KR20240097723A - Protective sheet for workpiece processing and manufacturing method of divided workpiece - Google Patents

Abstract

(Problem) For work processing, where electrification that occurs during processing of work pieces, etc. (i.e., work pieces or individual work groups) is sufficiently suppressed, and glue residue on the work pieces, etc., is suppressed when peeling the work processing protective sheet from the work pieces, etc. Providing a protective sheet, and providing a method of manufacturing a pieced workpiece cargo using the protective sheet for workpiece processing.
(Solution) A protective sheet for work processing in which an adhesive layer attached to a workpiece, a base material, and an antistatic layer are laminated in this order. The adhesive layer and the base material are in direct contact, and the side of the adhesive layer attached to the workpiece is electrically charged. It is a protective sheet for work processing in which the distance between the protective layer and the surface located on the substrate side is 300 μm or less.

Description

Manufacturing method of protective sheet for work processing and work reorganization cargo {PROTECTIVE SHEET FOR WORKPIECE PROCESSING AND MANUFACTURING METHOD OF DIVIDED WORKPIECE}

The present invention relates to a protective sheet for work processing and a method for manufacturing separate work pieces. In particular, it relates to a protective sheet for work processing that is preferably used in a method of grinding the back side of a work and breaking the work into pieces due to the stress, etc., and a method of manufacturing a piecework cargo using the protective sheet for work processing.

As various electronic devices become smaller and more functional, the semiconductor chips mounted on them are also required to be smaller and thinner. In order to make chips thinner, it is common to grind the back side of a semiconductor wafer to adjust the thickness. In addition, in order to obtain thinner chips, a groove of a predetermined depth is formed from the front side of the wafer with a dicing blade, then grinding is performed from the back side of the wafer, and the wafer is broken into pieces by grinding to obtain chips. In some cases, a method called DBG (Dicing Before Grinding) is used. In DBG, the backside grinding of the wafer and the separation of the wafer into pieces can be performed simultaneously, so thin chips can be manufactured efficiently.

Conventionally, when grinding the back side of a workpiece such as a semiconductor wafer or manufacturing individual workpieces such as semiconductor chips by DBG, the circuitry on the surface of the workpiece is protected, and the workpiece and multiple pieces of workpiece cargo (i.e., In order to hold the workpiece, it is common to attach a backgrinding tape as a protective sheet for workpiece processing, which consists of at least a base material and an adhesive layer, to the surface of the workpiece.

As an example of a backgrinding tape, Patent Document 1 and Patent Document 2 disclose an adhesive tape comprising a base material with a high Young's modulus, a buffer layer provided on one side of the base material, and an adhesive layer provided on the other side. .

In recent years, as a modification of the sun dicing method, a method has been proposed in which a modified area is provided inside the wafer with a laser and the wafer is separated into individual pieces using stress during grinding the back side of the wafer. Hereinafter, this method may be referred to as LDBG (Laser Dicing Before Grinding). In LDBG, the wafer is cut in the crystal direction starting from the modified region, so the occurrence of chipping can be reduced compared to the pre-dicing method using a dicing blade. In addition, compared to DBG, which forms grooves of a predetermined depth on the wafer surface with a dicing blade, there is no area where the wafer is shaved off with a dicing blade, that is, the kerf width is extremely small, resulting in excellent chip yield. do.

International Publication No. 2015/156389 Japanese Patent Publication No. 2015-183008

It is known that electrification occurs when processing a wafer as an example of a workpiece (for example, during dicing, back grinding, cleaning, peeling of a back grinding tape, etc.). When electrification occurs, cut dust generated when cutting the backgrinding tape and minute foreign matter present in the environment tend to adhere to the wafer or the chip, which is an example of work piece material.

For example, if cut dust or foreign matter adheres to the wafer during back grinding, the pressure during back grinding may focus on the attached foreign matter, and the wafer may be damaged starting from the foreign matter. In particular, when DBG is performed for the purpose of grinding a wafer thin, damage to the wafer is likely to occur due to a slight concentration of pressure. Additionally, for example, if the peeling charge generated when peeling the backgrinding tape from the wafer is excessive, there is a problem that it leads to the destruction of the circuit formed on the wafer. Therefore, it is necessary to suppress charging that occurs during wafer processing.

In order to suppress electrification that occurs during processing of such wafers, an anti-static layer is provided on the backgrinding tape. In particular, in order for the antistatic layer to fully exert its function of preventing peeling and charging, the antistatic layer is preferably disposed close to the interface between the wafer and the adhesive layer. For example, the antistatic layer may be disposed between the adhesive layer and the substrate.

However, the back grinding tape adheres strongly to the surface of the wafer when grinding the back side of the wafer and sufficiently protects the circuits, etc., and when the back grinding tape is peeled from the wafer after grinding the back side of the wafer, it leaves a residue on the wafer. Work-free peeling is required.

Here, when the antistatic layer is disposed between the adhesive layer and the substrate, the adhesive layer is in contact with the antistatic layer. However, since the adhesion between the adhesive layer and the antistatic layer is often poor, when peeling the backgrinding tape from the wafer, the adhesive layer tends to peel off from the antistatic layer, and there are cases where the adhesive layer remains as a residue on the wafer ( full left). When glue residue occurs, additional processes such as washing the wafer are required, which causes a problem in that production efficiency decreases.

The present invention has been made in consideration of this actual situation, and sufficiently suppresses electrification that occurs during processing of workpieces, etc. (i.e., workpieces or individual work groups), and furthermore, when peeling the protective sheet for workpiece processing from the workpieces, etc. The purpose is to provide a protective sheet for work processing in which glue residue is suppressed, and to provide a method for manufacturing a separate work piece cargo using the protective sheet for work processing.

The aspects of the present invention are as follows.

[1] A protective sheet for work processing in which an adhesive layer attached to the work, a base material, and an antistatic layer are laminated in this order,

The adhesive layer and the substrate are in direct contact,

This is a protective sheet for work processing in which the distance between the surface of the adhesive layer attached to the work and the surface of the antistatic layer located on the substrate side is 300 μm or less.

[2] The protective sheet for work processing further contains soft materials,

The protective sheet for work processing described in [1] is one in which the adhesive layer, the base material, the antistatic layer, and the soft material are laminated in this order.

[3] The protective sheet for work processing according to [1] or [2], wherein the thickness of the base material is 10 μm or more and 80 μm or less.

[4] The protective sheet for work processing according to any one of [1] to [3], wherein the antistatic layer has a thickness of 0.2 μm or more.

[5] The protective sheet for work processing according to any one of [1] to [4], wherein the surface resistivity of the surface of the adhesive layer attached to the work is greater than 1.0 × 10 ¹³ Ω/□.

[6] The protective sheet for work processing according to any one of [1] to [5], wherein the product of the Young's modulus of the protective sheet for work processing and the thickness of the protective sheet for work processing is 1.0 × 10 ⁵ N/m or more.

[7] Any of [1] to [6] used by attaching to the surface of the work in the process of breaking the work into pieces by grinding the back side of the work on which grooves are formed on the surface or modified areas inside. This is a protective sheet for work processing as described above.

[8] A process of attaching the protective sheet for work processing according to any one of [1] to [7] to the surface of a work having front and back surfaces;

A process of forming a groove on the surface of the work, or a process of forming a modified area inside the work,

A protective sheet for work processing is attached to the surface, and a work in which grooves or modified areas are formed is ground from the back side, and the grooves or modified areas are used as a starting point to separate the work pieces into a plurality of individual pieces;

A method for manufacturing separate work pieces including a step of peeling a protective sheet for work processing from a plurality of piece pieces of work.

According to the present invention, electrification that occurs during processing of works, etc. (i.e., works or individual work groups) is sufficiently suppressed, and also, when peeling the protective sheet for work processing from the work, etc., glue residue on the works, etc. is suppressed. A protective sheet for work processing can be provided, and a method for manufacturing a piece of workpiece cargo using the protective sheet for work processing can be provided.

1A is a cross-sectional schematic diagram showing an example of a protective sheet for workpiece processing according to this embodiment.
1B is a cross-sectional schematic diagram showing another example of a protective sheet for work processing according to this embodiment.
Figure 2 is a cross-sectional schematic diagram showing the protective sheet for work processing according to the present embodiment attached to the surface of a wafer.

Hereinafter, the present invention will be described in detail based on specific embodiments and using drawings. First, the main terms used in this specification will be explained.

A work refers to a plate-shaped body to which a protection sheet for work processing is attached and then divided into individual pieces. Examples of the work include circular wafers (including those with an orientation flat), rectangular panel level packages, and strips (single-shaped substrates) encapsulated with mold resin. and, among these, wafers are preferable from the viewpoint of making it easier to obtain the effects of the present invention. The wafer may be, for example, a semiconductor wafer such as a silicon wafer, gallium arsenide wafer, silicon carbide wafer, gallium nitride wafer, or indium phosphorus wafer, or an insulator wafer such as a glass wafer, lithium tantalum wafer, or lithium niobate wafer. , a reconstituted wafer made of a resin and a semiconductor used in the production of fan-out packages, etc. may be used. From the viewpoint of easily obtaining the effect of the present invention, the wafer is preferably a semiconductor wafer or insulator wafer, and a semiconductor wafer is more preferable.

Work reorganization refers to dividing the work into circuits to obtain work reorganization cargo. For example, when the work is a wafer, the separate work cargo is a chip, and when the work is a panel level package or a strip (single-type substrate) with mold resin encapsulation, the separate work cargo is a semiconductor package.

The “surface” of the work refers to the side on which circuits, etc. are formed or where circuits, etc. are scheduled to be formed, and the “back side” of the work refers to the side where circuits, etc. are not formed, or the side where circuits, etc. are scheduled to be formed. It refers to the side that is not scheduled to be formed.

DBG (Dicing Before Grinding) refers to a method of forming a groove of a predetermined depth on the surface of a wafer as a work, then grinding the wafer from the back side, and breaking the wafer into pieces by grinding. The grooves formed on the surface of the wafer are formed by methods such as blade dicing, laser dicing, or plasma dicing.

Additionally, LDBG (Laser Dicing Before Grinding) is a modified example of DBG and refers to a method of providing a modified area inside a wafer as a workpiece with a laser and dividing the wafer into pieces using stress during grinding the back side of the wafer.

The term “piece workpiece cargo group” refers to a plurality of piecework cargoes held on a protection sheet for work processing according to the present invention after the workpieces have been broken into pieces. These work piece cargoes, as a whole, have a shape similar to that of the work. In addition, the “chip group” refers to a plurality of chips held on the protection sheet for work processing according to the present invention after the wafer as the work has been separated into individual pieces. These chips, as a whole, have a shape similar to that of the wafer.

“(Meth)acrylate” is used as a word representing both “acrylate” and “methacrylate”, and the same applies to other similar terms.

“Energy rays” refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

Unless otherwise specified, “weight average molecular weight” is a polystyrene conversion value measured by gel permeation chromatography (GPC) method. Measurement by this method is performed, for example, using a high-speed GPC device “HLC-8120GPC” manufactured by TOSOH CORPORATION and a high-speed column “TSK guard column H _XL -H”, “TSK Gel GMH _XL ”, and “TSK Gel G2000 H _XL” 」(all manufactured by TOSOH CORPORATION) are connected in this order, and the detector is used as a differential refractometer under the conditions of column temperature: 40°C and liquid feeding rate: 1.0 mL/min.

The mass ratio in the description of the composition, such as the adhesive composition, is based on the active ingredient (solid content), and unless otherwise specified, the solvent is not included.

(1. Protection sheet for work processing)

The protective sheet for work processing is used when processing workpieces, etc. (i.e., workpieces or individual work groups) in which circuits, etc. are formed on one side (surface), and circuits, etc. are not formed on the other side (back side). . The surface of the workpiece or the like may be a surface on which the circuit is exposed, or may be the main surface of a protective layer formed on the circuit to protect the circuit. Additionally, convex electrodes such as bumps may be formed on the circuit.

Examples of processing of a workpiece or the like include grinding the back side of the workpiece. By grinding the back side of the work, it is possible to realize a reduction in the thickness of the individual work pieces obtained by dividing the work into pieces.

The protective sheet for work processing is temporarily attached to the surface of the work before grinding the back side of the work to protect the surface of the work. With the protective sheet for work processing attached to the surface of the work, the back side of the work is ground. After grinding is completed, the protective sheet for work processing is peeled off from the work or the work unit cargo group.

As described above, when processing a workpiece or the like, for example, when grinding the back side of a wafer, charging occurs in the workpiece or the workpiece load group. Additionally, for example, electrification (peel-off electrification) occurs even when the protective sheet for work processing is peeled off. If this charging is not alleviated, there is a risk that foreign substances, etc. may adhere to the workpieces, etc. (i.e., workpieces or separate workpiece cargo groups) due to the charging, and as a result, damage or cracks in the workpieces, etc. may occur. Alternatively, there is a risk that it may lead to destruction of the circuit formed on the workpiece, etc.

Therefore, in order to suppress such peeling and electrification, an antistatic layer is provided on a protective sheet for work processing.

Since peeling electrification occurs at the interface between the surface of the work or the work piece package and the adhesive layer of the protective sheet for work processing, in order to easily alleviate the electrification, an antistatic layer is disposed near the adhesive layer, especially the antistatic layer and the adhesive layer. Laminating and arranging adhesive layers is performed. In this case, a configuration in which an antistatic layer is formed on the base material and an adhesive layer is formed thereon is likely to be adopted.

When grinding the back side of a workpiece using a protective sheet for work processing with this structure, the adhesion between the antistatic layer and the adhesive layer tends to become insufficient, and when the protective sheet for work processing is peeled, the adhesive layer separates from the protective sheet for work processing. There were cases where it peeled off and remained as a residue on the surface of the work or work piece cargo group.

Therefore, the protective sheet for work processing according to the present embodiment sufficiently exhibits antistatic performance by keeping the distance between the antistatic layer and the surface of the adhesive layer where peeling charge is generated within a predetermined range. Additionally, by ensuring adhesion between the adhesive layer and the member of the protective sheet for work processing, the adhesive layer is prevented from peeling off from the protective sheet for work processing when the protective sheet for work processing is peeled off. Therefore, the protective sheet for work processing according to the present embodiment is attached to the surface of the work, especially in the process of dividing the work into individual work pieces by grinding the back side of the work on which grooves are formed on the surface or modified areas therein. It is suitable as a protective sheet for workpiece processing.

The configuration of the protective sheet for work processing according to the present embodiment having such effects will be described.

The protective sheet for work processing according to this embodiment has a configuration in which an adhesive layer, a base material, and an antistatic layer are laminated in this order. Specifically, the protective sheet 1 for work processing, as shown in FIG. 1A, has an antistatic layer 20 provided on one main surface 10a of the base material 10, and an antistatic layer 20 on the other main surface of the base material 10 ( 10b) has a configuration in which an adhesive layer 30 is provided on the top. Therefore, the substrate 10 and the adhesive layer 30 are in direct contact.

Since the base material and the adhesive layer are in direct contact, sufficient adhesion between the base material and the adhesive layer is ensured, so that even when the protective sheet for work processing is peeled from the work or the work piece cargo group, the adhesive layer does not peel from the base material, and the workpiece after peeling is not peeled off. Alternatively, it is possible to suppress the adhesive layer from remaining as a residue on the work piece cargo group. In particular, as shown in FIG. 1A, since the base material 10 exists between the adhesive layer 30 and the antistatic layer 20, the antistatic layer 20 and the adhesive layer ( 30) There is no such thing as direct contact.

In addition, in the protective sheet 1 for work processing shown in FIG. 1A, the distance between the surface 30a of the adhesive layer 30 attached to the workpiece and the surface 20a of the antistatic layer 20 located on the substrate side is ( D) is 300㎛ or less. In the protective sheet 1 for work processing shown in FIG. 1A, this distance D corresponds to the sum of the thickness of the adhesive layer 30 and the thickness of the base material 10.

By keeping the above-mentioned distance within the above-mentioned range, the protective sheet 1 for workpiece processing can exhibit anti-static performance, and thus excessive electrification (particularly peeling electrification) can be suppressed.

The above distance (D) is preferably 250 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less. In addition, the lower limit of the above distance is not limited as long as it satisfies the above-described configuration, but from the viewpoint of making it easier to obtain a protective sheet for work processing with more stable performance, it may be, for example, 20 ㎛ or more, and 35 ㎛ or more. It's okay to continue.

Furthermore, in this embodiment, it is preferable that the product of the Young's modulus of the protective sheet for work processing at 23°C and the thickness of the protective sheet for work processing is 1.0 × 10 ⁵ N/m or more. This product quantifies the overall resistance to tension of the protective sheet for work processing. When this product is within the above range, when the protective sheet for work processing is peeled from the work or the separate work load group, the already peeled protective sheet for work processing will not be removed until the protective sheet for work processing is completely peeled from the work or the separate work load group. It can prevent stretching. Accordingly, even within a relatively short operating distance of the peeling mechanism of the device used for peeling, it is possible to prevent the latter part of the protective sheet for work processing from remaining without being separated from the work or the work piece load group. If the protective sheet for work processing can be removed within a relatively short operating distance, the peeling time is shortened, so production efficiency can be improved and the risk of the device being destroyed by peeling and electrification can be reduced.

Young's modulus is measured according to JIS K 7127. In other words, measurement is performed in the same manner as the measurement method specified in JIS K 7127, but measurement conditions may be different. Specific measurement methods are explained in the examples.

The above product is more preferably 1.4 × 10 ⁵ N/m or more, and more preferably 1.8 × 10 ⁵ N/m or more. The upper limit of the above product is not particularly limited, but may be 9.9 × 10 ⁵ N/m or less from the viewpoint of making it easier to obtain a protective sheet for work processing with more stable performance.

Hereinafter, the components of the protective sheet for work processing will be described in detail.

(2. Description)

The base material is a membrane-like member responsible for the rigidity of the protective sheet for work processing. Therefore, the base material needs to be rigid enough to suppress vibrations during grinding of the back side of the workpiece and to stably support the workpiece. In this embodiment, the rigidity of the substrate is evaluated by Young's modulus. Specifically, it is preferable that the Young's modulus of the substrate at 23°C is 500 MPa or more.

When the Young's modulus of the base material is within the above range, the support and retention performance of the workpiece, etc. (i.e., workpiece or separate work load group) is improved, and breakage and cracks of the workpiece, etc. are reduced. In addition, it becomes easier to obtain a protective sheet for work processing in which the product of the Young's modulus at 23°C of the protective sheet for work processing and the thickness of the protective sheet for work processing is within the above-mentioned range. Additionally, workability when attaching the protective sheet for work processing to the workpiece also improves.

The Young's modulus at 23°C of the above-described base material is more preferably 750 MPa or more, more preferably 1000 MPa or more, and particularly preferably 3000 MPa or more. The upper limit of Young's modulus is not particularly limited, but may be 5500 MPa or less.

The Young's modulus at 23°C of the base material can be measured by the same method as the Young's modulus at 23°C of the protective sheet for work processing.

In the present embodiment, the thickness of the base material is preferably 8 μm or more and 130 μm or less, more preferably 10 μm or more and 80 μm or less, more preferably 20 μm or more and 70 μm or less, and especially 25 μm or more and 60 μm or less. desirable. When the thickness of the base material is within the above range, it becomes easy to satisfy the physical properties of the protective sheet for work processing described above.

(2.1 Base material)

As the material of the base material, a material may be selected so that the Young's modulus of the base material is within the above range. Examples of such materials include various resin films. The base material may be comprised of a single-layer film made of one resin film, or may be comprised of a multi-layer film in which a plurality of resin films are laminated.

In this embodiment, the resin film includes, for example, polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyester, polyimide, polyamide, polycarbonate, polyacetal, and modified poly. Films such as phenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, high-density polyethylene (HDPE, density: 942 kg/m3 or more), and biaxially stretched polyolefin can be mentioned. Among these, it is preferable that it is one or more films selected from polyester, polyamide, polyimide, high-density polyethylene, and biaxially oriented polyolefin, more preferably a film of polyester or high-density polyethylene, and a film of polyethylene terephthalate. It is more desirable.

Additionally, the base material may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet ray absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, etc., as long as the effect of the present invention is not impaired. Additionally, the substrate may be transparent or opaque, and may be colored or vapor-deposited as desired.

Additionally, adhesion treatment such as corona treatment may be applied to at least one main surface of the substrate to improve adhesion with other layers. Additionally, the base material may have a primer layer on at least one side of the main surface. That is, the primer layer is included in the substrate.

The primer layer forming composition for forming the primer layer is not particularly limited, but examples include compositions containing polyester resin, urethane resin, polyester urethane resin, acrylic resin, etc. The composition for forming a primer layer may contain a crosslinking agent, photopolymerization initiator, antioxidant, softener (plasticizer), filler, rust preventive, pigment, dye, etc., as needed.

The thickness of the primer layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm. Since the material of the primer layer is flexible, the effect on the Young's modulus is small, and the Young's modulus of the base material is substantially the same as the Young's modulus of the resin film even when it has a primer layer.

For example, the Young's modulus of the substrate can be controlled by selection of the resin composition, addition of a plasticizer, stretching conditions during production of the resin film, etc.

(3. Anti-static layer)

Since the antistatic layer has poor adhesion to the adhesive layer, it is preferably disposed so as not to contact the adhesive layer. In FIG. 1A , the antistatic layer 20 is disposed on one main surface 10a of the substrate 10, and the adhesive layer 30 is disposed on the other main surface 10b of the substrate 10. In the antistatic layer, the antistatic component can prevent the electrostatic voltage from increasing by leaking electrification resulting from the processing of the workpiece or the individual workpiece cargo group to which the workpiece processing protection sheet is attached. In this embodiment, when the surface resistivity of the antistatic layer is measured, the surface resistivity of the antistatic layer is 1.0 × 10 ⁸ Ω/□ or less. The unit of surface resistivity is sheet resistance, and it is a resistivity that includes thickness in the resistivity. In this embodiment, the surface resistivity is measured according to JIS K 7194. In other words, measurement is performed in the same manner as the measurement method specified in JIS K 7194, but measurement conditions may be different.

The thickness of the antistatic layer is preferably 0.2 μm or more, more preferably 0.4 μm or more, and still more preferably 0.6 μm or more from the viewpoint of the protective sheet for work processing demonstrating the above-mentioned antistatic properties. In addition, the thickness is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less from the viewpoint of easily obtaining a protective sheet for work processing with more stable performance.

In this embodiment, the composition of the antistatic layer is not particularly limited as long as the surface resistivity is within the above range. For example, binder polymers that provide film-forming properties for polyester resins, urethane resins, polyester urethane resins, acrylic resins, and polysiloxane resins, organic or inorganic conductive polymers, surfactants, and organic or inorganic conductive fine particles. It may be a composition containing an antistatic component such as the like. The binder polymer and the antistatic component may be partially bonded. Additionally, if necessary, it may contain a crosslinking agent, curing agent, photopolymerizable resin, photopolymerization initiator, antioxidant, softener (plasticizer), filler, rust preventive, pigment, dye, etc.

As conductive polymers, polythiophenes such as polythiophene, poly(3-methylthiophene), poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, polyvinyl sulfonate, polyacryl sulfonate, etc. Examples include polymers having a sulfonic acid group, polyacetylene, and polyaniline. Examples of the surfactant include anionic surfactants such as fatty acid sodium and monoalkyl sulfate; Cationic surfactants such as alkyltrimethylammonium salt and dialkyldimethylammonium salt; Zwitterionic surfactants such as sodium alkylamino fatty acid; Nonionic surfactants such as polyoxyethylene alkyl ether and alkyl monoglyceryl ether can be mentioned. Examples of conductive fine particles include tin oxide, indium oxide, silver, carbon black, and carbon nanotubes.

(4. Adhesive layer)

The adhesive layer is attached to the surface of the work having front and back surfaces (i.e., the surface on which circuits, electrodes, etc. are formed), protects the surface, and supports the work or the group of separate work pieces until peeled from the surface. The adhesive layer may be composed of one layer (single layer) or may be composed of two or more layers. When the pressure-sensitive adhesive layer has multiple layers, these multiple layers may be the same or different from each other, and the combination of the layers constituting these multiple layers is not particularly limited.

The thickness of the adhesive layer is preferably 10 μm or more and 300 μm or less, and more preferably 20 μm or more and 270 μm or less. When the thickness of the adhesive layer is within the above range, the adhesive properties of the adhesive layer can be sufficiently exhibited, and the irregularities (electrodes, grooves, etc.) existing on the surface of the work can be sufficiently followed, making it easy to bury the irregularities. Additionally, subsequent peeling from the work, etc. can be easily performed.

In addition, the thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer comprised of multiple layers means the total thickness of all layers constituting the adhesive layer.

In this embodiment, the adhesive layer preferably has the following physical properties.

(4.1 Surface resistivity)

In this embodiment, it is preferable that the surface resistivity of the adhesive layer is larger than 1.0 × 10 ¹³ Ω/□. In addition, this surface resistivity is the surface resistivity of the surface of the adhesive layer that is attached to the work, which is the adherend (the surface 30a of the adhesive layer in FIG. 1A). In addition, this surface resistivity is the surface resistivity after energy ray curing when the adhesive layer is energy ray curable.

If the surface resistivity is lower than the above range, for example, when a protective sheet for work processing is used in the DBG process, after the work is broken into pieces, the grinding water of the grinder is between the work pieces and the work piece pieces (kerf portion). In some cases, water may penetrate and the grinding water may come into contact with the adhesive surface. There is a risk that the surface resistivity of the pressure-sensitive adhesive layer may fluctuate due to contact with grinding water, and in particular, the surface resistivity may decrease. On the other hand, grinding water does not come into contact with the adhesive layer in contact with the work piece cargo. Accordingly, there is a risk that the surface resistivity, which was adjusted to be uniform before grinding, in the area corresponding to the cuff portion and the area corresponding to the workpiece piece cargo on the attachment surface of the adhesive layer, may be unintentionally damaged and become uneven after grinding. In addition, for example, when an antistatic component is contained in the adhesive to lower the surface resistivity of the adhesive surface, the antistatic component causes the adhesive layer to peel off when the adhesive layer is peeled from the work or the workpiece individual cargo group, causing the workpiece or individual workpieces to be separated. There is a risk that it may become residue on the cargo group and have a negative effect on the work or work reform cargo group.

The surface resistivity is preferably 2.0 × 10 ¹³ Ω/□ or more, and more preferably 5.0 × 10 ¹³ Ω/□ or more. On the other hand, the surface resistivity is preferably 9.9 × 10 ¹⁴ Ω/□ or less, and more preferably 5.0 × 10 ¹⁴ Ω/□ or less.

In this embodiment, the surface resistivity is measured according to JIS K 7194. In other words, measurement is performed in the same manner as the measurement method specified in JIS K 7194, but measurement conditions may be different. Specific measurement conditions are described later in the examples.

(4.2 Composition of adhesive layer)

The composition of the adhesive layer is not limited as long as it has adhesiveness sufficient to protect the surface of the work or the individual work group. In this embodiment, the pressure-sensitive adhesive layer is preferably composed of a pressure-sensitive adhesive composition, for example, an acrylic pressure-sensitive adhesive composition, a urethane-based pressure-sensitive adhesive composition, a rubber-based pressure-sensitive adhesive composition, or a silicone-based pressure-sensitive adhesive composition.

Moreover, it is preferable that the adhesive layer is an energy ray curable adhesive layer comprised of a composition for energy ray curable adhesives. Since the adhesive layer of the protective sheet for work processing is an energy ray-curable adhesive layer, when attached to a work, it adheres to the work with high adhesive strength, and when peeled from the work or work piece unit cargo group, the adhesive strength can be reduced by irradiating energy rays. . Therefore, while the circuits of the work or the work piece load group are appropriately protected, damage to the circuits, electrodes, etc. on the surface of the work or work piece load group is prevented when the protective sheet for work processing is peeled off.

In this embodiment, the composition for an energy ray-curable adhesive is preferably comprised of a composition for an acrylic adhesive. The composition for an acrylic adhesive contains an acrylic polymer.

The acrylic polymer may be any known acrylic polymer, but in this embodiment, an acrylic polymer containing a functional group is preferable. The functional group-containing acrylic polymer may be a homopolymer formed of one type of acrylic monomer, a copolymer formed of multiple types of acrylic monomers, or a copolymer formed of one type or multiple types of acrylic monomer and a monomer other than the acrylic monomer. .

In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing an alkyl (meth)acrylate and a functional group-containing monomer.

Examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl. (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate , n-octyl (meth)acrylate, etc.

A functional group-containing monomer is a monomer containing a reactive functional group. A reactive functional group is a functional group that can react with other compounds, such as a crosslinking agent described later. Examples of functional groups in the functional group-containing monomer include hydroxyl group, carboxyl group, and epoxy group, with hydroxyl group being preferable.

Examples of hydroxyl group-containing monomers include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylic acid. Hydroxyalkyl (meth)acrylate such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; Non-(meth)acrylic unsaturated alcohols (unsaturated alcohols that do not have a (meth)acryloyl skeleton) such as vinyl alcohol and allyl alcohol can be mentioned.

The acrylic polymer is preferably an energy ray-curable acrylic polymer having an energy ray-curable group obtained by reacting (for example, addition reaction) an energy ray-curable material having an energy ray-curable group with a functional group of the acrylic polymer. As the energy ray curable material having an energy ray curable group, a compound having one or more types selected from an isocyanate group, an epoxy group, and a carboxyl group in addition to the energy ray curable group is preferable, and a compound having an isocyanate group is more preferable. The isocyanate group can be added to the hydroxyl group of the functional group-containing acrylic polymer.

Examples of compounds having an isocyanate group include 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryl Royloxymethyl)ethyl isocyanate; An acryloyl monoisocyanate compound obtained by reaction of a diisocyanate compound or polyisocyanate compound and hydroxyethyl (meth)acrylate; An acryloyl monoisocyanate compound obtained by reaction of a diisocyanate compound or polyisocyanate compound, a polyol compound, and hydroxyethyl (meth)acrylate, etc. can be mentioned.

The composition for an adhesive preferably contains an energy ray-curable compound in addition to the acrylic polymer. As the energy ray curable compound, a monomer or oligomer that has an unsaturated group in the molecule and can be polymerized and cured by energy ray irradiation is preferable.

Examples of such energy ray-curable compounds include trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. , polyvalent (meth)acrylate monomers such as 1,4-butylene glycol di(meth)acrylate, 1,6-hexanediol (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate. , oligomers such as polyether (meth)acrylate and epoxy (meth)acrylate.

Among these, urethane (meth)acrylate oligomer is preferable because it has a relatively high molecular weight and is difficult to reduce the Young's modulus of the 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 12,000, more preferably 200 to 10,000, further preferably 400 to 8,000, and particularly preferably 600 to 6,000.

The content of the energy ray curable compound in the adhesive composition is preferably 3 to 100 parts by mass, more preferably 5 to 70 parts by mass, and still more preferably 7 to 40 parts by mass, based on 100 parts by mass of the acrylic polymer. am.

It is preferable that the composition for an adhesive further contains a crosslinking agent. The crosslinking agent, for example, reacts with a functional group to crosslink the molecules contained in the functional group-containing acrylic polymer.

Examples of the crosslinking agent include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates (crosslinking agents having an isocyanate group); Epoxy-based crosslinking agents such as ethylene glycol glycidyl ether (crosslinking agents having a glycidyl group); Aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine (crosslinking agents having an aziridinyl group); Metal chelate-based crosslinking agents such as aluminum chelate (crosslinking agents having a metal chelate structure); Isocyanurate-based crosslinking agents (crosslinking agents having an isocyanuric acid skeleton), etc. can be mentioned.

From the viewpoint of improving the cohesion of the adhesive and improving the adhesive strength of the adhesive layer, and from the viewpoint of ease of availability, it is preferable that the crosslinking agent is an isocyanate-based crosslinking agent.

The composition for an adhesive may further contain a photopolymerization initiator. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the curing reaction sufficiently progresses even when irradiated with relatively low-energy energy rays such as ultraviolet rays.

Examples of the photopolymerization initiator include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. Specifically, α-hydroxycyclohexylphenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, benzyl dimethyl ketal, tetramethylthiuram monosulfide, azobis. Isobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. are exemplified.

The composition for an adhesive may contain other additives within a range that does not impair the effect of the present invention. Other additives include, for example, tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When containing these additives, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass, based on 100 parts by mass of the acrylic polymer.

(5. Soft materials)

Additionally, the protective sheet for work processing may have other layers as long as the effect of the present invention is obtained. In this embodiment, as shown in FIG. 1B, in the protective sheet 1 for work processing, a soft material 40 is provided on the surface 20a on the base material side and the surface 20b on the opposite side of the antistatic layer 20. It is desirable that it is placed. That is, it is preferable that the adhesive layer 30, the base material 10, the antistatic layer 20, and the soft material 40 are laminated in this order.

A soft material is a layer that is softer than the base material. Specifically, the Young's modulus of the soft material at 23°C is lower than the Young's modulus of the base material at 23°C. Since the protective sheet for work processing has a soft material, when fixing a work to which the protective sheet for work processing is attached to the suction table for grinding the back side of the work, even if foreign matter, etc. is attached to the suction table, the soft material is embedded in the foreign matter, etc. Therefore, during back grinding, it is possible to suppress the occurrence of breakage or cracks in the workpiece, etc. (i.e., workpiece or separate workpiece load group) caused by foreign matter, etc.

The Young's modulus at 23°C of the soft material is preferably 50 MPa or more and 1000 MPa or less, more preferably 100 MPa or more and 750 MPa or less, and still more preferably 120 MPa or more and 450 MPa or less.

The Young's modulus at 23°C of the soft material can be measured by the same method as the Young's modulus at 23°C of the protective sheet for work processing.

The thickness of the soft material is preferably 10 μm or more and 75 μm or less, more preferably 25 μm or more and 60 μm or less, and still more preferably 30 μm or more and 55 μm or less. By setting the thickness of the soft material within the above range, as described above, it becomes easy to suppress the occurrence of breakage or cracks in the workpiece, etc. (i.e., workpiece or separate workpiece load group) caused by foreign matter, etc. during back grinding.

In this embodiment, the soft material is preferably comprised of a resin film. Resin films include polypropylene film, ethylene-vinyl acetate copolymer film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, and very low density polyethylene film (VLDPE, high density film). : 880 kg/m3 or more but less than 910 kg/m3), low-density polyethylene film (LDPE, density: 910 kg/m3 or more but less than 942 kg/m3) film, etc. may be used.

The surface of the soft material on the antistatic layer side may be subjected to an adhesion treatment such as corona treatment to improve adhesion to the antistatic layer, and an easily adhesive layer may be formed.

The composition for forming an easily adhesive layer is not particularly limited, but examples include compositions containing polyester resin, urethane resin, polyester urethane resin, acrylic resin, etc. The composition for forming an easily adhesive layer may contain a crosslinking agent, photopolymerization initiator, antioxidant, softener (plasticizer), filler, rust preventive, pigment, dye, etc. as needed.

The thickness of the easily adhesive layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm.

(6. Manufacturing method of protective sheet for work processing)

The method of manufacturing the protective sheet for work processing according to this embodiment is not particularly limited as long as it can form an antistatic layer and an adhesive layer on the main surface of the base material, and a known method may be used.

First, a composition for forming an antistatic layer, for example, a composition for an antistatic layer containing the above-mentioned components, or a composition obtained by diluting the composition for an antistatic layer with a solvent or the like (hereinafter referred to as a coating agent for the composition for an antistatic layer) (in some cases) is prepared. Similarly, as a pressure-sensitive adhesive composition for forming an adhesive layer, for example, a pressure-sensitive adhesive composition containing the above-mentioned components, or a composition obtained by diluting the pressure-sensitive adhesive composition with a solvent or the like (hereinafter referred to as a coating agent for the pressure-sensitive adhesive composition) (in some cases) is prepared.

Examples of the solvent include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

Next, the antistatic layer composition or the coating agent for the antistatic layer composition is applied to the peeling treated surface of the first release sheet by a known method, and if necessary, heated and dried to form an antistatic layer on the first release sheet. . Thereafter, the antistatic layer on the first release sheet and one side of the substrate are bonded together, and the first release sheet is removed.

In addition, as another method of forming an antistatic layer on a substrate, an antistatic layer composition or a coating agent for an antistatic layer composition is applied to one side of the substrate by a known method, and if necessary, the antistatic layer composition is heated and dried to form the antistatic layer on the substrate. A method of forming an antistatic layer is included.

Next, the pressure-sensitive adhesive composition or the coating agent for the pressure-sensitive adhesive composition is applied to the peel-treated surface of the second release sheet by a known method, and heat-dried as necessary to form an adhesive layer on the second release sheet. Thereafter, the adhesive layer on the second release sheet is bonded to the side of the base material on which the antistatic layer is not formed, thereby obtaining a protective sheet for work processing in which the adhesive layer, the base material, and the antistatic layer are laminated in this order. That is, the protective sheet for work processing shown in Fig. 1A is obtained. Additionally, the second release sheet may be removed as needed.

Additionally, if necessary, by attaching a resin film as a soft material including an easily adhesive layer to the surface of the antistatic layer of the protective sheet for work processing shown in FIG. 1A, the adhesive layer, the base material, the antistatic layer, and the soft material are A protective sheet for work processing laminated in this order is obtained. That is, the protective sheet for work processing shown in FIG. 1B is obtained.

(7. Manufacturing method of work reorganized cargo)

The protective sheet for work processing according to the present invention is preferably used in a processing method (DBG, LDBG, etc.) that separates the work into pieces when grinding the back side of the work. As a non-limiting example of the use of the protective sheet for work processing, the method for manufacturing the separate work pieces is explained in more detail below.

Specifically, the method for manufacturing the work piece cargo includes at least the following steps 1 to 4.

Step 1: A step of attaching the above protective sheet for work processing to the surface of a work having front and back surfaces.

Process 2: A process of forming a groove on the surface of the work, or a process of forming a modified area inside the work.

Process 3: A protective sheet for work processing is attached to the surface, and the work on which grooves or modified areas are formed is ground from the back side, and the grooves or modified areas are used as a starting point to separate the work pieces into multiple pieces.

Process 4: Process of peeling the protective sheet for work processing from a plurality of work piece cargoes (i.e., work piece piece cargo group)

Hereinafter, each step of the method for manufacturing the work piece cargo will be described in detail. In the explanation, a wafer is used as a specific example of a work, and a chip is used as a specific example of a work piece cargo.

(Process 1)

In step 1, as shown in FIG. 2, the main surface 30a of the adhesive layer 30 of the protective sheet 1 for work processing according to this embodiment is attached to the surface 100a of the wafer 100. The wafer may be a silicon wafer, or may be a wafer of gallium arsenide, silicon carbide, lithium tantalum, lithium niobate, gallium nitride, or indium phosphide, a glass wafer, or a reconstituted wafer. In this embodiment, the wafer is preferably a silicon wafer. The thickness of the wafer before grinding is not particularly limited, but is usually about 500 to 1000 μm.

Additionally, a circuit is formed on the surface of the wafer. The formed circuit may be exposed, or a circuit protection layer may be formed to protect the circuit. The circuit protective layer is usually formed by applying and thermally curing the composition that constitutes the circuit protective layer. Additionally, convex electrodes such as bumps and pillars may be formed in the circuit.

By attaching the protective sheet for work processing to the surface 100a of the wafer, the surface of the wafer is sufficiently protected. Additionally, the excess protective sheet for work processing remaining on the outer periphery of the wafer can be removed by cutting it to fit the shape of the wafer as needed.

This step 1 may be performed before step 2, which will be described later, or may be performed after step 2. For example, when forming a modified region on a wafer, it is preferable to perform step 1 before step 2 from the viewpoint of reducing the risk of the wafer being unintentionally broken into pieces when attaching a protective sheet for work processing. On the other hand, when forming a groove on the wafer surface 100a by dicing or the like, step 1 is performed after step 2. That is, a protective sheet for work processing is attached to the surface of the wafer on which the grooves are formed in Step 2, which will be described later.

(Process 2)

In step 2, grooves are formed on the surface of the wafer. Alternatively, a modified region is formed inside the wafer. In step 2, the grooves and modified regions are formed to follow the dividing line when the wafer is divided into chips in step 3, which will be described later.

The groove formed in this step 2 is a groove whose depth is shallower than the thickness of the wafer. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

In addition, the modified area is a brittle part of the wafer, and the wafer becomes thinner due to grinding in the grinding process, or the modified area of the wafer is destroyed when a force is applied due to grinding, forming a chip. This is the starting point for reorganization.

The formation of the modified region is performed by irradiation of a laser focused on the inside of the wafer, and the modified region is formed inside the wafer. Laser irradiation may be performed from the front surface 100a side of the wafer or the back surface 100b side. In addition, in the aspect of forming a modified region, when process 2 is performed after process 1 and laser irradiation is performed from the wafer surface 100a, the laser is irradiated to the wafer through a protective sheet for work processing.

A protective sheet for work processing is attached and the wafer on which grooves or modified regions are formed is placed on a chuck table and held by being attracted to the chuck table. At this time, the wafer is adsorbed with its surface side placed on the table side.

(Process 3)

After steps 1 and 2, the back side 100b of the wafer on the chuck table is ground to separate the wafer into a plurality of chips to obtain a chip group.

When grooves are formed on the wafer, back side grinding is performed to thin the wafer at least to a position reaching the bottom of the groove. By this back grinding, the groove becomes a notch penetrating the wafer, and the wafer is divided by the notch and individual chips are separated.

On the other hand, when a modified region is formed, the ground surface (back surface of the wafer) may reach the modified region by grinding, but it does not have to strictly reach the modified region. In other words, it is good to grind the wafer starting from the modified area to a position close to the modified area so that the wafer is broken and divided into chips. In addition, the actual separation of chips may be performed by attaching a pickup tape, which will be described later, and then stretching the pickup tape.

Additionally, dry polishing may be performed after completion of backside grinding using a grinding wheel and prior to picking up chips.

The shape of the individualized chips may be square, or may be elongated, such as a rectangle. Additionally, the thickness of the divided chips is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. According to LDBG, it is easy to set the thickness of the divided chips to 50 μm or less, more preferably 10 to 45 μm. Additionally, the size of the individualized chips is not particularly limited, but the chip size is preferably less than 600 mm2, more preferably less than 400 mm2, and even more preferably less than 120 mm2.

The protective sheet for work processing according to the present embodiment has an antistatic layer, and since the distance between the surface of the adhesive layer on the wafer side and the surface of the antistatic layer on the substrate side is within the above-mentioned range, even if the chip is thin and/or small. , charging is suppressed during wafer processing, and adhesion of cut dust and foreign matter is reduced, thereby suppressing the occurrence of cracks on the chip.

(Process 4)

Next, the protective sheet for work processing is peeled from the individual wafers (i.e., multiple chips). This process is performed, for example, by the following method.

When the adhesive layer of the protective sheet for work processing is an energy ray-curable adhesive layer, the adhesive layer is cured and shrunk by irradiating energy rays, thereby lowering the adhesive strength to the adherend (pieced wafer). For example, the illuminance of the energy ray is preferably 120 to 280 mW/cm2, and the light quantity of the energy ray is preferably 100 to 1000 mJ/cm2. As the energy ray, ultraviolet rays are preferable. Next, a pickup tape is attached to the back side of the separated wafer, and the position and orientation are adjusted to enable pickup. At this time, the ring frame placed on the outer peripheral side of the wafer is also bonded to the pickup tape, and the outer peripheral edge of the pickup tape is fixed to the ring frame. The wafer and ring frame may be bonded to the pickup tape at the same time or may be bonded at different timings. Next, the protective sheet for work processing is peeled from the plurality of chips (i.e., chip group) held on the pick-up tape using a tape peeling mechanism provided in a predetermined device.

Since the protective sheet for work processing according to the present embodiment has the above-described configuration, excessive peeling charging is suppressed even when the protective sheet for work processing is peeled from the wafer, and furthermore, the adhesive layer does not remain on the wafer when peeled from the protective sheet for work processing. (remaining grass) is suppressed.

In addition, since the protective sheet for work processing satisfies the above-mentioned physical properties, the entire protective sheet for work processing has a certain rigidity. Therefore, when the protective sheet for work processing is peeled from the chip group, the protective sheet for work processing that has already been peeled off increases. It is possible to prevent the latter part of the protective sheet for work processing from being left behind without being separated from the chip group.

Afterwards, a plurality of chips on the pickup tape are picked up. After that, it is fixed on a substrate or the like and the chip is mounted.

In addition, the pick-up tape is not particularly limited, but is comprised, for example, of an adhesive sheet including a base material and an adhesive layer provided on one side of the base material.

Although the embodiments of the present invention have been described above, the present invention is not limited in any way to the above-described embodiments, and may be modified into various aspects within the scope of the present invention.

[Example]

Hereinafter, the invention will be described in more detail using examples, but the invention is not limited to these examples.

(Example 1)

(1) Adhesive layer

(Preparation of composition for adhesive)

An acrylic polymer obtained by copolymerizing 50 parts by mass of n-butylacrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 30 parts by mass of 2-hydroxyethyl acrylate (2HEA), out of all the hydroxyl groups of the acrylic polymer. 2-methacryloyloxyethyl isocyanate (MOI) was reacted to add 80 mol% of hydroxyl groups to obtain an energy ray-curable acrylic polymer (Mw: 500,000).

To 100 parts by mass of this energy ray-curable acrylic polymer, 10 parts by mass of a polyfunctional urethane acrylate-based ultraviolet curable compound as an energy ray-curable compound (manufactured by Mitsubishi Chemical Corporation, product name “Jakwang UT-4332”), and an isocyanate-based crosslinking agent ( 0.38 parts by mass of Mitsui Chemicals, Inc., product name "TAKENATE D-101E", based on solid content, 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, and methyl ethyl A coating agent for an adhesive composition with a solid content concentration of 34% by mass was prepared by diluting with ketone.

(Formation of adhesive layer)

The coating agent of the adhesive composition described above is applied onto the peeled surface of a release sheet (manufactured by LINTEC Corporation, product name “SP-PET381031”, polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm). and dried to produce a release sheet with an adhesive layer having an adhesive layer with a thickness of 40 μm.

(2) Production of substrate with antistatic layer

As a base material, a PET film (thickness: 50 μm, Young's modulus at 23°C: 4000 MPa) was prepared.

On one side of the PET film, a polysiloxane resin having a siloxane bond as the main skeleton and also having a silanol group, and a composite agent containing a hydrophilic organic polymer are applied as a coating agent for an antistatic layer composition and dried to form an antistatic layer with a thickness of 1 μm. was formed on a PET film. With respect to the surface of the antistatic layer formed on the PET film, the surface resistivity was measured by the same method as the surface resistivity of the pressure-sensitive adhesive layer after energy ray curing, which will be described later. The surface resistivity was 1.5 × 10 ⁷ Ω/□.

(3) Soft materials

An easily adhesive layer with a thickness of 2㎛ is provided on the surface of the antistatic layer formed on the PET film, and the adhesive layer has a fracture energy of 61MJ/㎥, a density of 937kg/㎥, a Young's modulus at 23°C of 330MPa, and a thickness of 32㎛. , colorless and transparent low-density polyethylene were bonded together by a dry lamination method.

(4) Production of protective sheets for work processing

By bonding the adhesive layer of the release sheet with an adhesive layer to the side opposite to the surface of the PET film on which the antistatic layer and the soft material are formed, the adhesive layer, the base material, the antistatic layer, and the soft material are arranged in this order. A protective sheet for work processing with a peeling sheet attached was produced. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 2)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that PET film (thickness: 38 μm, Young's modulus at 23°C: 4060 MPa) was used as the base material. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 3)

As a soft material, peeling was carried out in the same manner as in Example 1, except that colorless and transparent low-density polyethylene with a breaking energy of 60MJ/㎥, a density of 937kg/㎥, a Young's modulus at 23°C of 320MPa, and a thickness of 50㎛ was used. A protective sheet for work processing with a sheet attached was obtained. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 4)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer was 80 μm. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 5)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer was 240 μm. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 6)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that the adhesive layer was formed using the following adhesive composition. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Preparation of composition for adhesive)

To an acrylic polymer obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (2 HEA), add 80 mol% of hydroxyl groups out of the total hydroxyl groups of the acrylic polymer, 2-Methacryloyloxyethyl isocyanate (MOI) was reacted to obtain an energy ray-curable acrylic polymer (Mw: 500,000).

To 100 parts by mass of this energy-ray curable acrylic polymer, 0.38 parts by mass based on solid content of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "TAKENATE D-101E"), and bis(2,4,6-) as a photopolymerization initiator. 1 part by mass of trimethylbenzoyl)phenylphosphine oxide was added and diluted with methyl ethyl ketone to prepare an adhesive composition coating agent with a solid content concentration of 30% by mass.

(Comparative Example 1)

An easily adhesive layer with a thickness of 2㎛ is provided on the side opposite to the side of the PET film on which the antistatic layer is formed, and the breaking energy is 61MJ/㎥, the density is 937kg/㎥, the Young's modulus at 23°C is 330MPa, and the thickness is. A protective sheet for work processing with a release sheet attached was prepared in the same manner as in Example 1, except that colorless and transparent low-density polyethylene with a thickness of 32 ㎛ and an easily adhesive layer were bonded by a dry lamination method, and an antistatic layer and an adhesive layer were bonded together. got it Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 7)

A release sheet was attached in the same manner as in Example 1, except that high-density polyethylene with a breaking energy of 20MJ/㎥, a density of 946kg/㎥, a Young's modulus at 23°C of 840MPa, and a thickness of 50㎛ was used as the substrate. A protective sheet for work processing was obtained. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Comparative Example 2)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 5, except that PET film (thickness: 100 μm, Young's modulus at 23°C: 4120 MPa) was used as the base material. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 8)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that PET film (thickness: 12 μm, Young's modulus at 23°C: 4100 MPa) was used as the base material. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

(Example 9)

A protective sheet for work processing with a release sheet attached was obtained in the same manner as in Example 1, except that the easily adhesive layer and the soft material were not formed. Layer composition of the protective sheet for work processing, the distance (D) between the surface attached to the work in the adhesive layer and the surface located on the base material side in the antistatic layer (sum of the thickness of the base material and the thickness of the adhesive layer), and protection for work processing. The thickness of the sheet is shown in Table 1.

[Table 1]

The measurement and evaluation methods in this example are as follows.

(Surface resistivity of adhesive layer after energy ray curing)

The protective sheet for work processing manufactured in Examples and Comparative Examples was cut to a size of 10 cm was irradiated and hardened. Specifically, ultraviolet rays with an illumination intensity of 230 mW/cm2 and a light quantity of 500 mJ/cm2 were irradiated using an ultraviolet irradiation device (manufactured by LINTEC Corporation, device name "RAD-2000"). Peel off the release sheet and measure the cured adhesive layer using a surface resistivity meter (Advantest Corporation, product name “R8252”) under the conditions of 23°C, 50%RH (relative humidity), and applied voltage of 100V in accordance with JIS K 7194. The surface resistivity was measured by . The same measurement was performed twice for each protective sheet for work processing, and the average was taken as the surface resistivity of the adhesive layer.

(Peeling charge voltage of protective sheet for work processing)

In an environment of 23°C and 50%RH (relative humidity), the protective sheet for work processing with the release sheet produced in the examples and comparative examples was peeled off while the release sheet was peeled off using a tape laminator for backgrinding (manufactured by LINTEC Corporation, device name). Using “RAD-3510”, table temperature: 23°C), it was attached to the surface of a silicon wafer (mirror surface, 8 inches) and left to stand for 30 minutes in the same environment. Under the same environment, using the tape peeling mechanism of the wafer mounter (manufactured by LINTEC Corporation, device name “RAD-2700F/12”), the protective sheet for work processing is removed from the silicon wafer under the conditions of a peeling speed of 600 mm/min and a table temperature of 40°C. During peeling, using a peeling charge meter (Prostat, product name "PFM-711A"), measure the voltage (maximum voltage during peeling) at a location 10 mm vertically away from the wafer surface at the peeling point of the adhesive layer on the wafer surface. was measured. The same measurement was performed for each workpiece processing protection sheet for 5 wafers each, and the average of the 5 measured values was taken as the peeling charge voltage value. Samples with a peeling electrification voltage of 500 V or less were judged to be good.

(Young’s modulus of the protective sheet for work processing and the product of the thickness of the protective sheet for work processing)

The protective sheet for work processing with release sheet produced in the examples and comparative examples was cut to a size of 130 mm in length and 15 mm in width. Next, in order to cure the soft material from the side, it was cured by irradiating ultraviolet rays with sufficient illuminance and light quantity. Specifically, ultraviolet rays with an illumination intensity of 230 mW/cm2 and a light quantity of 500 mJ/cm2 were irradiated using an ultraviolet irradiation device (manufactured by LINTEC Corporation, device name "RAD-2000"). After curing, the release sheet was removed to obtain a measurement sample for measuring Young's modulus.

In an environment of 23°C and 50%RH (relative humidity), the initial chuck-to-chuck distance (i.e. Under the condition that the measured length of the protective sheet for work processing was 100 mm, the sample for measurement was stretched in the longitudinal direction of the protective sheet for work processing, and the Young's modulus was measured. The value of Young's modulus at 23°C was calculated from the measurement results. The same measurement was performed twice for each protective sheet for work processing, and the average was taken as the Young's modulus (unit: MPa) of the protective sheet for work processing at 23°C. From the obtained Young's modulus value, "the product of the Young's modulus of the protective sheet for work processing and the thickness of the protective sheet for work processing" was calculated.

(Adhesion evaluation)

The protective sheet for work processing with release sheet manufactured in the examples and comparative examples was irradiated from the soft material side using an ultraviolet irradiation device (manufactured by LINTEC Corporation, device name “RAD-2000”) at an illuminance of 230 mW/cm2 and a light amount of 500 mJ/. The adhesive layer was cured by irradiating cm2 ultraviolet rays.

Next, the release sheet of the protective sheet for work processing with the release sheet is removed, and notches of 11 lines long and 11 lines horizontal at 5 mm intervals are made into the cured adhesive layer to create base lines (number of grids). : 100) shaped notch was formed. Additionally, the depth of the notch is greater than or equal to the thickness of the adhesive layer.

Then, a cellophane adhesive tape (manufactured by NICHIBAN CO., LTD., product name “Cellotape (registered trademark)”) was attached to the surface of the adhesive layer, and left for 20 minutes at 23°C and 50%RH (relative humidity). Then, while pressing the protective sheet for work processing with one hand, holding the end of the cellophane adhesive tape with the other hand, the cellophane adhesive tape is pulled in a direction perpendicular to the protective sheet for work processing, from the surface of the adhesive layer. It peeled off instantly.

After peeling off the cellophane adhesive tape, visually check the notches of the base wood on the adhesive layer of the protective sheet for work processing, count the number of grids where peeling between the adhesive layer and the surface where the adhesive layer was in contact is visible, and count the number of grids where peeling is visible between the adhesive layer and the surface where the adhesive layer was in contact. The adhesion between the adhesive layer of the protective sheet for work processing and the surface on which the adhesive layer was in contact was evaluated. Table 2 shows the number of grids (OK number) among 100 masses in which no peeling was observed between the adhesive layer and the surface on which the adhesive layer was in contact. It can be said that the greater the number of grids shown in Table 2, the better the adhesion between the adhesive layer and the surface on which the adhesive layer was in contact in the protective sheet for work processing after ultraviolet irradiation. That is, when the protective sheet for work processing attached to the work is peeled off from the work, the risk of glue remaining on the work is reduced.

(Peeling residual evaluation)

A protective sheet for work processing with a release sheet manufactured in Examples and Comparative Examples was applied to a silicon wafer (mirror surface, 8 inches) with a thickness of 730 ㎛, and while peeling off the release sheet, a back-grinding tape laminator (manufactured by LINTEC Corporation, device name) was used. It was attached using “RAD-3510F/12”, table temperature: 23°C.

Next, the back side of the silicon wafer was ground using a back side grinding device (manufactured by DISCO CORPORATION, device name “DGP8760”), and the grinding was completed when the thickness of the silicon wafer reached 30 μm.

After grinding, ultraviolet rays with an illumination intensity of 230 mW/cm2 and a light quantity of 500 mJ/cm2 are irradiated from the soft material side to the adhesive layer using an ultraviolet irradiation device (manufactured by LINTEC Corporation, device name “RAD-2000”). hardened. Using the same manufacturing method, for each workpiece processing protection sheet, two wafers with the workpiece processing protection sheet on which the adhesive layer was cured were prepared. One of them was used under normal conditions (peeling distance: 315 mm) using the tape peeling mechanism of a wafer mounter (manufactured by LINTEC Corporation, device name “RAD-2700”), and the other sheet was used under acceleration conditions (peeloff distance: 315 mm), which are more difficult than normal conditions ( The protective sheet for work processing was peeled from the silicon wafer at a peeling distance of 280 mm. The silicon wafer after peeling was observed, and the peeling state of the protective sheet for work processing was evaluated according to the following criteria.

○: The protective sheet for workpiece processing could be removed under both normal and accelerated conditions.

△: Under normal conditions, the protective sheet for work processing can be removed, but under accelerated conditions, it cannot be removed, and the protective sheet for work processing remains.

×: The protective sheet for workpiece processing remains without being removed under normal conditions.

The above measurements and evaluations were performed on the obtained samples (Examples 1 to 9 and Comparative Examples 1 and 2). The results are shown in Table 2.

[Table 2]

From Table 2, in the protective sheet for work processing, when the distance between the surface of the workpiece side of the adhesive layer and the surface of the antistatic layer on the substrate side is within the above-mentioned range and the substrate and the adhesive layer are in direct contact, peeling and charging occurs. It was confirmed that this was suppressed and the glue remaining in the adhesive layer could be suppressed.

1: Protection sheet for work processing
10: Description
20: Antistatic layer
30: Adhesive layer
40: Soft material

Claims (8)

A protective sheet for work processing in which an adhesive layer attached to the work, a base material, and an antistatic layer are laminated in this order,
The adhesive layer and the substrate are in direct contact,
A protective sheet for work processing, wherein the distance between the surface of the adhesive layer attached to the work and the surface of the antistatic layer located on the substrate side is 300 μm or less. According to paragraph 1,
The protective sheet for work processing further has a soft material,
A protective sheet for work processing, wherein the adhesive layer, the substrate, the antistatic layer, and the soft material are laminated in this order. According to claim 1 or 2,
A protective sheet for work processing, wherein the thickness of the base material is 10 μm or more and 80 μm or less. According to claim 1 or 2,
A protective sheet for work processing, wherein the antistatic layer has a thickness of 0.2 μm or more. According to claim 1 or 2,
A protective sheet for work processing, wherein the surface resistivity of the surface of the adhesive layer attached to the work is greater than 1.0 × 10 ¹³ Ω/□. According to claim 1 or 2,
A protective sheet for work processing, wherein the product of the Young's modulus of the protective sheet for work processing and the thickness of the protective sheet for work processing is 1.0 × 10 ⁵ N/m or more. According to claim 1 or 2,
A protective sheet for work processing that is attached to the surface of a work and used in the process of breaking the work into individual work pieces by grinding the back side of the work on which a groove is formed on the surface or a modified area is formed on the inside. A step of attaching the protective sheet for work processing according to claim 1 or 2 to the surface of a work having front and back surfaces;
A process of forming a groove on the surface of the work, or a process of forming a modified area inside the work,
A process of grinding a workpiece in which the protective sheet for work processing is attached to a surface and having the groove or the modified area formed thereon from the back side, and dividing the work into a plurality of individual pieces using the groove or the modified area as a starting point;
A method for producing piecework cargo, comprising a step of peeling the protective sheet for work processing from the plurality of piecework cargoes.