Formation method of water-soluble protective film and processing method of plate-like material

Abstract

To form a water-soluble protective film with thickness being uniform over a front surface of a plate-like material regardless of a state of the front surface of the plate-like material.SOLUTION: A formation method of a water-soluble protective film, for forming the water-soluble protective film onto a front surface of the plate-like material, comprises; a water-soluble resin sheet distribution step of distributing a thermal plastic water soluble resin sheet onto the front surface side of the plate-like material; and an integration step of forming the water-soluble resin sheet onto the plate-like material by integrating the water-soluble resin sheet and the plate-like material by welding or softening, through heating, the water-soluble resin sheet. Preferably, the water-soluble resin sheet contains a light absorbent.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for forming a water-soluble protective film on the surface of a plate-like object, and a method for processing a plate-like object by coating the surface of the plate-like object with a water-soluble protective film and processing the plate-like object. [Background technology]

[0002] When manufacturing device chips for use in electronic devices such as mobile phones and computers, first, a plate-like object (workpiece) such as a semiconductor wafer is prepared. Then, a plurality of planned division lines (streets) that intersect with each other are set on the surface of the plate-like object, devices are formed in each area partitioned by the planned division lines on the surface of the plate-like object, and the plate-like object is divided along the planned division lines to obtain individual device chips.

[0003] As a method for dividing a plate-like object, for example, a method is known in which a laser beam is irradiated onto the plate-like object along the intended dividing line, and the plate-like object is subjected to an ablation process (see Patent Document 1). However, when the ablation process is performed, molten material called debris scatters from the plate-like object, and the debris adheres to the surface of the plate-like object. It is not easy to remove the debris that has adhered to the plate-like object, and this is problematic because the debris reduces the quality of the device chips that are ultimately manufactured.

[0004] Therefore, before the plate-shaped object is subjected to ablation processing, a water-soluble protective film is formed on the surface of the plate-shaped object (see Patent Document 2). In this case, when the plate-shaped object is ablated by irradiating a laser beam through the protective film, the scattered debris adheres to the protective film. When the plate-shaped object is subsequently washed, the debris is easily removed together with the protective film.

[0005] The formation of a water-soluble protective film on a plate-like object is carried out by supplying liquid resin, which is the raw material of the protective film, to the surface of the plate-like object while the spinner table holding the plate-like object is rotating at high speed, spreading the liquid resin over the surface of the plate-like object by utilizing centrifugal force, and drying and solidifying the liquid resin. In other words, the protective film is formed on the plate-like object by spin coating. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-305420 [Patent Document 2] JP 2006-140311 A Summary of the Invention [Problem to be solved by the invention]

[0007] Here, various structures may be formed on the surface of the plate-like object, and protruding structures called bumps may also be formed. When the surface of the plate-like object has projections and recesses, the thickness of the protective film formed by spin coating becomes thin at the projections on the surface of the plate-like object, and a protective film of sufficient thickness cannot be formed in these areas.

[0008] One possible solution would be to form the protective film thicker overall, but this would consume a large amount of raw material for the protective film, making it inefficient, and would also make the protective film extremely thick in the recesses on the surface of the plate-like object. In order to perform sufficient ablation processing in the thick protective film area, the irradiation conditions of the laser beam would need to be strengthened, which would result in a problem of reduced processing efficiency for the plate-like object.

[0009] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a method for forming a protective film that forms a water-soluble protective film of uniform thickness on the surface of a plate-like object regardless of the condition of the surface of the plate-like object, and a method for processing the plate-like object. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a method for forming a water-soluble protective film, which forms a water-soluble protective film on the surface of a plate-like object, comprising: a water-soluble resin sheet disposing step of disposing a water-soluble resin sheet having thermoplasticity on the surface side of the plate-like object; and an integration step of heating the water-soluble resin sheet to melt or soften it, and integrating the water-soluble resin sheet and the plate-like object to form the water-soluble protective film on the plate-like object.

[0011] Preferably, the water-soluble resin sheet contains a light absorbing agent.

[0012] According to another aspect of the present invention, there is provided a method for processing a plate-like object, comprising: a water-soluble resin sheet disposing step of disposing a water-soluble resin sheet having thermoplasticity on the surface side of the plate-like object; an integration step of heating the water-soluble resin sheet to melt or soften it and integrating the water-soluble resin sheet and the plate-like object to form a water-soluble protective film on the plate-like object; a processing step of processing the plate-like object after the integration step; and a water-soluble protective film removal step of supplying a cleaning liquid to the plate-like object to remove the water-soluble protective film from the plate-like object after the processing step.

[0013] Preferably, in the processing step, a laser beam having a wavelength that is absorbed by the plate-like object is irradiated onto the plate-like object through the water-soluble protective film to process the plate-like object.

[0014] Alternatively, preferably, in the processing step, the water-soluble protective film is partially removed to partially expose the plate-like object from the water-soluble protective film, and the portion of the plate-like object exposed from the water-soluble protective film is processed.

[0015] More preferably, the water-soluble resin sheet contains a light absorbing agent. Effect of the Invention

[0016] According to a method for forming a protective film and a method for processing a plate-like object according to one aspect of the present invention, a water-soluble resin sheet having thermoplasticity is disposed on the surface side of the plate-like object, and the water-soluble resin sheet is melted or softened by heating to integrate the water-soluble resin sheet and the plate-like object, thereby forming a water-soluble protective film on the plate-like object.

[0017] In this case, even if the plate-like object has an uneven surface, the thickness of the water-soluble protective film does not vary depending on the location. That is, the convex parts of the surface of the plate-like object can be sufficiently protected, and the protective film does not become too thick even in the concave parts. Therefore, the raw material of the water-soluble protective film is not used more than necessary, and the processing of the plate-like object does not need to be performed with higher intensity than necessary.

[0018] Therefore, according to one aspect of the present invention, there is provided a method for forming a protective film that forms a water-soluble protective film of uniform thickness on the surface of a plate-like object regardless of the condition of the surface of the plate-like object, and a method for processing the plate-like object. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a perspective view showing a plate-like object. [Diagram 2] Figure 2(A) is a cross-sectional view showing a schematic diagram of a fixing device in the water-soluble resin sheet disposing step, and Figure 2(B) is a cross-sectional view showing an enlarged schematic diagram of a plate-like object having a water-soluble resin sheet disposed on its surface. [Diagram 3] FIG. 3(A) is a cross-sectional view showing a schematic diagram of a fixing device in the integration step, and FIG. 3(B) is a cross-sectional view showing an enlarged schematic diagram of a plate-like object having a water-soluble resin sheet fixed to its surface. [Figure 4] FIG. 11 is a cross-sectional view showing a plate-like object in an integration step according to a modified example. [Diagram 5] FIG. 2 is a cross-sectional view illustrating a laser processing apparatus in a processing step. [Figure 6] FIG. 4 is a cross-sectional view that illustrates a schematic diagram of a cleaning device in a water-soluble resin film removing step. [Figure 7]1 is a cross-sectional view that illustrates a schematic diagram of a plasma processing apparatus. [Figure 8] 4 is a flowchart showing the flow of each step of a method for processing a plate-shaped object. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] An embodiment according to one aspect of the present invention will be described with reference to the attached drawings. In the method for forming a water-soluble protective film and the method for processing a plate-like object according to this embodiment, a water-soluble protective film is formed on the surface of a plate-like object (workpiece) such as a semiconductor wafer having a plurality of devices formed on its surface. First, the plate-like object on whose surface a water-soluble protective film is formed will be described. Fig. 1 is a perspective view showing a typical example of a plate-like object 1.

[0021] The plate-like object 1 is, for example, a wafer made of a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor. Alternatively, the plate-like object 1 is, for example, a substantially disk-shaped substrate made of a material such as sapphire, glass, or quartz. The glass is, for example, alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, quartz glass, or the like.

[0022] Fig. 1 shows a schematic perspective view of a plate-like object 1, Fig. 2(A) shows a schematic cross-sectional view of the plate-like object 1, and Fig. 2(B) shows a schematic enlarged cross-sectional view of the plate-like object 1. A plurality of mutually intersecting division lines 3 are set on the front surface 1a of the plate-like object 1. Devices 5 such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) are formed in each region partitioned by the division lines 3. The plate-like object 1 is thinned by grinding from the back surface 1b side, and is divided along the division lines 3 to form individual device chips.

[0023] A surface 1a of the plate-like object 1 is provided with a plurality of protruding parts called bumps 7, which are made of, for example, a metal. The bumps 7 are each electrically connected to the device 5, and function as electrodes for inputting and outputting electrical signals to and from the device 5 when the plate-like object 1 is divided into device chips. The bumps 7 are made of, for example, a metal material such as gold, silver, copper, or aluminum. However, the bumps 7 do not necessarily have to be provided on the surface 1a of the plate-like object 1.

[0024] The outer peripheral region surrounding the region on the surface 1a of the plate-like object 1 where the multiple devices 5 are formed is called the outer peripheral surplus region 11. No devices 5 are formed in the outer peripheral surplus region 11 on the surface 1a of the plate-like object 1, and no bumps 7 serving as electrodes for the devices 5 are formed either. The region surrounded by the outer peripheral surplus region 11 on the surface 1a of the plate-like object 1 is called the device formation region 9. The device formation region 9 on the surface 1a of the plate-like object 1 is not flat, but has irregularities due to the patterns and bumps 7 that make up the devices 5. On the other hand, the outer peripheral surplus region 11 on the surface 1a is flat.

[0025] The plate-like object 1 on which the water-soluble protective film is formed is not limited to this. For example, it may be a package substrate formed by sealing a plurality of devices arranged on a flat surface with a sealing resin. By dividing the package substrate into individual devices, individual device chips sealed with a sealing resin can be formed. Since bumps that become electrodes for the individual devices are formed on the surface of the package substrate, the surface of the package substrate is not flat but has irregularities.

[0026] Individual device chips are obtained by dividing the plate-like object 1 along the division lines 3. The division of the plate-like object 1 is carried out, for example, by an ablation process in which a laser beam having a wavelength that is absorbent by the plate-like object 1 is irradiated onto the plate-like object 1 along the division lines 3. In the ablation process, the plate-like object 1 is melted and removed at the positions irradiated with the laser beam, and division grooves are formed.

[0027] When the plate-like object 1 is subjected to ablation processing, molten material called debris scatters around and adheres to the surface 1a of the plate-like object 1. It is difficult to remove the debris adhered to the plate-like object 1 by a normal cleaning process. Therefore, the debris remains in the device chips that are finally formed by dividing the plate-like object 1, degrading the quality of the device chips.

[0028] Therefore, it is known to supply a water-soluble liquid resin to the surface 1a of the plate-like object 1 and dry the liquid resin to form a water-soluble protective film on the surface 1a of the plate-like object 1 (spin coating). However, with this method, when the surface 1a of the plate-like object 1 has large irregularities, the thickness of the water-soluble protective film formed on the plate-like object 1 is not constant. For example, the water-soluble protective film is thinner on the convex parts of the surface 1a of the plate-like object 1 and thicker on the concave parts.

[0029] Therefore, in the method for forming a water-soluble protective film and the method for processing a plate-shaped object according to this embodiment, a water-soluble protective film of uniform thickness is formed on the surface 1a of the plate-shaped object (workpiece) 1 regardless of the shape of the surface 1a of the plate-shaped object (workpiece) 1.

[0030] 8 is a flow chart showing the flow of each step of the method for processing a plate-like object according to this embodiment. The method for forming a water-soluble protective film is carried out as a part of the process of the method for processing a plate-like object. Therefore, the method for processing a plate-like object according to this embodiment will be described below, and the method for forming a water-soluble protective film according to this embodiment will also be described.

[0031] In the method for processing a plate-like object according to this embodiment, first, a water-soluble resin sheet disposing step S10 and an integration step S20 are performed. In the water-soluble resin sheet disposing step S10, a water-soluble resin sheet having thermoplasticity is disposed on the surface 1a side of the plate-like object 1. Then, in the integration step S20, the water-soluble resin sheet is heated to melt or soften it, and the water-soluble resin sheet and the plate-like object 1 are integrated to form the water-soluble protective film on the plate-like object 1.

[0032] Here, the water-soluble resin sheet 13 is a thermoplastic sheet made of a water-soluble material such as polyvinyl alcohol (PVA) and has a thickness of 10 μm to 80 μm. The water-soluble resin sheet 13 does not have a glue layer (adhesive layer) and cannot be fixed to the plate-like object 1 as it is.

[0033] The PVA used in the water-soluble resin sheet 13 may contain other monomer units. Examples of such monomer units include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene, acrylic acid and its salts, and acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, Methacrylic acid esters such as i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts, and N-methylolacrylamide and its derivatives; Examples of the compound include methacrylamide derivatives such as acrylamide derivatives, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, N-methylolmethacrylamide and its derivatives, N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide, allyl ethers having polyalkylene oxide on the side chain, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether, nitriles such as acrylonitrile and methacrylonitrile, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride, allyl compounds such as allyl acetate and allyl chloride, maleic acid and its salts or esters, vinyl silyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

[0034] A plasticizer may be added to the water-soluble resin sheet 13 in order to improve conformability to the uneven shape of the surface 1a of the plate-like object 1. The plasticizer to be mixed in the water-soluble resin sheet 13 is not particularly limited as long as it is a plasticizer generally used for PVA, and examples thereof include polyhydric alcohols such as glycerin, diglycerin, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, and 1,3-butanediol; polyethers such as polyethylene glycol and polypropylene glycol; polyvinylamides such as polyvinylpyrrolidone; amide compounds such as N-methylpyrrolidone and dimethylacetamide; compounds in which ethylene oxide is added to polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol, or water. These may be used alone or in combination. Among these plasticizers, it is preferable to use glycerin, diglycerin, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, polyethylene glycol, and polyvinylpyrrolidone for the purpose of improving water solubility. Furthermore, it is particularly preferable to use glycerin, diglycerin, trimethylolpropane, polyethylene glycol, and polyvinylpyrrolidone as the plasticizer from the viewpoint of the effect of suppressing the decrease in water solubility of the water-soluble resin sheet 13 due to the bleed-out of the plasticizer.

[0035] The water-soluble resin sheet 13 preferably contains a light absorbing agent, and desirably has a light absorption coefficient of 1,000 / cm or more. For example, a benzophenone-based ultraviolet absorbing agent is mixed into the water-soluble resin sheet 13. In addition, as the light absorbing agent, titanium dioxide, cerium oxide, carbon black, zinc oxide, silicon powder, yellow iron oxide, sulfide pigment, nitroso pigment, nitro pigment, azo lake pigment, lake pigment, phthalocyanine pigment, threne pigment, quinacridone pigment, etc. may also be used.

[0036] The melting point of the light absorbent is, for example, preferably 50° C. or more and 250° C. or less, more preferably 60° C. or more and 220° C. or less, and even more preferably 80° C. or more and 200° C. or less. If the melting point of the light absorbent is lower than this range, the light absorbent will melt out of the water-soluble resin sheet 13 and adhere to the plate-like object 1 when the water-soluble resin sheet 13 is fixed to the plate-like object 1, as described below. On the other hand, if the melting point of the light absorbent is higher than this range, the light absorbent will not be appropriately dispersed in the water-soluble resin sheet 13 when the water-soluble resin sheet 13 is molded.

[0037] Next, a fixing device for carrying out the water-soluble resin sheet disposing step S10 and the integration step S20 will be described. Fig. 2(A) is a cross-sectional view showing a schematic example of a fixing device 12. The fixing device 12 is, for example, a chamber-like unit having a space capable of accommodating the plate-like object 1 therein, and has a function of adhering the water-soluble resin sheet 13 to the surface 1a of the plate-like object 1.

[0038] The fixing device 12 has a lower body 12a having a concave shape that opens upward, and an upper body 12b having a concave shape that is disposed above the lower body 12a and opens downward. The upper body 12b can be raised and lowered. The opening of the lower body 12a and the opening of the upper body 12b have the same shape, and when the upper body 12b is lowered onto the lower body 12a so that the openings overlap, a space that is isolated from the outside can be formed inside the upper body 12b and the lower body 12a. Each opening is larger than the plate-like object 1, and the plate-like object 1 can be accommodated in the space.

[0039] The lower body 12a is provided with a table-like plate-like object support part 14 that supports the plate-like object 1. The upper surface of the plate-like object support part 14 is a flat support surface 14a that supports the plate-like object 1. The height of the plate-like object support part 14 is adjusted so that when the plate-like object 1 is placed on the support surface 14a, the height of the surface 1a of the plate-like object 1 and the height of the opening of the lower body 12a are approximately the same. Alternatively, the height of the plate-like object support part 14 is adjusted so that the opening of the lower body 12a is higher than the surface 1a of the plate-like object 1.

[0040] In these cases, when the water-soluble resin sheet 13 is placed on the lower body 12a and adhered to the plate-like object 1 as described below, the water-soluble resin sheet 13 does not adhere to an unnecessarily large area of ​​the side of the plate-like object 1.

[0041] An exhaust unit 16 is connected to the bottom wall or side wall of the lower body 12a. The exhaust unit 16 has an exhaust path 16a, one end of which is connected to the lower body 12a and the other end of which is connected to a suction source 16b. A switching unit 16c constituted by a solenoid valve or the like may be provided in the exhaust path 16a, and the connection state between the suction source 16b and the lower body 12a may be switched by the switching unit 16c.

[0042] An exhaust unit 18 is connected to the ceiling or side wall of the upper body 12b. The exhaust unit 18 includes an exhaust path 18a having one end connected to the upper body 12b and the other end connected to a suction source 18b. A switching unit 18c constituted by a solenoid valve or the like may be provided in the exhaust path 18a, and the connection state between the suction source 18b and the upper body 12b may be switched by the switching unit 18c.

[0043] In the water-soluble resin sheet disposing step S10 performed by the fixing device 12, the plate-like object 1 is carried onto the plate-like object support section 14, and the plate-like object 1 is supported by the plate-like object support section 14, and then the surface 1a of the plate-like object 1 is covered with a water-soluble resin sheet 13. A resin film supply section (not shown) in which a plurality of water-soluble resin sheets 13 or a roll of water-soluble resin sheet 13 is prepared is provided adjacent to the fixing device 12. The water-soluble resin sheet 13 covering the plate-like object 1 is supplied from the resin film supply section.

[0044] A water-soluble resin sheet 13 larger than the opening of the lower body 12a is prepared in the resin film supply section so that a space 20a closed by the lower body 12a and the water-soluble resin sheet 13 can be formed when the water-soluble resin sheet 13 is transported onto the plate-like object 1. After the water-soluble resin sheet 13 is transported onto the plate-like object 1, the upper body 12b is lowered to contact the upper surface of the water-soluble resin sheet 13. Then, a space 20b closed by the upper body 12b and the water-soluble resin sheet 13 is formed.

[0045] When the water-soluble resin sheet 13 is disposed on the surface 1a of the plate-like object 1 in this manner, the inside of the chamber-like fixing device 12 is divided into an upper space 20b and a lower space 20a by the water-soluble resin sheet 13. Fig. 2(B) is an enlarged schematic cross-sectional view of the plate-like object 1 with the water-soluble resin sheet 13 disposed on the surface 1a.

[0046] Next, the fixing device 12 performs an integration step S20 in which the water-soluble resin sheet 13 and the plate-like object 1 are integrated together. That is, the water-soluble resin sheet 13 is fixed to the plate-like object 1. Fig. 3(A) is a cross-sectional view that typically shows the fixing device 12 in the integration step S20.

[0047] In the integration step S20 in the fixing device 12, the switching unit 16c is operated to connect the suction source 16b of the exhaust unit 16 to the lower body 12a, and the switching unit 18c is operated to connect the suction source 18b of the exhaust unit 18 to the upper body 12b. This causes the spaces 20a and 20b to be evacuated and reduced in pressure. Thereafter, the switching unit 18c is operated to separate only the suction source 18b, which reduces the pressure of the space 20b, from the upper body 12b, and the space 20b is opened to the atmosphere.

[0048] As a result, a large pressure difference is instantaneously generated between the spaces 20a and 20b sandwiching the water-soluble resin sheet 13. This pressure difference causes the water-soluble resin sheet 13 to adhere closely to the surface 1a of the plate-like object 1 so as to conform to the unevenness of the surface 1a. Fig. 3(B) is an enlarged schematic cross-sectional view of the plate-like object 1 with the water-soluble resin sheet 13 adhered closely to the surface 1a.

[0049] In the integration step S20, the water-soluble resin sheet 13 is heated at this time to melt or soften it, thereby integrating the water-soluble resin sheet 13 and the plate-like object 1. As a result, a water-soluble protective film is formed on the plate-like object 1.

[0050] For example, the fixing device 12 may have a heating unit (not shown) connected to the ceiling or side wall of the upper body 12b, which can supply heated gas. This heating unit has a function of supplying heated gas to the space 20b of the upper body 12b. This gas is, for example, air, nitrogen gas, or the like. Alternatively, the fixing device 12 includes a heating unit made of an electric heating wire or the like inside the table-shaped plate-like object support unit 14 that supports the plate-like object 1. This heating unit has a function of heating the water-soluble resin sheet 13 through the plate-like object 1 by heating the plate-like object support unit 14.

[0051] The water-soluble resin sheet 13 has thermoplasticity, and its flexibility is improved by heating. When the heating unit is operated to heat the water-soluble resin sheet 13, the water-soluble resin sheet 13 melts or softens. This causes the water-soluble resin sheet 13 to deform in accordance with the shape of the surface 1a of the plate-like object 1, and the water-soluble resin sheet 13 adheres closely to the surface 1a of the plate-like object 1. This process in which the water-soluble resin sheet 13 is heated under pressure and adheres closely to the plate-like object 1 can also be called thermocompression bonding.

[0052] Before reducing the pressure in the spaces 20a and 20b, the heating unit may supply heated gas to the space 20b to preheat and soften the water-soluble resin sheet 13. Alternatively, the space 20a and 20b may be reduced in pressure, the space 20b may be opened to the atmosphere, and then the heating unit may be operated to heat the water-soluble resin sheet 13, thereby promoting the deformation of the water-soluble resin sheet 13.

[0053] Here, the heating temperature of the water-soluble resin sheet 13 is not particularly limited. For example, the water-soluble resin sheet 13 has a storage modulus of 10 5 Over 10 7 It is preferable that the plate-like object 1 is fixed to the plate-like object 1 by heating the plate-like object 1 to a temperature below the temperature.

[0054] The storage modulus of the water-soluble resin sheet 13 is 10 7 If the storage modulus of the water-soluble resin sheet 13 exceeds 10, the water-soluble resin sheet 13 may not sufficiently conform to the unevenness of the surface 1a of the plate-like object 1, and a gap may occur between the water-soluble resin sheet 13 and the plate-like object 1. 7 If it is smaller than this, the water-soluble resin sheet 13 may not be able to maintain its shape and may flow on the surface 1a of the plate-like object 1. If the water-soluble resin sheet 13 flows on the surface 1a of the plate-like object 1, a water-soluble protective film of uniform thickness will not be formed on the surface 1a of the plate-like object 1.

[0055] Thereafter, the heating of the water-soluble resin sheet 13 is stopped, and the temperature of the water-soluble resin sheet 13 is returned to room temperature. Then, the water-soluble resin sheet 13 is fixed to the surface 1a of the plate-like object 1. By using the fixing device 12 as described above, the water-soluble resin sheet 13 can be fixed (thermocompression bonded) to the surface of the plate-like object 1.

[0056] After the water-soluble resin sheet 13 is fixed to the plate-like object 1, the exhaust unit 16 is stopped and the upper body 12b is raised. This allows the plate-like object 1 with the water-soluble resin sheet 13 fixed thereto to be removed. Thereafter, the water-soluble resin sheet 13 is cut along the outer periphery of the plate-like object 1 to obtain the plate-like object 1 with the water-soluble protective film disposed on the surface 1a. The water-soluble protective film formed on the plate-like object 1 by this method has a uniform thickness, reflecting the shape of the water-soluble resin sheet 13.

[0057] In the method for processing a plate-like object according to the present embodiment, the water-soluble resin sheet disposing step S10 and the integration step S20 are not limited to being performed by the fixing device 12, and may be performed by other fixing devices. Fig. 4 is a cross-sectional view showing the water-soluble resin sheet disposing step S10 and the integration step S20 according to a modified example. Fig. 4 shows a fixing device 22 according to a modified example.

[0058] The fixing device 22 will be described. The fixing device 22 includes a plate-like object support part 24 that supports the plate-like object 1. The upper surface of the plate-like object support part 24 is a flat support surface 24a that supports the plate-like object 1. A heating part 26 that can heat the water-soluble resin sheet 13 via the plate-like object 1 placed on the support surface 24a is provided inside the plate-like object support part 24. The heating part 26 is composed of, for example, an electric heating wire or the like.

[0059] The fixing device 22 also includes a pressure roller 28 that presses from above the water-soluble resin sheet 13 disposed on the surface 1a of the plate-like object 1. The pressure roller 28 can move in a direction parallel to the support surface 24a while pressing the water-soluble resin sheet 13 from above.

[0060] In the water-soluble resin sheet disposing step S10 according to the modified example, the plate-like object 1 is placed on the support surface 24a of the plate-like object support part 24. At this time, the orientation of the plate-like object 1 is determined so that the front surface 1a on which the water-soluble resin sheet 13 is placed faces upward and the back surface 1b faces downward. Then, the water-soluble resin sheet 13 having thermoplasticity is disposed on the front surface 1a side of the plate-like object 1 as shown in FIG.

[0061] Next, an integration step S20 according to the modified example is performed. First, the heating unit 26 is operated to heat the water-soluble resin sheet 13 through the plate-like object 1, thereby melting or softening the water-soluble resin sheet 13. Then, the pressure roller 28 rolls from one end to the other end of the plate-like object 1 while pressing the water-soluble resin sheet 13 against the plate-like object 1. This causes the water-soluble resin sheet 13 to be thermocompressed to the plate-like object 1. That is, the water-soluble resin sheet 13 and the plate-like object 1 are integrated.

[0062] Thereafter, the heating unit 26 is stopped to return the water-soluble resin sheet 13 to room temperature, and the water-soluble resin sheet 13 is cut along the outer periphery of the plate-like object 1, thereby providing a water-soluble protective film on the surface 1a of the plate-like object 1.

[0063] By carrying out the water-soluble resin sheet providing step S10 and the integration step S20, a water-soluble protective film is formed on the surface 1a of the plate-like object 1. This water-soluble protective film is formed by providing the water-soluble resin sheet 13 on the surface 1a of the plate-like object 1 and integrating it with the plate-like object 1. Therefore, unlike the case where a technique such as spin coating is carried out, a water-soluble protective film of uniform thickness is formed on the surface 1a of the plate-like object 1.

[0064] In the method for processing a plate-like object according to this embodiment, after the integration step S20 is performed, a processing step S30 is performed to process the plate-like object 1. In the processing step S30, the water-soluble protective film formed with a uniform thickness on the surface 1a of the plate-like object 1 is utilized to appropriately perform the processing.

[0065] 5 is a cross-sectional view showing a schematic diagram of a processing step S30 according to an example. In the processing step S30, for example, a laser beam 44 having a wavelength that is absorbed by the plate-like object 1 is irradiated onto the plate-like object 1 through a water-soluble protective film to process the plate-like object 1, thereby forming division grooves along the intended division lines 3 in the plate-like object 1. That is, the plate-like object 1 is subjected to an ablation process by the laser beam 44.

[0066] As shown in Fig. 5, a tape 15 called a dicing tape may be attached to the back surface 1b of the plate-like object 1 before processing, and a ring-shaped frame 17 made of a metal material or the like may be attached to the outer periphery of the tape 15. That is, in the processing step S30, the plate-like object 1 integrated with the tape 15 and the frame 17 may be processed. The plate-like object 1 supported by the tape 15 is easy to handle. Also, the chips formed by dividing the plate-like object 1 continue to be supported by the tape 15, so that the chips are also easy to handle.

[0067] 5 shows a schematic diagram of a laser processing apparatus 30 for ablation processing of a plate-like object 1. Here, the laser processing apparatus 30 will be described. The laser processing apparatus 30 includes a holding table (chuck table) 32 for holding the plate-like object 1 to be processed, and a laser processing unit 42 for irradiating the plate-like object 1 held by the holding table 32 with a laser beam.

[0068] The holding table (chuck table) 32 is connected to a rotary drive source (not shown) such as a motor, and is rotatable around a rotation axis perpendicular to the upper surface of the holding table 32. The surface (upper surface) of the holding table 32 serves as a holding surface 40 that sucks and holds the plate-like object 1. Clamps 34 are disposed around the holding surface 40 for fixing annular frame 17 that holds the plate-like object 1 via tape 15.

[0069] The holding table 32 includes a porous member 38 having the same diameter as the plate-like object 1, and a frame 36 that houses the porous member 38 while exposing it upward. A suction path (not shown) is formed inside the holding table 32, one end of which is connected to a suction source such as a pump, and the other end of the suction path is connected to the porous member 38. When the plate-like object 1 is placed on the porous member 38 and the plate-like object 1 is sucked by the suction source through the porous member 38 and the suction path, the plate-like object 1 is sucked and held on the holding table 32. That is, the upper surface of the porous member 38 becomes the holding surface 40.

[0070] The laser processing unit 42 has a function of focusing a laser beam 44, having a wavelength that is absorbent by the plate-like object 1, at a predetermined height position on the plate-like object 1. By moving the holding table 32 in a direction parallel to the holding surface 40 while irradiating the plate-like object 1 with the laser beam 44, the laser beam 44 can be scanned over various locations on the plate-like object 1.

[0071] When performing the processing step S30 with the laser processing device 30, first, the plate-like object 1 on which the water-soluble protective film 13a has been formed is placed on the holding surface 40 of the holding table 32. Then, the frame 17 is gripped by the clamps 34, and the plate-like object 1 is suction-held by the holding table 32 via the tape 15. Next, the holding table 32 is moved so that the focal point of the laser beam 44 of the laser processing unit 42 is positioned at the end of one of the planned division lines 3.

[0072] Thereafter, the plate-like object 1 is moved along the intended division lines 3 while being irradiated with a laser beam 44 from the laser processing unit 42, and the ablation processing of the plate-like object 1 is performed. When the ablation processing of the plate-like object 1 is performed, a division groove 21 is formed in the plate-like object 1. An example of the irradiation conditions of the laser beam is shown below. Laser medium: Nd:YAG Wavelength: 355nm Average power output: 5.0W Repetition frequency: 20kHz Focused spot diameter: 5.0μm Machining feed speed: 100mm / sec

[0073] After the laser beam 44 is irradiated onto the plate-like object 1 along one of the planned division lines 3, the plate-like object 1 is indexed and fed, and the laser beam 44 is similarly irradiated onto the plate-like object 1 along the other planned division lines 3. After the plate-like object 1 has been laser-processed along all of the planned division lines 3 in one direction, the holding table 32 is rotated, and the plate-like object 1 is similarly laser-processed along the planned division lines 3 in the other directions. When the plate-like object 1 has been laser-processed along all of the planned division lines 3, the processing of the plate-like object 1 is completed.

[0074] In the processing step S30, the laser beam 44 is irradiated onto the plate-like object 1 through the water-soluble protective film 13a. At this time, the water-soluble protective film 13a absorbs a part of the laser beam 44 and is processed, and the plate-like object 1 is partially melted to generate debris, and the debris 23 is scattered around the focusing position of the laser beam 44.

[0075] In the method for processing a plate-like object according to this embodiment, the surface 1a of the plate-like object 1 is covered with the water-soluble protective film 13a, so that the debris 23 does not come into direct contact with the surface 1a of the plate-like object 1, but adheres to the water-soluble protective film 13a. In other words, the surface 1a of the plate-like object 1 is protected by the water-soluble protective film 13a.

[0076] Here, if the water-soluble protective film 13a is thick or if the intensity of the laser beam 44 is insufficient, the water-soluble protective film 13a may not be sufficiently broken through even when the laser beam 44 is irradiated onto the plate-like object 1, and the debris 23 may not be properly discharged. However, if the water-soluble resin sheet 13, which was the raw material of the water-soluble protective film 13a, contains a light absorbing material, the water-soluble protective film 13a absorbs the laser beam 44 more suitably, the processing of the water-soluble protective film 13a is promoted, and the water-soluble protective film 13a is easily broken. As a result, the debris 23 is properly discharged.

[0077] When division grooves 21 are formed in the plate-like object 1 along each of the intended division lines 3, the plate-like object 1 is divided into individual chips 19. The formed chips 19 continue to be supported by the tape 15. After the processing of the plate-like object 1 using the water-soluble protective film 13a is thus completed, the plate-like object 1 (chips 19) is carried out of the laser processing device 30 while still supported by the tape 15. This completes the processing step S30.

[0078] In the method for processing a plate-like object according to this embodiment, after the processing step S30 is performed, a water-soluble protective film removing step S40 is performed in which a cleaning liquid is supplied to the plate-like object 1 to remove the water-soluble protective film 13a from the plate-like object 1. Fig. 6 is a cross-sectional view that typically shows the water-soluble protective film removing step S40.

[0079] The water-soluble protective film removing step S40 is performed, for example, by a cleaning device 46 shown in Fig. 6. The cleaning device 46 includes a spinner table 48 and a cleaning nozzle 58 that supplies a cleaning liquid 60 to the plate-like object 1 held on the spinner table 48.

[0080] The spinner table 48 is connected to a rotary drive source (not shown) such as a motor, and can rotate around a rotary axis perpendicular to the upper surface of the spinner table 48. The surface (upper surface) of the spinner table 48 serves as a holding surface 56 that sucks and holds the plate-like object 1. A clamp 50 for fixing the annular frame 17 is disposed around the holding surface 56.

[0081] The spinner table 48 includes a porous member 54 having the same diameter as the plate-like object 1, and a frame 52 that houses the porous member 54 while exposing it upward. A suction path (not shown) is formed inside the spinner table 48, one end of which is connected to a suction source such as a pump, and the other end of the suction path is connected to the porous member 54. When the plate-like object 1 is placed on the porous member 54 and the plate-like object 1 is sucked by the suction source through the porous member 54 and the suction path, the plate-like object 1 is sucked and held on the spinner table 48. That is, the upper surface of the porous member 54 becomes a holding surface 56.

[0082] The cleaning nozzle 58 may be movable in a plane parallel to the holding surface 56 along a trajectory that passes above the center of the holding surface 56. The cleaning nozzle 58 sprays a cleaning liquid 60 mainly composed of pure water, or a cleaning liquid 60 composed of a mixed fluid of pure water and high-pressure gas, toward the surface 1a of the plate-like object 1 held on the spinner table 48. A surfactant may be mixed into the cleaning liquid 60.

[0083] In the water-soluble protective film removal step S40, first, the processed plate-like object 1 is carried into the cleaning device 46 and held on the spinner table 48. Then, the frame 17 is fixed with a clamp 50. After that, the rotation of the spinner table 48 is started, and the supply of the cleaning liquid 60 to the surface 1a of the plate-like object 1 is started from the cleaning nozzle 58.

[0084] When the cleaning liquid 60 is supplied to the surface 1a of the plate-like object 1 (chip 19), the water-soluble protective film 13a dissolves in the cleaning liquid 60, and the water-soluble protective film 13a is removed. At this time, the debris 23 adhering to the water-soluble protective film 13a is washed away by the cleaning liquid 60. Therefore, the debris 23 is easily removed from the plate-like object 1 (chip 19).

[0085] After the removal of the water-soluble protective film 13a from the plate-like object 1 is completed, the supply of the cleaning liquid 60 from the cleaning nozzle 58 to the plate-like object 1 is stopped. If the rotation of the spinner table 48 is continued in this state, the plate-like object 1 (chips 19) is dried. Then, the rotation of the spinner table 48 is stopped, and the plate-like object 1 (chips 19) is carried out from the spinner table 48, whereby the chips 19 from which the water-soluble protective film 13a has been removed are obtained. This completes the water-soluble protective film removal step S40.

[0086] As described above, according to the processing method for a plate-like object (method for forming a water-soluble protective film) of this embodiment, even if the plate-like object 1 has an uneven shape on the surface 1a, the thickness of the water-soluble protective film 13a does not vary depending on the location. That is, the convex parts of the surface 1a of the plate-like object 1 can be sufficiently protected, and the water-soluble protective film 13a does not become too thick even in the concave parts. Therefore, the raw material of the water-soluble protective film 13a is not used more than necessary, and it is not necessary to process the plate-like object 1 with more intensity than necessary.

[0087] The present invention is not limited to the above embodiment and can be modified in various ways. For example, in the above embodiment, the laser processing device 30 (FIG. 5) is used in the processing step S30, and the plate-like object 1 is subjected to ablation processing. However, the plate-like object processing method according to one aspect of the present invention is not limited to this.

[0088] That is, the processing performed in processing step S30 using the water-soluble protective film 13a is not limited to the ablation processing by the laser beam 44. Moreover, the use of the water-soluble protective film 13a is not limited to the protection of the surface 1a of the plate-like object 1 from the debris 23.

[0089] For example, the water-soluble protective film 13a may be used as a mask (resist) for etching the plate-like object 1, and in the processing step S30, an etching process may be performed on the plate-like object 1. In other words, in the processing step S30, the water-soluble protective film 13a may be partially removed to partially expose the plate-like object 1 from the water-soluble protective film 13a, and the portion of the plate-like object 1 exposed from the water-soluble protective film 13a may be processed. Fig. 7 is a cross-sectional view that typically shows a plasma processing apparatus 62 in which the processing step S30 according to the modified example is performed.

[0090] The plasma processing apparatus 62 will be described. The plasma processing apparatus 62 includes a chamber 64 in which the plate-like object 1 is housed. The chamber 64 is made of a conductive material such as a metal and is grounded. The inside of the chamber 64 corresponds to a processing space 66 in which the plasma processing of the plate-like object 1 is performed.

[0091] An opening 64a for transporting the plate-like object 1 is provided in the side wall of the chamber 64. A gate (opening / closing door) 68 for opening and closing the opening 64a is provided outside the opening 64a. A moving mechanism (not shown) such as an air cylinder is connected to the gate 68, and the moving mechanism raises and lowers the gate 68 along the side wall of the chamber 64.

[0092] By lowering the gate 68 to expose the opening 64a, it becomes possible to carry the plate-like object 1 into the processing space 66 through the opening 64a, or to carry the plate-like object 1 out of the processing space 66 through the opening 64a. In addition, by raising the gate 68 to close the opening 64a, the processing space 66 is sealed.

[0093] An opening 64b that connects the inside and outside of the chamber 64 is provided in the bottom wall of the chamber 64. The opening 64b is connected to an exhaust device 72 such as a vacuum pump via a pipe 70. When the exhaust device 72 is operated with the processing space 66 sealed, the processing space 66 is exhausted and reduced in pressure.

[0094] A holding table (chuck table) 74 for holding the plate-like object 1 is provided in the processing space 66. The upper surface of the holding table 74 is a flat surface roughly parallel to the horizontal plane, and constitutes a holding surface 74a for holding the plate-like object 1.

[0095] An electrostatic chuck that holds the plate-like object 1 by electric force can be used as the holding table 74. For example, the holding table 74 is made of a dielectric material such as ceramics, and a disk-shaped electrode 76 is provided inside the holding table 74. The electrode 76 is disposed approximately parallel to the holding surface 74a, and is connected to a high-frequency power source 80 via a matching unit 78.

[0096] A cooling path (not shown) through which a cooling liquid such as water flows may be provided inside the holding table 74. The holding table 74 is cooled by causing the cooling liquid to flow through the cooling path and circulating inside the holding table 74.

[0097] A gas ejection head 82 is provided above the holding table 74. The gas ejection head 82 is made of a conductive material such as metal, and is inserted into an opening 64c provided in the upper wall of the chamber 64. An annular bearing 84 made of an insulating material is provided between the chamber 64 and the gas ejection head 82. The bearing 84 is provided so as to surround the gas ejection head 82, and insulates the chamber 64 from the gas ejection head 82.

[0098] The gas ejection head 82 is connected to a high-frequency power supply 88 via a matching device 86. In addition, an elevation mechanism (not shown) that raises and lowers the gas ejection head 82 in the vertical direction is connected to the gas ejection head 82. By raising and lowering the gas ejection head 82 with the elevation mechanism, the distance between the holding table 74 and the gas ejection head 82 is adjusted.

[0099] A gas diffusion space 82a to which gas for plasma processing is supplied is provided inside the gas ejection head 82. A plurality of gas supply paths 82b that connect the processing space 66 and the gas diffusion space 82a are provided on the lower surface side of the gas ejection head 82. A pair of gas supply paths 82c, 82d are provided on the upper surface side of the gas ejection head 82. The gas supply path 82c is connected to a gas supply source 92a via a pipe 90a, and the gas supply path 82d is connected to a gas supply source 92b via a pipe 90b.

[0100] The gas supply source 92a supplies a gas for plasma processing to the gas diffusion space 82a through the pipe 90a and the gas supply path 82c. Similarly, the gas supply source 92b supplies a gas for plasma processing to the gas diffusion space 82a through the pipe 90b and the gas supply path 82d. Then, the two types of gas are mixed in the gas diffusion space 82a. Note that, although FIG. 7 illustrates a configuration in which gas is supplied from two gas supply sources 92a and 92b to the gas ejection head 82, the number of gas supply sources connected to the gas ejection head 82 may be one or three or more.

[0101] When the plate-like object 1 is subjected to plasma treatment (plasma etching) using the plasma treatment device 62, the water-soluble protective film 13a is processed in advance and patterned into a predetermined shape. For example, a laser beam is irradiated onto the water-soluble protective film 13a along the division lines 3 of the plate-like object 1, and the water-soluble protective film 13a is partially removed. Then, the surface 1a of the plate-like object 1 is exposed along the division lines 3.

[0102] When processing step S30 is performed in the plasma processing apparatus 62, first, the gate 68 is lowered to expose the opening 64a. Then, the plate-like object 1 is carried into the processing space 66 through the opening 64a by a transport mechanism (not shown) and placed on the holding surface 74a of the holding table 74. When carrying in the plate-like object 1, it is preferable to raise the gas ejection head 82 and widen the gap between the holding table 74 and the gas ejection head 82.

[0103] Next, the gate 68 rises to close the opening 64a, and the processing space 66 is sealed. Then, a predetermined voltage is applied to the electrode 76 by the high frequency power supply 80. This generates dielectric polarization on the holding surface 74a side of the holding table 74, and an electrostatic adsorption force acts between the holding surface 74a and the plate-like object 1. As a result, the plate-like object 1 is adsorbed and held by the holding surface 74a.

[0104] Also, the height of the gas ejection head 82 is adjusted so that the holding table 74 and the gas ejection head 82 are disposed at a distance suitable for plasma processing. Furthermore, the exhaust device 72 is operated to exhaust the processing space 66 and reduce the pressure.

[0105] Next, gas for plasma processing is supplied from the gas supply source 92a and / or the gas supply source 92b to the gas diffusion space 82a. In addition, high-frequency power is applied to the gas ejection head 82 by the high-frequency power source 88. As a result, the gas in the gas diffusion space 82a is turned into plasma, and the gas in the plasma state is supplied and dispersed into the processing space 66 via the multiple gas supply paths 82b. Then, the gas in the plasma state is supplied to the plate-like object 1 on the holding table 74, and the plate-like object 1 is subjected to a predetermined plasma processing.

[0106] In this case, the surface 1a of the plate-like object 1 is partially protected by the water-soluble protective film 13a, and the gas in a plasma state acts on the plate-like object 1 exposed along the intended division lines 3, etching this portion of the plate-like object 1. That is, the water-soluble protective film 13a functions as a mask (resist) and plasma etching is performed on the plate-like object 1.

[0107] When division grooves 21 are formed along division lines 3 in plate-like object 1 by plasma etching, plate-like object 1 is divided into individual chips 19. This ends processing step S30.

[0108] After the processing step S30 is completed, the water-soluble protective film removing step S40 may be performed. That is, the plate-like object 1 (chip 19) is carried out from the plasma processing device 62 and carried into a cleaning device 46 as shown in Fig. 6, where the plate-like object 1 is washed with a cleaning liquid 60. In this case, the water-soluble protective film 13a is removed from the plate-like object 1 (chip 19) by the cleaning liquid 60.

[0109] In addition, the structures, methods, and the like according to the above-described embodiments and modified examples can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0110] 1 Plate-shaped object 1a surface 1b back side 3. Planned division line 5 Devices 7. Bump 9 Device formation area 11 Surplus outer area 13 Water-soluble resin sheet 13a Water-soluble protective film 15 Tape 17 Frame 19 Chips 21 Dividing groove 23 Debris 12,22 Fixation device 12a Lower body 12b Upper body 14,24 Plate-shaped object support part 14a,24a Support surface 16,18 Exhaust section 16a, 18a Exhaust passage 16b,18b Suction source 16c,18c switching section 20a,20b space 26 Heating section 28 Pressure roller 30 Laser processing equipment 32 Holding Table 34 Clamp 36 Frame 38 Porous Materials 40 Holding surface 42 Laser Processing Unit 44 Laser Beam 46 Cleaning Equipment 48 Spinner Table 50 Clamp 52 Frame 54 Porous Materials 56 Holding surface 58 Cleaning nozzle 60 Cleaning Solution 62 Plasma processing equipment 64 Chamber 64a,64b,64c opening 66 Processing Space 68 Gate 70 Piping 72 Exhaust system 74 Holding Table 74a Holding surface 76 Electrode 78 Matching box 80 High frequency power supply 82 Gas Ejection Head 82a Gas diffusion space 82b, 82c, 82d Gas supply lines 84 Bearings 86 Matching box 88 High frequency power supply 90a, 90b Piping 92a, 92b Gas supply source

Claims

1. A method for forming a water-soluble protective film on a surface of a plate-like object, comprising the steps of: a water-soluble resin sheet disposing step of disposing a water-soluble resin sheet having thermoplasticity on the front surface side of the plate-like object; an integration step of heating the water-soluble resin sheet to melt or soften it, and integrating the water-soluble resin sheet and the plate-like object to form the water-soluble protective film on the plate-like object; A method for forming a water-soluble protective film, comprising:

2. 2. The method for forming a water-soluble protective film according to claim 1, wherein the water-soluble resin sheet contains a light absorbing agent.

3. A method for processing a plate-like object, comprising the steps of: a water-soluble resin sheet disposing step of disposing a water-soluble resin sheet having thermoplasticity on a surface side of the plate-like object; an integration step of heating the water-soluble resin sheet to melt or soften it, and integrating the water-soluble resin sheet and the plate-like object to form a water-soluble protective film on the plate-like object; After carrying out the integration step, a processing step of processing the plate-like object; a water-soluble protective film removing step of removing the water-soluble protective film from the plate-like object by supplying a cleaning liquid to the plate-like object after the processing step is performed; A method for processing a plate-shaped object, comprising:

4. The method for processing a plate-like object according to claim 3, characterized in that in the processing step, a laser beam having a wavelength which is absorbed by the plate-like object is irradiated onto the plate-like object through the water-soluble protective film to process the plate-like object.

5. The method for processing a plate-like object as described in claim 3, characterized in that in the processing step, the water-soluble protective film is partially removed to partially expose the plate-like object from the water-soluble protective film, and the portion of the plate-like object exposed from the water-soluble protective film is processed.

6. 6. The method for processing a plate-like object according to claim 3, wherein the water-soluble resin sheet contains a light absorbing agent.

Images