Wafer processing method

Abstract

To propose a new technique that reliably prevents a broken part from adhering onto a device when a protruding portion of a die attach layer is broken.SOLUTION: A wafer processing method includes a bonding step of forming a die attach layer 20 in which a protruding portion 22 is formed on the outer periphery of a wafer 10 by attaching the wafer 10 to a sheet S via the die attach layer 20 having a diameter larger than the diameter of the wafer 10, and a protruding portion removing step of removing the protruding portion 22 from the sheet S by bringing a removing member 33 into contact with the protruding portion 22.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer.

Background Art

[0002] Conventionally, a die attach film has been widely used for mounting a device chip on a mounting substrate, and a tape called a two-in-one (2in1) in which a die attach layer by a die attach film is formed on a tape that is later expanded while holding a wafer is also widely used.

[0003] And, in consideration of the displacement of the wafer that occurs when the wafer is adhered onto the die attach layer formed on the tape, the diameter of the die attach layer is formed larger than the diameter of the wafer. For this reason, in a state where the wafer is adhered to the tape, an overhang portion of the die attach layer is formed on the outer periphery of the wafer.

[0004] On the wafer, for example, a modified layer serving as a division starting point is formed by a laser processing apparatus, and the modified layer is broken by expanding the tape to be fragmented into chips. At this time, the die attach film forming the die attach layer also breaks together with the chips.

[0005] Here, when the die attach film breaks, there is a concern that the overhang portion of the die attach film peels off from the tape and adheres to the surface of the divided chip. If the die attach film adheres to the device surface of the chip, it may damage the device or cause a mounting defect in a subsequent mounting process, which becomes a problem.

[0006] In view of the above points, for example, in Patent Document 1, an expand device that presses and stops the overhang portion of the die attach film to prevent scattering has been proposed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the configuration of Patent Document 1, it can be said that it is difficult to completely prevent the scattering of fragments of the die attach film, such as the die attach film adhered to the pressing member floating in the expand device and adhering to the device.

[0009] In addition, when the protruding portion of the die attach film breaks and adheres to the inside of the expand device, it may fall at an unexpected timing later and float in the expand device and adhere to the device. Therefore, improvement has been eagerly desired.

[0010] In view of the above problems, the present invention proposes a novel technique for surely preventing the broken portion from adhering to the device when the protruding portion of the die attach layer breaks.

Means for Solving the Problems

[0011] The problems to be solved by the present invention are as described above. Next, means for solving this problem will be described.

[0012] According to one aspect of the present invention, a sticking step of sticking the wafer to a sheet through a die attach layer having a diameter larger than the diameter of the wafer, so that a protruding portion of the die attach layer is formed on the outer periphery of the wafer; removing member For the protruding portion Adhere and transfer by pressing, a protruding portion removing step of removing the protruding portion from the sheet, and a wafer processing method comprising the steps is provided.

[0013] Also, according to one aspect of the present invention, the removing member is constituted by a tape having an adhesive layer laminated on a base material. A method for processing a wafer is provided.

[0014] Also, according to one aspect of the present invention, an annular frame having an opening formed at the center, the removing member covering the opening, a protective layer formed on the removing member corresponding to the wafer inside the opening, and a removing unit preparation step of preparing a removing unit having the above is further provided. In the protruding portion removing step, the protruding portion is removed by bringing the adhesive layer of the removing member into contact with the protruding portion while facing the protective layer of the removing unit to the wafer. A method for processing a wafer is provided.

[0015] Also, according to one aspect of the present invention, a dividing start point forming step of forming a dividing start point for dividing the die attach layer on the wafer before or after the sticking step, and an expand step of expanding the sheet to form a plurality of chips in which the die attach layer is laminated in a state where the dividing start point is formed on the wafer and the protruding portion is removed from the sheet. A method for processing a wafer is provided. A method for processing a wafer is provided.

[0016] Also, according to one aspect of the present invention, the sheet to which the wafer is attached is fixed to an annular frame for holding the wafer, positioning portions are formed on the annular frame for holding the wafer and the annular frame of the removing unit, respectively, and in the protruding portion removing step, the position of the protective layer is made to coincide with the position of the wafer by aligning the positioning portions of both annular frames. A method for processing a wafer is provided. A method for processing a wafer is provided.

Effects of the Invention

[0017] According to the present invention, before expanding the wafer, since the protruding portion of the die attach layer has been removed from the sheet, it is possible to prevent problems such as the protruding portion broken during expansion peeling off from the sheet and adhering to the surface of the divided chips.

Brief Description of Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1(A) shows a wafer 10 which is an example of a workpiece. On the surface 10a of the wafer 10, a plurality of devices 11 are formed at intervals, and division planned lines 13, 13 are set in a lattice pattern between the respective devices 11.

[0020] Hereinafter, a processing method using the present invention will be described according to the flowchart shown in FIG. 2.

[0021] <Adhesion step> As shown in FIG. 1(B), this is a step of forming an overhanging portion 22 of the die attach layer 20 on the outer periphery of the wafer 10 by attaching the back surface 10b of the wafer 10 to the sheet S via a die attach layer 20 having a diameter larger than the diameter of the wafer 10.

[0022] More specifically, as shown in FIG. 1(B), the die attach layer 20 is formed on the surface of the sheet S, and the back surface 10b of the wafer 10 is attached to the surface of the die attach layer 20. An annular frame F is attached to the surface of the sheet S so as to surround the wafer 10, and a wafer unit U in which the wafer 10 and the annular frame F are integrated is configured.

[0023] The die attach layer 20 is formed to have a larger diameter than the wafer 10 so as to surely house the wafer 10 inside, and the overhanging portion 22 protruding to the outer periphery of the wafer 10 is configured in an annular shape so as to surround the outer periphery of the wafer 10.

[0024] When the sheet S is configured as a so-called 2in1 tape, the die attach layer 20 is integrally laminated on the surface layer of the sheet S. In addition, a separate die attach film may be attached to the sheet S to form a die attach layer, or a liquid die attach agent may be applied to the sheet S to form a die attach layer.

[0025] <Division starting point formation step> Before or after the sticking step, a step of forming a starting point for dividing the die attach layer 20 on the wafer. This starting point for division is formed along the planned division line 13 (Fig. 1(A)).

[0026] For example, when forming a modified layer along the planned division line 13 inside the wafer 10 by laser processing, this modified layer becomes the starting point for dividing the wafer 10. Then, at this starting point for dividing the wafer 10, the wafer 10 is divided into chips, and the die attach layer 20 is also broken simultaneously when dividing the wafer into these chips. Therefore, the starting point for dividing the wafer 10 also becomes the starting point for dividing the die attach layer 20.

[0027] Also, by DBG processing (Dicing Before Grinding) or SDBG processing (Stealth Dicing Before Grinding), the wafer that has already been divided into chips can be transferred to the die attach layer 20 on the sheet S to be in the same state as Fig. 1(B). In this case, the gap (groove) between the chips becomes the starting point for dividing the die attach layer 20.

[0028] <Overhang removal step> As shown in Figs. 3(A) and 3(B), the removal member 30 For removes the overhang portion 22 Adhesion by making And transfer it, which is a step of removing the overhang portion 22 from the sheet S.

[0029] Figs. 3(A) and 3(B) are diagrams for explaining the first embodiment of the overhang removal step. The removal member 30 is composed of a cylindrical member rotatably supported at the tip of the arm 32, and its surface is composed of a material having tackiness (adhesiveness) to the die attach layer 20 (overhang portion 22).

[0030] Then, the removal member 30 is adhered so as to be pressed against the protruding portion 22, and the wafer unit U is rotated relative to the removal member 30, so that the portion of the protruding portion 22 of the die attach layer 20 moves to the side of the removal member 30. As shown in FIG. 3(B), the protruding portion 22 is removed from the sheet S.

[0031] FIGS. 4(A) to 4(D) are diagrams for explaining a second embodiment of the protruding portion removal step. In this second embodiment, a removal unit 34 having an annular frame 35 with an opening formed in the center, a removal member 33 covering the opening, and a protective layer 37 formed on the removal member 33 corresponding to the wafer 10 inside the opening is prepared, and the protruding portion removal step is performed.

[0032] FIG. 4(A) shows the surface configuration of the removal unit 34 in which the outer peripheral edge of the removal member 33 is adhered to the back side of the annular frame 35 to integrate the removal member 33 and the annular frame 35. The removal member 33 is formed of a tape having an adhesive layer laminated on a base material, and the surface 33a side thereof is formed of a surface without an adhesive layer.

[0033] FIG. 4(B) shows the back surface configuration of the removal unit 34. An adhesive layer 33n is formed on the back surface 33b of the removal member 33. Further, in the removal member 33, a non-adhesive protective layer 37 is formed at a position facing the wafer 10. The protective layer 37 is for preventing the adhesive layer 33n of the removal member 33 from adhering to the device formation region of the wafer 10. The protective layer 37 can be formed, for example, by adhering a non-adhesive film to the back surface 33b of the removal member 33.

[0034] As shown in FIG. 4(B), an annular protective layer 38 may be formed on the back surface 33b of the removal member 33 with a gap from the protective layer 37 so as to surround the protective layer 37. The annular protective layer 38 is for preventing the adhesive layer 33n of the removal member 33 from adhering to the annular frame F (FIG. 4(C)) of the wafer unit U. The annular protective layer 38 can be formed, for example, by attaching an annular film having no adhesiveness to the back surface 33b of the removal member 33.

[0035] As shown in FIG. 4(B), the adhesive layer 33n of the removal member 33 is exposed in the annular region between the protective layer 37 and the annular protective layer 38. Then, as shown in FIG. 4(C), the wafer unit U and the removal unit 34 are opposed to each other, and as shown in FIG. 4(D), both are brought into a state of being bonded together. At this time, the wafer 10 is covered with the protective layer 37, and the protruding portion 22 is covered with the adhesive layer 33n.

[0036] Then, as shown in FIG. 4(D), by pressing the roller 39 against the position corresponding to the protruding portion 22 from the surface 33a side of the removal member 33, the protruding portion 22 of the die attach layer 20 is adhered to the back surface 33b (adhesive layer 33n) of the removal member 33 and removed from the sheet S.

[0037] As described above, in the protruding portion removal step, the removal unit 34 is prepared in advance, and while the protective layer 37 of the removal unit 34 faces the wafer 10, the adhesive layer 33n of the removal member 33 For the protruding portion 22 Adhere is made And transfer to remove the protruding portion 22.

[0038] In addition, the diameter of the protective layer 37 facing the wafer 10 may be the same as the diameter of the wafer 10, or may be larger than the device formation region of the wafer 10 and smaller than the diameter of the wafer 10. Thereby, on the back surface 33b of the removal member 33, the region corresponding to the device formation region (the region where the device is formed) of the wafer 10 is masked by the protective layer 37, and the adhesive layer 33n of the removal member 33 adheres, preventing problems such as damage to the device.

[0039] Also, as shown in FIG. 4(C), when the wafer unit U and the removal unit 34 are opposed to each other, the following can be done to ensure that the protective layer 37 coincides with the position of the wafer 10.

[0040] That is, as shown in FIGS. 4(C) and (D), the sheet S to which the wafer 10 is attached is fixed to the annular frame F for holding the wafer. Positioning portions Fa and 35a are formed on the annular frame F for holding the wafer and the annular frame 35 of the removal unit 34, respectively. In the overhang portion removal step, the positions of the protective layer 37 are made to coincide with the position of the wafer 10 by aligning the positioning portions Fa and 35a of the two annular frames F and 35.

[0041] Thereby, by making the positions of the wafer 10 and the protective layer 37 coincide, it is possible to surely prevent the adhesive layer 33n of the removal member 33 from adhering to the wafer 10. The positioning portions Fa and 35a can be configured by, for example, notches formed in the outer peripheral portions of the annular frames F and 35. Also, the annular frames F and 35 may have the same shape or different shapes from each other, and are not particularly limited.

[0042] <Expand step> This is a step of expanding the sheet in a state where the division starting point is formed on the wafer and the overhang portion is removed from the sheet to form a plurality of chips with a die attach layer laminated thereon.

[0043] This expansion step can be implemented, for example, by an expansion device 80 shown in FIGS. 5(A) and 5(B). The expansion device 80 includes a frame holding means 81 for holding the annular frame F of the wafer unit U, and a driving means 84 which serves as a tape expansion means for expanding (expanding) the sheet S attached to the annular frame F held by the frame holding means 81.

[0044] The frame holding means 81 has a frame holding member 81a and a plurality of clamp mechanisms 81b disposed on the outer periphery of the frame holding member 81a. The upper surface of the frame holding member 81a forms a placement surface 81c for placing the annular frame F. The annular frame F placed on the placement surface 81c is fixed to the frame holding member 81a by the clamp mechanism 81b. The frame holding means 81 is supported by the driving means 84 so as to be movable forward and backward in the vertical direction.

[0045] An expansion drum 83 is disposed inside the annular frame holding member 81a. This expansion drum 83 has an inner diameter and an outer diameter that are smaller than the inner diameter of the annular frame F and larger than the outer diameter of the wafer 10 attached to the sheet S attached to the annular frame F.

[0046] The driving means 84 for moving the frame holding member 81a forward and backward in the vertical direction is composed of a plurality of air cylinders, and its piston rod 85 is connected to the lower surface of the frame holding member 81a.

[0047] The driving means 84 is configured to move the frame holding member 81a vertically between a reference position (FIG. 5(A)) where the placement surface 81c is substantially at the same height as the upper end of the expansion drum 83 and an expansion position (FIG. 5(B)) a predetermined amount below the upper end of the expansion drum 83.

[0048] In the above configuration, as shown in FIG. 5(A), the die attach layer 20 is cooled as the cooling atmosphere, and when the driving means 84 is driven to lower the frame holding member 81a while the annular frame F is clamped by the clamping mechanism 81b, as shown in FIG. 5(B), the sheet S expands while being held by the expanding drum 83 from below.

[0049] When the sheet S expands, an external force that spreads radially acts on the wafer 10 adhered to the sheet S, and due to this external force, starting from the modified layer, the wafer 10 is divided into chips C. Along with the division of this chip C, the portion of the die attach layer 20 that is integral with each chip C breaks and is divided together with the chip C.

[0050] In the above expand step, before expanding the wafer 10, since the protruding portion 22 (FIGS. 1(B) and 3(B)) of the die attach layer 20 has been removed from above the sheet S, it is possible to prevent problems such as the broken protruding portion 22 peeling off from the sheet S during expansion and adhering to the surface of the divided chip C.

[0051] In the above description, after forming the wafer unit U as shown in FIGS. 3(A) and 3(B), the protruding portion removal step is performed, and then the expand step is performed. However, it is also possible to form the wafer unit U after first performing the protruding portion removal step and the expand step.

[0052] Specifically, first, as shown in FIG. 6(A), the back surface 10b of the wafer 10 is adhered to the sheet 1S via a die attach layer 120 having a diameter larger than the diameter of the wafer 10. Next, as shown in FIG. 6(B), the protruding portion 122 is removed from above the sheet 1S by bringing the protruding portion 122 into contact with the removing member 130. At this time, the end portion of the sheet 1S is held by the clamps 51, 51.

[0053] Next, as shown in FIG. 6(C), by moving the clamps 51, 51 to expand the sheet 1S, the die attach layer 120 breaks together with the wafer 10 and is divided into chips C, C. At this time, the die attach layer 120 is cooled in a cooling atmosphere.

[0054] Also, when the chip C is divided, since the protruding portion 122 has been removed from the sheet 1S in advance, it is possible to prevent problems such as the broken protruding portion 122 peeling off from the sheet 1S and adhering to the surface of the divided chip C when expanding.

[0055] Next, as shown in FIG. 7(A), the wafer 10 is sucked and held by the holding table 54 via the sheet 1S, and the annular frame F is attached to surround the wafer 10 on the surface of the sheet 1S. At this time, by pressing the sheet 1S with the roller 56 from the lower side of the annular frame F, the annular frame F is firmly adhered to the sheet 1S. Also, at this time, the annular frame F is pressed from above by the pressing device 58.

[0056] Next, as shown in FIG. 7(B), at the position of the annular frame F, the outer peripheral portion of the sheet 1S is removed by pressing and rotating the cutter device 60 from the lower side of the sheet 1S, and a wafer unit U is formed as shown in FIG. 7(C).

[0057] In the wafer unit U formed in this way, a gap is formed between the chips C, C. Also, a die attach layer is formed on the back surface of each chip C, C.

Explanation of Reference Numerals

[0058] 10 Wafer 10a Surface 10b Back Surface 11 Device 13 Division Planned Line 20 Die Attach Layer 22 Protruding Portion 30 Removal Member 32 Arms 33 Removal member 33a Surface 33b Back surface 33n Adhesive layer 34 Removal unit 35 Annular frame 37 Protective layer 38 Annular protective layer 39 Roller C Chip F Annular frame 1S Sheet U Wafer unit

Claims

1. A sticking step of sticking the wafer to a sheet through a die attach layer having a diameter larger than the diameter of the wafer, so that an overhanging portion of the die attach layer is formed on the outer periphery of the wafer; An overhanging portion removing step of removing the overhanging portion from the sheet by adhering and moving the overhanging portion to a removing member. A method for processing a wafer, comprising:

2. The removing member is constituted by a tape having an adhesive layer laminated on a base material, The method for processing a wafer according to claim 1, wherein:

3. An annular frame having an opening formed at the center; The removing member covering the opening; A protective layer formed on the removing member corresponding to the wafer inside the opening; Further comprising a removing unit preparing step of preparing a removing unit having: In the overhanging portion removing step, while facing the protective layer of the removing unit to the wafer, the overhanging portion is removed by adhering and moving the adhesive layer to the removing member. The method for processing a wafer according to claim 2, wherein:

4. A dividing starting point forming step of forming a dividing starting point for dividing the die attach layer on the wafer before or after the sticking step; An expanding step of expanding the sheet to form a plurality of chips laminated with the die attach layer in a state where the dividing starting point is formed on the wafer and the overhanging portion is removed from the sheet. The method for processing a wafer according to any one of claims 1 to 3, wherein: The method for processing a wafer according to any one of claims 1 to 3, wherein:

5. The sheet to which the wafer is stuck is fixed to an annular frame for holding the wafer, Positioning portions are respectively formed on the annular frame for holding the wafer and the annular frame of the removing unit, In the overhanging portion removing step, the position of the protective layer is made to coincide with the position of the wafer by aligning the positioning portions of both annular frames. The method for processing a wafer according to claim 3, wherein: The method for processing a wafer according to claim 3, wherein:

6. A sticking step of sticking the wafer to a sheet through a die attach layer having a diameter larger than the diameter of the wafer, so that an overhanging portion of the die attach layer is formed on the outer periphery of the wafer; An overhanging portion removing step of removing the overhanging portion from the sheet by adhering and moving the overhanging portion to a removing member. A method for processing a wafer, comprising: The removal member is constituted by a tape having an adhesive layer laminated on a base material, an annular frame having an opening formed at the center, the removal member covering the opening, and a protective layer formed on the removal member corresponding to the wafer inside the opening, and further includes a removal unit preparation step of preparing a removal unit having the above, In the protruding portion removal step, while facing the protective layer of the removal unit to the wafer, the adhesive layer is adhered to and moved with respect to the removal member, thereby removing the protruding portion. Before or after the sticking step, a split start point forming step of forming a split start point for splitting the die attach layer on the wafer; An expand step of expanding the sheet to form a plurality of chips laminated with the die attach layer in a state where the split start point is formed on the wafer and the protruding portion is removed from the sheet. The sheet to which the wafer is adhered is fixed to an annular frame for wafer holding, Positioning portions are respectively formed on the annular frame for wafer holding and the annular frame of the removal unit, In the protruding portion removal step, the positions of the protective layers are made to coincide with the position of the wafer by aligning the positioning portions of both annular frames. A method for processing a wafer.

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