JP2014053350A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method capable of forming all embedded electrodes as through electrodes by exposing them from an insulating film and finishing heads of the through electrodes to the same plane as the insulating film.SOLUTION: A wafer processing method includes the steps of: thinning a wafer by grinding a rear surface of the wafer to such an extent that an embedded electrode 21 is not exposed (rear surface grinding step); forming the embedded electrode 21 as a through electrode 21 by protruding the embedded electrode 21 from the rear surface (etching step); coating the rear surface with an insulating film (insulating film coating step); exposing the embedded electrode 21 from the insulating film by removing the through electrode 21 protruding from the rear surface and finishing a head of the through electrode 21 to the same plane as the insulating film (finishing step); arranging a bump 31 in each through electrode 21 (bump arranging step); removing a carrier plate 25 by grinding it using a grinding wheel 30 (carrier place removing step); removing a resin 27 stuck to the wafer 11 with a solvent (resin removing step); replacing the wafer with a dicing tape by sticking the dicing tape to the rear surface of the wafer; and dividing the wafer into individual devices.

Description

  The present invention relates to a method for processing a wafer such as a semiconductor wafer.

  In recent years, in order to achieve high integration, high density, miniaturization, and thinning of semiconductor devices, a stacked type in which a plurality of semiconductor chips such as MCP (multi-chip package) and SIP (system in package) are stacked. Semiconductor packages have been proposed.

  Such a stacked semiconductor package is formed by stacking a plurality of semiconductor chips on a package substrate called an interposer. In general, the interposer and the semiconductor chip electrodes, or the electrodes of the stacked semiconductor chips are electrically connected with a gold wire, and then the semiconductor chip is molded and sealed with resin to the interposer. A semiconductor package is manufactured.

  However, in this method, since the gold wire bonded to the electrode of the semiconductor chip protrudes to the outer peripheral surplus region of the semiconductor chip, there is a problem that the package size becomes larger than the semiconductor chip.

  In addition, when the mold is sealed with the resin, the wire wire is deformed to cause a disconnection or a short circuit, or the air remaining in the mold resin expands upon heating and causes damage to the semiconductor package. .

  Therefore, a technique of providing a through electrode (via electrode) that penetrates the semiconductor chip in the thickness direction and connects to the electrode of the semiconductor chip in the semiconductor chip, stacking the semiconductor chips and joining the through electrodes and electrically connecting the electrodes. Have been proposed (see, for example, Japanese Patent Application Laid-Open Nos. 2004-207606 and 2004-241479).

  In this method, a plurality of semiconductor devices are formed on the surface of the silicon wafer, and from each semiconductor device, a plurality of embedded copper electrodes (copper posts) that are connected to the electrodes of the semiconductor device and extend to the back side of the silicon wafer are formed. A so-called TSV (Through Silicon Via) wafer is used.

  The embedded copper electrode has a height equal to or higher than the finished thickness of the semiconductor chip, and the back surface of the wafer is ground and polished by a grinding device to thin the wafer to a thickness just before the embedded copper electrode is exposed from the back surface. Thereafter, by selectively etching only the silicon wafer, the tip of the buried copper electrode protrudes from the back surface of the wafer to form a through electrode.

  When realizing such a stacked semiconductor package in which semiconductor chips are stacked, a carrier plate is generally adhered to the surface of the wafer with a resin or the like in order to improve the handling of the wafer (for example, Japanese Patent Application Laid-Open No. 2004-2004). -207606 and JP2011-243901).

JP 2004-207606 A JP 2004-241479 A JP 2004-207606 A JP 2011-243901 A

  The wafer processing method as described above includes many steps, but it is very difficult to remove the carrier plate from the wafer near the final stage of processing.

  Conventionally, for example, the carrier plate is peeled from the wafer by heating from the carrier plate side to soften the resin bonding the carrier plate and the wafer, but there is a problem that it takes a long time.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer processing method in which a carrier plate bonded to a wafer via a resin can be easily removed near the final stage of processing. Is to provide.

  According to the present invention, a plurality of embedded electrodes each having a device formed in each region partitioned by a plurality of scheduled division lines formed in a lattice pattern on the surface and reaching a depth equal to or greater than the finished thickness of the wafer. Is a wafer processing method in which a wafer having a chamfered portion on the outer peripheral edge is divided into individual devices, and a cutting blade is positioned on the outer peripheral edge of the wafer so that the wafer exceeds the finished thickness from the surface side. A chamfered portion removing step of cutting the wafer into a circular shape or completely cutting the wafer into a circular shape from the back side to remove the chamfered portion, and a carrier plate via a resin on the wafer surface before or after the chamfered portion removing step is performed And a carrier plate disposing step for disposing the plurality of embedded electrodes from the back surface of the wafer after the carrier plate disposing step. Embedded electrode detection step for detecting the depth of the tip of the wafer, and after performing the embedded electrode detection step, a back surface grinding step for grinding and thinning the back surface of the wafer to such an extent that the embedded electrode is not exposed on the back surface, After performing the back surface grinding process, the wafer is etched from the back surface of the wafer, and the embedded electrode protrudes from the back surface of the wafer to form a through electrode. After performing the etching step, an insulating film is formed on the back surface of the wafer. And after the insulating film coating step is performed, the through electrode protruding from the back surface of the wafer is removed and exposed from the insulating film, and the head of the through electrode is the same as the insulating film A finishing process for finishing the surface, a bump arranging process for arranging a bump on the head of each through electrode after the finishing process, and before performing the bump arranging process. After the carrier plate removing step for grinding and removing the carrier plate using a grinding wheel in which a grinding wheel is arranged in a ring shape, and after the carrier plate removing step is performed, the carrier plate is adhered to the wafer A resin removing step for removing the resin with a solvent, a transfer step for attaching a dicing tape to the back surface of the wafer, and transferring the wafer to the dicing tape, and after performing the transfer step, the wafer is separated into individual devices. And a dividing step of dividing the wafer into a wafer.

  According to the wafer processing method of the present invention, since the carrier plate itself is ground and removed, a difficult process of peeling the carrier plate can be omitted, and the carrier plate can be easily removed from the wafer.

  Furthermore, since the resin remaining after the grinding can be removed by dissolving with a solvent, a transfer step of sticking a dicing tape to the back surface of the wafer and transferring the wafer to the dicing tape can be continuously performed.

FIG. 1A is a front perspective view of a semiconductor wafer having a buried copper electrode with bumps, and FIG. 1B is a cross-sectional view thereof. It is a partial cross section side view which shows a chamfer part removal process. It is sectional drawing of the semiconductor wafer after a chamfer part removal process implementation. It is sectional drawing explaining a carrier plate arrangement | positioning process. It is sectional drawing which shows an embedded copper electrode detection process. It is a partial cross section side view which shows a back surface grinding process. It is sectional drawing of the wafer after back surface grinding process implementation. It is sectional drawing of the wafer after an etching process implementation. It is sectional drawing of the wafer after insulating film coating process implementation. It is sectional drawing of the wafer after finishing process implementation. It is sectional drawing of the wafer after bump provision process implementation. It is a partial cross section side view which shows a carrier plate removal process. It is sectional drawing after a carrier plate removal process implementation. It is sectional drawing explaining the resin removal process. It is sectional drawing which shows a transfer process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1A, a perspective view of a semiconductor wafer 11 having embedded copper electrodes with bumps to be processed by the processing method of the present invention is shown. FIG. 1B is a longitudinal sectional view thereof.

  A semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11a, and a plurality of division lines 13 are formed. A device 15 such as an IC or an LSI is formed in each of the areas partitioned by.

  As shown in FIG. 1B, from each semiconductor device 15 formed on the semiconductor wafer 11, a plurality of embedded copper electrodes 21 embedded at a depth equal to or larger than the finished thickness t1 of the device extend toward the back surface 11b. ing. A bump 23 is bonded to the upper end of each embedded electrode 21. The electrode 21 may be formed from other conductor materials.

  As shown in FIG. 1 (A), the semiconductor wafer 11 thus configured (hereinafter sometimes simply referred to as a wafer) 11 includes a device region 17 in which a plurality of semiconductor devices 15 are formed, An outer peripheral surplus area 19 surrounding the device area 17 is provided on the surface 11a. Further, as shown in FIG. 1B, an arc-shaped chamfered portion 11 e is formed on the outer peripheral portion of the wafer 11.

  In the wafer processing method of the present invention, first, a chamfered portion removing step for removing the chamfered portion 11e of the wafer 11 is performed. In this chamfered portion removing step, as shown in FIG. 2, the wafer 11 is sucked and held by the chuck table 10 of the cutting apparatus.

  In FIG. 2, reference numeral 12 denotes a cutting unit of a cutting apparatus. A spindle 16 is rotatably supported in a spindle housing 14, and a cutting blade 18 is attached to the tip of the spindle 16.

  In this chamfered portion removing step, the cutting blade 18 of the cutting unit 12 rotating at high speed is cut into the chamfered portion 11e of the wafer 11 by a predetermined depth from the surface 11a side, and the chuck table 10 is rotated at a low speed, as shown in FIG. As described above, a circular step portion 11 f is formed on the outer peripheral portion of the wafer 11.

  The cutting depth of the cutting blade 18 in this chamfered portion removing step is at least a depth exceeding the finished thickness of the wafer 11 from the surface 11a of the wafer 11, and forms a circular step portion 11f having a depth of about 100 μm, for example. As the cutting blade 18, for example, a washer blade having a thickness of about 1 to 2 mm is preferably used.

  The chamfered portion removing step shown in FIG. 2 is performed by cutting the cutting blade 18 into the chamfered portion 11e of the wafer 11, and grinding is performed by bringing the grinding wheel of the grinding wheel into contact with the chamfered portion 11e of the wafer 11. Thus, part or all of the chamfered portion 11e may be removed.

  All of the chamfered portions may be removed by complete cutting (full cutting). In that case, the chamfered portion removing step is performed after the carrier plate arranging step. The full cut may be performed from the back surface 11 b side of the wafer 11.

  A cross-sectional view of the wafer 11 after the chamfered portion removing step is shown in FIG. The circular step portion 11f is at least a depth exceeding the finished thickness of the wafer 11 from the surface 11a of the wafer 11, and has a depth of about 100 μm from the surface 11a of the wafer 11, for example.

  After performing the chamfered portion removing step, as shown in FIG. 4, a carrier plate disposing step of disposing the carrier plate 25 on the surface 11a of the wafer 11 via the resin 27 having adhesiveness is performed. The resin 27 acts as an adhesive, and the carrier plate 25 is adhered to the surface 11 a of the wafer 11 with the resin 27.

  The carrier plate 25 is made of, for example, a silicon wafer having a uniform thickness or glass. In the present embodiment, the carrier plate 25 is illustrated as being formed of glass. The thickness of the resin 27 is preferably about 20 μm, for example.

  After the carrier plate placement step, a buried copper electrode detection step for detecting the depth of the tip of the buried copper electrode 21 from the back surface 11b of the wafer 11 is performed. In this embedded copper electrode detection step, for example, as shown in FIG. 5, the carrier plate 25 is sucked and held by the chuck table 20 of the grinding apparatus, and the wafer 11 is imaged from the back surface 11b side by the infrared camera (IR camera) 22. To implement.

  Since infrared rays pass through the silicon wafer 11, the focal point of the IR camera 22 is changed to focus on the front surface 11a of the wafer 11, the tip of the embedded copper electrode 21, and the back surface 11b of the wafer 11 to detect the focal length. Thus, the height of the front surface 11a of the wafer 11, the front end of the embedded copper electrode 21 and the back surface 11b of the wafer 11 can be detected, and the depth of the front end of the embedded copper electrode 21 from the back surface 11b of the wafer can be detected. it can.

  The wafer 11 is imaged while moving the IR camera 21 in the direction of arrow A, the depth of all or a plurality of embedded copper electrodes 21 is detected, and the detected values are stored in a memory provided in the controller of the grinding apparatus. To do.

  After performing the embedded copper electrode detection process, a back surface grinding process is performed in which the back surface 11b of the wafer 11 is ground and thinned so that the embedded copper electrode 21 is not exposed on the back surface 11b of the wafer 11. In this back surface grinding step, the carrier plate 25 is sucked and held by the chuck table 20 of the grinding device, and the back surface 11b of the wafer 11 is exposed.

  In FIG. 6, the grinding unit 24 of the grinding apparatus includes a spindle 26 that is rotationally driven by a motor (not shown), a wheel mount 28 that is fixed to the tip of the spindle 26, and a grinding wheel 30 that is detachably attached to the wheel mount 28. Including. The grinding wheel 30 includes an annular wheel base 32 and a plurality of grinding wheels 34 fixed to the outer periphery of the lower end of the wheel base 32.

  In this back grinding process, while rotating the chuck table 20 in the direction indicated by the arrow a at 300 rpm, for example, the grinding wheel 30 is rotated in the direction indicated by the arrow b at, for example, 6000 rpm, and a grinding unit feed mechanism (not shown) is driven. The grinding wheel 34 of the grinding wheel 30 is brought into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 30 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed. While measuring the thickness of the wafer 11 with a contact-type or non-contact-type thickness measurement gauge, the wafer 11 is ground to a thickness just before the tip of the embedded copper electrode 21 is exposed on the back surface 11b of the wafer 11 as shown in FIG. To do.

  After performing the back grinding process, an etching process is performed in which the wafer 11 is selectively etched from the back surface 11b of the wafer 11 so that the embedded copper electrode 21 protrudes from the back surface 11b of the wafer 11 to form a through electrode. This etching step is preferably performed by plasma etching, for example.

  After performing the etching process, as shown in FIG. 9, an insulating film coating process for coating the back surface 11 b of the wafer 11 with the insulating film 29 is performed. By this insulating film coating step, the insulating film 29 is coated not only on the back surface 11 b of the wafer 11 but also on the tip surface of the through electrode 21.

  After performing the insulating film coating step, the portion of the through electrode 21 protruding from the back surface 11 b of the wafer 11 is removed to expose the through electrode 21 from the insulating film 29 and finish the head of the through electrode 21 on the same surface as the insulating film 29. Perform the process.

  In the present embodiment, this finishing step is performed by a chemical mechanical polishing method, so-called CMP (Chemical Mechanical Polishing). CMP is performed by supplying a polishing liquid (slurry) between the polishing pad and the object to be polished and sliding the polishing pad and the object to be rotated while rotating each other. A non-woven fabric is generally used as the polishing pad, and the surface of the object to be polished is polished with the polishing pad while supplying a polishing liquid (slurry) containing floating abrasive grains such as silica.

  In the present embodiment, the polishing film (slurry) is supplied while the polishing pad is brought into contact with the insulating film 29 and the wafer 11 and the polishing pad are slid relative to each other so that the insulating film covered with the through electrode 21 is provided. As shown in FIG. 10, the through electrode 21 is exposed from the insulating film 29 and the head of the through electrode 21 is finished on the same plane as the insulating film 29. As shown in FIG.

  After performing the finishing process by CMP, as shown in FIG. The bump 31 is made of, for example, solder, and the bump 31 made of solder is joined to the head of the through electrode 21. In the processing method of this embodiment, the bump disposing step may be performed after a carrier plate removing step and a solvent removing step which will be described later.

  After the bump placement step, as shown in FIG. 12, a protective tape 36 composed of a base material 38 and an adhesive layer 40 is adhered to the back surface 11b of the wafer 11, and the protective tape 36 is interposed by the chuck table 20 of the grinding apparatus. Then, the wafer 11 is held and the carrier plate 25 is exposed. At this time, the periphery of the protective tape 36 may be attached to an annular frame. In that case, the protective tape 36 is a dicing tape.

  Then, while rotating the chuck table 20 in the direction indicated by the arrow a at, for example, 300 rpm, the grinding wheel 30 is rotated in the direction indicated by the arrow b, for example, at 6000 rpm, and a grinding unit feeding mechanism (not shown) is driven to drive the grinding wheel 30. The grinding wheel 34 is brought into contact with the carrier plate 25.

  Then, the grinding wheel 30 is ground by a predetermined amount at a predetermined grinding feed speed, and the carrier plate 25 is ground and removed. Subsequently, the resin 27 is ground and the resin 27 is ground as shown in FIG. Finish the grinding leaving a thin layer.

  Next, as shown in FIG. 14, while rotating the wafer 11 having a thin layer of the resin 27 with the chuck table 20, the solvent 43 is dropped from the nozzle 42 onto the resin 27, and the solvent 43 is spread over the entire surface of the resin 27. The resin 27 is dissolved and removed by the solvent 43.

  After carrying out the resin removing step, as shown in FIG. 15, the rear surface 11b of the wafer 11 is stuck to the dicing tape T whose outer peripheral portion is stuck to the annular frame F, and the wafer 11 is transferred to the dicing tape T. You may implement a process. As a result, the wafer 11 is supported by the annular frame F via the dicing tape T.

  The wafer 11 is sucked and held via a dicing tape T on a chuck table of a cutting apparatus (not shown), and the wafer 11 is cut along the planned dividing line 13 to reach the dicing tape T by the cutting blade. The device 15 is divided. Each device 15 includes a plurality of through electrodes 21 having bumps 23 and 31 bonded to both ends.

  According to the wafer processing method of the above-described embodiment, since the carrier plate 25 itself is ground and removed, a difficult process of peeling the carrier plate 25 from the wafer 11 can be omitted, and the carrier plate 25 can be easily formed. Can be removed from the wafer 11. Further, the resin 27 remaining after grinding can be removed by dissolving with a solvent.

11 Semiconductor Wafer 11e Chamfer 13 Divided Line 15 Device 18 Cutting Blade 21 Embedded Copper Electrode (Penetration Electrode)
22 IR camera 23, 31 Bump 25 Carrier plate 29 Insulating film 30 Grinding wheel 34 Grinding wheel T Dicing tape F Annular frame

Claims (1)

A device is formed in each region partitioned by a plurality of division lines formed in a lattice pattern on the surface, and a plurality of embedded electrodes extending from each device to a depth greater than the finished thickness of the wafer are embedded. A wafer processing method for dividing a wafer having a chamfered portion on the outer peripheral edge into individual devices,
A chamfered portion removing step in which a cutting blade is positioned on the outer peripheral edge of the wafer and the wafer is cut into a circle beyond the finish thickness from the surface side, or the wafer is completely cut into a circle from the back side to remove the chamfered portion;
Before or after performing the chamfered portion removing step, a carrier plate disposing step of disposing a carrier plate via a resin on the surface of the wafer;
After performing the carrier plate placement step, embedded electrode detection step of detecting the depth of the tip of the plurality of embedded electrodes from the back surface of the wafer;
After performing the embedded electrode detection step, a back surface grinding step of grinding and thinning the back surface of the wafer to such an extent that the embedded electrode is not exposed on the back surface;
After performing the back surface grinding step, etching the wafer from the back surface of the wafer to etch the embedded electrode from the back surface of the wafer to be a through electrode, and
After performing the etching step, an insulating film coating step of coating an insulating film on the back surface of the wafer;
After performing the insulating film coating step, the through electrode protruding from the back surface of the wafer is removed and exposed from the insulating film, and the finishing step of finishing the head of the through electrode on the same surface as the insulating film;
After performing the finishing step, a bump disposing step of disposing a bump on the head of each through electrode;
Before or after performing the bump disposing step, a carrier plate removing step of grinding and removing the carrier plate using a grinding wheel in which a grinding wheel is disposed in a ring shape;
After carrying out the carrier plate removal step, a resin removal step of removing the resin stuck to the wafer with a solvent;
A transfer step of attaching a dicing tape to the back surface of the wafer, and transferring the wafer to the dicing tape;
A division step of dividing the wafer into individual devices after performing the transfer step;
A method for processing a wafer, comprising:

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