Sticking method

Abstract

To adhere a sticky tape to a workpiece with warpage while suppressing an adhesion defect.SOLUTION: An adhesion method for adhering a sticky tape to a workpiece which includes a metal film on a surface and in which warpage is generated by a stress of the metal film includes: a heating step of heating the workpiece to suppress the warpage of the workpiece; and an adhesion step of adhering the sticky tape to the workpiece in which the warpage is suppressed. Preferably, the adhesion method includes: before the heating step, a mounting step of mounting the workpiece on a chuck table; and before the adhesion step, a suction step of sucking and holding the workpiece, in which the warpage is suppressed, with the chuck table. More preferably, the adhesion method further includes after the suction step: a heating stop step of stopping the heating of the workpiece; and a carry-out step of stopping the suction and holding of the workpiece with the chuck table and carrying the workpiece, to which the sticky tape is adhered, out of the chuck table.SELECTED DRAWING: Figure 2

Description

Technical Field

[0006] , ,

[0001] The present invention relates to a method of attaching an adhesive tape to a workpiece having a metal film disposed on its surface.

Background Art

[0002] A device chip used in an electronic device such as a mobile phone or a computer is formed by dividing a wafer on which a plurality of devices are arranged side by side on the surface for each device. For dividing a plate-shaped workpiece such as a wafer, for example, a cutting device equipped with an annular cutting blade is used.

[0003] The cutting blade includes an annular grindstone portion. The grindstone portion includes a binder formed of a material such as metal or resin, and abrasive grains dispersed and fixed in the binder. The abrasive grains are formed of a material such as diamond or cBN (cubic Boron Nitride), and some of the abrasive grains are exposed on the surface of the grindstone portion. The cutting device cuts the workpiece by causing the grindstone portion to cut into the workpiece while rotating the cutting blade at a speed of about 30,000 revolutions per minute (see Patent Document 1).

[0004] An adhesive tape may be pre-attached to the workpiece cut by the cutting device. For example, the adhesive surface of the adhesive tape is brought into contact with one end of one surface of the workpiece, and the adhesive tape is brought into contact with the workpiece while sequentially expanding the contact area from this end to another end of this one surface. At this time, when the adhesive tape is pressed with a roller from above, the adhesive tape is attached to the workpiece.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] A metal film may form on the surface of a workpiece. Workpieces such as semiconductor wafers with a metal film may warp due to stress caused by the metal film. When adhesive tape is applied to a warped workpiece using a roller or similar tool, poor adhesion can occur. Specifically, if the workpiece warps concavely, the adhesive tape may not adhere well to the center of the workpiece's upper surface. Similarly, if the workpiece warps convexly, the adhesive tape may not adhere well to the outer periphery of the workpiece's upper surface.

[0007] This invention has been made in view of the above problems, and its objective is to provide an adhesive tape application method that suppresses adhesion defects when applying adhesive tape to a warped workpiece. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is a method for attaching an adhesive tape to a workpiece having a metal film on its surface and warping due to stress on the metal film, the method comprising: a heating step of heating the workpiece to suppress warping; and an attachment step of attaching the adhesive tape to the workpiece after the heating step, from which the warping has been suppressed.

[0009] Preferably, the process further includes a placement step of placing the workpiece on a chuck table before the heating step, and a suction step of holding the workpiece, whose warping has been suppressed, by suction on the chuck table before the bonding step.

[0010] Furthermore, preferably, the process further includes a heating stop step, which stops heating the workpiece after the suction step, and a discharge step, which stops the suction holding of the workpiece by the chuck table and discharges the workpiece with the adhesive tape attached from the chuck table after the heating stop step and the adhesive step.

[0011] Preferably, the chuck table is equipped with a heater, and in the heating step, the workpiece is heated by using the heater to raise the temperature of the chuck table. [Effects of the Invention]

[0012] In one embodiment of the present invention, a workpiece having a metal film on its surface and warping due to stress in the metal film is first heated to suppress the warping of the workpiece. Then, in this state, adhesive tape is applied to the workpiece whose warping has been suppressed. Compared to the workpiece before warping was suppressed, it is easier to apply the adhesive tape to the workpiece whose warping has been suppressed. In addition, the difference in ease of application of the adhesive tape to various parts of the workpiece surface is reduced, making it less likely for adhesive tape to be poorly applied due to the warping of the workpiece.

[0013] Therefore, according to one aspect of the present invention, a method for applying adhesive tape to a warped workpiece while suppressing adhesion defects is provided. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1(A) is a schematic cross-sectional view showing a workpiece placed on a chuck table, and Figure 1(B) is a schematic cross-sectional view showing a workpiece that has been heated and whose warping has been reduced. [Figure 2] Figure 2(A) is a schematic cross-sectional view showing a workpiece with adhesive tape applied to its surface by a roller, and Figure 2(B) is a schematic cross-sectional view showing a workpiece with adhesive tape applied to its surface. [Figure 3] Figure 3(A) is a flowchart showing an example of the flow of each step in the method of attaching adhesive tape to a workpiece, and Figure 3(B) is a flowchart showing another example of the flow of each step in the method of attaching adhesive tape to a workpiece. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the bonding method according to this embodiment, an adhesive tape is bonded to a workpiece having a metal film on its surface that has warped due to stress on the metal film. Figures 1(A) to 2(B) schematically show cross-sectional views of a workpiece 1 to which an adhesive tape is bonded using the bonding method according to this embodiment.

[0016] The workpiece 1 is, for example, a wafer formed from materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor materials. Alternatively, the workpiece 1 is a roughly disc-shaped substrate made of materials such as sapphire, glass, or quartz.

[0017] Multiple intersecting division lines are set on the surface 1a of the workpiece 1. Devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) are formed in each region demarcated by the division lines. By grinding the workpiece 1 from the back surface 1b to thin it, polishing the ground surface to flatten it, and dividing the workpiece 1 along the division lines, individual device chips can be formed. However, the workpiece 1 to which the adhesive tape is attached is not limited to this, and devices do not necessarily have to be formed on the surface 1a.

[0018] A metal film 3 may be formed on the surface 1a of the workpiece 1 for various applications and purposes. For example, the metal film 3 may be used as an electrode or wiring layer, as a layer constituting a device, or as a heat sink or shielding plate. The metal film 3 may be composed of, for example, aluminum, gold, silver, copper, chromium, tin, nickel, titanium, tungsten, molybdenum, tantalum, indium, zinc oxide, or a combination thereof. However, the constituent materials of the metal film 3 are not limited to these.

[0019] An adhesive tape 5 is attached to the workpiece 1 for protecting structures such as devices formed on the surface 1a, for supporting the thinned workpiece 1, for supporting chips formed by dividing the workpiece 1, or for other reasons. The adhesive tape 5 includes a base material layer and an adhesive layer provided on one surface side of the base material layer.

[0020] For the base material layer of the adhesive tape 5, resin materials such as polyolefin (PO), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), or polystyrene (PS) are used, for example. Also, silicone rubber, acrylic-based materials, epoxy-based materials, or the like are used for the adhesive layer of the adhesive tape 5.

[0021] When a metal film 3 is formed on the surface of the workpiece 1, the workpiece 1 may be warped due to the stress generated by the metal film 3. It is not easy to attach the adhesive tape 5 to the warped workpiece 1, and poor adhesion may occur. For example, when the workpiece 1 is warped in a concave shape, it is difficult to attach the adhesive tape 5 at the central portion of the surface 1a of the workpiece 1. Also, when the workpiece 1 is warped in a convex shape, it is difficult to attach the adhesive tape 5 at the outer peripheral portion of the surface 1a of the workpiece 1.

[0022] In recent years, there has been a strong demand for thinning of device chips formed by dividing the workpiece 1. In order to form thin device chips, the workpiece 1 before being divided is thinned by methods such as grinding. And compared with the workpiece 1 that has not been thinned, in the thinned workpiece 1, the relative thickness of the metal film 3 with respect to the workpiece 1 becomes larger. Therefore, in the thinned workpiece 1, the warpage caused by the metal film 3 becomes relatively larger, and it becomes increasingly difficult to attach the adhesive tape 5 to the workpiece 1.

[0023] Therefore, in the method for attaching the adhesive tape according to the present embodiment, the warp of the workpiece 1 is reduced, and the adhesive tape 5 is attached to the workpiece 1 with the reduced warp. In this case, it is less likely to cause poor adhesion of the adhesive tape 5 due to the warp, and the adhesive tape 5 can be properly attached to the workpiece 1. Hereinafter, the method for attaching the adhesive tape according to the present embodiment will be described in detail.

[0024] The main steps of the adhesive tape according to the present embodiment are carried out, for example, on a chuck table that can suck and hold the workpiece 1. FIG. 1(A) includes a cross-sectional view schematically showing the chuck table 2. First, the chuck table 2 will be described.

[0025] The chuck table 2 includes a flat frame body 4 formed of a material such as stainless steel, and a porous member 6 housed in a recess formed in the center of the upper surface of the frame body 4. The upper surface shape of the porous member 6 is a shape corresponding to the back surface 1b that becomes the adsorption surface of the workpiece 1. In the frame body 4, a suction passage 12 is formed whose upper end communicates with the recess for housing the porous member 6 and whose lower end communicates with the lower surface.

[0026] The suction passage 12 is connected to a suction source such as an external pump. When the workpiece 1 is placed on the upper surface of the chuck table 2 and this suction source is operated, a negative pressure acts on the workpiece 1 through the suction passage 12 and the porous member 6, and the workpiece 1 is sucked and held by the chuck table 2. That is, the upper surface of the chuck table 2 becomes the holding surface 8.

[0027] Further, the chuck table 2 may incorporate a heater 10 for heating the workpiece 1 to be sucked and held. The heater 10 is constituted by, for example, a heating wire. By adjusting the output of the heater 10, the temperature of the workpiece 1 can be controlled. However, the chuck table 2 does not have to include the heater 10, and the workpiece 1 sucked and held by the chuck table 2 may be heated by other methods.

[0028] Figure 3(A) is a flowchart showing an example of the flow of each step in the adhesive tape application method according to this embodiment. Each step will be described in detail below. In the adhesive tape application method according to this embodiment, first, a placement step S10 is performed in which the workpiece 1 is placed on the chuck table 2. Figure 1(A) is a schematic cross-sectional view showing the workpiece 1 placed on the chuck table 2.

[0029] In the placement step S10, the side to which the adhesive tape 5 will be attached should face upward. When attaching the adhesive tape 5 to the surface 1a side of the workpiece 1, the back side 1b should face the holding surface 8 of the chuck table 2, exposing the surface 1a upward. Note that a warped workpiece 1 cannot be held by the chuck table 2 by suction as is. This is because negative pressure will leak from the holding surface 8 even if the suction source of the chuck table 2 is activated.

[0030] Next, the heating step S20 is performed. In the heating step S20, the workpiece 1 is heated. In the heating step S20, for example, the heater 10 built into the chuck table 2 is used to raise the temperature of the chuck table 2. This heats the workpiece 1 that is held by suction on the chuck table 2.

[0031] If the chuck table 2 is not equipped with a heater 10, the workpiece 1 is heated by another method in the heating step S20. For example, a heat gun capable of blowing hot air is prepared, and the workpiece 1 is heated by applying hot air to it with the heat gun. Alternatively, for example, an infrared lamp capable of emitting infrared rays is prepared, and the workpiece 1 is heated by irradiating it with infrared rays using the infrared lamp.

[0032] When the workpiece 1 is heated, thermal expansion occurs in both the workpiece 1 and the metal film 3 as the temperature rises. However, because the workpiece 1 and the metal film 3 have different coefficients of thermal expansion, the amount of thermal expansion they undergo as the temperature rises differs from each other.

[0033] For example, if the thermal expansion coefficient of the metal film 3 is greater than that of the workpiece 1, the amount of expansion due to heating will be greater for the metal film 3 than for the workpiece 1. Then, as shown in Figure 1(A), if the workpiece 1 is warped so that the surface 1a on which the metal film 3 is formed is facing inward, the greater thermal expansion of the metal film 3 will suppress the warping of the workpiece 1. Figure 1(B) includes a schematic cross-sectional view showing the workpiece 1 whose warping has been suppressed by heating.

[0034] Furthermore, for example, if the thermal expansion coefficient of the metal film 3 is smaller than that of the workpiece 1, the amount of expansion due to heating will be smaller for the metal film 3 than for the workpiece 1. And if the workpiece 1 is warped so that the surface 1a on which the metal film 3 is formed faces outwards, the warping will be suppressed due to the smaller thermal expansion of the metal film 3.

[0035] In the heating step S20, it is preferable to heat the workpiece 1 to a temperature of 40°C to 100°C, and more preferably to 40°C to 60°C. The target temperature for heating the workpiece 1 should be appropriately selected considering the thickness and material of the workpiece 1, the thickness and material of the metal film 3, the degree of warping in the workpiece 1, etc. For example, if the workpiece 1 is a silicon wafer with a thickness of 45 μm and the metal film 3 is a silver film with a thickness of 30 μm, heating the workpiece 1 to about 50°C will significantly suppress the warping in the workpiece 1.

[0036] In the adhesive tape application method according to this embodiment, the suction step S30 is performed next. In the suction step S30, the workpiece 1, whose warping has been suppressed, is held in place by suction using the chuck table 2. If the warping of the workpiece 1 is suppressed, the holding surface 8 is covered by the workpiece 1, making it possible to hold it in place by suction using the chuck table 2. Therefore, with the workpiece 1 heated to a predetermined temperature, the suction source of the chuck table 2 is activated, and the workpiece 1 is held in place by suction using the chuck table 2.

[0037] Next, the adhesion step S40 is performed. In the adhesion step S40, the adhesive tape 5 is attached to the workpiece 1, which has had its warping suppressed. Figure 2(A) is a schematic cross-sectional view showing how the adhesive tape 5 is attached to the workpiece 1. A roller 14 that is longer than the diameter of the workpiece 1 is used to attach the adhesive tape 5 to the workpiece 1.

[0038] First, the adhesive tape 5 is attached to one end of the surface 1a of the workpiece 1. Then, the roller 14 is pressed down on the adhesive tape 5 from above this end of the workpiece 1. After that, the roller 14 is rolled over the adhesive tape 5, and the adhesive tape 5 is applied from this end to the other end of the surface 1a of the workpiece 1. When the roller 14 reaches the other end of the workpiece 1 and the adhesive tape 5 is applied to the entire surface 1a of the workpiece 1, the application step S40 is completed.

[0039] Figure 2(B) is a schematic cross-sectional view showing the workpiece 1 to which the adhesive tape 5 has been attached in the attachment step S40. In the attachment method according to this embodiment, the adhesive tape 5 is attached to the workpiece 1 while the warping of the workpiece 1 is suppressed, so the roller 14 can press the adhesive tape 5 uniformly as it rolls over the workpiece 1. Therefore, poor adhesion of the adhesive tape 5 to the workpiece 1 is less likely to occur.

[0040] Next, the heating stop step S50 is performed. In the heating stop step S50, the heating of the workpiece 1 is stopped. For example, if the workpiece 1 was being heated to a predetermined temperature by the heater 10 of the chuck table 2, the heating is stopped by stopping the heater 10.

[0041] Next, the unloading step S60 is performed. In the unloading step S60, the suction source of the chuck table 2 is stopped, and the suction holding of the workpiece 1 by the chuck table 2 is stopped. Then, the workpiece 1 with the adhesive tape 5 attached is unloaded from the chuck table 2. This results in a workpiece 1 with the adhesive tape 5 properly attached.

[0042] When the suction holding of the workpiece 1 by the chuck table 2 is released, the warping of the workpiece 1 returns to its original state due to the stress on the metal film 3. Therefore, when the workpiece 1 is held from above by suction using a transport unit with a suction mechanism, it is preferable to hold the workpiece 1 with the suction mechanism before releasing the suction holding of the workpiece 1 by the chuck table 2.

[0043] As described above, in the adhesive tape application method according to this embodiment, the warping of the workpiece 1 is suppressed and the difference in ease of application of the adhesive tape 5 at various points on the surface 1a of the workpiece 1 is reduced, thus making it less likely for poor adhesion of the adhesive tape 5 to occur due to the warping of the workpiece 1.

[0044] It should be noted that the present invention is not limited to the embodiments described above and can be implemented with various modifications. For example, in the above embodiments, the adhesion step S40 was performed before the heating stop step S50, but one aspect of the present invention is not limited thereto. That is, the adhesion step S40 may be performed after the heating stop step S50.

[0045] In this case, the temperature of the workpiece 1 decreases in the heating stop step S50, but since the workpiece 1 is held in place by suction on the chuck table 2 at this point, the warping of the workpiece 1 is not completely restored. Therefore, when the adhesion step S40 is performed afterward, the state in which the warping of the workpiece 1 is suppressed is maintained, and the adhesive tape 5 can be attached to the workpiece 1 without causing adhesion defects.

[0046] When the adhesion step S40 is performed after the heating stop step S50, the temperature of the workpiece 1 returns to room temperature when it is adhered to the adhesive tape 5. Therefore, the adhesive tape 5 is not heated, and it is possible to use an adhesive tape 5 that deteriorates at high temperatures. On the other hand, when the adhesion step S40 is performed before the heating stop step S50, the adhesive tape 5 is also heated, causing the adhesive tape 5 to soften and deform to conform well to the uneven shape of the surface 1a of the workpiece 1, which may increase the adhesion strength of the adhesive tape 5.

[0047] Furthermore, if the adhesion step S40 is performed before the heating stop step S50, even adhesive tapes 5 with weak or no adhesive strength at room temperature can be attached to the workpiece 1. For example, by heating the workpiece 1 to a predetermined temperature and then pressing the adhesive tape 5 onto the workpiece 1 using the roller 14, it is also possible to heat-press the adhesive tape 5 onto the workpiece 1. In any case, if the unloading step S60 is performed after the adhesion step S40 and the heating stop step S50, a workpiece 1 with the adhesive tape 5 attached is obtained.

[0048] In the above embodiment, the case in which the suction step S30 is performed after the heating step S20 has been described, but the present invention is not limited to this. That is, the heating step S20 and the suction step S30 may be performed simultaneously. For example, after performing the placement step S10, the suction source of the chuck table 2 is activated and the heater 10 is activated.

[0049] In this case, before the warping of the workpiece 1 is suppressed, negative pressure leaks from the holding surface 8, and the workpiece 1 is not held by the chuck table 2. Then, as the temperature of the workpiece 1 rises and the suppression of the warping of the workpiece 1 progresses, the holding surface 8 is covered by the workpiece 1 and the negative pressure no longer leaks. In this case, once the suppression of the warping of the workpiece 1 has progressed to a certain extent, the workpiece 1 is automatically held by the chuck table 2.

[0050] For example, depending on the material and thickness of the workpiece 1, the material and thickness of the metal film 3, and the heating temperature of the workpiece 1 in heating step S20, it is possible that thermal expansion of the metal film 3, etc., may proceed further after the warping of the workpiece 1 has been completely mitigated. In this case, the workpiece 1 will warp in the opposite direction from its original direction.

[0051] Furthermore, the warping of the workpiece 1 may gradually increase in the opposite direction from the initial warping, potentially becoming so large that it fails to be held in place by the chuck table 2. Therefore, if the suction source of the chuck table 2 is activated only after the workpiece 1 has been heated to a predetermined temperature, the chuck table 2 may fail to hold the workpiece 1 in place.

[0052] Therefore, if the operation of the chuck table 2 is started before the temperature of the workpiece 1 reaches a predetermined temperature by the heating step S20, the workpiece 1 will be held by the chuck table 2 by suction when the holding surface 8 is covered by the workpiece 1. Thus, in the adhesive tape application method according to one aspect of the present invention, the suction step S30 does not need to be started after the completion of the heating step S20, and the suction step S30 may be started before the completion of the heating step S20.

[0053] Furthermore, the structures, methods, etc., of the embodiments and modifications described above can be modified as appropriate, as long as they do not deviate from the scope of the present invention. [Explanation of symbols]

[0054] 1 Workpiece 1a surface 1b back side 3 Metal film 5 Adhesive tape 2 Chuck Table 4 Frame 6. Porous material 8 Holding surface 10 Heater 12 Suction path 14 rollers

Claims

1. A method for attaching adhesive tape to a workpiece having a metal film on its surface and which has warped due to stress on the metal film, A heating step in which the workpiece is heated to suppress warping of the workpiece, A bonding method characterized by comprising: a bonding step of bonding the adhesive tape to the workpiece after the heating step, from which warping has been suppressed.

2. Prior to the heating step, there is a placement step in which the workpiece is placed on the chuck table, The bonding method according to claim 1, further comprising a suction step of holding the workpiece, whose warping has been suppressed, by suction on the chuck table before the bonding step.

3. After the suction step, a heating stop step is performed to stop heating the workpiece, The adhesive method according to claim 2, further comprising, after the heating stop step and the adhesive step, a discharge step of stopping the suction holding of the workpiece by the chuck table and discharge the workpiece to which the adhesive tape has been attached from the chuck table.

4. The chuck table is equipped with a heater. The bonding method according to claim 2 or 3, characterized in that the heating step involves heating the workpiece by using the heater to raise the temperature of the chuck table.

Images