JP2007103615A - Substrate film for dicing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate film for dicing sheets having more improved expandability and improved rack recovery properties of used sheets in the dicing sheet used when performing the dicing machining of a semiconductor, or the like. <P>SOLUTION: The substrate film for dicing sheets comprises three layers of; a layer A containing an acryl-based resin, where an acryl acid ester constituent ranges from 60 to 80 wt.% and a methacrylic acid ester constituent ranges from 20 to 40 wt.%; a layer B containing an acid-modified hydrogenated styrene-based thermoplastic elastomer; and a layer C containing a thermoplastic ethylene-based resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a base film used for a dicing sheet used in a step of dicing a semiconductor wafer or the like into chips.

A semiconductor wafer made in advance with a large area is cut into chips (called dicing). In this dicing process, it is necessary to fix the semiconductor wafer. A dicing sheet is used for this fixing.
The sheet is composed of an adhesive layer and a base film. As the base film, a polyvinyl chloride film, a polyolefin film, or a film using other resins is generally used. However, the quantity of the polyvinyl chloride film is reduced due to environmental problems. It is a fact.

When a polyolefin film or a film using other resin is used as a substrate film for a dicing sheet, there is a problem in expandability after dicing, and a patent technology for solving this problem has been disclosed.
For example, a polyolefin film having a constant surface roughness and a constant in-plane retardation before and after stretching is specified as a dicing substrate film, and the film is mainly composed of crystalline polyethylene as front and back layers, with ethylene in the middle. This is achieved by laminating with a layer of amorphous polyolefin containing 40% by weight or more of any monomer component of propylene or butene-1. (See Patent Document 1)
Also, a terpolymer film having elasticity obtained by copolymerizing methacrylic acid and (meth) acrylic acid alkyl ester (C3-C8 alkyl group) with ethylene as a main component (60% by weight or more) is a dicing substrate film. Then, an adhesive layer is provided on this, and a dicing sheet consisting of three layers is formed by further laminating polyethylene or ethylene-vinyl acetate copolymer on a dicing tape consisting of two layers or the dicing substrate film. (See Patent Document 2)
Also, a multilayer structure polymer particle having a soft acrylic resin inside and a hard acrylic resin as an outermost layer or 0 to 50% by mass of a thermoplastic resin such as a highly polar ethylene resin, styrene resin, acrylic A film made of a blend of a polyester resin, a polyester resin, a nylon resin, or the like is used as a base, and a pressure-sensitive adhesive layer is provided on one side to form a pressure-sensitive adhesive sheet for dicing. (See Patent Document 3)

JP 2001-232683 A Japanese Patent Laid-Open No. 7-230972 JP 2004-79916 A

In general, a semiconductor wafer is first fixed to an adhesive surface of a dicing sheet and sent to a dicing process in a state of being stored in a rack. And here, it is first diced to a predetermined size by a dicer. Next, the tape is expanded, and a certain gap is created so that the diced semiconductor wafer can be easily picked up. And it is picked up by the picker. Thereafter, the used dicing sheet is collected in the storage rack, and the main process ends.
By the way, with the recent further miniaturization of semiconductor chips, the following two new problems have occurred in the above process.
First of all, after dicing into smaller pieces than before in the dicing process, when picking up the semiconductor chip in the next process, the semiconductor chip is fragmented. It could not be picked up, causing malfunctions.
Another is the collection of used dicing sheets. From where it is sent to the dicing process in the state of being stored in the rack to the rack recovery of the used dicing sheet, the machine performs all without passing through human hands. Therefore, if the size of the expanded sheet is larger than that before expanding the dicing sheet, it cannot be efficiently collected in the rack.

The efficient recovery to the rack is to recover the used sheet by heating it to a predetermined temperature and shrinking it. However, since the generally known dicing sheet has a small heat shrinkage at the temperature. Storing in the rack was difficult. The difficulty is that the smaller the size of the semiconductor chip, the greater the expansion of the sheet, and therefore the heat shrinkage during recovery cannot be accommodated in the rack without further shrinkage.

The present invention can be expanded more widely and uniformly as the semiconductor chip becomes smaller (hereinafter referred to as expandability), and the used dicing sheet can be collected in the rack more. The main problem was to find a substrate film for dicing sheets that can be easily performed (hereinafter referred to as rack recoverability).

The present invention includes an A layer containing an acrylic resin having an acrylic ester component of 80 to 60% by weight and a methacrylic ester component of 20 to 40% by weight, and a B layer containing an acid-modified hydrogenated styrene thermoplastic elastomer. Further, the present invention is characterized in that it is a substrate film for a dicing sheet in which a C layer containing a thermoplastic ethylene-based resin is laminated in three layers of A layer / B layer / C layer.

The present invention also provides a substrate for a dicing sheet in which the longitudinal and lateral restoration rates are 90% or more when stretched by 40% in the longitudinal and lateral directions and heated and contracted at 60 ° C. for 10 seconds. It is also characterized by being a film.

A base film for a dicing sheet having better extensibility can be obtained, and a semiconductor wafer or the like can be diced into small pieces and picked up easily and reliably.

In addition, the used dicing sheet can be stored and collected in the rack more reliably and easily.

In the present invention, the acrylic resin forming the A layer contains an acrylic ester component and a methacrylic ester component, and even if it is a copolymer of an acrylic ester and a methacrylic ester, the acrylic ester resin And a blend resin of methacrylic ester resin.
First, examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate, and methacrylic acid. Specific examples of the ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.
The acrylic ester component has soft properties, and its hardness is preferably (JIS K 6253 durometer type A) 40-90, more preferably 50-80.
Further, the methacrylic acid ester component has hard characteristics, and its hardness (JIS K 6253 durometer type D) is preferably 20 to 50, and more preferably 30 to 40.
The copolymer is obtained by copolymerizing acrylic acid ester as a main component and methacrylic acid ester as a copolymerization component.

The acrylic ester resin may be either a homopolymer using an acrylic ester as a monomer or a copolymer with another monomer copolymerizable with the acrylic ester.
In order for the acrylic ester resin to have rubber elasticity, n-butyl acrylate, 2-ethylhexyl acrylate or n-octyl acrylate is preferable, and n-butyl acrylate is more preferable.
Specific examples of other monomers copolymerizable with acrylic acid esters include methacrylic acid ester-based monomers such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and pentyl methacrylate. Examples of the monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, 1-vinylnaphthalene, and 3-methylstyrene. In order for the acrylic ester resin to have a soft characteristic, the acrylic ester is a main component, that is, the acrylic monomer is co-polymerized with all the monomers used to form the polymer. The proportion of polymerizable monomers is preferably used at less than 50% by weight.

Next, the methacrylic ester resin may be either a homopolymer using methacrylic acid as a monomer or a copolymer with another monomer copolymerizable with the methacrylic ester.
In order for the methacrylic acid resin to have a hard property, methyl methacrylate, ethyl methacrylate or propyl methacrylate is preferable, and methyl methacrylate is more preferable.
Examples of other monomers copolymerizable with methacrylic acid esters include acrylate ester-based monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and pentyl acrylate. Examples of the monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, 1-vinylnaphthalene, and 3-methylstyrene. In order for the methacrylic acid ester-based resin to have a hard characteristic, the methacrylic acid ester is the main component, that is, the methacrylic acid ester resin is co-polymerized with the methacrylic acid ester with respect to all monomers used to form the polymer. The proportion of polymerizable monomers is preferably used at less than 50% by weight.

Next, the ratio of the acrylic ester component and the methacrylic ester component in the acrylic resin is preferably 80 to 60 wt% for the acrylic ester component and 20 to 40 wt% for the methacrylic ester component, more preferably The acrylic ester component is 75 to 65% by weight, and the methacrylic ester component is 25 to 35% by weight.
The ratio of the acrylic acid ester component to the methacrylic acid ester component shows better extensibility when the acrylic acid ester component is in the range of 80 to 60% by weight and the methacrylic acid ester component is in the range of 20 to 40% by weight. Excellent rack recovery.

When the expansion amount of the base film for dicing sheet in the pick-up process is large, a problem such as film tearing may occur. In that case, a thermoplastic elastomer can be added to the acrylic resin of the A layer.
Examples of the thermoplastic elastomer include polystyrene-based elastomers, polyolefin-based elastomers, polyester-based elastomers, and polyamide-based elastomers, but polystyrene-based elastomers that have little decrease in transparency even when added to acrylic resins are preferable.

As the styrenic elastomer, a block copolymer of styrene and a conjugated diene such as butadiene, isoprene or 1,3-pentadiene is generally used, and among them, a block copolymer of styrene and butadiene is the most common. is there.
The block copolymer of styrene and conjugated diene preferably has a MFR of 3 to 10 g / 10 min at a temperature of 230 ° C. and a load of 21.2 N.

As the amount of styrene elastomer added increases, the rack recoverability of the substrate film for dicing sheets is affected. That is, if the dicing sheet base film once expanded does not shrink even when heated to 60 ° C., the rack recoverability deteriorates.
In such a case, the rack recoverability can be supplemented by adding a terpene resin.
As a terpene resin, as is generally known, a terpene monomer, that is, a terpene resin having α-pinene, β-pinene or dipentene as a skeleton, a styrene-modified terpene resin having this as a skeleton, or a phenol modification having this as a skeleton. Terpene resin. There are also saturated terpene resins hydrogenated with these terpene resins.
The terpene resin preferably has a molecular weight of 500 to 1400, a softening point of 80 to 150 ° C, and a glass transition point of 40 to 90 ° C. A phenol-modified copolymerized terpene resin and a glass transition point of 55 to 90 ° C. are preferable because of compatibility with an acrylic resin or a block copolymer resin composed of styrene and conjugated diene.

The proportion of the styrene elastomer and terpene resin that can be added can be exemplified as follows.
The addition amount of the styrene elastomer is preferably 3 to 20% by weight. When the styrene-based elastomer is in the range of 3 to 10% by weight, sufficient rack recoverability can be obtained without adding a terpene resin, but there is no particular problem even if a terpene resin is added.
When the styrene elastomer is in the range of more than 10% by weight to 20% by weight, it is better to add a terpene resin. It is preferable to add 5 to 23 parts by weight of terpene resin with respect to 100 parts by weight of blend resin of 80 to 89% by weight of acrylic resin and 11 to 20% by weight of styrene elastomer.
When the styrene-based elastomer exceeds 20% by weight, even if a terpene resin is further added, sufficient rack recoverability cannot be obtained, which is not preferable.

Next, the B layer will be described. The B layer is an adhesive layer between the A layer and the C layer for laminating both layers with a strong adhesive force.
The acid-modified hydrogenated styrene-based thermoplastic elastomer forming the B layer is, for example, as follows.
A thermoplastic elastomer in which a polystyrene segment and a diene segment such as polybutadiene, polyisoprene and the like are block-bonded is hydrogenated and further acid-modified. Here, when the diene segment is, for example, polybutadiene, when it is hydrogenated (hydrogenated), it becomes a poly (ethylene-butylene) segment, and when it is polyisoprene, it becomes a poly (ethylene-propylene) segment. This diene segment is preferably made of polybutadiene.
Acid modification is the same as acid modification generally performed with olefin resin, etc., and α, β-unsaturated carboxylic acid or its anhydride such as (meth) acrylic acid, maleic acid, maleic anhydride or fumaric acid is added. It is done by doing.
The acid-modified hydrogenated styrenic thermoplastic elastomer preferably has a density in the range of 0.88 to 0.99, and an MFR of 2 to 10 g / 10 min at a temperature of 230 ° C. and a load of 21.2 N.
In general, the acid-modified hydrogenated styrene thermoplastic elastomer is most preferably used alone, but other, for example, an ethylene copolymer resin (for example, ethylene and a C1-C4 acrylic ester) Copolymers) may be blended. However, the blend amount of other resins is preferably suppressed to less than 50% by weight.

Next, the C layer will be described. The layer C functions as a so-called anti-blocking layer that prevents film surfaces from blocking each other when the substrate film for dicing sheet is extruded and formed into a roll when rolled. Further, when the dicing sheet is expanded after the semiconductor is diced in the dicing process, there is an effect that the friction with the dicing cradle is reduced and the dicing sheet is smoothly expanded.
The thermoplastic ethylene resin forming the C layer is, for example, as follows.
Examples thereof include medium density polyethylene, low density polyethylene, linear low density polyethylene (having a C3 to C8 α-olefin as a copolymerization component), and a copolymer of ethylene and an acrylate ester. Among them, a copolymer of ethylene and an acrylate ester is preferable. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate.
The thermoplastic ethylene resin preferably has a density in the range of 0.91 to 0.96 and an MFR of 0.5 to 10 g / 10 min when the temperature is 190 ° C. and the load is 21.2 N.

And the thickness structure of the base film for dicing sheets which consists of three layers can be illustrated as follows.
The A layer is 30 to 200 μm, preferably 40 to 150 μm, the B layer is 5 to 50 μm, preferably 8 to 40 μm, and the C layer is 5 to 50 μm, preferably 10 to 40 μm.
When the thickness of the A layer is 30 to 200 μm, excellent expandability is exhibited, and rack recoverability is also excellent.
When the B layer is 5 to 50 μm, the B layer exhibits sufficient adhesion between the outer layer and the inner layer, and does not hinder the excellent expandability and rack recoverability of the A layer.
C layer is a layer provided to prevent blocking that occurs when the substrate film for dicing sheet is rolled up. When the thickness is 5 to 50 μm, excellent expandability of A layer and rack recovery Good anti-blocking property is exhibited without inhibiting the property.

When actually used as a dicing sheet, an adhesive layer is provided on the substrate film for dicing sheet.
As the pressure-sensitive adhesive used in this pressure-sensitive adhesive layer, generally known pressure-sensitive adhesive resins such as polyacrylic, polyvinyl alcohol, or chlorinated polyethylene are appropriately used.
The pressure-sensitive adhesive layer is provided on the A layer surface.

Next, the coextrusion method which can be illustrated as one of the preferable manufacturing means of the base film for three-layer dicing sheets is demonstrated.
In this co-extrusion method, three extruders are used, and a resin constituting the A layer, a resin constituting the B layer, and a resin constituting the C layer are charged into each extruder. After being melted and kneaded in the extruder, it is extruded from the multi-die (three layers) into a film shape, which is classified into a T-die method or an inflation method depending on the shape of the die. Any method may be used, but the T-die method is preferred from the viewpoint of film thickness accuracy.
The extruded three-layer film is cooled and wound through a roll of about 30 to 100 ° C.

The substrate film for dicing sheet thus obtained has excellent expandability and rack recoverability.

Hereinafter, examples will be described in more detail together with comparative examples.
The expandability and rack recoverability in each of the following examples were measured as follows.

-Expandability The obtained substrate film for dicing sheet is cut into a size of 300 mm x 300 mm to obtain a sample piece. Next, lines are put in a 10 mm × 10 mm grid on the entire surface of the sample piece.
Two frames with a hole with a diameter of 200 mm are prepared in the center, and the test piece is sandwiched between them so that the positions of the holes are exactly overlapped, and fixed so that the test piece does not move. Then, this frame is fixed horizontally. A cylinder having an outer diameter of 150 mm and an inner diameter of 140 mm is set on the lower side of the frame and at the center of the hole. Next, the sample is expanded by pushing up the cylinder by 40 mm at a speed of 200 cm / min. Then, the longitudinal and lateral lengths of the lattice positioned in the center in this pushed-up state are measured, the respective elongation (%) with respect to the original sample is obtained, and the ratio of the elongation is calculated. If the ratio is 1.3 or less, the extensibility is excellent, and if it exceeds 1.3, the extensibility is not good.

● Rack recoverability The following measurements are performed in the vertical and horizontal directions of the substrate film for dicing sheet obtained.
A line is put in a sample piece cut into a length of 100 mm and a width of 10 mm so that the distance between marked lines is 40 mm. This sample piece is set on a tensile tester “AGS100A” manufactured by Shimadzu Corporation with a distance between chucks of 40 mm (so that the marked line and the chuck are aligned), and stretched by 40% at a tensile speed of 200 mm / min. Then, after holding for 1 minute by the extension, the chuck is released and the sample piece is taken out. Next, warm air at which the surface temperature of the sample piece becomes 60 ° C. is blown for 10 seconds. When the sample piece returns to room temperature, the distance L (mm) of the marked line is measured. The longitudinal recovery rate (%) for 40% elongation is obtained from the following equation.
Restoration rate (%) = [{40− (L−40)} / 40] × 100
This same measurement is also performed on a sample piece cut to 10 mm length × 100 mm width. If the restoration ratio in the vertical and horizontal directions is 90% or more, the rack recoverability is excellent, and if less than 90%, the rack recoverability is not good.

Example 1
The resin used in each layer is as follows.
Layer A: acrylic resin (70% by weight of butyl acrylate and 30% by weight of methyl methacrylate) (Vicat softening point 70 ° C., MFR = 22 g / 10 minutes) 100% by weight
B layer: Acid-modified hydrogenated styrene thermoplastic elastomer resin (Asahi Kasei Chemicals Corporation, trade name Tuftec, variety M1913) 100% by weight
C layer: ethylene-butyl acrylate copolymer resin (manufactured by Atofina Japan Co., Ltd., trade name: Rotoril, variety 7BA01) 100% by weight
Each of the above resins is put into three extruders, the acrylic resin is 220 ° C., the acid-modified hydrogenated styrene thermoplastic elastomer resin is 200 ° C., and the ethylene-butyl acrylate copolymer resin is 200 ° C., respectively. Dissolved, laminated and extruded from a 220 ° C. T-die, cooled and solidified with a 60 ° C. take-up roll, and wound up to obtain a film.
The thickness constitution of the obtained film was 110 μm / 10 μm / 30 μm = 150 μm in the order of A layer / B layer / C layer.

A part of the obtained film was cut to prepare a sample piece, and expandability and rack recoverability were measured. The results are shown in Table 1.

(Example 2)
The resin used in each layer is as follows.
A layer: 93% by weight of acrylic resin (Vicat softening point 70 ° C., MFR = 22 g / 10 min) 70% by weight of butyl acrylate and 30% by weight of methyl methacrylate and styrene-butadiene block copolymer resin (JSR Corporation) Product name Dynalon variety 4630P) 7% by weight
B layer: 60% by weight of acid-modified hydrogenated styrene thermoplastic elastomer resin (Asahi Kasei Chemicals Co., Ltd., trade name Toughtec, variety M1913) and ethylene-methyl acrylate copolymer resin (manufactured by Atofina Japan Co., Ltd., trade name: Rotoril variety) 9MA02) 40% by weight
C layer: ethylene-methyl acrylate copolymer resin (trade name Rotoril variety 9MA02 manufactured by Atofina Japan Co., Ltd.) 100% by weight
A film was obtained in the same manner as in Example 1 using the above resin. The thickness structure of the obtained film was 100 μm / 35 μm / 15 μm = 150 μm in the order of A layer / B layer / C layer.

A part of the obtained film was cut to prepare a sample piece, and expandability and rack recoverability were measured. The results are shown in Table 1.

(Example 3)
The resin used in each layer is as follows.
A layer: Acrylic resin (Vicat softening point 70 ° C., MFR = 22 g / 10 min) of 70% by weight of butyl acrylate and 30% by weight of methyl methacrylate and styrene-butadiene block copolymer resin (JSR Corporation) Manufactured by trade name Dynalon variety 4630P) 15 parts by weight of phenol-modified terpene resin (manufactured by Yasuhara Chemical Co., Ltd., trade name YS Polyster, variety T115) with 15 parts by weight of mixed resin of 15% by weight
B layer: 60% by weight of acid-modified hydrogenated styrene thermoplastic elastomer resin (Asahi Kasei Chemicals Co., Ltd., trade name Toughtec, variety M1913) and ethylene-methyl acrylate copolymer resin (manufactured by Atofina Japan Co., Ltd., trade name: Rotoril variety) 9MA02) 40% by weight
C layer: ethylene-methyl acrylate copolymer resin (trade name Rotoril variety 9MA02 manufactured by Atofina Japan Co., Ltd.) 100% by weight
A film was obtained in the same manner as in Example 1 using the above resin. The thickness structure of the obtained film was 100 μm / 35 μm / 15 μm = 150 μm in the order of A layer / B layer / C layer.

A part of the obtained film was cut to prepare a sample piece, and expandability and rack recoverability were measured. The results are shown in Table 1.

(Comparative Example 1)
As layer A, the same conditions as in Example 1 except that 100% by weight of acrylic resin (Vicat softening point 80 ° C., MFR = 25 g / 10 min) which is 50% by weight of butyl acrylate and 50% by weight of methyl methacrylate is used. A film was obtained.
A part of the obtained film was cut to prepare a sample piece, and the expandability and the rack recoverability were measured. The results are shown in Table 1.

Claims (2)

A base film for a dicing sheet, wherein each layer includes the following components in a film composed of three layers of A layer / B layer / C layer.
Layer A: An acrylic resin having an acrylic ester component of 60 to 80% by weight and a methacrylic ester component of 20 to 40% by weight.
B layer: acid-modified hydrogenated styrene thermoplastic elastomer.
C layer: Thermoplastic ethylene resin. 2. The substrate for dicing sheet according to claim 1, wherein the restoration rate in the vertical direction and the horizontal direction is 90% or more when stretched by 40% in the vertical direction and the horizontal direction and contracted by heating at 60 ° C. for 10 seconds. the film.