Repairable and reworkable electronic packaging materials

Abstract

Compositions include an underfill comprising a polymer having monomer units having a substituted Diels-Alder moiety and an ester moiety. A first process includes obtaining an underfill comprising a polymer having monomer units having a substituted Diels-Alder moiety and an ester moiety. A second process includes providing a mixture including a curing agent and a monomer comprising a substituted Diels-Alder moiety and an ester moiety. The second process also includes curing the mixture to form the underfill. A third process includes providing a semiconductor device including the underfill. A semiconductor device includes the underfill.

Description

Background Technology

[0001] This invention relates to electronic packaging materials, and more specifically, to polymer underfills.

[0002] Various polymeric materials (e.g., adhesives, thermal interface materials, underfills) are used in the manufacture of semiconductors and microelectronic devices. For example, underfills can be used in electronic packages at the junctions between semiconductor chips and boards. When a semiconductor chip is attached to a board, an electrical connection is formed between electrical terminals on the chip and corresponding electrical terminals on the board. These connections can be made, for example, using metallic or polymeric materials applied as bumps (e.g., solder bumps) to the chip or board terminals. The resulting assembly can then be heated to reflow the metallic or polymeric material and solidify the connection. Gaps between the printed circuit board and the connected components can be filled with underfill, which can enhance the interconnect and absorb stress from mechanical shocks. Summary of the Invention

[0003] Various embodiments relate to compositions comprising an underfill. The underfill comprises a polymer having monomer units having substituted Diels-Alder moieties and ester moieties. In some embodiments, the underfill further includes a filler. In a further embodiment, the underfill may include a heat-latent base. The monomer units may have the following structures:

[0004] Each asterisked bond is a carbon atom leading to the polymer, and each R is an organic substituent. In some embodiments, the organic substituent comprises an alkyl group.

[0005] Another embodiment involves a process that includes obtaining an underfill comprising a polymer having monomer units having substituted Diels-Alder moieties and ester moieties. The underfill may be a composite material. In some embodiments, the process further includes repairing defects in the underfill by applying a thermal stimulus to the underfill. In a further embodiment, the process may include removing the underfill from a surface by treating the polymer with a solution containing reactants for depolymerization (e.g., an organic catalyst and an alcohol). Depolymerization may include an ester exchange reaction. The underfill may be located beneath at least one chip in a semiconductor device. In these cases, the process may include dissolving a layer of underfill at a selected chip location from the at least one chip, removing the selected chip and the dissolved underfill from the location, and attaching a new chip at the location. Furthermore, the process may include applying a thermal stimulus to soften a layer of underfill located at a selected chip location from the at least one chip, removing the selected chip from the softened layer of underfill, dissolving the layer of underfill via ester exchange, removing the dissolved underfill, and attaching a new chip at the location. In some embodiments, the process includes repairing defects in a layer of underfill beneath the selected chip by applying localized thermal stimulation at the selected chip. In the underfill polymer, the monomer unit may have the following structure:

[0006] In this configuration, each starred bond is a carbon atom leading to the polymer, and each R is an organic substituent. The organic substituent may be an alkyl group.

[0007] A further embodiment relates to a process comprising providing a mixture containing a curing agent and monomers comprising substituted Diels-Alder moieties and ester moieties. The process further includes curing the mixture to form an underfill. The monomers may have the following structures:

[0008] Each X is a portion containing a reactive group and each R is an organic substituent. In some embodiments, each X is a glycidyl group.

[0009] Another embodiment relates to a process that includes providing a semiconductor device comprising an underfill. Further embodiments relate to a semiconductor device including the underfill. In some embodiments, the semiconductor device includes a multi-chip module, wherein the underfill is a layer beneath at least one chip in the multi-chip module. Attached Figure Description

[0010] The accompanying drawings included in this application are incorporated in and form a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings are merely illustrative of certain embodiments and do not limit the scope of the invention.

[0011] Figure 1A This is a flowchart illustrating a process for providing bottom filler material according to some embodiments.

[0012] Figure 1B This illustrates rework according to some implementation methods. Figure 1A The flowchart of the bottom filler process.

[0013] Figure 1C This illustrates a reheal according to some implementation methods. Figure 1A The flowchart of the bottom filler process.

[0014] Figure 2 This is a chemical reaction diagram illustrating the process of forming a monomer having an ester moiety and a thermally reversible Diels-Alder dimer moiety according to some embodiments.

[0015] Figure 3 This is a chemical reaction diagram illustrating the process of forming a polymer for underfill or other encapsulation materials according to some embodiments.

[0016] Figure 4 This illustrates a re-fix according to some implementation methods. Figure 3 The diagram shows the chemical reaction diagram of the polymer process.

[0017] Figure 5 This illustrates depolymerization according to some implementation methods. Figure 3 The chemical reaction diagram of the polymer process.

[0018] While the invention can be modified and substituted in various ways, its details have been illustrated by example in the accompanying drawings and will be described in detail. However, it should be understood that the purpose is not to limit the invention to the specific embodiments described. Rather, the invention is intended to cover all modifications, equivalents, and substitutions that fall within the scope of the invention. Detailed Implementation

[0019] Embodiments of the present invention generally relate to electronic packaging materials, and more specifically, to epoxy-based underfill materials. While the invention is not necessarily limited to such applications, various aspects of the invention can be understood through the discussion of examples in this context.

[0020] Although the invention has been described with reference to specific embodiments, it should be understood that the invention is not limited to these examples, and many variations of these embodiments will readily occur to those skilled in the art upon reading this disclosure. Therefore, the invention can be further described by way of the following embodiments, but is not limited thereto, and is merely illustrative.

[0021] Embodiment 1: A composition comprising an underfiller, wherein the underfiller comprises a polymer having monomer units having substituted Diels-Alder moieties and ester moieties. An advantage of this underfiller is that the Diels-Alder moieties can undergo reverse dimerization, and the ester moieties can participate in transesterification reactions.

[0022] Embodiment 2: The composition according to Embodiment 1, wherein the bottom filler further comprises filler. This can advantageously promote heat conduction.

[0023] Embodiment 3: The composition according to Embodiment 1 or 2, wherein the underfill further comprises a thermally latent base. This can advantageously allow the underfill to depolymerize upon application of heat stimulation.

[0024] Embodiment 4: The composition according to any one of Embodiments 1-3, wherein the monomer unit has the following structure:

[0025] In this configuration, each starred bond is a carbon atom leading to the polymer, and each R is an organic substituent. An advantage is that the properties of the bottom filler can be tuned by changing the substituents and the ester moiety.

[0026] Embodiment 5: The composition according to Embodiment 4, wherein the organic substituent comprises an alkyl group. An advantage is that the alkyl group can be selected based on steric and / or reactivity, thereby allowing for changes in the properties of the polymer.

[0027] Implementation Method 6: A process comprising obtaining an underfill containing a polymer having monomer units having substituted Diels-Alder moieties and ester moieties. An advantage of this process is that the Diels-Alder moieties can undergo reverse dimerization, and the ester moieties can participate in transesterification.

[0028] Implementation Method 7: The process according to Implementation Method 6, wherein the bottom filler is a composite material. This can advantageously promote heat conduction.

[0029] Implementation Method 8: The process according to Implementation Method 6 or 7 further includes repairing defects in the underfill by applying thermal stimulation to the underfill. This can extend the life of the underfill by repairing cracks, voids, and other defects.

[0030] Embodiment 9: The process according to Embodiment 6 or 7 further includes removing the underfill from the surface by treating the polymer with a solution containing reactants for depolymerization. This can advantageously allow for the reuse of the cleaned surface.

[0031] Embodiment 10: The process according to Embodiment 9, wherein the reactants comprise an organic catalyst and an alcohol. These reactants advantageously allow for the removal of the underfill without damaging the surface.

[0032] Implementation Method 11: The process according to Implementation Method 9 or 10, wherein depolymerization includes an ester exchange reaction. Its advantage is that ester exchange can be performed using a variety of commonly used reactants and reaction conditions.

[0033] Implementation Method 12: The process according to any one of Embodiments 6-11, wherein the underfill is located beneath at least one chip in the semiconductor device. This can extend the device's lifespan because the underfill can be repaired via thermal stimulation, which can improve chip connectivity and prevent cracks from propagating into the device's components. Additionally, defective chips can be replaced by dissolving the underfill.

[0034] Implementation Method 13: The process according to Implementation Method 12 further includes dissolving the underfill layer at a selected chip location from the at least one chip, removing the selected chip and the dissolved underfill from the location, and attaching a new chip at the location. This can extend the device lifespan when the selected chip is defective.

[0035] Implementation Method 14: The process according to Implementation Method 12 further includes applying thermal stimulation to soften a layer of underfill located at a selected chip position from the at least one chip, removing the selected chip from the softened layer of underfill, dissolving the layer of underfill via ester exchange, removing the dissolved underfill, and attaching a new chip at that position. This can extend the device life when the selected chip is defective. Applying thermal stimulation can facilitate the easy removal of defective chips.

[0036] Implementation Method 15: The process according to Implementation Method 12 further includes repairing defects in a layer of underfill material beneath the at least one chip by applying localized thermal stimulation at selected chip locations. This can extend the lifespan of the underfill material by repairing cracks, voids, and other defects.

[0037] Embodiment 16: The process according to any one of Embodiments 6-15, wherein the single unit has the following structure:

[0038] In this configuration, each starred bond is a carbon atom leading to the polymer, and each R is an organic substituent. An advantage is that the properties of the provided underfill can be adjusted by changing the substituents and the ester moiety.

[0039] Embodiment 17: The process according to Embodiment 16, wherein the organic substituent is an alkyl group. An advantage is that the alkyl group can be selected based on steric and / or reactivity, thereby allowing for changes in the properties of the polymer.

[0040] Implementation Method 18: A process comprising: providing a mixture containing a curing agent and a monomer comprising a substituted Diels-Alder moiety and an ester moiety; and curing the mixture to form a bottom filler. An advantage of this process is that the Diels-Alder moiety can undergo reverse dimerization, and the ester moiety can participate in transesterification.

[0041] Embodiment 19: According to the process described in Embodiment 18, the monomer has the following structure:

[0042] In this system, each X is a moiety containing a reactive group and each R is an organic substituent. Its advantage lies in the ability to adjust the properties of the monomer by changing the substituents and the ester moiety.

[0043] Embodiment 20: The process according to Embodiment 19, wherein each X is a glycidyl-based portion. The glycidyl-based portion advantageously allows for the formation of an epoxy-based underfill.

[0044] Implementation Method 21: A process comprising providing a semiconductor device comprising an underfill containing a polymer having monomer units having substituted Diels-Alder moieties and ester moieties. An advantage of this process is that the Diels-Alder moieties can undergo reverse dimerization and the ester moieties can participate in transesterification.

[0045] Implementation Method 22: According to the process described in Implementation Method 21, the individual unit has the following structure:

[0046] In this configuration, each starred bond is a carbon atom leading to the polymer, and each R is an organic substituent. An advantage is that the properties of the bottom filler can be adjusted by changing the substituents and the ester moiety.

[0047] Embodiment 23: A semiconductor device comprising an underfill containing a polymer, wherein the polymer comprises monomeric units having substituted Diels-Alder moieties and ester moieties. An advantage of this underfill is that the Diels-Alder moieties can undergo reverse dimerization, and the ester moieties can participate in transesterification reactions.

[0048] Embodiment 24: The semiconductor device according to Embodiment 23, wherein the single unit has the following structure:

[0049] In this configuration, each starred bond is a carbon atom leading to the polymer, and each R is an organic substituent. An advantage is that the properties of the bottom filler can be adjusted by changing the substituents and the ester moiety.

[0050] Embodiment 25: A semiconductor device according to Embodiment 23 or 24, wherein the semiconductor device comprises a multi-chip module, and wherein the underfill is a layer beneath at least one chip in the multi-chip module. This can advantageously extend the lifespan of the semiconductor device because the underfill can be repaired to fix defects and prevent defect propagation into the device. The device lifespan can also be extended by depolymerizing the underfill to replace defective chips.

[0051] Various embodiments of the invention are described herein with reference to the accompanying drawings, wherein like reference numerals denote like components. Alternative embodiments may be devised without departing from the scope of the invention. Note that various connections and positional relationships (e.g., above, below, adjacent, etc.) are depicted between the elements in the following description and drawings. Unless otherwise stated, these connections and / or positional relationships may be direct or indirect, and this disclosure is not intended to be limiting in this respect. Thus, coupling of entities may refer to direct or indirect coupling, and positional relationships between entities may be direct or indirect positional relationships. As an example of an indirect positional relationship, the reference in this specification to forming layer "A" above layer "B" includes the case where one or more intermediate layers (e.g., layer "C") are between layer "A" and layer "B," provided that the relevant characteristics and functions of layer "A" and layer "B" are not substantially altered by the intermediate layers.

[0052] The following definitions and abbreviations are used to interpret the claims and the specification. As used herein, the terms “comprising,” “including,” “comprise,” “having,” “with,” “containing,” or “containing,” or any other variations thereof, are intended to cover non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.

[0053] For the purposes described below, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” and their derivatives shall apply to the described structures and methods, as oriented as shown in the accompanying drawings. The terms “overlapping,” “on top,” “on top,” “above,” “positioned on,” or “positioned on top” mean that a first element (such as a first structure) is present on a second element (such as a second structure), wherein an intermediate element, such as an interface structure, may exist between the first and second elements. The term “direct contact” means that the first element (such as a first structure) and the second element (such as a second structure) are connected at the interface of the two elements without any intermediate conductive, insulating, or semiconductor layer. It should be noted that the term “selective to,” such as “a first element selective to a second element,” means that the first element can be etched, and the second element can act as an etch stop.

[0054] As used herein, the articles “a” and “a (species)” preceding an element or component are intended to be non-restrictive in relation to the number of instances (i.e., occurrences) of the element or component. Thus, “a” or “a (species)” should be understood to include one (species) or at least one (species), and the singular form of an element or component also includes the plural, unless the number clearly indicates the singular.

[0055] As used herein, the terms “invention” or “the present invention” are non-limiting terms and are not intended to refer to any single aspect of a particular invention, but rather to cover all possible aspects described in the specification and claims.

[0056] Unless otherwise stated, ranges shown herein (e.g., time, concentration, temperature, etc.) include both endpoints and all numbers in between. Unless otherwise stated, the use of tildes (~) or terms such as “about,” “substantially,” “approximately,” “slightly less than,” and variations thereof is intended to include the degree of error associated with a measurement of a specific quantity based on equipment available at the time of application. For example, “about” can include a range of ±8%, 5%, or 2% of the endpoints of a given value, a range of values, or one or more ranges of values. Unless otherwise stated, the use of such terms related to ranges applies to both ends of the range (e.g., “about 1g-5g” should be interpreted as “about 1g-about 5g”) and, in relation to a list of ranges, applies to each range in the list (e.g., “about 1g-5g, 5g-10g, etc.” should be interpreted as “about 1g-about 5g, about 5g-about 10g, etc.”).

[0057] As used herein, the term “aliphatic” encompasses the terms alkyl, alkenyl, or alkynyl. Aliphatic groups or groups may have any degree of saturation, such as groups having only carbon-carbon single bonds (“alkyl” or “alkylene”), groups having one or more carbon-carbon double bonds (“alkenyl”), groups having one or more carbon-carbon triple bonds (“alkynyl”), and groups having a mixture of carbon-carbon single, double, and / or triple bonds.

[0058] As used herein, an "alkyl" group refers to a saturated aliphatic hydrocarbon group (e.g., C1-C4, C1-C6, or C1-C8 alkyl) containing at least one carbon atom. Alkyl groups can be straight-chain, branched, cyclic, or any combination thereof. Unless otherwise specifically limited, the term "alkyl" as used herein, as well as derived terms such as "alkoxy" and "thioalkyl," includes straight-chain, branched, and cyclic moieties within its scope. If an alkyl group is further bonded to another atom, it becomes an alkylene group or alkylene group. In other words, the term "alkylene" also refers to a divalent straight-chain or branched alkyl group. For example, -CH2CH3 is an ethyl, while -CH2CH2- is an ethylene. The term "alkylene," alone or as part of another substituent, refers to a saturated straight-chain or branched divalent hydrocarbon group obtained by removing two hydrogen atoms from a single carbon atom or two different carbon atoms of a starting alkane.

[0059] Examples of alkyl / partial or alkyl groups include methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, and 1-ethyl-2-methylpropyl. The alkyl or alkylene groups defined above may be unsubstituted or substituted with one or more substituents as described below.

[0060] As used herein, the term "cyclic" refers to a cyclic compound or group containing at least three carbon atoms, and the bonds between adjacent pairs of atoms can all be of the specified single bond type (involving two electrons), or some of them can be double or triple bonds (with four or six electrons, respectively). Examples of cyclic aliphatic groups can include phenyl, saturated cycloalkyl (e.g., cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl), etc.

[0061] As used herein, the term "amine" or "amino" includes a compound in which a nitrogen atom is covalently bonded to at least one carbon or heteroatom. The term "amine" or "amino" includes -NH2 and also includes a substituted moiety. The term includes "alkylamino," which comprises a group and compound in which nitrogen is combined with at least one additional alkyl group (e.g., a secondary or tertiary amine). As used herein, the term "imino" group or residue refers to a divalent group =NR, where R in this document represents H or an alkyl group as defined herein. As used herein, the term "imide" refers to a group or compound having a nitrogen atom covalently bonded to two carbonyl groups. As used herein, the term "furan" refers to a group or compound having a five-membered aromatic ring containing four carbon atoms and one oxygen atom.

[0062] As described herein, the compounds of the present invention may optionally be substituted with one or more substituents, such as those generally described above, or exemplified as in the specific categories, subclasses, and species of the invention. As described herein, any of the foregoing portions or those described below may optionally be substituted with one or more substituents described herein.

[0063] In the context of this invention, the term "substituted" means that one or more hydrogen atoms of the indicated base or group are independently replaced by the same or different substituents. Furthermore, the term "substituted" specifically provides one or more (e.g., two, three, or more) substituents commonly used in the art. However, it is generally known that substituents should be selected such that they do not adversely affect the useful properties or function of the compound.

[0064] In some embodiments, suitable substituents in the context of this invention may include halogen groups, perfluoroalkyl, perfluoroalkoxy, alkyl, alkenyl, alkynyl, hydroxyl, oxo group, mercapto, alkylthio, alkoxy, aryl or heteroaryl, aryloxy or heteroaryloxy, arylalkyl or heteroarylalkyl, arylalkoxy or heteroarylalkoxy, amino, alkyl and dialkylamino, carbamoyl, alkylcarbonyl, carboxyl, alkoxycarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, arylcarbonyl, aryloxycarbonyl, alkylsulfonyl, arylsulfonyl, cycloalkyl, cyano, C1 to C6 alkylthio, arylthio, nitro, ketone, acyl, borate or borate, phosphate or phosphoryl, aminosulfonyl, sulfonyl, sulfinyl, and combinations thereof.

[0065] In a further embodiment, the substituent or substituent group may include halogen, hydroxyl, alkyl, alkenyl, alkynyl, alkoxy, -NH2, amino (primary, secondary, or tertiary), nitro, thiol, thioether, imine, cyano, amide, phosphonate, phosphine, carboxyl, thiocarbonyl, sulfonyl, sulfonamide, ketone, aldehyde, ester, acetyl, acetoxy, carbamoyl, oxygen (O); haloalkyl (e.g., trifluoromethyl); aminoacyl and aminoalkyl Carbon-cyclic cycloalkyl groups, which can be monocyclic or fused or unfused polycyclic (e.g., cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl), or heterocyclic alkyl groups, which can be monocyclic or fused or unfused polycyclic (e.g., pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, or thiazinyl), and carbon-cyclic or heterocyclic, monocyclic or fused or unfused polycyclic aryl groups (e.g., phenyl, naphthyl, pyrrolidinyl, indolyl, furanyl, thiophenyl, imidazolyl, etc.). azole group, iso Azolyl, thiazolyl, triazolyl, tetrazolyl, pyrazolyl, pyridinyl, quinolinyl, isoquinolinyl, acridineyl, pyrazinyl, pyridazinyl, pyrimidinyl, benzimidazolyl, benzothiophene, or benzofuranyl), -CO2CH3, -CONH2, -OCH2CONH2; -SO2NH2, -OCHF2, -CF3, -OCF3.

[0066] Modifications or derivatives of the compounds disclosed throughout this specification are considered suitable for use in the methods and compositions of this invention. Derivatives can be prepared, and their properties can be detected by any method known to those skilled in the art for the desired properties. In some aspects, “derivative” means a chemically modified compound that still retains the desired effects of the compound before chemical modification.

[0067] For the sake of brevity, conventional techniques related to the manufacture of semiconductor devices and integrated circuits (ICs) may or may not be described in detail herein. Furthermore, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process with additional steps or functions not described in detail herein. In particular, the various steps in the manufacture of semiconductor devices and semiconductor-based ICs are well-known; therefore, for the sake of brevity, many conventional steps will only be briefly mentioned herein or will be omitted entirely without providing well-known process details.

[0068] It should also be understood that the material compounds (e.g., SiN or SiGe) will be described based on the listed elements. These compounds include elements in different proportions within the compound; for example, SiGe includes Si. x Ge (1-x) Where x is less than or equal to 1, and so on. Additionally, other elements may be included in the compound and still function according to this principle. Compounds with additional elements will be referred to herein as alloys.

[0069] Turning now to an overview of techniques more specifically related to aspects of the present invention, electronic packaging assemblies for semiconductor and microelectronic devices can generally include various polymeric materials, such as underfills, thermal interface materials (TIMs), adhesives, pastes, laminates, etc. For example, underfills can fill the gaps between printed circuit boards and connected components (e.g., semiconductor chips) to enhance the connection and absorb stress from mechanical shocks. Epoxy-based polymeric materials are commonly used in these packaging materials. Epoxy-based materials, often referred to as “two-component epoxy resins,” consist of an epoxy compound / monomer (component A) mixed with a curing agent or hardener (component B) such as a primary amine. However, cracks can form in the underfill and other components due to the effects of, for example, elevated temperatures on materials with different coefficients of thermal expansion (CTE). These cracks can propagate into surrounding components, leading to device unreliability or failure. For example, cracks in commonly used epoxy-based capillary underfills can reduce sidewall adhesion and propagate to the device's interlayer dielectric (ILD), solder, solder mask, etc.

[0070] Embodiments of the present invention can improve encapsulation yield and lifespan and allow for scaling of MCMs. In some embodiments, epoxy-based materials (e.g., capillary bottom fillers) are provided, comprising polymers formed by reacting an epoxy compound having an ester moiety and a substituted Diels-Alder dimer moiety (e.g., a dicyclopentadiene moiety) with an amine curing agent. Epoxy-based materials may include mixtures of polymers and additives such as fillers (e.g., silica particles), radical inhibitors, etc. In some embodiments, the properties of the material (e.g., particle size and composition, weight percentage (wt.%) of filler in the composite) can be tuned by selecting the filler, amine curing agent, ester group, and / or substituents on the Diels-Alder dimer moiety.

[0071] The disclosed epoxy-based materials can be repairable and reprocessable. Repair of cracks, voids, and other defects in components, including epoxy-based materials such as TIMs, underfills, adhesives, etc., can be achieved by applying heat to the thermally reversible Diels-Alder dimer portion of the polymer. In some embodiments, depolymerization and removal of the material from the substrate can be performed by treatment with a solution containing reactants for depolymerization. These reactants can react with the ester portion of the polymer in various ways. This allows for the removal of defective chips without grinding or other methods that could damage the underlying laminate and / or other device components.

[0072] Referring now to the accompanying drawings, the same numbers represent the same or similar elements. Figure 1A This is a flowchart illustrating process 100 for providing a bottom filler material according to some embodiments. A monomer having an ester moiety and an R-substituted, thermally reversible Diels-Alder dimer moiety can be provided. This is shown at operation 110. The monomer may have the following structure:

[0073] (1)

[0074] Each asterisked bond is a carbon atom leading to a portion containing a polymerizable reactive group, and each R group is an organic substituent. Examples of polymerizable reactive groups may include epoxy, styrene, α,β-unsaturated carbonyl, aziridine, dicarbonyl, etc. In some embodiments, the polymerizable reactive group may include a pH- or light-responsive portion, which may allow polymerization and / or depolymerization to occur in response to pH changes or exposure.

[0075] Examples of the R group in Formula 1 can be hydrocarbons, such as methyl, ethyl, propyl, butyl, etc., or other optionally substituted aliphatic groups. In some embodiments, the R group may be selected based on its spatial and / or reactive properties to modulate the properties of the monomer and / or underfill formed in process 100. For example, the physical properties of the underfill, including the amount of softening in response to heat stimulation, can be modulated by using branched or straight-chain hydrocarbon chains as the R group. In some embodiments, the R group may be selected to modulate the solubility of the substituted Diels-Alder monomer. Additionally, the R group can influence the polymerization of the monomer and may participate in crosslinking (see below). The monomer represented by Formula 1 is also referred to herein as a "substituted Diels-Alder monomer".

[0076] The properties of the underfill can also be tuned by selecting the ester group (the portion located at the asterisked bond). For example, the choice of reactive groups on these portions can determine the type of polymer formed from the substituted Diels-Alder monomer. In some embodiments, the monomer has substituents containing terminal epoxy groups. This will be discussed in more detail below. As those skilled in the art will understand, the properties of the underfill can also be tuned by selecting other substituents on the asterisked bond portions.

[0077] A mixture containing substituted Diels-Alder monomers can be cured. This is shown at operation 115. The mixture can be an underfill applied around solder balls located between the chip and the laminate. Curing can include polymerizing the Diels-Alder monomers with a curing agent at any temperature suitable for the monomer / curing agent. In some embodiments, the polymerization involves crosslinking of the R groups shown in Formula 1. For example, depending on the choice of reactants, curing can be carried out at temperatures of about 60°C, 90°C, 100°C, 120°C, etc. An amine curing agent can be used when the asterisked bond in Formula 1 is directed toward the part having an epoxy group. In the polymer formed by curing, the Diels-Alder monomer subunit can be described by Formula 1, wherein the asterisked bond is directed toward the carbon atom having the part that reacts with the curing agent, as will be understood by one of ordinary skill in the art.

[0078] Fillers can be added to a mixture of substituted Diels-Alder monomers and curing agents to form composite materials. For example, silica (SiO2) particles having an average or maximum perimeter of about 1 μm can be added to form a composite material with polymer 320 and up to about 90 wt.% filler. In some embodiments, the amount of filler is about 40-50 wt.% or 50-60 wt.%. Other examples of fillers that can be used in some embodiments may include polyhedral oligomeric silsesquioxane (POSS) particles, SiO2 particles of other sizes (e.g., about 1-50 μm), etc. The silica particles may optionally be functionalized (e.g., with glycidyl groups).

[0079] In some embodiments, thermally latent organic bases are also included in the mixture. Regarding Figure 1B This will be discussed in more detail. In a further embodiment, the bottom filler may include a free radical inhibitor (e.g., butylated hydroxytoluene (BHT), phenothiazine, etc.). This can reduce side effects that may hinder re-repair (see...). Figure 1C ).

[0080] Figure 1B This is a flowchart illustrating process 101 of reprocessing an underfill formed in process 100 according to some embodiments. A semiconductor device containing the underfill, such as a multi-chip module, can be obtained. This is shown at operation 125. The multi-chip module may have defective chips (or chiplets) to be removed and optionally replaced. A thermal stimulus may be applied to soften the underfill. This is shown at operation 130. In some embodiments, the thermal stimulus is applied locally at the sites of the defective chips. The temperature of the thermal stimulus can vary depending on the properties / structure of the polymer, which can be influenced by the selection of R groups located on the substituted Diels-Alder monomer, as described above. In some embodiments, the thermal stimulus is from about 90°C to 120°C.

[0081] Defective chips can be removed from the softened underfill. This is illustrated at operation 135. The underfill remaining at the location of the defective chip after its removal can then be removed using a depolymerization mixture. This is illustrated at operation 140. In other embodiments, operation 125 can be omitted, and the defective chip can be removed during the depolymerization of the underfill polymer. In these cases, heat may optionally be applied during treatment with the depolymerization mixture.

[0082] The depolymerization reaction may involve transesterification. For example, the depolymerization mixture used in operation 140 may be a solution containing an organic catalyst, an alcohol, and a solvent. For example, the organic catalyst may be an alkylamine (e.g., triethylamine, Hünig base, tributylamine, trioctylamine, etc.), an amino alcohol, a stimulus-responsive or thermally / photoactivated catalyst, etc. The alcohol may be, for example, methanol, ethanol, propanol, butanol, etc. Suitable solvents may include water, alcohols, amino alcohols, glycols, or combinations thereof. In some embodiments, one or more solvents may be used in combination with N-methyl-2-pyrrolidone (NMP). When an amino alcohol is used, the depolymerization mixture may include an alcohol and an amino alcohol serving as both a solvent and an organic catalyst.

[0083] Various transesterification reactions can be performed. In a further embodiment, depolymerization may involve alcoholysis, wherein the depolymerization mixture comprises a base and an alcohol (such as methanol, ethanol, isopropanol, etc.). The depolymerization reaction can produce carbonate byproducts in reactions with a base and a glycol such as propylene glycol. In another example, depolymerization may involve glycolysis, for example, when the depolymerization mixture comprises ethylene glycol and triethylamine (TEA). In yet another embodiment, depolymerization may involve ammonolysis, wherein the depolymerization mixture comprises a base and a primary amine (e.g., CH3(CH2)). n NH2, where n is an integer from 1 to 10.

[0084] The bottom filler includes a heat-latent base (such as alkylammonium (R3N) of 2-methyl-1-(benzenesulfonyl)propyl-2-ylpiperidine-1-carboxylate or 2-(3-benzoylphenyl)propionic acid). + In the embodiment of the salt, depolymerization at operation 140 can be assisted by thermal stimulation. The thermal decomposition of the base releases carbon dioxide (CO2) via a decarboxylation reaction, allowing the base molecules to act as catalysts for transesterification chemistry when combined with the solvent. In a further embodiment, depending on the bond formed between the -X group of compound 210 and the curing agent, depolymerization can proceed in response to pH changes or exposure.

[0085] Removing the underfill at operation 140 allows the new chip to attach to the site of the removed chip. This is in Figure 1A Not shown in the image.

[0086] Although discussed in the context of underfill, processes 100, 101, and 102 can be used for other applications, such as other encapsulation materials (e.g., TIM, adhesives, etc.).

[0087] Figure 1CThis is a flowchart illustrating process 102 of rework in process 100 to form an underfill according to some embodiments. A semiconductor device comprising the underfill can be obtained. This is shown at operation 145. The underfill may have cracks, voids, or other defects that may affect one or more chips in the device. Therefore, to soften the underfill, a thermal stimulus may be applied. This is shown at operation 150. Operation 150 may include raising the temperature of the underfill (e.g., to about 90-120°C). When the temperature of the underfill is raised (e.g., for about 30 minutes), reverse dimerization of the cyclopentadiene moiety can occur, thereby “softening” the polymer. In some embodiments, the underfill may include a free radical inhibitor (which can reduce side reactions while the polymer softens).

[0088] Thermal stimulation can be removed, allowing the chip / underfill to return to its operating temperature. This is illustrated at operation 155. As the underfill temperature decreases, the cyclopentadiene portion can re-dimerize, thus "repairing" the polymer. Examples of reverse dimerization and re-dimerization of the polymer are shown in [the diagram / illustration]. Figure 4 As shown in the image.

[0089] Figure 2 This is a chemical reaction diagram illustrating process 200 for forming a monomer (“substituted Diels-Alder monomer”) having an ester moiety and a thermally reversible Diels-Alder dimer moiety, according to some embodiments. The monomer may be generated in process 100 ( Figure 1A Examples of monomers provided at operation 110. In process 200, R-substituted dicyclopentadiene can be refluxed with sodium (Na(0)) to form sodium-substituted cyclopentadienide (Na... + [R-Cp - The intermediate can react with carbon dioxide (CO2) in tetrahydrofuran (THF) solution to form R-substituted dicyclopentadiene-dicarboxylic acid 205.

[0090] R-substituted dicyclopentadiene-dicarboxylic acid 205 can react with an X-substituted organic compound (X-CH2OH) having a hydroxyl moiety, wherein X comprises a reactive (polymerizable) group, such as an epoxy, styrene, α,β-unsaturated carbonyl, aziridine, dicarbonyl, etc. The X ligand can be one or more additional reactive or non-reactive moieties. Process 200 can form a substituted Diels-Alder monomer 210 having an ester group containing a -CH2X moiety (at the asterisked bond in Formula 1) by reaction with X-CH2OH. For example, X-CH2OH can be glycidyl (2,3-epoxy-1-propanol). In these cases, the substituted Diels-Alder monomer 210 can have a glycidyl ester moiety (see...). Figure 3 ).

[0091] Figure 3 This is a chemical reaction diagram illustrating process 300 for forming a polymer for underfill or other encapsulation materials according to some embodiments. Process 300 may be an extension of process 100. Figure 1A An example of the curing reaction at operation 115. In process 300, amine curing agent 305 can be added to the substituted Diels-Alder monomer 310. The R of the substituted Diels-Alder monomer 310... 1 Group equivalent to Figure 2 The R group shown in Formula 1. The monomer 310 shown can be an example of monomer 210 formed using glycidyl ether in process 200.

[0092] Adding curing agent 305 and subsequently curing produces polymer 320, which can be used in electronic packaging materials (e.g., as an underfill, TIM, adhesive, etc.). Polymer 320 has a thermally reversible dicyclopentadiene moiety, which allows for re-repair upon application of heat (see [link to product description]). Figure 1C and 4 Polymer 320 also has an ester portion, which allows for reprocessing (e.g., removal of the underfill, followed by removal and / or replacement of the corresponding chip). About Figure 1B and 4 Let's discuss this in more detail.

[0093] The amine curing agent 305 shown comprises two primary amine moieties (-NH2) bonded to carbon atoms from organic moieties, which form the remainder of the molecular structure of the amine curing agent 305. These organic moieties... Figure 2 It is usually composed of R 2This is indicated, and depends on the type of curing agent used, as will be understood by those skilled in the art. Amine curing agent 305 can be any suitable curing / hardening agent for epoxy resins. In some embodiments, amine curing agent 305 can be a curing agent commonly used in, for example, commercially available resins such as Stycast® 1266 (manufactured by Henkel AG & Co., KGaA) or SUMIRESIN EXCEL® CRP-4160G (Sumitomo Bakelite Co., Ltd.) (“4160G curing agent”). In some embodiments, amine curing agent 305 is 4,7,10-trioxatridecane-1,13-diamine or 4,4-methylenebis(2-ethylaniline).

[0094] Polymer 320 can be produced using conventional reaction conditions for epoxy resin formation. For example, depending on the choice of reactants, curing can be carried out at temperatures of approximately 60°C, 90°C, 100°C, 120°C, etc. Fillers can be added to a mixture of substituted Diels-Alder monomer 310 and curing agent 305 to form a composite material. In some embodiments, process 300 can use 4160G curing agent as amine curing agent 305 and glycidyl-functionalized silica particles with a median size distribution of 1.5 μm as fillers to form an underfill. In this embodiment, R on Diels-Alder monomer 310 1 The group can be methyl, although other R groups can be used. 1 Groups. This mixture of substituted Diels-Alder monomer 310, amine curing agent 305, and filler can be cured in a nitrogen atmosphere at approximately 100°C for about 2 hours. For example... Figure 3 and 4 As shown, the bottom filler can be repaired or reprocessed.

[0095] Reaction conditions, bottom packing components, and monomer 310 structure that can be used in process 300 (e.g., R) 1 Other examples of (groups) are discussed above regarding Figure 1A A discussion was held.

[0096] Figure 4 This is a chemical reaction diagram illustrating process 400 of a repair polymer 320 according to some embodiments. When a thermal stimulus is applied to the polymer or a material containing the polymer, the Diels-Alder units can undergo reverse dimerization. This can result in softening of the polymer / material, which can allow for the repair of defects in the material. Upon cooling (e.g., by removing the thermal stimulus), the substituted cyclopentadiene units can re-dimerize. Process 400 illustrates the above description of process 102 (… Figure 1CExamples of re-fixing discussed in operations 150 and 155.

[0097] Figure 5 This is a chemical reaction diagram illustrating a process 500 for depolymerizing polymer 320 according to some embodiments. In process 500, a depolymerization mixture suitable for transesterification can be used to remove cured underfill or other materials containing polymer 320 from a substrate. Transesterification can produce a monomer solution 510 that can be rinsed away. The above refers to process 101 (… Figure 1B Operation 140 discusses various examples of depolymerization mixtures and processes that can be used in process 500.

[0098] Various embodiments of the invention have been described, and these descriptions are for illustrative purposes only and are not intended to be exhaustive or limited to the described embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or technical improvements to technologies found in the market, or to enable those skilled in the art to understand the embodiments described herein.

Claims

1. A composition comprising: Bottom filler, wherein the bottom filler comprises: A polymer having monomer units having substituted Diels-Alder moieties and ester moieties.

2. The composition of claim 1, wherein the bottom filler further comprises a filler.

3. The composition according to claim 1, wherein the bottom filler further comprises a heat-latent alkali.

4. The composition according to claim 1, wherein the monomer unit has the following structure: ,in: Each asterisked bond is a carbon atom leading to the polymer; and Each R is an organic substituent.

5. The composition according to claim 4, wherein the organic substituent comprises an alkyl group.

6. Process, including: Obtain a bottom filler, the bottom filler comprising: A polymer having monomer units having substituted Diels-Alder moieties and ester moieties.

7. The process according to claim 6, wherein the bottom filler is a composite material.

8. The process of claim 6 further includes repairing defects in the underfill by applying thermal stimulation to the underfill.

9. The process of claim 6, further comprising removing the underfill from the surface by treating the polymer with a solution containing reactants for depolymerization.

10. The process of claim 9, wherein the reactants comprise an organic catalyst, an alcohol, and a solvent.

11. The process according to claim 9, wherein the depolymerization comprises an transesterification reaction.

12. The process of claim 6, wherein the underfill is located beneath at least one chip in the semiconductor device.

13. The process according to claim 12, further comprising: Dissolve the layer of the underfill at a selected chip location from the at least one chip; Remove the selected chip and dissolved underfill from the location; and Connect the new chip at the specified location.

14. The process according to claim 12, further comprising: Apply thermal stimulation to soften the layer of bottom filler located at a selected chip position from the at least one chip; Remove the selected chip from the softened layer of the bottom filler; The bottom filler layer is dissolved via transesterification; Remove the dissolved bottom filler; and Connect the new chip at the specified location.

15. The process of claim 12, further comprising repairing defects in the layer of the underfill beneath the selected chip by applying localized thermal stimulation at the selected chip from the at least one chip.

16. The process according to claim 6, wherein the single unit has the following structure: ,in: Each asterisked bond is a carbon atom leading to the polymer; and Each R is an organic substituent.

17. The process of claim 16, wherein the organic substituent comprises an alkyl group.

18. Process, including: A mixture is provided, the mixture comprising: hardener; and Monomers comprising substituted Diels-Alder moieties and ester moieties; and The mixture is cured to form a bottom filler.

19. The process according to claim 18, wherein the monomer has the following structure: ,in: Each X is a portion containing a reactive group; and Each R is an organic substituent.

20. The process of claim 19, wherein each X is a glycidyl group.

21. Process, including: A semiconductor device comprising an underfill material is provided, the underfill material comprising: A polymer having monomer units having substituted Diels-Alder moieties and ester moieties.

22. The process according to claim 21, wherein the single unit has the following structure: ,in: Each asterisked bond is a carbon atom leading to the polymer; and Each R is an organic substituent.

23. Semiconductor devices, including: A bottom filler comprising a polymer, wherein the polymer comprises: Monomer units having substituted Diels-Alder moieties and ester moieties.

24. The semiconductor device of claim 23, wherein the single-unit has the following structure: ,in: Each asterisked bond is a carbon atom leading to the polymer; and Each R is an organic substituent.

25. The semiconductor device of claim 23, wherein the semiconductor device comprises a multi-chip module.

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