Core-shell particle die attach material

Abstract

A die attach material is provided. In one example, the die attach material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material. The shell may include an alloy. The alloy may include a first element and a second element. The second element may segregate within one or more grain boundaries in the die attach material during bonding of the die attach material.

Description

Detailed Description of the Invention

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application is based on and claims the benefit of priority to U.S. Patent Application No. 18 / 074,079, filed December 2, 2022. This application claims priority to and the benefit of the entire contents of this cited application, which is incorporated by reference in its entirety.

[0002] [Technical field] FIELD OF THE DISCLOSURE The present disclosure relates generally to die attach materials. [Background technology] Semiconductor devices, including power semiconductor devices based on wide bandgap materials, can be formed on a semiconductor wafer as part of a semiconductor manufacturing process. The semiconductor wafer can be diced into multiple pieces, with each piece containing one or more semiconductor devices. Each of these pieces can be a semiconductor die. The semiconductor die may need to be bonded to other components as part of packaging the semiconductor device. For example, a semiconductor die, such as a wide bandgap semiconductor die, may need to be bonded to a conductive lead frame for use in a power discrete package or power module. The material used to bond the semiconductor die to other components may need to thermally, mechanically, and / or electrically connect the semiconductor die to the other components.

[0003] [Summary of the Invention] Aspects and advantages of each embodiment of the disclosure will be set forth in part in the description that follows, and in part may be learned from the description, or may be learned through practice of the embodiments.

[0004] An exemplary embodiment of the present disclosure is directed to a die attach material. The die attach material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material. The shell may include an alloy. The alloy may include a first element and a second element. The second element may segregate within one or more grain boundaries in the die attach material during bonding of the die attach material.

[0005] Another exemplary aspect of the present disclosure is directed to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material. The shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

[0006] Another exemplary aspect of the present disclosure is directed to a device. The device may include a die including a wide bandgap semiconductor material. The device may include a substrate. The device may include a die attach material between the die and the substrate. The die attach material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material, and the shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

[0007] Another exemplary aspect of the present disclosure is directed to a device. The device may include a substrate. The device may include a sintered material on the substrate. The sintered material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material, and the shell may include an alloy. The alloy may include complementary elements segregated within one or more grain boundaries of the sintered material.

[0008] Another exemplary aspect of the present disclosure is directed to a method. The method may include depositing a die attach material onto a substrate. The die attach material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell over the core. The core may include a conductive material and the shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo). The method may include bonding the die attach material.

[0009] Another exemplary embodiment of the present disclosure is directed to a method. The method may include adding a second solution to a first solution. The first solution may include core particles. The second solution may include a shell precursor and a complementary element precursor for forming a shell on the core particles. The shell may include an alloy. The alloy may include tungsten (W), cobalt (Co), or molybdenum (Mo).

[0010] These and other features, aspects, and advantages of various embodiments will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, explain associated principles.

[0011] Detailed descriptions of embodiments directed to those skilled in the art are provided herein and refer to the accompanying drawings, in which: [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 illustrates an example device having a semiconductor die attached to a substrate using a die attach material, according to an exemplary embodiment of the present disclosure. [Figure 2] FIG. 2 illustrates a core-shell particle of a die attach material according to an exemplary embodiment of the present disclosure. [Figure 3] FIG. 3 illustrates an example semiconductor device according to an exemplary embodiment of the present disclosure. [Figure 4]FIG. 4 illustrates an example device using die attach material to form an antenna, according to an exemplary embodiment of the present disclosure. [Figure 5] FIG. 5 illustrates an example device using die attach material to form interconnects, according to an exemplary embodiment of the present disclosure. [Figure 6] FIG. 6 illustrates a flowchart of an example method according to an exemplary embodiment of the present disclosure. [Figure 7] FIG. 7 illustrates a flowchart of an example method according to an exemplary embodiment of the present disclosure. [Figure 8] FIG. 8 illustrates a flowchart of an example method according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Detailed Description of the Invention] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the various drawings. Each example is provided by way of explanation of an embodiment, not to limit the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments without departing from the spirit and scope of the disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield a still further embodiment. Accordingly, it is intended that aspects of the disclosure cover such modifications and variations.

[0014] Exemplary aspects of the present disclosure are directed to die attach materials for use in semiconductor and other electronic applications, such as wide bandgap semiconductor device applications. Various die attach technologies implemented in the semiconductor industry have challenges and limitations. For example, silver semi-sintered or fully sintered process technologies can provide acceptable electrical, mechanical, and thermal properties for die attach applications. However, silver semi-sintered or fully sintered process technologies can be costly and have a high risk of electromigration, high voids / porosity, and high thermomechanical stress. Eutectic Au80Sn20 technology can also have similar limitations. Semi-sintered or fully sintered copper is a lower-cost, somewhat lower-performance option, but it can suffer from the challenges of requiring low temperatures and forming gas for the attachment process as well as storage. Lead (Pb)-based die attach solutions are not the best choice for achieving low thermal resistance and efficient current and power densities. Furthermore, lead (Pb)-based die attach materials do not meet the standards for lead-free certification.

[0015] Exemplary aspects of the present disclosure are directed to core-shell particle-based die attach materials, which may include paste-based or ink-based materials that include a plurality of metal core-shell microparticles and / or metal core-shell nanoparticles dispersed in a solution or grafted to a polymer matrix to form a metal-filled composite.

[0016] The core-shell particle structure may include a core made of a conductive material (e.g., an electrically conductive material), such as copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni). The core-shell particle may include a shell on the core. The shell may include an alloy. The alloy may include a first element and a second element. In exemplary embodiments, the first element of the alloy may be a conductive element such as silver (Ag), gold (Au), or palladium (Pd). The second element (also referred to as a complementary element) may segregate within the grain boundaries of the die attach material during bonding. In some embodiments, the second element may be tungsten (W), cobalt (Co), or molybdenum (Mo). For example, the alloy may be a silver-cobalt alloy (AgCo), a silver-tungsten alloy (AgW), and / or a silver-molybdenum alloy (AgMo).

[0017] The shell may reduce or prevent oxidation of the core. The shell may strengthen interparticle contact after bonding and reduce voids in the die attach material. In some examples, after bonding of the die attach material, the die attach material may form an intermetallic compound to inhibit the passage of electromigrating metals through the die attach material.

[0018] For purposes of illustration and explanation, aspects of the present disclosure are described with reference to die attach materials that attach a semiconductor die (e.g., a silicon carbide-based semiconductor die, a III-nitride-based semiconductor die, a silicon-based semiconductor die, etc.) to a substrate or other component. Those skilled in the art, using the disclosure provided herein, will understand that the materials provided herein may be used to attach any suitable component without departing from the scope of the present disclosure. In this regard, the term "die attach material" in this disclosure and claims shall refer to any material used to thermally, electrically, and / or mechanically connect two components.

[0019] In some examples, the core-shell particles may be dispersed in a solution to form the die attach material as an ink or paste. For example, in some embodiments, the core-shell particles may be dispersed in ethylene glycol. In some embodiments, the core-shell particles may be grafted into a polymer matrix to form the die attach material as an ink or paste.

[0020] The die attach material may be deposited on a substrate. A semiconductor die or other component may be placed on the die attach material. The die attach material may undergo bonding or a bonding process (e.g., sintering) to secure the semiconductor die or other component to the die attach material. As used herein, the terms "bonding" or "bonding process" refer to transitioning a material from a first form to a second form. The bonding process may or may not require adhering a component to the material. Sintering, reflow, annealing, curing, light irradiation, and ultraviolet light irradiation are examples of bonding processes and are encompassed by the term "bonding" or "bonding process" in this disclosure and claims.

[0021] In some embodiments, the shell may be formed on the core (e.g., plated onto the core) using an electroless process. The electroless process may include cleaning, sensitization / activation, and deposition. Activation may be achieved, for example, by immersing the core particles in a solution containing a mixture of tin chloride (SnCl) and palladium chloride (PdCl).

[0022] In some embodiments, core-shell particles may be formed, for example, by adding a second solution to a first solution. The first solution may include core particles and / or core precursors from which core particles are formed. Examples of core precursors may include copper sulfate (CuSO), copper nitrate (Cu(NO), copper chloride (CuCl), copper acetate (Cu(COCH), nickel acetate (Ni(CHCO), nickel sulfate (NiSO), etc.

[0023] The second solution may include a shell precursor and a complementary element precursor for forming a shell on the core particle. Examples of the shell precursor may include silver nitrate (AgNO), tetrachloroauric acid (H(AuCl)), palladium nitrate (Pd(NO)), palladium sulfate (PdSO). Examples of the complementary element precursor may include sodium tungstate dihydrate (NaWO), tungsten(VI) nitrate (W(NO)), cobalt nitrate (Co(NO)), cobalt sulfate (CoSO), sodium molybdate (NaMoO).

[0024] Aspects of the present disclosure provide numerous technical effects and advantages. For example, die attach materials according to exemplary embodiments of the present disclosure may exhibit improved aging stability, fewer defects and voids, lower risk of electromigration, and / or improved thermal, mechanical, and electrical properties compared to core-only or other core-shell particles. This is also a lead-free approach, potentially meeting lead-free certification standards.

[0025] Although terms such as "first," "second," etc. may be used herein to describe various elements, it should be understood that these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a first element could be referred to as a second element, and similarly, a second element could be referred to as a first element, without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that the words "comprises," "comprising," and / or "includes," when used herein, specify the presence of stated features, numbers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and / or groups thereof.

[0027] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Furthermore, it will be understood that terms used herein should be interpreted as having a meaning consistent with the meaning in the context of this specification and the related art, and should not be interpreted in an idealized or overly formal sense unless expressly defined as such in this specification.

[0028] When an element, such as a layer, region, or substrate, is referred to as being "on" or extending "onto" another element, it is understood that the element may be directly on or extending directly onto the other element, or that intervening elements may be present. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there are no intervening elements present. When an element is referred to as being "connected" or "coupled" to another element, it is understood that the element may be directly connected or coupled to the other element, and there may also be intervening elements present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0029] Relative terms such as "below," "above," "upper," "lower," "horizontal," "lateral," or "vertical" may be used herein to describe the relationship of one element, layer, or region to another element, layer, or region as shown in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation of the device depicted in the figures.

[0030] Embodiments of the present disclosure are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the present invention. The thicknesses of layers and regions in the drawings may be exaggerated for clarity. Additionally, variations in the shapes of the figures are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein, but are intended to include deviations in shapes that result, for example, from manufacturing. Similarly, it is understood that variations in dimensions due to standard deviations in manufacturing procedures are to be expected. As used herein, "approximately" or "about" includes values ​​within 10% of the nominal value.

[0031] Like numbers refer to like elements throughout, and thus, the same or similar numbers may be described with reference to other drawings even if not illustrated or described in the corresponding drawing. Also, elements not labeled with a reference number may be described with reference to other drawings.

[0032] Some embodiments of the present invention are described with reference to semiconductor layers and / or regions characterized as having a conductivity type, such as n-type or p-type, which refers to the majority carrier concentration within the layer and / or region. Thus, n-type material has a majority equilibrium concentration of negatively charged electrons, and p-type material has a majority equilibrium concentration of positively charged holes. Some materials may be designated with a "+" or "-" (e.g., n+, n-, p+, p-, n++, n--, p++, p--, etc.) to indicate a relatively high ("+") or low ("-") concentration of majority carriers compared to other layers or regions. However, such designations do not imply the presence of a particular concentration of majority or minority carriers in a given layer or region.

[0033] The drawings and specification disclose exemplary embodiments, and although specific terms are employed, they are used in a generic and descriptive sense only and are not intended to limit the scope of the invention as set forth in the following claims.

[0034] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. 1 illustrates a cross-sectional view of a semiconductor device 100 according to an exemplary embodiment of the present disclosure. The semiconductor device 100 may include a substrate 102. The substrate 102 may be, for example, a lead frame or other support structure for a wide bandgap power semiconductor device, such as a silicon carbide-based semiconductor power module or a discrete package. The substrate 102 may be, for example, a copper substrate 102, or may include other suitable conductive material(s).

[0035] The semiconductor device 100 may include a semiconductor die 104. The semiconductor die 104 may include one or more devices, such as one or more of a wide variety of power devices available for various applications, including power switching devices and / or power amplifiers. In some examples, the semiconductor die 104 may include one or more field effect transistor (FET) devices, including metal-oxide semiconductor field-effect transistors (MOSFETs), double-diffused metal-oxide semiconductor (DMOS) transistors, high electron mobility transistors (HEMTs), metal-semiconductor field-effect transistors (MESFETs), laterally diffused metal-oxide semiconductor (LDMOS) transistors, etc. In some embodiments, the semiconductor die 104 may include one or more diodes (e.g., Schottky diodes, light-emitting diodes, etc.).

[0036] In some embodiments, the semiconductor die 104 may be fabricated from a wide bandgap semiconductor material (e.g., having a bandgap of 1.40 eV or greater). For high power, high temperature, and / or high frequency applications, devices formed from wide bandgap semiconductor materials, such as silicon carbide (e.g., the bandgap of alpha silicon carbide at room temperature is 2.996 eV) and Group III nitrides (e.g., the bandgap of gallium nitride at room temperature is 3.36 eV), can provide higher electric field breakdown strengths and higher electron saturation velocities.

[0037] Aspects of the present disclosure are described with reference to wide bandgap semiconductors for purposes of illustration and explanation, and one skilled in the art will understand, with the disclosure provided herein, that die attach materials according to exemplary embodiments of the present disclosure may be used with any semiconductor or other material without departing from the scope of the present disclosure.

[0038] The semiconductor die 104 may be attached to the substrate 102 using a die attach material 106. The die attach material 106 may include a plurality of core-shell particles. The particles may be nucleocapsid particles. A nucleocapsid particle refers to a particle having a core (e.g., nucleus) surrounded by a shell material. The die attach material 106 may undergo a bonding process to mechanically, thermally, and / or electrically connect the semiconductor die 104 to the substrate 102.

[0039] 2 illustrates an external view of a die attach material 106 according to an exemplary embodiment of the present disclosure. The die attach material 106 may include a plurality of core-shell particles 108. Each core-shell particle 108 may have a core 110 and a shell 112 on the core 110. The core 110 may be a conductive material (e.g., an electrically conductive material). In some examples, the core 110 may include a metal, a metal oxide, a ceramic material, or an organic material. In some examples, the conductive material of the core 110 may include copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

[0040] The shell 112 may include a material having a first conductive element and a second element that segregates within the grain boundaries of the die attach material 106 after bonding. The shell 112 may inhibit or prevent oxidation of the core 110. In some embodiments, the shell 112 may include a metal oxide, a ceramic, or an organic material. In some embodiments, the shell 112 may include an alloy, such as a metal alloy. The first element of the alloy may be silver (Ag), gold (Au), palladium (Pd), or other suitable metal. The second element of the alloy may have limited solubility in the shell 112 (e.g., no solubility in the shell 112) to efficiently segregate within the grain boundaries of the die attach material 106 without requiring high temperatures (e.g., greater than about 200°C). For example, the second element of the alloy may be tungsten (W), cobalt (Co), or molybdenum (Mo).

[0041] In some embodiments, the core 110 may include copper (Cu) and the shell 112 may be a silver-tungsten (AgW) alloy having silver (Ag) as a first element and tungsten (W) as a second element. In some embodiments, the core 110 may include copper (Cu) as a conductive material and the shell 112 includes a silver-cobalt (AgCo) alloy having silver (Ag) as a first element and cobalt (Co) as a second element. In some embodiments, the core 110 may include copper (Cu) as a conductive material and the shell 112 includes a silver-molybdenum (AgMo) alloy having silver (Ag) as a first element and molybdenum (Mo) as a second element.

[0042] In some embodiments, the core-shell particles 108 may be nanoparticles. For example, the core 110 of each core-shell particle 108 may be less than about 1 μm in size. In some embodiments, the core-shell particles 108 may be microparticles. For example, the core 110 of each core-shell particle 108 may range in size from 1 μm to about 50 μm.

[0043] In some examples, the core-shell particles 108 may be dispersed in a solvent or other medium to provide an ink- or paste-like metal-filled composite prior to bonding. The solvent may be, for example, ethylene glycol. In some examples, the core-shell particles 108 may be mixed or grafted into a polymer matrix to form an ink or paste prior to bonding. The conductive ink or paste may be deposited (e.g., onto the substrate 102 of FIG. 1 ) using inkjet printing, dispense coating, screen printing, flexographic printing, gravure printing, spin coating, blade coating, spray coating, or other deposition technique(s). The die attach material 106 may transition from a first form to a second form through a bonding process.

[0044] 2 illustrates the transition of the die attach material from a first configuration 114 to a second configuration 116 as a result of bonding 118 of the die attach material. Bonding 118 may include sintering, reflowing, annealing, curing, photoirradiation, UV irradiation, laser irradiation, pulsed light irradiation, or other suitable process for transitioning the configuration of the die attach material 106. In the example of FIG. 2, bonding 118 may include sintering to form a sintered material.

[0045] As shown in FIG. 2 , after bonding 118, the first element 120 of the shell 112 is disposed around the core(s) 110 of the core-shell particle 108. The first element 120 of the shell 112 may be, for example, silver (Ag), gold (Au), or palladium (Pd). The second element 122 (represented by a dotted line) segregates within the grain boundaries of the die attach material 106. The second element 122 may be, for example, tungsten (W), cobalt (Co), or molybdenum (Mo). After bonding 118, the die attach material 106 may comprise an intermetallic compound 124. The intermetallic compound 124 can inhibit the passage of electromigration metals (e.g., copper) through the die attach material 106 after bonding 118 of the die attach material 106.

[0046] 3-5 illustrate example devices including die attach materials according to exemplary embodiments of the present disclosure. Figures 3-5 are provided for purposes of illustration and explanation. Those skilled in the art will appreciate, using the disclosure provided herein, that the die attach materials may be used in a variety of devices and / or applications without departing from the scope of the present disclosure.

[0047] FIG. 3 illustrates a cross-sectional view of a portion of a power module 128 according to an exemplary embodiment of the present disclosure. FIG. 3 is intended to depict the structure for identification and explanation purposes and is not intended to depict the structure to physical scale. The power module 128 may include a housing 130. The power module 128 may include a conductive substrate 132 (e.g., a patterned conductive substrate) onto which a semiconductor die 104 carrying one or more power devices (e.g., transistors, diodes, etc.) is attached using a die attach material 106 according to an exemplary embodiment of the present disclosure. The die attach material 106 may provide thermal, mechanical, and electrical connections between the semiconductor die 104 and the conductive substrate 132. In some embodiments, the semiconductor die 104 may also be connected to the conductive substrate 132 using wire bonds 134. The conductive substrate 132 may be mounted on a base layer 136 (e.g., an insulating layer). The space between the semiconductor die 104 and the housing 130 may be filled with an inert gel 138.

[0048] 4 illustrates a device 140 incorporating die attach material to form a device antenna 142 according to an exemplary embodiment of the present disclosure. More specifically, the device 140 may include a substrate 144, such as a dielectric substrate 144. The dielectric substrate 144 may have one or more conductive elements 146, such as one or more circuit pattern lines, that form transmission lines and / or mounting connections to the antenna 142. The die attach material 106 may be deposited onto the substrate 144 using inkjet printing, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, a spray coater, or other deposition technique(s). The die attach material 106 may undergo a bonding process to form the antenna 142 on the substrate 144.

[0049] FIG. 5 illustrates a cross-sectional view of at least a portion of a device 148 incorporating a die attach material 106 to form interconnects for the device 148, according to an exemplary embodiment of the present disclosure. FIG. 5 is intended to depict the structure for purposes of identification and explanation, and is not intended to depict the structure to physical scale. The device 148 may include a first layer 150 having one or more conductive portions or other portions requiring thermal and / or electrical connection. The device 148 may include a second layer 152 spaced apart from the first layer 150. The second layer 152 may have one or more conductive portions or other portions requiring thermal and / or electrical connection. The device 148 may include a third layer 154 (e.g., an insulating layer) disposed between the first layer 150 and the second layer 154. The insulating layer 154 may be patterned. The die attach material 106 may be deposited in or on the insulating layer (e.g., in one or more voids in the patterned insulating layer 154) and subjected to a bonding process to form traces 156 of the device 148. The traces 156 may electrically and / or thermally connect one or more portions of the first layer 150 to one or more portions of the second layer 152.

[0050] 6 illustrates a flowchart of an example method 200 according to an exemplary embodiment of the present disclosure. The steps of the example method are illustrated in FIG. 6 for purposes of illustration and explanation. Those skilled in the art, using the disclosure provided herein, will understand that they may adapt, modify, include, exclude steps not shown, and / or rearrange the methods described in the present disclosure without departing from the scope of the present disclosure.

[0051] At 202, the method may include depositing a die attach material onto the substrate. The die attach material may be any of the example die attach materials described herein. For example, the die attach material may be die attach material 106 described with reference to FIGS. 1 and 2. In some embodiments, the die attach material may be deposited onto the substrate using inkjet printing, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, a spray coater, or other deposition technique(s).

[0052] At 204, the method may include providing a semiconductor die or other component on the die attach material. In some examples, the semiconductor die may include a wide bandgap semiconductor die. For example, the semiconductor die may include a silicon carbide-based semiconductor and / or a III-nitride-based semiconductor. The semiconductor die may include one or more devices, such as one or more transistors, one or more diodes, or other devices.

[0053] At 206, the method may include attaching the semiconductor die to the substrate by bonding a die attach material, which may include subjecting the die attach material to any bonding process, such as sintering, reflow, annealing, curing, laser irradiation, pulsed light irradiation, ultraviolet irradiation, or other process.

[0054] In one example, bonding may include sintering the die attach material by exposing it to heat and / or applying pressure to the die attach material. For example, sintering the die attach material may include heating the die attach material to a temperature in the range of about 100°C to about 400°C, e.g., in the range of about 150°C to about 300°C, for about 30 minutes to about 120 minutes. The temperature may be selected so as not to liquefy the die attach material or cause it to reflow. Sintering the die attach material may also include applying pressure to the die attach material by applying force onto the semiconductor die. The force may be applied by applying a flat punch or other tool to the semiconductor die. The pressure may be in the range of 1 MPa to about 30 MPa, e.g., in the range of about 5 MPa to about 25 MPa, e.g., in the range of about 10 MPa to about 20 MPa. The pressure may be applied for a time period in the range of about 1 minute to about 15 minutes. Sintering the die attach material can cause the complementary elements of the shell of the core-shell particles (e.g., tungsten (W), cobalt (Co), or molybdenum (Mo)) to segregate within the grain boundaries of the sintered die attach material.

[0055] Other exemplary bonding processes may be performed on the die attach material without departing from the scope of the present disclosure. For example, in some embodiments, the die attach material may be exposed to a laser. In some embodiments, the die attach material may be subjected to a reflow process. In some embodiments, the die attach material may be exposed to high intensity pulsed light. In some embodiments, the die attach material may be exposed to ultraviolet light.

[0056] The synthesis of core-shell particles may use precursors of the core, shell, and complementary element, stabilizers / complexing agents, solvents, and / or reducing agents. In some examples, the core may be a metal, metal oxide, ceramic, or organic material. The shell may also be a metal oxide, ceramic, or organic material. The complementary element may be insoluble or have limited solid solubility in the shell, for example, so that it can efficiently segregate to grain boundaries even when high-temperature conditions are not available. The complementary element may be tungsten (W), cobalt (Co), or molybdenum (Mo).

[0057] In some instances, the redox potential of the core is lower than that of the oxidizing agent (e.g., the shell and the complementary element). Otherwise, reduction may be slow or may not occur. In some instances, this limitation imposed by the redox potential can be overcome by using an appropriate complexing agent. For example, thiourea can be used to adjust the attachment potential of copper (Cu) and tin (Sn) to form a copper core-tin shell structure.

[0058] Examples of core precursors may include one or more of copper sulfate (CuSO), copper nitrate (Cu(NO), copper chloride (CuCl), copper acetate (Cu(COCH), nickel acetate (Ni(CHCO), nickel sulfate (NiSO), etc.

[0059] Examples of shell precursors may include one or more of silver nitrate (AgNO3), tetrachloroauric acid (H(AuCl4)), palladium nitrate (Pd(NO3)2), palladium sulfate (PdSO4), and the like.

[0060] Examples of precursors of complementary elements (e.g., second elements of a metal alloy) may include one or more of sodium tungstate dihydrate (NaWO), tungsten(VI) nitrate (W(NO)), cobalt nitrate (Co(NO)), cobalt sulfate (CoSO), sodium molybdate (NaMoO), and the like.

[0061] Examples of stabilizers may include one or more of polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), ethylenediamine (EDA), dimethylhydantoin (DMH), and the like.

[0062] Examples of reducing agents are ethylene glycol (EG), sodium borohydride (NaBH4), monosodium phosphate (NaH2PO4), glucose (CH 12 O6), dimethylamine borane (DMAB), ascorbic acid (C6H8O6), and PVP, among others.

[0063] 7 illustrates a flow diagram of an example method 210 for forming core-shell particles (e.g., core-shell nanoparticles) of a die attach material in accordance with an exemplary embodiment of the present disclosure. The steps of the example method are shown in FIG. 7 for purposes of illustration and explanation. Those skilled in the art, using the disclosure provided herein, will understand that the methods described in the present disclosure may be adapted, modified, include steps not shown, exclude steps, and / or rearranged without departing from the scope of the present disclosure.

[0064] 7, at 212, the method 210 may include heating a base solution of a stabilizer and a reducing agent to a first temperature. The first temperature may range from about 50° C. to about 100° C. At 214, the method 210 may include adding a core precursor to the base solution to form a first solution. Examples of core precursors may include copper sulfate (CuSO), copper nitrate (Cu(NO), copper chloride (CuCl), copper acetate (Cu(COCH), nickel acetate (Ni(CHCO), nickel sulfate (NiSO), etc.

[0065] At 216, the method 210 may include heating the first solution having the core precursor to a second temperature. The second temperature may range from about 100° C. to about 175° C. At 218, the method 210 may include holding the first solution at about the second temperature for a treatment time to produce the core. The treatment time may range from about 5 minutes to about 30 minutes.

[0066] At 220, the method 210 may include adding a second solution to the first solution to form a shell on the core. The second solution may include a shell precursor and a complementary element precursor. Examples of shell precursors may include silver nitrate (AgNO), tetrachloroauric acid (H(AuCl)), palladium nitrate (Pd(NO)), palladium sulfate (PdSO), etc. Examples of precursors of complementary elements (e.g., the second element of a metal alloy) may include sodium tungstate dihydrate (NaWO), tungsten(VI) nitrate (W(NO)), cobalt nitrate (Co(NO)), cobalt sulfate (CoSO), sodium molybdate (NaMoO), etc. The second solution may be added to the first solution at a flow rate. The flow rate may range from about 1 mL / min to about 5 mL / min. The solution may be stirred for the second treatment period. The second treatment time may range from about 3 minutes to about 45 minutes. The resulting precipitate may comprise core-shell particles.

[0067] The core-shell particles may be separated from the solution, for example, using a centrifuge, at 222. The core-shell particles may be washed, for example, with deionized water or ethanol, at 224.

[0068] The following is provided as an example of producing core-shell particles using the example method 210 of FIG. [Example 1: Copper core with silver-tungsten alloy shell] A solution of PVP in EG (0.5-1 mM) is heated (50-100°C) under air or an inert gas (e.g., Ar / N2) purge. A solution of Cu(CO2CH3)2 in EG is added and the temperature is raised to 150°C for a period of time (e.g., 5-30 minutes, depending on the desired core size) to produce copper core particles. A mixed solution of AgNO3 and Na2WO4 in EG (e.g., 1-20 mM) is then slowly added (e.g., 1-5 mL / min) and stirred for an additional 5-30 minutes. The precipitate, containing core-shell particles with a copper core and a silver-tungsten alloy shell, is separated by centrifugation and washed with deionized water.

[0069] [Example 2: Copper core with silver-cobalt alloy shell] Copper (Cu) core particles are obtained by reducing CuSO4 in a solution of NaH2PO4 (reducing agent), DMH (stabilizing agent), and citric acid (complexing agent) in deionized water at a temperature of 50-80°C and a pH of 5.5-6.5 (adjusted with NaOH) for a certain period of time (e.g., 30-60 minutes). A mixed EG solution of AgNO3 and Co(NO3)2 is slowly added (e.g., 1-5 mL / min) to this mixture and stirred for an additional 30-60 minutes. The precipitate, containing core-shell particles with a copper core and a silver-cobalt alloy shell, is separated using a centrifuge and washed with deionized water.

[0070] 8 illustrates a flow diagram of an example method 230 for forming core-shell particles (e.g., core-shell microparticles) of die attach material in accordance with an exemplary embodiment of the present disclosure. The steps of the example method are shown in FIG. 8 for purposes of illustration and explanation. Those skilled in the art, using the disclosure provided herein, will understand that the methods described in the present disclosure may be adapted, modified, include, exclude steps not shown, and / or rearranged without departing from the scope of the present disclosure.

[0071] At 232, the method 230 may include cleaning the core particles. For example, the method may include cleaning dendritic copper particles having a size of about 1 μm to about 50 μm. The core particles may be cleaned, for example, with deionized water. In some embodiments, the core particles may be exposed to a weak acid solution (e.g., acetic acid) to remove any oxide layer on the core particles without damaging the core particles.

[0072] At 234, the method 230 may include activating the core particles. For example, the method may include soaking or exposing the core particles to a mixed solution of tin chloride (SnCl) and palladium chloride (PdCl) in deionized water.

[0073] At 236, the method 230 may include adding the core particles to a first solution having a reducing agent, a stabilizing agent, and / or a complexing agent. The first solution may be heated to a temperature in the range of about 50° C. to 60° C.

[0074] At 238, the method 210 may include adding a second solution to the first solution to generate a shell on the core-shell particles. The second solution may include a shell precursor and a complementary element precursor. Examples of shell precursors may include silver nitrate (AgNO), tetrachloroauric acid (H(AuCl)), palladium nitrate (Pd(NO)), palladium sulfate (PdSO), etc. Examples of precursors of complementary elements (e.g., the second element of a metal alloy) may include sodium tungstate dihydrate (NaWO), tungsten(VI) nitrate (W(NO)), cobalt nitrate (Co(NO)), cobalt sulfate (CoSO), sodium molybdate (NaMoO), etc. The second solution may be added to the first solution at a flow rate. The flow rate may range from about 1 mL / min to about 5 mL / min. The solution may be stirred for the second treatment period. The second treatment time may range from about 20 minutes to about 75 minutes. The resulting precipitate comprises core-shell particles.

[0075] The core-shell particles may be separated from the solution, for example, using a centrifuge, at 240. The core-shell particles may be washed, for example, with deionized water or ethanol, at 242.

[0076] The following is provided as an example of producing core-shell particles using the example method 230 of FIG. [Example 3: Large diameter copper particle as core, silver-cobalt alloy shell] Dendritic copper particles (e.g., 1-50 μm) are used as core particles. The core particles are briefly immersed in a weak acid solution (e.g., acetic acid) to remove the oxide layer without damaging the core. They are then activated by immersion in a mixed solution of tin chloride (SnCl2) and palladium chloride (PdCl2) in deionized water. The core particles are then washed with deionized water and added to a solution consisting of a reducing agent (NaBH4), DMH, and citric acid in deionized water at a temperature of 50-60°C and a pH of 6.5 (adjusted with NaOH) and stirred for 2-10 minutes. A mixed solution of AgNO3 and Co(NO3)2 in deionized water is then slowly added (e.g., at a rate of 1-5 mL / min) to this mixture and stirred for an additional 30-60 minutes. The precipitate is then separated by centrifugation and optionally washed with deionized water or ethanol.

[0077] Illustrative aspects of the present disclosure are provided in the following paragraphs, which examples may be combined to form various embodiments of the present disclosure. An exemplary embodiment of the present disclosure is directed to a die attach material. The die attach material may include a plurality of core-shell particles. Each core-shell particle may have a core and a shell over the core. The core may include a conductive material. The shell may include an alloy. The alloy may include a first element and a second element. The second element may segregate within one or more grain boundaries in the die attach material during bonding of the die attach material.

[0078] Some examples are directed to the die attach material of any preceding paragraph, wherein the second element of the alloy inhibits oxidation of the core. Some examples are directed to the die attach material of any of the preceding paragraphs, wherein after bonding of the die attach material, the die attach material forms an intermetallic compound to inhibit passage of electromigrating metals through the die attach material.

[0079] Some examples are directed to the die attach material described in any preceding paragraph, wherein the core comprises a metal, a metal oxide, a ceramic material, or an organic material. Some examples are directed to the die attach material described in any preceding paragraph, wherein the conductive material of the core includes copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

[0080] Some examples are directed to the die attach material of any preceding paragraph, wherein the first element of the alloy is silver (Ag). Some examples are directed to the die attach material of any preceding paragraph, wherein the second element of the alloy is tungsten (W), cobalt (Co), or molybdenum (Mo).

[0081] Some examples are directed to the die attach material described in any preceding paragraph, wherein a plurality of core-shell particles are dispersed in a solution. Some examples are directed to the die attach material of any of the preceding paragraphs, wherein the solution includes ethylene glycol.

[0082] Some examples are directed to the die attach material described in any preceding paragraph, wherein a plurality of core-shell particles are grafted to a polymer matrix. Some examples are directed to the die attach material of any preceding paragraph, wherein the core is less than about 1 μm in dimension.

[0083] Some examples are directed to the die attach material of any preceding paragraph, wherein the core has a dimension ranging from about 1 μm to about 50 μm. Some examples are directed to the die attach material of any preceding paragraph, wherein the core includes copper (Cu) as the conductive material and the alloy includes a silver-tungsten (AgW) alloy having silver (Ag) as a first element and tungsten (W) as a second element.

[0084] Some examples are directed to the die attach material of any preceding paragraph, wherein the core includes copper (Cu) as the conductive material and the alloy includes a silver-cobalt (AgCo) alloy having silver (Ag) as a first element and cobalt (Co) as a second element.

[0085] Some examples are directed to the die attach material of any preceding paragraph, wherein the core includes copper (Cu) as the conductive material and the alloy includes a silver-molybdenum (AgMo) alloy having silver (Ag) as a first element and molybdenum (Mo) as a second element.

[0086] Another exemplary aspect of the present disclosure is directed to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle may have a core and a shell over the core. The core may include a conductive material. The shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

[0087] Some examples are directed to the die attach material of any preceding paragraph, wherein the alloy comprises silver (Ag). Some examples are directed to the die attach material described in any preceding paragraph, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

[0088] Some examples are directed to the die attach material described in any preceding paragraph, wherein a plurality of core-shell particles are dispersed in a solution. Some examples are directed to the die attach material of any preceding paragraph, wherein the solution comprises ethylene glycol.

[0089] Some examples are directed to the die attach material described in any preceding paragraph, wherein a plurality of core-shell particles are grafted to a polymer matrix. Some examples are directed to the die attach material of any preceding paragraph, wherein the core is less than about 1 μm in dimension.

[0090] Some examples are directed to the die attach material of any preceding paragraph, wherein the core has a dimension ranging from about 1 μm to about 50 μm. Some examples are directed to a die attach material as described in any preceding paragraph, wherein the die attach material is lead (Pb)-free.

[0091] Another exemplary aspect of the present disclosure is directed to a device. The device may include a die including a wide bandgap semiconductor material. The device may include a substrate. The device may include a die attach material between the die and the substrate. The die attach material may include a plurality of core-shell particles. Each core-shell particle may have a core and a shell over the core. The core may include a conductive material, and the shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

[0092] Some examples are directed to the device of any preceding paragraph, wherein the alloy comprises silver (Ag). Some examples are directed to the device of any preceding paragraph, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

[0093] Some examples are directed to the device of any preceding paragraph, wherein the substrate comprises a conductive substrate. Some examples are directed to the device of any preceding paragraph, wherein the die comprises one or more transistor devices.

[0094] Some examples are directed to the device of any preceding paragraph, wherein the die attach material of claim 15 is lead (Pb)-free. Some examples are directed to the device of any preceding paragraph, wherein the substrate comprises a leadframe.

[0095] Some examples are directed to a device as described in any preceding paragraph, wherein the device is a power discrete package. Some examples are directed to a device as described in any preceding paragraph, wherein the device is a power module.

[0096] Another exemplary aspect of the present disclosure is directed to a device. The device may include a substrate. The device may include a sintered material on the substrate. The sintered material may include a plurality of core-shell particles. Each core-shell particle may have a core and a shell over the core. The core may include a conductive material, and the shell may include an alloy. The alloy may include complementary elements segregated within one or more grain boundaries of the sintered material.

[0097] Some examples are directed to the device of any preceding paragraph, wherein the complementary element comprises tungsten (W), cobalt (Co), or molybdenum (Mo). Some examples are directed to the device of any preceding paragraph, wherein the alloy comprises silver (Ag).

[0098] Some examples are directed to the device of any preceding paragraph, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni). Some examples are directed to a device as described in any preceding paragraph, wherein the complementary element inhibits penetration of electromigrating metal into the sintered material.

[0099] Some examples are directed to a device as described in any preceding paragraph, wherein the sintered material constitutes a die attach material for the device. Some examples are directed to a device as described in any preceding paragraph, wherein the sintered material constitutes an antenna for the device.

[0100] Some examples are directed to a device as described in any preceding paragraph, wherein the sintered material constitutes wiring for the device. Another exemplary aspect of the present disclosure is directed to a method. The method may include depositing a die attach material onto a substrate. The die attach material may include a plurality of core-shell particles. Each core-shell particle may have a core and a shell over the core. The core may include a conductive material, and the shell may include an alloy. The alloy may include one or more of tungsten (W), cobalt (Co), or molybdenum (Mo). The method may include bonding the die attach material.

[0101] Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises bonding the die attach material at a temperature ranging from about 100°C to about 400°C. Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises bonding the die attach material for a time ranging from about 30 minutes to about 120 minutes.

[0102] Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises bonding the die attach material at a pressure ranging from about 1 MPa to about 30 MPa. Some examples are directed to the method of any preceding paragraph, wherein depositing the die attach material on the substrate comprises depositing the die attach material by one or more of inkjet printing, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, or a spray coater.

[0103] Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises sintering the die attach material. Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises bonding the die attach material with a laser.

[0104] Some examples are directed to the method of any preceding paragraph, wherein bonding the die attach material comprises bonding the die attach material with pulsed light. Some examples are directed to a method as described in any preceding paragraph, wherein the bonding of the die attach material comprises an antenna or a trace on the substrate.

[0105] Some examples are directed to a method as described in any preceding paragraph, wherein bonding the die attach material adheres the semiconductor die to the substrate. Some examples are directed to a method as described in any preceding paragraph, wherein the alloy comprises silver (Ag).

[0106] Some examples are directed to a method as described in any preceding paragraph, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni). Another exemplary embodiment of the present disclosure is directed to a method. The method may include adding a second solution to a first solution. The first solution may include core particles. The second solution may include a shell precursor and a complementary element precursor for forming a shell on the core particles. The shell may include an alloy. The alloy may include tungsten (W), cobalt (Co), or molybdenum (Mo).

[0107] Some examples are directed to methods described in any of the preceding paragraphs, wherein the core is produced from a core precursor. Some examples are directed to a method according to any preceding paragraph, wherein the core precursor comprises one or more of copper sulfate (CuSO), copper nitrate (Cu(NO), copper chloride (CuCl), copper acetate (Cu(COCH), nickel acetate (Ni(CHCO), nickel sulfate (NiSO).

[0108] Some examples are directed to a method as described in any preceding paragraph, wherein the shell precursor comprises one or more of silver nitrate (AgNO), tetrachloroauric acid (H(AuCl)), palladium nitrate (Pd(NO)), and palladium sulfate (PdSO).

[0109] Some examples are directed to a method according to any preceding paragraph, wherein the complementary element precursor comprises one or more of sodium tungstate dihydrate (NaWO), tungsten(VI) nitrate (W(NO)), cobalt nitrate (Co(NO)), cobalt sulfate (CoSO), and sodium molybdate (NaMoO).

[0110] Some examples are directed to a method as described in any preceding paragraph, wherein the first solution comprises a reducing agent. Some examples are directed to methods described in any preceding paragraph, wherein the reducing agent is ethylene glycol (EG), sodium borohydride (NaBH), monosodium phosphate (NaHPO), glucose (CH 12 O6), dimethylamine borane (DMAB), ascorbic acid (C6H8O6), or polyvinylpyrrolidone (PVP).

[0111] Some examples are directed to a method according to any preceding paragraph, wherein the first solution comprises a stabilizer. Some examples are directed to the methods of any preceding paragraph, wherein the stabilizer comprises one or more of polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), ethylenediamine (EDA), or dimethylhydantoin (DMH).

[0112] Some examples are directed to a method described in any preceding paragraph, the method including heating a base solution comprising a stabilizer and a reducing agent to a first temperature, and adding a core precursor to the base solution to form a first solution.

[0113] Some examples are directed to the methods described in any preceding paragraph, wherein the first temperature ranges from about 50°C to about 100°C. Some examples are directed to a method described in any preceding paragraph, including heating a first solution having a core precursor to a second temperature and holding the first solution at a temperature near the second temperature for a processing time to produce a core.

[0114] Some examples are directed to the methods described in any of the preceding paragraphs, wherein the second temperature ranges from about 100°C to about 175°C. Some examples are directed to methods described in any of the preceding paragraphs, where the treatment time ranges from about 5 minutes to about 30 minutes.

[0115] Some examples are directed to a method as described in any preceding paragraph, wherein adding the second solution to the first solution comprises adding the second solution to the first solution at a flow rate ranging from about 1 mL / min to about 5 mL / min.

[0116] Some examples are directed to a method as described in any preceding paragraph, the method comprising activating the core particles with a mixture of tin chloride (SnCl) and palladium chloride (PdCl).

[0117] While the present subject matter has been described in detail with reference to specific exemplary embodiments thereof, it will be appreciated that those skilled in the art, upon gaining an understanding of the foregoing, may readily make alterations, variations, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is intended to be illustrative rather than limiting, and the disclosure of the present subject matter is not intended to exclude the inclusion of such modifications, variations, and / or additions to the present subject matter that would be readily apparent to those skilled in the art.

Claims

1. 1. A die attach material comprising: a plurality of core-shell particles, each core-shell particle having a core and a shell on the core; the core comprises a conductive material; a die attach material, wherein the shell comprises an alloy, the alloy comprising a first element and a second element, the second element segregating within one or more grain boundaries in the die attach material during bonding of the die attach material;

2. The die attach material of claim 1 , wherein the second element of the alloy inhibits oxidation of the core.

3. The die attach material of claim 1 , wherein after bonding, the die attach material forms an intermetallic compound to inhibit passage of electromigrating metals through the die attach material.

4. The die attach material of claim 1 , wherein the core comprises a metal, a metal oxide, a ceramic material, or an organic material.

5. The die attach material of claim 1 , wherein the conductive material of the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

6. The die attach material of claim 1 , wherein the first element of the alloy is silver (Ag).

7. The die attach material of claim 1 , wherein the second element of the alloy is tungsten (W), cobalt (Co), or molybdenum (Mo).

8. The die attach material of claim 1 , wherein the plurality of core-shell particles are dispersed in a solution.

9. The die attach material of claim 8 , wherein the solution comprises ethylene glycol.

10. The die attach material of claim 1 , wherein the plurality of core-shell particles are grafted to a polymer matrix.

11. The die attach material of claim 1 , wherein the core has a dimension of less than about 1 μm.

12. The die attach material of claim 1 , wherein the core has a size within a range of about 1 μm to about 50 μm.

13. 2. The die attach material of claim 1, wherein the core comprises copper (Cu) as the conductive material, and the alloy comprises a silver-tungsten (AgW) alloy having silver (Ag) as the first element and tungsten (W) as the second element.

14. 2. The die attach material of claim 1, wherein the core comprises copper (Cu) as the conductive material, and the alloy comprises a silver-cobalt (AgCo) alloy having silver (Ag) as the first element and cobalt (Co) as the second element.

15. 2. The die attach material of claim 1, wherein the core comprises copper (Cu) as the conductive material, and the alloy comprises a silver-molybdenum (AgMo) alloy having silver (Ag) as the first element and molybdenum (Mo) as the second element.

16. 1. A die attach material comprising: a plurality of core-shell particles, each core-shell particle having a core and a shell on the core; the core comprises a conductive material and the shell comprises an alloy; The die attach material, wherein the alloy comprises one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

17. The die attach material of claim 16 , wherein the alloy comprises silver (Ag).

18. The die attach material of claim 16 , wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

19. The die attach material of claim 16 , wherein the plurality of core-shell particles are dispersed in a solution.

20. The die attach material of claim 19 , wherein the solution comprises ethylene glycol.

21. The die attach material of claim 16 , wherein the plurality of core-shell particles are grafted to a polymer matrix.

22. The die attach material of claim 16 , wherein the core has a dimension of less than about 1 μm.

23. 17. The die attach material of claim 16, wherein the core has a size ranging from about 1 μm to about 50 μm.

24. The die attach material of claim 16 , wherein the die attach material is lead (Pb) free.

25. A device, a die comprising a wide bandgap semiconductor material; A substrate; a die attach material between the die and the substrate, the die attach material comprising a plurality of core-shell particles, each core-shell particle comprising a core and a shell over the core; the core comprises a conductive material and the shell comprises an alloy; The device, wherein the alloy comprises one or more of tungsten (W), cobalt (Co), or molybdenum (Mo).

26. 26. The device of claim 25, wherein the alloy comprises silver (Ag).

27. 26. The device of claim 25, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

28. The device of claim 25 , wherein the substrate comprises a conductive substrate.

29. 26. The device of claim 25, wherein the die comprises one or more transistor devices.

30. The device of claim 25 . The die attach material of claim 15 , wherein the die attach material is lead (Pb) free.

31. The device of claim 25 , wherein the substrate comprises a leadframe.

32. 31. The device of claim 30, wherein the device is a power discrete package.

33. 31. The device of claim 30, wherein the device is a power module.

34. A device, A substrate; a sintered material on the substrate; The sintered material comprises a plurality of core-shell particles, each core-shell particle comprising a core and a shell over the core, the core comprising a conductive material, and the shell comprising an alloy comprising complementary elements segregated within one or more grain boundaries of the sintered material.

35. 35. The device of claim 34, wherein the complementary element comprises tungsten (W), cobalt (Co), or molybdenum (Mo).

36. 35. The device of claim 34, wherein the alloy comprises silver (Ag).

37. 35. The device of claim 34, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

38. 35. The device of claim 34, wherein the complementary element inhibits passage of electromigrating metals into the sintered material.

39. 35. The device of claim 34, wherein the sintered material comprises a die attach material for the device.

40. 35. The device of claim 34, wherein the sintered material comprises an antenna for the device.

41. 35. The device of claim 34, wherein the sintered material comprises wiring for the device.

42. depositing a die attach material onto a substrate, the die attach material comprising a plurality of core-shell particles, each core-shell particle comprising a core and a shell over the core, the core comprising a conductive material, and the shell comprising an alloy, the alloy comprising one or more of tungsten (W), cobalt (Co), or molybdenum (Mo); bonding the die attach material.

43. 43. The method of claim 42, wherein bonding the die attach material comprises bonding the die attach material at a temperature in a range from about 100°C to about 400°C.

44. 43. The method of claim 42, wherein bonding the die attach material comprises bonding the die attach material for a time period ranging from about 30 minutes to about 120 minutes.

45. 43. The method of claim 42, wherein bonding the die attach material comprises bonding the die attach material at a pressure in a range from about 1 MPa to about 30 MPa.

46. 43. The method of claim 42, wherein applying the die attach material onto the substrate comprises applying the die attach material by one or more of an inkjet printer, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, or a spray coater.

47. 43. The method of claim 42, wherein bonding the die attach material comprises sintering the die attach material.

48. 43. The method of claim 42, wherein bonding the die attach material comprises bonding the die attach material with a laser.

49. 43. The method of claim 42, wherein bonding the die attach material comprises bonding the die attach material with pulsed light.

50. 43. The method of claim 42, wherein the application of the die attach material forms an antenna or a trace on the substrate.

51. 43. The method of claim 42, wherein the bonding of the die attach material bonds a semiconductor die to the substrate.

52. 43. The method of claim 42, wherein the alloy comprises silver (Ag).

53. 43. The method of claim 42, wherein the core comprises copper (Cu), tin (Sn), aluminum (Al), or nickel (Ni).

54. 1. A method comprising adding a second solution to a first solution, the first solution comprises core particles, and the second solution comprises a shell precursor and a complementary element precursor for forming a shell on the core particles; The method, wherein the shell comprises an alloy, the alloy comprising tungsten (W), cobalt (Co), or molybdenum (Mo).

55. 55. The method of claim 54, wherein the core is produced from a core precursor.

56. The core precursor is copper sulfate (CuSO ４ ), copper nitrate (Cu(NO ３ ) ２ ), copper chloride (CuCl ２ ), copper acetate (Cu(CO ２ CH ３ ) ２ ), nickel acetate (Ni(CH ３ CO ２ ) ２ ), nickel sulfate (NiSO ４ 56. The method of claim 55, comprising one or more of:

57. The shell precursor is silver nitrate (AgNO ３ ), tetrachloroauric acid (H(AuCl ４ )), palladium nitrate (Pd(NO ３ ) ２ ), palladium sulfate (PdSO ４ 55. The method of claim 54, comprising one or more of:

58. The complementary element precursor is sodium tungstate (VI) dihydrate (Na ２ WO ４ ), tungsten(VI) nitrate (W(NO ３ ) ６ ), cobalt nitrate (Co(NO ３ ) ２ ), cobalt sulfate (CoSO ４ ), sodium molybdate (Na ２ MoO ４ 55. The method of claim 54, comprising one or more of:

59. 55. The method of claim 54, wherein the first solution comprises a reducing agent.

60. The reducing agent is ethylene glycol (EG), sodium borohydride (NaBH ４ ), monosodium phosphate (NaH ２ P.O. ４ ), glucose (C ６ H １２ O ６ ), dimethylamine borane (DMAB), ascorbic acid (C ６ H ８ O ６ 60. The method of claim 59, comprising one or more of the following:

61. 55. The method of claim 54, wherein the first solution comprises a stabilizer.

62. 62. The method of claim 61, wherein the stabilizer comprises one or more of polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), ethylenediamine (EDA), or dimethylhydantoin (DMH).

63. The method comprises: heating a base solution comprising a stabilizer and a reducing agent to a first temperature; 55. The method of claim 54, comprising adding a core precursor to the base solution to form the first solution.

64. 64. The method of claim 63, wherein the first temperature ranges from about 50°C to about 100°C.

65. 64. The method of claim 63, further comprising heating the first solution having the core precursor to a second temperature and holding the first solution at a temperature near the second temperature for a processing time to produce the core.

66. 66. The method of claim 65, wherein the second temperature ranges from about 100°C to about 175°C.

67. 66. The method of claim 65, wherein the treatment time ranges from about 5 minutes to about 30 minutes.

68. 55. The method of claim 54, wherein adding the second solution to the first solution comprises adding the second solution to the first solution at a flow rate ranging from about 1 mL / min to about 5 mL / min.

69. The method comprises the steps of: ２ ) and palladium chloride (PdCl ２ 55. The method of claim 54, comprising activating the core particles with a mixture of

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