Metal nitride core-shell particle die attach material

Abstract

A die attach material is provided. In one example, the die attach material includes a plurality of core-shell particles. Each core-shell particle includes a core and a shell on the core. The core includes a conductive material. The shell includes a metal nitride.

Description

Detailed Description of the Invention

[0001] [Priority claim] This application is based on and claims the benefit of priority to U.S. Patent Application No. 18 / 169,518, filed February 15, 2023. This application claims priority to and the benefit of the entire contents of that cited application, and incorporates by reference the entire contents of that application.

[0002] [Field] The present disclosure relates generally to die attach materials. [background] Semiconductor devices, including power semiconductor devices based on wide bandgap materials, may be formed on a semiconductor wafer as part of a semiconductor manufacturing process. The semiconductor wafer may be diced into many individual pieces, each containing one or more semiconductor devices. Each of these pieces may be a semiconductor die. The semiconductor die may need to be attached to other components as part of a semiconductor device package. For example, a semiconductor die, such as a wide bandgap semiconductor die, may need to be attached to a conductive lead frame for use in a discrete power semiconductor package or power module. The materials used to attach the semiconductor die to other components may be required to provide thermal, mechanical, and / or electrical connections of the semiconductor die to the other components.

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

[0004] One exemplary embodiment of the present disclosure relates to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle comprises a core and a shell on the core. The core comprises a conductive material. The shell comprises a metal nitride.

[0005] Another exemplary embodiment of the present disclosure relates to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle includes a core and a shell on the core. The core includes copper, and the shell includes copper nitride. The die attach material can be an ink or a paste.

[0006] Another exemplary embodiment of the present disclosure relates to a device including a semiconductor die comprising a wide bandgap semiconductor material, a substrate, and a die attach material between the semiconductor die and the substrate, the die attach material including a plurality of bonded conductive particles and a metal nitride.

[0007] Another exemplary embodiment of the present disclosure relates to a device including a substrate, a sintered material on the substrate, the sintered material comprising a plurality of bonded copper particles and copper nitride.

[0008] Another exemplary embodiment of the present disclosure relates to a method including depositing a die attach material on a substrate, the die attach material comprising a plurality of core-shell particles, each core-shell particle comprising a core and a shell on the core, the core comprising a conductive material, and the shell comprising a metal nitride, and bonding the die attach material.

[0009] Another exemplary embodiment of the present disclosure relates to a method comprising oxidizing a plurality of conductive particles to form a plurality of oxidized conductive particles, and adding the oxidized conductive particles to a solution to form a metal nitride shell on the conductive particles, the solution comprising a compound, the compound including hydrogen and nitrogen.

[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. [Brief explanation of the drawings]

[0011] A detailed discussion of the embodiments directed to those skilled in the art is set forth in the specification, which refers to the attached figures below. [Figure 1] 1 depicts an exemplary device with a semiconductor die attached to a substrate using a die attach material, according to an exemplary embodiment of the present disclosure. [Figure 2] 1 depicts a core-shell particle of die attach material according to an exemplary embodiment of the present disclosure. [Figure 3] 1 depicts an exemplary semiconductor device according to an exemplary embodiment of the present disclosure. [Figure 4] 1 depicts an exemplary device using a die attach material to form an antenna, according to an exemplary embodiment of the present disclosure. [Figure 5] 1 depicts an exemplary device using a die attach material to form interconnects, according to an exemplary embodiment of the present disclosure. [Figure 6] 1 illustrates a flowchart of an exemplary method according to an exemplary embodiment of the present disclosure. [Figure 7] 1 illustrates a flowchart of an exemplary method according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Detailed explanation] Reference will now be made in detail to the embodiments, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the embodiment, not as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments without departing from the scope or spirit of the disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield yet a still further embodiment. Accordingly, it is intended that aspects of the disclosure cover all such modifications and variations.

[0013] Exemplary aspects of the present disclosure relate to die attach materials for use in semiconductor and other electronics applications, such as wide bandgap semiconductor device applications. Various techniques implemented in the semiconductor industry for die attach pose challenges and limitations. For example, semi-silver sintered or fully sintered silver process techniques provide acceptable electrical, mechanical, and thermal properties for die attach applications. However, semi-silver sintered or fully sintered silver process techniques can be costly and can be subject to high risks of electromigration, high voiding / porosity, and high thermomechanical stress. Eutectic Au80Sn20 techniques can also pose similar limitations. Semi-sintered or fully sintered copper is a lower-cost option, albeit with somewhat lower performance, due to the high oxidation susceptibility of copper, especially with small grain sizes. Semi-sintered or fully sintered copper can also pose challenges in that it requires low-temperature storage and forming gas during the deposition process to reduce oxidation. Lead (Pb)-based die attach solutions are not optimal options for achieving low thermal resistance and efficient current or power densities. Additionally, lead (Pb) based die attach materials do not meet certain lead-free certification standards.

[0014] An exemplary embodiment of the present disclosure relates to a core-shell particle-based die attach material. The die attach material may comprise a paste- or ink-based material including a plurality of metal core-shell microparticles and / or nanoparticles dispersed in a solution or grafted to a polymer matrix. The core-shell particle structure may include a core of a conductive material (e.g., an electrically conductive material) such as copper (Cu). A shell may be present on the core. The shell may include a metal nitride such as copper nitride (CuN). The metal nitride may reduce oxidation of the core, especially for copper particles.

[0015] During bonding of the die-attach material (e.g., sintering of the die-attach material), the metal nitride may decompose into metal and nitrogen gas. Some of the metal nitride may remain within the bonded die-attach material. For example, the metal nitride may be dispersed among bonded conductive particles within the bonded die-attach material.

[0016] Aspects of the present disclosure, for purposes of illustration and discussion, are discussed with reference to die-attach materials for attaching semiconductor dies (e.g., silicon carbide-based semiconductor dies, III-nitride-based semiconductor dies, silicon-based semiconductor dies, etc.) to substrates or other components. Using the disclosure provided herein, one of ordinary skill in the art will understand that the materials provided herein can be used to provide attachment of 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 is intended to refer to any material used to provide a thermal, electrical, and / or mechanical connection between two components.

[0017] The die-attach material may be deposited on a substrate. A semiconductor die or other component may be disposed on the die-attach material. The die-attach material may be subjected to a bonding or 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 causing a transition of a material from a first form to a second form. The bonding process may or may not require the attachment of a component to the material. Sintering, reflow, annealing, curing, exposure to light, and exposure to ultraviolet light are examples of bonding processes and are encompassed by the term "bonding" or "bonding process" in this disclosure and claims.

[0018] 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.

[0019] In some embodiments, the core-shell particles of the die attach material can be formed by oxidizing conductive core particles, such as copper particles. The oxidized conductive particles can be added to a solution to form a metal nitride shell on each of the conductive particles. The solution can include a compound. The compound can include hydrogen and nitrogen. For example, the compound can include ammonia (NH) and / or urea (HNCONH). The solution can further include methanol (CHOH). The solution with the oxidized conductive particles can be heated (e.g., heated in an autoclave) to form the core-shell particles. The core-shell particles can be dispersed in a solution (e.g., ethylene glycol) or grafted into a polymer matrix to form an ink or paste.

[0020] Aspects of the present disclosure provide numerous technical effects and benefits. For example, die attach materials including core-shell particles with metal nitride shells may exhibit improved thermal-mechanical and electrical properties, as well as improved aging stability, fewer defects and voids, lower annealing temperatures, and lower pressures, compared to, for example, die attach materials based solely on copper particles. In examples where the core-shell particles include copper cores with copper nitride shells, the copper core particles may be protected from oxidation by the copper nitride shell. The die attach materials may require relatively lower annealing temperatures and pressures during the bonding process (e.g., compared to die attach materials based solely on copper particles). Additionally, the bonding process can potentially be performed without the use of forming gas flow. The die attach materials may be lead-free and meet certain lead-free certification standards.

[0021] Although various elements may be described herein using the terms first, second, etc., it will be understood that these elements should not be 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.

[0022] 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 indicates otherwise. It will be further understood that the terms "comprise," "comprising," "including," and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0023] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the related art, and it will be further understood that terms used herein should not be interpreted in an idealized or overly formal sense unless expressly defined in this specification.

[0024] When an element, such as a layer, region, or substrate, is referred to as being "on" or extending "upon" another element, it will be understood that the element can be directly on or extending directly onto the other element, or that intervening elements can 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. When an element is referred to as being "connected" or "coupled" to another element, it will be understood that the element can be directly connected or coupled to the other element, or that intervening elements can be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0025] 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 depicted in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0026] 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 from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein, but rather to include deviations in shapes that, for example, result from manufacturing. Similarly, it will be understood that variations in dimensions are to be expected based on standard deviations in the manufacturing process. As used herein, "approximately" or "about" includes values ​​within 10% of the nominal value.

[0027] Like numbers refer to like elements throughout, and thus, like or similar numbers may be described with reference to other drawings even if not mentioned or described in the corresponding drawing. Additionally, elements not designated by a reference number may be described with reference to other drawings.

[0028] Some embodiments of this invention are described with reference to semiconductor layers and / or regions characterized as having a conductivity type, such as n-type or p-type, where conductivity type refers to the majority carrier concentration in that layer and / or region. Thus, N-type material has a majority equilibrium concentration of negatively charged electrons, while P-type material has a majority equilibrium concentration of positively charged holes. Some materials may be designated using a "+" or "-" (as in N+, N-, P+, P-, N++, N--, P++, or P--) to indicate a relatively higher ("+") or lower ("-") concentration of majority carriers compared to another layer or region. However, such notation does not imply the presence of a particular concentration of majority or minority carriers in the layer or region.

[0029] In the drawings and specification, there are disclosed exemplary embodiments, and although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limiting the scope, which is set forth in the following claims.

[0030] Referring now to the figures, exemplary embodiments of the present disclosure will now be described. 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 discrete package. The substrate 102 may be, for example, a copper substrate 102 or may include other suitable conductive materials.

[0031] 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 different applications, including, for example, a power switching device and / or a power amplifier. In some examples, the semiconductor die 104 may include one or more transistor devices, such as field effect transistor (FET) devices, including MOSFETs (metal oxide semiconductor field effect transistors), DMOS (double-diffused metal oxide semiconductor) transistors, HEMTs (high electron mobility transistors), MESFETs (metal semiconductor field effect transistors), LDMOS (latently diffused metal oxide semiconductor) transistor devices, etc. In some embodiments, the semiconductor die 104 may include one or more diodes (e.g., Schottky diodes, light emitting diodes, etc.).

[0032] In some embodiments, the semiconductor die 104 may be fabricated from a wide bandgap semiconductor material (e.g., having a bandgap greater than 1.40 eV). For high power, high temperature, and / or high frequency applications, devices formed in wide bandgap semiconductor materials such as silicon carbide (e.g., 2.996 eV bandgap for alpha silicon carbide at room temperature) and Group III nitrides (e.g., 3.36 eV bandgap for gallium nitride at room temperature) may provide higher electric field breakdown strengths and higher electron saturation velocities.

[0033] Aspects of the present disclosure are discussed with reference to wide bandgap semiconductors for purposes of illustration and discussion. Those skilled in the art will understand, using the disclosure provided herein, that die attach materials according to exemplary embodiments of the present disclosure can be used with any semiconductor or other material without departing from the scope of the present disclosure.

[0034] The semiconductor die 104 can be attached to the substrate 102 using a die attach material 106. The die attach material 106 can include a plurality of core-shell particles. The particles can 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 can be subjected to a bonding process that mechanically, thermally, and / or electrically connects the semiconductor die 104 to the substrate 102.

[0035] 2 depicts an embodiment 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 include a conductive particle 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 such as copper (Cu). The shell 112 may include a metal nitride such as copper nitride (CuN).

[0036] In some embodiments, the core-shell particles 108 may be nanoparticles. For example, the core 110 of each of the core-shell particles 108 may have a size of less than about 1 μm. In some embodiments, the core-shell particles 108 may be microparticles. For example, the core 110 of each of the core-shell particles 108 may have a size in the range of 1 μm to about 50 μm. In some examples, the shell 112 may have a thickness in the range of about 50 nm to about 100 nm.

[0037] In some examples, as discussed in more detail below with reference to FIG. 7 , core-shell particles 108 may be formed by subjecting conductive particle cores 110 (e.g., copper particles) to an oxidation process 114 to form an oxide shell 116 (e.g., copper oxide (CuO, CuO)) on each of the cores 110. The oxidation process 114 may include, for example, immersion in an NaOH solution, use of a plasma-based oxidation process, exposure to oxygen, etc. The oxidized cores 110 with the oxide shells 116 may be subjected to a process 118 to form a metal nitride shell 112 in place of the oxide shells 116. For example, the cores 110 with the oxide shells 116 may be mixed with a solution containing a compound. The compound may include hydrogen and nitrogen. For example, the compound may include ammonia (NH) and / or urea (HNCONH). The solution may further include methanol (CHOH). The solution with the oxidized conductive particle cores may be heated (eg, heated in an autoclave) to form core-shell particles 108.

[0038] In some examples, the core-shell particles 108 may be dispersed in a solvent or other medium to provide the die attach material 106 in the form of an ink or paste prior to bonding. The solvent may be, for example, ethylene glycol. In some examples, the core-shell particles 108 may be mixed with or grafted to a polymer matrix to form the 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, jetting, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, a spray coater, or other deposition techniques. The die attach material 106 may be subjected to a bonding process that transitions the die attach material 106 from the first morphology 124 to the second morphology 126.

[0039] 2 depicts the transition of die attach material 106 from a first configuration 124 to a second configuration 126 as a result of bonding 120 of die attach material 106. Bonding 120 may include sintering, reflowing, annealing, curing, exposure to light, exposure to ultraviolet light, exposure to a laser, exposure to pulsed light, or other suitable process for transitioning the configuration of die attach material 106. In the example of FIG. 2, bonding 120 may include sintering to form a sintered material.

[0040] 2, after bonding 120, the conductive particle cores 110 may be bonded together to form a bonded conductive particle core 110. The metal nitride shell 112 may decompose into a metal (e.g., copper) and nitrogen gas. A portion of the metal nitride 122 may remain within the die attach material 106. For example, a portion of the metal nitride 122 may be dispersed among some of the bonded conductive particle cores 110.

[0041] 3-5 depict exemplary devices including die attach materials according to exemplary embodiments of the present disclosure. Figures 3-5 are provided for purposes of illustration and discussion. Using the disclosure provided herein, one skilled in the art will understand that die attach materials can be used in a variety of devices and / or applications without departing from the scope of the present disclosure.

[0042] 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 structures for identification and explanation purposes and is not intended to depict the structures 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) to which a semiconductor die 104 containing 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 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). An inert gel 138 may fill the space between the semiconductor die 104 and the housing 130.

[0043] 4 depicts a device 140 incorporating a die attach material to form an antenna 142 for the device 140, 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 traces, that form transmission lines and / or mounting connections for the antenna 142. The die attach material 106 may be deposited on the substrate 144 using an inkjet printer, screen printer, flexographic printer, gravure printer, spin coater, blade coater, spray coater, or other deposition technique. The die attach material 106 may be subjected to a bonding process to form the antenna 142 on the substrate 144.

[0044] FIG. 5 depicts a cross-sectional view of at least a portion of a device 148 incorporating a die attach material 106 to form an interconnect for the device 148, according to an exemplary embodiment of the present disclosure. FIG. 5 is intended to represent the structure for identification and explanation purposes and is not intended to represent 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 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. Die attach material 106 may be deposited in or on the insulating layer (e.g., in one or more voids in patterned insulating layer 154) and subjected to a bonding process to form interconnects 156 for devices 148. Interconnects 156 may electrically and / or thermally connect one or more portions of first layer 150 with one or more portions of second layer 152.

[0045] 6 depicts a flowchart of an exemplary method 200 according to an exemplary embodiment of the present disclosure. FIG. 6 depicts exemplary method steps for purposes of illustration and discussion. Those skilled in the art, using the disclosure provided herein, will understand that the methods described in this disclosure may be adapted, modified, and may include steps not shown, omitted, and / or reordered without departing from the scope of the present disclosure.

[0046] At 202, the method may include depositing a die attach material on the substrate. The die attach material may be any of the exemplary die attach materials discussed herein. For example, the die attach material may be die attach material 106 discussed with reference to Figures 1 and 2. In some embodiments, the die attach material may be deposited on the substrate using an inkjet printer, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, a spray coater, or other deposition technique.

[0047] 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.

[0048] At 206, the method may include bonding the die attach material to attach the semiconductor die to the substrate, which may include subjecting the die attach material to any bonding process, such as sintering, reflowing, annealing, curing, exposure to a laser, exposure to pulsed light, exposure to ultraviolet radiation, or other process.

[0049] In one example, bonding may include sintering the die-attach material by exposing it to heat and / or pressure. 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, such as about 150°C to about 300°C, for about 30 minutes to about 120 minutes. The temperature may be selected so as not to cause liquefaction or reflow of the die-attach material. Sintering the die-attach material may also include subjecting the die-attach material to pressure by applying a 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, such as about 10 MPa to about 20 MPa, such as about 5 MPa to about 25 MPa. The pressure may be applied for a time period in the range of about 1 minute to about 15 minutes. The sintering process parameters provided in this disclosure are for illustrative purposes. Other sintering process parameters may be used without departing from the scope of the present disclosure.

[0050] 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.

[0051] During the bonding process, the metal nitride may decompose into metal and nitrogen gas. For example, in the example of a copper core particle with a copper nitride shell, the copper nitride may decompose during bonding as follows: 2Cu3N →6Cu+N2 7 depicts a flow diagram of an exemplary method 300 for forming core-shell particles of die attach material according to an exemplary embodiment of the present disclosure. FIG. 7 depicts exemplary method steps for purposes of illustration and discussion. Those skilled in the art, using the disclosure provided herein, will understand that the methods described in the present disclosure may be adapted, modified, and may include steps not shown, omitted, and / or rearranged without departing from the scope of the present disclosure.

[0052] Referring to 302 in FIG. 7 , the method 300 may include forming conductive particles 302. The conductive particles will serve as cores of core-shell particles of the die attach material. The conductive particles may be formed, for example, from copper. A variety of different methods may be used to form the conductive particles without departing from the scope of the present disclosure. In some examples, the conductive particles are dendritic copper particles. In some examples, the conductive particles may be formed by mixing a core precursor (e.g., a copper precursor) with a reducing agent and a stabilizer.

[0053] Exemplary core precursors may include, for example, 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. Exemplary stabilizers may include one or more of polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), ethylenediamine (EDA), dimethylhydantoin (DMH), citric acid HOC(COH)(CHCOH), etc. Exemplary reducing agents include ethylene glycol (EG), sodium borohydride (NaBH), monosodium phosphate (NaHPO), glucose (CH), etc. 12 O6), dimethylamine borane (DMAB), ascorbic acid (C6H8O6), and PVP, among others.

[0054] At 304, the method 300 may include washing the conductive particles. For example, the solution containing the conductive particles may be washed with, for example, ethanol and / or deionized water and filtered.

[0055] At 306, the method 300 may include oxidizing the conductive particles to form oxidized conductive particles. The oxidized conductive particles may include an oxide shell (e.g., a CuO or CuO shell). The conductive particles may be oxidized in various ways without departing from the scope of the present disclosure. For example, the conductive particles may be oxidized by immersion in an NaOH solution, using a plasma-based oxygenation process, exposure to oxygen, etc.

[0056] At 308, the method may include adding the oxidized conductive particles to a solution to form a metal nitride shell, such as a copper nitride (CuN) shell. The solution may contain a compound. The compound may include hydrogen and nitrogen. For example, the compound may include ammonia (NH) and / or urea (HNCONH). The solution may further include methanol (CHOH).

[0057] At 310, the method 300 may include heating the solution with the oxidized conductive particles to form core-shell particles. In some examples, the solution may be heated to a temperature in the range of about 180° C. to about 250° C. In some examples, the solution may be heated for a process period in the range of about 1 hour to about 6 hours. The core-shell particles may be washed (e.g., with ethanol and / or deionized water) and filtered.

[0058] At 312, the method 300 may include adding the core-shell particles to a solution to form an ink or paste. For example, the method 300 may include adding the core-shell particles to a solution including ethylene glycol. The method 300 may include mixing the core-shell particles with a polymer to form an ink or paste.

[0059] A specific example of forming a die attach material according to the exemplary embodiment of FIG. 7 is provided below. [Example] Copper particles were obtained by reducing CuSO (0.1 M) in a solution of NaHPO as a reducing agent and citric acid as a stabilizer at a temperature ranging from about 120°C to about 150°C and a pH of about 5.5 to about 6.5. The copper particles were stirred for a process period ranging from about 30 minutes to about 60 minutes. The solution was then washed (e.g., with ethanol / deionized water) and filtered. The surfaces of the copper particles were oxidized by immersion in a NaOH solution (0.1-1 M) at elevated temperatures to form copper particles with a copper oxide shell. The oxidized particles were then added to a solution of liquid ammonia (NH) and methanol (CHOH) and heated in an autoclave at an elevated temperature ranging from about 180°C to about 250°C for a process period ranging from about 1 hour to about 6 hours to produce core-shell particles having a copper core and a copper nitride shell. The substitution of the oxide shell with the copper nitride shell can be expressed as follows: 3Cu2O+2NH3 → 2Cu3N+3H2O The final product was then washed (e.g., ethanol / deionized water), filtered, functionalized, and then dispersed in a solvent or mixed / grafted to a polymer to form an ink or paste.

[0060] Exemplary aspects of the present disclosure are set forth below. Any of the following features or examples may be used in combination with any of the embodiments or features provided in this disclosure. One exemplary embodiment of the present disclosure relates to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle comprises a core and a shell on the core. The core comprises a conductive material. The shell comprises a metal nitride.

[0061] In some instances, the metal nitride reduces oxidation of the core. In some examples, the die attach material is an ink. In some examples, the die attach material is a paste.

[0062] In some instances, the metal nitride decomposes into metal and nitrogen gas during bonding of the die attach material. In some examples, the conductive material of the core includes copper, hi some examples, the metal nitride includes copper nitride.

[0063] In some examples, the plurality of core-shell particles is dispersed in a solution. In some examples, the solution includes ethylene glycol. In some examples, the plurality of core-shell particles is grafted to a polymer matrix.

[0064] In some instances, the core has a size of about 1 μm or less, in some instances, the core has a size in the range of about 1 μm to about 50 μm, and in some instances, the shell has a thickness in the range of about 50 nm to about 100 nm.

[0065] Another exemplary embodiment of the present disclosure relates to a die attach material. The die attach material includes a plurality of core-shell particles. Each core-shell particle includes a core and a shell on the core. The core includes copper, and the shell includes copper nitride. The die attach material may be an ink or a paste.

[0066] In some examples, the plurality of core-shell particles is dispersed in a solution. In some examples, the solution includes ethylene glycol. In some examples, the plurality of core-shell particles is grafted to a polymer matrix.

[0067] In some instances, the core has a size of about 1 μm or less, in some instances, the core has a size in the range of about 1 μm to about 50 μm, and in some instances, the shell has a thickness in the range of about 50 nm to about 100 nm.

[0068] In some examples, the die attach material is lead (Pb) free. Another exemplary embodiment of the present disclosure relates to a device including a semiconductor die comprising a wide bandgap semiconductor material, a substrate, and a die attach material between the semiconductor die and the substrate, the die attach material including a plurality of bonded conductive particles and a metal nitride.

[0069] In some examples, the plurality of bonded conductive particles comprises a plurality of bonded copper particles, hi some examples, the metal nitride comprises copper nitride. In some examples, the substrate comprises a conductive substrate. In some examples, the semiconductor die comprises one or more transistor devices. In some examples, the semiconductor die includes silicon carbide. In some examples, the semiconductor die comprises a III-nitride.

[0070] In some examples, the metal nitride is dispersed among the plurality of bonded conductive particles. In some examples, the substrate comprises a lead frame of a semiconductor package. In some examples, the device is a discrete power semiconductor package. In some examples, the device is a power module.

[0071] Another exemplary embodiment of the present disclosure relates to a device including a substrate, a sintered material on the substrate, the sintered material comprising a plurality of bonded copper particles and copper nitride.

[0072] In some instances, the sintered material forms a die attach material for the device. In some instances, the sintered material forms an antenna for the device. In some instances, the sintered material forms an interconnect for the device.

[0073] In some examples, the copper nitride is dispersed among the plurality of bonded copper particles. Another exemplary embodiment of the present disclosure relates to a method including depositing a die attach material on a substrate, the die attach material comprising a plurality of core-shell particles, each core-shell particle comprising a core and a shell on the core, the core comprising a conductive material, and the shell comprising a metal nitride, and bonding the die attach material.

[0074] In some examples, bonding the die attach material includes bonding the die attach material at a temperature in a range of about 100°C to about 300°C. In some examples, bonding the die attach material includes bonding the die attach material for a time period ranging from about 30 minutes to about 120 minutes.

[0075] In some examples, bonding the die attach material includes bonding the die attach material at a pressure in a range of about 1 MPa to about 30 MPa. In some examples, depositing the die attach material onto the substrate includes depositing the die attach material by one or more of an inkjet, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, or a spray coater.

[0076] In some examples, bonding the die attach material includes sintering the die attach material. In some examples, bonding the die attach material includes bonding the die attach material with a laser or with pulsed light.

[0077] In some instances, bonding the die attach material forms an antenna or interconnect on the substrate. In some examples, bonding the die attach material attaches a semiconductor die to the substrate.

[0078] In some examples, the core comprises copper, hi some examples, the metal nitride comprises copper nitride. In some instances, bonding the die attach material decomposes the die attach material into metal and nitrogen gas.

[0079] Another exemplary embodiment of the present disclosure relates to a method comprising oxidizing a plurality of conductive particles to form a plurality of oxidized conductive particles, and adding the oxidized conductive particles to a solution to form a metal nitride shell on the conductive particles, the solution comprising a compound, the compound including hydrogen and nitrogen.

[0080] In some examples, the conductive particles comprise copper particles, hi some examples, the metal nitride shell comprises copper nitride. In some examples, the compound is ammonia. In some examples, the compound is urea. In some examples, the solution further comprises methanol.

[0081] In some examples, the method further includes heating the solution having the oxidized conductive particles to produce a plurality of core-shell particles. In some examples, heating the solution includes heating the solution to a temperature in the range of about 180°C to about 250°C. In some examples, heating the solution includes heating the solution for a process period. In some examples, the process period is in the range of about 1 hour to about 6 hours.

[0082] In some examples, the method further includes adding the core-shell particles to a second solution to form an ink or paste. In some examples, the second solution is ethylene glycol. In some examples, the method includes mixing the core-shell particles with a polymer to form an ink or paste.

[0083] Although the present subject matter has been described in detail with reference to certain exemplary embodiments thereof, it will be understood that those skilled in the art, upon understanding the foregoing, may readily generate modifications to, variations of, and equivalents to, such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than limitation, and the disclosure of the subject matter does not exclude the inclusion of such modifications, variations, and / or additions to the subject matter as would be readily apparent to those skilled in the art.

Claims

1. A die attach material comprising: a plurality of core-shell particles, each core-shell particle comprising a core and a shell on said core; the core comprises a conductive material; The die attach material, wherein the shell comprises a metal nitride.

2. The die attach material according to claim 1, The metal nitride reduces oxidation of the core.

3. The die attach material according to claim 1, The die attach material is an ink.

4. The die attach material according to claim 1, The die attach material is a paste.

5. The die attach material according to claim 1, A die attach material, wherein the metal nitride decomposes into metal and nitrogen gas during bonding of the die attach material.

6. The die attach material according to claim 1, The conductive material of the core comprises copper.

7. The die attach material according to claim 6, The die attach material, wherein the metal nitride comprises copper nitride.

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

9. The die attach material according to claim 8, The die attach material, wherein the solution includes ethylene glycol.

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

11. The die attach material according to claim 1, The core of the die attach material has a size of about 1 μm or less.

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

13. The die attach material according to claim 1, The shell has a thickness in the range of about 50 nm to about 100 nm.

14. A die attach material comprising: a plurality of core-shell particles, each core-shell particle comprising a core and a shell on said core; the core comprises copper and the shell comprises copper nitride; The die attach material is an ink or a paste.

15. The die attach material according to claim 14, The die attach material, wherein the plurality of core-shell particles are dispersed in a solution.

16. The die attach material according to claim 15, The die attach material, wherein the solution includes ethylene glycol.

17. The die attach material according to claim 14, The die attach material, wherein the plurality of core-shell particles are grafted to a polymer matrix.

18. The die attach material according to claim 14, The core of the die attach material has a size of about 1 μm or less.

19. The die attach material according to claim 14, The core of the die attach material has a size in the range of about 1 μm to about 50 μm.

20. The die attach material according to claim 14, The shell has a thickness in the range of about 50 nm to about 100 nm.

21. The die attach material according to claim 14, The die attach material does not contain lead (Pb).

22. A device, a semiconductor die comprising a wide bandgap semiconductor material; A substrate; a die attach material between the semiconductor die and the substrate, the die attach material comprising a plurality of bonded conductive particles and a metal nitride; A device comprising:

23. 23. The device of claim 22, The device, wherein the plurality of bonded conductive particles comprises a plurality of bonded copper particles.

24. 23. The device of claim 22, The device, wherein the metal nitride comprises copper nitride.

25. 23. The device of claim 22, The device, wherein the substrate comprises a conductive substrate.

26. 23. The device of claim 22, The device, wherein the semiconductor die comprises one or more transistor devices.

27. 23. The device of claim 22, The device, wherein the semiconductor die comprises silicon carbide.

28. 23. The device of claim 22, The device, wherein the semiconductor die comprises a Group III nitride.

29. 23. The device of claim 22, The device, wherein the metal nitride is dispersed among the plurality of bonded conductive particles.

30. 23. The device of claim 22, The device, wherein the substrate comprises a lead frame of a semiconductor package.

31. 23. The device of claim 22, The device is a discrete power semiconductor package.

32. 23. The device of claim 22, The device is a power module.

33. A device, A substrate; a sintered material on the substrate; Equipped with The device, wherein the sintered material comprises a plurality of bonded copper particles and copper nitride.

34. 34. The device of claim 33, The sintered material forms a die attach material for the device.

35. 34. The device of claim 33, The sintered material forms an antenna for the device.

36. 34. The device of claim 33, The sintered material forms an interconnect for the device.

37. 34. The device of claim 33, The copper nitride is dispersed among the plurality of bonded copper particles.

38. 1. A method comprising: depositing a die attach material on a substrate, the die attach material comprising a plurality of core-shell particles, each core-shell particle comprising a core and a shell on the core, the core comprising a conductive material, and the shell comprising a metal nitride; Bonding the die attach material; The method comprises:

39. 39. The method of claim 38, The method, wherein bonding the die attach material comprises bonding the die attach material at a temperature in a range of about 100°C to about 300°C.

40. 39. The method of claim 38, The method, 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.

41. 39. The method of claim 38, The method, wherein bonding the die attach material comprises bonding the die attach material at a pressure in a range of about 1 MPa to about 30 MPa.

42. 39. The method of claim 38, The method, wherein depositing a die attach material onto the substrate comprises depositing the die attach material by one or more of an inkjet, a screen printer, a flexographic printer, a gravure printer, a spin coater, a blade coater, or a spray coater.

43. 39. The method of claim 38, The method, wherein bonding the die attach material comprises sintering the die attach material.

44. 39. The method of claim 38, The method, wherein bonding the die attach material comprises bonding the die attach material using a laser or using pulsed light.

45. 39. The method of claim 38, The method, wherein bonding the die attach material forms an antenna or interconnect on the substrate.

46. 39. The method of claim 38, The method, wherein bonding the die attach material attaches a semiconductor die to the substrate.

47. 39. The method of claim 38, The method wherein the core comprises copper.

48. 39. The method of claim 38, The method, wherein the metal nitride comprises copper nitride.

49. 39. The method of claim 38, The method, wherein bonding the die attach material decomposes the die attach material into metal and nitrogen gas.

50. 1. A method comprising: oxidizing the plurality of conductive particles to form a plurality of oxidized conductive particles; adding the oxidized conductive particles to a solution to form a metal nitride shell on the conductive particles, the solution including a compound, the compound including hydrogen and nitrogen; The method comprises:

51. 51. The method of claim 50, The method, wherein the conductive particles comprise copper particles.

52. 51. The method of claim 50, The method, wherein the metal nitride shell comprises copper nitride.

53. 51. The method of claim 50, The method wherein the compound is ammonia.

54. 51. The method of claim 50, The method, wherein the compound is urea.

55. 51. The method of claim 50, The method, wherein the solution further comprises methanol.

56. 51. The method of claim 50, The method further comprises heating the solution having the oxidized conductive wire particles to produce a plurality of core-shell particles.

57. 57. The method of claim 56, The method, wherein heating the solution comprises heating the solution to a temperature in the range of about 180°C to about 250°C.

58. 57. The method of claim 56, The method, wherein heating the solution comprises heating the solution for a process period.

59. 59. The method of claim 58, The process duration is in the range of about 1 hour to about 6 hours.

60. 57. The method of claim 56, further comprising: adding the core-shell particles to a second solution to form an ink or paste.

61. 61. The method of claim 60, The method wherein the second solution is ethylene glycol.

62. 57. The method of claim 56, further comprising: mixing the core-shell particles with a polymer to form an ink or paste.

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