Metal nitride core-shell particle chip bonding material

Abstract

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

Description

[0001] Priority Declaration

[0002] This application is based upon and claims the benefit of priority to U.S. patent application No. 18 / 169,518, filed on February 15, 2023. This application claims priority to, the benefit of, and incorporates by reference in its entirety, the cited application. Technical Field

[0003] The present disclosure generally relates to chip attach materials (die-attach materials). Background Art

[0004] Semiconductor devices (including power semiconductor devices based on wide bandgap materials) can be formed on semiconductor wafers as part of the semiconductor manufacturing process. The semiconductor wafer can be cut into many individual pieces, each piece containing one or more semiconductor devices. Each of these pieces can be a semiconductor die. As part of a semiconductor device package, the semiconductor die may need to be bonded to other components. 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 discrete power semiconductor package or power module. The material used to bond the semiconductor die to other components may need to provide thermal, mechanical, and / or electrical connections to the semiconductor die. Summary of the Invention

[0005] Aspects and advantages of the disclosed embodiments will be set forth in part in the following description, or may be learned from the description, or may be learned through practice of the disclosed embodiments.

[0006] An 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 a conductive material. The shell includes a metal nitride.

[0007] 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 ink or paste.

[0008] Another exemplary embodiment of the present disclosure relates to a device. The device includes a semiconductor die comprising a wide-bandgap semiconductor material. The device includes a substrate. The device includes a die attach material between the semiconductor die and the substrate. The die attach material includes a plurality of bonded conductive particles and a metal nitride.

[0009] Another exemplary embodiment of the present disclosure relates to a device. The device includes a substrate. The device includes a sintered material on the substrate. The sintered material includes a plurality of bonded copper particles and copper nitride.

[0010] Another exemplary embodiment of the present disclosure relates to a method. The method includes 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, wherein the core comprises a conductive material and the shell comprises a metal nitride. The method includes bonding the die attach material.

[0011] Another exemplary embodiment of the present disclosure relates to a method. The method includes oxidizing a plurality of conductive particles to form a plurality of oxidized conductive particles. The method includes adding the oxidized conductive particles to a solution containing a compound containing hydrogen and nitrogen to form a metal nitride shell on the conductive particles.

[0012] 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 the relevant principles. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] This specification discusses implementation methods for those skilled in the art in detail with reference to the accompanying drawings, wherein:

[0014] Figure 1 An example device is depicted having a semiconductor die attached to a substrate using a die attach material according to an example embodiment of the present disclosure;

[0015] Figure 2 depicts a core-shell particle of a die attach material according to an example embodiment of the present disclosure;

[0016] Figure 3 depicts an example semiconductor device according to an example embodiment of the present disclosure;

[0017] Figure 4 Depicts an example device using a die attach material to form an antenna according to an example embodiment of the present disclosure;

[0018] Figure 5 depicts an example device using a die attach material to form interconnects according to an example embodiment of the present disclosure;

[0019] Figure 6 A flowchart depicting an example method according to an example implementation of the present disclosure; and

[0020] Figure 7 A flowchart of an example method according to an example implementation of the present disclosure is depicted. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to the embodiments, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the embodiments and is not intended to limit the present disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to these embodiments without departing from the scope or spirit of the present disclosure. For example, a feature illustrated or described as part of one embodiment may be used in conjunction with another embodiment to produce yet further embodiments. Therefore, various aspects of the present disclosure are intended to encompass such modifications and variations.

[0022] Example aspects of the present disclosure relate to die attach materials for use in semiconductor applications and other electronic applications, such as wide-bandgap semiconductor device applications. Various technologies used for die attach in the semiconductor industry present challenges and limitations. For example, semi-silver or full-silver sintering process technologies offer acceptable electrical, mechanical, and thermal performance for die attach applications. However, semi-silver or full-silver sintering process technologies are costly and can present a higher risk of electromigration, high voids / porosity, and high thermomechanical stress. Similar limitations can also exist with eutectic Au80Sn20 technology. Semi-sintered or full-sintered copper is a lower-cost option, but offers slightly inferior performance due to the high oxidation sensitivity of copper, especially with small particle sizes. Semi-sintered or full-sintered copper can also present challenges due to the need for low-temperature storage and the use of forming gas during the deposition process to reduce oxidation. Lead (Pb)-based die attach solutions are not the best option for achieving low thermal resistance and efficient current or power density. Furthermore, lead (Pb)-based die attach materials do not meet certain lead-free certification standards.

[0023] An exemplary aspect of the present disclosure relates to a chip bonding material based on core-shell particles. The chip bonding material may include a paste-based or ink-based material, including a plurality of metal core-shell microparticles and / or metal core-shell nanoparticles dispersed in a solution or grafted to a polymer matrix. The structure of the core-shell particles may include a core of a conducting material (e.g., a conductive material), such as copper (Cu). The shell may be on the core. The shell may include a metal nitride, such as copper nitride (Cu3N). Relative to copper particles, metal nitrides may reduce oxidation of the core.

[0024] During the bonding process (e.g., sintering of the die attach material) of the die attach material, the metal nitride may decompose into metal and nitrogen. Some metal nitride may remain in the bonded die attach material. For example, the metal nitride may be dispersed between bonded conductive particles in the bonded die attach material.

[0025] For purposes of illustration and discussion, various aspects of the present disclosure are discussed with reference to die attach materials used to bond semiconductor dies (e.g., silicon carbide-based semiconductor dies, Group 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 bonding to any suitable component without departing from the scope of the present disclosure. In this regard, the term "die attach material" in the present disclosure and claims is intended to refer to any material used to provide a thermal, electrical, and / or mechanical connection between two components.

[0026] The chip bonding material can be deposited on a substrate. A semiconductor die or other component can be placed on the chip bonding material. The chip bonding material can be subjected to a bonding or bonding process (e.g., sintering) to secure the semiconductor die or other component to the chip bonding material. As used herein, the term "bonding" or "bonding process" refers to causing a material to transform from a first form to a second form. The bonding process may or may not require bonding the component to the material. Sintering, reflowing, annealing, curing, exposure to light, and exposure to ultraviolet light are all examples of bonding processes and are encompassed by the term "bonding" or "bonding process" in this disclosure and claims.

[0027] In some examples, the core-shell particles can be dispersed in a solution to form a die attach material that is ink or paste-like. For example, in some embodiments, the core-shell particles can be dispersed in ethylene glycol. In some embodiments, the core-shell particles can be grafted onto a polymer matrix to form a die attach material that is ink or paste-like.

[0028] In some embodiments, the core-shell particles of the chip bonding material can be formed by oxidizing conductive core particles (e.g., copper particles). The oxidized conductive particles can be added to a solution to form a metal nitride shell on each conductive particle. The solution may include a compound. The compound may include hydrogen and nitrogen. For example, the compound may include ammonia (NH3) and / or urea (H2NCONH2). The solution may further include methanol (CH3OH). The solution with the oxidized conductive particles can be heated (e.g., heated in an autoclave) to form core-shell particles. The core-shell particles can be dispersed in a solution (e.g., ethylene glycol) or grafted to a polymer matrix to form an ink or paste.

[0029] Various aspects of the present disclosure provide many technical effects and benefits. For example, compared to chip bonding materials based solely on, for example, copper particles, chip bonding materials comprising core-shell particles having a metal nitride shell can provide enhanced aging stability, lower defects and voids, lower annealing temperatures and lower pressures, and higher thermomechanical and electrical properties. In the example where the core-shell particles include a copper core having a copper nitride shell, the copper nitride shell can protect the copper core particles from oxidation. The chip bonding material can require a relatively low annealing temperature and a relatively low pressure during the bonding process (e.g., relative to chip bonding materials based solely on copper particles). In addition, the bonding process can be performed without the flow of forming gas. The chip bonding material does not contain lead and can meet certain lead-free certification standards.

[0030] It should be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of this disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items.

[0031] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an", and "the" also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprises", "comprising", "including", and / or "having" when used herein specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. It should also be understood that the terms used herein should be interpreted as having the same meaning as they have in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0033] It should be understood that when an element, such as a layer, region, or substrate, is referred to as being "on" or extending "on" another element, it can be directly on or directly extend onto the other element, or 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. It should also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0034] 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 illustrated in the figures. It should be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0035] Embodiments of the present disclosure are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments (and intermediate structures) of the invention. For clarity, the thicknesses of layers and regions in the drawings may be exaggerated. In addition, deviations from the shapes of the views are to be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be interpreted as limited to the specific shapes of the regions shown herein, but should include deviations in shape due to, for example, manufacturing. Similarly, it should be understood that variations in size are to be expected based on standard deviations in manufacturing procedures. As used herein, "approximately" or "about" includes values ​​within 10% of the nominal value.

[0036] Throughout, the same numbers represent the same elements. Therefore, even if not mentioned and described in the corresponding drawings, the same or similar numbers can be described with reference to other drawings. In addition, the elements not marked with reference numbers can be described with reference to other drawings.

[0037] 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 in the 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. Certain materials may be represented by "+" or "-" (as in N+, N-, P+, P-, N++, N--, P++, P--, etc.) to indicate a relatively greater ("+") or lesser ("-") concentration of majority carriers compared to another layer or region. However, such notation does not imply the presence of a particular concentration of majority carriers or minority carriers in a layer or region.

[0038] In the drawings and specification, typical embodiments have been disclosed, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limiting the scope set forth in the appended claims.

[0039] Referring now to the drawings, example embodiments of the present disclosure will be described.

[0040] Figure 1 A cross-sectional view of a semiconductor device 100 according to an example embodiment of the present disclosure is depicted. The semiconductor device 100 may include a substrate 102. The substrate 102 may be, for example, a lead frame or other supporting 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.

[0041] 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 variety of power devices that may be used in different applications, including, for example, power switching devices and / or power amplifiers. 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 (laterally 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.).

[0042] In some embodiments, the semiconductor die 104 can be made of 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 of wide-bandgap semiconductor materials such as silicon carbide (e.g., alpha silicon carbide has a bandgap of 2.996 eV at room temperature) and group III nitrides (e.g., gallium nitride has a bandgap of 3.36 eV at room temperature) can provide higher electric field breakdown strength and higher electron saturation velocity.

[0043] For purposes of illustration and discussion, various aspects of the present disclosure are discussed with reference to wide bandgap semiconductors. Using the disclosure provided herein, one of ordinary skill in the art will understand that the die attach materials according to example embodiments of the present disclosure can be used with any semiconductor material or other material without departing from the scope of the present disclosure.

[0044] Semiconductor die 104 may be bonded to substrate 102 using die attach material 106. Die attach material 106 may include a plurality of core-shell particles. The particles may be nucleocapsid particles. Nucleocapsid particles are particles having a core (e.g., a core) surrounded by a shell material. Die attach material 106 may be subjected to a bonding process to mechanically, thermally, and / or electrically connect semiconductor die 104 to substrate 102.

[0045] Figure 2 Various aspects of a die attach material 106 according to example embodiments of the present disclosure are depicted. 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 disposed 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 (Cu3N).

[0046] In some embodiments, core-shell particles 108 may be nanoparticles. For example, the core 110 of each core-shell particle 108 may have a size less than about 1 μm. In some embodiments, core-shell particles 108 may be microparticles. For example, the core 110 of each core-shell particle 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.

[0047] In some examples, see below. Figure 7 As discussed in more detail, conductive particle cores 110 (e.g., copper particles) can be subjected to an oxidation process 114 to form an oxide shell 116 (e.g., copper oxide (Cu2O, CuO)) on each core 110 to form core-shell particles 108. The oxidation process 114 can include, for example, immersion in a NaOH solution, use of a plasma-based oxidation process, exposure to oxygen, etc. The oxidized cores 110 having oxide shells 116 can be subjected to a process 118 that forms a metal nitride shell 112 in place of the oxide shells 116. For example, the cores 110 having oxide shells 116 can be mixed with a solution containing a compound. The compound can include hydrogen and nitrogen. For example, the compound can include ammonia (NH3) and / or urea (H2NCONH2). The solution can further include methanol (CH3OH). The solution having the oxidized conductive particle cores can be heated (e.g., in an autoclave) to form the core-shell particles 108.

[0048] In some examples, the core-shell particles 108 can 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 can be, for example, ethylene glycol. In some examples, the core-shell particles 108 can be mixed with or grafted to a polymer matrix to form an ink or paste prior to bonding. The conductive ink or paste can be deposited (e.g., deposited on a substrate) using an inkjet, dispenser, screen printer, flexographic printer, gravure printer, spin coater, blade coater, spray coater, or other deposition technique. Figure 1 The die attach material 106 may be subjected to a bonding process to transform the die attach material 106 from the first form 124 to the second form 126.

[0049] Figure 2 The die attach material 106 is depicted as transforming from a first form 124 to a second form 126 due to bonding 120 of the die attach material 106. Bonding 120 may include sintering, reflowing, annealing, curing, exposure to light, exposure to ultraviolet light, exposure to laser, exposure to pulsed light, or other suitable processes to transform the form of the die attach material 106. Figure 2 In an example, bonding 120 may include sintering to form a sintered material.

[0050] like Figure 2 As shown, after bonding 120, the conductive particle cores 110 may be bonded together to form bonded conductive particle cores 110. The metal nitride shells 112 may decompose into metal (e.g., copper) and nitrogen. A portion of the metal nitride 122 may remain in the die attach material 106. For example, a portion of the metal nitride 122 may be dispersed between some of the bonded conductive particle cores 110.

[0051] Figure 3-5 An example device including a die attach material according to an example embodiment of the present disclosure is depicted. Figure 3-5 For illustration and discussion purposes. Using the disclosure provided herein, one of ordinary skill in the art will appreciate that the die attach material can be used in a variety of devices and / or applications without departing from the scope of the present disclosure.

[0052] Figure 3 Depicted is a cross-sectional view of a portion of a power module 128 according to an example embodiment of the present disclosure. Figure 3The structures are intended to be shown for identification and description and are not intended to be shown 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 bonded using a die attach material 106 according to an example 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 bonding 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.

[0053] Figure 4 A device 140 is depicted that incorporates a die attach material to form an antenna 142 for the device 140, according to an example embodiment of the present disclosure. More particularly, the device 140 can include a substrate 144, such as a dielectric substrate 144. The dielectric substrate 144 can 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 can be deposited on the substrate 144 using an inkjet, screen printer, flexographic printer, gravure printer, spin coater, knife coater, spray coater, or other deposition technique. The die attach material 106 can be subjected to a bonding process to form the antenna 142 on the substrate 144.

[0054] Figure 5 Depicted is 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 example embodiment of the present disclosure. Figure 5 The structure is intended to be shown for identification and description purposes only and is not intended to be shown to physical scale. Device 148 may include a first layer 150 having one or more conductive portions or other portions that require thermal and / or electrical connection. 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 that require thermal and / or electrical connection. 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 within or on the insulating layer (e.g., in one or more gaps in the patterned insulating layer 154) and subjected to a bonding process to form interconnects 156 for device 148. Interconnects 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.

[0055] Figure 6 A flow chart of an example method 200 is depicted according to an example implementation of the present disclosure. Figure 6 Example method steps are depicted for purposes of illustration and discussion. Using the disclosure provided herein, one of ordinary skill in the art will understand that the methods described in this disclosure may be adjusted, modified, include steps not shown, omitted, and / or rearranged without departing from the scope of this disclosure.

[0056] At 202, the method may include depositing a die attach material on a substrate. The die attach material may be any of the example die attach materials discussed herein. For example, the die attach material may be a reference Figure 1 and Figure 2 The die attach material 106 is discussed. In some embodiments, the die attach material can be deposited on the substrate using an inkjet, screen printer, flexographic printer, gravure printer, spin coater, doctor blade coater, spray coater, or other deposition technique.

[0057] 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 semiconductor and / or a Group III nitride semiconductor. The semiconductor die may include one or more devices, such as one or more transistors, one or more diodes, or other devices.

[0058] At 206, the method may include bonding a die attach material to bond the semiconductor die to the substrate. Bonding may include subjecting the die attach material to any bonding process, such as sintering, reflowing, annealing, curing, laser exposure, pulsed light exposure, ultraviolet radiation exposure, or other processes.

[0059] In one example, bonding can include sintering the die attach material by exposing the die attach material to heat and / or pressure. For example, sintering the die attach material can 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 30 minutes to 120 minutes. The temperature can be selected so as not to liquefy the die attach material or cause reflow. Sintering the die attach material can also include subjecting the die attach material to pressure by applying a force to the semiconductor die. The force can be applied by applying a flat punch or other tool to the semiconductor die. The pressure range can be in the range of 1 MPa to about 30 MPa, such as about 5 MPa to about 25 MPa, such as about 10 MPa to about 20 MPa. The time period for applying pressure can be about 1 minute to about 15 minutes. The sintering process parameters provided in this disclosure are for example purposes only. Other sintering process parameters can be used without departing from the scope of this disclosure.

[0060] Other exemplary bonding processes may be performed on the die attach material without departing from the scope of this disclosure. For example, in some embodiments, the die attach material may be exposed to laser light. 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.

[0061] During the bonding process, the metal nitride can decompose into metal and nitrogen. For example, in the example of a copper core particle with a copper nitride shell, the copper nitride can decompose as follows during the bonding process:

[0062] 2Cu3N→6Cu+N2

[0063] Figure 7 A flow chart is depicted of an example method 300 of forming core-shell particles of a die attach material according to an example embodiment of the present disclosure. Figure 7 Example method steps are depicted for purposes of illustration and discussion. Using the disclosure provided herein, one of ordinary skill in the art will understand that the methods described in this disclosure may be adjusted, modified, include steps not shown, omitted, and / or rearranged without departing from the scope of this disclosure.

[0064] refer to Figure 7 At 302, method 300 may include forming conductive particles 302. The conductive particles will serve as cores of core-shell particles of a die attach material. The conductive particles may be formed, for example, from copper. Various 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.

[0065] Example nuclear precursors may include, for example, one or more of copper sulfate (CuSO4), copper nitrate (Cu(NO3)2), copper chloride (CuCl2), copper acetate (Cu(CO2CH3)2), nickel acetate (Ni(CH3CO2)2), nickel sulfate (NiSO4), etc. Example stabilizers may include one or more of the following: polyvinyl pyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), ethylenediamine (EDA), dimethylhydantoin (DMH), citric acid HOC(CO2H)(CH2CO2H)2, etc. Example reducing agents may include ethylene glycol (EG), sodium borohydride (NaBH4), sodium dihydrogen phosphate (NaH2PO4), glucose (C6H 12 O6), dimethylamine borane (DMAB), ascorbic acid (C6H8O6), PVP, etc.

[0066] At 304, method 300 can include cleaning the conductive particles. For example, the solution containing the conductive particles can be rinsed with ethanol and / or deionized water and then filtered.

[0067] At 306, method 300 may include oxidizing the conductive particles to form oxidized conductive particles. The oxidized conductive particles may include an oxide shell (e.g., Cu2O or CuO shell). The conductive particles may be oxidized in a variety of ways without departing from the scope of the present disclosure. For example, the conductive particles may be oxidized by immersing them in a NaOH solution, using a plasma-based oxidation process, exposing them to oxygen, and the like.

[0068] 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 (Cu3N) shell. The solution may contain a compound. The compound may include hydrogen and nitrogen. For example, the compound may include ammonia (NH3) and / or urea (H2NCONH2). The solution may further include methanol (CH3OH).

[0069] At 310, method 300 may include heating a solution having 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 treatment period in the range of about 1 hour to about 6 hours. The core-shell particles may be rinsed (e.g., with ethanol and / or deionized water) and filtered.

[0070] At 312, method 300 may include adding the core-shell particles to a solution to form an ink or paste. For example, method 300 may include adding the core-shell particles to a solution including ethylene glycol. Method 300 may include, at 312, mixing the core-shell particles with a polymer to form an ink or paste.

[0071] The following provides Figure 7 Specific examples of example embodiments forming die attach materials:

[0072] Example

[0073] In a solution of NaH2PO4 as a reducing agent and citric acid as a stabilizer, at a temperature in the range of about 120°C to about 150°C and at a pH of about 5.5 to about 6.5, stirring for a treatment period of about 30 minutes to about 60 minutes, copper particles are obtained by reducing CuSO4 (0.1M). The solution is then rinsed (e.g., with ethanol / deionized water) and filtered. The surface of the copper particles is oxidized by immersing them in a NaOH solution (0.1-1M) at high temperature to form copper particles with a copper oxide shell. Subsequently, the oxidized particles are added to a solution of liquid ammonia NH3 and methanol CH3OH and heated in an autoclave at a high temperature in the range of about 180°C to about 250°C for a treatment period of about 1 hour to about 6 hours to produce core-shell particles with a copper core and a copper nitride shell. Replacing the oxide shell with a copper nitride shell can be represented as follows:

[0074] 3Cu2O+2NH3→2Cu3N+3H2O

[0075] The final product is then washed (e.g., ethanol / deionized water), filtered, and functionalized before being dispersed in a solvent or mixed / grafted with a polymer to make an ink or paste.

[0076] The following describes exemplary aspects of the present disclosure. Any of the following features or examples may be used in combination with any embodiment or feature provided by the present disclosure.

[0077] An 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 a conductive material. The shell includes a metal nitride.

[0078] In some examples, the metal nitride reduces oxidation of the core.

[0079] In some examples, the die attach material is an ink. In some examples, the die attach material is a paste.

[0080] In some examples, the metal nitride decomposes into metal and nitrogen during the bonding process of the die attach material.

[0081] In some examples, the conductive material of the core includes copper. In some examples, the metal nitride includes copper nitride.

[0082] In some examples, the plurality of core-shell particles are dispersed in a solution. In some examples, the solution includes ethylene glycol. In some instances, the plurality of core-shell particles are grafted to a polymer matrix.

[0083] In some examples, the core has a size of about 1 μm or less. In some examples, the core has a size in a range of about 1 μm to about 50 μm. In some examples, the shell has a thickness in a range of about 50 nm to about 100 nm.

[0084] 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 in the form of ink or a paste.

[0085] In some examples, the plurality of core-shell particles are dispersed in a solution. In some examples, the solution includes ethylene glycol. In some instances, the plurality of core-shell particles are grafted to a polymer matrix.

[0086] In some examples, the core has a size of about 1 μm or less. In some examples, the core has a size in a range of about 1 μm to about 50 μm. In some examples, the shell has a thickness in a range of about 50 nm to about 100 nm.

[0087] In some examples, the die attach material is lead (Pb) free.

[0088] Another example embodiment of the present disclosure relates to a device. The device includes a semiconductor die containing a wide-bandgap semiconductor material. The device includes a substrate. The device includes a die attach material between the semiconductor die and the substrate. The die attach material includes a plurality of bonded conductive particles and a metal nitride.

[0089] In some examples, the plurality of bonded conductive particles includes a plurality of bonded copper particles. In some examples, the metal nitride includes copper nitride.

[0090] 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 comprises silicon carbide. In some examples, the semiconductor die comprises a Group III nitride.

[0091] In some examples, the metal nitride is interspersed between the plurality of bonded conductive particles.

[0092] In some examples, the substrate includes a lead frame of a semiconductor package.

[0093] In some examples, the device is a discrete power semiconductor package. In some examples, the device is a power module.

[0094] Another exemplary embodiment of the present disclosure relates to a device. The device includes a substrate. The device includes a sintered material on the substrate. The sintered material includes a plurality of bonded copper particles and copper nitride.

[0095] In some examples, the sintered material forms a die attach material for a device.

[0096] In some examples, the sintered material forms an antenna for a device.

[0097] In some examples, the sintered material forms interconnects for a device.

[0098] In some examples, copper nitride is interspersed between the plurality of bonded copper particles.

[0099] Another exemplary embodiment of the present disclosure relates to a method. The method includes 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, wherein the core comprises a conductive material and the shell comprises a metal nitride. The method includes bonding the die attach material.

[0100] In some examples, adhering the die attach material includes bonding the die attach material at a temperature in a range from about 100°C to about 300°C.

[0101] In some examples, bonding the die attach material includes bonding the die attach material for a time period in a range from about 30 minutes to about 120 minutes.

[0102] In some examples, bonding the die attach material includes bonding the die attach material under a pressure in a range from about 1 MPa to about 30 MPa.

[0103] In some examples, depositing the die attach material on 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 doctor blade coater, or a spray coater.

[0104] In some examples, bonding the die attach material includes sintering the die attach material.

[0105] In some examples, bonding the die attach material includes bonding the die attach material with a laser or with pulsed light.

[0106] In some examples, an antenna or interconnect is formed on a substrate in combination with the die attach material.

[0107] In some examples, the semiconductor die is attached to a substrate in combination with the die attach material.

[0108] In some examples, the core comprises copper. In some examples, the metal nitride comprises copper nitride.

[0109] In some examples, the die attach material is combined with the die attach material to decompose the die attach material into metal and nitrogen.

[0110] Another exemplary embodiment of the present disclosure relates to a method. The method includes oxidizing a plurality of conductive particles to form a plurality of oxidized conductive particles. The method includes adding the oxidized conductive particles to a solution containing a compound containing hydrogen and nitrogen to form a metal nitride shell on the conductive particles.

[0111] In some examples, the conductive particles include copper particles. In some examples, the metal nitride shell includes copper nitride.

[0112] In some examples, the compound is ammonia. In some examples, the compound is urea. In some examples, the solution further comprises methanol.

[0113] In some examples, the method further includes heating the solution containing 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 treatment period. In some examples, the treatment period is in the range of about 1 hour to about 6 hours.

[0114] 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 the ink or paste.

[0115] Although the subject matter has been described in detail with respect to specific example embodiments, it should be understood that those skilled in the art may readily make changes, variations, and equivalents to such embodiments upon gaining an understanding of the foregoing. Accordingly, the scope of the present disclosure is by way of example and not by way of limitation, and the present disclosure does not exclude the inclusion of such changes, variations, and / or additions to the subject matter as would be readily apparent to one of ordinary skill in the art.

Claims

1. A die bonding material comprising: a plurality of core-shell particles, each core-shell particle comprising a core and a shell on the core; wherein the core comprises a conductive material; and wherein the shell comprises a metal nitride. 2 . The die attach material according to claim 1 , wherein the metal nitride reduces oxidation of the core. The die attach material according to claim 1 , wherein the die attach material is ink. The die attach material according to claim 1 , wherein the die attach material is a paste. 5 . The die attach material according to claim 1 , wherein the metal nitride decomposes into metal and nitrogen during bonding of the die attach material. The die attach material of claim 1 , wherein the conductive material of the core comprises copper. 7 . The die attach material of claim 6 , wherein the metal nitride comprises copper nitride. The die attach material according to 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. The die attach material according to claim 1 , wherein the core has a size of about 1 μm or less. 12 . The die attach material of claim 1 , wherein the core has a size in a range from about 1 μm to about 50 μm. 13 . The die attach material of claim 1 , wherein the shell has a thickness in a range from about 50 nm to about 100 nm.

14. A chip bonding material comprising: a plurality of core-shell particles, each core-shell particle comprising a core and a shell on the core; wherein the core comprises copper and the shell comprises copper nitride; and The die bonding material is ink or paste. The die attach material according to claim 14 , wherein the plurality of core-shell particles are dispersed in a solution. The die attach material of claim 15 , wherein the solution comprises ethylene glycol.

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

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

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

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

21. The die attach material of claim 14, wherein the die attach material is free of lead (Pb).

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

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

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

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

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

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

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

29. The device of claim 22, wherein the metal nitride is interspersed between the plurality of bonded conductive particles.

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

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

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

33. A device comprising: substrate; and A sintered material is provided on the substrate, wherein the sintered material comprises a plurality of bonded copper particles and copper nitride.

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

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

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

37. The device of claim 33, wherein copper nitride is interspersed between the plurality of bonded copper particles.

38. 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, wherein the core comprises a conductive material and the shell comprises a metal nitride; as well as The die attach material is bonded.

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

40. The method of claim 38, wherein bonding the die attach material comprises bonding the die attach material for a time period in a range from about 30 minutes to about 120 minutes.

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

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

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

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

45. The method of claim 38, wherein an antenna or interconnect is formed on the substrate in combination with the die attach material.

46. ​​The method of claim 38, wherein a semiconductor die is attached to the substrate in conjunction with the die attach material.

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

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

49. The method of claim 38, wherein the die attach material is decomposed into metal and nitrogen in conjunction with the die attach material.

50. A method comprising: oxidizing the plurality of conductive particles to form a plurality of oxidized conductive particles; as well as The oxidized conductive particles are added to a solution containing a compound comprising hydrogen and nitrogen to form a metal nitride shell on the conductive particles.

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

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

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

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

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

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

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

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

59. The method of claim 58, wherein the treatment period is in the range of about 1 hour to about 6 hours.

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

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

62. 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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