JP2005279758A - Laser processing protection sheet and production method for laser-processed article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a laser-processed article using a laser processing protection sheet capable of effectively suppressing contamination on a surface of an article to be processed by decomposition products when the article to be processed is processed by UV absorption ablation of a laser beam and capable of enhancing processing accuracy and to provide a laser processing protection sheet used for the production method for the laser-processed article. <P>SOLUTION: The production method for the laser-processed article includes a step of using the laser processing protection sheet having at least an adhesive layer on a base material and having a specific heat ratio of <1 and bonding the adhesive layer of the laser processing protection sheet to a laser beam incident surface side of the article to be processed, a step of processing the laser processing protection sheet and the article to be processed by irradiating the same with the laser beam, and a step of peeling the laser processing protection sheet from the article to be processed after the processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to various workpieces such as sheet materials, circuit boards, semiconductor wafers, glass substrates, ceramic substrates, metal substrates, light emitting or receiving element substrates such as semiconductor lasers, MEMS substrates, semiconductor packages, cloth, leather, or paper. Further, the present invention relates to a method of manufacturing a laser processed product obtained by performing shape processing such as cutting, drilling, marking, grooving, scribing, or trimming by ultraviolet absorption ablation of laser light. Moreover, this invention relates to the protection sheet for laser processing used for the said manufacturing method.

  With the recent miniaturization of electrical and electronic equipment, parts are becoming smaller and higher definition. For this reason, high-definition and high-precision processing with an accuracy of ± 50 μm or less has been demanded for external processing of various materials. However, the conventional punching process such as press working has an accuracy of about ± 100 μm at most, and cannot meet the recent demand for higher precision. Also, high-definition and high-precision are required for drilling various materials, and it has become impossible to perform drilling with conventional drills or dies.

  In recent years, various methods for processing various materials using laser light have attracted attention as a solution. In particular, a processing method by ultraviolet absorption ablation of laser light, which has low thermal damage and enables high-definition processing, has attracted attention as a precise outer shape processing method and a fine drilling method.

  As the above technique, for example, as a method for dicing a workpiece, a method is proposed in which the workpiece is supported and fixed on a dicing sheet and the workpiece is diced with a laser beam (Patent Document 1). A method of dicing a semiconductor wafer by combining a water microjet and a laser has also been proposed (Patent Document 2). The dicing sheet described in the patent document is provided on the laser beam emitting surface side of the workpiece, and is used for supporting and fixing the workpiece (laser processed product) during dicing and in each subsequent process. .

By the way, when laser light is used, decomposition products such as carbon generated during laser processing adhere to the surface of the workpiece, and thus a post-treatment called desmear is necessary to remove it. Since the adhesion strength of the decomposed product becomes stronger in proportion to the power of the laser beam, there is a problem that it becomes difficult to remove the decomposed product in the post-treatment when the power of the laser beam is increased. In addition, in the case of a strong decomposition product, wet desmearing with a potassium permanganate aqueous solution or the like is generally performed, but there is also a problem that wet desmear has a large environmental load due to waste liquid treatment or the like. In particular, the surface side (laser light emitting surface side) of the workpiece that contacts the processing table or the adhesive sheet is not only the decomposed product of the workpiece, but also the processed table or adhesive sheet decomposed product by laser light irradiation. There is a tendency to adhere firmly to the surface. Therefore, there existed a problem that the improvement of the through-put of a process was prevented or the reliability of a cutting | disconnection and drilling was reduced.
JP 2002-343747 A JP 2003-34780 A

  The present invention provides a protective sheet for laser processing capable of effectively suppressing contamination of the surface of a workpiece by a decomposition product and increasing processing accuracy when processing the workpiece by ultraviolet absorption ablation of laser light. An object of the present invention is to provide a method for producing a laser-processed product using the above. Another object of the present invention is to provide a protective sheet for laser processing used in the method for manufacturing a laser processed product.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by a method for producing a laser processed product using the following protective sheet for laser processing (hereinafter also referred to as a protective sheet). The invention has been completed.

  That is, the present invention has at least a pressure-sensitive adhesive layer on the base material, and the specific heat of the base material relative to the specific heat of the workpiece to be used (specific heat ratio = specific heat of the base material of the protective sheet for laser processing / use) Using a protective sheet for laser processing having a specific heat of less than 1), a step of applying an adhesive layer of the protective sheet for laser processing to the laser light incident surface side of the workpiece, The present invention relates to a laser processing product manufacturing method including a step of irradiating and processing a protective sheet for laser processing and a workpiece, and a step of peeling the protective sheet for laser processing from the processed workpiece.

  The protective sheet is laminated on the laser light irradiation surface side (laser light incident surface side) of the work piece before laser processing the work piece by ultraviolet absorption ablation of laser light, and decomposed products and scattering generated by ablation. It is used to protect the workpiece surface from the object.

  As a protective sheet, what has an adhesive layer at least on a base material is used. By imparting adhesiveness to the protective sheet, it is possible to improve the adhesion of the interface between the protective sheet and the workpiece, so that the entry of the decomposed product into the interface can be suppressed, and as a result, It becomes possible to suppress contamination of the workpiece surface.

  In the production method of the present invention, the specific heat of the substrate relative to the specific heat of the workpiece to be used (specific heat ratio = specific heat of the substrate of the protective sheet for laser processing / specific heat of the workpiece to be used) is less than 1. It is necessary to select and use a certain protective sheet. The present inventors have found that there is a correlation between the specific heat of the material and the laser workability, and the smaller the specific heat, the easier the ablation occurs and the higher the laser workability. And it discovered that the contamination of the workpiece surface by a decomposition product can be effectively suppressed by selecting and using the protective sheet whose specific heat ratio is less than 1. The reason why there is a correlation between specific heat and laser processability as described above is not clear. It is thought to occur due to the mechanism of decomposition. When the specific heat of the material is small, the heat is easily absorbed and the temperature is likely to rise, and thermal decomposition is likely to occur, so that the laser processability is considered to be improved.

  The reason why the surface of the workpiece can be effectively suppressed from being decomposed by selecting and using a protective sheet having a specific heat ratio of less than 1 is considered as follows. Since the protective sheet having a specific heat ratio of less than 1 has a laser workability equal to or higher than that of the workpiece, it is etched by laser light simultaneously with the workpiece or prior to the workpiece. Therefore, the decomposition product of the workpiece is efficiently scattered from the etched portion of the protective sheet to the outside, and does not easily enter the interface portion between the protective sheet and the workpiece. As a result, it is considered that contamination of the workpiece surface can be effectively suppressed.

  The specific heat ratio is preferably 0.9 or less, and more preferably 0.8 or less. When the specific heat ratio is 1 or more, the workpiece is etched before the protective sheet is cut or perforated. In that case, there is no scattering path of the decomposition product generated by etching the workpiece, so that the decomposition product may enter the interface portion between the protective sheet and the workpiece and contaminate the workpiece surface. If the workpiece surface is contaminated with decomposition products as described above, it becomes difficult to peel off the protective sheet from the workpiece after laser processing the workpiece, or removal of decomposition products in post-processing is difficult. It tends to be difficult and the processing accuracy of the workpiece tends to decrease.

  In the laser processed product manufacturing method of the present invention, the workpiece is a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser emitting or receiving element substrate, a MEMS substrate, or a semiconductor. A package is preferred. The processing is preferably cutting or drilling.

  The present invention also relates to a protective sheet for laser processing used in the method for manufacturing a laser processed product. The protective sheet is preferably used particularly when a semiconductor chip is manufactured by dicing a semiconductor wafer.

  As the laser used in the present invention, a laser capable of ablation processing by absorbing ultraviolet light is used so as not to deteriorate the accuracy and appearance of the hole edge and the cut wall surface of the workpiece due to thermal damage during laser processing. . In particular, it is preferable to use a laser capable of condensing laser light in a narrow width of 20 μm or less and emitting ultraviolet light of 400 nm or less.

Specifically, a laser having an oscillation wavelength of 400 nm or less, for example, a KrF excimer laser with an oscillation wavelength of 248 nm, an XeCI excimer laser with 308 nm, a third harmonic (355 nm) or a fourth harmonic (266 nm) of a YAG laser, or In the case of a laser having a wavelength of 400 nm or more, a wavelength of 750 to 800 nm that can absorb light in the ultraviolet region through a multiphoton absorption process and can be cut to a width of 20 μm or less by multiphoton absorption ablation. Examples thereof include a laser having a pulse width of 1e- ⁹ seconds (0.000000001 seconds) or less with a nearby titanium sapphire laser or the like.

  The workpiece is not particularly limited as long as it can be processed by ultraviolet absorption ablation of the laser beam output by the laser, and examples thereof include various sheet materials, circuit boards, semiconductor wafers, glass substrates, ceramic substrates. And a light emitting or light receiving element substrate such as a semiconductor substrate, a semiconductor laser, a MEMS (Micro Electro Mechanical System) substrate, a semiconductor package, a metal material, cloth, leather, and paper.

  The manufacturing method of the present invention can be suitably used particularly for processing a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser light emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. .

  Examples of the various sheet materials include polyimide resins, polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, polycarbonate resins, silicone resins, and fluorine resins. Polymer films and nonwoven fabrics composed of, etc., sheets obtained by stretching or impregnating those resins with physical or optical functions, metal sheets such as copper, aluminum, stainless steel, or the above polymer films and / or Examples include a metal sheet laminated directly or via an adhesive.

  Examples of the circuit board include a single-sided, double-sided or multilayer flexible printed board, a rigid board made of glass epoxy, ceramic, or metal core board, an optical circuit formed on glass or polymer, or an opto-electric hybrid circuit board. It is done.

  Examples of the metal material include metalloids and alloys, such as gold, SUS, copper, iron, aluminum, stainless steel, silicon, titanium, nickel, and tungsten.

In the method for producing a laser processed product of the present invention, a protective sheet having at least an adhesive layer on a substrate is used. And it is necessary to select and use the protective sheet whose specific heat ratio is less than 1.

  Examples of the material for forming the base material include polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyimide, (meth) acrylic polymer, polyurethane, silicone rubber, and polyolefin polymer such as polyethylene, polypropylene, and polyethylene oxide. However, it is not limited to these. Among these, materials having a relatively small specific heat include polyethylene terephthalate, polyethylene naphthalate, polystyrene, polyurethane, and polycarbonate.

  The substrate may be a single layer or a multilayer. Moreover, various shapes, such as a film | membrane form and a mesh form, can be taken.

  The thickness of the base material is appropriately adjusted within a range that does not impair the operability and workability in each process such as bonding onto the work piece, cutting and punching of the work piece, and peeling and recovery of the cut piece. However, it is usually 500 μm or less, preferably about 3 to 300 μm, and more preferably 5 to 250 μm. The surface of the substrate is chemically treated by conventional surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric impact exposure, and ionizing radiation treatment to improve adhesion to the adhesive layer, retention, etc. Alternatively, physical treatment may be performed.

  As a material for forming the pressure-sensitive adhesive layer, known pressure-sensitive adhesives including (meth) acrylic polymers and rubber-based polymers can be used.

  Examples of the monomer component forming the (meth) acrylic polymer include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, and a hexyl group. Group, heptyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, and Examples thereof include alkyl (meth) acrylates having a linear or branched alkyl group having 30 or less carbon atoms, preferably 4 to 18 carbon atoms, such as a dodecyl group. These alkyl (meth) acrylates may be used alone or in combination of two or more.

  For the purpose of modifying the adhesiveness, cohesive strength, heat resistance, etc. of the (meth) acrylic polymer, monomer components other than those described above may be copolymerized. Examples of such monomer components include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid-containing monomers, anhydrous Acid anhydride monomers such as maleic acid and itaconic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6- (meth) acrylic acid Hydroxyl groups such as hydroxyhexyl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate Contains Nomers, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalene sulfonic acid Sulfonic acid group-containing monomers, phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate, (meth) acrylamide, (meth) acrylic acid N-hydroxymethylamide, (meth) acrylic acid alkylaminoalkyl esters (for example, dimethylamino) Ethyl methacrylate, t-butylaminoethyl methacrylate, etc.), N-vinylpyrrolidone, acryloylmorpholine, vinyl acetate, styrene, and acrylonitrile. These monomer components may be used alone or in combination of two or more.

  Moreover, a polyfunctional monomer etc. can also be used as a copolymerization monomer component as needed for the purpose of a crosslinking treatment of a (meth) acrylic polymer.

  Examples of polyfunctional monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and pentaerythritol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and urethane (meth) acrylate Etc., and the like. These polyfunctional monomers may be used individually by 1 type, and may use 2 or more types together.

  The amount of the polyfunctional monomer used is preferably 30% by weight or less, more preferably 20% by weight or less of the total monomer components from the viewpoint of adhesive properties and the like.

  For the preparation of the (meth) acrylic polymer, an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method is applied to a mixture containing one or more monomer components. It can be carried out.

  Examples of the polymerization initiator include peroxides such as hydrogen peroxide, benzoyl peroxide, and t-butyl peroxide. Although it is desirable to use it alone, it can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent include ionized salts such as sulfites, hydrogen sulfites, iron, copper, and cobalt salts, amines such as triethanolamine, and reducing sugars such as aldose and ketose. Azo compounds are also preferred polymerization initiators, and are 2,2′-azobis-2-methylpropioamidine, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis- Use N, N'-dimethyleneisobutylaminate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methyl-N- (2-hydroxyethyl) propionamide, etc. Can do. It is also possible to use two or more of the above polymerization initiators in combination.

  The reaction temperature is usually about 50 to 85 ° C., and the reaction time is about 1 to 8 hours. Among the production methods, a solution polymerization method is preferable, and a polar solvent such as ethyl acetate or toluene is generally used as a solvent for the (meth) acrylic polymer. The solution concentration is usually about 20 to 80% by weight.

  In order to increase the number average molecular weight of the (meth) acrylic polymer that is the base polymer, a crosslinking agent can be appropriately added to the pressure-sensitive adhesive. Examples of the crosslinking agent include polyisocyanate compounds, epoxy compounds, aziridine compounds, melamine resins, urea resins, anhydrous compounds, polyamines, and carboxyl group-containing polymers. In the case of using a crosslinking agent, the amount used is considered to be about 0.01 to 5 parts by weight with respect to 100 parts by weight of the base polymer, considering that the peeling adhesive strength does not decrease too much. Is preferred. In addition to the above-described components, the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer may include conventional additives such as various conventionally known tackifiers, anti-aging agents, fillers, anti-aging agents, and coloring agents. It can be included.

  In order to improve the peelability from the workpiece, the pressure-sensitive adhesive is preferably a radiation-curable pressure-sensitive adhesive that is cured by radiation such as ultraviolet rays or electron beams. In addition, when using a radiation curing type adhesive as an adhesive, since the radiation is irradiated to an adhesive layer after a laser processing, the said base material has sufficient radiolucency.

  Examples of the radiation curable pressure-sensitive adhesive include a radiation curable pressure-sensitive adhesive obtained by blending the aforementioned (meth) acrylic polymer with a radiation curable monomer component or oligomer component.

  Examples of the radiation-curable monomer component and oligomer component to be blended include urethane (meth) acrylate oligomer, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, tetraethylene glycol di (meth) acrylate, Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, and 1 Ester compounds composed of (meth) acrylic acid and polyhydric alcohol, such as 1,6-hexanediol di (meth) acrylate, 2-propenyl-3-butenyl isocyanurate DOO, and tris (2-methacryloxyethyl) include isocyanurate compounds such as isocyanurates. These may be used alone or in combination of two or more.

  The blending amount of the radiation curable monomer component or oligomer component is not particularly limited, but in consideration of the tackiness, it is based on 100 parts by weight of the base polymer such as a (meth) acrylic polymer constituting the pressure sensitive adhesive. The amount is preferably about 5 to 500 parts by weight, and more preferably about 70 to 150 parts by weight.

  Moreover, as a radiation curable adhesive, what has a carbon-carbon double bond in a polymer side chain or a principal chain, or the principal chain terminal can also be used as a base polymer. As such a base polymer, a polymer having a (meth) acrylic polymer as a basic skeleton is preferable. In this case, it is not necessary to add a radiation curable monomer component or oligomer component, and its use is optional.

  The radiation curable pressure-sensitive adhesive contains a photopolymerization initiator when cured by ultraviolet rays or the like. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α-methylacetophenone, methoxyacetophenone, and 2,2-dimethoxy-2-phenyl. Acetophenone compounds such as acetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1, benzoin ethyl ether, benzoin isopropyl Benzoin ether compounds such as ether and anisoin methyl ether, α-ketol compounds such as 2-methyl-2-hydroxypropylphenone, ketal compounds such as benzyldimethyl ketal, 2-naphthalenesulfonyl chloride Aromatic sulfonyl chloride compounds such as Lido, photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl Benzophenone compounds such as -4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2 Thioxanthone compounds such as 1,4-diethylthioxanthone and 2,4-diisopropylthioxanthone, camphorquinone, halogenated ketone, acyl phosphinoxide and acyl phosphonate.

  The blending amount of the photopolymerization initiator is preferably about 0.1 to 10 parts by weight with respect to 100 parts by weight of the base polymer such as a (meth) acrylic polymer constituting the pressure-sensitive adhesive, and more preferably is about 0.1. About 5 to 5 parts by weight.

  The said protective sheet can be manufactured by apply | coating an adhesive solution to the surface of a base material, and making it dry (it heat-crosslinks as needed), and forms an adhesive layer. Moreover, after forming an adhesive layer in a release liner separately, the method of bonding it to a base material etc. are employable. The pressure-sensitive adhesive layer may be a single layer or two or more layers. If necessary, a separator may be provided on the surface of the pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer preferably has a low content of low molecular weight substances from the viewpoint of preventing contamination of the workpiece. From this point, the number average molecular weight of the (meth) acrylic polymer is preferably 500,000 or more, more preferably 800,000 to 3,000,000.

  Although the thickness of an adhesive layer can be suitably selected in the range which does not peel from a to-be-processed object, it is preferable that it is about 5-300 micrometers, More preferably, it is about 10-100 micrometers, Especially preferably, it is about 10-50 micrometers.

  Further, the adhesive strength of the pressure-sensitive adhesive layer is preferably 20 N / 20 mm or less, more preferably based on the adhesive strength (90-degree peel value, peeling speed 300 mm / min) at normal temperature (before laser irradiation) to SUS304. 0.001 to 10 N / 20 mm, particularly preferably 0.01 to 8 N / 20 mm.

  The said separator is provided as needed in order to protect a label process or an adhesive layer. Examples of the constituent material of the separator include paper, polyethylene, polypropylene, and synthetic resin films such as polyethylene terephthalate. The surface of the separator may be subjected to release treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc., as necessary, in order to enhance the peelability from the pressure-sensitive adhesive layer. Further, if necessary, an ultraviolet transmission preventing treatment or the like may be performed so that the protective sheet does not react with environmental ultraviolet rays. The thickness of a separator is 10-200 micrometers normally, Preferably it is about 25-100 micrometers.

  Hereinafter, a method for producing a laser processed product by ultraviolet absorption ablation of laser light using a protective sheet having a specific heat ratio of less than 1 will be described. For example, in the case of cutting processing, as shown in FIGS. 1 and 3, the protective sheet 2, the workpiece 1, and the adhesive sheet 3 are bonded together by a known means such as a roll laminator or a press. The object-adhesive sheet laminate 4 is arranged on the suction plate 6 of the suction stage 5, and the laser beam 7 output from a predetermined laser oscillator is condensed on the laminate 4 by the lens on the protective sheet 2. While irradiating, cutting processing is performed by moving the laser irradiation position along a predetermined processing line. The pressure-sensitive adhesive sheet 3 provided on the laser beam emitting surface side of the workpiece plays a role of supporting and fixing the workpiece before laser processing, and plays a role of preventing the cut material from falling after the laser processing. A sheet with low laser processability is used. As the pressure-sensitive adhesive sheet 3, a general sheet in which a pressure-sensitive adhesive layer is laminated on a substrate can be used without particular limitation.

  As the laser beam moving means, a known laser processing method such as a galvano scan, an XY stage scan, or a mask imaging process is used.

  The laser processing conditions are not particularly limited as long as the protective sheet 2 and the workpiece 1 are completely cut, but the workpiece 1 is cut in order to avoid cutting up to the adhesive sheet 3. It is preferable to be within twice the energy condition.

In addition, the cutting margin (cutting groove) can be narrowed by narrowing the beam diameter of the laser beam condensing part.
It is preferable that the beam diameter (μm)> 2 × (laser beam moving speed (μm / sec) / laser beam repetition frequency (Hz)) is satisfied.

  Further, in the case of drilling, as shown in FIG. 2, a protective sheet obtained by bonding the protective sheet 2, the workpiece 1 and the adhesive sheet 3 by a known means such as a roll laminator or a press-workpiece- The pressure-sensitive adhesive sheet laminate 4 is disposed on the suction plate 6 of the suction stage 5, and laser light 7 output from a predetermined laser oscillator is condensed and irradiated on the protective sheet 2 by a lens on the laminate 4. To form holes.

  The hole is formed by a known laser processing method such as galvano scan, XY stage scan, or punching by mask imaging. The optimum laser processing condition may be determined based on the ablation threshold of the material to be processed. In order to avoid punching up to the pressure-sensitive adhesive sheet 3, it is preferable that the workpiece 1 is within twice the energy condition for punching.

  Further, by blowing a gas such as helium, nitrogen, oxygen, or the like onto the laser processing portion, it is possible to improve the efficiency of removing the decomposition products.

  Further, the semiconductor wafer (silicon wafer) is cut by bonding one side of the semiconductor wafer 8 to the adhesive sheet 3 provided on the suction stage 5 as shown in FIG. 4, and further installing the protective sheet 2 on the other side. Laser light 7 output from a predetermined laser oscillator is condensed and irradiated onto the protective sheet 2 by a lens, and cutting processing is performed by moving the laser irradiation position along a predetermined processing line. As a laser beam moving means, a known laser processing method such as galvano scan, XY stage scan, mask, or imaging processing is used. The cutting conditions of the semiconductor wafer are not particularly limited as long as the protective sheet 2 and the semiconductor wafer 8 are cut and the adhesive sheet 3 is not cut.

  In such a semiconductor wafer cutting process, after cutting into individual semiconductor chips, a method of picking up using a push-up pin called a needle by a conventionally known device such as a die bonder, or JP-A-2001-118862. Individual semiconductor chips can be picked up and collected by a known method such as the method shown.

  In the laser processed product manufacturing method of the present invention, the protective sheet 2 is peeled from the laser processed product 10 after the laser processing is completed. The method of peeling is not limited, but it is important to prevent the laser-processed product 10 from undergoing stress that causes permanent deformation during peeling. For example, when a radiation curable pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is cured by irradiation with radiation according to the type of the pressure-sensitive adhesive, thereby reducing the adhesiveness. By the irradiation of radiation, the adhesiveness of the pressure-sensitive adhesive layer is reduced by curing, and peeling can be facilitated. The means for radiation irradiation is not particularly limited. For example, the irradiation is performed by ultraviolet irradiation.

  In the manufacturing method of the laser processed product of the present invention, since the protective sheet having a specific heat ratio of less than 1 is used, the protective sheet is more easily etched than the workpiece, and the laser light irradiation portion of the protective sheet is sufficient. After being etched, the lower workpiece is etched. Therefore, the decomposition product of the workpiece is efficiently scattered from the etched portion of the protective sheet to the outside, so that contamination of the interface portion between the protective sheet and the workpiece can be suppressed. Therefore, according to the above manufacturing method, the decomposed material does not adhere to the interface portion between the protective sheet and the workpiece (laser processed product), so the protective sheet can be easily removed from the laser processed product after laser processing the workpiece. Can be peeled off, and the laser processing accuracy of the workpiece can be improved.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Measurement of number average molecular weight)
The number average molecular weight of the synthesized (meth) acrylic polymer was measured by the following method. The synthesized (meth) acrylic polymer was dissolved in THF at 0.1 wt%, and the number average molecular weight was measured by polystyrene conversion using GPC (gel permeation chromatography). Detailed measurement conditions are as follows.
GPC device: Tosoh HLC-8120GPC
Column: manufactured by Tosoh Corporation, (GMHHR-H) + (GMHHR-H) + (G2000HHR)
Flow rate: 0.8ml / min
Concentration: 0.1 wt%
Injection volume: 100 μl
Column temperature: 40 ° C
Eluent: THF

[Specific heat measurement]
The specific heat of the base material and workpiece used for a protective sheet was measured using the thermal analysis system (the Seiko Instruments make, DSC EXSTAR6000). Measurement was performed at a temperature rising rate of 10 ° C./min, and three DSC curves of an empty container, a sample, and a reference (water) were obtained. And the specific heat was calculated | required by the following formula.
Cps = (Ys / Yr) × (Mr / Ms) × Cpr
Cps: specific heat of the sample Cpr: specific heat of the reference (water: 4.2 J / (g · K))
Ys: DSC curve difference between sample and empty container Yr: DSC curve difference between reference and empty container Ms: Mass of sample Mr: Mass of reference

Example 1
A polyimide sheet (thickness: 100 μm, specific heat: 1.1 J / (g · K)) was used as a workpiece. An acrylic pressure-sensitive adhesive solution (1) curable by ultraviolet rays is applied on a base material (thickness 50 μm, specific heat 0.75 J / (g · K)) made of polyethylene naphthalate so that the specific heat ratio is less than 1. Application and drying were carried out to form a pressure-sensitive adhesive layer (thickness: 10 μm) to prepare a protective sheet. The specific heat ratio was 0.68.

  The acrylic pressure-sensitive adhesive solution (1) was prepared by the following method. 100 parts by weight of an acrylic polymer having a number average molecular weight of 700,000 obtained by copolymerizing butyl acrylate / ethyl acrylate / 2-hydroxyethyl acrylate / acrylic acid at a weight ratio of 65/35/4/1, dipenta as a photopolymerizable compound Add 90 parts by weight of erythritol monohydroxypentaacrylate, 5 parts by weight of benzyldimethyl ketal (Irgacure 651) as a photopolymerization initiator, and 2 parts by weight of a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) to 650 parts by weight of toluene. Acrylic pressure-sensitive adhesive solution (1) was prepared by dissolving in

  The prepared protective sheet was bonded to one side of the polyimide sheet with a roll laminator to prepare a polyimide sheet with a protective sheet.

  And the polyimide sheet with a protective sheet was arrange | positioned on the XY stage on which the adsorption board made from a glass epoxy resin was put. A third harmonic (355 nm) of a YAG laser having a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is condensed to a diameter of 25 μm on the surface of the polyimide sheet with a protective sheet by an fθ lens, and the laser light is 20 mm / second by a galvano scanner. Scanned at speed and cut. At this time, it was confirmed that the protective sheet and the polyimide sheet were cut. And the ultraviolet-ray was irradiated to the protective sheet, and the adhesive layer was hardened. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser light incident surface side) of the polyimide sheet was observed, no decomposition product (adhered matter) was observed.

Comparative Example 1
In Example 1, laser processing was performed on the polyimide sheet in the same manner as in Example 1 except that the protective sheet was not provided on one side of the polyimide sheet. Then, when the processing periphery part of the laser beam incident surface side of a polyimide sheet was observed, the scattered decomposition residue residue adhered in large quantities.

Comparative Example 2
In Example 1, a polyimide sheet was prepared in the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer sheet (thickness: 100 μm, specific heat: 2.2 J / (g · K)) was used as the base material of the protective sheet. Was laser processed. The specific heat ratio was 2.0.

  As a result, the protective sheet was not cut, the lower polyimide sheet was laser processed, and bubbles containing decomposition product residues were generated between the protective sheet and the polyimide sheet. And the ultraviolet-ray was irradiated to the protective sheet, and the adhesive layer was hardened. Thereafter, when the protective sheet was peeled off and the periphery of the opening on the laser light incident surface side of the polyimide sheet was observed, a large amount of polyimide decomposition product residue was adhered.

Example 2
A silicon wafer with a protective sheet was produced in the same manner as in Example 1 except that a silicon wafer (thickness: 100 μm, specific heat: 0.77 J / (g · K)) was used as the workpiece. The specific heat ratio was 0.97.

  Moreover, the said acrylic adhesive solution (1) was apply | coated and dried on the base material (100 micrometers in thickness) which consists of polyethylene, and the adhesive layer (10 micrometers in thickness) was formed, and the adhesive sheet was manufactured. The pressure-sensitive adhesive sheet was affixed to the back side of the silicon wafer with a protective sheet to produce a silicon wafer with a protective / pressure-sensitive adhesive sheet. Then, when it cut by the method similar to Example 1, the protective sheet and the silicon wafer were cut | disconnected, but the adhesive sheet was not cut | disconnected. And the ultraviolet-ray was irradiated to the protective sheet, and the adhesive layer was hardened. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser beam incident surface side) of the silicon wafer was observed, no decomposition product (adhered matter) was observed.

Example 3
The protective / adhesive sheet was prepared in the same manner as in Example 2 except that a polyurethane sheet (thickness 25 μm, 0.48 J / (g · K)) was used as the base material of the protective sheet so that the specific heat ratio was less than 1. An attached silicon wafer was prepared. The specific heat ratio was 0.62. Then, when it cut by the method similar to Example 1, the protective sheet and the silicon wafer were cut | disconnected, but the adhesive sheet was not cut | disconnected. And the ultraviolet-ray was irradiated to the protective sheet, and the adhesive layer was hardened. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser beam incident surface side) of the silicon wafer was observed, no decomposition product (adhered matter) was observed.

  As is clear from the above examples and comparative examples, the use of a protective sheet having a specific heat ratio of less than 1 can effectively suppress contamination of the surface of the workpiece due to the decomposition product. And since the decomposition product removal process after that can be simplified greatly, it not only can contribute to environmental load reduction but can also aim at the improvement of productivity.

It is a schematic process drawing which shows the example of the manufacturing method of the laser processed product in this invention. It is a schematic process drawing which shows the other example of the manufacturing method of the laser processed product in this invention. It is the schematic which shows the cross section of the laminated body processed by the ultraviolet absorption ablation of a laser beam. It is the schematic which shows the example of the dicing method of a semiconductor wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Protection sheet for laser processing 3 Adhesive sheet 4 Laminate 5 Adsorption stage 6 Adsorption plate 7 Laser light 8 Semiconductor wafer 9 Dicing frame 10 Laser processed product

Claims (4)

Specific heat of the base material with respect to the specific heat of the work piece to be used (specific heat ratio = specific heat of the base material of the protective sheet for laser processing / specific heat of the work piece to be used) having at least an adhesive layer on the base material ) Is less than 1 and uses a protective sheet for laser processing, a step of applying an adhesive layer of the protective sheet for laser processing on the laser light incident surface side of the workpiece, for laser processing by irradiating laser light A method for manufacturing a laser processed product, comprising: a step of processing a protective sheet and a workpiece; and a step of peeling the protective sheet for laser processing from the processed workpiece. 2. The laser processed product according to claim 1, wherein the workpiece is a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser light emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. Production method. The method for manufacturing a laser processed product according to claim 1, wherein the processing is cutting or drilling. The protective sheet for laser processing used for the manufacturing method of the laser processed product in any one of Claims 1-3.

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