Classifications

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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/40—Interconnections external to wafers or substrates, e.g. back-end-of-line [BEOL] metallisations or vias connecting to gate electrodes
  • H10W20/41—Interconnections external to wafers or substrates, e.g. back-end-of-line [BEOL] metallisations or vias connecting to gate electrodes characterised by their conductive parts
  • H10W20/44—Conductive materials thereof
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
  • H10P14/46—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials using a liquid
  • H10P14/47—Electrolytic deposition, i.e. electroplating; Electroless plating
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  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
  • H10P50/26—Dry etching; Plasma etching; Reactive-ion etching of conductive or resistive materials
  • H10P50/264—Dry etching; Plasma etching; Reactive-ion etching of conductive or resistive materials by chemical means
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  • H10P70/00—Cleaning of wafers, substrates or parts of devices
  • H10P70/20—Cleaning during device manufacture
  • H10P70/27—Cleaning during device manufacture during, before or after processing of conductive materials, e.g. polysilicon or amorphous silicon layers
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  • H10W20/00—Interconnections in chips, wafers or substrates
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  • H10W20/021—Manufacture or treatment of interconnections within wafers or substrates
  • H10W20/023—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/01—Manufacture or treatment
  • H10W20/021—Manufacture or treatment of interconnections within wafers or substrates
  • H10W20/023—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias
  • H10W20/0234—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias comprising etching via holes that stop on pads or on electrodes
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/01—Manufacture or treatment
  • H10W20/021—Manufacture or treatment of interconnections within wafers or substrates
  • H10W20/023—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias
  • H10W20/0238—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias comprising etching via holes through pads or through electrodes
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/01—Manufacture or treatment
  • H10W20/021—Manufacture or treatment of interconnections within wafers or substrates
  • H10W20/023—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias
  • H10W20/0245—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias comprising use of blind vias during the manufacture
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/01—Manufacture or treatment
  • H10W20/021—Manufacture or treatment of interconnections within wafers or substrates
  • H10W20/023—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias
  • H10W20/0261—Manufacture or treatment of interconnections within wafers or substrates the interconnections being through-semiconductor vias characterised by the filling method or the material of the conductive fill
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/01—Manufacture or treatment
  • H10W20/031—Manufacture or treatment of conductive parts of the interconnections
  • H10W20/056—Manufacture or treatment of conductive parts of the interconnections by filling conductive material into holes, grooves or trenches
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  • H10W20/00—Interconnections in chips, wafers or substrates
  • H10W20/20—Interconnections within wafers or substrates, e.g. through-silicon vias [TSV]
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  • H10W90/00—Package configurations
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  • H10W72/00—Interconnections or connectors in packages
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  • H10W80/00—Direct bonding of chips, wafers or substrates
  • H10W80/301—Bonding techniques, e.g. hybrid bonding
  • H10W80/331—Bonding techniques, e.g. hybrid bonding characterised by the application of energy for connecting
  • H10W80/333—Compression bonding
  • H10W80/334—Thermocompression bonding
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  • H10W90/00—Package configurations
  • H10W90/20—Configurations of stacked chips
  • H10W90/297—Configurations of stacked chips characterised by the through-semiconductor vias [TSVs] in the stacked chips
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  • H10W90/00—Package configurations
  • H10W90/701—Package configurations characterised by the relative positions of pads or connectors relative to package parts
  • H10W90/791—Package configurations characterised by the relative positions of pads or connectors relative to package parts of direct-bonded pads
  • H10W90/792—Package configurations characterised by the relative positions of pads or connectors relative to package parts of direct-bonded pads between multiple chips

Definitions

• the present invention generally relates to fabrication methods and resulting structures for semiconductor devices. More specifically, the present invention relates to the structure and formation of superconducting metal through silicon vias (TSV).
• TSV superconducting metal through silicon vias
• ICs integrated circuits
• ICs include semiconductor devices formed as a configuration of circuits on a semiconductor substrate.
• a complex network of signal paths will normally be routed to connect the circuit elements distributed on the surface of the substrate.
• Efficient routing of these signals across the device requires formation of multilevel or multilayered conductive networks, which can be formed using schemes, such as, for example, single or dual damascene wiring structures.
• Through-silicon-vias (TSV) are used as interconnects through bulk silicon wafers to reduce interconnect lengths and for 3D stacking. This concept has been around since the late 1950s.
• Metals used to fill the TSVs include tungsten and copper, which are deposited by chemical vapor deposition and electroplating, respectively.
• a TSV is a vertical electrical connection (via) passing completely through a silicon wafer or die.
• TSVs are a high performance interconnect techniques used as an alternative to wire-bond and flip chips to create 3D packages and 3D integrated circuits, compared to alternatives such as package-on-package, because the density of the vias is substantially higher, and because the length of the connections is shorter. Copper is
• a conductive seed layer such as PVD copper
• PVD copper a conductive seed layer
• Conformal plating deposits the copper at an equal rate over the whole surface, but has a high chance of voids forming in the via while bottom-up plating primarily deposits copper from the bottom of the via to form a void free fill.
• An alternate approach to bottom-up plating is to have the seed layer at the very bottom of the via only.
• a special copper plating solution is not necessary in this case and the copper only grows on the exposed seed layer.
• tungsten and copper have a low resistivity, neither are superconducting at a reasonable temperature (>1K) and a superconducting metal fill is desirable in technological application such as RSFQ circuitry.
• the present invention provides a method of fabricating a semiconductor device, the method comprising: patterning a layer of a first superconducting metal on a base substrate to form a first pattern of the superconducting metal; patterning a layer of a second superconducting metal on a cap substrate to form a second pattern of the superconducting metal; etching the second pattern of the second superconducting metal and the cap substrate to form vias, wherein a remaining portion of the second superconducting metal extends about a perimeter of the via on a top surface of the cap substrate; inverting the cap substrate and bonding the cap substrate to the base substrate; removing a portion of the cap substrate to expose and provide openings to the vias, wherein a bottom of the vias expose the first pattern of first superconducting metal; and filling the vias with a third superconducting metal to form a through-substrate-via.
• the present invention provides a method of fabricating a semiconductor device, the method comprising: patterning a layer of a first superconducting metal on a base substrate to form a first pattern of the superconducting metal; patterning a layer of a second superconducting metal on a cap substrate to form a second pattern of the superconducting metal; inverting the cap substrate and bonding the first superconducting metal to the second superconducting metal; forming vias by etching the cap substrate to the bonded second superconducting metal; wherein a bottom of the vias exposes a surface of the second superconducting metal; and filling the vias with a third superconducting metal to form a through-substrate-via from a bottom up.
• the present invention provides a semiconductor structure comprising: a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate comprises a plurality of through-silicon- vias to the thermocompression bonded superconducting metal layer; and an electroplated superconducting metal filling the through-silicon- vias.
• the present invention provides a semiconductor structure comprising: a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate comprises a plurality of through-silicon- vias to the thermocompression bonded superconducting metal layer.
• the present invention provides a method for filling through- silicon- vias with a superconducting metal, the method comprising: providing a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate comprises a plurality of the through-silicon-vias to the thermocompression bonded superconducting metal layer; and electroplating a second superconducting metal into the through-silicon-vias using the thermocompression bonded superconducting metal layer as a bottom electrode during the electroplating process, wherein the filling is from the bottom upwards.
• Embodiments of the present invention are generally directed to semiconductor structures and methods for forming the semiconductor structures.
• a non- limiting example method of fabricating the semiconductor device according to embodiments of the invention includes patterning a layer of a first superconducting metal on a base substrate to form a first pattern of the superconducting metal and patterning a layer of a second superconducting metal on a cap substrate to form a second pattern of the superconducting metal.
• the second pattern of the second superconducting metal and the cap substrate are etched to form vias, wherein a remaining portion of the second superconducting metal extends about a perimeter of the via on a top surface of the cap substrate.
• the cap substrate is inverted and bonded to the base substrate.
• a portion of the cap substrate is removed to expose and provide openings to the vias, wherein a bottom of the vias expose the first pattern of first superconducting metal.
• the vias are filled with a third superconducting metal to form a through-substrate-via.
• a non-limiting example method of fabricating a semiconductor device according to embodiments of the invention include patterning a layer of a first superconducting metal on a base substrate to form a first pattern of the superconducting metal.
• a layer of a second superconducting metal on a cap substrate is patterned to form a second pattern of the superconducting metal.
• the cap substrate is inverted and the first superconducting metal is bonded to the second
• Vias are formed by etching the cap substrate to the bonded second superconducting metal, wherein a bottom of the vias exposes a surface of the second superconducting metal.
• the vias are filled with a third superconducting metal to form a through substrate via from the bottom up.
• a non- limiting example semiconductor structure includes a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate includes a plurality of through-silicon- vias to the thermocompression bonded superconducting metal layer.
• the through-silicon-vias are filled with an electroplated superconducting metal.
• a non- limiting example semiconductor structure includes a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate includes a plurality of through-silicon-vias to the thermocompression bonded superconducting metal layer.
• superconducting metal includes providing a thermocompression bonded superconducting metal layer sandwiched between a first silicon substrate and a second silicon substrate, wherein the second substrate includes a plurality of the through-silicon-vias to the thermocompression bonded superconducting metal layer.
• a second superconducting metal is electroplated into the through-silicon-vias using the
• thermocompression bonded superconducting metal layer as a bottom electrode during the electroplating process, wherein the filling is from the bottom upwards.
• FIG. 1 is a top down view depicting a semiconductor device after a fabrication operation according to embodiments of the invention
• FIG. 2 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention
• FIG. 3 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 4 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 5 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 6 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 7 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 8 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 9 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention.
• FIG. 10 is a sectional view depicting a semiconductor device after a fabrication operation according to embodiments of the invention
• TSVs are used as interconnects through bulk silicon wafers to reduce interconnect lengths and for three dimensional stacking.
• Metals previously used to fill the TSVs included tungsten and copper, which can be deposited by chemical vapor deposition and electroplating respectively.
• copper can be electroplated using a conductive seed layer such as plasma vapor deposited (PVD) copper that is conformal to the via and the wafer surface.
• PVD plasma vapor deposited
• RSFQ circuitry uses superconducting devices, namely Josephson junctions, to process digital signals.
• information is stored in the form of magnetic flux quanta and transferred in the form of Single Flux Quantum (SFQ) voltage pulses.
• RSFQ is one family of superconducting or SFQ logic.
• Others include Reciprocal Quantum Logic (RQL), ERSFQ energy-efficient RSFQ version that does not use bias resistors, or the like.
• Josephson junctions are the active elements for RSFQ electronics, just as transistors are the active elements for semiconductor electronics.
• the present invention is generally directed to a bottoms-up electroplating process for depositing a superconducting metal in a TSV.
• spatially relative terms e.g., "beneath,” “below,” “lower,” “above,” “upper,” and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
• CMOS complementary metal-oxide semiconductor
• fin field-effect transistor CMOS
• FinFET metal-oxide-semiconductor field-effect transistor
• MOSFET metal-oxide-semiconductor field-effect transistor
• other semiconductor devices may or may not be explicitly shown in a given drawing. This does not imply that the layers and/or regions not explicitly shown are omitted from the actual devices.
• certain elements could be left out of particular views for the sake of clarity and/or simplicity when explanations are not necessarily focused on the omitted elements.
• the same or similar reference numbers used throughout the drawings are used to denote the same or similar features, elements, or structures, and thus, a detailed explanation of the same or similar features, elements, or structures will not be repeated for each of the drawings.
• the semiconductor devices and methods for forming same in accordance with embodiments of the present invention can be employed in applications, hardware, and/or electronic systems.
• Suitable hardware and systems for implementing embodiments of the invention can include, but are not limited to, personal computers, communication networks, electronic commerce systems, portable communications devices (e.g., cell and smart phones), solid-state media storage devices, functional circuitry, etc.
• Systems and hardware incorporating the semiconductor devices are contemplated embodiments of the invention. Given the teachings of embodiments of the invention provided herein, one of ordinary skill in the art will be able to contemplate other implementations and applications of embodiments of the invention.
• the semiconductor devices can include, but are not limited to CMOS, MOSFET, and FinFET devices, and/or semiconductor devices that use CMOS, MOSFET, and/or FinFET technology.
• invention or “present invention” are non-limiting terms and not intended to refer to any single aspect of the particular invention but encompass all possible aspects as described in the specification and the claims.
• the term "about” modifying the quantity of an ingredient, component, or reactant of the invention employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutions. Furthermore, variation can occur from inadvertent error in measuring procedures, differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods, and the like.
• the term “about” means within 10% of the reported numerical value.
• the term “about” means within 5% of the reported numerical value.
• the term “about” means within 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.
• TSV through-substrate- via
• FIGS. 1-5 there is shown a process in accordance with one or more embodiments of forming a bottoms-up superconducting TSV.
• a base substrate 12 e.g., a silicon wafer.
• a thin layer of a superconducting metal 14 is blanket deposited at a thickness of about 10 nanometers (nm) to about 5 microns ( ⁇ ) onto the base substrate 12.
• the superconducting metal is deposited at a thickness of about 10 nm to about 1000 nm, and in still other embodiments, the superconducting metal is deposited at a thickness of about 20 nm to about 500 nm.
• the superconducting metal can be aluminum, gallium, indium, lanthanum, molybdenum, niobium, rhenium, ruthenium, tin, tantalum, titanium, zinc, zirconium, alloys thereof, and the like.
• the superconducting metal generally in addition to being
• superconducting functions in a manner similar to a seed layer typically used in copper electroplating processes as will be discussed in greater detail below.
• the thin layer of superconducting metal 14 can be deposited onto the base substrate 12 without previous treatment by evaporation, sputtering or by electroplating. In some cases the substrate can be cleaned prior to deposition of superconducting metal 14, and in addition a relatively thin adhesion layer (e.g., a thickness of 2 nm to 20 nm) such as titanium or tantalum can be deposited prior to layer 14. The layer of superconducting metal 14 is then
• lithographically patterned which can include forming a photoresist (e.g., organic, inorganic or hybrid) atop the layer of the superconducting metal 14.
• a photoresist e.g., organic, inorganic or hybrid
• the photoresist can be formed utilizing a deposition process such as, for example, CVD, PECVD, spin-on coating or the like.
• the photoresist is exposed to a desired pattern of radiation.
• the exposed photoresist is developed utilizing a conventional resist
• a selective etching step can be performed to transfer the pattern from the patterned photoresist into at the layer of superconducting metal 14 stopping at the silicon layer.
• the etching step used in forming the patterned superconducting metal 14 can include a dry etching process (including, for example, reactive ion etching, ion beam etching, plasma etching or laser ablation), a wet chemical etching process or any combination thereof.
• FIG. 2 there is depicted a cap substrate 18.
• a layer of superconducting metal layer 16 is deposited onto a cap substrate 18.
• the superconducting metal 16 can be the same as the superconducting metal 14 formed on the base substrate 12.
• the layers of superconducting metals 14, 16 can be formed of aluminum.
• the cap substrate 18 can be of the same material as the base substrate 12, e.g., a silicon wafer.
• the superconducting metal 16 can be deposited at the same or different thickness as superconducting layer 14. Generally, superconducting metal 16 can be blanket deposited onto the cap susbtratel8 at a thickness of about 10 nanometers (nm) to about 5 microns ( ⁇ ). In one or more other embodiments, the superconducting metal is deposited at a thickness of about 10 nm to about 1000 nm, and in still other embodiments, the superconducting metal is deposited at a thickness of about 20 nm to about 500 nm.
• the superconducting metals 14, 16 can be dissimilar or similar depending on the desired application.
• the layer of superconducting metal 16 is then lithographically patterned in the manner described above.
• Vias 20 are then formed in the cap substrate 18 by lithographically patterning and anisotropically etching the silicon substrate.
• the vias 20 will be utilized to define the TSVs and extend partly through the cap substrate 18.
• the vias can extend to a depth of about 10 microns ( ⁇ ) to as much as about 350 ⁇ depending on the initial thickness into the silicon substrate, which typically have a thickness generally depending on diameter of about 275 ⁇ to about 775 ⁇ .
• the via depth into the cap substrate 18 is about 10 ⁇ to about 250 ⁇ , and in still other embodiments, the via depth into the cap substrate 18 is at about 20 ⁇ to about 150 ⁇ .
• the silicon substrate can be subjected to wet or dry etching to form the vias.
• the resulting pattern of the superconducting metal 16 and vias 20 in the cap substrate 18 are such that a portion of the superconducting material 16 surrounds a perimeter top surface about the via 20.
• the cap substrate 18 including the patterned superconducting metal 16 and vias 20 thereon is then inverted and bonded to the base substrate 12 such as by
• thermocompression bonding also referred to as diffusion bonding.
• the surrounding portions of the superconducting metal 16 in the cap substrate are mated to the corresponding patterned superconducting metal 14 on the base substrate 12. That is, the portion of the superconducting material 16 surrounding the perimeter top surface of the vias 20 contacts the corresponding patterned superconducting metal 14 on the base substrate 12. In this manner, the
• superconducting metals 14, 16 on each substrate 12, 18 can be brought together into atomic contact by applying force and heat simultaneously to bond the cap substrate 18 to the base substrate 12 as shown.
• the resulting structure includes the surrounding portion of
• the superconducting metal 16 about the perimeter from the cap substrate 18 is bonded to a corresponding portion of the superconducting metal 14 in the base substrate 12 whereas the inverted vias 20 include a superconducting metal layer (from the base substrate 12) at the bottom 22 of each via 20.
• thermocompression bonding aluminum on one substrate can be bonded to aluminum on another substrate by subjected the substrates to a bonding temperature from about 400 °C to about 450 °C with an applied force above 70 kN for 20 to 45 min, although higher or lower temperatures and forces can be used for different superconducting metals.
• the cap substrate 18 is subjected to a wafer backgrinding process to remove a portion of the cap substrate so as to expose and open the vias 20.
• the backgrinding process generally includes application of a slurry of coarse particles to coarsely grind the wafer and remove a bulk of the wafer thickness. A finer grit is then used to polish the wafer.
• the coarse grinding can be used to remove about 90 percent of the substrate.
• the superconducting metal surface 22 at the bottom of the vias 20 is cleaned to remove any oxide thereon.
• Cleaning can include applying an etchant configured to selectively remove the oxide and any residual slurry contaminants from the backgrinding process.
• the superconducting metal surface at the via bottom 22 can be prepped for filling by an optional electroless plating.
• a superconducting metal such as zinc or tin can be electrolessly plated onto an aluminum layer, which can promote adhesion of the fill material during a subsequent electroplating process.
• Aluminum by itself, is a very difficult substrate to directly plate thereon.
• the vias 20 are filled with a superconducting metal or metal alloy to form the TSV 24 by subjecting the substrate to an electroplating process by making electrical contact to the backside of the base substrate 14 and immersing the substrate into an electrolyte bath.
• the superconducting metal or metal alloy grows from the bottom up until the TSV is fully filled with the superconducting metal and ready for further processing.
• the previously deposited superconducting metals of layers 14, 16 function as a bottom electrode during the electroplating process
• the electrolyte bath can be made up of electrolyte solvent and one or more salts including a source of metal or metals to be electroplated. Often salts can also be present to improve conductivity and efficiency of the process.
• the solvent can be aprotic or at least very weakly acidic. In addition, the solvent should be such as to dissolve reasonable amounts of metal salts (sources of the metal being plated) and other salts to increase electrolyte
• the solvent should be stable not only to the substrate material being electroplated but under the condition of electroplating the metal.
• the non-aqueous solvent is chosen from various stable organic liquids such as nitriles, carbonates, amides, ketones, alcohols, glycols, ethers, and the like.
• Typical solvents are acetonitrile, benzonitrile, diglyme (diethylene glycol dimethyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), ethylene glycol, dimethyl formamide, acetamide, acetone, methyl isobutyl ketone, tetrahydrofuran,
• the solvent can be acetonitrile, propylene carbonate or methanol. Mixtures of the above solvents can be used as well as other substances that are stable, suitable for use in an electroplating process and not reactive to the material being electroplated. More acidic solvents can be used (even water) provided that the potential required to plate the metal protects the material being electroplated from reaction with water.
• the superconducting metals can be copper, tin, silver, lead, zinc, cadmium, indium, nickel, alloys thereof, and combinations of these metals.
• metals such as indium, tin, lead and tin-lead alloys are utilized because of ease of plating, availability, high electrical and thermal conductivity.
• the word metal should be understood to include various superconducting alloys (e.g., tin-lead alloy) and mixtures of metals as well as pure elemental metal.
• the metals are introduced into the electroplating bath usually in the form of a salt, preferably a salt soluble in the electrolyte solvent and with an anion which is stable under conditions of the electroplating process.
• Typical anions are nitrate, perchlorate, halide
• concentrations vary from about 0.001 Molar to saturation. Too low a concentration requires too much time to electroplate and too much replenishment during processing. Typically, concentrations are adjusted to maximize conductivity when combined with certain ionic (conducting) salts.
• the bath is typically made up of non-aqueous solvent described above, an electrochemically stable metal salt of the metal being plated (e.g., nitrate, perchlorate) and optionally a stable salt to increase ionic conductivity.
• concentrations are usually close to saturation, for example from about 1/10 the concentration of a saturated solution to the concentration of a saturated solution. By way of example, concentrations from 0.1 of saturated solutions to the concentration of the saturated solution can be used.
• the bath can contain conducting salts to increase the conductivity of the bath.
• These conducting salts are typically alkali-metal salts with stable anions with good solubility in the non-aqueous solvents.
• Typical anions are the same as for the metal salts given above (nitrate, perchlorate, halides, tetrafluoroborate (e.g. sodium tetrafluoroborate) and hexafluoroaresenate (e.g., lithium hexafluroarsenate).
• tetra alkylammonium salts such as tetrabutylammonium halides and tetraethyl ammonium halides.
• Concentrations of the conducting salts can vary from 0.001 molar to saturation and are usually determined so as to maximize conductivity of the bath. Generally, concentrations near saturation (within 0.1 of saturation to saturation) are preferred.
• the electroplating process is carried out in a conventional manner with a
• FIGS. 6-10 the process for forming the superconducting TSVs is shown in FIGS. 6-10.
• a base substrate 112 is provided, e.g., a silicon wafer.
• a thin layer of a superconducting metal 114 is blanket deposited at a thickness of about 10 nanometers (nm) to about 5 microns ( ⁇ ).
• nm nanometers
• ⁇ microns
• superconducting metal is deposited at a thickness of about 10 nm to about 1000 nm, and in still other embodiments, the superconducting metal is deposited at a thickness of about 20 nm to about 500 nm.
• the superconducting metal can be a metal as previously described.
• the layer of superconducting metal 114 is then lithographically patterned to form a patterned superconducting metal as shown.
• a cap substrate 118 is provided and thin layer of a superconducting metal 120 is blanket deposited at a thickness of about 10 nanometers (nm) to about 5 microns ( ⁇ ).
• the superconducting metal is deposited at a thickness of about 10 nm to about 1000 nm, and in still other embodiments, the superconducting metal is deposited at a thickness of about 20 nm to about 500 nm.
• the superconducting metal can be a metal as previously described.
• the layer of superconducting metal 120 is then lithographically patterned to form a patterned superconducting metal similar to that provided in FIG. 6.
• the cap substrate 118 is inverted and the patterned superconductor layer 120 is aligned with the corresponding patterned superconducting metal 114 on the base substrate 112 and subjected to thermocompression bonding to bond the cap substrate 118 to the base substrate 112.
• the cap substrate 118 is subjected to backgrinding process as described above to remove a portion of the cap substrate. The remaining thickness of the cap substrate 118 will be used to define the length of the TSV. The cap substrate 118 is then
• thermocompression bonded and patterned superconducting metals 114/120 are configured to land on the thermocompression bonded and patterned superconducting metals 114/120.
• the topmost exposed superconducting metal 120 is then cleaned and prepped if needed by electrolessly prepped as previously described using a superconductor such as zinc or tin to promote adhesion during the fill process
• Deposition is any process that grows, coats, or otherwise transfers a material onto the wafer.
• Available technologies include physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE) and more recently, atomic layer deposition (ALD) among others.
• Removal/etching is any process that removes material from the wafer. Examples include etch processes (either wet or dry), and chemical-mechanical planarization (CMP), and the like.
• Semiconductor doping is the modification of electrical properties by doping, for example, transistor sources and drains, generally by diffusion and/or by ion implantation. These doping processes are followed by furnace annealing or by rapid thermal annealing (RTA). Annealing serves to activate the implanted dopants. Films of both conductors (e.g., poly-silicon, aluminum, copper, etc.) and insulators (e.g., various forms of silicon dioxide, silicon nitride, etc.) are used to connect and isolate transistors and their components.
• conductors e.g., poly-silicon, aluminum, copper, etc.
• insulators e.g., various forms of silicon dioxide, silicon nitride, etc.
• semiconductor lithography is the formation of three- dimensional relief images or patterns on the semiconductor substrate for subsequent transfer of the pattern to the substrate.
• the patterns are formed by a light sensitive polymer called a photo-resist.
• lithography and etch pattern transfer steps are repeated multiple times. Each pattern being printed on the wafer is aligned to the previously formed patterns and slowly the conductors, insulators and selectively doped regions are built up to form the final device.

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