Wafer processing method

Abstract

To provide a wafer processing method by which a wafer having a passivation film stacked on a pattern layer can be processed with good quality.SOLUTION: A wafer processing method for processing a wafer 100 formed with a pattern layer 120 on a surface 111 of a substrate 110 and a passivation film 130 covering the pattern layer 120 along a scheduled dividing line 112, includes: a passivation film processing step of radiating a laser beam at a first output along the scheduled dividing line 112 to form a first processing groove 151 in the passivation film 130; a pattern layer processing step of radiating a laser beam 21 at a second output larger than the first output along the first processing groove 151 to form a second processing groove 152 in the pattern layer 120; and a substrate processing step of processing the substrate 110 along the second processing groove 152.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer in which a pattern layer is covered with a passivation film.

Background Art

[0002] A method of processing a passivation film and a pattern layer with a single laser is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the pattern layer becomes thick, it is necessary to form a processing groove with a laser beam having a larger output. When processing with the same output, problems such as peeling and brittleness of the passivation film occur.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a method for processing a wafer that can process a wafer in which a passivation film is laminated on a pattern layer with good quality.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, the present invention provides a wafer processing method for processing a wafer having a pattern layer and a passivation film covering the pattern layer formed on the surface of a substrate along a planned division line, comprising: a passivation film processing step of irradiating a laser beam with a first output along the planned division line to form a first processing groove in the passivation film; a pattern layer processing step of irradiating a laser beam with a second output greater than the first output along the first processing groove to form a second processing groove in the pattern layer; and a substrate processing step of processing the substrate along the second processing groove. The first-output laser beam irradiated in the passivation film processing step has a lower energy density per spot, a higher repetition frequency, and a faster feed rate of the laser beam's focal point relative to the wafer than the second-output laser beam irradiated in the pattern layer processing step. It is characterized by this.

[0007] The substrate processing step may involve dividing the substrate to produce multiple chips.

[0008] The passivation film may be made of polyimide.

[0009] The passivation film processing step may use a laser beam having a pulse width in the range of picoseconds or femtoseconds.

[0010] The first machining groove may be wider than the width of the second machining groove. [Effects of the Invention]

[0011] In this invention, the passivation film is processed with a first-output laser beam, and then the pattern layer is processed with a second-output laser beam that is greater than the first output. This suppresses thermal damage to the passivation film 130, thereby preventing peeling, deterioration, and damage, while enabling high-quality processing of the pattern layer. As a result, wafers in which the passivation film is laminated on the pattern layer can be processed with good quality. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart showing the processing procedure for the wafer processing method according to Embodiment 1. [Figure 2]FIG. 2 is a perspective view showing a wafer that is a processing target of the wafer processing method according to Embodiment 1. [Figure 3] FIG. 3 is a cross-sectional view of the wafer in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view for explaining the passivation film processing step in FIG. 1. [Figure 5] FIG. 5 is a cross-sectional view for explaining the pattern layer processing step in FIG. 1. [Figure 6] FIG. 6 is a cross-sectional view for explaining the substrate processing step in FIG. 1. [Figure 7] FIG. 7 is a cross-sectional view for explaining the passivation film processing step of the wafer processing method according to Embodiment 2. [Figure 8] FIG. 8 is a cross-sectional view for explaining the passivation film processing step of the wafer processing method according to Embodiment 2. [Figure 9] FIG. 9 is a cross-sectional view for explaining the passivation film processing step of the wafer processing method according to Embodiment 2. [Figure 10] FIG. 10 is a cross-sectional view for explaining the pattern layer processing step of the wafer processing method according to Embodiment 2. [Figure 11] FIG. 11 is a cross-sectional view for explaining the pattern layer processing step of the wafer processing method according to Embodiment 2. [Figure 12] FIG. 12 is a cross-sectional view for explaining the pattern layer processing step of the wafer processing method according to Embodiment 2. MODE FOR CARRYING OUT THE INVENTION

[0013] The mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention. <0000

[0014] [Embodiment 1] The wafer processing method according to Embodiment 1 of the present invention will be described based on the drawings. FIG. 1 is a flowchart showing the processing procedure of the wafer processing method according to Embodiment 1. The wafer processing method according to Embodiment 1 is a method for processing a wafer 100 as described later. As shown in FIG. 1, it includes a passivation film processing step 1001, a pattern layer processing step 1002, and a substrate processing step 1003.

[0015] FIG. 2 is a perspective view showing a wafer 100 which is a processing target of the wafer processing method according to Embodiment 1. FIG. 3 is a cross-sectional view of the wafer 100 in FIG. 2. As shown in FIGS. 2 and 3, the wafer 100 which is a processing target of the wafer processing method according to Embodiment 1 has a pattern layer 120 and a passivation film 130 covering the pattern layer 120 formed on the surface 111 of the substrate 110. The substrate 110 is, for example, a disk-shaped semiconductor wafer or an optical device wafer with silicon as the base material. The base material of the substrate 110 is not limited to this in the present invention, and may be sapphire, silicon carbide (SiC), gallium arsenide, etc. As shown in FIG. 2, the substrate 110 has a device region portion 113 of chip size formed in a region partitioned by a plurality of division planned lines 112 formed in a grid pattern on the flat surface 111.

[0016] The wafer 100 includes portions of each device region portion 113 of the substrate 110, portions of each pattern layer 120 formed on each device region portion 113, and portions of each passivation film 130, and a plurality of device chips (see FIG. 2) are respectively formed.

[0017] In Embodiment 1, the pattern layer 120 is a metal pattern layer for electronic circuits, electrodes, test element groups (TEGs), integrated circuits (ICs), etc. The pattern layer 120 has a thickness of 10 μm to 100 μm, and is sufficiently thicker than the passivation film 130, as shown in Figure 3. When the wafer 100 is divided into multiple device chips, the thickness of the pattern layer 120 may be about the same as or thicker than the substrate 110.

[0018] In Embodiment 1, the passivation film 130 is a polyimide film, but the present invention is not limited to this, and may also be an oxide film or a nitride film. The passivation film 130 has a thickness of 2 μm or more and 10 μm or less, and is sufficiently thinner than the pattern layer 120. The passivation film 130 is not a temporary protective film to be removed after the substrate processing step 1003, but is left on the upper surface of the multiple device chips manufactured by dividing the wafer 100 to protect the pattern layer 120 that constitutes the device chips and the device region portion 113 of the substrate 110. In other words, it is preferable that the passivation film 130 does not peel off even when the wafer 100 is divided into multiple device chips.

[0019] In Embodiment 1, as shown in Figure 2, a support member 141 is attached to the back surface 114 of the back surface 111 of the substrate 110, and an annular frame 142 is attached to the outer edge of the support member 141. However, the present invention is not limited to this. The support member 141 may be an adhesive tape having a base layer that is flexible and non-adhesive, and an adhesive layer laminated on the base layer that is flexible and adhesive, or a sheet made of a thermoplastic resin that does not have an adhesive layer. If the support member 141 is a thermoplastic resin sheet that does not have adhesive properties, polyolefin sheets, polyethylene sheets, polypropylene sheets, and polystyrene sheets are preferred, and it is attached to the frame 142 and wafer 100 by heat pressing. The support member 141 does not need to be in sheet shape from the beginning; powder or liquid may be supplied to the back surface 104 of the wafer 100 (the back surface 114 of the substrate 110), and then formed into a sheet that covers the back surface 104 of the wafer 100 by thermocompression bonding, pressing, or spin coating.

[0020] Figure 4 is a cross-sectional view illustrating the passivation film processing step 1001 of Figure 1. The passivation film processing step 1001 is a step in which a laser beam 11 is irradiated with a first output along the division line 112 to form a first processing groove 151 in the passivation film 130, as shown in Figure 4.

[0021] In the passivation film processing step 1001, as shown in Figure 4, the laser irradiator 10 irradiates the wafer 100 with a laser beam 11 of a wavelength absorbed by the passivation film 130 at a first output, toward the side of the wafer 100 on which the passivation film 130 is formed (the surface 101 of the wafer 100, the exposed surface 131 of the passivation film 130), while the wafer 100 is moved relative to the laser irradiator 10 along the division line 112 by a drive source (not shown), thereby laser processing (so-called ablation processing) the passivation film 130 along the division line 112 with the laser beam 11, removing the passivation film 130 along the division line 112 and forming a first processing groove 151 with a depth that penetrates the passivation film 130 and reaches the pattern layer 120.

[0022] The wafer processing method according to Embodiment 1 processes the passivation film 130 by irradiation with a laser beam 11, eliminating the need to process the passivation film 130 by lithography, thus reducing the cost associated with processing the passivation film 130.

[0023] Figure 5 is a cross-sectional view illustrating the pattern layer processing step 1002 of Figure 1. As shown in Figure 5, the pattern layer processing step 1002 is a step in which a laser beam 21 with a second output greater than the first output is irradiated along the first processing groove 151 formed in the passivation film processing step 1001 to form a second processing groove 152 in the pattern layer 120.

[0024] In the pattern layer processing step 1002, as shown in Figure 5, the laser irradiator 20 irradiates the pattern layer 120 with a laser beam 21 of a wavelength absorbed by the pattern layer 120 at a second output greater than the first output, toward the pattern layer 120 exposed on the bottom surface of the first processing groove 151 formed on the wafer 100. At the same time, the wafer 100 is moved relative to the laser irradiator 20 along the direction in which the first processing groove 151 extends by a drive source (not shown). This laser processes the pattern layer 120 along the direction in which the first processing groove 151 extends (so-called ablation processing) with the laser beam 21, removing the pattern layer 120 along the direction in which the first processing groove 151 extends, and forming a second processing groove 152 that penetrates the pattern layer 120 from the bottom surface of the first processing groove 151 to a depth that reaches the surface 111 of the substrate 110. Furthermore, the direction in which the first machining groove 151 extends is along the direction of the planned division line 112.

[0025] Here, the passivation film 130 processed in the passivation film processing step 1001 is a polyimide film, oxide film, or nitride film, and is thinner than the pattern layer 120. Therefore, if a laser beam with an average power capable of forming the second processing groove 152 on the pattern layer 120 is irradiated onto it, it is susceptible to thermal damage, peeling, deterioration, and damage. For this reason, it is necessary to process the pattern layer 120 by irradiating it with a laser beam with an average power lower than the average power suitable for forming the second processing groove 152 (dividing the pattern layer 120). On the other hand, the pattern layer 120 processed in the pattern layer processing step 1002 includes wiring structures including metal pattern layers such as electronic circuits, electrodes, inspection or evaluation elements, and integrated circuits. Since the second processing groove 152 cannot be formed by irradiating with a laser beam with an average output smaller than the average output suitable for forming the first processing groove 151 (dividing the passivation film 130) in the passivation film 130, it is necessary to process it by irradiating with a laser beam with an average output larger than the average output suitable for dividing the passivation film 130. For this reason, the wafer processing method according to Embodiment 1 comprises two steps: a passivation film processing step 1001 for processing the passivation film 130 and a pattern layer processing step 1002 for processing the pattern layer 120. By changing the laser beam irradiated in the two steps, it is possible to suppress thermal damage to the passivation film 130, thereby suppressing peeling, deterioration, and damage, while achieving good quality processing of the pattern layer 120.

[0026] Therefore, in the wafer processing method according to Embodiment 1, the first output, which is the average output of the laser beam 11 irradiated in the passivation film processing step 1001, is smaller than the second output, which is the average output of the laser beam 21 irradiated in the pattern layer processing step 1002. Alternatively, the energy density per spot of the laser beam 11 irradiated in the passivation film processing step 1001 is smaller than the energy density per spot of the laser beam 21 irradiated in the pattern layer processing step 1002. In Embodiment 1, since the passivation film 130 is a polyimide film that is sensitive to heat and may melt due to heat, the use of such a low-average-output laser beam 11 can suppress not only peeling, deterioration, and damage to the polyimide film but also melting, thus making the effect of suppressing thermal damage to the passivation film 130 more pronounced. Furthermore, even if the passivation film 130 is an oxide film or a nitride film, peeling, deterioration, and damage to the oxide film or nitride film can be suppressed. In Embodiment 1, since the pattern layer 120 is thicker, with a thickness of 10 μm to 100 μm, the effect of using a laser beam 21 with such a high average output becomes even more pronounced in enabling high-quality processing of the pattern layer 120. In Embodiment 1, the average output (first output) of the laser beam 11 is, for example, 1.1 W, and the average output (second output) of the laser beam 21 is, for example, 6.4 W.

[0027] The laser beam 11 is pulsed and preferably has a pulse width in the range of picoseconds or femtoseconds. Here, the pulse width in the range of picoseconds or femtoseconds is, in Embodiment 1, 10 -15 10 seconds or more -12 This refers to a pulse width of less than 10 seconds. The wafer processing method according to Embodiment 1 can further suppress thermal damage to the passivation film 130 in the passivation film processing step 1001 by setting the pulse width of the laser beam 11 to the range of picoseconds or femtoseconds. -15 For times less than a second, it is difficult with current technology, while for times less than a second, the pulse width of the laser beam 11 is 10 -12If the duration is longer than a second, there is a risk of significant thermal damage to the passivation film 130.

[0028] Furthermore, it is preferable that the laser beam 11 has a higher repetition frequency than the laser beam 21. Also, it is preferable that the feed rate of the focal point of the laser beam 11 on the wafer 100 is faster than that of the laser beam 21. In the wafer processing method according to Embodiment 1, by making the repetition frequency of the laser beam 11 higher than that of the laser beam 21 and the feed rate of the focal point of the laser beam 11 faster than that of the laser beam 21, it is possible to further suppress thermal damage to the passivation film 130 in the passivation film processing step 1001 while achieving good quality processing of the pattern layer 120. In Embodiment 1, the repetition frequency of the laser beam 11 is, for example, 3000 kHz, and the repetition frequency of the laser beam 21 is, for example, 800 kHz. Also, in Embodiment 1, the feed rate of the focal point of the laser beam 11 is, for example, 1000 mm / s, and the feed rate of the focal point of the laser beam 21 is, for example, 850 mm / s.

[0029] Furthermore, the width 161 of the first processing groove 151 formed in the passivation film processing step 1001 is wider than the width 162 of the second processing groove 152 formed in the pattern layer processing step 1002. Therefore, the wafer processing method according to Embodiment 1 can suppress the laser beam 21 irradiated to form the second processing groove 152 in the pattern layer processing step 1002 from irradiating the edge of the first processing groove 151 or the passivation film 130 by deviating from the first processing groove 151, thereby preventing the passivation film 130 from peeling off, deteriorating, or being damaged.

[0030] Figure 6 is a cross-sectional view illustrating the substrate processing step 1003 of Figure 1. As shown in Figure 6, the substrate processing step 1003 is a step in which the substrate 110 is processed along the second processing groove 152. The direction in which the second processing groove 152 extends is along the direction of the planned division line 112.

[0031] In the substrate processing step 1003, the substrate 110 is processed in various ways along the direction in which the second processing groove 152 extends, that is, along the planned division line 112, and the substrate 110 is further excavated downward in the thickness direction from the bottom surface of the second processing groove 152 to form a third processing groove 153 (see Figure 6). In the first embodiment, in the substrate processing step 1003, the bottom surface of the third processing groove 153 is further extended to the back surface 114 of the substrate 110 (back surface 104 of the wafer 100), penetrating the substrate 110, thereby dividing the substrate 110 along the planned division line 112, dividing the wafer 100, and manufacturing multiple device chips.

[0032] In the substrate processing step 1003, in Embodiment 1, a third processing groove 153 is formed with a width 163 that is narrower than the width 162 of the second processing groove 152. Therefore, the wafer processing method according to Embodiment 1 can suppress the processing of the passivation film 130 by accidentally processing the edge of the first processing groove 151 or deviating from the first processing groove 151 when forming the third processing groove 153 in the substrate processing step 1003, thereby preventing the passivation film 130 from peeling off, deteriorating or being damaged. It can also suppress the processing of the pattern layer 120 by accidentally processing the edge of the second processing groove 152 or deviating from the second processing groove 152, thereby preventing the pattern layer 120 from peeling off, deteriorating or being damaged.

[0033] In Embodiment 1, the substrate processing step 1003 can be carried out, for example, by the methods of the first, second, third, fourth, and fifth examples described below. However, the substrate processing step 1003 is not limited to these methods in the present invention, and may be carried out by combining parts of the methods of the first to fifth examples.

[0034] In the first example of the substrate processing step 1003, the step is performed by plasma etching. Specifically, the first example of the substrate processing step 1003 includes a side protective film deposition step in which the sides of the first processing groove 151, the second processing groove 152, and the third processing groove 153 are covered with a side protective film, and a deep cutting step in which the bottom surface of the second processing groove 152 or the bottom surface of the third processing groove 153 is further excavated downward in the thickness direction of the wafer 100 by plasma etching.

[0035] The side protection film deposition step involves supplying a predetermined plasma gas from the surface 101 side of the wafer 100 and depositing a side protection film with the supplied plasma gas. The deep cutting step involves, after depositing the side protection film in the side protection film deposition step, supplying a predetermined plasma gas different from that used in the side protection film deposition step from the surface 101 side of the wafer 100 and using the supplied plasma gas to remove the side protection film deposited on the bottom surface of the third processing groove 153, and then plasma etching the substrate 110 on the bottom surface of the third processing groove 153 to deep cut the third processing groove 153.

[0036] In the first example of the substrate processing step 1003, in Embodiment 1, a so-called Bosch process is performed, in which the side protective film deposition step and the deep etching step are repeated alternately in separate processes, thereby making the etching amount on the sides of the first processed groove 151, the second processed groove 152, and the third processed groove 153 sufficiently smaller than the etching amount on the bottom surface of the third processed groove 153, thereby forming a third processed groove 153 with a high aspect ratio. However, in the first example of the substrate processing step 1003, the present invention is not limited to this, and the side protective film deposition step and the plasma etching step may be performed simultaneously in parallel to form a third processed groove 153 with a high aspect ratio.

[0037] In the second example of the substrate processing step 1003, cutting is performed by cutting using a cutting blade. Specifically, in the second example of the substrate processing step 1003, a cutting blade thinner than 162 in width, which is mounted on the tip of a predetermined spindle and rotated around its axis along the Y-axis by the spindle, is moved along the Z-axis by a predetermined lifting unit to cut into the substrate 110 to a predetermined depth from the bottom of the second processing groove 152. Then, by using a predetermined drive source to feed the spindle (cutting blade) relative to the wafer 100 along the direction in which the second processing groove 152 extends, the cutting blade cuts the substrate 110 along the planned division line 112, forming a third processing groove 153 that penetrates the substrate 110 along the planned division line 112 and reaches the back surface 114 of the substrate 110, thereby dividing the substrate 110 along the planned division line 112.

[0038] In the third example of the substrate processing step 1003, the wafer 100 is processed by irradiating the substrate 110 with a laser beam of a wavelength that is transparent to the substrate 110. Specifically, in the third example of the substrate processing step 1003, a predetermined laser irradiator is used to irradiate the substrate 110, which is exposed at the bottom surface of the second processing groove 152 formed in the wafer 100, with a laser beam of a wavelength that is transparent to the substrate 110 of the wafer 100. At the same time, the wafer 100 is moved relative to the laser irradiator along the planned division line 112 by a drive source (not shown). This laser beam forms a modified layer and cracks extending from the modified layer toward the surface 111 and back surface 114 inside the substrate 110 along the planned division line 112. The modified layer or cracks are used as the third processing groove 153 to divide the substrate 110 along the planned division line 112. Here, the modified layer refers to a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding area. Examples include melted regions, cracked regions, dielectric breakdown regions, refractive index change regions, and regions where these regions are mixed.

[0039] In the fourth example of the substrate processing step 1003, in addition to irradiating with a laser beam similar to that in the third example, the process is further carried out by grinding the back surface 114 side of the substrate 110. Specifically, in the fourth example of the substrate processing step 1003, after irradiating with a laser beam similar to that in the third example to form a modified layer and cracks, a grinding wheel, which has grinding wheels arranged in a ring and mounted on the tip of a predetermined spindle and rotated around its axis along the Z-axis direction by the spindle, is moved along the Z-axis direction by a predetermined lifting unit to contact and press against the back surface 114 side of the substrate 110 of the wafer 100 positioned below. By grinding the substrate 110 to a predetermined thickness with the grinding wheels, the third processing groove 153 (crack) reaches the back surface 114 side, and the substrate 110 is divided along the planned division line 112.

[0040] In the fifth example of the substrate processing step 1003, the wafer 100 is processed by irradiating the substrate 110 with a laser beam of a wavelength that is absorbed by the substrate 110. Specifically, in the fifth example of the substrate processing step 1003, a predetermined laser irradiator is used to irradiate the substrate 110, which is exposed on the bottom surface of the second processing groove 152 formed in the wafer 100, with a laser beam of a wavelength that is absorbed by the substrate 110 of the wafer 100. At the same time, the wafer 100 is moved relative to the laser irradiator along the division line 112 by a drive source (not shown). This laser beam is used to laser process (so-called ablation) the substrate 110 along the division line 112, forming a third processing groove 153 that penetrates the substrate 110 along the division line 112 and reaches the back surface 114 of the substrate 110, thereby dividing the substrate 110 along the division line 112.

[0041] The wafer processing method according to Embodiment 1, having the configuration described above, processes the passivation film 130 with a first-output laser beam 11, and then processes the pattern layer 120 with a second-output laser beam 21 that is greater than the first output. This suppresses thermal damage to the passivation film 130, thereby preventing peeling, deterioration, and damage, while enabling high-quality processing of the pattern layer 120. As a result, the wafer 100 in which the passivation film 130 is laminated on the pattern layer 120 can be processed with good quality.

[0042] Furthermore, in the wafer processing method according to Embodiment 1, since the substrate processing step 1003 forms multiple device chips by dividing the substrate 110, even when the wafer 100 is divided into multiple device chips, the passivation film 130 can be suitably left to protect the pattern layer 120 that constitutes the device chip and the device region portion 113 of the substrate 110.

[0043] Furthermore, in the wafer processing method according to Embodiment 1, since the passivation film 130 is polyimide, the use of a laser beam 11 with a low average output suppresses not only peeling, deterioration, and damage to the polyimide film, which is sensitive to heat and prone to melting due to heat, but also melting. Therefore, the effect of suppressing thermal damage to the passivation film 130 becomes even more pronounced.

[0044] Furthermore, in the wafer processing method according to Embodiment 1, since the passivation film processing step 1001 uses a laser beam 11 having a pulse width in the range of picoseconds or femtoseconds, thermal damage to the passivation film 130 in the passivation film processing step 1001 can be further suppressed.

[0045] Furthermore, in the wafer processing method according to Embodiment 1, since the width 161 of the first processing groove 151 is wider than the width 162 of the second processing groove 152, it is possible to suppress the laser beam 21 irradiated in the pattern layer processing step 1002 from irradiating the edge of the first processing groove 151 or diverting from the first processing groove 151 to irradiate the passivation film 130, thereby preventing the passivation film 130 from peeling off, deteriorating, or being damaged.

[0046] [Embodiment 2] A wafer processing method according to Embodiment 2 of the present invention will be described based on the drawings. Figures 7, 8, and 9 are cross-sectional views illustrating the passivation film processing step 1001 of the wafer processing method according to Embodiment 2. Figures 10, 11, and 12 are cross-sectional views illustrating the pattern layer processing step 1002 of the wafer processing method according to Embodiment 2. Figures 7 to 12 use the same reference numerals as Embodiment 1, and their descriptions are omitted.

[0047] The wafer processing method according to Embodiment 2 is a modified version of Embodiment 1, in which the passivation film processing step 1001 and the pattern layer processing step 1002 are modified.

[0048] The passivation film processing step 1001 in Embodiment 2 is modified in which, as shown in Figure 7, an upper protective film 170 is formed on the surface 101 of the wafer 100 (exposed surface 131 of the passivation film 130) before irradiation with the laser beam 11, and as shown in Figure 8, the upper protective film 170 and the passivation film 130 are laser processed along the planned division line 112 with the laser beam 11 to form a first processing groove 151, and after the formation of the first processing groove 151, the upper protective film 170 is removed as shown in Figure 9.

[0049] In the passivation film processing step 1001 of Embodiment 2, for example, before irradiation with the laser beam 11, the wafer 100 is held with its surface 101 facing upward using a holding table (not shown), and while rotating the wafer 100 on the holding table by rotating the holding table around an axis parallel to the vertical direction, a liquid resin is discharged from a resin supply nozzle (not shown) toward the surface 101 of the wafer 100 on the holding table, thereby coating the passivation film 130 of the wafer 100 with liquid resin, and the coated liquid resin is dried to form an upper protective film 170 that protects the upper surface of the passivation film 130 of the wafer 100.

[0050] The liquid resin applied in the passivation film processing step 1001 in Embodiment 2 is a water-soluble resin, such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP). The upper protective film 170 formed in the passivation film processing step 1001 in Embodiment 2 prevents debris (processing scraps) from the passivation film 130, which is generated by laser processing by irradiation with the laser beam 11, from adhering to the upper surface of the passivation film 130. In the passivation film processing step 1001 in Embodiment 2, a water-soluble resin film is formed as the upper protective film 170.

[0051] In the passivation film processing step 1001 of Embodiment 2, for example, after the formation of the first processing groove 151, the wafer 100 is held by a holding table (not shown) with the surface 101 side (the side on which the upper protective film 170 is formed) facing upward, and the wafer 100 on the holding table is rotated by rotating the holding table around an axis parallel to the vertical direction, while a cleaning liquid is discharged from a cleaning liquid supply nozzle (not shown) toward the upper protective film 170 on the surface 101 side of the wafer 100 on the holding table, thereby removing the upper protective film 170. The cleaning liquid is, for example, pure water or a two-fluid mixture of pure water and compressed air, and dissolves the upper protective film 170, which is a water-soluble resin film.

[0052] The pattern layer processing step 1002 in Embodiment 2 is modified in which, before irradiation with the laser beam 21, an upper protective film 170 similar to that in the passivation film processing step 1001 in Embodiment 2 is formed on the surface 101 of the wafer 100 (exposed surface 131 of the passivation film 130) as shown in Figure 10, and then, as shown in Figure 11, the laser beam 21 is irradiated to laser process the upper protective film 170 and the pattern layer 120 along the planned division line 112 to form a second processing groove 152, and after the formation of the second processing groove 152, the upper protective film 170 is removed as shown in Figure 12.

[0053] The wafer processing method according to Embodiment 2 is modified in which, in Embodiment 1, the top protective film 170 is formed before irradiation with laser beams 11 and 21 in the passivation film processing step 1001 and the pattern layer processing step 1002, respectively, and the top protective film 170 is removed after irradiation with laser beams 11 and 21 (after the formation of the first processing groove 151 and the second processing groove 152). As such, it achieves the same effects as Embodiment 1.

[0054] Furthermore, the wafer processing method according to Embodiment 2 is a preferred configuration in which the top protective film 170 further suppresses peeling, deterioration, and damage to the passivation film 130, and reduces the risk of debris from the passivation film 130 and pattern layer 120 adhering to the exposed surface 131. However, the present invention is not limited thereto, and the wafer processing method according to Embodiment 1 may be carried out by omitting the formation of the top protective film 170 if there is little debris from the passivation film 130 and pattern layer 120 generated in the passivation film processing step 1001 and the pattern layer processing step 1002, respectively, or if the adhesion of debris to the exposed surface 131 of the passivation film 130 does not affect the quality of the device chip. In other words, the formation of the top protective film 170 is not essential to the present invention.

[0055] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. [Explanation of Symbols]

[0056] 11,21 Laser beam 100 wafers 110 circuit boards 101,111 surface 112 planned division lines 120 pattern layers 130 Passivation membrane 151 First machined groove 152 Second machining groove Width 161, 162, 163

Claims

1. A wafer processing method comprising processing a wafer having a pattern layer and a passivation film covering the pattern layer formed on the surface of a substrate along a planned division line, A passivation film processing step involves irradiating the passivation film with a laser beam at a first output along the planned division line to form a first processing groove in the passivation film, A pattern layer processing step involves irradiating a laser beam with a second output greater than the first output along the first processing groove to form a second processing groove in the pattern layer, The process includes a substrate processing step of processing the substrate along the second processing groove, A wafer processing method characterized in that the first output laser beam irradiated in the passivation film processing step has a lower energy density per spot of the laser beam, a higher repetition frequency, and a faster feed rate of the focal point of the laser beam relative to the wafer than the second output laser beam irradiated in the pattern layer processing step.

2. The wafer processing method according to claim 1, characterized in that the substrate processing step involves manufacturing a plurality of chips by dividing the substrate.

3. The wafer processing method according to claim 1, characterized in that the passivation film is polyimide.

4. The wafer processing method according to claim 1, characterized in that the passivation film processing step uses a laser beam having a pulse width in the range of picoseconds or femtoseconds.

5. The wafer processing method according to claim 1, characterized in that the first processing groove is wider than the width of the second processing groove.

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