JP6461892B2 - Surface protection sheet - Google Patents

Description

  The present invention relates to a surface protective sheet suitable for a workpiece grinding process.

  In recent years, with the high integration of electronic devices, demands for thinning and minimizing semiconductor chips are intensifying. When an extremely thin semiconductor chip is obtained and mounted on a device, a method of thinning by grinding a workpiece (workpiece) such as a semiconductor wafer before being divided into chips is employed. However, in this case, (1) there is a risk of breakage when handling a thin workpiece, and (2) there is a risk of breakage of the chip after dividing the work into chips.

As a method of dividing the workpiece into chips for avoiding the risk of (1) above, a workpiece dividing method called “first dicing method” is known. In the "first dicing method", a groove is formed on the front side of the workpiece along the planned dividing line, and the workpiece is subjected to thinning processing such as grinding until it reaches at least the groove from the back side of the workpiece, and is divided into chips. Is the method.
For example, in Patent Document 1, a groove is formed on the front surface side of a silicon substrate along a predetermined boundary line of pellets, a resin film is provided on the inner wall surface of the formed groove, and the groove reaches from the back surface side of the silicon substrate. Until now, a method of cutting a silicon substrate and dividing the silicon substrate into a plurality of pellets has been disclosed.

  Such a method eliminates the need for handling a thinned workpiece as compared with a normal process in which the workpiece is thinned and then divided into chips, thereby eliminating the risk of workpiece damage and the like. Excellent in terms.

In addition, regarding the risk of (2) above, inferior chip bending strength causes damage.
As a work dividing method for improving the bending strength of a chip, a method called “Stealth Dicing (registered trademark)” as disclosed in Patent Document 2 is known.
Stealth dicing is a method of forming a chip by forming a modified region inside a workpiece with laser light and applying a force to the workpiece, with the modified region serving as a starting point for cutting.
More specifically, an extensible film is attached to one surface of the workpiece, and the surface opposite to the surface on which the film is formed is the laser light incident surface, and the condensing point is aligned with the inside of the workpiece. Then, a modified region by multiphoton absorption is formed by irradiating with laser light. Then, by this modified region, a cutting start region is formed on the inner side of the laser light incident surface along a predetermined cutting line of the work by a predetermined distance, and the film is stretched, whereby the work is started from the cutting start region. Chips can be obtained by cutting the workpiece into a plurality of portions so as to be spaced apart from each other.

  Since such a method does not involve a process of cutting a workpiece with a rotating blade, it is possible to suppress the phenomenon of minute chipping at the end of the chip, so-called chipping, and to improve the chip bending strength. .

Furthermore, as a method for avoiding both the risks (1) and (2), the method of Patent Document 3 has been proposed.
In Patent Document 3, after using the above stealth dicing (registered trademark) to form a modified region inside the workpiece, grinding is performed from the back surface of the workpiece, the workpiece is made thin and easy to be cleaved, There is disclosed a method of dividing into individual chips by cutting with a processing pressure of a grinding wheel or the like.

Japanese Patent Laid-Open No. 06-085055 JP 2003-334812 A JP 2004-111428 A

By the way, the back grinding process of the workpiece is performed while exposing the workpiece to ultrapure water in order to wash away grinding waste generated during grinding.
In the method disclosed in Patent Document 3, when the modified region is cleaved (cleaved) by grinding the workpiece, the gap between the cleaved portions is very narrow. ) May intrude at a relatively strong momentum. A circuit or the like may be formed on the surface opposite to the grinding surface of the workpiece, and an adhesive sheet having an adhesive layer is usually attached to protect the surface.
However, water (sludge) that has entered the gap due to vibration during grinding enters the interface between the adhesive layer and the protected surface of the workpiece, and the protected surface is contaminated by the water in which the adhesive is dissolved. There is a case. Patent Document 3 does not discuss any method for suppressing such contamination of the surface to be protected.

  INDUSTRIAL APPLICABILITY The present invention is suitable as a surface protection sheet used in a backside grinding process of a workpiece on which a modified region is formed, and the workpiece is separated from a gap formed by cleaving the workpiece during the backside grinding process of the workpiece. An object of the present invention is to provide a surface protective sheet that can prevent contamination of the surface to be protected of the workpiece by suppressing water intrusion (sludge infiltration) on the surface to be protected.

The present inventors have found that a surface protective sheet in which a pressure-sensitive adhesive layer satisfying specific requirements is formed on a base material satisfying specific requirements can solve the above problems.
That is, the present invention provides the following [1] to [8].
[1] A surface protective sheet having a pressure-sensitive adhesive layer on a substrate and satisfying the following requirements (a) to (d).
(A) Young's modulus of the substrate is 450 MPa or more (b) Storage elastic modulus of the pressure-sensitive adhesive layer at 25 ° C. is 0.10 MPa or higher (c) Storage elasticity of the pressure-sensitive adhesive layer at 50 ° C. (D) The pressure-sensitive adhesive layer has a thickness of 30 μm or more. [2] The pressure-sensitive adhesive layer is composed of an energy ray-curable pressure-sensitive adhesive composition. Surface protection sheet.
[3] The surface protective sheet according to [1] or [2] above, wherein the thickness of the base material is 5 to 250 μm.
[4] The surface protective sheet according to any one of [1] to [3], wherein the base material includes a polyester film as a resin film.
[5] The base material is a second pressure-sensitive adhesive layer made of a resin film and a non-energy ray-curable pressure-sensitive adhesive composition having a thickness of 10 μm or less laminated on the resin film, or a thickness of 10 μm or less. The surface protective sheet according to any one of the above [1] to [4], which has an adhesive layer.
[6] The surface protection sheet is affixed to the workpiece when the modified region is formed by cleaving the modified region by cleaving the modified region to form a gap in the workpiece. The surface protective sheet according to any one of [1] to [5], which is a product.
[7] The surface protective sheet according to [6], wherein the surface protective sheet is affixed to a surface of the workpiece on which the unevenness is formed.
[8] The surface protective sheet according to [6] or [7] above, wherein the surface protective sheet is affixed to a workpiece heated to 40 to 80 ° C.

  The surface protective sheet of the present invention suppresses the intrusion of water (sludge intrusion) from the gap formed by cleaving the work during the back grinding process of the work to the protected surface of the work, thereby protecting the protected surface of the work Can prevent contamination. Therefore, it is suitable as a surface protection sheet used in the backside grinding process of the workpiece on which the modified region is formed.

It is sectional drawing of the surface protection sheet which shows an example of a structure of the surface protection sheet of this invention. It is a schematic diagram which shows an example of the use of the surface protection sheet of this invention.

In the following description, “weight average molecular weight (Mw)” is a value in terms of polystyrene measured by gel permeation chromatography (GPC), and specifically measured based on the method described in the examples. Value.
Moreover, the thicknesses of the base material (including the resin film, the second pressure-sensitive adhesive layer, and the easy-adhesion layer), the pressure-sensitive adhesive layer, and the release material constituting the surface protective sheet are measured according to JIS K7130. Specifically, it is a value measured based on the method described in the examples.
For example, “(meth) acrylate” is used as a word indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

[Configuration of surface protection sheet]
If the surface protection sheet of this invention has an adhesive layer on a base material, there will be no restriction | limiting in particular, For example, the surface protection sheet which has the structure shown in FIG.
The surface protective sheet 1a in FIG. 1 (a) is configured to have an adhesive layer 12 on a substrate 11, but further peeled off on the adhesive layer 12 like the surface protective sheet 1b in FIG. 1 (b). The material 13 may be included. The release material 13 is removed when a surface protection sheet is attached to a workpiece or the like.
Moreover, the surface protection sheet of this invention gave the peeling process to the surface on the opposite side to the surface in which the adhesive layer 12 of the base material 11 of the surface protection sheet 1a was formed, and wound the surface protection sheet 1a in roll shape. It is good also as a surface protection sheet.

  Here, the substrate 11 may be composed of only a single layer or may be composed of a multilayer in which two or more layers are laminated. Moreover, the base material 11 may have a configuration in which a second pressure-sensitive adhesive layer or an easy-adhesion layer different from the pressure-sensitive adhesive layer 12 is laminated on a single-layer or multi-layer resin film. Details of the substrate 11 are as described later.

The surface protective sheet of the present invention satisfies the following requirements (a) to (d).
(A) Young's modulus of the substrate is 450 MPa or more (b) Storage elastic modulus of the pressure-sensitive adhesive layer at 25 ° C. is 0.10 MPa or higher (c) Storage elasticity of the pressure-sensitive adhesive layer at 50 ° C. (D) The thickness of the pressure-sensitive adhesive layer is 30 μm or more. The Young's modulus of the substrate is a value measured according to JIS K-7127 (1999), Specifically, it is a value measured based on the method described in the examples.
Moreover, the storage elastic modulus in 25 degreeC and 50 degreeC of an adhesive layer is the value measured based on the method as described in an Example, and when an adhesive layer consists of energy-beam curable adhesive compositions, It means the storage elastic modulus at 25 ° C. and 50 ° C. before irradiation with energy rays.

By satisfy | filling the said requirements (a) and (b), the deformation | transformation of the surface protection sheet stuck to the workpiece | work can be suppressed by the vibration at the time of grinding of a workpiece | work, and sludge penetration | invasion of the to-be-protected surface of a workpiece | work can be suppressed.
In addition, by satisfying the above requirement (c), when the workpiece is heated and the surface protection sheet is attached (heat pasted) to the uneven portion of the circuit or the like, the adhesive layer follows the uneven portion of the workpiece, The non-contact area | region of an uneven | corrugated | grooved part and an adhesive layer can be decreased. As a result, it is possible to suppress a phenomenon in which the adhesive layer triggered by the presence of the non-contact area is peeled off from the workpiece and sludge intrusion occurs in the peeled area.
Further, by satisfying the above requirement (d), when unevenness such as a circuit on the adherend surface of the workpiece is formed, the non-contact area between the uneven portion of the workpiece and the pressure-sensitive adhesive layer can be reduced. . As a result, it is possible to suppress the phenomenon in which the adhesive layer triggered by the presence of the non-contact area is peeled off from the workpiece and sludge intrusion occurs in the peeled area as described above.

<Base material>
The base material used in the present invention is not particularly limited as long as it satisfies the above requirement (a).
The said base material may consist of a single layer film which consists of one resin film, and may consist of a multilayer film which the several resin film laminated | stacked.
In addition, when the surface protective sheet is peeled from the chip after manufacturing the chip from the workpiece, the resin film and the resin film are formed on the resin film from the viewpoint of expressing excellent peelability so that the adhesive of the surface protective sheet does not remain on the chip. The substrate may have a second pressure-sensitive adhesive layer (hereinafter also simply referred to as “second pressure-sensitive adhesive layer”) or an easy-adhesion layer made of a non-energy ray-curable pressure-sensitive adhesive composition.

The thickness of the substrate used in the present invention is preferably 5 to 250 μm, more preferably 10 to 200 μm, still more preferably 15 to 150 μm, and still more preferably 20 to 110 μm. When the thickness of the substrate is 5 μm or more, the deformation resistance (dimensional stability) at high temperatures is excellent. On the other hand, if the thickness of the base material is 250 μm or less, it becomes easy to adjust the Young's modulus to a predetermined value or more.
In the present invention, “the thickness of the substrate” refers to the total thickness of the substrate. For example, for a substrate formed by laminating a plurality of resin films, the total thickness of all the laminated resin films is the thickness of the substrate, and the resin film and the above-mentioned second pressure-sensitive adhesive layer or easy adhesion About the base material which has a layer, the sum total of the thickness of a resin film and a 2nd adhesive layer or an easily bonding layer is the thickness of the base material.

As defined in the above requirement (a), the Young's modulus of the substrate used in the present invention is 450 MPa or more, preferably 500 MPa or more, more preferably 1000 MPa or more, and further preferably 1500 MPa or more.
When the Young's modulus of the substrate is less than 450 MPa, the surface protective sheet attached to the workpiece is likely to be deformed by vibration during grinding of the workpiece, and it is difficult to suppress sludge intrusion on the protected surface of the workpiece. Absent.
The upper limit of the Young's modulus of the substrate used in the present invention is not particularly limited, but the Young's modulus of the substrate is preferably 10,000 MPa or less, more preferably 7000 MPa or less.

  In addition, the Young's modulus of the base material prescribed | regulated by the said requirement (a) is, for example, the kind of resin film used as the base material, and the type and thickness of the resin film to be laminated when the base material is a multilayer of the resin film It is possible to adjust by appropriately setting the number of layers, the material for forming the second pressure-sensitive adhesive layer or the easy-adhesion layer, the thickness of the layer, and the like.

About the adjustment method of the Young's modulus of a base material, it is possible to adjust based on the tendency of the following (1)-(3), for example. In the present invention, the method for adjusting the Young's modulus of the substrate is not limited to the method based on the following tendency, and the following tendency is merely an example.
(1) If the base material includes a resin film made of a resin based on a polymer having a cyclic structure in the main chain, such as a polyester film or a polycarbonate film, the Young's modulus of the base material is adjusted to a predetermined value or more. It tends to be easy.
(2) The Young's modulus of a base material falls by setting it as a base material containing a low density polyester-type film.
(3) In a substrate including a resin film made of a resin based on a polymer having a cyclic structure in the main chain, the Young's modulus tends to increase as the length of the straight chain structure of the main chain of the polymer is shorter. is there. For example, a base material including a polyethylene terephthalate film having a relatively short linear structure length even in the same polyester film is a group including a polybutylene terephthalate film having a relatively long linear structure length. Young's modulus is higher than the material.

(Resin film)
The resin film contained in the base material of the present invention is preferably a film having a high thickness accuracy from the viewpoint of stably holding the workpiece even when the workpiece is ground to an extremely thin thickness, for example, a polyester film or a polycarbonate film. Examples of the film include polystyrene film, polystyrene film, polyphenylene sulfide film, and cycloolefin polymer film.
Among these, a polyester film is preferable from the viewpoint of easily adjusting the Young's modulus of the substrate so as to satisfy the above viewpoint and the above requirement (a).

  As polyester which comprises a polyester-type film, the polyester obtained by polycondensing from an aromatic dibasic acid or its ester derivative, and diol or its ester derivative is mentioned, for example.

Specific examples of the polyester film include films made of polyester such as polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalenedicarboxylate. In addition, the film which consists of a copolymer of said polyester may be sufficient, and the film etc. which consist of a mixture of said polyester and a comparatively little other resin may be sufficient.
Among these, a polyethylene terephthalate film is preferable from the viewpoint of easy availability, high thickness accuracy, and easy adjustment of the Young's modulus of the substrate so as to satisfy the requirement (a).

In addition, when a pressure-sensitive adhesive layer made of an energy ray-curable pressure-sensitive adhesive is formed on a polyester-based film using a base material made only of a polyester-based film, Volume shrinkage may occur, the interfacial adhesion between the base material and the pressure-sensitive adhesive layer may be reduced, and interface destruction may occur between the base material and the pressure-sensitive adhesive layer. Therefore, the peelability of the surface protective sheet may be reduced.
In order to avoid such harmful effects, it is preferable to laminate a resin film such as a low-density polystyrene film on a polyester film to form a multilayer film. Moreover, you may provide the below-mentioned 2nd adhesive layer or an easily bonding layer on a polyester-type film.

In addition, you may make a resin film contain a well-known filler, a coloring agent, an antistatic agent, antioxidant, an organic lubricant, a catalyst, etc. within the range used as the base material which satisfy | fills the said requirements (a).
Moreover, even if the resin film is transparent, it may be colored or vapor-deposited as desired.

(Second pressure-sensitive adhesive layer / adhesive layer)
As a base material used by this invention, the base material which has the 2nd adhesive layer which consists of a resin film and the non-energy ray-curable adhesive laminated on this resin film, or an easily bonding layer is preferable. The second pressure-sensitive adhesive layer is different from the pressure-sensitive adhesive layer that satisfies the above requirements (b) to (d).
Adjustment of the thickness accuracy of the substrate is less affected by the provision of the second pressure-sensitive adhesive layer or the easy-adhesion layer on the thickness accuracy of the resin film before the second pressure-sensitive adhesive layer or the easy-adhesion layer is formed. Can be easily avoided.

By providing the second pressure-sensitive adhesive layer or the easy-adhesion layer on the resin film, when the surface protective sheet is peeled from the chip, the chip is allowed to exhibit excellent releasability so that the pressure-sensitive adhesive of the surface protective sheet does not remain on the chip. Can do.
The reason for this is as follows. That is, when using an energy ray-curable pressure sensitive adhesive for forming a pressure sensitive adhesive layer using a base material composed only of a polyester film, as described above, when the pressure sensitive adhesive is cured by energy ray irradiation, Volume shrinkage may occur, the interfacial adhesion between the base material and the pressure-sensitive adhesive layer may be reduced, and interface destruction may occur between the base material and the pressure-sensitive adhesive layer. However, by providing the second pressure-sensitive adhesive layer or the easy-adhesion layer, such an adverse effect can be avoided, and excellent peelability can be exhibited.

The pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer preferably contains a pressure-sensitive adhesive resin such as an acrylic resin, a rubber resin, or a silicone resin.
In addition, the pressure-sensitive adhesive composition forming the second pressure-sensitive adhesive layer includes a crosslinking agent, a photoinitiator, an antioxidant, a softener (plasticizer), a filler, a rust inhibitor, a pigment, You may contain dye etc.
Furthermore, when forming the pressure-sensitive adhesive layer by application of the pressure-sensitive adhesive composition, from the viewpoint of improving the applicability to the resin film and the like, and easily forming the pressure-sensitive adhesive layer, further adding an organic solvent, It is good also as the form of the solution of an adhesive composition.

  The thickness of the 2nd adhesive layer becomes like this. Preferably it is 10 micrometers or less, More preferably, it is 0.3-8 micrometers, More preferably, it is 1-6 micrometers. If the thickness of the second pressure-sensitive adhesive layer is 10 μm or less, even if non-uniformity occurs in the thickness of the second pressure-sensitive adhesive layer, the influence on the thickness accuracy of the entire substrate is small.

Although it does not specifically limit as a composition for easy-adhesion layer formation which forms an easy-adhesion layer, For example, the composition containing a polyester-type resin, a urethane-type resin, a polyester urethane-type resin, an acrylic resin etc. can be used. .
Among these, it is preferable that the composition for easily bonding layer forming which forms an easily bonding layer contains the compound which has an energy-beam polymeric group.
The energy ray polymerizable group is a group that is polymerized upon irradiation with energy rays such as ultraviolet rays and electron beams. For example, a group having an ethylenically unsaturated bond such as a (meth) acryloyl group, a vinyl group, or an aryl group. Can be mentioned. Among these, a compound having a (meth) acryloyl group is preferable.
Examples of the compound having a (meth) acryloyl group include urethane (meth) acrylate, (meth) acrylate-modified polyester, and the like.

By using such a composition containing a compound having an energy ray polymerizable group, an easy adhesion layer is formed, and after curing of the energy ray curable pressure-sensitive adhesive, the resin film and Adhesion with the pressure-sensitive adhesive layer is maintained.
For this reason, even if it is a case where a polyester-type film is used as a resin film, the peelability of a surface protection sheet can be made favorable.

The easy-adhesion layer-forming composition includes a crosslinking agent, a photoinitiator, an antioxidant, a softening agent (plasticizer), a filler, a rust inhibitor, a pigment, a dye, and the like as necessary. Etc. may be contained.
Furthermore, when forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition, it is easy to add an organic solvent from the viewpoint of improving the applicability to a resin film and the like and easily forming an easy-adhesion layer. It is good also as a form of the solution of the composition for contact bonding layer formation.

  Moreover, the thickness of an easily bonding layer is also preferably 10 micrometers or less from the viewpoint similar to the above, More preferably, it is 0.3-7 micrometers, More preferably, it is 0.5-5 micrometers.

  As a method for forming the second pressure-sensitive adhesive layer and the easy-adhesion layer, an organic solvent is added to make the composition into a solution, and the solution is applied onto a resin film by a known application method. Can be formed. Moreover, it is preferable to dry the coating film formed after application | coating at 50-120 degreeC, and to form a 2nd adhesive layer or an easily bonding layer.

<Adhesive layer>
As prescribed in the requirement (b) above, the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer of the surface protective sheet of the present invention is 0.10 MPa or more, preferably 0.12 MPa or more, more preferably 0.14 MPa. As mentioned above, More preferably, it is 0.17 MPa or more.
When the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer is less than 0.10 MPa, the surface protective sheet attached to the workpiece is easily deformed by vibration during grinding of the workpiece, and sludge intrusion on the protected surface of the workpiece is suppressed. This is not preferable because it becomes difficult.
In addition, although there is no restriction | limiting in particular as an upper limit of the storage elastic modulus in 25 degreeC of an adhesive layer, The storage elastic modulus in 25 degreeC of an adhesive layer becomes like this. Preferably it is 1.00 MPa or less.

Further, as defined in the above requirement (c), the storage elastic modulus at 50 ° C. of the pressure-sensitive adhesive layer of the surface protective sheet of the present invention is 0.20 MPa or less, preferably 0.16 MPa or less, more preferably 0. .13 MPa or less, more preferably 0.10 MPa or less.
When the storage elastic modulus at 50 ° C. of the pressure-sensitive adhesive layer exceeds 0.20 MPa, when the workpiece is heated and the surface protective sheet is stuck (heat-bonded) on the uneven portion of a circuit or the like, There is a tendency that the non-contact area expands around the concavo-convex portion of the workpiece without sufficiently contacting the agent layer. As a result, the pressure-sensitive adhesive layer is peeled off from the workpiece due to the presence of the non-contact area, and sludge intrusion occurs in the peeled area.
The lower limit of the storage elastic modulus at 50 ° C. of the pressure-sensitive adhesive layer is not particularly limited, but the storage elastic modulus at 50 ° C. of the pressure-sensitive adhesive layer is preferably 0.01 MPa or more, more preferably 0.06 MPa or more. is there.

The storage elastic modulus at 25 ° C. and 50 ° C. of the pressure-sensitive adhesive layer specified in the above requirements (b) and (c) can be adjusted by appropriately changing the composition of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer. is there.
That is, by appropriately setting the type of adhesive resin contained in the adhesive composition, the functional group, the weight average molecular weight, the type of monomer constituting the resin, the content of structural units derived from the monomer, etc. The storage elastic modulus of the pressure-sensitive adhesive layer to be formed can be adjusted to belong to the above range.

More specific methods for adjusting the storage elastic modulus at 25 ° C. and 50 ° C. of the pressure-sensitive adhesive layer can be adjusted based on the following trends (1) to (4), for example. In the present invention, the method for adjusting the storage elastic modulus at 25 ° C. and 50 ° C. of the pressure-sensitive adhesive layer is not limited to the method based on the following tendencies, and the following tendencies are merely examples.
(1) When an acrylic resin, preferably an acrylic copolymer, is used as the adhesive resin, it tends to be easily adjusted so that the storage elastic modulus of the formed adhesive layer belongs to the above range.
(2) When an acrylic copolymer having a monomer having a high glass transition temperature of a homopolymer such as methyl (meth) acrylate as a constituent unit is used, the storage elastic modulus of the formed pressure-sensitive adhesive layer tends to increase. is there. The storage elastic modulus tends to increase as the content of such monomer-derived structural units increases with respect to all the structural units of the acrylic copolymer.
(3) In the case where the pressure-sensitive adhesive layer is formed from the energy ray-curable pressure-sensitive adhesive composition, there is the following tendency. That is, by using the energy ray-curable adhesive resin (II) described later, a pressure-sensitive adhesive composition containing an energy ray-curable low molecular weight compound together with the non-energy ray-curable adhesive resin (I) is used. In comparison, since the energy ray-curable low molecular weight compound is not included or the content of the compound can be reduced, the storage elastic modulus tends to be easily adjusted to be in the above range.
(4) When the non-energy ray curable adhesive resin (I) or energy ray curable adhesive resin (II) described later is crosslinked, the storage elastic modulus tends to increase. Moreover, the storage elastic modulus tends to increase as the degree of crosslinking increases.

Moreover, as prescribed in the above requirement (d), the thickness of the pressure-sensitive adhesive layer of the surface protective sheet of the present invention is 30 μm or more, preferably 32 μm or more, more preferably 35 μm or more, and further preferably 38 μm or more. is there.
When the thickness of the pressure-sensitive adhesive layer is less than 30 μm, when irregularities such as circuits on the adherend surface of the workpiece are formed, the uneven portion of the workpiece and the pressure-sensitive adhesive layer are not sufficiently in contact with each other, There is a tendency for the non-contact area to expand around the uneven part of the workpiece. As a result, the pressure-sensitive adhesive layer is peeled off from the workpiece surface due to the presence of the non-contact area, and sludge intrusion occurs in the peeled area, which is not preferable.
In addition, there is no restriction | limiting in particular as an upper limit of the thickness of an adhesive layer, However, The thickness of an adhesive layer becomes like this. Preferably it is 200 micrometers or less.

The pressure-sensitive adhesive layer of the surface protective sheet of the present invention is preferably formed from an energy ray-curable pressure-sensitive adhesive composition. By irradiating the adhesive layer with energy rays and curing it, the adhesive strength of the surface protection sheet can be reduced, and the ground and divided chips on the surface protection sheet can be used for other pickup sheets, die attachment films, etc. The surface protective sheet can be easily removed by transferring to a sheet.
In the present invention, “energy beam” refers to ultraviolet rays, electron beams, etc., preferably ultraviolet rays.

  The energy ray-curable pressure-sensitive adhesive composition includes a non-energy ray-curable adhesive resin (I) (hereinafter also referred to as “adhesive resin (I)”) and an energy ray-curable low molecular weight compound. Product (I) or energy beam curable adhesive resin (II) in which an unsaturated group is introduced into the side chain of non-energy ray curable adhesive resin (I) (hereinafter referred to as “adhesive resin (II)”) Pressure-sensitive adhesive composition (II) and the like. In the present invention, the term “adhesive resin” refers to a resin that exhibits an adhesive property due to the addition of a plasticizing component, etc., although a composition composed essentially of an adhesive resin has no adhesive property. It is a concept that also includes widely.

The weight average molecular weight (Mw) of the non-energy ray curable adhesive resin (I) is preferably 250,000 to 1,500,000, more preferably 350,000 to 1,300,000, still more preferably 450,000 to 1,100,000, and even more preferably. Is 650,000-1050,000.
Moreover, as a weight average molecular weight (Mw) of energy-beam curable adhesive resin (II) which introduce | transduced the unsaturated group into the side chain, Preferably it is 300,000-1,600,000, More preferably, 400,000-1.4 million, Preferably it is 500,000 to 1,200,000, and more preferably 700,000 to 1,100,000.

Examples of the non-energy ray curable adhesive resin (I) include acrylic resins, rubber resins, and silicone resins.
Among these, an acrylic resin is preferable from the viewpoint of easily forming a pressure-sensitive adhesive layer that satisfies the conditions (b) and (c). Hereinafter, the acrylic resin will be described in detail.

(Acrylic resin)
The acrylic resin is preferably a resin containing a structural unit (p1) derived from an alkyl (meth) acrylate monomer having 4 or more carbon atoms (hereinafter also referred to as “monomer (p1)”).
The acrylic resin may be a homopolymer consisting only of the structural unit (p1) derived from the monomer (p1), but from the viewpoint of obtaining a pressure-sensitive adhesive layer satisfying the conditions (2) and (3), In addition to (p1), the structural unit (p2) and / or the functional group-containing monomer (p3) derived from an alkyl (meth) acrylate monomer having 1 to 3 carbon atoms (hereinafter also referred to as “monomer (p2)”) (hereinafter, A copolymer containing a structural unit (p3) derived from “monomer (p3)” is preferable.

  As carbon number of the alkyl group which a monomer (p1) has, from a viewpoint of improving the adhesive force of an adhesive sheet, Preferably it is 4-20, More preferably, it is 4-12, More preferably, it is 4-6. Further, the alkyl group of the monomer (p1) may be either a straight chain or a branched chain.

Examples of the monomer (p1) include butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth). ) Acrylate and the like.
In addition, you may use these monomers (p1) individually or in combination of 2 or more types.
Among these, butyl (meth) acrylate is preferable from the viewpoint of improving the adhesive strength of the adhesive sheet.

  When the acrylic resin is a copolymer, the content of the structural unit (p1) with respect to all the structural units of the acrylic resin is preferably 40 to 98% by mass, more preferably 45 to 95% by mass, and still more preferably 50. It is -90 mass%.

Examples of the monomer (p2) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and the like.
In addition, you may use these monomers (p2) individually or in combination of 2 or more types.
Among these, methyl (meth) acrylate is preferable from the viewpoint of obtaining a pressure-sensitive adhesive layer that satisfies the conditions (b) and (c).

  When the acrylic resin is a copolymer, the content of the structural unit (p2) with respect to all the structural units of the acrylic resin is preferably 1 to 30% by mass, more preferably 3 to 26% by mass, and still more preferably 6 ˜22 mass%.

The monomer (p3) means a monomer having a functional group that reacts with a cross-linking agent described later and can serve as a cross-linking origin or a functional group having a cross-linking promoting effect.
As a functional group which a monomer (p3) has, a hydroxyl group, a carboxy group, an amino group, an epoxy group etc. are mentioned, for example. Among these, a carboxy group or a hydroxyl group is preferable from the viewpoint of reactivity with the crosslinking agent.

Examples of the monomer (p3) include a hydroxyl group-containing monomer, a carboxy group-containing monomer, an amino group-containing monomer, and an epoxy group-containing monomer.
These monomers (p2) may be used alone or in combination of two or more.
Among these, a hydroxyl group-containing monomer and a carboxy group-containing monomer are preferable, and a hydroxyl group-containing monomer is more preferable.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meta ) Hydroxyalkyl (meth) acrylates such as acrylate and 4-hydroxybutyl (meth) acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.

  Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and citraconic acid, and anhydrides thereof. , 2-carboxyethyl methacrylate and the like.

  When the acrylic resin is a copolymer, the content of the structural unit (p3) with respect to all the structural units of the acrylic resin is preferably 1 to 35% by mass, more preferably 3 to 32% by mass, and still more preferably 6 -30 mass%.

  The acrylic resin used in the present invention is co-polymerized with acrylic monomers other than the structural units (p1) to (p3) such as styrene, α-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide. A structural unit derived from a polymerizable monomer may be included.

(Energy ray curable low molecular weight compound)
As the energy ray-curable compound blended in the pressure-sensitive adhesive composition (I), a monomer or oligomer having an unsaturated group in the molecule and capable of being polymerized and cured by irradiation with energy rays is preferable.
Examples of such energy ray curable compounds include trimethylolpropane tri (meth) acrylate, pentaerythritol (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4- Polyvalent (meth) acrylate monomers such as butylene glycol di (meth) acrylate, 1,6-hexanediol (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate, epoxy ( And meth) acrylates and oligomers thereof.
Among these, urethane (meth) acrylate or urethane (meth) acrylate oligomer is preferable from the viewpoint of relatively high molecular weight and difficulty in reducing the storage elastic modulus of the pressure-sensitive adhesive layer.

  The molecular weight (weight average molecular weight in the case of an oligomer) of the energy ray curable compound is preferably 100 to 12000, more preferably 200 to 10,000, still more preferably 400 to 8000, and still more preferably 600 to 6000.

  The content of the energy ray-curable compound in the pressure-sensitive adhesive composition (I) is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass with respect to 100 parts by mass of the non-energy ray curable adhesive resin. Part, more preferably 60 to 90 parts by weight.

(Energy ray curable adhesive resin (II))
The adhesive resin (II) is an energy beam curable adhesive resin in which an unsaturated group is introduced into the side chain of the non-energy ray curable adhesive resin (I) described above.
As the main chain of the adhesive resin (II), the above-mentioned adhesive resin (I) can be used, but it is easy to form an adhesive layer that satisfies the above conditions (b) and (c). Therefore, an acrylic resin is preferable, and an acrylic copolymer having the structural units (p1), (p2), and (p3) is more preferable.
Examples of the unsaturated group in the side chain of the adhesive resin (II) include a (meth) acryloyl group, a vinyl group, and an aryl group, and a (meth) acryloyl group is preferable.

The method for synthesizing the adhesive resin (II) includes, for example, copolymerizing a functional group-containing monomer to the adhesive resin (I) to provide a functional group, and providing both a substituent and an unsaturated group that can be bonded to the functional group. And a method in which the functional group of the copolymer is bonded to the substituent.
Examples of the functional group-containing monomer copolymerized with the adhesive resin (I) include the compounds mentioned as the monomer (p3).
Examples of the substituent bonded to the functional group include an isocyanate group and a glycidyl group.
Therefore, examples of the compound having both a substituent that can be bonded to the functional group and an unsaturated group include (meth) acryloyloxyethyl isocyanate, (meth) acryloyl isocyanate, glycidyl (meth) acrylate, and the like.

(Crosslinking agent)
The pressure-sensitive adhesive compositions (I) and (II) preferably further contain a crosslinking agent.
The main purpose of adding the cross-linking agent is that the non-energy ray curable adhesive resin (I) or the energy ray curable adhesive resin (II) such as a functional group derived from the monomer (p2) of the acrylic resin is used. It reacts with a functional group in the side chain to crosslink the adhesive resins.

Examples of crosslinking agents include tolylene diisocyanate, hexamethylene diisocyanate and the like, and isocyanate-based crosslinking agents such as adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; hexa [1- (2-methyl) -aziridinyl ] Aziridine type crosslinking agents such as triphosphatriazine; Chelate type crosslinking agents such as aluminum chelate; These crosslinking agents may be used alone or in combination of two or more.
Among these, an isocyanate-based crosslinking agent is preferable from the viewpoints of increasing cohesive force and improving adhesive force, and availability.

  The amount of the crosslinking agent is appropriately adjusted depending on the number of functional groups in the structures of the adhesive resins (I) and (II). From the viewpoint of promoting the crosslinking reaction, the adhesive resins (I) and (II) 100 Preferably it is 0.01-10 mass parts with respect to a mass part, More preferably, it is 0.03-7 mass part, More preferably, it is 0.05-4 mass part.

(Photopolymerization initiator)
The pressure-sensitive adhesive compositions (I) and (II) preferably further contain a photopolymerization initiator. By containing the photopolymerization initiator, the curing reaction can be sufficiently advanced even with relatively low energy energy rays such as ultraviolet rays.
Examples of the photopolymerization initiator include 1-hydroxy-cyclohexyl-phenyl-ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, and azobisisobutyrol. Nitrile, dibenzyl, diacetyl, 8-chloroanthraquinone and the like can be mentioned.
These photopolymerization initiators may be used alone or in combination of two or more.
The blending amount of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and still more preferably with respect to 100 parts by mass of the adhesive resins (I) and (II). It is 0.05-2 mass parts.

(Other additives)
The adhesive compositions (I) and (II) may contain other additives as long as the effects of the present invention are not impaired.
Examples of other additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and the like.
When mix | blending these additives, the compounding quantity of an additive becomes like this. Preferably it is 0.01-6 mass parts with respect to 100 mass parts of adhesive resin (I) and (II).

In addition, the adhesive compositions (I) and (II) may be further diluted with an organic solvent from the viewpoint of improving applicability to a substrate or a release sheet to form a solution of the adhesive composition. .
Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like.
In addition, these organic solvents may use the organic solvent used at the time of production | generation of adhesive resin (I) and (II) as it is, and it prepares so that the solution of this adhesive composition can be apply | coated uniformly. One or more organic solvents other than the organic solvents used at times may be added.

  The solid content concentration of the solution of the pressure-sensitive adhesive compositions (I) and (II) is preferably 5 to 60% by mass, more preferably 10 to 45% by mass, and still more preferably 15 to 30% by mass. It is preferable to mix a solvent.

<Release material>
Moreover, the surface protection sheet of this invention may have a peeling material further on the adhesive layer.
As the release material, a release sheet that has been subjected to a double-sided release process, a release sheet that has been subjected to a single-sided release process, or the like is used. Examples include a release material coated on a release material substrate.
Examples of the base material for the release material include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and plastic films such as polyolefin resin films such as polypropylene resin and polyethylene resin.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.
The thickness of the release material is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 150 μm.

[Method for producing surface protective sheet]
There is no restriction | limiting in particular as a manufacturing method of the surface protection sheet of this invention, It can manufacture by a well-known method. For example, the method of manufacturing the solution of the adhesive composition which mix | blended the above-mentioned organic solvent with a well-known coating method is mentioned.
Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

As a specific manufacturing method, as a manufacturing method of the surface protection sheet 1a in which the pressure-sensitive adhesive layer 12 is formed on the base material 11 as shown in FIG. 1A, for example, on one surface of the base material 11, A method of manufacturing by directly applying a solution of the adhesive composition and drying to form the adhesive layer 12, or a method of directly applying the solution of the adhesive composition to the release treatment surface of the release material, followed by drying and peeling Examples thereof include a method in which the pressure-sensitive adhesive layer 12 is formed on the material, the pressure-sensitive adhesive layer 12 and the base material 11 are bonded together, and then the release material is removed to manufacture.
Moreover, as a manufacturing method of the adhesive sheet 1c by which the peeling material 13 was laminated | stacked on the adhesive layer 12 formed on the base material 11 like FIG.1 (b), the above-mentioned adhesive sheet 1a is mentioned, for example. A method of manufacturing by bonding the surface of the pressure-sensitive adhesive layer 12 and the release material 13, or a solution of the pressure-sensitive adhesive composition is directly applied to the release-treated surface of the release material 13, and then dried and the pressure-sensitive adhesive on the release material 13. Examples of the method include forming the layer 12 and bonding the pressure-sensitive adhesive layer 12 and the base material 11 together.

The solid content concentration of the solution of the pressure-sensitive adhesive composition when an organic solvent is blended is preferably 10 to 60% by mass, more preferably 12 to 45% by mass, and still more preferably 15 to 30% by mass.
Moreover, after apply | coating the solution which melt | dissolved the adhesive composition in the organic solvent to the peeling layer surface of a base material or a peeling material, it is preferable to heat for 30 second-5 minutes at the temperature of 80-150 degreeC.

[Use of surface protection sheet]
Hereinafter, the use of the surface protective sheet of the present invention will be described.
The surface protective sheet of the present invention is suitable as a surface protective sheet used in the backside grinding process of the work on which the modified region is formed, and is formed by cleaving the work in the backside grinding process of the work. It is possible to prevent contamination of the protected surface of the workpiece by suppressing water intrusion (sludge infiltration) from the gap to the protected surface of the workpiece.

FIG. 2 is a schematic view showing an example of the use of the surface protective sheet of the present invention.
The surface protective sheet of the present invention is suitable as a surface protective sheet for a workpiece 50 such as a semiconductor wafer on which uneven portions 51 are formed by a circuit or the like as shown in FIG. By sticking the surface protection sheet 1 of the present invention to the surface (uneven portion 51 side) where the unevenness is formed, the circuit and the like can be protected in the back side cutting process of the workpiece.

  When the surface protective sheet of the present invention is applied to the uneven portion 51 side of the workpiece 50, the workpiece is preferably heated. The heating temperature of the workpiece is preferably 40 to 80 ° C, more preferably 45 to 60 ° C.

  In addition, in order for the surface protection sheet of this invention to satisfy | fill the said requirements (c) and (d), the adhesive layer 12 tracks the uneven | corrugated | grooved part 51 of the workpiece | work 50, the uneven | corrugated | grooved part 51 of the workpiece | work 50, the adhesive layer 12, The non-contact area can be reduced. As a result, it is possible to suppress a phenomenon in which the pressure-sensitive adhesive layer 12 is peeled off from the work 50 triggered by the presence of the non-contact area, and sludge intrusion occurs in the peeled area.

  Further, the modified region 52 is formed on the work 50 by using, for example, a stealth dicing (registered trademark) method described in Patent Document 2. The modified region 52 may be formed before or after the surface protection sheet 1 is attached to the workpiece 50.

And after sticking the surface protection sheet 1 of this invention to the uneven | corrugated | grooved part 51 side of the workpiece | work 50, it cuts from the back surface 50a of a workpiece | work, and passes through the cutting process which makes a workpiece | work the desired thickness.
The cutting process is performed while the work 50 is immersed in ultrapure water in order to wash away the generated cutting waste.

As shown in FIG. 2B, as the workpiece is cut, the modified region 52 inside the workpiece 50 is cleaved, and a gap 53 is formed.
When a conventional surface protection sheet is used, water (sludge) enters the gap 53 due to capillary action, and enters the interface between the circuit surface on the uneven portion 51 side and the pressure-sensitive adhesive layer 12, and the circuit surface of the workpiece. Is harmful.
However, the surface protective sheet of the present invention suppresses the deformation of the surface protective sheet attached to the workpiece by vibration during grinding of the workpiece by satisfying the above requirements (a) and (b). Sludge intrusion can be suppressed.

After the cutting process is completed, another sheet such as a pickup sheet or a die attachment film is attached to the back surface 50a of the workpiece. Here, when the pressure-sensitive adhesive layer 12 is made of an energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive force of the surface protective sheet can be reduced by irradiating the pressure-sensitive adhesive layer 12 with energy rays and curing it. The surface protective sheet can be easily removed.
And after removing a surface protection sheet, a workpiece | work can be divided | segmented into a chip | tip by giving external force to other sheets, such as a pickup sheet and a die attachment film.

In this case, examples of energy rays include ultraviolet rays and electron beams, and ultraviolet rays are preferable.
Exposure amount when the energy ray is ultraviolet is preferably 100~1000mJ / cm ^2, more preferably 300~700mJ / cm ^2.
When an electron beam is used as the energy beam, the acceleration voltage is preferably 10 to 1000 kV, and the irradiation dose is preferably selected in the range of 10 to 1000 krad.

As the weight average molecular weight (Mw) of the components used in the following production examples and the generated compound, values measured by the method described below were used.
<Weight average molecular weight (Mw)>
Using a gel permeation chromatograph device (product name “HLC-8020” manufactured by Tosoh Corporation), the value measured under the following conditions and measured in terms of standard polystyrene was used.
(Measurement condition)
・ Column: “TSK guard column HXL-H” “TSK gel GMHXL (× 2)” “TSK gel G2000HXL” (both manufactured by Tosoh Corporation)
-Column temperature: 40 ° C
・ Developing solvent: Tetrahydrofuran ・ Flow rate: 1.0 mL / min

Production Example 1
[Preparation of Acrylic Copolymer (1) and Adhesive Composition (1) Solution]
52 parts by mass of butyl acrylate, 20 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate were solution polymerized in an ethyl acetate solvent to obtain a non-energy ray-curable acrylic copolymer. An amount of methacryloyloxyethyl isocyanate having an isocyanate group number of 0.9 equivalent to the total number of hydroxyl groups of the acrylic copolymer thus obtained is added to the solution containing the acrylic copolymer and reacted. An energy ray-curable acrylic copolymer (1) (Mw: 1 million) having an energy ray polymerizable group in the chain was produced.
And as a crosslinking agent with respect to 100 mass parts of solid content of this acryl-type copolymer (1), 0.5 mass part (solid content of Nippon Polyurethane company make, brand name "Coronate L") is used as a crosslinking agent. Ratio) and 1-7-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by BASF AG) 0.57 parts by mass (solid content ratio) as a photopolymerization initiator, energy ray curable adhesive A solution of the agent composition (1) was prepared.

Production Example 2
[Preparation of Acrylic Copolymer (2) and Adhesive Composition (2) Solution]
84 parts by mass of butyl acrylate, 8 parts by mass of methyl methacrylate, 3 parts by mass of acrylic acid, and 5 parts by mass of 2-hydroxyethyl acrylate were solution-polymerized in an ethyl acetate solvent, and a non-energy ray curable acrylic copolymer ( 2) (Mw: 800,000) was produced.
And 80 mass parts (solid content ratio) of a urethane acrylate oligomer (Mw: 5,000) and a crosslinking agent as an energy ray curable compound with respect to 100 mass parts of the solid content of the acrylic copolymer (2). As an isocyanate-based crosslinking agent (trade name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) 1.0 part by mass (solid content ratio) and a photopolymerization initiator, 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Corporation, 0.57 parts by mass (solid content ratio) of trade name “Irgacure 184”) was blended to prepare a solution of the energy ray-curable pressure-sensitive adhesive composition (2).

Production Example 3
[Preparation of Acrylic Copolymer (3) and Adhesive Composition (3) Solution]
85 parts by mass of 2-ethylhexyl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate were solution polymerized in an ethyl acetate solvent to obtain a non-energy ray curable acrylic copolymer. An amount of methacryloyloxyethyl isocyanate having an isocyanate group number of 0.9 equivalent to the total number of hydroxyl groups of the acrylic copolymer thus obtained is added to the solution containing the acrylic copolymer and reacted. An energy ray-curable acrylic copolymer (3) (Mw: 1 million) having an energy ray polymerizable group in the chain was produced.
And as a crosslinking agent with respect to 100 mass parts of solid content of this acrylic copolymer (3), 1.0 mass part (solid content of Nippon Polyurethane Co., Ltd., brand name "Coronate L") is used as a crosslinking agent. Ratio) and 1-7-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by BASF AG) 0.57 parts by mass (solid content ratio) as a photopolymerization initiator, energy ray curable adhesive A solution of the agent composition (3) was prepared.

Production Example 4
[Preparation of Acrylic Copolymer (4) and Adhesive Composition (4) Solution]
84 parts by mass of butyl acrylate, 8 parts by mass of methyl methacrylate, 3 parts by mass of acrylic acid, and 5 parts by mass of 2-hydroxyethyl acrylate were solution-polymerized in an ethyl acetate solvent, and a non-energy ray curable acrylic copolymer ( 4) (Mw: 800,000) was generated.
And 10 mass parts (solid content ratio) of an isocyanate type crosslinking agent (Nippon Polyurethane Co., Ltd., brand name "Coronate L") as a crosslinking agent with respect to 100 mass parts of solid content of this acrylic copolymer (4). Was added to prepare a solution of the pressure-sensitive adhesive composition (4).

Examples 1-9, Comparative Examples 1-6
The PET film (manufactured by Lintec Co., Ltd.) subjected to silicone release treatment so that the pressure-sensitive adhesive composition prepared in any one of Production Examples 1 to 4 shown in Table 1 has a value after drying has the value shown in Table 1. The product was applied to the release-treated surface of the trade name “SP-PET 381031”) and dried at 100 ° C. for 1 minute to form an adhesive layer. And after bonding together the said adhesive layer and the base material shown in Table 1, the PET film was removed and the surface protection sheet was produced.

The base materials used in Examples and Comparative Examples are as follows.
Multi-layer substrate A: a substrate composed of only a multilayer resin film having a total thickness of 80 μm, comprising LDPE (low density polyethylene) / PET (polyethylene terephthalate) /LDPE=27.5 μm / 25.0 μm / 27.5 μm.
Multi-layer substrate B: a multi-layer resin film having a total thickness of 105 μm, comprising LDPE / PET / LDPE = 27.5 μm / 50.0 μm / 27.5 μm.
Single-layer substrate C: a single-layer resin film made of a 25 μm PET film (trade name “Diafoil T100-25” manufactured by Mitsubishi Plastics, Inc.).
Single-layer substrate D: A single-layer resin film made of a 75 μm PET film (trade name “Lumirror # 75T60” manufactured by Toray Industries, Inc.).
Single-layer substrate E: a single-layer resin film made of an 80 μm PBT (polybutylene terephthalate) film.
-Substrate F with pressure-sensitive adhesive layer: PET / PSA (non-energy ray-curable acrylic pressure-sensitive adhesive (second pressure-sensitive adhesive layer)) = 25 μm / 5 μm, a resin film with an easy-adhesion layer having a total thickness of 30 μm.
Base material G with easy adhesion layer: PET / easy adhesion layer (layer formed from a composition for forming an anchor coat layer in which an aziridine-based crosslinking agent is added to a polyester-based resin solution containing acrylate-modified polyester as a main component) = 25 μm A resin film with an easy adhesion layer having a total thickness of 27 μm, comprising / 2 μm.
Single-layer substrate H: Single-layer resin film composed of a 105 μm urethane acrylate cured film

  Each physical property of the base material and the pressure-sensitive adhesive layer constituting the surface protective sheet prepared in Examples and Comparative Examples was measured by the following methods. The measurement results are shown in Table 1.

<Measurement of Young's modulus of substrate>
As a test speed, 200 mm / min was selected, and Young's modulus of the base materials A to G was measured according to JIS K-7127 (1999).

<Measurement of storage elastic modulus of adhesive layer>
Using a viscoelasticity measuring device (manufactured by Rheometrics, device name “DYNAMIC ANALYZER RDAII”), obtained by laminating a single pressure-sensitive adhesive layer formed from the solution of the pressure-sensitive adhesive composition used in Examples and Comparative Examples. The storage elastic modulus G ′ of a sample having a diameter of 8 mm × thickness of 3 mm was measured by a torsional shear method at 1 Hz in an environment of 23 ° C. and 50 ° C.

<Thickness of base material and pressure-sensitive adhesive layer>
Regarding the thickness of the base material (including the resin film constituting the base material, the second pressure-sensitive adhesive layer, and the easy-adhesion layer), a constant pressure thickness measuring instrument (manufactured by Teclock Corporation, product name “PG-” 02 ").
In this example, for the thickness of the pressure-sensitive adhesive layer, the thickness of the surface protective sheet with the PET film subjected to the silicone release treatment was measured, and the base material and the PET subjected to the silicone release treatment were determined from the thickness. It is a value obtained by reducing the thickness of the film.
Moreover, about the thickness of the base material F with an adhesive layer, thickness is measured in the state which bonded the PET film which performed the silicone peeling process on the adhesive layer, and the thickness of the PET film which performed the silicone peeling process is reduced. Value.

  Moreover, the performance evaluation at the time of using the surface protection sheet produced by the Example and the comparative example for a semiconductor processing process was performed with the following method. The evaluation results are shown in Table 1.

<Evaluation of sludge intrusion>
On a table heated to room temperature (25 ° C.) and 50 ° C. using a tape grinder for back grind (manufactured by Lintec Corporation, device name “RAD-3510F / 12”), the diameter is 12 inches, the thickness is 730 μm, and the pattern is The surface protective sheets produced in the examples and comparative examples were laminated on the circuit surface of the wafer having the formed circuit surface.
Thereafter, using a stealth laser irradiation apparatus (manufactured by Tokyo Seimitsu Co., Ltd., apparatus name “ML300PlusWH”), a modified region was formed inside the wafer by performing stealth laser irradiation from the back surface opposite to the circuit formation surface of the wafer. . Then, using a polish grinder (manufactured by Tokyo Seimitsu Co., Ltd., device name “PG3000RM”), the wafer is ground from the back surface of the wafer while being exposed to ultrapure water, and at the same time, chips are separated into individual pieces of 20 μm thickness. I got a chip.
The evaluation of the presence or absence of sludge intrusion between the circuit surface of the wafer and the surface protective sheet was evaluated based on the following criteria based on the occurrence frequency of sludge intrusion by visually observing the entire circuit surface of the wafer after grinding.
A: A portion where sludge intrusion occurred was not observed.
B: Although a portion where minute sludge intrusion occurred was seen, a portion where sludge entered the circuit surface was not seen.
C: A portion where sludge entered the circuit surface was observed.

<Evaluation of peelability>
Using the mercury lamp built in the full-auto expander MAE300, UV irradiation is performed on the circuit surface of the chip to which the surface protection sheet is attached using the mercury lamp incorporated in the evaluation of the presence or absence of sludge intrusion. Was transferred to a pickup sheet, and the surface protective sheet was peeled off.
The presence or absence of adhesive remaining on the chip surface after the surface protective sheet was peeled off was observed visually and using a digital microscope (manufactured by Keyence Corporation, apparatus name “VHX-1000”). Based on the evaluation.
In addition, this test was done only about the thing with which the favorable evaluation (A or B) of the presence or absence of the said sludge penetration | invasion was obtained.
A: Adhesion of the adhesive to the chip surface was not observed in both visual observation and digital microscope observation.
B: Adhesive residue on the chip surface was observed in visual observation, observation of either or both of the digital microscopes.

When the surface protective sheets of Examples 1 to 9 were used for heat bonding to the wafer, the result was that sludge intrusion into the circuit surface was suppressed.
On the other hand, when heat-bonding was performed on the wafer using the surface protection of Comparative Examples 1 to 6, a portion where sludge entered the circuit surface was observed.

The surface protective sheet of the present invention suppresses the intrusion of water (sludge intrusion) from the gap formed by cleaving the work during the back grinding process of the work to the protected surface of the work, thereby protecting the protected surface of the work Can prevent contamination.
Therefore, stealth dicing (registered trademark) is used to form a modified region inside a workpiece such as a semiconductor wafer, and then grind from the back of the workpiece to obtain a chip, thereby protecting the surface of the workpiece used in the chip manufacturing method. It is suitable as a sheet.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Surface protection sheet 11 Base material 12 Adhesive layer 13 Release material 50 Work piece 50a Back side surface 51 of workpiece Uneven part 52 Modified area 53 Gap

Claims (10)

A surface protective sheet that has a pressure-sensitive adhesive layer on a substrate and is used in a back grinding process of a workpiece, and satisfies the following requirements (a) to (d).
(A) Young's modulus of the substrate is 450 MPa or more (b) Storage elastic modulus of the pressure-sensitive adhesive layer at 25 ° C. is 0.15 MPa or more (c) Storage of the pressure-sensitive adhesive layer at 50 ° C. (D) The pressure-sensitive adhesive layer has a thickness of 30 μm or more.   The surface protection sheet according to claim 1, wherein the pressure-sensitive adhesive layer is made of an energy ray-curable pressure-sensitive adhesive composition.   The surface protection sheet of Claim 1 or 2 whose thickness of the said base material is 5-250 micrometers.   The surface protection sheet in any one of Claims 1-3 in which the said base material contains a polyester-type film as a resin film.   The base material includes a resin film and a second pressure-sensitive adhesive layer made of a non-energy ray-curable pressure-sensitive adhesive composition having a thickness of 10 μm or less laminated on the resin film or an easy-adhesion layer having a thickness of 10 μm or less. The surface protection sheet according to any one of claims 1 to 4.   The surface protection sheet in any one of Claims 1-5 whose storage elastic modulus in 25 degreeC of the said adhesive layer is 0.17 Mpa or more.   The surface protection sheet according to any one of claims 2 to 6, wherein the energy ray-curable pressure-sensitive adhesive composition contains an acrylic resin, and the acrylic resin does not contain acrylamide as a constituent unit.   When the surface protection sheet forms a groove on the front side of the work along the planned dividing line, and grinds the work until it reaches at least the groove from the back side of the work, The surface protection sheet in any one of Claims 1-7 which is affixed.   The surface protection sheet according to claim 8, wherein the surface protection sheet is affixed to an inner wall surface of a groove formed on the front side of the workpiece.   The surface protection sheet according to claim 8 or 9, wherein the surface protection sheet is affixed to a workpiece heated to 40 to 80 ° C.