JP2009246250A - Method for forming thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a thin film in a desired region with high dimensional accuracy. <P>SOLUTION: The thin film made of semiconductor particles or conductive particles is formed on a substrate by a method for forming a thin film. In a location process, a dispersion solution in which the semiconductor particles or conductive particles with a particle diameter of 100 nm or less are dispersed is located in a predetermined region of the substrate. In an oscillation process, the substrate with the dispersion solution located thereon is oscillated at a frequency ≥20 KHz and ≤50 MHz to remove the dispersion solution in regions other than the predetermined region. In a solvent removal process, the solvent of the dispersion solution on the substrate is removed and the thin film made of the semiconductor particles or the conductive particles is formed on the substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thin film forming method, and more particularly, to a thin film forming method in which a thin film such as silicon or metal is accurately formed only in a predetermined region.

  In recent years, image devices such as TFTs (Thin Film Transistors) and solar cells use a technique of forming MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and power generation elements using silicon thin films. Since these devices have a large area and the amount of silicon used tends to increase, there is a strong demand for material reduction.

  As a method for obtaining a silicon thin film, a method of obtaining a silicon film by using a high-purity gas containing a silicon precursor such as monosilane and decomposing this gas in plasma is often used. In this method, it is possible to form a silicon thin film all over the substrate.

  On the other hand, from the viewpoint of reducing the amount of silicon material used, methods for obtaining a silicon thin film only in a predetermined region have been actively researched and developed. As a technique for forming a thin film for a predetermined region, for example, a coating film containing a silicon precursor is discharged from a nozzle onto a substrate to obtain a patterned coating film, and then a heat treatment is applied to the patterned silicon film. Is disclosed (see, for example, Patent Document 1).

  As another method, for example, a hydrophilic region and a water-repellent region pattern are provided on the thin film formation surface of the substrate, and the substrate is immersed in a solution containing noble metal fine particles. A technique for forming and forming a circuit pattern is disclosed (see, for example, Patent Document 2).

JP 2004-145333 A JP 2007-84850 A

  However, in the method of Patent Document 1, the shape of the droplet when the droplet of the coating liquid discharged from the nozzle reaches the substrate cannot be controlled. For this reason, there has been a problem that the dimensional accuracy of the pattern of the coating film finally formed on the substrate becomes insufficient.

  In the case of the method of controlling the location of the droplet by providing a hydrophilic region and a water-repellent region on the thin film formation surface of the substrate as in Patent Document 2, the droplet remains in the water-repellent region. In some cases, the dimensional accuracy of the pattern of the droplets finally formed on the substrate is insufficient.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the thin film formation method which can form a thin film with a sufficient dimensional accuracy in a desired area | region.

  In order to solve the above-described problems and achieve the object, a thin film forming method according to the present invention is a thin film forming method for forming a thin film made of semiconductor particles or conductive particles on a substrate, and the particle diameter is 100 nm or less. An arrangement step of disposing the dispersion liquid in which the semiconductor particles or the conductive particles are dispersed in a predetermined region of the substrate, and vibrating the substrate on which the dispersion liquid is disposed at a frequency of 20 KHz or more other than the predetermined region A vibration process for removing the dispersion liquid present in the region, and a solvent removal process for forming a thin film made of the semiconductor particles or conductive particles on the substrate by removing the solvent of the dispersion liquid on the substrate. It is characterized by including.

  According to the present invention, unnecessary droplets can be removed by vibrating the substrate after applying the droplets of the dispersion liquid to the surface of the substrate. As a result, a thin film made of an aggregate of silicon fine particles can be selectively and accurately formed at a desired position on the substrate, so that occurrence of a pattern shape defect of the thin film can be suppressed and a predetermined position can be obtained with a small amount of silicon raw material. In addition, the silicon thin film can be formed with high pattern accuracy.

  Embodiments of a thin film forming method according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

Embodiment 1 FIG.
FIG. 1 is a flowchart for explaining main steps of the thin film forming method according to the first embodiment of the present invention. FIGS. 2-1 to 2-8 are cross-sectional views for explaining in detail the main steps of the thin film forming method shown in FIG. In this embodiment mode, a method for forming a silicon thin film in a selective region on a substrate will be described with reference to FIGS. 1 and 2-1 to 2-8.

  First, in the first step, a dispersion A in which silicon fine particles having a particle diameter of 2 nm to 100 nm are dispersed is prepared (step S110). As the solvent for dispersing the silicon fine particles, for example, methanol or water is preferable. Since the precipitation of particles due to gravity occurs when the particle size of the silicon fine particles increases, the particle size of the silicon fine particles is preferably 100 nm or less. Moreover, the particle diameter of 2 nm or more can be produced from the current technical limit of the particle production technique.

  Further, since the silicon fine particles are water-repellent, it is preferable to use a technique of adding a surfactant to disperse the silicon fine particles when water is used as a solvent. Here, as the surfactant, for example, sodium lauryl sulfate is suitable. What is necessary is just to add about 1 wt%-3 wt% of surfactant.

  Next, in the second step, the droplets of the silicon fine particle dispersion A are patterned (selectively arranged) in selective areas on the substrate (step S120). The patterning of the droplets of the silicon fine particle dispersion A may be performed by using an existing ink jet, but a technique capable of patterning the droplets in a lump for a large area is disclosed below. .

  First, as shown in FIG. 2A, a substrate 11 to be deposited on which a silicon thin film is to be formed is prepared, and the entire surface of the deposition surface of the substrate 11 is subjected to a water repellency treatment. As shown, a water repellent layer 12 a is formed on the film forming surface of the substrate 11. Here, the water repellent treatment of the substrate is performed, for example, after the substrate 11 is baked at a temperature of 150 ° C. for 10 minutes and then exposed to a vapor containing hexamethylzine lazan (HMDS) to make the substrate surface water repellent. It is possible.

  By performing this water repellent treatment, the wettability of the surface of the substrate 11 with respect to water is in the range of 100 degrees to 120 degrees in terms of the wetting angle. Further, in addition to hexamethylzine lazan (HMDS), octadecyltrimethoxylane (ODS) may be used as another material.

  Next, UV irradiation (wavelength 248 nm) is performed on the surface of the substrate 11 on which the water repellent layer 12a is formed, and a part of the water repellent layer 12a is subjected to a hydrophilic treatment. UV irradiation can be performed, for example, by mask exposure using a mask used in photolithography as shown in FIG. That is, UV irradiation is performed only on a desired selection region using the plate-making mask 13 having a predetermined opening. By performing UV irradiation on the water repellent layer 12a, the UV irradiated region in the water repellent layer 12a loses water repellency and becomes a hydrophilic region 14 having hydrophilicity. The wettability of the hydrophilic region 14 with respect to water is in the range of 5 to 20 degrees in terms of the wetting angle, although it depends on the UV irradiation conditions. In addition, the region of the water repellent layer 12a that has not been irradiated with UV becomes the water repellent region 12 having water repellency as it is without losing water repellency.

  In this way, by performing UV irradiation only on a predetermined selective region, it is possible to pattern the water repellent layer 12a by separating the water repellent region 12 and the hydrophilic region 14 as shown in FIG. 2-4. It is. In addition to mask exposure, the selective region may be hydrophilized by collecting UV light and irradiating the water repellent layer 12a with a spot.

  When ODS is used for the water repellent treatment, it is preferable to use an Xe excimer lamp with a wavelength of 172 nm as UV irradiation. This is because short-wavelength light is required to obtain the energy necessary to dissociate the CC bond of ODS.

  Next, a dispersion A in which silicon fine particles are dispersed is dropped onto the surface of the substrate 11. Then, after the dispersion A containing silicon fine particles is dropped on the entire surface of the substrate 11, the substrate 11 is tilted to remove the excess dispersion A, whereby the droplet 15 of the dispersion A only in the hydrophilic region 14. Exists. As another method, the dispersion liquid A may be ejected aiming at the hydrophilic region 14 using an inkjet nozzle.

  Here, at the time when the dropping step of the dispersion liquid A is completed, due to an accidental factor such as scattering of the dispersion solution A, as shown in FIG. In the water-repellent region 12, a minute dispersion liquid A droplet 16 having a diameter of several microns remains.

  Next, in the third step, the substrate 11 on which droplets of the dispersion liquid A are placed is placed on the vibration table 17 and vibrated (step S130). The minute droplets adhering to the water-repellent region 12 are absorbed by the droplets in the hydrophilic region 14 or sprayed on the upper portion of the substrate 11 as shown in FIG. Here, spraying is also generated at the location of a large droplet in the hydrophilic region 14 due to this vibration, but since the amount of the original droplet is larger than that of the water-repellent region 12, the disappearance of the droplet does not occur. Thereby, as shown in FIGS. 2-7, the droplet of the dispersion liquid A can be patterned (selectively arranged) with high precision only in the hydrophilic region 14.

  As a means for vibrating the substrate 11, for example, it is effective to place the substrate 11 on a plate that vibrates with ultrasonic waves and swing the substrate 11. Although there is no particular difference in the difference depending on the direction of vibration, the frequency of vibration is preferably 20 KHz or more from the viewpoint of requiring energy for sufficiently moving the microdroplet. When the frequency of vibration is smaller than 20 KHz, it is necessary to increase the amplitude for swinging the substrate 11, and there is a possibility that the droplet shape of the hydrophilic region 14 may be broken by the swing. Further, when the frequency of vibration is 20 KHz, the fine droplets in the water-repellent region 12 can be removed with an amplitude of about 1 μm. The same effect can be obtained even at a higher frequency, for example, 300 KHz. On the other hand, if the frequency exceeds 50 MHz, a sufficient rocking effect cannot be obtained and the droplets cannot be removed.

  Next, in the fourth step, the solvent of the droplets of the dispersion liquid A is removed to obtain a thin film made of an aggregate of silicon fine particles in the hydrophilic region 14 (step S140). That is, the dispersion liquid A is evaporated to form a thin film of silicon fine particles in the hydrophilic region 14. For example, the dispersion A is dried by baking the substrate 11 in an atmosphere containing hydrogen at a pressure partial pressure of 1 KPa or more, and as shown in FIG. Obtainable. Here, since the dispersion A is previously removed from the water-repellent region 12 and selectively disposed only in the hydrophilic region 14, the silicon thin film 18 made of an aggregate of silicon fine particles is formed only in the hydrophilic region 14 with dimensional accuracy. can get.

  By performing the processing as described above, the silicon thin film 18 can be selectively and accurately formed on the hydrophilic region 14 of the substrate 11 with an aggregate of silicon fine particles.

  As described above, according to the thin film forming method according to the present embodiment, after the droplets of the dispersion A are applied to the surface of the substrate 11, the droplets in unnecessary regions are removed by vibrating the substrate 11. Can do. Further, ultrasonic waves can be used for the vibration of the substrate 11, and no large-scale equipment is required. As a result, a thin film made of an aggregate of silicon fine particles can be selectively and accurately formed at a desired position on the substrate 11, so that the occurrence of pattern shape defects in the thin film can be suppressed and a predetermined amount of silicon raw material can be used. It becomes possible to form a silicon thin film at a position with high pattern accuracy. That is, it is possible to minimize the amount of the thin film material used and to remove droplets in an unnecessary area.

  For example, in an image display device such as a TFT, a MOSFET configured using a silicon thin film may be formed in a predetermined region, but by using the thin film forming method according to the present embodiment, only a necessary region is formed. A silicon thin film can be formed, and the silicon material can be reduced. In addition, by reducing the amount of material used, the energy required for manufacturing the thin film can be similarly reduced, and generation of harmful substances due to energy consumption can be reduced. Therefore, according to the thin film formation method according to the present embodiment, it is possible to form a thin film with reduced environmental load.

  FIG. 3 shows a cross-sectional configuration of a concentrating solar cell as an example of a device manufactured using the thin film forming method according to this embodiment. In this solar cell, sunlight L incident from the glass substrate 31 side is reflected by a reflecting mirror 33 formed of an aluminum thin film on the surface of a bowl-shaped concave portion of a substrate 32 made of resin, for example, and is reflected on a power generation element 34 by light excitation. Incident. The current generated by the power generation element 34 is taken out by the electric wiring 35 connected to the power generation element 34.

  Although a laminated film of P-type silicon and N-type silicon can be used as the power generation element 34, the power generation element 34 can be formed using this manufacturing technique. By using this manufacturing technique, it is possible to form a silicon film only at a necessary location in the glass substrate 31, so that material can be reduced compared with a thin film forming technique such as sputtering or chemical vapor deposition, and there is little. Devices can be fabricated with materials and low cost.

  FIG. 4 shows an example of a TFT (Thin Film Transistor) element formed on the glass substrate 51 as an example of another device manufactured by using the thin film forming method according to this embodiment. In this TFT element, a gate electrode 55 is formed on a base layer 52 on a glass substrate 51 via a silicon film 53 and a gate oxide film 54. By applying a voltage to the gate electrode 55, the electrodes 56, This is an element that can vary the resistance value between the terminals 57. The outer surface of the TFT element is covered with a protective film 58.

  For example, in a liquid crystal display, a circuit for ON / OFF control of pixels may be formed on a display screen. In that case, a TFT element is required on the glass substrate. Therefore, by using this manufacturing technique, a silicon film necessary as a TFT can be formed only in a necessary region in the glass substrate 51. Therefore, compared with a thin film forming technique such as sputtering or chemical vapor deposition, the material Reduction is possible, and a device can be manufactured with less material and lower cost.

Embodiment 2. FIG.
In the second embodiment, another method for patterning (selecting and arranging) the droplets of the dispersion A described in the first embodiment in a selective region on the substrate (second step to third step) will be described. explain. 5A to 5E are cross-sectional views for explaining the position control of the droplets of the dispersion liquid A in the second embodiment.

  First, as shown in FIG. 5A, an insulating film 72 is formed so as to cover and incorporate a plurality of electrodes 73 on a substrate 71, and a water repellent layer 74 is formed on the insulating film 72. The size of the electrode 73 is smaller than the droplet. In FIG. 5A, as the plurality of electrodes 73, there are seven electrodes 73a, 73b, 73c, 73d, 73e, 73f, and 73g. The electrode is shown. The electrodes 73 a to 73 g are provided at a predetermined interval in the in-plane direction of the substrate 71. The water repellent layer 74 can be formed in the same manner as in the first embodiment.

  Next, as shown in FIG. 5B, a droplet 75 of the dispersion A in which silicon fine particles are dispersed is dropped on the substrate 71 on which the water repellent layer 74 is formed. At this time, since the size of the electrode 73 is smaller than the droplet, the droplet 75 exists over the plurality of electrodes 73. Here, for example, as shown in FIG. 5-3, when a voltage is applied with the electrode 73a, the electrode 73b and the electrode 73c as the negative electrode and the electrode 73d and the electrode 73e as the positive electrode, the surface charge of the droplet 75 is controlled by the voltage, The droplet 75 whose tension is reduced moves in the right direction (the direction from the electrode 73a to the electrode 73e) in FIG. That is, by controlling the surface tension between the droplet 75 and the water repellent layer 74 by controlling the potentials of the plurality of electrodes 73, different regions (a region having good wettability) of the droplet 75 on the surface of the water repellent layer 74. As shown in FIG. 5-3, finally, the droplet 75 moves at the position of the middle point of the electrode having a potential difference so as to balance the surface tension (region with good wettability) as shown in FIG. Stop and stabilize.

  For example, as shown in FIG. 5-4, when the voltage is applied with the electrode 73b, the electrode 73c and the electrode 73d as the negative electrode, and the electrode 73e and the electrode 73f as the positive electrode, the liquid droplet 75 further flows in the right direction in FIG. It can be moved in the direction from the electrode 73b to the electrode 73f. Finally, as shown in FIG. 5-5, the movement of the droplet 75 stops and stabilizes at just the middle point of the electrode having a potential difference so that the surface tension is balanced.

  In this way, by switching the potentials of the plurality of electrodes 73 formed under the water repellent layer 74, the droplet 75 disposed on the water repellent layer 74 can be moved to an arbitrary location.

  As described above, according to the present embodiment, by forming a water repellent layer on the plurality of electrodes 73 and switching the potential of the electrodes 73, the droplets of the dispersion A can be accurately collected in a large area. Patterning (selective arrangement) can be performed at an arbitrary position. Further, in this embodiment, since the position of the droplet can be controlled even on a substrate that is difficult to perform hydrophilic treatment / hydrophobic treatment, the droplet of the dispersion liquid A can be accurately obtained even when such a substrate is used. It is possible to perform patterning (selective arrangement) at an arbitrary position. In addition, wettability can be controlled even on substrates that are difficult to control wettability by chemicals or plasma.

Embodiment 3 FIG.
In the third embodiment, another method for removing the solvent of the droplet of the dispersion liquid A containing the silicon fine particles described in the first embodiment (fourth step) will be described. 6A to 6E are diagrams for explaining the thin film forming method according to the third embodiment, and are for explaining a method of obtaining a thin film by removing the solvent of the droplet of the dispersion A. It is sectional drawing.

  First, the steps described with reference to FIGS. 2-1 to 2-7 in the first embodiment are performed, and the droplet 15 of the dispersion A is patterned in the hydrophilic region 14 of the substrate 11 as shown in FIG. 6A. (Select placement). Next, another solvent B having a specific gravity lighter than that of the dispersion A is prepared, and the solvent B is placed on the substrate so that the solvent B covers the droplet 15 of the dispersion A as shown in FIG. Apply.

  The solvent of the dispersion A and the solvent B are solvents that do not completely dissolve when mixed with each other but cause two-layer separation. For example, when the solvent of the dispersion A is methanol, hexane is preferred as the solvent B that is phase-separated from methanol and has a lighter specific gravity than methanol. The specific gravity of hexane is 0.67, which is smaller than the specific gravity of 0.79 of methanol. Even when water is used as the solvent of the dispersion A, hexane and water are insoluble and the specific gravity of water is larger, so that hexane can be used as the solvent B.

  When the droplet 15 of the dispersion liquid A is covered with such a solvent B, the solvent of the dispersion liquid A slowly dissolves in the solvent B as shown in FIG. 6-3, and the silicon fine particles in the solvent of the dispersion liquid A The concentrated action works. Finally, as shown in FIG. 6-4, a silicon thin film 92 in which silicon fine particles are aggregated in the solvent B can be obtained. By removing the solvent B, the silicon fine particles are removed as shown in FIG. 6-5. The assembled silicon thin film 92 can be obtained on the substrate 11.

  By performing the processing as described above, the silicon thin film 18 can be selectively and accurately formed on the hydrophilic region 14 of the substrate 11 with an aggregate of silicon fine particles.

  As described above, according to the thin film formation method according to the present embodiment, a thin film made of an aggregate of silicon fine particles can be selectively and accurately formed at a desired position on the substrate 11. It is possible to suppress the occurrence of shape defects and to form a silicon thin film with high pattern accuracy at a predetermined position with a small amount of silicon raw material. Furthermore, according to the thin film forming method according to the present embodiment, the silicon fine particles of the dispersion A can be concentrated in the solvent B, so that impurities mixed from the atmosphere are blocked when the solvent is removed from the dispersion A. And a high-quality silicon thin film can be formed.

  In the above embodiment, the formation of the silicon thin film has been described as an example. However, it is possible to form a thin film other than the silicon thin film by applying the thin film forming method according to the present invention. For example, you may implement from the 1st process mentioned above using the particle | grains with a particle size of about 1 nm-100 nm which consist of metals containing gold | metal | money, silver palladium, rhodium, platinum, copper, and these alloys. For example, a dispersion liquid in which silver particles having a particle diameter of about 80 nm are dispersed in an organic solvent such as terpineol or toluene may be used.

  As described above, the thin film forming method according to the present invention is useful for forming a thin film with high dimensional accuracy in a desired region, and is particularly suitable as a method for obtaining a semiconductor thin film or a conductive thin film.

It is a flowchart for demonstrating the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating in detail the main processes of the thin film formation method concerning Embodiment 1 of this invention. It is the figure which showed the cross-sectional structure of the solar cell manufactured by the thin film formation method concerning Embodiment 1 of this invention. It is the figure which showed the cross-sectional structure of the TFT element manufactured by the thin film formation method concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating position control of the droplet of the dispersion liquid A in Embodiment 2 of this invention. It is sectional drawing for demonstrating position control of the droplet of the dispersion liquid A in Embodiment 2 of this invention. It is sectional drawing for demonstrating position control of the droplet of the dispersion liquid A in Embodiment 2 of this invention. It is sectional drawing for demonstrating position control of the droplet of the dispersion liquid A in Embodiment 2 of this invention. It is sectional drawing for demonstrating position control of the droplet of the dispersion liquid A in Embodiment 2 of this invention. It is sectional drawing for demonstrating the thin film formation method concerning Embodiment 3 of this invention. It is sectional drawing for demonstrating the thin film formation method concerning Embodiment 3 of this invention. It is sectional drawing for demonstrating the thin film formation method concerning Embodiment 3 of this invention. It is sectional drawing for demonstrating the thin film formation method concerning Embodiment 3 of this invention. It is sectional drawing for demonstrating the thin film formation method concerning Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Substrate 12 Water-repellent region 12a Water-repellent layer 13 Plate-making mask 14 Hydrophilic region 15 Droplet 16 Droplet 17 Shaking table 18 Silicon thin film 31 Glass substrate 32 Substrate 33 Reflector 34 Power generation element 51 Glass substrate 52 Gate electrode 52 Base layer 53 Silicon film 54 Gate oxide film 55 Gate electrode 56 Electrode 57 Electrode 58 Protective film 71 Substrate 72 Insulating film 73 Electrodes 73a, 73b, 73c, 73d, 73e, 73f, 73g Electrode 74 Water repellent layer 75 Droplet L Sunlight

Claims (6)

A thin film forming method for forming a thin film made of semiconductor particles or conductive particles on a substrate,
An arrangement step of disposing a dispersion liquid in which the semiconductor particles or conductive particles having a particle diameter of 100 nm or less are dispersed in a predetermined region of the substrate;
A vibration step of vibrating the substrate on which the dispersion is disposed at a frequency of 20 KHz or more and 50 MHz or less to remove the dispersion present in a region other than the predetermined region;
Removing the solvent of the dispersion liquid on the substrate to form a thin film comprising the semiconductor particles or conductive particles on the substrate;
A thin film forming method comprising: The semiconductor particles are silicon particles;
The thin film forming method according to claim 1. In the arrangement step,
Forming a plurality of regions having different wettability from each other on the substrate, and selectively disposing the dispersion in a region having good wettability among the plurality of regions;
The thin film forming method according to claim 1. In the arranging step, forming a plurality of regions having different wettability by forming a water-repellent region and a hydrophilic region on the substrate;
The thin film forming method according to claim 3. In the arrangement step,
On the substrate, a plurality of electrodes disposed at a predetermined interval in the in-plane direction of the substrate, an insulating film covering the plurality of electrodes, a water repellent layer disposed on the insulating film, Form the
Forming a plurality of regions having different wettability by controlling the wettability of the surface of the water repellent layer by independently controlling the potentials of the plurality of electrodes,
The thin film forming method according to claim 3. In the solvent removal step,
The dispersion liquid disposed on the substrate is covered with a solvent having a specific gravity that is light relative to the solvent of the dispersion liquid and that causes two-layer separation with the solvent of the dispersion liquid, and the solvent of the dispersion liquid is used as the other solvent Removing the solvent of the dispersion disposed on the substrate by absorbing,
The thin film forming method according to claim 1.

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