JP6985077B2 - Wafer processing method - Google Patents

Description

The present invention relates to a method for processing a wafer.

In the manufacturing process of a semiconductor wafer, the back surface is usually ground to thin the wafer, and then a processing step of forming at least one of an insulating film, wiring, electrodes and the like is performed under high temperature conditions. A protective tape is required to convey the thinned wafer, but the protective tape used for backside grinding may not have sufficient heat resistance under high temperature conditions in the processing process and may be deformed. For this reason, before the processing process under high temperature conditions, the protective tape for backside grinding is peeled off and a glass substrate or the like is adhered to the wafer for processing.

However, since it takes cost and man-hours to bond the substrate, backside grinding (so-called TAIKO (registered trademark) grinding) with a ring-shaped reinforcing portion left on the outer peripheral portion is performed, and the substrate is not adhered to the ring-shaped reinforcing portion under high temperature conditions. A machining method for performing the following machining steps is provided.

Further, there has been proposed a method for manufacturing a semiconductor wafer in which a support substrate is attached to the surface of the wafer and a back surface grinding process and a high temperature processing step are performed (see, for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 2013-038274 Japanese Unexamined Patent Publication No. 2004-214309

However, in TAIKO grinding, when the device region surrounded by the ring-shaped reinforcing portion of the wafer is thinned from, for example, about 10 μm to 20 μm, when the protective tape is peeled off after TAIKO grinding, the ring-shaped reinforcing portion and the device region ground on the back surface are removed. There was a risk that the wafer would break at the boundary with.

The present invention has been made in view of such problems, and an object of the present invention is to provide a method for processing a wafer that can prevent the TAIKO ground wafer from being damaged.

In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention comprises a device region in which a plurality of devices partitioned by a planned division line are formed on the surface and an outer peripheral surplus surrounding the device region. A method for processing a wafer having a region, which is a bonding process in which a protective sheet made of a polyimide resin having no adhesive layer and having heat resistance and formed in a disk shape is heat-bonded to the surface of the wafer, and the bonding. After performing the landing process, the back surface of the wafer corresponding to the device region is ground to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess, and after the grinding process, the ground surface is insulated. A processing step under high temperature conditions including the formation of at least one of a film, a wiring layer and an electrode, a removal step of removing the ring-shaped reinforcing portion after the processing step, and a wafer after the removal step. A transfer step of attaching a dicing tape to the back surface of the wafer and peeling off the protective sheet, a division step of dividing the wafer from the front surface side along the planned division line after the transfer step, and a chip after the division step. The protective sheet comprises a pick-up process for picking up the wafer, and the protective sheet is characterized by having heat resistance in the processing process.

The method for processing a waher of the present invention is a method for processing a waha having a device region in which a plurality of devices partitioned by a planned division line are formed on the surface and an outer peripheral surplus region surrounding the device region, and is an adhesive layer. A bonding step of heat-bonding a protective sheet made of a polyimide resin having heat resistance and having no heat to the surface of the wafer, and a wafer corresponding to the device region after the bonding process is performed. A grinding step of grinding the back surface to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess, and after performing the grinding step, the ground surface includes at least one of an insulating film, a wiring layer, and an electrode. A processing step under high temperature conditions, a division step of dividing the wafer from the grinding surface side into each chip along the planned division line after the processing process is performed, and a protective sheet side after the division step is performed. Bei example and a pickup step for picking up from the protective sheet the chip in a state adsorbed on the holding table, the protective sheet is characterized by having a heat resistance at the processing step.

Therefore, in the wafer processing method of the present invention, it is possible to prevent the TAIKO ground wafer from being damaged.

FIG. 1 is a plan view of a wafer to be processed in the wafer processing method according to the first embodiment. FIG. 2 is a flowchart showing a wafer processing method according to the first embodiment. FIG. 3 is a cross-sectional view showing a bonding process of the wafer processing method shown in FIG. FIG. 4 is a perspective view showing a grinding process of the wafer processing method shown in FIG. FIG. 5 is a side view showing a partial cross-sectional view of the grinding process of the wafer processing method shown in FIG. FIG. 6 is a cross-sectional view showing a wafer after the processing step of the wafer processing method shown in FIG. FIG. 7 is a cross-sectional view showing a wafer before the removal step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view showing a wafer after the removal step of the wafer processing method shown in FIG. FIG. 9 is a cross-sectional view showing the wafer after the transfer step of the wafer processing method shown in FIG. FIG. 10 is a cross-sectional view showing a wafer after the dividing step of the wafer processing method shown in FIG. FIG. 11 is a cross-sectional view showing a pickup process of the wafer processing method shown in FIG. FIG. 12 is a flowchart showing a wafer processing method according to the second embodiment. FIG. 13 is a cross-sectional view of the wafer after the dividing step of the wafer processing method shown in FIG. FIG. 14 is a cross-sectional view showing a pick-up process of the wafer processing method shown in FIG.

An embodiment (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
The method of processing the wafer according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a wafer to be processed in the wafer processing method according to the first embodiment. FIG. 2 is a flowchart showing a wafer processing method according to the first embodiment.

The wafer processing method according to the first embodiment is the wafer 1 processing method shown in FIG. In the first embodiment, the wafer 1 shown in FIG. 1 is a disk-shaped semiconductor wafer or an optical device wafer using silicon, sapphire, gallium arsenide, or the like as a substrate 2. As shown in FIG. 1, the wafer 1 surrounds the device region 6 in which the device 5 is formed in a plurality of regions partitioned by a grid-like division schedule line 4 on the surface 3, and the device 5 surrounds the device region 6. It has an outer peripheral surplus region 7 that is not formed.

As shown in FIG. 2, the wafer processing method according to the first embodiment includes a sticking process ST1, a grinding process ST2, a processing process ST3, a removal process ST4, a transfer process ST5, a division process ST6, and a pickup. The process ST7 is provided.

(Attachment process)
FIG. 3 is a cross-sectional view showing a bonding process of the wafer processing method shown in FIG. The sticking step ST1 is a step of sticking the heat-resistant protective sheet 20 to the surface 3 of the wafer 1. The protective sheet 20 is composed of a resin layer 21 made of a polyimide resin having a melting point of 300 ° C. or higher and 450 ° C. or lower, and is formed in a disk shape having substantially the same size as the wafer 1 in the first embodiment. That is, in the first embodiment, the protective sheet 20 does not have an adhesive layer. In the first embodiment, the resin layer 21 of the protective sheet 20 is made of a polyimide resin made from biphenyltetracarboxylic dianhydride as a raw material. Further, in the first embodiment, the resin layer 21 of the protective sheet 20 has a linear expansion coefficient of 12 ( ^10-6 / ° C.) or more and 22 ( ^10-6 / ° C.) or less. In the first embodiment, the resin layer 21 of the protective sheet 20 can be made of Upirex (registered trademark) manufactured by Ube Industries, Ltd.

In the sticking step ST1, as shown in FIG. 2, the protective sheet 20 is placed on the suction hot plate 30, the front surface 3 of the wafer 1 is placed on the protective sheet 20, and the surface 3 of the wafer 1 is placed on the back surface 8 of the wafer 1. Place 31 on it. In the sticking step ST1, the wafer 1 is pressed against the protective sheet 20 by the weight 31, and the protective sheet 20 is heated by the adsorption hot plate 30, and the protective sheet 20 is thermocompression bonded to the surface 3 of the wafer 1. Thermocompression bonding is a method in which materials of the same type or different types are heated to below the melting point and pressed to cause plastic deformation, and the surfaces of both are joined and bonded by contact. The wafer processing method proceeds to the grinding step ST2 after the protective sheet 20 is attached to the wafer 1 by thermocompression bonding, that is, after the attaching step ST1.

(Grinding process)
FIG. 4 is a perspective view showing a grinding process of the wafer processing method shown in FIG. FIG. 5 is a side view showing a partial cross-sectional view of the grinding process of the wafer processing method shown in FIG. In the grinding step ST2, after the attachment step ST1, the back surface 8 of the wafer 1 corresponding to the device region 6 is ground to form a circular recess 10 and a ring-shaped reinforcing portion 11 surrounding the circular recess 10. Is. That is, in the first embodiment, the grinding step ST2 is a step of grinding the wafer 1 so-called TAIKO (registered trademark).

In the grinding step ST2, the surface 3 of the wafer 1 is placed on the holding surface 42 of the holding table 41 of the grinding device 40 via the protective sheet 20, and the portion of the back surface 8 of the wafer 1 that overlaps the device region 6 in the thickness direction ( The grinding wheel 44 of the grinding unit 43 rotating around the axis is pressed against the corresponding portion). In the grinding step ST2, the portion of the back surface 8 of the wafer 1 that overlaps the device region 6 in the thickness direction is thinned to a predetermined thickness by the grinding wheel 44, and the portion of the back surface 8 that overlaps the device region 6 in the thickness direction is a circular recess. Form 10. In the grinding step ST2, the ring-shaped reinforcing portion 11 is formed in the outer peripheral surplus region 7 without thinning the portion of the back surface 8 of the wafer 1 that overlaps with the outer peripheral surplus region 7 in the thickness direction. In the method of processing a wafer according to the first embodiment, in the grinding step ST2, the device region 6, that is, the circular recess 10 is thinned to a thickness of 10 μm or more and 20 μm or less to form the circular recess 10. The wafer processing method proceeds to the processing process ST3 after the grinding process ST2.

(Processing process)
FIG. 6 is a cross-sectional view showing a wafer after the processing step of the wafer processing method shown in FIG. In the first embodiment, the processing step ST3 is a step of performing processing under high temperature conditions higher than normal temperature, including the formation of an insulating film 13 on the bottom surface 12 of the circular recess 10 which is the grinding surface, after the grinding step ST2 is performed. be. In the first embodiment, in the processing step ST3, the wafer 1 is placed in an oxidizing atmosphere having a temperature higher than room temperature for a predetermined time and subjected to thermal oxidation treatment to form an oxide film as an insulating film 13. In the present invention, in the processing step ST3, processing such as sputtering, annealing treatment, and sinter treatment may be performed under high temperature conditions higher than normal temperature to form a wiring layer (not shown) on the bottom surface 12 of the circular recess 10. After screen printing the solder, processing such as reflow processing may be performed under high temperature conditions higher than normal temperature to form an electrode (not shown) on the bottom surface 12 of the circular recess 10. That is, in the processing step ST3 of the wafer processing method of the present invention, at least one of the insulating film 13, the wiring layer and the electrode is formed on the bottom surface 12 of the circular recess 10 (that is, including the formation of any one). Since the protective sheet 20 is composed of only the resin layer 21 made of polyimide resin, it has heat resistance against high temperature conditions in the processing step ST3. The wafer processing method proceeds to the removal step ST4 after the processing step ST3.

(Removal process)
FIG. 7 is a cross-sectional view showing a wafer before the removal step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view showing a wafer after the removal step of the wafer processing method shown in FIG. In the removal step ST4, after the processing step ST3 is performed, the ring-shaped reinforcing portion 11 is removed by cutting slightly inside (indicated by the dotted line 14 in FIG. 7) from the boundary between the circular recess 10 and the ring-shaped reinforcing portion 11. It is a process.

In the removal step ST4, the surface 3 of the wafer 1 is placed on the holding surface of the holding table of the cutting apparatus (not shown) via the protective sheet 20, and the wafer 1 is sucked and held on the holding surface. In the removal step ST4, the cutting blade of the cutting device and the wafer 1 are relatively moved, and the cutting blade is cut slightly inward from the boundary as shown by the dotted line 14 in FIG. 7 over the entire circumference, and is shown in FIG. As shown, the ring-shaped reinforcing portion 11 is removed from the wafer 1. The wafer processing method proceeds to the transfer step ST5 after the removal step ST4.

(Transfer process)
FIG. 9 is a cross-sectional view showing the wafer after the transfer step of the wafer processing method shown in FIG. The transfer step ST5 is a step of attaching the dicing tape 22 to the back surface 8 which is the bottom surface 12 of the circular recess 10 of the wafer 1 after the removal step ST4 is performed. In the transfer step ST5, the dicing tape 22 is attached to the insulating film 13 on the back surface 8 which is the bottom surface 12 of the circular recess 10 of the wafer 1, and the protective sheet 20 is peeled off from the surface 3. The dicing tape 22 includes a resin layer made of synthetic resin and an adhesive layer laminated on the resin layer and attached to the back surface 8 of the wafer 1. The wafer processing method proceeds to the division step ST6 after the transfer step ST5.

(Division process)
FIG. 10 is a cross-sectional view showing a wafer after the dividing step of the wafer processing method shown in FIG. The division step ST6 is a step of dividing the wafer 1 from the surface 3 side along the planned division line 4 after the transfer step ST5 is performed.

In the first embodiment, in the dividing step ST6, the back surface 8 of the wafer 1 is placed on the holding surface of the holding table of the cutting apparatus (not shown) via the dicing tape 22, and the wafer 1 is sucked and held on the holding surface. In the dividing step ST6, the cutting blade of the cutting device and the wafer 1 are relatively moved along the scheduled division line 4, and the cutting blade is cut from the surface 3 side to the center of the dicing tape 22 in the thickness direction. As shown in 10, the wafer 1 is divided into individual chips 9. The chip 9 includes the device 5. The wafer processing method proceeds to the pickup process ST7 after the division step ST6.

(Pickup process)
FIG. 11 is a cross-sectional view showing a pickup process of the wafer processing method shown in FIG. The pick-up step ST7 is a step of picking up the individually divided chips 9 after the division step ST6 is performed.

In the first embodiment, in the pickup step ST7, as shown in FIG. 11, the pickup unit 60 sucks each chip 9 and picks up the chips 9 one by one from the dicing tape 22. The wafer processing method ends when all the chips 9 are picked up in the pickup process ST7.

In the wafer processing method according to the first embodiment, the resin layer 21 of the protective sheet 20 attached to the surface 3 of the wafer 1 in the attachment step ST1 has heat resistance to high temperature conditions in the processing step ST3. Therefore, the wafer processing method can be used in the processing process ST3 without replacing the protective sheet 20 attached to the wafer 1 before the grinding process ST2 after the grinding process ST2. For this reason, the wafer processing method is a processing step after the grinding step ST2 even if the device region 6 is thinned to a thickness of 10 μm or more and 20 μm or less, which is thinner than the conventional TAIKO grinding that thins the device region 6 to about 50 μm. There is no need to replace the protective sheet 20 before ST3. As a result, the wafer processing method can suppress the breakage of the wafer 1 at the boundary between the ring-shaped reinforcing portion 11 and the circular recess 10 after the TAIKO grinding, and suppress the damage of the TAIKO ground wafer. be able to.

Further, in the wafer processing method according to the first embodiment, the protective sheet 20 to be attached to the surface 3 of the wafer 1 in the attachment step ST1 is composed of the resin layer 21 and does not have an adhesive layer. Therefore, the wafer processing method can prevent the adhesive layer from melting and the protective sheet 20 from peeling off in the processing step ST3, and the melted adhesive layer from affecting the device 5. As a result, in the wafer processing method according to the first embodiment, the protective sheet 20 attached in the attaching step ST1 can also be used in the processing step ST3.

Further, in the wafer processing method according to the first embodiment, since the protective sheet 20 is attached to the surface 3 of the wafer 1 by thermocompression bonding in the attachment step ST1, the protective sheet 20 is composed of the resin layer 21 and does not have an adhesive layer. The sheet 20 can be reliably attached to the surface of the wafer 1.

Further, in the wafer processing method according to the first embodiment, the linear expansion coefficient of the resin layer 21 of the protective sheet 20 is 12 ( ^10-6 / ° C) or more and 22 ( ^10-6 / ° C) or less, which is normal. It is closer to the coefficient of linear expansion of the metal constituting the wiring layer or electrode than the resin. Therefore, in the wafer processing method according to the first embodiment, the protective sheet 20 expands in the same manner as the wafer 1 in the processing step ST3.

[Embodiment 2]
The method of processing the wafer according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a flowchart showing a wafer processing method according to the second embodiment. FIG. 13 is a cross-sectional view of the wafer after the dividing step of the wafer processing method shown in FIG. FIG. 14 is a cross-sectional view showing a pick-up process of the wafer processing method shown in FIG. In FIGS. 12, 13, and 14, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 12, the wafer processing method according to the second embodiment includes a pasting process ST1, a grinding process ST2, a processing process ST3, a division process ST6-2, and a pickup process ST7-2. After the processing step ST3, the dividing step ST6-2 and the pick-up process ST7-2 are carried out in order, and the attaching process ST1, the grinding process ST2 and the processing process ST3 are the same as those in the first embodiment.

In the dividing step ST6-2 of the wafer processing method according to the second embodiment, after the processing step ST3 is performed, the wafer 1 is moved along the scheduled division line 4 from the bottom surface 12 side of the circular recess 10 which is the grinding surface to each chip 9. It is a process of dividing into.

In the second embodiment, in the dividing step ST6-2, the surface 3 of the wafer 1 is placed on the holding surface 72 of the holding table 71 of the cutting device 70 via the protective sheet 20, and the wafer 1 is adsorbed on the holding surface 72. .. In the dividing step ST6, the cutting blade of the cutting device 70 and the wafer 1 (not shown) are relatively moved along the scheduled division line 4, and the cutting blade is moved from the bottom surface 12 side of the circular recess 10 to the center of the protective sheet 20 in the thickness direction. The wafer 1 is divided into individual chips 9 as shown in FIG. The wafer processing method according to the third embodiment proceeds to the pickup process ST7 after the division step ST6.

The pickup step ST7-2 of the wafer processing method according to the second embodiment is a step of picking up the chip 9 with the protective sheet 20 side adsorbed on the holding table 71 after the division step ST6 is performed.

In the second embodiment, in the pickup step ST7-2, the pickup unit 61 clamps each chip 9 with one chip 9 in a state where the protective sheet 20 side is attracted to the holding table 71, as shown in FIG. Pick up from the protective sheet 20 one by one. The wafer processing method ends when all the chips 9 are picked up in the pickup process ST7.

In the wafer processing method according to the second embodiment, the resin layer 21 of the protective sheet 20 that is adhered to the surface 3 of the wafer 1 in the bonding step ST1 has heat resistance under high temperature conditions in the processing step ST3. Therefore, the wafer processing method can be used in the processing process ST3 without replacing the protective sheet 20 attached to the wafer 1 before the grinding process ST2 after the grinding process ST2. Therefore, even if the wafer processing method is thinner than the conventional TAIKO grinding in which the device region 6 is thinned to about 50 μm until the device region 6 is 10 μm or more and the thickness is 20 μm or less, the grinding process ST2. It is not necessary to replace the protective sheet 20 before the subsequent processing step ST3. As a result, the wafer processing method can suppress the breakage of the wafer 1 at the boundary between the ring-shaped reinforcing portion 11 and the circular recess 10 after the TAIKO grinding, and suppress the damage of the TAIKO ground wafer. be able to.

Next, the inventor of the present invention confirmed the effect of the wafer processing method according to the first embodiment. The results are shown in Table 1.

For the product of the present invention in Table 1, the protective sheet 20 was attached to the surface 3 of the wafer 1 in the attachment process ST1, and the grinding process ST2 and the processing process ST3 were carried out. In Comparative Example 1, a protective sheet provided with the resin layer 21 and an adhesive layer made of an acrylic resin or an epoxy resin is used, and the adhesive layer of the protective sheet 20 is attached to the surface 3 of the wafer 1 in the attachment step ST1. Then, the grinding process ST2 and the processing process ST3 were carried out. Comparative Example 2 is attached using a BG (back grind) tape provided with a resin layer made of a polyolefin or polyethylene terephthalate and an adhesive layer made of an acrylic resin or an epoxy resin. In the landing step ST1, the adhesive layer of the protective sheet 20 was attached to the surface 3 of the wafer 1, and the grinding step ST2 and the processing step ST3 were carried out.

In Comparative Example 1, since the melting point of the acrylic resin constituting the adhesive layer of the protective sheet 20 is 150 ° C. and the melting point of the epoxy resin is 250 ° C., the adhesive layer of the protective sheet 20 has heat resistance in the processing step ST3. Due to lack of properties, the adhesive layer was melted and the protective sheet 20 was peeled off in the processing step ST3, and the melted adhesive layer affected the device 5. In Comparative Example 2, the polyolefin or polyethylene terephthalate constituting the resin layer of the BG tape has a melting point of about 150 ° C., the acrylic resin constituting the adhesive layer has a melting point of 150 ° C., and the epoxy resin has a melting point of 250 ° C. Since the temperature is high, the resin layer and the adhesive layer of the BG tape lack heat resistance in the processing step ST3, and the BG tape melts in the processing step ST3, or the melted BG tape affects the device 5. In contrast to Comparative Examples 1 and 2, the resin layer 21 of the protective sheet 20 did not melt in the processing step ST3, and there was no problem in the heat resistance of the protective sheet 20. Therefore, by attaching the protective sheet 20 having only the resin layer 21 made of the polyimide resin to the surface 3 of the wafer 1 in the attaching step ST1, the resin layer 21 of the protective sheet 20 has heat resistance in the processing step ST3. It became clear that it did not melt and did not affect the device 5.

The present invention is not limited to the above embodiment. That is, it can be variously modified and carried out within a range that does not deviate from the gist of the present invention.

1 Wafer 3 Surface 4 Scheduled division line 5 Device 6 Device area 7 Outer peripheral surplus area 8 Back surface 9 Tip 10 Circular recess 11 Ring-shaped reinforcement 12 Bottom surface (grinding surface)
13 Insulation film 20 Protective sheet 22 Dicing tape 71 Holding table ST1 Adhesion process ST2 Grinding process ST3 Processing process ST4 Removal process ST5 Transfer process ST6 Division process ST7 Pickup process

Claims (2)

A method for processing a wafer having a device region in which a plurality of devices partitioned by a planned division line are formed on the surface and an outer peripheral surplus region surrounding the device region.
A bonding process in which a protective sheet made of polyimide resin that does not have an adhesive layer and has heat resistance and is formed in a disk shape is thermocompression bonded to the wafer surface.
After performing the bonding step, a grinding step of grinding the back surface of the wafer corresponding to the device region to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess.
After performing the grinding step, a processing step under high temperature conditions including formation of at least one of an insulating film, a wiring layer and an electrode on the ground surface, and a processing step.
After performing the processing step, a removal step of removing the ring-shaped reinforcing portion and a removal step of removing the ring-shaped reinforcing portion.
After performing the removal step, a transfer step of attaching a dicing tape to the back surface of the wafer and peeling off the protective sheet, and a transfer step.
A division step of dividing the wafer from the surface side along the planned division line after the transfer step is performed, and a division step of dividing the wafer from the surface side.
A pickup process for picking up chips after performing the division process is provided.
The protective sheet is a method for processing a wafer, which is characterized by having heat resistance in the processing process. A method for processing a wafer having a device region in which a plurality of devices partitioned by a planned division line are formed on the surface and an outer peripheral surplus region surrounding the device region.
A bonding process in which a protective sheet made of polyimide resin that does not have an adhesive layer and has heat resistance and is formed in a disk shape is thermocompression bonded to the wafer surface.
After performing the bonding step, a grinding step of grinding the back surface of the wafer corresponding to the device region to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess.
After performing the grinding step, a processing step under high temperature conditions including formation of at least one of an insulating film, a wiring layer and an electrode on the ground surface, and a processing step.
After performing the processing step, a dividing step of dividing the wafer from the grinding surface side into each chip along the planned division line, and
After performing the division step, a pickup step of picking up the chip from the protective sheet with the protective sheet side adsorbed on the holding table is provided.
The protective sheet is a method for processing a wafer, which is characterized by having heat resistance in the processing process.

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