JP2006176725A - Pressure-sensitive adhesive sheet for laser processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet for laser processing when a material to be processed is processed by multi-photon absorption ablation of laser beams with high precision/high accuracy and effectively suppressing staining of the surface of the material to be processed with degradation products and to provide a method for easily producing laser processed products with good production efficiency by using the pressure-sensitive adhesive sheet for laser processing. <P>SOLUTION: The pressure-sensitive adhesive sheet for laser processing is used when the material to be processed is processed by the multi-photon absorption ablation of laser beams. In the pressure-sensitive adhesive sheet, at least a pressure-sensitive adhesive layer is provided on a substrate. Furthermore, the substrate has <0.4[(μm/pulse)/(J/cm<SP>2</SP>)] etching ratio (etching speed/energy fluence) when the substrate is irradiated with ultrashort pulse laser beams having ≤10<SP>-12</SP>s pulse width. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure-sensitive adhesive 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 of manufacturing a laser processed product obtained by subjecting an object to shape processing such as cutting, drilling, marking, grooving, scribing, or trimming by ultraviolet 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 technique, for example, a method of supporting and fixing a workpiece on a dicing sheet and dicing the workpiece with a laser beam has been proposed (Patent Document 1). And as said dicing sheet, it consists of the base material containing a support sheet, and the adhesive layer arrange | positioned on the single side | surface surface of the said base material, The said adhesive layer can be cut | disconnected by a laser beam, The said support sheet is a laser beam. Is disclosed that cannot be cut.

  A method of dicing a semiconductor wafer by combining a water microjet and a laser has also been proposed (Patent Document 2). And it has a non-radiation curable pressure-sensitive adhesive layer and a radiation curable pressure-sensitive adhesive layer on one side of the base material, and the base material is capable of transmitting a jet water flow of a water jet, and is non-radiation-curable. A laser dicing pressure-sensitive adhesive tape in which a mold pressure-sensitive adhesive layer is provided between a substrate and a radiation curable pressure-sensitive adhesive layer is disclosed.

  By the way, when laser light is used, decomposition products such as carbon generated from a workpiece, an adhesive tape, or an adsorption plate during laser processing adhere to the surface of the workpiece, so it is said to be desmear that removes it. Post-processing is required. Since the adhesion strength of the decomposed product becomes stronger in proportion to the power of the laser beam, if the power of the laser beam is increased, it tends to be difficult to remove the decomposed product in the post-treatment.

  When the dicing sheet described in Patent Document 1 is used, the pressure-sensitive adhesive layer is cut by thermal processing by the laser beam of the fundamental wave (wavelength 1064 nm) or ruby laser (wavelength 694 nm) of the YAG laser to be used. There is a risk that a decomposition product of the pressure-sensitive adhesive layer may enter the interface between the workpiece and the workpiece and adhere firmly at the interface portion. Therefore, it is difficult to peel the dicing sheet from the workpiece after laser processing, it is difficult to completely remove deposits even after post-processing, and the laser processing accuracy is reduced. There is. Further, since the laser beam can be focused only to about 50 μm, the cutting width becomes large, and there is a problem that it is not possible to cope with high definition and high accuracy that will be required in the future.

Further, when the adhesive tape described in Patent Document 2 is used in a method of dicing a semiconductor wafer by combining a water microjet and a laser, the thermal damage of the adhesive tape is reduced by the cooling effect of the water jet. It is considered that the pressure-sensitive adhesive layer and the base material can be prevented from melting and decomposing due to heat by laser irradiation. However, when the adhesive tape is used in a method of dicing a semiconductor wafer using only a laser, the adhesive layer or the substrate is melted by the heat of laser irradiation, or the adhesive is bonded to the interface between the adhesive sheet and the semiconductor wafer. The decomposition product of the layer or the base material may invade and adhere firmly at the interface portion, which may cause the same problem as described above. Further, when the water microjet is used, the cutting width at the time of dicing is defined by the diameter of the water jet, so there is a limit to reducing the cutting width, and the semiconductor chip manufacturing efficiency is inferior.
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. It aims at providing the adhesive sheet for processing. Another object of the present invention is to provide a method for producing a laser-processed product efficiently and easily using the pressure-sensitive adhesive sheet for laser processing.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following pressure-sensitive adhesive sheet for laser processing, and have completed the present invention.

That is, the present invention relates to a laser processing pressure-sensitive adhesive sheet used when processing a workpiece by multiphoton absorption ablation of laser light, wherein the pressure-sensitive adhesive sheet is provided with at least a pressure-sensitive adhesive layer on a substrate. The substrate has an etching rate (etching rate / energy fluence) of 0.4 [(μm / pulse) / (J /) when irradiated with an ultrashort pulse laser beam having a pulse width of 10 ⁻¹² seconds or less. It is related with the adhesive sheet for laser processing characterized by being less than cm < ² >)].

  The laser processing pressure-sensitive adhesive sheet is laminated on the workpiece at the suction stage surface side (laser light emission surface side) before laser processing the workpiece by multiphoton absorption ablation of laser light, and during and after the processing. Used to support and fix a workpiece (laser processed product) in each step.

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 hard to etch (it is hard to process), so that a rate is small. The calculation method of the etching rate is described in detail in the examples.

In the present invention, the etching of the substrate is effectively suppressed by using a substrate having an etching rate of less than 0.4 when irradiated with an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less. It is possible to prevent contamination of the surface of the workpiece due to the decomposed material of the base material or the suction plate. In addition, when the pressure-sensitive adhesive sheet for laser processing of the present invention is used, an ultrashort pulse laser having a pulse width of 10 ⁻¹² seconds or less can be used, so that it can be processed with high definition and high accuracy.

  The etching rate of the substrate is preferably 0.3 or less, and more preferably 0.2 or less. When the etching rate is 0.4 or more, since the laser energy utilization efficiency of the base material is increased, the etching of the base material tends to proceed easily. Therefore, decomposition products generated by etching the base material or decomposition products of the suction plate provided on the suction stage may enter the interface portion between the adhesive sheet and the workpiece and contaminate the workpiece surface. . If the surface of the workpiece is contaminated with decomposition products, it becomes difficult to peel the adhesive sheet from the workpiece after laser processing the workpiece, or it may be difficult to remove the decomposition products in post-processing. The processing accuracy of the workpiece tends to decrease.

  In the laser processing pressure-sensitive adhesive sheet, at least a pressure-sensitive adhesive layer is provided on a substrate. By imparting adhesiveness, not only can the work piece be sufficiently supported and fixed, but also the adhesion at the interface between the pressure sensitive adhesive sheet and the work piece can be improved. As a result, it is possible to suppress contamination of the surface of the workpiece by the decomposed product.

  Moreover, in this invention, it is preferable that the said base material contains a polyolefin-type resin, a cellulose-type resin, a polynorbornene-type resin, and a polyamide-type resin. The polyolefin resin is preferably polypropylene. Moreover, it is preferable that the functional group of the side chain of the said polyolefin resin is connected with the principal chain by the ether bond. By using the material as the base material forming material, it becomes easy to adjust the etching rate of the base material to less than 0.4.

The present invention includes the step (1) of installing the laser processing pressure-sensitive adhesive sheet on the laser beam emitting surface side of the workpiece, and irradiating the workpiece with an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less. The present invention relates to a method for producing a laser-processed product, comprising a step (2) for processing, and a step (3) for peeling off the laser-processed pressure-sensitive adhesive sheet from the processed workpiece.

  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 pressure-sensitive adhesive sheet for laser processing of the present invention is suitably 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 used is 10 ⁻¹² seconds or less, preferably 10 ⁻¹² to 10 ⁻¹⁵ seconds, more preferably 10 ⁻¹³ to 10 ⁻¹⁴ seconds. The used wavelength is about 100 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 pressure-sensitive adhesive sheet for laser processing of the present invention is particularly suitably used 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. be able to.

  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.

The pressure-sensitive adhesive sheet for laser processing of the present invention has at least a pressure-sensitive adhesive layer provided on a substrate, and the substrate was irradiated with an ultrashort pulse laser beam having a pulse width of 10 ⁻¹² seconds or less. The etching rate is less than 0.4.

  Examples of the base material forming material include polyethylene terephthalate, polystyrene, polycarbonate, polyimide, polyamide, (meth) acrylic polymer, cellulose resin, polynorbornene resin, polyethylene glycol, polytetramethylene glycol and other polyalkylene glycols. Examples thereof include resins, silicone rubbers, and polyolefin resins such as polyethylene, polypropylene, polybutadiene, polyvinyl alcohol, polymethylpentene, polyvinyl acetate, and ethylene-vinyl acetate copolymer. The ultrashort pulse laser has a very high peak intensity and is processed with multiphoton absorption, so that it is difficult to select a material for the substrate. As a result of screening many materials, it is particularly preferable that the material contains polypropylene, polyvinyl alcohol, ethylene-vinyl acetate copolymer, cellulose resin, polynorbornene resin, or polyamide resin. In addition, these resin may be used individually by 1 type, and may blend and use 2 or more types.

  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 to the workpiece, cutting and drilling of the workpiece, and peeling and recovery of the laser processed product. 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 subjected to conventional surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage bombardment exposure, and ionizing radiation treatment in order to improve adhesion, retention, etc. with adjacent materials such as adsorption plates. Chemical or physical treatment such as, or a coating treatment with a primer (for example, an adhesive substance described later) may be applied.

  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 weight 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 pressure-sensitive adhesive sheet for laser processing according to the present invention can be produced, for example, by applying a pressure-sensitive adhesive solution to the surface of the substrate and drying (heating and crosslinking as necessary) to form a pressure-sensitive adhesive layer. it can. 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 weight 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 laser processing pressure-sensitive adhesive 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 pressure-sensitive adhesive sheet for laser processing will be described. For example, in the case of cutting processing, as shown in FIGS. 1 and 3, the workpiece-adhesive sheet obtained by bonding the laser processing adhesive sheet 2 and the workpiece 1 by a known means such as a roll laminator or a press. The laminated body 3 is disposed on the suction plate 5 of the suction stage 4, and the laser beam 6 output from a predetermined laser oscillator is condensed and irradiated onto the workpiece 1 with a lens, and the laser irradiation position is predetermined. The workpiece 1 is cut by moving it along the machining line. The pressure-sensitive adhesive sheet 2 provided on the laser light emitting surface side of the workpiece 1 plays a role of supporting and fixing the workpiece 1 before laser processing, and plays a role of preventing the cut material from falling after the laser processing. A protective sheet may be provided on the laser beam incident surface side of the workpiece 1. The protective sheet is used to prevent a decomposition product or a scattered product generated by laser processing of the workpiece 1 from adhering to the surface of the workpiece 1.

  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 workpiece 1 is completely cut, but in order to avoid cutting up to the adhesive sheet 2, the energy processing conditions of the workpiece 1 are cut. It is preferable to be within 2 times.

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.

  In the case of drilling, as shown in FIG. 2, the workpiece-adhesive sheet laminate obtained by bonding the workpiece 1 and the laser processing adhesive sheet 2 by a known means such as a roll laminator or a press. 3 is disposed on the suction plate 5 of the suction stage 4, and laser light 6 output from a predetermined laser oscillator is condensed and irradiated onto the workpiece 1 by a lens to form a hole.

  The hole is formed by a known laser processing method such as galvano scan, XY stage scan, or punching by mask imaging. The laser processing condition may be determined as an optimum value based on the ablation threshold of the workpiece.

  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. Note that a protective sheet may be provided on the laser light incident surface side of the workpiece 1.

  In the case of semiconductor wafer cutting (dicing), one surface of the semiconductor wafer 7 is bonded to the laser processing adhesive sheet 2 provided on the suction stage 4 as shown in FIG. 4 and output from a predetermined laser oscillator. The laser beam 6 is condensed and irradiated on the semiconductor wafer 7 with a lens, and the laser irradiation position is moved along a predetermined processing line to perform cutting processing. As the laser beam moving means, a known laser processing method such as galvano scan, XY stage scan, mask, or image song processing is used. The processing conditions for the semiconductor wafer are not particularly limited as long as the semiconductor wafer 7 is cut and the adhesive sheet 2 is not cut. A protective sheet may be provided on the laser light incident surface side of the semiconductor wafer 7.

  In such a semiconductor wafer dicing process, after cutting into individual semiconductor chips (laser processed products), a method of picking up using a push-up pin called a needle by a conventionally known apparatus such as a die bonder, or JP-A-2001 2001 Individual semiconductor chips can be picked up and collected by a known method such as the method disclosed in Japanese Patent Publication No. 118862.

  In the laser processed product manufacturing method of the present invention, the laser processed product 9 is recovered by peeling off the pressure-sensitive adhesive sheet 2 after the end of laser processing. The method of peeling is not limited, but it is important that the laser-processed product 9 is not subjected to stress that causes permanent deformation during peeling. For example, when a radiation curable pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet 2, 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 method for producing a laser processed product of the present invention, since an adhesive sheet for laser processing having a substrate with an etching rate of less than 0.4 is used, an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less is used. Even when used, it is extremely difficult to etch. Therefore, it is possible to effectively suppress contamination due to a decomposition product at the interface portion between the laser processing pressure-sensitive adhesive sheet and the workpiece. Therefore, according to the manufacturing method, the decomposed material hardly adheres to the interface portion between the laser processing pressure-sensitive adhesive sheet and the workpiece (laser processed product). It can be easily peeled off from the laser processed product, and the laser processing accuracy of the workpiece can be improved. Moreover, even if a decomposition product is attached, it can be easily removed by post-processing, so that post-processing can be greatly simplified. 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 weight average molecular weight)
The weight 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 weight 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 5 pulses 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 3 (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
An acrylic pressure-sensitive adhesive solution (1) that can be cured by ultraviolet rays is applied onto a substrate made of polyvinyl alcohol (thickness: 100 μm, etching rate: 0) and dried to form a pressure-sensitive adhesive layer (thickness: 10 μm). An adhesive sheet for laser processing 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 weight average molecular weight of 900,000 obtained by copolymerizing butyl acrylate / acrylic acid at a weight ratio of 100/2, 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 above-prepared adhesive sheet for laser processing was bonded to one side of a polyimide film having a thickness of 25 μm with a roll laminator to prepare a polyimide film with an adhesive sheet. And the polyimide film with an adhesive sheet was arrange | positioned on the XY stage on which the adsorption board made from a 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 the surface of the polyimide film by an fθ lens to a diameter of 25 μm, and a laser beam is emitted at a speed of 20 mm / second by a galvano scanner. Scanned and cut with. At this time, the polyimide film was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of a polyimide film was observed, the decomposition product (adhesion) was not observed.

Comparative Example 1
In Example 1, the polyimide film was laser processed in the same manner as in Example 1 except that the adhesive sheet for laser processing was not provided on one side of the polyimide film. Then, when the process peripheral part of the laser beam emission surface side of a polyimide film was observed, the decomposition product of the glass epoxy resin used as an adsorption board had adhered in large quantities. In addition, nickel derived from stainless steel also adhered. Then, although the desmear process was performed using the potassium permanganate aqueous solution, the attached decomposition product was not able to be removed completely.

Comparative Example 2
In Example 1, the polyimide film was subjected to laser processing in the same manner as in Example 1 except that a polyethylene naphthalate film (thickness 50 μm, etching rate: 0.77) was used as the base material of the laser processing pressure-sensitive adhesive sheet. did. As a result, not only the polyimide film but also the adhesive sheet was completely cut. Then, when the adhesive sheet was peeled off and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emitting surface side) of the polyimide film was observed, a decomposition product (adhered matter) derived from the adhesive sheet or the adsorption plate was observed. It was.

Example 2
An acrylic pressure-sensitive adhesive solution (2) that can be cured by ultraviolet rays is applied on a laminated base material (thickness 100 μm, etching rate: 0) made of polyethylene / polypropylene / polyethylene, and dried to form a pressure-sensitive adhesive layer (thickness 20 μm). ) To obtain an adhesive sheet for laser processing.

  The acrylic pressure-sensitive adhesive solution (2) was prepared by the following method. 20 parts by weight of 2-methacryloyloxyethyl isocyanate with respect to 100 parts by weight of an acrylic polymer having a weight average molecular weight of 500,000 obtained by copolymerizing ethyl acrylate / butyl acrylate / 2-hydroxyethyl acrylate at a weight ratio of 50/50/16 Was added to introduce a carbon-carbon double bond into the polymer molecule inner chain (the length of the side chain at this time was 13 atoms). 100 parts by weight of this polymer, 3 parts by weight of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane, Coronate L), and 3 parts by weight of α-hydroxyketone (Irgacure 184) as a photopolymerization initiator are added to 350 parts by weight of toluene and dissolved uniformly. An acrylic pressure-sensitive adhesive solution (2) was prepared by mixing.

  A circuit is formed by exposure, development and etching processes on a two-layer substrate in which a 18 μm thick copper layer is formed on a 25 μm thick polyimide film, and an epoxy adhesive having a thickness of 15 μm on a 13 μm thick polyimide film. The cover film having the layer formed thereon was bonded onto the circuit to prepare a flexible printed board. The produced flexible printed circuit board and the pressure-sensitive adhesive sheet for laser processing were bonded together with a roll laminator to produce a flexible printed circuit board with an adhesive sheet.

  And the flexible printed circuit board with an adhesive sheet was arrange | positioned on the XY stage on which the ceramic suction plate made from an alumina was put, the adhesive sheet surface facing down. A titanium / sapphire pulse laser (wavelength 780 nm, pulse width 140 femtoseconds, repetition frequency 1 kHz, irradiation energy 7 mW) is focused on the surface of the flexible printed circuit board by an fθ lens to a diameter of 25 μm, and the laser light is 20 mm / second by a galvano scanner. Scanned and cut at speed. At this time, the flexible printed board was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of a flexible printed circuit board was observed, the decomposition product (adhesion) was not observed.

Example 3
An adhesive sheet for laser processing was prepared in the same manner as in Example 1 except that a base material (thickness 80 μm, etching rate: 0) made of an ethylene-vinyl acetate copolymer was used instead of the base material made of polyvinyl alcohol. Produced.

  The above-prepared adhesive sheet for laser processing was bonded to one side of a 18 μm thick copper foil with a roll laminator to prepare a copper foil with an adhesive sheet. And the copper foil with an adhesive sheet was arrange | positioned on the XY stage on which the adsorption board formed by spraying a zirconia on a stainless steel plate was mounted. A titanium / sapphire pulse laser (wavelength 780 nm, pulse width 140 femtoseconds, repetition frequency 1 kHz, irradiation energy 7 mW) is focused on a copper foil surface to a diameter of 25 μm by an fθ lens, and a laser beam is emitted at a speed of 10 mm / second by a galvano scanner. Scanned and cut with. At this time, the copper foil was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of copper foil was observed, the decomposition product (adhesion) was not observed.

Example 4
The same method as in Example 1 except that a base material made of polyamide (thickness 80 μm, etching rate: 0) was used instead of the base material made of polyvinyl alcohol, and the thickness of the adhesive layer was changed from 10 μm to 5 μm. Thus, an adhesive sheet for laser processing was prepared. Using the produced adhesive sheet, it was cut by the same method as in Example 3. At this time, the copper foil was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of copper foil was observed, the decomposition product (adhesion) was not observed.

Example 5
For laser processing in the same manner as in Example 1 except that cellophane (thickness 50 μm, etching rate: 0) was used instead of the substrate made of polyvinyl alcohol, and the thickness of the adhesive layer was changed from 10 μm to 5 μm. An adhesive sheet was prepared. Using the produced adhesive sheet, it was cut by the same method as in Example 3. At this time, the copper foil was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of copper foil was observed, the decomposition product (adhesion) was not observed.

Example 6
Example 1 except that a base material made of polynorbornene (thickness: 100 μm, etching rate: 0.28) was used instead of the base material made of polyvinyl alcohol, and the thickness of the adhesive layer was changed from 10 μm to 5 μm. A pressure-sensitive adhesive sheet for laser processing was produced in the same manner. Using the produced adhesive sheet, it was cut by the same method as in Example 3. At this time, the copper foil was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of copper foil was observed, the decomposition product (adhesion) was not observed.

Example 7
Example 1 was used except that a base material made of polypropylene (thickness 100 μm, etching rate: 0.28) was used instead of the base material made of polyvinyl alcohol, and the thickness of the adhesive layer was changed from 10 μm to 5 μm. A pressure-sensitive adhesive sheet for laser processing was prepared by the method described above. Using the produced adhesive sheet, it was cut by the same method as in Example 3. At this time, the copper foil was cut, but the adhesive sheet was not cut at all. Then, when the adhesive sheet was peeled and the laser processing peripheral part of the adhesive sheet bonding surface (laser light emission surface side) of copper foil was observed, the decomposition product (adhesion) was not observed.

  As is clear from the above examples and comparative examples, by using the laser processing pressure-sensitive adhesive sheet in which the etching rate of the substrate is less than 0.4, contamination of the laser light emitting surface side surface of the workpiece by the decomposed material is prevented. It can be effectively suppressed.

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 Laser processing adhesive sheet 2a Adhesive layer 2b Base material 3 Laminate 4 Adsorption stage 5 Adsorption plate 6 Laser beam 7 Semiconductor wafer 8 Dicing frame 9 Laser processed product

Claims (10)

In the pressure-sensitive adhesive sheet for laser processing used when processing a workpiece by multiphoton absorption ablation of laser light, the pressure-sensitive adhesive sheet is one in which at least a pressure-sensitive adhesive layer is provided on the base material. ^Has an etching rate (etching rate / energy fluence) of less than 0.4 [(μm / pulse) / (J / cm ² )] when irradiated with an ultrashort pulse laser beam having a pulse width of 10 ⁻¹² seconds or less. There is a pressure-sensitive adhesive sheet for laser processing. The pressure-sensitive adhesive sheet for laser processing according to claim 1, wherein the base material contains a polyolefin-based resin. The pressure-sensitive adhesive sheet for laser processing according to claim 2, wherein the polyolefin resin is polypropylene. The pressure-sensitive adhesive sheet for laser processing according to claim 2, wherein the functional group of the side chain of the polyolefin resin is connected to the main chain by an ether bond. The pressure-sensitive adhesive sheet for laser processing according to claim 1, wherein the base material contains a cellulose-based resin. The pressure-sensitive adhesive sheet for laser processing according to claim 1, wherein the base material contains a polynorbornene resin. The pressure-sensitive adhesive sheet for laser processing according to claim 1, wherein the base material contains a polyamide-based resin. The step (1) of installing the laser processing pressure-sensitive adhesive sheet according to any one of claims 1 to 7 on the laser beam emission surface side of the workpiece, and irradiating with an ultrashort pulse laser beam having a pulse width of ^10-12 seconds or less And a process (2) for processing the workpiece, and a process (3) for peeling the laser processing adhesive sheet from the processed workpiece. 9. The laser processed product according to claim 8, 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 of manufacturing a laser processed product according to claim 8 or 9, wherein the processing is cutting or drilling.

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