JP2022174198A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive structure that is stable even at high temperatures and a semiconductor module including the adhesive structure.

SOLUTION: An adhesive structure 2D includes: a noble metal of a noble metal layer 10; and an adhesive resin 18 bonded by interaction of the noble metal layer 10 with the noble metal. Here, the noble metal of the noble metal layer 10 and the adhesive resin 18 are bonded by σ donation in which electrons are donated from a part of a functional group constituting the adhesive resin 18 toward the noble metal of the noble metal layer 10 and π reverse donation in which electrons are donated from the noble metal of the noble metal layer 10 toward the functional group. The functional group constituting the adhesive resin 18 has both a lone electron pair and an empty antibonding π orbit (π^* orbit), and bonds by the σ donation and the π reverse donation can be formed.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

This embodiment relates to a semiconductor device.

Solders and conductive adhesives are used as bonding techniques for semiconductor devices in electronics in terms of electrical connection, heat resistance, and resistance to mechanical stress. Furthermore, semiconductor devices are generally fixed in a package with a sealing resin.

On the other hand, molecular theoretical research on adhesion at the metal/epoxy resin interface, research on the adhesion mechanism at the metal/epoxy resin interface by density functional theory, and theoretical research on the adhesion mechanism at the interface between epoxy resin and glass have also been disclosed.

JP 2009-182159 A

Shigeru Obinata, "Electronic Components and Mounting Technology Basic Lecture 'Conductive Adhesives' 3rd Basics of Conductive Adhesives (Part 2)", Journal of the Institute of Electronics Packaging Vol.9, No.7, 2006, pp. 581-586 Fumihiro Osako, Kazunari Yoshizawa, “Molecular study on adhesion of metal/epoxy resin interface”, Koubunshi Ronbunshu, Vol. 68, No.2, pp.72-80 (Feb., 2011) Takayuki Semoto, Yuta Tsuji, Kazunari Yoshizawa, “Study on adhesion mechanism of metal/epoxy resin interface by density functional theory”, Society for Molecular Science, 5th Symposium on Molecular Science (September 2011), 1P054 Chisa Higuchi, Hiroyuki Murata, Takayuki Semoto, Hiromasa Tanaka, Kazunari Yoshizawa, “Theoretical Study on Adhesion Mechanism of Epoxy Resin and Glass Interface”, Society for Molecular Science, 10th Symposium on Molecular Science (September 2016), 1P070 Kazunari Yoshizawa, Takayuki Semoto, Seiji Hitaoka, Chisa Higuchi, Yoshihito Shiota, and Hiromasa Tanaka, "Synergy of Electrostatic and van der Waals Interactions in the Adhesion of Epoxy Resin with Carbon-Fiber and Glass Surfaces", BCSJ Selected Paper, Bull. Chem Soc. Jpn, 2017, 90, 500-505, 2017 The Chemical Society of Japan.

Conventionally, it is empirically known that a conductive adhesive has difficulty adhering to gold (Au). As a countermeasure, the adhesion is improved by plasma treatment or the like. Plasma treatment is expected to have effects such as cleaning the surface, improving wettability, increasing surface roughness, and imparting OH groups. Semiconductor device bonding technology requires stricter quality in terms of design and manufacturing.

The inventors of the present invention have discovered, by molecular simulation technology, an adhesive structure that allows strong interaction between noble metals and resins and that is difficult to break even at high temperatures.

This embodiment provides a semiconductor device that is stable even at high temperatures.

According to one aspect of the present embodiment, a semiconductor device having a front surface and a back surface and having electrodes on the front surface, a first lead frame on which the semiconductor device is mounted, and the first lead frame are separated from each other. a second lead frame; a first noble metal layer formed on a surface of a portion of the first lead frame on which the semiconductor device is mounted, in a region wider than the semiconductor device; and the semiconductor device on the first noble metal layer. a bonding wire connecting the electrode of the semiconductor device and the second lead frame; the first lead frame, the first noble metal layer, and the first resin A semiconductor device is provided, comprising: a second resin layer covering a layer, the semiconductor device, the bonding wires, and a portion of the second lead frame.

According to this embodiment, it is possible to provide a semiconductor device that is stable even at high temperatures.

1 is a schematic cross-sectional structural view (die bonding) of a bonding structure according to an embodiment to which the present technology is applied; FIG. (a) A schematic cross-sectional structural view of a semiconductor module including an adhesive structure according to an embodiment to which the present technology is applied, (b) As a comparative example, a schematic diagram of a semiconductor module in a partially peeled and poorly bonded state FIG. 4C is a cross-sectional structural view, and (c) is a schematic cross-sectional structural view of a semiconductor module in a state of poor adhesion in which all parts are peeled off as a comparative example. FIG. 2 is a schematic structural diagram of a conductive resin layer; FIG. 2 is a schematic cross-sectional structural diagram (mold sealing) of an adhesive structure according to an embodiment to which the present technology is applied; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional structural diagram of a semiconductor module including an adhesive structure according to an embodiment to which the present technology is applied; FIG. 2 is a schematic structural diagram of a mold resin layer; (a) Molecular structure example (molecular simulation model) of bisphenol A type epoxy resin using dicyandiamide as a curing agent, applicable to the adhesive structure according to the embodiment, (b) As a comparative example, without the curing agent , an example of the molecular structure of a bisphenol A type epoxy resin. An example of a polymerized structure of a bisphenol A type epoxy resin (n=0, 1, . . . ). An example of the molecular structure of bisphenol A diglycidyl ether (DGEBA) corresponding to the case of n=0 in FIG. FIG. 2 is an example of the molecular structure of dicyandiamide, which is an example of a curing agent that can be applied to the adhesive structure according to the embodiment; FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a method for producing an epoxy resin that can be applied to an adhesive structure according to an embodiment, showing (a) an example molecular structure of DGEBA, (b) an example molecular structure of dicyandiamide ((B) structure), and (c ) An example of the molecular structure of the reaction product (epoxy resin) of DGEBA in FIG. 11(a) and dicyandiamide (structure (B)). FIG. 11 is an explanatory diagram of a method for producing an epoxy resin that can be applied to an adhesive structure according to an embodiment, including (a) a reaction product of DGEBA and dicyandiamide ((B) structure) shown in FIG. 11(c); An example of the molecular structure of the reaction product with DGEBA, (b) an example of the cyclized molecular structure of the reaction product shown in FIG. 12(a) by desorption of ammonia. Schematic explanatory drawing of the state in which the adhesive force between the noble metal surface and the molecular framework of the adhesive is weak. FIG. 4 is a schematic illustration of a state in which the adhesive force between the noble metal surface and the molecular skeleton of the adhesive is strong. (a) A method for forming a clean Au surface structure, which is a schematic illustration of the outermost surface structure of an Au plating layer formed using a process using a cyano complex as a raw material, (b) a clean Au surface structure Schematic explanatory view of the outermost surface structure of the Au plated layer formed by a forming method, which is a process using a non-cyano complex as a raw material, (c) Schematic explanatory view of a clean Au surface structure. (a) Schematic explanatory view of the outermost surface structure of the cyan-based noble metal plating layer, (b) Schematic explanatory drawing of the outermost surface structure of the dinitrodiammine-based noble metal plating layer. (a) Explanatory diagram of π back-donation in a complex, (b) Explanatory diagram of π-back donation in adhesion on a metal surface. Chemical formulas of functional groups applicable to the adhesive structure according to the embodiment, including (a) an example of a cyano group, (b) an example of a thiocyano group, (c) an example of a carbonyl group, and (d) an example of an ester group Examples, (e) examples of amide groups, (f) examples of azide groups, (g) examples of isocyano groups, (h) examples of sulfo groups, (i) examples of nitro groups. Relationship between peeling energy E and peeling distance Δr in the presence or absence of a curing agent. Relationship between adhesive stress F and peeling distance Δr in the presence or absence of a curing agent. Relationship between adhesive stress F and peeling distance Δr with dispersion force, density functional (DFT), and their sum as parameters (model with addition of curing agent). Relationship between adhesive stress F and peeling distance Δr with dispersion force, density functional (DFT), and their sum as parameters (model excluding curing agent). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional structural diagram of a semiconductor module including an adhesive structure according to an embodiment to which the present technology is applied (an example of a semiconductor module mounted on an SOP); (a) A schematic cross-sectional structural view near region A in FIG. 23, (b) A schematic cross-sectional structural view near region B in FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional structural diagram of a semiconductor module including an adhesive structure according to an embodiment to which the present technology is applied (an example of a semiconductor module mounted on a lead frame type MCP);

Next, this embodiment will be described with reference to the drawings. In the description of the drawings described below, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness of each component and the planar dimensions, etc., differs from the actual one. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. In addition, it goes without saying that there are portions with different dimensional relationships and ratios between the drawings.

Moreover, the embodiments shown below are intended to exemplify apparatuses and methods for embodying technical ideas, and do not specify the material, shape, structure, arrangement, etc. of each component. Various modifications can be made to this embodiment within the scope of the claims.

(Die bonding of semiconductor devices)
A schematic cross-sectional structure of a bonding structure 2D according to an embodiment to which the present technology is applied is represented as shown in FIG. Further, a schematic cross-sectional structure of a semiconductor module 4D including a bonding structure 2D according to an embodiment to which the present technology is applied is represented as shown in FIG. 2(a). As a comparative example, a schematic cross-sectional structure of a partially peeled semiconductor module 4A in a poorly bonded state is shown in FIG. 2B. is represented as shown in FIG. 2(c).

In a semiconductor module 4A in which a gold (Au) plating 10A is formed as a noble metal plating on a die pad, and a semiconductor device 14 is arranged on the Au plating 10A via a conductive resin layer 12A made of Ag paste, the Au plating 10A and the conductive If the adhesion with the resin layer 12A is weak, the die bonding is peeled off as shown in FIGS. Moreover, in the LED chip arranged on the package substrate, the Ag paste may be peeled off over the entire surface as shown in FIG. 2(c). In the laminated structure consisting of the semiconductor device 14/conductive resin layer 12A/Au plated 10A, there are many modes of peeling at the interface of the conductive resin layer 12A/Au plated 10A.

Molecular simulations and experiments were carried out to strengthen the adhesive interface between the gold surface and the epoxy resin. As a result, we have found an adhesive structure that is stable even at high temperatures. Details will be described below.

As shown in FIG. 1, an adhesive structure 2D according to an embodiment to which the present technology is applied includes a noble metal of the noble metal layer 10 and an adhesive resin 18 that is adhered by interaction with the noble metal of the noble metal layer 10. Prepare. Here, the noble metal of the noble metal layer 10 and the adhesive resin 18 are divided into σ-donation in which electrons are donated from a part of the functional groups constituting the adhesive resin 18 toward the noble metal, and Adhesion is achieved by π-back-donation, in which electrons are donated toward each other.

The functional group that constitutes the adhesive resin 18 has both a lone pair of electrons and an empty antibonding π orbital (π ^* orbital), and is capable of forming a bond by σ-donation and π-back-donation.

Moreover, the noble metal of the noble metal layer 10 may include at least one kind or a plurality of kinds selected from a group such as Au, Ag, Pt, Pd, Rh, Ru, Ir, and Os.

Also, the adhesive resin 18 may include at least one type or a plurality of types selected from the group of, for example, epoxy-based resin, acrylic-based resin, phenol-based resin, and silicone-based resin.

The functional group constituting the adhesive resin 18 is, for example, at least one or more selected from the group of cyano group, thiocyano group, carbonyl group, ester group, amide group, azide group, isocyano group, sulfo group, and nitro group. It is good to have a kind.

Adhesive resin 18 may also comprise an epoxy resin formed by the reaction of, for example, bisphenol A diglycidyl ether (DGEBA) and dicyandiamide.

Moreover, the noble metal layer 10 may be provided with a noble metal plating layer.

Moreover, the noble metal and the adhesive resin 18 may further contain hydrogen bonds in some bonds between the noble metal and the adhesive resin 18 . This is because, depending on the condition of the surface of the noble metal, a functional group capable of bonding with an OH group may be present on part of the clean surface.

As shown in FIG. 2A, a semiconductor module 4D including a bonding structure 2D according to an embodiment to which the present technology is applied includes a noble metal layer 10 and a conductive resin bonded to the noble metal layer 10 by interaction. It comprises a layer 12 and a semiconductor device 14 disposed on the conductive resin layer 12 . Here, the noble metal layer 10 and the conductive resin layer 12 have a σ-donation mechanism in which electrons are donated from part of the functional groups of the first adhesive resin 18 constituting the conductive resin layer 12 toward the noble metal of the noble metal layer 10 . and π back-donation in which electrons are donated from the noble metal of the noble metal layer 10 to the functional group of the first adhesive resin 18 .

Here, the schematic structure of the conductive resin layer 12 is expressed as shown in FIG.

The conductive resin layer 12 includes a first adhesive resin 18 and metal fillers 16 contained in the first adhesive resin 18, as shown in FIG. The metal filler 16 consists of metal particles. Here, Au, Ag, Pt, Pd, and the like, for example, can be applied as the metal material forming the metal particles.

The noble metal of the noble metal layer 10 may comprise at least one or more selected from the group of Au, Ag, Pt, Pd, Rh, Ru, Ir, and Os, for example.

Also, the first adhesive resin 18 may include at least one type or a plurality of types selected from the group of epoxy resins, acrylic resins, phenolic resins, silicone resins, and the like.

Also, the semiconductor device 14 may comprise, for example, a light emitting diode (LED), a semiconductor laser, a power semiconductor element, an integrated circuit, or a combination thereof.

According to the bonded structure according to the embodiment to which the present technology is applied, it is possible to prevent peeling in die bonding using a conductive resin layer, for example.

According to the adhesive structure according to one embodiment to which the present technology is applied, by performing σ-donation from the functional group derived from the curing agent of the first adhesive resin and simultaneously performing π-back-donation from the metal interface, It is possible to provide an adhesive structure that is stable even at high temperatures, and a semiconductor module that includes this adhesive structure.

(Mold encapsulation of semiconductor devices)
A schematic cross-sectional structure of a bonding structure 2S according to an embodiment to which the present technology is applied is represented as shown in FIG. A schematic cross-sectional structure of a semiconductor module 4S including a bonding structure 2S according to an embodiment to which the present technology is applied is represented as shown in FIG.

As shown in FIG. 4, a bonding structure 2S according to an embodiment to which the present technology is applied includes a precious metal of the precious metal layer 10 and a mold resin layer 20 bonded by interaction with the precious metal of the precious metal layer 10. Prepare. Here, the noble metal of the noble metal layer 10 and the mold resin layer 20 are divided into σ-donation in which electrons are donated from part of the functional groups of the second adhesive resin 19 constituting the mold resin layer 20 toward the noble metal, and Adhesion is achieved by π back-donation in which electrons are donated from the 10 noble metals to the functional groups of the second adhesive resin 19 .

A bonding structure 2S according to an embodiment to which the present technology is applied not only joins the precious metal layer 10 made of a metal frame on which the semiconductor device 14 is mounted and the mold resin layer 20, but also has a metal frame for external connection of the package. The same can be applied to the bonding between the noble metal layer 10 and the mold resin layer 20.

The functional group of the second adhesive resin 19 has both a lone pair of electrons and a vacant anti-bonding π orbital (π ^* orbital), and is capable of forming bonds by σ-donation and π-back-donation.

In addition, the noble metal and the mold resin layer 20 may further include hydrogen bonds in some bonds between the noble metal and the mold resin layer 20 . This is because, depending on the condition of the surface of the noble metal, a functional group capable of bonding with an OH group may be present on part of the clean surface.

Moreover, the noble metal of the noble metal layer 10 may include at least one kind or a plurality of kinds selected from a group such as Au, Ag, Pt, Pd, Rh, Ru, Ir, and Os.

In addition, the mold resin layer 20 may comprise at least one type or a plurality of types selected from the group of epoxy resins, acrylic resins, phenolic resins, silicone resins, and the like.

The functional group constituting the mold resin layer 20 is, for example, at least one or more selected from the group of cyano group, thiocyano group, carbonyl group, ester group, amide group, azide group, isocyano group, sulfo group, and nitro group. It is good to have a kind.

Moreover, the noble metal layer 10 may be provided with a noble metal plating layer.

As shown in FIG. 5, a semiconductor module 4S including a bonding structure 2S according to the second embodiment includes a noble metal layer 10, a conductive resin layer 12 that is bonded to the noble metal layer 10 by interaction, and a conductive resin layer 12. A semiconductor device 14 is arranged on the resin layer 12, and a mold resin layer 20 is further attached to the noble metal layer 10 by interaction.

Here, the noble metal layer 10 and the conductive resin layer 12 have a σ-donation mechanism in which electrons are donated from part of the functional groups of the first adhesive resin 18 constituting the conductive resin layer 12 toward the noble metal of the noble metal layer 10 . and π back-donation in which electrons are donated from the noble metal of the noble metal layer 10 to the functional group of the first adhesive resin 18 .

Further, the noble metal layer 10 and the mold resin layer 20 are separated from each other by σ-donation in which electrons are donated from part of the functional groups of the second adhesive resin 19 constituting the mold resin layer 20 toward the noble metal of the noble metal layer 10, π-back-donation in which electrons are donated from to the functional group.

A schematic structure of the mold resin layer 20 is represented as shown in FIG.

The mold resin layer 20 includes an adhesive resin 19 and fillers 22 contained in the adhesive resin 19, as shown in FIG. The mold resin layer 20 is non-conductive, and the filler 22 is made of ceramic particles. Here, for example, silica, alumina, or the like can be applied as the ceramic material of the ceramic particles. By adding the ceramic filler 22, control of the linear expansion coefficient and reliability are improved.

The noble metal of the noble metal layer 10 may comprise at least one or more selected from the group of Au, Ag, Pt, Pd, Rh, Ru, Ir, and Os, for example.

Also, the first adhesive resin 18 and the second adhesive resin 19 are at least one type or a plurality of types selected from the group of epoxy resins, acrylic resins, phenolic resins, silicone resins, and the like. Also good.

Further, the functional groups constituting the first adhesive resin 18 and the second adhesive resin 19 are, for example, cyano group, thiocyano group, carbonyl group, ester group, amide group, azide group, isocyano group, sulfo group, and nitro group. It may be provided with at least one type or a plurality of types selected from the group such as.

Also, the semiconductor device 14 may include, for example, an LED, a semiconductor laser, a power semiconductor, an integrated circuit, or a combination thereof.

According to the bonded structure according to one embodiment to which the present technology is applied, it is possible not only to prevent peeling in die bonding using a conductive resin layer, but also to achieve a strong bond between the mold resin layer and the metal frame. is also achievable.

According to the adhesive structure according to one embodiment to which the present technology is applied, σ donation is performed from the functional group derived from the curing agent of the first adhesive resin and the second adhesive resin, and at the same time, π back donation is performed from the metal interface. can provide a bonding structure that is stable even at high temperatures, and a semiconductor module that includes this bonding structure.

(molecular simulation model)
An example of the molecular structure (molecular simulation model) of a bisphenol A epoxy resin using dicyandiamide as a curing agent, which is applicable to the adhesive structure according to the present embodiment, is represented as shown in FIG. As an example, an example of the molecular structure of a bisphenol A type epoxy resin, excluding the curing agent, is represented as shown in FIG. 7(b).

(General structure of bisphenol A type epoxy resin)
An example of the polymerized structure (n=0, 1, . . . ) of the bisphenol A type epoxy resin is represented as shown in FIG. An example of the molecular structure of bisphenol A diglycidyl ether (DGEBA) corresponding to n=0 in FIG. 8 is represented as shown in FIG.

For liquid resins such as adhesives, the average value of n is said to be about 0.1 to 0.2. In the following reaction formula, the case of n=0 will be described as an example.

(Example of curing agent: dicyandiamide)
An example of the molecular structure of dicyandiamide, which is an example of a curing agent that can be applied to the adhesive structure according to this embodiment, is represented as shown in FIG. Since dicyandiamide has tautomerism, there are two structures (A) and (B) shown in FIG. Among these, structure (B) has a higher existence probability. Therefore, in the following reaction formulas, structure (B) will be described as an example.

(Curing reaction of bisphenol A type epoxy resin and dicyandiamide)
A method for producing an epoxy resin that can be applied to the adhesive structure according to the embodiment will be described.

FIG. 11A is an explanatory diagram of a method for producing an epoxy resin applicable to an adhesive structure according to an embodiment, and an example of the molecular structure of DGEBA is represented as shown in FIG. 11(a). An example of the molecular structure of dicyandiamide (structure (B)) is represented as shown in FIG. 11(b). An example of the molecular structure of the reaction product (epoxy resin) of DGEBA and dicyandiamide ((B) structure) is represented as shown in FIG. 11(c).

As the reaction progresses further, the reaction product of DGEBA and dicyandiamide (structure (B)) shown in FIG. is represented by As the reaction further progresses and ammonia is eliminated, an example of the cyclized molecular structure of the reaction product shown in FIG. 12(a) is represented as shown in FIG. 12(b). The curing reaction proceeds as the terminal epoxy group reacts further.

(Weak adhesive strength)
FIG. 13 is a schematic illustration of a state in which the adhesive strength due to hydrogen bonding between the noble metal surface and the molecular skeleton of the adhesive is weak. As the precious metal layer, the Au plating layer 30 and the adhesive resin made of epoxy resin having the molecular skeleton 24 will be described as an example.

The outermost surface of the noble metal plating is likely to be terminated with ligands that constitute the raw material complex. For example, in the case of Au plating, when gold (I) potassium cyanide (K[Au(CN) ₂ ]) is applied as a raw material, the surface structure of the Au plating layer 30 is terminated with CN-based functional groups 26. was found by analysis.

(Analysis results of the outermost surface of Au by XPS)
The outermost surface of the gold land portion of the package substrate was analyzed using X-ray Photoelectron Spectroscopy (XPS). As a result, about 50% Au, about 33.8% C, about 5.4% O, and about 1.0% Cu were detected on the outermost surface.

(Analysis results of the outermost surface of Au by TOF-SIMS)
A large amount of carbon (C) is detected on the outermost surface of the gold land portion of the package substrate. Au top surface analysis of the gold land portion was performed by mass spectrometry). As a result, AuC ₂ N ₂ , CuAu ₂ , NiAu ₂ , C ₃ N, C ₆ , Au ₄ and the like were detected. That is, according to the results of analysis of the outermost surface of Au by TOF-SIMS, AuCN-based/CN-based/C-based/Au metal/... are detected from the outermost surface. , about 8 Å (about 8 atomic layers). Therefore, it was identified that the outermost surface of Au formed by Au plating of the gold land portion was terminated with an AuCN system.

In other words, the outermost surface of the Au plating layer 30 is likely to be terminated with ligands that form the raw material complex. In this case, the adhesion is based on hydrogen bonding, and sufficient adhesion strength cannot be obtained. If hydrogen bonding (OH) is likely to occur, peeling is likely to occur at a high temperature of, for example, about 100° C. or higher.

The surface structure of the Au plating layer 30 is terminated with CN-based functional groups 26, as shown in FIG. As a result, the molecular skeleton 24 is bonded by hydrogen bonding (OH) by the OH group 28 to the CN bond on the Au surface terminated with the CN-based functional group 26 . The state of weak adhesion is a state of weak adhesion due to hydrogen bonding (OH) of the OH groups 28 . Here, the value of binding energy is, for example, about 5 kJ/mol to 40 kJ/mol. When the adhesive force is weak, the bonding energy is low, so the bond is likely to break under high temperature.

(In a state where the adhesive strength is strong)
A bonding structure capable of strongly interacting with Au was found by molecular simulation technology. About 1.5 times the adhesive strength is obtained as compared with the case where no interaction with Au occurs.

FIG. 14 is a schematic illustration of a state in which the adhesive strength is strong based on interactions that are more stable than hydrogen bonds by OH groups 28 due to σ-donation and π-back-donation simultaneously between the noble metal surface and the molecular skeleton 24 of the adhesive. is represented as shown in Hydrogen bonding by the OH groups 28 is difficult for a clean Au surface that is close to an ideal state, and functional groups other than the OH groups 28 can be bonded. As functional groups other than the OH group 28, for example, as shown in FIG. 14, a CN-based functional group 34, a CO-based functional group 32, or the like can be applied.

Molecular simulations revealed that these bonds are based on σ-donation and π-back-donation. A functional group with both a lone pair and an empty antibonding pi-orbital (π ^* -orbital) can simultaneously form σ-donating and π-backdonating bonds.

Here, the value of binding energy in a state of strong adhesion is, for example, about 100 kJ/mol or more. A lone electron pair is σ-donated from a part of the functional groups constituting the resin to the noble metal surface, and at the same time, an electron is donated from the noble metal surface to the functional group by π back-donation, It is possible to form adhesive structures based on interactions that are more stable than hydrogen bonding.

(Method for forming a clean Au surface structure)
FIG. 15(a) is a schematic illustration of the outermost surface structure of the Au plating layer 30 formed using a process using a cyano complex as a raw material, which is a method for forming a clean Au surface structure. be done.

As for the outermost surface structure of the Au plated layer 30, as shown in FIG. 15(a), the Au surface is terminated with a CN system. In the case of a process using a cyano complex as a raw material, for example, potassium dicyanoaurate (I) K[Au(CN) ₂ ] or potassium tetracyanoaurate(III) K[Au(CN) ₄ ] can be applied.

Next, by a physical sputtering technique using argon (Ar) plasma and a chemical interaction using hydrogen plasma, the CN-based functional group on the Au surface changes to CN → C _x H _y system + NH ₃ system. Since it can be decomposed, a clean Au surface structure can be formed as shown in FIG. 15(c).

A schematic explanatory view of the outermost surface structure of the Au plating layer 30 formed using a process using a non-cyano complex as a raw material, which is a method for forming a clean Au surface structure, is shown in FIG. 15(b). expressed.

As for the outermost surface structure of the Au plating layer 30, as shown in FIG. 15(b), the Au surface is terminated with SO ₃ -based functional groups. In the case of a process using a non-cyano complex as a raw material, for example, disulfite gold (I) sodium Na ₃ [Au(SO ₃ ) ₂ ] or the like can be applied.

Physical sputtering techniques using argon (Ar) plasma and chemical interaction using hydrogen plasma can then form a clean Au surface structure as shown in 15(c).

(Comparison of adhesive strength when various treatments are performed)
Bonded structures with oxygen (O ₂ ) plasma treatment exhibited approximately 30% less adhesion than those without. On the other hand, in the bonded structure subjected to the argon (Ar) plasma treatment, the adhesive strength increased by about 10% or more compared to the structure without the treatment. Oxygen (O ₂ ) plasma treatment oxidizes the CN functional groups on the Au surface into carboxylic acids and ketones, so that adhesion by hydrogen bonding becomes dominant and the adhesive strength is reduced. On the other hand, argon (Ar) plasma treatment can remove the CN functional groups on the Au surface, thus increasing the adhesive force.

(Adhesive force measurement at high temperature)
A high-temperature tensile test was performed on the Ag paste layer as the conductive resin layer, and the adhesive strength was evaluated by changing the temperature. As a result, the adhesive strength decreased by about 15% at 120°C and by about 48% at 180°C compared to room temperature. The relationship between the adhesive strength and the amount of displacement was almost the same at room temperature, 120° C. and 180° C., and the softened behavior of the cured resin was not observed.

From the above results, it was confirmed that the adhesive strength decreased at high temperatures, and it was presumed that the decrease in adhesive strength was likely due to the breakage of hydrogen bonds at the adhesive interface.

(Types of precious metal plating)
A schematic explanatory view of the outermost surface structure of the cyan-based noble metal plated layer is represented as shown in FIG. 16(a). Au or Ag, for example, can be applied to the noble metal atoms 50 forming the cyan-based noble metal plating layer 40 . In the case of Au plating, gold (I) potassium cyanide K[Au(CN) ₂ ] can be used as a raw material. In the case of Ag plating, silver (I) potassium cyanide K[Ag(CN) ₂ ] can be used as a raw material.

A schematic illustration of the outermost surface structure of the dinitrodiammine-based noble metal plated layer is represented as shown in FIG. 16(b). For the noble metal atoms 70 forming the dinitrodiammine-based noble metal plating layer 60, Pt or Pd, for example, can be applied. In the case of Pt plating, dinitrodiammineplatinum (II) cis-[Pt(NO ₂ ) ₂ (NH ₃ ) ₂ ] can be used as a raw material. In the case of Pd plating, dinitrodiammineplatinum (II) cis-[Pd(NO ₂ ) ₂ (NH ₃ ) ₂ ] can be used as a raw material.

Noble metals applicable to the bonding structure according to the present embodiment and the semiconductor module including this bonding structure are selected from the group of Au, Ag, Pt, Pd, Rh, Ru, Ir, Os, and the like, for example. At least one kind or a plurality of kinds can be mentioned.

(π back donation)
An explanatory diagram of σ-donation and π-back-donation in the complex is represented as shown in FIG. is represented by In FIG. 17(b), the filling band of the metal M _is represented by E _V , the conduction band by E _c , and the Fermi level of the metal M by _{E f} . there is

As shown in FIGS. 17(a) and 17(b), electrons are normally transferred from a ligand (LIGAND) of a specific functional group contained in a polymer chain such as a CO system or a CN system toward the metal M. Donated σ donation works. On the other hand, further donation of electrons from the metal M to the ligand is π back donation.

For example, an epoxy-based adhesive having an Au plating layer and a CN-based functional group has σ-donation in which electrons are donated from part of the CN-based functional group to Au, and electrons are transferred from Au to the CN-based functional group electrons are donated through π-back-donation. Here, π back-donation works between the Au5d orbital and the π ^* orbital of the CN system.

The results obtained using the molecular simulation technique are C—N distances=1.30 Å and 1.19 Å for σ donation at the HOMO level. On the other hand, CN=1.31 Å and 1.18 Å for π back donation at the LUMO level.

(Example of corresponding functional group)
Applicable functional groups are listed below. That is, chemical formulas of functional groups applicable to the adhesive structure according to the present embodiment, in which an example of a cyano group is shown in FIG. 18(a) and an example of a thiocyano group is shown in FIG. , examples of carbonyl groups are shown in FIG. 18(c), examples of ester groups are shown in FIG. 18(d), and examples of amide groups are shown in FIG. 18(e ), examples of azide groups are shown in FIG. 18(f), examples of isocyano groups are shown in FIG. 18(g), and examples of sulfo groups are shown in FIG. h) and examples of nitro groups are represented as shown in FIG. 18(i). Among these, cyano group, carbonyl group, ester group, amide group and the like are preferable from the viewpoint of stability.

(molecular simulation technology)
A theoretically stable molecular structure of a molecular model of a bisphenol A type epoxy resin + dicyandiamide system was calculated using a molecular simulation technique. As a result, it was found that it was not the OH group but the CN-based functional group derived from the curing agent that interacted with the Au surface. The molecular simulation will be described in detail below.

(Explanation on molecular simulation_1)
(Implementation procedure)
(1) Create a model structure of Au(111).

In the bulk structure optimization of Au, the program is VASP (density functional theory), the functional is GGA-PBE, the cutoff energy is 500 eV, the k-point mesh is 2π×0.05 Å ⁻¹ , the pseudopotential is PAW, and the dispersion Tkatchenko-Scheffler was used for force correction.

As a result, the (111) plane is cut out from the optimized structure.

(2) Next, a surface structure of Au is created.

A 5×5 slab model is created by extending the cut (111) plane. Here, the number of atoms: 5×5×3 (75 atoms). The bottom two layers were fixed and a 30 Å thick vacuum layer was formed on the Au.

(Explanation on molecular simulation_2)
(3) Create a model structure of epoxy resin.

-Selection of materials-
The epoxy resin was DGEBA+curing agent (dicyandiamide). A molecular model of the target epoxy resin corresponds to the structure of the chemical formula in FIG.

Next, molecular modeling was performed. For molecular modeling, the epoxy group of DGEBA and the amino group of dicyandiamide were subjected to an addition reaction, and for simplification, the glycidyl group on the unreacted side of DGEBA was substituted with a methyl group. As a result, the molecular structure shown in FIG. 7(a) is obtained. As a comparative example, a molecular model of a bisphenol A type epoxy resin without a curing agent corresponds to the structure of the chemical formula shown in FIG. 7(b).

Next, the placement of the molecular model was performed.

The molecular model prepared in the selection of the material system in (3) above was arranged in the vacuum layer of the Au slab model prepared in (2) above.

(Explanation on molecular simulation_3)
(Implementation procedure)
(4) Calculation of the most stable structure Search for the most stable structure by molecular dynamics calculation.

The program is Forcite, the time step is 1fs, the force field is COMPASS, the simulation time is 5ps, the temperature is 350K, the quench step is 250, the ensemble is NVE, and the minimize is smart.

Next, a structural optimization of the adhesion model is performed by the density functional theory. The initial structural model is the most stable structure found above, the program is VASP, the functional is GGA-PBE, the cutoff energy is 500 eV, the k-point mesh is 2π×0.05 Å ^-1 , the pseudopotential is PAW, Tkatchenko-Scheffler was used for dispersion force correction.

A difference electron density calculation was then performed. As a result, they found that no electron exchange occurred in the hydroxy group (OH), and that σ-donation and π-back-donation occurred in the cyano group.

(Explanation on molecular simulation_4)
(Implementation procedure)
(5) Calculate the adhesive stress.

In the adhesion model optimized by the calculation of the most stable structure in (4) above, the energy E when peeling off the epoxy molecule is calculated by the NEB (Nudged Elastic Band) method. The NEB method is a method for obtaining the minimum energy path (MEP) of the potential energy surface between two locally stable structures.

(Method for calculating adhesive stress)
The peeling energy E at the time of peeling off the epoxy molecule is approximated by Morse potential and represented by the formula (1).

E=D _e [1−exp(−aΔr)] ² (1)

However, a=ω _e (M/2D _e ) ^1/2 and Δr=r _e −r. D _e represents the dissociation energy, and Δr represents the peeling distance. r represents the bond distance of a diatomic molecule. Also, r _e is the equilibrium bond spacing, M is the reduced mass, and ω _e is the wave number of vibration.

Adhesion stress F can be estimated by differentiating the Morse potential approximation curve. The adhesive stress F is represented by the formula (2).

F=dE/dΔr (2)

(Explanation on molecular simulation_5)
(Implementation procedure)
(6) Calculation was performed using a molecular model for comparison.

To clarify the extent to which the functional groups of the curing agent contributed to the adhesion force, a similar calculation was performed with a model in which the curing agent portion was terminated with H. A molecular model for comparison corresponds to the structure of the chemical formula in FIG. 7(b).

(Effect of OH group)
In the molecular simulation of the adhesive structure between the Au surface and the epoxy resin, the effect of the OH group was examined. As a result, in the model where the OH group is far from the Au surface, the distance between Au-N = 2.527 Å, the distance between Au-OH = 5.689 Å, and the binding energy = -583.50 eV . On the other hand, in the model in which the OH group is close to the Au surface, the distance between Au-N = 3.313 Å, the distance between Au-OH = 3.119 Å, and the binding energy = -583.42 eV. The bond energy difference ΔE between the model in which the OH group is far from the Au surface and the model in which the OH group is close to the Au surface was ΔE=1.8 kcal.

In addition, electron transfer (π back-donation) was observed in the cyano group in both the model in which the OH group is close to the Au surface and the model in which the OH group is far from the Au surface, from the calculation results of the difference electron density.

(Effect of CN group of curing agent)
-Evaluation of adhesive stress-
The relationship between the peeling energy E and the peeling distance Δr in the presence or absence of the curing agent (comparison of potential energies) is expressed as shown in FIG.

From the change in potential energy, the curve with the curing agent tends to have a higher peeling energy E than the curve without the curing agent.

The relationship between the adhesive stress F and the peeling distance Δr in the presence or absence of the curing agent (comparison of displacement-stress curves) is expressed as shown in FIG.

The maximum adhesive stress F of the model with the addition of the curing agent is about 1150 (MPa). On the other hand, the maximum adhesive stress F of the model without the curing agent is about 800 (MPa).

In the molecular model of the gold surface and the bisphenol A type epoxy resin + dicyandiamide system, when the peeling distance Δr (Å) is 2 Å, 3 Å, and 4 Å, it can be stably peeled off at 4 Å. can.

(DFT and dispersion force)
FIG. 21 shows the relationship obtained by dividing the contribution of the adhesive force into the component F _disp due to the dispersion force and the other components (component F _DFT that can be calculated using a density functional (DFT)). Also, the relationship (model excluding the curing agent) in which the contribution of the adhesive force is divided into the component F _disp due to the dispersion force and the other (component F _DFT that can be calculated by DFT) is expressed as shown in FIG.

The total adhesion stress F _tot is represented by the formula (3).

F _tot =F _DFT +F _disp (3)

From the results of FIGS. 21 and 22, it can be seen that the influence of the adhesive stress F on the adhesive stress F is largely due to the adhesive stress F _disp of the dispersion force.

In summary, the adhesive stress between Au and the epoxy resin is greatly contributed by the dispersion force. In the model of epoxy resin containing a curing agent, π-back-donation at the cyano group contained in the curing agent contributes to adhesion.

(Semiconductor module mounted on SOP)
In the following description, description overlapping with the bonding structure and the semiconductor module including the bonding structure according to the embodiment to which the present technology is applied is omitted because it can be similarly applied.

A schematic cross-sectional structure of a semiconductor module 6 including a bonding structure according to an embodiment to which the present technology is applied is represented as shown in FIG. 23 . FIG. 23 shows an example of a semiconductor module mounted in a small outline package (SOP). A schematic cross-sectional structure near region A in FIG. 23 is represented as shown in FIG. 24(a), and a schematic cross-sectional structure near region B in FIG. 23 is represented as shown in FIG. 24(b). .

As shown in FIG. 23, the semiconductor module 6 mounted on the SOP includes a lead frame 66, a noble metal layer 10D formed on the lead frame 66, and a conductive resin layer 12 bonded to the noble metal layer 10D by interaction. , and a semiconductor device 14 disposed on the conductive resin layer 12 . Noble metal layer 10D and conductive resin layer 12, as shown in FIG. and π back-donation, in which electrons are donated from the noble metal of the noble metal layer 10D to the functional group of the first adhesive resin.

Further, the semiconductor module 6 mounted on the SOP, as shown in FIG. 23, has a mold resin layer 20 that adheres to the precious metal layer 10D through interaction. Noble metal layer 10D and mold resin layer 20 are separated by σ-donation in which electrons are donated from part of the functional groups of the second adhesive resin constituting mold resin layer 20 toward the noble metal of noble metal layer 10D, and Adhesion is achieved by π-back-donation in which electrons are donated from the noble metal to the functional groups of the second adhesive resin.

Furthermore, as shown in FIG. 23, the semiconductor module 6 mounted on the SOP comprises a lead frame 64 and a noble metal layer 10L formed on the lead frame 64 by a plating technique. In the noble metal layer 10L and the mold resin layer 20, as shown in FIG. 24(a), electrons are donated from part of the functional groups of the second adhesive resin forming the mold resin layer 20 toward the noble metal of the noble metal layer 10L. and π back donation in which electrons are donated from the noble metal of the noble metal layer 10L to the functional group of the second adhesive resin.

The entire semiconductor module 6 mounted on the SOP is resin-sealed with a mold resin layer 20, as shown in FIG. A bonding wire 62 is connected between the noble metal layer 10L and the semiconductor device 14 .

(Semiconductor module mounted on lead frame type MCP)
A schematic cross-sectional structure of a semiconductor module 6M including a bonding structure according to an embodiment to which the present technology is applied is represented as shown in FIG. FIG. 25 shows an example of a semiconductor module mounted on a lead frame type multi chip package (MCP: Multi Chip Package). A schematic cross-sectional structure in the vicinity of region A in FIG. 25 is represented in the same manner as in FIG. 24A, and a schematic cross-sectional structure in the vicinity of region B in FIG. 25 is represented in the same manner as in FIG.

As shown in FIG. 25, a semiconductor module 6M mounted on a lead frame type MCP includes a lead frame 64L, a noble metal layer 10D formed on the lead frame 64L, and a conductive resin bonded to the noble metal layer 10D by interaction. A layer 12D, a semiconductor device 14B arranged on the conductive resin layer 12D, a conductive resin layer 12U arranged on the semiconductor device 14B, and a semiconductor device 14A arranged on the conductive resin layer 12U. . In the noble metal layer 10D and the conductive resin layer 12D, as in FIG. 24B, electrons are transferred from a part of the functional groups of the first adhesive resin forming the conductive resin layer 12D toward the noble metal of the noble metal layer 10D. Bonding is achieved by σ-donation and π-back-donation in which electrons are donated from the noble metal of the noble metal layer 10D to the functional group of the first adhesive resin.

Furthermore, as shown in FIG. 25, the semiconductor module 6M mounted on the lead frame type MCP includes a mold resin layer 20 that adheres to the noble metal layer 10D through interaction. Noble metal layer 10D and mold resin layer 20 are separated by σ-donation in which electrons are donated from part of the functional groups of the second adhesive resin constituting mold resin layer 20 toward the noble metal of noble metal layer 10D, and Adhesion is achieved by π-back-donation in which electrons are donated from the noble metal to the functional groups of the second adhesive resin.

Further, the semiconductor module 6M mounted on the lead frame type MCP includes a lead frame 64 and a noble metal layer 10L formed on the lead frame 64 by plating technology, as shown in FIG. In the noble metal layer 10L and the mold resin layer 20, as shown in FIG. 24(a), electrons are donated from part of the functional groups of the second adhesive resin forming the mold resin layer 20 toward the noble metal of the noble metal layer 10L. and π back donation in which electrons are donated from the noble metal of the noble metal layer 10L to the functional group of the second adhesive resin.

The entire semiconductor module 6M mounted on the lead frame type MCP is resin-sealed with a mold resin layer 20, as shown in FIG. A bonding wire 62 is connected between the noble metal layer 10L and the semiconductor devices 14A and 14B.

The adhesive structure according to the present embodiment and the semiconductor device that can be mounted on the semiconductor module having this adhesive structure include, for example, LEDs, semiconductor lasers, power semiconductors, integrated circuits, or a combination thereof. can be

As integrated circuits, for example, for in-vehicle electronics, body control module (BCM: Body Control Module), advanced driver assistance system (ADAS: Advanced Driver Assistance System), main inverter (Main inverter), LED lamp module (LED Lamp Module ), an engine control unit (ECU), an integrated circuit for vehicle-mounted electronics such as a car audio system.

Further, the bonding structure according to the present embodiment and the semiconductor device that can be mounted on the semiconductor module having this bonding structure include any of Si-based or SiC-based IGBTs, diodes, MOSFETs, and GaN-based FETs. can be

Further, the adhesive structure according to the present embodiment and the semiconductor device that can be mounted on the semiconductor module provided with this adhesive structure include a one-in-one module, a two-in-one module, a four-in-one module, a six-in-one module, a seven-in-one module, and an eight-in-one module. It may have either a module, twelve-in-one module, or four-in-one module configuration.

According to this embodiment, it is possible to provide a bonding structure having a stable interface structure even at high temperatures, and a semiconductor module having this bonding structure. Bonded structures in which σ-donation and π-back-donation occur at the same time have more electrons shared, which can improve adhesion, especially at high temperatures.

[Other embodiments]
As noted above, although several embodiments have been described, the discussion and drawings forming part of the disclosure are to be understood as illustrative and not limiting. Various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art from this disclosure.

Thus, this embodiment includes various embodiments and the like that are not described here.

The bonded structure and semiconductor module of the present embodiment can be applied to various semiconductor modules such as LED modules, optical modules, IGBT modules, diode modules, and MOS modules (Si, SiC, GaN), integrated circuit technology, various package technologies, and the like. and can be applied to a wide range of application fields.

2D, 2S... bonding structure, 4D, 4S, 6, 6M... semiconductor module, 10, 10D, 10L... noble metal layer, 10A... gold (Au) plating, 12, 12D, 12U... conductive resin layer, 14, 14A , 14B... Semiconductor device, 16... Metal filler, 18, 19... Adhesive resin, 20... Mold resin layer, 22... Filler, 24... Molecular skeleton, 26, 34... CN-based functional group, 28... OH group, 30 ... Au plating layer, 32 ... CO-based functional group, 40 ... cyan noble metal plating layer, 50, 70 ... noble metal atom, 60 ... dinitrodiammine-based noble metal plating layer, 62 ... bonding wire, 64, 64L, 66 ... lead frame

Claims (17)

a semiconductor device having a front surface and a back surface, and having an electrode on the front surface;
a first lead frame on which the semiconductor device is mounted and a second lead frame separated from the first lead frame;
a first noble metal layer formed on a surface of a portion of the first lead frame on which the semiconductor device is mounted, in a region wider than the semiconductor device;
a first resin layer disposed on a portion of the first noble metal layer facing the semiconductor device;
a bonding wire connecting the electrode of the semiconductor device and the second lead frame;
A semiconductor device comprising: a second resin layer covering the first lead frame, the first noble metal layer, the first resin layer, the semiconductor device, the bonding wires, and a portion of the second lead frame. 2. The semiconductor device according to claim 1, wherein said first resin layer is a conductive resin layer, and said second resin layer is a non-conductive resin layer. 2. The semiconductor device according to claim 1, wherein said first noble metal layer comprises a plated layer and has a clean noble metal surface. 2. The semiconductor device according to claim 1, wherein said first noble metal layer includes Au or Ag plating, or Pt or Pd plating. 2. The semiconductor device according to claim 1, wherein said first noble metal layer contains at least one or more selected from the group of Au, Ag, Pt, Pd, Rh, Ru, Ir and Os. 3. The semiconductor device according to claim 2, wherein said first resin layer contains Ag paste or metal filler. 2. The semiconductor device according to claim 1, wherein said first resin layer and said second resin layer contain at least one type or a plurality of types selected from the group consisting of epoxy-based resin, acrylic-based resin, phenol-based resin, and silicone-based resin. . 2. The semiconductor device according to claim 1, wherein said semiconductor device comprises any one or a combination of LEDs, semiconductor lasers, power semiconductors, and integrated circuits that become hot during operation. 2. The semiconductor device according to claim 1, wherein said first noble metal layer is bonded to a CN-based functional group and/or a CO-based functional group of said first resin layer. 10. The semiconductor device according to claim 9, wherein said CN-based functional group is derived from a curing agent. The first noble metal layer and the first resin layer are composed of σ-donation in which electrons are donated toward the first noble metal layer from part of the functional groups constituting the first resin layer, and 2. The semiconductor device according to claim 1, wherein bonding is achieved by π-back-donation in which electrons are donated toward said functional group of said first resin layer. The first noble metal layer and the second resin layer are composed of σ donation in which electrons are donated from part of the functional groups constituting the first resin layer toward the first noble metal layer, and 2. The semiconductor device according to claim 1, wherein adhesion is achieved by π-back-donation in which electrons are donated toward said functional group of said second resin layer. further comprising a second noble metal layer formed on the surface of the portion of the second lead frame that is connected to the bonding wire;
The second noble metal layer and the second resin layer are composed of σ donation in which electrons are donated from part of the functional groups constituting the second resin layer toward the second noble metal layer, and 2. The semiconductor device according to claim 1, wherein adhesion is achieved by π-back-donation in which electrons are donated toward said functional group of said second resin layer. a conductive third resin layer disposed above the semiconductor device;
2. The semiconductor device according to claim 1, further comprising a second semiconductor device arranged on said third resin layer. 14. Any one of claims 11 to 13, wherein the functional group has both a lone pair of electrons and an empty anti-bonding π orbital (π* orbital), and is capable of forming a bond through the σ-donation and the π-back-donation. 1. The semiconductor device according to claim 1. The functional group includes at least one or more selected from the group consisting of a cyano group, a thiocyano group, a carbonyl group, an ester group, an amide group, an azide group, an isocyano group, a sulfo group, and a nitro group, claims 11- 14. The semiconductor device according to any one of 13. 2. The semiconductor device according to claim 1, wherein said semiconductor device comprises a power semiconductor element of one of a Si-based or SiC-based IGBT, a diode, a MOSFET, and a GaN-based FET, which reaches a high temperature during operation.

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