CN110272696B

CN110272696B - Adhesive tape for back grinding

Info

Publication number: CN110272696B
Application number: CN201910179977.7A
Authority: CN
Inventors: 守本宗弘; 田中广美
Original assignee: Maxell Ltd
Current assignee: Maxell Ltd
Priority date: 2018-03-14
Filing date: 2019-03-11
Publication date: 2022-12-23
Anticipated expiration: 2039-03-11
Also published as: TWI806973B; JP7092526B2; KR20190108503A; CN110272696A; KR102585832B1; JP2019161031A; TW201938729A

Abstract

The invention provides an adhesive tape for back grinding, which properly follows bumps and electrode protrusions when being adhered to a semiconductor wafer having concave-convex shapes such as bumps and electrode protrusions, and has extremely low generation rate of chip damage due to dent generation during back grinding, extremely low generation rate of bump parts and electrode protrusions damage when peeling the adhesive tape, and can be easily peeled without generating adhesive residue on an adhered surface, and can fully inhibit thickness deviation of the wafer after back grinding. An adhesive tape for back grinding, which comprises a substrate, and a semiconductor wafer comprising an intermediate resin layer and an adhesive layer formed on the substrate in this order, wherein the intermediate resin layer has a thickness of 0.15 × 10 at any temperature of 55-80 deg.C ⁶ ～1.51×10 ⁶ Pa, and a non-curable adhesive agent containing, as a main component, an acrylic adhesive polymer having an acid value of 2.0mgKOH/g or less and a hydroxyl value of 1.0 to 15.0 mgKOH/g.

Description

Adhesive tape for back grinding

Technical Field

The present invention relates to a back-grinding adhesive tape to be attached to protect a surface of a semiconductor wafer during back-grinding of the semiconductor wafer.

Background

A semiconductor wafer manufactured in a large diameter state is subjected to a back grinding process (hereinafter, also referred to as "back grinding") to form a predetermined circuit pattern on the surface of the semiconductor wafer through steps such as photoresist, etching, ion implantation, and polishing, to form an electrode by sputtering, and then, if necessary, to perform a back treatment (etching, polishing, and the like), a cutting process, and the like.

Structures such as circuits and electrodes are formed on the surface of the semiconductor wafer. In the back-grinding, in order to prevent the structure from being damaged by an external damage or contaminated by contact with grinding dust or grinding water, an adhesive tape called a back-grinding adhesive tape is stuck to the front surface of the semiconductor wafer in advance, and the adhesive tape is peeled from the semiconductor wafer after the back-grinding.

In order to prevent grinding dust or grinding water from entering the surface of the semiconductor wafer during back grinding, the adhesive tape for back grinding must be sufficiently adhered to the surface of the semiconductor wafer during adhesion. On the other hand, in order to prevent the structure on the surface of the semiconductor wafer from being damaged or contaminated, it is necessary to easily detach the adhesive tape for back grinding without leaving any adhesive (adhesive residue).

In recent years, with the miniaturization and high density of electronic devices, flip chip mounting has become mainstream as a method for mounting a semiconductor element with a minimum area. In this mounting method, a bump made of solder or gold is formed on an electrode of a semiconductor element, and the bump is electrically connected to a wiring on a circuit board. For example, in the case of wafer level packaging, a bumped semiconductor chip having a height of the bumps as high as 250 to 350 μm is used.

However, since the bumped semiconductor wafer has a large uneven shape on its surface, it is difficult to perform thin-film processing, and if back-grinding is performed using a normal adhesive tape, it is easy to cause a phenomenon such as (1) intrusion of grinding dust or grinding water, (2) cracking of the semiconductor wafer, (3) deterioration of thickness accuracy of the semiconductor wafer after back-grinding, and (4) indentation (depression) on the grinding surface. Further, since there is still a strong demand for a thinner polished thickness of a wafer after back grinding, adhesive tapes and sheets for surface protection of semiconductor wafers having various configurations and having higher performance have been developed.

Patent document 1 discloses a surface-protecting adhesive sheet for a semiconductor wafer, which is formed of a base material and formed of a material to be bonded, and which is preferably used for bonding to a surface to protect the surface when processing the back surface of a bonded body having a large surface irregularity, and which can be polished to a uniform thickness even when the bonded body is polished to be extremely thin, and which can prevent the occurrence of dentsAn intermediate layer on the substrate and an adhesive layer formed on the intermediate layer, wherein the elastic modulus of the intermediate layer at 40 deg.C is less than 1.0 × 10 ⁶ Pa。

Patent document 2 discloses an adhesive sheet for protecting a semiconductor wafer, which is obtained by laminating a substrate, at least one intermediate layer and an adhesive layer in this order, wherein the adhesive sheet for protecting a semiconductor wafer has a bonding temperature of 50 to 100 ℃ with respect to a semiconductor wafer, a loss tangent (tan δ) at the bonding temperature of the intermediate layer on the side in contact with the adhesive layer is 0.5 or more, and a loss modulus at the bonding temperature of the intermediate layer on the side in contact with the adhesive layer is 0.005 to 0.5MPa, in order to protect the surface of the wafer from unevenness, prevent grinding dust, grinding water, and the like from entering the surface of the wafer, and prevent the wafer from being damaged after polishing, when the back surface of the wafer is polished to a height difference or less between the unevenness formed on the surface of the wafer.

Patent document 3 discloses an adhesive tape for protecting a surface of a semiconductor wafer, which has an adhesive layer containing a (meth) acrylic polymer having an acid value of 20 to 50 (mgKOH/g) and a contact angle of 100 ° or more of pure water immediately after dropping to the surface of the adhesive layer and a contact angle of 65 ° or more of pure water after dropping for 10 minutes, wherein the adhesive tape for protecting a surface of a semiconductor wafer has an adhesive force layer on a base film, has an adhesive force of 0.3 to 10N/25mm at 23 ℃ and an adhesive force of 23 ℃ or less when heated to 50 ℃ with respect to stainless steel, and the contact angle of pure water immediately after dropping to the surface of the adhesive layer is 100 ° or more, and the adhesive tape for protecting a surface of a semiconductor wafer can be easily peeled off from a semiconductor wafer and can suppress adhesive residue even when a semiconductor wafer is polished.

Patent document 4 discloses an adhesive tape for protecting a semiconductor wafer surface, which is an adhesive tape for protecting a semiconductor wafer, which is firmly adhered to a semiconductor wafer during processing of the semiconductor wafer and can be peeled off without damage or adhesive residue of the semiconductor wafer during peeling, wherein a wafer having an unevenness of 20 μm or more on the wafer surface is heat-bonded at a temperature of 60 ℃ or more, the adhesive tape for a semiconductor wafer is composed of at least 3 layers of a base film having a melting point of 90 ℃ and a flexural modulus of 1GPa to 10GPa, an intermediate resin layer composed of 2 layers of an ethylene-methyl acrylate copolymer resin, an ethylene-ethyl acrylate copolymer resin, or an ethylene-butyl acrylate copolymer resin, and a polyethylene resin layer, the polyethylene resin layer is present on the base film side, and the layer ratio is polyethylene resin: copolymer resin layer =1: 9-5: 5, the thickness of the intermediate resin layer is more than the height of the bump, the melting point is in the range of 50-90 ℃, and the flexural modulus of elasticity is 1-100 MPa.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2000-212530

Patent document 2: japanese patent application laid-open No. 2010-258426

Patent document 3: japanese patent No. 5855299

Patent document 4: japanese patent laid-open publication No. 2016-164953

Disclosure of Invention

Problems to be solved by the invention

When the adhesive sheet of patent document 1 is used, generation of dents after back grinding and thickness variation of the wafer can be suppressed. However, since the intermediate layer is formed of an acrylic adhesive composition containing an acrylic adhesive and a diisocyanate-based curing agent, or a resin composition containing a photopolymerizable urethane acrylate-based oligomer and a photopolymerizable monomer, the elastic modulus at 40 ℃ is small, and tan δ in the range of 0 ℃ to 60 ℃ is large. That is, since the intermediate layer has high viscosity (flexibility), there is a possibility that adhesive dicing debris having viscosity may cause contamination of the wafer when the tape is cut along the outer periphery of the wafer after the adhesive sheet is bonded to the wafer, and when the bumped wafer having a higher bump height is subjected to back grinding to be thinner, the intermediate layer may ooze due to pressure applied to the adhesive sheet, and thus the breakage of the wafer and variation in the thickness of the wafer after grinding may not be sufficiently suppressed.

When the adhesive sheet of patent document 2 is used, the adhesive sheet can be bonded to the solder bumps on the surface of the semiconductor wafer without any voids, and even if the back surface of the semiconductor wafer is polished, the breakage rate of the semiconductor wafer and the incidence rate of the intrusion of polishing water can both be 0%. However, the loss tangent (tan. Delta.) of the intermediate layer at the bonding temperature (50 ℃ C. To 100 ℃ C.) is as large as 0.5 or more, and the loss modulus is as small as 0.005MPa to 0.5MPa. That is, since the intermediate layer has high viscosity (flexibility), the adhesive is embedded into the irregularities on the surface of the semiconductor wafer such as bumps together with the intermediate layer without any gap, and the fixing effect is enhanced, and for example, in the case of using an ultraviolet-curable adhesive as the adhesive, the adhesive may be difficult to peel off, and in this case, although the wafer is not damaged, the bump portion may be damaged due to the effect of the improvement in the elastic modulus of the adhesive after ultraviolet curing.

When the adhesive tape of patent document 3 is used, it can suitably follow the semiconductor wafer having a surface step of 50 μm or less, and the semiconductor wafer can be easily peeled from the semiconductor wafer without causing damage or leakage. However, when the adhesive tape is peeled, it must be heated to 50 ℃, and there is room for improvement in workability and temperature control. Further, since the (meth) acrylic polymer having an acid value of 20 to 50 (mgKOH/g) is contained in the adhesive layer, the initial adhesion to the wafer is high, and it is not clear whether or not the wafer with bumps having a higher bump height can be peeled off easily without leaving adhesive residue when the wafer with bumps is subjected to back polishing.

In the case of using the adhesive tape of patent document 4, even when high bumps are provided or when the pitch between the bumps is narrowed, the adhesive tape is heated and bonded to melt the intermediate resin layer during processing of the semiconductor wafer, so that the adhesive tape can completely follow the bumps and firmly adhere to the semiconductor wafer, and the thin-film semiconductor wafer can be peeled off without breakage or adhesive residue of the semiconductor wafer during peeling. However, the adhesive completely follows the irregularities on the surface of the semiconductor wafer such as bumps together with the intermediate layer, and the fixing effect is enhanced, and for example, in the case of using an adhesive containing a radiation-curable polymer as the adhesive, peeling may be difficult, and in this case, although the wafer is not damaged, the bump portion may be damaged due to the effect of the increase in the elastic modulus of the adhesive after ultraviolet curing.

As described above, any conventional adhesive tape or sheet for surface protection, which is used for a semiconductor wafer having a concave-convex shape such as bumps or electrode protrusions, cannot fully satisfy the wafer damage after back grinding, the generation rate of the bump damage, the bump peripheral portion, the adhesive residue property of the wafer surface, and the wafer thickness accuracy after grinding, and still leaves room for improvement.

The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide an adhesive tape for back grinding which suitably follows bumps and electrode protrusions when attached to a semiconductor wafer having irregularities such as bumps and electrode protrusions, and which has a very low incidence of chipping and wafer breakage when back grinding is performed, and further has a very low incidence of breakage of bump portions and electrode protrusions when the adhesive tape is peeled off, and which can be easily peeled off without leaving adhesive residue on the surface to be bonded, and which can sufficiently suppress variations in the thickness of the wafer after back grinding.

Means for solving the problems

In view of the above problems, the present inventors have conducted extensive studies and, as a result, have found that: the present invention has been accomplished by solving the above-mentioned conventional problems by providing an adhesive tape structure for a semiconductor wafer, which is heat-adhered to the surface of a semiconductor wafer having irregularities and comprises at least 3 layers of a base film, an intermediate resin layer and a non-radiation curable adhesive layer, and by defining the storage modulus (G') of the intermediate resin layer in the adhering temperature range and the acid value and hydroxyl value of the adhesive layer in specific ranges.

That is, the present invention provides an adhesive tape for back grinding of a semiconductor wafer having a base material, and an intermediate resin layer and an adhesive layer formed on the base material in this order, characterized in that,

the intermediate resin layer has a thickness of 0.15X 10 at any temperature of 55-80 deg.C ⁶ ～1.51×10 ⁶ A storage modulus (G') of Pa,

the adhesive layer is composed of a non-curable (non-curable by post application of external energy) adhesive containing, as a main component, an acrylic adhesive polymer having an acid value of 2.0mgKOH/g or less and a hydroxyl group value of 1.0 to 15.0 mgKOH/g.

Here, the intermediate resin layer has a thickness of 0.15X 10 at any temperature of 55 to 80 deg.C ⁶ ～1.51×10 ⁶ The storage modulus (G') of Pa is 0.15X 10 at a specific temperature in the range of 55 to 80 DEG C ⁶ ～1.51×10 ⁶ Pa。

The intermediate resin layer preferably has a thickness of 1.2 times or more the level difference of the uneven shape existing on the surface of the semiconductor wafer.

Further, the intermediate resin layer is preferably formed by containing ethylene-vinyl acetate copolymer (EVA).

Further, the ethylene-vinyl acetate copolymer (EVA) preferably contains 25 to 40 mass% of vinyl acetate.

Further, the substrate preferably has a thickness of 50 to 200 μm.

Further, the adhesive layer preferably has a thickness of 10 to 50 μm.

Further, when the adhesive tape is adhered to the surface of the semiconductor wafer with bumps and observed from the right above with a microscope, the diameter of the bump observed/measured through the adhesive tape is defined as r _b R is the diameter of a circular non-adhesive portion formed in the peripheral portion of the bump where the adhesive tape is not adhered to the surface of the semiconductor wafer _a Then r is _a /r _b The value of (b) is preferably 1.15 to 1.50.

Further, the height difference of the uneven shape existing on the surface of the semiconductor wafer is preferably 50 to 300 μm.

In one embodiment, the bonding temperature when the adhesive tape for back grinding is bonded to the semiconductor wafer is any one of 55 to 80 ℃.

Effects of the invention

The adhesive tape for back grinding of the present invention suitably follows bumps and electrode protrusions when it is adhered to a semiconductor wafer having irregularities such as bumps and electrode protrusions, and has a very low incidence of chipping and wafer breakage during back grinding, and further has a very low incidence of breakage of bump portions and electrode protrusions when the adhesive tape is peeled off, and can be easily peeled off without generating adhesive residue on the surface to be adhered, and can sufficiently suppress thickness variation of the wafer after back grinding.

Drawings

Fig. 1 is a sectional view showing a layer structure of an adhesive tape for back grinding according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of a semiconductor wafer with solder bumps to which an adhesive tape for back grinding according to an embodiment of the present invention is attached.

Fig. 3 is a plan view of a semiconductor wafer with solder bumps, to which an adhesive tape for back grinding according to an embodiment of the present invention is attached, as viewed through the adhesive tape.

Description of the symbols

1: a base material,

2: an intermediate resin layer,

3: an adhesive layer,

4: a semiconductor wafer,

5: and (7) solder bumps.

Detailed Description

Fig. 1 is a sectional view showing a layer structure of an adhesive tape for back grinding according to an embodiment of the present invention. The adhesive tape for back grinding of fig. 1 has a base material 1, and an intermediate resin layer 2 and an adhesive layer 3 formed in this order on the base material. As shown in fig. 2, the adhesive tape for back grinding of the present invention is used by being attached to the surface of a semiconductor wafer with solder bumps.

The constituent members and layer structure of the adhesive tape for back grinding of the present invention are not limited to the embodiment shown in fig. 1. The adhesive tape for back grinding of the present invention may have layers other than the substrate 1, the intermediate resin layer 2, and the adhesive layer 3.

The adhesive tape for back grinding may be provided with a release liner (not shown) for protecting the adhesion surface of the adhesive layer 3 before use. Such a release liner is not particularly limited, and may be appropriately selected from known release liners.

The substrate 1 may be any material having strength to withstand the use environment, and includes paper, a polymer material, cloth, a metal foil, and the like. Preferably, the resin composition is composed of a polymer material such as vinyl chloride, polystyrene, polyimide, polyamide, poly (tetrafluoroethylene), and polyester (e.g., polyethylene terephthalate, polyethylene naphthalate). Among them, in order to transport a thin and brittle semiconductor wafer without breakage after the back-grinding of the semiconductor wafer, a polyester film having high rigidity is preferably used as the substrate 1. Further, if a polyester film is used as the substrate 1, the substrate 1 can be prevented from sticking to the chuck table even after the back surface of the semiconductor wafer is polished because of high rigidity and no tackiness. These substrates are in the form of films, and the thickness is usually 50 to 200. Mu.m, preferably 75 to 100. Mu.m.

If the thickness of the base material is smaller than 50 μm, the rigidity may be insufficient and the warpage of the semiconductor wafer after back grinding may not be suppressed, and a dent may be generated on the surface of the semiconductor wafer after back grinding. If the thickness of the substrate is larger than 200 μm, the release liner may peel off when the adhesive tape is formed into a roll form, and the semiconductor wafer may be damaged when the adhesive tape is peeled off after the back grinding.

If necessary, as is well known in the art, the surface of the substrate can be modified before the resin composition of the intermediate resin layer is applied by applying the primer composition to the substrate or subjecting the substrate to corona treatment or flame treatment, thereby improving the adhesion between the resin composition of the intermediate resin layer and the substrate. In the case of substrates using polyethylene terephthalate or polyethylene naphthalate, the use of a primer is particularly suitable.

The intermediate resin layer 2 absorbs the level difference due to the uneven shape when the adhesive layer is attached to the surface of the semiconductor wafer, and maintains the surface of the substrate film, which is the upper layer thereof, in a flat state. In addition, the buffer layer also functions as an appropriate buffer layer for preventing the semiconductor wafer from being damaged by pressure and impact during back grinding. Here, the difference in level due to the uneven shape means a distance from the surface of the bonded surface where the bump or the protruding electrode is not formed to the highest position of the bump or the protruding electrode.

The intermediate resin layer 2 has a storage modulus (G') of 0.15X 10 at a temperature at which the adhesive tape is adhered to the surface of the semiconductor wafer ⁶ ～1.51×10 ⁶ Pa. If the storage modulus of the intermediate resin layer 2 at the pasting temperature is less than 0.15X 10 ⁶ Pa is too soft, and therefore, the projections and depressions fit into the surface to be bonded without any gap, and when the adhesive tape is peeled off, the bump portions may be broken, and adhesive residue may easily occur on the surface to be bonded. On the other hand, if the storage modulus of the intermediate resin layer 2 at the pasting temperature exceeds 1.51X 10 ⁶ Pa is too hard, and therefore, the ability to follow the irregularities of the surface to be bonded is reduced, and polishing debris or polishing water easily enters during back polishing. The storage modulus of the intermediate resin layer 2 at the pasting temperature is preferably 0.30 × 10 ⁶ Pa～1.00×10 ⁶ Pa。

The storage modulus (G') of the intermediate resin layer 2 at 23 ℃ is preferably 5.00X 10 ⁶ ～7.00×10 ⁶ Pa. When the adhesive tape is bonded to the surface of the semiconductor wafer, the adhesive tape is bonded to the surface of the semiconductor wafer at a temperature of about 40 ℃ from room temperature, but if the storage modulus (G') at 23 ℃ is in this range, the intermediate resin layer can be prevented from flowing or bleeding due to the pressure applied to the adhesive tape when the semiconductor wafer is subjected to back grinding after the adhesive tape is bonded to the surface of the semiconductor wafer, and therefore the adhesive tape can appropriately hold the semiconductor wafer, appropriately alleviate the impact at the time of back grinding, and can suppress the breakage of the semiconductor wafer at the time of back grinding of the semiconductor wafer, and can suppress the occurrence of dents on the surface of the semiconductor wafer after the back grinding, thereby reducing the variation in the thickness of the semiconductor wafer.

The intermediate resin layer 2 preferably contains a thermoplastic resin from the viewpoint of adjusting the storage modulus at the pasting temperature. One kind of thermoplastic resin may be used, or two or more kinds may be used in combination.

As representative examples of the thermoplastic resin, polyethylene (PE); polybutylene; ethylene copolymers such as ethylene-propylene copolymer (EPM), ethylene-propylene-diene copolymer (EPDM), ethylene-ethyl acrylate copolymer (EEA), ethylene-ethyl acrylate-maleic anhydride copolymer (EEAMAH), ethylene-glycidyl methacrylate copolymer (EGMA), ethylene-methacrylic acid copolymer (EMAA), and ethylene-vinyl acetate copolymer (EVA); a polyolefin copolymer; thermoplastic elastomers such as butadiene-based elastomers, ethylene-isoprene-based elastomers, and ester-based elastomers; a thermoplastic polyester; polyamide resins such as polyamide 12 copolymers; a polyurethane; a polystyrene-based resin; cellophane; acrylic resins such as polyacrylate and polymethyl methacrylate; polyvinyl chloride resins such as vinyl chloride-vinyl acetate copolymers.

The weight average molecular weight of the thermoplastic resin is preferably in the range of 20,000 to 300,000, and more preferably 30,000 to 250,000.

The intermediate resin layer 2 is preferably formed containing ethylene-vinyl acetate copolymer (EVA). When the intermediate resin layer contains an ethylene-vinyl acetate copolymer, even when the level difference due to the uneven shape of the surface of the semiconductor wafer is 50 to 300 μm, the intermediate resin layer is likely to have appropriate conformability to the uneven shape. In one embodiment, the intermediate resin layer is substantially formed of an ethylene-vinyl acetate copolymer.

The ethylene-vinyl acetate copolymer contains 25 to 40 mass% of vinyl acetate. If the vinyl acetate content of EVA is less than 25 mass%, the flexibility of the intermediate resin layer becomes insufficient, and the ability to follow the irregularities of the surface to be bonded is reduced, and if it exceeds 40 mass%, the intermediate resin layer becomes too flexible, and blocking is likely to occur after winding, making stable film formation difficult, and productivity is reduced.

In the case of an ethylene-vinyl acetate copolymer containing 25 to 40 mass% of vinyl acetate, the Melt Flow Rate (MFR) is particularly preferably 2 to 700g/10 min, more preferably 5 to 400g/10 min. If the melt flow rate is in this range, the intermediate resin layer can be stably melt-extruded and formed on the substrate 1 while having appropriate conformability to the surface roughness of the semiconductor wafer.

The intermediate resin layer 2 may contain other components within a range not impairing the characteristics. Examples of such components include tackifiers, plasticizers, softeners, fillers, antioxidants, and antiblocking agents. The intermediate resin layer 2 may be composed of 1 layer, or may have a multilayer structure composed of multiple layers of the same kind or different kinds. In the case where the intermediate resin layer has a multilayer structure, the thickness of the intermediate resin layer refers to the total thickness of the multiple layers.

The thickness of the intermediate resin layer 2 is determined by the difference in level due to the uneven shape of the surface to be bonded and the variation in level at the time of forming the uneven portion. The thickness of the intermediate resin layer is, for example, 1.2 times or more the height difference due to the uneven shape of the surface to be bonded. If the thickness of the intermediate resin layer is less than 1.2 times the height difference due to the uneven shape of the surface to be bonded, the height difference of the uneven shape of the surface to be bonded cannot be sufficiently absorbed and the surface cannot be bonded, and there is a possibility that polishing dust or polishing water enters during back-surface polishing. Further, when the adhesive tape is attached, since the convex portions of the unevenness of the surface to be bonded protrude from the base material, there is a possibility that the surface of the semiconductor wafer after back grinding is dented, and the thickness of the semiconductor wafer varies. The thickness of the intermediate resin layer is preferably 1.4 to 1.6 times the height difference due to the uneven shape.

The method of laminating the intermediate resin layer 2 on the substrate 1 is not particularly limited, and examples thereof include: a method of laminating the intermediate resin layer 2 with a substrate 1 prepared in advance while extruding the intermediate resin layer into a film shape by an extruder; a method of extruding the substrate 1 together with the intermediate resin layer 2; a method of applying a resin solution on the substrate 1 and drying the resin solution. Examples of the extrusion method include a T die extrusion method and an inflation method.

The adhesive layer 3 is formed of an adhesive having a minimum adhesive force required for preventing the intrusion of polishing dust or polishing water during back polishing and for holding the semiconductor wafer during back polishing, and is hermetically sealed by adhering to the surface of the semiconductor wafer. The adhesive layer 3 must be easily peeled off after the back grinding is completed, and the adhesive force of the adhesive is preferably as low as possible as long as the above characteristics are satisfied.

The adhesive force of the adhesive layer 3 to stainless steel at 25 ℃ is 0.10N/25mm or more and 0.50N/25mm or less. If the adhesive force of the adhesive layer is less than 0.10N/25mm, the sealing of the surface to be bonded becomes insufficient, and there is a possibility that polishing dust or polishing water may enter the surface to be bonded during back grinding. In addition, after the adhesive tape is attached to the surface of the semiconductor wafer having the uneven shape, the adhesive tape may be lifted from the wafer surface. If the adhesive force of the adhesive layer exceeds 0.50N/25mm, adhesive residue may occur on the surface to be bonded when peeling is performed after the back grinding is completed, and a structure, such as a circuit pattern, an electrode, or a bump, present on the surface to be bonded may be damaged.

The "adhesion" of the adhesive layer 3 to stainless steel means: the adhesive tape was adhered to stainless steel polished using No. 280 water-resistant abrasive paper prescribed in JIS R6253 by reciprocating a 2kg roll once at 23 ℃, and the 180-degree peel adhesion force was obtained when the adhered adhesive layer was peeled at 23 ℃ at a peel speed of 300 mm/min and an angle of 180 degrees.

The adhesive layer 3 is formed of an adhesive that does not remain on the surface to be adhered after being peeled off from the surface to be adhered. Examples of the adhesive constituting the adhesive layer 3 include acrylic adhesives. For example, even when air is held between the adhesive surfaces of the adhesive layers, specifically, even when air is mixed in the periphery of the bumps of the bumped semiconductor wafer, it is preferable that the adhesive contains an acrylic adhesive polymer as a main component so that no adhesive residue is generated on the adhered surfaces during peeling due to curing failure caused by oxygen barrier that occurs in radiation-curable acrylic adhesives, and that the adhesive is non-curable in a state of being finally processed into an adhesive tape.

The term "main component" means a component contained in an amount sufficient to determine the physical properties and characteristics of a material. The main component of the adhesive is usually contained in an amount of 50 mass% or more, 70 mass% or more, or 85 mass% or more. As the component of the adhesive other than the main component, additives such as a crosslinking agent, a plasticizer, a softening agent, a filler, and an antioxidant can be exemplified. The term "non-curable" means that the adhesive does not have curing properties when the adhesive layer is peeled off from the surface of the semiconductor wafer. That is, when the adhesive layer is peeled off from the surface of the semiconductor wafer, the adhesive is not cured by post-application of external energy such as radiation irradiation or heat. Specifically, the term "adhesive" refers to an adhesive in which no polymerization reaction site or crosslinking reaction site such as a photosensitive group or a thermosensitive group remains in a state of being finally processed into an adhesive tape.

The adhesive comprising an acrylic adhesive polymer preferably has an acid value of 2.0mgKOH/g or less and a hydroxyl value of 1.0 to 15.0 mgKOH/g. Here, the acid value is the amount (mg) of potassium hydroxide required to neutralize the acid component contained in 1g of the object. The hydroxyl number is the amount (mg) of potassium hydroxide required to acetylate the OH groups contained in 1g of the object. By setting the acid value and the hydroxyl value of the pressure-sensitive adhesive containing an acrylic pressure-sensitive adhesive polymer to the above ranges, the adhesive force can be set to the above appropriate ranges at the time of combining the substrate 1 and the intermediate resin layer 2, and as a result, it is possible to prevent grinding dust or grinding water from entering the surface to be bonded in the back grinding, and it is possible to easily peel the pressure-sensitive adhesive tape without leaving adhesive residue on the surface to be bonded after the back grinding.

If the acid value of the pressure-sensitive adhesive containing an acrylic pressure-sensitive adhesive polymer exceeds 2.0mgKOH/g, the peel strength of the pressure-sensitive adhesive layer becomes large, and adhesive residue is likely to occur on the surface to be bonded. The acid value of the adhesive containing an acrylic adhesive polymer is preferably 1.0mgKOH/g or less. The acid value of the adhesive containing an acrylic adhesive polymer is preferably 0, but in the case of using an acrylate, it is substantially difficult to completely remove the acid value.

If the hydroxyl value of the adhesive containing an acrylic adhesive polymer is less than 1.0mgKOH/g, particularly when a compound containing an isocyanate group reactive with a hydroxyl group is used as a crosslinking agent, the crosslinking density in the adhesive layer is reduced, the cohesive force is reduced, and therefore, adhesive residue is likely to occur on the surface to be bonded. If the hydroxyl value of the pressure-sensitive adhesive containing an acrylic pressure-sensitive adhesive polymer exceeds 15.0mgKOH/g, the peel strength of the pressure-sensitive adhesive layer becomes large, and adhesive residue is likely to occur on the surface to be bonded. The hydroxyl value of the adhesive containing the acrylic adhesive polymer is preferably 2.0 to 5.0mgKOH/g.

Specific examples of the acrylic adhesive polymer include: a (meth) acrylic polymer (A) having as a monomer component at least a (meth) acrylic monomer (a 1) containing an alkyl group.

Specific examples of the alkyl group-containing (meth) acrylic monomer (a 1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, and cyclohexyl (meth) acrylate. They may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate is preferred. In addition, in the case of using a plurality of kinds of the alkyl group-containing (meth) acrylic monomers (a 1), one kind may be used as a main monomer and the other may be used as a comonomer. The number of alkyl groups in the alkyl group-containing (meth) acrylic monomer (a 1) is not particularly limited, but is preferably 10 or less, more preferably 8 or less, in view of production cost. The alkyl group-containing (meth) acrylic monomer (a 1) is preferably a monomer having a glass transition temperature of a homopolymer of 0 ℃ or lower.

The total content of the alkyl group-containing (meth) acrylic monomer (a 1) in the (meth) acrylic polymer (a) is preferably 50 to 100% by mass based on the total amount of the monomer components.

The (meth) acrylic polymer (a) may be a copolymer having one of the above-mentioned alkyl group-containing (meth) acrylic monomers (a 1) as a main monomer, or a functional group-containing (meth) acrylic monomer as a comonomer. By using the functional group-containing (meth) acrylic monomer, other characteristics such as cohesive force can be improved.

Specific examples of the functional group-containing (meth) acrylic monomer include: hydroxyl group-containing (meth) acrylic monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate; epoxy group-containing (meth) acrylic monomers such as glycidyl (meth) acrylate; carboxyl group-containing (meth) acrylic monomers such as (meth) acrylic acid; (meth) acrylic acid-based amide group-containing monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide; amino group-containing (meth) acrylic monomers such as aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; cyano group-containing (meth) acrylic monomers such as (meth) acrylonitrile; alkoxy group-containing (meth) acrylic monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate. They may be used alone or in combination of two or more. Such a functional group-containing (meth) acrylic monomer is preferably a monomer having a glass transition temperature of a homopolymer higher than 0 ℃.

The total content of the functional group-containing (meth) acrylic monomer in the (meth) acrylic polymer (a) is preferably 0 to 30% by mass relative to the total amount of the monomer components, but may be appropriately adjusted so that the acid value of the adhesive finally containing the acrylic adhesive polymer is 2.0mgKOH/g or less and the hydroxyl group is in the range of 1.0 to 15.0 mgKOH/g.

In addition, the (meth) acrylic polymer (a) may further contain other monomers as comonomers in order to improve other characteristics such as cohesion. Examples of such other monomers include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; vinyl ester monomers such as vinyl acetate and vinyl propionate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; n-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole

And monomers having a nitrogen atom-containing ring such as oxazole, N-vinylmorpholine, N-vinylcaprolactam and N- (meth) acryloylmorpholine. They may be used alone or in combination of two or more. The total content of these other monomers is preferably 0 to 10% by mass relative to the total amount of the monomer components, but may be appropriately adjusted so that the acid value of the adhesive finally containing the acrylic adhesive polymer is 2.0mgKOH/g or less and the hydroxyl group is in the range of 1.0 to 15.0 mgKOH/g.

The polymerization method for synthesizing the (meth) acrylic polymer (a) includes conventionally known solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and the like, and among these methods, solution polymerization in which polymerization is uniformly carried out is preferred. Specific examples of the organic solvent used in the solution polymerization include ketone-based, ester-based, alcohol-based, and aromatic organic solvents. These organic solvents may be used alone or in combination of two or more. Among these, organic solvents which are generally good solvents for the (meth) acrylic polymer (a) and have a boiling point of 60 to 120 ℃, such as toluene, ethyl acetate, isopropyl alcohol, benzyl cellosolve, ethyl cellosolve, acetone, and methyl ethyl ketone, are preferable. Further, as the polymerization initiator, azo-bis-type initiators such as α, α' -azobisisobutyronitrile; organic peroxides such as benzoyl peroxide and the like.

The weight-average molecular weight MwA of the (meth) acrylic polymer (a) obtained in the above-described manner is preferably 10 to 100 ten thousand, more preferably 30 to 70 ten thousand. If the weight average molecular weight MwA is less than 10 ten thousand, the adhesive component may flow at a high temperature, the holding property may be lowered, and adhesive residue may be generated on the adherend. On the other hand, if the weight average molecular weight MwA is more than 100 ten thousand, the adhesive component may be gelled at the time of synthesis or coating, or the followability to the unevenness of the surface to be bonded may be reduced. In the present specification, the weight average molecular weight, the number average molecular weight, and the molecular weight distribution are measured values (solvent: tetrahydrofuran) in terms of polystyrene by GPC (gel permeation chromatography).

When the (meth) acrylic polymer (a) has a functional group-containing (meth) acrylic monomer as a comonomer, the adhesive layer 3 may contain a crosslinking agent that crosslinks with a functional group introduced into the molecule by the functional group-containing (meth) acrylic monomer. By using such a crosslinking agent, a three-dimensional crosslinked structure can be formed, and the cohesive force can be improved.

Specific examples of the crosslinking agent include a polyisocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a melamine resin-based crosslinking agent, a urea resin-based crosslinking agent, an acid anhydride compound-based crosslinking agent, a polyamine-based crosslinking agent, and a carboxyl group-containing polymer-based crosslinking agent. These crosslinking agents may be used alone or in combination. Among these, a polyisocyanate-based crosslinking agent having an isocyanate group with excellent reactivity is preferable.

The content of the crosslinking agent depends on the content of the functional group-containing (meth) acrylic monomer, but is preferably 0.1 to 10 parts by mass relative to 100 parts by mass of the (meth) acrylic polymer (a). The crosslinking temperature is preferably 20 to 70 ℃ and the crosslinking time is preferably 1 to 7 days.

The thickness of the adhesive layer 3 may be appropriately selected within a range that does not impair the level difference of the irregularities on the surface of the circuit pattern, the holding property of the semiconductor wafer, and the protective property, but is preferably 5 to 50 μm. More preferably 10 to 30 μm. If the thickness of the adhesive layer is less than 5 μm, the adhesive force is lowered, and grinding dust or grinding water may enter during back grinding. If the thickness of the adhesive layer exceeds 50 μm, the adhesive force increases, and adhesive residue may occur on the surface to be adhered when the adhesive tape is peeled off, and the structure such as a bump or a protruding electrode may be damaged.

The method for forming the adhesive layer 3 is not particularly limited, and is, for example, formed by a coating method. That is, the adhesive is diluted with an organic solvent such as toluene or ethyl acetate to obtain an adhesive layer coating solution. Next, the obtained adhesive layer coating liquid is applied to the surface of the intermediate resin layer 2 previously laminated on the substrate 1, dried, and cured to form the adhesive layer 3. A release liner is attached to the adhesive layer 3 as needed. Alternatively, the adhesive layer 3 may be formed by applying the adhesive layer coating liquid to the surface of the release liner once, drying the application liquid, and then bonding the application liquid and the release liner to the surface of the intermediate resin layer 2 laminated in advance on the substrate 1, followed by curing the application liquid. From the viewpoint of workability, the coating layer is preferably formed by the latter coating transfer method.

The adhesive tape for back grinding of the present invention is preferably applied to the surface of a semiconductor wafer having irregularities. Examples of the shape of the irregularities include the shape of a structure such as a protruding bump electrode or a circuit. The height difference of the uneven shape to which the adhesive tape for back grinding of the present invention can be applied is not particularly specified, but the height difference of the uneven shape existing on the surface to be bonded is preferably 50 to 300 μm.

When the adhesive tape for back grinding of the present invention is applied to back grinding, the adhesive tape for back grinding is heated to a temperature at which the adhesive layer and the intermediate resin layer have sufficient flexibility to deform along the uneven shape of the surface to be bonded, and the adhesive layer is bonded to the surface of the semiconductor wafer. The temperature for sticking the adhesive tape for back-grinding is usually 55 to 80 ℃, preferably 60 to 75 ℃.

As shown in FIG. 3, the adhesive tape for back grinding of the present invention is adhered to a semiconductor device with bumpsWhen the wafer surface is observed from the right above with a microscope, the diameter of the bump observed/measured through the adhesive tape is defined as r _b R is the diameter of a circular non-adhesive portion formed in the peripheral portion of the bump where the adhesive tape is not adhered to the surface of the semiconductor wafer _a Then r is _a /r _b The value of (b) is preferably 1.15 to 1.50.r is a radical of hydrogen _a /r _b The closer to 1.0, the more the value of (b) means that air is hardly mixed into the bump peripheral portion, and the adhesive tape completely follows the bump. However, if the adhesive tape completely follows, the possibility of breaking the bump portion of the semiconductor wafer when the adhesive tape is peeled off becomes high. The adhesive tape for back grinding of the invention is prepared by mixing _a /r _b The value of (d) is set to the above range to form a proper follow-up state not completely following the bump, so that when the adhesive layer 3 is combined, the semiconductor wafer can be prevented from being damaged during back grinding, the bump portion of the semiconductor wafer can be prevented from being damaged during peeling of the adhesive tape, and no adhesive residue is generated on the bonded surface. When a radiation-curable acrylic adhesive is applied to the adhesive as described above, if the adhesive does not completely follow the bump, the adhesive may remain on the surface to be bonded due to poor curing caused by oxygen barrier contained in the air, but since the adhesive layer of the back-grinding adhesive tape of the present invention is a non-curable adhesive layer having an appropriate adhesive force, as shown in fig. 2, even if air is mixed, for example, the adhesive tape can be peeled without leaving adhesive residue on the surface to be bonded. If r is _a /r _b If the value of (2) exceeds 1.50, the possibility of grinding dust or grinding water entering the bonded surface during back grinding increases.

After the back grinding is completed, the adhesive tape for back grinding of the present invention is peeled off by detaching the adhesive layer from the surface to be bonded. The adhesive layer is detached by separating the adhesive tape for back grinding from the surface of the semiconductor wafer. The adhesive contained in the adhesive layer is non-curable, and radiation irradiation or heating is not required for peeling.

The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" means "parts by mass".

Examples

(example 1)

< production of a laminate of a substrate and an intermediate resin layer >

As the substrate, a substrate was prepared by subjecting one surface of a polyethylene terephthalate (PET) film (thickness: 75 μm) to an easy adhesion treatment with an anchor coat layer (thickness: 1 μm) of a polyolefin resin. As the thermoplastic resin of the intermediate resin layer, an ethylene-vinyl acetate copolymer resin (EVA) (content of Vinyl Acetate (VA): 32 mass%, melt flow rate: 30g/10 min) was used, and an intermediate resin layer was formed on the anchor coat layer of the substrate by a melt extrusion method to a thickness of 350 μm, followed by subjecting the surface of the intermediate resin layer to corona treatment, and then a protective film was laminated on the corona-treated surface and wound up to produce a laminate of the substrate with the protective film and the intermediate resin layer.

< preparation of adhesive solution A >

100 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 44% by mass (acid value: 0.3mgKOH/g, hydroxyl value: 3.2mgKOH/g, molecular weight Mw:40 ten thousand, solvent: toluene), 2.07 parts by mass of a toluene diisocyanate-based crosslinking agent (solid content: 75% by mass), and 28.07 parts by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution A having a solid content of 35% by mass.

< formation of adhesive layer and production of adhesive tape for Back grinding >

The pressure-sensitive adhesive solution a was applied to the silicone-treated side of a silicone-treated release PET film (thickness: 38 μm) having one surface treated with silicone so that the thickness after drying was 20 μm, and the surface of the pressure-sensitive adhesive layer after drying was bonded to the surface on the intermediate resin layer side of the laminate of the base material and the intermediate resin layer from which most of the protective film was peeled off, and wound. Subsequently, the obtained roll was fed into the coating machine again, and after the release PET film was peeled off, a polyethylene protective film (thickness: 100 μm) was attached again to the surface of the adhesive layer. The roll was aged at 40 ℃ for 72 hours to prepare an adhesive tape for back grinding.

< measurement of adhesive force (= peeling force) >

The adhesive tape for back grinding was measured for adhesive force by the following method. The adhesive tape for back grinding was heated to 75 ℃ which was the same temperature as the temperature at which the adhesive tape for back grinding was adhered to a semiconductor wafer with bumps, described later, and a 2kg roll was reciprocated once to adhere the adhesive tape for back grinding to stainless steel polished using No. 280 water-resistant grinding paper prescribed in JIS R6253, and the 180-degree peel adhesion when the adhered adhesive layer was peeled at a peel speed of 300 mm/min and an angle of 180 degrees at 23 ℃ was measured.

The adhesive tape for back grinding had an adhesive force of 0.40N/25mm (pasting temperature 75 ℃).

< measurement of storage modulus (G') and loss tangent (tan. Delta.) >)

The intermediate resin layer used in the adhesive tape for back grinding was measured for storage modulus (G') and loss tangent (tan δ) by the following methods. A resin sample (thickness: 500 μm) for the intermediate resin layer was prepared, and dynamic viscoelasticity was measured by using a viscoelasticity measuring apparatus DMA6100 (product name) manufactured by Hitachi technologies, ltd., to determine the storage modulus. The measurement conditions were as follows: while applying a shear strain at a frequency of 1Hz, the temperature was changed from 0 ℃ to 85 ℃ at a temperature increase rate of 5 ℃/min, and values of loss modulus (G ') and storage modulus (G') at the respective temperatures were determined. The loss tangent (tan δ) was calculated using the following formula.

Loss tangent (tan δ) = loss modulus (G ")/storage modulus (G')

The storage modulus (G') of the intermediate resin layer used in the adhesive tape for back grinding at 75 ℃ is 0.37X 10 ⁶ Pa, loss tangent (tan. Delta.) was 0.30. Further, the storage modulus (G') at 23 ℃ was 5.62X 10 ⁶ Pa, loss tangent (tan. Delta.) was 0.08.

< backside grinding adhesive tape stuck on semiconductor wafer with bump >

As the bumped semiconductor wafer, a wafer was used in which solder bumps were provided on the surface of an 8-inch wafer (thickness 800 μm) at the following height and interval.

Height of solder bump: 250 μm

Diameter of solder bump: 350 μm

Solder bump pitch: 900 μm

A tape bonding machine was used, and a sample for polishing was prepared by bonding a pressure-sensitive adhesive tape for back polishing to a semiconductor wafer with bumps at a speed of 2.0mm/sec while applying a constant pressure of 0.45MPa at a bonding temperature of 75 ℃ using RAD 3510 (product name) manufactured by LINTEC. In this case, the thickness of the intermediate resin layer is 1.4 times with respect to the bump height.

(example 2)

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution B. The adhesive force of the adhesive tape for back grinding was 0.50N/25mm.

< preparation of adhesive solution B >

100 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 30% by mass (acid value: 1.9mgKOH/g, hydroxyl value: 3.2mgKOH/g, molecular weight Mw:50 ten thousand, solvent: toluene), 0.24 part by mass of a toluene diisocyanate-based crosslinking agent (solid content: 75% by mass), and 0.36 part by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution B having a solid content of 30% by mass.

(example 3)

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution C. The adhesive tape for back grinding had an adhesive force of 0.33N/25mm.

< preparation of adhesive solution C >

100 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 60% by mass (acid value: 0.1mgKOH/g, hydroxyl value: 15.0mgKOH/g, molecular weight Mw:45 ten thousand, solvent: toluene), 0.6 part by mass of a toluene diisocyanate-based crosslinking agent (solid content: 75% by mass), and 72.1 parts by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution C having a solid content of 35% by mass.

(example 4)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the temperature at which the back-grinding adhesive tape was adhered to the bumped semiconductor wafer was changed from 75 ℃ to 80 ℃. The storage modulus (G') of the intermediate resin layer used in the adhesive tape for back grinding at 80 ℃ is 0.19 × 10 ⁶ Pa, and a loss tangent (tan. Delta.) of 0.45. The adhesive force of the adhesive tape for back grinding was 0.43N/25mm (sticking temperature: 80 ℃).

(example 5)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the temperature at which the back-grinding adhesive tape was adhered to the bumped semiconductor wafer was changed from 75 ℃ to 55 ℃. The storage modulus (G') of the intermediate resin layer used in the adhesive tape for back grinding at 55 ℃ was 1.51 × 10 ⁶ Pa, and a loss tangent (tan. Delta.) of 0.13. The adhesive tape for back grinding had an adhesive force of 0.22N/25mm (sticking temperature 55 ℃ C.).

(example 6)

An adhesive tape for back grinding and a grinding sample were produced in the same manner as in example 1, except that an ethylene-vinyl acetate copolymer resin (EVA) (content of Vinyl Acetate (VA): 28 mass%, melt flow rate: 150g/10 min) was used as the thermoplastic resin of the intermediate resin layer. The adhesive tape for back grinding had an adhesive force of 0.33N/25mm (application temperature 75 ℃ C.). The intermediate resin layer used in the adhesive tape for back grinding has a storage modulus (G') of 0.15X 10 at 75 DEG C ⁶ Pa, a loss tangent (tan. Delta.) of 0.40, and a storage modulus (G') at 23 ℃ of 6.84X 10 ⁶ Pa, and a loss tangent (tan. Delta.) of 0.08.

(example 7)

Thermoplastic resin as intermediate resin layerAn adhesive tape for back grinding and a sample for grinding were produced in the same manner as in example 1 except that two ethylene-vinyl acetate copolymer resins (EVA) having different vinyl acetate contents (vinyl acetate (VA) content: 32 mass%, melt flow rate: 30g/10 min and Vinyl Acetate (VA) content: 42 mass%, melt flow rate: 70g/10 min) were mixed and melted at a mass ratio of 1 to prepare an EVA (vinyl acetate (VA) content: 37 mass%, melt flow rate: 50g/10 min). The adhesive tape for back grinding had an adhesive force of 0.45N/25mm (bonding temperature 75 ℃ C.). The intermediate resin layer used in the adhesive tape for back grinding has a storage modulus (G') of 0.18X 10 at 75 DEG C ⁶ Pa, a loss tangent (tan. Delta.) of 0.49, and a storage modulus (G') at 23 ℃ of 4.73X 10 ⁶ Pa, loss tangent (tan. Delta.) was 0.08.

(example 8)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the thickness of the intermediate resin layer was changed to 300 μm. In this case, the thickness of the intermediate resin layer is 1.2 times with respect to the bump height. The adhesive force of the adhesive tape for back grinding was 0.38N/25mm (bonding temperature: 75 ℃).

(example 9)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the thickness of the intermediate resin layer was changed to 400 μm. In this case, the thickness of the intermediate resin layer is 1.6 times with respect to the bump height. The adhesive force of the adhesive tape for back grinding was 0.40N/25mm (bonding temperature: 75 ℃).

(example 10)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the thickness of the base material was changed to 50 μm. The adhesive tape for back grinding had an adhesive force of 0.45N/25mm (bonding temperature 75 ℃ C.).

(example 11)

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the thickness of the base material was changed to 200 μm. The adhesive force of the adhesive tape for back grinding was 0.23N/25mm (bonding temperature: 75 ℃).

(example 12)

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the thickness of the adhesive layer was changed to 10 μm. The adhesive force of the adhesive tape for back grinding was 0.18N/25mm (bonding temperature: 75 ℃).

(example 13)

A back-polishing adhesive tape and a polishing sample were produced in the same manner as in example 1, except that the thickness of the adhesive layer was changed to 40 μm. The adhesive force of the adhesive tape for back grinding was 0.48N/25mm (bonding temperature: 75 ℃).

Comparative example 1

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution D. The adhesive force of the adhesive tape for back grinding was 0.82N/25mm (bonding temperature: 75 ℃).

< preparation of adhesive solution D >

An acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 40 mass% (acid value: 12.4mgKOH/g, hydroxyl value: 1.5mgKOH/g, molecular weight Mw:100 ten thousand, solvent: toluene), 1.2 parts by mass of a toluene diisocyanate-based crosslinking agent (solid content: 75 mass%), and 15.66 parts by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution D having a solid content of 35 mass%.

Comparative example 2

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution E. The adhesive tape for back grinding had an adhesive force of 0.12N/25mm (application temperature 75 ℃ C.).

< preparation of adhesive solution E >

100 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 35% by mass (acid value: 0.5mgKOH/g, hydroxyl value: 0.9mgKOH/g, molecular weight Mw:33 ten thousand, solvent: toluene), 0.1 part by mass of a cyclohexane diisocyanate-based crosslinking agent (solid content: 100% by mass), and 0.19 part by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution E having a solid content of 35% by mass.

Comparative example 3

A back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution F. The adhesive tape for back grinding had an adhesive force of 0.52N/25mm (application temperature 75 ℃ C.).

< preparation of adhesive solution F >

20 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 40% by mass (acid value: less than 1mgKOH/g, hydroxyl value: 43mgKOH/g, molecular weight Mw:10 ten thousand, solvent: ethyl acetate, toluene), 2.33 parts by mass of a cyclohexane diisocyanate-based crosslinking agent (solid content: 100% by mass), and 0.32 part by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution F having a solid content of 35% by mass.

Comparative example 4

A back-grinding adhesive tape and a grinding sample were prepared in the same manner as in example 1, except that the temperature at which the back-grinding adhesive tape was adhered to the bumped semiconductor wafer was changed from 75 ℃ to 85 ℃. The storage modulus (G') of the intermediate resin layer used in the adhesive tape for back grinding at 85 ℃ was 0.12 × 10 ⁶ Pa, loss tangent (tan. Delta.) was 0.60. The adhesive tape for back grinding had an adhesive force of 0.45N/25mm (sticking temperature 85 ℃ C.).

Comparative example 5

The temperature of the adhesive tape for back grinding adhered on the semiconductor chip with the bump is changed from 75 ℃ to 50 ℃, except thatExcept for this, a back-grinding adhesive tape and a grinding sample were produced in the same manner as in example 1. The storage modulus (G') of the intermediate resin layer used in the adhesive tape for back grinding at 50 ℃ is 1.88 × 10 ⁶ Pa, and a loss tangent (tan. Delta.) of 0.13. The adhesive tape for back grinding had an adhesive force of 0.11N/25mm (sticking temperature 50 ℃ C.).

Comparative example 6

An adhesive tape for back grinding and a grinding sample were prepared in the same manner as in example 1, except that the adhesive solution a was changed to the following adhesive solution G composed of an ultraviolet curable adhesive. The adhesive tape for back grinding was irradiated with ultraviolet rays from the substrate side (cumulative light amount: 300 mJ/cm) ² ) The post-adhesion was 0.02N/25mm (pasting temperature 75 ℃).

< preparation of adhesive solution G >

100 parts by mass of an acrylic pressure-sensitive adhesive comprising an acrylate copolymer having a solid content of 33% by mass (acid value: 6.5mgKOH/G, hydroxyl value: 40.0mgKOH/G, molecular weight Mw:60 ten thousand, solvent: ethyl acetate), 0.5 part by mass of a toluene diisocyanate-based crosslinking agent (solid content: 45% by mass), 0.7 part by weight of an α -hydroxyketone-based photopolymerization initiator, and 10.3 parts by mass of ethyl acetate were mixed and stirred to prepare a pressure-sensitive adhesive solution G having a solid content of 30% by mass.

The adhesive tapes for back grinding and the grinding samples prepared in examples 1 to 13 and comparative examples 1 to 6 were subjected to the following tests to evaluate their performances. The evaluation results are shown in tables 1 to 3 below.

< following ability of bump >

When a polishing sample obtained by adhering an adhesive tape for back polishing to the surface of a bumped semiconductor wafer was observed from the front side using a microscope "VHX-1000" (product name) manufactured by Kenzhi corporation, the diameter of any bump observed/measured through the adhesive tape was defined as r _b R is the diameter of a circular non-adhesive portion formed in the peripheral portion of the bump where the adhesive tape is not adhered to the surface of the semiconductor wafer _a Calculating r _a /r _b The bump followability was evaluated. In addition, regarding the measurement of each diameter, 4 points in each direction were measured, and the average value thereof was defined as r _b 、r _a The value of (c).

< incidence (%) of intrusion of polishing water (polishing debris)

Five polishing samples in which a back-polishing adhesive tape was attached to the surface of the bumped semiconductor wafer were polished from the back surface of the wafer to a thickness of 250 μm using a silicon wafer polisher "DFG8540" (product name) manufactured by disco corporation. The state of the intrusion of polishing water into the wafer surface was observed with a microscope for five semiconductor wafers with bumps after back grinding, and the incidence of the intrusion of polishing water was calculated by the following equation.

The generation rate of grinding water intrusion (%) = (number of pieces of grinding water intrusion/number of pieces of grinding) × 100

< percentage (%) breakage of bumped semiconductor wafer after back grinding >

The five bumped semiconductor wafers after back grinding were observed by eye observation or microscope observation for the state of breakage and crack generation of the wafers, and the breakage rate of the semiconductor wafers was calculated by the following equation.

Breakage rate (%) of semiconductor wafer = (number of pieces of broken wafer/number of pieces of polished wafer) × 100

< percentage (%) breakage of bump portion of bumped semiconductor wafer after back grinding >

The breakage state of the bump portion of each of the five back-polished bumped semiconductor wafers was observed with a microscope, and the breakage rate of the bump portion of the semiconductor wafer was calculated by the following equation.

Breakage rate (%) of bump portion of semiconductor wafer = (number of broken bumps/number of bumps of wafer) × 100

< Presence or absence of dimple Generation in bumped semiconductor wafer after Back-grinding >

The presence of dents on the polished surface of five semiconductor wafers with bumps after back-polishing was visually observed. Further, the maximum depth Rz of the dents was measured on the wafer on which the dents were visually observed by using a surface roughness meter "Surtoronic4" (product name) manufactured by Tylor Hobson, and the wafer was judged according to the following criteria.

Very good: no dent was observed by visual observation

O: the dents were observed by visual observation, but the maximum depth was less than 2.5 μm

X: the dents were observed by visual observation, but the maximum depth was 2.5 μm or more

< thickness variation of bumped semiconductor wafer after backside grinding >

For five semiconductor wafers with bumps after back grinding, thickness accuracy TTV (maximum thickness-minimum thickness) of the wafer surface was measured using a thickness system measuring apparatus "SemDex" (product name) manufactured by ISIS corporation. The measurement interval is in the X direction: 0.1mm, Y direction: 10mm, the entire surface of the wafer (200 mm. Times.200 mm range) was measured, and the determination was made according to the following criteria.

O: TTV less than 3 μm

X: TTV of 3 μm or more

< Presence or absence of adhesive residue on surface of bumped semiconductor wafer after peeling off adhesive tape for backside grinding >

The presence or absence of adhesive residue on the surface of the five bumped semiconductor wafers after back grinding was observed with a microscope.

[ Table 1]

[ Table 2]

[ Table 3]

As shown in tables 1 to 3, it can be seen that: the adhesive tape for back grinding of examples 1 to 13 appropriately follows the solder bumps when it is attached to the semiconductor wafer with solder bumps, and also hardly causes the occurrence of dents and the occurrence of wafer breakage during back grinding, and further hardly causes the occurrence of bump breakage during peeling of the adhesive tape, and can be easily peeled without generating adhesive residue on the wafer surface, and can sufficiently suppress variations in wafer thickness after back grinding.

In contrast, with the adhesive tape for back grinding of comparative example 1, the adhesive agent had a high acid value and was firmly adhered to the semiconductor wafer with solder bumps, and when the adhesive tape was peeled off, adhesive residue was generated on the solder bumps.

In the adhesive tape for back grinding of comparative example 2, the hydroxyl value of the adhesive was low, and crosslinking of the adhesive by the crosslinking agent was insufficient, so that cohesive force of the adhesive was insufficient, and when the adhesive tape was peeled off, adhesive residue was generated on the solder bump.

With the adhesive tape for back grinding of comparative example 3, the adhesive had a high hydroxyl value and was firmly adhered to the semiconductor wafer with solder bumps, and when the adhesive tape was peeled off, adhesive residue was generated.

In the adhesive tape for back grinding of comparative example 4, since the tape application temperature is higher than the predetermined temperature, the storage modulus of the intermediate layer resin is lowered and fitted into the irregularities of the semiconductor wafer with solder bumps without a gap, and when the adhesive tape is peeled off, the solder bumps are broken.

In the adhesive tape for back grinding of comparative example 5, since the tape application temperature is lower than the predetermined temperature, the energy storage modulus of the intermediate layer resin is high, and the adhesive tape does not follow the irregularities of the semiconductor wafer with solder bumps, and therefore grinding water penetrates during back grinding.

In the adhesive tape for back grinding of comparative example 6, air was mixed in the periphery of the solder bump of the semiconductor wafer with solder bump, and when the adhesive tape was peeled off due to poor curing at the time of ultraviolet irradiation, adhesive residue was generated around the solder bump.

Industrial applicability

According to the present invention, it is possible to provide an adhesive tape for back grinding which appropriately follows bumps and electrode protrusions when attached to a semiconductor wafer having irregularities such as bumps and electrode protrusions, and which has a very low incidence of chipping and wafer breakage during back grinding, and further has a very low incidence of breakage of bump portions and electrode protrusions when the adhesive tape is peeled off, and which can be easily peeled off without leaving adhesive residue on the surface to be bonded, and which can sufficiently suppress variations in the thickness of the wafer after back grinding.

Claims

1. A back-grinding adhesive tape for a semiconductor wafer having a base material, and an intermediate resin layer and an adhesive layer formed on the base material in this order,

the bonding temperature when the adhesive tape is bonded to the semiconductor wafer is set to any one of 55 to 80 ℃,

the intermediate resin layer has a thickness of 0.15X 10 at any temperature of 55-80 deg.C ⁶ ～1.51×10 ⁶ A storage modulus G' of Pa,

the adhesive layer is composed of a non-curable adhesive containing an acrylic adhesive polymer as a main component, wherein the acrylic adhesive polymer has an acid value of 2.0mgKOH/g or less and a hydroxyl value of 1.0 to 15.0 mgKOH/g.

2. The adhesive tape for back grinding according to claim 1, wherein the intermediate resin layer has a thickness of 1.2 times or more the level difference of the irregularities present on the surface of the semiconductor wafer.

3. The adhesive tape for back grinding according to claim 1 or 2, wherein the intermediate resin layer is formed by containing ethylene-vinyl acetate copolymer (EVA).

4. The adhesive tape for back grinding according to claim 3, wherein the ethylene-vinyl acetate copolymer contains 25 to 40 mass% of vinyl acetate.

5. The adhesive tape for back grinding according to claim 1 or 2, wherein the base material has a thickness of 50 to 200 μm.

6. The adhesive tape for back grinding according to claim 1 or 2, wherein the adhesive layer has a thickness of 5 to 50 μm.

7. The adhesive tape for back grinding according to claim 1 or 2, wherein when the adhesive tape is adhered to the surface of the semiconductor wafer and observed from the right above with a microscope, the diameter of the bump observed/measured through the adhesive tape is defined as r _b The diameter of a circular non-adhesive part formed by the adhesive tape in the peripheral part of the bump not adhering to the surface of the semiconductor wafer is defined as r _a Then r is _a /r _b The value of (A) is 1.15 to 1.50.

8. The adhesive tape for back grinding according to claim 1 or 2, wherein the height difference of the uneven shape existing on the surface of the semiconductor wafer is 50 to 300 μm.