JP7796606B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method.

A conventional processing method involves processing a wafer, which has functional layers including devices stacked on a substrate such as silicon, along planned division lines (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2007-173475

For example, the processing method disclosed in Patent Document 1 had the problem that the functional layer peeled off when a laser beam was irradiated onto the functional layer to form a processing groove. Therefore, a solution was taken to slow down the processing feed speed to prevent the functional layer from peeling off.

However, in this case, the thermal damage from the laser beam increases, resulting in a problem of reduced die strength of the device chips after separation.

The object of the present invention is to provide a wafer processing method that can suppress peeling of the functional layer.

In order to solve the above-mentioned problems and achieve the objectives, the wafer processing method of the present invention is a wafer processing method for processing a wafer having functional layers including devices stacked on a substrate along a planned dividing line, and is characterized by comprising: an affected region forming step in which a laser beam having a wavelength that is absorbed by the substrate and whose absorbency in the functional layer is lower than that of the substrate is applied along the planned dividing line under processing conditions that restrict continuous ablation processing of the functional layer, thereby forming two affected regions extending along the planned dividing line within the functional layer at a predetermined interval; a functional layer removal step in which, after the affected region forming step, a laser beam is applied between the affected regions to form a first processing groove that removes the functional layer; and a substrate processing step in which, after the functional layer removal step, the substrate is processed along the first processing groove.

In the wafer processing method, the functional layer may be an oxide film.

In the wafer processing method, the affected region formation step may involve irradiating a laser beam with a wavelength in the ultraviolet region.

In the wafer processing method, the output of the laser beam per spot irradiated in the affected area formation step may be smaller than the output of the laser beam per spot irradiated in the functional layer removal step.

The present invention has the effect of suppressing peeling of the functional layer.

FIG. 1 is a perspective view schematically showing a wafer to be processed by the wafer processing method according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing a main part of the wafer shown in FIG. FIG. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment. FIG. 4 is a cross-sectional view schematically showing a main part of the wafer during the affected region forming step of the wafer processing method shown in FIG. FIG. 5 is a plan view schematically showing a main part of the wafer after the affected region forming step of the wafer processing method shown in FIG. FIG. 6 is a plan view schematically showing another example of a main part of a wafer after the affected region forming step of the wafer processing method shown in FIG. FIG. 7 is a cross-sectional view schematically showing a main part of the wafer after the functional layer removing step of the wafer processing method shown in FIG. FIG. 8 is a cross-sectional view schematically showing a main part of the wafer after the substrate processing step of the wafer processing method shown in FIG. FIG. 9 is a plan view schematically showing a main part of a wafer in which grooves are formed on both edges of the dividing line by a conventional processing method. FIG. 10 is a flowchart showing the flow of the wafer processing method according to the second embodiment. FIG. 11 is a cross-sectional view schematically showing a main part of a wafer during the affected region forming step of the wafer processing method shown in FIG. FIG. 12 is a cross-sectional view schematically showing a main part of the wafer after the outer processing groove forming step of the wafer processing method shown in FIG. FIG. 13 is a cross-sectional view schematically showing a main part of the wafer after the functional layer removing step of the wafer processing method shown in FIG. FIG. 14 is a cross-sectional view schematically showing a main part of a wafer after the substrate processing step of the wafer processing method shown in FIG.

Modes for carrying out the present invention (embodiments) will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that would be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications to the configuration can be made without departing from the spirit of the present invention.

[Embodiment 1]
A wafer processing method according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view schematically showing a wafer to be processed by the wafer processing method according to the first embodiment. Fig. 2 is a cross-sectional view schematically showing a main part of the wafer shown in Fig. 1. Fig. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment.

(wafer)
The wafer processing method according to the first embodiment is a method for processing a wafer 1 shown in Fig. 1. In the first embodiment, the wafer 1 is a wafer such as a disk-shaped semiconductor wafer having a substrate 2 made of silicon or the like. As shown in Fig. 1, the wafer 1 has devices 5 formed in regions partitioned in a grid pattern by a plurality of planned dividing lines 4 formed in a grid pattern on the surface 3 of the wafer 1.

Device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), a CCD (Charge Coupled Device), or a memory (semiconductor memory device).

In embodiment 1, as shown in Figures 1 and 2, the wafer 1 has a functional layer 6 laminated on the surface of the substrate 2. In embodiment 1, the functional layer 6 is made of an oxide film ( _SiO2 ) and includes the above-mentioned device 5. The functional layer 6 is easily peeled off from the substrate 2 when the wafer 1 is cut from the front surface 3 side with a cutting blade. Thus, in embodiment 1, the wafer 1 has the functional layer 6 including the device 5 laminated on the substrate 2.

(Wafer Processing Method)
The wafer processing method according to the first embodiment is a method of processing a wafer 1, in which a functional layer 6 including devices 5 is stacked on a substrate 2, along planned division lines 4 that partition the wafer 1 into a plurality of devices 5. Note that in the first embodiment, the wafer processing method also includes a method of dividing (corresponding to processing) the wafer 1 along the planned division lines 4 into individual device chips 10 (shown in FIG. 1 ). Note that the device chips 10 include a portion of the substrate 2 and the devices 5.

As shown in FIG. 3, the wafer processing method includes an affected region forming step 101, an affected region forming step 101, and a substrate processing step 103. In embodiment 1, the wafer processing method includes, as shown in FIG. 1, adhering a disk-shaped tape 11 having a larger diameter than the wafer 1 to the back surface 9 behind the front surface 3, adhering an annular frame 12 to the outer edge of the tape 11, and processing the wafer 1 supported by the frame 12.

(Affected region forming step)
Fig. 4 is a cross-sectional view schematically showing a main part of a wafer during the affected region forming step of the wafer processing method shown in Fig. 3. Fig. 5 is a plan view schematically showing a main part of a wafer after the affected region forming step of the wafer processing method shown in Fig. 3. Fig. 6 is a plan view schematically showing another example of a main part of a wafer after the affected region forming step of the wafer processing method shown in Fig. 3.

In the affected area forming step 101, a laser beam 21 (shown in FIG. 4) having a wavelength that is absorbed by the substrate 2 and that is less absorbed by the functional layer 6 than by the substrate 2 is irradiated along the planned division line 4 under processing conditions that restrict continuous ablation of the functional layer 6, thereby forming two affected areas 13 (shown in FIG. 4) extending along the planned division line 4 at a predetermined distance within the functional layer 6. Continuous ablation refers to the formation of a continuous groove in the functional layer 6. A continuous groove refers to a groove that is formed uninterruptedly along the planned division line 4 in the area where the device chip 10 is formed, and that forms a recessed shape from the surface 3.

In embodiment 1, in affected area formation step 101, the laser processing device 20 shown in FIG. 4 suction-holds the back surface 9 of the wafer 1 on the holding surface of the holding table via tape 11, and clamps the frame 12 with the clamping unit. In embodiment 1, in affected area formation step 101, the laser processing device 20 images the front surface 3 of the wafer 1 with an imaging unit (not shown), detects the planned division line 4, and performs alignment to align the laser beam application unit 22 with the planned division line 4.

In embodiment 1, in the affected area forming step 101, the laser processing device 20 moves the wafer 1 and the laser beam application unit relative to each other along the planned dividing lines 4, while sequentially irradiating both widthwise edges of each planned dividing line 4 with a laser beam 21 from the laser beam application unit 22, the laser beam 21 having a wavelength that is absorbed by both the substrate 2 and the functional layer 6 of the wafer 1, as shown in FIG. 4. Note that in embodiment 1, in the affected area forming step 101, the laser processing device 20 sets the focal point 23 of the laser beam 21 at the interface 7 between the substrate 2 and the functional layer 6, and irradiates the laser beam 21 onto the wafer 1 along each planned dividing line 4; however, in the present invention, the focal point 23 may also be set on the surface 3 of the wafer 1, i.e., the surface of the functional layer 6.

Furthermore, in embodiment 1, the laser beam 21 irradiated onto the wafer 1 in the affected area formation step 101 has a wavelength that is absorbed by the substrate 2 and the functional layer 6, and therefore ablation processing is performed on both the substrate 2 and the functional layer 6. Furthermore, the laser beam 21 has a wavelength that is less absorbed by the functional layer 6 than by the substrate 2.

However, in embodiment 1, in the affected area forming step 101, the laser beam 21 is irradiated onto the wafer 1 at a wavelength that is less absorbable by the functional layer 6 than by the substrate 2, and at an output that restricts ablation of the functional layer 6, i.e., an output weaker than the output required for ablation of the functional layer 6. For this reason, in embodiment 1, in the affected area forming step 101, the laser processing device 20 heats and alters the functional layer 6 near the focal point 23 of the laser beam 21, thereby forming affected areas 13 extending along the planned division line 4 on both edges of the interior of the functional layer 6.

The altered region 13 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 altered region 13 is, for example, a melt-treated region, a crack region, a dielectric breakdown region, a refractive index change region, or a region in which these regions are mixed. Furthermore, in embodiment 1, the altered region 13 has lower thermal conductivity than other unaltered regions of the functional layer 6.

In embodiment 1, in the affected area forming step 101, the laser processing device 20 emits a laser beam from an oscillator having a wavelength of 355 nm, a repetition frequency of 200 kHz, and an average output of 1.0 W to 1.5 W. The laser beam emitted by the oscillator is then split into 10 beams along the longitudinal direction of the planned division line 4 for irradiation. Therefore, the average output per spot of the laser beam 21 actually irradiated onto the wafer 1 is 0.1 W to 0.15 W. That is, in embodiment 1, the affected area forming step 101 irradiates the wafer 1 with a laser beam 21 having a wavelength in the ultraviolet range.

Furthermore, in embodiment 1, in the affected area formation step 101, the relative speed of the laser beam 21 along the planned division line 4 relative to the wafer 1 (hereinafter referred to as the processing feed speed) is set to 30 mm/sec, and the spot at the focal point 23 of the laser beam 21 is set to a circle with a diameter of 6 μm to 8 μm.

Under these processing conditions, in the affected area forming step 101 in embodiment 1, the laser processing device 20 forms affected areas 13 extending along the planned division line 4 at both edges of the planned division line 4 inside the functional layer 6, forming two affected areas 13 at a predetermined interval inside the functional layer 6 for each planned division line 4, as shown in FIG. 5. In the present invention, when forming the affected areas 13 in the affected area forming step 101, pores 14 extending from the affected area 13 toward the surface 3 and opening onto the surface 3 may also be formed, as shown in FIG. 6. While FIG. 6 shows circular spot-shaped pores 14, processed grooves extending from the affected area 13 toward the surface 3, opening onto the surface 3, and extending in the longitudinal direction of the planned division line 4 may also be used instead. In the case of processed grooves, forming continuous processed grooves would result in film peeling of the functional layer 6, as in conventional technology. Therefore, the processing conditions, for example, the output per spot, are adjusted so that multiple openings reaching the surface 3 are formed discontinuously with a predetermined gap between them.

(Functional layer removal step)
Fig. 7 is a cross-sectional view schematically showing a main part of a wafer after the functional layer removal step of the wafer processing method shown in Fig. 3. The functional layer removal step 102 is a step of irradiating a laser beam 21 between the affected regions 13 after the affected region formation step 101 is performed, to form a first processed groove 15 that removes the functional layer 6.

In embodiment 1, in the functional layer removal step 102, the laser processing device 20 irradiates the wafer 1 with a laser beam 21 from the laser beam application unit 22 along the planned dividing lines 4 while moving the wafer 1 and the laser beam application unit 22 relatively along the planned dividing lines 4. Note that in embodiment 1, in the affected area formation step 101, the laser processing device 20 sets the focal point 23 of the laser beam 21 on the surface 3 of the functional layer 6 and irradiates the laser beam 21 at the center of each planned dividing line 4 in the width direction.

In embodiment 1, in functional layer removal step 102, the laser beam 21 is irradiated onto the wafer 1 under processing conditions that allow ablation of the functional layer 6, for example, at a stronger output per spot than the output in affected area formation step 101. Therefore, in embodiment 1, in functional layer removal step 102, the laser processing device 20 ablate the functional layer 6 and substrate 2 at the center of the width of each planned division line 4, removing a portion of these and forming a first processing groove 15 that divides the functional layer 6 at each planned division line 4, as shown in FIG. 7.

In embodiment 1, in the functional layer removal step 102, a laser beam having a wavelength of 355 nm, a repetition frequency of 40 kHz to 60 kHz, and an average output of 2.5 W to 5.0 W is emitted from an oscillator, and the laser beam 21 emitted by the oscillator is branched into two beams in the width direction of the planned division line 4 and irradiated. The average output per spot of the laser beam 21 is 1.25 to 2.5 W. Also, in embodiment 1, in the functional layer removal step 102, the processing feed rate is set to 100 mm/sec to 400 mm/sec, and the spot at the focal point 23 of the laser beam 21 is set to a circle with a diameter of 30 μm to 60 μm. That is, in embodiment 1, the functional layer removal step 102 irradiates the wafer 1 with a laser beam 21 having a wavelength in the ultraviolet range. Thus, in the wafer processing method according to embodiment 1, the output of the laser beam 21 per spot irradiated in the affected area formation step 101 is smaller than the output of the laser beam 21 per spot irradiated in the functional layer removal step 102.

In embodiment 1, in the functional layer removal step 102, the altered region 13 is cracked by the laser beam 21 before other regions of the functional layer 6, releasing the stress generated in the functional layer 6 and preventing cracks from occurring outside the functional layer 6 and separating the functional layer 6. This allows the laser processing device 20 to perform ablation processing on the functional layer 6 between the altered regions 13 of each planned division line 4, thereby forming first processing grooves 15 between each functional layer 6, with the substrate 2 exposed at the bottom, without peeling the functional layer 6. Furthermore, in conventional processing methods, when forming processing grooves in the functional layer 6, cracks occur when the functional layer 6 softened by the heat of the laser beam 21 is rapidly cooled. Therefore, the processing feed rate is slowed to allow heat to accumulate in the functional layer 6 during processing, preventing rapid cooling of the functional layer 6. However, in embodiment 1, the output per spot in the functional layer removal step 102 is small, so the thermal effect is also small, and cracks caused by rapid cooling can be prevented. This allows for a faster processing feed speed when forming the affected region 13, improving productivity.

(Substrate processing step)
Fig. 8 is a cross-sectional view schematically showing a main part of the wafer after the substrate processing step of the wafer processing method shown in Fig. 3. The substrate processing step 103 is a step of processing the substrate 2 along the first processing groove 15 after the functional layer removal step 102 is performed.

In embodiment 1, in the substrate processing step 103, the laser processing device 20 irradiates the wafer 1 with a laser beam 21 from the laser beam application unit 22 along the planned division lines 4 while moving the wafer 1 and the laser beam application unit 22 relatively along the planned division lines 4. Note that in embodiment 1, in the affected area formation step 101, the laser processing device 20 sets the focal point 23 of the laser beam 21 on the bottom surface of the first groove 15, and irradiates the laser beam 21 onto the bottom surface of the first groove 15 formed on each planned division line 4.

In embodiment 1, in substrate processing step 103, the wafer 1 is irradiated with a laser beam 21 under processing conditions that allow ablation of the substrate 2, for example, at an output greater than the output of affected area formation step 101. Therefore, in embodiment 1, in substrate processing step 103, the laser processing device 20 performs ablation on the exposed bottom surface of the first groove 15 formed at each planned division line 4, thereby forming a second groove 16 at the bottom surface of the first groove 15 that is narrower than the first groove 15, as shown in FIG. 8. In embodiment 1, in substrate processing step 103, the laser processing device 20 opens the second groove 16 on the back surface 9 of the wafer 1, i.e., penetrates the second groove 16 through the wafer 1, thereby dividing the wafer 1 into individual device chips 10. Thus, in embodiment 1, the wafer 1 is divided in substrate processing step 103 to produce a plurality of device chips 10.

As shown in Figure 9, the conventional processing method irradiates both widthwise edges of each planned division line 4 with a laser beam 21 of a wavelength absorbed by the functional layer, and ablates both edges of each planned division line 4 in the functional layer 6 to form a processed groove 200. In this process, the conventional processing method slows down the processing feed rate to prevent the functional layer 6 from cooling rapidly after thermal expansion due to irradiation with the laser beam 21, thereby maintaining the functional layer 6 in a soft, heated state and preventing it from cracking and peeling. However, with the conventional processing method, the flexural strength of the device chip 10 after division tends to decrease due to thermal damage.

In contrast to such conventional processing methods, the wafer processing method according to embodiment 1 forms an altered region 13 that acts as a breakwater by cracking the functional layer 6 at both edges of the planned division line 4 inside the functional layer 6 before other regions in the functional layer 6 in the altered region forming step 101. Therefore, even if the processing feed rate in the functional layer removal step 102 is faster than that in the altered region forming step 101, the altered region 13 becomes the starting point for cracking of the functional layer 6, and the altered region 13 cracks before other regions, releasing stress corresponding to the functional layer 6, thereby preventing peeling of the functional layer 6 outside the altered region 13.

As a result, the wafer processing method according to embodiment 1 has the effect of suppressing peeling of the functional layer 6.

In addition, the wafer processing method according to embodiment 1 allows the processing feed rate in the functional layer removal step 102 to be faster than that in the affected area formation step 101, thereby suppressing thermal damage caused by the laser beam 21 and improving the flexural strength of the device chip 10.

Note that Figure 9 is a plan view that schematically shows the main parts of a wafer in which processed grooves have been formed on both edges of the planned dividing line using a conventional processing method. Note that in Figure 9, the same parts as in embodiment 1 are designated by the same reference numerals, and their explanations are omitted.

[Embodiment 2]
A wafer processing method according to embodiment 2 will be described with reference to the drawings. FIG. 10 is a flowchart showing the flow of the wafer processing method according to embodiment 2. FIG. 11 is a cross-sectional view schematically showing a main part of a wafer during an affected region forming step of the wafer processing method shown in FIG. 10. FIG. 12 is a cross-sectional view schematically showing a main part of a wafer after an outer processing groove forming step of the wafer processing method shown in FIG. 10. FIG. 13 is a cross-sectional view schematically showing a main part of a wafer after a functional layer removing step of the wafer processing method shown in FIG. 10. FIG. 14 is a cross-sectional view schematically showing a main part of a wafer after a substrate processing step of the wafer processing method shown in FIG. 10. Note that in FIGS. 10, 11, 12, 13, and 14, the same parts as those in embodiment 1 are designated by the same reference numerals, and description thereof will be omitted.

The wafer processing method according to embodiment 2, like embodiment 1, is a method of dividing the wafer 1 into individual device chips 10 along the planned division lines 4. As shown in FIG. 10 , the wafer processing method according to embodiment 2 includes an affected region forming step 101, an outer processing groove forming step 110, an inner processing groove forming step 111, and a substrate processing step 103.

In embodiment 2, in the affected region forming step 101, as in embodiment 1, affected regions 13 extending along the planned division line 4 are formed on both edges of the planned division line 4 inside the functional layer 6, as shown in FIG. 11, so that two affected regions 13 are formed at a predetermined distance inside the functional layer 6 for each planned division line 4.

The outer processing groove forming step 110 is a step performed after the affected area forming step 101, in which the inner edge of the affected area 13 is removed to form outer processing grooves 17, the bottom surfaces of which expose the substrate 2, on both widthwise edges of each planned dividing line 4. In embodiment 2, in the outer processing groove forming step 110, the laser processing apparatus 20 irradiates the wafer 1 with a laser beam 21 from the laser beam application unit 22 along the planned dividing line 4 while moving the wafer 1 and the laser beam application unit 22 relative to each other along the planned dividing line 4.

In embodiment 1, in the affected area forming step 101, the laser processing device 20 sets the focal point 23 of the laser beam 21 on the inner edge of the affected area 13 on the surface 3 of the functional layer 6, and irradiates the laser beam 21 onto each affected area 13 of each planned division line 4. Note that the inner edge of the affected area 13 refers to the edge of the two affected areas 13 formed on each planned division line 4, closer to the center of the planned division line 4.

In embodiment 2, in the outer groove formation step 110, the laser beam 21 is irradiated onto the wafer 1 under processing conditions that allow ablation of the functional layer 6, for example, at a stronger output per spot than in the affected area formation step 101. Therefore, in embodiment 1, in the outer groove formation step 110, the laser processing device 20 performs ablation on the functional layer 6 on the inner edge of the affected area 13 of each planned division line 4, the inner edge of the affected area 13, and the upper surface of the substrate 2, removing portions of these. As shown in FIG. 12, this separates the functional layer 6 at each planned division line 4, removes the inner edge of the affected area 13, and forms an outer groove 17 whose bottom exposes the substrate 2.

In embodiment 2, in the outer groove forming step 110, a laser beam having a wavelength of 355 nm, a repetition frequency of 120 kHz to 200 kHz, and an average output of 0.1 W to 3.0 W is emitted from an oscillator, and the laser beam 21 emitted by the oscillator is branched into two beams in the width direction of the intended division line 4 and irradiated. Because it is branched, the average output per spot of the laser beam 21 is 0.05 W to 1.5 W. Also, in embodiment 1, in the outer groove forming step 110, the processing feed rate is set to 100 mm/sec to 400 mm/sec, and the spot at the focal point 23 of the laser beam 21 is a circle with a diameter of 6 μm to 8 μm.

In the second embodiment, in the inner processing groove forming step 111, as in the first embodiment, the laser processing device 20 performs ablation processing on the functional layer 6 and substrate 2 at the center of the width of each planned division line 4, removing a portion of them, thereby dividing the functional layer 6 at each planned division line 4 and forming an inner processing groove 15 that communicates with the outer processing groove 17, as shown in FIG. 13.

In embodiment 2, in the inner groove forming step 111, a laser beam having a wavelength of 355 nm, a repetition frequency of 40 kHz to 60 kHz, and an average output of 2.5 W to 5.0 W is emitted from an oscillator, and the laser beam 21 emitted by the oscillator is branched into two beams in the width direction of the planned division line 4 and irradiated. Because the laser beam 21 is branched, the average output per spot of the laser beam 21 is 1.25 W to 2.5 W. Also, in embodiment 1, in the functional layer removing step 102, the processing feed rate is set to 100 mm/sec to 400 mm/sec, and the spot at the focal point 23 of the laser beam 21 is a circle with a diameter of 30 μm to 60 μm. In embodiment 2, the outer groove forming step 110 and the inner groove forming step 111 are combined to form the functional layer removing step 102.

In embodiment 2, in substrate processing step 103, as in embodiment 1, the laser processing device 20 performs ablation on the bottom surface of the first groove 15, as shown in FIG. 14, to form a second groove 16 narrower than the first groove 15 in the bottom surface of the first groove 15, as shown in FIG. 14. In embodiment 2, in substrate processing step 103, the laser processing device 20 opens the second groove 16 on the back surface 9 of the wafer 1, i.e., penetrates the second groove 16 through the wafer 1, thereby dividing the wafer 1 into individual device chips 10.

The wafer processing method according to embodiment 2, like embodiment 1, has the effect of suppressing peeling of the functional layer 6 by forming, in the affected area formation step 101, affected areas 13 that have lower thermal conductivity than the functional layer 6 and are less likely to peel off from the substrate 2 at both edges of the planned division line 4 inside the functional layer 6.

The present invention is not limited to the above-described embodiment. In other words, various modifications can be made without departing from the gist of the present invention. For example, in the substrate processing step 103 of the present invention, the processing may involve cutting the bottom surface of the first groove 15 with a cutting blade, plasma etching the bottom surface of the first groove 15, or irradiating the substrate 2 with a laser beam with a focal point aligned with the interior of the substrate 2 to form a modified layer inside the substrate, and then applying an external force to divide the substrate starting from the modified layer. Also, in the present invention, it is not necessary to divide the wafer 1 into individual device chips 10 in the substrate processing step 103.

REFERENCE SIGNS LIST 1 wafer 2 substrate 3 front surface 4 planned division line 5 device 6 functional layer 9 back surface 10 device chip 13 affected region 15 first processed groove 21 laser beam 101 affected region forming step 102 functional layer removing step 103 substrate processing step

Claims (4)

A wafer processing method for processing a wafer having a functional layer including a device stacked on a substrate along a planned dividing line, comprising:
a modified region forming step of irradiating a laser beam having a wavelength that is absorbed by the substrate and that is less absorbed by the functional layer than by the substrate along the intended dividing line under processing conditions that restrict continuous ablation processing of the functional layer, thereby forming two modified regions extending along the intended dividing line within the functional layer at a predetermined interval;
a functional layer removing step of irradiating a laser beam between the affected regions after the affected region forming step to form a first groove for removing the functional layer;
A wafer processing method comprising: a substrate processing step of processing the substrate along the first processing groove after the functional layer removal step is performed. The wafer processing method described in claim 1, characterized in that the functional layer is an oxide film. The wafer processing method described in claim 1, characterized in that the affected region forming step involves irradiating a laser beam with a wavelength in the ultraviolet range. The wafer processing method described in claim 1, characterized in that the output of the laser beam per spot irradiated in the affected area formation step is smaller than the output of the laser beam per spot irradiated in the functional layer removal step.