Patent ID: 12205910

It should be understood that the reference number for any illustrated element that appears in multiple different figures has the same meaning across the multiple figures, and the mention or discussion herein of any illustrated element in the context of any particular figure also applies to each other figure, if any, in which that same illustrated element is shown.

DETAILED DESCRIPTION

Embodiments of the invention provide multi-material toothed bond pads, methods for forming such bond pads, and method for improved bonding of IC devices using such bond pads.

FIGS.3A and3Bshow cross-sectional side views showing the bonding of a die300to a mounting structure302using at least one multi-material toothed bond pad, according to an example embodiment of the present invention.FIG.3Ashows the arrangement prior to bonding, andFIG.3Bshows the arrangement after a solder bond. As used herein, a “mounting structure” may comprise an interposer, a package substrate, or any other integrated circuit device to which one or more die may be mounted.

As shown inFIG.3A, a bond pad304on a bottom side of the die300is aligned over a bond pad306on a top side of the mounting structure302. Bond pad304formed on die300may be formed from copper (Cu), aluminum (Al), nickel (Ni), gold (Au), or any other suitable bond pad material. Multi-material bond pad306may include (a) an array of vertically-extending projections, referred to herein as teeth,320formed from a first metal, and (b) a fill material322comprising a second metal arranged between the various teeth320, such that the two different metals of the teeth320and fill material322are arranged in an interlaced or interleaved manner. Bond pad306may include any number of teeth320, for example in the range of 2 to 10,000 teeth320. The term vertically-extending is used herein in the context of a mounting structure oriented horizontally, e.g., as shown in the various figures. If the relevant mounting structure of any disclosed embodiment is instead oriented vertically, the teeth will extend horizontally.

As used herein, a “tooth” may include any vertically-elongated structure, e.g., in the form of a tooth, spike, spire, blade, tube, or rod; may be symmetrical or asymmetrical around each axis; may or may not be tapered; and may have a sharp, smooth, dull, or rough upper tip or upper end, i.e., a tip or end of the tooth distal from the relevant mounting structure302. Teeth320may be formed from a material that grows a hard native oxide layer, for example aluminum which grows native aluminum oxide (Al2O3), tungsten which grows native tungsten oxide (WO3), or silicon which grows silicon dioxide (SiO2). In some embodiments, the teeth themselves be formed from a hard material, e.g., in the case of tungsten or silicon teeth.

Fill material322may be added between the various teeth320of each toothed bond pad306in any suitable manner, e.g., by depositing a layer of fill material extending down into the spaces between teeth320and removing portions of the fill material covering the tops of teeth320and between adjacent toothed bond pads306. In some embodiments, the fill material322may be added prior to the growth of the native oxide layer (e.g., Al2O3layer) to thereby provide direct contact between the fill material322and teeth320. In such embodiments, the native oxide layer may grow only on surfaces of teeth320that remain exposed after adding fill material322, e.g., surfaces at or near the upper ends or tips of teeth320. For example, in the embodiment shown inFIG.3A, a native oxide layer312comprising aluminum oxide (Al2O3) may form on exposed upper surfaces of each aluminum tooth320, while exposed upper surfaces of the silver fill material may remain substantially free of oxide. In other embodiments, one or more native oxide layer may form on both exposed upper surface areas of each tooth320and exposed upper surface areas of fill material322, depending on the composition of teeth320and fill material322.

Similar to oxide layer312, a thin native oxide layer310may also form on the mounting side of bond pad304(i.e., the side of bond pad304to be mounted to bond pad306), e.g., a native Al2O3or CuO layer, depending on the composition of bond pad304.

Each tooth320having a native oxide layer312formed on the upper end or tip of the tooth320may be referred to herein as an oxidized tooth, indicated at324. The upper ends or tips of the oxidized teeth324included in each bond pad306, including the native oxide layer312on each the upper end or tip of respective tooth320, may collectively define a hard, abrasive structure indicated at326. The abrasive structure326may be suitable for abrading or grinding against the native oxide layer310formed on bond pad304, to abrade, break, and/or remove the native oxide layers310and312on bond pads304and306, respectively, which may allow direct and/or eutectic bonding between the materials of bond pads304and306, as discussed below with reference toFIG.3B.

In some embodiments, teeth320may be roughened prior to formation of the native oxide312. For example, where a chlorine-based plasma etch (dry etch) is used to form the teeth320from an aluminum layer, various process parameters of the chlorine-based plasma etch may be selected or controlled to increase a porosity of the outer surfaces of teeth320(e.g., by creating small fissures or voids in the aluminum). As another example, an HCL wet etch may be performed to increase porosity of the aluminum surfaces.

The fill material322may comprise a metal, metal alloy, or other material that (a) may form a eutectic bond with an opposing bond pad or other bonding structure (e.g., comprising aluminum or copper) at a low eutectic temperature (e.g., below 500° C., below 400° C., or below 300° C.) and/or (b) is softer than the native oxide312formed on teeth320(e.g., Al2O3, WO3, or SiO2in the case of aluminum, tungsten, or silicon teeth320) and/or the material forming teeth320themselves (e.g., in the case of tungsten or silicon teeth320). For example, in some embodiments fill material322may comprise silver, tin, or indium, or a mixture of two or more of silver, tin, indium (e.g., a mixture of 75% Ag and 25% Sn), suitable to form a eutectic bond with an aluminum or copper bond pad306, for example, to form a strong, conductive bond between bond pads304and306. Fill material322may partially or completely fill the spaces between adjacent teeth320, depending on the particular embodiment.

Next, referring toFIG.3B, the die300may be bonded to mounting structure302by direct and/or eutectic bonding. In some embodiments, the die300may be pressed down toward mounting structure302while ultrasonic vibrations (including lateral vibrations) and/or heat are applied to at least one of the die300/bond pad304and mounting structure302/bond pad306. For example, an ultrasonic or thermosonic head may apply downward force, ultrasonic energy (causing vibrations) and/or heat to the die300, which heat is transferred to bond pad304. In addition, the mounting structure302may be heated by heating a chuck that supports the mounting structure302, which heat is transferred to multi-material bond pad306. Alternately, the bonding process may be performed in an oven.

During the ultrasonic or thermosonic bonding process, the abrasive structure326defined by the oxidized teeth324of bond pad306may abrade against the oxide layer310of bond pad304to abrade, break, and/or remove the native oxide layers310and312, allowing direct and/or eutectic bonding between bond pads304and306. For example, in embodiments including aluminum teeth320, the hard aluminum oxide layer312on each tooth320abrades the oxide layer312on bond pad304, and vice versa. In embodiments including harder teeth320, e.g., formed from tungsten or silicon, the teeth320may cooperate with the relevant oxide layer312on teeth320to abrade the oxide layer312on bond pad304.

Depending on the particular process parameters (for example, the selected materials of bond pads304and306, the temperature of bond pads304and306during bonding, the downward force applied to bond pad304, and the vibrational forces/movements caused by the ultrasonic energy), the resulting bonding may involve one or both of (a) direct bonding between bond pads304and306(e.g., between bond pad304, teeth320, and fill material322), and/or (b) eutectic bonding between bond pads304and306, wherein the fill material322(e.g., silver) may help form a eutectic IMC layer330between (a) bond pad304(e.g., aluminum) and (b) the fill material322(e.g., silver) and/or teeth320(e.g., aluminum) of306.

In some embodiments, the oxidized teeth324may be roughened prior to the bonding process, to further enhance the abrasive structure326for facilitating the bonding process. For example, the oxidized teeth324may be further oxidized, e.g., in an ash chamber, to increase the thickness and roughness of the oxide layer312on teeth320. As another example, a hydrogen chloride (HCL) wet etch may be performed on the oxidized teeth324to increase the porosity of the native oxide312and/or underlying tooth metal (e.g., aluminum), which may increase the surface roughness of the oxidized teeth324.

FIGS.4A and4Bshow cross-sectional side views showing a process of bonding two example dies400aand400bto a mounting structure402using multi-material toothed bond pads406, according to one example embodiment. In this example, mounting structure402is an interposer.FIG.4Ashows the arrangement prior to bonding dies400aand400bto interposer402, andFIG.4Bshows the arrangement after bonding dies400aand400b.

Each die400aand400bmay comprise any type of semiconductor die, e.g., a field programmable gate array (FPGA) or other processor die, a microcontroller, a serial/deserializer (SerDes) die, a memory idea, or any other type of die. As shown, each die400a,400bincludes at least one bond pad404formed in a passivation region414. Each bond pad404may be formed from copper (Cu), aluminum (Al), nickel (Ni), gold (Au), or any other suitable bond pad material. Passivation region414may comprise, for example, a region including oxide and oxynitride. A thin native oxide layer410may form on the bottom of each bond pad404.

Interposer402may comprise an interposer or other structure for mounting dies400a,400b, and may be supported on a chuck460. Interposer402may include circuitry including metal layers430formed over a silicon substrate432. Metal layers430may comprise aluminum or copper interconnect layers, for example, formed in a dielectric region434formed over interposer silicon substrate432. Dielectric region434may include any number of oxide layers or other dielectric layers. In some embodiments, interposer402may be a through-silicon via (TSV) interposer, which may include a number of TSV contacts438extending through the interposer silicon substrate432to provide conductive connection between metal layer(s)430to selected circuitry of a package substrate or other structure, e.g., as shown inFIG.5discussed below. In other embodiments, interposer402may be configured for wire-bond attachment to a package substrate or other structure using bond pads408(e.g., as shown inFIG.6, discussed below), and may thus omit TSV contacts438.

A plurality of multi-material toothed bond pads406and (optional) test or wire-bond pads408may be formed on a top side of the interposer402, and connected to a top metal layer430by conductive vias436, e.g., tungsten or copper vias. Each multi-material toothed bond pads406may correspond with bond pad306shown inFIGS.3A-3Band discussed above. Thus, each multi-material toothed bond pad406may include (a) an array of vertically-extending teeth420formed from a first material (e.g., aluminum) and a fill material422comprising a second material (e.g., silver) arranged between the various teeth420, such that the two different materials of the teeth420and fill material422are arranged in an interlaced or interleaved manner.

A native oxide layer412may form on exposed upper surfaces of each tooth420(e.g., an Al2O3layer412in the case of aluminum teeth420) to define oxidized teeth424, e.g., as discussed above regardingFIG.3A. In some embodiments, an underfill layer440, e.g., comprising epoxy, may be formed between bond pads406and/or408, which may provide physical support for dies400a,400b(once mounted) and/or provide a moisture seal for the circuitry of interposer402and dies400a,400b.

Test or wire-bond pads408may be formed together with multi-material toothed bond pads406, but may be formed as a solid metal pad (e.g., aluminum).

Referring toFIG.4B, dies400a,400bmay be bonded to interposer402by direct and/or eutectic bonding, similar to the bonding of die300to mounting structure302discussed above. The resulting populated interposer is indicated at470. For example, dies400a,400bmay be pressed down toward interposer402while heat and ultrasonic vibrations (including lateral vibrations) are applied to one or more relevant structures, e.g., dies400a,400b, bond pads404, interposer402, and/or bond pads406. For example, an ultrasonic or thermosonic head450may apply downward force, ultrasonic energy (causing vibrations) and/or heat to dies400a,400b. In addition, the interposer402and/or bond pads406may be heated by heating the chuck460supporting the interposer402, or by performing the bonding process in an oven.

As discussed above regardingFIG.3A, the upper ends or tips of the oxidized teeth424included in each bond pad406may collectively define a hard, abrasive structure426. During an ultrasonic or thermosonic bonding process, the abrasive structure426defined by oxidized teeth424may be suitable for abrading or grinding against the native oxide layer410formed on bond pads404of dies400a,400b, to abrade, break, and/or remove the native oxide layers410and412on bond pads404and406, respectively, which may allow direct and/or eutectic bonding between the materials of bond pads404and406. In addition, the abrasion caused by the abrasive structure426may generate localized friction heating, which may further facilitate the bonding process. Depending on the particular process parameters (for example, the selected materials of bond pads404and406, the downward force applied to bond pad404by ultrasonic or thermosonic head450, the vibrational forces/movements caused by the ultrasonic energy), and/or the temperature of bond pads404and406during bonding (e.g., as raised by application of heat from head450in embodiments in which head450comprises a thermosonic head, or from an oven, or other heating system), the resulting bonding may involve one or both of (a) direct bonding between each bond pad404and the teeth420and fill material422of the opposing bond pad406, and/or (b) eutectic bonding between each bond pad404and the teeth420and fill material422of the opposing bond pad406, wherein the fill material422may help form a eutectic IMC between bond pads404and406. As indicated above, in one embodiment teeth420are formed of aluminum and fill material422comprises silver.

In some embodiments, as discussed above, the teeth420may be roughened prior to or after formation of native oxide layer412on teeth420, to further enhance the abrasive properties of the oxidized teeth424. For example, teeth420may be roughened prior to formation of the native oxide412by controlling process parameters of a chlorine-based plasma etch to form teeth420to increase a porosity of the outer surfaces of teeth420(e.g., by creating small fissures or voids in the aluminum). As another example, an HCL wet etch may be performed to increase porosity of the surfaces of teeth420. As another example, after formation of the native oxide layer412, the oxidized teeth424may be further oxidized, e.g., in an ash chamber, to increase the thickness and roughness of the oxide layer412on teeth420. As yet another example, a hydrogen chloride (HCL) wet etch may be performed on the oxidized teeth424to increase the porosity of the native oxide412and/or underlying tooth metal (e.g., aluminum), e.g., to increase a surface porosity of a surface porosity of the teeth420to a porosity (percentage of void space) in the range of 5-40%, in some embodiments in the range of 20%-40%.

The populated interposer470shown inFIG.4B, including dies400aand400bbonded to interposer402, may be mounted to a package substrate or other structure in any suitable manner, e.g., using through silicon via (TSV) connections or by wire-bonding.

FIG.5is a cross-sectional side view showing the populated interposer470ofFIG.4Bmounted on a package substrate500, according to one example embodiment. In this embodiment, interposer470is a TSV interposer including a plurality of TSV contacts438, e.g., formed from copper. The package substrate500may include package substrate vias502, e.g., formed from copper, extending through the vertical thickness of the package substrate500. The package substrate500may be mounted to a printed circuit board (PCB)504or other electronic device, e.g., using a ball grid array (BGA)506or other solder mount.

FIG.6is a cross-sectional side view showing the populated interposer470ofFIG.4Bmounted on a package substrate600, according to another example embodiment. In this embodiment, interposer470may be mounted on package substrate600using an adhesive, and conductively connected to package substrate600by wire-bonds602formed between bond pads408on interposer470and bond pads604(e.g., solid aluminum pads) on package substrate600.

FIGS.7A-7Eare cross-sectional side views showing a process for forming a mounting structure including multi-material toothed bond pads, and bonding dies (e.g., horizontally-mounted dies, or HMDs) to such multi-material toothed bond pads, according to one embodiment of the present invention. In this example, the mounting structure is an interposer; however, in other embodiments the mounting structure may be a package substrate or any other suitable integrated circuit device. While the use of aluminum and silver are particularly detailed, this is not meant to be limiting in any way, and other materials may be utilized without exceeding the scope.

Referring first toFIG.7A, an interposer structure700is constructed by forming metal interconnect circuitry on an interposer substrate702(e.g., silicon substrate), which may include any number of metal layers704connected by vias706, formed in a dielectric region710including any number of oxide layers or other dielectric layers. In one example embodiment, metal layers704are formed from aluminum, and vias706are formed from tungsten. In another embodiment, metal layers704may be formed by copper damascene processing.

Next, referring toFIG.7B, a relatively thick aluminum layer (e.g., greater than 1 μm, greater than 2 μm, or greater than 3 μm thick) may be deposited on the top surface712of interposer structure700, and etched, e.g., using a chlorine-based plasma etch (dry etch), to define a plurality of aluminum structures including aluminum teeth720and, in some embodiments, at least one solid aluminum pad740. Each solid aluminum pad740may be a test pad or a wire-bond pad. Aluminum teeth720may be formed in localized groupings722, with each teeth grouping722including an array of individual teeth720separated from each other by open space or voids724. Each teeth grouping722defines a first component of a respective multi-material toothed bond pad being constructed. The illustrated example shows two teeth groupings722for two multi-material toothed bond pads being formed.

Each teeth grouping722may include any number of teeth720arranged in a one- or two-dimensional array of teeth720. Each teeth grouping722may include between 2 and 10,000 teeth720. Each tooth720may have any suitable shape and dimensions. For example, each tooth720may have a tapered shape, e.g., a generally conical or pyramid shape, with a sidewall taper defined by a taper angle θ relative to normal to top surface712. In some embodiments, each tooth720may have one, some or all of the following dimensional characteristics:(a) a vertical height Htooth(in the z-direction) in the range of 1 μm to 5 μm;(b) a lateral width Wtooth(in the x-direction and/or the y-direction into the page) in the range of 0.13 μm to 2 μm, defined at a base of the tooth720;(c) a height-to-width ratio Htooth/Wtoothof at least 2, or at least 3, or at least 4, or at least 5, or at least 10, or in the range of 2 to 10, for example in the range of 3 to 5;(d) a lateral spacing SPteeth(in the x-direction and/or the y-direction into the page) between a central axis of adjacent teeth in the range of 0.3 μm to 10 μm, e.g., in the range of 1 μm to 6 μm; and/or(e) a sidewall taper angle θ in the range of 0° to 45°, e.g., in the range of 5° to 30°.

Adjacent teeth720may be completely spaced apart from each other laterally by open space or voids724(e.g., as shown in the example embodiment ofFIG.7B), or may be physically conjoined for a partial height of the respective teeth720(e.g., such that each tooth720has a lower base portion conjoined with at least one adjacent tooth720and but an upper portion spaced apart (laterally) from each adjacent tooth720.

Each solid aluminum pad740(e.g., test pad or wire-bond pad) may be substantially wider than any one of the teeth720. For example, each solid aluminum pad740may have a width Wpad(in the x-direction and/or the y-direction into the page) in the range of 10 μm to 100 μm, e.g., in the range of 30 μm to 60 μm, and may have the same or different dimensions as each other solid aluminum pad(s)740.

Next, referring toFIG.7C, the exposed surfaces of teeth720, including top surfaces750and sidewall surfaces752, may be roughened, e.g., as discussed above with respect toFIGS.3B and4B. For example, where a chlorine-based plasma etch (dry etch) is used to form the teeth720from an aluminum layer, various process parameters of the chlorine-based plasma etch may be selected or controlled to increase a porosity of the surfaces750,752of teeth720(e.g., by creating small fissures or voids in the aluminum) to a porosity (percentage of void space) in the range of 5-40%, in some embodiments in the range of 20%-40%. As another example, an HCL wet etch may be performed to increase porosity of the aluminum surfaces of teeth720. As still another example, teeth720may be formed from silicon-doped aluminum, and a post-etch process may be performed to form SiO2nano-nodules at the surfaces, thereby increasing the surface roughness.

In some embodiments, the roughening techniques may increase an arithmetic mean roughness Ra of surfaces750,752, for example to a roughness value Ra above 5 nm, above 10 nm, above 15 nm, or above 20 nm.

Next, as shown inFIG.7D, the open spaces or voids724between teeth720in each teeth grouping722may be filled (partially or fully) with a second, different, material, such as silver, indicated at760, to define a multi-material toothed bond pad770from each teeth grouping722. For example, a layer of silver, e.g., with a thickness of 200 Å-2000 Å, may be deposited over the structure (extending over teeth720and the top surface712of interposer structure700) and etched back, e.g., using an anisotropic etch, to partially or fully fill the open spaces or voids724between teeth720in each teeth grouping722, and also cover the outer surfaces752of the outer teeth720in each teeth grouping722, as shown inFIG.7D. The etch may remove the silver layer on the top surfaces750of teeth720, to thereby expose the top teeth surfaces750.

As discussed above, a native oxide layer (Al2O3)764may grow on the exposed top surfaces750of teeth720, to define oxidized teeth754. In some embodiments, the oxidized teeth754may be roughened to further enhance the abrasive nature of the oxidized teeth754. For example, the oxidized teeth754may be further oxidized, e.g., in an ash chamber, to increase the thickness and roughness of the native oxide layer764on teeth720. As another example, a hydrogen chloride (HCL) wet etch may be performed on the oxidized teeth754to increase the porosity of the native oxide764and/or underlying tooth metal (e.g., aluminum), which may increase the surface roughness of the oxidized teeth754.

The oxidized and/or further roughened teeth754included in each multi-material toothed bond pad770may collectively define a hard, abrasive structure configured to abrade against the oxide layer of an opposing bond pad to abrade, break, and/or remove such oxide layer and the oxide layers764on oxidized teeth754, allowing direct and/or eutectic contact between bond pad770and the opposing bond pad, as discussed above.

Finally, as shown inFIG.7E, an underfill774, e.g., comprising an epoxy, may be deposited using a stencil or needle. The height of underfill774may be adjusted as needed based on the shape and/or dimensions of die(s) to be mounted to the interposer700.

As noted above, in some embodiments teeth720may be formed from silicon-doped aluminum (e.g., silicon doping in the range of 0.1 to 5%), and a post-etch process may be performed to form SiO2nano-nodules at the aluminum surfaces, to thereby increase the surface roughness. A rapid thermal anneal (RTA) may be performed to force the Si dopants within the aluminum to agglomerate and form sub-micron nodules. An O2re-ash oxidation process may then be performed to form SiO2nano-nodules at the surfaces of the aluminum teeth720, to thereby increase the surface roughness.

FIG.8illustrates an example of SiO2nano-nodules800formed on the top surfaces750of a pair of aluminum teeth720.

FIGS.9A and9Bshow cross-sectional views of an example process for forming multi-material toothed bond pads including an array of extremely small teeth defining a “grass-like” region, to form a very rough bond pad structure, according to one embodiment of the present invention.

As shown inFIG.9A, three grass-like regions902are formed on a top surface916of a mounting structure, e.g., interposer900, which may be similar to interposer700discussed above, e.g., including metal layers910and vias912formed in a dielectric region914over an interposer substrate920. Each grass-like region902may include an array of narrow teeth, spikes, spires, or “blades”904(referred to as teeth904, for simplicity) separated by open spaces or voids906, to form a grass-like structure. Grass-like regions902may be formed from silicon or aluminum or other suitable metal, and may be formed in any suitable manner. In some embodiments, each grass-like region902may comprise an array of silicon spires. For example, regions of silicon “grass” including an array of teeth904can be grown for each region902. As another example, as known in the art, regions of black-silicon teeth904may be formed by depositing a layer of black silicon and performing reactive ion etching (ME), e.g., as described in “A Survey on the Reactive Ion Etching of Silicon in Microtechnology” by H. V. Jansen, Han Gardeniers, M. J. Boer, M. Elwenspoek, and Jan Fluitman, Journal of Micromechanics and Microengineering, March 1996.

In some embodiments, chemical processing may be performed to produce black silicon with nanopores, which may further increase the roughness of each grass-like region902. It is known in the art that silicon can be conductive, especially when coated with silver or other suitable material, e.g., as fill material in the open spaces or voids906between the silicon teeth904in each grass-like region902.

As shown inFIG.9B, the open spaces or voids906between the teeth904in each grass-like region902may be filled (partially or fully) with silver or other suitable fill metal, indicated at930. For example, a layer of silver, e.g., with a thickness of 200 Å-2000 Å, may be deposited over the structure (extending over teeth904and the top surface916of interposer900) and etched back, e.g., using an anisotropic etch, to partially or fully fill the open spaces or voids906between vertically-extending teeth904in each grass-like region902, and also cover the outer surfaces922of the outer teeth904in each grass-like region902. The etch may remove the silver layer on the top surfaces924of vertically-extending teeth904, to thereby expose the top surfaces924of teeth904.

Each grass-like region902including teeth904and fill material930defines a grass-like bond pad940. The top of each grass-like bond pad940may have a roughness Ra great than 15 nm, e.g., in the range of 15-100 nm.

In addition, in some embodiments an underfill950, e.g., comprising an epoxy, may be deposited using a stencil or needle. The height of underfill950may be adjusted as needed based on the shape and/or dimensions of die(s) to be mounted to the interposer900.

FIG.10Ashows an example electron microscope image of an example grass-like region902formed from black silicon, from the paper “A Survey on the Reactive Ion Etching of Silicon in Microtechnology” referenced above.FIG.10Bshows an example electron microscope image of an individual single black silicon spire.

The multi-material toothed bond pads disclosed herein may be formed on any suitable integrated circuitry device. For example, in the example embodiments shown inFIGS.3A through9Band discussed above, the multi-material toothed bond pads are formed on the mounting structure (e.g. interposer or package substrate) to which one or more dies are mounted. In other embodiments, any of the multi-material toothed bond pads disclosed herein may instead be formed on each die, or may be formed both on the dies and the mounting structure, e.g., using any of the materials and techniques disclosed herein.

In addition, in some embodiments, a bond pad configured to bond with a toothed bond pad according to the present disclosure may have a three-dimensional shape designed to further improve bonding with the toothed bond pad, e.g., a three-dimensional shape including recesses or other geometries configured to receive the teeth of the toothed bond pad.

For example,FIGS.11A and11Bshow an example embodiment in which each die includes bond pads shaped to receive corresponding multi-material toothed bond pads on a mounting structure, e.g., interposer or package substrate.FIG.11Ashows a mounting structure1100including multi-material toothed bond pads1102, each including an array of teeth1110and fill material1112in the spaces between adjacent teeth1110.FIG.11Ashows dies1140aand1140bincluding bond pads1142shaped to receive the teeth1110of corresponding bond pads1102provided on mounting structure1100. In particular, each bond pad1142may include a plurality of protrusions1144that define openings or voids1146configured to receive teeth1110. Bond pads1142may be formed from aluminum or other suitable metal. In some embodiments, protrusions1144may be tapered, rounded, or otherwise configured to facilitate a self-alignment of each bond pad1142with a corresponding bond pad1102.

FIG.11Bshows dies1140aand1140bmounted to mounting structure1100, wherein the teeth1110of each bond pad1102are received in the openings or voids1146defined between protrusions1144of a corresponding bond pad1142. Similarly, protrusions1144of bond pad1142are received in the filled spaces1112between the teeth1110of bond pad1102.

In some embodiments, metal bumps, e.g., gold stud bumps, may be applied to the bond pads that engage with multi-material toothed bond pads according to the present disclosure, to further improve the bonding between the respective bond pads. For example,FIGS.12A and12Bshow an example embodiment in which gold stud bumps are applied to the bond pads of a die being mounted to a mounting structure having multi-material toothed bond pads.FIG.12Ashows an example mounting structure1200(e.g., interposer or package substrate) including multi-material toothed bond pads1202fully covered by an underfill region1210, e.g., comprising epoxy. Each multi-material toothed bond pad1202may include an array of aluminum teeth1204, each comprised of aluminum, and fill material1206, comprised of silver, in the spaces between adjacent teeth1204, e.g., as discussed above. A die1220with one or more solid aluminum bond pads1222may include a gold stud bump1230formed on or attached to each bond pad1222.

FIG.12Bshows die1220mounted to mounting structure1200, wherein the gold stud bumps punch through the underfill region1210(e.g., epoxy) and into the silver-filled spaces1206between the teeth1204of each bond pad1202. A thermosonic bonding process may be performed, which may form eutectic bonds between each gold bump1230and the aluminum and silver of each bond pad1202. Underfill region1210may provide a moisture seal for the mounted structure.