JP5097152B2 - Wafer peeling method - Google Patents

Description

  The present invention relates to a wafer peeling method for peeling a wafer bonded to a support substrate for thinning treatment from the support substrate.

  In recent years, the latest semiconductor device technology has thinned the backside of the wafer by laminating multiple layers of devices, but the wafer is used as a support to give strength to the wafer during this thinning process. Processing is done by pasting together. Generally, a support tape having an adhesive layer formed thereon is used as a support until the thickness is reduced to about 50 μm. However, when the thickness is reduced to about 20 to 40 μm, which is thinner than 50 μm, the support tape is not suitable. A sufficient supporting substrate such as ceramic, sapphire, silicon wafer, quartz glass or the like is used as a support, and the wafer is bonded to the supporting substrate with an adhesive such as wax.

  Conventionally, in order to peel off a wafer bonded to a support substrate, the bonded support substrate and the wafer are sucked and held by upper and lower chucks, and the adhesive layer that bonds the wafer and the support substrate is heated and melted. Then, the wafer is peeled from the support substrate by sliding the upper chuck in the lateral direction (see, for example, Patent Document 1). However, with such a method of peeling by sliding, scratches or cracks may be generated on the wafer device surface, or the support substrate may be damaged.

  In order to improve the drawbacks of slide peeling as described above, Patent Document 1 also describes an apparatus for peeling a wafer by rotating or rotating the upper chuck while lifting the wafer, but the wafer and the support substrate are in surface contact. Since the structure is relatively rotated in the state, there still remains a risk of causing damage such as scratches and cracks on the wafer and the support substrate, which is not satisfactory. In addition, when the support substrate is thick like a ceramic plate or when a plurality of wafers are bonded to one support substrate, it is bonded to a thick support substrate when heated by the upper and lower heating plates. It is difficult to melt the adhesive in a short time, and since the thinned wafer has processing strain, it is easy to spring back, and if multiple thin wafers peel from the support substrate at once, they will warp on the support substrate. The wafers cannot be sucked and transferred by a chuck or the like as they are, and the process is performed manually. This is difficult to automate and the process is very troublesome.

JP-A-6-268051 (paragraphs 0002 to 0009, claims 1, 2 and 19)

  SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer peeling method capable of peeling a wafer thinned by being bonded to a support substrate with an adhesive in a short time without causing damage such as scratches and cracks. .

  In order to solve the above problems, an apparatus and an adhesive that can vertically separate the wafer from the support substrate with a chuck that adsorbs the wafer and moves in the vertical direction are used instead of slide separation, and the wafer and the support substrate are chucked. What is necessary is just to heat up an adhesive in steps so that it may raise to some extent, before adsorb | sucking with a chuck | zipper, without heating to the melting temperature of an adhesive at a part at once, and a chuck | zipper part may lose adhesive force. That is, according to the present invention, the wafer is bonded to the support substrate using an adhesive that foams and decomposes to reduce the adhesive strength when heated, and the back surface of the wafer is ground and thinned, and then the wafer and the support substrate are bonded. The bonded body is placed on the demounting stage, and the bonded body of the wafer and the support substrate is heated to a temperature at which the adhesive does not foam / decompose at the demounting stage, and the adhesive is foamed / decomposed. The heated demount chuck is made to face the wafer attached to the support substrate, the demount chuck is lowered to adsorb the wafer, and the adhesive is foamed and decomposed by conduction heat from the demount chuck, A wafer peeling method is provided, wherein the demounting chuck is moved in the vertical direction to peel the wafer from the support substrate. Problem is resolved.

  Further, according to the present invention, there is provided a demounting chuck used in the above method, wherein the demounting chuck comprises an adsorption portion main body adsorbed on a wafer and a peeling chuck portion surrounding the outer periphery of the adsorption portion main body, A demounting chuck device is provided in which the part is made of stainless steel and the adsorbing part main body is made of a porous ceramic material.

  Further, according to the present invention, the demounting chuck is provided with the heater part having a heater integrally with the peeling chuck part, or provided with the heater part adjacent thereto, or separately from the demounting chuck. A demounting chuck device is provided in which a chuck heat retaining hot plate for heating the main body of the suction unit is provided on the body, and the above-mentioned problems are solved.

  The present invention is configured as described above, and a wafer is bonded to a support substrate by using an adhesive that foams and decomposes to reduce adhesive strength when heated, and after grinding and thinning the back surface of the wafer, The bonded body of the support substrate is placed on the demount stage, and the bonded body of the wafer and the support substrate is heated to a temperature at which the adhesive does not foam / decompose at the demount stage, and the adhesive is foamed / decomposed. The demount chuck heated to a temperature to be opposed to the wafer attached to the support substrate, the demount chuck is lowered to adsorb the wafer, and the adhesive is foamed by the conduction heat from the demount chuck. Since the demounting chuck was moved in the vertical direction and the wafer was peeled off from the support substrate, foaming and After the demounting chuck adsorbs the wafer, the adhesive heated to such a degree is heated by the conduction heat from the demounting chuck and foams and decomposes, so the wafer peels off from the support substrate at the demounting stage. There is no risk. Therefore, even if the adhesive layer is made thin to such an extent that the wafer and the support substrate do not come into contact with each other, for example, 1 to 2 μm, no scratch is caused on the back surface of the wafer. As described above, the wafer is not peeled off from the support substrate before being attracted to the demounting chuck, and the wafer is peeled off from the support substrate after being attracted to the demounting chuck. It can be transported, and accidents that warp or crack can be reliably prevented. In addition, the temperature is raised to a temperature close to the foaming temperature of the adhesive at the demounting stage, for example, about 20 to 70% of the foaming temperature, and then to the foaming / decomposition temperature at the demounting chuck portion, for example, the remaining 30 Since it is sufficient to raise the temperature by about 80%, the heating time at the demounting chuck portion can be shortened, and as a result, the peeling work efficiency can be improved.

  In addition, as described above, an adhesive that foams and decomposes by heating is used as the adhesive, so that the wafer can be easily peeled off from the support substrate, and can be easily peeled vertically by simply moving the demount chuck upward. And there is no risk of scratching or cracking the wafer or support substrate. At this time, after the wafer is adsorbed by the demounting chuck, the demounting chuck is raised by about several tens of μm from the lowered position so that a vacuum break does not occur between the chuck and the wafer before the adhesive foams. If it is controlled to start vertical movement after confirming that the wafer adhesive has been heated to the foaming temperature, a tensile force can be applied to the adhesive portion between the support substrate and the wafer. , The decomposition action proceeds efficiently, and the throughput of the peeling operation can be further improved.

  The demounting chuck includes an adsorption unit main body that adsorbs to a wafer and a peeling chuck unit that surrounds the outer periphery of the adsorption unit main body. The peeling chuck unit is made of stainless steel, and the adsorption unit main body is made of a porous ceramic material. If it is configured to have an adsorption action, it can efficiently heat the adsorption unit body and has excellent wear resistance. Even if it is used for a long time, the wafer adsorption surface will not be damaged, and the wafer will always be kept at the desired flatness. Can be held in. Furthermore, if the heater part is provided integrally with the peeling chuck part, or if the heater part is provided in the vicinity and the adsorption part body is heated, the heat conduction action to the adhesive can be performed reliably, and the demounting chuck and If the chuck heat retention hot plate is provided separately to heat the suction part main body, the configuration of the demount chuck can be simplified.

Explanatory drawing which shows the bonding state of a wafer and a support substrate. Explanatory drawing seen from the front which shows one Example of this invention. The explanatory view which showed one Example of this invention and was seen from the side. Sectional drawing which shows one Example of a demounting chuck | zipper. Sectional drawing which shows the other Example of a demounting chuck | zipper. Sectional drawing which shows the further another Example of a demounting chuck | zipper. Sectional drawing of a part of demounting chuck | zipper.

  2 and 3 are explanatory views showing an embodiment of the present invention. In the apparatus main body 4, a bonded body in which the wafer 2 is bonded to the support substrate 3 with an adhesive a as shown in FIG. 1 is provided, a demounting stage 5 for holding 1, a demounting chuck 6 for sucking the wafer 2, a vertical movement rail 7 for guiding the vertical direction, and a horizontal movement rail 8 for guiding the horizontal direction.

  The demount stage 5 has such a size that the bonded body 1 of the support substrate 3 and the wafer 2 can be placed, and has a built-in heater and a temperature control mechanism (not shown), and is rotated so that the wafer can be moved to the peeling position. It is possible to move left and right or back and forth. The bonded body 1 of the support substrate 3 and the wafer 2 is sucked and held on the demount stage, but may have an appropriate configuration that can be placed in a predetermined position and held in a stable state without being sucked. The heating temperature of the demount stage by the heater can be adjusted within a range of, for example, 50 to 250 ° C. so that the temperature of the adhesive can be raised to a temperature lower than the foaming / decomposition temperature. The temperature of the adhesive can be heated to about 20 to 70% of the foaming / decomposition temperature. This temperature is set to an appropriate temperature according to the type of adhesive. For example, when the wafer is naturally peeled off at 110 ° C. due to the strength of the spring back or starts to flow on the support substrate, it is not peeled off naturally. The temperature is raised only to about 75 ° C.

  A thinning process is performed on the support substrate 3 by attaching a plurality of wafers 2, for example, about 5 wafers of 3 inch size, and the thinning process is performed, but each wafer is processed with a single wafer type support substrate. (Not shown). As the adhesive, the wafer and the supporting substrate can be securely bonded at the temperature during the processing when the thinning process is performed, and when heated to a predetermined temperature at the time of peeling, the adhesive strength is reduced due to foaming / decomposition. A known appropriate adhesive is used. In the embodiment shown in the figure, the support substrate 3 is made of a disk-shaped ceramic block. However, quartz glass or other appropriate material can be used, and a porous material provided with a large number of fine through holes. It may be a quality support substrate.

Image camera 9 for detecting the position of the wafer 2 in the de-mount stage 5 set vignetting has moved the de-mount stage via the control device by the image camera.
This control device can be appropriately configured. For example, when the number of wafers attached to the support substrate is input to the control device, the wafer outer diameter is measured after cueing the attached wafer. The position of the orientation flat or notch is detected by an image camera and the wafer demounting position is recognized in advance. If the wafer is deviated from the recognized position, the demounting stage is rotated or left / right / front / rear to eliminate the deviation. The wafer is moved so that the wafer is positioned at the demount chuck position.

  The demount chuck 6 is constituted by a vacuum chuck, and is provided so as to be movable up and down in order to vertically peel the wafer, and is movable in the lateral direction to transfer the peeled wafer to a cleaning process. At this time, after the wafer 2 is adsorbed by the demounting chuck 6, it waits at the lowered position until the adhesive foams and decomposes, and the demounting chuck is raised after the adhesive foams and decomposes. However, it is preferable that the vacuum break does not occur between the chuck and the wafer before the adhesive is foamed and decomposed, that is, the wafer is not separated from the demount chuck, for example, a divisor from the lowered position where the wafer is sucked and held. The demount chuck may be raised about 10 μm in advance, stopped at that position, and controlled to rise when foaming / decomposition of the adhesive starts. In other words, a sensor (not shown) that confirms that the wafer adhesive has been heated to the foaming / decomposition temperature is provided on the demount stage and demount chuck, and after the temperature rise is confirmed, defoaming / decomposition starts. If the vertical movement of the mount chuck is controlled so as to start gradually, a tensile force can be applied to the adhesive portion between the support substrate 3 and the wafer 2, so that the disassembling action and the peeling work proceed efficiently.

  A fine leak detection mechanism is provided for detecting cracks or cracks in the wafer after the wafer 2 is peeled off as described above. In the embodiment shown in the figure, a sensor capable of detecting leak air is provided in a vacuum suction line connecting the demount chuck 6 and a vacuum source (not shown), and the sensor flows through a crack or crack of the wafer. When leak air is detected, an alarm device for stopping the device is started. In addition, when a melted adhesive or a cleaning fluid or other fluid is sucked into the vacuum suction line, a trap is provided in the middle of the line so that it can be removed automatically or manually.

  Conventionally used chucks that are heated by a heater, such as the above-mentioned demounting chuck, are generally configured to have a heat resistance of about 250 ° C. It is only subjected to heat treatment (abrasion-resistant surface treatment). For this reason, when the wafer was repeatedly adsorbed, the surface-treated portion and the surface of the metal material were rubbed down, and the abrasion material adhered to the wafer adsorbing surface. In the present invention, an adhesive capable of high temperature, for example, an adhesive at around 350 ° C., may be used. Therefore, the demount chuck does not cause thermal distortion even at about 450 ° C. and has excellent heat resistance. A structure is desirable.

  FIG. 4 shows an embodiment of the demounting chuck 6 according to the present invention that meets such a requirement. A heater portion 13 is integrally attached to the lower surface of the chuck body 11 on which the vacuum line 10 is formed via a heat insulating material 12. The heater portion 13 is made of a stainless material and has a heater 14 built therein. A peeling chuck portion 15 is attached below the heater portion 13, and an adsorption portion main body 16 that adsorbs to the wafer is provided inside the peeling chuck portion 15. The peeling chuck portion 15 is made of a stainless steel material, and the surface thereof is heat-treated to improve wear resistance and heat resistance, and at the same time, coated with a wear resistant and heat resistant resin such as Teflon (registered trademark) from the peripheral surface to the lower surface. It is. Moreover, the adsorption | suction part main body 16 is comprised with the porous ceramic material so that the vacuum effect | action from the said vacuum line 10 may act on a lower surface, The lower surface is finished flat. According to such a demounting chuck, the adsorption part main body is directly heated, and the temperature adjustment is easy.

  In the embodiment shown in FIG. 4, the heater unit is connected to the adsorption unit main body and directly heated, but may be heated indirectly. FIG. 5 shows an embodiment of an indirect heating method, wherein the chuck body 17 is rotatably held by a frame 18 that is guided by the longitudinally moving rail and moves up and down, and the heater portion 19 is placed on the lower surface of the frame. It is fixed via a heat insulating material 20. A peeling chuck portion 21 and a suction portion main body 22 made of the same material as those in the embodiment shown in FIG. 4 are provided below the chuck main body 17. It is heated indirectly by the heater unit 19. In this chuck, an annular outlet 23 is provided on the outer periphery of the adsorption unit main body 22, and two lines of a vacuum line 24 leading to a vacuum source and a gas supply line 25 leading to a gas supply source are formed in the chuck body 17, In order to adsorb the wafer, the adsorbing unit main body 22 is connected to a vacuum line so that the lower surface of the adsorbing unit main body is evacuated and air is blown out from the outlet 23 on the outer periphery of the adsorbing unit main body 22 in a ring shape. According to this configuration, even if the molten adhesive tries to wrap around the back surface of the wafer, it can be prevented from being blown off by air and attached to the back surface. Further, the wafer can be transferred to the cleaning process while the wafer is held by the chuck, and the cleaning liquid can be sprayed onto the lower surface and the periphery of the wafer for cleaning. When air is blown out from the air outlet at the time of cleaning, the cleaning liquid or the like can be prevented from entering the adsorbing unit main body from the wafer back surface periphery, and the wafer back surface periphery can be cleaned.

  The demount chuck shown in FIG. 6 is different from the embodiment shown in FIGS. 4 and 5 and does not include a heater. That is, the chuck body 26 similar to the embodiment shown in FIG. 4 has a vacuum line 27, a peeling chuck part 28, and a suction part body 29, but a connecting part 30 without a heater is provided in a part corresponding to the heater part 13. The connecting portion 30 is made of an aluminum material or a stainless material having a heat-treated surface. A chuck heat retaining hot plate 31 for heating the suction part main body is provided separately from the demounting chuck in the movement path of the demounting chuck. The temperature of the chuck heat retaining hot plate 31 can be varied within a range of, for example, about 100 to 180 ° C. according to the foaming / decomposition temperature of the adhesive, and is preferably heated to about 150 ° C. A demounting chuck is placed on the chuck heat retention hot plate, and the demounting chuck can be heated to a temperature at which the adhesive can be foamed and decomposed, for example, about 145 ° C.

  As shown in FIG. 7, if an elastic protrusion 32 such as a heat-resistant O-ring is provided so as to protrude slightly from the lower surface of the peeling chuck portion, for example, about 0.005 mm, the molten adhesion It is possible to prevent the agent or the like from wrapping around the back surface of the wafer, and if the chuck is transferred to the cleaning process while holding the peeled wafer and the cleaning liquid is sprayed onto the wafer, the cleaning liquid does not enter the suction unit body and the wafer It is possible to reliably clean up to the periphery of the back surface.

  Thus, an example of the operation of performing wafer peeling using the above apparatus will be described. The bonded body 1 on which the wafer 2 supporting substrate (ceramic block) 3 is bonded is placed on the demount stage 5 and this bonding is performed. The body 1 is heated to such an extent that the adhesive does not foam or decompose. On the other hand, the demounting chuck 6 is heated to a demounting temperature, for example, about 145 ° C., by the direct or indirect heater portions 13 and 19 or by the chuck heat retaining hot plate 31. When the demount chuck 6 and the support substrate (ceramic block) 3 are heated to a predetermined temperature, the demount chuck 6 is moved to face the wafer and the support substrate (ceramic block) 3 is moved to demount the wafer. Align with the chuck.

  Next, the demount chuck 6 is lowered, and the suction portion main bodies 16, 22, and 29 are attracted to the wafer 2. As a result, heat is transferred from the wafer 2 to the adhesive and the support substrate (ceramic block), and the adhesive is heated to about 130 ° C. after about 20 to 30 seconds. Begins. Therefore, when the demount chuck 6 is gradually moved in the vertical direction, the wafer 2 can be peeled from the support substrate 3. At this time, as described above, the demounting chuck is stopped at a position where it has been raised several tens of μm in advance, and can be peeled off more efficiently if the demounting chuck is raised after foaming / decomposition has started.

  The wafer peeled off by the demount chuck 6 is moved to the wafer transfer chuck 33. In this wafer transfer chuck 33, after the demount chuck 6 is lowered and the wafer is adsorbed to the wafer transfer chuck, the vacuum action of the demount chuck is turned off. It can be transferred while maintaining a flat state without being rounded by the spring back. When the wafer transferred to the transfer chuck is taken out by an appropriate robot or the like, it is only necessary to carry out substantially the same operation so that the wafer is not curled.

  After the wafer is peeled as described above, the ceramic block is rotated manually or automatically, the wafer is then made to correspond to the demount chuck, and the wafers are peeled one after another by the same operation.

DESCRIPTION OF SYMBOLS 1 Bonding body 2 Wafer 3 Support substrate 5 Demount stage 6 Demount chuck 11, 17, 26 Chuck main body 13, 19 Heater part 15, 21, 28 Separation chuck part 16, 22, 29 Adsorption part main body 31 Chuck insulation hot plate 33 Wafer transfer chuck

Claims (3)

The wafer is bonded to the support substrate using an adhesive that foams and decomposes when heated and the adhesive strength decreases, and after the wafer is ground and thinned, the bonded body of the wafer and the support substrate is placed on the demount stage. The demounting chuck and the support are heated to a temperature at which the adhesive is foamed and decomposed, and the bonded body of the wafer and the support substrate is heated to a temperature at which the adhesive does not foam and decompose at the demounting stage. The wafer affixed to the substrate is made to face, the demount chuck is lowered and the wafer is adsorbed. After the wafer is adsorbed by the demount chuck, the adhesive is foamed and decomposed by the conduction heat from the demount chuck. is allowed, before the adhesive is foamed, risen the de-mounted chuck to a position where a vacuum between the wafer and the de-mounting the chuck is not broken It was stopped after confirming that the adhesive until bubbling Decomposes temperature is heated, peeling method of the wafer, which comprises peeling the wafer by moving the de-mounted chuck in a vertical direction from the supporting substrate.   The wafer peeling method according to claim 1, wherein the temperature at which the bonded body of the wafer and the support substrate is heated at the demount stage is 20 to 70% of the foaming temperature of the adhesive.   The support substrate is a disk-shaped ceramic block, and a plurality of wafers are bonded to the support substrate, and the demount stage on which a bonded body of the wafer and the support substrate is mounted has the demount chuck that holds the wafer. The wafer peeling method according to claim 1, wherein the wafer is rotated or moved back and forth and back and forth so that the wafer to be peeled is located at a position to be adsorbed.

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