JP2006282794A - Adhesive tape for wafer dicing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive tape for wafer dicing, which does not worsen chipping during the dicing of small chips and has excellent expandability of chipping in a process of expanding. <P>SOLUTION: The adhesive tape for wafer dicing is characterized by having an intermediate layer as a layer constituting a supporting film or in between a supporting film and an adhesive agent layer coated on the above supporting film. The tape reversibly changes, softens and hardens, at ambient temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a so-called adhesive tape for wafer dicing that is used when a wafer is cut into chips.

  In a manufacturing process of a semiconductor device such as an IC or LSI, a dicing process is usually performed in which a wafer after pattern formation is cut and separated into individual chips after grinding the back surface in order to reduce the thickness. At that time, a full cut method is adopted in which the wafer is bonded and fixed to the wafer dicing adhesive tape in advance and cut to a part of the base film layer of the adhesive tape along the chip shape.

In the next process after dicing, each chip is picked up from the wafer dicing adhesive tape and mounted on the lead frame. At that time, the wafer dicing adhesive tape is radially extended to uniformly widen the chip interval. The so-called expanded state is used for picking up.
In recent years, the chip size to be diced is often less than 1 mm, and when expanding in the pick-up process, expandability is required to widen the chip interval and chipping (chipping) of the wafer cut surface is required when dicing the wafer. ) Is required.

On the other hand, a tape using vinyl chloride as a base material is disclosed as an adhesive tape for wafer dicing having excellent chipping properties and expandability (for example, Patent Document 1). However, a base film made of vinyl chloride generates a toxic gas containing a toxic halogen during incineration after use, and a stabilizer may be blended so as to withstand heat during dicing. Considering the effect of the chip on the chip is not preferable.
Further, although an adhesive tape for semiconductor wafer dicing using a side chain crystallizable polymer for the pressure sensitive adhesive layer is disclosed (for example, Patent Document 2), the side chain crystallizable polymer has a contamination property to a semiconductor wafer. It is bad and the characteristics of the obtained chip may be greatly impaired.

JP 2001-226647 A Japanese Patent Laid-Open No. 9-249858

  The present invention provides a pressure-sensitive adhesive tape for wafer dicing that does not impair the chipping property that occurs during dicing in a small chip and has excellent expandability of the chip interval in the expanding process.

  The inventors of the present invention have made various studies in order to overcome the problems in the process up to the step of obtaining chips by cutting the conventional wafer into small pieces, and as a result, at least the film-like support is configured. A wafer dicing pressure-sensitive adhesive tape having an intermediate layer that can be reversibly softened and cured by an atmospheric temperature between the film-shaped support and the pressure-sensitive adhesive layer applied to the film-shaped support as one layer. It has been found that the chip retainability during dicing is excellent, has an effect of suppressing chipping, and is excellent in expandability in the expanding process, and the present invention has been completed.

That is, the present invention
(1) As at least one layer constituting the film-like support or between the film-like support and the pressure-sensitive adhesive layer applied to the film-like support, the film-like support can be reversibly softened and cured depending on the ambient temperature. An adhesive tape for wafer dicing, comprising an intermediate layer;
(2) The adhesive tape for wafer dicing according to (1), wherein the base resin in the resin composition constituting the intermediate layer is a side chain crystalline polymer,
(3) The storage elastic modulus at 23 ° C. is 2.0 × 10 ⁶ Pa or higher, and the storage elastic modulus at the primary melting transition temperature Tm or higher is 3.0 × 10 ⁵ Pa or lower ( 2) Adhesive tape for wafer dicing as described above,
Is to provide.

  The adhesive tape for wafer dicing of the present invention can increase the expandability of the chip at the time of expansion without impairing the conventional required characteristics such as chip holding force at the time of dicing, chipping, etc. Even a microchip of less than 1 mm can be picked up without any problem.

In the present invention, as at least one layer constituting the film-like support or between the film-like support and the pressure-sensitive adhesive layer applied to the film-like support, reversibly softening-curing change depending on the ambient temperature. A possible intermediate layer is arranged.
Therefore, the pressure-sensitive adhesive tape for wafer dicing of the present invention reversibly changes its hardness by giving a temperature difference such as heating or cooling to the layer constituting the intermediate layer, and does not impair the chipping property by curing at the time of dicing. Since it can be processed and the chip interval can be widened by softening during expansion, it can be picked up well. Moreover, since the change proceeds quickly, the processing efficiency is not reduced.

This tape is used as follows, for example.
(A) Before dicing the wafer, the wafer dicing adhesive tape of the present invention is bonded in advance to the wafer grinding surface opposite to the circuit forming surface of the wafer at room temperature (for example, 23 ° C.).
(B) Next, in the process of dividing the wafer into small pieces by dicing, the chip is firmly formed by dicing using a cooling water having a cutting water temperature applied to the cutting blade and the wafer lower than the room temperature of 23 ° C. during the processing. Cured to a holdable hardness.
(C) A fixed frame is bonded to the pressure-sensitive adhesive surface of the pressure-sensitive adhesive tape for wafer dicing of the present invention, to which the wafer is fixed, and a temperature higher than room temperature (for example, 23 ° C.) on the back surface (base film surface) of the pressure-sensitive adhesive tape. It is expanded by placing it on the stage or blowing hot air.

  In the step (b), the intermediate layer of the pressure-sensitive adhesive tape for wafer dicing of the present invention is cured and chipping can be reduced, and in the step (c), the intermediate layer is softened so that sufficient expandability can be secured, and pick-up properties are improved. It becomes good.

  A side chain crystalline polymer is preferably used for the intermediate layer. When the DSC (Differential Scanning Calorimetry) measurement of the side chain crystalline polymer in the present invention is performed under a normal temperature and a heating rate of 10 ° C./min in an air atmosphere, a melting-temperature curve as shown in FIG. 1 is obtained. . The intermediate layer in the pressure-sensitive adhesive tape of the present invention exhibits a large endothermic peak as the temperature rises. The melting-temperature curve is almost flat before and after the endothermic peak is observed, and the point A where the melting-temperature curve before the endotherm is flat and the point B where the melting-temperature curve after the endotherm is flat are linear. tie. This straight line is taken as a baseline. When the temperature is further increased from the point A, the gradient of the heat quantity-temperature curve becomes maximum. A tangent line is drawn at this point C, and the point where the tangent line intersects the base line is the melting start temperature Ti. When the temperature is further increased beyond the point C, the endothermic curve reaches a peak. This point is the primary melting transition temperature Tm. In the present invention, the primary melting transition temperature Tm refers to a temperature at which a specific state of a polymer that is aligned in an ordered order is heated to cause a disordered state before heating. When the temperature is further increased, the melting completion point B is reached. The temperature at this time is the melting completion temperature Te. Such a change is reversibly performed in the side chain crystalline polymer in the present invention.

The intermediate layer of the wafer dicing pressure-sensitive adhesive tape of the present invention is preferably one that undergoes softening-curing change at the melting start temperature Ti among the side chain crystalline polymers. This polymer is softened by being heated to a temperature higher than the melting start temperature Ti, and is cured by being lower than this temperature.
The side chain crystalline polymer is preferably a polymer mainly composed of acrylic acid ester and methacrylic acid ester, and the side chain is preferably a linear alkyl group having 10 or more carbon atoms, more preferably 10 carbon atoms. It has 24 or less linear alkyl groups. Specific examples of the acrylic ester and methacrylic ester include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-butyl, and (meth) acrylic acid. Isobutyl, (meth) acrylic acid hexyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid-2-hydroxylethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid amide, (meth ) Glycidyl acrylate, (meth) acrylic acid-2-cyanoethyl, acrylonitrile and the like, but are not limited thereto.

Moreover, it is also preferable to use a thermoplastic resin that softens and cures at the glass transition temperature as the intermediate layer of the adhesive tape for wafer dicing of the present invention. This resin is softened by being heated to a temperature higher than the glass transition temperature, and is cured by being cooled below this temperature. Examples of such thermoplastic resins include styrene-butadiene copolymers. However, the glass transition temperature of the thermoplastic resin used for the wafer shape holding layer is not higher than the glass transition temperature of the film-like support constituting the adhesive tape. Such a thermoplastic resin is cured by cooling to at least the glass transition temperature, and can be diced without any problem.
The resin constituting the wafer-shaped holding layer of the adhesive tape is not limited to the above resin, and any resin may be used as long as it reversibly softens and cures at a predetermined temperature depending on the ambient temperature. .

  Furthermore, as an intermediate layer of the adhesive tape, a resin that is hardened by a chemical reaction such as an ultraviolet curable resin can be used in combination, but in this case, the intermediate layer is composed of at least two types of resins, each of which is cured by radiation irradiation. It consists of a curable resin, a side-chain crystalline polymer that has the property of crystallizing by cooling to a predetermined temperature, and / or a thermoplastic resin that softens when heated to a temperature higher than the glass transition temperature. Is preferred. As such a radiation curable resin, for example, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in a molecule that can be three-dimensional networked by light irradiation are widely used. Trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6 hexanediol Diacrylate, polyethylene glycol diacrylate, oligoester acrylate, and the like are widely applicable.

In addition to the above acrylate compounds, urethane acrylate oligomers can also be used. The urethane acrylate oligomer includes a polyol compound such as a polyester type or a polyether type, and a polyvalent isocyanate compound (for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diene). A terminal isocyanate urethane prepolymer obtained by reacting isocyanate, 1,4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc.) with an acrylate or methacrylate 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.) Such as those obtained by reaction.
The thickness of the intermediate layer is not particularly limited as long as it can maintain the wafer shape with the layer thickness at the time of curing. Preferably it is 10-200 micrometers, More preferably, it is 30-100 micrometers.

The hardness of the resin used for the intermediate layer is different between the state at room temperature and the state softened by heating, the storage elastic modulus at 23 ° C. is 2.0 × 10 ⁶ Pa or more, and the storage elastic modulus in the softened state is 5 It is preferably less than 0.0 × 10 ⁵ Pa. If the hardness is outside the above range, the effect of suppressing chipping during dicing is small, and if the elastic modulus in the softened state is higher than the above range, the expansion characteristics of the dicing tape during expansion are greatly impaired.

  As the substrate film in the dicing tape of the method of the present invention, usually plastic, rubber and the like are preferably used. About a base film, when using a radiation curing type adhesive for an adhesive, a transparent thing is selected, and when making it harden | cure by ultraviolet irradiation, a thing with good light transmittance is selected. Examples of such films include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ionomer. Α-olefin homopolymers or copolymers thereof, or mixtures thereof, thermoplastic elastomers such as polyurethane, styrene-ethylene-butene or pentene copolymers, etc., depending on the required properties of the substrate film You can choose arbitrarily.

  These base films can be manufactured using a conventionally known extrusion method. In the case of a base film obtained by laminating various resins, it is manufactured by a co-extrusion method, a lamination method, etc. An adhesive layer may be provided between the resins, as is normally done in the manufacturing method of the laminate film. The thickness of such a film is suitably 50 to 200 μm from the viewpoints of strength / elongation characteristics, radiation transparency, and dicing conditions.

  The adhesive provided on the base film does not cause problems such as damage to the wafer or contamination due to residual adhesive on the wafer surface when the dicing tape is peeled off from the wafer after dicing. There is no particular limitation as long as the adhesive is three-dimensionally reticulated by radiation, preferably UV curing, the adhesive strength is reduced, and residues such as adhesive are hardly generated on the wafer surface after peeling, and UV curing It is preferred to use a mold type adhesive. Such an ultraviolet curable pressure-sensitive adhesive is not particularly limited as long as the desired ultraviolet curable property is exhibited. For example, 100 parts by weight of an acrylic pressure-sensitive adhesive made of a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate is used. 5 to 200 parts by weight of a (meth) acrylate compound having an ultraviolet curable carbon-carbon double bond, a photoinitiator and a photosensitizer, and other conventionally known tackifiers and softeners , Antioxidants, and the like. The thickness of the radiation-curable pressure-sensitive adhesive layer is not particularly limited unless the chipping characteristics during dicing, chip retention, etc. are taken into consideration, but usually 5 to 50 μm is appropriate.

EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.
(Example 1) As a base film, on the film of ionomer resin Himiran 1856 (trade name, manufactured by Mitsui DuPont) having a thickness of 50 μm, as an intermediate layer, the side having a primary melting transition temperature at about 50 ° C. having a thickness of 50 μm After applying a resin layer composed of a chain crystalline polymer (a polymer mainly composed of an acrylate ester having a straight chain alkyl group having 10 or more carbon atoms as a side chain), a thickness of 10 μm is used as an adhesive layer. A dicing tape was prepared by applying a UV curable adhesive. The resin layer used for the intermediate layer had a hardness of 2.0 × 10 ⁷ Pa at normal temperature (23 ° C.) and 3.2 × 10 ⁴ Pa after softening (50 ° C.).

  As the test method for expandability, the wafer dicing adhesive tape is applied to the existing dicing tape laminating device UCTM-100 manual machine (Furukawa) on the opposite side of the circuit pattern surface of a silicon wafer with a 5-inch gold having a thickness of 200 μm. Bonding was performed under an environment of 23 ° C. using a product name manufactured by Denki Kogyo Co., Ltd. This 5-inch gold-attached silicon wafer was half-cut to a tape layer with a dicer and cut into chips (small pieces). Furthermore, ultraviolet rays were irradiated from the base film surface of the adhesive tape for wafer dicing to which the silicon wafer formed into chips by the ultraviolet irradiation machine in the next step was bonded.

In the next expanding step, a wafer dicing apparatus was used to expand the wafer dicing adhesive tape to which the chip-formed wafer was bonded while the stage was heated to 55 ° C., and the expandability was tested.
In the chipping evaluation, the same method as described above was used until the dicing step. After the ultraviolet irradiation, the silicon chip was taken out of the dicing tape, and the chipping on the back surface was observed and measured.

(Example 2)
A 50 μm thick resin layer similar to that of Example 1 consisting of a side chain crystalline polymer having a primary melt transition temperature at about 50 ° C. as an intermediate layer on a polypropylene film having a thickness of 50 μm as a base film. A dicing tape was prepared by applying an ultraviolet curable acrylic pressure-sensitive adhesive having a thickness of 10 μm as a pressure-sensitive adhesive layer. After this wafer dicing adhesive tape was bonded to the surface protective surface of the wafer in the same manner as in Example 1, the chipping property and the expandability were tested in the same manner as in Example 1.

(Comparative Example 1) In Example 1, as a base film, a 10 μm UV curable adhesive was applied on a film of ionomer resin Himiran 1856 (trade name, Mitsui DuPont) having a thickness of 100 μm, and dicing was performed. Tape was prepared. In other words, the side layer crystalline polymer layer, which is an intermediate layer, was not used. About this, the test similar to Example 1 was done except heating temperature having been 55 degreeC.

(Storage modulus measurement method)
Dynamic viscoelasticity measuring device Name: ARES Rheometrics, Inc. Frequency: 1 Hz

The evaluation criteria for each test are as follows.
(Dicing test conditions)
A dicing test of the semiconductor wafer was performed under the following conditions.
Dicing machine: DAD-340 (trade name) manufactured by DISCO
Blade: NBC-ZH2050 27HEDD (product) manufactured by DISCO
Blade rotation speed: 40000 rpm
Cutting speed: 100 mm / sec
Cutting thickness: 30 μm
Cutting water volume: 1.2 l / min
Cutting water set temperature: 18 ° C
Dicing size: 1 mm square Wafer: Si gold-deposited wafer Wafer size: 5 inches Wafer thickness: 200 μm
Wafer backside grinding roughness: # 2000 polished surface

The wafer dicing test was performed as described above, and the chipping was measured as follows.

(1) Chipping measurement and evaluation measurement place: Wafer back side (adhesive tape attachment surface)
Evaluation method and number of measurements: The maximum chipping (maximum chipping) average value per four sides of a cut chip (average value of one chip), and an arbitrary value of 50 chips in a wafer was measured, and the average value per chip Was calculated.
(Judgment)
Chipping determination: less than 50 μm
50μm or more and less than 70μm
71 μm or more was taken as x.

(2) Expandability evaluation Dicing was performed under the above conditions, and the expandability was evaluated under the following conditions. The wafer bonded to the tape by the UV irradiation device was irradiated with ultraviolet rays from the tape side. Thereafter, using a wafer expansion device, the interval between chips cut individually by the expanding process was expanded and evaluated. In the evaluation method, after the ultraviolet irradiation after dicing, the wafer outer diameter after expansion when the wafer outer diameter before expansion was 100% was measured as the expansion rate.

(UV irradiation conditions)
Ultraviolet irradiation device: Furukawa Electric Co., Ltd. UVM-200 (trade name)
Ultraviolet irradiation lamp: High pressure mercury lamp UVL2000RS (trade name) manufactured by USHIO
UV irradiation amount: 500 mJ (illuminance: 40 mW / cm @ 2, irradiation time: 12.5)

(Expanding condition)
Wafer expansion device: Model number: HS-1810 (trade name, manufactured by HUGLE ELECTRONICS)
Tape withdrawal during expansion: 30 mm
Stage heating temperature: 55 ° C
(Judgment)
Expansion property determination The expansion ratio of the outermost wafer diameter after expansion was measured when the outermost wafer diameter before expansion was taken as 100%.
Expansion rate: Less than 130%
Less than 131-160% ○
161% or more

Comprehensive judgment No problem in use ◎◎
Limited use: ○
There is a problem (failed): ×

  As can be seen from the examples in Table 1, the pressure-sensitive adhesive tape for wafer dicing of the present invention showed satisfactory results for both chipping properties and expandability, but Comparative Example 1 having no intermediate layer had problems with expandability. .

It is an example of the DSC chart of the intermediate | middle layer of the adhesive tape for wafer dicing of this invention.

Explanation of symbols

A: Point before the start of melting B: Point at the end of melting C: Point at which the gradient of the heat quantity-temperature curve is maximized Ti: Melting start temperature Tm: Primary melting transition temperature Te: Melting completion temperature

Claims (3)

An intermediate layer capable of reversibly softening and hardening depending on the ambient temperature is provided as at least one layer constituting the film-like support or between the film-like support and the adhesive layer applied to the film-like support. A pressure-sensitive adhesive tape for wafer dicing, comprising: The adhesive tape for wafer dicing according to claim 1, wherein the base resin in the resin composition constituting the intermediate layer is a side chain crystalline polymer. 3. The storage elastic modulus at 23 ° C. is 2.0 × 10 ⁶ Pa or more, and the storage elastic modulus at the primary melting transition temperature Tm or more is 3.0 × 10 ⁵ Pa or less. Wafer dicing adhesive tape.

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