JP2024124013A - Manufacturing method of electronic device - Google Patents

Abstract

The present invention provides a method for manufacturing an electronic device that can improve the adhesion between an electronic component and an adhesive film and protect the electronic component, even when the method includes a process in a vacuum atmosphere.
[Solution] A method for manufacturing an electronic device, comprising the steps of: (A) preparing a structure comprising an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component; and (B) treating, in a vacuum atmosphere, the surface of the electronic component in the structure opposite the circuit formation surface, wherein the adhesive film has a residual stress ratio of 55.0% or less at 100°C and a residual stress ratio of 5.0% or more and 90.0% or less at 150°C.
[Selected Figure] Figure 1

Description

The present invention relates to a method for manufacturing an electronic device.

Some manufacturing methods for electronic devices include a process of forming a circuit of an electronic component, and then performing processes such as back grinding, ion implantation, laser annealing, sputtering, etc. on the surface of the electronic component opposite to the surface on which the circuit is formed. In these processes, an adhesive film is attached to protect the surface on which the circuit is formed of the electronic component.
An example of a technique related to a manufacturing method for such an electronic device is described in Patent Document 1 (WO 2015/152010).

Patent Document 1 describes a protective film that has a polyimide substrate and a thermosetting adhesive layer provided on one surface of the polyimide substrate and is obtained from a composition containing an acrylic polymer (a), a thermal radical generator (b) having a 1-minute half-life temperature of 140° C. or more and 200° C. or less, and a crosslinking agent (c), and is attached to a circuit-forming surface of a semiconductor wafer. Patent Document 1 also describes a method for manufacturing a semiconductor device using the protective film described in Patent Document 1.
Patent Document 1 describes that when the protective film is applied to a manufacturing method for a semiconductor device including a step of attaching the protective film to the circuit-forming surface of a semiconductor wafer, thermally curing the thermosetting adhesive layer, and then performing vacuum heating while the protective film is still attached to the semiconductor wafer, it is possible to provide a protective film that protects the circuit-forming surface of the semiconductor wafer, suppresses the occurrence of lifting, and has excellent releasability when peeled off from the semiconductor wafer.

International Publication No. 2015/152010

In such a manufacturing method for electronic devices, if the adhesion between the electronic components and the adhesive film is insufficient, water or chemicals may penetrate between the electronic components and the adhesive film, causing deterioration of the electronic components.

The inventors' investigations have revealed that in a manufacturing method for electronic devices that includes a process in a vacuum atmosphere, in order to improve adhesion between the electronic components and the adhesive film and protect the electronic components, in the process of attaching the adhesive film to the circuit formation surface of the electronic components, it is necessary for the adhesive film to conform to the irregularities of the circuit formation surface of the electronic components (irregularity-following ability), and that in the process in a vacuum atmosphere, the adhesive film attached to the electronic components does not float (vacuum resistance).

Furthermore, according to the inventors' research, it has become clear that, although a method of making the adhesive film flexible can be used to improve the ability to conform to uneven surfaces, the adhesive film is prone to deformation in a vacuum atmosphere and is prone to floating away from electronic components. On the other hand, a method of making the adhesive film hard can be used to improve vacuum resistance, but it has become clear that this results in insufficient ability to conform to uneven surfaces when attached to electronic components. In other words, it has become clear that there is a trade-off between ability to conform to uneven surfaces and vacuum resistance.

The present invention has been made in consideration of the above circumstances, and provides a method for manufacturing an electronic device that can improve the adhesion between the electronic components and the adhesive film and protect the electronic components, even in a manufacturing method for an electronic device that includes a process in a vacuum atmosphere.

According to the present invention, the following method for manufacturing an electronic device is provided.

[1]
A step (A) of preparing a structure including an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component;
(B) treating a surface of the electronic component in the structure opposite to the circuit-forming surface in a vacuum atmosphere,
The pressure-sensitive adhesive film has a residual stress rate at 100° C. of 55.0% or less, calculated by the following method 1;
A method for manufacturing an electronic device, wherein a residual stress rate at 150° C. calculated by the following method 2 is 5.0% or more and 90.0% or less.
[Method 1]
The pressure-sensitive adhesive film is laminated to a thickness of 1.4±0.1 mm to prepare a measurement sample, and the measurement sample is cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% is continuously applied is measured under the following conditions: temperature: 100°C, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is defined as the stress residual rate [%] at 100°C.
[Method 2]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130° C. for 30 minutes to prepare a measurement sample. The measurement sample was cut to a width of 10 mm, and the stress when a strain of 2% was continuously applied was measured using a dynamic viscoelasticity measuring device under the following conditions: temperature: 150° C., deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at 150° C.
[2]
A step (A) of preparing a structure including an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component;
(B) treating a surface of the electronic component in the structure opposite to the circuit-forming surface in a vacuum atmosphere,
The pressure-sensitive adhesive film has a residual stress rate of 55.0% or less at a temperature at which the electronic component and the pressure-sensitive adhesive film are bonded together, the residual stress rate being calculated by the following method 3;
A method for manufacturing an electronic device, wherein the residual stress rate at the temperature of the structure in step (B) is 5.0% or more and 90.0% or less, as calculated by the following method 4.
[Method 3]
The adhesive film is laminated to a thickness of 1.4±0.1 mm to prepare a measurement sample, and the measurement sample is cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% is continuously applied is measured under the following conditions: temperature: temperature at which the electronic component and the adhesive film are bonded together, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress is measured [Pa]) × 100" is the stress residual rate [%] at the temperature at which the electronic component and the adhesive film are bonded together.
[Method 4]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130° C. for 30 minutes to prepare a measurement sample, and the measurement sample was cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% was continuously applied was measured under the following conditions: temperature: temperature of the structure in the step (B), deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at the temperature of the structure in the step (B).
[3]
The method for manufacturing an electronic device according to [1] or [2], wherein the temperature of the structure in the step (B) is 60° C. or higher and 230° C. or lower.
[4]
The method further comprises the step of heating the structure;
The method for manufacturing an electronic device according to any one of [1] to [3] above, wherein the heating step is a step prior to the step (B).
[5]
The method for manufacturing an electronic device according to any one of the above [1] to [4], wherein the step (B) is at least one selected from the group consisting of an ion implantation step, a metal film formation step, and an annealing treatment step.
[6]
The method for producing an electronic device according to any one of [1] to [5] above, further comprising a step (C) of removing the adhesive film from the electronic component.
[7]
The method for producing an electronic device according to any one of [1] to [6] above, further comprising a step (D) of back-grinding a surface of the electronic component opposite to the circuit-forming surface.
[8]
The method for manufacturing an electronic device according to any one of [1] to [7] above, wherein the adhesive film comprises a base layer, an irregularity-absorbing resin layer, and a thermosetting adhesive layer in this order.
[9]
The method for manufacturing an electronic device according to the above [8], wherein the adhesive film is provided so that the irregularity-absorbing resin layer and the thermosetting adhesive layer are in direct contact with each other.
[10]
The method for manufacturing an electronic device according to [8] or [9], wherein the thermosetting adhesive layer of the adhesive film contains a (meth)acrylic resin and a thermal polymerization initiator.
[11]
The method for producing an electronic device according to any one of the above [8] to [10], wherein the resin constituting the unevenness-absorbing resin layer includes at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene.
[12]
The method for producing an electronic device according to any one of the above [8] to [11], wherein the thickness of the irregularity-absorbing resin layer is 20 μm or more and 500 μm or less.
[13]
The method for manufacturing an electronic device according to any one of [8] to [12] above, wherein the resin constituting the base layer includes at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide.
[14]
The method for manufacturing an electronic device according to any one of [1] to [13] above, wherein the electronic device is a power semiconductor device.

According to the present invention, it is possible to provide a method for manufacturing an electronic device that can improve the adhesion between the electronic components and the adhesive film and protect the electronic components, even in a method for manufacturing an electronic device that includes a process in a vacuum atmosphere.

FIG. 2 is a cross-sectional view showing a schematic diagram of a structure in step (A) according to an embodiment of the present invention. 1 is a cross-sectional view showing a schematic diagram of a preferred layer structure of an adhesive film according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings, similar components are given the same reference numerals, and the description will be omitted as appropriate. The drawings are schematic diagrams and do not correspond to the actual dimensional ratios. Furthermore, the numerical range "A to B" represents A or more and B or less unless otherwise specified. Furthermore, in this embodiment, "(meth)acrylic" means acrylic, methacrylic, or both acrylic and methacrylic.
Unless otherwise specified, "the manufacturing method of the electronic device of this embodiment" means an embodiment including both "the manufacturing method of the electronic device of the first embodiment" and "the manufacturing method of the electronic device of the second embodiment."
The adhesive film of the first embodiment means an adhesive film used in the manufacturing method of the electronic device of the first embodiment. The adhesive film of the second embodiment has the same meaning as the adhesive film of the first embodiment.
Furthermore, unless otherwise specified, "the adhesive film of the present embodiment" refers to an embodiment including both the "adhesive film of the first embodiment" and the "adhesive film of the second embodiment."

<Method of Manufacturing Electronic Device>
A manufacturing method for an electronic device according to a first embodiment includes the steps of: preparing a structure including an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component; and treating a surface of the electronic component in the structure opposite the circuit formation surface side under a vacuum atmosphere, wherein the adhesive film has a residual stress ratio of 55.0% or less at 100°C and a residual stress ratio of 5.0% or more and 90.0% or less at 150°C.
Here, the residual stress ratio at 100° C. means a value calculated by the following method 1. Also, the residual stress ratio at 150° C. means a value calculated by the following method 2.
[Method 1]
A measurement sample is prepared by laminating adhesive films to a thickness of 1.4±0.1 mm, and the measurement sample is cut to a width of 10 mm. The measurement sample is measured using a dynamic viscoelasticity measuring device under the following conditions: temperature: 100°C, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, and stress when a strain of 2% is continuously applied is measured. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress is measured [Pa]) × 100" is defined as the residual stress rate [%] at 100°C.
[Method 2]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130°C for 30 minutes to prepare a measurement sample. The measurement sample was cut to a width of 10 mm, and the stress when a strain of 2% was continuously applied was measured using a dynamic viscoelasticity measuring device under the following conditions: temperature: 150°C, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at 150°C.

A manufacturing method for an electronic device according to a second embodiment includes a step (A) of preparing a structure having an electronic component having a circuit formation surface and an adhesive film bonded to the circuit formation surface side of the electronic component, and a step (B) of treating a surface of the electronic component in the structure opposite the circuit formation surface side under a vacuum atmosphere, wherein the adhesive film has a residual stress ratio of 55.0% or less at a temperature at which the electronic component and the adhesive film are bonded together, and a residual stress ratio of 5.0% or more and 90.0% or less at the temperature of the structure in step (B).
The residual stress ratio at the temperature at which the electronic component and the adhesive film are bonded together means a value calculated by the following method 3. Also, the residual stress ratio at the temperature of the structure in step (B) means a value calculated by the following method 4.
[Method 3]
A measurement sample is prepared by laminating adhesive films to a thickness of 1.4±0.1 mm, and the measurement sample is cut to a width of 10 mm. The measurement sample is measured using a dynamic viscoelasticity measuring device under the following conditions: temperature: temperature at which the electronic component and the adhesive film are bonded together, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, and the stress when a strain of 2% is continuously applied is measured. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress is measured [Pa]) × 100" is defined as the residual stress rate [%] at the temperature at which the electronic component and the adhesive film are bonded together.
[Method 4]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130° C. for 30 minutes to prepare a measurement sample, and the measurement sample was cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% was continuously applied was measured under the following conditions: temperature: temperature of the structure in step (B), deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at the temperature of the structure in step (B).

As described above, in a manufacturing method of an electronic device including a step in a vacuum atmosphere, there is a trade-off between conformability to irregularities and vacuum resistance.
The present inventors have conducted extensive research to achieve the above object, and have found that the residual stress ratio at 100° C. and the residual stress ratio at 150° C. of an adhesive film used in a method for manufacturing an electronic device are effective design indicators for improving the balance of performance between conformability and vacuum resistance.

In addition, the inventors have found that the measures of the residual stress rate at the temperature at which the electronic component and the adhesive film are bonded together and the residual stress rate at the temperature of the structure in step (B) of the adhesive film used in the manufacturing method for electronic devices are effective design indicators for improving the performance balance between conformability to irregularities and vacuum resistance.
Since the residual stress rate at the temperature at which the electronic component and the adhesive film are bonded is within a specific range, the adhesive film becomes soft when the electronic component and the adhesive film are bonded together, and the adhesive film can conform to the unevenness of the circuit formation surface of the electronic component. Also, since the residual stress rate in the structure in step (B) is within a specific range, deformation of the adhesive film is suppressed even in a step under a vacuum atmosphere, and lifting of the adhesive film bonded to the electronic component can be reduced.
As described above, according to the manufacturing method for electronic devices of this embodiment, the performance balance between unevenness-following ability and vacuum resistance is improved, so that the adhesion between electronic components and the adhesive film can be improved even in a manufacturing method for electronic devices that includes a process in a vacuum atmosphere.

The electronic device in this embodiment includes elements, devices, final products, etc. to which electronic engineering technology is applied, such as semiconductor devices, power semiconductor devices, semiconductor chips, semiconductor elements, printed wiring boards, electric circuit display devices, information and communication terminals, light-emitting diodes, physical batteries, and chemical batteries.
The electronic device of this embodiment is preferably a power semiconductor device. A power semiconductor device is a semiconductor device that controls and converts electric power, and generally has a rated current of 1 A or more.

Each step of the manufacturing method for the electronic device of this embodiment will be described below.

[Step (A)]
FIG. 1 is a cross-sectional view that illustrates a structure 100 in step (A).
In step (A), a structure 100 is prepared that includes an electronic component 10 having a circuit-formation surface 10A and an adhesive film 50 attached to the circuit-formation surface 10A side of the electronic component 10.

Such a structure 100 can be produced by attaching an adhesive film 50 to the circuit formation surface 10A of the electronic component 10.
The method of bonding the adhesive film 50 to the circuit-forming surface 10A of the electronic component 10 is not particularly limited, and the bonding can be performed by a known method. For example, the bonding may be performed manually or by a device called an automatic bonding machine to which a roll-shaped adhesive film 50 is attached.

When the circuit-forming surface 10A of the electronic device 10 is bonded, for example, the adhesive film 50 is heated. The heating temperature is appropriately set depending on the type of adhesive film 50, and is not particularly limited, but may be, for example, 40° C. or more, 45° C. or more, 50° C. or more, 60° C. or more, 70° C. or more, 80° C. or more, 90° C. or more, 95° C. or more, and may be 120° C. or less, 110° C. or less, or 105° C. or less.
Here, the temperature at which the electronic component and the adhesive film are bonded together in the measurement conditions of Method 3 means the heating temperature described above.

The electronic component 10 is not particularly limited as long as it has a circuit formation surface 10A, but examples thereof include a semiconductor wafer, a sapphire substrate, a lithium tantalate substrate, a molded wafer, a molded panel, a molded array package, a semiconductor substrate, etc., and a semiconductor wafer is preferred.
Examples of semiconductor wafers include silicon wafers, sapphire wafers, germanium wafers, germanium-arsenic wafers, gallium-phosphorus wafers, gallium-arsenic-aluminum wafers, gallium-arsenic wafers, and lithium tantalate wafers, with silicon wafers being preferred.

Circuits such as wiring, capacitors, diodes, transistors, etc. are formed on the surface of the circuit-forming surface 10A of the electronic component 10. The circuit-forming surface may be subjected to plasma treatment.
Furthermore, the circuit formation surface 10A of the electronic component 10 may be an uneven surface due to the presence of bump electrodes or the like.
Furthermore, the bump electrodes are bonded to electrodes formed on the mounting surface, for example, when mounting an electronic device on the mounting surface, to form an electrical connection between the electronic device and the mounting surface (the mounting surface of a printed circuit board, etc.).
Examples of the bump electrode include a ball bump, a printed bump, a stud bump, a plated bump, and a pillar bump. That is, the bump electrode is usually a convex electrode. These bump electrodes may be used alone or in combination of two or more kinds.
The height and diameter of the bump electrodes are not particularly limited, but are preferably 10 μm or more, more preferably 50 μm or more, and preferably 400 μm or less, more preferably 300 μm or less. The bump pitch is also not particularly limited, but is preferably 20 μm or more, more preferably 100 μm or more, and preferably 600 μm or less, more preferably 500 μm or less.
The metal species constituting the bump electrode is not particularly limited, and examples thereof include solder, silver, gold, copper, tin, lead, bismuth, and alloys thereof, but the adhesive film 50 is preferably used when the bump electrode is a solder bump. These metal species may be used alone or in combination of two or more.

[Step (B)]
In step (B), surface 10B of electronic component 10 in structure 100 opposite circuit-forming surface 10A is treated.
Step (B) is a step subsequent to step (A).

In step (B), a vacuum atmosphere means a low-pressure state in which the pressure is reduced below atmospheric pressure by a vacuum device, and may be, for example, 1000 Pa or less, 100 Pa or less, or 10 Pa or less.

Step (B) may be performed under high temperature conditions. When step (B) is performed under high temperature conditions, the temperature of the structure 100 in step (B) is preferably 60° C. or higher, more preferably 80° C. or higher, even more preferably 100° C. or higher, even more preferably 120° C. or higher, even more preferably 140° C. or higher, and is preferably 230° C. or lower, more preferably 210° C. or lower, even more preferably 190° C. or lower, even more preferably 170° C. or lower.
Here, the temperature of the structure in step (B) in the measurement conditions of method 4 means the temperature of structure 100 in the above-mentioned step (B).

In step (B), the method for treating surface 10B of electronic component 10 opposite circuit-forming surface 10A is not particularly limited, and may be a step in a known method for manufacturing electronic devices.
The step (B) is preferably at least one selected from the group consisting of an ion implantation step, a metal film formation step, and an annealing treatment step.

The method for manufacturing an electronic device according to the present embodiment preferably further includes a step of heating the structure 100. The heating step is a step prior to step (B). Note that the heating step only needs to be performed prior to step (B), and another step may be included between the heating step and step (B).
It is preferable to further include a step of heating the structure 100, since the resin contained in the adhesive film 50 is thermally cured, and the adhesive film 50 can be more effectively prevented from floating away from the electronic component 10 in the step (B).
The temperature of the structure 100 in the step of heating the structure 100 is preferably 60° C. or higher, more preferably 80° C. or higher, even more preferably 100° C. or higher, even more preferably 120° C. or higher, even more preferably 140° C. or higher, and is preferably 230° C. or lower, more preferably 210° C. or lower, even more preferably 190° C. or lower, even more preferably 170° C. or lower.

[Step (C)]
The method for producing an electronic device of the present embodiment preferably further includes the step (C) of removing the adhesive film 50 from the electronic component 10 .
Step (C) is a step subsequent to step (B). That is, in step (C), adhesive film 50 is removed from electronic component 10 in structure 100.

The method for removing the adhesive film 50 from the electronic component 10 is not particularly limited, and may be performed, for example, by peeling the adhesive film 50 from the electronic component 10 using a known method. The peeling may be performed, for example, manually or by a device called an automatic peeling machine.

The adhesive film 50 may be peeled off from the electronic component 10 at room temperature (around 25°C), or if the automatic peeling machine has a heating function, the adhesive film 50 may be peeled off after the structure 100 has been heated to a predetermined temperature (e.g., 40°C or higher and 90°C or lower).

The surface of the electronic component 10 after peeling off the adhesive film 50 may be cleaned as necessary. Cleaning methods include wet cleaning such as water cleaning or solvent cleaning, and dry cleaning such as plasma cleaning. In the case of wet cleaning, ultrasonic cleaning may be used in combination. The cleaning method can be selected appropriately depending on the degree of contamination on the surface of the electronic component 10.

[Step (D)]
The method for manufacturing an electronic device of this embodiment preferably further includes a step (D) of backgrinding surface 10B of electronic component 10 opposite circuit-forming surface 10A.
Step (D) is a step carried out between step (A) and step (B).
"Back grinding" means to thin the electronic component 10 to a predetermined thickness without damaging the electronic component 10. For example, the structure 100 is fixed to a chuck table or the like of a grinding machine, and the surface 10B of the electronic component 10 opposite the circuit formation surface 10A is ground.

In such a back grinding operation, electronic component 10 is ground until its thickness becomes equal to or less than a desired thickness. The thickness of electronic component 10 before grinding is appropriately determined depending on the diameter, type, etc. of electronic component 10, and the thickness of electronic component 10 after grinding is appropriately determined depending on the size of the resulting chip, type of circuit, etc.
Furthermore, when the electronic component 10 is half-cut or a modified layer is formed by laser irradiation, the electronic component 10 is divided into individual chips.

The back grinding method is not particularly limited, and a known grinding method can be adopted. Grinding can be performed while cooling the electronic component 10 and the grindstone by pouring water on them. If necessary, a dry polishing step, which is a grinding method that does not use grinding water, can be performed at the end of the grinding step.
After the back grinding is completed, chemical etching is performed as necessary. Chemical etching is performed by immersing the electronic component 10 with the adhesive film 50 attached in an etching solution selected from the group consisting of an acidic aqueous solution consisting of a single or mixed solution of hydrofluoric acid, nitric acid, sulfuric acid, acetic acid, etc., and an alkaline aqueous solution such as a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution. Etching is performed for the purpose of removing distortion generated on the back surface of the electronic component 10, further thinning the electronic component 10, removing oxide films, etc., and pretreatment when forming an electrode on the back surface. The etching solution is appropriately selected depending on the above purpose.

[Other steps]
The method for manufacturing an electronic device according to the present embodiment may include other steps in addition to those described above. As the other steps, any method known in the art for manufacturing electronic devices may be used.
For example, any process generally performed in the manufacturing process of electronic components, such as a resist process, a developing process, an ashing process, a sputtering process, a dicing process, a die bonding process, a wire bonding process, a flip chip connection process, a cure heating test process, a sealing process, a reflow process, etc., may be further performed.

<Adhesive film>
The adhesive film used in the method for producing an electronic device according to this embodiment will be described.

The pressure-sensitive adhesive film of the first embodiment has a residual stress ratio at 100°C of 55.0% or less, and a residual stress ratio at 150°C of 5.0% or more and 90.0% or less.
The residual stress rate of the adhesive film of the first embodiment at 100°C is, from the viewpoint of further improving the unevenness-following ability of the adhesive film, preferably 50.0% or less, more preferably 45.0% or less, even more preferably 40.0% or less, even more preferably 35.0% or less, even more preferably 30.0% or less, and even more preferably 28.0% or less, and the lower limit is not particularly limited, but may be, for example, 1.0% or more, or 2.0% or more.
The stress residual rate of the adhesive film of the first embodiment at 150°C is preferably 8.0% or more, more preferably 10.0% or more, even more preferably 12.0% or more, and even more preferably 14.0% or more, from the viewpoint of further improving the vacuum resistance of the adhesive film, and is preferably 87.0% or less, more preferably 85.0% or less, even more preferably 83.0% or less, and even more preferably 81.0% or less, from the viewpoint of further improving the performance balance of the adhesive film's unevenness-following ability and vacuum resistance.
The stress residual rate at 100°C and the stress residual rate at 150°C of the adhesive film of the first embodiment can be controlled, for example, by the layer structure of the adhesive film, the thickness and material of each layer, etc., and specifically, by the resin used in the unevenness-absorbing resin layer, the thermal polymerization initiator contained in the thermosetting adhesive layer, etc.

The adhesive film of the second embodiment is an adhesive film having a residual stress ratio of 55.0% or less at the temperature at which the electronic component and the adhesive film are bonded together, and a residual stress ratio of 5.0% or more and 90.0% or less at the temperature of the structure in step (B).
The residual stress rate of the adhesive film of the second embodiment at the temperature at which the electronic component and the adhesive film are bonded together is, from the viewpoint of further improving the conformability of the adhesive film to irregularities, preferably 50.0% or less, more preferably 45.0% or less, even more preferably 40.0% or less, even more preferably 35.0% or less, even more preferably 30.0% or less, and even more preferably 28.0% or less, and the lower limit is not particularly limited, but may be, for example, 1.0% or more, or 2.0% or more.
The stress residual rate at the temperature of the structure in step (B) of the adhesive film of the second embodiment is, from the viewpoint of further improving the vacuum resistance of the adhesive film, preferably 8.0% or more, more preferably 10.0% or more, even more preferably 12.0% or more, and even more preferably 14.0% or more, and from the viewpoint of further improving the performance balance of the adhesive film's unevenness-following ability and vacuum resistance, is preferably 87.0% or less, more preferably 85.0% or less, even more preferably 83.0% or less, and even more preferably 81.0% or less.
The residual stress rate of the adhesive film of the second embodiment at the temperature at which the electronic component and the adhesive film are bonded together and the residual stress rate of the structure in step (B) can be controlled, for example, by the layer structure of the adhesive film, the thickness and material of each layer, etc., and specifically, by the resin used in the unevenness-absorbing resin layer and the thermal polymerization initiator contained in the thermosetting adhesive layer, etc.

The overall thickness of the adhesive film of this embodiment is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 40 μm or more, even more preferably 60 μm or more, even more preferably 80 μm or more, and even more preferably 100 μm or more, from the viewpoint of further improving the handleability of the adhesive film, and is preferably 700 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less, even more preferably 250 μm or less, and even more preferably 200 μm or less, from the viewpoint of further improving the unevenness-following ability of the adhesive film.

The layer structure of the pressure-sensitive adhesive film of the present embodiment is not particularly limited, and may be a single-layer structure or a multi-layer structure, but a multi-layer structure is preferable.
FIG. 1 is a cross-sectional view showing a schematic diagram of a preferred layer structure of an adhesive film according to an embodiment of the present invention.
As shown in FIG. 1, the adhesive film 50 of this embodiment preferably comprises a base layer 20, an unevenness-absorbing resin layer 30, and a thermosetting adhesive layer 40, in that order, and more preferably, the unevenness-absorbing resin layer 30 and the thermosetting adhesive layer 40 are arranged so as to be in direct contact with each other.

Below, we will explain each layer that makes up the adhesive film 50 of this embodiment.

[Base layer]
The base layer 20 is a layer provided for the purpose of improving the balance of performance such as handleability, mechanical properties, and heat resistance of the pressure-sensitive adhesive film 50 .
The base layer 20 is not particularly limited, but may be, for example, a resin film.
The resin constituting the base layer 20 preferably contains at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide, and from the viewpoint of further improving vacuum resistance, it is more preferable that the resin contains polyethylene naphthalate.

The substrate layer 20 may be a single layer or two or more layers.
The resin film used to form the base layer 20 may be in the form of an unstretched film, or a uniaxially or biaxially stretched film.

The thickness of the base layer 20 is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and even more preferably 40 μm or more, from the viewpoint of further improving the handleability of the adhesive film 50, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, even more preferably 80 μm or less, and even more preferably 60 μm or less, from the viewpoint of further improving the unevenness-following ability of the adhesive film 50.

The substrate layer 20 may be subjected to a surface treatment to further improve adhesion to other layers. Specifically, corona treatment, plasma treatment, undercoat treatment, primer coat treatment, etc. may be performed.

[Roughness-absorbing resin layer]
The irregularity-absorbing resin layer 30 is a layer provided to further improve the balance of the performance of the adhesive film 50 between its irregularity-following ability and vacuum resistance.

The resin constituting the unevenness-absorbing resin layer 30 preferably contains at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene, more preferably contains one or two selected from the group consisting of ethylene-vinyl acetate copolymer and (meth)acrylic resin, and even more preferably contains ethylene-vinyl acetate copolymer.

The ethylene-vinyl acetate copolymer of the present embodiment is a copolymer of ethylene and vinyl acetate, for example, a random copolymer.
The content of structural units derived from vinyl acetate in the ethylene-vinyl acetate copolymer is preferably 5 mass% or more, more preferably 10 mass% or more, and even more preferably 15 mass% or more, from the viewpoint of further improving the performance balance between the unevenness-following ability and vacuum resistance of the adhesive film 50, and is preferably 50 mass% or less, more preferably 45 mass% or less, even more preferably 40 mass% or less, even more preferably 35 mass% or less, even more preferably 30 mass% or less, and even more preferably 25 mass% or less, from the viewpoint of further improving the performance balance between the unevenness-following ability and vacuum resistance of the adhesive film 50.
The vinyl acetate content can be measured in accordance with JIS K7192:1999.

The ethylene-vinyl acetate copolymer is preferably a binary copolymer consisting of only ethylene and vinyl acetate, but may contain at least one copolymer component selected from the following in addition to ethylene and vinyl acetate: vinyl ester monomers such as vinyl formate, vinyl glycolate, vinyl propionate, and vinyl benzoate; acrylic monomers such as acrylic acid, methacrylic acid, ethacrylic acid, or salts or alkyl esters of these; and the like. When copolymer components other than ethylene and vinyl acetate are contained, it is preferable that the amount of the copolymer components other than ethylene and vinyl acetate in the ethylene-vinyl acetate copolymer is 0.5% by mass or more and 5% by mass or less.

The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer, measured in accordance with JIS K7210:1999 under conditions of 190°C and a load of 2.16 kg, is preferably 0.1 g/10 min or more, more preferably 0.5 g/10 min or more, even more preferably 1.0 g/10 min or more, even more preferably 1.5 g/10 min or more, and even more preferably 2.0 g/10 min or more, from the viewpoint of further improving the moldability of the unevenness-absorbing resin layer 30, and is preferably 50 g/10 min or less, more preferably 40 g/10 min or less, even more preferably 20 g/10 min or less, even more preferably 10 g/10 min or less, even more preferably 5.0 g/10 min or less, and even more preferably 3.0 g/10 min or less, from the viewpoint of further improving the storage stability of the adhesive film 50.

The ethylene/α-olefin copolymer of the present embodiment is, for example, a copolymer obtained by copolymerizing ethylene with an α-olefin having 3 to 20 carbon atoms.
As the α-olefin, for example, α-olefins having 3 to 20 carbon atoms can be used alone or in combination of two or more. Preferably, the α-olefin has 3 to 10 carbon atoms, and more preferably, the α-olefin has 3 to 8 carbon atoms. Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Among them, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene are preferred from the viewpoint of availability. The ethylene-α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

The melting point of the resin constituting the unevenness-absorbing resin layer 30 is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably 80°C or higher, from the viewpoint of further improving the storage stability of the adhesive film 50, and is preferably 100°C or lower, more preferably 95°C or lower, more preferably 90°C or lower, and even more preferably 85°C or lower, from the viewpoint of further improving the unevenness-following ability of the adhesive film 50.
When the unevenness-absorbing resin layer 30 is made up of two or more types of resin, the melting point of the resin that makes up the unevenness-absorbing resin layer 30 is the peak temperature of the maximum melting peak measured by DSC.

The unevenness-absorbing resin layer 30 can be obtained, for example, by dry-blending or melt-kneading a resin and an additive to obtain a resin composition, and then extruding or coating and drying the resin composition. Additives may be added as necessary. Specific examples of additives include crosslinking agents and antioxidants.

The content of the thermal polymerization initiator contained in the resin composition for forming the unevenness-absorbing resin layer 30 is preferably less than 0.3 parts by mass, more preferably less than 0.1 parts by mass, even more preferably less than 0.01 parts by mass, and even more preferably 0.00 parts by mass, when the entire resin composition for forming the unevenness-absorbing resin layer 30 is taken as 100 parts by mass.
When the content of the thermal polymerization initiator contained in the resin composition for forming the unevenness-absorbing resin layer 30 is less than the above upper limit value, the moldability can be further improved when the unevenness-absorbing resin layer 30 is extrusion molded, and the unevenness-following ability of the adhesive film 50 can be further improved.
The thermal polymerization initiator means the same as the thermal polymerization initiator contained in the thermosetting adhesive layer described below.

The layer that is in direct contact with the irregularity-absorbing resin layer 30 preferably contains a thermal polymerization initiator.
When the layer in direct contact with the unevenness-absorbing resin layer 30 contains a thermal polymerization initiator, the vacuum resistance of the adhesive film 50 is further improved. Although the exact mechanism is unclear, the inventors consider that in the manufacturing process of an electronic device, when the temperature of the adhesive film 50 bonded to an electronic component becomes high (for example, 150° C. or higher), the thermal polymerization initiator contained in the layer in direct contact with the unevenness-absorbing resin layer 30 is diffused into the unevenness-absorbing resin layer 30, the resin constituting the unevenness-absorbing resin layer 30 hardens, the entire adhesive film 50 becomes hard, and the adhesive film 50 bonded to the electronic component becomes difficult to lift.

The thickness of the unevenness-absorbing resin layer 30 is preferably 20 μm or more, more preferably 30 μm or more, from the viewpoint of further improving the handleability of the adhesive film 50, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 150 μm or less, from the viewpoint of further improving the performance balance between the unevenness-following ability and vacuum resistance of the adhesive film 50.

[Thermosetting adhesive layer]
The thermosetting adhesive layer 40 is a layer provided for bonding the adhesive film 50 to the circuit-forming surface of the electronic component.
The thermosetting adhesive layer 40 can be composed of, for example, a known adhesive, and preferably contains a (meth)acrylic resin and a thermal polymerization initiator.

The resin contained in the thermosetting adhesive layer 40 may be a (meth)acrylic resin, a silicone resin, a urethane resin, an olefin resin, or a styrene resin. Of these, it is preferable to use a (meth)acrylic resin as the base polymer, since this makes it easy to adjust the adhesive strength.

Examples of the (meth)acrylic resin of the present embodiment include homopolymers of (meth)acrylic acid ester compounds, copolymers of (meth)acrylic acid ester compounds and comonomers, etc. Examples of the (meth)acrylic acid ester compounds include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, etc. These (meth)acrylic acid ester compounds may be used alone or in combination of two or more.
Examples of comonomers constituting the (meth)acrylic copolymer include vinyl acetate, (meth)acrylonitrile, styrene, (meth)acrylic acid, itaconic acid, (meth)acrylamide, methylol (meth)acrylamide, maleic anhydride, etc. These comonomers may be used alone or in combination of two or more.

The thermosetting adhesive layer 40 preferably contains a thermal polymerization initiator. The thermal polymerization initiator in this embodiment is, for example, at least one selected from the group consisting of a thermal radical polymerization initiator, a thermal cationic polymerization initiator, and a thermal anionic polymerization initiator, and is preferably a thermal radical polymerization initiator.

The thermal radical polymerization initiator of the present embodiment is, for example, at least one selected from the group consisting of peroxides and azo compounds, and is preferably a peroxide.
The peroxide of the present embodiment is preferably 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-butylperoxy)-cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-butylperoxymaleic acid, t-butylperoxy-3,3,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, or t-hexylperoxybenzone. The at least one selected from the group consisting of butyl peroxyacetate, t-butylperoxyacetate, 2,2-di(t-butylperoxy)butane, t-butylperoxybenzoate, n-butyl-4,4-di-(t-butylperoxy)valerate, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne.

The peroxide of this embodiment preferably contains at least one structure selected from the group consisting of the following formula (I) and the following formula (II) in the molecule, and more preferably contains the following formula (II) in the molecule.

In formula (I), the wavy lines indicate the attachment points.

In formula (II), the wavy lines indicate the bond points.

The one-minute half-life temperature of the thermal radical polymerization initiator of this embodiment is preferably 140°C or higher, more preferably 145°C or higher, even more preferably 150°C or higher, and preferably 200°C or lower, more preferably 195°C or lower, even more preferably 190°C or lower, even more preferably 185°C or lower, even more preferably 180°C or lower. When the one-minute half-life temperature of the thermal radical polymerization initiator is equal to or higher than the lower limit, the thermal radical polymerization initiator is less likely to thermally decompose when forming the thermosetting adhesive layer 40 in the manufacturing process of the adhesive film 50, and the unevenness-following ability of the adhesive film 50 is further improved, which is preferable. When the one-minute half-life temperature of the thermal radical polymerization initiator is equal to or lower than the upper limit, the thermal radical polymerization initiator decomposes at a temperature lower than the temperature at which the resin contained in the adhesive film 50 is excessively softened, and the vacuum resistance of the adhesive film 50 is further improved, which is preferable.

The hydrogen abstraction ability of the thermal radical polymerization initiator of this embodiment is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more, and the upper limit is not particularly limited, but may be 90% or less, or 80% or less. When the hydrogen abstraction ability of the thermal radical polymerization initiator of this embodiment is equal to or more than the above lower limit, the resin contained in the pressure-sensitive adhesive film 50 is more easily crosslinked, and the vacuum resistance of the pressure-sensitive adhesive film 50 is further improved, which is preferable.
Here, the hydrogen abstraction ability means a value calculated by a radical trapping method using α-methylstyrene dimer as a radical trapping agent.
More specifically, first, a thermal radical polymerization initiator is decomposed in the coexistence of α-methylstyrene dimer and cyclohexane. Among the radicals generated from the thermal radical polymerization initiator, radicals with weak hydrogen abstraction ability are captured by α-methylstyrene dimer. On the other hand, radicals with strong hydrogen abstraction ability abstract hydrogen from cyclohexane, generating a cyclohexyl radical. The cyclohexyl radical is captured by α-methylstyrene dimer and is led to a trapping product of the cyclohexyl radical. The hydrogen abstraction ability is the ratio (molar fraction) of the amount of the trapping product of the cyclohexyl radical to the theoretical amount of radicals generated.

The content of the thermal polymerization initiator contained in the thermosetting adhesive layer 40 is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of further improving the vacuum resistance of the adhesive film 50, when the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40 is taken as 100 parts by mass, and from the viewpoint of further improving the unevenness-following ability of the adhesive film 50, it is preferably 2.0 parts by mass or less, more preferably 1.8 parts by mass or less, and even more preferably 1.5 parts by mass or less.
Here, the content of the thermal polymerization initiator contained in the thermosetting adhesive layer 40 means the content of the thermal polymerization initiator in the adhesive for forming the thermosetting adhesive layer 40. That is, the content of the thermal polymerization initiator in this specification means the amount charged when forming the thermosetting adhesive layer 40. The contents of the crosslinking agent and the polyfunctional acrylate described below also mean the amount charged, like the thermal polymerization initiator.

The thermosetting adhesive layer 40 may contain a crosslinking agent.
Examples of the crosslinking agent of the present embodiment include epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol polyglycidyl ether; aziridine compounds such as tetramethylolmethane-tri-β-aziridinyl propionate, trimethylolpropane-tri-β-aziridinyl propionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide); and isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, and polyisocyanate.

When the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40 is taken as 100 parts by mass, the content of the crosslinking agent contained in the thermosetting adhesive layer 40 is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, even more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, even more preferably 2.3 parts by mass or more, from the viewpoint of further improving the performance balance of the unevenness-following ability and vacuum resistance of the adhesive film 50, and is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, even more preferably 5.0 parts by mass or less, even more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, from the viewpoint of further improving the performance balance of the unevenness-following ability and vacuum resistance of the adhesive film 50.

The thermosetting adhesive layer 40 may further contain a polyfunctional acrylate in addition to the (meth)acrylic resin. The polyfunctional acrylate in this embodiment is an acrylate having two or more radically reactive double bonds.
Examples of the polyfunctional acrylate of the present embodiment include urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, pentaerythritol polyacrylate, dipentaerythritol polyacrylate, ethoxylated isocyanuric acid triacrylate, trimethylolpropane triacrylate, and ditrimethylolpropane tetraacrylate.

When the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40 is taken as 100 parts by mass, the content of the polyfunctional acrylate contained in the thermosetting adhesive layer 40 is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 4.0 parts by mass or more, from the viewpoint of further improving the performance balance of the adhesive film 50's unevenness-following ability and vacuum resistance, and is preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, and even more preferably 12.0 parts by mass or less, from the viewpoint of further improving the performance balance of the adhesive film 50's unevenness-following ability and vacuum resistance.

The thickness of the thermosetting adhesive layer 40 is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, even more preferably 15 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, even more preferably 25 μm or less.

The thermosetting adhesive layer 40 can be formed, for example, by applying an adhesive coating liquid onto the irregularity-absorbing resin layer 30 .
The adhesive coating liquid can be applied by a conventionally known coating method, such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coat method, a comma coater method, a die coater method, etc. There are no particular limitations on the drying conditions for the applied adhesive, but it is generally preferable to dry the adhesive at a temperature range of 80 to 200° C. for 10 seconds to 10 minutes. More preferably, the adhesive is dried at 80 to 170° C. for 15 seconds to 5 minutes.

[Other layers]
An adhesive layer may be provided between each layer of the adhesive film 50. The adhesive layer can improve the adhesion between each layer.

An example of a method for producing the adhesive film 50 according to this embodiment will be described.
First, the unevenness-absorbing resin layer 30 is formed by extrusion molding on one surface of the base material layer 20. Next, an adhesive coating liquid is applied onto the unevenness-absorbing resin layer 30 and dried to form a thermosetting adhesive layer 40, thereby obtaining an adhesive film 50.

The above describes embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

The present invention is not limited to the above-described embodiment, and any modifications or improvements that can achieve the object of the present invention are included in the present invention.

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto.
Details regarding the preparation of the adhesive film used in the method for manufacturing an electronic device are as follows.

<Ingredients>
Base layer 1: polyethylene naphthalate film (manufactured by Toyobo Film Solutions Co., Ltd., product name: Teonex Q81, thickness: 50 μm)
Resin 1: Ethylene-vinyl acetate copolymer (manufactured by Dow Mitsui Polychemicals, product name: Evaflex EV460, melting point: 84°C, content of structural units derived from vinyl acetate: 19% by mass, MFR (190°C, 2.16 kg): 2.5 g/10 min)
Crosslinking agent 1: Isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: Olestar P49-75S)
Thermal polymerization initiator 1: Peroxide (manufactured by Nouryon Chemical Industries, Ltd., product name: Perkadox 12-XL25)
Photopolymerization initiator 1: α-aminoketone (manufactured by IGM Resins B.V., product name: Omnirad 379)
Multifunctional acrylate 1: Ditrimethylolpropane tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: AD-TMP)

<Preparation of (meth)acrylic polymer solution a>
n-Butyl acrylate (77 parts by mass), methyl methacrylate (16 parts by mass), 2-hydroxyethyl acrylate (7 parts by mass), and t-butylperoxy-2-ethylhexanoate (0.3 parts by mass) as a polymerization initiator were reacted in toluene (20 parts by mass) and ethyl acetate (80 parts by mass) at 85° C. for 10 hours. After completion of the reaction, the solution was cooled, and toluene (30 parts by mass), methacryloyloxyethyl isocyanate (7 parts by mass), and dibutyltin dilaurate (0.05 parts by mass) were added thereto, and the mixture was reacted at 85° C. for 12 hours while blowing in air, to obtain a (meth)acrylic polymer solution a.

<Preparation of (meth)acrylic polymer solution b>
n-Butyl acrylate (72 parts by mass), methyl methacrylate (18 parts by mass), 2-hydroxyethyl methacrylate (7 parts by mass), acrylic acid (3 parts by mass), and t-butylperoxy-2-ethylhexanoate (0.3 parts by mass) as a polymerization initiator were reacted in toluene (36 parts by mass) and ethyl acetate (53 parts by mass) at 85° C. for 10 hours. After completion of the reaction, the solution was cooled, and toluene (34 parts by mass) was added thereto to obtain a (meth)acrylic polymer solution b.

[Example 1]
(Preparation of adhesive coating solution for thermosetting adhesive layer)
To 100 parts by mass of the (meth)acrylic polymer solution a (solid content), thermal polymerization initiator 1 (0.8 parts by mass), crosslinking agent 1 (2.56 parts by mass), and polyfunctional acrylate 1 (10 parts by mass) were added to obtain an adhesive coating liquid for a thermosetting adhesive layer.

(Preparation of adhesive film)
Using an extrusion molding machine, resin 1 (100 parts by mass) was extrusion molded onto substrate layer 1. A laminated film was obtained in which a 70 μm-thick irregularity-absorbing resin layer was laminated on the substrate layer.
Next, the adhesive coating liquid for the thermosetting adhesive layer was applied to a silicone release-treated polyethylene terephthalate film (38 μm) and dried to form a thermosetting adhesive layer having a thickness of 20 μm. The obtained thermosetting adhesive layer was then bonded to the unevenness-absorbing resin layer side of the laminated film to obtain an adhesive film.

[Examples 2 to 4 and Comparative Example 2]
(Preparation of adhesive coating solution for thermosetting adhesive layer)
An adhesive coating liquid for a thermosetting adhesive layer was obtained in the same manner as in Example 1, except that the formulation of the adhesive coating liquid was as shown in Table 1.
(Preparation of adhesive film)
An adhesive film was obtained in the same manner as in Example 1, except that the thickness of the irregularity-absorbing resin layer was set to the thickness shown in Table 1.

[Example 5]
(Preparation of adhesive coating solution for thermosetting adhesive layer)
In the same manner as in Example 1, an adhesive coating solution for a thermosetting adhesive layer was obtained.

(Preparation of Coating Solution for Irregularity-Absorbing Resin Layer)
Crosslinking agent 1 (0.3 parts by mass) was added to (meth)acrylic polymer solution a (50 parts by mass) and (meth)acrylic polymer solution b (50 parts by mass) to obtain a coating liquid for an irregularity-absorbing resin layer.

(Preparation of adhesive film)
The coating liquid for the irregularity-absorbing resin layer was applied onto the base layer 1 and dried to form an irregularity-absorbing resin layer having a thickness of 40 μm, thereby obtaining a laminated film.
Next, the adhesive coating liquid for the thermosetting adhesive layer was applied to a silicone release-treated polyethylene terephthalate film (38 μm) and dried to form a thermosetting adhesive layer having a thickness of 20 μm. The obtained thermosetting adhesive layer was then bonded to the unevenness-absorbing resin layer side of the laminated film to obtain an adhesive film.

[Comparative Example 1]
(Preparation of Coating Solution for Thermosetting Adhesive Layer)
An adhesive coating liquid for a thermosetting adhesive layer was obtained in the same manner as in Example 1, except that the formulation of the adhesive coating liquid was as shown in Table 1.

(Preparation of adhesive film)
The adhesive coating liquid for the thermosetting adhesive layer was applied to a polyethylene terephthalate film (38 μm) that had been subjected to a silicone release treatment, and then dried to form a thermosetting adhesive layer having a thickness of 20 μm.
Next, the obtained thermosetting adhesive layer was attached to the base layer 1 to obtain an adhesive film.

<Measurement and evaluation methods>
(1) Measurement of residual stress rate of adhesive film at 100°C The adhesive film was laminated to a thickness of 1.4±0.1 mm by n sheets to prepare a measurement sample. Here, the measurement sample was laminated so that the base layer of the adhesive film and the thermosetting adhesive layer of the adhesive film adjacent thereto were in direct contact. The number of laminated sheets of the adhesive film was set to the number that made the thickness of the measurement sample close to 1.4 mm. In other words, the number of laminated sheets of the adhesive film differs depending on the thickness of the adhesive film, and therefore the number of laminated sheets of the adhesive film differs depending on the sample.
A measurement sample cut to a width of 10 mm was subjected to a dynamic viscoelasticity measuring device (EPLEXOR 500N, manufactured by Netzsch-Gabo) to measure stress when a strain of 2% was continuously applied under the following conditions: temperature: 100° C., deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The measurement sample was placed so that the long axis direction of the indenter in the upper jig was the same as the width direction of the measurement sample, and a strain was continuously applied in the thickness direction of the measurement sample.
The residual stress rate [%] at 100° C. was calculated by the formula "(stress at 600 seconds [Pa]/stress at the time when the largest stress was measured [Pa])×100".

(2) Measurement of residual stress rate of adhesive film at 150°C A measurement sample was prepared by the method described in (1). Then, the measurement sample was heat-treated at 130°C for 30 minutes using a constant temperature dryer (manufactured by Yamato Scientific Co., Ltd., DN-63H).
A measurement sample cut to a width of 10 mm was subjected to a dynamic viscoelasticity measuring device (EPLEXOR 500N, manufactured by Netzsch-Gabo) to measure stress when a strain of 2% was continuously applied under the following conditions: temperature: 150° C., deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The measurement sample was placed so that the long axis direction of the indenter in the upper jig was the same as the width direction of the measurement sample, and a strain was continuously applied in the thickness direction of the measurement sample.
The residual stress rate [%] at 150° C. was calculated by the formula "(stress at 600 seconds [Pa]/stress at the time when the largest stress was measured [Pa])×100".

(3) Measurement of residual stress rate at temperature for bonding electronic component and adhesive film A measurement sample was prepared by the method described in (1).
A dynamic viscoelasticity measuring device (EPLEXOR 500N, manufactured by Netzsch-Gabo) was used to measure the stress when a strain of 2% was continuously applied to a measurement sample cut to a width of 10 mm under the following conditions: temperature: attachment temperature in the evaluation of unevenness-following property described later in (4), deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The measurement sample was placed so that the long axis direction of the indenter in the upper jig was the same as the width direction of the measurement sample, and a strain was continuously applied in the thickness direction of the measurement sample.
The residual stress rate [%] at the temperature at which the electronic component and the adhesive film were bonded together was calculated using the formula "(stress at 600 seconds [Pa] / stress at the time when the greatest stress was measured [Pa]) x 100".

(4) Evaluation of Contour-Contour Properties A bonding device (manufactured by Takatori Corporation, product name: TPL-0612W) was used to bond an adhesive film to the circuit-formed surface of a wafer (8-inch power device simulated wafer, height of circuit-formed surface (thickness of polyimide): 10 μm, chip size: 10 mm × 10 mm, small pad size: 1 mm × 1 mm) under the following conditions: SP1: 800 Pa, SP2: 300 Pa, SP3: 100 Pa, bonding pressure: 0.2 MPa, bonding temperature: 100 ° C. The wafer to which the adhesive film was bonded was observed at any two points using a laser microscope (manufactured by Keyence Corporation, product name: VK-X1000) and evaluated according to the following criteria.
A (good): No lifting is observed near the 10 μm step of the polyimide. B (bad): Lifting is observed near the 10 μm step of the polyimide.

(5) Evaluation of Vacuum Resistance In the method described in (4), an adhesive film was attached to the circuit-formed surface of the wafer, and the wafer was left for at least 1 hour, after which the wafer was prebaked at 130°C for 30 minutes using a constant temperature dryer (manufactured by Yamato Scientific Co., Ltd., DN-63H). The wafer with the adhesive film attached was then heated in a vacuum constant temperature dryer (manufactured by Shimizu Rikagaku Kikai Seisakusho Co., Ltd., VOD6-4H) under conditions of vacuum pressure: 100 to 150 Pa, temperature: 150°C, and time: 15 minutes. During the heating process under reduced pressure, the presence or absence of lifting of the film was visually observed, and was evaluated according to the following criteria.
A (good): No floating of 0.5 mm or more in diameter is visually observed. B (poor): Floating of 0.5 mm or more in diameter is visually observed.

Evaluations were carried out for Examples 1 to 5 and Comparative Examples 1 and 2. The results are shown in Table 1.

From Table 1, it can be seen that the adhesive films of the examples were evaluated as being good in both their ability to conform to uneven surfaces and their ability to withstand vacuum. In other words, it can be seen that the method for manufacturing an electronic device using the adhesive film of this embodiment improves the balance of the performance of the ability to conform to uneven surfaces and their ability to withstand vacuum, and therefore improves the adhesion between the electronic components and the adhesive film and protects the electronic components, even in a method for manufacturing an electronic device that includes a process in a vacuum atmosphere.

10 Electronic component 10A Circuit-forming surface of electronic component 10B Surface opposite to the circuit-forming surface of electronic component 20 Base layer 30 Roughness-absorbing resin layer 40 Thermosetting adhesive layer 50 Adhesive film 100 Structure

Claims (14)

A step (A) of preparing a structure including an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component;
(B) treating a surface of the electronic component in the structure opposite to the circuit-forming surface in a vacuum atmosphere,
The pressure-sensitive adhesive film has a residual stress rate at 100° C. of 55.0% or less, calculated by the following method 1;
A method for manufacturing an electronic device, wherein a residual stress rate at 150° C. calculated by the following method 2 is 5.0% or more and 90.0% or less.
[Method 1]
The pressure-sensitive adhesive film is laminated to a thickness of 1.4±0.1 mm to prepare a measurement sample, and the measurement sample is cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% is continuously applied is measured under the following conditions: temperature: 100°C, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is defined as the stress residual rate [%] at 100°C.
[Method 2]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130° C. for 30 minutes to prepare a measurement sample. The measurement sample was cut to a width of 10 mm, and the stress when a strain of 2% was continuously applied was measured using a dynamic viscoelasticity measuring device under the following conditions: temperature: 150° C., deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at 150° C. A step (A) of preparing a structure including an electronic component having a circuit formation surface and an adhesive film attached to the circuit formation surface side of the electronic component;
(B) treating a surface of the electronic component in the structure opposite to the circuit-forming surface in a vacuum atmosphere,
The pressure-sensitive adhesive film has a residual stress rate of 55.0% or less at a temperature at which the electronic component and the pressure-sensitive adhesive film are bonded together, the residual stress rate being calculated by the following method 3;
A method for manufacturing an electronic device, wherein the residual stress rate at the temperature of the structure in step (B) is 5.0% or more and 90.0% or less, as calculated by the following method 4.
[Method 3]
The adhesive film is laminated to a thickness of 1.4±0.1 mm to prepare a measurement sample, and the measurement sample is cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% is continuously applied is measured under the following conditions: temperature: temperature at which the electronic component and the adhesive film are bonded together, deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress is measured [Pa]) × 100" is the stress residual rate [%] at the temperature at which the electronic component and the adhesive film are bonded together.
[Method 4]
A sample in which the adhesive film was laminated to a thickness of 1.4±0.1 mm was subjected to heat treatment at 130° C. for 30 minutes to prepare a measurement sample, and the measurement sample was cut to a width of 10 mm. Using a dynamic viscoelasticity measuring device, the stress when a strain of 2% was continuously applied was measured under the following conditions: temperature: temperature of the structure in the step (B), deformation mode: compression, upper jig: three-point bending (indenter tip: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen. The value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the largest stress was measured [Pa]) × 100" is the residual stress rate [%] at the temperature of the structure in the step (B). The method for manufacturing an electronic device according to claim 1 or 2, wherein the temperature of the structure in step (B) is 60°C or higher and 230°C or lower. The method further comprises the step of heating the structure;
The method for manufacturing an electronic device according to claim 1, wherein the heating step is a step prior to the step (B). The method for manufacturing an electronic device according to any one of claims 1 to 4, wherein step (B) is at least one selected from the group consisting of an ion implantation step, a metal film formation step, and an annealing treatment step. The method for manufacturing an electronic device according to any one of claims 1 to 5, further comprising a step (C) of removing the adhesive film from the electronic component. The method for manufacturing an electronic device according to any one of claims 1 to 6 further includes a step (D) of backgrinding the surface of the electronic component opposite the circuit formation surface. The method for manufacturing an electronic device according to any one of claims 1 to 7, wherein the adhesive film comprises a base layer, an irregularity-absorbing resin layer, and a thermosetting adhesive layer in this order. The method for manufacturing an electronic device according to claim 8, wherein the adhesive film is provided so that the unevenness-absorbing resin layer and the thermosetting adhesive layer are in direct contact with each other. The method for manufacturing an electronic device according to claim 8 or 9, wherein the adhesive film includes a thermosetting adhesive layer containing a (meth)acrylic resin and a thermal polymerization initiator. The method for manufacturing an electronic device according to any one of claims 8 to 10, wherein the resin constituting the unevenness-absorbing resin layer includes at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene. The method for manufacturing an electronic device according to any one of claims 8 to 11, wherein the thickness of the unevenness-absorbing resin layer is 20 μm or more and 500 μm or less. The method for manufacturing an electronic device according to any one of claims 8 to 12, wherein the resin constituting the base layer includes at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide. The method for manufacturing an electronic device according to any one of claims 1 to 13, wherein the electronic device is a power semiconductor device.

Images