JPH10279894A - Pressure-sensitive adhesive sheet and method for processing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure-sensitive adhesive sheet for processing semiconductor wafers, which does not emit a strong odor after being cured, is not problematic in submicron contamination due to the adhesive remaining not removed and peeling at the interface between the back of the chip and the sealing resin due to the contamination of the back of the wafer by forming a radiation-curing pressure-sensitive adhesive layer containing a polymerized photopolymerization initiator on at least either surface of a radiation-penetrating film base material. SOLUTION: 100 pts.wt. base polymer such as a natural rubber, a synthetic rubber or an acrylic polymer is mixed with 1-300 pts.wt. radiation-curing compound having a molecular weight of 10,000 or below and 0.1-10 pts.wt. polymerized photopolymerization initiator having a molecular weight of 1,000-100,000, desirably 2,000-100,000 to obtain a radiation-curing pressure-sensitive adhesive, Either surface of a radiation-penetrating film base material having a thickness of 30-500 μm, desirably 40-300 μm is coated with the above adhesive in a thickness of 5-100 μm to obtain a pressure-sensitive adhesive sheet. After this sheet is stuck to one surface of a semiconductor wafer, the other surface is subjected to grinding, dicing or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-curable adhesive sheet for processing semiconductor wafers and a semiconductor wafer processing method using the same.

[0002]

2. Description of the Related Art Normally, a semiconductor integrated circuit is formed by slicing a high-purity silicon single crystal or the like into a wafer, forming a predetermined circuit pattern such as an IC on the surface of the wafer, and incorporating the integrated circuit. The wafer is manufactured by grinding the back surface of the wafer with a grinder, reducing the thickness of the wafer to about 100 to 600 μm, and finally dicing and chipping. At the time of the above-mentioned grinding, an adhesive sheet is attached to the surface of the wafer to prevent breakage of the wafer and facilitate the grinding. At the time of dicing, an adhesive sheet is adhered to the back surface of the wafer, and the wafer is diced in a state where the wafer is bonded and fixed. The formed chip is picked up by a needle from the film substrate side and picked up. It is fixed on top.

[0003] Adhesive sheets used for such purposes need to have an adhesive force that does not peel during grinding or dicing, but easily peel off during grinding or pick-up after dicing. It is required that the adhesive strength be low enough not to damage the semiconductor wafer, and there is no adhesive residue on the wafer surface or wafer back surface.
It is desired that these surfaces are not contaminated.

In recent years, semiconductor wafers have tended to be larger in diameter and thinner, and an etching step for the back surface of the wafer with an acid has been added. In such a situation, the above-mentioned pressure-sensitive adhesive sheets have water resistance during processing, undamaged during processing or peeling, acid resistance during etching with an acid, easy peeling,
It is becoming increasingly difficult to balance various properties such as non-staining properties. In the dicing process, semiconductor packages having a LOC structure and those having a die pad area smaller than that of a chip are increasing. In these packages, unlike the conventional packages, the chip is different. The back surface of the semiconductor wafer is in direct contact with the sealing resin, so that the adhesion between the back surface of the semiconductor wafer and the package is not impaired.
Low contamination on the backside of the wafer is becoming more important.

[0005] As adhesive sheets for processing semiconductor wafers,
At present, attention is paid to radiation-curable pressure-sensitive adhesive sheets, that is, pressure-sensitive adhesive sheets obtained by providing a radiation-curable pressure-sensitive adhesive layer on one surface of a film substrate. This kind of adhesive sheet has a strong adhesive force under normal conditions, and by bonding it to the front or back surface of the wafer, a large adhesive force that can withstand the water pressure during grinding and dicing can be obtained. Also, good acid resistance can be expected depending on the selection of the adhesive composition and the like. On the other hand, when the above-mentioned processing is irradiated with radiation such as light to cure the above-mentioned adhesive layer, the adhesive strength thereof is significantly reduced. As a result, there are advantages in that good peeling easiness and good non-breakability of the wafer can be obtained, and relatively good results can be obtained in non-contamination of the wafer.

[0006]

However, such radiation-curable adhesive sheets generate a strong odor when cured by irradiating light, causing the worker to feel uncomfortable, In terms of health and hygiene, it was far from favorable. In addition, the non-staining property of the wafer after peeling is much better than other adhesive sheets, but contamination of micron order or submicron order due to adhesive residue may still occur. If the contamination is on the back surface of the wafer in the dicing process, when the semiconductor package is reflowed, it may cause separation at the boundary between the back surface of the chip and the sealing resin, thereby impairing the long-term reliability of the semiconductor integrated circuit. There was a problem.

In view of such circumstances, the present invention fulfills the processing purpose as a radiation-curable adhesive sheet for processing semiconductor wafers, which exhibits a large adhesive force during processing such as grinding and dicing. When peeling after processing, it can be peeled easily without causing damage to the wafer by curing by irradiation of radiation, does not generate strong odor after the above-mentioned curing, and has micron order or submicron order due to adhesive residue. The above-mentioned pressure-sensitive adhesive sheets which are free from contamination, and in particular there is no fear of peeling off at the boundary between the chip back surface and the sealing resin due to the above-mentioned contamination on the wafer back surface, and a semiconductor wafer processing method using the same. It is intended to provide.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object. As a result, the radiation-curable pressure-sensitive adhesive layer usually contains a known photopolymerization initiator such as benzophenone or thioxanthone. Is included.
When a specific photopolymerization initiator having a high molecular weight is added instead of the known initiator, strong odor after irradiation is eliminated, and contamination of micron order or submicron order due to adhesive residue is observed. It has been found that the present invention is no longer possible, and the present invention has been completed.

That is, the present invention is characterized in that a radiation-curable pressure-sensitive adhesive layer containing a polymerized photopolymerization initiator is provided on one surface of a radiation-permeable film substrate. Adhesive sheets for processing semiconductor wafers such as tapes and tapes (Claim 1), and the adhesive sheets having the above-described configuration are attached to a semiconductor wafer and subjected to required wafer processing.
Then, after the radiation-curable pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is cured by irradiation with radiation, the pressure-sensitive adhesive sheet is peeled off. It is related.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The radiation-curable pressure-sensitive adhesive layer in the present invention comprises a base polymer containing a radiation-polymerizable compound and a specific photopolymerization initiator, and usually further comprises a polyisocyanate. Compound, alkyl ether
It contains a known crosslinking agent such as a melamine compound, an epoxy compound, or a silane coupling agent. If necessary, a tackifier, a tackifier, a surfactant, other modifiers, and conventional components can be included to control the adhesive force to the semiconductor wafer. However, from the viewpoint of processing a semiconductor wafer, it is preferable that the amount of a surfactant, a compound exhibiting surface activity, and the like be as small as possible.

The base polymer is not particularly limited, and conventionally known base polymers can be widely used. For example, rubber polymers such as natural rubber and various synthetic rubbers, and acrylic polymers comprising a copolymer of an alkyl (meth) acrylate and another unsaturated monomer copolymerizable therewith, and the like. is there. These base polymers may have a carbon-carbon double bond polymerizable by radiation in the molecule.

The radiation-polymerizable compound is cured by irradiation with radiation to form a three-dimensional network, has at least two radiation-polymerizable carbon-carbon double bonds in the molecule, and has a low molecular weight of usually 10,000 or less. It is a molecular weight compound. The molecular weight is 5,000 or less, and the number of radiation-polymerizable carbon-carbon double bonds in the molecule is 2 to 6 so that the three-dimensional network of the pressure-sensitive adhesive layer is efficiently formed by irradiation with radiation. Are preferred.

[0013] Such radiation polymerizable compounds include:
For example, trimethylolpropane triacrylate,
Tetramethylol methane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1, 4-butylene glycol diacrylate, 1,6-hexanediol diacrylate,
Polyethylene glycol diacrylate, Tokuho 5-2
No. 5907 (particularly, the prior art section of this publication), an organopolysiloxane composition,
Commercially available oligoester acrylate, urethane acrylate and the like can be mentioned.

These radiation polymerizable compounds may be used alone or in combination of two or more. The amount used is
The amount is preferably 1 to 300 parts by weight based on 100 parts by weight of the base polymer. If the amount is less than 1 part by weight, the radiation-curable pressure-sensitive adhesive layer may be insufficiently three-dimensionally reticulated by irradiation with radiation, resulting in inferior peelability of the pressure-sensitive adhesive sheet from the wafer and the possibility of contamination of the wafer. is there. When the amount exceeds 300 parts by weight, there is a problem that the thickness accuracy of the pressure-sensitive adhesive layer before irradiation with radiation is deteriorated.

As the photopolymerization initiator, a polymerized one, usually having a molecular weight of 1,000 to 100,000, preferably 2,000 to 100,000 is used. When such a high molecular weight photopolymerization initiator is used, when the pressure-sensitive adhesive layer is cured by irradiating radiation such as light, even when this pressure-sensitive adhesive layer generates heat, it is caused by volatilization or decomposition due to heat, etc. Odor generation is no longer observed, and the adhesive layer has an appropriate cohesive force. As a result, the adhesive residue on the wafer during peeling is reduced, and the conventional micron-coating method is used.
Wafer contamination of the order of magnitude or submicron is prevented.

As such a photopolymerization initiator, it is preferable to use a benzoin type, a carbonyl type or the like, and those having a plurality of these groups in a polymer, for example, a polyvinyl benzoin type or a polyvinyl ketone type are preferable. Used for Commercially available products include "ESACURE KIP100" and "ESACURE KIP100" by Siebel Hegner (distributor).
URE KIP150 ". "ESAC
URE KIP150 ”is an oligo {2-hydroxy-2-methyl-1- [4] represented by the following structural formula (1).
-(1-methylvinyl) phenyl] propanone}.

[0017]

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Other photopolymerization initiators represented by the following structural formula (2) [J. Polymer. Sci
Apolymer Chem 24.875 ('8
6)], those represented by the following structural formula (3) or (4) (JP-A-50-130886, J-Wako-Polysion), represented by the following structural formula (5) Thing [Te
trahedron Lett 323 ('74)],
Those represented by the following structural formula (6) [Eur. Poly
mer J .; 14.317 ('78)] and those represented by the following structural formula (7) [J. Polymer. Scic
hem, ed. , 19.855 ('81)].

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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The photopolymerization initiator is used in an amount of usually 0.1 to 10 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the base polymer. 0.
If the amount is less than 1 part by weight, three-dimensional network formation by irradiation of the pressure-sensitive adhesive layer with radiation is insufficient, and good peelability cannot be obtained, and this causes wafer contamination. Further, even if it is used in excess of 10 parts by weight, not only the effect corresponding thereto is not obtained, but also the photopolymerization initiator may remain on the wafer.

In addition, together with the specific photopolymerization initiator,
Isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, benzyldimethylketal, α-hydroxychlorohexylphenyl ketone, 2-hydroxymethylphenyl Other photopolymerization initiators such as enylpropane may be used together as long as the effects of the present invention are not impaired. If necessary, an amine compound such as triethylamine, tetraethylpentamine or dimethylaminoethanol can be used as a photopolymerization accelerator together with these photopolymerization initiators.

In the present invention, a radiation-curable composition comprising the above-mentioned base polymer, a radiation-polymerizable compound, a specific photopolymerization initiator, and, if necessary, a cross-linking agent and other compounding ingredients on one side of a film substrate. By directly applying the mold adhesive and drying by heating, or by once applying and drying on release paper and then transferring it to one side of the film substrate,
A radiation-curable pressure-sensitive adhesive layer having a thickness of usually 5 to 100 μm is formed to obtain a sheet-like, tape-like or other pressure-sensitive adhesive sheet for processing a semiconductor wafer. In this case, the above-mentioned pressure-sensitive adhesive layer may have a multilayer structure having different components.

Since the film substrate is irradiated with radiation from the film substrate side at the time of peeling, the film substrate needs to be radiation-transmissive, and has a shock absorbing ability at the time of processing a wafer and a strength enough to withstand washing water. And a material and thickness suitable for them are selected. It is desirable that the surface of the film substrate on which the pressure-sensitive adhesive layer is formed be subjected to a corona treatment in order to improve the anchoring property of the pressure-sensitive adhesive layer.

Such a film substrate includes polyethylene, polypropylene, ethylene-propylene copolymer,
Polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, ethylene-vinyl acetate copolymer, polybutene-1, poly-4-methylpentene-1,
Films such as ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer, polyurethane, polymethylpentene, polybutadiene and the like can be mentioned. Their thickness is usually 30 to 500 μm, preferably 40 to 300 μm.

In the present invention, in order to process a semiconductor wafer using the adhesive sheet having the above structure, first, the adhesive sheet having the above structure is attached to the front or back surface of the semiconductor wafer. In this state, necessary wafer processing such as grinding and dicing of the back surface of the wafer may be performed by a conventional method. At this time, since the above-mentioned adhesive sheets have a large adhesive strength, there is no trouble such as peeling during processing, a desired processing purpose can be achieved, and no inconvenience such as breakage of the wafer occurs.

After the processing, the radiation-curable pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is cured by irradiating radiation such as light (ultraviolet light) or an electron beam from the film substrate side of the pressure-sensitive adhesive sheet. . Since the adhesive force is remarkably reduced by this curing, the above-mentioned adhesive sheets can be easily peeled off from the wafer, and the subsequent pick-up operation can be easily performed in the dicing process.
Moreover, no strong odor is generated after the curing,
There is no worry about causing workers unpleasant feelings or causing health and hygiene problems. In addition, no contamination of the micron order or submicron order due to the adhesive residue after peeling was observed, and therefore, the peeling at the boundary between the chip back surface and the sealing resin due to the above-described contamination of the wafer back surface as in the conventional case, etc. There is no inconvenience.

[0032]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

Example 1 A monomer mixture consisting of 80 parts of n-butyl acrylate, 15 parts of ethyl acrylate and 5 parts of acrylic acid was treated with 150 parts of ethyl acetate and 0.1 part of azoisobutyronitrile under nitrogen. Solution polymerization was carried out at 60 ° C. for 12 hours under an air stream to obtain an acrylic polymer solution A having a weight average molecular weight of 560,000.

In this solution A, an acrylic polymer 100 was used.
Parts, 100 parts of urethane acrylate as a radiation polymerizable compound, 2 parts of a polyisocyanate compound and 0.5 part of an epoxy compound as a crosslinking agent, and "ESACURE" which is a commercially available photopolymerization initiator. K
IP150 "(Siebel Hegner-Distributor) was mixed uniformly to prepare a radiation-curable pressure-sensitive adhesive solution.

The radiation-curable pressure-sensitive adhesive solution having a thickness of 5
One side of a separator made of a 0 μm polyester film is applied so that the thickness after drying becomes 30 μm.
After drying at 20 ° C. for 3 minutes, the resultant was laminated on a 100 μm-thick polyethylene film base material to prepare an adhesive sheet for processing a semiconductor wafer.

Example 2 In the acrylic polymer solution A of Example 1, 80 parts of pentaerythritol hexaacrylate as a radiation-polymerizable compound and 100 parts of acrylic polymer per 100 parts of an acrylic polymer, and tolylene diisocyanate as a crosslinking agent were used. 3 parts and 5 parts of a polymerized photopolymerization initiator (the same as in Example 1) were uniformly mixed to prepare a radiation-curable pressure-sensitive adhesive solution. Further, an adhesive sheet for processing a semiconductor wafer was prepared in the same manner as in Example 1 using this.

Example 3 A monomer mixture consisting of 30 parts of 2-ethylhexyl acrylate, 70 parts of methyl acrylate and 10 parts of acrylic acid was mixed with 200 parts of ethyl acetate and 0.2 parts of benzoyl peroxide in a nitrogen stream. Solution polymerization was performed at 60 ° C. for 12 hours to obtain an acrylic polymer solution B having a weight average molecular weight of 800,000.

In this solution B, an acrylic polymer 100 was added.
Parts by weight, 50 parts of pentaerythritol tetraacrylate as a radiation polymerizable compound, 3 parts of tolylene diisocyanate as a cross-linking agent, and "ESACURE KIP100" which is a commercially available photopolymerization initiator.
(Siebel Hegner-Distributor) 5 parts, mix evenly,
A radiation-curable pressure-sensitive adhesive solution was prepared. Further, the adhesive sheet for processing a semiconductor wafer was used in the same manner as in Example 1 using this.
Was made.

Example 4 In the acrylic polymer solution B of Example 3, based on 100 parts of the acrylic polymer, 120 parts of urethane acrylate as a radiation polymerizable compound and tolylene diisocyanate 3 as a crosslinking agent were used. , And 5 parts of a polymerized photopolymerization initiator (the same as in Example 3) were uniformly mixed to prepare a radiation-curable pressure-sensitive adhesive solution. In addition, Example 1
In the same manner as in the above, an adhesive sheet for processing a semiconductor wafer was produced.

Comparative Example 1 α-Hydroxycyclohexylphenyl ketone (molecular weight: 204.20) was used in place of 3 parts of the polymerized photopolymerization initiator.
3) A radiation-curable pressure-sensitive adhesive solution was prepared in the same manner as in Example 1, except that 10 parts were used. Further, an adhesive sheet for processing a semiconductor wafer was prepared in the same manner as in Example 1 using this.

Comparative Example 2 α-Hydroxycyclohexylphenyl ketone (molecular weight: 204.20) was used in place of 5 parts of the polymerized photopolymerization initiator.
3) A radiation-curable pressure-sensitive adhesive solution was prepared in the same manner as in Example 2, except that 5 parts were used. Further, an adhesive sheet for processing a semiconductor wafer was prepared in the same manner as in Example 1 using this.

Comparative Example 3 A radiation-curable adhesive was prepared in the same manner as in Example 3, except that 5 parts of 2,4-diethylthioxanthone (molecular weight: 250) was used instead of 5 parts of the polymerized photopolymerization initiator. An agent solution was prepared. Further, an adhesive sheet for processing a semiconductor wafer was prepared in the same manner as in Example 1 using this.

Comparative Example 4 A radiation-curable adhesive was prepared in the same manner as in Example 4 except that 10 parts of 2,4-diethylthioxanthone (molecular weight: 250) was used instead of 5 parts of the polymerized photopolymerization initiator. An agent solution was prepared. Further, an adhesive sheet for processing a semiconductor wafer was prepared in the same manner as in Example 1 using this.

The adhesive sheets for processing semiconductor wafers of Examples 1 to 4 and Comparative Examples 1 to 4 described above were used to determine whether or not odor was generated after curing by irradiation of radiation, and to apply the radiation to the semiconductor wafer. The wafer contamination when peeled later was examined by the following method. The results were as shown in Table 1.

<Measurement of Odor and Wafer Contamination> The adhesive sheet for processing a semiconductor wafer was peeled off from the separator to remove
Affixed to an inch mirror wafer, allowed to stand for 1 hour, and a high-pressure mercury lamp [Nitto Denko Corporation UV irradiator UM-1
10, the irradiation intensity was 46 mJ / cm ² · sec], and the ultraviolet ray was irradiated for 10 seconds (irradiation amount: 460 mJ / cm ² ) to cure the pressure-sensitive adhesive layer.

The presence or absence of odor after curing was examined. The case where no odor was felt was evaluated as ○, and the case where strong odor was felt was evaluated as x. After curing, the adhesive sheet was peeled off from the wafer, and a laser surface inspection device (LS-5000, manufactured by Hitachi Electronics Engineering Co., Ltd.) was used to remove 0.28 μm or more of the adhesive sheet remaining on the mirror wafer. The number of particles was examined, and if the number was 10 or less, it was evaluated that wafer contamination was low.

[0047]

As is evident from the results shown in Table 1, the adhesive sheets for processing semiconductor wafers of Examples 1 to 4 of the present invention did not show any odor after being cured by irradiation with ultraviolet rays. It can be seen that the contamination is very low. In addition to the above test, when the semiconductor wafer was actually ground or diced using the semiconductor wafer processing adhesive sheets of Examples 1 to 4, the adhesive strength under normal conditions was large. In addition, there was no trouble such as peeling during processing, and when peeling was performed by irradiating ultraviolet rays after processing, the wafer could be easily peeled without damaging the wafer. At that time, no odor after ultraviolet irradiation was felt, and it was found that the non-staining property of the wafer was satisfactory.

[0049]

As described above, according to the present invention, when processing such as grinding and dicing, a large adhesive force is exhibited, thereby achieving the intended processing purpose. It can be easily peeled off without causing damage to the wafer by curing, and it does not generate a strong odor after the above-mentioned curing, and no contamination of micron order or submicron order due to adhesive residue is observed. A radiation-curable adhesive sheet for processing a semiconductor wafer can be provided, which is free from the possibility of peeling at the boundary between the chip back surface and the sealing resin due to the contamination, and a semiconductor wafer processing method using the same. Can be provided.

Claims (2)

[Claims] 1. A pressure-sensitive adhesive sheet for processing semiconductor wafers, wherein a radiation-curable pressure-sensitive adhesive layer containing a polymerized photopolymerization initiator is provided on one surface of a radiation-transmissive film base material. Kind. 2. The adhesive sheet for processing a semiconductor wafer according to claim 1 is attached to a semiconductor wafer to perform required wafer processing, and then the radiation of the adhesive sheet is irradiated by irradiation of radiation. A method of processing a semiconductor wafer, comprising: after curing a curable pressure-sensitive adhesive layer, peeling off the pressure-sensitive adhesive sheets.