heat transfer gas is constant on the back surface of the sample as in the comparative example shown in FIG. 4, the sample temperature is higher in the sample temperature immediately above the push-up pin hole and therefore the sample temperature becomes non-uniform in the surface. .

  On the other hand, in the embodiment shown in FIG. 4, the heat transfer gas pressure A in the push-up pin hole is controlled to be higher than the heat transfer gas pressure B other than the push-up pin hole, so that the heat input to the sample from above the sample. When the heat is transferred to the sample stage or electrostatic chuck, the heat transfer performance in the push-up pin hole is improved and the amount of heat transfer to the heat transfer gas in the push-up pin hole is increased. The heat transfer in the horizontal direction is eliminated inside the sample immediately above the hole, and the sample temperature becomes uniform in the plane.

  Next, an embodiment of a vacuum processing method using the plasma etching apparatus configured as described above will be described with reference to FIG. The sample is carried into the vacuum container via a lock chamber and a vacuum transfer chamber (not shown) and placed on the sample stage. Thereafter, the electrostatic chucking power source is turned on to hold the sample and the sample table in electrostatic chucking via the electrostatic chuck, and supply of heat transfer gas is started (time a1 in FIG. 5). Thereafter, the heat transfer gas pressure is set to be higher than the surroundings at the push-up pin hole, that is, A> B (in this embodiment, A = 1.5B).

  Thereafter, introduction of an etching gas is started, microwaves are introduced, and a bias power source is turned on to generate plasma and start processing (time a2 in FIG. 2). Since the heat transfer gas pressure is A> B while the sample is processed, the sample temperature can be made uniform in the plane. Regarding this pressure, preferably 5B> A> B, and 3B ≧ A ≧ 1.5B is suitable for practical use. The heat transfer gas supplied to the push-up pin hole 206 and the heat transfer gas supplied to the heat transfer gas supply hole 205 are not necessarily the same, but the configuration can be simplified by making them the same. In this embodiment, when the process is terminated, the one supplied later is stopped first. For example, after the etching gas is stopped, the heat transfer gas supply is stopped. Because of the residual pressure of the heat transfer gas, the wafer can be removed with a weak push-up pin pressure. According to the vacuum processing method executed in this way, the sample temperature can be made uniform in the plane when there is heat input such as plasma during the processing of the sample.

  As described above, according to this embodiment, the sample temperature is made uniform in the surface by controlling the heat transfer gas pressure in the push-up pin hole higher than the heat transfer gas pressure other than the push-up pin hole. A vacuum processing apparatus and a vacuum processing method can be provided.

  A second embodiment of the present invention will be described below with reference to FIG. The matters described in the first embodiment and not described in the present embodiment are the same as those in the first embodiment.

  FIG. 6 shows details of the sample stage as the second embodiment. The second embodiment is different from the first embodiment in the structure of the electrostatic chuck. In the second embodiment, the dielectric film of the electrostatic chuck is provided on the entire upper surface of the electric insulating layer, and irregularities are formed on the upper surface of the dielectric film, and a heat transfer gas is supplied to the concave portion. The sample stage of this embodiment is installed in the plasma vacuum processing apparatus shown in FIG. 1, and the heat transfer gas distribution is controlled to a higher pressure inside the push-up pin hole than outside the push-up pin hole as shown in FIG. (A = 2B in this embodiment) If the vacuum processing method as shown in FIG. 5 is performed, the sample temperature should be uniform in the surface when there is heat input such as plasma during the sample processing. Can do.

  As described above, according to this embodiment, the sample temperature is made uniform in the surface by controlling the heat transfer gas pressure in the push-up pin hole higher than the heat transfer gas pressure other than the push-up pin hole. A vacuum processing apparatus and a vacuum processing method can be provided. Furthermore, according to the present embodiment, it is possible to secure a wide electrostatic chuck region, and it is possible to attract the sample evenly over a wide region instead of local electrostatic adsorption.

  The present invention can be applied to an apparatus that holds a sample by an electrostatic chuck and performs vacuum processing by controlling the temperature of the sample.

1: sample, 2: sample stage, 3: processing chamber, 4: electrostatic chuck, 101: lid, 102: vacuum chamber, 103: shower plate, 104: valve, 105: vacuum pump, 106: focus ring, 107: Gas introduction hole, 108: processing gas supply device, 109: gas pool, 110: shower plate through hole, 111: antenna, 112: microwave oscillator, 113: coil, 114: high frequency power supply, 115: electrostatic adsorption power supply, 116 : Heat transfer gas supply device, 117: Control device, 200: Electrical insulating film, 201: Electrostatic adsorption electrode, 202: Dielectric film, 203: Outermost convex portion, 204: Ring-shaped convex portion, 205: Gas supply hole 206: Push-up pin hole, 207: Valve, 208: Valve, 209: Seal, 210: Push-up pin, 211: Push-up pin driving device.

Claims (9)

A processing chamber that is evacuated to a predetermined pressure; a sample stage that is provided in the processing chamber and has an electrostatic chuck on which a sample is placed; temperature variable means for changing the temperature of the electrostatic chuck; and the electrostatic chuck In a vacuum processing apparatus comprising a heat transfer gas supply means for supplying a heat transfer gas between a sample held by a sample placement surface of the electrostatic chuck,
A heat transfer gas supply hole and a push-up pin hole for placing a push-up pin for the sample are provided so as to penetrate the sample placement surface of the electrostatic chuck, and the sample is supported on the sample placement surface of the electrostatic chuck. A convex portion that is spaced apart from the outer peripheral portion and the inside thereof, the push-up pin hole is provided in a plane of the convex portion, and the heat transfer gas supply hole is provided in addition to the convex portion, and the push-up pin A vacuum processing apparatus comprising a control means for controlling the heat transfer gas pressure in the hole portion to be higher than the heat transfer gas pressure other than the convex portion. A convex portion that is disposed in the vacuum processing chamber and that supports the sample on the sample mounting surface of the electrostatic chuck is provided apart from the outer peripheral portion and the inside thereof, and a push-up pin hole is provided in the surface of the convex portion, In a vacuum processing method in which a heat transfer gas supply hole holds a sample by electrostatic adsorption on a sample table provided in addition to the convex portion and controls the sample temperature to process the sample.
A vacuum processing method, wherein a heat transfer gas having a pressure higher than a heat transfer gas pressure supplied to a portion other than the convex portion is supplied to the push-up pin hole to process the sample. In a vacuum processing apparatus having a sample stage provided with a mechanism for adsorbing a sample, a processing chamber in which the sample stage is arranged, and an exhaust unit for exhausting the processing chamber,
The sample stage is provided in a ring-shaped convex region, a push-up pin hole provided in the ring-shaped convex region, a concave region provided inside the ring convex region, and the concave region. Heat transfer gas supply holes,
The pressure of the heat transfer gas supplied to the push pin hole is set to a value exceeding the pressure of the heat transfer gas supplied to the heat transfer gas supply hole. . The vacuum processing apparatus according to claim 3, wherein
The said ring-shaped convex part area | region is provided twice, The said hole for push-up pins is provided in the inner ring-shaped convex part area | region, The vacuum processing apparatus characterized by the above-mentioned. In the vacuum processing apparatus according to claim 3 or 4,
The vacuum processing apparatus, wherein the mechanism for adsorbing the sample is an electrostatic chuck. The vacuum processing apparatus according to any one of claims 3 to 5,
A vacuum processing apparatus, wherein the heat transfer gas supplied to the push-up pin hole and the heat transfer gas supplied to the heat transfer gas supply hole have the same supply source. The vacuum processing apparatus according to any one of claims 3 to 6,
The vacuum processing apparatus, wherein the mechanism for adsorbing the sample is provided in the convex region. The vacuum processing apparatus according to any one of claims 3 to 6,
The vacuum processing apparatus, wherein the mechanism for adsorbing the sample is provided in the recessed area. The vacuum processing apparatus according to any one of claims 3 to 8,
The vacuum processing apparatus is a dry etching apparatus.

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