JP4026619B2 - Semiconductor device storage method and semiconductor device manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing and storing a semiconductor device and a method for manufacturing a semiconductor device, and more particularly to a method for storing a pod replaced with an inert gas.

  In general, a semiconductor device is manufactured by performing a number of processes such as etching, film deposition, and ion implantation on a semiconductor substrate, a glass substrate, or the like. However, since the processing capacity of the manufacturing facility differs depending on the type of manufacturing process, a substrate waiting for processing stays in a manufacturing facility with low processing capacity.

  If the semiconductor device is left as it is, particles and chemical contaminants in the clean room adhere to the surface of the semiconductor device. In addition, a natural oxide film may be formed on the surface of the semiconductor device due to oxygen in the air while waiting for processing, which may adversely affect electrical characteristics.

  In order to avoid such inconvenience, the semiconductor device staying in the manufacturing process has been conventionally stored in a cassette carrier, placed in a carrier box, and stored in a storage (clean stocker).

  At present, miniaturization has progressed, and it becomes difficult to ensure cleanliness simply by storing the carrier box in a storage. Further, with the increase in the substrate diameter, pods such as BOUP (Bottom Opening Unified Pod) and FOUP (Front Opening) The storage method using Unified Pod has been shifted.

  Pods are superior in airtightness and cleanliness compared to conventional carrier boxes. As a result, the storage itself is not required to have a high degree of cleanliness. Moreover, the process itself stored in the storage was reduced.

  However, the semiconductor device manufacturing process includes processes that require a higher degree of cleanness than usual, such as a gate oxide film forming process and a wiring forming process.

  For those processes that require high cleanliness, replace the inside of the pod with an inert gas and store it, or supply a pod with an inert gas supply port and exhaust port to allow a certain amount of inert gas to flow. Circulating methods are used.

  Patent Document 1 discloses a semiconductor device storage method using a FOUP having a gas supply port and a gas suction port on the bottom surface and a gas inlet on the door surface.

  The FOUP is mounted on a load port device having a gas supply means for supplying an inert gas and an exhaust means, and the inside of the FOUP is forcibly exhausted to a negative pressure by the exhaust means, and then the inert gas is discharged from the gas supply means. Supply in FOUP. At this time, the negative pressure state in the FOUP is maintained at a lower pressure than the outside.

Next, the FOUP is stored in a storage box in which a forced flow of inert gas is flowed, and a gas suction port provided on a base part in the storage room and a gas suction port on the bottom surface are joined to each other. The gas is suctioned to forcibly make a negative pressure and lower than the pressure in the storage device, so that clean inert gas in the storage device flows into the pod.
JP 2003-92345 A

  However, these methods need to have a function of maintaining a reduced pressure state in a pod or a storage and a function of filling with an inert gas, which complicates the structure of the pod and the like and significantly increases the cost. .

  In addition, pods such as FOUP are molded from high-performance plastic and have the property of allowing moisture to permeate the plastic itself.

  Further, gas containing organic matter is generated from the pod itself or a sealing material (packing) used to maintain airtightness, and the organic matter diffuses into the pod.

  Organic substances diffusing into the pod include, for example, high boiling point organic substances such as di-2-ethylhexyl phthalate and di-n-butyl phthalate, and low melting point organic substances represented by a toluene / butyl acetate system. Of these two types of organic substances, the high melting point organic substance directly affects the semiconductor device, and the low melting point organic substance itself does not affect the semiconductor device. However, if moisture exists in the atmosphere, the high melting point organic substance becomes a high melting point organic substance. May also change, and it will also have an adverse effect.

  Since the pod is structurally assembled with multiple parts, it is impossible to maintain a perfect airtight state. According to the inventors' evaluation, it has been found that the oxygen concentration improves in a few hours.

  Therefore, even if an inert gas is put into the pod and stored at a higher pressure than the outside air, the inert gas diffuses out of the pod and is affected by the storage environment around the pod. As a result, the semiconductor device is oxidized by moisture, grows a natural oxide film, and is contaminated with high melting point organic substances including those formed by reaction between low melting point organic substances and moisture.

  In addition, there is a method in which an inert gas is always introduced by providing a gas supply port, a gas inlet and a gas suction port in the pod, and further providing a gas introduction and gas exhaust system on the storage side.

  These require modification of pods and storages, resulting in increased failure rates, particles, and costs due to an increase in the number of components.

  In this method, since the pod can always be filled with an inert gas, it is difficult to be affected by high melting point organic substances and low melting point organic substances. However, since an air flow is generated in the pod, there are many particles and the influence of moisture.

  Furthermore, as described above, the method disclosed in Patent Document 1 also increases the cost due to the increase in the number of components and the use of a large amount of inert gas.

  In this method, the pod is depressurized, so that it is difficult to be adversely affected by organic matter and moisture, but an irregular air flow is generated in the pod, so there are many particles. Moreover, since the negative pressure state is always maintained, mechanical stress is applied to the pod and the life is shortened.

  Accordingly, an object of the present invention is to provide a simple and low-cost manufacturing and storage method of a semiconductor device without increasing the number of constituent parts of the pod and the storage by using the pressure difference between the pod and the storage. is there.

  In order to solve the above problems, a method for storing a semiconductor device according to the present invention includes a step of storing the substrate in a pod in which a detachable lid and a casing having one open surface are in close contact or fitted, and Introducing the inert gas of 1 into the inert gas atmosphere in the pod, and storing the second inert gas atmosphere purified to a higher purity than the impurity gas in the storage chamber It has a process for storing and storing pods.

  The first inert gas and the second inert gas are preferably the same type of gas.

  The pod is preferably BOUP or FOUP.

  The pressure in the storage is preferably higher than the pressure in the pod and the pressure outside the storage.

  More preferably, the pressure in the storage is 1.5 to 5 times the pressure in the pod.

  More preferably, the pressure in the pod is higher than the pressure outside the storage.

  The storage has at least one of a particle filter or a chemical filter, and the inert gas is introduced into the storage through at least one of the particle filter or the chemical filter. preferable.

  More preferably, the humidity inside the storage and the pod is kept at 2.0% or less.

  In the storage step, it is more preferable that the total amount of organic substances adhering to the substrate is about 1 ng or less.

  The semiconductor device manufacturing method of the present invention includes a first substrate processing step, and a step of storing the substrate in a pod in which a detachable lid and a housing having an open surface are in close contact or fitted. A step of introducing a first inert gas to make the inside of the pod into the inert gas atmosphere, and a storage container maintained in a second inert gas atmosphere purified to a higher purity than the impurity gas. A step of storing and storing the pod therein.

  The first inert gas and the second inert gas are preferably the same type of gas.

  A second substrate processing step may be further provided after the storage step.

  The first substrate processing step and the second substrate processing step preferably form part of any one of a copper wiring formation step, a gate formation step, and an HSG electrode formation step.

  According to the semiconductor device storage method of the present invention, the pressure in the pod and the storage is controlled to an optimum pressure difference, that is, the pressure in the storage is controlled to 1.5 to 5.0 times the pressure in the pod. As a result, an inert gas with a high degree of cleanness can be naturally diffused into the pod, so that no irregular air flow is generated in the pod, and adhesion of foreign matter from the pod to the semiconductor device occurs. do not do.

  Further, by setting the water concentration in the storage and the pod to 2.0% or less, it is possible to prevent organic contamination from the high-performance plastic and growth of the natural oxide film.

  According to the method for manufacturing a semiconductor device of the present invention, organic contamination on the surface of the semiconductor device and the growth of a natural oxide film can be prevented with a simple configuration, the manufacturing cost can be reduced, the manufacturing yield can be greatly improved, and the semiconductor device can be manufactured. Quality improvement can be realized at the same time.

  A semiconductor device storage method and manufacturing method according to embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a schematic configuration of a semiconductor device storage method according to the first embodiment of the present invention.

  As shown in FIG. 1, there is a pod 102 for storing a plurality of semiconductor devices 100, for example, semiconductor device storage cassettes 101 in which 25 8-inch semiconductor devices 100 are stored in stages, and the pods 102 are detachable. The lid 103 and the housing 104 having an open surface on one surface are in close contact with or fitted to each other.

  Furthermore, there is a storage room 105 with excellent sealing property and high cleanliness for storing the pod 102, a door 106 for loading / unloading the pod 102 on the front surface of the storage room 105, and storage in the upper part of the storage room 105. The inert gas supply line 112 for supplying an inert gas for replacing the atmosphere in the storage 105, the inert gas supply valve 107, the chemical filter 108, the particle removal filter 109, and the storage in the lower part of the storage 105 An inert gas exhaust valve 110 for exhausting the atmosphere in the storage 105, an inert gas exhaust line 113, and a base 111 on which the pod 102 is placed are provided.

  The base 111 is shaped and dimensioned so that the gap between the detachable lid 103 of the pod 102 and the housing 104 having an open surface on one surface is not covered, and the surface is a lattice.

  In the storage 105, an inert gas is introduced from an inert gas supply line 112 at the top of the storage 105, and the flow rate of the inert gas is controlled by the inert gas supply valve 107 to remove the chemical filter 108 and the particles. The product is supplied into the storage through the filter 109.

  The inert gas exhaust valve 110 below the storage 105 discharges the inert gas to the outside of the storage 105 through the inert gas exhaust line 113 at a slightly lower flow rate than the gas supply flow rate.

  The inventors conducted a detailed study on the correlation between the relationship between the pressure in the pod and the storage and the cleanliness on the semiconductor device.

  If the pod is forced to be depressurized at all times, inert gas is always introduced from the storage, but in the pod, there is an irregular air flow from the combination of components, slight gaps, and the inert gas inlet. The inventors have found that this occurs, and this promotes adhesion of particles to the semiconductor device.

  The present invention pays attention to this irregular air flow and regulates the pressure relationship between the pod and the storage to suppress the generation of the irregular air flow and reduce the adhesion of particles and the like.

  That is, the pressure in the storage is set to a positive pressure rather than the pressure in the pod, and the atmosphere in the storage is regulated to have a higher purity than the atmosphere in the pod. As a result, the inside of the storage is kept at a very high cleanness, and no airflow is generated to move the foreign matter into the pod.

  On the other hand, the pressure is averaged by the natural diffusion of the inert gas, and the pod and the storage are in the same pressure state. During storage, air is not generated because the pod and the storage are kept at the same pressure, so particles do not adhere to the semiconductor device.

In the present embodiment, BOUP is used as the pod 102, the inert gas pressure in the BOUP is fixed at 2 Pa, and the inert gas pressure in the storage 105 is in the range of 2 Pa to 10 Pa. High purity nitrogen gas (hereinafter referred to as PN ₂ ) was used as an inert gas. In this embodiment, PN ₂ having a dew point of −90 ° C. or less and a cleanliness of 5 / cf (0.1 μm) is used.

The pressure in the storage was adjusted by the PN ₂ flow rate to be introduced, and was controlled within the range of 10 l / min to 120 l / min.

The degree of cleanliness in the storage is 2 (pieces / ft ³ ) of foreign matters of 0.12 μm or more.

(Particle reduction effect)
FIG. 2 is a diagram showing the correlation between the pressure in the storage and the adhesion ratio of particles in Embodiment 1 of the present invention. The PN ₂ pressure in the BOUP was fixed at 2 Pa, and an RCA cleaned silicon wafer was used as an evaluation monitor.

  The silicon wafer was set at the bottom of the cassette. The pressure was measured by introducing a differential pressure gauge into the filter unit incorporated in BOUP. The standing time in each condition is 2 hours. The number of particles of 0.12 μm or more was measured with a laser type inspection apparatus before and after standing.

  The particle adhesion ratio is the ratio of the number of adhered particles at each pressure when the number of adhered particles is 1 when the storage is in a vacuum state (= 0 Pa).

  As can be seen from FIG. 2, the adhesion ratio is reduced in the range from 3 Pa to 10 Pa in the storage compared to the vacuum state. It is presumed that the generation of irregular airflow generated in the pod was suppressed within this pressure range.

  If the pressure in the storage is lower than within this pressure range, the particles flow up due to the gas stream flowing from the pod to the storage, increasing the adhesion ratio, and the pressure in the storage will be higher than this pressure range. If it is high, it is presumed that the flow rate of the gas that diffuses from the storage to the pod is too large and particles are rolled up.

  In this embodiment, the pressure in the pod is fixed at 2 Pa. However, as described above, the airflow generated in the pod is generated by the difference between the pressure in the storage and the pressure in the pod. Therefore, from the results shown in FIG. 2, it can be said that the particle adhesion ratio can be reduced if the pressure in the storage is 1.5 to 5 times the pressure in the pod.

  FIG. 3 is a diagram showing the storage method dependence of the number of adhered particles in Embodiment 1 of the present invention.

  The evaluation monitor used the above-described RCA-cleaned silicon wafer, and after storage for 12 hours, particles having a size of 0.12 μm or more were measured using a laser type inspection apparatus.

As for the number of particles, the case of storing in a conventional pod purged only with N ₂ gas is set as 1.

As can be seen from FIG. 3, the number of particles is reduced by 5% in the N ₂ introduction type in which N ₂ gas is introduced into the pod and kept flowing, and by 43% in the storage method of the present invention.

This suggests that a sufficient effect cannot be obtained even if N ₂ is forcibly introduced only into the pod, and the storage method of the present invention has a very high effect in preventing the adhesion of foreign matter. Is.

(Regarding growth suppression of natural oxide film)
FIG. 4 is a diagram showing the correlation between the moisture concentration in the storage and the growth amount of the natural oxide film in the first embodiment of the present invention. As an evaluation monitor, a silicon wafer that was washed with dilute hydrofluoric acid (washed with HF: H ₂ O = 100: 1 for 3 minutes) after RCA cleaning was used. The wafer was placed in a pod filled with PN ₂ and the amount of natural oxide film after storing for 4 hours was measured by spectroscopic ellipsometry.

The water concentration is adjusted by the opening time of the storage, and PN ₂ gas is not introduced after the release. The moisture concentration was measured by installing a wireless moisture measuring device in the storage.

  As can be seen from FIG. 4, if the water concentration in the storage is 2.0% or less, the growth amount of the natural oxide film can be controlled to 0.4 nm or less, that is, the atomic weight of silicon constituting the oxide film can be controlled to 1 atom or less. I understood.

  FIG. 5 is a diagram showing the storage method dependence of the growth amount of the natural oxide film in the first embodiment of the present invention. The evaluation monitor used a silicon wafer that had been washed with dilute hydrofluoric acid after the RCA cleaning described above, and the growth amount of the natural oxide film was measured by spectroscopic ellipsometry after storage for 8 hours. Measurement was performed at 49 points on the wafer surface, and the average values were compared.

The growth amount of the natural oxide film is compared with the case where it is stored in a conventional pod purged only with N ₂ gas.

As it can be seen from FIG. 5, while the N ₂ gas as compared with the conventional in N ₂ introduced expression continues to flow is introduced into the pod has grown 38% inhibition of the natural oxide film, the storage method of the present invention Was found to be suppressed by 85.6%. This suggests that a sufficient effect cannot be obtained by controlling the moisture concentration only in the pod, and proves that the atmosphere control of the storage room for storing the pod is important.

(About reduction of organic matter adhesion)
FIG. 6 is a diagram showing the storage method dependence of the organic matter adhesion amount in the first embodiment of the present invention. The wafer was stored in the pod for 12 hours, and the amount of organic matter deposited was measured by gas chromatography mass spectrometry after heating the wafer.

The amount of organic matter adhered is compared with the case where it is stored in a conventional pod purged only with N ₂ gas.

As it can be seen from FIG. 6, whereas the N ₂ gas are conventional and compared 38% organic matter adhesion of inhibition by N ₂ introduced expression continues to flow is introduced into the pod, in the storage method of the present invention 41 % Was found to be suppressed. It can be said that the storage method of the present invention has a high effect of preventing the adhesion of organic matter.

  As described above, according to the present invention, there is an extremely high effect in suppressing organic matter contamination, particle adhesion, and natural oxide film growth on a semiconductor device.

(Modification 1)
FIG. 7 is a diagram showing a modification of the semiconductor device storage method according to the first embodiment of the present invention. In FIG. 7, a partition plate 114 is provided in the storage 105 to divide the space for storing the pods 102 individually, and a plurality of them are stored in the horizontal direction.

  According to the above configuration, since leakage of the inert gas at the time of carrying in / out of the pod 102 can be minimized, it is easy to keep the atmosphere in the storage cabinet highly severe while suppressing the flow rate of the inert gas. Thus, the cost can be further reduced.

(Modification 2)
FIG. 8 is a diagram showing another modified example of the semiconductor device storage method according to the first embodiment of the present invention. In FIG. 8, the inert gas discharged from the exhaust valve 110 passes through the inert gas exhaust line 113 and is introduced into the inert gas mixing box 115. Next, after removing moisture in the inert gas by the moisture removing device 116, the moisture is removed from the inert gas supply valve 107 through the chemical filter 108 and the particle removing filter 109 and into the storage 105.

  According to the above configuration, since the inert gas can be circulated and used, the gas usage fee can be reduced and the cost can be further reduced.

  It should be noted that the same effect can be obtained even if the configuration of the present embodiment is applied to the configuration of the first modification.

(Embodiment 2)
9 and 10 are explanatory diagrams of a gate forming process of the semiconductor device according to the second embodiment of the present invention.

  The silicon wafer 201 on which an element isolation layer, a well layer, and the like (not shown) are formed is RCA cleaned in a cleaning apparatus 202, and further diluted with a diluted hydrofluoric acid diluted several hundred times with pure water. The natural oxide film formed on the surface where the silicon is exposed is removed (FIG. 9A).

  Next, in a waiting process until a gate oxide film is formed on the silicon wafer 201, the wafer 201 is stored in the semiconductor device storage cassette 101, further stored in the pod 102, and then stored in the storage 105. (FIG. 9B). As the wafer storage method in this step, the storage method of the present invention shown in the first embodiment is used.

  Next, the gate oxide film 204 is formed on the silicon wafer 201 using the single wafer gate oxide film forming apparatus 203 (FIG. 9C).

  In the waiting process of the polysilicon film on the silicon wafer 201 on which the gate oxide film 204 is formed, the wafer 201 is stored in the storage cassette 101 for the semiconductor device, further stored in the pod 102, and then stored in the storage 105. Store (FIG. 9 (d)). As the wafer storage method in this step, the storage method of the present invention shown in the first embodiment is used.

  Next, a polysilicon film 206 is formed on the silicon wafer 201 using the polysilicon growth apparatus 205 (FIG. 10E). It should be noted that it is preferable to continuously process from RCA cleaning to polysilicon film formation with as little time as possible.

After introducing impurities into the polysilicon film 206, heat treatment is performed, and patterning is performed by known photolithography and dry etching to obtain the gate electrode 207 (FIG. 10F). Further, after depositing a SiO ₂ film or SiN film on the gate electrode 207, these films are etched back to form sidewalls 208 on the side surfaces of the gate electrode 207 (FIG. 10G).

As described above, according to the present embodiment, by using the storage method of the present invention in the waiting step before forming the gate oxide film, the growth of the natural oxide film can be suppressed, and the gate oxide film can be made thinner. Is possible. Furthermore, the imperfection of the silicon / SiO ₂ interface accompanying the growth of the natural oxide film can be reduced, and the reliability of the gate oxide film can be greatly improved. In addition, since the above-described effect can be obtained with a simple configuration, the cost of manufacturing equipment can be suppressed and the cost can be reduced.

  In addition, by using the storage method of the present invention in the waiting step before forming the polysilicon film for the gate electrode, it is possible to reduce the adhesion of organic substances on the gate oxide film, and to significantly improve the reliability of the gate oxide film. Note that the effect of improving the reliability of the gate oxide film due to the reduction in the amount of organic matter deposited is more noticeable when the storage method of the present invention is used in the waiting process before forming the gate oxide film.

  Furthermore, in the waiting process before forming the gate oxide film and the waiting process before forming the polysilicon film for the gate electrode, the amount of adhered particles can be greatly reduced by using the storage method of the present invention. The accompanying cost can be reduced.

In this embodiment, an oxide film is used for the gate insulating film and a polysilicon film is used for the gate electrode. However, the gate insulating film and the gate electrode are made of different materials, for example, an HfO ₂ film or the like as the gate insulating film or the gate electrode. For example, tungsten or aluminum may be used.

In addition, as shown in the first and second embodiments, PN ₂ is advantageous in terms of cost as the gas introduced into the pod and the storage, but other inert gas may be used.

  In the second embodiment, the gate forming process is shown as an example. However, an HSG (Hemi-Spherical Grain) electrode formation in which hemispherical irregularities are formed on the surface of a polysilicon electrode used as a copper wiring forming process or a lower electrode of a DRAM Even if the method of the present invention is applied to the process, the yield and the improvement of reliability are remarkably achieved.

  The method for storing and manufacturing a semiconductor device according to the present invention is a method for storing and manufacturing a semiconductor device in a stable state with a simple configuration, and is useful in manufacturing LSIs, liquid crystal substrates, and the like.

Schematic showing the storage method of the semiconductor device concerning Embodiment 1 of the present invention. The figure which showed the correlation with the pressure in the storage in Embodiment 1 of this invention, and the adhesion ratio of a particle The figure which showed the storage method dependence of the particle adhesion number in Embodiment 1 of this invention The figure which showed the correlation with the moisture concentration in the storage in Embodiment 1 of this invention, and the growth amount of a natural oxide film The figure which showed the storage method dependence of the growth amount of the natural oxide film in Embodiment 1 of this invention The figure which showed the storage method dependence of the organic substance adhesion amount in Embodiment 1 of this invention The figure which showed the modification of the storage method of the semiconductor device in Embodiment 1 of this invention The figure which showed another modification of the storage method of the semiconductor device in Embodiment 1 of this invention Explanatory drawing of the gate formation process of the semiconductor device in Embodiment 2 of this invention Explanatory drawing of the gate formation process of the semiconductor device in Embodiment 2 of this invention

Explanation of symbols

100 Semiconductor Device 101 Storage Cassette for Semiconductor Device 102 Pod
103 Lid 104 Case 105 Storage 106 Door 107 Inert gas supply valve 108 Chemical filter 109 Particle removal filter 110 Inert gas exhaust valve 111 Base 112 Inert gas supply line 113 Inert gas exhaust line 114 Partition plate 115 Inert Gas mixing box 116 Moisture removal apparatus 201 Silicon wafer 202 Cleaning apparatus 203 Single wafer gate oxide film forming apparatus 204 Gate oxide film 205 Polysilicon growth apparatus 206 Polysilicon film 207 Gate electrode 208 Side wall

Claims (13)

A step of detachable lid and one surface for accommodating the board in pods and a housing contact or fitted with an open surface,
Introducing a first inert gas to bring the inside of the pod into the first inert gas atmosphere;
A method for storing a semiconductor device, comprising: storing and storing the pod in a storage box maintained in a second inert gas atmosphere purified to a higher purity than the first inert gas. 2. The semiconductor device storage method according to claim 1, wherein the first inert gas and the second inert gas are the same type of gas. 3. The semiconductor device storage method according to claim 1, wherein the pod is BOUP or FOUP. 3. The semiconductor device storage method according to claim 1, wherein a pressure in the storage is higher than a pressure in the pod and a pressure outside the storage. 4. 5. The semiconductor device storage method according to claim 4, wherein the pressure in the storage is 1.5 to 5 times the pressure in the pod. 6. The semiconductor device storage method according to claim 4, wherein the pressure in the pod is higher than the pressure outside the storage. The storage has at least one of a particle filter or a chemical filter, and the inert gas is introduced into the storage through at least one of the particle filter or the chemical filter. 3. The semiconductor device storage method according to claim 1, wherein the semiconductor device is stored. 3. The semiconductor device storage method according to claim 1, wherein the humidity in the storage and the pod is kept at 2.0% or less. 3. The semiconductor device storage method according to claim 1, wherein, in the storage step, a total amount of organic substances adhering to the substrate is about 1 ng or less. A first substrate processing step;
A step of detachable lid and one surface for accommodating the board in pods and a housing contact or fitted with an open surface,
Introducing a first inert gas to bring the inside of the pod into the first inert gas atmosphere;
A method for manufacturing a semiconductor device, comprising: storing and storing the pod in a storage room maintained in a second inert gas atmosphere purified to a higher purity than the first inert gas. 11. The method of manufacturing a semiconductor device according to claim 10, wherein the first inert gas and the second inert gas are the same type of gas. The method for manufacturing a semiconductor device according to claim 10, further comprising a second substrate processing step after the storage step. 13. The semiconductor according to claim 12, wherein the first substrate processing step and the second substrate processing step form part of any one of a copper wiring formation step, a gate formation step, and an HSG electrode formation step. Device manufacturing method.

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