JP2005311389A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of activating a dopant element added to a semiconductor and of performing gettering processing by a short-time heat treatment. <P>SOLUTION: An amorphous semiconductor film is formed on a substrate, and then a metal element for promoting crystallization is added into the surface of the amorphous semiconductor film. Thereafter, a first heat treatment is applied to the amorphous semiconductor film so as to crystallize the amorphous semiconductor film into a semiconductor film having a crystal structure. Using a cooling gas, a first cooling process is conducted on the semiconductor film having the crystal structure. Thereafter, a second heat treatment is conducted on the semiconductor film having the crystal structure to remove the metal element from the semiconductor film having the crystal structure; and then, by using the cooling gas, a second cooling process is applied to the semiconductor film having the crystal structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat treatment method and a heat treatment apparatus to which the heat treatment method is applied. In particular, the present invention relates to a heat treatment apparatus for heating a substrate or a formed product on the substrate with a heated gas, and a heat treatment method using the same.

  In the manufacturing process of a semiconductor device, heat treatment for the purpose of oxidation, diffusion, gettering, recrystallization after ion implantation, etc. is incorporated into a semiconductor or a semiconductor substrate. A typical example of an apparatus for performing these heat treatments is a hot wall type horizontal or vertical furnace annealing furnace, which is widely used.

  A horizontal or vertical furnace annealing furnace is a batch-type apparatus that processes a large number of substrates at once. For example, in a vertical furnace annealing furnace, a substrate is placed horizontally and in parallel on a susceptor made of quartz, and is moved into and out of a reaction tube by an elevator that is driven up and down. A heater is installed on the outer periphery of the bell jar type reaction tube, and the substrate is heated by the heater. In view of this configuration, a relatively long time is required for the temperature raising time until the predetermined heating temperature is reached and the temperature lowering time for cooling to a temperature at which it can be taken out.

  By the way, MOS transistors and the like used in integrated circuits are required to have extremely high processing accuracy as elements are miniaturized. In particular, it is necessary to minimize the diffusion of impurities to form a shallow junction. However, the process that takes time to raise and lower the temperature as in the furnace annealing furnace described above makes it difficult to form a shallow junction.

  The Rapid Thermal Anneal (hereinafter referred to as RTA) method has been developed as a heat treatment technique for rapid heating and rapid cooling. The RTA apparatus rapidly heats a substrate or a formed material on the substrate using an infrared lamp or the like, and can perform heat treatment in a short time.

  As another form of transistor, a thin film transistor (hereinafter referred to as TFT) is known. TFTs have attracted attention as a technology that enables an integrated circuit to be formed directly on a glass substrate. The technology is being applied to new electronic devices such as liquid crystal display devices. In particular, TFTs that form impurity regions such as source and drain regions in a polycrystalline semiconductor film formed over a glass substrate require activation and heat treatment to alleviate strain. However, the glass substrate has only a strain point of about 600 to 700 ° C. and has a drawback that it is easily broken by thermal shock.

  In a conventional vertical or horizontal furnace annealing furnace, the heating temperature is increased when the size of the substrate is increased regardless of whether the substrate for forming the integrated circuit is a semiconductor or an insulating material such as glass or ceramic. It becomes difficult to ensure uniformity. In order to ensure the uniformity of the temperature within the substrate surface and between the substrates, it is necessary to widen the interval (pitch) between the substrates to be processed placed horizontally and in parallel from the characteristics of the gas flowing in the reaction tube. is there. For example, if one side of the substrate exceeds 500 mm, the substrate interval needs to be 30 mm or more.

  Therefore, when the substrate to be processed is enlarged, the apparatus is necessarily enlarged. In addition, since a large number of substrates are processed in a lump, the weight increases by itself, and it is necessary to make a susceptor for placing a substrate to be processed strong. For this reason, the weight increases, and the operation of the machine for carrying in / out the substrate to be processed becomes slow. In addition to increasing the floor area occupied by the heat treatment apparatus, it also affects the construction cost of the building in order to ensure the load resistance of the floor. Thus, the enlargement of the apparatus has a vicious circle.

  On the other hand, the RTA method is premised on single-wafer processing, and the load on the apparatus does not increase extremely. However, there is a difference in the absorptance of the lamp light used as the heating means depending on the characteristics of the substrate to be processed and the formed material thereon. For example, when a metal wiring pattern is formed on a glass substrate, the metal wiring is preferentially heated, causing a phenomenon in which the glass substrate is broken due to local distortion. Therefore, complicated control such as adjusting the temperature rising rate is required for heat treatment.

  The present invention aims to solve the above-described problems, and provides a method for activating and gettering an impurity element added to a semiconductor by a short time heat treatment, and a heat treatment apparatus capable of such heat treatment. The purpose is to do.

  In order to solve the above problems, the configuration of the heat treatment apparatus of the present invention includes n (n> 2) treatment chambers, preheating chambers, and cooling chambers for performing heat treatment, and is provided corresponding to each treatment chamber. A heat treatment apparatus for heating a substrate using a gas heated by the n heating means as a heat source, wherein a gas supply means is connected to a gas inlet of the cooling chamber, and an outlet of the cooling chamber is a heat exchanger And the inlet of the m-th (1 ≦ m ≦ (n−1)) processing chamber is connected to the outlet of the m-th gas heating means to connect to the first gas-heating means. An inlet of the chamber is connected to an outlet of the nth gas heating means, an outlet of the nth processing chamber is connected to a heat exchanger, and an outlet of the heat exchanger is a gas inlet of the preheating chamber It is the heat processing apparatus connected to.

  The number of processing chambers connected by gas pipes can be arbitrary. That is, another configuration of the heat treatment apparatus of the present invention includes n (n> 2) processing chambers and gas heating means, and introduces an m-th (1 ≦ m ≦ (n−1)) processing chamber. The inlet is connected to the outlet of the mth gas heating means, the inlet of the nth processing chamber is connected to the outlet of the nth gas heating means, and the outlet of the nth processing chamber is connected to the heat exchanger. It is a heat treatment apparatus for heating a substrate using a gas connected to and heated by a heating means as a heat source.

  By heating the substrate to be processed with the heated gas, the substrate can be heated with good uniformity without being affected by the material of the formed material. Accordingly, heat treatment can be performed without causing local distortion, and it becomes easy to complete the heat treatment by rapid heating even on a fragile substrate such as glass.

  By providing a preheating chamber and a cooling chamber in addition to the heat treatment chamber, useless energy consumption can be reduced. That is, by introducing a cold (approximately room temperature) gas supplied from the gas supply means into the cooling chamber, the substrate after the heat treatment can be cooled. As a result, the temperature of the gas rises, but by supplying this to the gas heating means via the heat exchanger, the thermal energy for heating the gas can be saved. In addition, by introducing high temperature gas discharged from the heat exchanger into the preheating chamber and heating the cooled substrate (about room temperature), the time required for heating in the processing chamber can be shortened, and the heating gas Temperature change can be reduced. Thereby, the thermal energy required for gas heating can be saved.

  The heat treatment method using the heat treatment apparatus having the above-described structure includes n (n> 2) treatment chambers for performing heat treatment, a preheating chamber, and a cooling chamber, and the gas heated by the n heating means is used as a heat source. A heat treatment method for heating a substrate as follows: a gas heated by an m-th (1 ≦ m ≦ (n−1)) heating means by n (n> 2) processing chambers and gas heating means The gas supplied to the m-th processing chamber is heated by the (m + 1) -th heating means and supplied to the (m + 1) -th processing chamber, and the substrate disposed in the n-th processing chamber is heated. The gas supplied to the nth processing chamber is supplied to the heat exchanger, used as a heat source for heating the gas supplied from the gas supply means, and the gas supplied from the gas supply means is supplied to the cooling chamber. The first gas heating hand passes the gas discharged from the cooling chamber through the heat exchanger. It is supplied to a heat treatment method characterized by supplying a gas discharged from the heat exchanger in the preheating chamber.

  By providing the preheating chamber and the cooling chamber, the time required for the heat treatment can be shortened. In addition, a large number of substrates can be processed efficiently by combining with a batch-type processing method that processes a plurality of substrates at once.

  As the gas applied in the present invention, an inert gas such as nitrogen or a rare gas, a reducing gas such as hydrogen, or an oxidizing gas such as oxygen, nitrous oxide, or nitrogen dioxide can be used.

  If an inert gas such as nitrogen or a rare gas is used, heat treatment for crystallization of the amorphous semiconductor film, heat treatment for gettering, ion implantation or ion doping (method of implanting ions without mass separation) It can be applied to heat treatment for the purpose of subsequent recrystallization and activation.

  When hydrogen diluted with hydrogen or an inert gas is used as a reducing gas such as hydrogen, hydrogenation treatment for compensating for defects (dangling bonds) in the semiconductor can be performed.

  When an oxidizing gas such as oxygen, nitrous oxide, or nitrogen dioxide is used, an oxide film can be formed over the semiconductor substrate or the semiconductor film.

  As described above, according to the present invention, the heat treatment of the substrate to be processed is not restricted by the shape or size of the substrate to be processed, and a robust susceptor is not required even if the substrate to be processed is enlarged. Therefore, the size can be reduced accordingly. The heat treatment method of the present invention and the heat treatment apparatus to which the heat treatment method is applied are a batch processing method, and a method of heating a substrate to be processed by a heated gas. Therefore, even if the substrate size is increased, heat treatment can be performed with good uniformity. It can also be applied to heat treatment of a substrate having a side length exceeding 1000 mm. Therefore, it is not necessary to use a large-scale heating means. Further, by providing the preheating chamber and the cooling chamber, it is possible to perform the preheating and cooling at the same time, thereby increasing the number of processed sheets per unit time.

  The heat treatment method of the present invention can be applied to heat treatment of a semiconductor substrate forming an integrated circuit, heat treatment of an insulating substrate on which a TFT is formed, heat treatment of a metal substrate, and the like. For example, it can be applied to heat treatment of a large mother glass substrate on which a TFT is formed. There is no need to increase the size of the jig for holding the substrate. Furthermore, crystallization of an amorphous semiconductor film, gettering, impurity activation, hydrogenation, semiconductor surface oxidation, and the like can be performed in a short time. Such processing can also be incorporated into the manufacturing process of the semiconductor element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a heat treatment apparatus to which the heat treatment method of the present invention is applied. The heat treatment apparatus of the present invention includes a plurality of gas supply means, a plurality of gas heating means, a plurality of processing chambers, a heat exchanger, a preheating chamber, and a cooling chamber.

  The gas supplied from the gas supply means 107 is introduced into the cooling chamber. In the cooling chamber, the substrate after the heat treatment is arranged for a certain period. The supplied gas contributes to lowering the temperature of the substrate, thereby increasing the temperature of the supplied gas at a temperature of about room temperature. If there is no substrate after the heat treatment, the gas passes through this chamber as it is.

  The gas discharged from the cooling chamber passes through the heat exchanger 108 and is supplied to the first gas heating means 111a or 112a. The first gas heating means 111a heats the gas to a predetermined temperature.

  The discharge port of the second gas heating means 111b is connected to an introduction port provided in the first processing chamber 101a by a gas pipe and supplies heated gas. In the first processing chamber 101a, there are provided a substrate holding means, a shower plate for spraying heated gas to the substrate, and the like. The supplied gas heats the substrate and is discharged from an outlet provided in the first processing chamber 101a.

  The treatment chamber is formed using quartz or ceramic in order to prevent contamination from the wall material when the heated gas is introduced. Further, when the size of the substrate is increased, it is difficult to form a processing chamber with quartz according to the size, and in this case, ceramic may be applied. The structure of the holding means is configured to minimize the contact area with the substrate. The gas supplied to the processing chamber 101a passes through the shower plate and is blown onto the substrate. Fine openings are formed in the shower plate at predetermined intervals so that the heated gas can be sprayed uniformly on the substrate. By providing the shower plate, the substrate can be heated with good uniformity even if the area of the substrate is increased.

  The structure of such a processing chamber is the same in the second processing chamber 101b, the third processing chamber 101c, the fourth processing chamber 101d, and the fifth processing chamber 101e.

  The gas discharged from the first processing chamber 101a is then supplied to the second processing chamber 101b and used again for heating the substrate. In this process, the temperature of the gas is lowered, so that the second gas heating means 111b controls the temperature so as to reach a predetermined temperature. The discharge port provided in the first processing chamber 101a and the introduction port of the second heating unit 111b are connected by a gas pipe, and the discharge port of the second heating unit 111b and the second processing chamber 101b are provided. It is connected to the inlet by a gas pipe. Although not shown, these gas pipes may be provided with heat retaining means.

  Similarly, the heated gas supplied to the second processing chamber 101b is used for heating the substrate, and then supplied to the third processing chamber 101c via the third gas heating means 111c. The gas supplied to the third processing chamber 101c and used for heating is supplied to the fourth processing chamber 101d via the four gas heating means 111d. The gas used for heating supplied to the fourth processing chamber 101d is supplied to the fifth processing chamber 101e through the fifth gas heating means 111e.

  The gas discharged from the fifth processing chamber 101e is supplied to the heat exchanger 108, and is used to heat the gas supplied from the cooling chamber 106 to the first gas heating means 111a. Further, it is then supplied to the preheating chamber 105 and used to heat the substrate disposed there.

  In FIG. 1, a heat treatment chamber 101 is connected to a first treatment chamber to a fifth treatment chamber via a gas heating means. The configuration of the heat treatment chambers 102, 103, and 104 is the same. With such a configuration, it is possible to perform heat treatment with different heating temperatures for each heat treatment chamber. Of course, the number to be connected is not limited and can be arbitrary.

  The substrates are installed one by one in one processing chamber. By connecting each processing chamber in series with a gas pipe and flowing a continuously heated gas, the amount of gas used can be saved, and the energy required for heating can be saved. .

  The heat exchanger 108 is provided to preheat the gas supplied from the first gas supply means 107 to the first gas heating means 111a in advance. The gas can be heated in advance by the heat of the gas discharged from each processing chamber.

  An example of this heat exchanger is shown in FIG. A high-temperature gas flows into the heat exchanger, and a pipe provided with fins as shown in the figure and a cold (usually about room temperature) gas flow in and pipes similarly provided with fins are installed. The casing 400 is filled with oil 403 as a medium for transferring heat. The fins are provided in order to improve the heat exchange efficiency. With such a configuration, the high-temperature gas transmits heat to the oil 403 and is discharged at a low temperature. The heat causes the cold gas to be heated by passing through the heat exchanger. Here, a simple example of the heat exchanger is shown, but the configuration of the heat exchanger applicable to the heat treatment apparatus according to the present invention is not limited to FIG. 5, and other configurations may be adopted.

  FIG. 4 shows an example of the configuration of the gas heating means. In FIG. 4, an endothermic body 303 is provided inside a cylinder 301 through which gas passes. The heat absorber 303 is made of high-purity titanium or tungsten, or silicon carbide, quartz, or silicon. The cylinder 301 is formed of translucent quartz or the like, and heats the heat absorbing body 303 by radiation of a light source 302 provided on the outside thereof. The gas is heated in contact with the endothermic body 303. However, by providing a light source outside the cylinder 301, contamination is prevented and the purity of the gas to be passed can be maintained. The inside of the housing 300 may be evacuated to increase the heat insulating effect.

  Next, an example of a heat treatment procedure using the heat treatment apparatus having the configuration shown in FIG. 1 will be described. The substrate placed in the preheating chamber 105 is heated to a predetermined temperature by the gas supplied from the heat exchanger 108. The heating temperature can be up to about 100 to 450 ° C. For example, when heated to 450 ° C., dehydrogenation treatment of the amorphous silicon film formed on the substrate is possible. Then, the substrate heated in the preheating chamber 105 is moved to each of the processing chambers 101a to 101e of the heat treatment chamber 101, where heat treatment is performed. The heating temperature is heated to a predetermined temperature by the first to fifth gas heating means 111a to 111e.

  After the heat treatment for a certain time is completed, the substrate is moved to the cooling chamber 106. A room temperature gas supplied from the gas supply means 107 is supplied to the cooling chamber 106, whereby the substrate is cooled. Accordingly, the heat-treated substrate disposed in the cooling chamber 106 can be rapidly cooled. Also, the gas absorbs the heat of the substrate and rises to a temperature above room temperature. This gas is further heated by the heat exchanger 108 and then supplied to the first heating means 111a. The substrate cooled to a predetermined temperature is collected.

  By providing the preheating chamber and the cooling chamber, it is possible to perform preheating and cooling at the same time, and the number of processed sheets per unit time can be increased.

  In order to save the amount of gas used and improve the thermal efficiency, it is desirable to reduce the internal volume of the processing chamber as much as possible. The dimensions in the processing chamber are determined by the size of the substrate and the operating range of the transfer means for taking in and out the substrate. Since the transfer means requires an operation range of about 10 mm in order to take in and out the substrate, one dimension of the processing chamber is determined by the thickness of the substrate and the minimum operation range of the transfer means.

  The heat treatment method of the present invention and the heat treatment apparatus to which the heat treatment method is applied are premised on batch-type treatment, but the substrate to be treated is heated directly by heating the gas. The substrate to be processed can be quickly cooled by cooling it with a gas at room temperature. Of course, care must be taken when using a substrate that is vulnerable to thermal shock, such as glass, but unlike in the case of conventional RTA, the substrate is destroyed by rapid heating, unlike instantaneous heating of several microseconds to seconds. There is no end to it.

  The gas used for heating or cooling can be selected depending on the application of heat treatment. If an inert gas such as nitrogen or a rare gas is used, heat treatment for crystallization of the amorphous semiconductor film, heat treatment for gettering, ion implantation or ion doping (method of implanting ions without mass separation) It can be applied to heat treatment for the purpose of subsequent recrystallization and activation. When hydrogen diluted with hydrogen or an inert gas is used as a reducing gas such as hydrogen, hydrogenation treatment for compensating for defects (dangling bonds) in the semiconductor can be performed. When an oxidizing gas such as oxygen, nitrous oxide, or nitrogen dioxide is used, an oxide film can be formed over the semiconductor substrate or the semiconductor film.

  The heat treatment apparatus to which the heat treatment method of the present invention described above is applied can be applied to heat treatment of various objects to be processed. For example, the present invention can be applied to a heat treatment of a semiconductor substrate forming an integrated circuit, a heat treatment of an insulating substrate on which a TFT is formed, a heat treatment of a metal substrate, and the like. For example, it can be applied to heat treatment of a glass substrate on which a TFT is formed. Even if the substrate size is not only 600 × 720 mm but also 1200 × 1600 mm, the substrate can be heated with good uniformity. Further, it is not necessary to increase the size of the jig for holding the substrate.

  FIG. 2 shows an embodiment of the heat treatment apparatus of the present invention. In FIG. 2, a first gas heating means 208 is provided corresponding to the first processing chamber 201, and a second gas heating means 209 is provided corresponding to the second processing chamber 202. The processing chamber 203 is provided with a third gas heating means 210 correspondingly, the fourth processing chamber 204 is provided with a fourth gas heating means 211 and the fifth processing chamber 205 is provided with a Five gas heating means 212 are provided correspondingly. In addition, a first gas supply unit 206, a second gas supply unit 207, and a heat exchanger 213 are provided, and these pipes have the same configuration as the heat treatment apparatus described in the embodiment.

  The first gas supply means 206 supplies a gas for heating, and is supplied to the heat exchanger 213 through a cooling chamber (not shown) here. Further, the gas discharged from the heat exchanger 213 is supplied to a preheating chamber (not shown).

  In each processing chamber, the substrate 218 held in the cassette 217 is transferred by the transfer means 216 and placed on the holding means 215. Each processing chamber takes in and out the substrate by opening and closing the gate valve.

  FIG. 3 shows a configuration of a heat treatment apparatus having a plurality of treatment chambers. Heat treatment chambers 501 and 502, first gas supply means 506 and 509, second gas supply means 507 and 510, and gas heating means 508 and 511 are provided. The heat treatment chambers 501 and 502 are stacked in a plurality of stages, and gas heating means are provided correspondingly. Such a configuration may be referred to FIG. A preheating chamber 520 and a cooling chamber 530 are vertically arranged between the heat treatment chambers 501 and 502. The cassettes 505a to 505c are applied when holding and transporting the substrate. The substrate is used to move between the cassettes 505 a to 505 c, the processing chambers 501 and 502, the preheating chamber 520, and the cooling chamber 530 by the transport unit 504.

  The number of processing chambers can be determined by the time required for the heat treatment and the operation speed of the transfer means (that is, the speed at which the substrate can be moved). If the tact time is about 10 minutes, 3 to 10 stages can be installed in the processing chambers 501 and 502.

  FIG. 5 shows an example of the configuration of the heat treatment apparatus based on the mass batch processing method, but it is not necessary to be limited to this configuration and arrangement, and any other arrangement can be adopted. Since the heat treatment apparatus shown in this embodiment is a batch processing method and heats a substrate to be processed with a heated gas, heat treatment can be performed with good uniformity even if the size of the substrate is increased. For example, the present invention can be applied to a heat treatment of a substrate having a side length exceeding 1000 mm.

  Such a heat treatment method and a heat treatment apparatus using the heat treatment method of the present invention are not limited by the form and size of the substrate to be processed. The single wafer processing does not require a robust susceptor even if the substrate to be processed is enlarged, and the size can be reduced accordingly. Further, the heating means does not need a large scale, and power consumption can be saved.

  An example in which heat treatment accompanying crystallization and gettering of a semiconductor film is performed using the heat treatment method of the present invention and a heat treatment apparatus to which the heat treatment method is applied will be described with reference to FIG.

In FIG. 8A, the material of the substrate 600 is not particularly limited; however, barium borosilicate glass, aluminoborosilicate glass, quartz, or the like can be preferably used. An inorganic insulating film having a thickness of 10 to 200 nm is formed on the surface of the substrate 600 as the blocking layer 601. An example of a suitable blocking layer is a silicon oxynitride film manufactured by a plasma CVD method, and a first silicon oxynitride film manufactured from SiH ₄ , NH ₃ , and N ₂ O is formed to a thickness of 50 nm, A second silicon oxynitride film formed from SiH ₄ and N ₂ O and having a thickness of 100 nm is applied. The blocking layer 601 is provided so that the alkali metal contained in the glass substrate does not diffuse into the semiconductor film formed thereon, and can be omitted when quartz is used as the substrate.

For the semiconductor film (first semiconductor film) 602 having an amorphous structure formed over the blocking layer 601, a semiconductor material containing silicon as a main component is used. Typically, an amorphous silicon film, an amorphous silicon germanium film, or the like is applied, and the film is formed to a thickness of 10 to 100 nm by a plasma CVD method, a low pressure CVD method, or a sputtering method. In order to obtain high-quality crystals, the concentration of impurities such as oxygen and nitrogen contained in the semiconductor film 502 having an amorphous structure is preferably reduced to 5 × 10 ¹⁸ / cm ³ or less. These impurities interfere with the crystallization of the amorphous semiconductor, and also increase the density of trapping centers and recombination centers even after crystallization. For this purpose, it is desirable not only to use a high-purity material gas, but also to use an ultrahigh vacuum-compatible CVD apparatus equipped with a mirror surface treatment (electropolishing treatment) in the reaction chamber and an oil-free vacuum exhaust system.

  After that, a catalytic metal element that promotes crystallization is added to the surface of the semiconductor film 602 having an amorphous structure. Metal elements having a catalytic action for promoting crystallization of semiconductor films include iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), and osmium (Os). , Iridium (Ir), platinum (Pt), copper (Cu), gold (Au), etc., and one or more selected from these can be used. Typically, nickel is used, and a catalyst-containing layer 603 is formed by applying a nickel acetate salt solution containing 1 to 100 ppm of nickel in terms of weight with a spinner. Crystallization can be performed in a shorter time as the nickel content increases.

  In this case, in order to improve the familiarity of the solution, as the surface treatment of the semiconductor film 602 having an amorphous structure, an extremely thin oxide film is formed with an ozone-containing aqueous solution, and the oxide film is formed using hydrofluoric acid and hydrogen peroxide solution. After etching with the mixed solution, a clean surface is formed, and then an ultrathin oxide film is formed again by treatment with an aqueous solution containing ozone. Since the surface of the semiconductor film such as silicon is inherently hydrophobic, the nickel acetate salt solution can be uniformly applied by forming the oxide film in this way.

  Needless to say, the catalyst-containing layer 603 is not limited to such a method, and may be formed by sputtering, vapor deposition, plasma treatment, or the like. Further, the catalyst-containing layer 603 may be formed before forming the semiconductor film 602 having an amorphous structure, that is, on the blocking layer 601.

  A heat treatment for crystallization is performed while the semiconductor film 602 having an amorphous structure and the catalyst-containing layer 603 are kept in contact with each other. For the heat treatment, a heat treatment apparatus having the structure shown in FIG. 1 is used. FIG. 6 is a graph for explaining the heat treatment process. Hereinafter, the heat treatment process will be described with reference to the graph.

  Nitrogen, argon, or the like can be used as the heating gas. The substrate 600 on which the amorphous semiconductor film is formed is transferred from the cassette to the preheating chamber by the transfer means, and heated to a predetermined temperature in advance. Then, it moves to a processing chamber and closes a gate valve. After the gate valve is closed, heated nitrogen is flowed and the reaction tube is heated while being filled with nitrogen.

  Then, the nitrogen flow rate is increased, and the nitrogen gas supplied by the gas heating means is heated to the first temperature. The heating temperature can be adjusted by the power supplied to the heating element or the supply amount of the power and nitrogen. Here, the substrate is heated to 550 ± 50 ° C. as the first temperature (step of temperature increase 1 shown in FIG. 6). The time required to raise the temperature is only 2 minutes.

  When the substrate reaches the first temperature, the state is maintained for 3 minutes. At this stage, crystal nuclei are formed in the amorphous semiconductor film (nucleation stage shown in FIG. 6). Thereafter, it is heated to a second temperature for crystallization. The substrate is heated by setting the heating nitrogen gas to 675 ± 25 ° C. (step of temperature increase 2 shown in FIG. 6). When the second temperature is reached, the temperature is maintained for 5 minutes to perform crystallization (crystallization stage shown in FIG. 6). Of course, the nitrogen gas for heating is continuously supplied for the period up to now.

  When the predetermined time has passed, the supply of the heating nitrogen gas is stopped, and the cooling nitrogen gas is supplied. It may be nitrogen gas at room temperature. Then, the substrate is rapidly cooled (step of temperature decrease shown in FIG. 6). This time is about 3 minutes. When the substrate cools to about 300 ° C., the substrate is taken out of the processing chamber by the transfer means and transferred to the cooling chamber. Here, the substrate is further cooled to 150 ° C. or lower, and the transfer stage shown in FIG. 6). Then, the heat treatment for crystallization is completed by transferring the substrate to the cassette.

  The time from carrying the substrate into the heat treatment apparatus and taking it out after heat treatment is 13 minutes. Thus, by using the heat treatment apparatus and heat treatment method of the present invention, the heat treatment for crystallization can be performed in a very short time.

  In this manner, a semiconductor film (first semiconductor film) 604 having a crystal structure illustrated in FIG. 8B can be obtained.

In order to further increase the crystallization rate (the ratio of crystal components in the total volume of the film) and repair defects remaining in the crystal grains, a semiconductor film 604 having a crystal structure as shown in FIG. It is also effective to irradiate with laser light. As the laser, excimer laser light having a wavelength of 400 nm or less, and second and third harmonics of a YAG laser are used. In any case, a pulse laser beam having a repetition frequency of about 10 to 1000 Hz is used, and the laser beam is condensed to 100 to 400 mJ / cm ² by an optical system and has a crystal structure with an overlap ratio of 90 to 95%. Laser treatment may be performed on the semiconductor film 604.

A catalytic element (nickel here) remains in the semiconductor film (first semiconductor film) 605 having a crystal structure thus obtained. Although it is not uniformly distributed in the film, it remains at a concentration exceeding 1 × 10 ¹⁹ / cm ³ if it is an average concentration. Of course, various semiconductor elements including TFTs can be formed even in such a state, but the element is removed by gettering by the method described below.

  First, as shown in FIG. 8D, a thin barrier layer 606 is formed on the surface of a semiconductor film 605 having a crystal structure. Although the thickness of a barrier layer is not specifically limited, You may substitute for the chemical oxide formed simply by processing with ozone water. Similarly, chemical oxide can be formed by treatment with an aqueous solution in which sulfuric acid, hydrochloric acid, nitric acid or the like and hydrogen peroxide are mixed. As another method, the oxidation treatment may be performed by generating ozone by plasma treatment in an oxidizing atmosphere or ultraviolet irradiation in an oxygen-containing atmosphere. Alternatively, a thin oxide film may be formed by heating to about 200 to 350 ° C. using a clean oven to form a barrier layer. Alternatively, a barrier layer may be formed by depositing an oxide film of about 1 to 5 nm by plasma CVD, sputtering, vapor deposition, or the like.

  A semiconductor film (second semiconductor film) 607 is formed thereon with a thickness of 25 to 250 nm by plasma CVD or sputtering. Typically, an amorphous silicon film is selected. Since this semiconductor film 607 is removed later, it is desirable that the semiconductor film 607 be a film having a low density in order to increase the selection ratio between the semiconductor film 605 having a crystal structure and etching. For example, when an amorphous silicon film is formed by a plasma CVD method, the substrate temperature is set to about 100 to 200 ° C., and 25 to 40 atomic% of hydrogen is contained in the film. The same applies to the case where the sputtering method is employed, and a large amount of hydrogen can be contained in the film by sputtering with a mixed gas of argon and hydrogen at a substrate temperature of 200 ° C. or lower. In addition, when a rare gas element is added during film formation by sputtering or plasma CVD, the rare gas element can be simultaneously incorporated into the film. A gettering site can be formed even with the rare gas element thus taken in.

Thereafter, a rare gas element is added to the semiconductor film 607 at a concentration of 1 × 10 ^{20 to} 3 × 10 ²² / cm ³ by ion doping or ion implantation. Although the acceleration voltage is arbitrary, since it is a rare gas element, ions of the rare gas implanted may pass through the semiconductor film 607 and the barrier layer 606 and partly reach the semiconductor film 605 having a crystal structure. Absent. Since the rare gas element itself is inactive in the semiconductor film, even if there is a region containing a concentration of about 1 × 10 ¹³ to 1 × 10 ²⁰ / cm ³ near the surface of the semiconductor film 605, There is no significant effect on device characteristics. Further, a rare gas element may be added at the stage of forming the semiconductor film 607.

  As the rare gas element, one or more selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) are used. In the present invention, in order to form a gettering site, these rare gas elements are used as an ion source and implanted into a semiconductor film by an ion doping method or an ion implantation method. There are two meanings of implanting ions of these rare gas elements. One is to form a dangling bond by implantation to give distortion to the semiconductor film, and the other is to give distortion by implanting the ions between the lattices of the semiconductor film. Implanting inert gas ions can satisfy both of these simultaneously, but the latter is particularly noticeable when using an element with a larger atomic radius than silicon, such as argon (Ar), krypton (Kr), and xenon (Xe). It is done.

  In order to reliably achieve gettering, it is necessary to perform heat treatment thereafter. FIG. 7 is a graph illustrating the heat treatment process, which will be described below with reference to the graph. Similarly, the heat treatment apparatus of the present invention is used for the heat treatment. In order to efficiently process a large number of substrates, it is desirable to use an apparatus configured as shown in FIG. Nitrogen, argon, or the like can be used as the heating gas.

  The substrate 600 on which the structure of FIG. 8D is formed is set from the cassette into the reaction tube by the transfer means, and then the gate valve is closed. In the meantime, it is considered that nitrogen is continuously supplied from the gas supply means into the reaction tube to minimize the mixing of outside air. After closing the gate valve, the nitrogen flow rate is increased and the reaction tube is filled with nitrogen to replace it.

  Then, the nitrogen flow rate is increased, and the nitrogen gas supplied by the gas heating means is heated to the third temperature. The heating temperature can be adjusted by the power supplied to the heating element or the supply amount of the power and nitrogen. Here, the third temperature is set to 675 ± 25 ° C., and the substrate is heated (the temperature rising stage shown in FIG. 7). The time required to raise the temperature is 2 minutes.

  When the substrate reaches the third temperature, the state is maintained for 3 minutes. As a result, gettering is performed (step of gettering shown in FIG. 7). In the gettering, the catalytic element in the gettering region (capture site) is released by thermal energy and moves to the gettering site by diffusion. Accordingly, the gettering depends on the processing temperature, and the gettering proceeds in a shorter time as the temperature is higher. As shown by an arrow in FIG. 8E, the direction in which the catalyst element moves is a distance of about the thickness of the semiconductor film, and gettering is completed in a relatively short time.

  When the predetermined time has passed, the supply of the heating nitrogen gas is stopped and the cooling nitrogen gas is supplied. It can be nitrogen gas at room temperature. Then, the substrate is rapidly cooled (step of temperature decrease shown in FIG. 7). This time is about 3 minutes. When the substrate cools to about 300 ° C., the substrate is taken out of the processing chamber by the transfer means, and the substrate is transferred to the buffer cassette. Here, the substrate is further cooled to 150 ° C. or lower, and the transfer stage shown in FIG. 7). Then, the heat treatment for gettering is completed by transferring the substrate to the cassette.

  It takes 9 minutes to carry the substrate into the heat treatment apparatus, heat treat it, and take it out. As described above, the heat treatment for gettering can be performed in a very short time by using the heat treatment apparatus and the heat treatment method of the present invention.

Note that the semiconductor film 607 containing a rare gas element at a concentration of 1 × 10 ²⁰ / cm ³ or more is not crystallized even by this heat treatment. This is presumably because the rare gas element remains in the film without being re-emitted even in the above processing temperature range and inhibits crystallization of the semiconductor film.

Thereafter, the amorphous semiconductor 607 is selectively etched and removed. As an etching method, dry etching without using plasma with ClF ₃ , or an aqueous solution containing hydrazine or tetraethylammonium hydroxide (chemical formula (CH ₃ ) ₄ NOH) at a concentration of 20 to 30%, preferably 25%, It can be easily removed by heating to 50 ° C. At this time, the barrier layer 606 becomes an etching stopper and remains almost unetched. The barrier layer 606 may then be removed with hydrofluoric acid.

Thus, a semiconductor film 608 having a crystal structure in which the concentration of the catalytic element is reduced to 1 × 10 ¹⁷ / cm ³ or less as shown in FIG. 8F can be obtained. The thus formed semiconductor film 608 having a crystal structure is formed as a thin rod-like or thin flat rod-like crystal by the action of the catalytic element, and each crystal grows in a specific direction as viewed macroscopically. The semiconductor film 608 having such a crystal structure can be applied not only to the active layer of a TFT but also to a photoelectric conversion layer of a photosensor or a solar cell.

  A method for manufacturing a TFT using a semiconductor film manufactured according to Embodiment 2 will be described with reference to FIGS. In the TFT manufacturing process described in this embodiment, the heat treatment method and heat treatment apparatus of the present invention can be used.

  First, in FIG. 9A, semiconductor films 702 and 703 which are separated into island shapes from the semiconductor film manufactured in Example 2 over a light-transmitting substrate 700 made of aluminoborosilicate glass or barium borosilicate glass. Form. Further, between the substrate 700 and the semiconductor film, a first insulating film 701 in which one or a plurality selected from silicon nitride, silicon oxide, and silicon nitride oxide is combined is formed with a thickness of 50 to 200 nm.

Thereafter, as shown in FIG. 9B, a second insulating film 704 is formed with a thickness of 80 nm. The second insulating film 704 is used as a gate insulating film and is formed using a plasma CVD method or a sputtering method. As the second insulating film 704, a silicon oxynitride film formed by adding O ₂ to SiH ₄ and N ₂ O can reduce the fixed charge density in the film and is a preferable material for the gate insulating film. Needless to say, the gate insulating film is not limited to such a silicon oxynitride film, and an insulating film such as a silicon oxide film or a tantalum oxide film may be used as a single layer or a stacked structure.

  A first conductive film for forming a gate electrode is formed over the second insulating film 704. There is no limitation on the type of the first conductive film, but a conductive material such as aluminum, tantalum, titanium, tungsten, molybdenum, or an alloy thereof can be used. As a structure of the gate electrode using such a material, a stacked structure of tantalum nitride or titanium nitride and tungsten or molybdenum tungsten alloy, a stacked structure of tungsten and aluminum, or copper can be employed. In the case of using aluminum, a material to which 0.1 to 7% by weight of titanium, scandium, neodymium, silicon, copper, or the like is added in order to improve heat resistance is used. The first conductive film is formed with a thickness of 300 nm.

  Thereafter, a resist pattern is formed, and gate electrodes 705 and 706 are formed. Although not shown, a wiring connected to the gate electrode can be formed at the same time.

As shown in FIG. 9C, an n-type semiconductor region is formed in a self-aligning manner using this gate electrode as a mask. For doping, phosphorus is implanted by an ion implantation method or an ion doping method (herein, a method of implanting ions that are not mass-separated). The phosphorus concentration in this region is in the range of 1 × 10 ²⁰ to 1 × 10 ²¹ / cm ³ .

Subsequently, as illustrated in FIG. 9D, a mask 709 that covers one semiconductor film 703 is formed, and a p-type semiconductor region 710 is formed in the semiconductor film 702. Boron is used as an impurity to be added, and is added at a concentration 1.5 to 3 times that of phosphorus in order to invert the n-type. The phosphorus concentration in this region is in the range of 1.5 × 10 ^{20 to} 3 × 10 ²¹ / cm ³ .

  Thereafter, as shown in FIG. 9E, a third insulating film 711 made of a silicon oxynitride film or a silicon nitride film is formed to a thickness of 50 nm by plasma CVD.

  Then, heat treatment is performed to recover and activate the crystallinity of the n-type and p-type semiconductor regions. The heat treatment is performed in substantially the same manner as in FIG. The fourth temperature suitable for activation is 450 ± 50 ° C., and heat treatment may be performed for 1 to 10 minutes.

  Nitrogen, argon, or the like can be used as the heating gas. The activation is performed by heating the gas to a temperature of 500 ° C. and performing a heat treatment for 3 minutes. Alternatively, a reducing atmosphere in which hydrogen is added to the gas may be used. Hydrogenation can also be performed simultaneously with the added hydrogen.

  The substrate is transferred from the cassette to the preheating chamber by the conveying means, and heated to a predetermined temperature in advance. Then, it moves to a processing chamber and closes a gate valve. After the gate valve is closed, heated nitrogen is flowed and the reaction tube is heated while being filled with nitrogen. Thereafter, the time from when the substrate is carried into the processing chamber and after the heat treatment is taken out is about 8 to 9 minutes even if the time required for temperature rise is 2 minutes and the time required for cooling is 3 minutes. Thus, by using the heat treatment apparatus and heat treatment method of the present invention, the heat treatment for activation can be performed in a very short time.

  When heat treatment by the RTA method is performed in a state where the gate electrode is formed on the glass substrate, the gate electrode selectively absorbs the radiation of the lamp light and is locally heated to damage the glass substrate. There is a case. Since the heat treatment according to the present invention is heating by gas, there is no such influence.

  The fourth insulating film 712 illustrated in FIG. 9F is formed using a silicon oxide film or silicon oxynitride. Alternatively, the surface may be planarized by forming with an organic insulating material such as polyimide or acrylic.

  Next, a contact hole reaching the impurity region of each semiconductor film from the surface of the fourth insulating film 712 is formed, and wiring is formed using Al, Ti, Ta, or the like. In FIG. 9F, reference numerals 713 and 714 denote source lines or drain electrodes. Thus, an n-channel TFT and a p-channel TFT can be formed. Although each TFT is shown here as a single unit, a CMOS circuit, NMOS circuit, or PMOS circuit can be formed using these TFTs.

  In the heat treatment method of the present invention and the heat treatment apparatus to which the heat treatment method is applied, an inert gas and a kind selected from oxygen, nitrous oxide, and nitrogen dioxide are mixed into the gas to be heated to obtain an oxidizing gas. An oxide film can be formed on the surface.

  FIG. 10 shows an example. A field oxide film for element isolation or gate insulation is formed on a single crystal silicon substrate by mixing 1 to 30% of oxygen with nitrogen as a heating gas and performing heat treatment at 700 to 850 ° C. A film can be formed.

  10A, an n well 802 and a p well 803 are formed on a substrate 801 made of single crystal silicon having a relatively high resistance (eg, n-type, about 10 Ωcm). Thereafter, the field oxide film 805 is formed by using the heat treatment method of the present invention using a mixed gas of oxygen and nitrogen as a heating gas. At this time, boron (B) may be selectively introduced into the semiconductor substrate by an ion implantation method to form a channel stopper. The heating temperature is 700 to 850 ° C.

  Similarly, a silicon oxide film 806 to be a gate insulating film is formed. The apparatus used for forming the field oxide film 805 and the silicon oxide film 806 is an apparatus having the structure shown in FIG.

Subsequently, as shown in FIG. 10B, a polycrystalline silicon film for gate is formed with a thickness of 100 to 300 nm by a CVD method. The polycrystalline silicon film for the gate may be doped with phosphorus (P) at a concentration of about 10 ²¹ / cm ³ in advance in order to reduce the resistance, or may be concentrated after the polycrystalline silicon film is formed. An n-type impurity may be diffused. Here, in order to further reduce the resistance, a silicide film is formed with a thickness of 50 to 300 nm on the polycrystalline silicon film. As the silicide material, molybdenum silicide (MoSix), tungsten silicide (WSix), tantalum silicide (TaSix), titanium silicide (TiSix), or the like can be used. The silicide material may be formed according to a known method. Then, the polycrystalline silicon film and the silicide film are etched to form gates 807 and 808. The gates 807 and 808 are formed of polycrystalline silicon films 807a and 808a and silicide films 807b and 808b.
It has a two-layer structure.

  Thereafter, as shown in FIG. 10C, the source and drain regions 820 of the n-channel MOS transistor and the source and drain regions 824 of the p-channel MOS transistor are formed by ion implantation. Of course, the heat treatment method and heat treatment apparatus of the present invention can also be applied to heat treatment for recrystallization and activation of these source and drain regions. The heating nitrogen gas is heated by a heating means so that the heating temperature is 700 to 850 ° C, preferably 850 ° C. By this heat treatment, the impurities are activated and the resistance of the source and drain regions is reduced.

  In this way, an n-channel MOS transistor 831 and a p-channel MOS transistor 830 are completed. The structure of the transistor described in this embodiment is merely an embodiment, and the present invention is not necessarily limited to the manufacturing process and structure illustrated in FIGS. A CMOS circuit, an NMOS circuit, or a PMOS circuit can be formed using these transistors. Various circuits such as a shift register, a buffer, sampling, a D / A converter, and a latch can be formed, and a semiconductor device such as a memory, a CPU, a gate array, and a RISC can be manufactured. Such a circuit can be operated at high speed by being composed of MOS, and can reduce power consumption by setting the drive voltage to 3 to 5V.

The cross-section figure which shows one Embodiment of the heat processing apparatus to which the heat processing method of this invention is applied. The cross-section figure which shows one Embodiment of the heat processing apparatus to which the heat processing method of this invention is applied. The layout figure which shows one Embodiment of the heat processing apparatus to which the heat processing method of this invention is applied. The figure explaining an example of the gas heating means applicable to the heat processing apparatus of this invention. The figure explaining an example of the heat exchanger applicable to the heat processing apparatus of this invention. The graph explaining the change of the substrate temperature in the crystallization process using the heat processing method of this invention. The graph explaining the change of the substrate temperature in the gettering process using the heat treatment method of the present invention. Sectional drawing explaining the manufacturing process of a semiconductor film to which the heat processing method and heat processing apparatus of this invention are applied. Sectional drawing explaining the manufacturing process of TFT to which the heat processing method and heat processing apparatus of this invention are applied. Sectional drawing explaining the heat processing process of the semiconductor substrate to which the heat processing method and heat processing apparatus of this invention are applied.

Explanation of symbols

101, 102, 103, 104 Heat treatment chamber 105 Preheating chamber 106 Cooling chamber 107 Gas supply means 108 Heat exchangers 111a to 111e Gas heating means 112a to 112e Gas heating means 113a to 113e Gas heating means 114a to 114e Gas heating means

Claims (12)

Forming an amorphous semiconductor film on the substrate;
A metal element that promotes crystallization is added to the surface of the amorphous semiconductor film;
By performing a first heat treatment on the amorphous semiconductor film, the amorphous semiconductor film is crystallized to form a semiconductor film having a crystal structure,
First cooling the semiconductor film having the crystal structure using a cooling gas,
By performing a second heat treatment on the semiconductor film having a crystal structure, the metal element is removed from the semiconductor film having the crystal structure,
A method for manufacturing a semiconductor device, characterized in that second cooling is performed on the semiconductor film having the crystal structure by using a cooling gas. Forming a first amorphous semiconductor film on a substrate;
Adding a metal element that promotes crystallization to the surface of the first amorphous semiconductor film;
A first heat treatment is performed on the first amorphous semiconductor film to crystallize the first amorphous semiconductor film to form a semiconductor film having a crystal structure;
First cooling the semiconductor film having the crystal structure using a cooling gas,
Forming a second amorphous semiconductor film on the semiconductor film having the crystal structure;
A second heat treatment is performed, and the metal element that promotes crystallization is transferred from the semiconductor film having the crystal structure to the second amorphous semiconductor film by diffusion;
A method for manufacturing a semiconductor device, characterized in that second cooling is performed on the semiconductor film having the crystal structure by using a cooling gas. Forming a first amorphous semiconductor film on a substrate;
Adding a metal element that promotes crystallization to the surface of the first amorphous semiconductor film;
A first heat treatment is performed on the first amorphous semiconductor film to crystallize the first amorphous semiconductor film to form a semiconductor film having a crystal structure;
First cooling the semiconductor film having the crystal structure using a cooling gas,
Forming a barrier layer on the semiconductor film having the crystal structure;
Forming a second amorphous semiconductor film on the barrier layer;
Performing a second heat treatment to move the metal element that promotes crystallization by diffusion from the semiconductor film having the crystal structure to the second amorphous semiconductor film through the barrier layer;
A method for manufacturing a semiconductor device, characterized in that second cooling is performed on the semiconductor film having the crystal structure by using a cooling gas. Forming a first amorphous semiconductor film on a substrate;
Adding a metal element that promotes crystallization to the surface of the first amorphous semiconductor film;
A first heat treatment is performed on the first amorphous semiconductor film to crystallize the first amorphous semiconductor film to form a semiconductor film having a crystal structure;
First cooling the semiconductor film having the crystal structure using a cooling gas,
Irradiating the semiconductor film having the crystal structure with a laser,
Forming a barrier layer on the semiconductor film having the crystal structure;
Forming a second amorphous semiconductor film on the barrier layer;
Performing a second heat treatment to move the metal element that promotes crystallization by diffusion from the semiconductor film having the crystal structure to the second amorphous semiconductor film through the barrier layer;
A method for manufacturing a semiconductor device, characterized in that second cooling is performed on the semiconductor film having the crystal structure by using a cooling gas. Forming an inorganic insulating film on the substrate;
Forming a first amorphous semiconductor film on the inorganic insulating film;
Adding a metal element that promotes crystallization to the surface of the first amorphous semiconductor film;
A first heat treatment is performed on the first amorphous semiconductor film to crystallize the first amorphous semiconductor film to form a semiconductor film having a crystal structure;
First cooling the semiconductor film having the crystal structure using a cooling gas,
Irradiating the semiconductor film having the crystal structure with a laser,
Forming a barrier layer on the semiconductor film having the crystal structure;
Forming a second amorphous semiconductor film on the barrier layer;
Performing a second heat treatment to move the metal element that promotes crystallization by diffusion from the semiconductor film having the crystal structure to the second amorphous semiconductor film through the barrier layer;
A method for manufacturing a semiconductor device, characterized in that second cooling is performed on the semiconductor film having the crystal structure by using a cooling gas.   6. The method for manufacturing a semiconductor device according to claim 2, wherein a rare gas element is added to the second amorphous semiconductor film by an ion doping method or an ion implantation method.   7. The method for manufacturing a semiconductor device according to claim 1, wherein nitrogen gas or a rare gas is used as the cooling gas.   In any one of Claims 1 thru | or 7, As the metal element which accelerates | stimulates the crystallization, 1 type selected from Ni, Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu or Au, or A method for manufacturing a semiconductor device, wherein a plurality of types of metal elements are used.   9. The method for manufacturing a semiconductor device according to claim 1, wherein a solution containing the metal element that promotes crystallization is applied.   9. The method for manufacturing a semiconductor device according to claim 1, wherein the metal element that promotes crystallization is added by a sputtering method, an evaporation method, or a plasma treatment.   11. The method for manufacturing a semiconductor device according to claim 1, wherein a heated gas is used as the first heat treatment and the second heat treatment.   12. The method for manufacturing a semiconductor device according to claim 11, wherein nitrogen or argon gas is used as the heated gas.

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