WO2024134951A1 - Epoxy resin composition, cured product, and semiconductor device - Google Patents

Abstract

Provided are: an epoxy resin composition that yields a cured product that can prevent warping of a board and peeling from a chip; a cured product using the same; and a semiconductor device. The epoxy resin composition contains an epoxy resin, a filler, and at least one selected from a curing agent and a curing catalyst. The epoxy resin contains a flexible epoxy resin, and the content of flexible epoxy resin is from 8.0 mass% to 25.0 mass% relative to the epoxy resin.

Description

Epoxy resin composition, cured product, and semiconductor device

The present invention relates to an epoxy resin composition, a cured product, and a semiconductor device.

In recent years, semiconductor devices such as electronic devices have become larger and thinner, and it is becoming increasingly important to densely pack the semiconductor elements (also called chips) that make up the semiconductor device. For this reason, packaging methods for semiconductor elements have been improved. Traditionally, semiconductor elements have been packaged after being diced into individual pieces. This packaging method is not suitable for large semiconductor devices because the package is larger than the chip. For this reason, a technology that packages at the wafer level (wafer-level chip-size packaging technology) has come to be used, where packaging is done before the chips are cut up after the circuit formation is complete.

Wafer-level packaging usually involves a process of sealing between the semiconductor element and the substrate, where a cured resin composition called an encapsulant is inserted to improve the semiconductor element's moisture resistance, heat resistance, and reliability against external stress. One method of sealing is the compression mold method, in which an encapsulant is inserted into the cavity below the semiconductor element and the encapsulant is cured while applying pressure (see, for example, Patent Document 1).

JP 2021-161206 A

In wafer-level mounting, in addition to the process of fixing the semiconductor element to the substrate and the process of sealing the space between the semiconductor element and the substrate with a resin composition, there is also a process of forming a layer that electrically connects the semiconductor element to the solder balls (the so-called rewiring layer formation process). Generally, depending on the order of the rewiring layer formation process and the sealing process with a resin composition, there are two methods called the chip-first method (wherein the semiconductor element is placed on the substrate and sealed with resin, and then a wiring layer is formed on top of that) and the chip-last method (wherein a rewiring layer is formed on a wafer-like support made of silicon or the like, then the semiconductor element is placed on top of it and sealed, and finally the support is removed). In particular, in the chip-first method, since the rewiring layer is formed on the resin composition, it is required that the cured resin composition does not cause problems such as peeling off from the semiconductor element during the rewiring layer formation process.

Furthermore, in wafer-level mounting, the mounted substrate is diced to separate the IC chip packages. Since the dicing process requires minimal warping of the substrate, there has been a demand for resin compositions that can prevent substrate warping.

The objective is to provide an epoxy resin composition that hardens to prevent warping of the substrate and peeling from the chip, as well as a hardened product and a semiconductor device that use the same.

　Conventional resin compositions have used epoxy resins that combine epoxy resins with flexible epoxy resins to prevent warping of the substrate. However, epoxy resin compositions that contain a large amount of flexible epoxy resins can peel off from the semiconductor element when immersed in the developing solution used in the rewiring layer formation process.

After studying this phenomenon, the inventors noticed that cured products made from epoxy resin compositions containing a large amount of flexible epoxy resin contain fine void bubbles called microvoids within the cured product. They discovered that these microvoids easily trap solvents in the cured product, worsening the resistance of the cured product to solvents (solvent resistance), and that the deterioration of the solvent resistance of the cured product is the cause of peeling from the semiconductor element. The inventors then conducted extensive research into the proportion of flexible epoxy resin, leading to the completion of this invention. In this invention, microvoids refer to voids with a maximum width of 0.5 μm or less when a cross section is observed using an SEM image (accelerating voltage: 1 kV, magnification: 5000 times).

In order to achieve the above object, one embodiment of the present invention is an epoxy resin composition that contains an epoxy resin, a filler, and at least one selected from a curing agent and a curing catalyst, the epoxy resin contains a flexible epoxy resin, and the content of the flexible epoxy resin is 8.0% by mass to 25.0% by mass relative to the epoxy resin.

According to the present invention, it is possible to provide an epoxy resin composition that gives a cured product that can prevent warping of a substrate and peeling from a chip, as well as a cured product and a semiconductor device using the same.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Epoxy resin composition)
The epoxy resin composition according to the embodiment contains an epoxy resin, a filler, and at least one selected from a curing agent and a curing catalyst, and further contains other components as required.

<Epoxy resin>
The epoxy resin includes a flexible epoxy resin and other epoxy resins.

<<Flexible epoxy resin>>
The flexible epoxy resin is contained in order to prevent warping of a substrate on which a cured product of the epoxy resin composition is placed. In an embodiment, the flexible epoxy resin refers to an epoxy resin that satisfies the following three conditions:
1. Number average molecular weight: 800 to 2,500
2. Epoxy equivalent: 400 g/eq. to 1,200 g/eq.
3. No condensed polycyclic hydrocarbons in the molecule

The number average molecular weight of the flexible epoxy resin is 800 to 2,500, and preferably 800 to 2,000. If the number average molecular weight is less than 800, the substrate may warp significantly, and if it exceeds 2,500, the ratio of microvoids increases, solvent resistance deteriorates, and peeling from the chip may occur. The number average molecular weight can be measured using a general method for measuring number average molecular weight. For example, it can be measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as the elution solvent.

The epoxy equivalent of the flexible epoxy resin is 400 g/eq. to 1,200 g/eq., and preferably 400 g/eq. to 1,000 g/eq. If the epoxy equivalent is less than 400 g/eq., the substrate may warp significantly, and if it exceeds 1,200 g/eq., the ratio of microvoids in the cured product may increase, causing peeling from the semiconductor element during the rewiring formation process. Here, the epoxy equivalent is the mass of the resin containing one equivalent of epoxy groups, as defined in JIS K7236:2001. Note that "eq." is an abbreviation of "equivalent."

Specific examples of flexible epoxy resins include aliphatic epoxy resins. Examples of aliphatic epoxy resins include polyalkylene glycol type epoxy resins. Examples of polyalkylene glycol type epoxy resins include polytetramethylene glycol type epoxy resins, polyethylene glycol type epoxy resins, and polypropylene glycol type epoxy resins.

The flexible epoxy resin may be synthesized as appropriate, or a commercially available product may be used. Commercially available products include, for example, YX7400N (polytetramethylene glycol type epoxy resin, epoxy equivalent 440 g/eq., average molecular weight 880, manufactured by Mitsubishi Chemical Corporation), Epogo-se PT polymer type (polytetramethylene glycol type epoxy resin, epoxy equivalent 1,072 g/eq., average molecular weight 2,140, manufactured by Yokkaichi Chemical Co., Ltd.), Epogo-se PT general grade (polytetramethylene glycol type epoxy resin, epoxy equivalent weight 435g/eq., average molecular weight 700-800, Yokkaichi Chemical Co., Ltd.), SR-8EGS (polytetramethylene glycol type epoxy resin, epoxy equivalent weight 262g/eq., average molecular weight 510-550, Sakamoto Yakuhin Kogyo Co., Ltd.), PG-207GS (polytetramethylene glycol type epoxy resin, epoxy equivalent weight 300-330g/eq., average molecular weight 600-660, Nippon Steel Chemical & Material Co., Ltd.), etc.

The content of the flexible epoxy resin is 8.0% by mass to 25.0% by mass, more preferably 8.0% by mass to 16.5% by mass, and even more preferably 9.0% by mass to 16.5% by mass, relative to the total epoxy resin. When the content of the flexible epoxy resin falls within this range, it is possible to prevent wafer warpage, suppress the occurrence of microvoids, improve solvent resistance, and prevent peeling from the chip.

<<Other epoxy resins>>
The other epoxy resin is an epoxy resin other than the flexible epoxy resin described above. The other epoxy resin is not particularly limited as long as it is a variety of epoxy resins generally used for semiconductor encapsulation and can be appropriately used depending on the purpose, but an epoxy resin that is liquid at room temperature (25°C) is preferred. The epoxy equivalent of the other epoxy resin is preferably 50 g/eq. to 10,000 g/eq., more preferably 50 g/eq. to 1,000 g/eq., and even more preferably 100 g/eq. to 500 g/eq.

Other epoxy resins include, for example, glycidylamine type epoxy resins, alicyclic epoxy resins, bisphenol type epoxy resins, biphenyl type epoxy resins, aminophenol type epoxy resins, and naphthalene type epoxy resins. Examples of glycidylamine type epoxy resins include diglycidyl aniline, diglycidyl toluidine, tetraglycidyl-m-xylylenediamine tetraglycidyl bis(aminomethyl)cyclohexane, and the like. Examples of alicyclic epoxy resins include vinyl(3,4-cyclohexene) dioxide, 2-(3,4-epoxycyclohexyl)-5,1-spiro-(3,4-epoxycyclohexyl)-m-dioxane, and the like. Examples of bisphenol type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and the like. Examples of bisphenol A type epoxy resins include p-glycidyloxyphenyl dimethyl trisbisphenol A diglycidyl ether. Examples of biphenyl type epoxy resins include biphenyl aralkyl type epoxy resins, 3,3',5,5'-tetramethyl-4,4'-diglycidyloxybiphenyl. Examples of aminophenol type epoxy resins include triglycidyl-p-aminophenol. Examples of naphthalene type epoxy resins include 1,6-bis(2,3-epoxypropoxy)naphthalene.

The number of epoxy groups contained in one molecule of other epoxy resins may be one (monofunctional epoxy resin) or two or more (multifunctional epoxy resin), but from the standpoint of reliability (thermal cycle property), two or more (multifunctional epoxy resin) is preferred. There is no particular limit to the upper limit of the number of epoxy groups, and it can be selected appropriately depending on the purpose, but five or less is preferred. Examples of monofunctional epoxy resins include p-tert-butylphenyl glycidyl ether. Examples of multifunctional epoxy resins include diepoxy resins such as 1,4-phenyldimethanol diglycidyl ether; triepoxy resins such as trimethylolpropane triglycidyl ether and glycerin triglycidyl ether. In addition to the above, hydantoin-type epoxy resins such as 1,3-diglycidyl-5-methyl-5-ethylhydantoin; epoxy resins with a silicone skeleton such as 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane; and epoxy resins with a skeleton derived from plants may also be used.

The other epoxy resins may be used alone or in combination of two or more. Among these, aminophenol type epoxy resins, bisphenol type epoxy resins, and glycidylamine type epoxy resins are preferred from the standpoint of reliability. It is preferable to contain more aminophenol type epoxy resins than other epoxy resins as the other epoxy resins, since this increases the glass transition point of the epoxy resin composition.

Other epoxy resins may be appropriately synthesized or commercially available. Commercially available products include, for example, RE410S (bisphenol F type liquid epoxy resin, epoxy equivalent 178 g/eq, average molecular weight 360, manufactured by Nippon Kayaku Co., Ltd.) and EP-3950L (glycidylamine type liquid epoxy resin, epoxy equivalent 95 g/eq, average molecular weight 270, manufactured by ADEKA Corporation).

The content of the epoxy resin (flexible epoxy resin and other epoxy resin) in the epoxy resin composition is preferably 10.0% by mass to 27.0% by mass, and more preferably 15.0% by mass to 21.0% by mass, based on the total epoxy resin composition. When a bisphenol type epoxy resin is used as the other epoxy resin, the content of the bisphenol type epoxy resin is preferably 20% by mass to 30% by mass, based on the total amount of epoxy resin. When a glycidylamine type epoxy resin is used as the other epoxy resin, the content of the glycidylamine type epoxy resin is preferably 50% by mass to 70% by mass, based on the total amount of epoxy resin.

<Curing agent, curing catalyst>
The epoxy resin composition according to the embodiment contains at least one of a curing agent and a curing catalyst. The curing agent is contained to cure the epoxy resin, and the curing catalyst is contained to promote the curing of the epoxy resin. Either the curing agent or the curing catalyst may be used alone or in combination, but it is preferable to use them in combination in order to increase the curing speed.

<<Curing agent>>
The curing agent is not particularly limited as long as it can cure the epoxy resin, and can be appropriately selected according to the purpose. Examples of the curing agent include amine-based curing agents, phenol-based curing agents, and acid anhydride-based curing agents. Examples of the amine-based curing agent include aromatic amines. Examples of the aromatic amine include methylenedianiline, m-phenylenediamine, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminodiphenyl sulfone. Examples of the phenol-based curing agent include phenol novolac resin, cresol novolac resin, naphthol-modified phenol resin, dicyclopentadiene-modified phenol resin, and p-xylene-modified phenol resin. Examples of the acid anhydride curing agent include methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, alkylated tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhymic anhydride, dodecenyl succinic anhydride, methylnadic anhydride, etc. These may be used alone or in combination of two or more.

The curing agent may be either a synthetic one or a commercially available product. Examples of commercially available products include MEH-8005 (phenol-based curing agent, manufactured by Meiwa Kasei Co., Ltd.) and HN-2200 (acid anhydride-based curing agent, manufactured by Showa Denko Materials Co., Ltd.).

The content of the curing agent is not particularly limited and can be selected appropriately depending on the purpose. The stoichiometric equivalent ratio with the epoxy resin (curing agent equivalent/epoxy group equivalent) is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and even more preferably 0.08 to 0.30. The content (ratio) of the curing agent is preferably 1% by mass to 30% by mass, and more preferably 4% by mass to 15% by mass, based on the epoxy resin composition excluding the filler. If the content of the curing agent is within this numerical range, it is advantageous in that warping of the substrate can be prevented and sufficient adhesive strength is exhibited.

<<Curing catalyst>>
The curing catalyst is not particularly limited as long as it is a curing catalyst generally used in a resin composition and can be appropriately selected according to the purpose, and examples thereof include tertiary amine compounds (excluding heterocyclic compounds containing a nitrogen atom), phosphorus-based curing accelerators, and heterocyclic compounds containing a nitrogen atom. These may be used alone or in combination of two or more. Among these, heterocyclic compounds containing a nitrogen atom are preferred from the viewpoint of reliability (thermal cycle property). A heterocyclic compound containing a nitrogen atom refers to a compound in which a nitrogen atom is a constituent atom of a heterocycle.

Heterocyclic compounds containing nitrogen atoms include, for example, imidazoles such as 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole; diazabicyclo Examples of such compounds include undecene (DBU), DBU-phenol salt, DBU-octylate salt, DBU-p-toluenesulfonate, DBU-formate salt, DBU-orthophthalate salt, DBU-phenol novolac resin salt, DBU-based tetraphenylborate salt, diazabicyclononene (DBN), DBN-phenol novolac resin salt, diazabicyclooctane, pyrazole, oxazole, thiazole, imidazoline, pyrazine, morpholine, thiazine, indole, isoindole, benzimidazole, purine, quinoline, isoquinoline, quinoxaline, cinnoline, and pteridine. These compounds may be used alone or in combination of two or more. Among these, from the viewpoint of reactivity, (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole are preferred.

The curing catalyst may be a synthetic product or a commercially available product. Examples of commercially available products include 2MZA (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, manufactured by Shikoku Chemical Industry Corporation), 2E4MZ (2-ethyl-4-methylimidazole, manufactured by Shikoku Chemical Industry Corporation, 2-phenyl-4-methyl-5-hydroxymethylimidazole), and 2P4MHZ (2-phenyl-4-methyl-5-hydroxymethylimidazole, manufactured by Shikoku Chemical Industry Corporation).

The amount of the curing catalyst is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of reactivity, it is preferably 0.1% by mass to 10% by mass, and more preferably 0.5% by mass to 5% by mass, based on the total epoxy resin composition.

<Filler>
The filler is contained in order to adjust the properties of the cured product of the epoxy resin composition (mainly the linear expansion coefficient, elastic modulus, and water absorption). The type of filler is not particularly limited and can be appropriately selected depending on the purpose. Examples of the filler include silica such as fused silica and crystalline silica; calcium carbonate, clay, aluminum, alumina, silicon nitride, silicon carbide, boron nitride, calcium silicate, potassium titanate, aluminum nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, aluminum hydroxide, magnesium hydroxide, zinc borate, and zinc molybdate. These may be used alone or in combination of two or more. Among these, silica filler is preferred from the viewpoint of being able to increase the loading amount.

The filler may be surface-treated. There are no particular limitations on the surface treatment agent, and it can be selected appropriately depending on the purpose. For example, a silane coupling agent can be used.

There are no particular limitations on the silane coupling agent, and it can be selected appropriately depending on the purpose. Examples include epoxy-based, methacryl-based, amino-based, vinyl-based, glycidoxy-based, and mercapto-based agents.

The volume average particle size of the filler is not particularly limited and can be appropriately selected depending on the purpose. For example, 0.1 μm to 9.0 μm is preferable, and 0.2 μm to 8.0 μm is more preferable. In this embodiment, the volume average particle size refers to the volume average particle size D50 (particle size that is 50% cumulative from the small diameter side of the volume-based particle size distribution) measured using a laser diffraction method.

The shape of the filler is not particularly limited and can be selected appropriately depending on the purpose. Examples include spherical, irregular, and scale-like shapes.

The filler content is preferably 50% by mass to 95% by mass, more preferably 60% by mass to 90% by mass, and even more preferably 65% by mass to 85% by mass, based on the total epoxy resin composition.

The filler content in an epoxy resin composition can be measured by the following method. First, weigh out the epoxy resin composition into a crucible. The weighed cured product is heated to 850°C at a rate of 20°C/min and held at this temperature for 30 minutes. After cooling, the residue (ignition residue) remaining in the crucible is weighed. The filler content is calculated from the amount of filler obtained.

<Other ingredients>
The other components are not particularly limited as long as they are those used in ordinary epoxy resin compositions and can be appropriately selected depending on the purpose, and examples thereof include colorants such as dyes, pigments, and carbon black; silicone oils; surfactants; antioxidants; antimony oxides such as antimony trioxide, antimony tetraoxide, and antimony pentoxide; conventionally known flame retardants such as brominated epoxy resins; ion trapping agents; leveling agents; antioxidants; antifoaming agents; reactive diluents; elastomers, etc. These may be used alone or in combination of two or more.

There are no particular limitations on the content of other ingredients, and they can be selected appropriately depending on the purpose, so long as they do not impair the effects of the present invention.

<Physical Properties of Epoxy Resin Composition>
<<Microvoids>>
In this embodiment, the microvoid refers to a gap (void) having a maximum width of 0.5 μm or less when a cross section of a cured product is observed with a scanning electron microscope (SEM) under conditions of an acceleration voltage of 1 kV and a magnification of 5,000 times. Since the microvoid has a property of absorbing a solvent, a cured product having many microvoids is a cured product that absorbs a lot of solvent and has poor solvent resistance. Therefore, the degree of occurrence of microvoids is an index of solvent resistance. When an epoxy resin composition that produces a cured product having many microvoids is used as an encapsulant, if the cured product comes into contact with a solvent, the solvent is absorbed into the cured product, and the adhesion between the semiconductor element (chip) encapsulated by the cured product and the cured product decreases, causing peeling.

The proportion of microvoids (microvoid ratio) is measured as follows. The epoxy resin composition is heated at 150°C for 1 hour to produce a cured product. The resulting cured product is sliced at equal intervals of 50 nm using a focused ion beam (FIB: COBRA (manufactured by Orsay Physics)), and each slice is observed using an SEM (AURIGA (manufactured by Carl Zeiss), accelerating voltage: 1 kV, magnification: 5,000x). In an SEM image, components with different electron densities are shown as images of different shades. In other words, the filler, resin components, and voids appear on the image as different shades. The obtained successive SEM images are superimposed using 3D image processing software (Dragonfly (Ver. 2022.1, manufactured by Object Research System)) to construct a 3D structure. Then, filler, resin components, and voids are set from the contrast difference of the obtained 3D structure, and then a machine learning segmentation function is used to divide the image and recognize the shading of each area, recognizing and extracting the filler, resin components, and microvoids, and calculating the volume ratio of each component. The obtained volume ratios can be used to calculate the microvoid ratio according to the following formula. The proportion of microvoids (microvoid ratio) is preferably 38% or less, and more preferably 30% or less.

<<Solvent resistance>>
A solvent is used in the rewiring layer formation process. Therefore, the cured product is likely to be exposed to the solvent. Therefore, it is desirable for the cured product to have solvent resistance, which is the property of not dissolving in a solvent. In this embodiment, the solvent resistance is evaluated based on the degree of change in mass when the cured product is immersed in a solvent. Specifically, the cured product of the epoxy resin composition is immersed in a solvent for a predetermined time, and the mass change rate before and after immersion in the solvent is calculated and evaluated. The mass change rate is preferably 0.50% or less, more preferably 0.30% or less.

The solvents and immersion times used to evaluate solvent resistance are, for example, 30 minutes in propylene glycol monomethyl ether acetate heated to 60°C, 20 minutes in ethyl lactate at room temperature, 30 minutes in a 2.38% solution of tetramethylammonium hydroxide at room temperature, and 30 minutes in a solution of propylene glycol monomethyl ether acetate:propylene glycol monomethyl ether = 3:7 heated to 60°C.

<<Applications>>
The epoxy resin composition according to the embodiment can be suitably used as a liquid compression mold material since it becomes a cured product that can prevent warping of the substrate and peeling from the chip. In particular, since it contains a flexible epoxy resin, it has good injectability, which is a property that allows it to be injected into fine grooves, and can be suitably used for mounting on semiconductor devices that need to be mounted in finer grooves (fine pitch). For example, even in a fine gap where the distance between the substrate and the semiconductor element (chip) is 15 μm or less, or a fine location where the bump pitch (distance between the centers of the bumps) is 150 μm or less, the epoxy resin composition can be injected to seal the semiconductor element. And, the epoxy resin composition according to the embodiment can prevent warping of the substrate and peeling from the chip even when these fine locations are sealed. As a result, it is possible to prevent cracks in the cured product, which are the cause of peeling between the cured product and the chip, and to prevent the occurrence of cracks between the cured product and the chip.

<Method of producing epoxy resin composition>
The method for producing the epoxy resin composition according to the embodiment is not particularly limited and can be appropriately selected depending on the purpose. For example, the method includes mixing and stirring the above-mentioned components.

If the epoxy resin is solid, it is preferable to liquefy and fluidize it by heating or other means before mixing.

The components may be mixed simultaneously, or some of the components may be mixed first and the remaining components may be mixed later. For example, if it is difficult to uniformly disperse the filler in the epoxy resin, the epoxy resin and filler may be mixed first and the remaining components may be mixed later.

The equipment used for mixing and stirring is not particularly limited and can be selected appropriately depending on the purpose. Examples include a roll mill, ball mill, bead mill, Raikai mixer, Henschel mixer, planetary mixer, etc.

(Cured product)
The cured product according to the embodiment is obtained by curing the above-mentioned epoxy resin composition. The size and shape of the cured product are not particularly limited and can be appropriately selected depending on the purpose.

The method for producing the cured product is not particularly limited and can be selected appropriately depending on the purpose, but examples include heating, transfer molding, and compression molding. The above-mentioned epoxy resin composition is thermosetting, and at temperatures of 100°C to 200°C, it is preferable for it to cure in 0.1 to 3 hours, and preferably 0.25 to 2 hours.

(Semiconductor device)
The semiconductor device according to the present embodiment includes a support, a semiconductor element, and the cured product of the epoxy resin composition described above. For example, the cured product of the epoxy resin composition may be obtained by filling and sealing a gap between the semiconductor element and the support with the epoxy resin composition.

<Support>
The support is not particularly limited as long as it is capable of fixing a semiconductor element, and can be appropriately selected depending on the purpose. For example, a substrate and the like can be mentioned.

<<Substrate>>
The substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a lead frame, a pre-wired tape carrier, a wiring board, glass, a silicon wafer, etc. The size, shape, and material of the substrate are not particularly limited as long as they are commonly used as substrates, and can be appropriately selected depending on the purpose.

<Semiconductor element>
The semiconductor element is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include active elements such as semiconductor chips, transistors, diodes, and thyristors, and passive elements such as capacitors, resistors, resistor arrays, coils, and switches. The size, shape, and material of the semiconductor element are not particularly limited as long as they are used as ordinary semiconductor elements, and can be appropriately selected depending on the purpose.

The cured product of the epoxy resin composition is filled into the gap between the support and the semiconductor element. There is no particular limit to the thickness of the cured product of the epoxy resin composition, and it can be appropriately selected depending on the purpose, for example, 10 μm or more and 800 μm or less. There is no particular limit to the shape of the epoxy resin composition, and it can be appropriately selected depending on the purpose. The cured product of the epoxy resin composition is placed in the gap between the support and the semiconductor element, thereby encapsulating the semiconductor element.

The method for manufacturing the semiconductor device according to this embodiment is not particularly limited and can be appropriately selected depending on the purpose. For example, the semiconductor device can be manufactured by a process of filling with an epoxy resin composition and a process of curing the epoxy resin composition.

The step of filling the epoxy resin composition is a step of filling the gap between the support and the semiconductor element with the epoxy resin composition. There is no particular limit to the method of filling the epoxy resin composition, and it can be appropriately selected depending on the purpose, and examples of the method include a dispensing method, a casting method, and a printing method. There is no particular limit to the amount of the epoxy resin composition to be filled, and it can be appropriately selected depending on the purpose, and examples of the amount include an amount that results in a thickness of the cured product of 10 μm or more and 800 μm or less.

The step of curing the epoxy resin composition is a step of curing the epoxy resin composition between the support and the semiconductor element. The method of curing the epoxy resin composition is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include transfer molding or compression molding of the support, the epoxy resin composition, and the semiconductor element.
Example

(Examples 1 to 14, Comparative Examples 1 to 3)
The components in the formulations shown in Tables 1 to 4 were mixed using a triple roll mill to uniformly disperse each component, thereby obtaining epoxy resin compositions.

The flexible epoxy resins used in the examples and comparative examples are as follows.
Flexible epoxy resin 1 (diglycidyl ether of polytetramethylene glycol, epoxy equivalent 440 g/eq., average molecular weight 880, product name: YX7400N, manufactured by Mitsubishi Chemical Corporation)
Flexible epoxy resin 2 (diglycidyl ether of polytetramethylene glycol, epoxy equivalent 1,072 g/eq., average molecular weight 2,140, product name: Epogo-se-PT polymer type, manufactured by Yokkaichi Chemical Co., Ltd.)

The epoxy resins (epoxy resins other than flexible epoxy resins) used in the examples and comparative examples are as follows.
Epoxy resin 1 (glycidylamine type liquid epoxy resin, epoxy equivalent 95 g/eq., average molecular weight 270, product name: EP-3950L, manufactured by ADEKA Corporation) Epoxy resin 2 (bisphenol F type liquid epoxy resin, epoxy equivalent 178 g/eq., average molecular weight 360, product name: RE410S, manufactured by Nippon Kayaku Co., Ltd.)
Epoxy resin 3 (bisphenol F type liquid epoxy resin, epoxy equivalent 160 g/eq., average molecular weight 360, product name: YDF870GS, manufactured by Nippon Steel Chemical & Material Co., Ltd.)

The curing agents used in the examples and comparative examples are as follows.
Curing agent 1 (phenolic curing agent, hydroxyl equivalent 139 to 143 g/eq., product name: MEH-8005, manufactured by Meiwa Kasei Co., Ltd.)
Hardener 2 (acid anhydride hardener, product name: HN-2200, manufactured by Showa Denko Materials Co., Ltd.)

The curing catalysts used in the examples and comparative examples are as follows.
Curing catalyst (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, product name: 2MZA, manufactured by Shikoku Chemical Industries Co., Ltd.)

The fillers used in the examples and comparative examples are as follows.
Filler 1 (average particle size 0.3 μm, product name: SE1050SMO, manufactured by Admatechs Co., Ltd.)
Filler 2 (average particle size 0.6 μm, product name: SE2200SME, manufactured by Admatechs Co., Ltd.)
Filler 3 (average particle size 0.05 μm, product name: YA050C-SM1, manufactured by Admatechs Co., Ltd.)

Other components used in the examples and comparative examples are as follows.
・Black 4 (Carbon Black, manufactured by Orion Engineered Carbons Co., Ltd.)
KBM-403 (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

The resulting epoxy resin composition was measured and evaluated for microvoids, solvent resistance, warpage, and elastic modulus. The evaluation results are shown in Tables 1 to 4.

<Microvoids>
Each of the obtained epoxy resin compositions was heated under the condition of 150°C/1 hour to prepare a cured product. The obtained cured product was sliced at equal intervals of 50 nm using a focused ion beam (FIB) and observed with an SEM (accelerating voltage: 1 kV, magnification: 5,000 times) each time. In an SEM image, components with different electron densities are represented as images of different shades. That is, the filler, resin component, and voids appear on the image as different shades. The obtained continuous SEM images were superimposed using 3D image processing software to construct a 3D structure. After that, the filler, resin component, and voids were set from the contrast difference of the obtained 3D structure, and then the image was divided and a machine learning segmentation function that recognizes the shade of each region was used to recognize and extract the filler, resin component, and microvoids, and the volume fraction (%) of each component was calculated. The microvoid ratio was calculated from the following formula using the obtained volume fraction, and evaluated based on the following evaluation criteria. The volume fraction of the filler is not involved in the calculation of the microvoid ratio. The following equipment and 3D image processing software were used in measuring the microvoids.
FIB: COBRA (manufactured by OrsayPhysics)
SEM: AURIGA (manufactured by Carl Zeiss)
3D image processing software: Dragonfly (Ver. 2022.1, manufactured by Object Research System)

-Evaluation criteria-
A: 0.0% to 30.0%
B: 30.1% to 38.0%
C: 38.1% or more

<Solvent resistance>
Each epoxy resin composition was cured at 150°C for 1 hour to prepare a test piece measuring 70 mm wide, 150 mm long, and 500 μm thick. The initial mass of the test piece was measured, and then the piece was immersed in propylene glycol monomethyl ether acetate heated to 60°C for 30 minutes. After immersion, the propylene glycol monomethyl ether acetate adhering to the surface was removed, and the mass was measured. The mass increase (corresponding to the mass change rate) was calculated from the following formula, and the test piece was evaluated based on the following evaluation criteria.

-Evaluation criteria-
A: 0.00% to 0.30%
B: 0.31% to 0.50%
C: 0.51% or more

＜Warping＞
Using a molding device (WCM-300, manufactured by Apic Yamada Co., Ltd.), each epoxy resin composition was placed on a silicon wafer with a diameter of 300 mm and a thickness of 775 μm, and molded to a diameter of 292 mm and a thickness of 500 μm under conditions of 120° C./400 seconds, and then cured at 150° C./1 hour. The warpage of the obtained silicon wafer molded product was measured with a shadow moire type warpage measuring device (Thermoray AXP2.0, manufactured by Therma Precision Co., Ltd.), and the warpage was evaluated based on the following evaluation criteria.

-Evaluation criteria-
A: Warpage is 10,000 μm or less. B: Warpage is 10,000 μm or more, or the wafer is cracked.

<Elastic modulus>
Each epoxy resin composition was cured at 150°C for 1 hour to prepare a test piece measuring 10.0 mm wide, 50.0 mm long, and 2.0 mm thick. The storage modulus of the obtained test piece was measured at 30°C by the DCB method using a viscoelasticity analyzer (viscoelasticity measuring device DMA7100, manufactured by Hitachi High-Tech Science Corporation). The measurement conditions were as follows:
Frequency: 1Hz
Strain amplitude: 10 μm
Heating rate: 3°C/min

The microvoid evaluation results and the solvent resistance evaluation results for Examples 1 to 14 and Comparative Examples 1 to 3 are consistent. This makes it clear that a high microvoid ratio leads to poor solvent resistance, and that one of the causes of poor solvent resistance (peeling from the chip) of the cured product of the epoxy resin composition is the occurrence of microvoids within the cured product.

The epoxy resin compositions of Examples 1 to 14 were all rated as "B" or higher for microvoids and solvent resistance, and all were rated as "A" for warpage. In contrast, Comparative Example 1, in which the proportion of flexible epoxy resin relative to the epoxy resin was 26.4% by mass, was rated as "C" for microvoids and solvent resistance, and it was revealed that solvent resistance deteriorates when the proportion of flexible epoxy resin relative to the epoxy resin exceeds 25% by mass. In Comparative Example 2, in which the proportion of flexible epoxy resin relative to the epoxy resin was 7.0% by mass, the warpage was rated as "B," and it was revealed that warpage deteriorates when the proportion of flexible epoxy resin relative to the epoxy resin is less than 8.0% by mass. Furthermore, Comparative Example 3, which does not contain epoxy resin, caused wafer cracking during the warpage evaluation, and the warpage of the substrate was further deteriorated compared to Comparative Example 2. From these results, it was revealed that by setting the content of flexible epoxy resin to 8.0% by mass to 25.0% by mass relative to the epoxy resin, it is possible to suppress microvoids, improve solvent resistance, and prevent substrate warpage.

In Examples 1 to 7 and 10 to 11, in which the content of flexible epoxy resin was 8.0% to 16.5% by mass relative to the epoxy resin, the microvoids and solvent resistance were rated as "A," whereas in Examples 8 to 9 and 12 to 13, in which the content of flexible epoxy resin was 16.5% by mass or more relative to the epoxy resin, the microvoids and solvent resistance were rated as "B." These results demonstrate that by setting the content of flexible epoxy resin to 8.0% to 16.5% by mass relative to the epoxy resin, it is possible to suppress microvoids and further improve solvent resistance.

Although the embodiments and examples of the present invention have been described, these are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. The embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

Claims (10)

Contains an epoxy resin, a filler, and at least one selected from a curing agent and a curing catalyst;
The epoxy resin comprises a flexible epoxy resin,
The content of the flexible epoxy resin is 8.0% by mass to 25.0% by mass relative to the epoxy resin. 2. The epoxy resin composition according to claim 1, wherein the content of the flexible epoxy resin is 8.0% by mass to 16.5% by mass based on the epoxy resin. 3. The epoxy resin composition according to claim 1, wherein the flexible epoxy resin is an aliphatic epoxy resin. 3. The epoxy resin composition according to claim 1, wherein the epoxy resin comprises at least one selected from the group consisting of bisphenol-type epoxy resins and glycidylamine-type epoxy resins. 3. The epoxy resin composition according to claim 1, wherein the curing agent is at least one selected from the group consisting of a phenol-based curing agent, an amine-based curing agent, and an acid anhydride-based curing agent. 3. The epoxy resin composition according to claim 1, wherein the content of the curing agent is 4% by mass to 15% by mass based on the epoxy resin composition excluding the filler. 3. The epoxy resin composition according to claim 1, which is used as a liquid compression molding material. 3. The epoxy resin composition according to claim 1, which is used for sealing semiconductor chips having a bump pitch of 150 μm or less. A cured product obtained from the epoxy resin composition according to claim 1 or 2. A semiconductor device having the cured product according to claim 9.