JP4897312B2 - Fixed carrier - Google Patents

Description

  The present invention relates to a fixed carrier for a semiconductor wafer that is thinned by back grinding using a grinding fluid.

  For example, in the case of a 300 mm type, the semiconductor wafer is formed to a thickness of about 775 μm so that it does not warp in the previous process of semiconductor manufacturing. Since it is not suitable for a semiconductor package, in a process called a back grinding process, it is thinned to 100 μm or less in some cases by grinding the back surface, and then separated into individual chips in a dicing process.

  In the semiconductor wafer back grinding process, first, a flexible protective sheet (also referred to as a BG sheet) is attached to protect the pattern formation surface of the semiconductor wafer (not shown), and the size thereof is slightly larger than that of the semiconductor wafer. Then, the semiconductor wafer is set on a plurality of tables on a turntable in the back grinding apparatus, and the turntable is rotated to place and position the semiconductor wafer in the work area of the grinding apparatus.

  The protective sheet is, for example, a solvent-resistant film having a thickness of 50 to 200 μm based on EVA or soft PVC, and an acrylic, urethane, butadiene, or silicone adhesive layer having a thickness of 10 to 60 μm. And are discarded without being reused after use as a disposable product.

  Once the semiconductor wafer is placed in the work area of the grinding machine, the back surface of the semiconductor wafer is ground while flowing a polishing liquid such as pure water with a rotating grindstone, and then the back surface of the semiconductor wafer is etched by about 1 μm with chemicals for grinding. By removing the accompanying damage layer, the semiconductor wafer is thinned (see Patent Document 1).

  After the semiconductor wafer is thinned, the etched back surface of the semiconductor wafer is fixed to a hollow carrier jig with an adhesive tape used in the dicing process, specifically UV tape, and then the pattern forming surface of the semiconductor wafer. If the protective sheet is peeled off, the semiconductor wafer supported by the carrier jig can be separated into individual chips with a grindstone called a blade.

By the way, in the back grinding process of the semiconductor wafer, as described above, the protective sheet is attached to the pattern forming surface of the semiconductor wafer one by one, and the protective sheet is disposed of after use, so that a large amount of waste is suppressed. There is a big problem that you can't. In order to solve this problem, the applicant has proposed a fixed carrier that can be used repeatedly.
JP-A-2005-93882

  Since the fixed carrier proposed by the applicant can be used repeatedly as described above, it is not necessary to dispose of the protective sheet after use, and the generation of a large amount of waste can be suppressed.

  However, the applicant wants to make various improvements to the fixed carrier to add value and stimulate technological breakthroughs without being satisfied with only such effects. Specifically, during the back-grinding process, the grinding fluid enters the fixed carrier to reduce the reliability for repeated use, or the grinding fluid adheres to the semiconductor wafer handling device and other peripheral devices, causing contamination. Since there is a possibility of fear, we hope to prevent and prevent these.

  The present invention has been made in view of the above, and a fixed carrier capable of eliminating the possibility that the reliability of repeated use decreases due to the ingress of the grinding liquid or that the grinding liquid adheres to the peripheral device of the semiconductor wafer and causes contamination. The purpose is to provide.

In the present invention, in order to solve the above problems, at least for a semiconductor wafer to be thinned by back grinding using a grinding fluid,
A substrate having rigidity, a recess provided in the substrate, a plurality of support protrusions provided in the recess, and supported by the plurality of support protrusions so as to cover the recesses and detachably sticking and holding the semiconductor wafer An adhesive layer, a supply / exhaust path that is provided on the substrate and guides the gas in the recesses covered by the adhesive layer to the outside based on driving of the negative pressure source, and a ventilation waterproof that regulates the intrusion of the grinding fluid into the supply / exhaust path Including
The substrate is configured in a multilayer structure, and a flexible thin film is interposed between the substrate layers as a breathable waterproof material, and this thin film is positioned in the middle of the supply / discharge path .

  Here, the semiconductor wafer in the claims is not particularly limited to the 200 mm type or the 300 mm type. On this semiconductor wafer, orientation flats and notches for discriminating crystal orientation and facilitating alignment are appropriately formed. Further, the substrate of the fixed carrier and the ventilation waterproofing material can be formed in a circular shape, an elliptical shape, a rectangular shape, a polygonal shape or the like in a plan view.

  The recess, the adhesive layer, and the supply / discharge path are not particularly limited. Further, the plurality of support protrusions may be regularly arranged in the recesses, or may be irregularly arranged. The plurality of support protrusions may be integrated with the recess or may be a separate structure. The support protrusion can be formed in a truncated cone shape, a prism shape, a truncated pyramid shape, or the like.

  According to the present invention, the ventilation waterproof material is provided in the supply / discharge path communicating with the concave portion of the substrate to restrict the ingress of the grinding fluid, so that the grinding fluid enters the fixed carrier to reduce the reliability for repeated use. Can be prevented. In addition, since the ventilation waterproof material allows only the gas to pass through the supply / exhaust passage without passing the grinding fluid, it may interfere with the deformation of the adhesive layer while following the support protrusion as the gas is sucked into the recess. Absent.

According to the present invention, there is an effect that it is possible to eliminate the possibility that the reliability related to repeated use of the fixed carrier is lowered due to the penetration of the grinding fluid. Further, there is an effect that it is possible to prevent the contamination from being caused by the grinding liquid adhering to peripheral devices such as a semiconductor wafer handling device. In addition, since the breathable waterproof material is a flexible thin film that covers the supply / discharge path, even if the mounting surface of the supply / discharge path is irregular, the supply / discharge path can be covered accurately and good sealing properties can be obtained. Can do. Further, since the thin film is sandwiched between the substrate layers, a strong water stop structure can be expected, and the thin film can be prevented from being peeled off from the supply / discharge path due to the inflow of the grinding fluid.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A fixed carrier 20 in this embodiment includes a rigid substrate 21 set on a back grinding apparatus 1 as shown in FIGS. An elastically deformable adhesive layer 25 that detachably attaches and holds the recessed hole 22 formed in the substrate 21, a plurality of support protrusions 24 disposed in the recessed hole 22, and the semiconductor wafer W to be back-ground. A supply / exhaust path 26 that guides the air in the recessed hole 22 covered with the adhesive layer 25 to the outside, and a ventilation waterproof film 30 that prevents the grinding fluid of the back grinding apparatus 1 from entering the supply / exhaust path 26. And the semiconductor wafer W can be stored in a state where it is held in a substrate storage container such as a wafer cassette 5 · 5A or FOUP.

  As shown in FIGS. 1 and 2, the back grinding apparatus 1 includes a turntable 4 that is rotatably installed on a gantry 2 that is a main body, and a fixed carrier 20 that is rotatably supported on the turntable 4. A plurality of chuck tables 6 that are detachably mounted and held, a grinding device 7 that grinds the back surface of the semiconductor wafer W held by the fixed carrier 20 on the chuck table 6 through rough grinding and finish grinding, and the grinding processing And a cleaning device 10 for the semiconductor wafer W.

  The gantry 2 is formed long in the front-rear direction, and the handling device 3 is installed at the front center of the work surface, and the plane circular turntable 4 can be rotated with the upper part exposed at a substantially center portion of the work surface. The grinding device 7 is erected on the rear part of the work surface so as to face the rear part of the surface of the turntable 4 from above. On both the left and right sides of the handling device 3, a wafer cassette 5 in which a plurality of thick semiconductor wafers W before back grinding held by the fixed carrier 20 are arranged and stored, and a thin semiconductor wafer after back grinding held by the fixed carrier 20 are stored. A wafer cassette 5A for aligning and storing W is mounted.

  The turntable 4 is formed into a large-diameter disk shape using a predetermined material, for example, and a plurality of chuck tables 6 are supported at intervals in the circumferential direction of the exposed upper surface. It functions to change the position of the chuck table 6 in the direction of the handling device 3 or the direction of the grinding device 7 by rotating at an angle.

  The chuck table 6 is configured to be a flat planar circle by fitting a porous ceramic disk to a stainless steel frame, for example, and based on the pressure reduction of a vacuum device (not shown) in the gantry 2, the semiconductor wafer W It functions to detachably mount and hold the fixed carrier 20 holding the adhesive. At the position corresponding to the supply / discharge path 26 of the fixed carrier 20 in the chuck table 6, sealing is applied so as not to depressurize the inside of the recessed hole 22 covered with the adhesive layer 25.

  The grinding device 7 includes a rough grinding device 8 that performs rough grinding processing on the back surface of the semiconductor wafer W from above with a rotating grindstone 8a of about # 320 to 360 through a grinding liquid, and is disposed adjacent to the rough grinding device 8 for rough grinding. The rear surface of the processed semiconductor wafer W is provided with a finish grinding device 9 that performs a finish grinding process with a rotating grindstone 9a of about # 2000 from above through a grinding liquid.

  The substrate 21 of the fixed carrier 20 is formed as a flat thin plate having a thickness of about 0.5 to 2.0 mm using a predetermined material as shown in FIGS. It is a large flat circle, and is formed in a size that can be stored in the wafer cassette 5 or 5A or the substrate storage container. Examples of the material of the substrate 21 include metal materials such as aluminum alloy, magnesium alloy and stainless steel, resin molding materials such as polyamide (PA), polycarbonate (PC), polypropylene (PP), acrylic and polyvinyl chloride, and glass. It is done.

  The thickness of the substrate 21 is in the range of 0.5 to 2.0 mm, preferably about 1.0 mm. This is because a thinned semiconductor is formed when the thickness of the substrate 21 is less than 0.5 mm. This is because the semiconductor wafer W may be bent or bent when it is handled. On the contrary, if the thickness of the substrate 21 exceeds 2.0 mm, the substrate 21 may be caught when being taken in and out of the wafer cassette 5 or 5A, etc., which may cause trouble.

  As shown in FIG. 4, the recessed hole 22 is formed in a shallow recess in most of the substrate 21 except for the peripheral edge of the substrate 21, and is formed in a planar circle having a size substantially corresponding to the semiconductor wafer W. The semiconductor wafer W is substantially opposed to the peripheral edge portion of the semiconductor wafer W through the adhesive layer 25. The recessed hole 22 is formed to a depth of about 0.05 to 0.5 mm, preferably about 0.2 mm, and a plurality of support protrusions 24 that support the adhesive layer 25 from below are provided in parallel on the bottom surface. .

  The plurality of support protrusions 24 are regularly arranged on the bottom surface of the recess hole 22 by a molding method, a sand blasting method, an etching method, or the like, for example, and each support protrusion 24 is approximately the same height and length as the depth of the recess hole 22. It is formed in a cylindrical shape.

  As shown in FIGS. 3 and 4, the adhesive layer 25 is made of, for example, ethylene-methyl methacrylate, silicone rubber, urethane elastomer, linear low density polyethylene (LLPE), ethylene-methyl methacrylate copolymer, olefin-based heat. Using a plastic elastomer, a propylene-olefin copolymer, an acrylic adhesive / olefin base elastomer film, etc., it is formed into a planar circular thin film larger than the semiconductor wafer W and adhered to the surface peripheral portion of the substrate 21. At the same time, it is bonded to each of the plurality of support protrusions 24, covers the recessed hole 22, and divides a space for air circulation between the bottom surface.

  As shown in FIG. 4, the supply / discharge path 26 is perforated in the lower part of the substrate 21, and the downstream part thereof is detachably connected to the vacuum pump 27 via a communication hole 29 of the peeling table 28, a peeling hand (not shown) or the like. Based on the driving of the vacuum pump 27, the air in the recessed hole 22 covered with the adhesive layer 25 is exhausted to the outside to function as a negative pressure. Then, by this air exhaust, the flat adhesive layer 25 is deformed into an uneven shape in the direction of the bottom surface of the recessed hole 22 while following the plurality of support protrusions 24, and is partially separated from the semiconductor wafer W to be in close contact with the semiconductor. The wafer W can be easily peeled off.

  The size of the supply / discharge path 26 is not particularly limited, but is preferably 2 mm or less so as not to adversely affect the back grinding operation. Further, the peeling table 28 is formed in, for example, a substantially flat disk shape and is installed outside the back grinding apparatus 1 together with the vacuum pump 27, and the substrate 21 of the fixed carrier 20 carried out from the back grinding apparatus 1 is attached and detached. Mount freely.

  As shown in the figure, the air-permeable waterproof membrane 30 is a flexible waterproof and moisture-permeable material, such as a porous PTFE sheet (trade name Gore-Tex (registered trademark), which allows air to pass through but does not allow liquids such as grinding fluid made of pure water to pass through. )) Or the like, and is bonded to the bottom surface of the recessed hole 22 to cover the opening of the supply / discharge path 26.

  In the above, when the semiconductor wafer W is thinned to a thickness of 100 μm or less by back grinding and separated into individual chips in the dicing process, first, the fixed carrier 20 in which the semiconductor wafer W is adhesively held in advance in the wafer cassette 5. Is stored in the back grinding apparatus 1, the fixed carrier 20 is transferred from the wafer cassette 5 to the chuck table 6 of the turntable 4 by the handling apparatus 3, and the fixed carrier 20 is opposed to the chuck table 6 and held under reduced pressure. .

  When the fixed carrier 20 is thus mounted on the chuck table 6, the turntable 4 rotates to convey the chuck table 6 from the handling device 3 side to the grinding device 7 side, and the fixed carrier 20 rotates together with the chuck table 6. The back surface of the semiconductor wafer W on which the grinding device 7 rotates is sequentially ground with the rotating grindstones 8a and 9a of the rough grinding device 8, the finish grinding device 9, and the grinding liquid, and the wafer cassette 5A is accommodated.

At the time of the grinding operation, the ventilation waterproofing film 30 controls the flow of the grinding fluid through the supply / discharge passage 26 and flows into the recessed hole 22, thereby causing contamination of the adhesive layer 25 of the fixed carrier 20 and the semiconductor wafer W. There is nothing at all.
Thereafter, the back surface of the semiconductor wafer W is etched by about 1 μm with a chemical by an etching apparatus (not shown), and a damaged layer due to grinding is removed. By removing the damaged layer, the semiconductor wafer W is completely thinned.

  Next, the etched back surface of the semiconductor wafer W is fixed to a hollow carrier jig through an adhesive tape used in the dicing process, specifically UV tape, and the semiconductor wafer W is removed from the fixed carrier 20. . Specifically, a vacuum pump 27 connected via a peeling table 28, a peeling hand, or the like is driven to deform the adhesive layer 25 of the fixed carrier 20 into irregularities in the direction of the bottom surface of the recessed hole 22, thereby providing a semiconductor. Since the wafer W can be easily peeled off, it can be easily detached from the fixed carrier 20.

  At this time, since the air-permeable waterproof film 30 allows only air to pass through the supply / discharge passage 26 without passing the grinding liquid, there is no hindrance to the deformation of the adhesive layer 25 due to air suction.

  When the semiconductor wafer W is supported on the carrier jig by the UV tape, the surplus portion of the UV tape can be cut, and the semiconductor wafer W arranged in the hollow portion of the carrier jig can be separated into individual chips with a grindstone.

  According to the above configuration, the air-permeable waterproof film 30 covers the supply / discharge path 26 communicating with the recessed hole 22 and blocks the inflow of the grinding fluid during the back grinding process, so that the grinding fluid enters the fixed carrier 20 and repeats. It does not reduce reliability for use. Further, it is possible to eliminate the possibility that the grinding liquid adheres to the handling device 3 of the semiconductor wafer W and other peripheral devices to cause contamination. Furthermore, if a flexible porous PTFE sheet is used as the breathable waterproof membrane 30, excellent processability, adhesion, and chemical resistance can be obtained.

  Next, FIG. 5 shows a second embodiment of the present invention. In this case, the substrate 21 of the fixed carrier 20 is formed not in a single layer structure but in a multilayer structure, and the substrate layer 21a and the substrate layer are formed. A breathable waterproof film 30 is interposed between the air vent waterproof film 21 a and the vented waterproof film 30 so as to be positioned in the middle of the supply / discharge path 26. The other parts are the same as those in the above embodiment, and the description thereof is omitted.

  In this embodiment, the same effect as that of the above embodiment can be expected, and since the ventilation waterproof film 30 is sandwiched between the substrate layer 21a and the substrate layer 21a, a strong water stop structure can be expected. It is obvious that the air-permeable waterproof membrane 30 can be prevented from being peeled off from the supply / exhaust passage 26 due to the inflow of water.

  Next, FIG. 6 shows a third embodiment of the present invention. In this case, a flat circular ventilation waterproof film 30 covering the opening of the supply / discharge path 26 is bonded to the bottom surface of the recess hole 22. Attaching holes 31 that fit into the plurality of support protrusions 24 are formed in the peripheral edge of the breathable waterproof film 30. The other parts are the same as those in the above embodiment, and the description thereof is omitted.

  In this embodiment, the same effect as that of the above embodiment can be expected, and the mounting hole 31 at the peripheral edge of the breathable waterproof film 30 is fitted into the support protrusion 24 to regulate its positional deviation and dropout. It is obvious that the structure can prevent the breathable waterproof film 30 from peeling off due to the ingress of the grinding fluid.

  In addition, although the single ventilation waterproof membrane 30 was shown in the said embodiment, it is not limited to this at all, For example, you may laminate | stack and use the several ventilation waterproof membrane 30. FIG. In addition, although the ventilation waterproof film 30 is formed using a porous PTFE sheet, it may be formed of a known material other than the porous PTFE sheet that allows air to pass but does not allow liquid such as grinding liquid to pass. Further, as shown in FIG. 7, the peripheral portion 23 of the recess hole 22 is provided with a suppression body 32 that suppresses the vibration of the semiconductor wafer W, and the suppression body 32 is inwardly directed from the inner surface of the peripheral portion 23 of the recess hole 22. You may form from the several comb tooth 33 which protrudes in this.

  In this way, since there are a plurality of comb teeth 33 in the holding portion of the fixed carrier 20 that holds the peripheral edge of the semiconductor wafer W facing each other, even if the position is slightly shifted when setting the semiconductor wafer W on the fixed carrier 20, The periphery of the semiconductor wafer W can be fixed uniformly. Accordingly, since the peripheral portion of the semiconductor wafer W does not partially vibrate in the back grinding process, the vibrating portion peels off from the fixed carrier 20 and the grinding liquid enters between the fixed carrier 20 and the semiconductor wafer W. The fear can be suppressed very effectively, and contamination of the semiconductor wafer W can be greatly expected.

It is a plane explanatory view showing typically the back grinding device in the embodiment of the fixed carrier concerning the present invention. It is side surface explanatory drawing which shows typically the back grinding apparatus in embodiment of the fixed carrier which concerns on this invention. It is a plane explanatory view showing typically an embodiment of a fixed carrier concerning the present invention. It is a section explanatory view showing typically an embodiment of a fixed carrier concerning the present invention. It is a section explanatory view showing typically the 2nd embodiment of the fixed carrier concerning the present invention. It is a section explanatory view showing typically a 3rd embodiment of a fixed carrier concerning the present invention. It is principal part top explanatory drawing which shows typically 4th Embodiment of the fixed carrier which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back grinding apparatus 3 Handling apparatus 4 Turntable 6 Chuck table 7 Grinding apparatus 8 Rough grinding apparatus 9 Finish grinding apparatus 20 Fixed carrier 21 Substrate 21a Substrate layer 22 Recessed hole (recessed part)
24 Support protrusion 25 Adhesive layer 26 Supply / exhaust path 27 Vacuum pump (negative pressure source)
28 Peeling table 30 Breathable waterproof membrane (breathable waterproof material, thin film)
31 Mounting hole W Semiconductor wafer

Claims (1)

A fixed carrier for a semiconductor wafer that is thinned by at least a back grind using a grinding fluid,
A substrate having rigidity, a recess provided in the substrate, a plurality of support protrusions provided in the recess, and supported by the plurality of support protrusions so as to cover the recesses and detachably sticking and holding the semiconductor wafer An adhesive layer, a supply / exhaust path that is provided on the substrate and guides the gas in the recesses covered by the adhesive layer to the outside based on driving of the negative pressure source, and a ventilation waterproof that regulates the intrusion of the grinding fluid into the supply / exhaust path Including
A fixed carrier comprising a substrate having a multilayer structure, a flexible thin film interposed between the substrate layer and the substrate layer as a breathable waterproof material, and the thin film being positioned in the middle of the supply / discharge path .

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