Liquid compression molding or encapsulant compositions

Abstract

The present invention provides a thermosetting resin composition that can be used for liquid compression molding encapsulation of reconfigured wafers. Compared to reconfigured wafers encapsulated with known encapsulation materials, the encapsulated molded wafers provide improved warpage resistance.

Description

Background Art Technical Field

[0002] Provided are thermosetting resin compositions useful in liquid compression molding ("LCM") or encapsulation applications that provide improved warpage resistance compared to LCM or encapsulation using known materials.

[0003] Brief description of related technologies

[0004] As semiconductor packaging evolves, the requirements for material encapsulation are also changing. To protect electronic components such as semiconductor devices, transfer molding, which applies a solid epoxy resin composition, has been a common approach. However, as semiconductor devices become thinner and more densely packed, this approach has become limited by flow defects near small openings and potential damage to certain delicate components.

[0005] Therefore, LCM or encapsulation has been developed as a processing technology that helps protect electronic devices. Compared with transfer molding, LCM or encapsulation is advantageous because the resin can flow more easily into narrow gaps and there is less possibility of damaging electronic components. Many semiconductor wafer-level packages ("WLP") have used LCM to encapsulate thin and delicate devices.

[0006] However, LCM or encapsulation has many problems in meeting the commercial scale needs and reliability required by the semiconductor packaging industry, especially for WLP.

[0007] Warpage is a common problem with many cured LCMs or liquid encapsulants. This is particularly prevalent with anhydride-cured epoxy compositions. As package sizes increase and thicknesses decrease, warpage can become too severe to meet process requirements, potentially leading to semiconductor package failure.

[0008] To address the warpage issue, many LCMs, or liquid encapsulants, have been formulated to lower the modulus and glass transition temperature (“Tg”). However, when going down this path, the encapsulated package has little chance of passing reliability testing.

[0009] LCMs or liquid encapsulants cured with anhydrides generally have poor viscosity stability at room temperature or upon heat ramping. Viscosity instability can lead to manufacturing difficulties and process uncertainties.

[0010] Conventional materials used to form molded wafers either do not possess the desired physical properties to provide improved resistance to wafer warpage or do not allow them to be applied by liquid compression molding techniques.

[0011] In the past, attempts have been made to address the warpage problem. For example, U.S. Patent No. 9,263,360 relates to and claims a thermosetting resin composition comprising: a thermosetting resin matrix comprising an epoxy resin component, an epoxy curing agent consisting of a novolac resin component, an optional combination of additional components, wherein the additional components are selected from episulfide resins, oxazines, oxazolines, cyanates, maleimides, nadimides, itaconimides, and combinations thereof; a block copolymer, a silica filler, and an optional catalyst and accelerator. Here, the block copolymer is an amphiphilic block copolymer selected from: a copolymer made of polystyrene, 1,4-polybutadiene, and syndiotactic poly(methyl methacrylate); a polymethyl methacrylate-block-polybutyl acrylate-block polymethyl methacrylate copolymer; and combinations thereof. The silica filler constitutes 50% to 90% by weight of the composition.

[0012] Furthermore, U.S. Patent No. 8,847,415 relates to and claims a liquid compression molding curable resin composition comprising a curable resin matrix, a curing component comprising a cationic catalyst and an oxidizing agent, wherein when cured, the composition exhibits a DSC peak below 140° C. and a delta temperature between the onset temperature and the DSC peak below 20° C.

[0013] U.S. Patent No. 9,263,360 provides a thermosetting resin composition comprising: a thermosetting resin matrix, a block copolymer, a silica filler, and a curing component comprising a combination of an anhydride or phenolic resin and an imidazole. When cured, the composition exhibits a modulus in the range of about 22 GPas or less at room temperature, a CTEα1 less than or equal to 10 ppm, and a T of about -70°C to -30°C, for example. g1 and T of about 100°C to 150°C g2 Multiple Tg.

[0014] Also in unrelated art, U.S. Patent No. 6,727,325 relates to and claims an epoxy resin composition comprising: an epoxy resin before curing, and an inclusion compound comprising a tetrakisphenol compound represented by a specified formula and a compound that reacts with epoxy groups of the epoxy resin to cure the resin.

[0015] Despite these recent efforts, it remains desirable to provide alternative LCM or encapsulant materials that exhibit improved viscosity stability at room temperature and provide improved resistance to wafer warpage, thereby providing end users with multiple options and sources of solutions to the recurring problem of wafer warpage. Summary of the Invention

[0016] Provided are thermosetting resin compositions that improve viscosity stability and reduce warpage of molded wafers after curing. More specifically, the compositions of the present invention are useful as liquid compression molding encapsulants that exhibit low warpage after compression molding and oven curing while maintaining the physical properties of the molding compound.

[0017] The composition exhibits a low storage modulus at room temperature (e.g., about 25 GPa or less at room temperature, desirably in the range of about 10 to about 20 GPa, such as about 5 to about 9 GPa), a low coefficient of thermal expansion ("CTE") (α1 < 15 ppm; α2 < 30 ppm), and at least one glass transition temperature [Tg above about 135°C as measured by thermomechanical analysis ("TMA")] g ].

[0018] Additionally and importantly, the composition exhibits a viscosity change of less than 30% within 24 hours at room temperature (25° C.) as measured by a rheometer (ARES Rheometer from TI), and a warpage of less than about 3 cm (e.g., less than about 2 cm) after curing under compression molding conditions. This combination of physical properties shows promise in overcoming some of the significant technical hurdles currently facing the semiconductor packaging industry (particularly with respect to liquid encapsulant viscosity instability and wafer warpage).

[0019] Thus, in one aspect, a thermosetting resin composition is provided, the reaction product of which comprises a thermosetting resin matrix (e.g., an epoxy resin component), a filler, and a curing component comprising a combination of (1) an inclusion compound comprising a tetraphenol compound and (2) a nitrogen-containing curing agent (e.g., imidazole and its derivatives).

[0020] In another aspect, a method of improving warpage resistance of a molded wafer is provided, comprising:

[0021] providing a wafer having one or more silicon chips arranged thereon;

[0022] providing a thermosetting resin composition as thus described in contact with said wafer; and

[0023] The wafer and the thermosetting resin composition are exposed to conditions that facilitate the thermosetting resin composition to flow around the wafer and cure into a reaction product of the thermosetting resin composition. The cured reaction product can improve the warpage resistance of the molded wafer by about 50%, desirably at least about 65%, and even more desirably at least about 80%, compared to a molded wafer made of a material other than the materials disclosed herein. The wafer is composed of silicon, and the composition is disposed on the wafer at a thickness less than about 50% of the wafer thickness, for example, less than about 33% of the wafer thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Depicts a process flow diagram for the liquid compression molding encapsulation process for wafer-level packaging applications. DETAILED DESCRIPTION

[0025] The thermosetting resin composition as described above comprises, among other ingredients, a thermosetting resin matrix (eg an epoxy resin component).

[0026] Examples of epoxy resin components include epoxides made from bisphenol A, bisphenol F, bisphenol S, bisphenol E, biphenyl, or combinations thereof. Additionally, two or more different bisphenol epoxides (or hydrogenated versions thereof) within the same resin type (e.g., A, F, S, or E) may be used.

[0027] Commercially available examples of desirable bisphenol epoxides for use herein include bisphenol-F epoxides [e.g., RE-404-S from Nippon Kayaku, Japan, and EPICLON 830 (RE1801), 830S (RE1815), 830A (RE1826), and 830W from Dai Nippon Ink & Chemicals, Inc., and RSL1738 and YL-983U from Resolution] and bisphenol-A epoxides (e.g., YL-979 and 980 from Resolution).

[0028] The bisphenol epoxides commercially available from Dai Nippon, as described above, are advertised as liquid, undiluted epichlorohydrin-bisphenol F epoxides (which have lower viscosities than conventional epoxides based on bisphenol A epoxide) and have similar physical properties to liquid bisphenol A epoxides. Bisphenol F epoxides have lower viscosities than bisphenol A epoxides (all other factors being the same between the two types of epoxides), which provides lower viscosity and, therefore, faster-flowing underfill encapsulant materials. The EEWs of the four bisphenol F epoxides range from 165 to 180. The viscosities at 25°C are 3,000 to 4,500 cps (except for RE1801, which has an upper viscosity limit of 4,000 cps). The bisphenol A epoxides have EEWs (g / eq) between 180 and 195, and viscosities at 25°C between 100 and 250 cps.

[0029] The bisphenol epoxides commercially available from Resolution as described above are advertised as low chloride containing liquid epoxides. RSL-1738 bisphenol A epoxide is reported to have a total chloride content between 500 and 700 ppm, and YL-983U has a total chloride content between 150 and 350 ppm.

[0030] Suitable epoxides for use herein also include polyglycidyl derivatives of phenolic compounds, such as those commercially available under the tradename EPON, such as EPON 828, EPON 1001, EPON 1009, and EPON 1031 from Resolution; DER 331, DER 332, DER 334, and DER 542 from Dow Chemical Co.; and BREN-S from Nippon Kayaku. Other suitable epoxides include polyepoxides prepared from polyols and the like, and polyglycidyl derivatives of phenol-formaldehyde novolacs, such as DEN 431, DEN 438, and DEN 439 from Dow Chemical. Cresol analogs are also commercially available under the tradename ARALDITE (e.g., ARALDITE ECN 1235, ARALDITE ECN 1273, and ARALDITE ECN 1299 from Ciba Specialty Chemicals Corporation). SU-8 is a bisphenol-A type epoxy novolac available from Resolution. Polyglycidyl adducts of amines, amino alcohols, and polycarboxylic acids can also be used in the present invention. Commercially available resins include GLYAMINE 135, GLYAMINE 125, and GLYAMINE 115 from FIC Corporation; ARALDITE MY-720, ARALDITE 0500, and ARALDITE 0510 from Ciba Specialty Chemicals; and PGA-X and PGA-C from Sherwin-Williams Co.

[0031] In addition to bisphenol epoxides, other epoxy compounds may also be included in the epoxy component. For example, cycloaliphatic epoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carbonate, or hydrogenated forms of bisphenol or biphenyl epoxides may be used.

[0032] Monofunctional, difunctional, or polyfunctional reactive diluents may also be used to adjust viscosity and / or lower Tg, such as butyl glycidyl ether, cresol glycidyl ether, polyethylene glycol glycidyl ether, or polypropylene glycol glycidyl ether. Suitable monofunctional epoxy co-reactant diluents for use herein include those having a viscosity lower than that of the epoxy component, typically less than about 250 cps.

[0033] The monofunctional epoxy co-reactant diluent should have an epoxy group with an alkyl group of from about 6 to about 28 carbon atoms, examples of which include C 6-28 Alkyl glycidyl ether, C 6-28 Fatty acid glycidyl esters and C 10-28 Alkylphenol glycidyl ether.

[0034] Where such monofunctional epoxy coreactant diluents are included, they may be present in amounts up to about 5 wt % to about 15 wt %, such as about 8 wt % to about 12 wt %, based on the total weight of the thermosetting resin matrix.

[0035] The epoxy resin component should be present in the composition in an amount ranging from about 10 wt % to about 95 wt %, desirably about 20 wt % to about 80 wt %, such as about 60 wt %, based on the total weight of the thermosetting resin matrix.

[0036] In addition to the epoxy resin component, other reactive components may be included, such as an episulfide resin component, an oxazine component, an oxazoline component, a cyanate ester component, and / or a maleimide-, nadicimide-, or itaconimide-containing component.

[0037] As the episulfide resin, any of the aforementioned epoxides in which the oxirane oxygen atom is replaced by a sulfur atom can be used.

[0038] Oxazines can be encompassed by the following structures

[0039]

[0040] wherein R1-R8 are each independently selected from hydrogen, C 1-40 Alkyl, C 2-40 members of an alkenyl group, the latter two of which are optionally interrupted by one or more of O, N, S, C=O, COO, or NHC=O, or substituted by one or more of OH, OR, NRR, SH, SR, COOH, COOR, NHCOOH, or NHCOOR, wherein R is selected from C 1-40 Alkyl, C 2-40 Alkenyl or C 6-20 Aryl,

[0041] X is a linkage broadly selected from alkylene, alkenylene or arylene, optionally interrupted by one or more of O, NR, S, C=O, COO or NHC=O, or substituted by one or more of OH, OR, NRR, SH, SR, COOH, COOR, NHCOOH or NHCOOR, wherein R is selected from C 1-40 Alkyl, C 2-40 Alkenyl or C 6-20 Aryl,

[0042] m and n are each independently 1 or 2, and

[0043] k is 0 to 6.

[0044] The oxazine resin component should be present in the composition in an amount ranging from about 10 wt % to about 95 wt %, desirably about 20 wt % to about 80 wt %, for example about 60 wt %, based on the total weight of the thermosetting resin matrix.

[0045] A more specific example of the oxazine resin component is a benzoxazine resin, an example of which can be encompassed by the structure

[0046]

[0047] wherein o is 1-4, X is defined as follows, R1 is an alkyl group such as methyl, ethyl, propyl or butyl, or

[0048]

[0049] wherein p is 1-4, Y is as defined below, and R4 is selected from hydrogen, halogen, alkyl or alkenyl.

[0050] X and Y in the above benzoxazine structure may be independently selected from monovalent or multivalent groups including:

[0051] - a hydrocarbyl or substituted hydrocarbyl species typically having from about 6 to about 500 carbon atoms, wherein the hydrocarbyl species is selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl, arylalkyl, arylalkenyl, alkenylaryl, arylalkynyl, or alkynylaryl, provided, however, that X can be aryl only when X comprises a combination of two or more different species;

[0052] - an alkylene or substituted alkylene species typically having from about 6 to about 500 carbon atoms, wherein the alkylene species is selected from alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, arylene, alkylarylene, arylalkylene, arylalkenylene, alkenylarylene, arylalkynylene, or alkynylarylene,

[0053] - heterocyclic or substituted heterocyclic species generally having from about 6 to about 500 carbon atoms,

[0054] - polysiloxane, and

[0055] - polysiloxane-polyurethane block copolymer, and

[0056] A combination of one or more of the above and a linker selected from the group consisting of: a covalent bond, -O-, -S-, -NR-, -NR-C(O)-, -NR-C(O)-O-, -NR-C(O)-NR-, -SC(O)-, -SC(O)-O-, -SC(O)-NR-, -OS(O)2-, -OS(O)2-O-, -OS(O)2-NR-, -OS(O)-, -OS(O)-O-, -OS(O)2- )-NR-, -O-NR-C(O)-, -O-NR-C(O)-O-, -O-NR-C(O)-NR-, -NR-OC(O)-, -NR-OC(O)-O-, -NR-OC(O )-NR-, -O-NR-C(S)-, -O-NR-C(S)-O-, -O-NR-C(S)-NR-, -NR-OC(S)-, -NR-OC(S)-O-, -NR-OC(S) -NR-, -OC(S)-, -OC(S)-O-, -OC(S)-NR-, -NR-C(S)-, -NR-C(S)-O-, -NR-C(S)-NR-, -SS(O)2-, - SS(O)2-O-, -SS(O)2-NR-, -NR-OS(O)-, -NR-OS(O)-O-, -NR-OS(O)-NR-, -NR-OS(O)2-, -NR-OS( wherein each R is independently hydrogen, alkyl or substituted alkyl.

[0057] As will be readily appreciated by those skilled in the art, when one or more of the above-described "X" or "Y" linking groups cooperate to form an appendage to the benzoxazine group, a wide variety of organic chains can be generated, such as alkoxy, alkylthio, aminoalkyl, carboxyalkyl, oxyalkenyl, thioalkenyl, aminoalkenyl, carboxyalkenyl, oxyalkynyl, thioalkynyl, aminoalkynyl, carboxyalkynyl, oxocycloalkyl, thiocycloalkyl, aminocycloalkyl, carboxycycloalkyl, oxocycloalkenyl, thiocycloalkenyl, aminocycloalkenyl, carboxycycloalkenyl, heterocycle, oxoheterocycle, thioheterocycle, aminoheterocycle, carboxyheterocycle, oxoaryl, thioaryl, aminoaryl, aryl, oxoheteroaryl, thioheteroaryl, aminoheteroaryl, carboxyheteroaryl, oxoalkylaryl, thioalkylaryl, aminoalkylaryl, carboxyalkylaryl, oxoarylalkyl, thioarylalkyl, aminoarylalkyl, carboxyarylalkyl, oxoarylalkenyl, thioarylalkenyl, aminoarylalkenyl, carboxyarylalkenyl, oxoalkenylaryl, thioalkenylaryl, aminoalkenylaryl, carboxyalkenylaryl, oxoarylalkynyl, thioarylalkynyl, aminoarylalkynyl, carboxyarylalkynyl, oxoalkynylaryl, thioalkynylaryl, aminoalkynylaryl or carboxyalkynylaryl, oxoalkylene, thioalkylene, aminoalkylene, carboxy alkylene, oxoalkenylene, thioalkenylene, aminoalkenylene, carboxyalkenylene, oxoalkynylene, thioalkynylene, aminoalkynylene, carboxyalkynylene, oxocycloalkylene, thiocycloalkylene, aminocycloalkylene, carboxycycloalkylene, oxocycloalkenylene, thiocycloalkenylene, aminocycloalkenylene, carboxycycloalkenylene, oxoarylene, thioarylene, aminoarylene, carboxyarylene, oxoalkylarylene, thioalkylarylene, aminoalkylarylene, carboxyalkylarylene, oxoarylalkylene, thioarylalkylene, aminoarylalkylene, carboxyarylalkylene, oxoarylalkenylene, thioarylalkenylene, aminoarylalkenylene, carboxyarylalkenylene, oxoalkenylarylene, thioalkenylarylene, aminoalkenylarylene, carboxyalkenylarylene, oxoarylalkynylene, thioarylalkynylene, aminoarylalkynylene, carboxyarylalkynylene, oxoalkynylarylene, thioalkynylarylene, aminoalkynylarylene, carboxyalkynylarylene, heteroarylene, oxoheteroarylene, thioheteroarylene, aminoheteroarylene, carboxyheteroarylene, a divalent or multivalent cyclic moiety containing a heteroatom, a divalent or multivalent cyclic moiety containing an oxygen heteroatom, a divalent or multivalent cyclic moiety containing a sulfur heteroatom, a divalent or multivalent cyclic moiety containing an amino heteroatom, a divalent or multivalent cyclic moiety containing a carboxyl heteroatom, and the like.

[0058] The benzoxazine resin component should be present in the composition in an amount ranging from about 10 wt % to about 95 wt %, desirably from about 20 wt % to about 80 wt %, for example about 60 wt %, based on the total weight of the thermosetting resin matrix.

[0059] As the cyanate ester component, a compound having the following general structural formula can be used:

[0060]

[0061] Here m is 2 to 5, R 1 is a residue containing an aromatic nucleus. 1 It should contain at least 6 carbon atoms and can be derived, for example, from aromatic hydrocarbons such as benzene, biphenyl, naphthalene, anthracene, pyrene, etc. The aromatic residue can also be derived from a polynuclear aromatic hydrocarbon in which at least two aromatic rings are linked to each other via a bridging group, for example in which the bridging members have the formula:

[0062]

[0063] where R a and R b are the same or different and each represents a hydrogen atom or an alkyl group containing 1 to 4 carbon atoms. 1 Also included are residues derived from novolac-type phenolic resins, i.e., the cyanate esters of these phenolic resins. 1 Other ring-linked non-reactive substituents may also be present.

[0064] Examples of useful cyanate esters include, for example: 1,3-dicyanatobenzene; 1,4-dicyanatobenzene; 1,3,5-tricyanatobenzene; 1,3-, 1,4-, 1,6-, 1,8-, 2,6-, or 2,7-dicyanonaphthalene; 1,3,6-tricyanonaphthalene; 4,4'-dicyano-biphenyl; bis(4-cyanophenyl)methane and 3,3',5,5'-tetramethylbis(4-cyanophenyl)methane; 2,2-bis(3,5-dichlorophenyl)methane; 1,3-bis[4-cyanophenyl-1-(methylethylidene)]benzene and cyanated bisphenol-terminated polycarbonate or other thermoplastic oligomers.

[0065] Other cyanate esters include those disclosed in U.S. Patent Nos. 4,477,629 and 4,528,366, the disclosures of each of which are expressly incorporated herein by reference; those disclosed in British Patent No. 1,305,702; and those disclosed in International Patent Publication No. WO 85 / 02184, the disclosures of each of which are expressly incorporated herein by reference.

[0066] Cyanate esters particularly contemplated for use herein are commercially available from Huntman Advanced Materials of Tarrytown, New York under the trade designation "AROCY" [1,1-bis(4-cyanatophenylethane)]. The structures of four contemplated "AROCY" cyanate esters are

[0067]

[0068] The cyanate ester resin component should be present in the composition in an amount ranging from about 10 wt % to about 95 wt %, desirably about 20 wt % to about 80 wt %, such as about 60 wt %, based on the total weight of the thermosetting resin matrix.

[0069] As maleimide, nadicimide or itaconimide, compounds having the following corresponding general structural formulae can be used:

[0070]

[0071] Here m is 1-15, p is 0-15, and each R 2 are independently selected from hydrogen or lower alkyl (e.g. C 1-5 ), and J is a monovalent or multivalent group comprising an organic or organosiloxane group, and combinations of two or more thereof, such as defined as "X" and "Y" with respect to the benzoxazine structure above.

[0072] Monovalent or polyvalent groups include hydrocarbyl or substituted hydrocarbyl species typically having from about 6 to about 500 carbon atoms. The hydrocarbyl species can be alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl, arylalkyl, arylalkenyl, alkenylaryl, arylalkynyl, and alkynylaryl.

[0073] Additionally, X can be a hydrocarbylene or substituted hydrocarbylene species typically having from about 6 to about 500 carbon atoms. Examples of hydrocarbylene species include, but are not limited to, alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, arylene, alkylarylene, arylalkylene, arylalkenylene, alkenylarylene, arylalkynylene, and alkynylarylene.

[0074] The maleimide, itaconamide or nadic imide may be in liquid or solid form.

[0075] In a desired embodiment, the maleimide, itaconamide, or nadicimide functional groups are separated by multivalent groups of sufficient length and branching to render the maleimide-containing compound liquid. The maleimide, itaconamide, or nadicimide compound may comprise a spacer between the maleimide functional groups comprising a branched alkylene group between the maleimide, itaconamide, or nadicimide functional groups.

[0076] In the case of a maleimide-containing compound, the maleimide compound is desirably stearylmaleimide, oleylmaleimide, biphenylmaleimide or 1,20-bismaleimide-10,11-dioctyl-eixosane, or a combination thereof.

[0077] Also in the case of maleimide-containing compounds, the maleimide compound can be prepared by the reaction of maleic anhydride with dimeric amide, or prepared from aminopropyl-terminated polydimethylsiloxane, polyoxypropyleneamine, polytetramethylene oxide-bis-p-aminobenzoate, or combinations thereof.

[0078] Particularly desirable maleimides and nadic imides include

[0079]

[0080] where R 5 and R 6 Each is selected from alkyl, aryl, aralkyl, or alkaryl groups having from about 6 to about 100 carbon atoms, said groups being present or absent substituted or interrupted by members selected from silane, silicon, oxygen, halogen, carbonyl, hydroxyl, ester, carboxylic acid, urea, urethane, carbamate, sulfur, sulfonate, and sulfone.

[0081] Other desirable maleimides, nadic imides, and itaconimides include

[0082]

[0083]

[0084]

[0085]

[0086] or

[0087]

[0088] The maleimide, nadicimide or itaconimide should be present in the composition in an amount ranging from about 10 wt % to about 95 wt %, desirably from about 20 wt % to about 80 wt %, for example about 60 wt %, based on the total weight of the thermosetting resin matrix.

[0089] As filler components, many materials may be available. For example, inorganic fillers may be available, particularly in cases where the coefficient of thermal expansion ("CTE") between the semiconductor chip to be mated and sealed and the substrate is to be more closely matched. Fillers affect the CTE and can therefore be used to reduce the thermal expansion of the cured material, thereby reducing warpage. The filler component can often include reinforcing silica, such as fused spherical silica, and can be untreated or treated to change the chemical properties of its surface. However, the filler component should include particles with an average particle size distribution in the range of 0.1 to 75 microns, for example, in the range of 0.1 to 50 microns. Commercially available examples of such particles are sold by Tatsumori or Denka in Japan. In addition, nano-sized silica powders, such as those sold by Nanoresins in Germany under the trade name NANOPOX, can be added. NANOPOX fillers are monodispersed silica filler dispersions in epoxy resins at a level of up to about 50% by weight available from Nanoresins in Germany. NANOPOX fillers are generally considered to have a particle size of about 5 nm to about 80 nm.

[0090] Nanoresins also produces materials under the NANOPOX E trademark. For example, Nanoresins reports that NANOPOX E-branded products enable complete impregnation of electronic components that are otherwise difficult to seal and offer a wide range of mechanical and thermal properties, such as reduced shrinkage and thermal expansion, fracture toughness, and modulus. The table below lists information on four prominent NANOPOX E products from Nanoresins:

[0091]

[0092] 1 Diglycidyl ester of bisphenol

[0093] 2 Diglycidyl ester of bisphenol

[0094] 3 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexyl carbonate

[0095] Nanoresins reports that significant improvements in key properties in epoxy formulations can be achieved through the use of NANOPOX E brand products. For example:

[0096] Lower viscosity of formulations compared to conventional reinforcing fillers

[0097] No precipitation

[0098] Increased fracture toughness, impact resistance and modulus

[0099] Improved scratch and wear resistance

[0100] Reduced shrinkage and thermal expansion

[0101] • Improvement or at least no negative impact on many desired properties such as thermal stability, chemical resistance, glass transition temperature, weathering resistance and dielectric properties.

[0102] Compared with the corresponding matrix resin, the processing properties are basically unchanged.

[0103] According to the manufacturer, the NANOPOX E brand product is a colloidal silica sol in an epoxy resin matrix. According to the manufacturer, the dispersed phase is composed of surface-modified spherical SiO nanoparticles with a diameter lower than 50nm and a very narrow particle size distribution. These spheres are only a few nanometers in size and are distributed in the resin matrix without agglomerates. According to the manufacturer, this produces a very low dispersion viscosity, and the dispersion has an SiO content of no more than 40% by weight. As reported by the manufacturer, the nanoparticles are chemically synthesized from an aqueous sodium silicate solution. Compared to processes in which powdered fillers are dispersed using a high-speed dispersor or other equipment using high shear energy, the adhesive is not damaged in this process.

[0104] Other desirable materials for use as filler components include those composed of or comprising alumina, silicon nitride, aluminum nitride, silicon dioxide-coated aluminum nitride, boron nitride, or combinations thereof.

[0105] When used, the filler component should be used in an amount ranging from about 50 to about 90 weight percent of the composition, such as from about 60 to about 90 weight percent, desirably from about 70 to about 90 weight percent, based on the total weight of the composition.

[0106] The curing component should be a latent curing component.

[0107] The curing component includes a combination of (1) an inclusion compound (e.g., a tetrakisphenol compound) and (2) a nitrogen-containing compound (e.g., imidazole and its derivatives). Examples of the inclusion compound as described above include tetrakisphenol compounds, such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3,5-dimethyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-chloro-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3,5-dichloro-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-bromo-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3,5-dibromo-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-tert-butyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3,5-di ... 1,1,2,2-tetrakis(3-chloro-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-bromo-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-methoxy-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-tert-butyl-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-chloro-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-bromo-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-methoxy-5-methyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-tert-butyl-5-methyl-4-hydroxyphenyl)ethane, ,1,2,2-tetrakis(3-chloro-5-bromo-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(3-chloro-5-phenyl-4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis[(4-hydroxy-3-phenyl)phenyl]ethane, 1,1,3,3-tetrakis(4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-methyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-chloro-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3,5-dichloro-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-bromo-4-hydroxyphenyl)propane, 1,1,3,3- Tetrakis(3,5-dibromo-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-phenyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3,5-diphenyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-methoxy-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3,5-dimethoxy-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3-tert-butyl-4-hydroxyphenyl)propane, 1,1,3,3-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 1,1,4,4-tetrakis(4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3-methyl-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3,1,1,4,4-tetrakis(3-chloro-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3,5-dichloro-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3-methoxy-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3,5-dimethoxy-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3-bromo-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3,5-dibromo-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3-tert-butyl-4-hydroxyphenyl)butane, 1,1,4,4-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)butane, and combinations thereof.

[0108] Nitrogen-containing compounds include amines, amides, and imidazoles, to name a few.

[0109] As the amine, for example, aliphatic amines, alicyclic and heterocyclic amines, aromatic amines and modified amines can be used.

[0110] As the aliphatic amines, some or all of the following may be used: ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, dimethylaminopropylamine, diethylaminopropylamine, trimethylhexamethylenediamine, pentanediamine, bis(2-dimethylaminoethyl)ether, pentamethyldiethylenetriamine, alkyl-tertiary monoamines, 1,4-diazabicyclo(2,2,2)octane(triethylenediamine), N,N,N′,N′-tetramethylhexamethylenediamine, N,N,N′,N′-tetramethylpropylenediamine, N,N,N′,N′-tetramethylethylenediamine, N,N-dimethylcyclohexylamine, dimethylaminoethoxyethoxyethanol, dimethylaminohexanol, and combinations thereof.

[0111] As alicyclic and heterocyclic amines, some or all of the following may be used: piperidine, piperidine, menthanediamine, isophoronediamine, methylmorpholine, ethylmorpholine, N,N',N"-tris(dimethylaminopropyl)hexahydro-s-triazine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane adacto, N-aminoethylpiperadine, trimethylaminoethylpiperadine, bis(4-aminocyclohexyl)methane, N,N'-dimethylpiperidine, 1,8-diazabicyclo(4,5,0)undecene-7, and combinations thereof.

[0112] As the aromatic amine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzylmethylamine, dimethylbenzylamine, m-xylenediamine, pyridine, picolinamide, and combinations thereof may be used.

[0113] As the modified polyamine, polyamines to which epoxy compounds are added, polyamines to which Michael reaction is added, polyamines to which Mannich reaction is added, polyamines to which thiourea is added, ketone-terminated polyamines, and combinations thereof can be used.

[0114] As imidazole, some or all of the following can be used: imidazole and its derivatives, for example, isoimidazole; imidazole; alkyl-substituted imidazoles, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-dimethylimidazole, butylimidazole, 2-heptadecenyl-4-methylimidazole, 2-methylimidazole, 2-undecenylimidazole, 1-vinyl-2-methylimidazole, 2-n-heptadecylimidazole, 2-undecylimidazole, 2-heptadecylimidazole , 2-phenylimidazole, 2-ethyl 4-methylimidazole, 1-benzyl-2-methylimidazole, 1-propyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-guanidine aminoethyl-2-methylimidazole and the addition product of imidazolemethylimidazole and the addition product of imidazole and trimellitic acid, 2-n-heptadecyl-4-methylimidazole, etc., usually among them each alkyl substituent containing no more than about 17 carbon atoms, desirably no more than about 6 carbon atoms; aryl-substituted imidazoles such as phenylimidazole, benzylimidazole, 2-methyl-4,5-diphenylimidazole, 2,3,5-triphenylimidazole, 2-phenylimidazole, 1-(dodecylbenzyl)-2-methylimidazole, 2-(2-hydroxy-4-tert-butylphenyl)-4,5-diphenylimidazole, 2-(2-methoxyphenyl)-4,5-diphenylimidazole, 2-(3-hydroxyphenyl)- 4,5-diphenylimidazole, 2-(p-dimethylaminophenyl)-4,5-diphenylimidazole, 2-(2-hydroxyphenyl)-4,5-diphenylimidazole, bis(4,5-diphenyl-2-imidazole)-benzene-1,4,2-naphthyl-4,5-diphenylimidazole, 1-benzyl-2-methylimidazole, 2-p-methoxyphenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole (commercially available from Shikoku, Tokyo, Japan under the trade name 2PHZ), and combinations thereof.

[0115] Commercially available examples of imidazoles include imidazole, CUREZOL 1B2MZ (benzyl-2-methylimidazole) and CUREZOL 2P4MZ (2-phenyl-4-methylimidazole) from Sigma-Aldrich Corporation (each commercially available from Air Products and Chemicals Inc.), and ARBADUR 9719-1 (2-ethyl-4-methylimidazole) from Huntsman Advanced Materials Americas Inc.

[0116] As the amide compound, polyamide obtainable by polymerization of a dimer acid and a polyamine can be given; and as examples of the ester compound, reactive carbonyl compounds such as aryl and thioaryl esters of carboxylic acids can be used.

[0117] As other nitrogen-containing compounds, dicyandiamide, guanidine, organic hydrazide, diaminomaleonitrile, amineimide, boron trifluoride-piperidine complex, boron trifluoride-monoethylamine complex, and combinations thereof can be used.

[0118] The ratio of inclusion compound to nitrogen-containing compound should be from about 2.5:1 to about 0.5:1 on a molar basis.

[0119] Commercially available curing components include those available from Nippon Soda under the trade name NISSOCURE.

[0120] The curing component may be present in an amount of about 0.1 wt % to about 20 wt %, such as about 2 wt % to about 12 wt %, based on the total resin composition.

[0121] As illustrated in the examples below, a variety of additives may be included. Of particular note, however, are dispersants, such as those available from BYK Chemie under the DYSPERBYK trade name.

[0122] The following examples are offered for illustrative purposes.

[0123] Example

[0124] Today, reconfigured wafers are typically constructed to have an 8" or 12" diameter. In use, the thermosetting resin composition used to encapsulate the wafer can be dispensed onto or around the central portion of the wafer by air pressure or by piston dispense. In addition to reconfigured wafers, the LCM of the present invention can also be molded on blank wafers and trenched wafers.

[0125] This is followed by exposure to liquid compression molding conditions (eg, at a temperature of about 110° C. to 130° C. for a time period of about 120 to 420 seconds). See e.g. Figure 1 After such exposure, the compression molded wafer can be placed in a conventional oven for a post-mold cure at a temperature of about 120° C. to less than about 150° C., such as at a temperature of about 120° C. to about 130° C., for a period of about 15 minutes to 1 hour. Desirably, an 8" thick 600 μm molded wafer should exhibit warpage of substantially less than about 3 mm bow across the wafer.

[0126] Two control compositions (samples 1 and 2) were prepared: one with a block copolymer (in accordance with U.S. Patent No. 9,263,360) and the other without. Sample 2 had FORTEGRA-100 as the block copolymer. Each control composition was based on a thermosetting resin, a silica filler, a curing agent, an additive, and a colorant. In addition, four compositions (samples 3-6) were prepared according to the present invention. All compositions were evaluated for viscosity stability and applied to a carrier having a silicon chip disposed thereon and molded as described above.

[0127] The viscosity stability was measured by placing the composition in a rheometer (ARES) at room temperature to measure the viscosity profile at the initial time (t=0 hours) and after 24 hours at various shear rates (T=25°C, gap=0.5 mm, plate diameter=25 mm) to compare the viscosity increase.

[0128] The warpage of the molded wafer can be measured by a Nikon NEXIV scanning system, or by using Shadow Moirè measurements in the X and Y directions, or also by estimation with a ruler.

[0129] The warpage of the molded wafers was measured after molding and post-molding processes.

[0130] Referring to Table 1 , shown below are control compositions (Sample Nos. 1 and 2) and four compositions of the present invention (Sample Nos. 3-6) formulated with the stated components in the stated amounts.

[0131] Table 1

[0132]

[0133] 1. Bisphenol A epoxy resin, Resolution Performance Products LLC, Houston, TX

[0134] 2. Bisphenol F epoxy resin, Resolution Performance Products LLC, Houston, TX.

[0135] Used to prepare carbon black premix

[0136] 3. Alicyclic epoxides

[0137] 4. Alicyclic anhydrides

[0138] 5. HP4032D

[0139] 6. DYSBERBYK 145 (1,2-Ethanediamine, polymer with aziridine, N-[3-[(2-ethylhexyl)oxy]-3-oxypropyl] derivative, compds. with polyethylene-polypropylene glycol)

[0140] Each composition was prepared by mixing the ingredients together using a mechanical mixer until dissolution into a homogeneous solution was observed. Silica filler was then added at room temperature with continued mixing for a period of approximately 30-60 minutes, until a viscous paste having a substantially uniform consistency was obtained. The sample was then transferred to a container until ready for use.

[0141] The composition was dispensed onto and around the center of a silicon wafer serving as a carrier. After compression molding at a temperature of about 120°C to less than about 130°C for a period of about 200 seconds to about 400 seconds, the composition was observed to be about 60 to about 80% cured, but the surface was not tacky. The thus-molded wafer was then placed in a conventional oven for post-molding curing at a temperature of about 120°C to about 150°C for a period of about 15 minutes to about 1 hour.

[0142] In its intended use, the composition of the present invention can be dispensed onto the active side of a reconfigured wafer and molded at elevated pressure (about 98 kN) and an elevated temperature of about 110° C. to about 130° C. for a period of about 3 minutes to 7 minutes. The molded wafer assembly can then be exposed to an elevated temperature of about 130° C. to about 150° C. for a period of about 1 hour to about 2 hours. Desirably, an 8" thick 600 μm silicon wafer should exhibit warpage of approximately less than about 3 cm, desirably less than about 2 cm, after curing after molding, using 200 μm of cured material.

[0143] The molded wafer may be debonded, coated with a redistribution layer, have solder bumps applied, and then diced into individual semiconductor packages.

[0144] Referring to Table 2, certain physical properties observed are shown below, including mechanical properties such as modulus, CTE (α1 or 1, and α2 or 2), and Tg; which were measured after first exposing the sample to compression molding conditions at a temperature of about 120°C to less than about 130°C for a period of about 200 seconds to about 400 seconds, and then exposing it to a temperature in an oven of about 120°C to about 150°C for an additional period of about 15 minutes to about 1 hour.

[0145] Table 2

[0146]

[0147] “Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermomechanical Analysis,” ASTM International Designation: E831-06 (“E831-06”), published in April 2006, describes a test method for “determining the apparent linear thermal expansion coefficient of solid materials by using thermomechanical analysis techniques.” See also Paragraph 1.1 of E831-06. Use this common method to measure CTE α 1 or 1.

[0148] “Standard Test Method for Plastics: Dynamic Mechanical Properties: In Flexure (Three-Point Bending),” ASTM International designation: D5023–01, (“D 5023-01”), published in November 2001, discloses a test method “intended to provide a means of determining the temperature-dependent modulus of various plastics.” See alsoEmphasis is placed on paragraph 1.2 of D 5023-01. This common method is used to measure the storage modulus.

[0149] To achieve high Tg and low warpage on flip-chip semiconductor packages, low temperature curing conditions (below about 130°C) have been shown to affect warpage when using compositions that exhibit rapid gelation after exposure to such low temperature curing conditions. The Tg of the cured composition should be equal to or higher than the temperature used to cure the composition; the Tg should be above 90°C, desirably above 125°C. If the composition cures slowly or at higher temperatures, the stress-free point between the mold and substrate assembly is high. Warpage at room temperature is caused by cooling the compression molded semiconductor package from the curing temperature to room temperature.

[0150] In order to obtain high reliability of thermal cycling performance of such compression molded semiconductor packages between -55°C and 125°C, the liquid compression molding material should have a Tg measured by TMA after reflow at 260°C above 90°C and desirably above 125°C, a DSC peak below 140°C, and a delta temperature between the onset and the DSC peak below 20°C.

[0151] As shown in Table 2, one of the control compositions (Sample No. 1) exhibited a high Tg and a low CTE. However, this composition exhibited two problems: (1) viscosity increased by more than 30% after storage at room temperature for 24 hours; and (2) warpage after curing was large, significantly exceeding 3 cm.

[0152] The other control composition (Sample No. 2) showed much improved warpage - about 0.4 cm. However, this composition also showed an increase in viscosity of more than 30% after storage at room temperature for 24 hours.

[0153] The compositions of the present invention exhibited improved viscosity stability and reduced warpage. More specifically, Sample No. 3 exhibited a viscosity increase of less than 30% after storage at room temperature for 24 hours. Furthermore, Sample No. 3 exhibited improved warpage of 2.0 cm.

[0154] Similarly, sample number 4 also exhibited this viscosity behavior and a warp of 0.06 cm, while sample number 5 had the same viscosity and showed zero warp.

[0155] Sample No. 6 showed improved viscosity stability and improved warpage resistance - 2.0 cm after storage at room temperature for 24 hours.

[0156] The compositions of the present invention achieve the following properties:

[0157] a) when cured, the storage modulus at room temperature (25° C.) measured by DMA (three-point bending method, at 5° C. / min) is in the range of 25 GPas or less,

[0158] b) during curing, the CTEα1 measured by TMA (at a heating rate of 5°C / min) is less than or equal to 15 ppm, and the CTEα2 is less than or equal to 30 ppm,

[0159] c) when cured, at least one Tg measured by TMA (three point bending method, at a heating rate of 5°C / min) is higher than 135°C,

[0160] d) As an encapsulating agent, the viscosity change within 24 hours at room temperature (25° C.) as measured by a rheometer (ARES Rheometer from TI) is less than 30%.

Claims

1. A thermosetting resin composition comprising a thermosetting resin matrix, a silica filler, and a curing component comprising a combination of an inclusion compound containing a tetraphenol compound and a nitrogen-containing curing agent, wherein the composition has a viscosity increase of less than about 30% after storage at room temperature for 24 hours relative to the initial viscosity of the composition before storage, and Wherein, when cured on a wafer, the wafer comprising the cured composition exhibits a warpage of less than about 3 cm after oven curing.

2. The composition of claim 1 , wherein upon curing, the cured composition has the following set of physical properties: (a) The storage modulus at room temperature is in the range of 25 GPas or less, (b) The coefficient of thermal expansion (CTE) α1 is less than or equal to 15 ppm, (c) CTEα2 is less than or equal to 30 ppm, and (d) a plurality of glass transition temperatures (Tg) greater than about 135°C as measured by thermomechanical analysis (TMA).

3. The composition of claim 1 , wherein when cured, the cured composition exhibits a plurality of Tgs as measured by TMA greater than about 160° C., and when cured on a wafer, the wafer comprising the cured composition exhibits a warpage of less than about 2 cm as measured by molding a 200 μm thick layer of the composition onto an 8″ silicon wafer having a thickness of 600 μm at a temperature of 130° C. to 150° C. for a period of time of 10 minutes to 1 hour.

4. The composition of claim 1, wherein the wafer is comprised of silicon and the composition is disposed on the wafer at a thickness that is less than about 50% of the thickness of the wafer.

5. A method for improving the warpage resistance of a molded wafer encapsulated by the thermosetting resin composition according to claim 1, wherein the method comprises the steps of: providing wafers; providing the thermosetting resin composition according to claim 1 in contact with the wafer; and The wafer and the thermosetting resin composition are exposed to conditions that facilitate the thermosetting resin composition to flow about the wafer and cure into a reaction product of the thermosetting resin composition, wherein the cured reaction product of the thermosetting resin composition is capable of improving the warpage resistance of a wafer molded with the cured reaction product of the thermosetting resin composition by 50% or more as compared to a wafer molded with a material other than the cured reaction product of the thermosetting resin composition.

6. The method according to claim 5, wherein the warpage resistance of the wafer molded with the cured reaction product of the thermosetting resin composition is improved by 65% ​​or more compared to a wafer molded with a material other than the cured reaction product of the thermosetting resin composition.

7. The method according to claim 5, wherein the warpage resistance of the wafer molded with the cured reaction product of the thermosetting resin composition is improved by 80% or more compared to a wafer molded with a material other than the cured reaction product of the thermosetting resin composition.

8. A product formed by the method of claim 5.

9. The composition of claim 1, wherein the thermosetting resin matrix comprises an epoxy resin component, an episulfide resin component, an oxazine component, an oxazoline component, a cyanate ester component, and / or a component containing maleimide, nadicimide, or itaconimide.

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