Protective film agent for laser processing and processing method for workpiece

Abstract

To provide a protective film agent for laser processing, capable of forming a suitable protective film on the surface of a workpiece to be processed using a laser beam with a wavelength of 532 nm.SOLUTION: A protective film agent for laser processing consists of a solution containing a water-soluble resin, an organic solvent, and a light absorbing agent, and the absorbance of the solution at a wavelength of 532 nm (in a 200-fold diluted solution converted absorbance) is 0.05 or more per 1 cm of optical path length, or consists of a solution containing a water-soluble resin, an organic solvent, and a polyhydroxyanthraquinone derivative.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a protective film agent for laser processing for forming a protective film on the surface of a workpiece to be laser processed, and a method for processing a workpiece in which laser processing is performed in a state in which a protective film is formed on the surface of the workpiece using this protective film agent for laser processing. [Background technology]

[0002] Device chips such as ICs and LSIs are essential components in various electronic devices such as mobile phones and personal computers. These chips are manufactured by dividing a workpiece such as a wafer (e.g., a silicon wafer) on which many devices are formed into regions containing individual devices.

[0003] An example of a device used to divide a workpiece is a laser processing device, which processes the workpiece by irradiating it with a laser beam having a wavelength of, for example, 355 nm, causing ablation (laser ablation).

[0004] However, when laser ablation occurs in a workpiece, molten material (debris) from the workpiece (e.g., silicon) may scatter and adhere to the workpiece's surface, which may result in a reduction in the quality of chips obtained by dividing the workpiece.

[0005] In view of this, it has been proposed to form a protective film by applying a protective film agent for laser processing, which consists of a solution containing a water-soluble resin, an organic solvent, and an ultraviolet absorber, to the surface of the workpiece before irradiating the workpiece with a laser beam, and then drying this solution (see, for example, Patent Document 1).

[0006] This prevents debris from adhering to areas of the workpiece surface that are not irradiated with the laser beam. Note that because the protective film contains an ultraviolet absorber, the areas of the protective film that are irradiated with the laser beam are removed by laser ablation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-140311 Summary of the Invention [Problem to be solved by the invention]

[0008] A laser beam with a wavelength of 355 nm is generally the third harmonic (triple wave) of a laser beam (fundamental wave) generated using Nd:YAG or the like as a laser medium. Specifically, a laser beam with a wavelength of 355 nm is obtained by passing a laser beam with a wavelength of 1064 nm through two wavelength conversion crystals such as an LBO crystal, a BBO crystal, and a KTP crystal.

[0009] However, when a laser beam passes through two wavelength conversion crystals in this way, its power (output) is greatly reduced. Therefore, laser processing equipment has been developed that can irradiate the workpiece with a laser beam with a wavelength of 532 nm, which is the second harmonic (double wave) obtained by passing this fundamental wave laser beam through a single wavelength conversion crystal.

[0010] A 532 nm wavelength laser beam passes through fewer wavelength conversion crystals than a 355 nm wavelength laser beam, and has a higher conversion efficiency from a 1064 nm wavelength laser beam. Therefore, it is easier to ensure high output with a 532 nm wavelength laser beam. Therefore, when using a laser beam to cut a workpiece (laser full cut processing), it is preferable to use a 532 nm wavelength laser beam.

[0011] Specifically, when a workpiece is processed (laser processed) using a laser processing device that irradiates a laser beam with a wavelength of 532 nm, chip productivity can be improved. However, a protective film agent for laser processing that can form a suitable protective film on the processing surface of a workpiece processed using a laser beam with a wavelength of 532 nm has not yet been developed.

[0012] Specifically, when a workpiece having a protective film formed on its surface using an existing protective film agent for laser processing is irradiated with a laser beam having a wavelength of 532 nm, the laser beam passes through the protective film without being absorbed by it. In this case, the heat generated by the laser processing increases the temperature at the interface between the protective film and the workpiece. As a result, there are problems such as peeling of the protective film from the processed surface and surface burns on the processed surface.

[0013] In view of this, the object of the present invention is to provide a protective film agent for laser processing that can form a suitable protective film on the processing surface of a workpiece that is processed using a laser beam with a wavelength of 532 nm, and a processing method for a workpiece that performs laser processing with a protective film formed on the processing surface using this protective film agent for laser processing. [Means for solving the problem]

[0014] According to one aspect of the present invention, there is provided a protective film agent for laser processing, which comprises a solution containing a water-soluble resin, an organic solvent, and a light absorber, wherein the absorbance of the solution at a wavelength of 532 nm (absorbance converted into a 200-fold diluted solution) is 0.05 or more per 1 cm of optical path length. The pH of the solution is 3 or more and less than 5. A protective film agent for laser processing is provided. Furthermore, in the protective film agent for laser processing according to one aspect of the present invention, the light absorber is preferably a polyhydroxyanthraquinone derivative.

[0015] difference Furthermore, one aspect of the present invention Face In the protective film agent for laser processing, the polyhydroxyanthraquinone derivative is preferably carminic acid.

[0016] The present invention AnotherAccording to the aspect, the ink composition is made of a solution containing a water-soluble resin, an organic solvent, and a polyhydroxyanthraquinone derivative, the absorbance of the solution at a wavelength of 532 nm (converted to an absorbance of a 200-fold diluted solution) is 0.05 or more per 1 cm of optical path length; The polyhydroxyanthraquinone derivative is carminic acid, and a protective film agent for laser processing is provided. 。

[0018] In addition, in the protective film agent for laser processing of the present invention, the pH of the solution is 3 or more. 4 It is preferable that:

[0019] According to yet another aspect of the present invention, there is provided a method for processing a workpiece, comprising: a protective film forming step of applying the above-mentioned protective film agent for laser processing to the surface of the workpiece to be processed to form a protective film that covers the surface of the workpiece; and a processing step of irradiating the workpiece with a laser beam having a wavelength that is absorbed by the workpiece and the protective film through the protective film to process the workpiece. [Effects of the Invention]

[0020] By using the protective film agent for laser processing of the present invention, a protective film suitable for use on the surface of a workpiece to be processed using a laser beam with a wavelength of 532 nm can be formed. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1(A) is a perspective view that schematically shows a workpiece, and FIG. 1(B) is a cross-sectional view that schematically shows a part of the workpiece. [Figure 2] FIG. 2 is a perspective view schematically showing a frame unit including a workpiece. [Figure 3] FIG. 3(A) is a perspective view that schematically shows the protective film forming step, and FIG. 3(B) is a cross-sectional view that schematically shows a part of the workpiece on which the protective film has been formed. [Figure 4] FIG. 4 is a perspective view schematically showing the processing steps. [Figure 5]Figure 5(A) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 1 after laser processing has been performed on the workpiece, Figure 5(B) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 2 after laser processing has been performed on the workpiece, Figure 5(C) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 3 after laser processing has been performed on the workpiece, Figure 5(D) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Comparative Example 1 after laser processing has been performed on the workpiece, Figure 5(E) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Comparative Example 2 after laser processing has been performed on the workpiece, and Figure 5(F) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Comparative Example 3 after laser processing has been performed on the workpiece. [Figure 6] FIG. 6(A) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 1, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.05 per 1 cm of optical path length. FIG. 6(B) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 1, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.15 per 1 cm of optical path length. FIG. 6(C) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 1, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.34 per 1 cm of optical path length. Figure 6(D) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 1 after laser processing has been performed, and Figure 6(E) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 1, which has been prepared so that the absorbance (absorbance converted to a 200-fold diluted solution) is 0.97 per cm of optical path length, after laser processing has been performed. [Figure 7]7(A) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 2, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.05 per 1 cm of optical path length. FIG. 7(B) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 2, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.15 per 1 cm of optical path length. FIG. 7(C) shows an image of a workpiece after laser processing on which a protective film has been formed using the protective film agent of Example 2, which has been prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.34 per 1 cm of optical path length. Figure 7(D) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 2 after laser processing has been performed, and Figure 7(E) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 2, which has been prepared so that the absorbance (absorbance converted to a 200-fold diluted solution) is 0.97 per cm of optical path length, after laser processing has been performed. [Figure 8]FIG. 8(A) shows an image of a workpiece after laser processing on which a protective film was formed using the protective film agent of Example 3, which was prepared so that the absorbance (converted to a 200-fold diluted solution) per 1 cm of optical path length was 0.05. FIG. 8(B) shows an image of a workpiece after laser processing on which a protective film was formed using the protective film agent of Example 3, which was prepared so that the absorbance (converted to a 200-fold diluted solution) per 1 cm of optical path length was 0.15. FIG. 8(C) shows an image of a workpiece after laser processing on which a protective film was formed using the protective film agent of Example 3, which was prepared so that the absorbance (converted to a 200-fold diluted solution) per 1 cm of optical path length was 0.34. Figure 8(D) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 3 after laser processing has been performed, and Figure 8(E) shows an image of a workpiece on which a protective film has been formed using the protective film agent of Example 3, which has been prepared so that the absorbance (absorbance converted to a 200-fold diluted solution) is 0.97 per cm of optical path length, after laser processing has been performed. DETAILED DESCRIPTION OF THE INVENTION

[0022] A protective film agent for laser processing according to one embodiment of the present invention (hereinafter simply referred to as "protective film agent") comprises a solution containing a water-soluble resin, an organic solvent, and a light absorber. The water-soluble resin is the main component of the protective film formed on the processing surface of the workpiece using the protective film agent. The organic solvent also reduces the surface tension of the protective film agent, reducing coating unevenness when the protective film agent is applied (e.g., spin-coated) to the workpiece. The organic solvent also improves the solubility of the light absorber in the protective film agent solution. The light absorber also absorbs a laser beam with a wavelength of 532 nm, causing laser ablation in the protective film.

[0023] Examples of the water-soluble resin contained in the protective film agent include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol, polyethylene oxide, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyacrylic acid, poly-N-vinylacetamide, polystyrene sulfonic acid, special nylon, phenolic resin, methylolmelamine resin, polyglycerin, and graft polymers thereof (e.g., polyvinyl alcohol grafted with polyvinylpyrrolidone). The protective film agent may also contain two or more of these water-soluble resins.

[0024] The protective film agent may also contain a water-soluble resin whose properties change in response to an external stimulus (e.g., whose viscosity changes depending on the temperature). For example, the protective film agent may contain a water-soluble resin whose viscosity increases when the temperature is high and decreases when the temperature is low. When such a water-soluble resin is contained in the protective film agent, the protective film containing the water-soluble resin can be introduced into grooves formed by irradiating the workpiece with a laser beam.

[0025] Specifically, a protective film containing a water-soluble resin is first formed on the workpiece surface at a high temperature, and then a laser beam is irradiated onto the protective film and the workpiece to form grooves on the workpiece surface. The temperature is then lowered to reduce the viscosity of the protective film, i.e., to give the protective film fluidity, allowing the protective film present around the groove to flow into the groove.

[0026] Commercially available polyvinylpyrrolidone (PVP) comes in several varieties, including K-17, K-25, K-30, K-40, K-50, K-60, K-80, K-85, K-90, and K-120. These products are classified according to their K value, which is calculated by applying the relative viscosity (25°C) measured with a capillary viscometer to the Fikentscher viscosity formula. For example, powder products with a K value of around 90 are labeled "PVP K-90."

[0027] There are also several types of powdered polyvinyl alcohol (PVA) products available commercially. These powdered products are classified according to their degree of polymerization and degree of saponification. PVA with a degree of saponification of 98.0 mol% or more is also referred to as a fully saponified product. PVA with a degree of saponification of 98.0 mol% or less but 90.0 mol% or more is also referred to as an intermediate saponified product. PVA with a degree of saponification of 90.0 mol% or less but 78.5 mol% or more is also referred to as a partially saponified product.

[0028] As the degree of polymerization of this PVA increases, the viscosity of the solution containing this PVA also increases. Therefore, when the protective film agent is a solution containing PVA, the degree of polymerization of this PVA is preferably 200 to 2000, and more preferably 300 to 500. This allows the protective film agent to be smoothly delivered within the device for supplying the protective film agent to the workpiece, and makes it easy to apply the protective film agent to the workpiece surface by spin coating or the like, thereby covering the entire area with a protective film.

[0029] Furthermore, when the protective film agent is a solution containing PVA, the PVA is preferably partially saponified, and more preferably has a degree of saponification of 82 mol% or less, which makes the protective film formed using the protective film agent more soluble in water and makes it easier to wash the protective film off the workpiece processed using a laser beam.

[0030] Examples of organic solvents contained in the protective film agent include methyl alcohol, ethyl alcohol, isopropyl alcohol, esters, alkylene glycol monoalkyl ethers, alkylene glycols, and alkylene glycol monoalkyl ether acetates. As the alkylene glycol monoalkyl ether, propylene glycol monomethyl ether (PGME) is preferred. The protective film agent may contain two or more of these organic solvents.

[0031] In addition, taking into consideration its safety and the resistance of the adhesive layer of the dicing tape attached to the workpiece, the weight of the organic solvent contained in the protective film agent is preferably 20 wt% or less of the total weight of the protective film agent, and more preferably 15 wt% or less.

[0032] For example, by incorporating PGME into a protective film agent, the surface tension of the protective film agent can be reduced, making it easier to apply the protective film agent to the processing surface of a workpiece by spin coating or other methods, thereby covering the entire area with a protective film.

[0033] When applying the protective film agent to the processing surface of a workpiece by spin coating, for example, the workpiece with the protective film agent supplied to its processing surface may be rotated at a rotational speed of 1500 rpm to 3000 rpm for 30 seconds to 180 seconds. Alternatively, the workpiece may be rotated at a low rotational speed of 1000 rpm or less to spread the protective film agent over the entire processing surface, and then rotated at a rotational speed of 1500 rpm to 3000 rpm to coat the entire processing surface of the workpiece with a protective film.

[0034] The light absorber contained in the protective film agent is, for example, an anthocyanin derivative, a phthalocyanine derivative, a flavonoid derivative, a quinacridone derivative, an azobenzene derivative, a perylene derivative, a diketopyrrole derivative, an indigo derivative, or a polyhydroxyanthraquinone derivative. In particular, the light absorber is preferably a polyhydroxyanthraquinone derivative.

[0035] Examples of polyhydroxyanthraquinone derivatives include compounds represented by the following structural formulas (alizarin, quinizarin, anthrarufin, chrysazin, anthrafravic acid, aloe emodin, 1,5-diamino-4,8-dihydroxyanthraquinone, 4,5-dihydroxyanthraquinone-2-carboxylic acid, purpurin, emodin, mitoxantrone, doxorubicin, daunorubicin, and carminic acid (CA)).

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] In particular, carminic acid (CA) is preferred as the light absorber contained in the protective film agent for the following reasons. First, CA has high absorbance for light with a wavelength of 532 nm. Therefore, when processing a workpiece (laser processing) with a laser beam with a wavelength of 532 nm through a protective film formed using the protective film agent, the protective film containing CA as a light absorber is easily removed by laser ablation. As a result, in this laser processing, problems with laser processing due to the protective film remaining do not occur.

[0041] In addition, CA has high solubility in water. Therefore, the CA contained in this protective film can be easily washed away after laser processing. In addition, CA has high fluorescence intensity. Therefore, after a protective film is formed on the processing surface of a workpiece, it can be easily confirmed whether the protective film covers the entire processing surface by irradiating the protective film with excitation light and detecting the fluorescence generated.

[0042] CA also has high light resistance and heat resistance. Therefore, even if a protective film agent containing CA as a light absorber is stored for a long period of time, the molecular structure of CA is unlikely to change. CA is also used as a coloring agent for processed foods, and is easily available.

[0043] The protective film agent further contains water, preferably pure water, and may also contain additives for improving various properties.

[0044] Examples of additives contained in the protective film agent include ascorbic acid (AA), trimethylol propane (TMP), triethanol amine (TEA), methyl p-hydroxy benzoate (MPB), etc. The protective film agent may contain two or more of these additives.

[0045] Forming a protective film using a protective film agent containing ascorbic acid (AA) can improve the color stability of the protective film. Furthermore, trimethylolpropane (TMP) has high solubility in water. Therefore, forming a protective film using a protective film agent containing TMP allows the TMP contained in the protective film to be easily washed away after laser processing. Furthermore, when the protective film contains TMP, the thickness of the protective film can be increased and carbonization of the protective film can be suppressed when laser ablation occurs in the protective film.

[0046] Furthermore, adding triethanolamine (TEA) to the protective film agent can prevent the protective film agent from deteriorating during storage. Specifically, the protective film agent may undergo ion exchange treatment to remove metal impurities such as sodium (Na) and potassium (K). This ion exchange treatment may lower the pH of the protective film agent (e.g., pH less than 3.0). In this case, if the protective film agent is stored at a low storage temperature for a long period of time (e.g., at 10°C for one month), it may become gelatinous.

[0047] In response to this, adding TEA to the protective film agent after ion exchange treatment can shift the pH toward neutral. This can prevent the protective film agent from gelling at low storage temperatures. Furthermore, if the pH of the protective film agent is shifted toward neutral (e.g., pH exceeds 5.0) by adding a pH adjuster such as TEA, there is a risk of bacteria (general bacteria, heterotrophic bacteria, fungi, etc.) growing in the protective film agent during long-term storage. The growth of such bacteria can be inhibited by adding methyl p-hydroxybenzoate (MPB) or the like to the protective film agent.

[0048] However, in order to reduce the manufacturing cost of the protective film agent and improve its productivity, it is preferable that the protective film agent contain fewer additives. In view of these points, the protective film agent is preferably prepared so that its pH is between 3 and 5, and more preferably between 3 and 4. [Example]

[0049] Examples of the present invention will be described below. First, protective film agents of Examples 1 to 3 containing various materials shown in the table below were prepared.

[0050] [Table 1]

[0051] Specifically, we prepared two solutions: a first solution in which a powdered water-soluble resin (polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)) was dissolved in water, and a second solution in which a powdered light absorber (carminic acid (CA)) and an additive (methyl p-hydroxybenzoate (MPB)) were dissolved in an organic solvent (propylene glycol monomethyl ether (PGME)). The PVA used here had a degree of polymerization of 300 and a degree of saponification of 78.5 mol% to 81.5%. The PVP used had a K value of approximately 90.

[0052] Next, the second solution was subjected to ion exchange treatment and filtration, and then an additive (triethanolamine (TEA)) was added to obtain a third solution. In this way, the protective film agents of Examples 1 to 3 were obtained.

[0053] Additionally, protective film agents of Comparative Examples 1 to 3 containing the various materials shown in the table below were prepared. Briefly, the protective film agents of Comparative Examples 1 to 3 differ from the protective film agents of Examples 1 to 3 in that they do not contain CA as a light absorber but contain ferulic acid (FA), an ultraviolet absorber. FA is a compound commonly used as a light absorber contained in a protective film formed on the processing surface of a workpiece processed using a laser beam with a wavelength of 355 nm.

[0054] [Table 2]

[0055] Specifically, a fourth solution was prepared by dissolving a powdered water-soluble resin (PVA or PVP) and an additive (trimethylolpropane (TMP) and / or ascorbic acid (AA)) in water, and a fifth solution was prepared by dissolving a powdered light absorber (FA) in an organic solvent (PGME). The PVA used had a degree of polymerization of 300 and a degree of saponification of 78.5 mol% to 81.5%. The PVP used had a K value of approximately 90.

[0056] Next, the fifth solution was subjected to ion exchange treatment and filtration to reduce metal impurities (particularly sodium) contained in the fifth solution. In this way, the protective film agents of Comparative Examples 1 to 3 were obtained.

[0057] The viscosity at 25°C of each of the protective film agents of Examples 1 to 3 and Comparative Examples 1 to 3 obtained in this manner and the absorbance at a wavelength of 532 nm of the solutions that constituted each of these protective film agents (absorbance converted into a 200-fold diluted solution) were as shown in the table below.

[0058] [Table 3]

[0059] The absorbance was evaluated by diluting each protective film agent 200 times with pure water, and measuring the absorption spectrum of the diluted solution sealed in a quartz prismatic cell with an optical path length of 1 cm.

[0060] Next, a protective film forming step was carried out in which each of the protective film agents of Examples 1 to 3 and Comparative Examples 1 to 3 was applied to the workpiece surface to form a protective film that covers the workpiece surface. First, the workpiece on which a protective film is formed on the workpiece surface will be described below.

[0061] Fig. 1(A) is a perspective view showing a workpiece having a protective film formed on its surface, and Fig. 1(B) is a cross-sectional view showing a part of the workpiece. The workpiece 11 shown in Fig. 1(A) and Fig. 1(B) is a disk-shaped wafer having an orientation flat formed on its outer edge to indicate the crystal orientation.

[0062] The workpiece 11 has a substrate 13 made of silicon (Si), and an impurity region doped with impurities is provided on a portion of the surface (upper surface) of the substrate 13. A functional layer 15 including a plurality of insulating films and a plurality of conductive films is laminated on the surface of the substrate 13. The workpiece 11 is divided into a plurality of regions by a plurality of streets 17 set in a lattice pattern.

[0063] A device (IC, etc.) 19 is formed by a part of the substrate 13 (impurity region and intrinsic semiconductor region where no impurities are present) and a part of the functional layer 15 (insulating film and conductive film) included in each of the multiple regions. The functional layer 15 in the region where the device 19 is provided is slightly thicker than the functional layer 15 of the multiple streets 17. In other words, the device 19 is a convex portion that protrudes slightly above the multiple streets 17.

[0064] Next, a frame unit including the workpiece 11 will be described. Fig. 2 is a perspective view showing a frame unit including the workpiece 11. The frame unit 21 shown in Fig. 2 has an annular frame 23 made of a metal material. The annular frame 23 has an opening with a diameter larger than that of the workpiece 11.

[0065] Additionally, the outer peripheral region of a disk-shaped tape 25 is attached to the annular frame 23 so as to close the opening, and the substrate 13 side of the workpiece 11 is attached to the central region of the tape 25. In this way, the workpiece 11 is integrated with the annular frame 23 via the tape 25.

[0066] Next, the protective film forming step will be described. Fig. 3(A) is a perspective view that schematically shows the protective film forming step. Note that the annular frame 23 and tape 25 of the frame unit 21 are omitted in Fig. 3(A). In this protective film forming step, a spin coater 30 shown in Fig. 3(A) was used.

[0067] The spin coater 30 has a chuck table 32 that holds the workpiece 11. The chuck table 32 is connected to a rotary drive source (not shown) such as a motor, and rotates around a rotation axis that is a straight line that is approximately parallel to the vertical direction.

[0068] A disk-shaped porous plate (not shown) is provided on the upper surface of the chuck table 32. This porous plate is made of a porous material and is connected to a suction source (not shown) such as an ejector. When this suction source is activated, the workpiece 11 is sucked and held on the surface of the porous plate.

[0069] A nozzle 34 is disposed above the chuck table 32. The nozzle 34 supplies a liquid protective film agent 27 toward the vicinity of the center of the upper surface of the porous plate. The nozzle 34 is connected to a supply source (not shown) of the protective film agent 27 via a flow path (not shown).

[0070] In the protective film forming process, first, the workpiece 11 was placed on the chuck table 32 so that the substrate 13 side of the workpiece 11 faced the porous plate of the chuck table 32 via the tape 25. Next, the suction source was activated to suck and hold the substrate 13 side of the workpiece 11 on the chuck table 32.

[0071] Next, a predetermined amount of liquid protective film agent 27 was supplied from the nozzle 34 to the functional layer 15 side of the workpiece 11. Next, the rotary drive source was operated to rotate the chuck table 32. The rotation speed of the chuck table at this time was 2000 rpm, and the rotation time was 60 seconds.

[0072] That is, the protective film agent 27 was applied by spin coating to the functional layer 15 side of the workpiece 11. Next, the supply of the protective film agent 27 from the nozzle 34 was stopped, and the protective film agent 27 was dried. As a result, a protective film 29 was formed that covered the functional layer 15 side of the workpiece 11.

[0073] 3(B) is a cross-sectional view showing a schematic view of a portion of the workpiece 11 on which the protective film 29 is formed. The protective film 29 includes regions whose thickness varies depending on the unevenness formed by the device 19 slightly protruding above the multiple streets 17, and is formed so that the upper surface thereof is flat.

[0074] Furthermore, the film thickness (film thickness at the portion overlapping with the plurality of streets 17) of the protective film 29 formed using each of the protective film agents of Examples 1 to 3 and Comparative Examples 1 to 3 was as shown in the table below.

[0075] [Table 4]

[0076] Next, a laser beam having a wavelength of 532 nm was irradiated onto the workpiece 11 through a protective film 29 formed on the surface (the surface to be processed) of the workpiece 11 facing the functional layer 15, thereby performing a processing step of processing the workpiece 11. Fig. 4 is a perspective view showing a schematic view of the processing step. Note that the annular frame 23 and tape 25 of the frame unit 21 are omitted from Fig. 4.

[0077] 4 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction perpendicular to the X-axis and Y-axis directions (vertical direction). In this processing step, a laser processing device 40 shown in FIG. 4 was used.

[0078] The laser processing device 40 has a chuck table 42 that holds the substrate 13 side of the workpiece 11 by suction. This chuck table 42 has a rotation drive source, a porous plate, a suction source, etc., similar to those of the chuck table 32. Note that a detailed description of the components of the chuck table 42 will be omitted.

[0079] In addition, below the chuck table 42, there are provided an X-axis movement mechanism (not shown) that moves the chuck table 42 along the X-axis direction, and a Y-axis movement mechanism (not shown) that moves the chuck table 42 along the Y-axis direction.

[0080] A laser beam irradiation unit 50 that irradiates a pulsed laser beam is provided above the porous plate (not shown) of the chuck table 42. The laser beam irradiation unit 50 irradiates the chuck table 42 with a laser beam having a wavelength of 532 nm from its head 52.

[0081] Specifically, the laser beam irradiation unit 50 has a laser oscillator that generates a laser beam with a wavelength of 1064 nm using Nd:YAG as a laser medium, and this laser beam is then converted into a laser beam with a wavelength of 532 nm by passing through a wavelength conversion crystal.

[0082] Furthermore, a frequency setting unit (not shown) that sets the repetition frequency of the laser beam generated in the laser oscillator is provided in the laser beam irradiation unit 50. This frequency setting unit sets the repetition frequency of the laser beam to a predetermined frequency.

[0083] The repetition frequency of the laser beam emitted from the head 52 is set to a predetermined frequency in the range of 5 kHz to 50,000 kHz by the frequency setting unit. The repetition frequency may also be set to a predetermined frequency in the range of 50 kHz to 1,000 kHz.

[0084] The pulse width of the laser beam is a predetermined value in the range of 10 fs to 300 ns (fs stands for femtosecond). The output of the laser beam is a predetermined value in the range of 0.01 W to 100.0 W. The beam width at the focal point of the laser beam (spot diameter of the focal spot) is a predetermined length of 1 μm to 100 μm. The movement speed (feed rate) of the chuck table 42 when the laser beam is irradiated from the head 52 toward the chuck table 42 is a predetermined value in the range of 20 mm / s to 10,000 mm / s.

[0085] An imaging unit 54 is provided adjacent to the head 52. The imaging unit 54 includes a light source unit (not shown) that irradiates the workpiece 11 held on the chuck table 42 with visible light, and an imaging element (not shown) that captures an image of the light reflected from the workpiece 11.

[0086] In the processing step, first, the workpiece 11 was placed on the chuck table 32 so that the substrate 13 side of the workpiece 11 faced the porous plate of the chuck table 42 via the tape 25. Next, the suction source was activated, and the substrate 13 side of the workpiece 11 was sucked and held by the chuck table 42.

[0087] Next, based on the image formed by imaging the multiple streets 17 on the functional layer 15 side of the workpiece 11 using the imaging unit 54, the chuck table 42 was rotated so that some of the multiple streets 17 were parallel to the X-axis direction and the remaining parts were parallel to the Y-axis direction.

[0088] Next, the chuck table 42 was moved along the X-axis direction while irradiating the functional layer 15 side of the workpiece 11 with a laser beam having a wavelength of 532 nm from the head 52, thereby performing laser processing on the workpiece 11. This cut the protective film 29 and the workpiece 11, exposing the tape 25 in the area overlapping with the removed workpiece 11.

[0089] The power (output) of this laser beam was 7 W, and its repetition frequency was 100 kHz. The movement speed of the chuck table 42 was 300 mm / s, and the overlap rate of the pulsed laser beam irradiated onto the workpiece 11 was 90%.

[0090] Next, the same laser beam was irradiated to cut the protective film 29 and the workpiece 11 at all of the multiple streets 17, thereby exposing the tape 25 in the area overlapping with the removed workpiece 11. Next, the imaging unit 54 was used to image the area (intersection) where a pair of streets 17 on the functional layer 15 side of the workpiece 11 intersect at right angles to form an image.

[0091] Fig. 5(A) shows an image of an intersection of the workpiece 11 after laser processing has been performed on the workpiece 11 in which a protective film 29 has been formed on the functional layer 15 side using the protective film agent of Example 1. Similarly, Fig. 5(B), Fig. 5(C), Fig. 5(D), Fig. 5(E), and Fig. 5(F) show images of an intersection of the workpiece 11 after laser processing has been performed on the workpiece 11 in which a protective film 29 has been formed on the functional layer 15 side using each of the protective film agents of Examples 2 and 3 and Comparative Examples 1 to 3.

[0092] 5(A) to 5(F), it was found that when any of the protective film agents of Examples 1 to 3 was used, laser processing of the workpiece 11 was performed more satisfactorily than when any of the protective film agents of Comparative Examples 1 to 3 was used. In other words, it was found that by using the protective film agents of Examples 1 to 3, a protective film suitable for processing using a laser beam with a wavelength of 532 nm could be formed.

[0093] Furthermore, the amount of carminic acid (CA) contained in each of the protective film agents of Examples 1 to 3 was adjusted to prepare 15 types of protective film agents whose absorbance at a wavelength of 532 nm (absorbance converted to a 200-fold diluted solution) per cm of optical path length was 0.05, 0.15, 0.34, 0.49, or 0.97.

[0094] Then, as described above, an image was formed by capturing an image of the intersection of the workpiece 11 after laser processing was performed on the workpiece 11, which had a protective film 29 formed on the surface facing the functional layer 15 using each of the 15 types of protective film agents.

[0095] 6A shows an image of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 1, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.05 per cm of optical path length. Similarly, FIGS. 6B, 6C, 6D, and 6E show images of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 1, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.15, 0.34, 0.49, or 0.97 per cm of optical path length.

[0096] 7(A) shows an image of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 2, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.05 per cm of optical path length. Similarly, FIGS. 7(B), 7(C), 7(D), and 7(E) show images of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 2, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.15, 0.34, 0.49, or 0.97 per cm of optical path length.

[0097] 8A shows an image of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 3, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.05 per cm of optical path length. Similarly, FIGS. 8B, 8C, 8D, and 8E show images of the intersection of the workpiece 11 after laser processing on the workpiece 11, in which a protective film 29 is formed on the functional layer 15 side using the protective film agent of Example 3, which is prepared so that the absorbance (converted to a 200-fold diluted solution) is 0.15, 0.34, 0.49, or 0.97 per cm of optical path length.

[0098] As shown in Figures 6(A) to 6(E), 7(A) to 7(E), and 8(A) to 8(E), it was found that if the absorbance (absorbance converted to a 200-fold diluted solution) of the protective film agent solutions of Examples 1 to 3 is 0.05 or more, excessive processing defects do not occur in laser processing. Furthermore, it was found that if this absorbance is 0.15 or more, laser processing of the workpiece 11 can be performed more satisfactorily.

[0099] Furthermore, after the laser processing, the frame unit 21 was transported to a cleaning device (not shown) by a transport arm (not shown), and the surface of the workpiece 11 was cleaned by the cleaning device. This cleaning was performed by spraying cleaning water (e.g., pure water) onto the workpiece 11. As a result, the protective film 29 was removed from the workpiece 11 together with the debris (water washing removal).

[0100] This cleaning is preferably performed by two-fluid cleaning, high-pressure cleaning, steam two-fluid cleaning, micro-nano bubble water cleaning, or the like. The cleaning water (e.g., water) used in this cleaning may be at room temperature or may be heated. If it is difficult to remove the protective film 29 from the workpiece 11 by water cleaning alone, the protective film 29 may be removed from the workpiece 11 by plasma treatment, ultraviolet (e.g., 185 nm and / or 254 nm) irradiation, excimer light (e.g., 172 nm) irradiation, cleaning using ozone water, or the like. This completes the laser processing of the workpiece 11.

[0101] In addition, the structures, methods, etc. according to the above embodiments can be modified as appropriate without departing from the scope of the present invention. For example, in the above, spin coating was described as a method for applying a protective film agent to the surface of a workpiece to be processed and covering the entire area with a protective film. However, other methods besides spin coating, such as spray (ultrasonic, electrostatic) coating, inkjet printing, etc., may also be used. Furthermore, after spin coating, the protective film may be further dried by baking, xenon pulse irradiation, infrared irradiation, etc.

[0102] Furthermore, since the light absorber contained in the protective film agent of the present invention has absorbance at a wavelength of 355 nm in addition to a wavelength of 532 nm, the protective film agent of the present invention can also be used as a protective film agent for forming a protective film on the processing surface of a workpiece that is to be laser processed using a laser beam with a wavelength of 355 nm. [Explanation of symbols]

[0103] 11: Workpiece 13: Substrate 15: Functional layer 17: Street 19: Device 21: Frame unit 23: Annular frame 25: Tape 27: Protective film agent 29:Protective film 30: Spin coater 32: Chuck table 40: Laser processing equipment 42: Chuck table 50: Laser beam irradiation unit 52: Head 54: Imaging unit

Claims

1. A protective film agent for laser processing, which is made of a solution containing a water-soluble resin, an organic solvent, and a light absorber, the absorbance of the solution at a wavelength of 532 nm (converted to an absorbance of a 200-fold diluted solution) is 0.05 or more per 1 cm of optical path length; The protective film agent for laser processing, wherein the pH of the solution is 3 or more and less than 5.

2. The light absorber is a polyhydroxyanthraquinone derivative. The protective film agent for laser processing according to claim 1.

3. The polyhydroxyanthraquinone derivative is carminic acid. The protective film agent for laser processing according to claim 2.

4. A solution comprising a water-soluble resin, an organic solvent, and a polyhydroxyanthraquinone derivative, the absorbance of the solution at a wavelength of 532 nm (converted to an absorbance of a 200-fold diluted solution) is 0.05 or more per 1 cm of optical path length; The protective film agent for laser processing, wherein the polyhydroxyanthraquinone derivative is carminic acid.

5. The pH of the solution is 3 or more and 4 or less. The protective film agent for laser processing according to any one of claims 1 to 4.

6. A method for processing a workpiece, comprising: a protective film forming step of applying the protective film agent for laser processing according to any one of claims 1 to 5 to a processing surface of the workpiece to form a protective film that covers the processing surface; a processing step of irradiating the workpiece with a laser beam having a wavelength that is absorbed by the workpiece and the protective film through the protective film, thereby processing the workpiece; A method for processing a workpiece, comprising:

Images