Machining method for workpiece

Abstract

To provide a new technique for thinning a workpiece after constituting a laminate in which the workpiece is stuck to a support substrate.SOLUTION: A machining method for a workpiece includes: an adhesive material supply step of laying an adhesive material on a support substrate; a facing step of causing the workpiece to face the adhesive material; a laminate forming step of pressing the adhesive material with the workpiece and integrating the workpiece and the support substrate to form a laminate; a support substrate grinding step of grinding and planarizing an exposed surface of the support substrate of the laminate; and a thinning step of grinding and thinning the exposed surface of the workpiece of the laminate to a predetermined thickness after the support substrate grinding step.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for processing a plate-like object, and more particularly to a method for grinding a plate-like object to thin it to a predetermined thickness. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, for example, when thinning a plate-like workpiece such as a semiconductor wafer, the rigidity of the workpiece decreases significantly as the workpiece is thinned, causing cracks, deflections, etc. to occur during transportation and processing. To prevent this problem, a known process involves bonding the workpiece to a rigid support substrate (support substrate) via an adhesive material to form a laminate, and then grinding the laminated workpiece.

[0003] Furthermore, with regard to such a grinding method, for example, as disclosed in Patent Document 2, it is known that the workpiece is fixed to the surface of a support substrate via a liquid resin that serves as an adhesive material, and then ground to a predetermined thickness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-207606 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-119578 Summary of the Invention [Problem to be solved by the invention]

[0005] When performing processing such as that disclosed in Patent Document 2, it is necessary to achieve small variations in thickness after bonding the workpiece, adhesive material, and support substrate, in other words, high flatness. If the flatness is low (thickness variations are large), it can cause cracks and chipping during grinding. Furthermore, the limit of thinning also depends on this flatness, in other words, there are cases where thinning to the desired thickness is not possible due to low flatness.

[0006] In the apparatus configuration disclosed in Patent Document 2, for example, the post-bonding accuracy (resin thickness variation) is heavily dependent on the parallelism caused by the component accuracy and assembly error of each component of the apparatus. Specifically, although the parallelism between the stage (upper base, holding means) that holds the workpiece by suction and the stage (surface plate) on which the support substrate and liquid resin are laid can be improved by adjustment, component tolerances and assembly error make it impossible to achieve the desired accuracy. The thickness variation of the bonded resin determines the limit to how thin the laminated workpiece can be when ground. This can lead to problems such as the workpiece not reaching the desired thickness, or even if it does reach the desired thickness, the workpiece's thickness variation can be so great that the post-processing quality is poor.

[0007] In view of the above problems, the present invention proposes a novel technique for thinning a workpiece after forming a laminate by laminating the workpiece to a support substrate. [Means for solving the problem]

[0008] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0009] According to one aspect of the present invention, there is provided a method for processing a workpiece, comprising: an adhesive material supplying step of laying an adhesive material on a support substrate; a facing step of bringing the workpiece facing the adhesive material; a laminate forming step of pressing the adhesive material with the workpiece to integrate the workpiece and the support substrate to form a laminate; a support substrate grinding step of grinding and flattening the exposed surface of the support substrate of the laminate; and a thinning step of grinding the exposed surface of the workpiece of the laminate to thin it to a predetermined thickness after the support substrate grinding step.

[0010] According to another aspect of the present invention, the adhesive material is a liquid resin that solidifies in response to an external stimulus.

[0011] According to one embodiment of the present invention, the support substrate is made of silicon, glass, or resin.

[0012] According to one aspect of the present invention, in the support substrate grinding step, the amount of grinding of the support substrate is greater than the thickness variation of the laminate.

[0013] According to one aspect of the present invention, the same grinding wheel is used in the support substrate grinding step and the thinning step.

[0014] According to one aspect of the present invention, the support substrate and the workpiece are made of the same material. [Effects of the Invention]

[0015] The present invention provides the following effects. That is, according to one aspect of the present invention, even if the components of the device for forming the laminate cannot ensure high parallelism due to component tolerances or installation errors, the exposed surface of the workpiece of the laminate can be held horizontal. This allows the back surface of the workpiece, which is parallel to the horizontal plane, to be uniformly thinned during grinding, thereby increasing the thinning limit, i.e., allowing for even thinner chips. Furthermore, eliminating thickness variation can improve the quality of the final chips manufactured. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram showing an outline of the configuration of a pressing device. [Figure 2] 1A is a diagram illustrating a support substrate disposing step, and FIG. 1B is a diagram illustrating an adhesive material supplying step. [Figure 3] 1A is a diagram illustrating a facing step, and FIG. 1B is a diagram illustrating a laminate formation step. [Figure 4] (A) is a diagram showing the state of ultraviolet irradiation, and (B) is a diagram showing the state of a laminate formed. [Figure 5] 1A is a diagram showing a support substrate grinding step, and FIG. 1B is a diagram showing a state in which the support substrate is ground. [Figure 6] 1A is a diagram illustrating thickness variations in a laminate, and FIG. 1B is a diagram illustrating how height differences occur. [Figure 7] 1A is a diagram showing the amount of grinding, and FIG. 1B is a diagram showing the state after the support substrate is retrieved. [Figure 8] (A) A diagram illustrating the thinning step, and (B) a diagram showing how the workpiece is ground. [Figure 9] 1A is a diagram illustrating how thickness variations do not occur according to the present invention, and FIG. 1B is a diagram illustrating how thickness variations occur in a comparative example not according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an outline of the configuration of a pressing device, which is an example of a device for forming a laminate. Fig. 1 shows how a wafer W, which is a workpiece, is brought into contact with resin 25, which is an adhesive material, laid on the upper surface of a support substrate 31, in the pressing device 1.

[0018] The pressing device 1 is configured to include a table 2, a holding means 4 (holding pad), a lifting means 6, an ultraviolet light irradiation means 5, a resin supplying means 3, and a control device 7 for controlling various operating parts.

[0019] The table 2 has a horizontal upper surface 2a and is configured to transmit ultraviolet light, and is made of a transparent material such as glass. A suction groove that leads to a suction source (not shown) is formed on the horizontal upper surface 2a, and by generating negative pressure on the upper surface 2a, the upper surface 2a is configured to function as a suction holding surface.

[0020] The holding means 4 is disposed above the horizontal upper surface 2a of the table 2, and its horizontal lower surface 4a has suction grooves formed therein, which communicate with a suction source (not shown). By generating a negative pressure on the lower surface 4a, the lower surface 4a functions as a suction-holding surface. The lower surface 4a holds the upper surface of the wafer W, which is the workpiece, by suction, exposing the lower surface. The upper surface of the wafer W held by suction is the surface that will be ground later, e.g., the back surface on which devices will not be formed, while the lower surface of the wafer W is the surface on which devices will be formed (the device surface). Note that both surfaces of the wafer W may not have devices formed on them. Furthermore, the workpiece may be a semiconductor device wafer, or may be various plate-shaped workpieces such as ceramics and glass, or a bonded wafer formed by bonding multiple wafers together.

[0021] The holding means 4 is fixed to the underside of the lifting base 61 of the lifting means 6, and moves up and down together with the lifting base 61. The lifting means 6 has an actuator (not shown), and the lifting base 61 moves up and down by operating the actuator.

[0022] The ultraviolet light irradiation means 5 is disposed below the table 2 and has a light source 5a for emitting ultraviolet light. As will be described in detail later, the ultraviolet light passes through the table 2 and the support substrate 31 and solidifies the resin 25.

[0023] The resin supply means 3 has a supply nozzle 3a for supplying liquid resin 25 onto the upper surface of a support substrate 31 arranged on the table 2. The supply nozzle 3a is configured to be movable by an actuator (not shown), and can be positioned at a supply position where the supply nozzle 3a is positioned at the center of the table 2, and at a retracted position where the supply nozzle 3a is away from the table 2. The supply nozzle 3a is connected to a resin supply source (not shown), and can supply a predetermined amount of resin 25 onto the upper surface of the support substrate 31.

[0024] Next, a processing method using the pressing device configured as above will be described.

[0025] <Support substrate placement step> As shown in FIG. 2(A), this is a step in which a support substrate 31 is placed on a table 2.

[0026] Specifically, the support substrate 31 is disposed so that the center of the support substrate 31 is aligned with approximately the center of the horizontal upper surface 2a of the table 2. The TTV (Total Thickness Variation) of the support substrate 31 is preferably 3 μm or less, and more preferably 1 μm or less.

[0027] The material of the support substrate 31 may be silicon, glass, resin, or the like. The shape of the support substrate 31 may be a circular plate, or may be a rectangular plate, for example.

[0028] <Adhesive material supply step> As shown in FIG. 2(B), this is a step of laying a resin 25, which is an adhesive material, on a support substrate 31.

[0029] Specifically, a supply nozzle 3a is positioned above the approximate center of an upper surface 31a of the support substrate 31, and a predetermined amount of resin 25 is supplied to the upper surface 31a by dripping resin 25 from the supply nozzle 3a. The resin 25 is, for example, an ultraviolet-curable resin, such as "Regilock" (registered trademark) manufactured by Disco Corporation. After solidification, the resin 25 transmits ultraviolet light.

[0030] <Face-to-face steps> As shown in FIG. 3(A), this is a step in which a wafer W, which is a workpiece, is placed facing a resin 25, which is an adhesive material.

[0031] Specifically, a negative pressure is generated on the lower surface 4a of the holding means 4 to suction-hold the back surface Wb of the wafer W. The wafer W is, for example, a semiconductor device wafer having devices formed on the front surface Wa exposed on the lower side, but is not particularly limited to this.

[0032] In the example of FIG. 3(A), the holding means 4 is tilted, so that the surface Wa of the wafer W is inclined at an angle θ so that the right side is lower.

[0033] <Laminate formation step> As shown in FIG. 3(B), this is a step in which the adhesive material (resin 25) is pressed by the workpiece (wafer W) to integrate the workpiece (wafer W) and the support substrate 31 to form a laminate 41.

[0034] Specifically, first, the supply nozzle 3a (FIG. 1) is retracted away from a position below the holding means 4, and the wafer W held by the holding means 4 is lowered by the elevating means 6 (FIG. 1). When the lower surface (front surface Wa) of the wafer W reaches the resin 25, the resin 25 is spread without leaving any gaps between the wafer W and the support substrate 31. Note that the resin 25 covers the front surface Wa of the wafer W, and therefore the devices formed on the front surface Wa are also covered with the resin 25.

[0035] Next, as shown in Fig. 4(A), ultraviolet light UV is irradiated from below by the ultraviolet light irradiation means 5 (Fig. 1), and the ultraviolet light is irradiated onto the resin 25 through the table 2 and the support substrate 31 to solidify the resin 25. As a result, the resin 25 is solidified to form a resin layer, and the wafer W and the support substrate 31 are bonded and integrated via the resin layer made of the resin 25.

[0036] Next, as shown in FIG. 4(B), the suction holding by the holding means 4 is released and the holding means 4 is retracted upward, so that the stack 41 is placed on the table 2.

[0037] In this embodiment, ultraviolet light is used as an external stimulus for solidifying the resin 25, but other external stimuli may also be used, such as heat, and in this case, a thermosetting resin may be used as the resin.

[0038] Furthermore, when ultraviolet irradiation is used as a means of external stimulus, the support substrate 31 needs to be a transparent material such as glass or resin that transmits ultraviolet rays, whereas when heat is used as a means of external stimulus, it is not necessary for the support substrate 31 to transmit ultraviolet rays, and therefore it is possible to use, for example, a plate material such as silicon made of the same material as the wafer W. Furthermore, for the resin 25, it is also possible to use a UV curable resin (delayed curing) whose curing reaction progresses with a time lag after ultraviolet irradiation.

[0039] <Support substrate grinding step> As shown in FIGS. 5(A) and 5(B), this is a step of grinding and flattening the exposed surface 31b of the support substrate 31 of the laminate 41.

[0040] 5(A), first, the back surface Wb of the wafer W of the stack 41 is held by the holding surface 71a of the chuck table 71 of the grinding device 70, and the back surface (exposed surface 31b) of the support substrate 31 opposite the wafer W is exposed upward. At this time, the exposed surface 31b is inclined at an angle θ corresponding to the inclination of the holding means 4 described above.

[0041] The grinding device 70 is mainly composed of a chuck table 71 and a grinding unit 72, and grinds the exposed surface 31b of the support substrate 31 and, as will be described later, the back surface Wb of the wafer W. Suction grooves (not shown) are formed in the holding surface 71a of the chuck table 71, and the stack 41 is sucked and held on the holding surface 71a by generating negative pressure in the suction grooves. The chuck table 71 is configured to rotate by a rotation mechanism (not shown).

[0042] The grinding unit 72 has a grinding wheel 74 in which a plurality of grinding stones 74a are arranged at intervals in an annular shape. The grinding wheel 74 is rotated at a predetermined speed by a rotation mechanism (not shown) and is fed for grinding at a predetermined speed by a grinding feed mechanism (not shown).

[0043] Then, as shown in FIG. 5(B), the exposed surface 31b of the support substrate 31 is ground and flattened by a grinding unit 72, which is a grinding means of the grinding device.

[0044] Grinding is performed so that the grinding amount of the support substrate is greater than the thickness variation of the laminate. Specifically, for example, when a height difference D occurs between the lowest position H1 and the highest position H2 in a state where the exposed surface 31b is inclined at an angle θ as shown in Figures 6(A) and 6(B) and the exposed surface 31b is held on the holding surface 71a, this height difference D is regarded as the variation.

[0045] In this case, by grinding so that the grinding amount K is greater than the height difference D, as shown in Figure 7(A), the exposed surface 31b of the support substrate 31 after grinding can be made horizontal, as shown in Figure 7(B).

[0046] By using a support substrate 31 having a sufficient thickness, it is possible to prevent the support substrate 31 from remaining and the resin 25 from being exposed even after grinding is performed by the grinding amount K. Note that after the support substrate 31 is thinned by grinding, a part of the resin 25 may be exposed.

[0047] <Thinning step> As shown in FIGS. 8(A) and 8(B), this is a step in which the exposed surface (back surface Wb) of the workpiece (wafer W) of the laminate 41 is ground to thin it to a desired thickness after the support substrate grinding step.

[0048] Specifically, first, as shown in Fig. 7(B), the stack 41 that has undergone the support substrate grinding step is removed from the chuck table 71, and the stack 41 is turned over, and as shown in Fig. 8(A), the holding surface 71a of the chuck table 71 holds the exposed surface 31b of the support substrate 31 of the stack 41. This leaves the back surface Wb of the wafer W opposite the support substrate 31 exposed upward.

[0049] In this state, the back surface Wb of the wafer W is parallel to the exposed surface 31b of the support substrate 31 after grinding and parallel to the holding surface 71a of the chuck table 71, so that the back surface Wb of the wafer W is horizontal and not tilted.

[0050] The grinding device 70 used in the thinning step can be the same as the one used in the support substrate grinding step. In this case, the same grinding wheel 74a can be used in the support substrate grinding step and the thinning step, allowing two processes to be performed using one device. Also, for example, if the wafer W and the support member 31 contain the same material, a common grinding wheel 74a can be used. The grinding device 70 used in the thinning step can be a different grinding device from the one used in the support substrate grinding step.

[0051] Then, as shown in FIG. 8(B), the back surface Wb of the wafer W is ground by a grinding unit 72, which is a grinding means of the grinding device, to thin the wafer W to a predetermined thickness (finishing thickness).

[0052] According to the above-described embodiment, even if, for example, as shown in FIG. 3(A), the lower surface 4a of the holding means 4, which is a component of the device (pressing device 1) for forming the laminate, is inclined and not parallel to the horizontal upper surface 2a of the table 2, or even if high parallelism cannot be ensured due to component tolerances or installation errors of various components, the exposed surface (back surface Wb) of the wafer W of the laminate 41 can be held horizontal during grinding, as shown in FIG. 8(A).

[0053] As a result, as shown in Figure 9(A), the back surface Wb of the wafer W, which is parallel to the horizontal plane H, can be uniformly thinned during grinding, increasing the limit of thinning, i.e., it is possible to process the wafer W thinner. Also, a thinned wafer W with no thickness variation can be obtained. Eliminating thickness variation can improve the quality of the chips that are ultimately manufactured.

[0054] 9(B) shows a comparative example that does not conform to this embodiment, in which a wafer W, which is a workpiece, is integrated with a support substrate 131 via a resin layer 132. Since the support substrate 131 is not ground, the back surface Wb of the wafer W is tilted, and the wafer W is not uniformly thinned during grinding, resulting in thickness variations. Such thickness variations may result in poor quality of the chips that are ultimately manufactured. [Explanation of symbols]

[0055] 1 Pressing device 2 tables 2a Top side 3. Resin supply means 3a Supply nozzle 4 Holding means 4a Bottom side 5 Ultraviolet light irradiation means 5a light source 6 Lifting means 7 Control Device 25 Resin 31 Support substrate 31a Top surface 31b Exposed surface 41 Laminate 61 Lifting Platform 70 Grinding equipment 71 Chuck table 71a Holding surface 72 Grinding Unit 74 Grinding Wheel 74a Grinding wheel D Height difference H horizontal plane H1 lowest position H2 highest position K grinding amount UV ultraviolet light W wafer Wa surface Wb back side θ angle

Claims

1. an adhesive material supplying step of laying an adhesive material on a support substrate; a facing step of placing the workpiece facing the adhesive material; a laminate formation step of pressing the adhesive material with the workpiece to integrate the workpiece and the support substrate to form a laminate; a support substrate grinding step of grinding and flattening the exposed surface of the support substrate of the laminate; a thinning step of grinding the exposed surface of the workpiece of the laminate to a predetermined thickness after the support substrate grinding step.

2. The adhesive material is a liquid resin that solidifies upon application of an external stimulus.

2. The method for processing a workpiece according to claim 1.

3. The support substrate is silicon, glass, or resin.

2. The method for processing a workpiece according to claim 1.

4. In the support substrate grinding step, the grinding amount of the support substrate is larger than the thickness variation of the laminate.

2. The method for processing a workpiece according to claim 1.

5. In the support substrate grinding step and the thinning step, grinding is performed using the same grinding wheel.

2. The method for processing a workpiece according to claim 1.

6. The support substrate and the workpiece are composed of the same material.

6. A method for processing a workpiece according to claim 1.

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