JP2006160993A - Protective sheet for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective sheet for laser beam machining, enabling a workpiece to be processed in high precision/high accuracy when the workpiece is processed by multiphoton absorption abrasion of a laser beam, and capable of effectively reducing the staining of the surface of the workpiece by a decomposition product; and to provide a method for producing a laser beam-machined product by using the protective sheet for the laser beam machining. <P>SOLUTION: The protective sheet for the laser beam machining, used when processing the workpiece by the multiphoton absorption abrasion of the laser beam has at least a base material the etching rate (etching speed/energy fluence) of which is ≥0.4 [(μm/pulse)/(J/cm<SP>2</SP>)] when the base material is irradiated with ultrashort pulse laser beam having ≤10<SP>-12</SP>sec pulse width. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a protective sheet for laser processing used when processing a workpiece by multiphoton absorption ablation of laser light. In addition, the present invention is applicable to various processing 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. The present invention relates to a method for manufacturing a laser processed product obtained by subjecting an object to shape processing such as cutting, drilling, marking, grooving, scribing, or trimming by multiphoton absorption ablation of laser light.

  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. 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.
JP 2002-343747 A JP 2003-34780 A

  The present invention provides a laser capable of processing a workpiece with high definition and high accuracy and effectively suppressing contamination of the workpiece surface due to a decomposition product when processing the workpiece by multiphoton absorption ablation of laser light. An object is to provide a protective sheet for processing. It is another object of the present invention to provide a method for producing a laser processed product using the laser processing protective sheet.

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

That is, a laser processing protective sheet used when processing a workpiece by multiphoton absorption ablation of laser light, the protective sheet having at least a base material, and the base material is a pulse The etching rate (etching rate / energy fluence) when irradiated with an ultrashort pulse laser beam having a width of 10 ⁻¹² seconds or less is 0.4 [(μm / pulse) / (J / cm ² )] or more. The present invention relates to a protective sheet for laser processing.

The protective sheet is laminated on the laser beam irradiation surface side (laser beam incident surface side) of the workpiece before laser processing the workpiece by multiphoton absorption ablation of laser beam, It is used to protect the workpiece surface from scattered objects. The etching rate which is a value obtained by dividing the etching rate (μm / pulse) of the substrate by the energy fluence (J / cm ² ) of the laser used indicates the degree of laser processability of the substrate. It shows that it is easy to etch, so that a rate is large. The calculation method of the etching rate is described in detail in the examples.

  In the present invention, by using a protective sheet having a substrate etching rate of 0.4 or more, contamination of the surface of the workpiece by the decomposed product can be effectively suppressed. The reason is considered as follows. When the etching rate of the base material is 0.4 or more, since the laser energy utilization efficiency of the base material is large, the base material is etched by the ultrashort pulse laser beam before the workpiece. The underlying workpiece is etched after the laser irradiation part of the protective sheet is etched, but the decomposed material of the workpiece is efficiently scattered outside from the etched portion of the protective sheet. It becomes difficult to enter the interface with the workpiece, and as a result, contamination of the workpiece surface can be suppressed.

  The etching rate of the substrate is preferably 0.5 or more, and more preferably 0.7 or more. When the etching rate is less than 0.4, the energy transfer to the workpiece, which is a light energy absorber, increases, and the substrate is transmitted through the protective sheet before it is sufficiently etched by the ultrashort pulse laser beam. The workpiece is etched by the laser beam. In such a case, there is no scattering path for 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.

  It is preferable that the said protective sheet is what is provided with the adhesive layer on the base material. 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 this invention, it is preferable that the said base material contains an aromatic polymer or silicone rubber. By using an aromatic polymer or silicon rubber as the base material forming material, it becomes easy to adjust the etching rate of the base material to 0.4 or more.

The present invention provides the step (1) of installing the protective sheet for laser processing according to any one of claims 1 to 4 on the laser beam incident surface side of the workpiece, and an ultrashort pulse having a pulse width of 10 ⁻¹² seconds or less. A process for producing a laser-processed product comprising a step (2) of processing a protective sheet for laser processing and a workpiece by irradiating a laser beam, and a step (3) of peeling the protective sheet for laser processing from the processed workpiece. , Regarding.

  The workpiece is preferably 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. Moreover, it is preferable that the said process is a process which cuts or drills a to-be-processed object.

  The protective sheet of the present invention is preferably used particularly when a semiconductor chip is produced by dicing a semiconductor wafer.

  The laser used in the present invention is non-thermal processing that does not go through a thermal processing process in order not to deteriorate the precision and appearance of the hole edge and the cutting wall surface of the workpiece due to thermal damage during laser processing. An ultrashort pulse laser that can be ablated by multiphoton absorption and can be focused to a narrow width of 20 μm or less is used.

Examples of the ultrashort pulse laser include a laser using a titanium / sapphire crystal as a medium, and a femtosecond pulse laser obtained by reproducing and amplifying a dye laser. The pulse width of the ultrashort pulse laser to be used is 10 ⁻¹² seconds or less, preferably 10 ⁻¹² to 10 ⁻¹⁵ seconds. Usually, about ^10-13 seconds are used. The used wavelength is about 200 to 800 nm, and the repetition frequency is about 1 Hz to 80 MHz, preferably 10 Hz to 500 kHz. The output of the laser pulse is about several mW to several hundred mW. The irradiation energy of the ultrashort pulse laser is determined in accordance with the numerical aperture of the objective lens used when irradiating the material (the narrowing of the light source), the moving speed of the laser focus, and the like.

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

  The protective sheet 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 imparted with physical or optical functions by stretching or impregnating those resins, 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.

The protective sheet of the present invention is a sheet used when a workpiece is processed by multiphoton absorption ablation of laser light. The protective sheet has at least a base material, and the base material has an etching rate of 0.4 or more when irradiated with an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less.

  Examples of the base material forming 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. Although it is mentioned, it is not limited to these. Among these, it is preferable to use an aromatic polymer, and it is particularly preferable to use polyimide, polyethylene terephthalate, polystyrene, or polycarbonate. It is also preferable to use silicon rubber.

  It is preferable to add a filler to the substrate. The filler is a material added to increase the etching rate to 0.4 or more. For example, pigments, dyes, dyes, fine metal particles such as Au, Cu, Pt, and Ag, and inorganic metals such as metal colloids and carbon. Examples include fine particles.

  The dye only needs to absorb light having a specific wavelength of the laser to be used. As the dye, various dyes such as a basic dye, an acid dye, and a direct dye can be used. Examples of the dye or pigment include nitro dye, nitroso dye, stilbene dye, pyrazolone dye, thiazole dye, azo dye, polyazo dye, carbonium dye, quinoanyl dye, indophenol dye, indoaniline dye, indamine dye, quinoneimine dye, Azine dye, oxidation dye, oxazine dye, thiazine dye, acridine dye, diphenylmethane dye, triphenylmethane dye, xanthene dye, thioxanthene dye, sulfur dye, pyridine dye, pyridone dye, thiadiazole dye, thiophene dye, benzoisothiazole dye, Dicyanoimidazole dye, benzopyran dye, benzodifuranone dye, quinoline dye, indigo dye, thioindigo dye, anthraquinone dye, benzophenone dye, benzoquinone dye, naphtho Examples include quinone dyes, phthalocyanine dyes, cyanine dyes, methine dyes, polymethine dyes, azomethine dyes, condensed methine dyes, naphthalimide dyes, perinone dyes, triarylmethane dyes, xanthene dyes, aminoketone dyes, oxyketone dyes, and indigoid dyes. . These may be used alone or in combination of two or more.

  The dye or pigment may be a nonlinear optical pigment. The nonlinear optical dye is not particularly limited, and is a known nonlinear optical dye (for example, benzene-based nonlinear optical dye, stilbene-based nonlinear optical dye, cyanine-based nonlinear optical dye, azo-based nonlinear optical dye, rhodamine-based nonlinear optical dye, biphenyl). Non-linear optical dyes, chalcone non-linear optical dyes, and cyanocinnamic acid non-linear optical dyes).

  Furthermore, as the dye or pigment, a so-called “functional pigment” can also be used. The functional dye is composed of, for example, a carrier generating material and a carrier transfer material. Examples of the carrier generating material include perylene pigments, quinone pigments, squarylium dyes, azurenium dyes, thiapyrylium dyes, bisazo pigments, and the like. Examples of the carrier transfer material include oxadiazole derivatives, oxazole derivatives, pyrazoline derivatives, hydrazone derivatives, and arylamine derivatives.

  The amount of the filler added can be appropriately adjusted depending on the etching rate of the base polymer itself to be used, but is usually about 3 parts by weight, preferably about 2 parts by weight with respect to 100 parts by weight of the base polymer. .

  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 with 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 for 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.

  Other monomer components include, for example, 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 Examples thereof include sulfonic acid group-containing monomers and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. 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. These are preferably used alone, but 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.

  As the radiation curable pressure-sensitive adhesive, those having a radiation curable functional group such as a carbon-carbon double bond and exhibiting adhesiveness can be used without particular limitation. 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, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol. Examples include tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and 1,4-butylene glycol di (meth) acrylate. 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, more preferably about 0.1 to 10 parts by weight with respect to 100 parts by weight of the base polymer such as (meth) acrylic polymer constituting the pressure-sensitive adhesive. About 5 to 5 parts by weight.

  The protective sheet of the present invention can be produced, for example, by applying a pressure-sensitive adhesive solution to the surface of a substrate and drying (by heat-crosslinking as necessary) to form a pressure-sensitive 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. 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 300,000 or more, more preferably 400,000 to 3,000,000.

  Although the thickness of an adhesive layer can be suitably selected in the range which does not peel from a workpiece, it is about 5-300 micrometers normally, Preferably it is about 10-100 micrometers, More preferably, it is about 20-50 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 multiphoton absorption ablation of laser light using the protective sheet of the present invention 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 prevents the fall of the cut material after 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 condensing part of the laser beam.
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.

  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 is cut by bonding one surface of the semiconductor wafer 8 to the adhesive sheet 3 provided on the suction stage 5 as shown in FIG. 4 and further providing the protective sheet 2 on the other surface side to obtain a predetermined laser oscillator. The laser beam 7 output from the laser beam is condensed and irradiated on the protective sheet 2 by a lens, and the laser irradiation position is moved along a predetermined processing line to perform cutting processing. 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 processing conditions for 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 Japanese Patent Application Laid-Open No. 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 an etching rate of 0.4 or more is used, the protective sheet is easily etched by the laser beam before the workpiece, and the protective sheet After the laser beam irradiating part is sufficiently etched, the work piece in the lower layer 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 decomposition product does not adhere to the interface portion between the protective sheet and the workpiece (laser processed product), so that the protective sheet can be easily removed from the laser processed product after laser processing the workpiece. It can be peeled off and the laser processing accuracy of the workpiece can be improved. In addition, throughput can be improved by increasing the power of the laser. Furthermore, since an ultrashort pulse laser can be used, a workpiece can be processed with high definition and high accuracy.

  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

[Measurement of etching rate]
A titanium / sapphire pulse laser (wavelength 780 nm, pulse width 140 femtoseconds, repetition frequency 1 kHz, irradiation energy 7 mW) is focused by an fθ lens at a magnification of 10 times the objective lens, and the substrate is used under the condition of a pulse number of 5 (pulse) Irradiated the surface. After irradiation, the depth (μm) of the holes formed in the substrate was measured with an optical microscope. The etching rate is calculated by the following formula.
Etching rate = hole depth (μm) / number of pulses (pulse)
The energy fluence of the titanium / sapphire pulse laser was 2 (J / cm ² ). The etching rate is calculated by the following formula from the etching rate and the energy fluence.
Etching rate = etching rate (μm / pulse) / energy fluence (J / cm ² )

Example 1
On a base material made of polystyrene (thickness 20 μm, etching rate: 0.59), an acrylic pressure-sensitive adhesive solution (1) curable by ultraviolet rays is applied and dried to form a pressure-sensitive adhesive layer (thickness 10 μm). A protective sheet was obtained.

  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 900,000 obtained by copolymerizing butyl acrylate / acrylic acid at a weight ratio of 60/1, 90 parts by weight of dipentaerythritol monohydroxypentaacrylate as a photopolymerizable compound, and initiation of photopolymerization As an agent, 5 parts by weight of benzyldimethyl ketal (Irgacure 651) was added to 650 parts by weight of toluene, and uniformly dissolved and mixed to prepare an acrylic pressure-sensitive adhesive solution (1).

  The protective sheet prepared above was bonded to one side of a 100 μm thick silicon wafer with a roll laminator to prepare a silicon wafer with a protective sheet. And the silicon wafer with a protection sheet was arrange | positioned on the XY stage on which the adsorption board made from glass epoxy resin was put. A titanium / sapphire pulse laser (wavelength 780 nm, pulse width 140 femtoseconds, repetition frequency 1 kHz, irradiation energy 7 mW) is focused on a silicon wafer surface with a protective sheet to a diameter of 25 μm by an fθ lens, and laser light is emitted by a galvano scanner at 20 mm / mm. Scanned and cut at a rate of seconds. At this time, it was confirmed that the protective sheet and the silicon wafer were cut. 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.

Comparative Example 1
In Example 1, laser processing was performed on the silicon wafer in the same manner as in Example 1 except that the protective sheet was not provided on one side of the silicon wafer. Thereafter, when the processing peripheral portion on the laser light incident surface side of the silicon wafer was observed, a large amount of scattered decomposition residue adhered.

Comparative Example 2
In Example 1, laser processing was performed on the silicon wafer by the same method as in Example 1 except that a polyvinyl alcohol sheet (thickness: 100 μm, etching rate: 0) was used as the base material of the protective sheet. As a result, the protective sheet was not cut, the lower silicon wafer was laser processed, and bubbles containing decomposition product residues were generated between the protective sheet and the silicon wafer. When the protective sheet was peeled off and the periphery of the opening on the laser light incident surface side of the silicon wafer was observed, a large amount of decomposition residue of the silicon wafer adhered.

Example 2
The acrylic pressure-sensitive adhesive solution (1) is applied on a base material made of silicon rubber sheet (thickness 20 μm, etching rate: 0.48) and dried to form a pressure-sensitive adhesive layer (thickness 10 μm) for protection. A sheet was obtained.

  A circuit was formed on a two-layer substrate in which a copper layer having a thickness of 18 μm was formed on a polyimide film having a thickness of 25 μm by an exposure / development / etching process, thereby producing a flexible printed circuit board. The produced flexible printed circuit board and the said protective film were bonded together with the roll laminator, and the flexible printed circuit board with a protective sheet was produced.

  And the flexible printed circuit board with a protective sheet was arrange | positioned on the XY stage on which the ceramic suction plate made from alumina was put, the protective sheet surface facing up. A titanium / sapphire pulse laser (wavelength 780 nm, pulse width 140 femtoseconds, repetition frequency 1 kHz, irradiation energy 7 mW) is focused on a flexible printed circuit board with a protective sheet by a fθ lens to a diameter of 25 μm, and laser light is 20 mm by a galvano scanner. Scanning was performed by scanning at a speed of / sec. At this time, it was confirmed that the protective sheet and the flexible printed board were cut. 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 a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

Example 3
In Example 2, the flexible printed circuit board was subjected to laser processing in the same manner as in Example 2 except that a polymethylpentene film (thickness 13 μm, etching rate: 0.53) was used as the base material of the protective sheet. As a result, it was confirmed that the protective sheet and the flexible printed board were cut. 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 a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

Example 4
In Example 2, the flexible printed circuit board was laser-processed by the same method as Example 2 except having used the polyethylene terephthalate film (100 micrometers in thickness, etching rate: 0.48) as a base material of a protection sheet. As a result, it was confirmed that the protective sheet and the flexible printed board were cut. 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 a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

  As is clear from the above examples and comparative examples, the use of a protective sheet having a base material etching rate of 0.4 or more can effectively suppress contamination of the surface of the workpiece due to the decomposition product.

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 multiphoton absorption ablation of the 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 (7)

A protective sheet for laser processing used when processing a workpiece by multiphoton absorption ablation of laser light, wherein the protective sheet has at least a base material, and the base material has a pulse width. The etching rate (etching rate / energy fluence) when irradiated with an ultrashort pulse laser beam of 10 ⁻¹² seconds or less is 0.4 [(μm / pulse) / (J / cm ² )] or more. Protective sheet for laser processing. The protective sheet for laser processing according to claim 1, wherein the protective sheet is provided with an adhesive layer on a substrate. The protective sheet for laser processing according to claim 1 or 2, wherein the base material contains an aromatic polymer. The protective sheet for laser processing according to any one of claims 1 to 3, wherein the substrate contains silicon rubber. The step (1) of installing the protective sheet for laser processing according to any one of claims 1 to 4 on the laser beam incident surface side of the workpiece, and irradiating an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less And a step (2) of processing the protective sheet for laser processing and the workpiece, and a step (3) of peeling the protective sheet for laser processing from the processed workpiece. 6. The laser processed product according to claim 5, 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 emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. Production method. The method of manufacturing a laser processed product according to claim 5 or 6, wherein the processing is cutting or drilling.

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