JP7698976B2 - Manufacturing method for device chips - Google Patents

Description

The present invention relates to a method for manufacturing device chips.

As a method for mounting semiconductor chips having connection terminals (bumps) made of solder or the like, a method is known in which semiconductor chips are joined together via a paste-like or film-like resin layer for sealing that is provided in advance on the semiconductor chip (see Patent Document 1). In the above-mentioned semiconductor chip manufacturing process, in order to accommodate thinning and multi-layer stacking of device chips, a resin layer is formed on the front surface of a wafer whose back surface has been ground and thinned, and dicing is performed from the resin layer side, which has attracted attention as a method for easily obtaining semiconductor chips with a resin layer formed thereon.

JP 2016-92188 A

However, when cutting the thinned wafer with a cutting blade, there was a problem that backside chipping frequently occurred. To solve this problem, a method of dicing by ablation through irradiation with a laser beam was investigated. However, a new problem was revealed: because the resin layer is sensitive to heat, the resin hardens due to the heat of the laser beam. This means that the resin does not expand during the thermocompression bonding carried out at the mounting stage, causing chip defects.

The present invention was made in consideration of these problems, and its purpose is to provide a method for manufacturing device chips that can suppress the thermal effects on the resin layer that occur during the division process using a laser beam.

In order to solve the above-mentioned problems and achieve the object, the method for manufacturing a device chip of the present invention is a method for manufacturing a device chip by dividing a wafer, on which a plurality of devices are formed in areas partitioned by planned division lines set in a grid pattern on a surface, into individual devices, and includes a resin layer forming step of forming a resin layer on the surface side of the wafer, a resin layer processing step of irradiating a laser beam with a first output along the planned division lines from the side on which the resin layer is formed to form laser processed grooves in the resin layer, and a wafer cutting step of irradiating a laser beam with a second output greater than the first output along the laser processed grooves to cut the wafer after the resin layer processing step ,
The wafer cutting step is characterized in that the laser beam is adjusted so as not to irradiate the sidewalls of the laser processed grooves .

The device chip manufacturing method of the present invention may further include a protective film forming step of forming a protective film on the side on which the resin layer is formed after the resin layer forming step and before the resin layer processing step, and a protective film removing step of removing the protective film after the wafer cutting step.

In addition, in the device chip manufacturing method of the present invention, the resin layer may be an insulating film.

The present invention can suppress the thermal effects on the resin layer that occur during the splitting process using a laser beam.

FIG. 1 is a perspective view of a wafer to be processed in a method for manufacturing device chips according to an embodiment. FIG. 2 is a flow chart showing the flow of the method for manufacturing the device chip according to the embodiment. FIG. 3 is a perspective view showing an example of the resin layer forming step shown in FIG. 2. As shown in FIG. FIG. 4 is a side view, partly in section, showing an example of the protective film forming step shown in FIG. FIG. 5 is a cross-sectional view showing a main part of the wafer in a state after the protective film forming step shown in FIG. FIG. 6 is a side view, partly in section, showing an example of the resin layer processing step shown in FIG. 2 . FIG. 7 is a cross-sectional view showing a main part of the wafer in a state after the resin layer processing step shown in FIG. 6 in FIG. FIG. 8 is a side view, partially in section, showing an example of the wafer cutting step shown in FIG. 2 . FIG. 9 is a cross-sectional view showing a main part of the wafer in a state after the wafer cutting step shown in FIG. FIG. 10 is a side view, partially in section, showing an example of the protective film removing step shown in FIG. 2. As shown in FIG. FIG. 11 is a cross-sectional view showing a main part of the wafer in a state after the protective film removing step shown in FIG. 10 in FIG.

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 manufacturing a device chip 18 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a wafer 10 to be processed in the method for manufacturing a device chip 18 according to the embodiment. The wafer 10 is a disk-shaped semiconductor wafer, an optical device wafer, or the like, with silicon (Si), sapphire _{( Al2O3} ), gallium arsenide (GaAs), silicon carbide (SiC), or the like, serving as a substrate 11. In the embodiment, the substrate 11 is a silicon substrate having a thickness of 30 μm or more and 50 μm or less.

The wafer 10 has a plurality of planned division lines 13 set in a grid pattern on the surface 12 of the substrate 11, and a plurality of devices 14 formed in the areas partitioned by the planned division lines 13. The devices 14 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integration), image sensors such as CCDs (Charge Coupled Devices) or CMOSs (Complementary Metal Oxide Semiconductors), etc. The surface of the wafer 10 opposite the surface 12 on which the devices 14 are formed is referred to as the back surface 15.

In the embodiment, the wafer 10 is a TSV (Through-Silicon Via) wafer having a through electrode 16 (see FIG. 4, etc.) that penetrates the substrate 11 in a region corresponding to the device 14, and an electrode bump 17 that is connected to the through electrode 16 on the surface 12 side of the substrate 11. The electrode bump 17 has a height of about 200 μm and protrudes from the surface of the device 14. The wafer 10 may be an interposer wafer having, for example, a through electrode 16 that penetrates the substrate 11 in a region corresponding to the device 14, and a redistribution layer (wiring layer) that is connected to the through electrode 16 on the surface 12 side of the substrate 11.

The wafer 10 is divided into individual devices 14 along the planned division lines 13, and is singulated into device chips 18. Note that although the device chips 18 are square-shaped in FIG. 1, they may also be rectangular-shaped.

Next, a method for manufacturing the device chip 18 according to the embodiment will be described. FIG. 2 is a flow chart showing the flow of the method for manufacturing the device chip 18 according to the embodiment. The method for manufacturing the device chip 18 according to the embodiment includes a resin layer forming step 1, a protective film forming step 2, a resin layer processing step 3, a wafer cutting step 4, and a protective film removing step 5.

(Resin layer formation step 1)
Fig. 3 is a perspective view showing an example of the resin layer forming step 1 shown in Fig. 2. The resin layer forming step 1 is a step of forming a resin layer 22 on the front surface 12 side of the wafer 10. In the embodiment, before forming the resin layer 22 on the front surface 12 side of the wafer 10, the wafer 10 is fixed to an annular frame 20 and a tape 21.

The frame 20 has an opening larger than the outer diameter of the wafer 10, and is made of a material such as metal or resin. The tape 21 is an adhesive tape for fixing the wafer 10 to the frame 20. The tape 21 includes, for example, a base layer made of synthetic resin, and a glue layer made of adhesive synthetic resin laminated on the base layer. When fixing the wafer 10 to the annular frame 20 and tape 21, first, the tape 21 is attached to the back side of the frame 20, and then the wafer 10 is positioned at a predetermined position in the opening of the frame 20, and the back side 15 is attached to the tape 21.

In the embodiment, the resin layer 22 is an insulating film made of a resin having adhesive properties, for example, NCF (Non Conductive Film). The outer diameter of the resin layer 22, which is a film, is approximately equal to the outer diameter of the wafer 10. In the embodiment, the thickness of the resin layer 22 is 15 μm. In the resin layer formation step 1, as shown in FIG. 3, the resin layer 22 is attached from the surface 12 side of the wafer 10 fixed to the frame 20 and tape 21 so as to cover the entire surface 12 of the wafer 10. The resin layer 22 is adhered in a state where it covers the entire surface 12 of the wafer 10 so as to absorb the unevenness between the planned division lines 13 and the devices 14.

(Protective film formation step 2)
Fig. 4 is a side view, partially in cross section, showing an example of protective film forming step 2 shown in Fig. 2. Fig. 5 is a cross-sectional view showing a main part of the wafer 10 in a state after Fig. 4 of protective film forming step 2 shown in Fig. 2. Protective film forming step 2 is a step of forming a protective film 23 on the side of the wafer 10 on which the resin layer 22 has been formed. Protective film forming step 2 is performed after resin layer forming step 1 and before resin layer processing step 3.

As shown in FIG. 4, in the protective film formation step 2 of the embodiment, the protective film 23 is formed using a protective film forming device 30. In the embodiment, the protective film forming device 30 includes a spin coater. The protective film forming device 30 includes a chuck table 31 having a holding surface 32, a clamp member 33, a rotating shaft member 34, and a resin supply nozzle 35. The protective film forming device 30 may be a protective film forming unit mounted on a laser processing device 40 described below.

In the protective film forming step 2, first, the back surface 15 side of the wafer 10 is sucked and held on the holding surface 32 of the chuck table 31 via the tape 21, and the outer periphery of the frame 20 is fixed with the clamp member 33. Next, while the chuck table 31 is rotated around its axis by the rotating shaft member 34, liquid resin 36 is dropped from the resin supply nozzle 35 onto the resin layer 22 formed on the front surface 12 of the wafer 10. At this time, the resin supply nozzle 35 may be moved back and forth in the radial direction of the wafer 10. The dropped liquid resin 36 flows from the center side to the outer periphery side on the resin layer 22 formed on the front surface 12 of the wafer 10 due to the centrifugal force generated by the rotation of the chuck table 31, and is applied to the entire surface of the resin layer 22.

The resin 36 is, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP). In the present invention, for example, Hogomax (registered trademark) manufactured by Disco Corporation can be used as the resin 36. In the protective film formation step 2, the liquid resin 36 applied to the entire surface of the resin layer 22 on the front surface 12 side of the wafer 10 is dried, and as shown in FIG. 5, a protective film 23 made of the water-soluble resin 36 is formed on the resin layer 22 formed on the front surface 12 side of the wafer 10. In the embodiment, the thickness of the protective film 23 is about 5 μm or more and 15 μm or less.

(Resin layer processing step 3)
Fig. 6 is a side view partially in cross section showing an example of the resin layer processing step 3 shown in Fig. 2. Fig. 7 is a cross-sectional view showing a main part of the wafer 10 in a state after Fig. 6 of the resin layer processing step 3 shown in Fig. 2. The resin layer processing step 3 is a step of irradiating a laser beam 45 with a first output along the planned division line 13 from the side where the resin layer 22 is formed, to form a laser processed groove 24 in the resin layer 22. The resin layer processing step 3 is performed after the resin layer formation step 1. The resin layer processing step 3 of the embodiment is further performed after the protective film formation step 2.

As shown in FIG. 6, in the resin layer processing step 3 of the embodiment, the laser processing groove 24 is formed using a laser processing device 40. The laser processing device 40 includes a chuck table 41 having a holding surface 42, a clamp member 43, a laser beam irradiation unit 44, and a moving unit (not shown) that moves the chuck table 41 and the focal point of the laser beam emitted from the laser beam irradiation unit 44 relatively.

In the resin layer processing step 3, first, the back surface 15 side of the wafer 10 is sucked and held to the holding surface 42 of the chuck table 41 via the tape 21, and the outer periphery of the frame 20 is fixed with the clamp member 43. Next, the laser beam 45 is irradiated onto the side of the wafer 10 on which the resin layer 22 is formed, while the chuck table 41 and the focal point of the laser beam emitted from the laser beam irradiation unit 44 are moved relative to each other along the planned division line 13.

The laser beam 45 irradiated in the resin layer processing step 3 is a laser beam with a wavelength that is absorbent for the resin layer 22 and the protective film 23, and is irradiated with a first output. In the embodiment, the first output laser beam 45 has an output of 5 W, 5 passes, a repetition frequency of 300 kHz, and a feed speed of 1000 mm/s. The focal point position of the laser beam 45 may be fixed on the surface of the resin layer 22 as in the embodiment, or may be changed. The laser beam 45 may also be branched and irradiated in the processing feed direction.

As shown in FIG. 7, in resin layer processing step 3, a laser beam 45 with a focal point positioned on the surface of the resin layer 22 is irradiated along the planned division lines 13 to form laser processed grooves 24 along the planned division lines 13. That is, the laser beam 45 removes the resin layer 22 and protective film 23 covering the surface 12 of the wafer 10 in the areas corresponding to the planned division lines 13, forming the laser processed grooves 24. The laser processed grooves 24 expose the substrate 11 by removing parts of the resin layer 22 and protective film 23 in the areas corresponding to the planned division lines 13.

At this time, a heat-affected zone 25 (HAZ) is formed on the sidewall of the laser-machined groove 24, where the resin is hardened by the thermal effect of the irradiation of the laser beam 45. The first output laser beam 45 for removing the resin in the resin layer processing step 3 has a lower output than the second output laser beam 46 for cutting the substrate 11 of the wafer 10 in the wafer cutting step 4 described below. This makes it possible to suppress the thermal effect on the resin of the resin layer 22 and the protective film 23, which are sensitive to heat.

Furthermore, in the embodiment, the resin layer 22 formed on the front surface 12 side of the wafer 10 is further covered with a protective film 23. Because the front surface side, which is most affected by the heat of the laser beam 45 and where the heat-affected layer 25 is large, is covered with the protective film 23, the width 26 of the heat-affected layer 25 in the resin layer 22 can be reduced.

(Wafer cutting step 4)
Fig. 8 is a side view partially in cross section showing an example of the wafer cutting step 4 shown in Fig. 2. Fig. 9 is a cross-sectional view showing a main part of the wafer 10 in a state after Fig. 8 of the wafer cutting step 4 shown in Fig. 2. The wafer cutting step 4 is a step of irradiating a laser beam 46 along the laser processed groove 24 with a second output larger than the first output to cut the wafer 10. The wafer cutting step 4 is performed after the resin layer processing step 3.

As shown in FIG. 8, in the embodiment, in wafer cutting step 4, the wafer 10 is cut using the laser processing device 40 used in the resin layer processing step 3, but a laser processing device different from the laser processing device 40 used in the resin layer processing step 3 may be used.

In the wafer cutting step 4, the chuck table 41 and the focal point of the laser beam emitted from the laser beam irradiation unit 44 are moved relative to each other along the laser processing grooves 24 formed in the resin layer 22 and protective film 23 on the surface 12 side of the wafer 10, while the laser beam 46 is irradiated onto the surface 12 side of the substrate 11 exposed from the resin layer 22 of the wafer 10.

The laser beam 46 irradiated in the wafer cutting step 4 is a laser beam with a wavelength that is absorbent for the substrate 11, and is irradiated with a second output power that is greater than the first output power. In the embodiment, the second output power laser beam 46 has an output power of 7 W, a number of passes of 15, a repetition frequency of 300 kHz, and a feed speed of 1000 mm/s.

The focal point of the laser beam 46 may be fixed at the height of the surface of the resin layer 22 as in the embodiment, or may be changed to, for example, the surface 12 of the substrate 11. The laser beam 46 may be branched and irradiated in the processing feed direction. In the wafer cutting step 4, the laser beam 46 is adjusted so that it is not irradiated to the side walls of the laser processed groove 24. The laser beam 46 is adjusted so that it is not irradiated to the side walls of the laser processed groove 24, for example, by shaping the beam shape. The laser beam 46 may also be adjusted so that it is not irradiated to the side walls of the laser processed groove 24, for example, by adjusting the output, the position of the focal point, etc.

As shown in FIG. 9, in the wafer cutting step 4, the wafer 10 is divided along the division lines 13 and singulated into device chips 18 by irradiating the laser beam 46, whose focal point is positioned at the height of the surface of the resin layer 22, along the laser processing grooves 24. At this time, the laser processing grooves 24 remove the areas of the resin layer 22 and the protective film 23 along the division lines 13, exposing the substrate 11. Therefore, the laser beam 46 is directly irradiated to the surface 12 of the substrate 11 along the division lines 13, and is not irradiated to the resin layer 22 and the protective film 23, which are the side walls of the laser processing grooves 24. This makes it possible to suppress the expansion of the heat-affected layer 25.

(Protection film removal step 5)
Fig. 10 is a side view, partially in cross section, showing an example of protective film removing step 5 shown in Fig. 2. Fig. 11 is a cross-sectional view showing a main part of the wafer 10 in a state after Fig. 10 of protective film removing step 5 shown in Fig. 2. The protective film removing step 5 is a step of removing the protective film 23. The protective film removing step 5 is performed after the wafer cutting step 4.

As shown in FIG. 10, in the protective film removal step 5 of the embodiment, the protective film 23 made of a water-soluble resin covering the surface of the resin layer 22 formed on the front surface 12 side of the wafer 10 is washed and removed with a cleaning liquid 56 by a cleaning device 50. The cleaning device 50 includes a chuck table 51 having a holding surface 52, a clamp member 53, a rotating shaft member 54, and a cleaning liquid supply nozzle 55.

The cleaning device 50 may also be a device that is used in combination with the protective film forming device 30. More specifically, the chuck table 51, clamp member 53, and rotating shaft member 54 of the cleaning device 50 may also be used in combination with the chuck table 31, clamp member 33, and rotating shaft member 34 of the protective film forming device 30. The cleaning device 50 may also be a cleaning unit mounted on the laser processing device 40.

In the protective film removal step 5, first, the back surface 15 side of the wafer 10 is sucked and held on the holding surface 52 of the chuck table 51 via the tape 21, and the outer periphery of the frame 20 is fixed with the clamp member 53. Next, while the chuck table 51 is rotated about its axis by the rotating shaft member 54, the cleaning liquid 56 is supplied from the cleaning liquid supply nozzle 55 toward the resin layer 22 formed on the front surface 12 of the wafer 10. At this time, the cleaning liquid supply nozzle 55 may be moved back and forth in the radial direction of the wafer 10.

The cleaning liquid 56 is, for example, pressurized water whose water pressure is adjusted to about 10 MPa or more and 12 MPa or less in a water channel upstream of the cleaning liquid supply nozzle 55. The cleaning liquid 56 is, for example, pure water. The cleaning liquid 56 may be bubble water mixed with air. It may also be a so-called two-fluid cleaning in which water and air are mixed together.

The supplied cleaning liquid 56 flows from the center to the outer periphery over the resin layer 22 formed on the surface 12 of the wafer 10 due to centrifugal force generated by the rotation of the chuck table 31, and cleans the protective film 23 covering the surface of the resin layer 22. By cleaning the protective film 23 covering the surface of the resin layer 22, the surface of the resin layer 22 is exposed, as shown in FIG. 11. This makes it possible to obtain a device chip 18 in which the resin layer 22 is formed on the surface 12 of the substrate 11.

As described above, in the manufacturing method of the device chip 18 of the embodiment, the resin layer 22 is processed at a low output (first output) and then the substrate 11 is processed at a high output (second output), thereby making it possible to reliably divide the substrate 11 while suppressing the thermal effects on the resin layer 22 that occur during laser processing.

In addition, the laser processing grooves 24 formed by low-power processing can limit the direction in which high-temperature debris and plasma are scattered during high-power processing when cutting the substrate 11, which can also help suppress the thermal effects caused by debris adhesion and plasma diffusion.

Furthermore, by forming a protective film 23 that covers the surface of the resin layer 22, the heat-affected layer 25 can be suppressed. When the protective film 23 is formed as in the embodiment, the resin layer 22 is processed with a first output, and the substrate 11 is processed with a second output, the width 26 of the heat-affected layer 25 is about 45 μm. In contrast, for example, when the protective film 23 is formed and the resin layer 22 and the substrate 11 are processed with a laser beam of the same output, the width 26 of the heat-affected layer 25 is about 60 μm. Furthermore, for example, when the protective film 23 is not formed and the resin layer 22 and the substrate 11 are processed with a laser beam of the same output, the width 26 of the heat-affected layer 25 is about 80 μm.

In the embodiment, it is preferable that the resin layer processing step 3 and the wafer cutting step 4 are performed consecutively, and the protective film removal step 5 is performed immediately after the wafer cutting step 4 is performed. Here, "immediately after the wafer cutting step 4 is performed" refers to the time after the wafer cutting step 4 is performed and the time required for the wafer 10 on which the wafer cutting step 4 is performed by the laser processing device 40 to be transported to the cleaning device 50 has elapsed. By performing the protective film removal step 5 immediately after the resin layer processing step 3 and the wafer cutting step 4 are performed, the debris attached to the protective film 23 during the laser processing can be removed before it gradually changes in quality and becomes difficult to remove.

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 resin layer processing step 3 shown in Figures 6 and 7 of the embodiment, the resin layer 22 and the protective film 23 in the area corresponding to the planned division line 13 are removed to expose the substrate 11, but in the present invention, it is not necessary to expose the substrate 11. In other words, if a predetermined amount of the resin layer 22 in the area along the planned division line 13 is removed after the resin layer processing step 3, the effect of suppressing the expansion of the heat-affected layer 25 in the wafer cutting step 4 can be obtained in the same way.

REFERENCE SIGNS LIST 10 wafer 11 substrate 12 front surface 13 planned division line 14 device 15 back surface 18 device chip 22 resin layer 23 protective film 24 laser processed groove 25 heat affected layer 26 width 45, 46 laser beam

Claims (3)

A method for manufacturing device chips by dividing a wafer having a plurality of devices formed in areas defined by dividing lines set in a grid pattern on a surface thereof into individual devices, the method comprising the steps of:
a resin layer forming step of forming a resin layer on the front surface side of the wafer;
a resin layer processing step of irradiating a laser beam with a first output from the side where the resin layer is formed along the intended division line to form a laser processed groove in the resin layer after the resin layer forming step;
a wafer cutting step of irradiating a laser beam along the laser processing groove with a second output greater than the first output after the resin layer processing step, thereby cutting the wafer;
Including,
In the wafer cutting step, the laser beam is adjusted so as not to irradiate the sidewall of the laser processed groove .
A method for manufacturing a device chip. a protective film forming step of forming a protective film on the side on which the resin layer is formed after the resin layer forming step and before the resin layer processing step;
a protective film removing step of removing the protective film after the wafer cutting step;
Further comprising:
The method for producing the device chip according to claim 1 . The resin layer is an insulating film.
The method for producing the device chip according to claim 1 or 2 .

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