JP2024101316A - Processing method of workpiece - Google Patents

Abstract

To provide a processing method of a workpiece in which a thinned workpiece can be peeled off from a support substrate without damaging the workpiece.SOLUTION: A processing method of a workpiece comprises: a support substrate fixing step 1 of fixing a support substrate on one surface of a workpiece via wax; a grinding step 2 of grinding the other surface side of the workpiece on one surface of which the support substrate is fixed, and thinning to a predetermined thickness; a protective sheet laying step 3 of laying a protective sheet containing thermoplastic resin to a grinding surface of the workpiece that was ground in the grinding step 2; a heating step 4 of heating the protective sheet and wax in the state where the protective sheet is laid on the grinding surface to thermally press a heated protective sheet to the workpiece; and a support substrate peeling step 5 of peeling off the workpiece from the support substrate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for processing a workpiece.

In the manufacturing process of semiconductor devices, a step of grinding the back surface of a semiconductor wafer to thin it is carried out in order to make the device have the desired thickness. In recent years, the miniaturization of equipment that mounts semiconductor devices has created a demand for device chips to be as thin as possible, but since thinned semiconductor wafers are difficult to handle, a method is used in which the front surface side of the semiconductor wafer is attached to a support substrate before grinding, and the semiconductor wafer is peeled off from this support substrate after grinding (see Patent Document 1).

JP 2010-027857 A

The most common method for attaching a support substrate is to create a wax film using solid wax that has been melted by heating, and then fix the semiconductor wafer and support substrate via the wax film. However, when fixing using this method, there is a possibility that warping caused by grinding stress or the like will be released when the semiconductor wafer is peeled off from the support substrate, causing the semiconductor wafer to crack.

The present invention was made in consideration of these problems, and its purpose is to provide a method for processing a workpiece that can peel off the thinned workpiece from the supporting substrate without damaging it.

In order to solve the above-mentioned problems and achieve the object, the method for processing a workpiece of the present invention is characterized by comprising a support substrate fixing step of fixing a support substrate to one surface of the workpiece via wax, a grinding step of grinding the other surface of the workpiece with the support substrate fixed to the one surface to thin it to a predetermined thickness, a protective sheet laying step of laying a protective sheet containing a thermoplastic resin on the grinding surface of the workpiece ground in the grinding step, a heating step of heating the protective sheet and the wax with the protective sheet laid on the grinding surface and thermocompressing the heated protective sheet to the workpiece, and a support substrate peeling step of peeling the workpiece from the support substrate.

In addition, in the method for treating a workpiece of the present invention, it is preferable that the melting temperature of the wax is lower than the temperature at which the protective sheet is thermocompressed to the workpiece.

The present invention allows the thinned workpiece to be peeled off from the supporting substrate without damaging it.

FIG. 1 is a flowchart showing a flow of a method for processing a workpiece according to an embodiment of the present invention. FIG. 2 is a perspective view showing an example of the support substrate fixing step shown in FIG. FIG. 3 is a perspective view showing another example of the support substrate fixing step shown in FIG. 1. As shown in FIG. FIG. 4 is a side view, partly in section, showing one state of the grinding step shown in FIG. FIG. 5 is a side view, partly in section, showing one state of the grinding step shown in FIG. FIG. 6 is a side view, partly in section, showing one state of the protective sheet laying step shown in FIG. 1. FIG. FIG. 7 is a side view, partly in section, showing one state of the heating step shown in FIG. FIG. 8 is a side view, partly in section, showing one state of the support substrate peeling step shown in FIG. FIG. 9 is a side view, partially in cross section, showing one state of the modified layer forming step in the first application mode. FIG. 10 is a side view, partly in section, showing one state of the modified layer forming step in the second application mode. FIG. 11 is a side view, partially in cross section, showing one state of the dividing step in the second application mode. FIG. 12 is a side view, partially in cross section, showing one state of the dividing step in the second application mode.

The following describes in detail the form (embodiment) for carrying out the present invention with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, or modifications of the configuration can be made without departing from the spirit of the present invention.

[Embodiment]
A method for processing a workpiece 10 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a flow chart showing the flow of the method for processing a workpiece 10 according to the embodiment. The method for processing a workpiece 10 is a method in which grinding is performed in a state in which the workpiece 10 is fixed to a support substrate 30, and then a protective sheet 50 is laid on the workpiece 10 and the support substrate 30 is peeled off from the workpiece 10. As shown in Fig. 1, the method for processing a workpiece 10 according to the embodiment includes a support substrate fixing step 1, a grinding step 2, a protective sheet laying step 3, a heating step 4, and a support substrate peeling step 5.

(Support Substrate Fixing Step 1)
Fig. 2 is a perspective view showing an example of the support substrate fixing step 1 shown in Fig. 1. Fig. 3 is a perspective view showing another example of the support substrate fixing step 1 shown in Fig. 1. The support substrate fixing step 1 is a step of fixing a support substrate 30 to one surface 11 of a workpiece 10 via wax 20.

The workpiece 10 is a wafer such as a disk-shaped _{semiconductor} device wafer or an optical device wafer, whose substrate is made of, for example, silicon (Si), sapphire ( _Al2O3 ), gallium arsenide (GaAs), silicon carbide (SiC), lithium tantalate ( _LiTa3 ), etc. The workpiece 10 has a plurality of planned dividing lines (see planned dividing lines 15 in Figs. 9 to 12) set in a lattice pattern on the surface (one surface 11) of the substrate, and devices formed in areas partitioned by the planned dividing lines.

The device may be, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a MEMS (Micro Electro Mechanical Systems). The workpiece 10 is divided along the planned division lines into individual devices and manufactured into chips. The chip includes a portion of the substrate and a device on the substrate. The planar shape of the chip is, for example, a square or rectangular shape. Note that the workpiece 10 is not limited to a disk shape in the present invention, and may be other plate shapes such as a resin package substrate or a metal substrate.

Wax 20 is a bonding material for fixing one surface 11 of workpiece 10 to support substrate 30, and is formed of, for example, a thermoplastic resin. Wax 20 has a melting start temperature of about 60°C, which is lower than the temperature at which protective sheet 50, described below, is thermocompressed to workpiece 10. In this specification, thermocompression bonding refers to, for example, protective sheet 50 softening without melting, and being pressed against grinding surface 14 of workpiece 10 after grinding (see FIG. 5), thereby adhering to grinding surface 14.

2, the support substrate 30 is disk-shaped with the same diameter as the workpiece 10. In addition, in the support substrate fixing step 1, a disk-shaped support substrate 30-1 with a diameter larger than the workpiece 10 may be used as in another example shown in FIG. 3. The support substrate may also be formed with a shape and size that sufficiently covers the workpiece 10. One surface 31 and the other surface 32 of the support substrate 30 are formed parallel to each other. The support substrate 30 is formed of a material that is equal to or less brittle than the workpiece 10, and is equal to or less likely to break than the workpiece 10. For example, a glass plate or a silicon wafer is used as the support substrate 30.

In the support substrate fixing step 1, for example, first, wax 20 is applied to one of the surfaces 11 of the workpiece 10 and one of the surfaces 31 of the support substrate 30. Next, one of the surfaces 11 of the workpiece 10 and one of the surfaces 31 of the support substrate 30 to which wax 20 has been applied is bonded to the other. For example, liquid wax 20 is applied to one surface 11 of the workpiece 10 by spin coating, and then the surface 11 is fixed by applying pressure to one surface 31 of the heated support substrate 30.

Alternatively, the solid wax 20 may be placed between one surface 11 of the workpiece 10 and one surface 31 of the support substrate 30 and then heated and pressurized to melt the wax 20 and spread it over the entire surface of the workpiece 10. The wax 20 hardens as it cools below its softening point, and the workpiece 10 can be fixed to the support substrate 30 via the wax 20.

(Grinding step 2)
4 and 5 are side views partially in cross section showing one state of the grinding step 2 shown in Fig. 1. The grinding step 2 is a step of grinding the other surface 12 side of the workpiece 10 having the support substrate 30 fixed to one surface 11 to thin it down to a predetermined thickness 13. In the grinding step 2 of the embodiment, the other surface 12 side of the workpiece 10 is ground by a grinding device 40 shown in Figs. 4 and 5 to thin it down to the predetermined thickness 13.

As shown in Figures 4 and 5, the grinding device 40 includes a holding table 41, a spindle 42 which is a rotating shaft member, a grinding wheel 43 attached to the lower end of the spindle 42, a grinding stone 44 attached to the underside of the grinding wheel 43, and a grinding fluid supply unit (not shown). The grinding wheel 43 rotates on an axis parallel to the axis of the holding table 41.

In grinding step 2, first, the other surface 32 of the support substrate 30 is suction-held on the holding surface of the holding table 41. Next, while the holding table 41 is rotated about its axis, the grinding wheel 43 is rotated about its axis. Grinding fluid is supplied to the processing point by a grinding fluid supply unit (not shown), and the grinding wheel 44 of the grinding wheel 43 is brought closer to the holding table 41 at a predetermined feed rate, so that the other surface 12 of the workpiece 10 is ground by the grinding wheel 44, thinning it down to the predetermined thickness 13 shown in FIG. 5.

(Protective sheet laying step 3)
Fig. 6 is a side view, partially in cross section, showing one state of the protective sheet laying step 3 shown in Fig. 1. The protective sheet laying step 3 is a step of laying a protective sheet 50 containing a thermoplastic resin on the grinding surface 14 of the workpiece 10 ground in the grinding step 2. In the protective sheet laying step 3 of the embodiment, the protective sheet 50 is pressed against the grinding surface 14 of the workpiece 10 by a roller 55 shown in Fig. 6.

The protective sheet 50 is a sheet for protecting the grinding surface 14 side of the workpiece 10. The protective sheet 50 is a resin sheet formed of a thermoplastic resin that is heat-pressed at a temperature of about 80°C to 120°C. The protective sheet 50 includes, for example, a polyolefin-based sheet or a polyethylene-based sheet having a thickness of 20 μm to 80 μm, and in the embodiment, is a sheet having a thickness of 80 μm. The protective sheet 50 may be a single layer or a laminate. The protective sheet 50 is, for example, a GluFree (registered trademark) sheet manufactured by Disco Corporation that does not have a glue layer and is composed only of a non-adhesive and stretchable base layer.

In protective sheet laying step 3, first, the other surface 32 of the support substrate 30 is placed on the holding surface of the holding table 56 so that the grinding surface 14 of the workpiece 10 faces upward. In protective sheet laying step 3, next, one surface 51 of the protective sheet 50, which is larger and covers the entire grinding surface 14 of the workpiece 10, is aligned so that it faces the grinding surface 14 of the workpiece 10.

In the protective sheet laying step 3, the roller 55 is then rolled on one side 51 of the protective sheet 50 and the other side 52 opposite thereto, from one end of the workpiece 10 to the other end. This causes the protective sheet 50 to be pressed against the grinding surface 14 of the workpiece 10. The roller 55 may, for example, have a heat source and be capable of heating the protective sheet 50. The protective sheet 50 is heat-pressed by the roller 55 while being heated, so that it is spread out in a softened state against the grinding surface 14. This makes it possible to prevent air bubbles from entering between the grinding surface 14 and the protective sheet 50 in the heating step 4 described below.

(Heating step 4)
Fig. 7 is a side view, partially in cross section, showing one state of heating step 4 shown in Fig. 1. Heating step 4 is a step of heating the protective sheet 50 and the wax 20 in a state in which the protective sheet 50 is laid on the grinding surface 14, and thermocompressing the heated protective sheet 50 to the workpiece 10. In heating step 4 of the embodiment, the protective sheet 50 and the wax 20 are heated by a heating device 60 shown in Fig. 7.

The heating device 60 is a hot plate having a heat source 61 and capable of heating the holding surface 62 (upper surface). The holding table 56 used in the protective sheet laying step 3 may be a heating device 60 in which heating by the heat source 61 is stopped. In the heating step 4, the other surface 32 of the support substrate 30 is placed on the holding surface 62 of the heated heating device 60, thereby heating the wax 20 and the protective sheet 50 via the support substrate 30 and the workpiece 10.

At this time, the heating temperature of the heat source 61 is preset so that the protective sheet 50 is heated to a temperature above its softening point and below its melting point, and the wax 20 is heated to a temperature above its softening point. Specifically, the protective sheet 50 and the wax 20 are heated to a temperature of about 50°C or higher and 200°C or lower. Specifically, since the melting start temperature of the wax 20 is about 60°C, and the compression temperature of the protective sheet 50 is about 80°C or higher and 120°C or lower, it is preferable to heat to a temperature of about 80°C or higher and 120°C or lower.

The protective sheet 50 laid on the grinding surface 14 of the workpiece 10 is softened by heating, and one side 51 adheres to the grinding surface 14. In addition, since the melting temperature of the wax 20 is lower than the temperature at which the protective sheet 50 is thermocompressed to the workpiece 10, when the protective sheet 50 is heated to the point where it is thermocompressed to the workpiece 10, the wax 20 interposed between the workpiece 10 and the support substrate 30 melts.

The heating step 4 is not limited to a method of heating using a hot plate, and any method can be used as long as it can heat the wax 20 and the protective sheet 50 simultaneously.

(Support Substrate Peeling Step 5)
8 is a side view showing, in partial cross section, one state of the support substrate peeling step 5 shown in FIG. The support substrate peeling step 5 is a step of peeling the workpiece 10 from the support substrate 30. In the support substrate peeling step 5, the protective sheet 50 thermocompressed to the workpiece 10 in the heating step 4 and the workpiece 10 are lifted up against the support substrate 30 placed on the holding surface 62 of the heating device 60, thereby peeling the workpiece 10 from the support substrate 30. Since the wax 20 is sufficiently heated and melted by the heating step 4, the workpiece 10 can be easily peeled off from the support substrate 30. Therefore, the workpiece 10 can be peeled off from the wax 20 without releasing the warp caused by grinding stress or the like.

When the workpiece 10 is peeled off from the support substrate 30 and the protective sheet 50 is carried out of the heating device 60 together with the workpiece 10, the protective sheet 50 cools below its softening point and hardens, becoming integrated with the workpiece 10. In this way, the workpiece 10 can be peeled off from the wax 20 and transferred to the protective sheet 50.

As described above, the method for processing the workpiece 10 according to the embodiment involves grinding the back surface (other surface 12) of the workpiece 10 fixed to the support substrate 30 by the wax 20, and then laying a protective sheet 50 made of a thermoplastic resin on the grinding surface 14 and heating it, thereby peeling off the wax 20 and integrating the protective sheet 50 with the grinding surface 14. This has the effect of peeling off the workpiece 10 from the wax 20 without releasing the warp, and transferring the workpiece 10 to the protective sheet 50.

[First Application Mode]
Next, a first application form of the method for processing the workpiece 10 of the present invention will be described. In the first application form, after the support substrate fixing step 1 and before the grinding step 2, a modified layer 16 (see FIG. 9) is formed inside the workpiece 10 (modified layer forming step), and in the grinding step 2, the modified layer 16 is removed and the workpiece 10 is divided along the modified layer 16 into chips.

The modified layer 16 refers to a region in which the density, refractive index, mechanical strength, or other physical properties are different from those of the surrounding area. The modified layer 16 is, for example, a melt-processed region, a crack region, an insulation breakdown region, a refractive index change region, or a region in which these regions are mixed. The modified layer 16 has a lower mechanical strength, etc. than other parts of the workpiece 10.

(Modified layer forming step)
Fig. 9 is a side view partially in cross section showing one state of the modified layer forming step in the first application form. In the modified layer forming step shown in Fig. 9, a modified layer 16 is formed inside the workpiece 10 by stealth dicing using a laser processing device 70. The laser processing device 70 includes a holding table 71, a laser beam irradiation unit 72, an imaging unit (not shown), and a moving unit (not shown) that moves the holding table 71 and the laser beam irradiation unit 72 relatively.

In the modified layer formation step shown in FIG. 9, first, the other surface 32 of the support substrate 30 is suction-held on the holding table 71. Next, the holding table 71 is moved to a predetermined processing position by a moving unit (not shown). Next, the planned division line 15 is detected by capturing an image of the workpiece 10 with an imaging unit (not shown). Once the planned division line 15 has been detected, alignment is performed to align the planned division line 15 of the workpiece 10 with the irradiation portion of the laser beam irradiation unit 72.

In the modified layer formation step, the focal point 74 of the laser beam 73 is then positioned inside the workpiece 10. In this state, the focal point 74 is moved relatively in the processing feed direction along the planned division line 15 while irradiating the workpiece 10 with the laser beam 73 from the other surface 12 side. The laser beam 73 is a laser beam with a wavelength that is transparent to the workpiece 10, for example, infrared rays (IR). By irradiating the laser beam 73 along the planned division line 15, a modified layer 16 is formed inside the workpiece 10 along the planned division line 15.

In this case, in the modified layer formation step, the height of the focal point 74 of the laser beam 73 may be changed and the laser beam 73 may be irradiated multiple times, or a laser beam 73 having multiple focal points 74 spaced apart in the thickness direction of the workpiece 10 may be irradiated to form multiple modified layers 16 that overlap in the thickness direction of the workpiece 10. Cracks 17 extend from the modified layers 16 in the thickness direction of the workpiece 10, and the modified layers 16 and the cracks 17 are connected to form lattice-shaped division starting points along the planned division lines 15.

(Grinding step 2)
In the first application form, the procedure for grinding the other surface 12 side of the workpiece 10 on which the modified layer 16 is formed is the same as in the grinding step 2 of the embodiment. In the grinding step 2 of the first application form, a crack extends from the modified layer 16 as a starting point to one surface 11 and the other surface 12 of the workpiece 10 due to a grinding stress acting from a grinding wheel 43 (see FIGS. 4 and 5), and the workpiece 10 is divided along the planned division line 15 with the modified layer 16 as a division starting point, and is singulated into individual device chips.

[Second Application Form]
Next, a second application of the method for processing the workpiece 10 of the present invention will be described. In the second application, after the grinding step 2 and before the protective sheet laying step 3, a modified layer 16 is formed inside the workpiece 10 (modified layer forming step), and after the support substrate peeling step 5, the workpiece 10 is divided into chips along the modified layer 16 by expanding (dividing step).

(Modified layer forming step)
10 is a side view showing one state of the modified layer forming step in the second application form, partially in cross section. In the modified layer forming step shown in FIG. 10, the modified layer 16 is formed inside the workpiece 10 by stealth dicing using a laser processing device 70, as in the modified layer forming step in the first application form. In the procedure of the modified layer forming step in the second application form, the "other surface 12 of the workpiece 10" in the procedure of the modified layer forming step in the first application form may be replaced with the "ground surface 14 of the workpiece 10".

(Division Step)
11 and 12 are side views partially in cross section showing one state of the dividing step in the second application form. The dividing step is carried out on the workpiece 10 in which the modified layer 16 has been formed in the modified layer forming step, after the protective sheet laying step 3, the heating step 4, and the support substrate peeling step 5. In the dividing step, an external force is applied to the workpiece 10 in which the modified layer 16 has been formed in the modified layer forming step, and the workpiece 10 is divided along each of the planned dividing lines 15 into chips.

As shown in Figures 11 and 12, in the division step, an expandable tape 91 is attached and transferred to one surface 11 of the workpiece 10, and then an expansion device 80 applies an external force to the expandable tape 91 in the radial direction to divide the workpiece 10. The expansion device 80 includes a holding table 81, a clamp member 82, a lifting unit 83, a push-up member 84, and a roller member 85. The push-up member 84 is cylindrical and is provided on the outer periphery of and coaxial with the holding table 81. The roller member 85 is provided on the same plane as or slightly above the holding surface of the holding table 81, and at the upper end of the push-up member 84, so as to be freely rotatable.

In the division step, first, the protective sheet 50 (see FIG. 8) attached to the grinding surface 14 side of the workpiece 10 is peeled off, and an expandable tape 91 is attached to one surface 11 of the workpiece 10 and to an annular frame 90. The frame 90 is made of metal or resin and is an annular plate with an opening larger than the outer diameter of the workpiece 10. The expandable tape 91 is, for example, in the form of a sheet including a base layer made of an expandable synthetic resin and a glue layer laminated on the base layer and made of an expandable and adhesive synthetic resin.

The expandable tape 91 is, for example, attached to one surface 11 of the workpiece 10 and to the annular frame 90, and then cut to a shape and size that covers the opening of the frame 90. The workpiece 10 is positioned at a predetermined position in the opening of the frame 90, and one surface 11 is attached to the expandable tape 91, thereby fixing the workpiece 10 to the frame 90 and the expandable tape 91.

As shown in FIG. 11, in the division step, one surface 11 of the workpiece 10 is then placed on the holding surface of the holding table 81 via the expanding tape 91, and the outer periphery of the frame 90 is fixed with the clamping member 82. At this time, the roller member 85 abuts against the expanding tape 91 between the inner edge of the frame 90 and the outer edge of the workpiece 10.

As shown in FIG. 11, in the division step, the holding table 81 and the push-up member 84 are then raised together by the lifting unit 83. At this time, since the outer periphery of the expanding tape 91 is fixed by the clamp member 82 via the frame 90, the portion between the inner edge of the frame 90 and the outer edge of the workpiece 10 is expanded in the planar direction. Furthermore, the roller member 85 provided at the upper end of the push-up member 84 reduces friction with the expanding tape 91.

In the division step, as a result of the expansion of the expandable tape 91, a radial tensile force acts on the expandable tape 91. When the radial tensile force acts on the expandable tape 91, as shown in Figures 10 and 11, the workpiece 10 to which the expandable tape 91 is attached is divided at the modified layer 16 along the planned division line 15 as the fracture starting point, and is divided into individual device chips 18.

After the workpiece 10 is divided into device chips 18, the device chips 18 are picked up from the expanding tape 91 by a well-known picker in a pick-up process, for example. In the division step of the second application form, the device chips 18 are diced with the back surface (grinding surface 14) facing up, so that the device chips 18 need to be turned upside down in the next pick-up process or die bonding process, for example.

In the second application form described above, a tape different from the protective sheet 50 is used as the expandable tape 91, but if the protective sheet 50 has expandability, the protective sheet 50 can be used as is. In this case, in the division step, the device chip 18 is divided into individual pieces with the front surface (one surface 11) facing upward, so that, for example, in the subsequent pick-up process or die bonding process, there is no need to turn the device chip 18 upside down.

The present invention is not limited to the above embodiment. In other words, various modifications can be made without departing from the gist of the present invention. For example, in the protective sheet laying step 3, a vacuum state (low pressure state) may be created to lay the protective sheet 50 in close contact with the grinding surface 14.

REFERENCE SIGNS LIST 10 Workpiece 11, 31, 51 One side 12, 32, 52 Other side 13 Thickness 14 Grinding surface 15 Planned division line 16 Modified layer 17 Crack 18 Device chip 20 Wax 30, 30-1 Support substrate 50 Protective sheet

Claims (2)

A method for treating a workpiece, comprising the steps of:
a support substrate fixing step of fixing a support substrate to one surface of the workpiece via wax;
a grinding step of grinding the other surface side of the workpiece having the support substrate fixed to the one surface to thin the workpiece to a predetermined thickness;
a protective sheet laying step of laying a protective sheet containing a thermoplastic resin on the ground surface of the workpiece ground in the grinding step;
a heating step of heating the protective sheet and the wax in a state where the protective sheet is laid on the grinding surface, and thermocompressing the heated protective sheet to the workpiece;
a support substrate peeling step of peeling the workpiece from the support substrate. 2. The method for treating a workpiece according to claim 1, wherein the melting temperature of the wax is lower than the temperature at which the protective sheet is thermocompression bonded to the workpiece.

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