Workpiece machining sheet, method for manufacturing machined workpiece, and method for using workpiece machining sheet

Abstract

[Problem] To provide a workpiece machining sheet capable of, when a machined workpiece is joined directly to a wafer, suppressing increases in the area of a void in a joining section between the machined workpiece and the wafer or between machined workpieces. [Solution] A workpiece machining sheet used to machine a workpiece for manufacturing a machined product to be directly joined, wherein: when 10 μL of toluene solvent, obtained as a result of immersing the workpiece machining sheet having a size of 80 mm × 100 mm in 15 g of toluene at 25°C for 24 hours, is measured by gel permeation chromatography and the measurement result is represented in a chromatogram in which the vertical axis indicates detected voltage and the horizontal axis indicates elution time from the toluene solvent introduction to the elution from a column, the peak area of detected components within a range from an elution time, corresponding to a situation in which the number average molecular weight calculated in terms of standard polystyrene is 2,500,000, to an elution time, corresponding to a situation in which the number average molecular weight calculated in terms of standard polystyrene is 200, is 4,000 mV·s or less.

Description

Workpiece processing sheet, method for manufacturing a workpiece, and method for using the workpiece processing sheet.

[0001] The present invention relates to a workpiece processing sheet, a method for manufacturing a workpiece, and a method for using the workpiece processing sheet. In particular, it relates to a workpiece processing sheet used when processing a workpiece for manufacturing a workpiece to be directly joined, a method for manufacturing a workpiece using the workpiece processing sheet, and a method for using the workpiece processing sheet.

[0002] A chip on which circuits such as semiconductor chips are formed is a processed workpiece obtained by processing (e.g., dicing) a workpiece (e.g., a wafer) on which multiple circuits are formed. A known method for high-density chip mounting is the use of chip-on-wafer (CoW) technology. In this method, multiple chips smaller than the wafer are placed on the circuit surface of a wafer to obtain a chip-on-wafer, and then the chip-on-wafer is diced to obtain a stacked chip. In addition, in such chip-on-wafers, another chip may be stacked on top of the chips already placed on the wafer.

[0003] Such chips are often placed or stacked on a wafer via a thin adhesive layer, such as a die bonding film. In recent years, a method that does not use an adhesive layer has been known: direct transfer bonding (DTB), in which the bonding surface of the chip and the bonding surface of the wafer are treated and then directly bonded.

[0004] Patent Document 1 discloses a method of pressing a chip having a plasma-activated surface with a chip transfer member to bring it into close contact with the plasma-activated surface of a substrate.

[0005] Patent No. 6900006

[0006] When direct bonding is performed, an adhesive sheet may be applied to the bonding surface of the chip in the preceding process to protect it. The adhesive sheet is removed before direct bonding, but at this time, residue from the adhesive sheet may be left on the bonding surface of the chip. If the bonding surface of the chip and the bonding surface of the wafer are directly bonded with this residue present, air bubbles will form at the interface (bonding area) between the bonding surfaces due to the residue, and these will remain as lifting or peeling (voids) even after direct bonding.

[0007] When the area of ​​voids at the joint becomes large, even if the chip and wafer appear to be joined externally, problems such as poor conductivity between the chip's circuitry and the wafer's circuitry can occur. Furthermore, in chip-on-wafer configurations, when another chip is stacked on top of a chip already bonded to a wafer, the side of the chip bonded to the wafer, opposite to the side bonded to the wafer, also becomes a bonded surface. Therefore, if residue is present on this opposite side, the area of ​​voids at the joint between the chips can also increase, leading to problems.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a workpiece processing sheet that can suppress the expansion of the area of ​​voids at the joint between a workpiece and a wafer, or at the joint between two workpieces, when a workpiece is directly bonded to a wafer, a method for manufacturing a workpiece using the workpiece processing sheet, and a method for using the workpiece processing sheet.

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

[0010] [1] A workpiece processing sheet used for processing workpieces to manufacture workpieces to be directly joined, wherein the workpiece processing sheet 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 sheet 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 sheet 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] In gel permeation chromatography measurement, the peak area of ​​the detected component in the range from the elution time corresponding to a standard polystyrene number-average molecular weight of 10,000 to the elution time corresponding to a standard polystyrene number-average molecular weight of 200 is 4,000 mV·s or less, which is the workpiece processing sheet described in [1].

[0012] [3] A workpiece processing sheet according to [1] or [2], wherein the adhesive force to the silicon wafer is 300 mN / 25 mm or less.

[0013] The workpiece processing sheet described in any of [1] to [3] is defined as the peeling trigger time, which is the time until a peeling trigger is formed at the interface between the workpiece processing sheet and the silicon chip when a rectangular silicon chip with sides of 5 mm and a thickness of 30 μm, attached to the workpiece processing sheet described in any of [4], is pushed up from the workpiece processing sheet side, and the peeling trigger time is 5 seconds or less.

[0014] [5] A workpiece processing sheet according to any one of [1] to [4], having a base material and an adhesive layer.

[0015] [6] The workpiece processing sheet described in [5], wherein the base material does not contain a polyvinyl chloride film containing a plasticizer.

[0016] [7] The workpiece processing sheet described in [5] or [6] is wherein the following immersion test is performed on the adhesive layer, 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) An adhesive layer 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 in contact with the adhesive layer. (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. 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.

[0017] [8] A workpiece processing sheet according to any one of [5] to [7], wherein the gel fraction of the adhesive layer is 95% or more.

[0018] [9] A workpiece processing sheet according to any one of [5] to [8], wherein the adhesive layer is composed of an energy ray curable adhesive.

[0019]

[10] A workpiece processing sheet according to any one of [5] to [9], wherein the adhesive layer is composed of an acrylic adhesive.

[0020]

[11] A method for manufacturing a workpiece, comprising the steps of: attaching a workpiece processing sheet described in any of [1] to

[10] to the surface of a workpiece having a surface and a back surface facing the surface, for manufacturing a workpiece to be directly joined; and separating the workpiece to which the workpiece processing sheet has been attached into individual pieces to obtain a plurality of workpieces.

[0021] A method for using a workpiece processing sheet as described in any of [1] to

[10] , wherein the workpiece processing sheet has a surface and a back surface facing the surface, and is used to obtain multiple workpieces by attaching it to the surface of a workpiece for manufacturing workpieces to be directly joined, and then separating the workpiece into individual pieces.

[0022] A method for using a workpiece processing sheet as described in any of [1] to

[10] , wherein the workpiece processing sheet has a surface and a back surface facing the surface, and is used to attach to the back surfaces of multiple workpieces obtained by separating workpieces for manufacturing workpieces to be directly joined.

[0023] According to the present invention, a workpiece processing sheet can be provided that can suppress the expansion of void area at the joint between a workpiece and a wafer, or at the joint between two workpieces, when a workpiece is directly bonded to a wafer; a method for manufacturing a workpiece using the workpiece processing sheet; and a method for using the workpiece processing sheet.

[0024] Figure 1 is a diagram illustrating a method for calculating the peak area after GPC measurement of components derived from the workpiece processing sheet. Figure 2 is a schematic cross-sectional diagram showing an example of a workpiece processing sheet according to this embodiment. Figure 3(A) is a schematic cross-sectional diagram illustrating the process of attaching the workpiece processing sheet according to this embodiment to a wafer (workpiece), and Figure 3(B) is a schematic cross-sectional diagram illustrating the process of separating the wafer (workpiece) attached to the workpiece processing sheet according to this embodiment into individual pieces. Figure 4(A) is a schematic cross-sectional diagram illustrating the process of attaching a carrier sheet to a chip (workpiece), and Figure 4(B) is a schematic cross-sectional diagram illustrating the process of peeling the workpiece processing sheet from the chip (workpiece) to which the carrier sheet has been attached. Figures 5(A) and (B) are schematic cross-sectional diagrams illustrating the process of directly bonding a chip (workpiece) to a wafer. Figure 6 is a schematic cross-sectional diagram of a chip-on-wafer in which a chip (workpiece) is directly bonded to a wafer. Figure 7 is a schematic cross-sectional diagram illustrating the process of grinding the back surface of a wafer.

[0025] 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.

[0026] A workpiece refers to a plate-like body to which a workpiece processing sheet 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.

[0027] Workpiece segmentation refers to dividing a workpiece into individual circuits 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.

[0028] 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.

[0029] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

[0030] "Energy rays" refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

[0031] 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.

[0032] (1. Workpiece Processing Sheet) The workpiece processing sheet is a sheet used when processing a workpiece. An example of a workpiece is one in which a circuit, electrodes, etc. are formed on at least one surface. In such a workpiece, the other surface does not have a circuit, electrodes, etc. formed on it, or electrodes such as through electrodes may be formed on it. In this embodiment, the workpiece is a workpiece for manufacturing a workpiece that will be directly joined. The surface may be the surface in which the circuit is exposed, or it may be the main surface of a protective layer formed on the circuit to protect it. Electrodes may also be formed on the circuit.

[0033] The workpiece processing sheet according to this embodiment is used to process workpieces for manufacturing workpieces that will be directly joined. In this embodiment, examples of workpiece processing include dicing (fragmentation of workpieces) and backside grinding of workpieces.

[0034] In the process of separating a workpiece into individual pieces, a workpiece processing sheet is attached to the front or back surface of the workpiece, and the workpiece is then fixed to a frame via the workpiece processing sheet. Subsequently, the workpiece is separated into individual pieces, and the separated pieces (workpiece processed objects) are peeled off the workpiece processing sheet. By using a workpiece processing sheet, it is possible to hold the workpiece during separation to suppress misalignment, and to suppress scattering of the workpiece processed objects after separation.

[0035] In backside grinding of a workpiece, a workpiece processing sheet is attached to the surface of the workpiece, and the workpiece is then fixed to the frame via the workpiece processing sheet. After that, the backside of the workpiece is ground. After grinding is complete, the workpiece processing sheet is peeled off the workpiece. By using a workpiece processing sheet, the surface of the workpiece is protected during backside grinding, and contamination of circuits, etc., by the ingress of abrasive material, cooling water, etc., into the workpiece surface, as well as damage to circuits, etc., due to the force applied during backside grinding, can be suppressed.

[0036] Therefore, the workpiece processing sheet according to this embodiment may be a so-called dicing sheet or a backgrind sheet. Furthermore, the workpiece processing sheet according to this embodiment may be a carrier sheet used for fixing, temporarily fixing, transporting, etc., of a workpiece or workpiece in various processes.

[0037] As described above, as a method for mounting chips as workpiece processed products at high density, a method using chip-on-wafer (CoW) is known. In chip-on-wafer, the circuit surfaces (bonding surfaces) of a plurality of chips are arranged on the circuit surface (bonding surface) of a wafer or the circuit surface (bonding surface) of another chip, and are electrically and mechanically connected. As a method for bonding a chip to a wafer or for bonding a chip to a chip, a method of directly bonding a chip to a wafer without using a film-like adhesive (direct transfer bonding: DTB) is known.

[0038] In direct bonding, since the bonding surface of the chip and the bonding surface of the wafer or the bonding surface of another chip are in contact, if foreign matter not derived from the chip and the wafer exists at the interface (bonding portion) between the bonding surfaces, floating of the chip or peeling (void) between the chip and the wafer may be formed at the bonding portion due to the foreign matter. Such voids cannot be observed from the outside, and even if voids are formed, they may not affect the bonding between the chip and the wafer or the like. However, when the area of the voids at the bonding portion becomes large, the circuit surface of the chip and the circuit surface of the wafer or the like are not sufficiently connected, resulting in problems such as poor conduction. A work processing sheet is attached to the bonding surface of the chip in the pre-process (work processing) of direct bonding. Therefore, even after the work processing sheet is peeled off, components derived from the work processing sheet may occur as the above-mentioned foreign matter (residue) at the bonding portion.

[0039] On the other hand, since the work processing sheet according to the present embodiment has physical properties described later, even if the work processing sheet is attached to the work and then peeled off, generation of residua derived from the work processing sheet in the workpiece processed product obtained by processing the work can be suppressed.

[0040] (1.1. Peak area after GPC measurement of components derived from the workpiece processing sheet) The above residue is unlikely to be the residue generated during the peeling of the workpiece processing sheet, and is considered to be the residue that occurs over time when various processes are performed after the workpiece processing sheet is attached to the workpiece. The inventors of the present invention推测 that such a residue is a component that easily migrates to the contacting substance among the components of the workpiece processing sheet and exists independently (freely) from the workpiece processing sheet.

[0041] In this embodiment, as a method for evaluating the easily migratable components, a method is adopted in which the workpiece processing sheet is immersed in a solvent and the solvent after immersion is evaluated by gel permeation chromatography (GPC). Thereby, the components presumed to be the cause of the voids generated during direct bonding can be extracted and analyzed. That is, the components that are easily eluted into the solvent by immersion are regarded as the easily migratable components.

[0042] In this embodiment, first, the following immersion test is performed. A workpiece processing sheet 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 workpiece processing sheet used for the immersion test, a workpiece processing sheet having the above size may be used, or a predetermined workpiece processing sheet may be processed to obtain a workpiece processing sheet having a size of 80 mm × 100 mm. When the workpiece processing sheet is energy ray curable, the workpiece processing sheet after energy ray irradiation is used. The workpiece processing sheet having a size of 80 mm × 100 mm is immersed so that the entire surface comes into contact with toluene. The thickness of the workpiece processing sheet is arbitrary as long as it can be immersed so that the entire surface comes into contact with toluene. In this embodiment, in consideration of handling properties and the like, it is preferable to wrap the workpiece processing sheet with a mesh sheet or the like made of a material insoluble in toluene and immerse it. After the immersion is completed, the workpiece processing sheet and, if necessary, the mesh sheet or the like are removed from toluene to obtain the toluene solvent that has contacted the workpiece processing sheet. When a constituent component elutes from the workpiece processing sheet by immersion, the obtained toluene solvent contains the component.

[0043] Next, the obtained toluene solvent is analyzed by gel permeation chromatography (GPC). In this embodiment, the following GPC measurement principle is used to evaluate the components that are easily transferred.

[0044] 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.

[0045] 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 1 shows an example of a chromatogram. In Figure 1, the detection voltage is shown on the vertical axis as the detection intensity.

[0046] 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.

[0047] In this embodiment, 10 μL of toluene solvent 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 sheet, the detection voltage will remain constant regardless of the elution time (baseline B in Figure 1).

[0048] On the other hand, if the toluene solvent after the immersion test contains components (detected components) derived from the workpiece processing sheet, the detection voltage changes relative to the baseline and forms a peak P, as shown in Figure 1, 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 1. 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.

[0049] In this embodiment, the peak area of ​​the detected component (hatched area PA in Figure 1) 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.

[0050] 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 sheet 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).

[0051] 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 sheet is energy ray curable, the peak area is the peak area of ​​the workpiece processing sheet after energy ray irradiation.

[0052] 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 derived from the workpiece processing sheet can be suppressed. The elution time corresponding to a number-average molecular weight equivalent to 10,000 is 750 seconds (12.5 minutes).

[0053] 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.

[0054] (1.2. Gel fraction of workpiece processing sheet) In this embodiment, the gel fraction of the workpiece processing sheet is preferably 90% or more. This strengthens the solid properties of the crosslinked structure in the workpiece processing sheet and suppresses the amount of easily migrating components. As a result, it becomes easier to set the peak area of ​​components derived from the workpiece processing sheet 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 sheet is energy ray curable, the gel fraction is the gel fraction after energy ray irradiation.

[0055] In this embodiment, the method for measuring the gel fraction of the workpiece processing sheet can utilize the immersion test described above. Specifically, a workpiece processing sheet having dimensions 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 sheet with the mesh sheet or the like described above. After the immersion is complete, the workpiece processing sheet 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 sheet 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.

[0056] (1.3. Adhesive strength of workpiece processing sheet) In this embodiment, it is preferable that the adhesive strength of the workpiece processing sheet when peeled from the silicon wafer is 300 mN / 25 mm or less. This facilitates the transfer of the workpiece or workpiece from the workpiece processing sheet, which is attached to the workpiece or workpiece processed object in the pre-processing step before direct bonding, to the carrier sheet that holds the workpiece or workpiece processed object during direct bonding. Note that if the workpiece processing sheet is energy ray curable, this adhesive strength is the adhesive strength after energy ray curing.

[0057] The adhesive strength may be 250 mN / 25 mm or less, 200 mN / 25 mm or less, or 150 mN / 25 mm or less. When the workpiece processing sheet has an adhesive layer as described later, the adhesive strength is the adhesive strength when the adhesive layer is peeled from the silicon wafer. The method for measuring the adhesive strength will be explained in the embodiments described later.

[0058] (1.4. Peeling trigger time) Furthermore, when a silicon chip with sides of 5 mm and a thickness of 30 μm, which is attached to the workpiece processing sheet according to this embodiment, is pushed up from the workpiece processing sheet side, the time until a peeling trigger is formed at the interface between the workpiece processing sheet and the silicon chip is defined as the peeling trigger time, and it is preferable that the peeling trigger time is 5 seconds or less.

[0059] The delamination trigger is the region at the interface between the workpiece processing sheet and the silicon chip where delamination of the silicon chip from the workpiece processing sheet first occurs. Once a delamination trigger is formed, the delamination of the silicon chip proceeds easily, starting from the trigger. Therefore, if the delamination trigger time is short, the delamination of the silicon chip proceeds quickly, making it easier to pick up the silicon chip from the workpiece processing sheet.

[0060] The inventors have found a correlation between the delamination trigger time and the bonding state of the silicon chip when direct bonding is performed, particularly when the silicon chip is thin (for example, 50 μm or less). As the thickness of a substrate, such as a silicon chip, decreases, the adhesion to the workpiece processing sheet tends to increase. In direct bonding, after the bonding surface of the silicon chip held by the workpiece processing sheet (which acts as a carrier sheet) contacts the bonding surface of the wafer by pressure, if the workpiece processing sheet is energy-ray curable, bonding is completed by peeling the workpiece processing sheet from the silicon chip after energy-ray irradiation. At this time, if peeling from the workpiece processing sheet does not proceed quickly, it is thought that uneven pressure on the bonding surface, increased pressure for peeling, etc., will negatively affect the bonding state of the silicon chip after direct bonding. Therefore, by shortening the delamination trigger time, the silicon chip becomes easier to peel from the workpiece processing sheet, allowing bonding to proceed uniformly and resulting in a better bonding state. In other words, by evaluating the delamination trigger time, it is possible to evaluate the bonding state of the chip after direct bonding (DTB) when the chip thickness is thin.

[0061] Furthermore, in the above, the surface of the silicon chip to which the workpiece processing sheet, which serves as a carrier sheet, is attached becomes the bonding surface when another silicon chip is directly bonded onto that silicon chip. As described above, on the surface to which the workpiece processing sheet is attached according to this embodiment, the generation of residue originating from the workpiece processing sheet is suppressed, so even when the silicon chip is directly bonded to another silicon chip, the expansion of the void area is suppressed, and the bonding state is improved.

[0062] The delamination trigger time can be measured by on-site observation. In this embodiment, a high-speed camera is used to photograph the process of pushing up the silicon chip attached to the workpiece processing sheet, and the delamination of the silicon chip is identified. The time from the start of the pushing up process until the first delamination of the silicon chip from the workpiece processing sheet occurs is measured and defined as the delamination trigger time. Specific conditions will be explained in the embodiments described later.

[0063] (1.5. Configuration of the workpiece processing sheet) The workpiece processing sheet according to this embodiment can have any configuration as long as the peak area of ​​its derived components after GPC measurement satisfies the above range. For example, the workpiece processing sheet may consist of one layer or multiple layers. In this embodiment, in order to reliably hold the workpiece or workpiece, the workpiece processing sheet preferably has a base material and an adhesive layer, and more preferably a base material and an adhesive layer formed on at least one main surface of the base material. If the workpiece processing sheet is energy ray curable, it is preferable that the adhesive layer of the workpiece processing sheet is energy ray curable.

[0064] Figure 2 shows an example of a workpiece processing sheet 1 having a base material and an adhesive layer. In the workpiece processing sheet 1, the adhesive layer 20 is arranged on one main surface 10a of the base material 10.

[0065] The workpiece processing sheet is not limited to the configuration described above, and may have other layers depending on the application, as long as the effects of the present invention are obtained. For example, when the workpiece processing sheet is used for backside grinding, an intermediate layer may be placed between the base material 10 and the adhesive layer 20 to relieve the stress applied to the workpiece during backside grinding, or an easy-to-adhere adhesive layer may be provided between the base material and the adhesive layer to improve their adhesion. In addition, layers with functions such as an antistatic layer may be formed between the outermost layer of the base material, the adhesive layer, and other layers.

[0066] (2. Base Material) The base material is a film-like component that provides rigidity to the workpiece processing sheet. Therefore, the base material only needs to be made of a material that can hold the workpiece or workpiece before, during, and after processing.

[0067] The substrate may consist of one layer (single layer) or of two or more layers. If the substrate has multiple layers, these layers may be identical or different from one another, and there are no particular restrictions on the combination of layers that make up these multiple layers.

[0068] The thickness of the base material can be set according to the application of the workpiece processing sheet. In this embodiment, the thickness of the base material may be 20 μm or more, 25 μm or more, or 50 μm or more. Alternatively, the thickness of the base material may be 450 μm or less, 400 μm or less, or 350 μm or less.

[0069] Note that the thickness of the base material refers to the total thickness of the base material. For example, the thickness of a base material composed of multiple layers refers to the sum of the thicknesses of all the layers that make up the base material.

[0070] (2.1. Peak area of ​​components derived from the substrate after GPC measurement) In this embodiment, it is preferable that the peak area obtained by performing the immersion test and GPC measurement described in (1.1) on the substrate instead of the workpiece processing sheet is 3000 mV·s or less. If the peak area of ​​components derived from the substrate after GPC measurement is within the above range, it becomes easier to make the peak area of ​​components derived from the workpiece processing sheet after GPC measurement within the above range. The peak area of ​​components derived from the substrate after GPC measurement may be 1000 mV·s or less, 500 mV·s or less, or 200 mV·s or less. The lower limit of the peak area is 0 mV·s.

[0071] (2.2. Material of the base material) The material of the base material should be selected according to the application of the workpiece processing sheet. Examples of such materials include various resin films. The base material may consist of a single-layer film made of one resin film, or it may consist of a multi-layer film made by laminating multiple resin films.

[0072] In this embodiment, examples of resin films include polyethylene films such as low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, and high-density polyethylene (HDPE) film; polyolefin films such as polypropylene film, ethylene-propylene copolymer film, polybutene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film; ethylene copolymer films such as ethylene-vinyl acetate copolymer film, ethylene-(meth)acrylic acid copolymer film, and ethylene-(meth)acrylic acid ester copolymer film; polyester films such as polyethylene terephthalate film and polybutylene terephthalate film; polyurethane film; polyurethane acrylate film; polyimide film; polystyrene film; polycarbonate film; and fluororesin film. Modified films such as crosslinked films and ionomer films may also be used.

[0073] Among the above, when the workpiece processing sheet is used as a dicing sheet, polyolefin films and ethylene copolymer films are preferred as the resin film. Among polyolefin films, polyethylene films are preferred, and low-density polyethylene (LDPE) films are particularly preferred. Among ethylene copolymer films, ethylene-(meth)acrylic acid copolymer films are preferred. When the workpiece processing sheet is used as a backgrind sheet, polyolefin films, polyurethane acrylate films, and polyester films are preferred as the resin film. These resin films make it easier to satisfy the above-mentioned physical properties and achieve suitability for each process.

[0074] On the other hand, in this embodiment, polyvinyl chloride-based films such as polyvinyl chloride films and polyvinyl chloride copolymer films are undesirable. In particular, when a polyvinyl chloride-based film containing a plasticizer is included in the substrate, the above-mentioned peak area tends to increase. Therefore, it is preferable that the substrate does not contain a polyvinyl chloride-based film containing a plasticizer.

[0075] At least one main surface of the substrate can be subjected to surface treatment by oxidation, embossing, or other methods, or to primer treatment, in order to improve adhesion with other layers. Examples of oxidation methods include corona discharge treatment, plasma discharge treatment, chromium oxidation (wet), flame treatment, hot air treatment, ozone treatment, and ultraviolet irradiation treatment. Examples of embossing methods include sandblasting and thermal spraying.

[0076] Furthermore, the base material may contain lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc., to the extent that it does not impair the effects of the present invention. The base material may be transparent or opaque, but it is preferably transparent.

[0077] (3. Adhesive Layer) The adhesive layer is attached to the surface of the workpiece (i.e., the surface on which circuits, electrodes, etc. are formed), protecting the surface and holding the workpiece or workpiece processed object. Furthermore, when the adhesive layer of the workpiece processing sheet according to this embodiment is peeled off from the surface, it suppresses the generation of residue originating from the adhesive layer on the surface of the workpiece processed object. As a result, the formation of voids at the interface between the workpiece processed object and the wafer during direct bonding can be suppressed.

[0078] The adhesive layer may consist of one layer (single layer) or of two or more layers. If the adhesive layer has multiple layers, these layers may be identical or different from each other, and there are no particular restrictions on the combination of layers that make up these multiple layers.

[0079] The thickness of the adhesive layer can be set according to the intended use of the workpiece processing sheet. In this embodiment, the thickness of the adhesive layer may be 1 μm or more and 50 μm or less, 2 μm or more and 30 μm or less, or 3 μm or more and 20 μm or less.

[0080] Note that the thickness of the adhesive layer refers to the total thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the sum of the thicknesses of all the layers that make up the adhesive layer.

[0081] (3.1. Peak area of ​​components derived from the adhesive layer after GPC measurement) In this embodiment, it is preferable that the peak area obtained by performing the immersion test and GPC measurement described in (1.1) on the adhesive layer instead of the workpiece processing sheet is 4000 mV·s or less. If the peak area of ​​components derived from the adhesive layer after GPC measurement is within the above range, it becomes easier to make the peak area of ​​components derived from the workpiece processing sheet after GPC measurement within the above range. The peak area of ​​components derived from the adhesive layer after GPC measurement may be 2600 mV·s or less, 2000 mV·s or less, or 800 mV·s or less. The lower limit of the peak area is 0 mV·s. Note that if the adhesive layer is energy ray curable, the peak area is the peak area of ​​the adhesive layer after GPC measurement after energy ray irradiation.

[0082] (3.2. Gel fraction of the adhesive layer) In this embodiment, the gel fraction of the adhesive layer is preferably 90% or more. This strengthens the solid properties of the crosslinked structure in the adhesive layer and suppresses the amount of easily migrated components. As a result, it becomes easier to set the peak area of ​​the components derived from the workpiece processing sheet 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 adhesive layer is energy ray curable, the gel fraction is the gel fraction of the adhesive layer after energy ray irradiation.

[0083] In this embodiment, the method for measuring the gel fraction of the adhesive layer can be the same as the method for measuring the gel fraction of the workpiece processing sheet, utilizing the immersion test described above. Specifically, an adhesive layer 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 adhesive layer with the mesh sheet or the like described above. After the immersion is complete, the adhesive layer 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 adhesive layer 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.

[0084] (3.3. Composition of the adhesive layer) The composition of the adhesive layer should be determined so as to exhibit sufficient tackiness and re-peelability to protect or hold the surface of the workpiece or workpiece and then peel off. In this embodiment, the adhesive layer is preferably composed of an adhesive 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, the adhesive is preferably an acrylic adhesive.

[0085] 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 sheet from the workpiece or workpiece, irradiating the adhesive layer with energy rays makes it easier to peel off the workpiece processing sheet.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] First, we will explain the case where the energy-ray curable adhesive is mainly composed of an acrylic polymer that has energy-ray curability.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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).

[0101] 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).

[0102] 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).

[0103] 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).

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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)).

[0110] 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).

[0111] 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.

[0112] 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.

[0113] 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).

[0114] Examples of the release agent (F) include free epoxy components, alkylene glycol-based components, polymerizable branched polymer components, and silicone-based components. When an energy ray-curable adhesive contains an release agent (F), the silicon chip to which the workpiece processing sheet is attached, especially thin silicon chips, tends to peel off from the workpiece processing sheet when the sheet is pushed up. In other words, the inclusion of an release agent (F) tends to shorten the aforementioned peeling trigger time. As a result, the bonding state of the silicon chip after direct bonding (DTB) tends to be better.

[0115] 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).

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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).

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] (4. Method for manufacturing workpiece processing sheets) The method for manufacturing workpiece processing sheets according to this embodiment can employ known methods.

[0128] First, a substrate is prepared. For example, a predetermined resin film may be prepared as the substrate, or a predetermined resin composition may be melt-kneaded and extruded into a sheet using an extruder to produce the substrate. The T-die method is preferred for extrusion molding. Alternatively, the substrate may be prepared by irradiating an energy-ray-curable composition with energy rays.

[0129] As an adhesive composition for forming an adhesive layer, 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 an adhesive coating agent) is prepared.

[0130] 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.

[0131] Next, an adhesive composition or a coating agent of the adhesive composition is applied to the release surface of the release sheet by a known method, and if necessary, heated and dried to form an adhesive layer on the release sheet. Then, the adhesive layer on the release sheet and the substrate are bonded together to obtain a workpiece processing sheet in which the adhesive layer and the substrate are laminated. The release sheet may be removed as necessary when using the workpiece processing sheet.

[0132] (5. Method of using the workpiece processing sheet, method of manufacturing the workpiece, and method of joining the workpieces) The workpiece processing sheet according to this embodiment has a front surface and a back surface facing the front surface, and is suitably used to obtain multiple workpieces by attaching it to the surface of a workpiece for manufacturing a workpiece to be directly joined, and then separating the workpiece into individual pieces. This protects and maintains the surfaces of the workpiece and the workpieces, while keeping the surface of the workpiece to be directly joined clean. The workpiece processing sheet according to this embodiment may also be used as a carrier sheet to be attached to the back surface of the workpiece. This allows the workpiece to be transported to the next process (direct joining process) while keeping the back surface of the workpiece clean.

[0133] Next, as methods that include the use of a workpiece processing sheet according to this embodiment, a method of processing a workpiece to manufacture a workpiece, and a method of directly joining workpieces obtained by processing a workpiece (DTB) will be specifically described.

[0134] The method for manufacturing a workpiece preferably comprises the following steps 1 and 2. The method for joining workpieces preferably comprises the following steps 1 to 4. The workpiece is a workpiece for manufacturing workpieces to be directly joined. Step 1: A step of attaching the workpiece processing sheet to the surface of a workpiece having a surface and a back surface facing the surface. Step 2: A step of separating the workpiece with the workpiece processing sheet attached into individual pieces to obtain a plurality of workpieces. Step 3: A step of transferring the obtained plurality of workpieces from the workpiece processing sheet to a carrier sheet or another workpiece processing sheet. Step 4: A step of directly joining the workpieces to a wafer.

[0135] The following describes each step of the manufacturing method and joining method for the above-mentioned workpieces. For the explanation, the workpiece sheet shown in Figure 2 is used as a specific example of a workpiece sheet, a wafer as a specific example of a workpiece, and a chip as a specific example of a workpiece.

[0136] (Step 1) In Step 1, as shown in Figure 3(A), the surface 50a of the wafer 50 and the ring frame 100 are attached to the main surface 20a of the adhesive layer of the workpiece processing sheet 1 according to this embodiment, thereby fixing the wafer 50 and the ring frame 100. By attaching the workpiece processing sheet to the surface of the wafer, the surface of the wafer is kept clean even after Step 2 is performed. In this embodiment, the wafer is preferably a silicon wafer.

[0137] (Step 2) In Step 2, as shown in Figure 3(B), the wafer 50 and ring frame 100 fixed to the workpiece processing sheet 1 are set in a dicing device (not shown), and the wafer 50 is diced to obtain a plurality of chips 51. Examples of known dicing methods for dicing the wafer include blade dicing, stealth dicing (registered trademark), plasma dicing, laser dicing, and water dicing. In other words, in Step 2, the workpiece processing sheet functions as a dicing sheet.

[0138] In addition, in step 2, an expansion process may be performed to widen the spacing between chips to facilitate direct bonding of chips, or to completely divide the wafer, by stretching the workpiece processing sheet.

[0139] By performing steps 1 and 2, the workpiece (wafer) is fragmented, and multiple workpiece chips are obtained. In other words, workpiece chips with clean surfaces suitable for direct bonding can be manufactured.

[0140] (Step 3) In Step 3, the multiple chips held on the workpiece processing sheet are transferred onto a carrier sheet. The carrier sheet is preferably adhesive in order to hold the chips. In this embodiment, the carrier sheet is preferably made of a base material and an adhesive layer formed on the main surface of one of the base materials. Furthermore, the adhesive layer of the carrier sheet is preferably energy ray curable.

[0141] If the adhesive layer of the workpiece processing sheet is energy ray curable, the adhesive layer is cured by irradiating it with energy rays before transfer to reduce its adhesive strength. First, as shown in Figure 4(A), the adhesive layer 81 of the carrier sheet 80 is attached to the back surface 51b of the obtained chips 51. Next, as shown in Figure 4(B), the workpiece processing sheet is peeled off from the surface 51a of the chips 51 held on the carrier sheet 80. As a result, the chips are transferred from the workpiece processing sheet to the carrier sheet. Since the workpiece processing sheet according to this embodiment has the above-described characteristics, the generation of residue on the surface of the chips is suppressed even when the workpiece processing sheet is peeled off.

[0142] In step 3, instead of the carrier sheet described above, the material may be transferred to a different workpiece processing sheet. That is, in step 3, the other workpiece processing sheet functions as a carrier sheet and is attached to the back surface of multiple chips.

[0143] (Step 4) In Step 4, 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.

[0144] As shown in Figure 5(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 aligned to the planned bonding position by an alignment mechanism (not shown). Next, as shown in Figure 5(B), the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 are brought into contact and fixed to the planned bonding position for bonding. As a method for bringing the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 into contact, an example is to use a pressing mechanism 110 to press from the back surface 51b side (carrier sheet 80 side) of the chip 51 to bring it into contact with the wafer 60.

[0145] 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 6. Since the generation of residue at the bonding surface of the chips is suppressed in step 3, the expansion of the void area during direct bonding is suppressed. The same procedure can be followed in step 3 if a different workpiece processing sheet is used instead of the carrier sheet.

[0146] In step 4, 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.

[0147] By performing steps 1 to 4, the workpiece (wafer) is fragmented, and the resulting workpiece chips are directly bonded to the wafer. In other words, the workpiece chips can be directly bonded while maintaining a clean surface.

[0148] (Step 5) The above method for manufacturing a workpiece may include, in addition to steps 1 and 2, a step (step 5) of grinding the back surface of the workpiece (wafer). The above method for joining workpieces may include, in addition to steps 1 to 4, a step (step 5) of grinding the back surface of the workpiece (wafer). Step 5 can be performed before step 2.

[0149] In step 5, as shown in Figure 7, the surface 50a of the wafer 50 and the ring frame 100 are attached to the main surface 20a of the adhesive layer 20 of the workpiece processing sheet 1 according to this embodiment, thereby fixing the wafer 50 and the ring frame 100 together. By attaching the workpiece processing sheet to the surface of the wafer, the surface of the wafer is kept clean even after performing step 5.

[0150] The wafer 50 and ring frame 100, fixed to the workpiece processing sheet 1, are set in a grinding device (not shown), and the back surface 50b of the wafer 50 is ground. In other words, in step 5, the workpiece processing sheet functions as a back grind sheet.

[0151] The workpiece processing sheet attached to the wafer in step 5 may be the same as the workpiece processing sheet attached to the wafer in step 1, or it may be a different workpiece processing sheet. In other words, the workpiece processing sheet according to this embodiment may serve as both a backgrind sheet and a dicing sheet. Alternatively, after the completion of step 5, the workpiece processing sheet used as a backgrind sheet may be peeled off, and the workpiece processing sheet used as a dicing sheet may be attached to the surface of the wafer after back-grinding (step 1) and then step 2 may be performed.

[0152] Furthermore, in the method for manufacturing workpieces and the method for joining workpieces, steps 2 and 5 may be performed integrally. In this case, methods such as DBG (Dicing Before Grinding), LDBG (Laser Dicing Before Grinding), PDBG (Plasma Dicing Before Grinding), and pre-grinding stealth dicing (registered trademark) can be employed. That is, by forming grooves or modified regions on the wafer and then performing backside grinding, the wafer can be separated into individual pieces.

[0153] (Step 6) The above method for joining workpieces may include, in addition to steps 1 to 4 above, a step (step 6) in which another workpiece (another chip) is directly joined to the back surface of a workpiece (chip) that has been directly joined to a wafer. Step 6 is performed after step 4.

[0154] In step 6, in a chip-on-wafer where chips are directly bonded to a wafer, another chip is directly bonded to the same chip. This results in a chip-on-wafer with chips stacked on a wafer. Therefore, in step 6, direct bonding can be performed in the same manner as in step 4, except for directly bonding the chips together.

[0155] When performing step 6, it is preferable to use a separate workpiece processing sheet as the carrier sheet in step 3. In step 6, the back surface of the chip directly bonded to the wafer becomes the bonding surface in direct bonding. Since the separate workpiece processing sheet used as the carrier sheet is attached to the back surface of the workpiece (chip 51 in Figure 3(B)) obtained by piecewise separating the workpiece (wafer 50 in Figure 3(A)), the bonding surface (back surface) is kept as clean as the surface of the workpiece (chip) until direct bonding. Therefore, the generation of residue on the bonding surface is suppressed, and the expansion of the void area can be suppressed even when another chip is directly bonded. It is preferable that the workpiece processing sheet according to this embodiment is attached to the surface of the other chip.

[0156] 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.

[0157] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0158] (Example 1) (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.

[0159] (2) Adhesive layer (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 polymer was then reacted with 2-methacryloyloxyethyl isocyanate (MOI) 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.

[0160] 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 polymers in Examples 2-6 and Comparative Examples 1-5, 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

[0161] 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.

[0162] (Formation of adhesive layer) The adhesive composition described above was applied to the release-treated surface of a release sheet (Lintec Corporation, product name "SP-PET381031", polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38 μm), and dried to form an energy-ray curable adhesive layer i with a thickness of 10 μm on the release sheet.

[0163] (3) Preparation of workpiece processing sheet A workpiece processing sheet having the structure of base material (thickness 80 μm) / adhesive layer (thickness 10 μm) / release sheet was prepared by laminating the adhesive layer of the release sheet to one main surface of the base material prepared in (1).

[0164] (Example 2) A workpiece processing sheet was obtained in the same manner as in Example 1, except that an energy-ray curable adhesive layer ii was formed instead of adhesive layer i using the following adhesive composition coating agent.

[0165] (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).

[0166] 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.

[0167] (Example 3) Substrate C was prepared in the same manner as in Example 1, except that an ethylene-(meth)acrylic acid copolymer resin composition was used instead of a low-density polyethylene resin composition. A workpiece processing sheet was prepared in the same manner as in Example 1, except that substrate C was used instead of substrate A.

[0168] (Example 4) A workpiece processing sheet was prepared in the same manner as in Example 3, except that an adhesive layer ii was formed instead of adhesive layer i.

[0169] (Example 5) A workpiece processing sheet was obtained in the same manner as in Example 1, except that an energy-ray curable adhesive layer iii was formed instead of adhesive layer i using the following adhesive composition coating agent.

[0170] (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.

[0171] 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 1 part 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.

[0172] (Example 6) A workpiece processing sheet was obtained in the same manner as in Example 1, except that an energy-ray curable adhesive layer iv was formed instead of adhesive layer i using the following adhesive composition coating agent.

[0173] (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.

[0174] 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.

[0175] (Comparative Example 1) Substrate B was prepared by the same method as in Example 1, except that a polyvinyl chloride resin composition was used instead of a low-density polyethylene resin composition. A workpiece processing sheet was prepared by the same method as in Example 1, except that substrate B was used instead of substrate A.

[0176] (Comparative Example 2) A workpiece processing sheet was prepared in the same manner as in Comparative Example 1, except that an adhesive layer ii was formed instead of adhesive layer i.

[0177] (Comparative Example 3) A workpiece processing sheet was obtained in the same manner as in Comparative Example 1, except that an energy-ray non-curing adhesive layer v was formed using the following adhesive composition coating agent.

[0178] (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).

[0179] 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.

[0180] (Comparative Example 4) A workpiece processing sheet was prepared in the same manner as in Comparative Example 3, except that base material A was used instead of base material B.

[0181] (Comparative Example 5) A workpiece processing sheet was prepared in the same manner as in Comparative Example 3, except that base material C was used instead of base material B.

[0182] The obtained samples (Examples 1-6 and Comparative Examples 1-5) were evaluated as follows. The results are shown in Table 1.

[0183] (Peak area after GPC measurement of components derived from workpiece processing sheets) Workpiece processing sheets from Examples 1-4 and Comparative Examples 1-5 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 measurement samples. An immersion test was performed on these measurement samples by immersing them 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. For workpiece processing sheets from Examples 1-4 and Comparative Examples 1-2, the illuminance was 230 mW / cm². 2 Total light intensity 190 mJ / cm 2A sheet for workpiece processing, irradiated with ultraviolet light under the specified irradiation conditions, was cut and subjected to an immersion test.

[0184] 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

[0185] (Gel fraction of workpiece processing sheet) After the immersion test described above, the section, nylon mesh sheet, and fasteners were all removed from toluene and dried at 90°C for 3 hours. They were then allowed to stand for 1 hour at 23°C and 50% relative humidity to conditioned humidity. The total mass of the section, nylon mesh sheet, and fasteners after conditioning (M51) was measured. Using this M51, along with the mass of the section before the immersion test (M11), the mass of the nylon mesh sheet (M2), and the mass of the fasteners (M3), the gel fraction of the workpiece processing sheet was calculated using the following formula (1). The results are shown in Table 1. Gel fraction of workpiece processing sheet = 100 × (M51 - M2 - M3) / (M11 - M2 - M3) (1)

[0186] (Adhesive strength of workpiece processing sheets) Workpiece processing sheets prepared in the examples and comparative examples were cut to a width of 25 mm to prepare test pieces. The adhesive layer of the test piece 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 adhesive strength (adhesive strength without UV irradiation) was measured. The results are shown in Table 1.

[0187] For Examples 1-4 and Comparative Examples 1 and 2, the adhesive layer of a separate test specimen was attached to a silicon mirror wafer using a roller with a mass of 2 kg. Ultraviolet light at an irradiance of 230 mW / cm² was then applied to the adhesive layer of this test specimen from the substrate side of the workpiece processing sheet. 2 , light intensity 190mJ / cm 2 After curing the 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.

[0188] (Peak area of ​​components derived from the substrate after GPC measurement) Instead of the workpiece processing sheet, the above immersion test was performed on prepared substrates A to C, and GPC measurement was performed on the recovered toluene solvent under the above measurement conditions to calculate the peak area of ​​the substrate after GPC measurement. The results are shown in Table 1.

[0189] (Peak area after GPC measurement of components derived from the adhesive layer) Instead of the workpiece processing sheet, the above immersion test was performed on the prepared adhesive layers i to v, and GPC measurements were performed on the recovered toluene solvent under the above measurement conditions to calculate the peak area after GPC measurement of the adhesive layer. For adhesive layers i to iv, the illuminance was 230 mW / cm². 2 Total light intensity 190 mJ / cm 2 The samples were irradiated with ultraviolet light under the specified irradiation conditions and then subjected to immersion testing. The results are shown in Table 1.

[0190] (Gel fraction of the adhesive layer) Instead of using a sheet for workpiece processing, the above immersion test was performed on the prepared adhesive layers i to v, and the gel fraction of the adhesive layer was calculated from the above formula (1) using the remaining sections after the test. The results are shown in Table 1.

[0191] (Evaluation of DTB feasibility (Condition 1)) The release sheets were peeled off from the workpiece processing sheets of the examples and comparative examples, and the exposed adhesive layer was attached to the surface opposite the polished surface (non-polished surface), i.e., the front surface, of a dry-polished silicon wafer (diameter: 12 inches, thickness: 150 μm) using a tape mounter device (Lintec Corporation, product name "RAD-2700F / 12"), and the adhesive layer was also attached to the ring frame.

[0192] A silicon wafer with a workpiece processing sheet attached was blade-diced using a dicing device (DISCO Corporation, product name "DFD6362") along with a ring frame to obtain individual silicon chips from the silicon wafer. The dicing size was 6 mm x 6 mm. Next, the workpiece processing sheet was stretched using an expander to widen the spacing between silicon chips to 0.03 mm. 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 was cured by irradiating it with ultraviolet light under the specified irradiation conditions.

[0193] Next, a carrier sheet (Lintec Corporation, product name "D-485H") was attached to the side of the silicon chip that did not have the workpiece processing sheet attached (the polished surface), i.e., the back surface, using a tape mounter device (Lintec Corporation, product name "RAD-2700F / 12"). After attaching the carrier sheet, the workpiece processing sheet was peeled off from the side of the silicon chip opposite to the polished surface (the non-polished surface) using a tape peeling device, obtaining a laminate of the carrier sheet and the silicon chip with the polished surface of the silicon chip attached to the adhesive layer of the carrier sheet.

[0194] Subsequently, plasma irradiation treatment was performed on the exposed surface (non-polished surface) of the silicon chip held on the carrier sheet. 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 chip was to be joined.

[0195] With respect to the laminate of the carrier sheet and the silicon chip after the plasma irradiation treatment, ultraviolet irradiation was performed from the base material side of the carrier sheet under the following conditions to cure the adhesive layer of the carrier sheet. Irradiation device: manufactured by Rintec Co., Ltd., RAD-2000m / 12 Illuminance: 230 mW / cm 2 Integrated light quantity: 190 mJ / cm 2

[0196] In the laminate of the carrier sheet after ultraviolet irradiation and the silicon chip after plasma irradiation treatment, the exposed surface (bonding surface) of the silicon chip after plasma irradiation treatment was arranged to face the bonding surface of the silicon wafer, and the silicon chip was pressed at 5 N for 0.5 seconds from the surface opposite to the bonding surface with a pressing tool of the same size as the silicon chip, and direct bonding (DTB) was performed by bringing it into contact with the silicon wafer. In Examples 1 to 6 and Comparative Examples 1 to 5, the above direct bonding was performed on 10 silicon chips, and the bonding state was evaluated according to the following criteria. The results are shown in Table 1. A: The state where 10 silicon chips were maintained joined for 1 minute or more after immediately reversing the silicon wafer after direct bonding. B: There was a silicon chip that dropped in less than 1 minute after immediately reversing the silicon wafer after direct bonding. F: There was a silicon chip that did not bond even after direct bonding.

[0197] (Evaluation of Void Area Ratio) Direct bonding (DTB) was performed by pressing the plasma-irradiated surface of a silicon chip (size: 6 mm × 6 mm × 150 μm (thickness)) obtained in the same "Evaluation of DTB Feasibility (Condition 1)" above against the plasma-irradiated surface of a silicon wafer (diameter: 8 inches, thickness: 750 μm) prepared in the above "Evaluation of DTB Feasibility (Condition 1)" with a pressing tool of the same size as the silicon chip at 5 N for 0.5 seconds. Using a scanning ultrasonic flaw detector (Sonoscan, product name "D9600TMCSAM"), the silicon chip after direct bonding was observed from the side opposite to 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 void area ratio relative to the area of ​​the bonding area. In Examples 1 to 6 and Comparative Examples 1 and 2, the bonding area was observed for 50 chips, and the average value of the void area ratio was determined. A void area ratio of 15% or less was considered good. The results are shown in Table 1. For Comparative Examples 3 to 5, the evaluation of the bonding state was "F" in "Evaluation of DTB feasibility (Condition 1)," so the void area ratio was not evaluated.

[0198] (Pickup Test) The silicon chip to be used for the pickup test was fabricated as follows. First, a silicon wafer with a thickness of 725 μm was prepared. Next, a protective film to be attached to the prepared silicon wafer was fabricated as follows.

[0199] An energy-ray curable adhesive layer iii (thickness: 5 μm) was formed on the peeled surface of the first release film (Lintec Corporation, product name "SP-PET382150", a polyethylene terephthalate (PET) film with silicone release treatment) using the adhesive composition of Example 5 in the same manner as in Example 5. Next, the peeled surface of the second release film (Lintec Corporation, product name "SP-PET381031", a polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38 μm) was bonded to the surface of the adhesive layer iii to obtain a laminate in which the adhesive layer iii (protective film) was placed between the release films. The second release film was peeled off from the obtained laminate and the exposed protective film was attached to one side of the prepared silicon wafer. Then, the first release film was peeled off. The side of the silicon wafer with the protective film attached was designated as the front surface.

[0200] Next, using a dicing device (DISCO Corporation, product name "DFD6363"), the silicon wafer was half-cut (diced) to a depth of 50 μm (total depth 55 μm) from the surface of the silicon wafer, penetrating the 5 μm thick protective film on the surface where the protective film was attached, thereby forming a 5 mm x 5 mm square region.

[0201] After half-cutting, the energy-ray curable adhesive layer of the backgrind sheet (Lintec Corporation, product name "E-3100UN") was bonded to the protective film. This resulted in a laminate of the backgrind sheet, protective film, and silicon wafer. In this laminate, the side of the silicon wafer that did not have the backgrind sheet and protective film attached was designated as the back surface.

[0202] In the resulting laminate, the back surface of the silicon wafer (the side without the backgrind sheet and protective film) was ground using a back grinding device (Disco Corporation, device name "DGP8761") until the silicon wafer thickness was 30 μm, thereby separating the silicon wafer into individual pieces. After separation, the backgrind sheet and protective film were subjected to an illuminance of 230 mW / cm² from the backgrind sheet side. 2 , cumulative light intensity 380 mJ / cm 2 The adhesive layer and protective film of the backgrind sheet were cured by irradiating them with ultraviolet light under these irradiation conditions.

[0203] Next, the adhesive layers of the workpiece processing sheets from Examples 1-6 and Comparative Examples 1-5 were attached to the grinding surface (back surface) and ring frame of the individualized silicon wafers. Then, the backgrind sheet and protective film were peeled off from the surface of the individualized silicon wafers. This resulted in laminates of workpiece processing sheets and silicon chips, in which the back surfaces of multiple silicon chips were attached to the workpiece processing sheets from Examples 1-6 and Comparative Examples 1-5. The size of the silicon chips was 5 mm × 5 mm × 30 μm (thickness).

[0204] The resulting laminate was irradiated with ultraviolet light from the substrate side of the workpiece processing sheet under the following conditions to cure the adhesive layer of the workpiece processing sheet: Irradiation device: Lintec RAD-2000m / 12; Illuminance: 230mW / cm² 2 Total luminous intensity: 190 mJ / cm 2

[0205] Next, using a pickup die bonding device (Canon Machinery Co., Ltd. "BESTEMD510"), a block the same size as the silicon chip was pushed up from the workpiece processing sheet side for 0.5 seconds under conditions of a pickup height of 500 μm and a pickup speed of 1 mm / s, thereby detaching 30 silicon chips from the adhesive layer of the workpiece processing sheet. In addition, a high-speed camera (Shinano Kenshi Co., Ltd., Plexlogger) was used to observe the delamination behavior at the interface between the adhesive layer and the silicon chip from the start to the end of the silicon chip push-up, and the time until a delamination trigger was formed at the interface (delamination trigger time) was measured. The obtained delamination trigger times were evaluated according to the following criteria. The results are shown in Table 1. A: Delamination trigger time less than 0.3 seconds B: Delamination trigger time 0.3 seconds or more and 0.5 seconds or less F: No delamination trigger was confirmed within 0.5 seconds

[0206] (Evaluation of DTB feasibility (Condition 2)) Using the laminate of the workpiece processing sheet and silicon chip obtained in the "Pickup Test" described above, the surface of the obtained silicon chip (unground surface) and the polished surface of the silicon wafer (diameter: 8 inches, thickness: 750 μm) were subjected to plasma irradiation treatment using the same method as in "Evaluation of DTB feasibility (Condition 1)" described above. Direct bonding (DTB) was then performed, and the bonding state was evaluated according to the same criteria as in "Evaluation of DTB feasibility (Condition 1)". The results are shown in Table 1.

[0207]

[0208] Table 1 shows that in Examples 1 to 6, where the workpiece processing sheet has the above-described physical properties, it was confirmed that even when the workpiece obtained using the workpiece processing sheet is directly bonded to a wafer, the expansion of the void area at the interface of the bonded portion can be suppressed.

[0209] On the other hand, in Comparative Examples 1 and 2, although the bonding state of direct bonding under Condition 1 was not problematic, a large void area ratio was confirmed. Therefore, it was confirmed that Comparative Examples 1 and 2 have a high probability of experiencing poor conductivity, etc. In Comparative Examples 3 to 5, the peak area after GPC measurement of the adhesive layer was large, so it was confirmed that direct bonding under Condition 1 is highly unlikely to be possible.

[0210] Furthermore, in Examples 5 and 6, the peeling trigger time in the pickup test was short, resulting in good peeling of the silicon chip from the workpiece processing sheet when the workpiece processing sheet was used as the carrier sheet. It was confirmed that the bonding state of direct bonding under Condition 2, which is a stricter condition than Condition 1, was better than that of Examples 1 to 4, which had a longer peeling trigger time. Moreover, since the back surface of the silicon chip can be kept clean, even when another silicon chip is directly bonded to the back surface of the silicon chip, the expansion of the void area can be suppressed.

[0211] 1...Workpiece processing sheet 10...Substrate 20...Adhesive layer 50...Workpiece (wafer) 51...Workpiece processed product (chip) 60...Wafer 70...Chip-on-wafer 80...Carrier sheet

Claims

1. A workpiece processing sheet used for processing workpieces to manufacture workpieces to be directly joined, wherein the workpiece processing sheet 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 sheet 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 sheet 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 the toluene solvent to elution from the column on the horizontal axis. 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 sheet according to claim 1, wherein, in gel permeation chromatography measurement, the peak area of ​​the detected component in the range from the elution time corresponding to a standard polystyrene number-average molecular weight of 10,000 to the elution time corresponding to a standard polystyrene number-average molecular weight of 200 is 4,000 mV·s or less.

3. The workpiece processing sheet according to claim 1 or 2, wherein the adhesive force to the silicon wafer is 300 mN / 25 mm or less.

4. The workpiece processing sheet according to claim 1 or 2, wherein when a rectangular silicon chip with sides of 5 mm and a thickness of 30 μm, which is attached to the workpiece processing sheet according to claim 1 or 2, is pushed up from the workpiece processing sheet side, the time until a peeling trigger is formed at the interface between the workpiece processing sheet and the silicon chip is defined as the peeling trigger time, and the peeling trigger time is 5 seconds or less.

5. A workpiece processing sheet according to claim 1 or 2, comprising a base material and an adhesive layer.

6. The workpiece processing sheet according to claim 5, wherein the base material does not contain a polyvinyl chloride film containing a plasticizer.

7. The workpiece processing sheet according to claim 5, wherein the following immersion test is performed on the adhesive layer, 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) An adhesive layer 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 in contact with the adhesive layer. (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 the 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.

8. The workpiece processing sheet according to claim 5, wherein the gel fraction of the adhesive layer is 95% or more.

9. The workpiece processing sheet according to claim 5, wherein the adhesive layer is composed of an energy ray curable adhesive.

10. The workpiece processing sheet according to claim 5, wherein the adhesive layer is composed of an acrylic adhesive.

11. A method for manufacturing a workpiece, comprising the steps of: attaching a workpiece processing sheet according to claim 1 or 2 to the surface of a workpiece having a surface and a back surface opposite to the surface, for manufacturing a workpiece to be directly joined; and separating the workpiece to which the workpiece processing sheet has been attached into individual pieces to obtain a plurality of workpieces.

12. A method for using the workpiece processing sheet according to claim 1 or 2, wherein the sheet has a surface and a back surface facing the surface, and is used to obtain a plurality of workpieces by attaching it to the surface of a workpiece for manufacturing workpieces to be directly joined, and then separating the workpiece into individual pieces.

13. A method for using the workpiece processing sheet according to claim 1 or 2, wherein the sheet has a surface and a back surface facing the surface, and is used to be attached to the back surfaces of a plurality of workpieces obtained by separating workpieces for manufacturing workpieces to be directly joined.

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