US20180342661A1 - Fin-based devices based on the thermoelectric effect - Google Patents
Fin-based devices based on the thermoelectric effect Download PDFInfo
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- US20180342661A1 US20180342661A1 US15/605,289 US201715605289A US2018342661A1 US 20180342661 A1 US20180342661 A1 US 20180342661A1 US 201715605289 A US201715605289 A US 201715605289A US 2018342661 A1 US2018342661 A1 US 2018342661A1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/851—Thermoelectric active materials comprising inorganic compositions
- H10N10/855—Thermoelectric active materials comprising inorganic compositions comprising compounds containing boron, carbon, oxygen or nitrogen
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/10—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects
- H10N10/17—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects characterised by the structure or configuration of the cell or thermocouple forming the device
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/01—Manufacture or treatment
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- H01L35/32—
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier
- H01L27/04—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being a semiconductor body
- H01L27/10—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being a semiconductor body including a plurality of individual components in a repetitive configuration
- H01L27/105—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being a semiconductor body including a plurality of individual components in a repetitive configuration including field-effect components
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- H01L35/22—
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- H01L35/34—
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
Definitions
- the present invention relates to semiconductor device fabrication and integrated circuits and, more specifically, to structures that include semiconductor fins and methods for forming a structure that includes semiconductor fins.
- thermoelectric effect finds application in various devices, such as temperature sensors, thermoelectric generators, and thermoelectric coolers.
- Thermocouples are a widely used type of temperature sensor that operate based on the thermoelectric effect. Thermocouples may be used to measure temperature and to assess temperature changes. As a result of the thermoelectric effect, a thermocouple produces a temperature-dependent voltage that can be interpreted to measure temperature.
- a fin-type field-effect transistor is a non-planar device structure that may be more densely packed in an integrated circuit than planar field-effect transistors.
- a FinFET may include a fin consisting of a body of semiconductor material, heavily-doped source/drain regions formed in sections of the fin body, and a gate electrode that wraps about the fin body between the source/drain regions.
- Advanced semiconductor process nodes suffer from excessive local heat generation that may be caused during operation by high switching frequencies and/or high off-state leakage currents.
- the local heat generation may benefit from on-chip thermal management, as well on-chip heat sensing and engineered heat transfer.
- a method includes forming a first fin comprised of n-type semiconductor material, forming a second fin comprised of p-type semiconductor material, and forming a conductive strap coupling an end of the first fin with an end of the second fin.
- a structure in an embodiment of the invention, includes a first fin comprised of n-type semiconductor material, a second fin comprised of p-type semiconductor material, the second fin having an end, and a conductive strap coupling an end of the first fin with an end of the second fin.
- FIG. 1 is a top view of a structure at an initial fabrication stage of a processing method in accordance with embodiments of the invention.
- FIG. 2 is a top view of the structure at a fabrication stage subsequent to FIG. 1 .
- FIG. 2A is a cross-sectional view of the structure of FIG. 2 taken generally along line 2 A- 2 A in FIG. 2 .
- FIG. 2B is a cross-sectional view similar to FIG. 2A in accordance with alternative embodiments of the invention.
- FIG. 3 is a top view of a structure at an initial fabrication stage of a processing method in accordance with alternative embodiments of the invention.
- FIG. 4 is a cross-sectional view of the structure of FIG. 3 taken generally along line 4 - 4 in FIG. 3 .
- FIG. 5 is a top view of the structure at a fabrication stage subsequent to FIG. 3 .
- FIG. 6 is a cross-sectional view of an n-type semiconductor fin of the structure at a fabrication stage subsequent to FIG. 1 of a processing method in accordance with alternative embodiments of the invention.
- FIG. 7 is a cross-sectional view of a p-type semiconductor fin of the structure at a fabrication stage subsequent to FIG. 1 of a processing method in accordance with alternative embodiments of the invention.
- FIG. 8 is a cross-sectional view of the n-type semiconductor fin at a fabrication stage subsequent to FIG. 6 .
- FIG. 9 is a cross-sectional view of the p-type semiconductor fin at a fabrication stage subsequent to FIG. 7 .
- a substrate 10 may be a bulk substrate or a device layer of a silicon-on-insulator substrate that is doped to produce alternating doped regions 12 and 14 .
- the regions 12 may be formed by a masked implantation into the epitaxial layer of the substrate 10
- the regions 14 may be formed by a complementary masked implantation into the epitaxial layer of the substrate 10 .
- the regions 12 and the regions 14 are composed of semiconductor material having opposite conductivity types (i.e., n-type and p-type).
- the regions 12 may include a concentration of an n-type dopant from Group V of the Periodic Table (e.g., phosphorus (P) and/or arsenic (As)) that is effective to impart n-type electrical conductivity to the constituent semiconductor material
- the regions 14 may be composed of a silicon-germanium (SiGe) alloy and include a concentration of p-type dopant from Group III of the Periodic Table (e.g., boron (B), aluminum (Al), gallium (Ga), and/or indium (In)) in a concentration that is effective to impart p-type electrical conductivity to the constituent semiconductor material.
- fins 16 , 18 are formed using the regions 12 , 14 of the substrate 10 and that project in a vertical direction relative to the top surface of the regions 12 , 14 .
- the fins 16 , 18 are three-dimensional bodies arranged in lengthwise parallel lines that may be formed by photolithography and etching processes, such as self-aligned double patterning (SADP) or self-aligned quadruple patterning (SAQP).
- SADP self-aligned double patterning
- SAQP self-aligned quadruple patterning
- the fins 16 extend lengthwise between opposite ends 25 and the fins 18 likewise extend lengthwise between opposite ends 27 .
- Shallow trench isolation regions 20 are formed to isolate the fins 16 , 18 , and may be composed of a dielectric material, such as an oxide of silicon (e.g., silicon dioxide (SiO 2 )).
- the fins 16 formed by patterning the regions 12 are composed of n-type semiconductor material.
- the fins 18 formed by patterning the regions 14 are composed of p-type semiconductor material.
- a single fin 16 is depicted as formed from each region 12 and a single fin 18 is depicted as formed from each region 14 .
- multiple fins 16 may be formed from each region 12 and/or multiple fins 18 may be formed from each region 14 .
- fins 16 are formed from each of multiple regions 12 and fins 18 are formed from each of multiple regions 14 .
- a minimum number of regions 12 is one and a minimum number of regions 14 is one, and the maximum number of multiple regions 12 and the minimum number of multiple regions 14 is limited by the device design.
- An on-chip structure 22 is formed using the fins 16 , 18 by connecting the fins 16 with the fins 18 in an alternating manner with conductive straps or connections 24 .
- the fins 16 connected with the fins 18 are located adjacent to each other, and the connections 24 extend between an end 25 of fin 16 and an end 27 of fin 18 .
- the connections 24 may be electrically-conductive features (e.g., metal features) that are formed by middle-of-line (MOL) processing, such as features of a trench silicide layer formed in an interlayer dielectric layer (not shown) of a lowermost metallization level.
- MOL middle-of-line
- the fins 16 , 18 when linked by the connections 24 , form a plurality of segments that extend back and forth to define a continuous serpentine path for current flow.
- a current flowing through the structure 22 is constrained to flow in one direction through the full length of one of the fins 16 and then in an opposite direction through the full length of one of the fins 18 with the changes in current direction provided by the connections 24 .
- the changes in direction are provided by the connections 24 , which act as bridges furnishing the links between fins 16 and fins 18 .
- the segments defined by fins 16 are comprised of semiconductor material with one conductivity type
- the segments defined by fins 18 are comprised of semiconductor material with the opposite conductivity type.
- each of the segments of the structure 22 includes one of the fins 16 or one of the fins 18 .
- each of the segments may include two or more of the fins 16 connected in parallel with the associated connection 24 or two or more of the fins 18 connected in parallel with the associated connection 24 .
- the end 25 of one of the fins 16 and the end 27 of one of the fins 18 terminate the segments of the structure 22 at its extrema.
- These terminating ends 25 , 27 lack one of the connections 24 , but instead include conductive features 23 that are available for establishing an external interconnection to the structure 22 .
- the conductive features 23 are formed in the same manner on the terminating end 25 of one of the fins 16 and the terminating end 27 of one of the fins 18 that are free and not connected to other segments by the connections 24 .
- These terminating ends 25 may represent the input and output locations for the connected segments of the structure 22 .
- Device structures 26 of an integrated circuit may be formed on the substrate 10 as part of a chip.
- the device structures 26 may be, for example, field-effect transistors and, in particular, may be fin-type field-effect transistors constructed using fins formed in conjunction with the formation of fins 16 , 18 .
- the device structures 26 are powered and generate heat energy that operates to heat the substrate 10 , which furnishes a temperature gradient that is transferred by thermal conduction to the fins 16 , 18 .
- the fins 16 , 18 which are composed of semiconductor materials having different conductivity types, respond to the temperature gradient through the movement of free charge carriers to generate a current by the thermoelectric effect. If the free charge carriers are positive (the semiconductor material of fins 18 is p-type), positive charge carriers will move toward the cooler ends of fins 18 . Similarly, negative free charges (the semiconductor material of fins 16 is n-type) will move toward the cooler ends of fins 16 .
- An external device 42 may be coupled with the conductive feature 23 on the fin 16 at the end 25 terminating the structure 22 and with the conductive feature 23 on the fin 18 at the end 25 that terminates the structure 22 .
- the coupling between the structure 22 and the external device 42 may be facilitated by, for example, additional overlying metallization levels formed by back-end-of-line (BEOL) processing.
- BEOL back-end-of-line
- the external device 42 which may be located off chip, may include temperature measurement electronics that can receive and amplify a current generated by the structure 22 by the thermoelectric effect and produce a temperature measurement representative of the thermal environment of the structure 22 on the substrate 10 . In this mode of operation, the structure 22 may operate as a thermocouple that provides temperature sensing by the thermoelectric effect.
- the external device 42 may be a load that receives a current from the structure 22 in order to harvest thermoelectric energy generated when the structure 22 is heated by the operation of the device structures 26 .
- the external device 42 may be a power supply that supplies a current to the structure 22 and thereby causes the structure 22 to operate by the thermoelectric effect as a Peltier cooler. In this mode of operation, the structure 22 can be used in connection with thermal management on the chip to cool the device structures 26 .
- the fins 16 , 18 may be located on a dielectric layer 21 that is formed by laterally etching the substrate 10 to undercut the fins 16 , 18 with a cavity and then filling the resultant cavity with a dielectric material, such as silicon dioxide (SiO 2 ), having a thermal conductivity that is less than the thermal conductivity of the semiconductor material of the substrate 10 .
- a dielectric material such as silicon dioxide (SiO 2 )
- the dielectric layer 21 provides full thermal isolation of the fins 16 , 18 from the substrate 10 , and may operate to improve the figure of merit relating to the ability to efficiently produce thermoelectric power.
- the thermal conductivity of the fins 16 and the fins 18 may be reduced through the introduction of alternating compressive strain and tensile strain.
- the substrate 10 may be modified to provide the alternating compressive and tensile strains to the fins 16 , 18 .
- the substrate 10 may be a strain-relaxed buffer (SRB) substrate that includes an SRB layer 28 at its top surface.
- the SRB layer 28 is formed to account for lattice mismatch between the substrate 10 and an epitaxial semiconductor material of different lattice structure grown on the substrate 10 .
- An example is the epitaxial growth of silicon-germanium (SiGe) on a substrate that is composed of silicon.
- the germanium content of the semiconductor material of the SRB layer 28 is gradually increased (e.g., linearly or stepwise graded) with increasing distance from the silicon substrate 10 .
- the crystal structure of the semiconductor material of the SRB layer 28 gradually transitions from that of silicon near the substrate 10 to that of a silicon-germanium alloy of a given composition at the top of the SRB layer 28 .
- the composition at the top surface of the SRB layer 28 may be twenty (20) atomic percent germanium and eighty (80) atomic percent silicon.
- Epitaxial layers 30 and 32 are formed on the top surface of the SRB layer 28 .
- the epitaxial layers 30 may be formed by epitaxially growing a uniform layer of its semiconductor material (e.g., silicon) on the top surface of the SRB layer 28 , and then patterning the layer of semiconductor material.
- the epitaxial layers 32 are epitaxially grown from the areas on the top surface of the SRB layer 28 in the areas opened by the patterning and not covered by the epitaxial layers.
- a chemical mechanical polishing (CMP) process may be employed to remove topography and provide a planarized surface.
- the epitaxial layers 30 may be composed of a material (e.g., silicon) that is lattice mismatched with the semiconductor material of the SRB layer 28 to incorporate tensile stress.
- silicon has a smaller lattice constant than the silicon-germanium of the SRB layer 28 at its top surface and will include tensile strain arising from tensile stress.
- the epitaxial layers 32 may be composed of a material (e.g., silicon-germanium) that is lattice mismatched with the semiconductor material of the epitaxial layers 30 and with the semiconductor material of the SRB layer 28 .
- the composition of the epitaxial layers 32 may be forty (40) atomic percent germanium and sixty (60) atomic percent silicon on an SRB layer 28 having a composition of twenty (20) atomic percent germanium and eighty (80) atomic percent silicon at the top surface. Due to the higher germanium content, the silicon-germanium of the epitaxial layers 32 will have a larger lattice constant than the silicon-germanium of the SRB layer 28 at its top surface and will include compressive strain arising from compressive stress.
- the process continues with the deposition of an epitaxial layer on the epitaxial layers 30 , 32 , followed by the formation of the regions 12 , 14 , and the formation of the fins 16 , 18 from the regions 12 , 14 as described in the context of FIG. 1 .
- the fins 16 , 18 may be doped, after being formed, to have the appropriate conductivity types by introducing dopants through a set of masked ion implantations.
- multiple fins 16 composed of n-type semiconductor material and multiple fins 18 composed of p-type semiconductor material may be formed and connected as a group by the connections 24 .
- the process flow continues as described in connection with FIG. 2 to complete the structure 22 on the epitaxial layers 30 , 32 with multiple fins 16 and multiple fins 18 in each segment of the structure 22 .
- the fins 16 and the fins 18 will cross over the strained epitaxial layers 30 and 32 in an alternating manner. Stress is transferred from the strained epitaxial layers 30 and 32 to the overlying sections of the fins 16 , which induces tensile and compressive strains that alternate along the length of the fins 16 . Similarly, stress is transferred from the strained epitaxial layers 30 and 32 to the overlying sections of the fins 18 , which induces tensile and compressive strains that alternate along the length of the fins 18 .
- the thermal conductivity of the fins 16 and the fins 18 may be reduced by introducing the lengthwise alternating compressive and tensile strains in a different manner. Specifically, the construction of the fins 16 and the fins 18 may be modified to provide the alternating compressive and tensile strains.
- the fins 16 , 18 are formed from the doped semiconductor materials of the regions 12 , 14 as described in the context of FIGS. 1 and 2 .
- the fins 16 , 18 are then patterned along their lengths to remove spaced-apart sections.
- an etch mask 35 is applied that covers sections of the fins 16 , 18 .
- the etch mask 35 may comprise a set of dummy gates and sidewall spacers formed as part of a replacement metal gate process being used to form field-effect transistors (e.g., device structures 26 ) on a different portion of the substrate 10 . Unmasked sections of the fins 16 , 18 are removed with an etching process.
- the unmasked sections of the fins 16 , 18 may be completely removed, as shown in the representative embodiment. In alternative embodiments, the unmasked sections of the fins 16 , 18 may be recessed and only partially removed (e.g., removal of 80 percent of the thickness).
- the masked sections 36 of the fins 16 and the masked sections 38 of the fins 18 are preserved, and are spaced apart lengthwise by open gaps.
- the open gaps between the masked sections 36 of the fins 16 and the open gaps between the masked sections 38 of the fins 18 are filled with sections 40 of an epitaxial-grown semiconductor layer, and the etch mask 35 is removed.
- the removal of the etch mask 35 may coincide with the removal of dummy gates in the replacement gate process forming field-effect transistors on the different portion of the substrate 10 .
- An anneal may be performed to diffuse dopant from the sections 36 of fins 16 to the sections 40 and from the sections 38 of fins 18 to the sections 40 and/or ion implantations may be used to dope the sections 40 to match the conductivity type of the fins 16 or the conductivity type of the fins 18 .
- the sections 40 of the semiconductor layer may be composed of a silicon-germanium alloy and the fins 16 , 18 may be composed of silicon.
- the sections 40 of the semiconductor layer may be composed of silicon and the fins 16 , 18 may be composed of a silicon-germanium alloy, which would require that the epitaxial layer that is patterned to form the fins 16 , 18 be composed of the silicon-germanium alloy.
- the methods as described above are used in the fabrication of integrated circuit chips.
- the resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (e.g., as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form.
- the chip is mounted in a single chip package (e.g., a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (e.g., a ceramic carrier that has either or both surface interconnections or buried interconnections).
- the chip may be integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either an intermediate product or an end product.
- references herein to terms such as “vertical”, “horizontal”, “lateral”, etc. are made by way of example, and not by way of limitation, to establish a frame of reference.
- Terms such as “horizontal” and “lateral” refer to a direction in a plane parallel to a top surface of a semiconductor substrate, regardless of its actual three-dimensional spatial orientation.
- Terms such as “vertical” and “normal” refer to a direction perpendicular to the “horizontal” and “lateral” direction.
- Terms such as “above” and “below” indicate positioning of elements or structures relative to each other and/or to the top surface of the semiconductor substrate as opposed to relative elevation.
- a feature “connected” or “coupled” to or with another element may be directly connected or coupled to the other element or, instead, one or more intervening elements may be present.
- a feature may be “directly connected” or “directly coupled” to another element if intervening elements are absent.
- a feature may be “indirectly connected” or “indirectly coupled” to another element if at least one intervening element is present.
Abstract
Description
- The present invention relates to semiconductor device fabrication and integrated circuits and, more specifically, to structures that include semiconductor fins and methods for forming a structure that includes semiconductor fins.
- The thermoelectric effect finds application in various devices, such as temperature sensors, thermoelectric generators, and thermoelectric coolers. Thermocouples are a widely used type of temperature sensor that operate based on the thermoelectric effect. Thermocouples may be used to measure temperature and to assess temperature changes. As a result of the thermoelectric effect, a thermocouple produces a temperature-dependent voltage that can be interpreted to measure temperature.
- A fin-type field-effect transistor (FinFET) is a non-planar device structure that may be more densely packed in an integrated circuit than planar field-effect transistors. A FinFET may include a fin consisting of a body of semiconductor material, heavily-doped source/drain regions formed in sections of the fin body, and a gate electrode that wraps about the fin body between the source/drain regions.
- Advanced semiconductor process nodes suffer from excessive local heat generation that may be caused during operation by high switching frequencies and/or high off-state leakage currents. The local heat generation may benefit from on-chip thermal management, as well on-chip heat sensing and engineered heat transfer.
- Improved structures that include semiconductor fins and methods for forming a structure that includes semiconductor fins are needed.
- In an embodiment of the invention, a method includes forming a first fin comprised of n-type semiconductor material, forming a second fin comprised of p-type semiconductor material, and forming a conductive strap coupling an end of the first fin with an end of the second fin.
- In an embodiment of the invention, a structure includes a first fin comprised of n-type semiconductor material, a second fin comprised of p-type semiconductor material, the second fin having an end, and a conductive strap coupling an end of the first fin with an end of the second fin.
- The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given below, serve to explain the embodiments of the invention.
-
FIG. 1 is a top view of a structure at an initial fabrication stage of a processing method in accordance with embodiments of the invention. -
FIG. 2 is a top view of the structure at a fabrication stage subsequent toFIG. 1 . -
FIG. 2A is a cross-sectional view of the structure ofFIG. 2 taken generally alongline 2A-2A inFIG. 2 . -
FIG. 2B is a cross-sectional view similar toFIG. 2A in accordance with alternative embodiments of the invention. -
FIG. 3 is a top view of a structure at an initial fabrication stage of a processing method in accordance with alternative embodiments of the invention. -
FIG. 4 is a cross-sectional view of the structure ofFIG. 3 taken generally along line 4-4 inFIG. 3 . -
FIG. 5 is a top view of the structure at a fabrication stage subsequent toFIG. 3 . -
FIG. 6 is a cross-sectional view of an n-type semiconductor fin of the structure at a fabrication stage subsequent toFIG. 1 of a processing method in accordance with alternative embodiments of the invention. -
FIG. 7 is a cross-sectional view of a p-type semiconductor fin of the structure at a fabrication stage subsequent toFIG. 1 of a processing method in accordance with alternative embodiments of the invention. -
FIG. 8 is a cross-sectional view of the n-type semiconductor fin at a fabrication stage subsequent toFIG. 6 . -
FIG. 9 is a cross-sectional view of the p-type semiconductor fin at a fabrication stage subsequent toFIG. 7 . - With reference to
FIG. 1 and in accordance with embodiments of the invention, asubstrate 10 may be a bulk substrate or a device layer of a silicon-on-insulator substrate that is doped to produce alternatingdoped regions regions 12 may be formed by a masked implantation into the epitaxial layer of thesubstrate 10, and theregions 14 may be formed by a complementary masked implantation into the epitaxial layer of thesubstrate 10. Theregions 12 and theregions 14 are composed of semiconductor material having opposite conductivity types (i.e., n-type and p-type). In an embodiment in which thesubstrate 10 is composed of silicon, theregions 12 may include a concentration of an n-type dopant from Group V of the Periodic Table (e.g., phosphorus (P) and/or arsenic (As)) that is effective to impart n-type electrical conductivity to the constituent semiconductor material, and theregions 14 may be composed of a silicon-germanium (SiGe) alloy and include a concentration of p-type dopant from Group III of the Periodic Table (e.g., boron (B), aluminum (Al), gallium (Ga), and/or indium (In)) in a concentration that is effective to impart p-type electrical conductivity to the constituent semiconductor material. - With reference to
FIGS. 2, 2A in which like reference numerals refer to like features inFIG. 1 and at a subsequent fabrication stage,fins regions substrate 10 and that project in a vertical direction relative to the top surface of theregions fins fins 16 extend lengthwise betweenopposite ends 25 and thefins 18 likewise extend lengthwise betweenopposite ends 27. Shallowtrench isolation regions 20 are formed to isolate thefins - The
fins 16 formed by patterning theregions 12 are composed of n-type semiconductor material. Thefins 18 formed by patterning theregions 14 are composed of p-type semiconductor material. In the representative embodiment, asingle fin 16 is depicted as formed from eachregion 12 and asingle fin 18 is depicted as formed from eachregion 14. However,multiple fins 16 may be formed from eachregion 12 and/ormultiple fins 18 may be formed from eachregion 14. In the representative embodiment,fins 16 are formed from each ofmultiple regions 12 andfins 18 are formed from each ofmultiple regions 14. However, a minimum number ofregions 12 is one and a minimum number ofregions 14 is one, and the maximum number ofmultiple regions 12 and the minimum number ofmultiple regions 14 is limited by the device design. - An on-
chip structure 22 is formed using thefins fins 16 with thefins 18 in an alternating manner with conductive straps orconnections 24. Thefins 16 connected with thefins 18 are located adjacent to each other, and theconnections 24 extend between anend 25 offin 16 and anend 27 offin 18. Theconnections 24 may be electrically-conductive features (e.g., metal features) that are formed by middle-of-line (MOL) processing, such as features of a trench silicide layer formed in an interlayer dielectric layer (not shown) of a lowermost metallization level. - The
fins connections 24, form a plurality of segments that extend back and forth to define a continuous serpentine path for current flow. A current flowing through thestructure 22 is constrained to flow in one direction through the full length of one of thefins 16 and then in an opposite direction through the full length of one of thefins 18 with the changes in current direction provided by theconnections 24. The changes in direction are provided by theconnections 24, which act as bridges furnishing the links betweenfins 16 andfins 18. The segments defined byfins 16 are comprised of semiconductor material with one conductivity type, and the segments defined byfins 18 are comprised of semiconductor material with the opposite conductivity type. In the representative embodiment, each of the segments of thestructure 22 includes one of thefins 16 or one of thefins 18. In an alternative embodiment, each of the segments may include two or more of thefins 16 connected in parallel with theassociated connection 24 or two or more of thefins 18 connected in parallel with theassociated connection 24. - The
end 25 of one of thefins 16 and theend 27 of one of thefins 18 terminate the segments of thestructure 22 at its extrema. These terminatingends connections 24, but instead includeconductive features 23 that are available for establishing an external interconnection to thestructure 22. When theconnections 24 are formed, theconductive features 23 are formed in the same manner on the terminatingend 25 of one of thefins 16 and the terminatingend 27 of one of thefins 18 that are free and not connected to other segments by theconnections 24. Theseterminating ends 25 may represent the input and output locations for the connected segments of thestructure 22. -
Device structures 26 of an integrated circuit may be formed on thesubstrate 10 as part of a chip. Thedevice structures 26 may be, for example, field-effect transistors and, in particular, may be fin-type field-effect transistors constructed using fins formed in conjunction with the formation offins device structures 26 are powered and generate heat energy that operates to heat thesubstrate 10, which furnishes a temperature gradient that is transferred by thermal conduction to thefins - The
fins fins 18 is p-type), positive charge carriers will move toward the cooler ends offins 18. Similarly, negative free charges (the semiconductor material offins 16 is n-type) will move toward the cooler ends offins 16. - An
external device 42 may be coupled with theconductive feature 23 on thefin 16 at theend 25 terminating thestructure 22 and with theconductive feature 23 on thefin 18 at theend 25 that terminates thestructure 22. The coupling between thestructure 22 and theexternal device 42 may be facilitated by, for example, additional overlying metallization levels formed by back-end-of-line (BEOL) processing. Theexternal device 42, which may be located off chip, may include temperature measurement electronics that can receive and amplify a current generated by thestructure 22 by the thermoelectric effect and produce a temperature measurement representative of the thermal environment of thestructure 22 on thesubstrate 10. In this mode of operation, thestructure 22 may operate as a thermocouple that provides temperature sensing by the thermoelectric effect. Alternatively, theexternal device 42 may be a load that receives a current from thestructure 22 in order to harvest thermoelectric energy generated when thestructure 22 is heated by the operation of thedevice structures 26. Alternatively, theexternal device 42 may be a power supply that supplies a current to thestructure 22 and thereby causes thestructure 22 to operate by the thermoelectric effect as a Peltier cooler. In this mode of operation, thestructure 22 can be used in connection with thermal management on the chip to cool thedevice structures 26. - With reference to
FIG. 2B in which like reference numerals refer to like features inFIG. 2A and in accordance with alternative embodiments, thefins dielectric layer 21 that is formed by laterally etching thesubstrate 10 to undercut thefins substrate 10. Thedielectric layer 21 provides full thermal isolation of thefins substrate 10, and may operate to improve the figure of merit relating to the ability to efficiently produce thermoelectric power. - With reference to
FIGS. 3 and 4 in which like reference numerals refer to like features inFIG. 1 and in accordance with alternative embodiments, the thermal conductivity of thefins 16 and thefins 18 may be reduced through the introduction of alternating compressive strain and tensile strain. In an embodiment, thesubstrate 10 may be modified to provide the alternating compressive and tensile strains to thefins substrate 10 may be a strain-relaxed buffer (SRB) substrate that includes anSRB layer 28 at its top surface. TheSRB layer 28 is formed to account for lattice mismatch between thesubstrate 10 and an epitaxial semiconductor material of different lattice structure grown on thesubstrate 10. An example is the epitaxial growth of silicon-germanium (SiGe) on a substrate that is composed of silicon. The germanium content of the semiconductor material of theSRB layer 28 is gradually increased (e.g., linearly or stepwise graded) with increasing distance from thesilicon substrate 10. As a result, the crystal structure of the semiconductor material of theSRB layer 28 gradually transitions from that of silicon near thesubstrate 10 to that of a silicon-germanium alloy of a given composition at the top of theSRB layer 28. For example, the composition at the top surface of theSRB layer 28 may be twenty (20) atomic percent germanium and eighty (80) atomic percent silicon. - Epitaxial layers 30 and 32 are formed on the top surface of the
SRB layer 28. The epitaxial layers 30 may be formed by epitaxially growing a uniform layer of its semiconductor material (e.g., silicon) on the top surface of theSRB layer 28, and then patterning the layer of semiconductor material. The epitaxial layers 32 are epitaxially grown from the areas on the top surface of theSRB layer 28 in the areas opened by the patterning and not covered by the epitaxial layers. A chemical mechanical polishing (CMP) process may be employed to remove topography and provide a planarized surface. - The epitaxial layers 30 may be composed of a material (e.g., silicon) that is lattice mismatched with the semiconductor material of the
SRB layer 28 to incorporate tensile stress. For example, silicon has a smaller lattice constant than the silicon-germanium of theSRB layer 28 at its top surface and will include tensile strain arising from tensile stress. The epitaxial layers 32 may be composed of a material (e.g., silicon-germanium) that is lattice mismatched with the semiconductor material of theepitaxial layers 30 and with the semiconductor material of theSRB layer 28. For example, the composition of theepitaxial layers 32 may be forty (40) atomic percent germanium and sixty (60) atomic percent silicon on anSRB layer 28 having a composition of twenty (20) atomic percent germanium and eighty (80) atomic percent silicon at the top surface. Due to the higher germanium content, the silicon-germanium of theepitaxial layers 32 will have a larger lattice constant than the silicon-germanium of theSRB layer 28 at its top surface and will include compressive strain arising from compressive stress. - With reference to
FIG. 5 in which like reference numerals refer to like features inFIGS. 3, 4 and at a subsequent fabrication stage, the process continues with the deposition of an epitaxial layer on theepitaxial layers regions fins regions FIG. 1 . Thefins multiple fins 16 composed of n-type semiconductor material andmultiple fins 18 composed of p-type semiconductor material may be formed and connected as a group by theconnections 24. The process flow continues as described in connection withFIG. 2 to complete thestructure 22 on theepitaxial layers multiple fins 16 andmultiple fins 18 in each segment of thestructure 22. - Along their respective lengths, the
fins 16 and thefins 18 will cross over the strainedepitaxial layers epitaxial layers fins 16, which induces tensile and compressive strains that alternate along the length of thefins 16. Similarly, stress is transferred from the strainedepitaxial layers fins 18, which induces tensile and compressive strains that alternate along the length of thefins 18. - With reference to
FIGS. 6, 7 in which like reference numerals refer to like features inFIG. 2 and in accordance with alternative embodiments, the thermal conductivity of thefins 16 and thefins 18 may be reduced by introducing the lengthwise alternating compressive and tensile strains in a different manner. Specifically, the construction of thefins 16 and thefins 18 may be modified to provide the alternating compressive and tensile strains. - To that end, the
fins regions FIGS. 1 and 2 . Thefins etch mask 35 is applied that covers sections of thefins etch mask 35 may comprise a set of dummy gates and sidewall spacers formed as part of a replacement metal gate process being used to form field-effect transistors (e.g., device structures 26) on a different portion of thesubstrate 10. Unmasked sections of thefins fins fins masked sections 36 of thefins 16 and themasked sections 38 of thefins 18 are preserved, and are spaced apart lengthwise by open gaps. - With reference to
FIGS. 8, 9 in which like reference numerals refer to like features inFIG. 6, 7 and at a subsequent fabrication stage, the open gaps between themasked sections 36 of thefins 16 and the open gaps between themasked sections 38 of thefins 18 are filled withsections 40 of an epitaxial-grown semiconductor layer, and theetch mask 35 is removed. The removal of theetch mask 35 may coincide with the removal of dummy gates in the replacement gate process forming field-effect transistors on the different portion of thesubstrate 10. An anneal may be performed to diffuse dopant from thesections 36 offins 16 to thesections 40 and from thesections 38 offins 18 to thesections 40 and/or ion implantations may be used to dope thesections 40 to match the conductivity type of thefins 16 or the conductivity type of thefins 18. - In an embodiment, the
sections 40 of the semiconductor layer may be composed of a silicon-germanium alloy and thefins sections 40 of the semiconductor layer may be composed of silicon and thefins fins - The methods as described above are used in the fabrication of integrated circuit chips. The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (e.g., as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case, the chip is mounted in a single chip package (e.g., a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (e.g., a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case, the chip may be integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either an intermediate product or an end product.
- References herein to terms such as “vertical”, “horizontal”, “lateral”, etc. are made by way of example, and not by way of limitation, to establish a frame of reference. Terms such as “horizontal” and “lateral” refer to a direction in a plane parallel to a top surface of a semiconductor substrate, regardless of its actual three-dimensional spatial orientation. Terms such as “vertical” and “normal” refer to a direction perpendicular to the “horizontal” and “lateral” direction. Terms such as “above” and “below” indicate positioning of elements or structures relative to each other and/or to the top surface of the semiconductor substrate as opposed to relative elevation.
- A feature “connected” or “coupled” to or with another element may be directly connected or coupled to the other element or, instead, one or more intervening elements may be present. A feature may be “directly connected” or “directly coupled” to another element if intervening elements are absent. A feature may be “indirectly connected” or “indirectly coupled” to another element if at least one intervening element is present.
- The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (20)
Priority Applications (5)
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US15/605,289 US20180342661A1 (en) | 2017-05-25 | 2017-05-25 | Fin-based devices based on the thermoelectric effect |
TW107108258A TWI741163B (en) | 2017-05-25 | 2018-03-12 | Semiconductor structures and methods of forming the same |
DE102018207670.7A DE102018207670B4 (en) | 2017-05-25 | 2018-05-16 | Fin-based devices based on the thermoelectric effect and manufacturing methods |
CN201810545835.3A CN108963062B (en) | 2017-05-25 | 2018-05-25 | Fin-based device based on thermoelectric effect |
US16/448,544 US11038092B2 (en) | 2017-05-25 | 2019-06-21 | Fin-based devices based on the thermoelectric effect |
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CN (1) | CN108963062B (en) |
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US11871668B2 (en) * | 2020-01-31 | 2024-01-09 | Stmicroelectronics S.R.L. | Thermoelectric generator |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5430322A (en) * | 1992-09-08 | 1995-07-04 | Agency Of Industrial Science And Technology | Thermoelectric element sheet in which thermoelectric semiconductors are mounted between films |
US20030025174A1 (en) * | 2001-05-22 | 2003-02-06 | Yeda Research And Development Co., Ltd. | Thermoelectric infrared detector |
US20050060884A1 (en) * | 2003-09-19 | 2005-03-24 | Canon Kabushiki Kaisha | Fabrication of nanoscale thermoelectric devices |
US20050112872A1 (en) * | 2003-11-25 | 2005-05-26 | Canon Kabushiki Kaisha | Fabrication of nanoscale thermoelectric devices |
US9219215B1 (en) * | 2007-08-21 | 2015-12-22 | The Regents Of The University Of California | Nanostructures having high performance thermoelectric properties |
US20160079508A1 (en) * | 2014-09-11 | 2016-03-17 | Korea University Research And Business Foundation | Thermoelectric generator module and method for manufacturing the same |
US20170047498A1 (en) * | 2015-08-14 | 2017-02-16 | Toyota Motor Engineering & Manufacturing North America, Inc. | Electronic Assemblies Incorporating Heat Flux Routing Structures for Thermoelectric Generation |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6060656A (en) | 1997-03-17 | 2000-05-09 | Regents Of The University Of California | Si/SiGe superlattice structures for use in thermoelectric devices |
US7038234B2 (en) | 2001-12-12 | 2006-05-02 | Hi-Z Technology, Inc. | Thermoelectric module with Si/SiGe and B4C/B9C super-lattice legs |
US20090236087A1 (en) * | 2008-03-19 | 2009-09-24 | Yamaha Corporation | Heat exchange device |
KR101249292B1 (en) | 2008-11-26 | 2013-04-01 | 한국전자통신연구원 | Thermoelectric device, thermoelecric device module, and forming method of the same |
US20120070947A1 (en) * | 2010-09-16 | 2012-03-22 | Globalfoundries Inc. | Inducing stress in fin-fet device |
US8441092B2 (en) * | 2010-12-06 | 2013-05-14 | Stmicroelectronics Pte. Ltd. | Thermoelectric cooler system, method and device |
US10312426B2 (en) | 2011-03-08 | 2019-06-04 | Purdue Research Foundation | Giant cross-plane seebeck effect in oxide metal semiconductor superlattices for spin-magnetic thermoelectric devices |
GB2530675B (en) | 2013-06-18 | 2019-03-06 | Intel Corp | Integrated thermoelectric cooling |
KR102334301B1 (en) * | 2014-07-24 | 2021-12-02 | 삼성전자주식회사 | Thermoelectric element, method of manufacturing the same and semiconductor device including the same |
US11424399B2 (en) | 2015-07-07 | 2022-08-23 | Taiwan Semiconductor Manufacturing Co., Ltd. | Integrated thermoelectric devices in Fin FET technology |
-
2017
- 2017-05-25 US US15/605,289 patent/US20180342661A1/en not_active Abandoned
-
2018
- 2018-03-12 TW TW107108258A patent/TWI741163B/en active
- 2018-05-16 DE DE102018207670.7A patent/DE102018207670B4/en active Active
- 2018-05-25 CN CN201810545835.3A patent/CN108963062B/en active Active
-
2019
- 2019-06-21 US US16/448,544 patent/US11038092B2/en active Active
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5430322A (en) * | 1992-09-08 | 1995-07-04 | Agency Of Industrial Science And Technology | Thermoelectric element sheet in which thermoelectric semiconductors are mounted between films |
US20030025174A1 (en) * | 2001-05-22 | 2003-02-06 | Yeda Research And Development Co., Ltd. | Thermoelectric infrared detector |
US20050060884A1 (en) * | 2003-09-19 | 2005-03-24 | Canon Kabushiki Kaisha | Fabrication of nanoscale thermoelectric devices |
US20050112872A1 (en) * | 2003-11-25 | 2005-05-26 | Canon Kabushiki Kaisha | Fabrication of nanoscale thermoelectric devices |
US9219215B1 (en) * | 2007-08-21 | 2015-12-22 | The Regents Of The University Of California | Nanostructures having high performance thermoelectric properties |
US20160079508A1 (en) * | 2014-09-11 | 2016-03-17 | Korea University Research And Business Foundation | Thermoelectric generator module and method for manufacturing the same |
US20170047498A1 (en) * | 2015-08-14 | 2017-02-16 | Toyota Motor Engineering & Manufacturing North America, Inc. | Electronic Assemblies Incorporating Heat Flux Routing Structures for Thermoelectric Generation |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11871668B2 (en) * | 2020-01-31 | 2024-01-09 | Stmicroelectronics S.R.L. | Thermoelectric generator |
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DE102018207670A1 (en) | 2018-11-29 |
TWI741163B (en) | 2021-10-01 |
TW201901926A (en) | 2019-01-01 |
US20190319180A1 (en) | 2019-10-17 |
US11038092B2 (en) | 2021-06-15 |
DE102018207670B4 (en) | 2022-03-10 |
CN108963062B (en) | 2022-07-05 |
CN108963062A (en) | 2018-12-07 |
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