Embodiments of the disclosure are in the field of semiconductor structures and processing and, in particular, to nanoribbon transistors with subfin isolation that includes source/drain epi protection.
Gate-all-around (GAA) transistors have begun being utilized as scaling continues to reduce feature sizes of transistor devices. In a GAA device, such as a nanoribbon or nanowire architecture, the semiconductor channels are formed as part of a fin with alternating sacrificial layers. During processing, the sacrificial layers are removed from the fin and a gate stack is provided around the semiconductor channels. However, scaling to smaller critical dimensions in GAA technologies is not without issue. Particularly, a stronger subfin implant is needed to suppress leakage current as the channel length is reduced. High energy dose implants carry the risk of introducing defects into the active semiconductor channels.
On solution is to remove the subfin from the device. Removal of the subfin and replacement with a dielectric, such as an interlayer dielectric (ILD) can minimize subfin leakage issues. However, removing the subfin typically results in damage to the epitaxially grown source/drain region. As such, there is currently no suitable approach for mitigating subfin leakage without also damaging the epitaxially grown source/drain regions.
Embodiments described herein comprise nanoribbon transistors with subfin isolation that includes source/drain epi protection. In the following description, numerous specific details are set forth, such as specific integration and material regimes, in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known features, such as integrated circuit design layouts, are not described in detail in order to not unnecessarily obscure embodiments of the present disclosure. Furthermore, it is to be appreciated that the various embodiments shown in the Figures are illustrative representations and are not necessarily drawn to scale.
Certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, “below,” “bottom,” and “top” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, and “side” describe the orientation and/or location of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import.
As noted above, the scaling to smaller channel lengths results in the need to provide greater protection against subfin leakage. Typically, this is done by having a heavy dopant implant into the subfin. However, such high energy/dose implants introduce the risk of defects in the active channels. Additionally, removing the semiconductor subfin is also not currently a possibility. This is due to the damage that an etching process will have on the exposed source/drain regions.
Accordingly, embodiments disclosed herein include GAA structures with a barrier between the source/drain region and the underlying subfin. The barrier can function as an etchstop layer that allows for an etching of the subfin without damaging the source/drain region. As such, subfin leakage can be avoided since the subfin is removed and replaced with an ILD. Additionally, there is no need for high energy implants that would otherwise damage the semiconductor channels.
In some embodiments, the barrier has a u-shaped cross-section. The u-shaped cross-section is the result of the barrier being conformally deposited into the source/drain trench before the source/drain region is grown. The u-shape may include a horizontal section and a pair of vertical sections. The vertical sections may extend up from the horizontal section and contact a bottom surface of the source/drain region. In yet another embodiment, the barrier further comprises wings that extend laterally away from the vertical sections. The wings provide even greater protection to the source/drain regions during the etching of the subfin.
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While shown as a single material, it is to be appreciated that the gate stack 112 may comprises a gate dielectric over the semiconductor channels 110, a workfunction metal, and a fill metal. The gate dielectric may be, for example, any suitable oxide such as silicon dioxide or high-k gate dielectric materials. Examples of high-k gate dielectric materials include, for instance, 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.
When the work function metal will serve as an N-type workfunction metal, the work function metal preferably has a workfunction that is between about 3.9 eV and about 4.2 eV. N-type materials that may be used to form the work function metal include, but are not limited to, hafnium, zirconium, titanium, tantalum, aluminum, and metal carbides that include these elements, i.e., titanium carbide, zirconium carbide, tantalum carbide, hafnium carbide and aluminum carbide. When the work function metal will serve as a P-type workfunction metal, the work function metal preferable has a workfunction that is between about 4.9 eV and about 5.2 eV. P-type materials that may be used to form the work function metal include, but are not limited to, ruthenium, palladium, platinum, cobalt, nickel, and conductive metal oxides, e.g., ruthenium oxide. In an embodiment, the gate fill metal may comprise materials such as polysilicon, silicon nitride, silicon carbide, or various suitable metals or metal alloys, such as aluminum (Al), tungsten (W), titanium (Ti), tantalum (Ta), copper (Cu), titanium nitride (TiN), or tantalum nitride (TaN), for example.
In an embodiment, spacers 114 and 116 may isolate the channel region from the source/drain regions 120. The spacers 114 and 116 may comprise dielectric materials, such as silicon oxides, silicon nitrides, and the like. In an embodiment, the spacers 114 may be a different material than the spacers 116. In other embodiments, the spacers 114 may be substantially similar in material composition as the spacers 116.
In an embodiment, source/drain regions 120 are provided on opposite ends of the semiconductor channels 110. The fin may be etched to form a recess that is filled with an epitaxially grown semiconductor to form the source/drain regions 120. In an embodiment, the source/drain regions 120 may comprise a silicon alloy that may be in-situ doped silicon germanium, in-situ doped silicon carbide, or in-situ doped silicon. In alternate implementations, other silicon alloys may be used. For instance, alternate silicon alloy materials that may be used include, but are not limited to, nickel silicide, titanium silicide, cobalt silicide, and possibly may be doped with one or more of boron and/or aluminum. In some implementations, a chemical vapor deposition (CVD) process may be used for the epitaxial deposition of the source/drain regions 120. Source/drain contacts 122 may be provided over the source/drain regions 120. The source/drain contacts 122 may comprise any suitable material or materials. For example, the source/drain contacts 122 may comprise metals or metal alloys, such as aluminum (Al), tungsten (W), titanium (Ti), tantalum (Ta), copper (Cu), titanium nitride (TiN), or tantalum nitride (TaN), for example.
In an embodiment, the transistor device 100 is provided over a dielectric substrate 102, such as an interlayer dielectric (ILD). In an embodiment, ILD materials may comprise a layer of a dielectric or insulating material. Examples of suitable dielectric materials include, but are not limited to, oxides of silicon (e.g., silicon dioxide (SiO2)), doped oxides of silicon, fluorinated oxides of silicon, carbon doped oxides of silicon, various low-k dielectric materials known in the arts, and combinations thereof. The interlayer dielectric material may be formed by techniques, such as, for example, CVD, physical vapor deposition (PVD), or by other deposition methods.
The replacement of a semiconductor subfin with a dielectric substrate 102 allows for substantially eliminating subfin leakage. As such, the heavy doping process needed in the case of a semiconductor subfin is avoided all together. However, it is to be appreciated that the removal of the semiconductor subfin is not without issue. Accordingly, embodiments disclosed herein include a transistor device 100 that further comprises a barrier 130. The barrier 130 protects the bottom surface of the source/drain region 120 during the etching process used to remove the semiconductor subfin.
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In an embodiment, the barrier 130 may be a material that is etch selective to the semiconductor subfin. For example, the barrier 130 may comprise an oxide or a nitride. In a particular embodiment, the barrier 130 may be the same material as the spacers 116. Particularly, as will be described in greater detail below, the spacers 116 and the barrier 130 may be formed with the same deposition process.
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In an embodiment, the substrate 201 represents a general workpiece object used to manufacture integrated circuits. The semiconductor substrate 201 often includes a wafer or other piece of silicon or another semiconductor material. Suitable semiconductor substrates include, but are not limited to, single crystal silicon, polycrystalline silicon and silicon on insulator (SOI), as well as similar substrates formed of other semiconductor materials, such as substrates including germanium, carbon, or group III-V materials.
In an embodiment, a sacrificial gate electrode 213 is provided over the nanowire stack 205. The sacrificial gate electrode 213 may be disposed over a top surface of the nanowire stack 205 and wrap down the sides of the nanowire stack 205 (into and out of the plane of
In an embodiment, a source/drain trench 241 is provided through the nanowire stack 205. The source/drain trench 241 is located where the source/drain will be located in the final structure. In an embodiment, the source/drain trench 241 extends through an entire thickness of the nanowire stack 205 and extends into the substrate 201. The source/drain trench 241 may be formed with an etching process.
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After removal of the sacrificial layers 211, a gate stack 212 is disposed over the nanowires 210. The gate stack 212 may comprise a gate dielectric in direct contact with the nanowires 210. A workfunction metal may then be disposed over the gate dielectric. A fill metal may then be disposed over the workfunction metal. Materials suitable for the gate dielectric, workfunction metal, and fill metal are described in greater detail above, and will not be repeated here.
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In an embodiment, the barrier 330 may comprise a u-shaped cross-section with wings. For example, the barrier 330 comprises a horizontal portion 331 and a pair of vertical portions 332 extend up to the source/drain region 320. Additionally, a pair of wings 333 may extend out from the vertical portions 332. The wings 333 provide additional protection to the source/drain region 320 during the substrate removal and replacement. In an embodiment, an insulating plug 335 may fill the space between the barrier 330 and the source/drain region 320.
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In an embodiment, a sacrificial gate electrode 413 is provided over the nanowire stack 405. The sacrificial gate electrode 413 may be disposed over a top surface of the nanowire stack 405 and wrap down the sides of the nanowire stack 405 (into and out of the plane of
In an embodiment, a source/drain trench 441 is provided through the nanowire stack 405. The source/drain trench 441 is located where the source/drain will be located in the final structure. In an embodiment, the source/drain trench 441 extends through an entire thickness of the nanowire stack 405 and extends into the substrate 401 past the buried sacrificial layer 417. The source/drain trench 441 may be formed with an etching process.
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After removal of the sacrificial layers 411, a gate stack 412 is disposed over the nanowires 410. The gate stack 412 may comprise a gate dielectric in direct contact with the nanowires 410. A workfunction metal may then be disposed over the gate dielectric. A fill metal may then be disposed over the workfunction metal. Materials suitable for the gate dielectric, workfunction metal, and fill metal are described in greater detail above, and will not be repeated here.
In an embodiment, the processing in
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Depending on its applications, computing device 500 may include other components that may or may not be physically and electrically coupled to the board 502. 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 506 enables wireless communications for the transfer of data to and from the computing device 500. 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 506 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 500 may include a plurality of communication chips 506. For instance, a first communication chip 506 may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip 506 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
The processor 504 of the computing device 500 includes an integrated circuit die packaged within the processor 504. In an embodiment, the integrated circuit die of the processor may comprise a nanowire or nanoribbon transistor with a barrier layer between the source/drain region and the ILD replacement substrate, as described herein. 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 506 also includes an integrated circuit die packaged within the communication chip 506. In an embodiment, the integrated circuit die of the communication chip may comprise a nanowire or nanoribbon transistor with a barrier layer between the source/drain region and the ILD replacement substrate, as described herein.
In further implementations, another component housed within the computing device 500 may comprise a nanowire or nanoribbon transistor with a barrier layer between the source/drain region and the ILD replacement substrate, as described herein.
In various implementations, the computing device 500 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 500 may be any other electronic device that processes data.
The interposer 600 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 600 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 600 may include metal interconnects 608 and vias 610, including but not limited to through-silicon vias (TSVs) 612. The interposer 600 may further include embedded devices 614, 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 600. In accordance with embodiments of the disclosure, apparatuses or processes disclosed herein may be used in the fabrication of interposer 600.
Thus, embodiments of the present disclosure may comprise a nanowire or nanoribbon transistor with a barrier layer between the source/drain region and the ILD replacement substrate.
The above description of illustrated implementations of embodiments of the disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. While specific implementations of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize.
These modifications may be made to the disclosure in light of the above detailed description. The terms used in the following claims should not be construed to limit the disclosure to the specific implementations disclosed in the specification and the claims. Rather, the scope of the disclosure is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.
Example 1: a semiconductor device, comprising: a substrate, wherein the substrate is a dielectric material; a vertical stack of semiconductor channels over the substrate; a source at a first end of the semiconductor channels; a drain at a second end of the semiconductor channels; and a barrier between a bottom surface of the source and the substrate.
Example 2: the semiconductor device of Example 1, wherein a width of the barrier is substantially equal to a width of the source.
Example 3: the semiconductor device of Example 1 or Example 2, wherein the barrier has a u-shaped cross-section.
Example 4: the semiconductor device of Examples 1-3, wherein the barrier is a dielectric material that is a different material than the substrate.
Example 5: the semiconductor device of Examples 1-4, further comprising: a gate stack around the vertical stack of semiconductor channels, wherein edge surfaces of the gate stack are contacted by spacers.
Example 6: the semiconductor device of Example 5, wherein the spacers and the barrier comprise the same material.
Example 7: the semiconductor device of Examples 1-6, wherein an oxide is provided between the barrier and the source.
Example 8: the semiconductor device of Examples 1-7, wherein a bottom surface of the source is below a top surface of the substrate.
Example 9: the semiconductor device of Examples 1-8, wherein a cross-section of the barrier is u-shaped with lateral wings.
Example 10: the semiconductor device of Example 9, further comprising a semiconductor region contacting the lateral wings.
Example 11: the semiconductor device of Example 9 or Example 10, wherein the lateral wings are on opposite sides of the u-shape.
Example 12: a method of forming a semiconductor device, comprising: providing a fin with alternating sacrificial layers and channel layers over a semiconductor substrate; forming a source trench in the fin, wherein the source trench extends into the semiconductor substrate; laterally recessing the sacrificial layers to form lateral recesses; disposing a cavity spacer in the lateral recesses and the source trench; etching the cavity spacer to isolate a barrier at a bottom of the source trench; growing a source in the source trench; replacing the sacrificial layers with a gate stack; removing the semiconductor substrate; and disposing an interlayer dielectric (ILD) over a backside of the semiconductor device.
Example 13: the method of Example 12, wherein the barrier has a u-shaped cross-section.
Example 14: the method of Example 13, wherein the barrier further comprises lateral wings.
Example 15: the method of Example 14, wherein removing the semiconductor substrate comprises an etching process, and wherein the lateral wings protect corners of the source.
Example 16: the method of Example 15, wherein portions of the semiconductor substrate above the wings are not removed.
Example 17: the method of Examples 12-16, further comprising: forming a mask over the bottom of the spacer prior to etching the cavity spacer to isolate the barrier at the bottom of the source trench.
Example 18: a nanowire device, comprising: a dielectric substrate; a stack of nanowire channels surrounded by a gate stack; a source at an end of the nanowire channels, wherein the source extends into the dielectric substrate; and a barrier between a bottom surface of the source and the dielectric substrate.
Example 19: the nanowire device of Example 18, wherein the barrier has a u-shaped cross-section.
Example 20: the nanowire device of Example 19, wherein vertical arms of the barrier directly contact the bottom surface of the source.
Example 21: the nanowire device of Example 19 or Example 20, wherein the barrier further comprises lateral wings extending out from sides of the barrier.
Example 22: the nanowire device of Examples 18-21, wherein a width of the source is substantially equal to a width of the barrier.
Example 23: the electronic system, comprising: a board; a package substrate coupled to the board; and a die coupled to the package substrate, wherein the die comprises: a substrate, wherein the substrate is a dielectric material; a vertical stack of semiconductor channels over the substrate; a source at a first end of the semiconductor channels; a drain at a second end of the semiconductor channels; and a barrier between a bottom surface of the source and the substrate.
Example 24: the electronic system of Example 23, wherein the barrier has a u-shaped cross-section.
Example 25: the electronic system of Example 24, wherein the barrier further comprises lateral wings.