Workpiece processing film and workpiece processing method

Abstract

[Problem] To provide a workpiece processing film and a workpiece processing method with which it is possible to hold a workpiece while keeping an attachment surface clean by being attached to the workpiece during workpiece processing. [Solution] This workpiece processing film is used for processing a workpiece, wherein: the workpiece processing film is a substrate-less double-sided adhesive film; and when 10 μL of a toluene solvent, obtained by immersing a workpiece processing film having a size of 80 mm×100 mm in 15 g of toluene at 25ºC for 24 hours, is measured by gel permeation chromatography, and the measurement results are shown as a chromatogram in which the vertical axis is a detection voltage and the horizontal axis is an elution time from the introduction of the toluene solvent to the elution from a column, the peak area of a detection component from an elution time corresponding to a time when the number-average molecular weight in terms of standard polystyrene is 2,500,000 to an elution time corresponding to a time when the number-average molecular weight in terms of standard polystyrene is 200 is at most 4,000 mV∙sec.

Description

Work processing film and work processing method

[0001] The present invention relates to a work processing film and a work processing method. In particular, it relates to a work processing film attached to a surface of a work that requires low contamination during work processing, and a method for processing a work using the work processing film.

[0002] A chip on which a circuit such as a semiconductor chip is formed is a work processed product obtained by processing (for example, dicing) a work (for example, a wafer) on which a plurality of circuits are formed. As a method for mounting chips at high density, a method using chip-on-wafer (CoW) is known. In this method, after obtaining a chip-on-wafer by arranging a plurality of chips smaller in size than the wafer on the rotating surface of the wafer, the chip-on-wafer is diced to obtain a stacked chip.

[0003] Such chips are often arranged on a wafer through a thin adhesive layer such as a die bonding film. In recent years, as a method that does not use an adhesive layer, a method of directly bonding (direct transfer bonding: DTB) after treating the bonding surface of the chip and the bonding surface of the wafer is known.

[0004] Patent Document 1 discloses that a chip having a plasma-activated surface is pressed by a chip transfer member and adhered to the plasma-activated surface of a substrate.

[0005] Japanese Patent No. 6900006

[0006] When obtaining a chip as a processed product, in the previous process, processing such as grinding and singulation is performed on a work such as a wafer. In such a process, in order to protect and hold the work and the work processed product, an adhesive sheet for processing is attached to and peeled from the work and the work processed product. In particular, when the work is ground to make it thinner, when the adhesive sheet is peeled from the work after grinding, it is necessary to handle the thinned work alone and send it to the next process. Since the thinned work is not held by an adhesive sheet or the like, it is easily warped. As a result, cracks, cracks, etc. may occur in the work.

[0007] Furthermore, in a workpiece, the surfaces on which circuits (including various elements) are formed must be kept clean in order for them to perform as intended. For example, if the bonding surface of a workpiece (chip) obtained by pieceping a workpiece is not kept clean (contaminated) and is bonded to a wafer by DTB, air bubbles may form at the interface (bonding area) between the bonding surface of the workpiece and the bonding surface of the wafer due to the contamination of the bonding surface. These bubbles may remain as lifting or peeling (voids) even after direct bonding. If the area of ​​such voids becomes large, problems such as poor conductivity between the circuits of the workpiece and the circuits of the wafer may occur.

[0008] This invention has been made in view of the above circumstances, and aims to provide a workpiece processing film that can hold a workpiece while maintaining the cleanliness of the application surface by being attached to the workpiece during processing, and a workpiece processing method using the workpiece processing film.

[0009] The embodiments of the present invention are as follows.

[0010] [1] A workpiece processing film used for processing workpieces, wherein the workpiece processing film is a substrate-less double-sided adhesive film, and the workpiece processing film is subjected to the following immersion test, and the peak area of ​​the detected component calculated by performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) A workpiece processing film having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent that the workpiece processing film came into contact with. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

[0011] [2] The workpiece processing film is the workpiece processing film described in [1], wherein the workpiece processing film is energy ray curable.

[0012] [3] The workpiece is a workpiece for manufacturing a workpiece that is directly joined, as described in [1] or [2].

[0013] [4] A workpiece processing film according to any one of [1] to [3], wherein the adhesive strength to the silicon wafer is 500 mN / 25 mm or less.

[0014] [5] A method for processing a workpiece, comprising the steps of: attaching a workpiece processing film described in any of [1] to [4] to the surface of a workpiece having a surface and a back surface opposite to the surface; forming grooves on the surface of the workpiece to which the workpiece processing film is attached, or forming a modified layer region inside the workpiece; laminating a back grind sheet on the workpiece processing film after forming grooves or a modified layer region; grinding the back surface of the workpiece to which the workpiece processing film and the back grind sheet are laminated on the surface and grooves are formed on the surface or a modified layer region is formed inside, thereby separating the workpiece into individual pieces starting from the grooves or modified layer region; and peeling off the workpiece processing film and the back grind sheet from the workpiece after back grinding.

[0015] [6] The workpiece processing method according to [5], wherein the workpiece processing film is energy ray curable, and after the step of separating the workpiece into individual pieces, and before the step of peeling off the workpiece processing film and the back grind sheet, the workpiece processing film is irradiated with energy rays to cure the workpiece processing film.

[0016] [7] The workpiece processing method described in [5] or [6], wherein the step of peeling off the workpiece processing film and back grind sheet is performed after the adhesive sheet has been attached to the back surface of the workpiece after back surface grinding.

[0017] [8] A method for processing a workpiece as described in any of [5] to [7], wherein the workpiece is a workpiece for manufacturing a workpiece to be directly joined.

[0018] According to the present invention, a workpiece processing film can be attached to a workpiece during processing, thereby maintaining the cleanliness of the attachment surface while holding the workpiece in place, and a method for processing a workpiece using the workpiece processing film can be provided.

[0019] Figure 1 is a schematic cross-sectional view showing an example of a workpiece processing sheet equipped with a workpiece processing film according to this embodiment. Figure 2 is a diagram illustrating a method for calculating the peak area after GPC measurement of components derived from the workpiece processing film. Figure 3A is a schematic cross-sectional view illustrating the process of attaching the workpiece processing film according to this embodiment to a wafer (workpiece). Figure 3B is a schematic cross-sectional view illustrating the process of forming grooves on the surface of a wafer (workpiece) to which the workpiece processing film according to this embodiment has been attached. Figure 4A is a schematic cross-sectional view illustrating the process of grinding the back surface of a wafer (workpiece) to which the workpiece processing film according to this embodiment has been attached and grooves have been formed. Figure 4B is a schematic cross-sectional view illustrating the process of separating a wafer (workpiece) into individual pieces by grinding the back surface of the wafer (workpiece). Figure 5A is a schematic cross-sectional view illustrating the process of attaching an adhesive sheet to the back surface of a plurality of chips (workpieces). Figure 5B is a schematic cross-sectional view illustrating the process of peeling off the workpiece processing film and backgrind sheet according to this embodiment from a plurality of chips (workpieces) to which an adhesive sheet has been attached to the back surface. Figure 6 is a schematic cross-sectional diagram illustrating how multiple chips (workpieces) are transferred to a carrier sheet. Figures 7(A) and 7(B) are schematic cross-sectional diagrams illustrating the process of directly bonding chips (workpieces) to a wafer. Figure 8 is a schematic cross-sectional diagram of a chip-on-wafer where chips (workpieces) are directly bonded to the wafer.

[0020] The present invention will be described in detail below with reference to the drawings, based on specific embodiments. First, the main terms used in this specification will be explained.

[0021] A workpiece refers to a plate-like body to which a workpiece processing film is attached and then processed. Examples of workpieces include circular wafers (including those having an orientation flat), rectangular panel-level packages, and strips (strip-shaped substrates) with molded resin encapsulation. Among these, wafers are preferred from the viewpoint of easily obtaining the effects of the present invention. Wafers may be semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphate wafers, or insulating wafers such as glass wafers, lithium tantalate wafers, and lithium niobate wafers. They may also be reconfigured wafers made of resin and semiconductors used in the manufacture of fan-out packages, etc. From the viewpoint of easily obtaining the effects of the present invention, semiconductor wafers or insulating wafers are preferred as wafers, and semiconductor wafers are more preferred.

[0022] Workpiece segmentation refers to dividing a workpiece into circuits (including various elements) to obtain processed parts. For example, if the workpiece is a wafer, the processed part is a chip; if the workpiece is a panel-level package or a strip (a strip-shaped substrate) with molded resin encapsulation, the processed part is a semiconductor package.

[0023] The "front surface" of a workpiece refers to the surface on which circuits, electrodes, etc. are formed, the surface on which the same number of circuits, electrodes, etc. are formed as on the other surface (back surface), or the surface on which circuits, electrodes, etc. are planned to be formed. The "back surface" of a workpiece refers to the surface on which circuits, electrodes, etc. are not formed, the surface on which the same number of circuits, electrodes, etc. are formed as on the other surface (front surface), or the surface on which circuits, electrodes, etc. are not planned to be formed.

[0024] DBG (Dicing Before Grinding) is a method in which grooves of a predetermined depth are formed on the surface side of a workpiece, and then the workpiece is ground from the back side, thereby breaking down the workpiece into individual pieces. The grooves formed on the surface side of the workpiece are created by methods such as blade dicing, laser dicing, and plasma dicing.

[0025] The pre-grinding stealth dicing (registered trademark) method is a variation of DBG, in which a fragile modified layer region is created inside the workpiece (e.g., wafer) using a laser, and cracks originating from the modified layer region are propagated by stress during back-side grinding of the workpiece, thereby fragmenting the workpiece into individual pieces.

[0026] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

[0027] "Energy rays" refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

[0028] A release sheet is a sheet that supports an adhesive in a removable manner. The term "sheet" is used as a concept that includes films, without limiting the thickness.

[0029] In descriptions of compositions such as adhesive compositions, the mass ratios are based on the active ingredient (solid content), and unless otherwise specified, the solvent is not included.

[0030] (1. Film for workpiece processing) The film for workpiece processing is a film used when processing a workpiece. An example of a workpiece is one in which circuits, electrodes, etc. are formed on at least one surface. In such a workpiece, the other surface may not have circuits, electrodes, etc. formed on it, or electrodes such as through electrodes may be formed on it. The surface may be the surface in which the circuits, etc. are exposed, or it may be the main surface of a protective layer formed to protect the circuits, etc. Also, electrodes may be formed on the circuits, etc. In this embodiment, the workpiece is preferably a workpiece for manufacturing a workpiece that will be directly joined. That is, the film for workpiece processing according to this embodiment is preferably used to process a workpiece for manufacturing a workpiece that will be directly joined.

[0031] In this embodiment, examples of workpiece processing include grinding of the workpiece (e.g., back grinding of the workpiece) and dicing of the workpiece. Processing that integrates back grinding and dicing of the workpiece is also exemplified. In such processing, DBG, pre-grinding stealth dicing method, etc., can be employed, and the wafer is diced by forming grooves or modified layer regions on the wafer and then performing back grinding.

[0032] In back grinding of workpieces, or in DBG (Deep Back Grinding) or pre-grinding stealth dicing methods, a back grind sheet having a base material and an adhesive layer may be attached to the surface of the workpiece to protect it. Furthermore, since the surface of the workpiece is the circuit surface, it needs to be kept clean in order for the circuit to perform its intended function or performance.

[0033] However, if the rigidity of the back grind sheet base material is low, there is a problem that cracks or fissures may occur in the workpiece or the pieced workpiece when the workpiece becomes thinner due to back grinding. On the other hand, even if the rigidity of the back grind sheet base material is high, the surface of the workpiece may be contaminated by components derived from the back grind sheet base material or adhesive layer. When the surface of the workpiece is contaminated, there is a problem that the pieced workpiece (e.g., chips) obtained by pieced workpieces may not be able to perform the intended function or performance.

[0034] The workpiece processing film according to this embodiment has the configuration and physical properties described later, so by applying it to a surface of a workpiece that needs to be protected (a surface on which circuits, etc., are formed), contamination of that surface is suppressed and the workpiece can be held in place. Furthermore, the workpiece processing film according to this embodiment is preferably used together with a back grind sheet used for back grinding of the workpiece in order to suppress cracking of the workpiece, etc.

[0035] (1.1. Structure of the film for workpiece processing) The film for workpiece processing according to this embodiment is a substrate-free double-sided adhesive film. That is, the film for workpiece processing is composed of a layered adhesive (adhesive layer) and has no substrate. In this embodiment, the film for workpiece processing is usually used in the form of a sheet for workpiece processing from the perspective of handling properties.

[0036] Fig. 1 shows an example of the sheet 10 for workpiece processing. In Fig. 1, the film 1 for workpiece processing has two opposing main surfaces 1a and 1b. On the main surface 1a, a first release sheet 21 for supporting the film 1 for workpiece processing is disposed, and on the main surface 1b, a second release sheet 22 for supporting the film 1 for workpiece processing is disposed. By having such a configuration, the handling property of the film for workpiece processing is improved.

[0037] In the sheet 1 for workpiece processing shown in Fig. 1, it is preferable to increase the peeling force of one release sheet (for example, the first release sheet 21) to make it a double-peeling type release sheet, and to reduce the peeling force of the other release sheet (for example, the second release sheet 22) to make it a light-peeling type release sheet.

[0038] The adhesive may be composed of one layer (single layer) or may be composed of two or more layers. When the adhesive has a plurality of layers, these plurality of layers may be the same as or different from each other, and the combination of the layers constituting these plurality of layers is not particularly limited.

[0039] The thickness of the film for workpiece processing (adhesive) can be set according to the use of the film for workpiece processing and the like. In this embodiment, the thickness of the film for workpiece processing may be 1 μm or more and 100 μm or less, or may be 2 μm or more and 50 μm or less, or may be 3 μm or more and 20 μm or less.

[0040] Note that the thickness of the film for workpiece processing means the thickness of the entire film for workpiece processing. For example, the thickness of the film for workpiece processing composed of a plurality of adhesive layers means the total thickness of all the layers constituting the film for workpiece processing.

[0041] (1.2. Peak area after GPC measurement of components derived from workpiece processing film) The inventors hypothesized that the above-mentioned contamination of the workpiece surface was caused by residue resulting from the migration of some of the components of the adhesive sheet (adhesive layer, substrate, etc.) attached to the surface. Since such residue is impossible to observe visually, it was hypothesized that such components are easily migrated components that exist independently (freely) from the adhesive sheet attached to the surface. In this embodiment, the above-mentioned easily migrated components are controlled in the workpiece processing film attached to the surface.

[0042] In this embodiment, a method is employed to evaluate easily migratory components by immersing the workpiece processing film in a solvent and evaluating the solvent after immersion using gel permeation chromatography (GPC). Components that readily dissolve into the solvent upon immersion are considered easily migratory components. It is presumed that such components, for example, increase the area of ​​voids generated during direct bonding.

[0043] In this embodiment, first, the following immersion test is performed. A work processing film (adhesive) having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C as a solvent for 24 hours. As the work processing film to be subjected to the immersion test, a work processing film having the above size may be used, or a predetermined work processing film may be processed to obtain a work processing film having a size of 80 mm × 100 mm and used. When the work processing film is energy ray curable, the work processing film after energy ray irradiation is used. The work processing film having a size of 80 mm × 100 mm is immersed so that the entire surface comes into contact with toluene. The thickness of the work processing film is arbitrary as long as the entire surface can be immersed in toluene. Further, in this embodiment, in consideration of handling properties and the like, it is preferable to wrap the work processing film with a mesh sheet or the like made of a material insoluble in toluene and immerse it. After the immersion is completed, the work processing film and, if necessary, the mesh sheet or the like are removed from toluene to obtain the toluene solvent that has come into contact with the work processing film. When a constituent component elutes from the work processing film by immersion, the obtained toluene solvent contains the component.

[0044] Next, the obtained toluene solvent is analyzed by gel permeation chromatography (GPC). In this embodiment, the following GPC measurement principle is used to evaluate components that are likely to migrate.

[0045] When a sample solution containing the target molecule is introduced into a column packed with porous granular packing material, the distance the molecules travel through the column differs depending on their size. Therefore, the time it takes for molecules to reach the column outlet after being introduced (elution time) differs depending on their molecular size. For example, larger molecules have difficulty entering the pores of the packing material and are discharged from the column without reaching the deepest part of the column (without penetration). As a result, the elution time is short. On the other hand, smaller molecules can easily enter the pores of the packing material and are discharged from the column after reaching the deepest part of the column (after penetration). As a result, the elution time is long. Therefore, the molecular size can be measured by the difference in elution time from the column.

[0046] Molecules eluted from the column are detected by a detector. An example of a detector is an RI detector. When many molecules of the same size are detected, the detection intensity increases. Therefore, by plotting the elution time from the column against the detection intensity, a distribution of molecules by size (chromatogram) can be obtained. Figure 2 shows an example of a chromatogram. In Figure 2, the detection voltage is shown on the vertical axis as the detection intensity.

[0047] Furthermore, a calibration curve showing the relationship between elution time and molecular weight is created using standard samples with known molecular weights. From the created calibration curve, the relationship between elution time and the molecular weight of the standard sample is calculated. In this embodiment, polystyrene is used as the standard sample, and the elution time is correlated with the number-average molecular weight (Mn) of standard polystyrene. By using the number-average molecular weight of the molecule to be detected, evaluation can be performed with high sensitivity.

[0048] In this embodiment, 10 μL is taken from the toluene solvent after the immersion test, and the 10 μL of toluene solvent is measured by gel permeation chromatography. From the measurement results, a chromatogram is obtained with the detection voltage on the vertical axis and the elution time on the horizontal axis. If the toluene solvent after the immersion test does not contain components derived from the workpiece processing film, the detection voltage will remain constant regardless of the elution time (baseline B in Figure 2).

[0049] On the other hand, if the toluene solvent after the immersion test contains components (detected components) derived from the workpiece processing film, the detection voltage changes relative to the baseline and forms a peak P, as shown in Figure 2, depending on the number-average molecular weight (elution time) and amount of the component in terms of standard polystyrene. Multiple peaks may be present. The amount of the detected component can be calculated as the peak area from the chromatogram shown in Figure 2. Specifically, the peak area is calculated as the area enclosed by the baseline and the line indicating the change in detection voltage in the chromatogram.

[0050] In this embodiment, the peak area of ​​the detected component (hatched area PA in Figure 2) is calculated in the obtained chromatogram within the range from the elution time corresponding to a standard polystyrene-equivalent number-average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene-equivalent number-average molecular weight of 200. The peak area is 4000 mV·s or less.

[0051] The peak area reflects the amount of the detected component whose number-average molecular weight is in the range of 2 to 2.5 million. Furthermore, by limiting the range of the number-average molecular weight, the molecular weight of the detected component reflected in the peak area is limited to a predetermined range, thus eliminating the influence of toluene, etc., used in the immersion test on the peak area. Therefore, a peak area of ​​4000 mV·s or less indicates that the amount of the component with a number-average molecular weight in the range of 2 to 2.5 million is below a predetermined amount. By having a low amount of such components, residue derived from the workpiece processing film can be suppressed. In the examples described later, the corresponding elution time when the standard polystyrene-equivalent number-average molecular weight is 200 is 960 seconds (16 minutes), and the corresponding elution time when the standard polystyrene-equivalent number-average molecular weight is 2.5 million is 522 seconds (8.7 minutes).

[0052] The peak area is preferably small, and may be 3000 mV·s or less, 2000 mV·s or less, 1000 mV·s or less, or 300 mV·s or less. The lower limit of the peak area is 0 mV·s. The peak area can be calculated, for example, using analysis software attached to the GPC measurement device. If the workpiece processing film is energy ray curable, the peak area is the peak area of ​​the workpiece processing film (adhesive layer after curing) after energy ray irradiation.

[0053] Furthermore, in the chromatogram, it is preferable that the peak area of ​​the detected component in a range narrower than the above range for the number-average molecular weight equivalent to standard polystyrene is within a predetermined range. Specifically, it is preferable that the peak area of ​​the detected component in the range from the elution time corresponding to a number-average molecular weight equivalent to 10,000 to the elution time corresponding to a number-average molecular weight equivalent to 200 is 4,000 mV·s or less. By keeping the amount of components with number-average molecular weights in the range of 200 to 10,000 below a predetermined amount, residue originating from the workpiece processing film can be suppressed. The elution time corresponding to a number-average molecular weight equivalent to 10,000 is 750 seconds (12.5 minutes).

[0054] The peak area is preferably small, and may be 3000 mV·s or less, 2000 mV·s or less, 1000 mV·s or less, or 300 mV·s or less. The lower limit of the peak area is 0 mV·s.

[0055] (1.3. Gel fraction of workpiece processing film) In this embodiment, the gel fraction of the workpiece processing film is preferably 90% or more. This strengthens the solid properties of the crosslinked structure in the workpiece processing film, thereby suppressing the amount of easily migrating components. As a result, it becomes easier to set the peak area of ​​the components derived from the workpiece processing film after GPC measurement within the range described above. The gel fraction may be 93% or more, 95% or more, or 97% or more. Note that if the workpiece processing film is energy ray curable, the gel fraction is the gel fraction after energy ray irradiation.

[0056] In this embodiment, the method for measuring the gel fraction of the workpiece processing film can utilize the immersion test described above. Specifically, a workpiece processing film having a size of 80 mm x 100 mm is immersed in 15 g of toluene at 25°C for 24 hours. At this time, it is preferable to wrap the workpiece processing film with the mesh sheet or the like described above. After the immersion is complete, the workpiece processing film and, if necessary, the mesh sheet or the like are recovered from the toluene, and the gel fraction can be calculated from the mass of the workpiece processing film before and after immersion, and, if necessary, the mass of the mesh sheet or the like. A specific method for measuring the gel fraction will be described in the examples below.

[0057] (1.4. Adhesion of the workpiece processing film) In this embodiment, it is preferable that the adhesive force when the workpiece processing film is peeled off from the silicon wafer is 500 mN / 25 mm or less. This makes it easier to suppress the formation of visible adhesive residue that remains on the workpiece when peeling the workpiece processing film together with the backgrind sheet from the workpiece or workpiece. Note that if the workpiece processing film is energy ray curable, this adhesive force is the adhesive force after energy ray curing.

[0058] The adhesive strength may be 400 mN / 25 mm or less, 350 mN / 25 mm or less, or 250 mN / 25 mm or less. The method for measuring the adhesive strength will be explained in the examples described later.

[0059] (2. Composition of the adhesive) The adhesive constituting the workpiece processing film may be any adhesive that satisfies the above-described physical properties. In this embodiment, it is preferable that the adhesive is formed using an adhesive composition. Examples of adhesives include acrylic adhesives, urethane adhesives, rubber adhesives, silicone adhesives, polyester adhesives, and polyvinyl ether adhesives. In this embodiment, it is preferable that the adhesive is an acrylic adhesive.

[0060] The adhesive may be energy ray curable, energy ray non-curable, energy ray foamable, or heat foamable. In this embodiment, the adhesive is preferably energy ray curable. Since the adhesive strength of an energy ray curable adhesive decreases upon energy ray irradiation, when peeling the workpiece processing film together with the back grind sheet from the workpiece or workpiece, irradiating the adhesive constituting the workpiece processing film with energy rays makes it easier to peel off the workpiece processing film and suppresses adhesive residue caused by the workpiece processing film.

[0061] In this embodiment, the energy-ray curable adhesive may be mainly composed of an energy-ray curable polymer, or it may be mainly composed of a mixture of an energy-ray curable polymer and an energy-ray curable polyfunctional monomer and / or oligomer. Furthermore, it may be mainly composed of a mixture of an energy-ray curable polymer and an energy-ray curable polyfunctional monomer and / or oligomer.

[0062] In this embodiment, the energy-ray curable adhesive is preferably an acrylic adhesive formed using an acrylic adhesive composition. The acrylic adhesive composition contains an acrylic polymer.

[0063] The acrylic polymer may be a homopolymer formed from one type of acrylic monomer, a copolymer formed from multiple types of acrylic monomers, or a copolymer formed from one or more types of acrylic monomers and monomers other than acrylic monomers.

[0064] First, we will explain the case where the energy-ray curable adhesive is mainly composed of an acrylic polymer that has energy-ray curability.

[0065] The energy-ray curable acrylic polymer is preferably a (meth)acrylic acid ester (co)polymer (A) (hereinafter sometimes referred to as "energy-ray curable polymer (A)") in which an energy-ray curable functional group (energy-ray curable group) is introduced into the side chain. This energy-ray curable polymer (A) is preferably obtained by reacting an acrylic copolymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a substituent bonded to the functional group.

[0066] The acrylic copolymer (a1) consists of structural units derived from functional group-containing monomers and structural units derived from (meth)acrylic acid ester monomers or their derivatives.

[0067] The functional group-containing monomer as a constituent unit of the acrylic copolymer (a1) is preferably a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, amino group, substituted amino group, or epoxy group within its molecule.

[0068] More specific examples of the above-mentioned functional group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc., which can be used individually or in combination of two or more.

[0069] As the (meth)acrylic acid ester monomer constituting the acrylic copolymer (a1), alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and benzyl (meth)acrylates with an alkyl group having 1 to 20 carbon atoms are used. Among these, alkyl (meth)acrylates with an alkyl group having 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are particularly preferred.

[0070] The acrylic copolymer (a1) typically contains 3 to 100% by mass, preferably 5 to 40% by mass, of structural units derived from the functional group-containing monomer, and typically contains 0 to 97% by mass, preferably 60 to 95% by mass, of structural units derived from (meth)acrylic acid ester monomer or its derivative.

[0071] The acrylic copolymer (a1) can be obtained by copolymerizing a functional group-containing monomer as described above with a (meth)acrylic acid ester monomer or its derivative by a conventional method. In addition to these monomers, dimethylacrylamide, vinyl formate, vinyl acetate, styrene, etc., may also be copolymerized.

[0072] An energy-ray curable polymer (A) is obtained by reacting an acrylic copolymer (a1) having the above-mentioned functional group-containing monomer units with an unsaturated group-containing compound (a2) having substituents bonded to the functional group.

[0073] The substituents of the unsaturated group-containing compound (a2) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic copolymer (a1). For example, when the functional group is a hydroxyl group, an amino group, or a substituted amino group, an isocyanate group or an epoxy group is preferred as the substituent, and when the functional group is an epoxy group, an amino group, a carboxyl group, or an aziridinyl group is preferred as the substituent.

[0074] Furthermore, the unsaturated group-containing compound (a2) contains 1 to 5, preferably 1 to 2, energy-ray polymerizable carbon-carbon double bonds per molecule. Specific examples of such unsaturated group-containing compounds (a2) include, for example, 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by the reaction of a diisocyanate compound or polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by the reaction of a diisocyanate compound or polyisocyanate compound with a polyol compound with hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

[0075] The unsaturated group-containing compound (a2) is usually used in a ratio of 10 to 100 mol%, preferably 20 to 95 mol%, relative to the functional group-containing monomer of the acrylic copolymer (a1).

[0076] In the reaction between the acrylic copolymer (a1) and the unsaturated group-containing compound (a2), the reaction temperature, pressure, solvent, time, presence or absence of a catalyst, and type of catalyst can be appropriately selected depending on the combination of functional groups and substituents. As a result, the functional groups present in the acrylic copolymer (a1) react with the substituents in the unsaturated group-containing compound (a2), introducing unsaturated groups into the side chains of the acrylic copolymer (a1), and yielding an energy-ray curable polymer (A).

[0077] The weight-average molecular weight of the energy-ray curable polymer (A) obtained in this manner is preferably 10,000 or more, particularly preferably 150,000 to 1,500,000, and even more preferably 200,000 to 1,000,000. The above weight-average molecular weight (Mw) is a standard polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0078] Even if the energy-ray curable adhesive mainly consists of an energy-ray curable polymer (A), the energy-ray curable adhesive may further contain an energy-ray curable monomer and / or oligomer (B).

[0079] As the energy-ray curable monomer and / or oligomer (B), for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

[0080] Examples of such energy-ray curable monomers and / or oligomers (B) include monofunctional acrylic acid esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, polyfunctional acrylic acid esters such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and dimethylol tricyclodecane di(meth)acrylate, as well as polyester oligo(meth)acrylate and polyurethane oligo(meth)acrylate.

[0081] When an energy-ray-curable monomer and / or oligomer (B) is incorporated, the content of the energy-ray-curable monomer and / or oligomer (B) in the energy-ray-curable adhesive is preferably 5 to 80% by mass, and particularly preferably 20 to 60% by mass.

[0082] In this case, when ultraviolet light is used as the energy ray for curing the energy ray-curable adhesive, it is preferable to add a photopolymerization initiator (C). This reduces the polymerization curing time and the amount of light irradiation.

[0083] Examples of photopolymerization initiators (C) include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexylphenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, and 2,2-dimethoxy-1,2-diphenylethane-1-one. These may be used individually or in combination of two or more.

[0084] The photopolymerization initiator (C) is preferably used in an amount of 0.1 to 10 parts by mass, particularly 0.5 to 6 parts by mass, per 100 parts by mass of the energy-ray curable polymer (A) (or, if an energy-ray curable monomer and / or oligomer (B) is included, per 100 parts by mass of the total amount of the energy-ray curable polymer (A) and the energy-ray curable monomer and / or oligomer (B)).

[0085] In energy-ray curable adhesives, other components may be added as appropriate, in addition to the components mentioned above. Examples of other components include polymer components or oligomer components (D) that do not possess energy-ray curability, crosslinking agents (E), and release agents (F).

[0086] Examples of polymer components or oligomer components (D) that do not possess energy ray curability include polyacrylic acid esters, polyesters, polyurethanes, polycarbonates, and polyolefins, with a preferred polymer or oligomer having a weight-average molecular weight (Mw) of 3,000 to 2,500,000.

[0087] As the crosslinking agent (E), a polyfunctional compound that has reactivity with the functional groups of the energy ray curable polymer (A) can be used. Examples of such polyfunctional compounds include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, aziridine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, metal alkoxide compounds, metal chelate compounds, metal salts, ammonium salts, and reactive phenolic resins.

[0088] By incorporating a polymer component or oligomer component (D) that does not possess energy ray curability and a crosslinking agent (E) into an energy ray curable adhesive, the tackiness and peelability before curing, strength after curing, adhesion to other layers, and storage stability can be improved. The amounts of components (D) and (E) are not particularly limited and are appropriately determined in the range of 0 to 40 parts by mass per 100 parts by mass of the energy ray curable polymer (A).

[0089] Examples of the easy-release agent (F) include free epoxy components, alkylene glycol-based components, polymerizable branched polymer components, and silicone-based components. When the energy ray-curable adhesive contains the easy-release agent (F), it tends to become easier to peel off silicon chips from the workpiece processing sheet, especially silicon chips with a thickness of 50 μm or less.

[0090] The free epoxy component is preferably an epoxy group-containing compound that is included in the adhesive layer in a free state. The free state means that the epoxy group-containing compound is substantially unreacted with the energy ray-curable polymer (A) and is not incorporated into the matrix of the gel component of the energy ray-curable polymer (A).

[0091] Examples of epoxy group-containing compounds include compounds having at least one epoxy group in their molecule and capable of heat curing with an epoxy curing agent. Examples include bisphenol A type, bisphenol F type, bisphenol S type, biphenyl type, phenol novolac type, and cresol novolac type epoxy resins. The molecular weight of the epoxy group-containing compound is preferably relatively low, preferably 300 to 2000, and more preferably 350 to 1000.

[0092] When the release agent (F) contains a free epoxy component, it is preferable that the free epoxy component be used in amounts of 0.5 to 50 parts by mass, and more preferably 2.5 to 25 parts by mass, in a total of 100 parts by mass of all components constituting the adhesive layer.

[0093] The alkylene glycol component is preferably an alkylene glycol-modified rosin ester obtained by esterifying rosins, polyalkylene glycol monoalkyl ethers, polyhydric alcohols, and α,β-unsaturated carboxylic acids, at least one of polyethylene glycol and polytetramethylene ether glycol having a number average molecular weight of 200 or more and 3000 or less, and polypropylene glycol having a number average molecular weight of 200 or more and 3000 or less, and more preferably an alkylene glycol-modified rosin ester.

[0094] When the adhesive layer contains an alkylene glycol-based component as an easy-release agent (F), it is preferable that the alkylene glycol-based component is used in an amount of 0.05 to 10 parts by mass, and more preferably 0.05 to 5 parts by mass, in a total of 100 parts by mass of all components constituting the adhesive layer.

[0095] The polymerizable branched polymer component is an energy-ray curable monomer and / or oligomer (B) that is a polymer having energy-ray polymerizable groups and a branched structure. The polystyrene-equivalent weight-average molecular weight (Mw) of the polymerizable branched polymer component is preferably 1,000 or more and 100,000 or less, and more preferably 3,000 or more and 30,000 or less. The number of energy-ray polymerizable groups in one molecule of the polymerizable branched polymer component is not limited.

[0096] When the peeling agent (F) includes a polymerizable branched polymer component, it is preferable that the polymerizable branched polymer component is used in an amount of 0.01 parts by mass or more and less than 8.0 parts by mass, and more preferably 0.1 parts by mass or more and 5.0 parts by mass or less, per 100 parts by mass of the energy ray curable polymer (A).

[0097] The silicone component is preferably a silicone-based oil or silicone acrylate. When the adhesive (F) contains a silicone component, it is preferable that the silicone component is used in an amount of 0.01 to 1.0 parts by mass, and more preferably 0.05 to 0.5 parts by mass, out of a total of 100 parts by mass of all components constituting the adhesive layer.

[0098] Next, we will describe a case in which the energy-ray curable adhesive mainly consists of a mixture of a polymer component that does not possess energy-ray curability and an energy-ray curable polyfunctional monomer and / or oligomer.

[0099] As a polymer component that does not possess energy-ray curability, for example, a component similar to the acrylic copolymer (a1) described above can be used. The content of the polymer component that does not possess energy-ray curability in the energy-ray curable adhesive is preferably 20 to 99.9% by mass, and particularly preferably 30 to 80% by mass.

[0100] As the energy-ray curable polyfunctional monomer and / or oligomer, the same as component (B) described above is selected. The blending ratio of the non-energy-ray curable polymer component to the energy-ray curable polyfunctional monomer and / or oligomer is preferably 10 to 150 parts by mass of the polyfunctional monomer and / or oligomer per 100 parts by mass of the polymer component, and particularly preferably 25 to 100 parts by mass of the polyfunctional monomer and / or oligomer.

[0101] In this case as well, a photopolymerization initiator (C) and a crosslinking agent (E) can be appropriately added, as described above. Furthermore, the peeling agent (F) can also be added in the amounts described above.

[0102] (3. Method for manufacturing workpiece processing film and workpiece processing sheet) The method for manufacturing the workpiece processing film and workpiece processing sheet according to this embodiment can employ known methods.

[0103] First, an adhesive composition for forming a workpiece processing film (adhesive) is prepared, for example, an adhesive composition containing the above-mentioned components, or a composition obtained by diluting the adhesive composition with a solvent or the like (hereinafter sometimes referred to as the adhesive coating agent).

[0104] Examples of solvents include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

[0105] Next, an adhesive composition or a coating agent of the adhesive composition is applied to the release surface of a release sheet (for example, a first release sheet) by a known method, and if necessary, heated and dried to form an adhesive on the release sheet. This yields a workpiece processing film formed on the first release sheet.

[0106] By bonding the peel-treated surface of another release sheet (for example, a second release sheet) to the exposed surface of the workpiece processing film formed on the first release sheet, the workpiece processing sheet 10 shown in Figure 1 is obtained. The first and second release sheets are removed when the workpiece processing sheet is used.

[0107] (4. Method for processing workpieces and method for manufacturing processed workpieces) The workpiece processing film according to this embodiment is used for processing workpieces. In this embodiment, as a non-limiting example of the use of the workpiece processing film, a method of using the workpiece processing film together with a backgrind sheet when performing back grinding and framing of a workpiece as an integrated process will be described in more detail below.

[0108] The workpiece processing method according to this embodiment specifically comprises at least the following steps 1 to 5. The workpiece may also be a workpiece for manufacturing a workpiece that will be directly joined. Step 1: A step of attaching the above-mentioned workpiece processing film to the surface of a workpiece having a surface and a back surface opposite to the surface. Step 2: A step of forming grooves on the surface of the workpiece to which the workpiece processing film has been attached, or a step of forming a modified layer region inside the workpiece. Step 3: A step of laminating a back grind sheet on the workpiece processing film after forming grooves or a modified layer region. Step 4: A step of grinding the back surface of the workpiece to which the workpiece processing film and back grind sheet have been laminated on the surface and grooves have been formed on the surface or a modified layer region has been formed inside, thereby separating the workpiece into individual pieces starting from the grooves or modified layer region. Step 5: A step of peeling off the workpiece processing film and back grind sheet from the workpiece after back surface grinding.

[0109] The following describes in detail each step of the processing method for the above-mentioned workpiece. In the following explanation, a wafer will be used as a specific example of the workpiece.

[0110] (Step 1) In Step 1, as shown in Figure 3A, the workpiece processing film 1 according to this embodiment is attached to the surface 50a of the wafer 50. Circuits, sensors, etc. are formed on the surface of the wafer. The formed circuits, etc. may be exposed, or a protective layer may be formed to protect the circuits, etc. When using the workpiece processing sheet 10 shown in Figure 1, the second release sheet 22 is peeled off, the workpiece processing film 1 is attached to the surface, and then the first release sheet 21 is peeled off.

[0111] By attaching the workpiece processing film to the surface of the wafer, the wafer surface (protected surface) is protected, and the migration of components derived from the workpiece processing film to the surface is suppressed, thereby keeping the wafer surface clean. 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 280 to 780 μm.

[0112] (Step 2) In Step 2, grooves are formed on the surface of the wafer, or a modified layer region is formed inside the wafer. In Step 2, the grooves and modified layer region are formed along the dividing lines that will be used when the wafer is divided and made into individual pieces in Step 4, which will be described later.

[0113] When forming grooves on the surface of a wafer, as shown in Figure 3B, the grooves 55 penetrate the workpiece processing film 1 and are formed to a depth shallower than the thickness of the wafer 50. Therefore, a notch is formed in the workpiece processing film 1. Grooves can be formed by known dicing methods such as blade dicing, laser dicing, plasma dicing, and water dicing. In this embodiment, the workpiece processing method according to this embodiment is preferred when forming grooves by blade dicing.

[0114] When forming grooves on a wafer by attaching a laminate (protective sheet) of a highly rigid substrate and an adhesive layer to the wafer surface instead of the workpiece processing film according to this embodiment, substrate chips are generated during groove formation. These chips can penetrate the adhesive in contact with the wafer surface, contaminating the surface, or causing adhesive residue when the workpiece processing film is peeled off. Furthermore, when forming grooves by blade dicing or laser dicing, slight irregularities in the cross-section of the formed grooves can cause the substrate, softened by heat during dicing, to become entangled, worsening the peelability. Therefore, the substrate-less nature of the workpiece processing film according to this embodiment can suppress the above problems.

[0115] Furthermore, when forming grooves by blade dicing, the process is usually carried out while supplying cooling water. However, since the workpiece surface is protected by a workpiece processing film, the intrusion of cooling water and other substances into the surface is suppressed.

[0116] When a modified layer region is formed inside a wafer, the modified layer region is a brittle part within the wafer. After the formation of the modified layer region, grinding thins the wafer, or the force applied during grinding causes the modified layer region of the wafer to break down, becoming the starting point for fragmentation into chips.

[0117] The modified layer region is formed by irradiating the wafer with a laser focused on the inside of the wafer, and the modified layer region is formed inside the wafer. The laser irradiation may be performed from the front side or the back side of the wafer. Furthermore, the laser irradiation may be performed before or after step 1. If the laser irradiation is performed from the wafer surface after step 1, the laser will be irradiated onto the wafer through the workpiece processing film. Even when forming the modified layer region, the wafer surface is protected by the workpiece processing film, and the cleanliness of the surface is not affected by the processing environment.

[0118] (Step 3) In Step 3, as shown in Figure 4A, after Step 2, the backgrind sheet 30 is layered and bonded to the workpiece processing film 1 which is attached to the surface 50a of the wafer 50. In back grinding of the wafer, which will be described later, the backgrind sheet is usually attached to the surface of the wafer. On the other hand, in this embodiment, the workpiece processing film is already attached to the surface of the wafer in Step 1. Furthermore, as shown in Figure 3B, if grooves are formed on the surface of the wafer, the backgrind sheet 30 is laminated to the workpiece processing film 1 which has cuts formed on it, as shown in Figure 4A.

[0119] In this embodiment, as shown in Figure 4A, the backgrind sheet 30 preferably has a highly rigid base material 31 and an adhesive layer 32 formed on one side of the base material 31. The base material of the backgrind sheet is preferably a resin film with a tensile modulus of 500 MPa or more. The adhesive layer of the backgrind sheet is composed of a known adhesive.

[0120] Therefore, when the backgrind sheet is bonded to the workpiece processing film, the adhesive layer 32 of the backgrind sheet 30 is bonded to the workpiece processing film 1. Since the workpiece processing film is also made of adhesive, the workpiece processing film and the backgrind sheet adhere closely together. Consequently, by bonding the backgrind sheet to the wafer, the wafer surface is protected during the back grinding process described later, while the wafer is held stably.

[0121] (Step 4) In Step 4, the wafer 50 fixed to the backgrind sheet 30, as shown in Figure 4A, is placed on a chuck table (not shown) with its front surface 50a side facing up, and is held in place by the chuck table. This ensures that the workpiece processing film, wafer, and ring frame on the backgrind sheet are held in place by the chuck table. Subsequently, the back surface 50b of the wafer 50 is ground using, for example, a grinding wheel or the like provided by a grinding device (not shown).

[0122] As shown in Figure 4B, as back grinding progresses and the grinding surface reaches the tip of the groove, the wafer is fragmented, and multiple chips 51 are obtained as workpieces. The wafer may be completely fragmented, or only a portion of the wafer may be fragmented. At this time, the workpiece processing film 1 is also fragmented into the same shape as the chips 51. Since the fragmented wafer (multiple chips) is held by the back grinding sheet 30, the occurrence of damage and cracks is suppressed, and it maintains almost the same shape as the wafer before fragmentation.

[0123] The thickness of the wafer (pieced wafer) after back grinding is, for example, about 5 μm to 300 μm. By performing steps 1 to 4, multiple chips can be manufactured from a wafer as a workpiece. In other words, the workpiece processing method according to this embodiment includes a method for manufacturing workpieces.

[0124] (Step 5) In Step 5, the workpiece processing film and backgrind sheet are peeled off the wafer after back grinding. The workpiece processing film is composed of a substrate-less adhesive and adheres closely to the adhesive layer of the backgrind sheet. Therefore, when peeling off the backgrind sheet, the workpiece processing film follows the backgrind sheet sufficiently, and the workpiece processing film can be peeled off from the individual wafers without any visible residue of the workpiece processing film remaining on the individual wafers (without any adhesive residue).

[0125] Furthermore, if a protective sheet having a substrate and an adhesive layer is used instead of the workpiece processing film according to this embodiment, the adhesive layer of the backgrind sheet is attached to the substrate of the protective sheet. As a result, when the backgrind sheet is peeled off, the adhesive layer of the backgrind sheet tends to peel off from the substrate of the protective sheet, and the adhesive layer of the protective sheet does not follow the backgrind sheet well. Consequently, even after peeling off the backgrind sheet, a portion of the adhesive layer of the protective sheet tends to remain on the individual wafer pieces. Therefore, the workpiece processing film according to this embodiment, being a substrate-less double-sided adhesive film, peels off well from the individual workpiece pieces together with the backgrind sheet.

[0126] In this embodiment, if the workpiece processing film is energy ray curable, it is preferable to irradiate the workpiece processing film with energy rays to cure and shrink it, thereby reducing its adhesive strength to the adherend (wafer after backside grinding) before peeling off the workpiece processing film. That is, if the workpiece processing film is energy ray curable in step 5, it is preferable to have a step (step 6) in which the workpiece processing film is irradiated with energy rays to cure the workpiece processing film. This improves the peelability of the workpiece processing film.

[0127] Furthermore, in this embodiment, it is preferable to attach an adhesive sheet to the back surface of the wafer after back grinding, then peel off the workpiece processing film and back grind sheet, and transfer the wafer after back grinding to the adhesive sheet. That is, in step 5, as shown in Figure 5A, it is preferable to have a step (step 7) in which the adhesive layer 42 of the adhesive sheet 40 is attached to the back surface 51b of the plurality of chips 51, and the adhesive layer 42 is also attached to the ring frame 100, and then peel off the workpiece processing film 1 and back grind sheet 30 from the plurality of chips 51, as shown in Figure 5B. As a result, the plurality of chips 51 are attached to the adhesive sheet 40, making it easy to transport the chips to the next step as a whole without them falling apart. It is preferable that the adhesive layer of the adhesive sheet is energy ray curable. In this case, it is preferable to perform step 6 in step 7. In this embodiment, the adhesive sheet may be a pickup sheet or a carrier sheet.

[0128] (5. Method for joining workpieces) In this embodiment, the resulting workpieces (chips) have cracks and other defects suppressed, and the surface (circuit surface) of the workpieces is kept clean, so they can be suitably used for direct joining, for example. The method for directly joining workpieces (DTB) will be described in detail below.

[0129] The method for joining workpieces preferably comprises the following steps 8 and 9: Step 8: A step of transferring the obtained workpieces to a carrier sheet. Step 9: A step of directly joining the workpieces to a wafer.

[0130] The following describes each step of the joining method for workpieces. A wafer will be used as a specific example of the workpiece, and a chip will be used as a specific example of the workpiece.

[0131] (Step 8) In Step 8, the multiple chips held on the backgrind sheet in Step 5 are transferred onto the carrier sheet. The carrier sheet is an example of the adhesive sheet in Step 7. The transfer to the carrier sheet can be performed in the same way as in Step 7, by attaching the carrier sheet to the back surface of the multiple chips and then peeling off the workpiece processing film and backgrind sheet from the surface of the multiple chips. As a result, as shown in Figure 6, the multiple chips 51 are transferred from the workpiece processing film and backgrind sheet to the carrier sheet 80. Therefore, if Step 5 has Step 7, Step 8 may be Step 7.

[0132] (Step 9) In Step 9, the chip is directly bonded to the wafer. Before direct bonding, it is preferable that the bonding surface (surface) of the chip and the bonding surface (circuit surface) of the wafer are treated to improve bonding properties. Such treatment may be a physical treatment or a chemical treatment. Specifically, plasma treatment to activate the bonding surface is an example.

[0133] As shown in Figure 7(A), the chip 51 held on the carrier sheet 80 is transported so that the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 face each other, and is positioned at the planned bonding location by an alignment mechanism (not shown). Next, as shown in Figure 7(B), the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 are brought into contact and fixed at the planned bonding location for bonding. An example of a method for bringing the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 into contact is to use a pressing mechanism 110 to press from the back surface 51b side (carrier sheet 80 side) of the chip 51 and bring it into contact with the wafer 60.

[0134] Subsequently, if the adhesive layer of the carrier sheet is energy-ray curable, the adhesive layer is irradiated with energy rays to harden it, reducing its adhesive strength and allowing the carrier sheet to be peeled off the chip. By repeating this process, a chip-on-wafer 70 is obtained in which multiple chips 51 are directly bonded to a wafer 60, as shown in Figure 8. Since the bonding surface of the chips is kept clean after going through steps 1 to 7, the area of ​​lifting or peeling (voids) at the bonding area after direct bonding can be reduced.

[0135] In step 9, it is preferable to further anneal the wafer on which the multiple chips are fixed in order to improve the bonding between the chips and the wafer. An example of an annealing process is a process in which the chips and wafer are heated while being pressed together.

[0136] By performing steps 8 and 9, the workpiece (wafer) is fragmented, and the resulting workpiece (chip) is directly bonded to the wafer. In other words, the workpiece (chip) can be directly bonded while maintaining a clean surface.

[0137] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention.

[0138] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0139] (Example 1) (1) Preparation of workpiece processing sheet A workpiece processing sheet including a workpiece processing film was prepared as follows using a coating agent containing the following adhesive composition.

[0140] (Preparation of Adhesive Composition) An acrylic polymer was obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA). This acrylic polymer was then reacted with 2-methacryloyloxyethyl isocyanate (MOI) so as to add to 80 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic polymer. The molecular weight of the obtained acrylic polymer was measured by the method shown below, and the weight-average molecular weight (Mw) was 500,000.

[0141] The weight-average molecular weight (Mw) is the weight-average molecular weight on a standard polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). The molecular weight of the acrylic polymer in the adhesive composition described later was also measured using the same method. (Measurement conditions) ・GPC analyzer: Tosoh Corporation, HLC-8020 ・GPC column (passed in the following order): Tosoh Corporation TSK guard column HXL-H, TSK gel GMHXL (x2), TSK gel G2000HXL ・Measurement solvent: Tetrahydrofuran ・Measurement temperature: 40°C

[0142] To 100 parts by mass of this energy-ray curable acrylic polymer, 1 part by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L") and 3 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, product name "Omnirad 184") were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for an adhesive composition.

[0143] (Preparation of workpiece processing film) The adhesive composition described above was applied to the peeled surface of a first release sheet (Lintec Corporation, product name "SP-PET502150", polyethylene terephthalate (PET) film with silicone release treatment, thickness: 50 μm), and dried to form an energy-ray curable adhesive layer i (workpiece processing film) with a thickness of 10 μm on the release sheet. Next, the peeled surface of a second release sheet (Lintec Corporation, product name "SP-PET381031", polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38 μm) was bonded to the surface of the adhesive film i to produce a workpiece processing sheet having the configuration of "first release sheet / workpiece processing film (adhesive layer i) / second release sheet".

[0144] (2) Preparation of the backgrind sheet A polyethylene terephthalate (PET) film (thickness: 50 μm) was prepared as the base material D for the backgrind sheet. The adhesive composition described above was applied to the peeled surface of the second release sheet and dried to form an energy-ray curable adhesive layer i with a thickness of 10 μm on the second release sheet. The adhesive layer of the second release sheet was bonded to one main surface of the prepared base material to produce a backgrind sheet having the configuration of "base material D / adhesive layer i / second release sheet".

[0145] (Example 2) A workpiece processing sheet and a backgrind sheet were obtained in the same manner as in Example 1, except that an energy-ray curable adhesive layer ii was formed in place of the adhesive layer i of the backgrind sheet using the following adhesive composition coating agent.

[0146] (Preparation of adhesive composition) 80 parts by mass of n-butyl acrylate (BA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer (Mw: 500,000).

[0147] A coating agent for an adhesive composition was prepared by adding 70 parts by mass of UV-curable polyfunctional urethane acrylate oligomer (manufactured by Dainichi Seika Kogyo Co., Ltd., product name "EXL810TL"), 1 part by mass of isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 3 parts by mass of photopolymerization initiator (manufactured by IGM Resins, product name "Omnirad184") to 100 parts by mass of acrylic polymer and diluting with methyl ethyl ketone.

[0148] (Example 3) A workpiece processing sheet and a backgrind sheet were obtained in the same manner as in Example 1, except that an energy-ray non-curing adhesive layer iii was formed in place of the adhesive layer i of the backgrind sheet using the following adhesive composition coating agent.

[0149] (Preparation of adhesive composition) 80 parts by mass of n-butyl acrylate (BA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer (Mw: 500,000).

[0150] A coating agent for an adhesive composition was prepared by adding 70 parts by mass of a polymerized rosin ester tackifier (manufactured by Arakawa Chemical Co., Ltd., product name "Bensel D-125", softening point 125°C) and 1 part by mass of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L") to 100 parts by mass of an acrylic polymer, and then diluting with methyl ethyl ketone.

[0151] (Example 4) A workpiece processing sheet and a backgrind sheet were obtained by the same method as in Example 3, except that an adhesive layer ii was formed instead of adhesive layer i as the workpiece processing film.

[0152] (Example 5) A workpiece processing sheet and a backgrind sheet were obtained in the same manner as in Example 1, except that an energy-ray curable adhesive layer iv was formed instead of the adhesive layer i as a workpiece processing film using the following adhesive composition coating agent.

[0153] (Preparation of Adhesive Composition) An acrylic polymer was obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA). This acrylic polymer was then reacted with 2-methacryloyloxyethyl isocyanate (MOI) so as to add to 80 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic polymer. The molecular weight of the obtained acrylic polymer was measured by the method shown below, and the weight-average molecular weight (Mw) was 500,000.

[0154] To 100 parts by mass of this energy-ray curable acrylic polymer, 1 part by mass of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), 3 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, product name "Omnirad 184"), and 2 parts by mass of an easy-release agent (alkylene glycol-modified rosin ester) were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for an adhesive composition.

[0155] (Comparative Example 1) A resin composition of low-density polyethylene was melted, and the molten material was extruded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Laboplastmill") to produce a base material A consisting of a resin film with a thickness of 80 μm. An adhesive layer i with a thickness of 10 μm was formed on the peeled surface of the second release sheet. By laminating the adhesive layer i of the second release sheet to one main surface of the prepared base material A, a protective sheet having the configuration of "base material A / workpiece processing film (adhesive layer i) / second release sheet" was produced.

[0156] Next, an adhesive layer iii with a thickness of 10 μm was formed on the peeled surface of the second release sheet. By laminating the adhesive layer iii of the second release sheet to one main surface of the prepared base material A, a backgrind sheet having the configuration of "base material A / adhesive layer iii / second release sheet" was produced.

[0157] (Comparative Example 2) Substrate C was prepared by the same method as in Comparative Example 1, except that an ethylene-(meth)acrylic acid copolymer resin composition was used instead of a low-density polyethylene resin composition. A protective sheet and a backgrind sheet were prepared by the same method as in Comparative Example 1, except that substrate C was used instead of substrate A.

[0158] (Comparative Example 3) Substrate B was prepared by the same method as in Comparative Example 1, except that a polyvinyl chloride resin composition was used instead of a low-density polyethylene resin composition. A protective sheet was prepared by the same method as in Comparative Example 1, except that substrate B was used instead of substrate A, and adhesive layer ii was formed instead of adhesive layer i as a workpiece processing film. A backgrind sheet was prepared by the same method as in Comparative Example 1, except that substrate B was used instead of substrate A.

[0159] (Comparative Example 4) A protective sheet was prepared in the same manner as in Comparative Example 1, except that base material B was used instead of base material A, and adhesive layer iii was formed instead of adhesive layer i as a workpiece processing film. A backgrind sheet was prepared in the same manner as in Comparative Example 1, except that base material C was used instead of base material A.

[0160] (Comparative Example 5) A backgrind sheet was prepared in the same manner as in Comparative Example 1, except that adhesive layer i was formed instead of adhesive layer iii. No workpiece processing sheet was prepared.

[0161] (Comparative Example 6) Only the backgrind sheet was prepared using the same method as in Comparative Example 5, except that base material B was used instead of base material A.

[0162] (Comparative Example 7) Only the backgrind sheet was prepared using the same method as in Comparative Example 5, except that base material C was used instead of base material A.

[0163] (Comparative Example 8) Only the backgrind sheet was prepared using the same method as in Comparative Example 5, except that base material D was used instead of base material A.

[0164] (Comparative Example 9) A backgrind sheet was prepared using the same method as in Comparative Example 8, except that an adhesive layer ii was formed instead of adhesive layer i.

[0165] The obtained samples (Examples 1-5 and Comparative Examples 1-9) were evaluated as follows. The results are shown in Table 1.

[0166] (Peak area after GPC measurement of components derived from workpiece processing film) Workpiece processing films obtained by peeling off the first and second release sheets from the workpiece processing sheets of Examples 1 to 5 were cut into 80 mm x 100 mm sections. These sections were wrapped in a nylon mesh sheet measuring 100 mm x 150 mm with a mesh size of 200 and secured with fasteners such as staples to be used as the measurement sample. This measurement sample was subjected to an immersion test by immersing it in 15 g of toluene at 25°C for 24 hours. After the test, all remaining sections, nylon mesh sheets, and fasteners were removed from the toluene, and the toluene solvent was recovered.

[0167] The above immersion test was performed on the laminates of the adhesive layer and substrate obtained by peeling the second release sheet from the protective sheets of Comparative Examples 1 to 4, and the toluene solvent was recovered.

[0168] Furthermore, the workpiece processing films of Examples 1 to 5 and the adhesive layers of Comparative Examples 1 to 3 were subjected to an illuminance of 230 mW / cm². 2 Total light intensity 190 mJ / cm 2 Workpiece processing films or adhesive layers that had been irradiated with ultraviolet light under the specified irradiation conditions were subjected to immersion tests.

[0169] The recovered toluene solvent was measured by gel permeation chromatography (GPC) under the following conditions. From the measurement results, the peak area was calculated from the elution time from 8.7 minutes (equivalent to a standard polystyrene number-average molecular weight of 2.5 million) to 16 minutes (equivalent to a standard polystyrene number-average molecular weight of 200) using the software included with the GPC analyzer (EcoSEC Data Analysis Version 1.16). The results are shown in Table 1. <Measurement Conditions> ・GPC measuring device: Tosoh Corporation, HLC-8320 ・GPC column (passed in the following order): Tosoh Corporation TSK gel superHZ1000 (1 column), TSK gel superHZ2000 (2 columns), TSK gel superHZ2500 (1 column), TSK gel superHZM-M (2 columns) ・Measurement solvent: Tetrahydrofuran ・Measurement temperature: 40℃ ・Sample input volume: 10 μL ・Detector: RI detector

[0170] (Peak area of ​​components derived from the backgrind sheet after GPC measurement) Instead of the workpiece processing film or adhesive layer, the above immersion test was performed on the backgrind sheets of Examples 1 to 5 and Comparative Examples 1 to 9. GPC measurements were performed on the recovered toluene solvent under the above measurement conditions, and the peak area of ​​the substrate after GPC measurement was calculated. The results are shown in Table 1.

[0171] (Adhesion of workpiece processing film) The second release sheet was peeled off from the workpiece processing sheets prepared in Examples 1 to 5, and the exposed workpiece processing film was bonded to the easy-adhesion layer of a polyethylene terephthalate (PET) film having an easy-adhesion layer to obtain a laminate of first release sheet / workpiece processing film / easy-adhesion layer / PET film. The obtained laminate was cut to a width of 25 mm to make a test piece. The first release sheet was peeled off from the test piece, and the workpiece processing film was attached to a silicon mirror wafer without a circuit surface using a roller with a mass of 2 kg. After being left in the dark for 1 hour, the test piece was peeled off at a peeling speed of 300 mm / min at a 180° angle to the silicon mirror wafer in accordance with JIS Z 0237, and the adhesion force (adhesion force without UV irradiation) was measured. The results are shown in Table 1. In addition, for the test pieces of Examples 1 to 5, delamination occurred at the interface between the easily adhesive layer of the PET film and the workpiece processing film during peeling, rather than at the interface between the workpiece processing film and the silicon mirror wafer. Therefore, in Table 1, this is indicated as "unmeasurable".

[0172] The protective sheets prepared in Comparative Examples 1 to 4 were cut to a width of 25 mm to prepare test specimens. The second release sheet was peeled off the test specimen, and the adhesive layer of the protective sheet was attached to a silicon mirror wafer without a circuit surface using a roller with a mass of 2 kg. After being left in the dark for 1 hour, the test specimen was peeled off at a peeling speed of 300 mm / min at a 180° angle to the silicon mirror wafer in accordance with JIS Z 0237, and the adhesive strength (adhesive strength without UV irradiation) was measured. The results are shown in Table 1.

[0173] For Examples 1 to 5 and Comparative Examples 1 to 3, a separate test specimen was prepared, and the workpiece processing film or adhesive layer was attached to the silicon mirror wafer in the same manner as described above. After attachment, the workpiece processing film or adhesive layer was exposed to ultraviolet light from the PET film or substrate side at an irradiance of 230 mW / cm². 2 , light intensity 190mJ / cm 2After curing the workpiece processing film or adhesive layer by irradiation under the specified conditions, the test piece was peeled off at a peeling speed of 300 mm / min so that it was at a 180° angle to the silicon mirror wafer, in accordance with JIS Z 0237, and the adhesive strength (adhesive strength after UV irradiation) was measured. The results are shown in Table 1.

[0174] (Wafer Crack Evaluation 1) The second release sheet was peeled off from the workpiece processing sheets of Examples 1 to 5 and the protective sheets of Comparative Examples 1 to 4. The exposed workpiece processing film or adhesive layer was then attached to an 8-inch diameter, 725 μm thick silicon mirror wafer using a backgrind tape laminator (Lintec Corporation, device name "RAD-3510F / 12"). Subsequently, in Examples 1 to 5, the first release sheet was peeled off to obtain a laminate of the workpiece processing film and the silicon mirror wafer, while in Comparative Examples 1 to 4, a laminate of the substrate, adhesive layer, and silicon mirror wafer was obtained. Next, using a dicing device (DISCO Corporation, product name "DFD6363"), while supplying cooling water, the silicon mirror wafer was half-cut (diced) to a depth of 60 μm on the surface to which the workpiece processing film or adhesive layer was attached, forming a 6 mm x 6 mm square region.

[0175] After half-cutting, the second release sheet was peeled off from the backgrind sheets of Examples 1 to 5 and Comparative Examples 1 to 4, and the exposed adhesive layer was laminated to the workpiece processing film or substrate using a backgrind tape laminator (Lintec Corporation, device name "RAD-3510F / 12"). As a result, in Examples 1 to 5, a laminate of the backgrind sheet, workpiece processing film, and silicon mirror wafer was obtained, and in Comparative Examples 1 to 4, a laminate of the backgrind sheet, substrate, adhesive layer, and silicon mirror wafer was obtained.

[0176] Next, the backside of the laminate with the backgrind sheet was placed on a suction table, and using a back-side grinding device (Disco Corporation, device name "DGP8761"), the backside of the silicon mirror wafer (the side where the backgrind sheet and the workpiece processing film or adhesive layer are not attached) was ground while supplying cooling water until the thickness of the silicon mirror wafer was 30 μm, and the silicon mirror wafer was separated into individual pieces by DBG. The silicon mirror wafer was visually inspected for the presence or absence of cracks after back-side grinding. The observation results were evaluated according to the following criteria. In this example, "A" is preferred. The results are shown in Table 1. A: No cracks F: Cracks present

[0177] (Evaluation of the peelability of the film for workpiece processing from the workpiece) After performing the above "Wafer crack evaluation 1", an ultraviolet irradiation device (Lintec Corporation, RAD-2000m / 12) is used to irradiate the backgrind sheet side at an irradiance of 230 mW / cm². 2 , cumulative light intensity 500 mJ / cm 2 The adhesive layers of the workpiece processing films of Examples 1 to 5, the protective sheets of Comparative Examples 1 to 3, and the backgrind sheets of Examples 1 to 2 and 5 were cured by irradiating them with ultraviolet light under the specified irradiation conditions.

[0178] Next, on the individualized silicon mirror wafer, a carrier sheet (Lintec Corporation, product name "D-485H") was attached to the side (grinding surface) where the workpiece processing film or adhesive layer and the backgrind sheet were not attached, using a tape mounter device (Lintec Corporation, product name "RAD-2700F / 12"). At this time, the carrier sheet was also attached to the ring frame. After attaching the carrier sheet, the backgrind sheet was peeled off by hand from the non-grinding surface of the individualized silicon mirror wafer. The non-grinding surface of the individualized silicon mirror wafer after peeling was observed and visually evaluated according to the following criteria to determine whether the workpiece processing film or adhesive layer remained as a visible residue. In this example, "A" is preferred. The results are shown in Table 1. A: No residue B: Of the area where the workpiece processing film or adhesive layer was applied, the area where the workpiece processing film or adhesive layer remained is more than 0% but less than 10% C: Of the area where the workpiece processing film or adhesive layer was applied, the area where the workpiece processing film or adhesive layer remained is 10% or more

[0179] (Wafer Crack Evaluation 2) In wafer crack evaluation 2, backside grinding was performed using a different process than the DBG performed in wafer crack evaluation 1, and the cracks after backside grinding were evaluated in the same way as in wafer crack evaluation 1. The second release sheet was peeled off from the back-grind sheets of Comparative Examples 5 to 9, and the exposed adhesive layer was attached to a silicon mirror wafer with a diameter of 8 inches and a thickness of 725 μm using a back-grind tape laminator (Lintec Corporation, device name "RAD-3510F / 12"). This obtained a laminate of the back-grind sheet and the silicon mirror wafer.

[0180] Next, the back-grind sheet side of the laminate was placed on a suction table, and back-grinding was performed using a back-grinding device (Disco Corporation, device name "DGP8761") while supplying cooling water, until the silicon mirror wafer thickness reached 30 μm. The silicon mirror wafer after back-grinding was visually inspected for the presence or absence of cracks. The observation results were evaluated according to the following criteria. In this example, "A" is preferred. The results are shown in Table 1. A: No cracks F: Cracks present

[0181] (Evaluation of void area ratio) For Examples 1 to 5, after the "evaluation of the peelability of the workpiece processing film from the workpiece," the dicing sheet was stretched using an expander to widen the spacing between silicon chips to 0.03 mm, and then plasma irradiation treatment was performed on the exposed surface of the silicon chips held on the dicing sheet (the surface to which the workpiece processing film was attached). Similarly, plasma irradiation treatment was also performed on the polished surface of the silicon wafer (diameter: 8 inches, thickness: 750 μm) to which the silicon chips would be bonded.

[0182] The silicon chip was positioned so that the plasma-irradiated surface (bonding surface) of the silicon chip faced the plasma-irradiated surface (bonding surface) of the silicon wafer. The silicon chip was pressed from the side opposite the bonding surface using a pressing tool of the same size as the silicon chip, bringing it into contact with the silicon wafer and directly bonding them. Using a scanning ultrasonic flaw detector (Sonoscan, product name "D9600TMCSAM"), the silicon chip after direct bonding was observed from the side opposite the bonding surface to check for the presence or absence of lifting or peeling (voids) at the bonding area between the silicon chip and the wafer. After confirmation, image analysis of the bonding area was performed to determine the area ratio of voids to the area of ​​the bonding area. In each example, the bonding area was observed for 50 chips, and the average value of the void area ratio was calculated. A void area ratio of 15% or less was judged to be good. The results are shown in Table 1. Note that for Comparative Examples 1 to 4, the peelability evaluation in "Evaluation of Peelability of Work Processing Film from Workpiece" was "B" or "C", so the void area ratio was not evaluated.

[0183] For Comparative Examples 8 and 9, the backgrind sheet was peeled off from the laminate of the backgrind sheet and silicon mirror wafer after "Wafer Crack Evaluation 2". On the silicon mirror wafer, a dicing sheet (Lintec Corporation, product name "D-485H") was attached to the surface from which the backgrind sheet had been peeled off (non-grinding surface) using a tape mounter device (Lintec Corporation, product name "RAD-2500m / 12"). At this time, the dicing sheet was also attached to the ring frame.

[0184] The silicon wafer was placed in a dicing apparatus (DISCO Corporation, product name "DFD6363") along with a ring frame, and blade dicing was performed while supplying cooling water to obtain silicon chips from the silicon mirror wafer. The dicing size was 6 mm x 6 mm. Subsequently, the dicing sheet was stretched using an expander to widen the spacing between silicon chips to 0.03 mm, and then an ultraviolet irradiation device (Lintec Corporation, RAD-2000m / 12) was used to irradiate the substrate side at an illuminance of 230 mW / cm². 2 Total light intensity 190 mJ / cm 2 The adhesive layer of the dicing sheet was cured by irradiating it with ultraviolet light under the specified irradiation conditions.

[0185] Next, a carrier sheet (Lintec Corporation, product name "D-485H") was attached to the side of the silicon chip that did not have the dicing sheet attached (the grinding surface) using a tape mounter device (Lintec Corporation, product name "RAD-2500m / 12"). After attaching the carrier sheet, the dicing sheet was peeled off from the side of the silicon chip opposite to the grinding surface (the non-grinding surface) using a tape peeling device, and the silicon chip was transferred from the dicing sheet to the carrier sheet.

[0186] Plasma irradiation was performed on the exposed surface (the surface to which the backgrind sheet was attached) of the silicon chip held on the carrier sheet. Similarly, plasma irradiation was also performed on the polished surface of the silicon wafer (diameter: 8 inches, thickness: 750 μm) to which the silicon chip would be bonded.

[0187] The silicon chip was positioned so that its plasma-treated surface (bonding surface) faced the plasma-treated surface (bonding surface) of the silicon wafer. Using a pressing tool the same size as the silicon chip, the silicon chip was pressed from the side opposite the bonding surface, bringing it into contact with the silicon wafer and directly bonding them. Using a scanning ultrasonic flaw detector (Sonoscan, product name "D9600TMCSAM"), the silicon chip after direct bonding was observed from the side opposite the bonding surface to check for lifting or delamination (voids) at the bonding area between the silicon chip and the wafer. After confirmation, image analysis of the bonding area was performed to determine the area ratio of voids to the area of ​​the bonding area. In each comparative example, the bonding area was observed for 50 chips, and the average value of the void area ratio was calculated. The results are shown in Table 1. Note that for comparative examples 5 to 7, the evaluation of the void area ratio was not performed because the evaluation in "Wafer Crack Evaluation 2" was "F".

[0188]

[0189] Table 1 shows that Examples 1 to 5, in which the workpiece processing film is composed solely of a substrate-less adhesive and possesses the above-mentioned physical properties, when used together with a known backgrind sheet, did not cause cracks or other damage to the wafer after grinding, and did not leave any residue on the workpiece after peeling. Furthermore, it was confirmed that even when the workpiece processed using this workpiece processing film was directly bonded to the wafer, the expansion of the void area at the interface of the bonded portion could be suppressed.

[0190] On the other hand, in Comparative Examples 1 to 4, although no cracks or other defects occurred in the wafer after grinding, it was confirmed that a portion of the adhesive layer remained on the workpiece as residue because a laminate of the adhesive layer and the substrate was used as a protective sheet. Furthermore, in Comparative Examples 5 to 9, it was confirmed that cracks or other defects occurred in the wafer after grinding, or that the bonding surface of the workpiece was contaminated, resulting in an increased void area ratio.

[0191] 1...Film for workpiece processing 10...Sheet for workpiece processing 21...First release sheet 22...Second release sheet 30...Backgrind sheet 31...Substrate 32...Adhesive layer 50...Workpiece (wafer) 51...Workpiece processed product (chip) 60...Wafer 70...Chip-on-wafer 80...Carrier sheet

Claims

1. A workpiece processing film used for processing workpieces, wherein the workpiece processing film is a substrate-less double-sided adhesive film, and the peak area of ​​the detected component calculated by performing the following immersion test on the workpiece processing film and performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) A workpiece processing film having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent that the workpiece processing film came into contact with. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

2. The workpiece processing film according to claim 1, wherein the workpiece processing film is energy ray curable.

3. The workpiece processing film according to claim 1 or 2, wherein the workpiece is a workpiece for manufacturing a workpiece to be directly joined.

4. The workpiece processing film according to claim 1 or 2, wherein the adhesive force to a silicon wafer is 500 mN / 25 mm or less.

5. A method for processing a workpiece, comprising the steps of: attaching a workpiece processing film according to claim 1 or 2 to the surface of a workpiece having a surface and a back surface opposite to the surface; forming grooves on the surface of the workpiece to which the workpiece processing film is attached, or forming a modified layer region inside the workpiece; laminating a back grind sheet on the workpiece processing film after forming the grooves or modified layer region; grinding the back surface of the workpiece to which the workpiece processing film and the back grind sheet are laminated on the surface and the grooves or modified layer region are formed inside the surface, thereby separating the workpiece into individual pieces starting from the grooves or modified layer region; and peeling off the workpiece processing film and the back grind sheet from the workpiece after back grinding.

6. The workpiece processing method according to claim 5, wherein the workpiece processing film is energy ray curable, and the method further comprises the step of curing the workpiece processing film by irradiating it with energy rays after the step of separating the workpiece and before the step of peeling off the workpiece processing film and the backgrind sheet.

7. The workpiece processing method according to claim 5, wherein the step of peeling off the workpiece processing film and the back grind sheet is performed after an adhesive sheet has been attached to the back surface of the workpiece after back surface grinding.

8. The method for processing a workpiece according to claim 5, wherein the workpiece is a workpiece for manufacturing a workpiece to be directly joined.

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