JP2014067944A - Wafer processing method - Google Patents

Abstract

To provide a wafer processing method capable of preventing breakage of a wafer when a support member is peeled from a thinly ground wafer.
One adhesive layer (A1) of a double-sided adhesive tape (DT) having an adhesive layer (A1, A2) is brought into contact with the surface (W1) of the wafer (W), and the double-sided adhesive tape is adhered to the wafer. The first adhering step, and the other adhesive layer (A2) of the double-sided adhesive tape is brought into contact with the surface (S1) of the metal support member (S) and curved in a range that can be elastically deformed. A second bonding process for bonding the wafer to the wafer, a grinding process for grinding the back surface (W2) of the wafer to thin the wafer to a predetermined finished thickness (t), and an ultraviolet ray on the adhesive layer of the double-sided adhesive tape through the wafer. A pressure-sensitive adhesive layer curing step for curing the pressure-sensitive adhesive layer to reduce the adhesive strength, and a removing step for curving the support member and the double-sided pressure-sensitive adhesive tape to remove the support member and the double-sided pressure-sensitive adhesive tape from the wafer; did.
[Selection] Figure 5

Description

  The present invention relates to a wafer processing method, and more particularly to a wafer processing method in which a wafer attached to a support member is ground and thinned to a predetermined thickness.

  In recent years, it has been required to thin an optical device wafer in order to realize a small and light optical device. The optical device wafer is thinned by grinding the back surface after the optical device is formed in each region partitioned by the division lines on the front surface. In this thinning, in order to protect the optical device, it is common to attach a protective tape to the surface of the optical device wafer (see, for example, Patent Document 1).

  By the way, the rigidity of the optical device wafer is remarkably lowered as it is thinned. For this reason, the optical device wafer is greatly warped as the grinding process proceeds, and there is a high possibility that a crack or a crack will occur. Further, when the outer peripheral portion of the optical device wafer is made into a knife edge and becomes thin, there is a risk that cracks, cracks, chips, etc. may occur in the outer peripheral portion.

  In order to solve the above-mentioned problems associated with grinding, a method of attaching and grinding an optical device wafer as a workpiece on a rigid support member has been proposed (for example, see Patent Document 2). In this method, since the optical device wafer is reinforced by supporting the optical device wafer with the support member made of a rigid body, it is possible to prevent the optical device wafer from being warped by suppressing warpage of the optical device wafer during grinding.

JP-A-5-198542 JP 2006-346836 A

  In the above-described grinding method, the optical device wafer that is a workpiece is fixed to the surface of the support member via, for example, a liquid resin serving as a fixing material, and is ground to a predetermined thickness. The ground optical device wafer is separated from the support member so that the resin is softened and then peeled off. However, since the rigidity of the thinned optical device wafer is extremely low, the optical device wafer may be damaged when the support member is peeled off.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wafer processing method capable of preventing breakage of a wafer when a support member is peeled from a thinly ground wafer.

  The wafer processing method of the present invention is a wafer processing method in which the back surface of the wafer is ground and thinned, and a double-sided adhesive tape in which an adhesive layer made of an ultraviolet curable adhesive is formed on both surfaces of a base sheet. A first adhesion step for adhering one adhesive layer to the surface of the wafer, and after the first adhesion step, the other adhesive layer of the double-sided adhesive tape is exposed on the upper surface to hold the back side of the wafer The double-sided adhesive is sequentially applied from one end to the other end in the outer diameter direction while bending a metal support member that is held on the table and has a thickness that can be bent by an external force within the range of the elastic deformation region. After pressing the other adhesive layer of the tape and attaching the supporting member to the other adhesive layer of the double-sided adhesive tape attached to the wafer, after the second attaching step, Hold the support member on the holding table to A grinding step for shaving and thinning to a predetermined thickness, and the base sheet of the wafer and the double-sided pressure-sensitive adhesive tape are formed of a material that transmits ultraviolet rays. An adhesive layer curing step for irradiating one and the other adhesive layer with ultraviolet rays to reduce the adhesive strength of the one and the other adhesive layer, and after carrying out the adhesive layer curing step, the support member and the double-sided adhesive tape And a removing step of curving and peeling from the wafer.

  According to this configuration, the support member formed to have a thickness that can be bent by an external force is attached to the double-sided adhesive tape while being curved within the range of the elastic deformation region. Air bubbles and the like are not mixed in between, and the adhesion between the support member and the double-sided pressure-sensitive adhesive tape can be improved. Further, the double-sided pressure-sensitive adhesive tape and the support member can be peeled without damaging the wafer because the double-sided pressure-sensitive adhesive tape having an adhesive layer curable with ultraviolet rays is irradiated with ultraviolet rays to reduce the adhesive force and then the support member is curved. Thus, since the support member which can be bent is stuck to a wafer using the double-sided adhesive tape whose adhesive strength falls with ultraviolet rays, the sticking property and peelability of the support member can be improved. Further, it is possible to prevent the wafer from being damaged when the support member is peeled from the thinly processed wafer.

  ADVANTAGE OF THE INVENTION According to this invention, the wafer processing method which can prevent the damage of a wafer at the time of peeling a supporting member from the wafer ground thinly can be provided.

It is a figure which shows a mode that a double-sided adhesive tape is affixed on a wafer in the 1st adhesion process of this Embodiment. It is a figure which shows a mode that a supporting member is affixed on a wafer via a double-sided adhesive tape in the 2nd adhesion process of this Embodiment. It is a figure which shows a mode that a wafer is ground in the grinding process of this Embodiment. It is a figure which shows a mode that the adhesion layer is hardened | cured in the adhesion layer hardening process of this Embodiment. It is a figure which shows a mode that a supporting member and a double-sided adhesive tape are removed from a wafer in the removal process of this Embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following, a wafer processing method using an optical device wafer as a processing target will be described. However, the wafer to be processed according to the present invention is not limited to an optical device wafer.

  The wafer processing method of the present embodiment includes a first attaching step, a second attaching step, a grinding step, an adhesive layer curing step, and a removing step. In the first attaching step, one adhesive layer A1 of the double-sided adhesive tape DT including the adhesive layers A1 and A2 is brought into contact with the surface W1 of the wafer W, and the double-sided adhesive tape DT is attached to the wafer W (see FIG. 1). ). In the second sticking step, the surface S1 of the metal support member S is brought into contact with the other adhesive layer A2 of the double-sided pressure-sensitive adhesive tape DT, and the support member S is curved within a range in which it can be elastically deformed. (See FIG. 2).

  In the grinding step, the back surface W2 side of the wafer W is ground to thin the wafer W to a predetermined finish thickness t (see FIG. 3). In the adhesive layer curing step, ultraviolet rays UV are applied to the adhesive layers A1 and A2 of the double-sided adhesive tape DT through the wafer W to cure the adhesive layers A1 and A2 and reduce the adhesive force (see FIG. 4). In the removing step, the support member S and the double-sided adhesive tape DT are curved to remove the support member S and the double-sided adhesive tape DT from the wafer W (see FIG. 5).

  In the present embodiment, the metal support member S formed to have a thickness that can be bent by an external force is attached to the double-sided adhesive tape DT while being bent within a range that can be elastically deformed. Mixing can be prevented and adhesion between the support member S and the double-sided pressure-sensitive adhesive tape DT can be improved. Further, after the UV adhesive UV irradiates the double-sided adhesive tape DT including the adhesive layers A1 and A2 that are cured by the ultraviolet UV to reduce the adhesive force, the support member S and the double-sided adhesive tape DT are curved and peeled from the wafer W. Therefore, the supporting member S and the double-sided adhesive tape DT can be removed without damaging the wafer W. Details of the wafer processing method according to the present embodiment will be described below.

  The wafer W to be processed by the processing method of the present embodiment is an optical device wafer in which a gallium nitride compound semiconductor layer (not shown) is laminated on the surface of a sapphire substrate having a disk shape (see FIG. 1). On the surface W1 of the wafer W, a grid-like division planned line (not shown) is provided, and an optical device (not shown) is formed in each area partitioned by the division planned line.

  In the wafer processing method according to the present embodiment, first, a first adhering step of adhering the double-sided adhesive tape DT to the surface W1 side of the wafer W is performed. FIG. 1 is a diagram illustrating a state in which the double-sided pressure-sensitive adhesive tape DT is stuck to the wafer W in the first sticking step. As shown in FIG. 1, the double-sided pressure-sensitive adhesive tape DT includes adhesive layers A1 and A2 on both main surfaces of a base sheet B made of PET (polyethylene terephthalate), and has the same area as the wafer W. It has a disk shape. The adhesive layers A1 and A2 are formed of an ultraviolet curable adhesive that cures with ultraviolet UV (FIG. 4). For this reason, if the double-sided pressure-sensitive adhesive tape DT is irradiated with ultraviolet rays UV, the adhesive strength of the double-sided pressure-sensitive adhesive tape DT can be greatly reduced.

  In the first sticking step, first, the back surface W2 side of the wafer W is held on the holding table 11 of the sticking apparatus 1 so that the front surface W1 faces upward. And in a part of outer periphery of the wafer W, the surface W1 of the wafer W and the adhesive layer A1 of the double-sided adhesive tape DT are brought into contact, and the vicinity of the contact portion is pressed from the adhesive layer A2 side by the roller 12 of the sticking apparatus 1. . The double-sided adhesive tape DT is affixed to the front surface W1 of the wafer W by moving the roller 12 in the opposite direction (the direction indicated by the arrow a1 in FIG. 1) sandwiching the center of the wafer W while keeping the pressing force by the roller 12 constant. Worn. In the first attaching step, the release paper RP is attached to the adhesive layer A2 of the double-sided adhesive tape DT, and the adhesive layer A2 and the roller 12 are not in contact with each other. The release paper RP is peeled off from the adhesive layer A2 when the first sticking step is completed.

  A 2nd sticking process is implemented after a 1st sticking process. FIG. 2 is a diagram illustrating a state in which the support member S is attached to the wafer W via the double-sided adhesive tape DT in the second attaching step. In the second sticking step, the back surface W2 side of the wafer W is held on the holding table 11 of the sticking device 1 as in the first sticking step. That is, the wafer W is disposed so that the adhesive layer A2 of the attached double-sided adhesive tape DT faces upward.

  Next, the support member S is positioned above the wafer W so that the adhesive layer A2 of the double-sided adhesive tape DT and the surface S1 of the support member S face each other. Then, a part of the outer periphery of the support member S (held portion S3) is held by a holding portion (not shown) located above the holding table 11. Further, another part (contact part S4) of the support member S located on the opposite side of the held part W3 across the center is brought into contact with a part of the outer periphery of the double-sided adhesive tape DT from above. As a result, the adhesive layer A2 and the surface S1 of the support member S are in contact with each other at a part of the outer periphery of the double-sided adhesive tape DT. Thereafter, as shown in FIG. 2A, the roller 12 is pressed in the opposite direction (indicated by the arrow a2 in FIG. 2A) across the center of the wafer W by pressing the vicinity of the contact portion S4 with the roller 12 from the back surface S2 side of the support member S. Move.

  The support member S is a disk-shaped aluminum plate having a larger area than the wafer W, and is formed to a thickness (for example, 0.3 mm to 0.7 mm) that can be bent by an external force. For this reason, when the vicinity of the contact portion S4 is pressed by the roller 12 while the held portion S3 is held upward, the support member S is curved. In the present embodiment, the support member S is curved within a range that allows elastic deformation (within the range of the elastic deformation region). Here, the elastically deformable range refers to a range in which the support member S can return to the original flat disk shape by releasing the pressing by the roller 12 or holding the held portion S3. If the holding position of the held portion S3, the diameter of the roller 12, the pressing force by the roller 12, and the like are appropriately set, the support member S can be curved within a range in which it can be elastically deformed.

  As described above, the supporting member S is attached to the adhesive layer A2 by moving the roller 12 to the held portion S3 side while applying a pressing force so that the supporting member S is curved within the elastically deformable range. Worn. That is, the wafer W is bonded to the metal support member S via the double-sided adhesive tape DT that serves as a fixing material (FIG. 2B). Thus, by sticking the support member S while curving in the elastic deformation region, it is possible to prevent air bubbles from being mixed between the support member S and the adhesive layer A2, and the support member S and the double-sided adhesive tape DT. Adhesion can be improved.

  The surface S1 of the support member S is rougher than the surface W1 of the wafer W. For this reason, the contact area between the support member S and the adhesive layer A2 is larger than the contact area between the wafer W and the adhesive layer A1, and the double-sided adhesive tape DT is firmly bonded to the support member S side. Thus, by making the surface S1 of the support member S rougher than the surface W1 of the wafer W, the support member S and the double-sided pressure-sensitive adhesive tape DT can be easily separated in the subsequent removal step. The surface roughness of the support member S can be adjusted by, for example, sand blasting or rough grinding.

  A grinding process is implemented after a 2nd sticking process. FIG. 3 is a diagram showing how the wafer W is ground in the grinding process. In the grinding process, as shown in FIG. 3, the back surface W <b> 2 side of the wafer W is ground by the grinding device 2. The grinding device 2 includes a holding table 21 having a suction surface made of a porous ceramic material. A rotation mechanism (not shown) is provided below the holding table 21, and the holding table 21 is rotated around the rotation axis C1. The wafer W is held on the holding table 21 via the support member S.

  A grinding wheel 22 is provided above the holding table 21 so as to be movable up and down. The grinding wheel 22 is connected to a rotation mechanism (not shown) and is rotated around the rotation axis C2. A grinding wheel 23 is disposed below the grinding wheel 22. By rotating the holding table 21 and the grinding wheel 22 in a state where the grinding wheel 23 is in contact with the back surface W2 of the wafer W, the back surface W2 side of the wafer W is ground. The grinding wheel 22 is rotated at a higher speed than the holding table 21.

  A height gauge (not shown) is provided in the vicinity of the holding table 21 so that the thickness of the wafer W can be measured. By grinding while measuring the thickness of the wafer W with this height gauge, the wafer W is thinned to the finished thickness t. In the processing method of the present embodiment, the wafer W is supported by the metal support member S via the double-sided adhesive tape DT. The double-sided pressure-sensitive adhesive tape DT uses a base material sheet B made of PET that is not easily deformed compared to a liquid resin or the like.

  After the grinding process, an adhesive layer curing process is performed. FIG. 4 is a diagram illustrating how the adhesive layers A1 and A2 are cured in the adhesive layer curing step. In the adhesive layer curing step, as shown in FIG. 4, ultraviolet light (ultraviolet light) UV is irradiated onto the adhesive layers A <b> 1 and A <b> 2 of the double-sided adhesive tape DT by the ultraviolet irradiation device 3. The ultraviolet irradiation device 3 includes a holding table 31 that holds the support member S and an ultraviolet light source 32 above the holding table 31. The support member S is held on the holding table 31 of the ultraviolet irradiation device 3, and the ultraviolet ray UV is irradiated from the ultraviolet source 32 to the back surface W 2 side of the wafer W.

  The wafer W is composed of a sapphire substrate that transmits ultraviolet light UV having a predetermined wavelength. Moreover, the base material sheet B of the double-sided pressure-sensitive adhesive tape DT is made of PET that transmits ultraviolet rays UV having a predetermined wavelength. For this reason, the irradiated ultraviolet rays UV pass through the wafer W and the base sheet B and reach the adhesive layers A1 and A2. The adhesive layers A1 and A2 irradiated with ultraviolet rays UV are cured by a chemical reaction, and the adhesive force is reduced. Before or after the adhesive layer curing step, the protective tape T stretched on the annular frame F is attached to the back surface W2 of the wafer W (see FIG. 5).

  A removal process is implemented after the adhesion layer hardening process. FIG. 5 is a diagram showing how the support member S and the double-sided adhesive tape DT are removed from the wafer W in the removing step. In the removal step, as shown in FIG. 5, a part of the outer periphery of the support member S (the gripped portion S5) is gripped and pulled in the opposite direction across the center (the direction indicated by the arrow a3 in FIG. 5).

  Since the support member S is formed with a bendable thickness, the support member S is bent when a tensile force as described above is applied. Here, the support member S is curved beyond the elastically deformable range. That is, this curvature corresponds to plastic deformation. In addition, since the adhesive force of the adhesive layer A1 is reduced by the adhesive layer curing step, the support member S and the double-sided adhesive tape DT are both peeled from the wafer W. Although the adhesive strength of the adhesive layer A2 is also reduced by the adhesive layer curing step, since the double-sided adhesive tape DT is firmly bonded to the support member S side, the support member S and the double-sided adhesive tape DT are peeled together. .

  Thus, by using the metal support member S formed to have a thickness that can be bent by an external force, the support member S can be bent and the peelability can be improved. The removal process is performed by, for example, a peeling device (not shown), but may be performed manually by an operator. Further, in the removing step, the support member S may be curved within a range that can be elastically deformed. If the support member S is curved within a range in which the support member S can be elastically deformed, the support member S after peeling can be reused, so that the cost for processing the wafer W can be suppressed.

  As described above, according to the wafer processing method of the present embodiment, the double-sided pressure-sensitive adhesive tape is bent while the support member S formed to a thickness that can be bent by an external force is elastically deformable. Since it sticks to DT, it is not necessary to mix bubbles between the support member S and the double-sided pressure-sensitive adhesive tape DT, and the adhesion between the support member S and the double-sided pressure-sensitive adhesive tape DT can be improved.

  In addition, a support member formed to have a thickness that can be bent by an external force after irradiating UV UV to the double-sided pressure-sensitive adhesive tape DT including the adhesive layers A1 and A2 that are cured by ultraviolet UV. Since S is curved, the double-sided adhesive tape DT and the support member S can be peeled without damaging the wafer W. Thus, since the support member S which can be bent is stuck to the wafer W using the double-sided pressure-sensitive adhesive tape DT whose adhesive strength is reduced by the ultraviolet ray UV, the sticking property and the peelability of the support member S can be improved. . And damage of the wafer W at the time of peeling the support member S from the wafer W processed thinly can be prevented.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, although the case where the optical device wafer consisting of a sapphire substrate is used as the processing target is shown in the above embodiment, the processing target is not limited to this. At least a wafer that can transmit ultraviolet rays in the adhesive layer curing step can be used as a processing target. For example, various glass substrates may be processed.

  Moreover, in the said embodiment, although the case where an aluminum plate is used as a supporting member is shown, a supporting member is not restricted to this. Any member may be used as long as it has both high supportability in the back grinding process and high peelability in the removal process. For example, a stainless plate or a copper plate having high rigidity can be processed into an appropriate thickness and used. Further, the shape of the support member is not limited to the disc shape, and may be an arbitrary shape.

  Moreover, in the said embodiment, although PET is used as a base material sheet of a double-sided adhesive tape, a base material sheet may be comprised with another material. Any material can be used for the base sheet as long as it can transmit ultraviolet rays in the adhesive layer curing step and is not easily deformed compared to a liquid resin or the like.

  Moreover, in the said embodiment, although the surface of the supporting member is made rougher than the surface of a wafer, the surface of a supporting member may be smooth. If the double-sided pressure-sensitive adhesive tape cannot be removed by the above-described removal step, a step of removing the double-sided pressure-sensitive adhesive tape after the support substrate S is removed may be added.

  In addition, the configurations, methods, and the like according to the above-described embodiments can be changed as appropriate without departing from the scope of the object of the present invention.

  The present invention is useful when grinding an optical device wafer or the like to a predetermined thickness.

DESCRIPTION OF SYMBOLS 1 Adhering device 2 Grinding device 3 Ultraviolet irradiation device 11 Holding table 12 Roller 21 Holding table 22 Grinding wheel 23 Grinding wheel 31 Holding table 32 Ultraviolet light source A1, A2 Adhesive layer B Base sheet DT Double-sided adhesive tape F Frame S Support member S1 , W1 Front surface S2, W2 Back surface S3 Holding portion S4 Contact portion S5 Holding portion T Protection tape UV UV W Wafer a1, a2, a3 Arrow t Finish thickness

Claims (1)

A wafer processing method for grinding and thinning the back surface of a wafer,
A first adhering step of adhering one adhesive layer of a double-sided adhesive tape having an adhesive layer made of an ultraviolet curable adhesive on both surfaces of a base sheet to the surface of the wafer;
After the first sticking step, the other adhesive layer of the double-sided adhesive tape is exposed on the upper surface, the back side of the wafer is held on the holding table, and the metal is formed to a thickness that can be bent by external force. The support member made of plastic is pressed against the other adhesive layer of the double-sided adhesive tape sequentially from one end to the other end while curving within the elastic deformation region, and the support member is adhered to the wafer. A second attaching step for attaching to the other adhesive layer of the double-sided adhesive tape;
After the second sticking step, a grinding step for holding the support member on a holding table and grinding the back surface of the wafer to reduce the thickness to a predetermined thickness;
The base sheet of the wafer and the double-sided pressure-sensitive adhesive tape is formed of a material that transmits ultraviolet light, and after performing the grinding step, the one and the other pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape are irradiated with ultraviolet light. An adhesive layer curing step for reducing the adhesive strength of one and the other adhesive layer;
After performing the adhesive layer curing step, the removing step of curving the support member and the double-sided adhesive tape and peeling from the wafer;
A wafer processing method comprising:

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