JP6301987B2 - Dicing adhesive tape and semiconductor wafer full-cut dicing method - Google Patents

Description

  The present invention relates to a dicing adhesive tape used for cutting a semiconductor wafer, a semiconductor package, and the like, and a semiconductor wafer full-cut dicing method.

  The process of processing a semiconductor wafer or the like into a semiconductor chip and mounting it on an electronic device is, for example, a process of attaching a semiconductor wafer surface protective tape to the pattern surface of the semiconductor wafer, grinding the back surface of the semiconductor wafer, and reducing the thickness. A process, a process of mounting a semiconductor wafer that has been ground and thinned in the above process on a dicing tape (a dicing adhesive tape), a process of peeling the adhesive tape for processing a semiconductor wafer from a semiconductor wafer, and a semiconductor wafer by dicing After a step of dividing, a die bonding step of bonding the divided semiconductor chip to the lead frame, a molding step of sealing the semiconductor chip with a resin for external protection is performed.

In this series of processes, the dicing tape is used at least from the dicing process to the pick-up process, and the object to be cut such as a semiconductor wafer is diced, washed, dried, expanded, pick-up with the dicing tape attached. Each process of mounting is performed.
Here, expanding refers to an operation of stretching a dicing tape after dicing, cleaning, and drying to divide the semiconductor wafer and the die bonding film into semiconductor chips along the planned dividing line, thereby widening the interval between the semiconductor chips.

  As a dicing method in the dicing step, blade dicing, laser ablation, and stealth dicing are known. Blade dicing is a dicing method that performs cutting while pressing a diamond blade that rotates at high speed against the semiconductor wafer. Laser ablation uses laser light of a wavelength that is absorbed by the target material to melt the semiconductor wafer from the surface layer. / Stealth dicing is a laser processing method that digs a groove hole while evaporating. The stealth dicing condenses laser light having a wavelength that passes through the target material inside the semiconductor wafer, and is called a stealth dicing layer (SD layer). In this dicing method, a starting layer is selectively formed and an external force such as a tape expand is applied to cause a crack extending from the SD layer to propagate to the front and back surfaces.

Here, with blade dicing, half-cutting that cuts about 2/3 of the thickness of the semiconductor wafer has been the mainstream. However, as the size of the semiconductor wafer increases, the entire semiconductor wafer is mounted on the tape mount. Full cuts to cut are becoming mainstream.
Blade dicing is the most widely used dicing method, but since it is a contact type, physical stress is applied, chipping occurs on the front and back surfaces, and large contact frictional heat is generated during cutting, Cooling water is required, and further, treatment of sewage generated by cutting is also required.

In addition, in addition to the above, a part to be cut such as a semiconductor wafer may be cut at the same time as the pressure-sensitive adhesive layer of the dicing tape or a part of the base film. At this time, a part of the base film is melted by frictional heat with the dicing blade and further stretched, whereby thread-like dicing waste may be generated on the dicing line. Adhesive is attached to this thread-like waste, and if a large amount of such thread-like waste adheres to the chip and is sealed, the thread-like waste is thermally decomposed by the heat of sealing, destroying the semiconductor package. Or cause malfunction. If the pressure-sensitive adhesive is attached to the thread-like waste, it is difficult to remove it by washing, and the yield is extremely reduced.
In recent years, thinning of semiconductor wafers has progressed, and dicing waste is exposed on the surface of the semiconductor wafer after dicing, and it is strongly required to prevent the generation of thread-like dicing waste.

  In order to solve such problems, with the aim of increasing the degree of crosslinking of the resin constituting the base film of the dicing tape, an electron beam of 1 to 50 Mrad is irradiated so that the gel fraction becomes 65% or more. It has been proposed to use an ethylene- (meth) acrylic acid copolymer cross-linked to (see Patent Document 1).

JP 2005-033059 A

  However, in the resin described in Patent Document 1, although the degree of crosslinking increases, on the contrary, the elasticity and strength of the base film may be reduced by irradiation with an electron beam. That is, in order to prevent the generation of thread-like dicing waste, it is necessary to irradiate a certain amount of electron beams, but the resin proceeds to a point where crosslinking is not necessary due to this electron beam irradiation. In some cases, the elasticity is lowered and the brittleness becomes fragile.

  Moreover, in recent years, semiconductor chips have been miniaturized, and in order to maintain a sufficient distance between the semiconductor chips in the expanding process, higher expanding performance than before has been required.

As described above, when the elasticity and strength of the base film are lowered, the base film is broken in an expanding process performed after dicing, and there is a problem in coexistence with prevention of generation of dicing waste. .

  The present invention has been made in view of the prior art as described above, and can reduce dicing waste generated during dicing in a dicing adhesive tape used when cutting a semiconductor wafer, a semiconductor package or the like, and It is an object of the present invention to provide a dicing adhesive tape having excellent expandability.

In order to achieve the above-mentioned problems, the present inventors have intensively studied, and as a result, dicing waste is generated again, i.e., when dicing a semiconductor wafer to which a dicing adhesive tape is attached. The temperature of the base film rises due to the frictional heat of the blade and becomes high temperature, ii) A part of the base film that becomes high temperature and softens is stretched by the dicing blade, iii) The stretched base film Was considered and examined in detail that re-solidifies with cooling water during dicing and remains as dicing waste.
Based on this, as a result of various investigations on the resin of the base film, the base film is difficult to be stretched by the blade by using a specific resin having a predetermined gel fraction value for the base film of the adhesive tape for dicing. In addition, even if it is stretched, it has a predetermined tear strength value, so that the dicing debris breaks up in the middle of growing into a long thread shape and is washed with cooling water at the time of dicing. It has been found that dicing debris can be prevented from being exposed on the surface, and that the adhesive tape for dicing can be prevented from breaking during expansion, and both of these preventions can be achieved, and the present invention has been completed based on this finding.

That is, the said subject of this invention was achieved by the following means.
<1> An adhesive tape for dicing having an adhesive layer on at least one surface of a substrate film,
The base film is made of an ethylene- (meth) acrylic acid copolymer ionomer resin, and the base film has a gel fraction of 30 to 50%,
The dicing pressure-sensitive adhesive tape is characterized in that the tear strength by the trouser tear method of JIS K 7128-1 in the longitudinal direction (MD) and the transverse direction (TD) of the dicing pressure-sensitive adhesive tape is 5 to 12 N / mm. .
<2> The pressure-sensitive adhesive for dicing according to <1>, wherein the pressure-sensitive adhesive layer is composed of a radiation-curable pressure-sensitive adhesive containing a polymer having a radiation-polymerizable carbon-carbon double bond in a side chain as a component. tape.
<3> A full cut dicing method for a semiconductor wafer, wherein the dicing adhesive tape according to <1> or <2> is used, and a dicing blade is cut into a base film of the dicing adhesive tape.

According to the present invention, it is possible to provide a dicing adhesive tape that can reduce dicing waste generated during dicing when cutting a semiconductor wafer, a semiconductor package, or the like and has excellent expandability.
As a result, it has become possible to both prevent the occurrence of dicing waste in the dicing process and prevent the tape breakage of the dicing adhesive tape in the expanding process, which has been conventionally considered difficult.

<< Adhesive tape for dicing >>
The pressure-sensitive adhesive tape for dicing of the present invention has a pressure-sensitive adhesive layer on at least one surface of a base film, the base film is made of an ionomer resin of an ethylene- (meth) acrylic acid copolymer, and the group The gel fraction of the material film is 30 to 50%, and the tear strength by the trouser tear method of JIS K 7128-1 in the machine direction (MD) and the transverse direction (TD) of the adhesive tape for dicing is 5 to 12 N / mm is there.
Hereinafter, it demonstrates in detail from a base film in order.

<Base film>
The base film may be a single layer or a laminate in which a plurality of layers are laminated. In the present invention, the base film is a single layer base film.
In the present invention, the base film is made of an ionomer resin of an ethylene- (meth) acrylic acid copolymer.
Here, the ionomer resin of an ethylene- (meth) acrylic acid copolymer is a resin obtained by crosslinking at least a copolymer having ethylene and (meth) acrylic acid as constituent components of a polymer with metal ions. Note that “(meth) acrylic acid” means both acrylic acid and methacrylic acid, and either one or a mixture thereof may be used. The same applies to other similar terms.

Examples of the metal ion that can be used for the ionomer resin include potassium ion, sodium ion, lithium ion, magnesium ion, and zinc ion. Among them, zinc ion (Zn ²⁺ ) stabilizes the crosslinked structure, Thereby, it is preferable in terms of making it difficult to produce dicing waste. In addition, the neutralization degree by the cation in the carboxy group of the copolymer is preferably 40 to 75 mol%.

  10-98 mass% is preferable, as for content of the ethylene component of the copolymer in the ionomer resin of an ethylene- (meth) acrylic acid copolymer, 30-98 mass% is more preferable, and 50-98 mass% is more preferable. 60 to 98% by mass is particularly preferable.

  In the present invention, the copolymer in the ionomer resin of ethylene- (meth) acrylic acid copolymer is a terpolymer or other quaternary copolymer composed of other copolymerization monomers in addition to ethylene and (meth) acrylic acid. Although it may be a copolymer, a binary or ternary copolymer is preferable, and a binary copolymer of ethylene and (meth) acrylic acid is more preferable.

As a copolymerization monomer other than ethylene and (meth) acrylic acid, any compound may be used as long as it is a compound having an ethylenic double bond.
Examples include α-olefin, (meth) acrylic acid ester, styrene, vinyl acetate, norbornene, acetylene, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, propiolic acid, acetylene, and the like.

  An α-olefin is an alkene having a carbon-carbon double bond in the α-position, that is, at the terminal. The α-olefin preferably has 3 to 24 carbon atoms, and examples thereof include propylene, 1-butene, 1-hexene and 1-octene.

  The (meth) acrylic acid ester preferably has 1 to 24 carbon atoms, more preferably 1 to 8 carbon atoms in the alcohol part. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylic acid t -Butyl, hexyl (meth) acrylate, octyl (meth) acrylate, 2-methylpropyl (meth) acrylate, 2-ethylpropyl (meth) acrylate, 2-methylbutyl (meth) acrylate, (meth) acrylic Examples include 2-ethylbutyl acid, 2-methylhexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 1,2-dimethylbutyl (meth) acrylate, and the like.

  Of these copolymer monomers, (meth) acrylic acid esters are preferred.

  The content of the copolymerization monomer component is preferably 1 to 20% by mass based on the mass of the ternary copolymer. In this case, the content of the (meth) acrylic acid component is based on the mass of the ternary copolymer. 1 to 20% by mass is preferable.

The mass average molecular weight of the ionomer resin of the ethylene- (meth) acrylic acid copolymer is preferably 1,000 to 5,000,000, and more preferably 10,000 to 4,000,000.
In the present invention, the mass average molecular weight is a polystyrene-reduced mass average molecular weight by a conventional method.

  The ionomer resin of the ethylene- (meth) acrylic acid copolymer may be one kind or a combination of two or more kinds.

  Although the thickness of a base film is 50-200 micrometers normally, in this invention, 70-180 micrometers is preferable. If the base film has such a thickness, the cutting depth of the dicing blade can be sufficiently secured.

In the present invention, the gel fraction of the base film is 30 to 50%.
The gel fraction of the base film indicates the degree of crosslinking of the resin, and the gel fraction of the base film is preferably 35 to 50%, more preferably 40 to 50%.
When the gel fraction is high, the effect of preventing the generation of dicing waste is high, but the elasticity and strength of the base film are lowered, and the base film is easily broken in the expanding step. Further, when the gel fraction is low, a large amount of dicing waste is generated, and it becomes difficult to achieve both elasticity and strength and expandability.

  The gel fraction of a base film is adjusted with the structure of the ionomer resin of an ethylene- (meth) acrylic acid copolymer. Since it crosslinks by making metal ions such as zinc and sodium act on the copolymer of ethylene and acrylic acid, the gel fraction can be adjusted by changing the content of acrylic acid and the type of metal. .

  When the base film is melted with a specific solvent, the gel fraction is defined as the portion that remains undissolved as a gel (the cross-linked portion remains as a gel). It is a ratio (percentage) to the material film mass.

Specifically, the gel fraction can be determined as follows.
(1) Wrapped in a stainless steel mesh (for example, No. 400, manufactured by Nippon Wire Mesh Industrial Co., Ltd., mass measurement completed) and immersed in a 120 ° C. xylene solution for 24 hours.
(2) Leave in a well-ventilated place at room temperature (25 ° C.) for 2 hours.
(3) After vacuum drying at 80 Pa for 16 hours at 10 Pa (7.5 × 10 ⁻² torr) or less, the total mass of the remaining base film and wire mesh is measured.
(4) The gel fraction is determined according to the following formula.

Gel fraction (%) =
{(Total mass of base film and wire mesh after immersion in xylene)-(mass of wire mesh)} / (base film mass before immersion in xylene) × 100

  The gel fraction can be adjusted by the type of resin constituting the base film, the degree of crosslinking, the type of pressure-sensitive adhesive, and the like.

<Adhesive layer>
The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer is not particularly limited, but an acrylic pressure-sensitive adhesive whose base polymer is a (meth) acrylic copolymer is preferable. In the present invention, the pressure-sensitive adhesive is limited to this as long as it has a holding property that does not cause separation from the semiconductor wafer during expansion and a property that facilitates separation from the semiconductor chip during pickup. However, the pressure-sensitive adhesive layer can be formed of various pressure-sensitive adhesives. As such an adhesive, for example, an adhesive having a base polymer such as rubber, silicone, or polyvinyl ether can be used.

  In order to add cohesion to these base polymers, a crosslinking agent can be blended. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, an aziridine-based crosslinking agent, and an amine resin corresponding to the base polymer. Further, the pressure-sensitive adhesive can contain various additive components as desired within the range in which the object of the present invention is not impaired.

  As the pressure-sensitive adhesive, a radiation curable, heat-foaming, or pressure-sensitive pressure-sensitive adhesive can be used. As the radiation-curable pressure-sensitive adhesive, a pressure-sensitive adhesive that is cured by ultraviolet rays, an electron beam, or the like and easily peels at the time of peeling can be used. As the heat-foaming pressure-sensitive adhesive, a pressure-sensitive adhesive that can be easily peeled off by a foaming agent or an expansion agent by heating can be used. As the radiation curable pressure-sensitive adhesive, for example, those described in JP-B-1-56112 and JP-A-7-135189 are preferably used, but are not limited thereto.

(Radiation curable adhesive)
In the present invention, it is preferable to use a radiation curable pressure-sensitive adhesive.
The radiation curable pressure-sensitive adhesive is only required to have a property of being cured by radiation to form a three-dimensional network, and is roughly divided into 1) having a radiation-polymerizable carbon-carbon double bond (ethylenic double bond) in the side chain. Compared with a pressure-sensitive adhesive composed of a base resin (polymer) and 2) a normal rubber-based or (meth) acrylic pressure-sensitive base resin (polymer), at least two radiation-polymerizable carbon-carbon molecules in the molecule. The pressure-sensitive adhesive is classified into a low molecular weight compound having a heavy bond (ethylenic double bond) (hereinafter referred to as a radiation polymerizable low molecular weight compound) and a photopolymerization initiator.

  In the present invention, if the dicing adhesive tape contains a large amount of a low molecular weight compound, after the dicing adhesive tape is applied to a semiconductor wafer, if the period of time until irradiation or pick-up process is long, the low molecular weight component is dicing. By moving to the interface between the adhesive tape for the semiconductor and the semiconductor chip, the adhesiveness is remarkably increased, and a phenomenon that the peeling between the adhesive tape for dicing and the semiconductor chip during pick-up becomes heavy is observed. For this reason, the adhesive which consists of base resin (polymer) which has a radiation-polymerizable carbon-carbon double bond (ethylenic double bond) in a side chain is preferable.

1) Adhesive comprising a base resin having a radiation polymerizable carbon-carbon double bond in the side chain The adhesive having a radiation polymerizable carbon-carbon double bond in the side chain is preferably a (meth) acrylic adhesive, It is particularly preferable that the base resin contains a (meth) acrylic polymer or a (meth) acrylic polymer as a main component.
Here, a (meth) acrylic polymer as a main component means that the (meth) acrylic polymer component is at least 50% by mass or more, preferably 80% by mass or more (100% by mass or less).

  The (meth) acrylic polymer has a radiation-polymerizable carbon-carbon double bond (ethylenic double bond) at least in the side chain, so that it can be cured by irradiation, and further has a functional group such as an epoxy group or a carboxyl group. It may have a group.

The (meth) acrylic polymer having a radiation-polymerizable carbon-carbon double bond in the side chain may be produced by any method. For example, a (meth) acrylic having a functional group (α) in the side chain. Polymer and radiation-polymerizable carbon-carbon double bonds such as (meth) acryloyl group and (meth) acryloyloxy group, and the side chain functional group of this (meth) acrylic polymer Those obtained by reacting a compound having a functional group (β) capable of reacting with (α) are preferred.
The group having a radiation-polymerizable carbon-carbon double bond may be any group as long as it has a non-aromatic ethylenic double bond, but a (meth) acryloyl group, a (meth) acryloyloxy group, (Meth) acryloylamino group, allyl group, 1-propenyl group and vinyl group (including styrene or substituted styrene) are preferable, and (meth) acryloyl group and (meth) acryloyloxy group are more preferable.
Examples of the functional groups (α) and (β) include a carboxy group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group (—N═C═O).

  Here, when one functional group of the functional group (α) and the functional group (β) is a carboxy group, a hydroxyl group, an amino group, a mercapto group, or a cyclic acid anhydride group, the other functional group is , An epoxy group, and an isocyanate group. When one functional group is a cyclic acid anhydride group, examples of the other functional group include a carboxy group, a hydroxyl group, an amino group, and a mercapto group. In addition, when one functional group is an epoxy group, the other functional group may be an epoxy group.

As the functional group (α), a carboxy group and a hydroxyl group are preferable, and a hydroxyl group is particularly preferable.
The (meth) acrylic polymer having a functional group (α) in the side chain is a (meth) acrylic monomer having a functional group (α), preferably a (meth) acrylic ester [(particularly, a functional group in the alcohol part). It can be obtained by using (having (α)) as a monomer component.
The (meth) acrylic polymer having a functional group (α) in the side chain is preferably a copolymer, and this copolymerization component is a (meth) acrylic acid alkyl ester, in particular, a functional group ( α) and (meth) acrylic acid alkyl esters in which a group having a radiation-polymerizable carbon-carbon double bond is not substituted are preferred.

Examples of (meth) acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2 -Ethylhexyl acrylate, dodecyl acrylate, decyl acrylate hexyl acrylate, and the corresponding methacrylates.
Although the (meth) acrylic acid ester may be one type or two or more types, it is preferable to use those having an alcohol part having 5 or less carbon atoms and those having 6 to 12 carbon atoms.

  In addition, since a glass transition point (Tg) becomes so low that a monomer with large carbon number of an alcohol part is used, the thing of a desired glass transition point can be obtained. In addition to the glass transition point, it is also preferable to blend a low molecular compound having a carbon-carbon double bond such as vinyl acetate, styrene or acrylonitrile for the purpose of improving compatibility and various performances. The content of is preferably in the range of 5% by mass or less.

  Examples of (meth) acrylic monomers having a functional group (α) include acrylic acid, methacrylic acid, cinnamic acid, itaconic acid, fumaric acid, phthalic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycols Monoacrylates, glycol monomethacrylates, N-methylolacrylamide, N-methylolmethacrylamide, allyl alcohol, N-alkylaminoethyl acrylates, N-alkylaminoethyl methacrylates, acrylamides, methacrylamides, maleic anhydride, Some of the isocyanate groups of itaconic anhydride, fumaric anhydride, phthalic anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and polyisocyanate compounds Alkoxy group and a photopolymerizable carbon - like those urethanization a monomer having a carbon-carbon double bond.

  Among these, acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycidyl acrylate, glycidyl methacrylate are preferable, and acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylate Are more preferable, and 2-hydroxyalkyl acrylates and 2-hydroxyalkyl methacrylates are more preferable.

The functional group (β) in the compound having a radiation-polymerizable carbon-carbon double bond and a functional group (β) is preferably an isocyanate group, and has, for example, an isocyanate (—N═C═O) group in the alcohol part ( Examples include (meth) acrylic acid esters, and (meth) acrylic acid alkyl esters substituted with an isocyanate (—N═C═O) group are particularly preferable. Examples of such a monomer include 2-isocyanatoethyl methacrylate and 2-isocyanatoethyl acrylate.
Moreover, the compound illustrated with the (meth) acrylic-type monomer which has a functional group ((alpha)) as a preferable compound in case a functional group ((beta)) is other than an isocyanate group is mentioned.

  The compound having a radiation-polymerizable carbon-carbon double bond and a functional group (β) is added to the side chain functional group (α) in addition to the (meth) acrylic polymer having the functional group (α) in the side chain. ), Preferably by reacting with a hydroxyl group, a polymerizable group can be incorporated into the copolymer, and the adhesive strength after irradiation can be reduced.

  In the synthesis of the (meth) acrylic copolymer, as the organic solvent when the reaction is carried out by solution polymerization, ketone, ester, alcohol, and aromatic solvents can be used, among which toluene, Generally a good solvent of a (meth) acrylic polymer, such as ethyl acetate, isopropyl alcohol, benzene methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, and a solvent having a boiling point of 60 to 120 ° C. is preferable. As the polymerization initiator, radical generators such as azobis compounds such as α, α'-azobisisobutyronitrile and organic peroxide compounds such as benzoyl peroxide are usually used. At this time, if necessary, a catalyst and a polymerization inhibitor can be used in combination, and a (meth) acrylic copolymer having a desired molecular weight can be obtained by adjusting the polymerization temperature and the polymerization time. In terms of adjusting the molecular weight, it is preferable to use a solvent such as mercaptan or carbon tetrachloride. This reaction is not limited to solution polymerization, and other methods such as bulk polymerization and suspension polymerization may be used.

The mass average molecular weight of the base resin [preferably (meth) acrylic copolymer] having a radiation-polymerizable carbon-carbon double bond in the side chain is preferably about 200,000 to 1,000,000.
If the mass average molecular weight exceeds 1,000,000, when irradiated, the adhesive after irradiation is not flexible and is brittle, so that adhesive residue is left on the surface of the semiconductor chip during peeling. If the mass average molecular weight is less than 200,000, the cohesive force before radiation irradiation is small and the adhesive force is weak, so that the semiconductor chip cannot be held sufficiently during dicing, and there is a possibility of chip fly. In addition, curing is insufficient after irradiation, and adhesive residue is left on the surface of the semiconductor chip during peeling. In order to prevent these as much as possible, the mass average molecular weight is preferably 200,000 or more.

The introduction amount of the radiation-polymerizable carbon-carbon double bond of the base resin having a radiation-polymerizable carbon-carbon double bond in the side chain is the iodine value [g of iodine (I ₂ ) added to 100 g of the base resin]. 0.5-20 are preferable and 5-15 are more preferable. If the iodine value is less than 0.5, the effect of reducing the adhesive strength after irradiation is reduced, resulting in insufficient curing of the adhesive, causing adhesive residue, and if the iodine value exceeds 20, adhesion after irradiation. In addition to the insufficient fluidity of the adhesive, the adhesive is brittle, the adhesive cured at the time of peeling is torn off and adhesive residue is generated, and the base resin has a radiation-polymerizable carbon-carbon double bond in the side chain It lacks stability and is difficult to manufacture.

  The glass transition point of the base resin having a radiation-polymerizable carbon-carbon double bond in the side chain is preferably −70 to −35 ° C., more preferably −70 to −40 ° C. If the glass transition point is lower than -70 ° C, the fluidity of the pressure-sensitive adhesive is high and causes glue residue. If the glass transition point is higher than -35 ° C, the fluidity is insufficient and it is difficult to adjust to the back surface of the semiconductor wafer. It will cause peeling from the wafer.

The acid value of the base resin having a radiation-polymerizable carbon-carbon double bond in the side chain [the number of mg of potassium hydroxide necessary for neutralizing free fatty acid present in 1 g of the base resin] is 0.5 to 30 is preferable and 1-20 is more preferable.
Hydroxyl value of base resin having radiation-polymerizable carbon-carbon double bond in side chain [when 1 g of base resin is acetylated, mg of potassium hydroxide necessary to neutralize acetic acid bonded to hydroxyl group ] Is preferably 5 to 100, more preferably 10 to 80.
By doing in this way, it is excellent in the adhesive residue prevention effect at the time of peeling of the adhesive tape for dicing further.

  In addition, the acid value and the hydroxyl value are prepared by a (meth) acrylic polymer having a functional group (α) in the side chain, a radiation-polymerizable carbon-carbon double bond, and this (meth) acrylic. In the step of reacting a compound having a functional group (β) capable of reacting with the functional group (α) of the side chain of the system polymer, it can be prepared as desired by leaving an unreacted functional group.

When a base resin having a radiation-polymerizable carbon-carbon double bond in the side chain is cured by irradiation, a photopolymerization initiator such as isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chloro Thioxanthone, dodecyl thioxanthone, dimethyl thioxanthone, diethyl thioxanthone, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenyl propane and the like can be used.
The blending amount of these photopolymerization initiators is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the base resin. If the blending amount is too small, the reaction is insufficient, and if the blending amount is too large, the low molecular components increase, thereby affecting the contamination.

The pressure-sensitive adhesive made of a base resin having a radiation-polymerizable carbon-carbon double bond in the side chain preferably contains a crosslinking agent.
Such a crosslinking agent may be any, but a crosslinking agent selected from the group of polyisocyanates, melamine / formaldehyde resins and epoxy resins is preferred.
Of these, polyisocyanates are preferred in the present invention.

  The polyisocyanates are not particularly limited, and examples thereof include 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4′-diphenyl ether diisocyanate, 4,4 ′-[2,2-bis (4 -Phenoxyphenyl) propane] aromatic isocyanate such as diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate Lysine diisocyanate, lysine triisocyanate and the like. Specifically, Coronate L (made by Nippon Polyurethane Co., Ltd., trade name) or the like can be used.

  Specific examples of the melamine / formaldehyde resin include Nicalac MX-45 (trade name, manufactured by Sanwa Chemical Co., Ltd.), Melan (trade name, manufactured by Hitachi Chemical Co., Ltd.), and the like.

  As the epoxy resin, TETRAD-X (trade name, manufactured by Mitsubishi Chemical Corporation) or the like can be used.

0.1-10 mass parts is preferable with respect to 100 mass parts of base resins, and, as for the compounding quantity of a crosslinking agent, 1-10 mass parts is more preferable.
After application of the pressure-sensitive adhesive, the base resin forms a cross-linked structure with the cross-linking agent, and the cohesive force of the pressure-sensitive adhesive can be improved.

  When the blending amount of the crosslinking agent is less than 0.1 parts by mass, the effect of improving the cohesive force is not sufficient, and the adhesive has high fluidity and causes adhesive residue, and the adhesive surface and the adherend surface are easily misaligned. Sometimes peel off. When the amount of the cross-linking agent exceeds 10 parts by mass, a cross-linking structure is rapidly formed during the mixing and application of the pressure-sensitive adhesive, and the curing reaction proceeds, so that workability is impaired. Moreover, the softness | flexibility of an adhesive will be impaired and it will cause the peeling at the time of an expansion.

2) Adhesive containing a radiation-polymerizable low molecular weight compound The main component of the adhesive containing a radiation-polymerizable low molecular weight compound is not particularly limited, and is a known chlorinated polypropylene resin or acrylic used for the adhesive. Resin [(meth) acrylic resin], polyester resin, polyurethane resin, epoxy resin and the like can be used.
As this pressure-sensitive adhesive, it is preferable to prepare a pressure-sensitive adhesive by appropriately blending a photopolymerization initiator, a curing agent and the like in addition to an acrylic resin as a base resin and a radiation polymerizable low molecular weight compound.

As the radiation-polymerizable low molecular weight compound, a low molecular weight compound having at least two radiation-polymerizable carbon-carbon double bonds in a molecule that can be three-dimensionally reticulated by irradiation is used.
Specifically, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoester (meth) acrylate, and the like are applicable.

  In addition to the above (meth) acrylate compounds, urethane (meth) acrylate oligomers can also be used as radiation-polymerizable low molecular weight compounds. Urethane (meth) acrylate oligomers include a polyester compound or a polyether compound such as a polyether type and a polyvalent isocyanate compound (for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3 (Xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate, etc.) are reacted with a terminal isocyanate urethane prepolymer (hydroxy) having a hydroxyl group (for example, , 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, etc.) Obtained by.

In addition, you may add a photoinitiator to an adhesive.
Examples of photopolymerization initiators include isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, dodecyl thioxanthone, dimethyl thioxanthone, diethyl thioxanthone, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenyl propane, and the like. Can be used.
The blending amount of these photopolymerization initiators is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the base resin. If the blending amount is too small, the reaction is insufficient, and if the blending amount is too large, the low molecular components increase, thereby affecting the contamination.

The pressure-sensitive adhesive preferably contains a crosslinking agent.
Such a crosslinking agent is preferably the crosslinking agent mentioned in the pressure-sensitive adhesive made of a base resin having a radiation-polymerizable carbon-carbon double bond in the side chain.
0.1-10 mass parts is preferable with respect to 100 mass parts of base resins, and, as for the compounding quantity of a crosslinking agent, 1-10 mass parts is more preferable.

  The thickness of the pressure-sensitive adhesive is not particularly limited and may be appropriately set. In the present invention, 5 to 30 μm is preferable.

  In order to protect the pressure-sensitive adhesive layer before use, the pressure-sensitive adhesive tape for dicing of the present invention preferably has a release film temporarily adhered to the upper surface of the pressure-sensitive adhesive layer.

<Characteristics of dicing adhesive tape>
The adhesive tape for dicing of the present invention has a tear strength of 5-12 N / mm in the longitudinal (MD) and transverse (TD) JIS K 7128-1 trouser tear methods.
By setting the tear strength within this range, the generation of dicing waste is suppressed at 5 to 12 N / mm. When the tear strength exceeds 12 N / mm, the base film is not broken in the process of being stretched by the dicing blade, and tends to be long thread-like dicing waste. Further, when the tear strength is less than 5 N / mm, breakage tends to occur starting from a dicing line on the dicing adhesive tape during expansion.

<< Dicing Method of Semiconductor Wafer with Dicing Adhesive Tape >>
The semiconductor wafer dicing method itself using the dicing adhesive tape of the present invention can be carried out in the same manner as a normal method, but a full-cut dicing method in which a dicing blade cuts into the base film of the dicing adhesive tape. Is particularly preferred.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

  First, after preparing the base films 1A to 1I and the adhesives 2A and 2B shown in Table 1 below, the thickness of the adhesives 2A and 2B after drying is 5 μm on the base films 1A to 1I. Adhesives 2A and 2B were applied to the substrate and dried at 110 ° C. for 3 minutes to prepare dicing adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 5 shown in Table 2 below.

(Base film)
As the base films 1A to 1I, base films having a thickness of 100 to 150 μm shown in Table 1 below were used.

・ Ionomer resin A of ethylene- (meth) acrylic acid copolymer
An ionomer resin that is a copolymer of an ethylene component and methacrylic acid and is cross-linked with the metal ion Zn ²⁺

・ Ionomer resin B of ethylene- (meth) acrylic acid copolymer
An ionomer resin C which is a copolymer of an ethylene component and methacrylic acid and is cross-linked with a metal ion Zn ²⁺ and an ionomer resin C of an ethylene- (meth) acrylic acid copolymer
An ionomer resin that is a copolymer of an ethylene component and acrylic acid and is cross-linked with the metal ion Zn ²⁺

・ Ionomer resin D of ethylene- (meth) acrylic acid copolymer
An ionomer resin that is a copolymer of an ethylene component and methacrylic acid and is crosslinked with the metal ion Na ⁺

・ Ionomer resin E of ethylene- (meth) acrylic acid copolymer
An ionomer resin that is a copolymer of an ethylene component and acrylic acid and is cross-linked with the metal ion Na ⁺

PP / elastomer copolymer Thermoplastic elastomer in which a small amount of ethylene-propylene rubber is dispersed in polypropylene. Ethylene-vinyl acetate copolymer. Copolymer of ethylene component and vinyl acetate. Ethylene- (meth) acrylic acid copolymer. The ionomer resin A was irradiated with an electron beam of 5 Mrad on the ionomer resin A of an ethylene- (meth) acrylic acid copolymer.

(Preparation of adhesive)
Adhesives 2A and 2B were prepared as follows.

<Adhesive 2A>
The pressure-sensitive adhesive 2A is an acrylic pressure-sensitive adhesive having a radiation curable carbon-carbon double bond in the side chain as a base resin.
70 mol% of 2-ethylhexyl acrylate, 20 mol% of 2-hydroxyethyl acrylate and 10 mol% of methyl methacrylate were blended and copolymerized in an ethyl acetate solution to obtain a polymer solution of (meth) acrylic copolymer. To 100 parts by mass of this polymer, 5.0 parts by mass of 2-methacryloyloxyethyl isocyanate (trade name, Karenz MOI manufactured by Showa Denko KK) is added and reacted in this solution to the hydroxyl group of the copolymer side chain. An acrylic copolymer polymer having a double bond-containing group in the side chain was synthesized by adding a double bond-containing group derived from the above.
The acrylic copolymer polymer having a double bond-containing group in the side chain has a mass average molecular weight of 600,000, a glass transition temperature (Tg) of −64 ° C., and a radiation curable carbon-carbon double bond content of 0.6 meq / g. It was.

  For 100 parts by mass of the acrylic copolymer having a double bond-containing group, 1 part by mass of Coronate L (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) is used as a curing agent, and α-hydroxycyclohexyl phenyl ketone is used as a photopolymerization initiator. 3 masses of was obtained, and the adhesive composition of adhesive 2A was obtained.

<Adhesive 2B>
The pressure-sensitive adhesive 2B is an acrylic pressure-sensitive adhesive containing a radiation polymerizable low molecular weight compound.
A polymer solution of (meth) acrylic copolymer was obtained by blending 25 mol% 2-ethylhexyl acrylate, 55 mol% 2-hydroxyethyl acrylate and 20 mol% methyl methacrylate and copolymerizing them in an ethyl acetate solution.
The obtained (meth) acrylic copolymer had a mass average molecular weight of 300,000 and a glass transition temperature (Tg) of -30 ° C.

  1 part by mass of coronate L (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a radiation-polymerizable low molecular weight compound as a radiation-polymerizable low molecular weight compound and 80 parts by mass of a tetramethylolmethane tetraacrylate as a curing agent with respect to 100 parts by mass of a (meth) acrylic copolymer. As a photopolymerization initiator, 5 masses of α-hydroxycyclohexyl phenyl ketone was blended to obtain a pressure-sensitive adhesive composition of pressure-sensitive adhesive 2B.

The pressure-sensitive adhesives 2A and 2B were applied on the base films 1A to 1I so that the dry film thickness was 5 μm, dried at 110 ° C. for 3 minutes, and Examples 1 to 5 and Comparative Examples shown in Table 2 below. 1 to 5 adhesive tapes for dicing were produced.

(Evaluation test)
In the adhesive tapes for dicing of Examples 1 to 5 and Comparative Examples 1 to 5, as shown below, the tear test, the gel fraction, the number of dicing scraps generated, and the expandability were evaluated.

[Tear test]
The tear strength in the machine direction (MD) and transverse direction (TD) of the adhesive tape for dicing was measured by the trouser tear method of JIS K 7128-1.

[Gel fraction of base film]
The gel fraction was measured by the following procedure.
(1) The base film whose mass was measured was wrapped in a stainless steel mesh (No. 400, manufactured by Nippon Wire Mesh Commerce Co., Ltd., weight measurement completed) and immersed in a 120 ° C. xylene solution for 24 hours.
(2) It was left at room temperature in a well-ventilated place for 2 hours.
(3) After vacuum drying at 80 Pa for 16 hours at 10 Pa (7.5 × 10 ⁻² torr) or less, the total mass of the remaining base film and wire mesh was measured.
(4) The gel fraction was calculated by the following formula.

Gel fraction (%) =
{(Total mass of base film and wire mesh after immersion in xylene)-(mass of wire mesh)} / (base film mass before immersion in xylene) × 100

[Dicing waste generation number]
With respect to the semiconductor wafer diced under the following conditions, dicing waste exposed on the semiconductor wafer from the surface side of the semiconductor wafer was observed with an optical microscope (100 times), and the number of dicing waste was counted.

(Dicing conditions)
Dicing machine: DAD-340 manufactured by DISCO Corporation
Dicing blade: NBC-ZH2030-27HCDD manufactured by DISCO Corporation
Dicing blade rotation speed: 50,000 rpm
Cutting speed: 80 mm / s
Cooling water volume: 20 ml / s
Dicing size: 2mm square Dicing blade depth of cut into adhesive tape for dicing: 40μm

[Expandable]
For semiconductor wafers diced under the following conditions, the expandability evaluation was performed under the following conditions. When the rupture of the adhesive tape for dicing did not occur, “○”, and when rupture occurred, “X”. .

(Dicing conditions)
Dicing machine: DAD-340 manufactured by DISCO Corporation
Dicing blade: NBC-ZH2030-27HCDD manufactured by DISCO Corporation
Dicing blade rotation speed: 50,000 rpm
Cutting speed: 80 mm / s
Cooling water volume: 20 ml / s
Dicing size: 2mm square Dicing blade depth of cut into adhesive tape for dicing: 40μm

(Expanding condition)
Expanding device: CAP-300II manufactured by Canon Machinery Co., Ltd.
Expandable expansion amount: 10mm

  The obtained results are summarized in Table 2 below.

  The adhesive tape for dicing of Example 1 has tear strengths in the ranges of MD: 5.5 N / mm, TD: 10.0 N / mm and 5 to 12 N / mm, and the gel fraction is 42%, which is 30 to 50%. Therefore, only one dicing scrap was found on the semiconductor wafer surface, which was good. Also, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Example 2 has a tear strength within the range of MD: 7.3 N / mm, TD: 10.9 N / mm and 5 to 12 N / mm, and a gel fraction of 44%, 30 to 50%. Therefore, only three dicing scraps were observed on the semiconductor wafer surface, which was good. Also, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Example 3 has tear strengths in the ranges of MD: 5.7 N / mm, TD: 10.3 N / mm and 5 to 12 N / mm, and the gel fraction is 42%, which is 30 to 50%. Therefore, only two dicing scraps were found on the semiconductor wafer surface, which was good. Also, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Example 4 has a tear strength of MD: 5.0 N / mm, TD: 5.9 N / mm and 5 to 12 N / mm, and a gel fraction of 50%, which is 30 to 50%. Therefore, dicing waste was good because generation of dicing waste was not observed on the semiconductor wafer surface. Also, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Example 5 has a tear strength of MD: 10.2 N / mm, TD: 11.8 N / mm and a range of 5 to 12 N / mm, and a gel fraction of 35%, which is 30 to 50%. Therefore, only nine dicing scraps were found on the semiconductor wafer surface, which was good. Also, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Comparative Example 1 has a tear strength of MD: 22.0 N / mm, TD: 19.0 N / mm and outside the range of 5 to 12 N / mm, and the gel fraction is 16%, which is 30 to 50%. Therefore, 67 dicing scraps were generated on the surface of the semiconductor wafer. However, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Comparative Example 2 has a tear strength of MD: 15.3 N / mm, TD: 17.1 N / mm and outside the range of 5 to 12 N / mm, and the gel fraction is 28%, 30 to 50%. Therefore, as many as 31 dicing scraps were observed on the semiconductor wafer surface. However, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Comparative Example 3 has a tear strength of MD: 96.7 N / mm, TD: 129.3 N / mm and out of the range of 5 to 12 N / mm, and the gel fraction is also 5% and 30 to 50%. Therefore, as many as 97 dicing scraps were observed on the semiconductor wafer surface. However, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Comparative Example 4 has a tear strength of MD: 70.1 N / mm, TD: 70.4 N / mm and outside the range of 5 to 12 N / mm, and the gel fraction is also 5% and 30 to 50%. Therefore, as many as 181 dicing scraps were observed on the semiconductor wafer surface. However, the expandability was good and no breakage was observed.

  The adhesive tape for dicing of Comparative Example 5 has a tear strength of MD: 3.2 N / mm, TD: 4.8 N / mm and out of the range of 5 to 12 N / mm, and the gel fraction is also 60% and 30 to 50%. Although there was no dicing waste on the surface of the semiconductor wafer and generation was not confirmed, tape breakage occurred during the evaluation of expandability.

  The dicing pressure-sensitive adhesive tapes of Examples 1 to 5 of the present invention are all 5 in the measurement of tearing strength in the machine direction (MD) and transverse direction (TD) of the pressure-sensitive adhesive tape for dicing by the trouser tear method of JIS K 7128-1. It is within the range of -12 N / mm, and the gel fraction of the base film in the gel fraction measurement satisfies that it is in the range of 30-50%. When using the adhesive tape for dicing which concerns on an example form, while generating generation | occurrence | production of dicing waste, it turned out that the tape fracture | rupture in an expansion process can be prevented.

  As described above, by using the dicing adhesive tape of the present invention, the productivity of the dicing adhesive tape is excellent, that is, it is possible to achieve both prevention of dicing dust generation and expandability.

  As a result, it can be seen that the dicing adhesive tape of the present invention is a dicing adhesive tape suitable for dicing a semiconductor wafer by a full-cut dicing method.

Claims (3)

A pressure-sensitive adhesive tape for dicing having an adhesive layer on at least one surface of a base film,
The base film is made of an ethylene- (meth) acrylic acid copolymer ionomer resin, and the base film has a gel fraction of 30 to 50%,
The dicing pressure-sensitive adhesive tape is characterized in that the tear strength by the trouser tear method of JIS K 7128-1 in the longitudinal direction (MD) and the transverse direction (TD) of the dicing pressure-sensitive adhesive tape is 5 to 12 N / mm. .    2. The dicing pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive layer comprises a radiation-curable pressure-sensitive adhesive comprising a polymer having a radiation-polymerizable carbon-carbon double bond in a side chain as a component.   A full cut dicing method for a semiconductor wafer, wherein the dicing adhesive tape according to claim 1 or 2 is used, and a dicing blade is cut into a base film of the dicing adhesive tape.