JP4429692B2 - Adhesive tape for protecting semiconductor wafer and method for producing semiconductor wafer using the same - Google Patents

Description

  The present invention relates to a semiconductor wafer protective adhesive tape used for thinning grinding of a semiconductor wafer and transportation of the thinned wafer in thinning grinding processing of a semiconductor wafer applied to an IC card, a smart card, etc. The present invention relates to a method of manufacturing a semiconductor wafer using

  As semiconductor wafers, compound semiconductors such as silicon and gallium-arsenide are generally well known, and among them, silicon is frequently used. This silicon wafer is sliced and manufactured to a thickness of about 500 to 1000 μm from a high purity silicon ingot obtained by a single crystal pulling method. A large number of integrated circuit patterns are formed on the wafer by processing the silicon wafer thus manufactured by various methods. Next, when the wafer on which this circuit pattern is formed is sealed in a package adapted for various devices or adapted for various mounting methods, the wafer back surface is called a backside grinder in order to reduce the thickness to a predetermined thickness. It is thinned by grinding with an apparatus. Furthermore, a stress relief process represented by chemical etching, CMP (Chemical Mechanical Polishing) or the like may be performed for the purpose of removing grinding distortion such as a crushed layer at the time of grinding as necessary.

  At this time, the protective adhesive is applied to the surface of the semiconductor wafer on which the circuit pattern is formed in order to prevent contamination by grinding dust or chemicals in grinding processing and stress relief processing, and damage of the wafer itself due to impact during grinding processing. Affix the tape. After finishing the grinding of the backside of the wafer, the protective adhesive tape attached to the wafer surface is irradiated with ultraviolet rays in the case of an ultraviolet curable adhesive tape, and other protective adhesive tapes are specially post-processed. There is no need, and after peeling and storing in a wafer cassette, it is conveyed to a dicing process.

  By the way, in these conventional wafer back grinding methods, when the wafer thickness after the back grinding is as thick as 300 μm or more, the wafer itself is hardly warped or bent by the grinding of the wafer. Therefore, since the wafer after grinding is a flat wafer like the wafer not subjected to grinding, it can be transferred to the next process with the wafer shape after grinding and stored in a wafer cassette. Was also possible.

  On the other hand, with the expansion of mounting applications to mobile devices in recent years, three-dimensional high-density mounting packages such as a stack type CSP (chip size package) are rapidly spreading. Accordingly, as the chip area and the package projected area are made the same and the package thickness is made thinner, the mounted chip itself must be made thinner, that is, the thickness of the semiconductor wafer itself must be made extremely thin, 25-100 μm. I had to do it. However, it is difficult for the wafer thinned in this way to maintain a flat shape before grinding after grinding. In other words, significant warping / deflection occurs after grinding, and deformation such as warping of the edge of the wafer is likely to occur. Due to such deformation, there is a problem that a vacuum suction error in the suction arm for transporting the wafer to the next process is likely to occur, and the wafer itself is bent when stored in the wafer cassette, so that the storage itself cannot be performed. Was.

  As a method for solving these problems, Japanese Patent Application Laid-Open No. 2002-69396 discloses a backside grinding of a semiconductor wafer using an adhesive tape comprising a low elastic modulus film as an outer layer and a high elastic modulus film as an inner layer. And a method for suppressing warpage and transport is disclosed. According to this, since the inner layer is formed of a film having a high storage elasticity, even when the semiconductor wafer is thinned and the rigidity is lowered, the warpage can be prevented. Moreover, since the outermost layers on both the front and back surfaces are formed of a film having a low storage elastic modulus, the flexibility sufficiently absorbs the level difference even when the unevenness level on the circuit forming surface of the semiconductor wafer is large. It is possible to absorb stress and the like in grinding the back surface of the wafer. Furthermore, since the base film layer has a layer structure that is substantially symmetrical in the thickness direction in terms of storage elastic modulus and thickness, the semiconductor wafer is thinned and warped due to residual stress of the circuit protective film, etc. Even if this occurs, it can be corrected.

JP 2002-69396 A (page 3)

  However, with the above-mentioned adhesive tape, even if it is possible to hold and transport the thinned wafer shape, when the tape is peeled off from the wafer after the wafer thinning grinding process is finished, the tape is peeled off from a very thin and brittle wafer. This is very difficult and causes a problem that the wafer is easily damaged.

  The present invention maintains the performance in maintaining and transporting the shape of these thinned wafers, and facilitates tape peeling from a wafer that is easily damaged after thin film grinding, thereby protecting the surface during grinding of a semiconductor wafer thin film. It is an object of the present invention to provide a pressure-sensitive adhesive tape and a method for producing a semiconductor wafer using the same.

Protective adhesive tape for semiconductor wafer according to claim 1, pressure-sensitive adhesive layer on the outer surface of one of the base film of the support having the two base film and the wafer shape-retaining layer formed therebetween is formed A protective pressure-sensitive adhesive tape, wherein the temperature of the protective pressure-sensitive adhesive tape changes between the temperature exceeding the softening point of the wafer-shaped holding layer and room temperature, so that the wafer-shaped holding layer softens reversibly. In this case, the wafer shape-retaining layer contains a side chain crystalline polymer having a primary melting transition temperature higher than room temperature (23 ° C.) .

In protecting adhesive tape of the semiconductor wafer according to claim 2, said wafer shape-retaining layer is cured shape retention of the wafer is high rounding by cooling, but is Ru heightened peelable softened by applying heat It is characterized by.

4. The adhesive tape for protecting a semiconductor wafer according to claim 3, wherein the softening point of the wafer shape retaining layer is in the range of 30 to 100.degree .

5. The adhesive tape for protecting a semiconductor wafer according to claim 4 , wherein the base film is made of polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene having ultraviolet transparency. -Engineering of any of homopolymers or copolymers of vinyl acetate copolymer, ethylene-acrylic acid copolymer, ionomer α-olefin, or a mixture thereof, polyethylene terephthalate, polycarbonate, polymethyl methacrylate It is made of any one of thermoplastic elastomers of plastic, polyurethane, styrene-ethylene-butene-, or pentene copolymer .

6. The adhesive tape for protecting a semiconductor wafer according to claim 5 , wherein the adhesive layer is an ultraviolet curable adhesive .

7. The adhesive tape for protecting a semiconductor wafer according to claim 6 , wherein the adhesive layer is UV-cured with respect to 100 parts by weight of an acrylic adhesive composed of a copolymer of at least 2-ethylhexyl acrylate and n-butyl acrylate. It comprises 5 to 200 parts by weight of a (meth) acrylate compound having a carbon-carbon double bond and a photoinitiator and a photosensitizer .

The adhesive tape for protecting a semiconductor wafer of the present invention is applied to an IC card, a smart card or the like, and is particularly effective in grinding and transporting a semiconductor wafer that has been made extremely thin. by having the wafer shape-retaining layer can be reversibly rise to changes in, retain a flat shape of the semiconductor wafer is thinned, a yet easy peeling of the wafer from the protective adhesive tape, storage and peeling Can be effectively prevented. Moreover, it is possible to manufacture a thinned semiconductor wafer using an existing line or apparatus as it is.

In the adhesive tape for protecting a semiconductor wafer according to the present invention, an adhesive layer 2 is formed on a support 1 composed of a plurality of substrate films 3 as shown in FIG. reversibly softened - wafer shape-retaining layer 4 which changes the cure is formed. That is, as shown in FIG. 1, the pressure-sensitive adhesive layer 2, the base film 3, the wafer shape holding layer 4, and the support 1 composed of the base film 3 have a four-layer structure.

Reversibly softened - wafer shape-retaining layer 4 of varying cure, by providing a temperature difference said heating or cooling, reversibly hardness changes, i.e. the wafer is thinned by curing a flexible state shape retention has a heightened Ru nature and is characterized by comprising a wafer shape-retaining layer 4.

The wafer shape holding layer 4 of the protective pressure-sensitive adhesive tape in the present invention preferably has a property of hardening (hardening) so that the shape holding property of the thinned wafer is enhanced by cooling to room temperature (23 ° C.). The wafer shape holding layer 4 is made of a material that reversibly softens and hardens. The softening point is slightly different depending on the application, usage method, etc., but is preferably selected in the range of 30 to 100 ° C, more preferably in the range of 40 to 60 ° C. Curing may be caused, and a temperature different from this temperature range may be selected.
Furthermore, the wafer shape-retaining layer 4 is a first-order melt transition temperature comprising at least room temperature (23 ° C.) higher than the side chain crystalline polymer. In the present invention, the primary melting transition temperature refers to a temperature at which a specific part of a polymer that is aligned in an ordered order is heated to be in a disordered state before heating.

  The thickness of the wafer shape holding layer 4 is not particularly limited as long as the wafer shape can be held by the layer thickness at the time of curing, but is preferably 10 to 200 μm, more preferably 30 to 100 μm.

For the base film 3 in the protective pressure-sensitive adhesive tape of the present invention, usually plastic, rubber or the like is preferably used. About the base film 3, when using a radiation-curing-type adhesive for the adhesive layer 2, a thing with a light transmittance is selected when a radiation transparent thing is hardened by ultraviolet irradiation. Examples of such a base film 3 include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. A homopolymer or copolymer of any α-olefin of ionomer, or a mixture thereof, polyethylene terephthalate, polycarbonate, polymethylmethacrylate engineering plastic, polyurethane, styrene-ethylene-butene- or pentene copolymer Any thermoplastic elastomer of the polymer can be mentioned and can be arbitrarily selected according to the required properties of the base film.
These base films can be manufactured using a conventionally known extrusion method, but in the case of a base film obtained by laminating various resins, it is manufactured by a co-extrusion method, a lamination method, etc. An adhesive layer may be provided between the resins, as is normally done in the manufacturing method of the laminate film. The thickness of such a base film is suitably 30 to 200 μm from the viewpoint of strength / elongation characteristics and radiation transmission.

  Moreover, although the kind of base film 3 may be the same, you may differ, respectively. When the type of the base film 3 is different, it is preferable that the thermal contraction rate becomes smaller as the distance from the pressure-sensitive adhesive layer 2 increases. By doing in this way, in addition to the holding | maintenance by the hardness of the wafer shape holding | maintenance layer 4, it becomes possible to give repulsion with respect to the curvature of a wafer also by the difference in the shrinkage rate of each base film 3. FIG. Therefore, it is possible to further suppress warping during cassette storage.

  In order to exert the function of the adhesive tape for protecting a semiconductor wafer according to the present invention, it is necessary to heat to a temperature exceeding the transition point and to cool to a temperature lower than the transition point from the heated state. is there. Here, if necessary, the tape itself can be colored or discolored so that it can be visually confirmed that the protective adhesive tape for the semiconductor wafer has been heated to that temperature.

  When the adhesive tape for protecting a semiconductor wafer according to the present invention is applied to the adhesive tape for protection on the surface of the semiconductor wafer, back grinding of the wafer, transportation, and peeling from the adhesive tape for protecting the wafer are as follows: There are such advantages.

That is, since the tape is cured during transportation, the warpage can be prevented even when the rigidity of the wafer is reduced after the wafer is ground. In addition, since the tape is softened when the wafer is peeled from the protective adhesive tape, the protective adhesive tape is bent 180 degrees in a state where the wafer is adsorbed by the existing protective adhesive tape peeling device. Can be peeled off.

As the pressure-sensitive adhesive layer 2 provided on the support 1, when the protective pressure-sensitive adhesive tape is peeled off from the wafer after completion of the thinning grinding process, damage to the wafer or contamination due to the pressure-sensitive adhesive remaining on the wafer surface, etc. The adhesive is not particularly limited as long as it does not cause a defect, but the adhesive exhibits a three-dimensional network by radiation, preferably ultraviolet curing, and the adhesive force decreases and the adhesive remains on the wafer surface after peeling. It is preferable to use an ultraviolet curable pressure-sensitive adhesive that is less likely to produce a product.
Such an ultraviolet curable pressure-sensitive adhesive is not particularly limited as long as the desired ultraviolet curable property is exhibited. For example, 100 parts by weight of an acrylic pressure-sensitive adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate is used. 5 to 200 parts by weight of a (meth) acrylate compound having an ultraviolet curable carbon-carbon double bond, a photoinitiator and a photosensitizer, and other conventionally known tackifiers and softeners , Antioxidants, and the like. The thickness of the radiation-curable pressure-sensitive adhesive layer 2 provided on the support 1 is usually suitably 10 to 200 μm in order to improve the adhesion to the pattern surface.

The semiconductor wafer manufactured using the adhesive tape for protecting a semiconductor wafer of the present invention is applied to an IC card, a smart card or the like.
The semiconductor wafer thinning grinding process includes, for example, the following steps.
(A) A step of bonding a protective adhesive tape to the surface of the semiconductor wafer before polishing the wafer (b) After the back surface grinding of the semiconductor wafer is finished, the protective adhesive tape is attached to the wafer before taking out the semiconductor wafer from the grinding apparatus. A step of curing to a hardness that allows the shape to be kept flat (c) a step of transporting the semiconductor wafer while being bonded to the protective adhesive tape

  In the present invention, in the above-described step (a), it is preferable to bond the protective adhesive tape while heating to a temperature higher than the softening point of the wafer shape holding layer 4. Moreover, in said process (b), it is preferable to make it harden | cure the adhesive tape for protection by hardening the wafer shape holding | maintenance layer 4 in the process cooled from room temperature by the heat_generation | fever at the time of grinding to room temperature. .

  Further, when these shape-retaining layers 4 are used in combination with a resin that is hardened by a chemical reaction such as an ultraviolet curable resin, an ultraviolet curable resin or the like is irradiated with an ultraviolet ray as an intermediate step between the steps (a) and (b). It is preferable to perform the step of hardening in advance by a predetermined method.

  EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
On the film of ethylene vinyl acetate copolymer (EVA) having a thickness of 100 μm, the first melting transition temperature (primary melting transition temperature: before heating, aligned in an ordered order at about 50 ° C. with a thickness of 30 μm. Resin layer (acrylic having a linear alkyl group having 10 or more carbon atoms as a side chain) composed of a side chain crystalline polymer having a temperature at which a specific portion of the polymer is heated and becomes a disordered state) A set of polymers coated with an acid ester as a main component was prepared. And the wafer shape maintenance layer 4 is formed by bonding two surfaces of these resin layers together. Further, the wafer shape holding layer 4 is sandwiched between two ethylene vinyl acetate copolymer (EVA) films to be the base film 3 by bonding, whereby the support 1 is formed. A protective adhesive tape was prepared by applying an ultraviolet curable adhesive having a thickness of 30 μm as an adhesive layer 2 on either surface of the two base films 3. As shown in FIG. 1, the produced protective adhesive tape is composed of a base film 3 (base 1) made of an ethylene vinyl acetate copolymer (EVA) film, and a wafer shape holding layer made of a side chain crystalline polymer. 4 and a four-layer structure of a base material film 3 (base material 2) made of an ethylene vinyl acetate copolymer (EVA) film 3 and a pressure-sensitive adhesive layer 2 made of an ultraviolet curable pressure sensitive adhesive. (In FIG. 1, the uppermost layer is the base film 3 which becomes the base 1).
This protective adhesive tape is bonded to the surface of a semiconductor wafer with a diameter of 8 inches, heated to 50 ° C using an existing protective adhesive tape bonding device (DR8500II manufactured by Nitto Denko Corporation). Then, the wafer thickness was finished to 50 μm by grinding the back side of the wafer using a backside grinder (DFG850 manufactured by Disco Corporation). Next, the wafer is cooled to a room temperature (23 ° C.) that is not higher than the first melting transition temperature on the wafer adsorption fixing stage of the backside grinder, and the wafer shape holding layer 4 is cured to a hardness capable of holding the wafer shape. Then, as the transportability to the next process, it was confirmed whether or not the wafer could be stored in the wafer cassette and whether or not the wafer was damaged. Furthermore, using an existing protective tape peeling device (HR8500II, manufactured by Nitto Denko Corporation), the protective adhesive tape was irradiated with ultraviolet rays of 500 mJ / cm2, and then the protective tape was heated to 50 ° C. and softened. The thinned wafer was peeled off, and the peelability was tested for the ease of peeling and whether the thinned wafer was damaged. The results are shown in Table 1 below.

(Example 2)
Side chain having a primary melt transition temperature at about 50 ° C. as a wafer shape holding layer on a polyethylene terephthalate (PET) film having a thickness of 50 μm and a film of ethylene vinyl acetate copolymer (EVA) having a thickness of 100 μm. A support layer 1 was formed by applying a resin layer composed of a polymer composed mainly of an acrylic ester similar to that in Example 1 composed of a crystalline polymer to a thickness of 30 μm and bonding them together. . An acrylic pressure-sensitive adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate having a thickness of 30 μm was applied as the pressure-sensitive adhesive layer 2 to the ethylene vinyl acetate copolymer (EVA) film side of the support 1. A protective adhesive tape was prepared. As shown in FIG. 1, the produced protective adhesive tape is composed of a base film 3 (base 1) made of a polyethylene terephthalate (PET) film, a wafer shape holding layer 4 made of a side chain crystalline polymer, and ethylene. It has a four-layer structure of a base material 1 consisting of a base film 3 (base material 2) made of a vinyl acetate copolymer (EVA) film and a pressure-sensitive adhesive layer 2 made of an ultraviolet curable pressure sensitive adhesive. . The heat shrinkage of the base film 3 (base 1) made of polyethylene terephthalate (PET) film is the heat of the base film 3 (base 2) made of ethylene vinyl acetate copolymer (EVA) film. Less than shrinkage. After this protective adhesive tape was bonded to the surface of the semiconductor wafer in the same manner as in Example 1, the wafer transportability and peelability after the thin film grinding treatment were tested in the same manner as in Example 1. The results are shown in Table 1 below.

(Example 3)
An acrylic ester similar to that of Example 1 consisting of a side chain crystalline polymer having a primary melting transition temperature of about 40 ° C. as a wafer shape retaining layer 4 is mainly formed on a polyethylene terephthalate (PET) film having a thickness of 50 μm. A resin layer composed of a polymer as a component is applied to a thickness of 50 μm, and a reversible microcapsule form in which a thermochromic composition is encapsulated on a 100 μm-thick ethylene vinyl acetate copolymer (EVA) film. A support 1 was formed by applying 3 μm of a thermochromic pigment (“Metamocolor” (registered trademark) manufactured by Pilot Ink Co., Ltd.) and bonding them together. An acrylic pressure-sensitive adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate having a thickness of 30 μm was applied as the pressure-sensitive adhesive layer 2 to the ethylene vinyl acetate copolymer (EVA) film side of the support 1. A protective adhesive tape was prepared. The produced protective adhesive tape turned blue at 45 ° C. exceeding the primary melting transition temperature of the wafer shape holding layer 4, and it was possible to visually confirm that the transition was completed. After this protective adhesive tape was bonded to the surface of the semiconductor wafer in the same manner as in Example 1, the wafer transportability and peelability after the thin film grinding treatment were tested in the same manner as in Example 1. The results are shown in Table 1 below.

(Comparative Example 1)
In Example 1, except that an acrylic adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate was used instead of the resin layer made of a side chain crystalline polymer, Similar protective adhesive tapes were prepared and tested for wafer transportability and peelability after thin film grinding. The results are shown in Table 1 below.

(Comparative Example 2)
In Example 1, a resin layer made of a side chain crystalline polymer similar to Example 1 was formed on a film (base material 1) of ethylene vinyl acetate copolymer (EVA) having a thickness of 100 μm to a thickness of 60 μm. An acrylic pressure-sensitive adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate having a thickness of 30 μm directly on a resin layer made of a side chain crystalline polymer without being bonded. A protective pressure-sensitive adhesive tape coated with was prepared and tested for wafer transportability and peelability after thin film grinding. The results are shown in Table 1 below.

(Comparative Example 3)
In Example 2, a protective adhesive tape similar to Example 2 was prepared, except that the adhesive was applied not to the ethylene vinyl acetate copolymer film (EVA) side but to the polyethylene terephthalate film (PET) side, The wafer transportability and peelability after thin film grinding were tested. The results are shown in Table 1 below.

The evaluation criteria for each test are as follows.
(1) Thin film grindability ○: No wafer breakage or microcracking.
X: Wafer breakage or microcracking occurred.
(2) Transportability in BG device ○: Can be transported by suction with a vacuum suction arm.
×: Absorption error occurred in the vacuum adsorption arm.
(3) Storability of wafer cassette ○: Can be stored well and does not contact the upper and lower wafers.
×: Cannot be stored well, or the upper and lower tiers are bent by the wafer after storage
Contact the wafer.
(4) Compatibility with existing peeling device ○: The wafer can be peeled without damage.
X: The wafer cannot be peeled off or the wafer after peeling is damaged.

In Comparative Example 1 in Table 1 above, since a normal pressure-sensitive adhesive was applied instead of the wafer shape holding layer 4, peeling from the thin film wafer was very difficult. Further, as in Comparative Example 2, when the base film was only one layer without performing bonding, the warp after the back surface grinding was large. Moreover, also when arrange | positioning so that the thermal contraction rate of the base film A may become larger than the thermal contraction rate of the base film B like the comparative example 3, the curvature of the wafer after back grinding similarly to the comparative example 2 Became big.
On the other hand, in Example 1 and Example 2 according to the method of the present invention, all of the thin film grindability, the transportability in the BG apparatus, the wafer cassette storage performance, and the compatibility with the existing peeling apparatus are good. Manufacturing can be realized efficiently.

  The pressure-sensitive adhesive tape of the present invention can be used as a protective pressure-sensitive adhesive tape at the time of semiconductor wafer grinding, reduces the warpage even in the case of a thinned wafer, and protects the semiconductor wafer during grinding that facilitates tape peeling from the wafer. Can be used as an adhesive tape.

It is sectional drawing which shows an example of the adhesive tape for wafer protection of this invention.

DESCRIPTION OF SYMBOLS 1 Support body 2 Adhesive layer 3 Base film 4 Wafer shape maintenance layer

Claims (6)

A protective pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer formed on the outer surface of one base film of a support having two base films and a wafer shape holding layer formed therebetween, the protective adhesive By changing the temperature of the atmosphere of the tape between the temperature exceeding the softening point of the wafer shape holding layer and the room temperature, the wafer shape holding layer is reversibly softened and cured , and the wafer shape holding layer is A pressure-sensitive adhesive tape for protecting a semiconductor wafer, comprising a side chain crystalline polymer having a primary melting transition temperature higher than at least room temperature (23 ° C.) . Protection of the semiconductor wafer according to claim 1 wherein the wafer shape-retaining layer, wherein the shape retention of the wafer was cured by cooling the high words, those are Ru heightened peelable softened by applying heat Adhesive tape. 3. The adhesive tape for protecting a semiconductor wafer according to claim 1, wherein a softening point of the wafer shape holding layer is in a range of 30 to 100 ° C. 4 . The base film is made of polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer having ultraviolet transparency, Alphaomer homopolymer or copolymer of any ionomer, or a mixture thereof, polyethylene terephthalate, polycarbonate, polymethylmethacrylate engineering plastic, polyurethane, styrene-ethylene-butene- or pentene copolymer The adhesive tape for protecting a semiconductor wafer according to any one of claims 1 to 3, wherein the adhesive tape is made of any one of thermoplastic elastomers . The adhesive tape for protecting a semiconductor wafer according to any one of claims 1 to 4, wherein the adhesive layer is an ultraviolet curable adhesive. The pressure-sensitive adhesive layer has an ultraviolet curable carbon-carbon double bond with respect to 100 parts by weight of an acrylic pressure-sensitive adhesive composed of a copolymer of at least 2-ethylhexyl acrylate and n-butyl acrylate. The pressure-sensitive adhesive tape for protecting a semiconductor wafer according to claim 5 , comprising 5 to 200 parts by weight of a compound, a photoinitiator and a photosensitizer .

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