JP2018067587A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a satisfactorily laser process on a wafer without worsening the machining quality even if the wafer is one with a functional film.SOLUTION: A wafer processing method is arranged to divide a wafer (W) along scheduled division lines (L), provided that the wafer has a functional film (12) formed on a surface side of a silicon substrate (11), and a plurality of devices (D) formed on the surface side of the silicon substrate and defined by the scheduled division lines. The wafer processing method comprises the steps of: cutting in the wafer to the silicon substrate along each scheduled division line from the side the functional film thereof by a cutting blade (21) to remove, by the cutting blade, the functional film which is molten when irradiated with a laser beam of a wavelength which the silicon substrate absorbs; and applying a laser beam of a wavelength which the silicon substrate absorbs in each cutting groove (13) where the functional film is removed, thereby dividing the wafer along the scheduled division lines into the plurality of devices (D).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for processing a wafer having a functional film formed on the surface.

  As a method for processing a wafer such as a semiconductor wafer or an optical device wafer, there has been proposed a method of dividing a wafer by ablation processing using a laser beam having a wavelength that absorbs the wafer (for example, see Patent Document 1). In the processing method described in Patent Document 1, a processing groove is formed by irradiating a pulse laser beam along a planned division line of the wafer, and the wafer is divided into individual chips by breaking along the processing groove. Since laser processing has a narrow processing width, it is particularly suitable for processing a wafer with a surface film formed as narrow as the width of a line to be divided is several tens of μm or less.

JP-A-10-305420

  However, there is a wafer in which the functional film on the surface of the substrate is melted when the substrate is irradiated with a laser beam having an absorptive wavelength. When the normal laser processing is performed on the wafer on which such a functional film is formed, there is a problem that the processing quality is greatly deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wafer processing method that can perform laser processing satisfactorily without reducing processing quality even for a wafer with a functional film. One.

  In one embodiment of the present invention, a wafer processing method divides a wafer including a substrate, a functional film formed on the surface side of the substrate, and a plurality of devices defined by the division line, along the division line. This is a processing method that is performed by cutting a wafer from a functional film side of a wafer along a planned division line to a substrate with a cutting blade, and the functional film that melts when irradiated with a laser beam having an absorptive wavelength with respect to the substrate. A functional film removing step that exposes the substrate by removing, and a laser beam that irradiates a laser beam having a wavelength that absorbs the substrate into the cutting groove from which the functional film has been removed, and divides the laser beam into a plurality of devices along the planned division line An irradiation step.

  According to this configuration, the functional film is removed by the cutting blade, the cutting groove is formed along the division line, and the laser beam is irradiated to the substrate exposed from the cutting groove to divide the wafer into individual devices. Since the laser beam having a narrow processing width is irradiated to the substrate through the cutting groove, the functional film is not melted by the laser beam. Therefore, it is possible to satisfactorily process a wafer in which a functional film that is melted by laser beam irradiation is formed on the surface and the line to be divided is narrow without reducing the processing quality.

  According to the present invention, the functional film on the surface of the wafer is removed with a cutting blade to form a cutting groove along the planned dividing line, and a laser beam is irradiated along the cutting groove, so that the planned dividing line is narrow and the surface is cut. Thus, a wafer on which a functional film is formed can be satisfactorily processed.

It is a perspective view of the wafer of this Embodiment. It is explanatory drawing of the processing method of the wafer of a comparative example. It is explanatory drawing of the processing method of the wafer of this Embodiment.

  Hereinafter, the processing method of the present embodiment will be described with reference to the accompanying drawings. First, a wafer to be processed will be described. FIG. 1 is a perspective view of a wafer according to the present embodiment. FIG. 2 is an explanatory view of a wafer processing method of a comparative example.

  As shown in FIG. 1, the wafer W is formed such that a plurality of devices D partitioned by lattice-shaped division lines L are formed on the surface side of the silicon substrate (substrate) 11 and covers the surface side of the silicon substrate 11. A functional film 12 is formed. A dicing tape T is attached to the back surface of the wafer W, and the wafer W is supported by a ring frame F attached to the outer periphery of the dicing tape T. The wafer W is not limited to the one in which the functional film 12 is formed on the silicon substrate 11, and the wafer W may be one in which the functional film 12 is formed on another semiconductor substrate such as gallium arsenide or an inorganic material substrate such as sapphire. Good.

  By the way, as shown in FIG. 2A, a wafer W with a functional film 12 includes a narrow one whose dividing line L has a width of several tens of μm or less, and is usually ablation processing using a laser beam having a narrow processing width. The wafer W is divided. When a laser beam having a wavelength that absorbs the silicon substrate 11 is irradiated from the surface side of the wafer W, the silicon substrate 11 is partially sublimated by laser ablation, but the functional film 12 is not sublimated but is heated. It was melted. For this reason, there is a problem that the melt of the functional film 12 adheres in the processing groove 15 of the silicon substrate 11 and the processing quality of the wafer W deteriorates.

  Further, as shown in FIG. 2B, a method in which the functional film 12 and the silicon substrate 11 are cut in two stages using cutting blades having different widths is also conceivable. In this case, since the width of the division line L of the wafer W is too narrow, even if a narrow cutting blade 21 capable of cutting the first-stage functional film 12 can be prepared, as indicated by a virtual line, 2 A narrower cutting blade that can cut the silicon substrate 11 at the stage cannot be prepared. Although it is conceivable to simultaneously cut the functional film 12 and the silicon substrate 11 with the narrow cutting blade 21, there is a problem that a crack occurs on the back surface of the wafer W and the processing quality of the wafer W deteriorates.

  Thus, on the surface side of the wafer W, there exists the functional film 12 that melts when irradiated with a laser beam having a wavelength that absorbs the silicon substrate 11, and the wafer W is scheduled to be divided for cutting with the cutting blade 21. Line L is too narrow. Therefore, in the method for processing the wafer W according to the present embodiment, the functional film 12 is removed from the surface side of the wafer W along the division line L by cutting, and the silicon substrate 11 exposed along the division line L is removed. Cutting is done by laser processing. As a result, the functional film 12 is formed on the surface side, and the wafer W in which the width of the planned division line L is narrow can be divided satisfactorily.

  Hereinafter, the wafer processing method will be described in detail with reference to FIG. FIG. 3 is an explanatory diagram of the wafer processing method of the present embodiment. 3A is a diagram showing an example of the functional film removing step of the present embodiment, and FIG. 3B is a diagram showing an example of the laser beam irradiation step of the present embodiment.

  As shown in FIG. 3A, a functional film removal step is first performed. In the functional film removing step, the wafer W is held on the chuck table 22 of the cutting device (not shown) via the dicing tape T, and the ring frame F around the wafer W is held by the clamp unit 23. When the cutting blade 21 is positioned on the division line L outside the wafer W in the radial direction, the cutting blade 21 is lowered to a depth at which the upper portion of the silicon substrate 11 can be cut, and the chuck table 22 cuts against the cutting blade 21. Sent. As the cutting blade 21, a blade having a blade width narrower than the narrow width of the division line L of the wafer W is used.

  Thus, the cutting blade 21 cuts the wafer W from the functional film 12 side to the middle of the silicon substrate 11, and the silicon substrate 11 is exposed from the front surface side of the wafer W along the division line L. By repeating this cutting process, the wafer W is cut along all the planned division lines L, and lattice-like cutting grooves 13 are formed in the functional film 12 of the wafer W. In this way, the functional film 12 that melts when the silicon substrate 11 is irradiated with a laser beam having an absorptive wavelength is removed from the surface side of the wafer W along the division line L by the cutting blade 21. .

  Next, as shown in FIG. 3B, the laser beam irradiation step is performed after the functional film removal step is performed. In the laser beam irradiation step, the wafer W is held on the chuck table 26 of a laser processing apparatus (not shown) via the dicing tape T, and the ring frame F around the wafer W is held by the clamp portion 27. Further, the injection port of the processing head 25 is positioned directly above the cutting groove 13 (division line L) of the wafer W, and a laser beam is irradiated from the processing head 25 toward the silicon substrate 11 exposed from the cutting groove 13. The laser beam is adjusted to a wavelength having absorptivity with respect to the silicon substrate 11.

  Then, the processing head 25 is moved relative to the wafer W while the condensing point of the laser beam is adjusted, so that the silicon substrate 11 is ablated along the cutting groove 13. By repeating this processing feed, the laser beam is irradiated onto the silicon substrate 11 along all the cutting grooves 13 of the wafer W, and the wafer W is divided into a lattice shape along all the planned division lines L. At this time, the spot diameter of the laser beam is adjusted to be smaller than the groove width of the cutting groove 13, and the functional film 12 is not melted by the heat of the laser beam because the functional film 12 is not irradiated with the laser beam.

  Thus, a laser beam having a wavelength that absorbs the silicon substrate 11 is irradiated into the cutting groove 13 from which the functional film 12 has been removed, and the wafer W is applied to the plurality of devices D along the division line L. Divided. Since the functional film 12 does not melt, it is divided without deteriorating the processing quality of the wafer W. Ablation means that when the irradiation intensity of the laser beam exceeds a predetermined processing threshold, it is converted into electronic, thermal, photochemical and mechanical energy on the solid surface, resulting in neutral atoms, molecules, positive and negative ions. , A phenomenon in which radicals, clusters, electrons, and light are explosively emitted and the solid surface is etched.

  In the processing method of the wafer W according to the present embodiment, the functional film removal step and the laser beam irradiation step can be performed to satisfactorily process the wafer W having the functional film 12 on the surface with the narrow division lines L. . In addition, the narrow division | segmentation scheduled line L has shown the line of the width | variety which can cut the functional film 12 from the wafer W by cutting, but cannot divide the wafer W completely by cutting. That is, the narrow division line L is a width narrower than a limit width necessary for full cutting by cutting, and the limit width is a minimum width at which the divided chip does not become defective due to cracks, that is, The width that can be stably manufactured by the cutting blade 21 (width with good thickness accuracy) is shown. The functional film 12 is a film that is melted by heat when irradiated with a laser beam having a wavelength that sublimates (ablates) the substrate (the silicon substrate 11 in the present embodiment).

  As described above, according to the processing method of the wafer W of the present embodiment, the functional film 12 on the surface is removed by the cutting blade 21 and the cutting groove 13 is formed along the planned division line L. The silicon substrate 11 exposed from the laser beam is irradiated with a laser beam, and the wafer W is divided into individual devices D. Since the laser beam having a narrow processing width is applied to the silicon substrate 11 through the cutting groove, the functional film 12 is not melted by the laser beam. Therefore, the functional film 12 that is melted by the irradiation of the laser beam is formed on the surface, and the wafer W having the narrow division line L can be processed satisfactorily without reducing the processing quality.

  In the present embodiment, a silicon substrate is exemplified as the wafer substrate, but the present invention is not limited to this configuration. The substrate of the wafer only needs to be formed of a material capable of forming a processing groove by ablation processing. The functional film of the wafer is not particularly limited as long as it is a film that imparts various functions such as an insulating function to the substrate.

  Further, in the present embodiment, the configuration for processing a wafer with a narrow division line is illustrated, but the present invention is not limited to this configuration. The present invention can also be applied to a wafer whose division line is not narrow.

  Moreover, although this Embodiment and the modified example were demonstrated, what combined the said embodiment and modified example entirely or partially as another embodiment of this invention may be sufficient.

  The embodiments of the present invention are not limited to the above-described embodiments and modifications, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by technological advancement or another derived technique, the method may be used. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea of the present invention.

  In the present embodiment, the processing method for dividing a wafer into individual devices has been described. However, the present invention is applied to other processing objects with a functional film that can be laser processed satisfactorily without reducing processing quality. Is also possible.

  As described above, the present invention has an effect that even a wafer with a functional film can be satisfactorily laser-processed without deteriorating the processing quality, in particular, a silicon substrate with a functional film. This is useful for processing methods that divide into devices.

11 Silicon substrate 12 Functional film 13 Cutting groove 21 Cutting blade 25 Processing head D Device L Divided line W Wafer

Claims (1)

A processing method for dividing a wafer including a substrate, a functional film formed on the surface side of the substrate, and a plurality of devices partitioned by the division line, along the division line,
Cut from the functional film side of the wafer to the substrate with a cutting blade along the planned dividing line, and remove the functional film that melts when irradiated with a laser beam having an absorptive wavelength with respect to the substrate. A functional film removing step for exposing the substrate;
A laser beam irradiation step of irradiating a laser beam having a wavelength that absorbs the substrate into the cutting groove from which the functional film has been removed, and dividing the laser beam into a plurality of devices along the planned division line. Processing method.

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