Wafer grinding method

Abstract

To grind a wafer to a uniform thickness while keeping the rear surface of the wafer flat even if the wafer has a plurality of projecting electrodes on the surface.SOLUTION: A wafer grinding method according to the present invention includes a first liquid curable resin supplying step of supplying a first liquid curable resin having a curing shrinkage rate of less than 1% to a front surface of a wafer to cover projecting electrodes with the first liquid curable resin, thereby planarizing the front surface of the wafer, a first liquid curable resin curing step of curing the first liquid curable resin to form a first curable resin layer, and a bonding step of supplying a second liquid curable resin to the first curable resin layer to bond the first curable resin layer and a support substrate to each other. An integrating step of curing the second liquid curable resin to form a second curable resin layer and integrating the wafer and the supporting substrate through the first curable resin layer and the second curable resin layer, and a grinding step of grinding a back surface of the wafer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for grinding a wafer having a plurality of devices with protruding electrodes (bumps) formed on its surface. [Background technology]

[0002] For example, in the manufacturing process of semiconductor chips, the surface of a disk-shaped semiconductor wafer (hereinafter simply referred to as a "wafer") is divided into a large number of rectangular areas by planned division lines called streets that are arranged in a grid pattern, and devices such as ICs and LSIs are formed in each rectangular area. Then, the wafer on which a large number of devices are formed is cut along the planned division lines with, for example, a cutting blade of a cutting machine called a dicer, to obtain a plurality of semiconductor chips.

[0003] Semiconductor chips are used in various electronic devices such as PCs (personal computers) and mobile phones (smartphones). In order to meet the recent demand for thinner and smaller electronic devices, wafers are ground using a grinding machine to a thickness of, for example, 50 μm or less. In general wafer grinding, a protective tape (BG tape (Backgrind tape)) is attached to the front surface of the wafer (the surface on which devices are formed), the wafer is held on the holding surface of a chuck table with the protective tape facing downward, and while the chuck table and the wafer held thereon are rotated at a predetermined speed, a rotating grinding wheel is brought into contact with the back surface of the wafer to grind the back surface of the wafer.

[0004] In the above-described wafer grinding, the wafer sinks into the adhesive layer of the protective tape due to the grinding load and is deformed, which may cause grinding defects such as cracks, chips, and chipping in the wafer.

[0005] Therefore, for example, Patent Document 1 proposes a grinding method in which a wafer is fixed to a flat support substrate made of highly rigid glass or the like with a liquid hardening resin, and the back surface of the wafer is ground with a grinding wheel. With this grinding method, even if a grinding load acts on the wafer, the wafer is fixed to a highly rigid support substrate, so grinding defects such as cracks, chips, and chipping are prevented.

[0006] Incidentally, among the multiple devices formed on the surface of a wafer, some have protruding electrodes such as multiple bumps (metal electrodes), and for wafers on whose surface devices having such protruding electrodes are formed, the grinding method shown in FIG. 4 has conventionally been adopted.

[0007] That is, in a method for grinding a wafer W on whose surface a device having protruding electrodes BP is formed, as shown in Fig. 4(a), a support substrate 6 made of optically transparent glass is placed on the flat upper surface of a light-transmitting glass table 1, and the wafer W is suction-held on the lower surface of a holding table 3 arranged above the support substrate 6. Here, the back surface of the wafer W (the upper surface in Fig. 4(a)) is sucked onto the lower surface of the holding table 3, and a plurality of protruding electrodes BP protrude from the front surface of the wafer W (the lower surface in Fig. 4(a)).

[0008] In the above state, a predetermined amount of liquid curing resin r is dropped onto the center of the upper surface of the support substrate 6 from a resin nozzle 4 arranged above the support substrate 6 between the support substrate 6 and the holding table 3 (wafer W). Here, an ultraviolet curing type liquid resin is used as the liquid curing resin r.

[0009] As described above, when a predetermined amount of liquid hardening resin r is dropped from the resin nozzle 4 onto the center of the upper surface of the support substrate 6, as shown in Figure 4(b), the holding table 3 and the wafer W held by suction on its underside are lowered by a vertical movement mechanism (not shown), and the liquid hardening resin r dropped onto the upper surface of the support substrate 6 is spread by the descending wafer W, and the multiple protruding electrodes BP protruding from the surface of the wafer W are covered with the liquid hardening resin r.

[0010] Next, when the multiple UV lamps 5 arranged below the glass table 1 are turned on from the state shown in Figure 4(b) as shown in Figure 4(c), ultraviolet (UV) rays emitted upward from each UV lamp 5 pass through the glass table 1 and the support substrate 6 and are irradiated onto the liquid curable resin r, which is then cured by the ultraviolet (UV) rays. As a result, as shown in Figure 4(d), the wafer W having multiple protruding electrodes BP protruding from its surface is fixed to the support substrate 6 by the cured cured resin layer R, and the wafer W is held with the support substrate 6 facing downward on the holding surface of a chuck table (not shown) of a grinding machine, and its back surface (the upper surface of Figure 4(d)) is ground flat by a grinding wheel (not shown). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-187281 Summary of the Invention [Problem to be solved by the invention]

[0012] However, in the conventional method for grinding a wafer W shown in FIG. 4, in the state shown in FIG. 4(b) before the liquid curable resin r cures, the thickness t1 of the portion where the protruding electrode BP of the liquid curable resin r exists is smaller than the thickness t2 of the other portion (the portion where the protruding electrode BP does not exist) by the height h of the protruding electrode BP (t1 = t2 - h < t2). Therefore, a difference in the amount of curing shrinkage of the liquid curable resin r occurs between the portion where the protruding electrode BP of the liquid curable resin r exists (portion with thickness t1) and the portion where the protruding electrode BP does not exist (portion with thickness t2), and the amount of curing shrinkage of the portion where the protruding electrode BP of the liquid curable resin r exists (portion with thickness t1) is smaller than the amount of thermal shrinkage of the portion where the protruding electrode BP does not exist (portion with thickness t2).

[0013] Then, as shown in FIG. 4(d), the thickness t2' of the portion where the protruding electrode BP does not exist in the cured resin layer R formed by curing the liquid curable resin r becomes smaller than the thickness t1' of the portion where the protruding electrode BP exists (t2' < t1'), and as a result, the back surface of the wafer W (the upper surface in FIG. 4(d)) does not become a flat surface, and undulations with a height difference δ in which valleys and ridges are alternately repeated occur on the back surface of the wafer W. Therefore, when grinding the back surface of the wafer W with such undulations, there is a problem that the thickness of the wafer W does not become constant and variations occur in the thickness of the wafer W.

[0014] The present invention has been made in view of the above problems, and an object thereof is to provide a method for grinding a wafer that can keep the back surface flat and grind the wafer to a uniform thickness even for a wafer having a plurality of protruding electrodes on its surface.

Means for Solving the Problem

[0015] To achieve the above-mentioned object, the present invention provides a method for grinding a wafer having a surface partitioned by a plurality of planned dividing lines arranged in a grid pattern, each of which has a device having a protruding electrode formed in each of a plurality of regions, the method comprising: a first liquid curing resin supplying step of supplying a first liquid curing resin having a curing shrinkage rate of less than 1% onto the surface of the wafer to cover the protruding electrodes with the first liquid curing resin, thereby planarizing the surface of the wafer; a first liquid curing resin curing step of curing the first liquid curing resin to form a first cured resin layer after the first liquid resin supplying step; a bonding step of supplying a second liquid curing resin to the first cured resin layer to bond the first cured resin layer to a supporting substrate after the first liquid resin curing step; an integration step of curing the second liquid curing resin to form a second cured resin layer after the bonding step, and integrating the wafer and the supporting substrate via the first cured resin layer and the second cured resin layer; and a grinding step of grinding the back surface of the wafer after the integration step. Here, it is preferable that the first liquid curing resin is a urethane acrylate resin having a cure shrinkage rate of less than 1%, and the second liquid curing resin is an epoxy resin. [Effects of the Invention]

[0016] According to the present invention, in the first liquid curing resin supply step, a first liquid curing resin having a cure shrinkage rate of less than 1% is supplied onto the surface of the wafer, and the protruding electrodes are coated with the first liquid curing resin to flatten the surface of the wafer. Then, in the next first liquid curing resin curing step, the first liquid curing resin is cured to form a first cured resin layer. Therefore, the difference in the amount of cure shrinkage of the first liquid curing resin, which hardly undergoes cure shrinkage, depending on whether or not the protruding electrodes are present, is kept negligibly small.

[0017] Therefore, the thickness of the first cured resin layer formed by the first liquid cured resin is kept constant, and in the next bonding step, a second liquid cured resin is supplied to the first cured resin layer to bond the first cured resin layer to the support substrate, and in the next integration step, the second liquid cured resin is cured to form a second cured resin layer, and in the next integration step, the wafer and support substrate are integrated via the first cured resin layer and the second cured resin layer, so that the wafer is fixed to and integrated with the highly rigid support substrate.

[0018] Thus, the back surface (surface to be ground) of the wafer fixed to the support substrate via the first cured resin layer of a constant thickness formed by the curing of the first liquid curing resin, which hardly undergoes any curing shrinkage and therefore the difference in the amount of curing shrinkage depending on whether or not there are protruding electrodes is kept to a negligible level, and the second cured resin layer formed by the curing of the second liquid curing resin, which has a constant amount of curing shrinkage because there are no protruding electrodes to begin with, is made into a flat surface and does not develop any undulations.

[0019] Therefore, in the subsequent grinding step, the flat back surface of the wafer is ground to obtain a wafer of uniform thickness. Furthermore, since the wafer is fixed to a highly rigid support substrate, and in the grinding step, the wafer is ground by a grinding wheel while being held on the holding surface of a chuck table with the support substrate facing downward, the wafer is not deformed by the grinding load, and grinding defects such as cracks, chips, or chipping do not occur in the wafer.

[0020] When epoxy resin is used as the UV-curable resin, it has the advantages of high adhesive strength, low cure shrinkage, and high hardness. However, because the curing initiator contains a photoacid generator, it generates acid upon UV irradiation, which can corrode the metal protruding electrodes. For this reason, epoxy resin cannot be used as the first liquid curable resin that covers the protruding electrodes, but it can be used as the second liquid curable resin that does not come into contact with the protruding electrodes. In contrast, urethane acrylate resin, which does not generate acid upon UV irradiation and has a cure shrinkage of less than 1%, can be used as the first liquid curable resin that comes into contact with the protruding electrodes. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. [Figure 2] 1 is a flowchart showing the steps of a wafer grinding method according to the present invention. [Figure 3A] 3 is a vertical cross-sectional view showing a first liquid curable resin supplying step (supply of first liquid curable resin) in the wafer grinding method according to the present invention. FIG. [Figure 3B] 3 is a vertical cross-sectional view showing a first liquid curable resin supplying step (pressing of the first liquid curable resin) in the wafer grinding method according to the present invention. FIG. [Figure 3C] 3 is a vertical cross-sectional view showing a curing step (curing of a first liquid curing resin) in the wafer grinding method according to the present invention. FIG. [Figure 3D] 3 is a vertical cross-sectional view showing a hardening step (peeling off a release film) in the wafer grinding method according to the present invention. FIG. [Figure 3E] 4 is a vertical cross-sectional view showing a bonding step (supply of a second liquid curable resin) in the wafer grinding method according to the present invention. FIG. [Figure 3F] 4 is a vertical cross-sectional view showing a bonding step (hardening of a second liquid hardening resin) in the wafer grinding method according to the present invention. FIG. [Figure 3G] 3 is a vertical cross-sectional view showing an integration step in the wafer grinding method according to the present invention. FIG. [Figure 3H] 3 is a vertical cross-sectional view showing a grinding step in the wafer grinding method according to the present invention. FIG. [Figure 4] 1A and 1B are longitudinal cross-sectional views showing a conventional wafer grinding method, in which (a) shows the supply of liquid curing resin, (b) shows the pressing of the liquid curing resin, (c) shows the curing of the liquid curing resin, and (d) shows the wafer after the liquid curing resin has cured. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0023] [Wafer composition] As shown in Fig. 1, the wafer W to be ground by the method of the present invention is a thin, disk-shaped member made of a single-crystal silicon base material, and its surface (the top surface in Fig. 1) is formed with a grid of linear dividing lines L called streets that intersect at right angles to one another. Devices D such as ICs and LSIs are formed in a plurality of rectangular regions defined by the dividing lines L on the surface of the wafer W. Each device D has a plurality of protruding electrodes (bumps) BP protruding from its surface, and each protruding electrode BP is made of a precious metal such as gold (Au) or platinum (Pt), or an alloy such as tin (Sn)-copper (Cu).

[0024] Furthermore, a mark M such as a V-notch indicating the crystal orientation of the wafer W is formed on a part of the outer periphery of the wafer W. As the mark M indicating the crystal orientation, an orientation flat formed by cutting a part of the outer periphery of the wafer W in a straight line is used.

[0025] [Wafer grinding method] Next, a method for grinding a wafer W according to the present invention will be described. As shown in FIG. 2, this grinding method includes the following steps: 1) First liquid curing resin supply step: 2) First liquid curing resin curing step: 3) Bonding step: 4) Integration step: 5) Grinding step: The above steps are carried out in order to grind the wafer W to a uniform thickness. Each step will be explained below.

[0026] 1) First liquid curing resin supply step: The first liquid curing resin supplying step is a step of supplying a first liquid curing resin r1 having a cure shrinkage rate of less than 1% onto the surface of the wafer W to coat the protruding electrodes BP with the first liquid curing resin r1, thereby planarizing the surface of the wafer W. That is, in this first liquid curing resin supplying step, as shown in Fig. 3A, a thin optically transparent release film 2 is placed on the flat upper surface of a horizontal optically transparent glass table 1, and the wafer W is suction-held on the lower surface of a holding table 3 that is horizontally and can be raised and lowered above the glass table 1. Here, the back surface of the wafer W (the upper surface in Fig. 3A) is sucked onto the lower surface of the holding table 3, and a plurality of protruding electrodes (bumps) BP protrude from the front surface of the wafer W (the lower surface in Fig. 3A).

[0027] In the above state, a predetermined amount of first liquid curing resin r1 is dropped onto the center of the upper surface of the release film 2 on the glass table 1 from a resin nozzle 4 arranged between the glass table 1 and the upper holding table 3 (wafer W). Here, an ultraviolet-curing liquid resin such as a urethane acrylate resin with a cure shrinkage rate of less than 1% is used as the first liquid curing resin r1. In this embodiment, a urethane acrylate resin (cure shrinkage rate: 0.7%) from the UF series (grade: UF-07DF) manufactured by Kyoeisha Chemical Co., Ltd. is used as the first liquid curing resin r1.

[0028] As described above, when a predetermined amount of first liquid curing resin r1 is dropped from resin nozzle 4 onto the center of the upper surface of release film 2 on glass table 1, as shown in Fig. 3B, holding table 3 and wafer W held by suction on its lower surface are lowered by a vertical movement mechanism (not shown), and the first liquid curing resin r1 dropped onto the upper surface of release film 2 is spread by wafer W descending together with holding table 3, and the multiple protruding electrodes BP protruding from the surface of wafer W are coated with first liquid curing resin r1. Here, in this embodiment, urethane acrylate resin is used as the first liquid curing resin r1 that comes into contact with metal protruding electrodes BP, as described above. This urethane acrylate resin does not contain a photoacid generator in the curing initiator, so it does not generate acid when irradiated with ultraviolet light, and therefore the problem of acid corrosion of metal protruding electrodes BP does not occur.

[0029] 2) First liquid curing resin curing step: The first liquid curing resin curing step is a step performed after the first liquid curing resin supplying step, and in this first liquid curing resin curing step, as shown in Fig. 3C, a plurality of UV lamps 5 arranged below the glass table 1 are turned on. Then, ultraviolet rays (UV) emitted upward from each UV lamp 5 pass through the glass table 1 and the release film 2 and are irradiated onto the first liquid curing resin r1, and the first liquid curing resin r1 irradiated with this ultraviolet light is cured, and a first cured resin layer R1 (see Fig. 3D) is formed between the wafer W and the release film 2.

[0030] As described above, once the first cured resin layer R1 is formed between the wafer W and the release film 2, the holding table 3 is raised together with the wafer W, the first cured resin layer R1, and the release film 2 by a vertical movement mechanism (not shown), and these are separated from the glass table 1. Then, the wafer W, the first cured resin layer R1, and the release film 2 are removed from the holding table 3, and as shown in FIG. 3D, the wafer W is turned over so that the front surface of the wafer W and the release film 2 face upward. Then, from this state, one end of the release film 2 is grasped and pulled up in the direction of the arrow, thereby peeling and removing the release film 2 from the first cured resin layer R1.

[0031] 3) Bonding step: The bonding step is a step in which a second liquid curing resin r2 is supplied to the first cured resin layer R1 formed in the first liquid curing resin curing step to bond the first cured resin layer R1 to the support substrate 6. That is, in this bonding step, as shown in Fig. 3E, a light-transmitting glass support substrate 6 is placed on the flat upper surface of a glass table 1, and a wafer W is suction-held on the lower surface of a holding table 3 that is horizontally and can be raised and lowered above the support substrate 6. Here, the back surface of the wafer W (the upper surface in Fig. 3E) is sucked onto the lower surface of the holding table 3, and a plurality of protruding electrodes BP protrude from the front surface of the wafer W (the lower surface in Fig. 3E), and these protruding electrodes BP are covered with a first cured resin layer R1.

[0032] In this state, a predetermined amount of second liquid curing resin r2 is dropped onto the center of the upper surface of the support substrate 6 from a resin nozzle 7 arranged between the support substrate 6 and the upper holding table 3 (the wafer W and the first curing resin layer R1). Here, an ultraviolet-curing epoxy resin is used as the second liquid curing resin r2. This epoxy resin has the advantages of high adhesive strength, low cure shrinkage, and high hardness. However, because the curing initiator contains a photoacid generator, it generates acid upon exposure to ultraviolet light, which can corrode the metal protruding electrodes BP. For this reason, epoxy resin cannot be used for the first liquid curing resin r1 that covers the protruding electrodes BP, but epoxy resin can be suitably used for the second liquid curing resin r2 that does not come into contact with the protruding electrodes BP.

[0033] As described above, when a predetermined amount of second liquid curable resin r2 is dropped from the resin nozzle 7 onto the center of the upper surface of the support substrate 6 on the glass table 1, as shown in Figure 3F, the holding table 3 and the wafer W held by suction on its underside are lowered together with the first cured resin layer R1 by a vertical movement mechanism not shown, and the second liquid curable resin r2 dropped onto the center of the upper surface of the support substrate 6 is spread by the descending wafer W, and the first cured resin layer R1 and the support substrate 6 are bonded together by the second liquid curable resin r2.

[0034] 4) Integration step: The integration step is a step performed after the bonding step, in which the second liquid curing resin r2 is cured to form a second cured resin layer R2 (see Figure 3G), and the wafer W and the support substrate 6 are integrated via the first cured resin layer R1 and the second cured resin layer R2.

[0035] That is, in this integration step, as shown in Fig. 3G, a plurality of UV lamps 5 arranged below the glass table 1 are turned on. Then, ultraviolet (UV) rays emitted upward from each UV lamp 5 pass through the glass table 1 and the support substrate 6 and are irradiated onto the second liquid curable resin r2. The second liquid curable resin r2 irradiated with this UV light is cured, and a second cured resin layer R2 is formed between the first cured resin layer R1 and the support substrate 6 (see Fig. 3H). When the second cured resin layer R2 is formed between the first cured resin layer R1 and the support substrate 6 in this manner, the wafer W and the support substrate 6 are integrated via the first cured resin layer R1 and the second cured resin layer R2.

[0036] 5) Grinding step: The grinding step is a step of grinding the back surface of the wafer W that has been integrated with the support substrate 6 via the first cured resin layer R1 and the second cured resin layer R2 in the integration step. That is, in this grinding step, as shown in Fig. 3H, the wafer W that has been integrated with the support substrate 6 via the first cured resin layer R1 and the second cured resin layer R2 is suction-held on the holding surface (upper surface) of the chuck table 10 of the grinding device with the support substrate 6 facing downward.

[0037] Here, the chuck table 10 is a disk-shaped member that is rotated at a predetermined speed around an axial center CL1 in the direction of the arrow shown by a rotation mechanism not shown, and the holding surface on its upper surface is selectively connected to a suction source not shown, such as a vacuum pump or an ejector.

[0038] A grinding wheel 20 of the grinding unit is disposed above the wafer W, and this grinding wheel 20 is detachably mounted on a disk-shaped wheel mount 22 attached to the lower end of a vertical spindle 21. Here, the grinding wheel 20 is composed of a disk-shaped base 20a and multiple block-shaped grinding stones 20b attached in an annular shape to the underside of the base 20a. The wheel mount 22 and grinding wheel 20 attached to the spindle 21 rotate at a predetermined speed in the same direction as the spindle 21 when the spindle 21 is rotated around the axis CL2 in the direction of the arrow shown in the figure (the same direction as the rotation direction of the chuck table 10) by a spindle motor (not shown). The grinding unit can be moved up and down by a vertical movement mechanism (not shown).

[0039] As shown in FIG. 3H, when the chuck table 10 and the wafer W held by it by suction via the support base 6 are rotated at a predetermined speed around the axial center CL1 in the direction of the arrow by a rotation mechanism not shown, and the spindle 21 and the grinding wheel 20 attached to the lower end of the spindle 21 via a wheel mount 22 are rotated at a predetermined speed around the axial center CL2 in the direction of the arrow by a spindle motor not shown, both are positioned so that the circumscribed circle of the grinding stone 20b of the grinding wheel 20 passes through the center of the wafer W.

[0040] From the above state, the grinding wheel 20 is lowered by a vertical movement mechanism (not shown), and when the grinding stone 20b of the grinding wheel 20 comes into contact with the back surface of the wafer W (the upper surface in FIG. 3H), the entire back surface of the wafer W is ground by the grinding stone 20b. During the grinding process of the wafer W, grinding water is supplied from a grinding water supply source (not shown) to the contact portion (grinding portion) between the wafer W and the grinding stone 20b, and this grinding water cools and lubricates the contact portion (grinding portion) between the wafer W and the grinding stone 20b, and also washes away and removes grinding debris generated by grinding the wafer W. Here, pure water is preferably used as the grinding water.

[0041] During the grinding process of the wafer W by the grinding wheel 20b, the thickness of the wafer W is measured by a thickness measuring device (not shown), and when the thickness of the wafer W reaches a predetermined thickness, the grinding process of the wafer W is completed. When the grinding of the wafer W is completed, the wafer W is removed from the support substrate 6 by, for example, the following method.

[0042] That is, when an ablation laser that passes through the support substrate 6 is focused on the second cured resin layer R2, the support substrate 6 is separated from the second cured resin layer R2, and the support substrate 6 can be easily peeled off from the second cured resin layer R2. Here, because the outer periphery of the surface of the wafer W from which the protruding electrodes BP protrude has been subjected to edge trimming processing, a small gap is formed between the outer periphery of the surface of the wafer and the first cured resin layer R1. Therefore, the claws of a clamping mechanism can be inserted into this gap to grip the outer peripheries of the first cured resin layer R1 and the second cured resin layer R2, and the wafer W can be separated from the first cured resin layer R1 and the second cured resin layer R2. Ultimately, the wafer W can be removed from the support substrate 6.

[0043] As described above, in the method for grinding a wafer W according to the present invention, in the first liquid curing resin supply step, a first liquid curing resin r1 having a curing shrinkage rate of less than 1% is supplied onto the surface of the wafer W, and the protruding electrodes BP are covered with the first liquid curing resin r1, thereby flattening the surface of the wafer W. Then, in the next first liquid curing resin curing step, the first liquid curing resin r1 is cured to form a first cured resin layer R1. Therefore, the difference in the amount of curing shrinkage of the first liquid curing resin r1, which hardly undergoes curing shrinkage, depending on whether or not the protruding electrodes BP are present, is kept negligibly small.

[0044] Therefore, the thickness of the first cured resin layer R1 formed by the first liquid cured resin r1 is kept constant, and in the next bonding step, the second liquid cured resin r2 is supplied to the first cured resin layer R1 to bond the first cured resin layer R1 to the support substrate 6, and in the next integration step, the second liquid cured resin r2 is cured to form the second cured resin layer R2, and in the next integration step, the wafer W and the support substrate 6 are integrated via the first cured resin layer R1 and the second cured resin layer R2, so that the wafer W is fixed to and integrated with the highly rigid support substrate 6.

[0045] Therefore, the back surface (surface to be ground) of the wafer W fixed to the support substrate 6 via the first cured resin layer R1 of a constant thickness formed by the curing of the first liquid cured resin r1, which hardly undergoes any curing shrinkage and therefore the difference in the amount of curing shrinkage depending on whether or not the protruding electrodes BP are present is kept small enough to be negligible, and the second cured resin layer R2 formed by the curing of the second liquid cured resin r2, which has a constant amount of curing shrinkage because the protruding electrodes BP are not present to begin with, is made into a flat surface, and no undulations as shown in Figure 4(d) occur on this surface.

[0046] Therefore, in the subsequent grinding step, a wafer W with a uniform thickness can be obtained by grinding the flat back surface of the wafer W. Furthermore, the wafer W is fixed to the highly rigid support substrate 6, and in the grinding step, the wafer W is ground by the grinding wheel 20b while being held on the holding surface of the chuck table 10 with the support substrate 6 facing downward. Therefore, the wafer W is not deformed by the grinding load, and grinding defects such as cracks, chips, or chipping do not occur in the wafer W.

[0047] When epoxy resin is used as the UV-curable resin, it has the advantages of high adhesive strength, low cure shrinkage, and high hardness. However, because the curing initiator contains a photoacid generator, it generates acid when exposed to UV light, which can corrode the metal bump electrodes BP. For this reason, epoxy resin cannot be used for the first liquid curable resin r1 that covers the bump electrodes BP, but it can be used suitably for the second liquid curable resin r2 that does not come into contact with the bump electrodes BP. In contrast, urethane acrylate resin, which does not generate acid when exposed to UV light, can be used suitably for the first liquid curable resin r1 that comes into contact with the bump electrodes BP, thereby eliminating the problem of acid corrosion of the metal bump electrodes BP.

[0048] In the above embodiment, ultraviolet-curable liquid resins are used for the first liquid curing resin r1 and the second liquid curing resin r2, but other liquid resins, such as thermosetting resins, can also be used for the first liquid curing resin r1 and the second liquid curing resin r2.

[0049] Furthermore, the present invention is not limited to the application of the above-described embodiments, and it goes without saying that various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0050] 1: Glass table, 2: Release film, 3: Holding table, 4: Resin nozzle, 5: UV lamp, 6: supporting substrate, 7: resin nozzle, 10: chuck table, 20: grinding wheel, 20a: base, 20b: grinding stone, 21: spindle, 22: Wheel mount, BP: Protruding electrode (bump), CL1: axial center of chuck table, CL2: axial center of spindle, D: device, L: planned division line, M: mark, r1: first liquid hardening resin, r2: second liquid hardening resin, R1: first cured resin layer, R2: second cured resin layer, W: wafer

Claims

1. A method for grinding a wafer having a surface divided by a plurality of planned dividing lines arranged in a grid pattern, in each of which a device having a protruding electrode is formed, comprising the steps of: a first liquid curing resin supplying step of supplying a first liquid curing resin having a cure shrinkage rate of less than 1% onto the surface of the wafer to cover the protruding electrodes with the first liquid curing resin, thereby planarizing the surface of the wafer; a first liquid curable resin curing step of curing the first liquid curable resin to form a first cured resin layer after the first liquid curable resin supplying step; a bonding step of supplying a second liquid curable resin to the first cured resin layer after the first liquid resin curing step to bond the first cured resin layer to a support substrate; an integration step of, after the bonding step, curing the second liquid curable resin to form a second cured resin layer, and integrating the wafer and the support substrate via the first cured resin layer and the second cured resin layer; a grinding step of grinding the back surface of the wafer after the integration step; A wafer grinding method comprising the steps of:

2. 2. The wafer grinding method according to claim 1, wherein the first liquid hardening resin is a urethane acrylate resin.

3. 2. The wafer grinding method according to claim 1, wherein the second liquid hardening resin is an epoxy resin.

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