JP5603757B2 - Laser dicing adhesive sheet and method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive sheet used in a process of condensing laser light inside a semiconductor wafer affixed to a pressure-sensitive adhesive sheet and expanding the pressure-sensitive adhesive sheet to separate the semiconductor wafer. Moreover, it is related with the manufacturing method of the semiconductor device using this adhesive sheet.

  After a circuit is formed on the surface of the semiconductor wafer, a grinding process is performed on the back side of the wafer, and a back grinding process for adjusting the thickness of the wafer and a dicing process for dividing the wafer into a predetermined chip size are performed.

  With the spread of IC cards in recent years, the semiconductor chip that is a constituent member thereof is being made thinner. For this reason, it has been required to reduce the thickness of a conventional wafer having a thickness of about 350 μm to 50 to 100 μm or less.

  As the wafer that is a brittle member becomes thinner, the risk of breakage increases during processing and transportation. When such an ultra-thin wafer is cut by a dicing blade that rotates at high speed, chipping or the like occurs particularly on the back side of the semiconductor wafer, and the die strength of the chip is significantly reduced.

For this reason, a laser dicing method has been proposed in which a dicing line is formed while a modified portion is selectively formed by irradiating the inside of a semiconductor wafer with a laser beam, and the wafer is cleaved starting from the modified portion (patent) Reference 1).

In Patent Document 2, a laminated pressure-sensitive adhesive sheet (two layers of pressure-sensitive adhesive sheets comprising a base material and a pressure-sensitive adhesive layer) is attached to an ultrathin semiconductor wafer, and laser light is laminated and laminated from the side of the laminated pressure-sensitive adhesive sheet. After forming the modified part by irradiating the inside of the semiconductor wafer through the sheet, the adhesive sheet is expanded after peeling off the outermost adhesive sheet, so that the semiconductor wafer is divided along the dicing line. A laser dicing method to produce is disclosed.

However, when laser light is transmitted through the pressure-sensitive adhesive sheet used in such a laser dicing method, the straightness of the laser light may be lost due to the large phase difference of the pressure-sensitive adhesive sheet. If the straightness of the laser beam is lost, it may be difficult to focus the laser beam on the inside of the semiconductor wafer, and the wafer may not be precisely processed. In addition, when a semiconductor chip is manufactured by laser dicing using such an adhesive sheet, sufficient laser light cannot be condensed inside the wafer, so that a sufficient modified portion cannot be formed and may not be divided into chips. there were. Further, since the Young's modulus of the pressure-sensitive adhesive sheet is high, the pressure-sensitive adhesive sheet is not sufficiently stretched even if the pressure-sensitive adhesive sheet is expanded, and it is difficult to chip the wafer with a high yield. Furthermore, the outermost pressure-sensitive adhesive sheet must be peeled off before the expanding step, and the manufacturing process is complicated.

Japanese Patent No. 3762409 JP 2007-123404 A

The present invention seeks to solve the problems associated with the prior art as described above. That is, according to the present invention, in the laser dicing method, since the laser beam can be easily condensed inside the semiconductor wafer, the modified portion can be formed more precisely in the wafer, and the bending strength is high. An object of the present invention is to provide an adhesive sheet capable of easily manufacturing semiconductor chips with a high yield. Moreover, it aims at providing the manufacturing method of the semiconductor device using this adhesive sheet.

The gist of the present invention aimed at solving such problems is as follows.
(1) a substrate, Ri Do from the one side to the formed adhesive layer, after forming the modified portion therein wafer by laser beam irradiation, the pressure-sensitive adhesive for laser dicing used in the step of cutting and separating into individual chips A sheet,
The Young's modulus at 23 ° C. of the pressure-sensitive adhesive sheet is 30 to 600 MPa,
The linear transmittance of the pressure-sensitive adhesive sheet at a wavelength of 1064 nm is 80% or more,
A pressure-sensitive adhesive sheet for laser dicing, wherein a phase difference of the pressure-sensitive adhesive sheet at a wavelength of 1064 nm is 100 nm or less.

(2) The adhesive sheet for laser dicing according to (1), wherein the substrate is produced by a cast film forming method or a calender film forming method.

(3) The adhesive for laser dicing according to (1) or (2), wherein the arithmetic average height Ra of the roughness curve of the substrate on the surface opposite to the surface on which the pressure-sensitive adhesive layer is formed is less than 0.1 μm. Sheet.

(4) The pressure-sensitive adhesive sheet for laser dicing according to any one of (1) to (3), wherein the substrate is a single layer.
(5) The pressure-sensitive adhesive sheet for laser dicing according to any one of (1) to (4), wherein the substrate is a polyvinyl chloride film or a polyurethane acrylate film.
(6) After pasting a square silicon wafer having a thickness of 100 μm and a size of 50 mm × 50 mm on the adhesive layer, a modified portion is formed inside the silicon wafer, and the adhesive sheet is formed under the condition of pulling down 10 mm at 300 mm / min. The pressure-sensitive adhesive sheet for laser dicing according to any one of claims (1) to (5), wherein the chip division rate when expanded to produce a 2 mm x 2 mm chip is 98% or more.
(7) A process of applying the laser dicing adhesive sheet according to any one of (1) to (6) to the back surface of a semiconductor wafer having a circuit formed on the surface,
The semiconductor wafer is divided by the step of irradiating the semiconductor wafer with laser light from the base material side of the pressure-sensitive adhesive sheet to form a modified portion inside the wafer, and the expansion of the pressure-sensitive adhesive sheet. A manufacturing method of a semiconductor device including a step of forming a chip.

According to the pressure-sensitive adhesive sheet for laser dicing according to the present invention, since a precise modified portion is formed inside the wafer and the expandability is good, a semiconductor chip having a high bending strength can be easily produced with a high yield. Can do. In addition, the semiconductor wafer is irradiated with laser light from the base material side of the adhesive sheet through the adhesive sheet to form a precise modified portion inside the wafer, and the semiconductor wafer can be divided into chips by expanding the adhesive sheet. Therefore, the manufacturing process of the semiconductor device can be simplified.

Sectional drawing of the adhesive sheet for laser dicing which concerns on this invention is shown. The top view of the circuit formation surface of a semiconductor wafer is shown. 1 shows one step of a method of manufacturing a semiconductor device according to the present invention.

Hereinafter, the pressure-sensitive adhesive sheet for laser dicing according to the present invention will be specifically described with reference to the drawings. As shown in FIG. 1, the adhesive sheet 10 for laser dicing which concerns on this invention consists of the base material 1 and the adhesive layer 2 formed in the single side | surface.

The Young's modulus at 23 ° C. of the pressure-sensitive adhesive sheet 10 for laser dicing is 30 to 600 MPa, preferably 100 to 500 MPa, and more preferably 200 to 400 MPa. When the physical properties of the pressure-sensitive adhesive sheet 10 are in the above range, the pressure-sensitive adhesive sheet 10 can be uniformly stretched in the expanding step. On the other hand, when the Young's modulus at 23 ° C. of the pressure-sensitive adhesive sheet 10 is larger than 600 MPa, it is difficult to expand the pressure-sensitive adhesive sheet 10. Moreover, when the Young's modulus at 23 ° C. of the pressure-sensitive adhesive sheet 10 is smaller than 30 MPa, the pressure-sensitive adhesive sheet 10 becomes soft and difficult to handle.

Moreover, the linear transmittance | permeability of the adhesive sheet 10 for laser dicing in wavelength 1064nm is 80% or more, Preferably it is 90 to 100%, More preferably, it is 92 to 99%. Furthermore, the phase difference of the pressure-sensitive adhesive sheet 10 for laser dicing at a wavelength of 1064 nm is 100 nm or less, preferably 50 nm or less, more preferably 10 nm or less, and particularly preferably 1 nm or less.

  The semiconductor wafer 11 is attached to the pressure-sensitive adhesive layer 2 of the pressure-sensitive adhesive sheet 10. Next, the focusing point is set inside the wafer, and laser light is irradiated from the base material 1 side of the pressure-sensitive adhesive sheet 10 through the pressure-sensitive adhesive sheet, and the wafer is modified along a virtual scheduled cutting line 18 that divides the circuit. A mass part is formed. Thereafter, the adhesive sheet 10 is expanded, whereby the wafer 11 is made into chips. Since the optical properties of the pressure-sensitive adhesive sheet 10 are in the above range, the laser beam can be easily condensed inside the wafer, so that the modified portion can be formed more precisely in the wafer, and the bending strength is high. Semiconductor chips can be easily manufactured with high yield.

  When the pressure-sensitive adhesive layer 2 of the pressure-sensitive adhesive sheet 10 is formed of an energy ray-curable pressure-sensitive adhesive, which will be described later, the Young's modulus, linear transmittance, and phase difference of the pressure-sensitive adhesive sheet change before and after irradiation with energy rays. There is. The expanding step is usually performed before energy beam irradiation, but may be performed after energy beam irradiation. Therefore, the Young's modulus of the pressure-sensitive adhesive sheet defined in the present invention is usually a physical property value before energy beam irradiation, but a pressure-sensitive adhesive sheet that satisfies the above physical property value after energy beam irradiation is also included in the scope of the present invention. In particular, it is preferable that the physical property values are satisfied in the expanding step. Further, the linear transmittance and the phase difference are physical properties in the state at the time of laser light irradiation, and any of them may be before or after the energy ray irradiation as long as the above physical properties are satisfied.

Such an adhesive sheet 10 for laser dicing is obtained, for example, by forming an adhesive layer 2 on one side of a substrate 1 as shown in FIG. When the roughness of the surfaces on both sides of the substrate 1 is different, it is preferable that the surface of the substrate 1 opposite to the surface on which the adhesive layer 2 is formed is a smooth surface. As long as the substrate 1 satisfies the above physical properties, the film forming method is not limited, but it is desirable to select a film forming method in which the polymer chains are less likely to be oriented. Examples of such a film forming method include a cast film forming method, a bank forming method using a calendar film forming method and a T-die film forming method. In particular, in the present invention, it is preferably produced without stretching by a cast film forming method or a calender film forming method. In addition, the extrusion film-forming method etc. which have the process of extending | stretching a base material in a manufacturing process have a possibility that the polymer chain which comprises a base material may orientate by an extending process, and may impair the linearity of a laser beam.

  Examples of the substrate 1 include unstretched polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyurethane film, polyurethane acrylate film, and ethylene vinyl acetate copolymer. A film, an ionomer resin film, and a film made of a water additive or a modified product thereof are used. These crosslinked films and copolymer films are also used, and among them, polyvinyl chloride films, polyurethane films, and polyurethane acrylate films are preferable in consideration of expandability. The above-mentioned base material may be one kind alone, or may be a composite film in which two or more kinds are combined.

  As will be described later, when the pressure-sensitive adhesive layer 2 is formed of an ultraviolet curable pressure-sensitive adhesive and ultraviolet rays are used as energy rays to be irradiated to cure the pressure-sensitive adhesive, a substrate that is transparent to the ultraviolet rays is used. preferable. In addition, when using an electron beam as an energy beam, it does not need to be transparent. In addition to the above film, a transparent film or an opaque film colored with these can be used.

  Moreover, in order to improve adhesiveness with an adhesive, the upper surface of the base material 1, ie, the base material surface on the side where the adhesive layer 2 is provided, may be subjected to corona treatment or a primer layer. Various coatings may be applied to the surface opposite to the pressure-sensitive adhesive layer 2. The pressure-sensitive adhesive sheet 10 is manufactured by providing a pressure-sensitive adhesive layer on the base material as described above. The thickness of the substrate 1 is preferably in the range of 40 to 150 μm, more preferably 50 to 100 μm, particularly preferably 50 to 80 μm.

  The arithmetic average height Ra of the roughness curve of the substrate 1 on the surface opposite to the surface on which the pressure-sensitive adhesive layer 2 is formed is preferably less than 0.1 μm, more preferably less than 0.08 μm. By setting the arithmetic average height Ra of the roughness curve of the base material 1 on the surface opposite to the surface on which the pressure-sensitive adhesive layer 2 is formed within the above range, the straightness of the laser beam is not impaired, so that the wafer interior is more precise. A reforming part can be formed. Therefore, the semiconductor wafer can be divided with a high yield by the expanding process.

  Specifically, the cast film forming method is a method in which a liquid composition (resin before curing, resin solution, etc.) forming the film is cast into a thin film, and then the coating film is cured to form a film. This is a method for manufacturing the material 1. For example, the base material 1 can be manufactured by casting a liquid composition on a process sheet or the like in a thin film, and then irradiating the coating film with an energy ray to polymerize and cure to form a film. Moreover, after irradiating energy rays and semi-curing a liquid composition, the process sheet | seat may be piled up on it, the energy rays may be irradiated, it may be hardened, and the base material 1 may be manufactured. According to such a manufacturing method, the formation of fish eyes is small. Moreover, the uniformity of the film thickness is also high, and the thickness accuracy is usually within 2%.

  In the calendar film forming method, a raw material resin is melted with a heated rotating roller, and a plurality of rolls having a passage for a heat medium are used inside, and the melt-kneaded resin is rolled between calender rolls to form a substrate 1. This is a method of molding. It is possible to produce a pressure-sensitive adhesive sheet having a high linear transmittance and a small phase difference by using the base material 1 formed by the cast film forming method and the calender film forming method with low stress applied to the resin during film formation. it can.

  The pressure-sensitive adhesive layer 2 can be formed of various conventionally known pressure-sensitive adhesives. Such an adhesive is not limited at all, but, for example, an adhesive such as rubber-based, acrylic-based, silicone-based, or polyvinyl ether is used. In addition, an energy ray curable adhesive, a heat-foaming adhesive, or a water swelling adhesive can be used. As the energy ray curable (UV curable, electron beam curable, etc.) type adhesive, it is particularly preferable to use an ultraviolet curable adhesive.

  When forming the pressure-sensitive adhesive layer 2 with an energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition in which an energy ray-curable pressure-sensitive adhesive component and, if necessary, a photopolymerization initiator are blended. Furthermore, in order to improve various physical properties, the said adhesive composition may contain other components (crosslinking agent etc.) as needed. Examples of the crosslinking agent include organic polyvalent isocyanate compounds, organic polyvalent epoxy compounds, and organic polyvalent imine compounds. Hereinafter, the energy ray-curable pressure-sensitive adhesive component will be specifically described using an acrylic pressure-sensitive adhesive as an example.

  The energy ray-curable pressure-sensitive adhesive component contains an acrylic polymer (A) in order to impart sufficient pressure-sensitive adhesiveness and film-forming property (sheet processability) to the pressure-sensitive adhesive composition, and energy ray-curable compound (B). Containing. The energy ray-curable compound (B) also contains an energy ray-polymerizable group, has a function of being polymerized and cured when irradiated with energy rays such as ultraviolet rays and electron beams, and reducing the adhesive strength of the pressure-sensitive adhesive composition. Moreover, as what has the property of said component (A) and (B), the energy-beam curable adhesive polymer (henceforth component (AB)) by which an energy-beam polymeric group is couple | bonded with the principal chain or the side chain. May be used). Such an energy ray curable pressure-sensitive adhesive polymer (AB) has a property having both adhesiveness and energy ray curable properties.

  A conventionally well-known acrylic polymer can be used as an acrylic polymer (A). The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 10,000 to 2,000,000, and more preferably 100,000 to 1,500,000. The glass transition temperature (Tg) of the acrylic polymer (A) is preferably in the range of −70 to 30 ° C., more preferably in the range of −60 to 20 ° C.

  As a monomer which comprises the said acrylic polymer (A), a (meth) acrylic acid ester monomer or its derivative (s) is mentioned. For example, an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) Acrylates and the like; (meth) acrylates having a cyclic skeleton such as cycloalkyl (meth) acrylate, benzyl (meth) acrylate, isobornyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl Acrylate, imide acrylate, etc .; 2-hydroxyethyl (meth) acrylate having a hydroxyl group, 2-hydroxypropyl (meth) acrylate, etc., acrylic acid, methacrylic acid, Con acid, glycidyl methacrylate, and glycidyl acrylate. The acrylic polymer (A) is preferably an acrylic copolymer obtained by copolymerizing vinyl acetate, acrylonitrile, styrene, or the like.

  The energy ray curable compound (B) is a compound that is polymerized and cured when irradiated with energy rays such as ultraviolet rays and electron beams. Examples of the energy beam polymerizable compound include low molecular weight compounds (monofunctional and polyfunctional monomers and oligomers) having an energy beam polymerizable group, and specifically include trimethylolpropane triacrylate and tetramethylolmethane. Acrylates such as tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, dicyclopentadiene dimethoxydiacrylate, Cyclic aliphatic skeleton-containing acrylates such as isobornyl acrylate, polyethylene glycol diacrylate, oligoester acrylate, urethane acrylate Goma, epoxy-modified acrylates, polyether acrylates, acrylate compounds such as itaconic acid oligomer is used. Such a compound has at least one polymerizable double bond in the molecule, and usually has a molecular weight of about 100 to 30,000, preferably about 300 to 10,000.

  Generally, the component (B) is used in a proportion of 10 to 400 parts by weight, preferably about 30 to 350 parts by weight, relative to 100 parts by weight of the component (A).

  The energy ray-curable pressure-sensitive adhesive polymer (AB) having the properties of the components (A) and (B) has an energy ray polymerizable group bonded to the main chain or side chain.

  The main skeleton of the energy ray curable adhesive polymer is not particularly limited, and may be an acrylic copolymer that is widely used as an adhesive.

  The energy beam polymerizable group bonded to the main chain or side chain of the energy beam curable adhesive polymer is, for example, a group containing an energy beam polymerizable carbon-carbon double bond, and specifically, (meth) acryloyl. Examples include groups. The energy beam polymerizable group may be bonded to the energy beam curable pressure-sensitive adhesive polymer via an alkylene group, an alkyleneoxy group, or a polyalkyleneoxy group.

  The weight average molecular weight (Mw) of the energy ray curable adhesive polymer (AB) to which the energy ray polymerizable group is bonded is preferably 10,000 to 2,000,000, more preferably 100,000 to 1,500,000. preferable. The glass transition temperature (Tg) of the energy ray curable adhesive polymer (AB) is preferably in the range of −70 to 30 ° C., more preferably in the range of −60 to 20 ° C.

  The energy ray curable adhesive polymer (AB) reacts with the acrylic adhesive polymer containing a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group, for example, with the functional group. It is obtained by reacting a substituent with a polymerizable group-containing compound having 1 to 5 energy beam polymerizable carbon-carbon double bonds per molecule. Acrylic adhesive polymer is a monomer that comprises (meth) acrylic acid ester monomer or derivative thereof having a functional group such as hydroxyl group, carboxyl group, amino group, substituted amino group, and epoxy group, and component (A) described above. A copolymer consisting of Examples of the polymerizable group-containing compound include (meth) acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth) acryloyl isocyanate, allyl isocyanate, glycidyl (meth) acrylate; (meth) acrylic acid Etc.

  The energy ray curable adhesive component containing the acrylic polymer (A) and the energy ray curable compound (B) or the energy ray curable adhesive polymer (AB) as described above is cured by energy ray irradiation. Specifically, ultraviolet rays, electron beams, etc. are used as the energy rays.

  Examples of photopolymerization initiators include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone Examples include 2,4,6-trimethylbenzoyldiphenylphosphine oxide. When ultraviolet rays are used as energy rays, the irradiation time and irradiation amount can be reduced by adding a photopolymerization initiator.

  The thickness of the pressure-sensitive adhesive layer 2 is preferably in the range of 1 to 20 μm, more preferably 2 to 15 μm, and still more preferably 3 to 10 μm. When the thickness of the pressure-sensitive adhesive layer 2 is in the above range, it is possible to hold the semiconductor wafer satisfactorily and prevent chips and ring frames from falling off during expansion. Moreover, the pick-up process of a semiconductor chip can be favorably performed because the thickness of the adhesive layer 2 exists in the said range.

  In addition, a release sheet may be laminated on the pressure-sensitive adhesive layer 2 in order to protect the pressure-sensitive adhesive layer before use. The release sheet is not particularly limited. For example, a film made of a resin such as polyethylene terephthalate, polypropylene, or polyethylene or a foamed film thereof, paper such as glassine paper, coated paper, laminated paper, silicone-based, fluorine A system and a release agent such as a long chain alkyl group-containing carbamate can be used.

  The method of providing the pressure-sensitive adhesive layer 2 on the surface of the base material 1 may be such that the pressure-sensitive adhesive layer 2 applied and formed on the release sheet so as to have a predetermined film thickness is transferred to the surface of the base material 1. The pressure-sensitive adhesive layer 2 may be formed by directly applying to the surface of the material 1.

  Next, a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet 10 according to the present invention will be described. A method for manufacturing a semiconductor device according to the present invention will be described by taking as an example the case where the semiconductor wafer 11 having the circuit 13 formed on the surface thereof is chipped. FIG. 2 shows a plan view of the circuit surface side of the semiconductor wafer 11 having the circuit 13 formed on the surface thereof. Note that the planned cutting line 18 is a virtual line that partitions the circuits 13.

  The semiconductor wafer 11 may be a silicon wafer or a compound semiconductor wafer such as gallium / arsenic. The formation of the circuit 13 on the wafer surface can be performed by various methods including conventionally used methods such as an etching method and a lift-off method. In the circuit forming process of the semiconductor wafer, a predetermined circuit 13 is formed. The circuit 13 is formed in a lattice shape on the surface of the inner peripheral portion 14 of the wafer 11. The thickness of the wafer 11 before grinding is not particularly limited, but is usually about 500 to 1000 μm.

  At the time of back grinding, an adhesive sheet called a surface protective sheet is attached to the circuit surface in order to protect the circuit 13 on the surface. In the back surface grinding, the circuit surface side (that is, the surface protection sheet side) of the wafer 11 is fixed by a chuck table or the like, and the back surface side where the circuit 13 is not formed is ground by a grinder. As a result, the thickness of the semiconductor wafer 11 after grinding is not particularly limited, but is usually about 50 to 200 μm. After the back grinding step, a step of removing the crushed layer generated by grinding may be performed.

  Subsequent to the back grinding step, if necessary, the back surface may be subjected to processing that generates heat such as an etching process, or processing performed at a high temperature such as vapor deposition of a metal film or baking of an organic film on the back surface. In addition, when processing at high temperature, the process to a back surface is normally performed after peeling a surface protection sheet.

After the back surface grinding, as shown in FIG. 3, the pressure-sensitive adhesive layer 2 of the laser dicing pressure-sensitive adhesive sheet 10 according to the present invention is attached to the back surface of the wafer 11, and the wafer 11 is diced. In addition, when the surface protective sheet is stuck on the wafer surface, the surface protective sheet is peeled off before or after sticking the adhesive sheet 10. Generally, the adhesive sheet 10 is attached to the back surface of the wafer by an apparatus called a mounter, but is not particularly limited.

  Next, as shown in FIG. 3, the laser beam is irradiated to the wafer 11 from the base material 1 side of the pressure-sensitive adhesive sheet 10 through the pressure-sensitive adhesive sheet 10. The laser light source 3 is a device that generates light having a uniform wavelength and phase, and the types of laser light include Nd-YAG laser, Nd-YVO laser, Nd-YLF laser, and titanium sapphire laser that generate pulsed laser light. And the like that cause multiphoton absorption. The wavelength of the laser light is preferably 800 to 1100 nm, and more preferably 1064 nm.

  The laser beam is irradiated inside the wafer, and a modified portion is formed inside the wafer along the planned cutting line 18. The number of times the laser beam scans one scheduled cutting line may be one time or multiple times. Preferably, the irradiation position of the laser beam and the position of the line 18 to be cut between the circuits are monitored, and the laser beam is irradiated while aligning the laser beam.

  When the expanded portion is formed after forming the modified portion inside the wafer by laser light irradiation, the adhesive sheet 10 expands, and the semiconductor wafer 11 is cut and separated into individual chips 12 starting from the modified portion inside the wafer. . Also, the wafer 11 can be cut and separated into chips 12 by scratching the adhesive sheet 10 from the base 1 side using a jig or the like simultaneously with the expansion. The expansion is preferably performed at a speed of 5 to 600 mm / min. Thereafter, the chip 12 is picked up by a pickup device, and a semiconductor device is manufactured through a bonding process. In the case where the pressure-sensitive adhesive layer 2 is formed of an energy ray-curable pressure-sensitive adhesive, it is preferable to irradiate energy rays before the pickup process in order to reduce the adhesive strength of the pressure-sensitive adhesive and make it easier to peel off the chip.

Having described an example of using the laser dicing adhesive sheet 10 of the present invention, the laser dicing adhesive sheet 10 of the present invention, normal semiconductor wafer, glass substrate, ceramic substrate, an organic material substrate such as an FPC, or precision It can be used for dicing various articles such as metal materials such as parts.

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

< Laser dicing conditions>
The pressure-sensitive adhesive sheet of Example or Comparative Example was attached to the back surface of the following silicon wafer, and laser light was irradiated from the pressure-sensitive adhesive sheet side into the silicon wafer under the following conditions. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the laser beam was irradiated before energy beam irradiation.
-Equipment: Nd-YAG laser-Wavelength: 1064 nm
・ Repetition frequency: 100 kHz
・ Pulse width: 30 nm
・ Cut speed: 100 mm / second ・ Wafer material: Silicon ・ Wafer thickness: 100 μm
-Wafer size: 50mm x 50mm (square)
・ Adhesive sheet size: Approximately 207mmφ
・ Cut chip size: 2mm x 2mm

<Young's modulus of the adhesive sheet>
The Young's modulus of the pressure-sensitive adhesive sheet was measured using a universal tensile tester (Tensilon RTA-T-2M manufactured by Orientec Co., Ltd.) in accordance with JIS K7161: 1994 under an environment of 23 ° C. and 50% humidity at a tensile rate of 200 mm / Measured in minutes. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the Young's modulus of the adhesive sheet before energy ray irradiation was measured.

<Linear transmittance of adhesive sheet>
From the substrate side of the pressure-sensitive adhesive sheet, linear transmittance was measured (measurement wavelength: 200 to 1200 nm) using an ultraviolet-visible spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and a measurement value at a wavelength of 1064 nm was read. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the linear transmittance | permeability of the adhesive sheet before energy ray irradiation was measured.

<Phase difference of adhesive sheet>
A phase difference was measured (measurement wavelength: 800 to 1100 nm) using a retardation film inspection apparatus (RETS-100 manufactured by Otsuka Electronics Co., Ltd.) and a detector (MCPD-7700 manufactured by Otsuka Electronics Co., Ltd.), and a measurement value at a wavelength of 1064 nm was read. . The case where the phase difference was 100 nm or less was judged as “good”, and the case where it was larger than 100 nm was judged as “impossible”. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the phase difference of the adhesive sheet before energy ray irradiation was measured.

<Arithmetic mean height Ra of the roughness curve of the substrate>
Based on JIS B0601: 2001, using a surface roughness meter (SURFTEST SV-3000 manufactured by Mitsutoyo), the surface roughness of the substrate on the surface opposite to the surface on which the pressure-sensitive adhesive layer is formed is measured at 10 points, and the average value thereof Was the arithmetic average height Ra of the roughness curve of the substrate. The cut-off value λc was 0.25 mm, and the evaluation length Ln was 4 mm.

<Expandability of adhesive sheet>
The pressure-sensitive adhesive sheet of Example or Comparative Example was attached to a ring frame for an 8-inch wafer, and expanded (drawn 10 mm) at 300 mm / min using an expanding device (DDS 2010, manufactured by Disco Corporation). The case where it was able to expand without problems was defined as “good”, and the case where the adhesive sheet dropped from the ring frame or the adhesive sheet was torn was regarded as “bad”. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the expandability of the adhesive sheet before energy ray irradiation was evaluated.

<Chip division ratio>
After pasting the adhesive sheet of the example or comparative example on the ring frame for the silicon wafer and the 8-inch wafer and irradiating the laser through the adhesive sheet under the above laser dicing conditions to form a modified portion inside the wafer Using an expanding apparatus (DDS2010, manufactured by Disco Corporation), the pressure-sensitive adhesive sheet was expanded under the conditions of 300 mm / min and 10 mm withdrawal, and the wafer was chipped. The number of chips cut into the cut chip size (the number of completely separated chips) was visually counted, and the number of chips formed on the wafer (the total number of virtual chips) was converted into chips. The number of chips (chip division ratio) was calculated and evaluated according to the following criteria. A semiconductor chip can be manufactured with a high yield as the chip division ratio increases. In addition, when using an energy ray hardening-type adhesive layer for the adhesive layer of an adhesive sheet, the adhesive sheet was expanded before energy ray irradiation.
(Standard)
A: 99.5% or more B: 98% or more and less than 99.5% C: 50% or more and less than 98% D: 25% or more and less than 50% E: Less than 25%

Example 1
Acrylic copolymer (2-ethylhexyl acrylate / vinyl acetate / acrylic acid / methyl methacrylate / 2-hydroxyethyl methacrylate = 18.5 / 75/1/5 / 0.5 (mass ratio), Mw = 600,000, Tg = Energy ray curable adhesive in which 60 parts by weight of bifunctional urethane acrylate oligomer (Mw = 8000) and 60 parts by weight of hexafunctional urethane acrylate oligomer (Mw = 2000) are blended with respect to 100 parts by weight of 5 ° C.). 3 parts by weight of a photopolymerization initiator (“Irgacure 184” manufactured by Ciba Specialty Chemicals) and 1.6 parts by weight of a polyvalent isocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) are blended into the components (all in terms of solid content) To obtain a pressure-sensitive adhesive composition.

The above-mentioned pressure-sensitive adhesive composition was applied to a release film (SP-PET3811 (S) manufactured by Lintec Corporation), and then dried (100 ° C. for 1 minute in an oven) to prepare a pressure-sensitive adhesive layer having a thickness of 10 μm. Next, a 80 μm-thick polyvinyl chloride film (Young's modulus = 280 MPa) manufactured by a calendering method was used as a substrate, and the pressure-sensitive adhesive layer was transferred to obtain a pressure-sensitive adhesive sheet for laser dicing . For this pressure-sensitive adhesive sheet, the “Young's modulus of the pressure-sensitive adhesive sheet”, “Linear transmittance of the pressure-sensitive adhesive sheet”, “Phase difference of the pressure-sensitive adhesive sheet”, and “Arithmetic average height Ra of the roughness curve of the substrate” were measured. Sheet expandability "and" chip split ratio "were evaluated. The results are shown in Table 1.

(Example 2)
Except that the thickness of the substrate was 50 μm, a pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1, and measurement and evaluation were performed. The Young's modulus of the base material was 280 MPa. The results are shown in Table 1.

(Example 3)
A pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1 except that a 80 μm-thick polyvinyl chloride film (Young's modulus = 550 MPa) produced by a calendering method was used as the substrate, and measurement and evaluation Went. The results are shown in Table 1.

Example 4
Urethane acrylate oligomer (polypropylene glycol (Mw = 700) / isophorone diisocyanate / 2-hydroxyethyl acrylate = 4/5/2 (mass ratio), Mw = 4500), 100 parts by weight of isobornyl acrylate and photopolymerization 1 part by weight of an initiator (“Darocur 1173” manufactured by Ciba Specialty Chemicals) was blended (all blending ratios in terms of solid content) to obtain a mixture.

After applying the above mixture to a release film (SP-PET3811 (S), manufactured by Lintec Corporation), the film was irradiated with ultraviolet rays (220 mW / cm ² , 1500 mJ / cm ² ) to peel off the release film to obtain a thickness as a substrate. A 100 μm polyurethane acrylate film (Young's modulus = 350 MPa) was obtained. Except using this base material, the adhesive sheet for laser dicing was obtained like Example 1, and it measured and evaluated. The results are shown in Table 1.

(Example 5)
A laser dicing adhesive sheet was prepared in the same manner as in Example 4 except that the following base material (polyurethane acrylate film with a coat layer) was used and the adhesive layer was transferred to the surface of the base material on which the coat layer was not formed. Obtained, measured and evaluated. The results are shown in Table 1.

  100 parts by weight of bifunctional epoxy acrylate and 100 parts by weight of silica filler having an average particle size of 0.5 μm were sufficiently stirred to obtain a mixture. The mixture was applied to a release film (SP-PET3811 (S) manufactured by Lintec Corporation) so that the thickness after drying was 5 μm and dried to obtain a coating layer.

After applying the mixture described in Example 4 to the above-mentioned coat layer, ultraviolet rays were irradiated (220 mW / cm ² , 1500 mJ / cm ² ), the release film was peeled off, and a polyurethane acrylate film with a coat layer ( Young's modulus = 321 MPa) was obtained. The base material had a thickness of 100 μm.

(Comparative Example 1)
A pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1 except that an 80 μm-thick ethylene / methacrylic acid copolymer film (Young's modulus = 120 MPa) produced by an extrusion film forming method was used as the substrate. Measurement and evaluation were performed. The results are shown in Table 1.

(Comparative Example 2)
A pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1 except that the same base material as in Comparative Example 1 was used and the pressure-sensitive adhesive layer was transferred to the surface opposite to the surface to which the pressure-sensitive adhesive layer was transferred in Comparative Example 1. Measurement and evaluation were performed. The results are shown in Table 1.

(Comparative Example 3)
A pressure-sensitive adhesive sheet for laser dicing was obtained and measured in the same manner as in Example 1 except that a biaxially stretched polyethylene terephthalate film (Young's modulus = 4500 MPa) with a thickness of 50 μm produced by an extrusion film forming method was used as the substrate. And evaluated. The results are shown in Table 1.

(Comparative Example 4)
A pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1 except that a 50 μm-thick polyimide film (Young's modulus = 5200 MPa) was used as the substrate, and measurement and evaluation were performed. The results are shown in Table 1. The polyimide film was prepared by extruding a polyamic acid solution onto a metal belt, drying it, and imidizing at 500 ° C.

(Comparative Example 5)
A pressure-sensitive adhesive sheet for laser dicing was obtained in the same manner as in Example 1, except that a biaxially stretched polypropylene film (Young's modulus = 520 MPa) having a thickness of 100 μm produced by an extrusion film forming method was used as a substrate. Evaluation was performed. The results are shown in Table 1.

The adhesive sheets for laser dicing of Examples 1 to 4 were good in both expandability and chip division rate. In particular, in Example 4, since the phase difference was small, the chip division ratio was very good. On the other hand, since the adhesive sheet for laser dicing of Example 5 has an arithmetic average height Ra of the roughness curve of the base material on the surface opposite to the surface on which the pressure-sensitive adhesive layer is formed, it is not less than 0.1 μm. Compared to 4, the chip split rate was slightly lower.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Adhesive layer 3 ... Laser light source 5 ... Ring frame 10 ... Adhesive sheet 11 for laser dicing ... Semiconductor wafer 12 ... Chip 13 ... Circuit 14 ... Inner peripheral part 18 ... Planned cutting line (virtual)

Claims (7)

A substrate, the Ri Do from one surface to the formed adhesive layer, after forming the modified portion therein wafer by laser beam irradiation, a laser dicing adhesive sheet used in the step of cutting into individual chips And
The Young's modulus at 23 ° C. of the pressure-sensitive adhesive sheet is 30 to 600 MPa,
The linear transmittance of the pressure-sensitive adhesive sheet at a wavelength of 1064 nm is 80% or more,
A pressure-sensitive adhesive sheet for laser dicing, wherein a phase difference of the pressure-sensitive adhesive sheet at a wavelength of 1064 nm is 100 nm or less. The pressure-sensitive adhesive sheet for laser dicing according to claim 1, wherein the substrate is produced by a cast film forming method or a calender film forming method. The pressure-sensitive adhesive sheet for laser dicing according to claim 1 or 2, wherein the arithmetic average height Ra of the roughness curve of the substrate on the surface opposite to the surface on which the pressure-sensitive adhesive layer is formed is less than 0.1 µm. The adhesive sheet for laser dicing according to any one of claims 1 to 3, wherein the substrate is a single layer. The pressure-sensitive adhesive sheet for laser dicing according to any one of claims 1 to 4, wherein the substrate is a polyvinyl chloride film or a polyurethane acrylate film. After pasting a square silicon wafer having a thickness of 100 μm and a size of 50 mm × 50 mm to the adhesive layer, a modified portion is formed inside the silicon wafer, and the adhesive sheet is expanded under the condition of pulling out 10 mm at 300 mm / min, The pressure-sensitive adhesive sheet for laser dicing according to any one of claims 1 to 5, wherein a chip division rate when producing a 2 mm x 2 mm chip is 98% or more. A process of attaching the adhesive sheet for laser dicing according to any one of claims 1 to 6 , to the back surface of a semiconductor wafer having a circuit formed on the surface,
The semiconductor wafer is divided by the step of irradiating the semiconductor wafer with laser light from the base material side of the pressure-sensitive adhesive sheet to form a modified portion inside the wafer, and the expansion of the pressure-sensitive adhesive sheet. A manufacturing method of a semiconductor device including a step of forming a chip.

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