JP3152685B2 - Wafer dicing method and radiation irradiation apparatus used in the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wafer dicing method and a radiation irradiating apparatus used in the method.

[0002]

BACKGROUND OF THE INVENTION Semiconductor wafers of silicon, gallium arsenide and the like are manufactured in a large diameter state, and this wafer is cut and separated (diced) into element pieces and then transferred to the next step, a mounting step. . At this time, each step of dicing, washing, drying, expanding, pickup, and mounting is added to the semiconductor wafer in a state of being pasted on the adhesive sheet in advance.

[0003] Such an adhesive sheet used in the steps from the dicing step to the pick-up step of a semiconductor wafer has a sufficient adhesive force to the wafer chip from the dicing step to the drying step, and the wafer is picked up during the pick-up. It is desired that the chip has such an adhesive strength that an adhesive does not adhere to the chip.

[0004] Such an adhesive sheet is disclosed in
0-196,956 and JP-A-60-223,
No. 139, a pressure-sensitive adhesive sheet coated with a pressure-sensitive adhesive comprising a low molecular weight compound having at least two or more photopolymerizable carbon-carbon double bonds in a molecule, which can be three-dimensionally reticulated by light irradiation, on a substrate surface. Proposed. These proposals are pressure-sensitive adhesive tapes in which a radiation-curable pressure-sensitive adhesive is applied on a radiation-transparent substrate, and the radiation-curable compound contained in the pressure-sensitive adhesive is cured by irradiation with radiation to form a three-dimensional net-like adhesive. It is based on the principle that a fluidized structure is provided to significantly reduce its fluidity.

[0005] The conventional pressure-sensitive adhesive sheet as exemplified above has the following problems, particularly in the expanding step. The expanding step is a step of widening the interval between the diced element pieces (chips) and facilitating chip pickup. When the conventional adhesive sheet for attaching a wafer is used, there is a difference between an extension rate (expansion rate) of a portion where the wafer is attached and an extension rate of a portion where the wafer is not attached. It was difficult to get the spacing. That is, since the expansion rate of the portion where the wafer is attached is smaller than the expansion rate of the portion where the wafer is not attached, in the expanding step, the portion where the wafer is not attached is preferentially extended. And
The portion to which the wafer was attached did not extend much, and it was necessary to expand excessively in order to obtain a sufficient chip interval. In addition, due to the above-mentioned problems, the substrate used may be limited.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 2-265258 discloses that an adhesive is applied only to a surface portion of a base material to which a wafer is to be adhered, and only to that portion. A dicing apparatus capable of performing ultraviolet irradiation is disclosed. However, this method has a large number of steps and its effect is not sufficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and has a difference between an expansion ratio of a portion to which a wafer is attached and an expansion ratio of a portion to which no wafer is attached. It is an object of the present invention to solve the above problem in the expanding step caused by the above. Another object of the present invention is to increase the material margin of the base material by solving the above problems.

[0008]

SUMMARY OF THE INVENTION A wafer dicing method according to the present invention comprises:
The wafer adhered on the adhesive layer of the adhesive sheet for attaching a wafer, which has a base material and an adhesive layer whose adhesive strength decreases when irradiated with radiation, is cut and separated into element pieces, and the adhesive is applied. In the wafer dicing method of irradiating the layer with radiation to reduce the adhesive strength of the pressure-sensitive adhesive layer and picking up element pieces, in irradiating the pressure-sensitive adhesive layer with radiation, a wafer is adhered to the pressure-sensitive adhesive layer. The radiation dose applied to the portion where the wafer is not adhered is 90% or less of the radiation dose applied to the portion where the wafer is not attached.

Further, the radiation irradiating apparatus according to the present invention is used in the above-mentioned wafer dicing method, wherein a wafer is attached between a radiation generating section of the apparatus and a base material of an adhesive sheet for attaching a wafer. A filter provided with a radiation attenuating portion having substantially the same shape as the wafer attached to the adhesive sheet is provided.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a wafer dicing method according to the present invention and a radiation irradiation apparatus used in the dicing method will be described more specifically.

The pressure-sensitive adhesive sheet 1 for attaching a wafer used in the present invention has a substrate 2 as shown in FIG.
And an adhesive layer 3. Before use, in order to protect this pressure-sensitive adhesive layer 3, it is preferable to temporarily adhere a peelable sheet 4 to the upper surface of the pressure-sensitive adhesive layer 3 as shown in FIG.

The shape of the pressure-sensitive adhesive sheet used in the present invention is as follows:
It can take any shape such as a tape or a label. Hereinafter, the base material 2 and the pressure-sensitive adhesive layer 3 used in the present invention will be sequentially described.

As the substrate 2, a substrate having radiation transparency is used. Various types of such base materials have been conventionally known. For example, when using ultraviolet rays as radiation, polyester, polyethylene,
Polypropylene, polybutene, polybutadiene, vinyl chloride, vinyl chloride copolymer, ionomer resin, ethylene- (meth) acrylic acid copolymer, ethylene- (meth)
Substrates made of a resin such as an acrylate ester copolymer, polystyrene, polycarbonate, and polyamide, and substrates obtained by applying a silicone resin or the like to the surface of these resin substrates and subjecting them to release treatment can be used. When an electron beam is used as the radiation, a fluororesin or a colored opaque film is used. Further, for the purpose of the present invention, it is preferable to use a substrate having a Young's modulus of about 10 ² to 10 ⁴ Kg / cm ² .

As the substrate 2, one kind of the above-mentioned resin film may be used alone, or a laminated film obtained by laminating two or more kinds may be used. The thickness of the substrate as described above is usually 10 to 300 μm, preferably 50 to 300 μm.
１５０150 μm.

[0015] In the pressure-sensitive adhesive sheet of the present invention, as will be described later, the electron beam (EB) or ultraviolet (U)
The substrate 2 is not required to be transparent in the case of EB irradiation, but needs to be transparent in the case of UV irradiation.

As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 3, conventionally known pressure-sensitive adhesives can be widely used, but acrylic pressure-sensitive adhesives are preferred. A copolymer with an acrylic polymer selected from a polymer and a copolymer and other functional monomers, and a mixture of these polymers are used.

Further, in order to enhance the compatibility with the oligomer described later, a monomer such as acrylic acid or methacrylic acid, acrylonitrile, vinyl acetate or the like may be copolymerized. The molecular weight of the acrylic polymer obtained by polymerizing these monomers is 2.0 × 10 ^{5 to} 10.0 × 10 ⁵ , preferably 4.0 × 10 ^{5 to} 8.0 × 10 ⁵ . is there.

By including a radiation-polymerizable compound in the pressure-sensitive adhesive layer as described above, the adhesive force can be reduced by irradiating the pressure-sensitive adhesive layer with radiation after cutting and separating the wafer. Examples of such a radiation polymerizable compound include, for example, JP-A-60-196,956.
Low molecular weight compounds having at least two or more photopolymerizable carbon-carbon double bonds in a molecule which can be three-dimensionally reticulated by light irradiation as disclosed in JP-A No. 60-223139 and JP-A-60-223139. Widely used.

Further, as the radiation polymerizable compound, a urethane acrylate oligomer can be used in addition to the acrylate compound described above. Such a urethane acrylate oligomer has a molecular weight of particularly 3000 to 30000, preferably 3000 to 100.
When it is 00, more preferably 4000 to 8000, an extremely excellent pressure-sensitive adhesive sheet can be obtained. That is, the adhesive force of the pressure-sensitive adhesive sheet before the irradiation is sufficiently large, and the adhesive force is sufficiently reduced after the radiation irradiation, so that the pressure-sensitive adhesive does not remain on the chip surface when the wafer chip is picked up.

The mixing ratio of the acrylic pressure-sensitive adhesive to the urethane acrylate oligomer in the pressure-sensitive adhesive of the present invention is such that the urethane acrylate oligomer is used in an amount of 50 to 900 parts by weight with respect to 100 parts by weight of the acrylic pressure-sensitive adhesive. Preferably. In this case, the resulting pressure-sensitive adhesive sheet has a large initial adhesive strength, and the adhesive strength is significantly reduced after irradiation, so that wafer chips can be easily picked up from the pressure-sensitive adhesive sheet.

If necessary, the pressure-sensitive adhesive layer 3 may contain, in addition to the above-mentioned pressure-sensitive adhesive and a radiation-polymerizable compound, a compound which is colored by irradiation with radiation. By including a compound to be colored in the pressure-sensitive adhesive 3 by such radiation irradiation, after the pressure-sensitive adhesive sheet is irradiated with radiation, the sheet is colored, and thus the detection accuracy when detecting a wafer chip by an optical sensor is improved. As a result, malfunction does not occur when picking up a wafer chip. In addition, an effect is obtained that it is immediately possible to visually determine whether or not radiation has been applied to the adhesive sheet.

The compound that is colored by irradiation with radiation is a compound that is colorless or pale before irradiation with radiation, but is a compound that becomes colored by irradiation with radiation. A preferred specific example of this compound is a leuco dye.

In some cases, in addition to the above-mentioned pressure-sensitive adhesive and the radiation-polymerizable compound, the light-scattering inorganic compound powder such as silica powder, alumina powder, silica-alumina powder and mica powder may be contained in the pressure-sensitive adhesive layer 3. Can also be contained. The light scattering inorganic compound powder is applied to the pressure-sensitive adhesive layer 3
Even if the surface of an adherend such as a semiconductor wafer is grayed or blackened for some reason, when the adhesive sheet is irradiated with radiation such as ultraviolet rays, the adhesive force of the grayed or blackened portion is increased even if the grayed or blackened part is irradiated. Therefore, the effect is obtained that the adhesive is not sufficiently attached to the surface of the wafer chip when the wafer chip is picked up, and that the adhesive has sufficient adhesive strength before the irradiation of radiation.

Further, in the present invention, abrasive grains may be dispersed in the base material. This abrasive has a particle size of 0.5 to 100 μm.
m, preferably 1 to 50 μm, and a Mohs hardness of 6
-10, preferably 7-10. Specifically, green carborundum, artificial corundum, optical emery, white alundum, boron carbide, chromium oxide
(III), cerium oxide, diamond powder and the like are used. Such abrasive grains are preferably colorless or white. Such abrasive grains are contained in the base material 2 in an amount of 0.5 to
It is present in an amount of 70% by weight, preferably 5 to 50% by weight. Such abrasive grains are particularly preferably used when the cutting blade is used at a depth that cuts not only into the wafer but also into the base material 2.

By including the abrasive grains in the base material as described above, the cutting blade cuts into the base material, and even if an adhesive is adhered to the cutting blade, clogging can be easily performed by the polishing effect of the abrasive grains. Can be removed.

Further, by mixing an isocyanate-based curing agent into the above-mentioned pressure-sensitive adhesive, the initial adhesive strength can be set to an arbitrary value. As such a curing agent,
Specifically, a polyvalent isocyanate compound such as 2,4
-Tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate,
1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-
2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like are used.

Further, in the case of UV irradiation in the above-mentioned pressure-sensitive adhesive, by mixing a UV initiator, the polymerization curing time by UV irradiation and the amount of UV irradiation can be reduced.

Specific examples of such a UV initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
Benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone and the like can be mentioned.

In order to protect the pressure-sensitive adhesive layer 3 before using the pressure-sensitive adhesive sheet to be used in the present invention, a peelable sheet 4 is temporarily provided on the upper surface of the pressure-sensitive adhesive layer 3 as shown in FIG. It is preferable to keep it sticky. As the releasable sheet 4, a conventionally known sheet is used without any particular limitation.

In the wafer dicing method according to the present invention, the wafer is diced using the above-mentioned pressure-sensitive adhesive sheet for attaching a wafer. When the peelable sheet 4 is provided on the upper surface of the adhesive sheet 1, the sheet 4 is removed, and then the adhesive sheet 3 is placed with the adhesive layer 3 of the adhesive sheet 1 facing upward,
As shown in FIG. 3, a semiconductor wafer A to be diced is attached to the upper surface of the pressure-sensitive adhesive layer 3. Various processes of dicing, cleaning, and drying are added to the wafer A in this state of attachment. At this time, the wafer chips are sufficiently adhered and held on the pressure-sensitive adhesive sheet by the pressure-sensitive adhesive layer 3, so that the wafer chips do not fall off during the respective steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base.
At this time, prior to or at the time of pickup, as shown in FIG. 5, the adhesive layer 3 of the adhesive sheet 1 is irradiated with radiation B such as ultraviolet (UV) or electron beam (EB). The radiation polymerizable compound contained therein is polymerized and cured.

The irradiation of the pressure-sensitive adhesive sheet 1 is performed from the surface of the substrate 2 on which the pressure-sensitive adhesive layer 3 is not provided. Therefore, as described above, when UV is used as the radiation, the substrate 2 needs to be light-transmitting, but when EB is used as the radiation, the substrate 2 does not necessarily need to be light-transmitting. Absent.

When irradiating the radiation, the pressure-sensitive adhesive layer of the portion where the wafer is stuck (hereinafter, may be referred to as a wafer stuck portion) has the adhesive layer of the portion where the wafer is not stuck. A relatively small amount of radiation is applied compared to the amount of radiation applied to the agent layer (hereinafter sometimes referred to as a wafer non-adhered portion). The radiation dose applied to the wafer attachment portion is 1 to 90%, preferably 5 to 60%, particularly preferably 5 to 30% of the radiation dose applied to the wafer non-attachment portion.

When the pressure-sensitive adhesive layer 3 is irradiated with radiation to polymerize and cure the radiation-polymerizable compound, the adhesive strength of the wafer bonding portion is reduced to such an extent that the wafer can be picked up, but the expansion ratio is reduced. Does not drop much. On the other hand, since a large amount of radiation is applied to the non-wafer-attached portion, the curing proceeds sufficiently and the expansion rate is greatly reduced. As a result, in the expanding step, only the portion where the wafer is not attached is not preferentially extended, and the portion where the wafer is attached is also extended, so that a desired chip interval can be obtained. It will be easier.

As described above, in order to control the amount of radiation applied to the wafer attachment portion and the amount of radiation applied to the non-wafer attached portion, a radiation irradiation apparatus according to the present invention (see FIG. 5). Is used. Irradiation is performed in a closed vessel equipped with a deoxygenator. At the upper or lower part of the closed container, a window having radiolucency 5 is provided.
UV light is applied through Irradiation is performed in an inert atmosphere after exhausting oxygen sufficiently. Between the radiation generating section 7 and the base material of the pressure-sensitive adhesive sheet for attaching a wafer, there is provided a filter 6 having a radiation attenuating section 6a having substantially the same shape as the wafer adhered to the pressure-sensitive adhesive sheet for attaching a wafer. . The filter 6 is installed such that the radiation attenuating portion 6a and the wafer A face each other.
By irradiating radiation through such a filter 6, a relatively small amount of radiation is applied to the wafer attachment portion, and a relatively large amount of radiation is applied to the non-wafer attached portion. Become like

The radiation attenuating portion 6a contains a compound having a function of reflecting or absorbing radiation and attenuating the amount of transmitted radiation (hereinafter sometimes referred to as a radiation attenuating compound). As such a radiation attenuating compound, various compounds can be used without any particular limitation. In the present invention, particularly preferably used radiation attenuating compounds include ultraviolet absorbing compounds such as benzophenone-based compounds, benzotriazole-based compounds, salcylate-based compounds, and cyanoacrylate-based compounds;
Organic pigments such as azo pigments, phthalocyanine pigments and condensed polycyclic pigments represented by anthraquinone and perylene; or lead, lead hydroxide, barium, barium hydroxide,
Compounds having an electron beam shielding effect, such as barium stearate, can be mentioned. These are used alone or in combination of two or more.

The thickness of the radiation attenuating portion 6a depends on the radiation attenuating compound contained in the radiation attenuating layer, and cannot be said to be any more, but is generally 0.5 to 20 μm, preferably about 1 to 8 μm. is there.

The radiation transmittance of such a radiation attenuating section 6a is 1 to 90%, preferably 5 to 60%, and particularly preferably 5 to 30%. When radiation is applied from the substrate side of the pressure-sensitive adhesive sheet to be bonded to a wafer through the filter as described above, the amount of radiation applied to the wafer-bonded portion of the pressure-sensitive adhesive layer 3 is attenuated, and A large amount of radiation is applied. As a result, the pressure-sensitive adhesive layer in the non-wafer-attached portion is sufficiently cured, and the expansion rate in the expanding step is reduced. Further, since the pressure-sensitive adhesive layer at the wafer attachment portion does not sufficiently cure, the expansion ratio in the expanding step does not decrease so much. Although the pressure-sensitive adhesive layer at the wafer attachment portion does not sufficiently cure, the adhesive force is sufficiently low to pick up the wafer.

Since the expansion rate of the pressure-sensitive adhesive layer in the non-wafer-attached portion is low and the expansion rate in the pressure-sensitive adhesive layer in the wafer-adhered portion does not decrease so much, the adhesion of the wafer-non-adhered portion is not affected even when expanding. Only the agent layer is not preferentially stretched, and it becomes easy to obtain a desired chip interval.

After the expanding step, as shown in FIG. 7, the chips A ₁ , A ₂ ... A to be picked up by the needle rod 6 from the lower surface of the base material 2 according to a conventional method.
₅ are picked up, and the chips A ₁ ... Are picked up by, for example, a suction collet 7 and mounted on a predetermined base. Thus, the wafer chips A ₁ , A ₂
By picking up the chips, you can easily pick up the chips because there is sufficient chip spacing, and the adhesion is sufficiently reduced, so that good quality chips without contamination can be obtained. Can be

[0041]

As described above, according to the wafer dicing method and the radiation irradiating apparatus used in the method according to the present invention, it is easy to obtain a desired chip interval in the expanding step, and an excessive Eliminates the need for expanding.

[0042]

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

[0043]

Example 1 An acrylic polymer (copolymer of n-butyl acrylate and acrylic acid) was used as a substrate, using a soft vinyl chloride film (containing 30% of a plasticizer, thickness 80 μm) as an adhesive on the substrate. 100 parts by weight and a molecular weight of 80
100 parts by weight of a urethane acrylate-based oligomer of No. 00 and 10 parts by weight of a curing agent (aromatic diisocyanate-based) were cast on a release material composed of a polyethylene terephthalate film (38 μm) obtained by subjecting the composition to silicone treatment. A laminated adhesive tape was prepared.

As a filter, a filter was prepared by printing an acrylic polymer containing 3 parts by weight of 2,4-dihydroxybenzophenone on a glass in a 5-inch wafer shape by screen printing.

After the 5-inch wafer was attached to the adhesive tape, the wafer was mounted on a flat frame, and then cut into 5 mm square chips with a 50 μm-thick diamond blade. After this, the illuminance 2
An ultraviolet ray of 00 mW / cm ² was irradiated for 2 seconds.

Next, the dicing tape was expanded by 15% using an expanding jig. The expansion rate of the portion where the wafer was attached was 8 to 10%.

[0047]

Example 2 Example 2 was repeated except that an ethylene-methacrylic acid copolymer was used as a substrate.

The expansion rate of the portion where the wafer is attached is 5 to 7
%Met.

[0049]

Comparative Example 1 The same procedure as in Example 1 was carried out except that ultraviolet light was irradiated through glass without using a filter.

The expansion rate of the portion where the wafer is stuck is 3 to 5
%Met.

[0051]

Comparative Example 2 The same operation as in Example 1 was performed except that ultraviolet light was irradiated through glass without using a filter.

The expansion rate of the portion where the wafer was attached was 1%.

[Brief description of the drawings]

FIG. 1 is a sectional view of an adhesive sheet used in the present invention.

FIG. 2 is a cross-sectional view of the pressure-sensitive adhesive sheet used in the present invention.

FIG. 3 is a cross-sectional view showing a state where a wafer is adhered to an adhesive sheet used in the present invention.

FIG. 4 is a sectional view showing a state where the wafer is diced.

FIG. 5 is a view showing a state in which a diced wafer is irradiated with radiation.

FIG. 6 is a schematic diagram of a filter used in the present invention.

FIG. 7 is an explanatory diagram of a pickup step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 2 ... Substrate 3 ... Adhesive layer 4 ... Releasable sheet 5 ... Window of closed container 6 ... Filter 6a ... Radiation attenuation part 7 ... Radiation generating part 8 ... Push-up needle rod 9 ... Suction collet A ... Wafer B …radiation

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/301

Claims (2)

(57) [Claims] 1. A wafer attached on an adhesive layer of an adhesive sheet for attaching a wafer, comprising a base material and an adhesive layer whose adhesive strength decreases when irradiated with radiation, is cut into element pieces. In the wafer dicing method of separating and irradiating the pressure-sensitive adhesive layer with radiation to reduce the adhesive force of the pressure-sensitive adhesive layer and picking up the element pieces, the irradiation of the pressure-sensitive adhesive layer with the wafer includes the steps of: The radiation dose applied to the area where
A wafer dicing method, wherein a radiation dose applied to a portion where a wafer is not stuck is 90% or less. 2. A wafer adhered on an adhesive layer of an adhesive sheet for attaching a wafer, comprising a base material and an adhesive layer whose adhesive strength decreases when irradiated with radiation, is cut into element pieces. In a radiation irradiating apparatus used for wafer dicing for separating and irradiating the adhesive layer with radiation to reduce the adhesive strength of the adhesive layer and picking up element pieces, a radiation generating part of the apparatus and a wafer sticking adhesive A radiation irradiation apparatus, comprising: a filter provided with a radiation attenuator having substantially the same shape as a wafer attached to a pressure-sensitive adhesive sheet for attaching a wafer, between the sheet and a base material of the sheet.