Semiconductor Die, Semiconductor Device and Method for Forming a Semiconductor Die

A semiconductor die is provided. The semiconductor die comprises a plurality of transistors arranged at a front side of a semiconductor substrate and an electrically conductive structure. A top surface of the electrically conductive structure is contacted at the front side of the semiconductor substrate and a bottom surface of the electrically conductive structure is contacted at a backside of the semiconductor substrate. Further, the semiconductor die comprises a backside metallization layer stack attached to the backside of the semiconductor substrate. A first portion of a wiring structure is formed in a first metallization layer of the backside metallization layer stack and a second portion of the wiring structure is formed in a second metallization layer of the backside metallization layer stack. Further, a tapered vertical connection is formed between the first portion of the wiring structure and the second portion of the wiring structure, wherein the first metallization layer is closer to the semiconductor substrate than the second metallization layer. A width of the tapered vertical connection increases towards the first metallization layer.

FIELD

The present disclosure relates to the field of semiconductor devices. In particular, examples relate to a semiconductor die, a semiconductor device and a method for forming a semiconductor die.

BACKGROUND

The shrinkage of advanced semiconductor technologies is mandatory to create silicon dies with new and improved functionality. This shrinkage is limited by an input/output (I/O) of signals and/or a power functionality of a silicon die due to the footprint of elements (e.g., of vias). For example, a connection via a back-end-of-line (BEOL) stack may be long and on high power and at high switching rates challenging to realize. Further, the connection may be limited by a rate of change of current that the connection can provide without drops or spikes in the current to cause fails in the functionality. Via sizes, copper thickness and path lengths are limiting factors of the BEOL stack. Thus, there may be a need for an improved concept for providing power to the silicon die.

DETAILED DESCRIPTION

FIG.1shows a cross-sectional view of a semiconductor die100. The semiconductor die100comprises a plurality of transistors133arranged at a front side of a semiconductor substrate112and an electrically conductive structure140. A top surface of the electrically conductive structure142is contacted at the front side of the semiconductor substrate112and a bottom surface of the electrically conductive structure144is contacted at a backside of the semiconductor substrate114. Further, the semiconductor die100comprises a backside metallization layer stack120attached to the backside of the semiconductor substrate114. A first portion of a wiring structure152of the backside metallization layer stack is formed in a first metallization layer122of the backside metallization layer stack120and a second portion of the wiring structure154is formed in a second metallization layer124of the backside metallization layer stack120. Further, a tapered vertical connection156is formed between the first portion of the wiring structure152and the second portion of the wiring structure154. The first metallization layer122is closer to the semiconductor substrate110than the second metallization layer124. A width of the tapered vertical connection156increases towards the first metallization layer122.

By attaching the backside metallization layer stack120to the semiconductor substrate110an improved electrical connection for the plurality of transistors133can be provided and/or a manufacturing process can be eased. For example, attaching the backside metallization layer stack120may avoid the forming of trough substrate vias (TSV) or nano TSVs to electrically connect or power the plurality of transistors133. Thus, a tradeoff between the connection of the plurality of transistors133and a structure density for thick silicon substrate (which enable an improved warpage and easier handling in the manufacturing) may be omitted. For example, also the generation of nano TSVs, which requires very thin wafer handling, which is a complex process with risk for higher yield loss, as it is challenging to hit the electrically conductive line140of the semiconductor substrate110on each dimension from the backside of the silicon substrate114, can be omitted by attaching the backside metallization layer stack120to the semiconductor substrate110.

The backside metallization layer stack120can be manufactured/processed separately from the semiconductor substrate110. Thus, all processes to generate the backside metallization layer stack120may be done on an, e.g., optimized front-end-of-line (FEOL) process and/or independent of the functional process node. For example, a contact interface structure to connect the backside metallization layer stack120to the electrically conductive line140of the semiconductor substrate110can be formed. Since, the contact interface structure is formed separately of the semiconductor substrate manufacturing process an overall assembly yield may be improved, by scrap low yielding backside metallization layer stacks120(e.g., formed on a wafer) before attaching them to a semiconductor substrate110, compared to a TSVs process on the semiconductor substrate110, where every TSV defect result in direct yield loss. Thus, by manufacturing/processing the backside metallization layer stack120separately from the semiconductor substrate110a yield of the semiconductor device manufacturing can be increased.

Further, additional materials to improve the functionality of the semiconductor device100can be implemented into the backside metallization layer stack120(e.g. special dielectric for caps or magnetic material for coils) without influencing the (functional) semiconductor substrate110. This way, the backside metallization layer stack120can be adjusted to a use case without limitation due to a lack of process capability of the semiconductor substrate110.

The electrically conductive structure140may be an electrically conductive line140or may comprise an electrically conductive line140. The electrically conductive line140may run laterally in a trench, which extends vertically into the semiconductor substrate110. The top surface of the electrically conductive line140may be coplanar with the front side surface of the semiconductor substrate110or may protrude from the front side surface of the semiconductor substrate110. The top surface of the electrically conductive line140may be contacted by one or more vias and/or one or more contact structures one or more transistors. The electrically conductive line140may extend to the back side of the semiconductor substrate110(if the semiconductor substrate is thin). In this case, the bottom surface of the electrically conductive structure140may be the bottom surface of the electrically conductive line140. In this way, a connection from front side to back side may be implemented with low effort, since the number of necessary process steps may be kept low. Alternatively, a through substrate via may be connected to the electrically conductive line (e.g. if the semiconductor substrate is thick). For example, the through substrate via may extend from a bottom surface of the electrically conductive line140to the backside of the semiconductor substrate. In this case, the bottom surface of the electrically conductive structure140may be the bottom surface of the through substrate via.

The electrically conductive line140may be formed of any appropriate conductive material, such as copper, silver, nickel, gold, aluminum, other metals or alloys, or combinations of materials, for example. The electrically conductive line140may be an electrically conductive trace.

The wiring structure150may be formed of any appropriate conductive material, such as copper, silver, nickel, gold, aluminum, other metals or alloys, or combinations of materials, for example.

AlthoughFIG.1(and others of the accompanying drawings) illustrate a specific number and arrangement of the electrically conductive line140in the semiconductor substrate110and of the wiring structure150in the backside metallization layer stack120these are simply illustrative, and any suitable number and arrangement may be used.

In some embodiments, the electrically conductive line140and/or the wiring structure150may comprises a pillar of conductive material (e.g., a metal, such as copper), a through-hole plated with a conductive material, a via filled with a conductive material, a vertical or planer trace, a wire, a contact structure, a wiring structure or any other conductive trace along which electrical signals are to flow, e.g., the first portion or the second portion to contact the electrically conductive line140at the front side112and/or and the backside of the semiconductor substrate114, respectively. Other conductive elements may be disposed between or around multiple different vias in an electrically conductive line140/wiring structure150. For example, the wiring structure150may comprise wiring traces in the at least one the first122or second metallization layer124. For example, the wiring structure150may comprise vias in an interlayer dielectric (ILD) layer.

As can be seen inFIG.1the wiring structure150comprises a tapered vertical connection156, e.g., a tapered via. The thickness of the tapered vertical connection156is at a first end157larger as at an opposing second end158. The first end157is closer to the backside of the semiconductor substrate114as the second end158. For example, the tapered vertical connection156has a tapered cross-sectional configuration, where the tapered vertical connection walls taper so as to form a reduced cross-sectional dimension in a direction from the first metallization layer122toward the second metallization layer124.

The tapered vertical connection156may be directly electrically connected with the first portion152and/or the second portion of the wiring structure154.

The semiconductor substrate110may comprise any type of substrate. For example, the semiconductor substrate110may comprise or may be composed of a single crystal of a material which may include, but is not limited to, silicon, germanium, silicon-germanium, germanium-tin, silicon-germanium-tin, or a group III-V compound semiconductor material. The semiconductor substrate110may be a bulk substrate or may be part of a semiconductor-on-insulator SOI substrate.

The backside metallization layer stack120may be attached to the backside of the semiconductor substrate114by a direct bonding (DB) process, e.g., a front side of the backside metallization layer stack (and the backside of the semiconductor substrate114) may comprise a DB region. For example, a (hybrid) bond pad may be formed on a front side of the backside metallization layer stack, e.g., the first portion152may be the (hybrid) bond pad. As described above the first portion152(e.g., the (hybrid) pond pad) can be formed separately from the semiconductor substrate110processing, thus an alignment on a thick, good processable substrate (e.g., a wafer) upfront on the exact location where they are needed, e.g., to contact the electrically conductive line140at the backside of the semiconductor substrate114, can be achieved.

As used herein, the term “direct bonding” is used to include metal-to-metal bonding techniques (e.g., copper-to-copper bonding, or other techniques in which the DB contacts of opposing DB interfaces are brought into contact first, then subject to heat and compression) and hybrid bonding techniques (e.g., techniques in which the DB dielectric of opposing DB interfaces are brought into contact first, then subject to heat and sometimes compression, or techniques in which the DB contacts and the DB dielectric of opposing DB interfaces are brought into contact substantially simultaneously, then subject to heat and compression). In such techniques, the DB contacts and the DB dielectric at one DB interface are brought into contact with the DB contacts and the DB dielectric at another DB interface, respectively, and elevated pressures and/or temperatures may be applied to cause the contacting DB contacts and/or the contacting DB dielectrics to bond. In some embodiments, this bond may be achieved without the use of intervening solder or an anisotropic conductive material, while in some other embodiments, a thin cap of solder may be used in a DB interconnect to accommodate planarity, and this solder may become an intermetallic compound (IMC) in the DB region during processing. In some embodiments, this bond may be achieved by use of copper-copper bonding. DB interconnects may be capable of reliably conducting a higher current than other types of interconnects; for example, some conventional solder interconnects may form large volumes of brittle IMCs when current flows, and the maximum current provided through such interconnects may be constrained to mitigate mechanical failure.

A DB dielectric may include one or more dielectric materials, such as one or more inorganic dielectric materials. For example, a DB dielectric may include silicon and nitrogen (e.g., in the form of silicon nitride); silicon and oxygen (e.g., in the form of silicon oxide); silicon, carbon, and nitrogen (e.g., in the form of silicon carbonitride); carbon and oxygen (e.g., in the form of a carbon-doped oxide); silicon, oxygen, and nitrogen (e.g., in the form of silicon oxynitride); aluminum and oxygen (e.g., in the form of aluminum oxide); titanium and oxygen (e.g., in the form of titanium oxide); hafnium and oxygen (e.g., in the form of hafnium oxide); silicon, oxygen, carbon, and hydrogen (e.g., in the form of tetraethyl orthosilicate (TEOS)); zirconium and oxygen (e.g., in the form of zirconium oxide); niobium and oxygen (e.g., in the form of niobium oxide); tantalum and oxygen (e.g., in the form of tantalum oxide); and combinations thereof.

A DB contact may include a pillar, a pad, or other structure. The DB contacts may have a same structure at both DB interfaces (a front side of the backside metallization layer stack and the backside of the semiconductor substrate114), or the DB contacts at different DB interfaces may have different structures. For example, in some embodiments, a DB contact in one DB interface may include a metal pillar (e.g., a copper pillar), and a complementary DB contact in a complementary DB interface may include a metal pad (e.g., a copper pad) recessed in a dielectric. A DB contact may include any one or more conductive materials, such as copper, manganese, titanium, gold, silver, palladium, nickel, copper and aluminum (e.g., in the form of a copper aluminum alloy), tantalum (e.g., tantalum metal, or tantalum and nitrogen in the form of tantalum nitride), cobalt, cobalt and iron (e.g., in the form of a cobalt iron alloy), or any alloys of any of the foregoing (e.g., copper, manganese, and nickel in the form of manganin). In some embodiments, the DB dielectric and the DB contacts of a DB interface may be manufactured using low-temperature deposition techniques (e.g., techniques in which deposition occurs at temperatures below degrees Celsius, or below degrees Celsius), such as low-temperature plasma-enhanced chemical vapor deposition (PECVD).

The semiconductor die100may take any suitable form. For example, the semiconductor die100may be a processor die (e.g. CPU, GPU or DSP), a memory die, a sensor die, or a platform controller hub, or may include any combination of circuits having these functions.

In an example, the first portion of the wiring structure152may be a contact interface structure connected to the bottom surface of the electrically conductive line. For example, the contact interface structure may be a (hybrid) bond pad. Thus, the electrically line140, e.g., the bottom surface of the electrically conductive line144, may be electrically connected to the contact interface structure.

In an example, the backside metallization layer stack120may further comprise a bonding surface layer arranged besides the contact interface structure comprising at least one of silicon carbon nitride, silicon oxide or polyimide. The bonding surface layer and the hybrid bonding pads may be utilized to perform a hybrid bonding process. Hybrid bonding is a technique to bond metal-electrode and insulator interfaces, such as Cu/SiO2hybrid surface (e.g., the first portion of the wiring structure152and the bonding layer).

In an example, a length of the contact interface structure may be at most 160 nm, or at most 130 nm or at most 100 nm and/or at least 30 nm or at least 60 nm or at least 80 nm. In an example, a minimal lateral dimension of the bottom surface of the electrically conductive line 144 may be at most 160 nm, or at most 130 nm or at most 100 nm and/or at least 30 nm or at least 60 nm or at least 80 nm.

In an example, a thickness of the first metallization layer122may be at most 200 nm, or at most 150 nm, at most 100 nm, at most 80 nm, at most 60 nm or at most 40 nm and/or at least 40 nm or at least 60 nm or at least 80 nm. In an example, a thickness of the semiconductor substrate 110 may be at most 300 nm, or at most 200 nm, at most 100 nm, at most 80 nm, at most 50 nm or at most 20 nm and/or at least 20 nm or at least 50 nm or at least 80 nm.

In an example, the plurality of transistors133may comprise at least one of a fin field-effect transistor, a nanowire transistor, a ribbon transistor or a gate all around transistor. A gate all around transistor is a structure where the gate contacts the channel from all sides.

In an example, the electrically conductive line140may be electrically insulated from the semiconductor substrate110.

In an example, a layer (e.g., the first metallization layer122or the second metallization layer124) of the backside metallization layer stack120may comprise a dielectric material of a capacitor, e.g., silicon oxide, silicon nitride, etc. In an example, a layer (e.g., the first metallization layer122or the second metallization layer124) of the backside metallization layer stack120may comprise a magnetic material of an inductor, e.g., iron oxide, iron platinum, etc. In an example, a layer (e.g., the first metallization layer122or the second metallization layer124) of the backside metallization layer stack120may comprise a material with a thermal conductivity of at least 1 W/mK, at least 2 W/mK or at least 3 W/mK.

In an example, the backside metallization layer stack120may further comprise a circuit element (e.g., a capacitor, resistor, inductor, etc.) electrically connected to the electrically conductive line140. Thus, an integration of the circuit element can be eased by integrating a necessary circuit element into the backside metallization layer stack120instead of into the semiconductor substrate110.

In an example, the semiconductor die100may further comprise circuitry comprising at least one transistor of the plurality of transistors. The circuit element is electrically connected to the transistor of the circuitry via the electrically conductive line140. Thus, a circuitry can be provided in an eased way utilizing the electrically conductive line140.

In an example, the semiconductor die100may further comprise a front side wiring layer stack formed on the front side of the semiconductor substrate112. The front side wiring layer stack comprises a front side wiring structure electrically connected to the wiring structure of the backside metallization layer stack. For example, the front side wiring layer stack may be formed with FEOL and/or BEOL process(es).

More details and aspects are mentioned in connection with the examples described below. The example shown inFIG.1may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples described below (e.g.,FIGS.2-6).

FIG.2shows a cross-sectional view of another example of a semiconductor die200. The semiconductor die200comprises a semiconductor substrate210and a backside metallization layer stack220. The backside metallization layer stack220comprises a wiring structure250, which comprises a first portion of the wiring structure252, e.g., a hybrid bond pad252, a tapered vertical connection256and a second portion of the wiring structure254. The second portion of the wiring structure254may be a contact interface structure, e.g., to electrically contact the backside metallization layer stack220to, e.g., a redistribution layer, a package substrate, a lead frame, etc.

Further, the semiconductor die200comprises a front side wiring layer stack280, which comprises a front wiring structure282, e.g., to electrically connect the plurality of transistors to an external electrical signal (e.g., a power supply). The front side wiring layer stack280may be attached to the front side of the semiconductor substrate210. The front wiring structure282may be electrically connected to the wiring structure250.

For example, the electrically conductive line240of the semiconductor substrate210may be electrically connected via a bottom surface of the electrically conductive line244with the hybrid bond pad252and the front wiring structure282may be electrically connected with a front surface of the electrically conductive line242with the front wiring structure282, e.g., via a contact interface structure (e.g., a bond pad).

For example, the second portion of the wiring structure254may act as a backside metallization, e.g., the second portion of the wiring structure254may be uncovered.

By attaching the backside metallization layer stack220to the semiconductor substrate210both can be manufactured/processed separately, as described above. For example, the front side wiring layer stack280may be formed by FEOL and/or BEOL process(es) excluding dielectric material and the backside metallization layer stack220may be formed by FEOL and/or BEOL process(es) including dielectric material and also the forming of a backside metallization.

The attaching may be performed by a hybrid bonding process utilizing the hybrid bond pad252. The hybrid bond pad252may be directly bonded to the bottom surface of the electrically conductive line244via hybrid bonding. This way, an interconnect for an electrical signal, e.g., a power supply, a VSS, etc. may be formed in an improved way from the backside of the semiconductor die200to the electrically conductive line240via the wiring structure250.

More details and aspects are mentioned in connection with the examples described above and/or below. The example shown inFIG.2may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples describe above (e.g.,FIG.1) and/or below (e.g.,FIGS.3-6).

FIG.3shows an example of a method300for forming a semiconductor die. The method300comprises forming310a plurality of transistors arranged at a front side of a semiconductor substrate and an electrically conductive structure. A top surface of the electrically conductive structure is contacted at the front side of the semiconductor substrate and a bottom surface of the electrically conductive structure is uncovered at a backside of the semiconductor substrate. Further, the method300comprises forming320a backside metallization layer stack and attaching330the backside metallization layer stack to the backside of the semiconductor substrate.

The electrically conductive structure may be an electrically conductive line or may comprise an electrically conductive line. The electrically conductive line may run laterally in a trench, which extends vertically into semiconductor substrate. The top surface of the electrically conductive line may be coplanar with the front side surface of the semiconductor substrate or may protrude from the front side surface of the semiconductor substrate. The top surface of the electrically conductive line may be contacted by one or more vias and/or one or more contact structures one or more transistors. The electrically conductive line may extend to the back side of the semiconductor substrate (of the semiconductor substrate is thin). In this case, the bottom surface of the electrically conductive structure may be the bottom surface of the electrically conductive line. In this way, a connection from front side to back side may be implemented with low effort, since the number of necessary process steps may be kept low. Alternatively, a through substrate via may be connected to the electrically conductive line (e.g. if the semiconductor substrate is hick). For example, the through substrate via may extend from a bottom surface of the electrically conductive line to the backside of the semiconductor substrate. In this case, the bottom surface of the electrically conductive structure may be the bottom surface of the through substrate via.

For example, analogous to method300, the plurality of transistors may be formed on a semiconductor wafer instead of on a semiconductor substrate. This way, a plurality of plurality of transistors can be formed with an eased manufacturing process. Further, the semiconductor wafer can be used to attach the plurality of plurality of transistors to a plurality of backside metallization layer stacks. For example, the plurality of backside metallization layer stacks may be formed on a carrier, e.g., a wafer, and thus the attachment may be performed by a wafer-to-wafer process, e.g., a wafer-to-wafer bonding process. This way, an alignment for attaching can be increased. The semiconductor wafer comprising the plurality of plurality of transistors and the carrier comprising the plurality of backside metallization layer stacks can be alignment more accurately compared to a semiconductor substrate and a backside metallization layer stack, because handling can be improved, e.g., a wafer-to-wafer bonding process is more accurate. Thus, a plurality of semiconductor dies can be formed in improved manufacturing process, which may increase a yield of the manufacturing process.

After attaching the semiconductor wafer to the carrier to form the plurality of semiconductor dies the carrier may be removed and the semiconductor waver may be diced to separate the plurality of semiconductor dies. The separated semiconductor dies can then be attached to a package substrate to provide a packed semiconductor die.

More details and aspects are mentioned in connection with the examples described above and/or below. The example shown inFIG.3may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples describe above (e.g.,FIGS.1-2) and/or below (e.g.,FIGS.4-6).

FIG.4shows an example of a method for forming a semiconductor die. TheFIGS.4a-4fshow an example of a method for forming a semiconductor substrate for the semiconductor die. In an example, the method may comprise forming an etch stop layer inside the semiconductor substrate, The etch stop layer is located at a depth larger than a depth of the trench for the electrically conductive line.FIG.4ashows a semiconductor substrate (e.g., a thick wafer) with an etch stop layer490. The brighter area in the middle of the semiconductor substrate illustrates a break in the semiconductor substrate, to reflect that the semiconductor substrate has full thickness.

In an example, the method may further comprise forming the electrically conductive line comprising forming a trench into the semiconductor substrate from the front side of the semiconductor substrate and filling the trench with electrically conductive material of the electrically conductive line. Further, removing a part of the semiconductor substrate from the backside of the semiconductor substrate to uncover the bottom surface of the electrically conductive line may be comprised.

For a hybrid bonding connection to a bottom of the electrically conductive line each trench for forming the electrically conductive line need to be embedded deep in the Si-Bulk and stop right over the etch layer. The forming of the trench may comprise for example, forming a very deep trench439for an electrically conductive line, such like a deep buried power rail (BPR) may be formed. As can be seen inFIG.4ba trench for a normal deep BPR may have a larger distance to the etch stop layer490as the very deep trench439for the very deep BPR. In an example, a distance between the etch stop layer and the trench439may be at most 100 nm, at most 70, at most 50 nm, at most 30 nm or at most 10 nm and/or at least 10 nm, at least 30 or at least 50 nm, which may be only achieved for the very deep BPR. When generating the very deep trench439for the very deep BPR (e.g., a via) a depth of the very deep trench439may be stopped right above the etch stop layer490. Further, the very deep trench439may be isolated against the semiconductor substrate.

As can be seen inFIG.4cthe electrically conductive line440and the plurality of transistors may be formed after forming the trenches. After forming the very deep trench439the very deep trench may be filled (e.g., by any suitable conductive material) to form the electrically conductive line440, e.g., the very deep BPR440.

FIG.4dshows the semiconductor substrate with the front wiring structure480, which is attached to the front side of the semiconductor substrate. The front wiring structure480may be formed by FEOL and/or BEOL process(es).

FIG.4eshows a flipped semiconductor substrate. A carrier system492may be attached to a front side of the front wiring structure (and thus at the side of the active side of the semiconductor substrate). The carrier system492may reduce warping during a removing of the backside of the semiconductor substrate. Further, the carrier system492may be used for following processes, such like alignment with the backside metallization layer stack, which may increase an alignment accuracy.

In an example, the method may further comprise removing a first part of the semiconductor substrate from the backside until the etch stop layer is reached. Removing the first part comprises at least one of mechanical etching, dry etching or wet etching. As can be seen inFIG.4f, after a first removing process of the backside of the semiconductor substrate, the very deep BPR may be not yet uncovered. For example, the first removing process may be used to remove the backside of the semiconductor substrate to the etch stop layer. This may comprise/be performed by grinding down the backside of the semiconductor substrate till the etch stop layer (e.g., with mechanical and/or wet/dry etch processes).

In an example, the method may further comprise uncovering the bottom surface of the electrically conductive structure by removing a second part of the semiconductor substrate by at least one of chemical mechanical planarization or plasma etching. For example, removing the second part may comprise/be performed by a more accurate process as removing the first part, thus a processing time of the semiconductor substrate may be decreased, and an accuracy may be increased. A surface area of the very deep PBR may be uncovered after removing the second part, as can be seen inFIG.4g. For example, the bottom surface of the electrically conductive line as described above (e.g., with respect toFIG.1) may be the uncovered surface area of the very deep BPR.

FIG.4hshows a cross-sectional view of the backside metallization layer stack before attaching it to the semiconductor substrate. The backside metallization layer stack may be a thick backside wafer with a backside metallization stack (e.g., the tapered vertical connection and the second portion of the wiring structure as described above) and the hybrid bond pads (e.g., the first portion of the wiring structure as described above).

For the backside metallization layer stack, including the (fine) hybrid bond pad, a dedicated substrate/wafer may be generated. In an example, the method may further comprise forming the backside metallization layer stack on a carrier. In an example, the carrier comprises or is made of at least one of stainless steel, glass or semiconductor material.

Starting on a such a carrier, e.g., a thick silicon wafer or a stiff carrier wafer (e.g. stainless steel or any other stiff material), first the thick copper layers may be formed, followed by a planarization process to get rid of topography. Finally, the hybrid bond pad may be generated with a dimension of at most 120 nm, or at most 100 nm, or at most 80 nm, or at most 60 nm with front end processes and within materials for annealing to the wafer-to-wafer interface (e.g. silicon carbon nitride, silicon oxide, polyimide, etc.) besides the hybrid bond pad.

Optionally, since the backside metallization layer stack is processed separately from the semiconductor device, partial other materials for electrical or thermal improvements/functionality of the backside metallization layer stack may be generated layer by layer, such like a functional wafer. This could be a special dielectric a magnetic material and/or a material for better thermal power dissipation.

In an example, forming the backside metallization layer stack may comprises forming a first portion of a wiring structure of the backside metallization layer stack in a first metallization layer of the backside metallization layer stack and forming a second portion of the wiring structure in a second metallization layer of the backside metallization layer stack. Further, the method may comprise forming a tapered vertical connection between the first portion of the wiring structure and the second portion of the wiring structure. The first metallization layer is closer to the semiconductor substrate than the second metallization layer and a width of the tapered vertical connection increases towards the first metallization layer. In an example, forming the tapered vertical connection comprises forming a tapered via in the backside metallization layer stack (see e.g.,FIG.4h).

As can be seen inFIG.4ithe semiconductor substrate and the backside metallization layer stack are attached to each other. For example, the first portion of the wiring structure, e.g., a hybrid bond pad, may be electrically connected with the bottom surface of the electrically conductive line, e.g., via hybrid bonding. In an example, attaching the backside metallization layer stack comprises or is done by a wafer bonding process. For example, the (preprocessed) backside metallization layer stack may be mounted with a wafer-to-wafer bonding process on the backside of the (functional) semiconductor substrate comprising the front side wiring layer stack.

In an example, the method may further comprises aligning the carrier to the semiconductor substrate for attaching the backside metallization layer stack to the semiconductor substrate so that the bottom surface of the electrically conductive structure is connected to a contact interface structure of the backside metallization layer stack. This way, a wafer-to-wafer bonding process may be comprised or done. Due to the very good accuracy of the wafer-to-wafer bonding process, the small uncovered bottom surface of the electrically conductive line with, e.g., at most 100 nm minimal lateral dimension (e.g., a side length), can be met with the first portion of the wiring structure (e.g., the hybrid bonding pad). Thus, the wafer-to-wafer bonding process may increase a yield of the manufacturing of the semiconductor die, since wafer-to-wafer bonding is a high precision bonding process. For example, a connection between the bottom surface of the electrically conductive line and the first portion of the wiring structure may be seamless due to the hybrid bonding interface. As the backside metallization layer stack itself may be formed on a thick carrier a handling may be improved, which may lead to generate a very smooth and flat surface for the wafer-to-wafer bonding process. For example, if required an additional carrier system could be used.

In an example, the bonding process comprises or is done by a hybrid bonding process. Hybrid bonding extends direct bonding with embedded metal pads in the bond interface (e.g., the first portion of the wiring structure), allowing for face-to-face connection of wafers. This way, in comparison to non-hybrid bonding a precision of the bonding process may be increased.

Hybrid bonding is a direct bonding process using, e.g., a plasma treatment of the substrates prior to bonding whereas the wafer surface consists out of dielectric and metal interconnects on the same surface plane, e.g., the front side of the backside metallization layer stack. Room temperature contacting of the wafers (pre-bonding) and thermal annealing for strengthening the bond may be comprised during a hybrid bonding process. In an example, a temperature of the backside of the semiconductor substrate may be at least 25° C., at least 50° C. or at least 75° C. and/or at most 150° C., at most 125° C. or at most 100° C. during attaching the backside metallization layer stack. In an example, the backside of the semiconductor substrate may be pressed to the backside of the semiconductor substrate with a pressure of at least 2 bar, at least 1 bar or at least 0.5 bar (normal atm).

FIG.4jshows the finished semiconductor die process to generate a semiconductor die comprising an electrical connection to the electrically conductive line of the semiconductor substrate on the backside of the semiconductor die via the wiring structure of the backside metallization layer stack. In an example, the method may further comprise removing the carrier from the backside metallization layer stack after attaching the backside metallization layer stack to the backside of the semiconductor substrate. Further, the carrier of the semiconductor substrate may be removed.

To remove the respective carrier of the semiconductor substrate and the backside metallization layer stack a grinding process may be comprised or done. For example, grinding of the (thick) carrier of the backside metallization layer stack e.g. the thick silicon wafer (or any other material acted like a carrier and revel it) to uncover the second portion of the wiring structure, e.g., a backside metallization, may be done. The same may be done on the other side of the semiconductor die with the carrier of the semiconductor substrate to uncover, e.g., C4 pads of the (functional) front side wiring layer stack.

Concluding, with the method described with reference toFIG.4complicated tiny TSV processes can be omitted by utilizing a hybrid pond pad to electrically connect the electrically conductive line of the semiconductor substrate.

More details and aspects are mentioned in connection with the examples described above and/or below. The example shown inFIG.4may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples describe above (e.g.,FIGS.1-3) and/or below (e.g.,FIGS.5-6).

FIG.5shows a cross-sectional view of a semiconductor device505. In an example, the semiconductor device505comprises a semiconductor die500as described above (e.g., with respect toFIG.1,FIG.2andFIGS.4a-4j) and a package substrate530attached to a front side of the semiconductor die500. The semiconductor die500comprises a semiconductor substrate comprising a front side wiring layer stack and a backside metallization layer stack.

For example, with connection technics (e.g. a Through Mold Via and a RDL process), the backside metallization layer stack, e.g. a backside metallization, can be connected to generate a functional package, e.g., following assembly processes may be bumping of the C4 pads of the (functional) front side wiring layer stack and attaching the semiconductor die500to a packing substrate530.

In an example, a redistribution layer506may be formed on a backside of the semiconductor die504. The redistribution layer506may be electrically connected to a second contact interface structure of the backside metallization layer stack. In an example, the second portion of the wiring structure may be the second contact interface structure connected to the backside metallization layer stack.

In an example, an interconnect structure508may be arranged laterally besides the semiconductor die500and extending from the redistribution layer506to the package substrate530. This way, a connection between the backside of the semiconductor die504and the front side of the package substrate can be achieved.

In an example, the semiconductor device505may further comprise a mold compound509embedding the semiconductor die500and the interconnect structure508. In this case, the interconnect structure508may be a through mold via.

A semiconductor device505described above or below may be a semiconductor package comprising a semiconductor die500. The semiconductor device505may be a processor (e.g. CPU, GPU or DSP), a memory or any other integrated circuit.

More details and aspects are mentioned in connection with the examples described above and/or below. The example shown inFIG.5may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples describe above (e.g.,FIGS.1-4) and/or below (e.g.,FIG.6).

FIG.6illustrates a computing device600. The computing device600houses a board602. The board602may include a number of components, including but not limited to a processor604and at least one communication chip606. A semiconductor device as described above (e.g., with respect toFIG.5) may be the processor604as shown inFIG.6. For example, the processor604may comprise the semiconductor die as described with reference toFIG.1.

The processor604is physically and electrically coupled to the board602. In some embodiments the at least one communication chip606is also physically and electrically coupled to the board602. In further embodiments, the communication chip606is part of the processor604.

Depending on its applications, computing device600may include other components that may or may not be physically and electrically coupled to the board602. These other components include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth). The communication chip606enables wireless communications for the transfer of data to and from the computing device600. The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip606may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device600may include a plurality of communication chips606. For instance, a first communication chip606may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip606may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others. The processor604of the computing device600includes an integrated circuit die packaged within the processor604. In some embodiments, the integrated circuit die of the processor includes one or more devices that are assembled in an ePLB or eWLB based POP package that that includes a mold layer directly contacting a substrate, in accordance with embodiments. The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.

The communication chip606also includes an integrated circuit die packaged within the communication chip606. In accordance with another embodiment, the integrated circuit die of the communication chip includes one or more devices that are assembled in an ePLB or eWLB based P0P package that that includes a mold layer directly contacting a substrate, in accordance with embodiments.

More details and aspects are mentioned in connection with the examples described above. The example shown inFIG.6may comprise one or more optional additional features corresponding to one or more aspects mentioned in connection with the proposed concept or one or more examples described above (e.g.,FIGS.1-5).

An example (e.g., example 1) relates to a semiconductor die, comprising a plurality of transistors arranged at a front side of a semiconductor substrate, an electrically conductive structure, wherein a top surface of the electrically conductive structure is contacted at the front side of the semiconductor substrate and a bottom surface of the electrically conductive structure is contacted at a backside of the semiconductor substrate and a backside metallization layer stack attached to the backside of the semiconductor substrate, wherein a first portion of a wiring structure of the backside metallization layer stack is formed in a first metallization layer of the backside metallization layer stack, a second portion of the wiring structure is formed in a second metallization layer of the backside metallization layer stack, and a tapered vertical connection is formed between the first portion of the wiring structure and the second portion of the wiring structure, wherein the first metallization layer is closer to the semiconductor substrate than the second metallization layer, wherein a width of the tapered vertical connection increases towards the first metallization layer.

Another example (e.g., example 2) relates to a previously described example (e.g., example 1) wherein the first portion of the wiring structure is a contact interface structure connected to the bottom surface of the electrically conductive structure.

Another example (e.g., example 3) relates to a previously described example (e.g., the example 2) wherein the backside metallization layer stack further comprises a bonding surface layer arranged besides the contact interface structure comprising at least one of silicon carbon nitride, silicon oxide or polyimide.

Another example (e.g., example 4) relates to a previously described example (e.g., one of the examples 2-3) wherein a length of the contact interface structure is at most 100 nm.

Another example (e.g., example 5) relates to a previously described example (e.g., one of the examples 1-4) wherein a minimal lateral dimension of the bottom surface of the electrically conductive structure is at most 100 nm.

Another example (e.g., example 6) relates to a previously described example (e.g., one of the examples 1-5) wherein a thickness of the first metallization layer is at most 100 nm.

Another example (e.g., example 7) relates to a previously described example (e.g., one of the examples 1-6) wherein a thickness of the semiconductor substrate is at most 100 nm.

Another example (e.g., example 8) relates to a previously described example (e.g., one of the examples 1-7) wherein the plurality of transistors comprises at least one of a fin field-effect transistor, a nanowire transistor, a ribbon transistor or a gate all around transistor.

Another example (e.g., example 9) relates to a previously described example (e.g., one of the examples 1-8) wherein the electrically conductive structure is electrically insulated from the semiconductor substrate.

Another example (e.g., example 10) relates to a previously described example (e.g., one of the examples 1-9) a layer of the backside metallization layer stack comprises a dielectric material of a capacitor, e.g., Silicon Oxide or Silicon Nitride compositions.

Another example (e.g., example 11) relates to a previously described example (e.g., one of the examples 1-10) wherein a layer of the backside metallization layer stack comprises a magnetic material of an inductor , e.g., a Ferro Oxide (iron oxide) or Ferro Platinum (iron platinum) compositions.

Another example (e.g., example 12) relates to a previously described example (e.g., one of the examples 1-11) a layer of the backside metallization layer stack comprises a material with a thermal conductivity of at least 1 W/mK.

Another example (e.g., example 13) relates to a previously described example (e.g., one of the examples 1-12) wherein the backside metallization layer stack comprises a circuit element electrically connected to the electrically conductive structure.

Another example (e.g., example 14) relates to a previously described example (e.g., the example 13) further comprising circuitry comprising at least one transistor of the plurality of transistors, wherein the circuit element is electrically connected to the transistor of the circuitry via the electrically conductive structure.

Another example (e.g., example 15) relates to a previously described example (e.g., one of the examples 1-14) further comprising a front side wiring layer stack formed on the front side of the semiconductor substrate, wherein the front side wiring layer stack comprises a front side wiring structure electrically connected to the wiring structure of the backside metallization layer stack.

An example (e.g., example 16) relates to a semiconductor device, comprising a semiconductor die as describe above (e.g., one of the examples 1 -15) and a package substrate attached to a front side of the semiconductor die.

Another example (e.g., example 17) relates to a previously described example (e.g., the example 16) further comprising a redistribution layer formed on a backside of the semiconductor die, wherein the redistribution layer is electrically connected to a second contact interface structure of the backside metallization layer stack.

Another example (e.g., example 18) relates to a previously described example (e.g., the example 17) wherein the second portion of the wiring structure is the second contact interface structure connected to the backside metallization layer stack.

Another example (e.g., example 19) relates to a previously described example (e.g., one of the examples 17-18) further comprising an interconnect structure arranged laterally beside the semiconductor die and extending from the redistribution layer to the package substrate.

Another example (e.g., example 20) relates to a previously described example (e.g., the example 19) further comprising a mold compound embedding the semiconductor die and the interconnect structure.

An example (e.g., example 21) relates to a method for forming a semiconductor device, comprising forming a plurality of transistors arranged at a front side of a semiconductor substrate and an electrically conductive structure, wherein a top surface of the electrically conductive structure is contacted at the front side of the semiconductor substrate and a bottom surface of the electrically conductive structure is uncovered at a backside of the semiconductor substrate, forming a backside metallization layer stack and attaching the backside metallization layer stack to the backside of the semiconductor substrate.

Another example (e.g., example 22) relates to a previously described example (e.g., example 21) wherein forming the backside metallization layer stack comprises forming a first portion of a wiring structure of the backside metallization layer stack in a first metallization layer of the backside metallization layer stack, forming a second portion of the wiring structure in a second metallization layer of the backside metallization layer stack and forming a tapered vertical connection is between the first portion of the wiring structure and the second portion of the wiring structure, wherein the first metallization layer is closer to the semiconductor substrate than the second metallization layer and wherein a width of the tapered vertical connection increases towards the first metallization layer.

Another example (e.g., example 23) relates to a previously described example (e.g., the example 22) wherein forming the tapered vertical connection comprises forming a tapered via in the backside metallization layer stack.

Another example (e.g., example 24) relates to a previously described example (e.g., one of the examples 21-23) wherein attaching the backside metallization layer stack comprises a wafer bonding process.

Another example (e.g., example 25) relates to a previously described example (e.g., the example 24) wherein the bonding process comprises a hybrid bonding process.

Another example (e.g., example 26) relates to a previously described example (e.g., one of the examples 21-25) wherein a temperature of the backside of the semiconductor substrate is at least 25° C. during attaching the backside metallization layer stack.

Another example (e.g., example 27) relates to a previously described example (e.g., one of the examples 21-26) wherein the backside of the semiconductor substrate is pressed to the backside of the semiconductor substrate with a pressure of at least 1 bar.

Another example (e.g., example 28) relates to a previously described example (e.g., one of the examples 21-27) further comprising forming the backside metallization stack layer on a carrier.

Another example (e.g., example 29) relates to a previously described example (e.g., the example 28) wherein the carrier comprises at least one of stainless steel, glass or semiconductor material.

Another example (e.g., example 30) relates to a previously described example (e.g., one of the examples 28-29) further comprising aligning the carrier to the semiconductor substrate for attaching the backside metallization layer stack to the semiconductor substrate so that the bottom surface of the electrically conductive structure is connected to a contact interface structure of the backside metallization layer stack.

Another example (e.g., example 31) relates to a previously described example (e.g., one of the examples 28-30) further comprising removing the carrier from the backside metallization layer stack after attaching the backside metallization layer stack to the backside of the semi conductor substrate.

Another example (e.g., example 32) relates to a previously described example (e.g., one of the examples 21-31) wherein forming the electrically conductive structure comprises forming a trench into the semiconductor substrate from the front side of the semiconductor substrate, filling the trench with electrically conductive material of the electrically conductive structure and removing a part of the semiconductor substrate from the backside of the semiconductor substrate to uncover the bottom surface of the electrically conductive structure.

Another example (e.g., example 33) relates to a previously described example (e.g., the example 32) further comprising forming an etch stop layer inside the semiconductor substrate, wherein the etch stop layer is located at a depth larger than a depth of the trench for the electrically conductive structure.

Another example (e.g., example 34) relates to a previously described example (e.g., the example 33) wherein a distance between the etch stop layer and the trench is at most 50 nm.

Another example (e.g., example 35) relates to a previously described example (e.g., one of the examples 33-34) further comprising removing a first part of the semiconductor substrate from the backside until the etch stop layer is reached, wherein removing the first part comprises at least one of mechanical etching, dry etching or wet etching.

Another example (e.g., example 36) relates to a previously described example (e.g., the example 35) further comprising uncovering the bottom surface of the electrically conductive structure by removing a second part of the semiconductor substrate by at least one of chemical mechanical planarization or plasma etching.