Expansion control for bonding

Abstract

Disclosed is an element and a bonded structure including the element. The element has a non-conductive region having a cavity extending from a contact surface through at least a thickness of the non-conductive region, and the element has a contact feature formed in the cavity. The non-conductive region is configured for direct bonding to the non-conductive region of a second element. A contact pad of the element is configured for direct bonding to a contact pad of the second element. The contact pad may include a first conductive material and a second conductive material. The first conductive material may have a unit cell size greater than a unit cell size of the second conductive material. The first conductive material may be a metal alloying material. The first conductive material may be a metal silicide and the second material may be a metal. The bonded conductive contact may include a conductive material and an alloying element, the amount of the alloying element may vary through a thickness of the bonded conductive contact.

Description

[Technical field]

[0001] The technical field relates to conductive features with controllable expansion rates.

[0002] [Citation to Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 320,525, filed March 16, 2022, entitled "EXPANSION CONTROL FOR BONDING," which is incorporated by reference in its entirety. [Background technology]

[0003] Semiconductor devices, such as integrated device dies or chips, may be mounted or stacked on other devices. For example, the semiconductor device may be mounted on a carrier, such as a package substrate, an interposer, a reconstituted wafer or device, or the like. As another example, a semiconductor device may be stacked on top of another semiconductor device, such as a first integrated device die stacked on a second integrated device die. Each of the semiconductor devices may have conductive pads that mechanically and electrically bond the semiconductor devices to one another. There continues to be a need for improved methods of forming conductive pads for reliable bonding. Summary of the Invention

[0004] Disclosed is an element and a bonded structure including the element. The element has a non-conductive region having a cavity extending from a contact surface through at least a thickness of the non-conductive region, and the element has a contact feature formed in the cavity. The non-conductive region is configured for direct bonding to the non-conductive region of a second element. A contact pad of the element is configured for direct bonding to a contact pad of the second element. The contact pad may include a first conductive material and a second conductive material. The first conductive material may have a unit cell size greater than a unit cell size of the second conductive material. The first conductive material may be a metal alloying material. The first conductive material may be a metal silicide and the second material may be a metal. The bonded conductive contact may include a conductive material and an alloying element, the amount of the alloying element may vary through a thickness of the bonded conductive contact.

[0005] The detailed description will now be described with reference to the accompanying drawings, in which the same reference numbers are used in different figures to indicate similar or identical items.

[0006] For purposes of this description, the illustrated devices and systems are shown as having a large number of components. Various embodiments of the devices and systems described herein may have fewer components and such embodiments will remain within the scope of the invention. Alternatively, other embodiments of the devices and / or systems may include additional components or various combinations of the components described and these embodiments will remain within the scope of the invention. [Brief description of the drawings]

[0007] [Figure 1A-1B] FIG. 1A is a schematic cross-sectional side view of a two element structure before annealing, according to one embodiment, and FIG. 1B is a schematic cross-sectional side view of the bonded structure after annealing, according to one embodiment. [Figure 2A]1C-1D are schematic cross-sectional views illustrating various steps in a process of forming the bonded structure of FIG. 1B, according to one embodiment. [Figure 2B] 1C-1D are schematic cross-sectional views illustrating various steps in a process of forming the bonded structure of FIG. 1B, according to one embodiment. [Figure 2C] 1C-1D are schematic cross-sectional views illustrating various steps in a process of forming the bonded structure of FIG. 1B, according to one embodiment. [Figure 2D] 1C-1D are schematic cross-sectional views illustrating various steps in a process of forming the bonded structure of FIG. 1B, according to one embodiment. [Figure 2E] 1C-1D are schematic cross-sectional views illustrating various steps in a process of forming the bonded structure of FIG. 1B, according to one embodiment. [Diagram 3] FIG. 1C illustrates material properties of various materials that can be used for the contact pads shown in FIGS. 1A and 1B. [Figure 4] FIG. 1C illustrates material properties of various materials that can be used for the contact pads shown in FIGS. 1A and 1B. [Diagram 5] 1 is a schematic cross-sectional side view of a structure according to one embodiment. [Figure 6] 6 is a schematic cross-sectional side view of the bonded structure of FIG. 5 after annealing the structure, in accordance with one embodiment. [Figure 7] FIG. 1 illustrates material properties of various metals in combination with copper. [Figure 8A-8B] FIG. 8A is a schematic cross-sectional side view of a device according to one embodiment, and FIG. 8B is a schematic cross-sectional side view of the device of FIG. 8A after the device has been annealed. [Figure 9A] 1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. [Figure 9B] 1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. [Figure 9C]1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. [Figure 9D] 1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. [Figure 9E] 1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. [Figure 9F] 1A-1D are schematic cross-sectional views illustrating various steps in a process of forming a bonded structure according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present disclosure relates to a method for controlling the growth and expansion of metal grains of conductive pads in devices, such as microelectronic devices. Various embodiments disclosed herein may be advantageous for direct metal bonding, direct hybrid bonding. For example, two or more semiconductor devices (integrated device dies, wafers, etc.) may be stacked or bonded together to form a bonded structure. The conductive contact pads of one device may be electrically connected to corresponding conductive contact pads of another device. Any suitable number of devices may be stacked in the bonded structure. The methods and bond pad structures described herein may also be useful in other technical contexts.

[0009] In some embodiments, the elements are directly bonded to each other without adhesive. In various embodiments, a non-conductive (e.g., semiconductive or inorganic dielectric) material of a first element can be directly bonded to a corresponding non-conductive (e.g., semiconductive or inorganic dielectric) or dielectric field region of a second element without adhesive. In various embodiments, a conductive region (e.g., metal pad) of a first element can be directly bonded to a corresponding conductive region (e.g., metal pad) of a second element without adhesive. The non-conductive material may be referred to as a non-conductive bonding region or bonding layer of the first element. In some embodiments, a non-conductive material of a first element can be directly bonded to a corresponding non-conductive material of a second element using adhesive-free bonding techniques, such as direct bonding techniques disclosed in at least U.S. Patent Nos. 9,564,414, 9,391,143, and 10,434,749, the entire contents of each of which are incorporated herein by reference for all purposes. In other applications, the bonded structure may include direct bonding of a non-conductive material of a first component to a conductive material of a second component, such that the conductive material of the first component conforms in intimate contact with the non-conductive material of the second component.

[0010] In various embodiments, the direct bond can be formed without an intervening adhesive. For example, the semiconducting or non-conductive bonding surfaces can be polished to a high degree of smoothness. The bonding surfaces can be cleaned and exposed to a plasma and / or an etchant to activate the surfaces. In some embodiments, the surfaces can be terminated with chemical species after or during activation (e.g., during a plasma and / or etch process). Without being bound by theory, in some embodiments, an activation process can be performed to break chemical bonds at the bonding surfaces, and a termination process can provide one or more additional chemical species at the bonding surfaces that improve the bonding energy during direct bonding. In some embodiments, activation and termination are performed in the same step, for example, using a plasma or a wet etchant to both activate and terminate the surfaces. In other embodiments, the bonding surfaces can be terminated in a separate process to provide additional chemical species for direct bonding. In various embodiments, the terminating chemical species can include nitrogen. Additionally, in some embodiments, the bonding surfaces can be exposed to fluorine. For example, one or more fluorine peaks may occur near the layers and / or bonding interface. Thus, in a direct bonded structure, the bonding interface between the two dielectrics may comprise a very smooth interface with high nitrogen content and / or fluorine peaks at the bonding surface. Additional examples of activation and / or termination treatments can be found throughout U.S. Patent Nos. 9,564,414, 9,391,143, and 10,434,749, each of which is incorporated by reference and incorporated herein in its entirety for all purposes.

[0011] In various embodiments, the conductive contact pads of the first component may also be directly bonded to the corresponding conductive contact pads of the second component. For example, direct hybrid bonding techniques may be used to provide conductor-to-conductor (hereinafter, "inter-conductor") direct bonds along with bond interfaces that include covalently direct-bonded dielectric-to-dielectric (hereinafter, "inter-dielectric") surfaces that have been pretreated as described above. In various embodiments, conductor-to-conductor (e.g., contact pad-to-contact pad) direct bonds and non-conductor-to-non-conductor hybrid bonds may be formed using direct bonding techniques as disclosed at least in U.S. Patent Nos. 9,716,033 and 9,852,988, each of which is incorporated by reference herein in its entirety and for all purposes. The bond structures described herein may also be useful for direct metal bonding or other bonding techniques without non-conductive region bonding.

[0012] In some embodiments, the inorganic dielectric bonding interfaces may be pretreated and directly bonded together without an intervening adhesive as described above. The conductive contact pads, which may be surrounded by non-conductive field regions, may also be directly bonded together without an intervening adhesive. In some embodiments, the respective contact pads may be recessed below the outer surface (e.g., top surface) of the dielectric field region or non-conductive bonding region, for example, by less than 30 nm, less than 20 nm, less than 15 nm, or less than 10 nm, and may be recessed in the range of 2 nm to 20 nm, or in the range of 4 nm to 10 nm. The non-conductive bonding regions may be directly bonded together without an adhesive at room temperature in some embodiments, and the bonded structure may then be annealed. During annealing, the contact pads may thermally expand relative to the non-conductive bonding regions and contact each other, thereby forming metal-to-metal direct bonds. Beneficially, high density pads can be connected across the direct bond interface (e.g., at small or fine pitch for regular arrays) through the use of Direct Bond Interconnect (DBI®) hybrid bonding technology, commercially available from Adeia, Inc., San Jose, Calif. In various embodiments, the contact pads may include copper, although other suitable metals may be suitable.

[0013] Thus, in a direct bonding process, a first element may be directly bonded to a second element without an intervening adhesive. In some configurations, the first element may comprise a singulated element, such as a singulated integrated device die. In other configurations, the first element may comprise a carrier or substrate (e.g., a wafer) that includes a plurality (e.g., tens, hundreds, or more) of device regions that, when singulated, form a plurality of integrated device dies. Similarly, the second element may comprise a singulated element, such as a singulated integrated device die. In other configurations, the second element may comprise a carrier or substrate (e.g., a wafer).

[0014] As described herein, the first and second elements can be directly bonded together without adhesive, which is different from a cladding process. Thus, the first and second elements can be comprised of non-cladding elements. Furthermore, the direct bonded structure, unlike cladding layers, can include defect areas along the bond interface where nanovoids exist. The nanovoids can form due to activation (e.g., exposure to plasma) of the bonding surface. As described above, the bond interface can include condensed material resulting from activation and / or final chemical treatment processes. For example, in embodiments utilizing nitrogen plasma for activation, a nitrogen peak can form at the bond interface. In embodiments utilizing oxygen plasma for activation, an oxygen peak can form at the bond interface. In some embodiments, the bond interface can be comprised of silicon oxynitride, silicon oxycarbonitride, or silicon carbonitride, and the level of nitrogen present at the bonding interface represents the nitrogen termination of at least one of the elements prior to direct bonding. In some embodiments, nitrogen and nitrogen-related components can be absent at the bonding interface. As described herein, the direct bond includes a covalent bond that is stronger than a van der Waals bond. The bonding layer may further include a polished surface that is planarized to a high degree of smoothness.

[0015] In various embodiments, the intermetallic bonds between the contact pads may be bonded such that the copper grains grow into one another across the bond interface. In some embodiments, the copper may have grains oriented vertically along 111 crystallographic planes to enhance diffusion of the copper across the bond interface. In some embodiments, the misorientation of the 111 crystallographic planes in the conductive material may be within ±30° of the vertical direction as viewed from the surface of the conductive material. In some embodiments, the crystallographic misorientation may be within ±20° or within ±15° of the vertical direction. The bond interface may extend substantially all the way to at least a portion of the bonded contact pads such that there are substantially no gaps between the non-conductive bonded regions at or near the bonded contact pads. In some embodiments, a barrier layer may be provided under the contact pads (which may, for example, comprise copper). However, in other embodiments, there may not be a barrier layer under the contact pads, as described, for example, in U.S. Pat. No. 11,195,748, the entire contents of which are incorporated herein by reference for all purposes.

[0016] The annealing temperature and duration for forming a direct metal bond may affect the consumption of the thermal budget by the annealing. It may be desirable to reduce the annealing temperature and / or shorten the annealing time to minimize the thermal budget consumption. <111> Surface diffusion of atoms along 111 crystal planes can be three to four orders of magnitude faster than along 100 or 110 crystal planes. Also, metals (e.g., Cu) with grains oriented along 111 crystal planes may have higher surface mobility compared to conventional back end of line (BEOL) copper. Furthermore, low temperature direct metal-to-metal bonding is made possible by the high creep rate of the Cu and conductive pad surface reconstruction on the 111 crystal planes. Therefore, it may be advantageous to have 111 crystal planes on the bonding surface to reduce annealing time and / or annealing temperature for direct bonding (e.g., direct hybrid bonding). The advantage of having 111 crystal planes may be especially pronounced at low temperatures, since metal surface diffusion (e.g., Cu surface diffusion) also slows down when the annealing temperature is reduced. Thus, in various embodiments disclosed herein, the crystal structure may have grains with a 111 texture that is preferentially oriented vertically or parallel to facilitate metal diffusion (e.g., copper diffusion) during direct bonding. In some embodiments, the misorientation of the 111 crystal planes in the conductive material may be within ±30° of the vertical direction as viewed from the surface of the conductive material. In some embodiments, the crystal misorientation may be within ±20° or ±15° of the vertical direction.

[0017] The metal layer may be formed by a process selected to plate a copper (Cu) layer with Cu in a 111 crystal orientation. The Cu layer may be deposited, for example, from a non-superfilling or superfilling electroplating bath with a plating chemistry selected to optimize effective filling of voids (e.g., vias, trenches) in the substrate, but not to optimize the direct intermetallic bonding that occurs during direct hybrid bonding. Subsequent metal processing, as described below, may facilitate subsequent bonding, so that any desired plating chemistry may be used to optimize other considerations, such as the filling mentioned above. The microstructure (e.g., grain size) of the deposited or coated metal layer may be stabilized, for example, by an annealing step separate from the subsequent annealing step of direct hybrid bonding.

[0018] As discussed above, the contact pads can expand relative to the non-conductive bonding regions and can contact each other to form a metal-metal direct bond. Sufficient expansion during annealing can contribute to good metal-metal bonding. For example, the expansion of the contact pads can be caused primarily by the thermal expansion of the material of the contact pads (e.g., copper) relative to the non-conductive bonding regions. In some embodiments, the bonding temperature (e.g., annealing temperature) for bonding the contact pads can be reduced by judiciously forming the contact pads from a material having an atomic unit cell that is relatively larger than the unit cell size of copper, for example. The contact pads can expand, at least in part, due to an increase in the unit cell size of the contact pads. The unit cell size may refer to the deposition of an atomic unit cell of a material at room temperature at sea level or atmospheric pressure. Room temperature may be about 25° C., and sea level or atmospheric pressure may be about 101325 Pa or 760 mmHg. A unit cell is the smallest portion of a crystal lattice that describes the three-dimensional pattern of the entire crystal. For example, at atmospheric pressure and room temperature, the unit cell size of cobalt is 10.913 Å. 3 and the unit cell size of titanium is 34.714 Å.3 and the unit cell size of nickel is 10.722 Å. 3 and the unit cell size of silicon is 40.888 Å. 3 Some contact pad materials have a lower coefficient of thermal expansion than other contact pad materials, and some contact pad materials are more costly or less suitable for direct bonding than other contact pad materials. Various embodiments disclosed herein use two or more different conductive materials to form the contact pads, which allows for satisfactory direct bonding between the contact pads at a relatively low material cost and with a relatively low thermal budget. For example, the contact pads may be made of two or more conductive materials that have an increased coefficient of thermal expansion than one of the conductive material types to allow for such satisfactory direct bonding.

[0019] Figure 1A is a schematic cross-sectional side view of a structure 1 including two elements (e.g., a first element 2 and a second element 3) before annealing according to one embodiment, and Figure 1B is a schematic cross-sectional side view of a bonded structure 1' (structure 1 of Figure 1A after annealing) according to one embodiment.

[0020] The first element 2 may have a non-conductive region 10 (e.g., a non-conductive or dielectric field region), a barrier layer 12, and a contact pad or conductive feature 14. The contact pad 14 may include a first conductive material 16 and a second conductive material 18. Similarly, the second element 3 may have a non-conductive region 20 (e.g., a non-conductive or dielectric field region), a barrier layer 22, and a contact pad or conductive feature 24. The contact pad 24 may include a first conductive material 26 and a second conductive material 28. The first element 2 and the second element 3 may be bonded together along a bonding interface 30. In some embodiments, the non-conductive region 10 and the non-conductive region 20 may be directly bonded together without an intervening adhesive. In some embodiments, the second conductive material 18 of the first element 2 and the second conductive material 28 of the second element 3 may be directly bonded together without an intervening adhesive. In the illustrated embodiment, the structure 1 and the bonding structure 1' have identical elements 2, 3, however, the structures 1, 1' can in some embodiments have different elements bonded to each other.

[0021] A barrier layer 12 may be disposed between the non-conductive material 10 and the contact pads 14. In some embodiments, the barrier layer 12 may isolate the non-conductive materials 10, 20 from the contact pads 14, 24 to prevent or reduce diffusion of the conductive materials 16, 18, 26, 28 into the non-conductive materials 10, 20. In some embodiments, the barrier layer 12 may include a sputtered cobalt layer.

[0022] In some embodiments, the thermal expansion coefficient, deposition growth rate, and / or unit cell size of the first conductive material 16 may be greater than the thermal expansion coefficient, deposition growth rate, and / or unit cell size of the second conductive material 18. Certain material properties, such as the thermal expansion coefficient, deposition growth rate, and unit cell size, of the first and second conductive materials 16, 18 may vary with ambient conditions. For example, the material properties of the first and second conductive materials 16, 18 may vary with temperature or pressure. As will be appreciated by those skilled in the art, if no conditions are specified, ambient conditions are room temperature at sea level. When properties of two or more materials are compared herein, the properties of the materials are compared under the same conditions.

[0023] In some embodiments, the second conductive material 18 may have a deposition increase ratio of at least 10% relative to the deposition increase ratio of the second conductive material 18 or the material of the back end of line (BEOL) layers (not shown) underlying the first and second conductive materials 16, 18. For example, the first conductive material 16 may have a deposition increase ratio in the range of 10% to 50%, 10% to 275%, 50% to 500%, or 50% to 275% relative to the deposition increase ratio of the second conductive material 18 or the material of the back end of line (BEOL) layers (not shown) underlying the first and second conductive materials 16, 18. In some embodiments, the unit cell size of the first conductive material 16 may be at least 1.3 times the unit cell size of the second conductive material 18. For example, the unit cell size of the first conductive material 16 may be at least 1.5, 2, 3, or 5 times the unit cell size of the second conductive material 18. In some embodiments, the first conductive material 16 may be comprised of a metal silicide or an alloying metal. Some exemplary materials for the first conductive material 16 are seen, for example, in FIGS. 3-4. In some embodiments, upon annealing at a particular temperature, the volume expansion (amount) of the alloy formed between the first conductive material 16 and the second conductive material 18 may be at least 10% greater than the volume expansion (amount) of the first conductive material 16 or the second conductive material 18. In addition, other embodiments may include devices having one or more BEOL layers. The BEOL layers may include metallization layers (conductive traces embedded in an insulating layer) formed (e.g., deposited) on the backside of the barriers of the devices 1, 2. For example, a metallization layer may be formed directly on the back surface of the barrier to contact the barrier. In some embodiments, the BEOL layers may include multiple layers, and the topmost layer of the BEOL layers may comprise a bonding layer. The volume expansion of the bonding layer (conductive material 18, 28) of the first conductive feature or the second conductive feature is at least 10% more than the volume expansion of the BEOL layers located below the bonding layer.Selection of the materials for the first and second conductive materials 16, 18 as disclosed herein may be essential to enable satisfactory direct bonding between the contact pads 14, 24 at relatively low material costs and with a relatively low thermal budget.

[0024] In some embodiments, the first conductive material 16 may be embedded under the second conductive material 18 (e.g., at least partially disposed under the second conductive material 18). For example, the first conductive material 16 may be fully embedded under the second conductive material 18. For example, as shown in FIG. 1B, the second conductive material 18 may be fully encapsulated within the space between the barrier layer 12 and the overlying second conductive material 18. In some embodiments, the first conductive material 16 and the second conductive material 18 may combine to form an alloy. The thermal expansion coefficient or unit cell size of the formed alloy may be greater than the thermal expansion coefficient or unit cell size of the precursor (first conductive material 16 or 18). In other embodiments, the first conductive material 16 and the second conductive material 18 may not combine with each other.

[0025] In some embodiments, the first conductive material 16 may be exposed on the contact surface of the contact pad 14. In some embodiments, it may be beneficial to select a material for the second conductive material 18, 28 that is compatible with a chemical mechanical polishing (CMP) process in preparation for direct bonding. A CMP-compatible material is one that has a hardness that does not cause excessive smearing or dishing during the polishing process. Because the first conductive material 16, 26 is embedded under the second conductive material 18, 28, the first conductive material 16, 26 may or may not be compatible with the CMP process.

[0026] The thickness of the first conductive material 16 may be less than the thickness of the second conductive material 18. The thickness of the first conductive material 16, 26 may be determined, at least in part, by the material expansion coefficient of the first conductive material 16, 26 and the gap between the contact pads 14, 24 before annealing. In some embodiments, depending on the depth of the cavity, the thickness of the first conductive material 16, 26 may be in the range of, for example, 20 nm to 20,000 nm, 30 nm to 17,500 nm, 40 nm to 15,000 nm, 50 nm to 10,000 nm, 50 nm to 7,000 nm, or 50 nm to 500 nm. Selecting the thickness of the first conductive material 16, 26 from these ranges may be responsible for enabling sufficient direct bonding between the contact pads 14, 24 at a relatively low material cost and with a relatively low thermal budget.

[0027] 2A-2E are schematic cross-sectional views of various steps in a process of forming a bonded structure 1′ according to an embodiment. In FIG. 2A, a cavity 19 may be formed in the non-conductive material 10. In some embodiments, the cavity 19 may be formed by selective etching of the non-conductive material 10. In FIG. 2B, a barrier layer 12 and a first conductive material 16 may be provided within the cavity 19. The first conductive material 16 may be comprised of a plurality of constituent elements 16a, 16b. For example, the barrier layer 12 and the first conductive material 16 may be provided by electrolytic layer deposition (ALD), sputtering and plating or a combination thereof. The plating step may comprise electroless or electrolytic deposition. At least a portion of the first conductive material 16 may be removed, for example, by an etching (e.g., dry or wet etching) process and / or a photography process. In FIG. 2C, in some embodiments, a second barrier layer 13 may be provided in the cavity on the first conductive layer 16. In some embodiments, the first conductive material 16 may be encapsulated between the first barrier layer 12 and the second barrier layer 13. In other embodiments, the second barrier layer 13 may not be provided (see FIG. 1A). In FIG. 2D, a second conductive material 18 may be provided. The surface of the non-conductive material 10 and / or the surface of the second conductive material 18 may be polished, for example by CMP, to prepare the device for direct bonding to another device. In some embodiments, after polishing the surface of the non-conductive material 10 and / or the surface of the second conductive material 18, the surface of the second conductive material 18 may be recessed relative to the surface of the non-conductive material 10. In FIG. 2E, the device may be directly bonded to another device (e.g., direct hybrid bonding). The components may be direct bonded after cleaning and activating the bonding surfaces of one or both of the components by known methods.For example, the activation process may include cleaning at least one of the bonding surfaces of the components to remove undesired particles, and / or exposing the bonding surface to one or more plasma treatments, rinsing the bonding surface, and drying the bonding surface. The rinsing solvent for rinsing may comprise deionized (DI) water or a low molecular weight alcohol. The non-conductive material of the component may be directly bonded to the non-conductive material of the other component. After bonding the non-conductive materials of the two components, the structure may be annealed at high temperature to bond the second conductive material to the contact pads of the other component. In some embodiments, the first conductive material 16 may be alloyed with, for example, the first and / or second barrier layers 12, 13, the alloy having a unit cell size larger than the unit cell size of the second conductive material 18. For example, the alloy may comprise a copper zinc alloy, a magnesium alloy, or a cobalt silicide alloy.

[0028] 3 and 4 show material properties of various materials that can be used for the contact pads 14, 24 shown in FIGS. 1A and 1B. The alloy deposition increase shown in FIG. 3 is the alloy deposition increase percentage for each of the silicide alloys listed in FIG. 3 compared to copper. The silicide alloys listed in FIG. 3 may be exemplary of the first conductive material 16, 26. The materials listed in FIG. 4 may be exemplary of the first conductive material 16, 26. In some embodiments, brass, bronze, or cadmium copper alloys may be electroplated from an alkaline bath containing a suitable complexing agent placed in the damascene cavity. As shown in FIG. 3, the first conductive material 16, 26 may be comprised of copper, titanium, nickel, brass, magnesium, manganese, zinc, tin, bronze, or cadmium. Beneficially, providing an embedded first conductive material 16, 26 can reduce the annealing temperature sufficient to cause metal expansion and direct electrical contact between opposing pads (e.g., between opposing second conductive materials 18, 28). Increasing the expansion characteristics of the first conductive material 16, 26 compared to the second conductive material 18, 28 can facilitate improved direct bond yields at lower temperatures while still providing a CMP-compatible surface of the second conductive material 18, 28 to enable pre-treatment for direct bonding.

[0029] In some embodiments where the first conductive material 16, 26 is made of nickel (Ni) and the second conductive material 18, 28 is made of silicon (Si), a nickel silicide (Ni2Si) layer can be formed. For a device with a pre-bonding thickness of 2 μm and a contact recess dimension of 20 nm, the nickel silicide layer thickness should be 27 nm or more based on 533% of the nickel silicide and volume expansion to compensate for the recess without expansion due to the coefficient of thermal expansion (CTE). The relationship between the recess dimension change (ΔL), the volume expansion (V1), and the layer thickness (L1) can be expressed by the following equation (Equation 1), which is shown in the following table (Table 1). TIFF2025509316000002.tif9150 TIFF2025509316000003.tif27153 Table 1

[0030] In some embodiments, the first conductive material 16, 26 may be comprised of copper (Cu) and the second conductive material 18, 28 may be comprised of magnesium (Mg). The inclusion of a combination of copper and magnesium in the contact pads allows for a lower anneal temperature for bonding the contact pads to a corresponding pad of another device compared to the inclusion of only copper in the contact pads. For example, the anneal temperature may be reduced by approximately 125° C. under some conditions. The following table (Table 2) shows a comparison between several parameters of a copper pad (wherein both the first and second conductive materials are comprised of copper) and a multi-layer pad containing 50% copper and 50% magnesium (wherein the first conductive material is comprised of magnesium and the second conductive material is comprised of copper). TIFF2025509316000004.tif64153 Table 2

[0031] In Table 2, α Cu represents the CTE of copper, α1 represents the CTE of the first conductive material, L Cu where L represents the thickness of the copper layer (second conductive material), L1 represents the thickness of the second conductive material, ΔT represents the change in temperature relative to the original temperature of 25° C., and ΔL represents the dimensional change of the recess before and after annealing. The relationship between these parameters can be expressed by the following equation (Equation 2): TIFF2025509316000005.tif7150

[0032] FIG. 6 is a schematic cross-sectional side view of a structure 4 including a first element 5 and a second element 6 prior to annealing according to one embodiment. FIG. 6 is a schematic cross-sectional side view of a bonded structure 4' (after annealing the structure 4 of FIG. 5) according to one embodiment. Unless otherwise noted, the components in FIGs. 5 and 6 may be the same as or generally similar to the components in FIGs. 1A and 1B.

[0033] The first element 5 may include a non-conductive region 10, a barrier layer 12, and a contact pad or conductive feature 44. The contact pad 44 may include a first material 46, a first layer of a second conductive material 48a, and a second layer of a second conductive material 48b. In some embodiments, the first conductive material 46 may be vertically sandwiched between the first layer 48a and the second layer 48b. Similarly, the second element 6 may include a non-conductive region 20 and a barrier layer 22, and a contact pad or conductive feature 54. The contact pad 54 may include a first conductive material 56, a first layer of a second conductive material 58a, and a second layer of a second conductive material 58b. The first element 5 and the second element 6 may be bonded together (e.g., direct hybrid bonded) along a bonding interface 30. In some embodiments, the non-conductive region 10 and the non-conductive region 20 may be directly bonded to each other without an intervening adhesive. In various embodiments, the first conductive material 46, 56 may be comprised of an alloying element (e.g., an alloying metal) that, upon annealing, forms a metal alloy with the second conductive material. For example, the first conductive material 46, 56 may be comprised of zinc (Zn), beryllium (Be), palladium (Pd), aluminum (Al), or similar materials. The annealing process may form the contact pads 44, 54 into different configurations, thereby forming the contact pads 44', 54'. For example, the first conductive material 46, 56, the first layer 48a, 58a, and the second layer 48b, 58b may at least partially form an alloy 60, 62. After annealing the structure 4 of FIG. 5, the contact pads 44' and the contact pads 54' may expand and contact each other, and also form a metal alloy. If alloys 60, 62 are formed prior to annealing to bond contact pads 44' and 54', alloys 60, 62 may be compatible with CMP processes for pre-treatment to enable direct bonding. In some embodiments, contact pads 44' and contact pads 54' may be directly bonded to one another without an intervening adhesive.In some embodiments, the contact pads 44' and 54' may be comprised of alloying elements with a gradient (e.g., a gradient of the first conductive material 46, 56). In the illustrated embodiment, the structure 4 and the bonded structure 4' include identical elements 5, 6, but in other embodiments, the structure 4 may include different elements bonded together. In some embodiments, the resistivity of the alloy 60, 62 created by bonding the elements 5, 6 may be less than 20 times, less than 15 times, less than 10 times, or less than 5 times greater than the resistivity of the BEOL layer material underlying the bonding layer. For example, the alloy 60, 62 may include a low resistivity metal (e.g., nickel) and the BEOL layer material may include a high resistivity metal (e.g., copper).

[0034] Figure 7 shows an example of the first conductive material. Figure 7 also shows the metallurgical properties of various metals combined with copper. The volume expansion of the pad can be calculated by the following equation (Equation 3): TIFF2025509316000006.tif10150

[0035] For example, if we apply copper-zinc alloy (Cu3Zn) to equation 3, the equation can be expressed as follows: TIFF2025509316000007.tif13150

[0036] Figure 8A is a schematic cross-sectional side view of element 7 according to one embodiment. Figure 8B is a schematic cross-sectional side view of element 7' after annealing of element 7 of Figure 8A. Unless otherwise noted, the components shown in Figures 8A and 6 may be the same as or generally similar to the components in Figures 1A, 1B, 5, and 6.

[0037] The element 7 may include a non-conductive region 10, a barrier layer 12, and a contact pad or conductive feature 64. The contact pad 64 may include a first conductive material 66, a first layer 68a of a second conductive material, and a second layer 68b of a second conductive material. In some embodiments, the second layer 68b may be omitted. The first conductive material 66 and the second conductive material (first layer 68a and second layer 68b) may be selected to increase the surface roughness of the alloy conductive feature 70 during annealing. The first conductive material 66 may be located at or near the contact surface of the contact pad 64. In some embodiments, the first conductive material 66 may be located within 25% of the thickness of the contact pad 64 from its contact surface.

[0038] In some embodiments, the first conductive material 66 may be comprised of an alloy material. In some embodiments, the first conductive material may have a hexagonal crystal structure and the second conductive material (first layer 68a and second layer 68b) may have a face-centered cubic structure. For example, the first conductive material 66 may be comprised of titanium and the second conductive material (first layer 68a and second layer 68b) may be comprised of copper. After annealing the element 7, the contact pad 64 may form an orthorhombic crystal structure. When the orthorhombic crystal structure is created, the surface roughness of the contact pad 64 may be increased. The contact pad 64' may have spikes or whiskers as a result of the formation of the orthorhombic crystal structure. The surface roughness of the surface of the alloy conductive feature 70 of the element 7 may be in the range of 3 nm to 100 nm, or in the range of 3 nm to 50 nm. The surface roughness of the alloy conductive features 70 should be less than 1 nm, and preferably less than 0.5 nm, higher than the roughness of the bonding layer of the non-conductive regions. Bonding alloy conductive features 70 with relatively rough surface morphology at high temperatures results in the corresponding conductive features more effectively spanning the recesses between the conductive features. Spanning the recesses initiates physical contact (at lower temperatures) between opposing element metal conductive features, thereby facilitating the formation of metallurgical bonds at lower temperatures.

[0039] 9A-9F are schematic cross-sectional views of various steps in a process of forming a bonded structure 9, according to one embodiment. In FIG. 9A, a cavity 19 may be formed in a non-conductive material 20. In some embodiments, the cavity 19 may be formed by selective etching. In FIG. 9B, a barrier layer 12, a first conductive material 66, and a second conductive material (e.g., first and second layers 68a, 68b) may be provided in the cavity 19 and at least partially on a surface of the non-conductive material 10. For example, the first conductive material 66 and the second conductive material (first and second layers 68a, 68b) may be provided by sputtering, plating, or a combination of each of these. In FIG. 9C, the surface of the non-conductive material 10 and / or the second layer 68b of the second conductive material may be polished, for example by CMP, to form an element (e.g., first element 7). In some embodiments, the second layer 68b may be recessed relative to the surface of the non-conductive material 10. In FIG. 9D, an element (first element 7) may be bonded to another element (second element 8) after sufficient pretreatment of at least one of the surfaces of the first and second elements 7,8 to allow for direct bonding (e.g., direct hybrid bonding). The non-conductive material 10 of the first element 7′ may be directly bonded to the non-conductive material 82 of the second element 8. After bonding the non-conductive materials 10,82 of the two elements 7,8, the structure may be annealed to bond the second conductive material 68b to the contact pads 80 of the second element 8. During the bonding process, the first conductive material 66 and the second conductive material (first and second layers 68a,68b) may at least partially alloy to form the alloy conductive features 70. In FIG. 9D, nanoscale roughness, spikes, protrusions, or whiskers may be formed on the contact surfaces of the alloy conductive features 70 and / or contact pads 80 of the elements 7,8. A nanoscale roughened bonding surface of the conductive material of the first element 7 or the second element 8 can be formed by judicious selection of materials having different crystal lattice symmetries for the first material 66 and the second material (first layer and second layer 68a, 68b) as described above.Other known methods, for example applying dry or wet etchants, can be used to etch away very little of the grain boundaries of the conductive material of the first element 7 or the second element 8. FIG. 9E shows the bonded structure 9 of FIG. 9D after a first period of time after bonding the first and second elements 7,8 at elevated temperatures. The contact pads of the elements 7,8 can diffuse into each other over time. During the first period of time, nanoscale roughened surfaces, spikes, protrusions, or whiskers can be observed in some embodiments. FIG. 9F shows the bonded structure 9 of FIG. 9E after a second period of time after bonding the first and second elements 7,8. The second period of time is longer than the first period of time. After the second period of time, the nanoscale roughened surfaces, spikes, protrusions, or whiskers may not be visible in some embodiments. In other embodiments, after the second period of time, the nanoscale roughened surfaces, spikes, protrusions, or whiskers can be observed.

[0040] In some embodiments, the bonded structures disclosed herein may have a void between the contact pads of one component and the contact pads of another component, where gas in the void may act to push the material of the contact pads to the inner surface.

[0041] In one aspect, an element is disclosed having a contact surface. The element may have a non-conductive region with a cavity, the cavity extending from the contact surface at least partially through a thickness of the non-conductive region, and the element may further have a contact pad formed in the cavity. The contact pad includes a first conductive material and a second conductive material. The first conductive material has a unit cell size greater than a unit cell size of the second conductive material. The first conductive material is a metal alloying material. The non-conductive region is configured for direct bonding to the non-conductive region of a second element, and the contact pad of the element is configured for direct bonding to the contact pad of the second element.

[0042] In one embodiment, the unit cell size of the first conductive material is at least 1.3 times the unit cell size of the second conductive material.

[0043] In one embodiment, the device further comprises a barrier layer conformally disposed along the surface of the cavity.

[0044] In one embodiment, the first conductive material is disposed between a bottom surface of the cavity and a second conductive material.

[0045] In one embodiment, the first conductive material is completely embedded under the second conductive material.

[0046] In one embodiment, the first conductive material is not exposed.

[0047] In one embodiment, the second conductive material is copper.

[0048] In one embodiment, the first conductive material has a characteristic forming temperature of less than 230° C. The first conductive material has a characteristic forming temperature of less than 130° C.

[0049] In one embodiment, the first conductive material is a metal silicide, the metal silicide including nickel, titanium, or cobalt.

[0050] In one embodiment, the first conductive material includes zinc, titanium, or nickel.

[0051] In one embodiment, the second conductive material has a face-centered cubic structure and the first conductive material has a hexagonal structure. The second conductive material is made of copper and the first conductive material is made of titanium. The resistivity of the first conductive material is higher than the resistivity of the second conductive material. The resistivity of the first conductive material is less than 40 times the resistivity of the second conductive material. The resistivity of the first conductive material is less than 20 times the resistivity of the second conductive material. The thickness of the second conductive material is greater than the thickness of the first conductive material.

[0052] In one embodiment, the first conductive material is a chemical mechanical polishing compatible material.

[0053] In one embodiment, in one aspect, a first element is disclosed having a contact surface. The first element may have a non-conductive region with a cavity, the cavity extending from the contact surface at least partially through a thickness of the non-conductive region, and the first element may further have a contact pad formed in the cavity. The contact pad includes a metal and a metal silicide. The metal silicide has a unit cell size greater than a unit cell size of the metal. The non-conductive region is configured for direct bonding to the non-conductive region of a second element, and the metal is configured for direct bonding to the contact pad of the second element.

[0054] In one embodiment, the first element further comprises a barrier layer conformally disposed along a surface of the cavity.

[0055] In one embodiment, a metal silicide is provided between the bottom surface of the cavity and the metal.

[0056] In one embodiment, the metal silicide is completely buried under the metal.

[0057] In one embodiment, the metal is not exposed.

[0058] In one embodiment, the metal is copper.

[0059] In one embodiment, the metal suicide is the metal alloying material.

[0060] In one embodiment, the metal suicide has a characteristic forming temperature of less than 230°C.

[0061] In one embodiment, the metal suicide includes nickel, titanium, or copper.

[0062] In one embodiment, the resistivity of the metal silicide is higher than the resistivity of the metal. The resistivity of the metal silicide is less than 40 times the resistivity of the metal. The resistivity of the metal silicide is less than 20 times the resistivity of the metal.

[0063] In one embodiment, the thickness of the metal is greater than the thickness of the metal silicide.

[0064] In one embodiment, the metal and the metal silicide do not react with each other.

[0065] In one embodiment, the metal comprises copper and the metal suicide comprises zinc.

[0066] In one embodiment, the metal silicide is a chemical mechanical polishing compatible material.

[0067] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first non-conductive region and a first conductive feature, and a second element having a second non-conductive region directly bonded to the first non-conductive region and a second conductive feature directly bonded to the first conductive feature to form a bonded conductive contact. The bonded conductive contact includes a first conductive material and a second conductive material. The first conductive material has a unit cell size that is greater than the unit cell size of the second conductive material. The first conductive material is an alloy that includes the second conductive material.

[0068] In one embodiment, the bonded conductive contacts are comprised of alloying elements with graded properties.

[0069] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first non-conductive region and a first conductive feature, and a second element having a second non-conductive region directly bonded to the first non-conductive region and a second conductive feature directly bonded to the first conductive feature to form a bonded conductive contact. The bonded conductive contact includes a first conductive material and a second conductive material. The first conductive material has a unit cell size that is greater than the unit cell size of the second conductive material. The first conductive material is comprised of a metal silicide.

[0070] In one embodiment, the first element further comprises a barrier layer disposed between the first non-conductive region and the first conductive feature.

[0071] In one embodiment, the metal suicide includes nickel, titanium, or copper.

[0072] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first non-conductive region and a first conductive feature, and a second element having a second non-conductive region directly bonded to the first non-conductive region and a second conductive feature directly bonded to the first conductive feature to form a bonded conductive contact. The bonded conductive contact includes a conductive metal and an alloying element. The amount of the alloying element varies across a thickness of the bonded conductive contact.

[0073] In one embodiment, the first element further comprises a barrier layer disposed between the first non-conductive region and the first conductive feature.

[0074] In one embodiment, the first conductive feature is comprised of a metal silicide, the metal silicide including nickel, titanium, or copper.

[0075] In one embodiment, the bonded conductive contacts have an orthorhombic crystal structure.

[0076] In one embodiment, the bonded conductive contacts have a unit cell size that is greater than the unit cell size of the conductive material.

[0077] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first non-conductive region and a first conductive feature, and a second element having a second non-conductive region directly bonded to the first non-conductive region and a second conductive feature directly bonded to the first conductive feature to form a bonded conductive contact. The bonded conductive contact has a lower crystal symmetry structure than the first conductive feature.

[0078] In one embodiment, the bonded conductive contacts have an orthorhombic or hexagonal crystal structure.

[0079] In one embodiment, the bonded conductive contacts are comprised of alloying elements with graded properties.

[0080] In one embodiment, the first element further comprises a barrier layer disposed between the first non-conductive region and the first conductive feature.

[0081] In one embodiment, the bonded conductive contacts are made of a copper titanium alloy.

[0082] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first contact surface. The first element may have a first non-conductive region having a first cavity, the cavity extending at least partially through a thickness of the first non-conductive region from the first contact surface, and the bonded structure may further include a first contact pad formed in the first cavity. The first contact pad includes a first conductive material and a second conductive material. The first conductive material has a unit cell size greater than a unit cell size of the second conductive material. The first conductive material is a metal alloying material. The bonded structure may further include a second element having a second contact surface directly bonded to the first contact surface. The second element has a second non-conductive region directly bonded to the first non-conductive region and a second contact pad directly bonded to the first contact pad.

[0083] In one embodiment, the bonded structure further comprises a barrier layer conformally disposed along a surface of the first cavity.

[0084] In one embodiment, the first conductive material is disposed between a bottom surface of the first cavity and the second conductive material. The first conductive material may be completely embedded under the second conductive material. The directly bonded first and second contact pads may form a bonded conductive contact having an orthorhombic crystal structure. The directly bonded contact pads may be made of a copper-titanium alloy.

[0085] In one embodiment, the directly bonded first and second contact pads are comprised of alloying elements with graded properties.

[0086] In one aspect, a method of forming a device is disclosed that may include forming a cavity in a non-conductive material, providing a first conductive material in the cavity having a first unit cell size, providing a second conductive material in the cavity overlying the first conductive material having a second unit cell size, and polishing a surface of the non-conductive material and a surface of the second conductive material, where the first unit cell size is larger than the second unit cell size.

[0087] In one embodiment, forming the cavity comprises etching a portion of the non-conductive material.

[0088] In one embodiment, the method further comprises conformally disposing a barrier layer along the surfaces of the cavity.

[0089] In one embodiment, providing the first conductive material includes plating the first conductive material.

[0090] In one embodiment, the second conductive material is copper.

[0091] In one embodiment, the first conductive material is a metal alloying material.

[0092] In one embodiment, the first conductive material has a characteristic forming temperature of less than 230°C.

[0093] In one embodiment, the first conductive material is a metal silicide, the metal silicide including nickel, titanium, or copper.

[0094] In one embodiment, the first conductive material includes aluminum, zinc, titanium, or nickel.

[0095] In one embodiment, the second conductive material has a face-centered cubic structure and the first conductive material has a hexagonal structure.

[0096] In one embodiment, the second conductive material comprises copper and the first conductive material comprises titanium.

[0097] In one embodiment, the resistivity of the first conductive material is higher than the resistivity of the second conductive material. The resistivity of the first conductive material is less than 40 times the resistivity of the second conductive material. The resistivity of the first conductive material is less than 20 times the resistivity of the second conductive material.

[0098] In one embodiment, the thickness of the second conductive material is greater than the thickness of the first conductive material.

[0099] In one embodiment, the polishing step comprises polishing a surface of the non-conductive material and a surface of the second conductive material with a chemical mechanical polishing compatible material.

[0100] In one embodiment, the element is formed without annealing. A method of forming a bonded structure having the element and a second element with a contact pad may include annealing the first conductive material, the second conductive material, and the contact pad, thereby expanding the first conductive material, the second conductive material, and the contact pad to form a bonded conductive contact. The annealing step may create an alloy between the first conductive material and the second conductive material.

[0101] In one aspect, a method of forming a device is disclosed. The method may include forming a cavity in a non-conductive material, providing a first barrier layer in the cavity, providing a first conductive material in the cavity having a first unit cell size, providing a second barrier layer in the cavity over the first conductive material, providing a second conductive material in the cavity over the second barrier layer having a second unit cell size, and polishing a surface of the non-conductive material and a surface of the second conductive material. The first unit cell size is larger than the second unit cell size.

[0102] In one embodiment, forming the cavity comprises etching a portion of the non-conductive material.

[0103] In one embodiment, providing the first conductive material includes plating the first conductive material.

[0104] In one embodiment, the second conductive material is copper.

[0105] In one embodiment, the first conductive material is a metal alloying material.

[0106] In one embodiment, the first conductive material has a characteristic forming temperature of less than 230°C.

[0107] In one embodiment, the first conductive material is a metal suicide.

[0108] In one embodiment, the second conductive material has a face-centered cubic structure and the first conductive material has a hexagonal structure, the second conductive material is comprised of copper and the first conductive material is comprised of titanium.

[0109] In one embodiment, the resistivity of the first conductive material is higher than the resistivity of the second conductive material. The resistivity of the first conductive material is less than 40 times the resistivity of the second conductive material. The resistivity of the first conductive material is less than 20 times the resistivity of the second conductive material.

[0110] In one embodiment, the thickness of the second conductive material is greater than the thickness of the first conductive material.

[0111] In one embodiment, the polishing step comprises polishing a surface of the non-conductive material and a surface of the second conductive material with a chemical mechanical polishing compatible material.

[0112] In one embodiment, the device is formed without annealing.

[0113] In one aspect, a method of forming a device is disclosed that may include forming a cavity in a non-conductive material, providing a first conductive material having a hexagonal crystal structure, providing a second conductive material having a face-centered cubic structure, and polishing a surface of the non-conductive material and a surface of the first conductive material.

[0114] In one embodiment, forming the cavity comprises etching a portion of the non-conductive material.

[0115] In one embodiment, providing the first conductive material includes plating the first conductive material.

[0116] In one embodiment, the second conductive material is copper.

[0117] In one embodiment, the first conductive material has a characteristic forming temperature of less than 230°C.

[0118] In one embodiment, the second conductive material comprises copper and the first conductive material comprises titanium.

[0119] In one embodiment, the resistivity of the first conductive material is higher than the resistivity of the second conductive material.

[0120] In one embodiment, the thickness of the second conductive material is greater than the thickness of the first conductive material.

[0121] In one embodiment, the polishing step comprises polishing a surface of the non-conductive material and a surface of the second conductive material with a chemical mechanical polishing compatible material.

[0122] In one embodiment, the element is formed without annealing. A method of forming a bonded structure having the element and a second element with a contact pad may include annealing the first conductive material, the second conductive material, and the contact pad, thereby expanding the first conductive material, the second conductive material, and the contact pad to form a bonded conductive contact. The annealing step may create an alloy between the first conductive material and the second conductive material.

[0123] In one aspect, a method of forming a bonded structure is disclosed. The method may include providing a first element having a first non-conductive region and a first conductive feature. The first conductive feature includes a first conductive material and a second conductive material. The first conductive material has a unit cell size greater than a unit cell size of the second conductive material. The first conductive material is a metal alloying material. The method may include providing a second element having a second non-conductive region and a second conductive feature. The method may include direct bonding the first non-conductive region and the second non-conductive region, and annealing the first conductive feature and the second conductive feature, thereby bonding the first conductive material of the first conductive feature and the second conductive feature.

[0124] In one embodiment, providing the first element includes forming a cavity in the first non-conductive region and at least partially filling the cavity with a first conductive material. Forming the cavity may comprise etching a portion of the non-conductive material. The method may further include conformally providing a barrier layer along a surface of the cavity. Providing the first conductive feature may include plating the first conductive feature.

[0125] In one embodiment, the first conductive material is copper.

[0126] In one embodiment, the second conductive material has a characteristic forming temperature of less than 230°C.

[0127] In one embodiment, the second conductive material is a metal silicide, the metal silicide including nickel, titanium, or copper.

[0128] In one embodiment, the second conductive material includes aluminum, zinc, titanium, or nickel.

[0129] In one embodiment, the first conductive material has a face-centered cubic structure and the second conductive material has a hexagonal structure, the first conductive material is comprised of copper and the second conductive material is comprised of titanium.

[0130] In one embodiment, the resistivity of the second conductive material is higher than the resistivity of the first conductive material. The resistivity of the second conductive material is less than 40 times the resistivity of the first conductive material. The resistivity of the second conductive material is less than 20 times the resistivity of the first conductive material.

[0131] In one embodiment, the thickness of the first conductive material is greater than the thickness of the second conductive material.

[0132] In one embodiment, the method further includes polishing the surface of the non-conductive material and the surface of the first conductive material with a chemical mechanical polishing compatible material.

[0133] In one embodiment, the annealing step includes annealing the first conductive feature and the second conductive feature at a temperature between 100°C and 200°C.

[0134] In one embodiment, the annealing step includes annealing the first conductive feature and the second conductive feature at a temperature between 100°C and 150°C.

[0135] In one embodiment, the annealing step alloys the first conductive material with the second conductive material.

[0136] In one aspect, a method of forming a bonded structure is disclosed. The method may include providing a first element having a first non-conductive region and a first conductive feature. The first conductive feature includes a first conductive material and a second conductive material. The method may include providing a second element having a second non-conductive region and a second conductive feature, direct bonding the first non-conductive region and the second non-conductive region, and annealing the first conductive feature and the second conductive feature to bond the first conductive material of the first conductive feature to the second conductive feature and to alloy the first conductive material and the second conductive material.

[0137] In one aspect, an element is disclosed having a contact surface. The element may have a non-conductive region with a cavity, the cavity extending from the contact surface at least partially through a thickness of the non-conductive region, and the element may further have a contact pad formed in the cavity, the contact pad including a first conductive material and a second conductive material. The first conductive material is a metallic alloying material configured to alloy with the second conductive material. The alloy has a unit cell size greater than a unit cell size of the second conductive material. The non-conductive region is configured for direct bonding to the non-conductive region of a second element. The contact pad of the element is configured for direct bonding to the contact pad of the second element.

[0138] In one aspect, an element is disclosed having a contact surface. The element may have a non-conductive region with a cavity, the cavity extending from the contact surface at least partially through a thickness of the non-conductive region, and the element may further have a contact pad formed in the cavity. The contact pad includes a first conductive material and a second conductive material. The first conductive material has a unit cell size greater than a unit cell size of the second conductive material. The first conductive material has a coefficient of thermal expansion greater than a coefficient of thermal expansion of the second conductive material. The non-conductive region is configured for direct bonding to the non-conductive region of a second element. The contact pad of the element is configured for direct bonding to the contact pad of the second element.

[0139] In one aspect, an element is disclosed having a contact surface. The element can have a non-conductive region with a cavity, the cavity extending from the contact surface at least partially through a thickness of the non-conductive region, and the element can have a contact pad formed in the cavity, the contact pad having a roughened contact surface. The non-conductive region is configured for direct bonding to the non-conductive region of a second element, and the contact pad of the element is configured for direct bonding to the contact pad of the second element.

[0140] In one embodiment, the roughened contact surface has spikes.

[0141] In one embodiment, the contact pads have an orthorhombic structure.

[0142] In one embodiment, the surface roughness of the contact surface is in the range of 3 nm to 100 nm.

[0143] In one embodiment, the surface roughness of the contact surface is in the range of 3 nm to 50 nm.

[0144] In one embodiment, the surface roughness of the contact surface is higher than the roughness of the bonding surface of the non-conductive region.

[0145] In one aspect, a bonded structure is disclosed. The bonded structure may include a first element having a first non-conductive region with a cavity and a conductive contact feature disposed within the cavity. The conductive contact feature includes a first conductive material and a second conductive material. The bonded structure may further include a second element directly bonded to the non-conductive region of the first element. The conductive contact feature has a unit cell that is larger than a unit cell size that is larger than a unit cell of the first conductive material or the second conductive material.

[0146] In one embodiment, the conductive contact feature comprises an alloy of a first conductive material and a second conductive material.

[0147] In one embodiment, the conductive contact feature is direct bonded to a second conductive contact feature of a second component without an intervening adhesive.

[0148] Unless the context clearly requires otherwise, throughout the specification and claims, the terms "comprise", "comprising", "include", "including" and the like are to be construed in an inclusive sense, i.e., "including, but not limited to", as opposed to an exclusive or exhaustive sense. As used generally herein, the term "coupled" means two or more elements that are either directly connected to each other or connected to each other by one or more intermediate elements. Similarly, as used generally herein, the term "coupled" means two or more elements that are either directly connected to each other or connected to each other by one or more intermediate elements. Additionally, the terms "herein," "above," "below," and words of similar import as used herein refer to the application as a whole and not to any particular portion of the application. Furthermore, as used herein, when a first element is described as "on" or "over" a second element, the first element may be directly located on or over the second element such that the first element and the second element are in direct contact, or the first element may be indirectly located on or over the second element such that one or more elements are interposed between the first element and the second element. Where the context permits, terms in the above Detailed Description using the singular or plural may include the plural or singular, respectively. The term "or" in reference to a list of two or more items includes all of the following interpretations of that term: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0149] Furthermore, conditional terms used in the specification, particularly "can," "could," "might," "may," "eg," "for example," "such as," and the like, unless expressly specified otherwise or understood otherwise within the context in which they are used, are generally intended to imply that certain embodiments include certain features, elements, and / or conditions and that other embodiments do not include certain features, elements, and / or conditions. Thus, such conditional terms are generally not intended to imply that features, elements, and / or conditions are present in any required manner for one or more embodiments.

[0150] Although certain embodiments have been described, these embodiments are provided by way of example only and are not intended to limit the scope of the invention. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms, and furthermore, various omissions, substitutions, and modifications in the form of the methods and systems described herein may be made without departing from the scope of the invention. For example, although blocks are shown in a given arrangement, alternative embodiments may perform substantially the same functions with different components and / or circuit topologies, and some blocks may be deleted, moved, added, divided, combined, and / or modified. Each of these blocks may be embodied in a wide variety of ways. Any suitable combination of elements and acts of the various embodiments described above may be combined to provide further embodiments. The scope of the invention as set forth in the appended claims and equivalents thereto is intended to include such forms or modifications within the scope and spirit of the invention.

Claims

1. An element having a contact surface, wherein the element is It has a nonconductive region with a cavity, the cavity extending from the contact surface and at least partially penetrating the thickness of the nonconductive region, The device has a contact pad formed within the cavity, the contact pad comprising a first conductive material and a second conductive material, the first conductive material having a unit cell size larger than the unit cell size of the second conductive material, and the first conductive material being a metal alloy material. An element wherein the non-conductive region is configured to directly bond to the non-conductive region of a second element, and the contact pad of the element is configured to directly bond to the contact pad of the second element.

2. The element according to claim 1, wherein the unit cell size of the first conductive material is at least 1.3 times the unit cell size of the second conductive material.

3. The element according to claim 1, further comprising a barrier layer conformally provided along the surface of the cavity, wherein the first conductive material is provided between the bottom surface of the cavity and the second conductive material.

4. The element according to claim 1, wherein the first conductive material is completely embedded beneath the second conductive material.

5. The element according to claim 1, wherein the first conductive material has a characteristic molding temperature of less than 230°C.

6. The element according to claim 5, wherein the first conductive material has a characteristic molding temperature of less than 130°C.

7. The element according to claim 1, wherein the first conductive material is a metal silicide, and the metal silicide comprises nickel, titanium, or cobalt.

8. The element according to claim 1, wherein the first conductive material comprises zinc, titanium, or nickel.

9. The element according to claim 1, wherein the second conductive material has a face-centered cubic structure, and the first conductive material has a hexagonal crystal structure.

10. The element according to claim 9, wherein the second conductive material is made of copper, the first conductive material is made of titanium, and the resistivity of the first conductive material is higher than the resistivity of the second conductive material.

11. The element according to claim 1, wherein the resistivity of the first conductive material is less than 40 times the resistivity of the second conductive material.

12. The element according to claim 1, wherein the thickness of the second conductive material is greater than the thickness of the first conductive material.

13. The element according to claim 1, wherein the first conductive material is a material suitable for chemical mechanical polishing.

14. A bonded structure, A first element having a first non-conductive region and a first conductive feature portion, The device comprises a second non-conductive region directly bonded to the first non-conductive region, and a second conductive feature portion directly bonded to the first conductive feature portion to constitute a bonded conductive contact. The bonded conductive contact comprises a first conductive material and a second conductive material, wherein the first conductive material has a unit cell size larger than the unit cell size of the second conductive material, and the first conductive material is an alloy comprising the second conductive material, wherein the bonded structure.

15. The bonded conductive contact is made of an alloying element having gradient properties, as described in claim 14.

16. A bonded structure, It has a first element having a first contact surface, and the first element is Having a first nonconductive region comprising a first cavity, the first cavity extending from the first contact surface and at least partially penetrating the thickness of the first nonconductive region, The first conductive material has a first contact pad formed within the first cavity, the first contact pad comprising a first conductive material and a second conductive material, the first conductive material having a unit cell size larger than the unit cell size of the second conductive material, and the first conductive material being a metal alloy material. The second element has a second contact surface that is directly bonded to the first contact surface, and the second element is The first nonconductive region has a second nonconductive region that is directly bonded to it. A bonded structure having a second contact pad that is directly bonded to the first contact pad.

17. The bonded structure according to claim 16, further comprising a barrier layer conformally provided along the surface of the first cavity.

18. The bonded structure according to claim 16, wherein the first conductive material is provided between the bottom surface of the first cavity and the second conductive material.

19. The bonded structure according to claim 18, wherein the directly bonded first contact pad and second contact pad constitute a bonded conductive contact having an orthorhombic structure, and the directly bonded contact pad is made of a copper-titanium alloy.

20. The bonded structure according to claim 18, wherein the direct-bonded first contact pad and second contact pad are made of an alloying element having gradient properties.

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