Die attachment film, dicing die bonding film, and semiconductor device manufacturing method

Abstract

This die attachment film is used for bonding a second semiconductor chip to a plurality of spacers disposed around a first semiconductor chip on a substrate, such that the second semiconductor chip covers the first semiconductor chip while straddling the space between the plurality of spacers. The die attachment film presents a minimum melt viscosity of 2000 Pa·s or greater and 9800 Pa·s or less in a range of 90-180°C. The minimum melt viscosity is a value obtained by measuring the dynamic viscoelasticity of the die attachment film in a temperature range including the range of 90-180°C under the condition of a temperature increase rate of 5°C / min and a frequency of 4Hz.

Description

Die attach film, dicing die bonding film, and method for manufacturing semiconductor device

[0001] The present disclosure relates to a die attach film, a dicing die bonding film, and a method for manufacturing a semiconductor device.

[0002] In a semiconductor device having multiple semiconductor chips, other semiconductor chips may be adhered to multiple support pieces arranged as spacers around the semiconductor chip on a substrate using an adhesive film (die attach film, DAF) (see, for example, Patent Document 1).

[0003] JP 2023-102570 A

[0004] The present disclosure relates to a die attach film used to adhere a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, and relates to suppressing voids, sink marks, and sagging in the die attach film that accompanies thermal curing.

[0005] The present disclosure includes the following: [1] A die attach film used to adhere a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, the die attach film exhibiting a minimum melt viscosity of 2000 Pa·s or more and 9800 Pa·s or less in the temperature range of 90 to 180°C, the minimum melt viscosity being a value determined by measuring the dynamic viscoelasticity of the die attach film in a temperature range that includes the range of 90 to 180°C under conditions of a heating rate of 5°C / min and a frequency of 4 Hz. [1'] An application or use of a die attach film for adhering a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, wherein the die attach film exhibits a minimum melt viscosity of 2000 Pa·s or more and 9800 Pa·s or less in the range of 90 to 180°C, and the minimum melt viscosity is a value determined by measuring the dynamic viscoelasticity of the die attach film in a temperature range including the range of 90 to 180°C under conditions of a heating rate of 5°C / min and a frequency of 4 Hz. [2] A die attach film used to adhere a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, the die attach film comprising a thermosetting component, an elastomer, and an inorganic filler, the elastomer content being 20% ​​by mass or more and 30% by mass or less, and the inorganic filler content being 35% by mass or more and 45% by mass or less, based on the mass of the die attach film.[2'] An application or use of a die attach film for adhering a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, wherein the die attach film comprises a thermosetting component, an elastomer, and an inorganic filler, and the content of the elastomer is 20% by mass or more and 30% by mass or less, and the content of the inorganic filler is 35% by mass or more and 45% by mass or less, based on the mass of the die attach film. [3] The die attach film according to [1] or [2], wherein a wire is connected to the first semiconductor chip, and the die attach film is used to adhere the second semiconductor chip so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, and the wire is embedded in the die attach film. [4] The die attach film according to any one of [1] to [3], which is used to attach a second semiconductor chip to the first semiconductor chip and a plurality of the spacers so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers. [5] The die attach film according to any one of [1] to [4], which exhibits a loss modulus of 200 MPa or less at -2°C under a condition of a frequency of 10 Hz. [6] A dicing die bonding film comprising: a dicing film; and the die attach film according to any one of [1] to [5], which is provided on the dicing film.[7] A method for manufacturing a semiconductor device, comprising: preparing an intermediate structure having a substrate, a first semiconductor chip provided on the substrate, and a plurality of spacers arranged around the first semiconductor chip on the substrate; arranging a second semiconductor chip and an adhesive-backed chip having a die attach film provided on the second semiconductor chip on the plurality of spacers of the intermediate structure such that the die attach film is interposed between the spacers and the second semiconductor chip and the second semiconductor chip covers the first semiconductor chip while spanning the plurality of spacers, thereby forming a pre-adhesive body having the intermediate structure and the adhesive-backed chip; and heating the pre-adhesive body, thereby forming an adhesive body in which the second semiconductor chip is adhered to the plurality of spacers by the hardened die attach film, wherein the die attach film is the die attach film according to any one of [1] to [5]. [8] The method according to [7], wherein a wire is connected to the first semiconductor chip, and in the adhesive structure, the second semiconductor chip is adhered to the plurality of spacers by the cured die attach film and the wire is embedded in the cured die attach film. [9] The method according to [7] or [8], further comprising: preparing a laminate having a dicing die bonding film having a dicing film and the die attach film, and a plurality of the second semiconductor chips formed by dicing a semiconductor wafer, the plurality of second semiconductor chips being arranged on one die attach film; and dividing the die attach film by stretching the dicing film while cooling the laminate, thereby forming the adhesive-attached chips having the individual die attach films.

[10] The method according to any of [7] to [9], wherein in the adhesive structure, the second semiconductor chip is adhered to the plurality of spacers and the first semiconductor chip by the cured die attach film.

[0006] With regard to a die attach film used to adhere a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, voids, sink marks, and sagging of the die attach film due to thermocompression bonding and thermosetting can be suppressed.

[0007] 1 is a process diagram showing an example of a method for manufacturing a semiconductor device. FIG. 2 is a process diagram showing an example of a method for manufacturing a semiconductor device. FIG. 3 is a process diagram showing an example of a method for manufacturing a semiconductor device. FIG. 4 is a process diagram showing an example of a method for manufacturing a semiconductor device. FIG. 5 is a process diagram showing an example of a method for manufacturing a semiconductor device. FIG. 6 is a process diagram showing an example of a method for preparing an adhesive-attached chip. FIG. 7 is a process diagram showing an example of a method for preparing an adhesive-attached chip. FIG. 8 is a plan view showing a preliminary bonded body for evaluating the DA performance of a die attach film. FIG. 9 is a cross-sectional view showing a preliminary bonded body for evaluating the DA performance of a die attach film. FIG. 10 is a cross-sectional view showing a preliminary bonded body for evaluating the DA performance of a die attach film. FIG. 11 is a cross-sectional view showing a preliminary bonded body for evaluating the DA performance of a die attach film. FIG. 12 is an example of a cross-sectional photograph of a bonded body. FIG. 13 is an example of a cross-sectional photograph of a bonded body. FIG. 14 is an example of a cross-sectional photograph of a bonded body.

[0008] The present invention is not limited to the following examples. In the following examples, the components (including steps, etc.) are not essential unless specifically stated. The size of the components in each drawing is conceptual, and the relative size relationships between the components are not limited to those shown in each drawing. The numerical values ​​and their ranges exemplified below do not limit the present disclosure.

[0009] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0010] In this specification, (meth)acrylate means acrylate or its corresponding methacrylate, and the same applies to other similar expressions such as (meth)acryloyl group, (meth)acrylic copolymer, etc.

[0011] 1 to 5 are process diagrams that schematically show an example of a method for manufacturing a semiconductor device. The method shown in FIGS. 1 to 5 includes preparing an intermediate structure 15 (FIG. 1) that includes a substrate 1, a first semiconductor chip T1 provided on the substrate 1, and a plurality of spacers 3 arranged around the first semiconductor chip T1 on the substrate 1, and then arranging a second semiconductor chip T2 and an adhesive-attached chip TA that includes a die attach film 12a provided on the second semiconductor chip T2 on the plurality of spacers 3 of the intermediate structure 15 so that the die attach film 12a is interposed between the spacers 3 and the second semiconductor chip T2 and the second semiconductor chip T2 covers the first semiconductor chip T1 while spanning the plurality of spacers 3, thereby forming a preliminary adhesive body 5 that includes the intermediate structure 15 and the adhesive-attached chip TA. 0 (FIG. 2); heating the preliminary adhesive body 50 to thereby form an adhesive body 55 in which the second semiconductor chip T2 is adhered to the plurality of spacers 3 by the hardened die attach film 12a (FIG. 3); stacking a third semiconductor chip T3 and a fourth semiconductor chip T4 in order on the surface of the second semiconductor chip T2 opposite the substrate 1 with a die attach film 13 that is the same as or different from the die attach film 12 interposed therebetween to thereby form an adhesive body 56 having a plurality of semiconductor chips including the first semiconductor chip T1 and the second semiconductor chip T2 (FIG. 4); and forming a sealing layer 60 that seals the adhesive body 56 to obtain the semiconductor device 100 (FIG. 5).

[0012] 6 to 8 are process diagrams schematically illustrating an example of a method for preparing an adhesive-attached chip TA. The method shown in Figures 6 to 8 includes preparing a laminate 35 having a dicing die bonding film 30 having a die attach film 12 and a dicing film 20, and a plurality of second semiconductor chips T2 formed by dicing a semiconductor wafer T0, the plurality of second semiconductor chips T2 being arranged on one die attach film 12, stretching the dicing film 20 while cooling the laminate 35 to divide the die attach film 12, thereby forming adhesive-attached chips TA having individual die attach films 12a, and picking up the adhesive-attached chips TA from the dicing film 20.

[0013] The laminate 35 for forming the adhesive-backed chips TA is formed by a half-cut dicing method that includes, for example, forming grooves G on one side of the semiconductor wafer T0 by half-cutting the semiconductor wafer T0, grinding the semiconductor wafer T0 from the side opposite the grooves G on a back-grinding tape 25 to divide the semiconductor wafer T0 into a plurality of second semiconductor chips T2, as shown in Fig. 6(b) , and attaching a dicing die bonding film 30 to the side of the semiconductor chips T2 opposite the back-grinding tape 25 as shown in Fig. 6(c) The method for dividing the semiconductor wafer T0 is not limited to the half-cut dicing method, and may be, for example, a stealth dicing method.

[0014] The thickness of the second semiconductor chip T2 may be, for example, 1 μm or more and 100 μm or less. The width (maximum width or length of one side) of the second semiconductor chip T2 may be, for example, 20 mm or less. The width (maximum width or length of one side) of the second semiconductor chip T2 may be, for example, 3 mm or more and 15 mm or less, or 5 mm or more and 10 mm or less.

[0015] The dicing die bonding film 30 is a laminated film having a dicing film 20 and a die attach film 12. The dicing film 20 may have a base film 21 and an adhesive layer 22 provided on the base film 21. Typically, the die attach film 12 is provided on the adhesive layer 22 side. The dicing film 20 and the adhesive layer 22 have ends that extend outward beyond the ends of the die attach film 12.

[0016] Examples of the substrate film 21 include resin films such as polytetrafluoroethylene film, polyethylene terephthalate film, polyethylene film, polypropylene film, polymethylpentene film, and polyimide film. The substrate film 21 may be a resin film whose surface has been treated by primer application, UV treatment, corona discharge treatment, polishing treatment, or etching treatment. The thickness of the substrate film 21 may be, for example, 20 μm or more and 200 μm or less.

[0017] The adhesive layer 22 can be a layer formed from an adhesive commonly used in dicing films. The adhesive constituting the adhesive layer 2 may be an ultraviolet-curable adhesive or a non-ultraviolet-curable adhesive. An ultraviolet-curable adhesive is an adhesive whose adhesiveness decreases when irradiated with ultraviolet light. When the dicing film 20 has the adhesive layer 22 formed from an ultraviolet-curable adhesive, the adhesive strength of the adhesive layer 2 may be decreased by ultraviolet light irradiation, for example, before the adhesive-attached chip TA is picked up. The thickness of the adhesive layer 2 may be, for example, 1 μm or more and 20 μm or less.

[0018] The dicing die bonding film 30 is attached to the second semiconductor chips T2 while being heated as needed, with the die attach film 12 facing the second semiconductor chips T2. The heating temperature for attaching the dicing die bonding film 30 may be, for example, 60°C or higher and 80°C or lower.

[0019] 7(a), a dicing ring DR is attached to the dicing film 20 of the laminate 35. The dicing ring DR is attached to the end of the dicing film 20 (adhesive layer 22) that protrudes from the die attach film 12 so as to surround the second semiconductor chip T2 on the die attach film 12. Before or after the dicing ring DR is attached, the backgrinding tape 25 is peeled off from the second semiconductor chip T2.

[0020] 7B, while the laminate 35 is being cooled, the dicing film 20 is stretched by a cooling expander that pushes up the region of the dicing film 20 inside the dicing ring DR with the ring Ra. By stretching the dicing film 20, the die attach film 12 is divided. By dividing the die attach film 12, an adhesive-attached chip TA having the second semiconductor chip T2 and the singulated die attach film 12 is formed on the dicing film 20. The temperature to which the laminate 35 is cooled may be, for example, −15° C. or higher and 0° C. or lower.

[0021] After the ring Ra is lowered, the region of the dicing film 20 between the dicing ring DR and the adhesive-backed chips TA may be heated by a heater H, as shown in (a) of Figure 8. Thermal contraction of the dicing film 20 in the heated area may further widen the gap (kerf width) between the adhesive-backed chips TA.

[0022] After the adhesive strength of the adhesive layer 22 is reduced by ultraviolet irradiation or the like, as shown in Fig. 8(b), the individual adhesive-coated chips TA pushed up by the push-up jig 42 are picked up by a suction collet 44. The picked-up adhesive-coated chips TA are used in the manufacturing method of the semiconductor device shown in Figs. 1 to 5, for example.

[0023] In the method of FIGS. 1 to 5, in addition to the adhesive-attached chip TA, an intermediate structure 15 having a substrate 1, a first semiconductor chip T1 and a spacer 3, as shown in FIG. 1, is prepared.

[0024] The first semiconductor chip T1 may be adhered to the substrate 1 by a die attach film 11 that may be the same as or different from the die attach film 12. The first semiconductor chip T1 may be connected to a wire w on the surface opposite to the substrate 1. The first semiconductor chip T1 may be a controller chip. The substrate 1 may be an organic substrate or a metal substrate such as a lead frame. The thickness of the substrate 1 may be, for example, 90 μm or more and 300 μm or less. The spacer 3 may be one that is commonly used in semiconductor devices having a dolmen structure, and may be, for example, a support including a semiconductor chip.

[0025] When the height of the first semiconductor chip T1 from the substrate 1 is h1 and the height of the spacer 3 from the substrate 1 is h2, h1 and h2 may be the same or different. When h1 and h2 are different, voids, sink marks, or sagging of the die attach film 12a tend to occur easily during thermal curing. When h1 is smaller than h2, sink marks of the die attach film 12a may easily occur near the edge of the first semiconductor chip T1. When h1 is larger than h2, a portion of the die attach film 12a may easily sag along the edge surface of the first semiconductor chip T1. The difference between h1 and h2 may be, for example, 0 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more, or may be 20 μm or less. As described below, a die attach film 12a that exhibits a specific minimum melt viscosity under a frequency of 4 Hz can effectively suppress voids, sink marks, and sagging that accompany thermal curing, even when the difference between h1 and h2 is relatively large. The height h1 of the first semiconductor chip T1 from the substrate 1 may be, for example, 50 μm or more and 100 μm or less. The height h2 of the spacer 3 from the substrate 1 may be, for example, 30 μm or more and 120 μm or less.

[0026] The thickness of the first semiconductor chip T1 may be, for example, 1 μm or more and 100 μm or less. The width (maximum width or length of one side) of the first semiconductor chip T1 may be, for example, 20 mm or less. The width (maximum width or length of one side) of the first semiconductor chip T1 may be 3 mm or more and 15 mm or less, or 5 mm or more and 10 mm or less. A wire w may be connected to the first semiconductor chip T1.

[0027] 2, a second semiconductor chip T2 and a die attach film 12a (adhesive-attached chip TA) are disposed on an intermediate structure 15 such that the die attach film 12 is interposed between the intermediate structure 15 and the second semiconductor chip T2. In the example of FIG. 2, in a pre-adhesive body 50 having the intermediate structure 15 and the adhesive-attached chip TA, the die attach film 12a is disposed on the spacer 3 of the intermediate structure 15, and the die attach film 12a and the first semiconductor chip T1 are spaced apart. If the height h1 of the first semiconductor chip T1 is the same as or greater than the height h2 of the spacer 3, the first semiconductor chip T1 and the die attach film 12 may be in contact with each other in the pre-adhesive body 50 before being heated.

[0028] When the die attach film 12a is thermally cured by heating the preliminary adhesive body 50, an adhesive body 55 is formed in which the second semiconductor chip T2 is adhered to the intermediate structure 15 (the spacer 3 and the first semiconductor chip T1), as shown in Fig. 3. The die attach film 12a after thermal curing contacts the first semiconductor chip T1 due to flow associated with thermal curing, and may have part of the wire w connected to the first semiconductor chip T1 embedded therein. The die attach film 12a after thermal curing does not necessarily have the wire w embedded therein.

[0029] The heating temperature of the pre-adhesive body 50 to form the adhesive body 55 may be constant or variable. The heating temperature may be up to 90° C. or higher and 180° C. The pre-adhesive body 50 may be heated under pressure, atmospheric pressure, or reduced pressure.

[0030] Next, as shown in FIG. 4 , wires w are provided to connect the second semiconductor chip T2 and the substrate 1. Furthermore, a third semiconductor chip T3 and a fourth semiconductor chip T4 may be stacked in this order on the surface of the second semiconductor chip T2 opposite the substrate 1, with the same or a different die attach film 13 interposed therebetween as the die attach film 12a. This forms an adhesive body 56 including the first semiconductor chip T1, the second semiconductor chip T2, and one or more additional semiconductor chips. Wires w may be provided to connect the third semiconductor chip T3 or the fourth semiconductor chip T4 to the substrate 1. In the case of the adhesive body 56 shown in FIG. 4 , the number of semiconductor chips stacked on the spacer 3 is three, but this number may be four or more and may be ten or less.

[0031] 5, a semiconductor device 100 having a dolmen structure is obtained by forming a sealing layer 60 that seals an adhesive body having multiple semiconductor chips including a first semiconductor chip T1 and a second semiconductor chip T2. The sealing layer 60 may fill the space between the first semiconductor chip and the spacer 3. If the die attach film 12a is locally deformed due to sink marks, sagging, or the like, the sealing layer 60 may penetrate into that area, which may cause defects such as cracks in the second semiconductor chip T2. The semiconductor device 100 may be, for example, a 3D NAND flash memory.

[0032] Details of examples of die attach films (particularly die attach films 12 and 12a) that can be used to manufacture a semiconductor device in the above-exemplified method are described below.

[0033] The die attach film may exhibit a minimum melt viscosity of 2000 Pa·s or more and 9800 Pa·s or less at a frequency of 4 Hz in the range of 90 to 180° C. The minimum melt viscosity here is the melt viscosity (shear viscosity or complex viscosity η ) determined by measuring the dynamic viscoelasticity of the die attach film in a temperature range including the range of 90 to 180° C. at a temperature rise rate of 5° C. / min and a frequency of 4 Hz. ＊) The melt viscosity of the die attach film usually decreases with increasing temperature, and then increases with the progress of the curing reaction. According to the findings of the present inventors, when the minimum melt viscosity of the die attach film in dynamic viscoelasticity measurement, particularly at a frequency of 4 Hz, is 2000 Pa·s or more and 9800 Pa·s or less, the occurrence of voids, sink marks, and sagging of the die attach film due to thermal curing can be effectively suppressed. From the same perspective, the minimum melt viscosity of the die attach film in dynamic viscoelasticity measurement at a frequency of 4 Hz can be 2100 Pa·s or more, 2200 Pa·s or more, 2300 Pa·s or more, 2400 Pa·s or more, 2500 Pa·s or more, 2600 Pa·s or more, 2700 Pa·s or more, 2800 Pa·s or more, 2900 Pa·s or more, 3000 Pa·s or more. The viscosity may be 3100 Pa·s or more, 3200 Pa·s or more, 3300 Pa·s or more, 3400 Pa·s or more, or 3500 Pa·s or more, and may be 9500 Pa·s or less, 9000 Pa·s or less, 8000 Pa·s or less, 7000 Pa·s or less, 6000 Pa·s or less, 5000 Pa·s or less, or 4000 Pa·s or less.

[0034] The die attach film may exhibit a loss modulus of 200 MPa or less at -2°C under conditions of a frequency of 10 Hz. If the loss modulus, which corresponds to viscosity, is low at a low temperature of -2°C, the die attach film is likely to stably break when stretched under cooling. From a similar perspective, the loss modulus of the die attach film at -2°C under conditions of a frequency of 10 Hz may be 190 MPa or less, or 180 MPa or less, or may be 50 MPa or more.

[0035] The loss modulus of the die attach film at -2°C can be a value determined by measuring the dynamic viscoelasticity of the die attach film in a temperature range including -2°C under conditions of a temperature rise rate of 3°C / min and a frequency of 10 Hz.

[0036] The thickness of the die attach film may be, for example, 10 μm or more, or 20 μm or more, or may be 200 μm or less, 150 μm or less, 120 μm or less, 80 μm or less, or 60 μm or less.

[0037] The die attach film may be, for example, a thermosetting adhesive containing a thermosetting component, an elastomer, and an inorganic filler.

[0038] The thermosetting component may include a thermosetting resin. The thermosetting resin here is a compound capable of forming a crosslinked structure by a curing reaction, including a reaction with a curing agent and / or self-polymerization. Examples of thermosetting resins include epoxy resins, which are compounds having epoxy groups. Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, stilbene epoxy resins, triazine skeleton-containing epoxy resins, fluorene skeleton-containing epoxy resins, triphenol phenol methane epoxy resins, biphenyl epoxy resins, xylylene epoxy resins, biphenyl aralkyl epoxy resins, naphthalene epoxy resins, and diglycidyl ether compounds derived from polyfunctional phenolic compounds or polycyclic aromatic compounds (such as anthracene). These may be used alone or in combination of two or more. The epoxy resin may include a combination of an o-cresol novolac type epoxy resin and a bisphenol F type epoxy resin and / or a bisphenol A type epoxy resin.

[0039] The thermosetting component may contain a curing agent that reacts with the thermosetting resin. The curing agent combined with the epoxy resin as the thermosetting resin may contain, for example, a phenolic resin. Examples of phenolic resins used as curing agents include novolac phenolic resins, allylated bisphenol A, allylated bisphenol F, allylated naphthalenediol, phenol aralkyl resins, and naphthol aralkyl resins. These may be used alone or in combination of two or more.

[0040] The total content of the thermosetting resin and the curing agent may be, for example, 10% by mass or more or 15% by mass or more, based on the mass of the die attach film, or 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less.

[0041] The die attach film may contain an imidazole compound. The imidazole compound is a compound having an imidazole ring and can function as a curing accelerator that accelerates the curing reaction between an epoxy resin and its curing agent (such as a phenolic resin). The imidazole compound may be, for example, at least one selected from the group consisting of 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. The content of the imidazole compound may be 0.03% by mass or more, or 1.0% by mass or less, 0.90% by mass or less, 0.80% by mass or less, 0.70% by mass or less, 0.60% by mass or less, 0.5% by mass or less, 0.40% by mass or less, 0.30% by mass or less, 0.20% by mass or less, 0.10% by mass or less, or 0.09% by mass or less, based on the mass of the die attach film.

[0042] The elastomer may be, for example, an acrylic rubber. The acrylic rubber is an elastomer containing monomer units derived from a (meth)acrylic acid ester. The content of the structural units derived from a (meth)acrylic acid ester in the acrylic rubber may be, for example, 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the total amount of the acrylic rubber. The acrylic rubber may contain monomer units derived from a (meth)acrylic acid ester having a crosslinkable functional group such as an epoxy group, an alcoholic or phenolic hydroxyl group, and a carboxyl group. The acrylic resin may be a copolymer containing a (meth)acrylic acid ester and an acrylonitrile as monomer units.

[0043] The glass transition temperature (Tg) of an elastomer (e.g., acrylic resin) may be −50° C. or higher, −30° C. or higher, 0° C. or higher, or 3° C. or higher, or may be 50° C. or lower, 45° C. or lower, 40° C. or lower, 35° C. or lower, 30° C. or lower, or 25° C. or lower. The glass transition temperature (Tg) refers to a value measured using a DSC (differential scanning calorimeter) (e.g., "Thermo Plus 2" manufactured by Rigaku Corporation). The Tg of the elastomer can be adjusted to a desired range by adjusting the type and content of the structural units constituting the elastomer (structural units derived from (meth)acrylic acid esters in the case of acrylic resins).

[0044] The weight average molecular weight (Mw) of the elastomer (e.g., acrylic rubber) may be 100,000 or more, 200,000 or more, or 300,000 or more, or may be 3,000,000 or less, 2,000,000 or less, or 1,000,000 or less. When the Mw of the elastomer is within this range, the viscoelasticity of the die attach film 12 tends to be easily controlled appropriately. Mw refers to a value measured by gel permeation chromatography (GPC) and converted using a calibration curve based on standard polystyrene.

[0045] Commercially available examples of acrylic rubber include SG-70L, SG-708-6, WS-023 EK30, SG-280 EK23, and SG-P3 (all manufactured by Nagase ChemteX Corporation), and H-CT-865 (manufactured by Resonac Corporation).

[0046] When the elastomer content is high, the minimum melt viscosity of the die attach film tends to be high. When the elastomer content is low, the loss modulus of the die attach film at -2°C tends to be low. From these viewpoints, the elastomer content may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the mass of the die attach film 12, or may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less.

[0047] The inorganic filler may be, for example, particles containing at least one inorganic material selected from aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, boron nitride, and silica. The inorganic filler may include a silica filler.

[0048] The average particle size of the inorganic filler may be 0.01 μm or more, or 0.03 μm or more, or may be 1.5 μm or less, 1.0 μm or less, 0.8 μm or less, 0.08 μm or less, or 0.06 μm or less. Two or more inorganic fillers with different average particle sizes may be combined. The average particle size means a value calculated from the BET specific surface area.

[0049] When the content of inorganic filler is large, the minimum melt viscosity of the die attach film tends to increase, and the loss modulus of the die attach film tends to decrease at −2° C. The content of inorganic filler may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more, or may be 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less, based on the mass of the die attach film.

[0050] For example, when the elastomer content is 20% by mass or more and 30% by mass or less and the inorganic filler content is 35% by mass or more and 45% by mass or less, based on the mass of the die attach film, it is easy to satisfy both a minimum melt viscosity of 2000 Pa·s or more and 9800 Pa·s or less at a frequency of 4 Hz in the range of 90 to 180°C, and a loss modulus of 200 MPa or less at -2°C.

[0051] The die attach film may further contain a coupling agent. The coupling agent may be a silane coupling agent. Examples of silane coupling agents include γ-ureidopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltrimethoxysilane. These may be used alone or in combination of two or more. The die attach film may further contain other components such as a pigment, an ion scavenger, and an antioxidant.

[0052] The present invention is not limited to the following examples. 1. Preparation of die attach film Adhesive varnishes were prepared containing the following materials in the amounts (unit: parts by mass) shown in Table 1. The elastomer and inorganic filler contents shown in Table 1 are the amounts of solids (acrylic rubber or silica filler) excluding the solvent. (A) Epoxy Resin N-500P-10 (trade name, manufactured by DIC Corporation, o-cresol novolac type epoxy resin, epoxy equivalent: 203 g / eq) EXA-830CRP (trade name, manufactured by DIC Corporation, bisphenol F type epoxy resin, epoxy equivalent: 158 to 168 g / eq) (B) Curing Agent (Phenolic Resin) MEH-7800M (trade name, manufactured by Meiwa Chemical Industry Co., Ltd., phenol novolac type phenolic resin, hydroxyl group equivalent: 175 g / eq, softening point: 61 to 90°C) (C) Inorganic Filler Silica Filler 1 (silica filler dispersion, average particle size: 0.50 μm) Silica Filler 2 (silica filler dispersion, average particle size: 0.30 μm) Silica Filler 3 (silica filler dispersion, average particle size: 0.016 μm) (D) Elastomer SG-P3 (trade name, manufactured by Nagase ChemteX Corporation, acrylic rubber, weight average molecular weight: 800,000, Tg: 12°C, cyclohexanone solution) (E) Coupling agent A-189 (trade name, manufactured by Nippon Unicar Co., Ltd., γ-mercaptopropyltrimethoxysilane) A-1160 (trade name, manufactured by Nippon Unicar Co., Ltd., 3-ureidopropyltriethoxysilane) (F) Curing accelerator 2PZ-CN (trade name, manufactured by Shikoku Chemicals Corporation, 1-cyanoethyl-2-phenylimidazole)

[0053] Each prepared adhesive varnish was filtered through a 500-mesh filter. Each filtered adhesive varnish was vacuum degassed. The vacuum degassed adhesive varnish was applied to a polyethylene terephthalate (PET) film (support film) that had been subjected to a release treatment. The coating was dried in two stages, at 90°C for 5 minutes and then at 130°C for 5 minutes, to form a B-stage die attach film (thickness: 20 μm) on the support film.

[0054] 2. Evaluation (1) Minimum Melt Viscosity Eight film pieces of a predetermined size were cut out from the die attach film. They were laminated using a rubber roll on a hot plate at 70°C to prepare a 400 μm thick laminate. This laminate was punched out with a φ9 mm punch to prepare a disk-shaped sample with a circular surface approximately 9 mm in diameter. The sample was attached to the measurement jig of a rotational viscoelasticity measuring device (manufactured by TA Instruments Japan, Inc., product name: ARES-RDA). The gap of the measurement jig was adjusted so that the load applied to the sample at this point was 10 to 15 g. Next, the dynamic viscoelasticity of the sample was measured under the following conditions. From the measurement results, the minimum melt viscosity (minimum value of shear viscosity) in the range of 90 to 180°C was read. Measurement conditions: Disc plate: Aluminum, circular (8 mm diameter) Measurement frequency: 4 Hz Heating rate: 5°C / min Distortion: 5% Measurement temperature: 35 to 180°C Initial load: 100 g

[0055] (2) Loss Modulus at -2°C A plurality of die attach films were laminated using a rubber roll on a hot plate at 70°C to form a laminate with a thickness of 120 μm. A rectangular parallelepiped measurement sample having a surface size of 4 mm wide x 25 mm long was cut out from this laminate. The sample was mounted in a dynamic viscoelasticity measuring device (Rheogel-E4000, manufactured by UBM Co., Ltd.), and the dynamic viscoelasticity of the sample was measured under the following conditions. From the measurement results, the loss modulus at -2°C was read and used as the loss modulus of the die attach film at 150°C. Measurement conditions: Measurement mode: Tension Chuck distance: 20 mm Heating rate: 3°C / min Frequency: 10 Hz Load: Automatic static load Measurement temperature: -10 to 30°C

[0056] The measurement results of the dynamic viscoelasticity of each die attach film are shown in Table 1. For Comparative Example 1, the minimum melt viscosity at a frequency of 1 Hz is also shown in the table.

[0057]

[0058] (3) DA Performance Figures 9, 10, 11, and 12 show preliminary bonded structures for evaluating the DA performance of die attach films. Figure 9 is a plan view of the preliminary bonded structure 50A, and Figure 10 is a cross-sectional view of line X-X in Figure 9. The preliminary bonded structure 50A includes a substrate 1, a first semiconductor chip T1 measuring 1.6 mm x 4.5 mm, two spacers 3 measuring 3.6 mm x 2.5 mm, and a second semiconductor chip T2 measuring 4.0 mm x 12 mm. On the substrate 1, the two spacers 3 are disposed on either side of the first semiconductor chip T1. The first semiconductor chip T1 and the spacers 3 are bonded to the substrate 1 via a die attach film 11. h1 is the combined height of the die attach film 11 and the first semiconductor chip T1 from the substrate 1, and h2 is the combined height of the die attach film 11 and the spacers 3 from the substrate 1. In the case of the preliminary adhesive body 50A in Fig. 10, h1 is 65 µm, h2 is 75 µm, and h1 < h2. The preliminary adhesive body 50B in Fig. 11 differs from the preliminary adhesive body 50A in that h1 is 75 µm, and h1 = h2. The preliminary adhesive body 50C in Fig. 12 differs from the preliminary adhesive body 50A in that h1 is 85 µm, and h1 > h2.

[0059] An adhesive-backed chip was prepared, including a second semiconductor chip T2 and a die attach film attached thereto. The die attach film used was the die attach film of Comparative Example 1 or Example 2 prepared in "1. Preparation of Die Attach Film." The prepared adhesive-backed chip was laminated on a spacer 3 so as to cover the first semiconductor chip T1, forming pre-adhesive bodies 50A, 50B, and 50C. The pre-adhesive bodies 50A, 50B, and 50C were pressed together for 1.5 seconds using a heat press at 120°C. The heat press pressure was set to 45 N for the pre-adhesive body 50A and 30 N for the pre-adhesive bodies 50B and 50C. The die attach film was cured by this thermocompression bonding, forming a bonded body in which the second semiconductor chip T2 was adhered to the spacer 3 and the first semiconductor chip T1.

[0060] The interface between the cured die attach film and the first semiconductor chip T1 in the formed adhesive body was observed in reflection mode at 75 MHz using an ultrasonic digital imaging diagnostic device (manufactured by Insight Co., Ltd., product name: IS-350), and the area ratio of voids at the specified interface was determined. If the area ratio was 5% or more, it was determined that voids were present.

[0061] The formed bonded body was cut in half, and the shape of the cured die attach film in the cross section was observed using an optical microscope. Near the edge of the first semiconductor chip T1, if the thickness t1 of the die attach film in the portion that sagged below the die attach film-side main surface of the first semiconductor chip T1 was a maximum of 26 μm or more, it was determined that sagging was present. If a portion of the edge of the first semiconductor chip T1 where the thickness t2 of the die attach film had decreased to a minimum of 10 μm or less due to sink marks was observed, it was determined that sink marks were present.

[0062] FIG. 13 is a cross-sectional photograph of a bonded body formed from the preliminary bonded body 50C of Comparative Example 1. Dragging with a maximum thickness t1 of 26 μm was observed. FIG. 14 is a cross-sectional photograph of a bonded body formed from the preliminary bonded body 50C of Example 2. The maximum thickness t1 was 20 μm or less. FIG. 15 is a cross-sectional photograph of a bonded body formed from the preliminary bonded body 50A of Comparative Example 1. Dragging with a thickness t2 of 10 μm or less was observed. FIG. 16 is a cross-sectional photograph of a bonded body formed from the preliminary bonded body 50A of Example 2. No dragging with a thickness t1 of 26 μm or more or sink marks with a thickness t2 of 10 μm or less were observed. Table 2 shows the observation results for voids, sagging, and sink marks.

[0063]

[0064] (2) Cooling Separability A dicing die bonding film was prepared by laminating each die attachment film prepared in "1. Preparation of Die Attach Film" with a dicing tape having an adhesive layer. In the dicing die bonding film, the adhesive layer protruded beyond the edge of the die attachment film. Grooves corresponding to silicon chips having a size of 4 × 12 mm were formed on one side of a silicon wafer by half-cut dicing. A back-grinding tape was attached to the surface of the silicon wafer on which the grooves were formed. The surface of the silicon wafer on which the grooves were formed was ground using a grinder-polisher device from the side opposite the back-grinding tape until the thickness of the silicon wafer was 50 μm, thereby singulating the silicon wafer. A die attachment film of the dicing die bonding film was attached to the side of the silicon chip formed by singulation opposite the back-grinding tape while heating to 70 °C. The adhesive layer protruding from the die attachment film was attached to a dicing ring, and then the back-grinding tape was peeled off from the silicon chip. Next, using a die separator (DDS2300, manufactured by Disco Corporation), the dicing film of the dicing die bonding film was stretched by cooling and expanding under the following cooling and expanding conditions, thereby dividing the die attach film. The dicing film was then shrunk by heating (heat shrinking) under the following heating conditions. (Cooling and Expanding Conditions) Cooling temperature: -2°C Cooling time: 100 seconds Push-up amount: 21 mm Push-up speed: 300 mm / sec Holding time after push-up: 3 seconds (Heating Conditions) Heater temperature: 250°C Heater rotation speed: 4° / sec Push-up amount: 12 mm Tape cooling waiting time: 3 seconds After the dicing film shrunk, the pressure-sensitive adhesive layer was irradiated with ultraviolet light under the following conditions, thereby reducing the adhesive strength of the pressure-sensitive adhesive layer. (Ultraviolet Irradiation Conditions) Ultraviolet irradiance: 80 mW / cm ２ UV irradiation dose: 130 mJ / cm ２

[0065] After the cooling separation test, the entirety of the formed adhesive-backed chips was irradiated with light. If the die attach film was properly separated between adjacent adhesive-backed chips and light passed through without being blocked by the die attach film, the result was rated as "A." If there were areas where light did not pass through because the die attach film was not properly separated, the result was rated as "B."

[0066]

[0067] The evaluation results of cooling splittability are shown in Table 3. A comparison of Example 1 with Examples 2 and 3 confirmed that good cooling splittability was exhibited when the loss modulus at -2°C was 200 MPa or less. Furthermore, the evaluation results of cooling splittability in Comparative Example 2 confirmed that a moderately low minimum melt viscosity also contributed to improving cooling splittability.

[0068] 1...substrate, 3...spacer, 11, 12, 13...die attach film, 12a...individualized die attach film, 15...intermediate structure, 20...dicing film, 21...base material film, 22...adhesive layer, 30...dicing die bonding film, 35...laminated body, 42...push-up jig, 44...suction collet, 50, 50A, 50B, 50C...preliminary adhesive body, 55, 56...adhesive body, 60...sealing layer, 100...semiconductor device, T0...semiconductor wafer, T1...first semiconductor chip, T2...second semiconductor chip, TA...adhesive-attached chip, DR...dicing ring, G...groove, H...heater, Ra...ring, w...wire.

Claims

1. A die attach film used to adhere a second semiconductor chip to a plurality of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, the die attach film exhibiting a minimum melt viscosity of 2000 Pa·s or more and 9800 Pa·s or less in the range of 90 to 180°C, the minimum melt viscosity being a value determined by measuring the dynamic viscoelasticity of the die attach film in a temperature range including the range of 90 to 180°C under conditions of a heating rate of 5°C / min and a frequency of 4 Hz.

2. A die attach film used to adhere a second semiconductor chip to a number of spacers arranged around a first semiconductor chip on a substrate so that the second semiconductor chip covers the first semiconductor chip while spanning between the spacers, the die attach film comprising a thermosetting component, an elastomer, and an inorganic filler, the elastomer content being 20% ​​by mass or more and 30% by mass or less, and the inorganic filler content being 35% by mass or more and 45% by mass or less, based on the mass of the die attach film.

3. A die attach film as described in claim 1 or 2, wherein a wire is connected to the first semiconductor chip, and the die attach film is used to adhere the second semiconductor chip such that the second semiconductor chip covers the first semiconductor chip while spanning between a plurality of the spacers, and the wire is embedded in the die attach film.

4. A die attach film as described in claim 1 or 2, which is used to adhere a second semiconductor chip to the first semiconductor chip and a plurality of the spacers so that the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers.

5. A die attach film according to claim 1 or 2, which exhibits a loss modulus of 200 MPa or less at -2°C under a frequency of 10 Hz.

6. A dicing die bonding film comprising: a dicing film; and a die attach film according to claim 1 or 2 provided on the dicing film.

7. A method for manufacturing a semiconductor device comprising: preparing an intermediate structure having a substrate, a first semiconductor chip provided on the substrate, and a plurality of spacers arranged around the first semiconductor chip on the substrate; arranging a second semiconductor chip, and an adhesive-attached chip having a die attach film provided on the second semiconductor chip, on the plurality of spacers of the intermediate structure such that the die attach film is interposed between the spacer and the second semiconductor chip and the second semiconductor chip covers the first semiconductor chip while spanning between the plurality of spacers, thereby forming a pre-adhesive body having the intermediate structure and the adhesive-attached chip; and heating the pre-adhesive body, thereby forming an adhesive body in which the second semiconductor chip is adhered to the plurality of spacers by the hardened die attach film, wherein the die attach film is the die attach film defined in claim 1 or 2.

8. The method according to claim 7, wherein a wire is connected to the first semiconductor chip, and in the adhesive, the second semiconductor chip is adhered to the spacers by the cured die attach film, and the wire is embedded in the cured die attach film.

9. The method of claim 7, further comprising: preparing a laminate having a dicing die bonding film having a dicing film and the die attach film, and a plurality of the second semiconductor chips formed by dicing a semiconductor wafer, the plurality of second semiconductor chips being arranged on one of the die attach films; and dividing the die attach film by stretching the dicing film while cooling the laminate, thereby forming the adhesive-attached chips having the individualized die attach films.

10. The method of claim 7, wherein in the adhesive body, the second semiconductor chip is adhered to the plurality of spacers and the first semiconductor chip by the cured die attach film.

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