Embodiments of the present disclosure generally relate to the field of semiconductor packaging, and in particular to gates in a transistor structure.
Continued growth in virtual machines, cloud computing, and portable devices will continue to increase the demand for high density transistors within chips and packages.
Embodiments described herein may be related to apparatuses, processes, and techniques directed to a transistor structure that includes a monolayer within an oxide material on a gate metal. The monolayer may be referred to as a monolayer sheet, a two dimensional (2D) channel, transition metal dichalcogenides (TMD) materials, a nanosheet, or a nanoribbon. In embodiments, the monolayer includes a semiconductor material. In embodiments, a monolayer may include multiple monolayer sheets that are stacked on top of each other, for example, three monolayer sheets that are stacked on top of each other. In embodiments, there may be a stack of monolayer/oxidematerial/gate metal structures of arbitrary depth. In embodiments, an edge of the monolayer may couple with a surface of one or more contact metals.
In legacy implementations, a gate length may be on the order of 15 nm. In order to shrink this gate length distance, silicon thickness needs to be reduced. However, and these legacy implementations, a silicon thickness that is too thin may cause a mobility decrease and result in a defective transistor.
In embodiments, by using one or more monolayers within a gate structure, distances between layers may be reduced to 6 nm or less, which may also allow an increase in the number of monolayers within the gate structure.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.
For the purposes of the present disclosure, the phrase “A and/or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
The description may use perspective-based descriptions such as top/bottom, in/out, over/under, and the like. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments described herein to any particular orientation.
The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.
The term “coupled with,” along with its derivatives, may be used herein. “Coupled” may mean one or more of the following. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term “directly coupled” may mean that two or more elements are in direct contact.
Various operations may be described as multiple discrete operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent.
As used herein, the term “module” may refer to, be part of, or include an ASIC, an electronic circuit, a processor (shared, dedicated, or group) and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
Various Figures herein may depict one or more layers of one or more package assemblies. The layers depicted herein are depicted as examples of relative positions of the layers of the different package assemblies. The layers are depicted for the purposes of explanation, and are not drawn to scale. Therefore, comparative sizes of layers should not be assumed from the Figures, and sizes, thicknesses, or dimensions may be assumed for some embodiments only where specifically indicated or discussed.
Various embodiments may include any suitable combination of the above-described embodiments including alternative (or) embodiments of embodiments that are described in conjunctive form (and) above (e.g., the “and” may be “and/or”). Furthermore, some embodiments may include one or more articles of manufacture (e.g., non-transitory computer-readable media) having instructions, stored thereon, that when executed result in actions of any of the above-described embodiments. Moreover, some embodiments may include apparatuses or systems having any suitable means for carrying out the various operations of the above-described embodiments.
In embodiments, each of the monolayers 110 may be made up of a single monolayer. In other embodiments, each of the monolayers 110 may be multiple monolayers that are stacked on top of each other. In embodiments, an edge of the monolayer may couple directly with the source 104 or the drain 106 through an edge coupling, as discussed in greater detail below.
Similarly, second transistor structure 300b may include a plurality of gate metals 308b that are each surrounded by a gate oxide layer 312b, with a monolayer 310b within the gate oxide layer 312b. Edges of the respective monolayers 310b couple with a first contact metal 330b and a second contact metal 332b. In embodiments, the first contact metal 330b may surround a fill metal 334, and the second contact metal 332b may also surround a fill metal 334. A first electrical contact 336b may be electrically coupled with the gate metal 308b, and a second electrical contact 338b may be electrically coupled with the second contact metal 332b. In embodiments, if the gate oxide layer 312b includes aluminum, this will be considered a Pmos transistor.
Note that there are only three layers of monolayers 310a, 310b shown, however there may be multiple layers. In embodiments, there may be seven or more layers. In addition, each of the monolayers 310a, 310b itself may be made of a plurality of monolayers that are stacked on top of each other. For example, there may be up to three stacked monolayers that make up one monolayer 310a, 310b. In embodiments, there may be plurality of monolayers that have a tri-layer stack or other layer stack that may include MoS2, WS2, or MoS2.
On top of the sacrificial layer 404, a monolayer 406 may be applied, which may also be referred to as a 2D Transition Metal Dichalcogenide (TMD), and may be similar to monolayer 310a, 310b of
On top of the monolayer 406, another sacrificial layer 408, which may be similar to sacrificial layer 404, may be applied, onto which another monolayer 410, which may be similar to monolayer 406, may then be applied. Another sacrificial layer 412, which may be similar to sacrificial layer 408, may then be applied onto the monolayer 410. In this embodiment, there are two stacked monolayers 406, 410, which may also be referred to as two stacked nanoribbons. In other embodiments there may be an arbitrary number of stacked monolayers, up to and including eight or more stacked monolayers. On top of sacrificial layer 412, a hard mask 414 is added, which may be a silicon carbide (SiC) hard mask.
At block 502, the process includes applying a first oxide layer on a substrate.
At block 504, the process further includes forming a first gate metal on the oxide layer.
At block 506, the process further includes forming another oxide layer on top of the first gate metal.
At block 508, the process further includes forming a monolayer on the other oxide layer.
Implementations of embodiments of the invention may be formed or carried out on a substrate, such as a semiconductor substrate. In one implementation, the semiconductor substrate may be a crystalline substrate formed using a bulk silicon or a silicon-on-insulator substructure. In other implementations, the semiconductor substrate may be formed using alternate materials, which may or may not be combined with silicon, that include but are not limited to germanium, indium antimonide, lead telluride, indium arsenide, indium phosphide, gallium arsenide, indium gallium arsenide, gallium antimonide, or other combinations of group III-V or group IV materials. Although a few examples of materials from which the substrate may be formed are described here, any material that may serve as a foundation upon which a semiconductor device may be built falls within the spirit and scope of the present invention.
A plurality of transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFET or simply MOS transistors), may be fabricated on the substrate. In various implementations of the invention, the MOS transistors may be planar transistors, nonplanar transistors, or a combination of both. Nonplanar transistors include FinFET transistors such as double-gate transistors and tri-gate transistors, and wrap-around or gate-all-around transistors such as nanoribbon and nanowire transistors. Although the implementations described herein may illustrate only Finfet transistors, it should be noted that the invention may also be carried out using planar transistors.
Each MOS transistor includes a gate stack formed of at least two layers, a gate dielectric layer and a gate electrode layer. The gate dielectric layer may include one layer or a stack of layers. The one or more layers may include silicon oxide, silicon dioxide (SiO2) and/or a high-k dielectric material. The high-k dielectric material may include elements such as hafnium, silicon, oxygen, titanium, tantalum, lanthanum, aluminum, zirconium, barium, strontium, yttrium, lead, scandium, niobium, and zinc. Examples of high-k materials that may be used in the gate dielectric layer include, but are not limited to, hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. In some embodiments, an annealing process may be carried out on the gate dielectric layer to improve its quality when a high-k material is used.
The gate electrode layer is formed on the gate dielectric layer and may consist of at least one P-type workfunction metal or N-type workfunction metal, depending on whether the transistor is to be a PMOS or an NMOS transistor. In some implementations, the gate electrode layer may consist of a stack of two or more metal layers, where one or more metal layers are workfunction metal layers and at least one metal layer is a fill metal layer.
For a PMOS transistor, metals that may be used for the gate electrode include, but are not limited to, ruthenium, palladium, platinum, cobalt, nickel, and conductive metal oxides, e.g., ruthenium oxide. A P-type metal layer will enable the formation of a PMOS gate electrode with a workfunction that is between about 4.9 eV and about 5.2 eV. For an NMOS transistor, metals that may be used for the gate electrode include, but are not limited to, hafnium, zirconium, titanium, tantalum, aluminum, alloys of these metals, and carbides of these metals such as hafnium carbide, zirconium carbide, titanium carbide, tantalum carbide, and aluminum carbide. An N-type metal layer will enable the formation of an NMOS gate electrode with a workfunction that is between about 3.9 eV and about 4.2 eV.
In some implementations, the gate electrode may consist of a “U”-shaped structure that includes a bottom portion substantially parallel to the surface of the substrate and two sidewall portions that are substantially perpendicular to the top surface of the substrate. In another implementation, at least one of the metal layers that form the gate electrode may simply be a planar layer that is substantially parallel to the top surface of the substrate and does not include sidewall portions substantially perpendicular to the top surface of the substrate. In further implementations of the invention, the gate electrode may consist of a combination of U-shaped structures and planar, non-U-shaped structures. For example, the gate electrode may consist of one or more U-shaped metal layers formed atop one or more planar, non-U-shaped layers.
In some implementations of the invention, a pair of sidewall spacers may be formed on opposing sides of the gate stack that bracket the gate stack. The sidewall spacers may be formed from a material such as silicon nitride, silicon oxide, silicon carbide, silicon nitride doped with carbon, and silicon oxynitride. Processes for forming sidewall spacers are well known in the art and generally include deposition and etching process steps. In an alternate implementation, a plurality of spacer pairs may be used, for instance, two pairs, three pairs, or four pairs of sidewall spacers may be formed on opposing sides of the gate stack.
As is well known in the art, source and drain regions are formed within the substrate adjacent to the gate stack of each MOS transistor. The source and drain regions are generally formed using either an implantation/diffusion process or an etching/deposition process. In the former process, dopants such as boron, aluminum, antimony, phosphorous, or arsenic may be ion-implanted into the substrate to form the source and drain regions. An annealing process that activates the dopants and causes them to diffuse further into the substrate typically follows the ion implantation process. In the latter process, the substrate may first be etched to form recesses at the locations of the source and drain regions. An epitaxial deposition process may then be carried out to fill the recesses with material that is used to fabricate the source and drain regions. In some implementations, the source and drain regions may be fabricated using a silicon alloy such as silicon germanium or silicon carbide. In some implementations the epitaxially deposited silicon alloy may be doped in situ with dopants such as boron, arsenic, or phosphorous. In further embodiments, the source and drain regions may be formed using one or more alternate semiconductor materials such as germanium or a group III-V material or alloy. And in further embodiments, one or more layers of metal and/or metal alloys may be used to form the source and drain regions.
One or more interlayer dielectrics (ILD) are deposited over the MOS transistors. The ILD layers may be formed using dielectric materials known for their applicability in integrated circuit structures, such as low-k dielectric materials. Examples of dielectric materials that may be used include, but are not limited to, silicon dioxide (SiO2), carbon doped oxide (CDO), silicon nitride, organic polymers such as perfluorocyclobutane or polytetrafluoroethylene, fluorosilicate glass (FSG), and organosilicates such as silsesquioxane, siloxane, or organosilicate glass. The ILD layers may include pores or air gaps to further reduce their dielectric constant.
Depending on its applications, computing device 600 may include other components that may or may not be physically and electrically coupled to the board 602. 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 chip 606 enables wireless communications for the transfer of data to and from the computing device 600. 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 chip 606 may 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 device 600 may include a plurality of communication chips 606. For instance, a first communication chip 606 may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip 606 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
The processor 604 of the computing device 600 includes an integrated circuit die packaged within the processor 604. In some implementations of the invention, the integrated circuit die of the processor includes one or more devices, such as MOS-FET transistors built in accordance with implementations of the invention. 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 chip 606 also includes an integrated circuit die packaged within the communication chip 606. In accordance with another implementation of the invention, the integrated circuit die of the communication chip includes one or more devices, such as MOS-FET transistors built in accordance with implementations of the invention.
In further implementations, another component housed within the computing device 600 may contain an integrated circuit die that includes one or more devices, such as MOS-FET transistors built in accordance with implementations of the invention.
In various implementations, the computing device 600 may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a tablet, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device 600 may be any other electronic device that processes data.
The interposer 700 may be formed of an epoxy resin, a fiberglass-reinforced epoxy resin, a ceramic material, or a polymer material such as polyimide. In further implementations, the interposer 700 may be formed of alternate rigid or flexible materials that may include the same materials described above for use in a semiconductor substrate, such as silicon, germanium, and other group III-V and group IV materials.
The interposer 700 may include metal interconnects 708 and vias 710, including but not limited to through-silicon vias (TSVs) 712. The interposer 700 may further include embedded devices 714, including both passive and active devices. Such devices include, but are not limited to, capacitors, decoupling capacitors, resistors, inductors, fuses, diodes, transformers, sensors, and electrostatic discharge (ESD) devices. More complex devices such as radio-frequency (RF) devices, power amplifiers, power management devices, antennas, arrays, sensors, and MEMS devices may also be formed on the interposer 700. In accordance with embodiments of the invention, apparatuses or processes disclosed herein may be used in the fabrication of interposer 700.
The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit embodiments to the precise forms disclosed. While specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the embodiments, as those skilled in the relevant art will recognize.
These modifications may be made to the embodiments in light of the above detailed description. The terms used in the following claims should not be construed to limit the embodiments to the specific implementations disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.
The following paragraphs describe examples of various embodiments.
Example 1 is a transistor structure comprising: a gate metal; a gate oxide on a side of the gate metal; and a monolayer on the gate oxide, the monolayer having a first side and a second side opposite the first side, wherein a first portion of an edge of the monolayer between the first side and the second side of the monolayer is coupled with a surface of a first contact metal, and wherein a second portion of the edge of the monolayer between the first side and the second side of the monolayer is coupled with a surface of a second contact metal.
Example 2 includes the transistor structure of example 1, wherein the monolayer includes a selected one or more of: sulfur (S), selenium (Se), tellurium (Te), tungsten (W), and molybdenum (Mo).
Example 3 includes the transistor structure of example 1, wherein the monolayer has a thickness of 3.3 angstroms (Å).
Example 4 includes the transistor structure of example 1, wherein the surface of the first contact metal or the second contact metal is substantially perpendicular to the first side or the second side of the monolayer.
Example 5 includes the transistor structure of example 1, wherein a distance along the first side of the monolayer between the surface of the first contact metal and the surface of the second contact metal is less than or equal to 15 nm.
Example 6 includes the transistor structure of example 1, wherein the monolayer further includes multiple monolayers that form a monolayer stack.
Example 7 includes the transistor structure of example 6, wherein the multiple monolayers are directly physically coupled with each other.
Example 8 includes the transistor structure of any one of examples 1-7, wherein the gate metal is a first gate metal and the monolayer is a first monolayer; and further comprising: a plurality of other gate metals in a stack below the first gate metal, wherein a gate oxide layer is above and below each of the other gate metals; a plurality of other monolayers, each other monolayer, respectively, above each of the plurality of the other gate metals and within the gate oxide layer; and wherein a first portion of an edge of each of the other monolayers between the first side and the second side of the monolayer is coupled with the surface of the first contact metal, and wherein a second portion of the edge of each of the monolayers is coupled with a surface of the second contact metal.
Example 9 includes the transistor structure of example 8, wherein a distance between a first monolayer and one of the other monolayers ranges from 6 nm to 10 nm.
Example 10 includes the transistor structure of example 8, wherein each of the plurality of monolayers further includes multiple monolayers.
Example 11 includes the transistor structure of example 8, wherein a number of the plurality of other gate metals is six or more.
Example 12 is a method comprising: applying a fist oxide layer on a substrate; forming a first gate metal on the oxide layer; forming another oxide layer on top of the first gate metal; and forming a monolayer on the other oxide layer.
Example 13 includes the method of example 12, wherein the monolayer has a first side and a second side opposite the first side; and wherein forming a monolayer on the oxide layer further includes: physically coupling a first portion of an edge of the monolayer between the first side and the second side with a surface of a first contact metal; and physically coupling a second portion of the edge of the monolayer with a surface of a second contact metal.
Example 14 includes the method of example 12, wherein a distance along the first side of the monolayer between the surface of the first contact metal and the surface of the second contact metal is less than or equal to 15 nm.
Example 15 includes the method of example 12, wherein forming a monolayer on the oxide layer further includes forming a plurality of monolayers on the oxide layer, wherein the monolayers are stacked on each other.
Example 16 includes the method of any one of examples 12-15, wherein the monolayer includes a selected one or more of: sulfur (S), selenium (Se), tellurium, tungsten (W), and molybdenum (Mo).
Example 17 includes the method of any one of examples 12-15, wherein the monolayer has a thickness of 3.3 angstroms (Å).
Example 18 is a system comprising: a substrate; and a transistor structure on the substrate, the transistor structure comprising: a gate metal; a gate oxide on a side of the gate metal, the gate oxide including hafnium (Hf); and a monolayer on the gate oxide, the monolayer having a first side and a second side opposite the first side, wherein a first portion of an edge of the monolayer between the first side and the second side of the monolayer is coupled with a surface of a first contact metal, and wherein a second portion of the edge of the monolayer between the first side and the second side of the monolayer is coupled with a surface of a second contact metal.
Example 19 includes the system of example 18, wherein the transistor structure is a first transistor structure, the gate metal as a first gate metal, the gate oxide is a first gate oxide, and the monolayer is a first monolayer; and further comprising: a second transistor structure on the substrate, the second transistor structure comprising: a second gate metal; a second gate oxide on a side of the second gate metal, the second gate oxide including aluminum (Al); and a second monolayer on the second gate oxide, the second monolayer having a first side and a second side opposite the first side, wherein a first portion of an edge of the second monolayer between the first side and the second side of the second monolayer is coupled with a surface of a third contact metal, and wherein a second portion of the edge of the second monolayer between the first side and the second side of the second monolayer is coupled with a surface of a fourth contact metal.
Example 20 includes the system of any one of examples 18-19, wherein the monolayer includes a plurality of monolayers stacked on each other.