US20120193715A1 - Structure with isotropic silicon recess profile in nanoscale dimensions - Google Patents
Structure with isotropic silicon recess profile in nanoscale dimensions Download PDFInfo
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- US20120193715A1 US20120193715A1 US13/442,008 US201213442008A US2012193715A1 US 20120193715 A1 US20120193715 A1 US 20120193715A1 US 201213442008 A US201213442008 A US 201213442008A US 2012193715 A1 US2012193715 A1 US 2012193715A1
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- trench
- semiconductor material
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 13
- 229910052710 silicon Inorganic materials 0.000 title claims description 13
- 239000010703 silicon Substances 0.000 title claims description 13
- 239000004065 semiconductor Substances 0.000 claims abstract description 209
- 239000000463 material Substances 0.000 claims abstract description 139
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 46
- 239000011737 fluorine Substances 0.000 claims abstract description 46
- 125000006850 spacer group Chemical group 0.000 claims abstract description 37
- 239000010410 layer Substances 0.000 claims description 102
- 230000003647 oxidation Effects 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 8
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 239000012212 insulator Substances 0.000 claims description 7
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 6
- 239000004020 conductor Substances 0.000 claims description 6
- 229910021419 crystalline silicon Inorganic materials 0.000 claims description 5
- 229910001339 C alloy Inorganic materials 0.000 claims description 4
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- AXQKVSDUCKWEKE-UHFFFAOYSA-N [C].[Ge].[Si] Chemical compound [C].[Ge].[Si] AXQKVSDUCKWEKE-UHFFFAOYSA-N 0.000 claims description 4
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 229910021483 silicon-carbon alloy Inorganic materials 0.000 claims description 4
- 125000001153 fluoro group Chemical group F* 0.000 claims description 3
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 2
- 229910000673 Indium arsenide Inorganic materials 0.000 claims description 2
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 claims description 2
- 239000002178 crystalline material Substances 0.000 claims description 2
- 229910052732 germanium Inorganic materials 0.000 claims description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 2
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 claims description 2
- 239000002356 single layer Substances 0.000 claims description 2
- 230000000873 masking effect Effects 0.000 abstract description 3
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- 238000000034 method Methods 0.000 description 11
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- 239000007789 gas Substances 0.000 description 8
- 238000004544 sputter deposition Methods 0.000 description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
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- OQNXPQOQCWVVHP-UHFFFAOYSA-N [Si].O=[Ge] Chemical compound [Si].O=[Ge] OQNXPQOQCWVVHP-UHFFFAOYSA-N 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 230000005669 field effect Effects 0.000 description 2
- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium oxide Inorganic materials O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 description 2
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- PVADDRMAFCOOPC-UHFFFAOYSA-N oxogermanium Chemical compound [Ge]=O PVADDRMAFCOOPC-UHFFFAOYSA-N 0.000 description 2
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- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005513 bias potential Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- AFYPFACVUDMOHA-UHFFFAOYSA-N chlorotrifluoromethane Chemical compound FC(F)(F)Cl AFYPFACVUDMOHA-UHFFFAOYSA-N 0.000 description 1
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- RWRIWBAIICGTTQ-UHFFFAOYSA-N difluoromethane Chemical compound FCF RWRIWBAIICGTTQ-UHFFFAOYSA-N 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 229910052743 krypton Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
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- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 1
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- 238000012546 transfer Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/7842—Field effect transistors with field effect produced by an insulated gate means for exerting mechanical stress on the crystal lattice of the channel region, e.g. using a flexible substrate
- H01L29/7848—Field effect transistors with field effect produced by an insulated gate means for exerting mechanical stress on the crystal lattice of the channel region, e.g. using a flexible substrate the means being located in the source/drain region, e.g. SiGe source and drain
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/308—Chemical or electrical treatment, e.g. electrolytic etching using masks
- H01L21/3083—Chemical or electrical treatment, e.g. electrolytic etching using masks characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
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- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/16—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic System
- H01L29/161—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic System including two or more of the elements provided for in group H01L29/16, e.g. alloys
- H01L29/165—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic System including two or more of the elements provided for in group H01L29/16, e.g. alloys in different semiconductor regions, e.g. heterojunctions
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66568—Lateral single gate silicon transistors
- H01L29/66636—Lateral single gate silicon transistors with source or drain recessed by etching or first recessed by etching and then refilled
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
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- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02367—Substrates
- H01L21/0237—Materials
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02612—Formation types
- H01L21/02617—Deposition types
- H01L21/02636—Selective deposition, e.g. simultaneous growth of mono- and non-monocrystalline semiconductor materials
- H01L21/02639—Preparation of substrate for selective deposition
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10S438/00—Semiconductor device manufacturing: process
- Y10S438/938—Lattice strain control or utilization
Definitions
- This invention relates to methods of laterally offsetting sidewalls of a trench in a semiconductor substrate relative to sidewalls of overlying structures and structures formed by the same.
- Etching in a vertical direction is an integral component of semiconductor processing technology.
- An isotropic etch employs wet chemicals or reactant gases that etch a material isotropically.
- the etch rate of isotropic etch processes are difficult to control on a nanoscale, i.e., on a scale from 0.1 nm to 10 nm, because the etch rate is sensitive to temperature and/or supply of etchant.
- Plasma processing provides a more precise control of the etch rate.
- Plasma etch chambers are designed to etch anisotropically in a vertical direction.
- Advanced semiconductor chips require a high degree of profile control, where the extent of vertical etching may be difficult to control.
- the ion energy due to the plasma self-bias potential is the ultimately lowest ion energy attainable in plasma reactors, while still enabling a reasonable degree of vertical etching.
- a trench is formed by an anisotropic etch in a semiconductor material layer employing a masking layer.
- An adsorbed fluorine layer is formed on the exposed surfaces of a semiconductor structure including the bottom surface and the sidewalls of the trench at a cryogenic temperature.
- a sputtering process performed at a cryogenic temperature removes horizontal portions of the adsorbed fluorine layer so that the remaining adsorbed fluorine layer is present only on vertical sidewalls of the semiconductor structure including the sidewalls of the trench.
- the temperature of the semiconductor structure is raised above the cryogenic temperature to enable reaction of the adsorbed fluorine layer with the semiconductor material in a lateral direction.
- the adsorbed fluorine layer removes a controlled amount of the underlying semiconductor material by chemically reacting and removing the semiconductor material.
- the amount of removal of the semiconductor material is in the range of monolayers of the semiconductor material, thereby providing a lateral etch by a nanoscale dimension.
- a trench is formed by an anisotropic etch in a semiconductor material layer employing a masking layer, which can be gate spacers.
- the crystallographic orientations of the sidewalls of the trench are selected to provide a lower oxidation rate than the crystallographic orientation of the bottom surface of the trench.
- a contiguous oxide liner having a thicker bottom portion relative to thinner sidewall portions is formed by oxidation.
- the contiguous oxide liner is isotropically etched to remove the thinner sidewall portions.
- the semiconductor material is laterally etched by a plasma-based etch at a controlled rate in a chemistry that is somewhat selective to the oxide layer atop the horizontal surface, thereby preventing etch of the semiconductor material underneath the oxide layer.
- the remaining horizontal portion of the contiguous oxide is subsequently removed, and the trench can be filled with a different semiconductor material to provide stress to neighboring semiconductor regions, which can include a channel of a field effect transistor.
- a method of forming a semiconductor structure includes forming a trench in a semiconductor material layer, and forming an adsorbed fluorine layer on vertical surfaces of the trench, while horizontal surfaces of the trench do not have adsorbed fluorine thereupon.
- another method of forming a semiconductor structure includes forming a trench in a semiconductor material layer; forming a contiguous semiconductor oxide liner on sidewalls and a bottom surface of the trench; exposing sidewall surfaces of the trench by removing vertical portions of the contiguous semiconductor oxide liner while a remaining horizontal semiconductor oxide portion of the contiguous semiconductor oxide liner overlies a portion of the semiconductor material layer located underneath the trench; and laterally etching the sidewall surfaces of the trench while the remaining horizontal semiconductor oxide portion covers the portion of the semiconductor material layer located underneath the trench.
- a semiconductor structure includes a gate structure located on a semiconductor material layer including a first semiconductor material, the gate structure including a gate dielectric, a gate conductor, and a gate spacer; a semiconductor material portion embedded in the semiconductor material layer, the semiconductor material portion including a second semiconductor material that is different from the first semiconductor material; and a non-planar interface region between the first semiconductor material and the second semiconductor material, wherein the non-planar interface region includes a first horizontal interface portion at a first depth from the gate dielectric, a second horizontal interface portion at a second depth from the gate dielectric, and a non-horizontal interface portion adjoined to the first horizontal interface portion and the second horizontal interface portion and underlying the gate spacer.
- the semiconductor structure includes a trench in a semiconductor material layer; and an adsorbed fluorine layer located on vertical surfaces of the trench, while horizontal surfaces of the trench do not have adsorbed fluorine thereupon.
- FIG. 1 is a vertical cross-sectional view of a first exemplary structure before formation of a trench according to a first embodiment of the present invention.
- FIG. 2 is a vertical cross-sectional view of the first exemplary structure after forming a trench according to the first embodiment of the present invention.
- FIG. 3 is a vertical cross-sectional view of the first exemplary structure after forming a contiguous adsorbed fluorine layer according to the first embodiment of the present invention.
- FIG. 4 is a vertical cross-sectional view of the first exemplary structure after removal of horizontal portions of the contiguous adsorbed fluorine layer to provide adsorbed fluorine layer present only on vertical surfaces according to the first embodiment of the present invention.
- FIG. 5 is a vertical cross-sectional view of the first exemplary structure after lateral etching of the sidewalls of the trench according to the first embodiment of the present invention.
- FIG. 6 is a vertical cross-sectional view of the first exemplary structure after formation of an embedded semiconductor material portion according to the first embodiment of the present invention.
- FIG. 7 is a vertical cross-sectional view of a second exemplary structure after forming a contiguous semiconductor oxide liner according to a second embodiment of the present invention.
- FIG. 8 is a vertical cross-sectional view of the second exemplary structure after removing vertical portions of the contiguous semiconductor oxide liner according to the second embodiment of the present invention.
- FIG. 9 is a vertical cross-sectional view of the second exemplary structure after laterally etching a semiconductor material employing a horizontal semiconductor oxide portion according to the second embodiment of the present invention.
- FIG. 10 is a vertical cross-sectional view of the second exemplary structure after removing the horizontal semiconductor oxide portion according to the second embodiment of the present invention.
- FIG. 11 is a vertical cross-sectional view of the second exemplary structure after formation of an embedded semiconductor material portion according to the second embodiment of the present invention.
- FIG. 12 is a vertical cross-sectional view of a variation of the second exemplary structure after formation of an embedded semiconductor material portion according to the second embodiment of the present invention.
- the present invention relates to methods of laterally offsetting sidewalls of a trench in a semiconductor substrate relative to sidewalls of overlying structures and structures formed by the same, which are now described in detail with accompanying figures.
- the drawings are not necessarily drawn to scale.
- a first exemplary structure includes a substrate 8 , a first gate structure 20 A located on a top surface of the substrate 8 , and a second gate structure 20 B located on the top surface of the substrate 8 and laterally spaced from the first gate structure 20 A.
- the substrate 8 includes a semiconductor material layer 10 , which is comprised of a semiconductor material.
- the semiconductor material of the semiconductor material layer 10 can be selected from, but is not limited to, silicon, germanium, silicon-germanium alloy, silicon carbon alloy, silicon-germanium-carbon alloy, gallium arsenide, indium arsenide, indium phosphide, III-V compound semiconductor materials, II-VI compound semiconductor materials, organic semiconductor materials, and other compound semiconductor materials.
- the semiconductor material of the semiconductor material layer 10 is a single crystalline material.
- the semiconductor material layer 10 can be a single crystalline silicon layer.
- the substrate 8 may include a buried insulator layer 9 . Further, the substrate 8 may include a handle substrate (not shown) located beneath the buried insulator layer 9 , if present.
- the first gate structure 20 A can include a first gate dielectric 22 A, a first gate conductor 24 A, a first gate spacer 26 A, and a first dielectric cap 28 A.
- the second gate structure 20 B can include a second gate dielectric 22 B, a second gate conductor 24 B, a second gate spacer 26 B, and a second dielectric cap 28 B.
- the first and second gate dielectrics ( 22 A, 22 B) can be a silicon-oxide-based gate dielectric material or a high dielectric constant (high-k) dielectric material such as a dielectric metal oxide, having a dielectric constant greater than 4 . 0 .
- the first and second gate conductors ( 24 A, 24 B) can be a doped semiconductor material, a metallic material, or a combination thereof.
- the first and second gate dielectrics ( 26 A, 26 B) can be a dielectric material such as silicon nitride, silicon oxynitride, or a combination of silicon oxide and silicon nitride.
- the outer surfaces of the first and second gate dielectrics ( 26 A, 26 B) include a semiconductor nitride or a semiconductor oxynitride such as silicon nitride or silicon oxynitride.
- the first and second dielectric caps ( 28 A, 28 B) can be a dielectric material such as silicon nitride, silicon oxynitride, or a combination of silicon oxide and silicon nitride.
- the top surfaces of the first and second dielectric caps ( 28 A, 28 B) include a semiconductor nitride or a semiconductor oxynitride such as silicon nitride or silicon oxynitride.
- a trench 30 is formed by etching an exposed portion of the semiconductor material layer 10 between the first and second gate structures ( 20 A, 20 B).
- the trench 30 can be formed by an anisotropic etch that etches the semiconductor material of the semiconductor material layer 10 selective to the dielectric materials of the first and second gate spacers ( 26 A, 26 B) and the first and second dielectric caps ( 28 A, 28 B). If the buried insulator layer 9 is present, the depth of the trench 30 is selected to be less than the depth of the buried insulator layer 9 .
- the trench 30 has a bottom surface and sidewalls. The bottom surface of the trench 30 is a horizontal surface, and the sidewalls of the trench 30 are typically substantially vertical.
- the periphery of the sidewalls of the trench 30 can coincide with outer peripheries of the first and second gate spacers ( 26 A, 26 B) at which the outer sidewalls of the first and second gate spacers ( 26 A, 26 B) contact a top surface of the semiconductor material layer 10 .
- the first exemplary structure is placed in a cryogenic environment, which has an ambient temperature below ⁇ 40 degrees Celsius, and preferably below ⁇ 100 degrees Celsius. Placement of the first exemplary structure in a cryogenic environment can be effected by providing a cryogenic chamber and inserting the first exemplary structure into the cryogenic chamber.
- the cryogenic chamber is a vacuum enclosure that provides a cryogenic temperature and low residual gas pressure.
- the cryogenic chamber is filled with a fluorine-containing gas.
- the fluorine-containing gas includes any gas that contains fluorine atoms that adsorb to a surface at a cryogenic temperature.
- the fluorine-containing gas can be, but is not limited to F 2 , CClF 3 , CF 4 , SF 6 , XeF 2 , CHF 3 , CH 2 F 2 , CH 3 F, C 4 F 6 , C 5 F 8 , C 4 F 8 or any combination thereof.
- a contiguous adsorbed fluorine layer 80 is formed on exposed surfaces of the first exemplary semiconductor structure at the cryogenic temperature because the fluorine-containing gas is adsorbed on the cold surfaces of the first exemplary structure.
- the surfaces on which the contiguous adsorbed fluorine layer 80 is formed include the bottom surface and the sidewalls of the trench 30 .
- the contiguous adsorbed fluorine layer 80 contiguously extends over all of the exposed surfaces of the first exemplary semiconductor structure without a hole or a discontinuity.
- the contiguous adsorbed fluorine layer 80 is formed on all surfaces of the trench 30 , i.e., on horizontal and vertical surfaces of the trench 30 .
- the contiguous adsorbed fluorine layer 80 can be a monolayer of fluorine atoms that are atomically bonded to an underlying semiconductor material in the semiconductor material layer 10 .
- the cryogenic chamber can be equipped with sputtering capability to provide ions that impinge upon the first exemplary structure in a direction that is substantially normal to the bottom surface 31 of the trench 30 .
- Ions that can be employed to sputter and remove horizontal portions of the contiguous adsorbed fluorine layer 80 include, but are not limited to, Kr, He, Ne, Ar, Xe, H 2 , N 2 , and O 2 .
- the ion sputtering destroys the chemical bonding between the adsorbed atoms and the underlying semiconductor material so that the horizontal surface of the trench 30 does not have adsorbed fluorine thereupon after the sputtering. Horizontal portions of the contiguous adsorbed fluorine layer 80 are thus removed, and vertical portions of the contiguous adsorbed fluorine layer 80 remain to constitute the adsorbed fluorine layers 82 , which cover all of the vertical sidewalls of the trench 30 and a lower portion of the outer sidewalls of the first and second gate spacers ( 26 A, 26 B).
- Each of the adsorbed fluorine layers 82 contiguously extends over a vertical portion of an outer surface of one of the first and second gate spacers ( 26 A, 26 B).
- the sputtering is performed at a cryogenic temperature below ⁇ 40 degrees Celsius, and preferably below ⁇ 100 degrees Celsius.
- the sputtering can be performed in another cryogenic chamber after transporting the first exemplary semiconductor structure into the other cryogenic chamber.
- the ambient conditions of the first exemplary structure is maintained at a cryogenic temperature and in vacuum or in an inert ambient to prevent the contiguous adsorbed fluorine layer 80 from becoming volatile.
- the remaining vertical portions of the contiguous adsorbed fluorine layer 80 constitute the adsorbed fluorine layers 82 , which cover all of the vertical sidewalls of the trench 30 and a lower portion of the outer sidewalls of the first and second gate spacers ( 26 A, 26 B).
- the horizontal bottom surface of the trench 30 does not have adsorbed fluorine thereupon.
- Each of the adsorbed fluorine layers 82 contiguously extends over a vertical portion of an outer surface of one of the first and second gate spacers ( 26 A, 26 B).
- the sputtering is performed at a cryogenic temperature below ⁇ 40 degrees Celsius, and preferably below ⁇ 100 degrees Celsius.
- the temperature of the first exemplary structure is raised above ⁇ 40 degrees Celsius.
- the first exemplary structure may be exposed to an ambient at a room temperature between 5 degrees Celsius and 35 degrees Celsius.
- the sidewalls of the trench 30 are laterally etched by the adsorbed fluorine layers 82 .
- the adsorbed fluorine layers 82 and the vertical surfaces of the trench 30 are subjected to a temperature at which the adsorbed fluorine layers 82 etch the underlying semiconductor material on the vertical surfaces of the trench 80 by reacting with the underlying semiconductor material of the semiconductor material layer 10 .
- the amount of etched semiconductor material is measured in monolayers, and is typically from 1 to 4 atomic layers of the semiconductor material in the semiconductor material layer 10 .
- the lateral recess width RW is from 0.3 nm to 1.5 nm depending on the crystallographic orientation of the semiconductor material at the sidewalls of the trench 30 .
- an embedded semiconductor material portion 50 is formed by filling the trench 30 with another semiconductor material, which is typically a different material than the semiconductor material of the semiconductor material layer 10 .
- the semiconductor material of the embedded semiconductor material portion 50 can generate mechanical stress in a portion of the semiconductor material layer 10 located around the embedded semiconductor material portion 50 .
- the semiconductor material of the semiconductor material layer 10 and the semiconductor material of the embedded semiconductor material portion 50 can be single crystalline semiconductor materials that are epitaxially aligned to each other.
- the material of the embedded semiconductor material portion can be selected from, but is not limited to, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy.
- the vertical interfaces between the semiconductor material layer 10 and the embedded semiconductor material portion 50 are laterally offset by the lateral recess width RW from outer peripheries of the first and second gate spacers ( 26 A, 26 B) at which the first and second gate spacers ( 26 A, 26 B) contact the embedded semiconductor material portion 50 .
- a second exemplary structure according to a second embodiment of the present invention is derived from the first exemplary structure in FIG. 2 according to the first embodiment of the present invention.
- a limitation is imposed on the crystallographic orientation of the bottom surface of the trench 30 and the crystallographic orientations of the sidewalls of the trench 30 at a step corresponding to FIG. 2 .
- the bottom surface of the trench 30 has a crystallographic orientation that provides a greater oxidation rate for the semiconductor material of the semiconductor material layer 10 than crystallographic orientations of the sidewalls of the trench 30 .
- the semiconductor material layer 10 is a single crystalline silicon layer and the bottom surface of the trench 30 has a ⁇ 111> orientation, and the sidewall surfaces of the trench 30 can have ⁇ 110> orientation.
- the semiconductor material layer 10 is a single crystalline silicon layer and the bottom surface of the trench 30 has a ⁇ 110> orientation, and the sidewall surfaces of the trench 30 can have a ⁇ 100> orientation.
- any combination of crystallographic orientations for the bottom surface and sidewalls of the trench 30 can be employed as long as the bottom surface of the trench 30 has a higher oxidation rate than the sidewalls of the trench 30 .
- the bottom of said trench can by oxidized to a greater depth than the sidewalls by exposing the structure to an oxygen plasma, where the ion energy is greater than the plasma potential alone. Due to the geometry of the reactor, high energy ions will react with the bottom trench forming an oxide of thickness t 1 , whereas the sidewalls of the trench only react with plasma neutrals and scattered ions, forming a thinner oxide of thickness t 2 . Gate structures can be masked during this process. In this case, the crystallographic orientation of the bottom surface of the trench need not have a greater oxidation rate for thermal oxidation than sidewall surfaces of the trench because the geometry employed in the plasma oxidation induces greater oxidation rate on the bottom surfaces of the trench than on the sidewall surfaces of the trench.
- a contiguous semiconductor oxide liner 40 is formed on all exposed surfaces of the trench 30 including the sidewalls and the bottom surface of the trench 30 .
- the contiguous semiconductor oxide liner 40 is formed by converting the semiconductor material in the semiconductor material layer 10 into a semiconductor oxide. For example, if the semiconductor material in the semiconductor material layer 10 is silicon, the semiconductor oxide is silicon oxide.
- the first thickness t 1 of the horizontal portion of the contiguous semiconductor oxide liner 40 is greater than the second thickness t 2 of the vertical portions of the contiguous semiconductor oxide liner 40 .
- the isotropic etch can be a wet etch or a dry etch.
- a dilute hydrofluoric acid can be employed to provide a slow etch rate if the contiguous semiconductor oxide liner 40 includes silicon oxide, a germanium oxide, or silicon-germanium oxide.
- an etchant gas such as HCl, SF 6 , XeF 2 , CF 4 or NF 3 can be employed.
- the duration of the etch is controlled so that the amount of removal of the contiguous semiconductor oxide liner 40 is greater than the second thickness t 2 and is lesser than the first thickness t 1 .
- sidewall surfaces 33 of the trench are exposed as vertical portions of the contiguous semiconductor oxide liner 40 are removed by the etch process.
- a remaining horizontal semiconductor oxide portion of the contiguous semiconductor oxide liner 40 which is herein referred to as a horizontal semiconductor oxide portion 42 , overlies the portion of the semiconductor material layer 10 located underneath the trench 42 . Edges of the horizontal semiconductor oxide portion 42 contact the sidewall surfaces 33 of the trench 30 at this step.
- the exposed semiconductor material on the sidewall surfaces 33 of the trench 30 is laterally etched while the horizontal semiconductor oxide portion 42 covers the portion of the semiconductor material layer 10 located underneath the trench 30 , thereby preventing etching of the semiconductor material underneath the bottom surface of the trench 30 .
- the sidewall surfaces 33 of the trench 30 can be laterally etched by a dry etch or a wet etch.
- the sidewall surfaces 33 of the trench 30 are laterally etched by a plasma etch, which is a dry etch.
- a plasma etch is employed to etch the sidewall surfaces 33 of the trench 30 , the etch process can benefit from a precision control of the etch rate and enhanced uniformity of the etch rate, which are typically associated with the plasma etch.
- the sidewall surfaces 33 of the trench 30 are laterally etched while the horizontal semiconductor oxide portion 42 remains at the bottom of the trench 30 . Because the lateral etch makes the sidewall surfaces 33 of the trench recede from the original positions as the etch progresses, the horizontal semiconductor oxide portion 42 does not cover a peripheral portion of the bottom surface of the trench 30 as the lateral etch progresses.
- the horizontal semiconductor oxide portion 42 is removed to expose the portion of the semiconductor material layer 10 located underneath.
- the horizontal semiconductor oxide portion 42 can be removed selective to the semiconductor material layer 10 .
- the horizontal semiconductor oxide portion 42 can be removed by a wet etch employing a hydrofluoric acid (HF) solution or a dry etch employing HF in a vapor phase.
- HF hydrofluoric acid
- the center portion of the trench 30 can have a first depth D 1
- the peripheral portions of the trench 30 can have a second depth D 2 .
- the central portion of the trench 30 corresponds to the area over which the horizontal semiconductor oxide portion 42 is present during the lateral etch of the trench 30 .
- the peripheral portions of the trench corresponds to the area over which the horizontal semiconductor oxide portion 42 is not present during the lateral etch of the trench 30 .
- a first non-planar surface region 62 A is formed on the side of the first gate stack 20 A
- a second non-planar surface region 62 B is formed on the side of the second gate stack 20 B.
- Each of the first and second non-planar surface regions ( 62 A, 62 B) includes a sub-region having the first depth D 1 and a sub-region having the second depth D 2 .
- an embedded semiconductor material portion 50 is formed by filling the trench 30 with another semiconductor material, which is typically a different material than the semiconductor material of the semiconductor material layer 10 .
- the semiconductor material of the embedded semiconductor material portion 50 can generate mechanical stress in a portion of the semiconductor material layer 10 located around the embedded semiconductor material portion 50 .
- the semiconductor material of the semiconductor material layer 10 and the semiconductor material of the embedded semiconductor material portion 50 can be single crystalline semiconductor materials that are epitaxially aligned to each other.
- the material of the embedded semiconductor material portion can be selected from, but is not limited to, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy.
- the embedded semiconductor material portion 50 contacts the semiconductor material layer 10 at a first horizontal interface located at the first depth D 1 from the first and second gate dielectrics ( 22 A, 22 B) and at a second horizontal interface located at the second depth D 2 from the first and second gate dielectrics ( 22 A, 22 B).
- a first non-planar interface region 63 A is formed on the side of the first gate stack 20 A
- a second non-planar interface region 63 B is formed on the side of the second gate stack 20 B.
- Each of the first and second non-planar interface regions ( 63 A, 63 B) includes a portion of a first horizontal interface, i.e., a “first horizontal interface portion,” a portion of a second horizontal interface, i.e., a “second horizontal interface portion,” and a non-horizontal interface portion adjoined to the first horizontal interface portion and the second horizontal interface portion.
- the first non-planar interface region 63 A underlies the first gate spacer 26 A
- the second non-planar interface region 63 B underlies the second gate spacer 26 B.
- the embedded semiconductor material portion 50 contacts the semiconductor material layer 10 at a first vertical interface located underneath the first gate spacer 26 A and at second vertical interface located underneath the second gate spacer 26 B.
- first vertical interface underlies the first gate spacer 26 A
- second vertical interface underlies the second gate spacer 26 B.
- the lateral offset LO is the most proximal lateral distance between each of the first and second vertical interfaces and the outer peripheries of the first and second gate spacers ( 26 A, 26 ) at which the first and second gate spacers contact the embedded semiconductor material portion 50 .
- the lateral offset LO can be increased by increasing the time period of the lateral etch of the sidewall surfaces 33 of the trench 30 at a step corresponding to FIG. 9 .
- the lateral offset LO is greater than the lateral width of the bottom portions of the first and second gate spacers ( 26 A, 26 B).
- the first vertical interface underlies the first gate dielectric 22 A
- the second vertical interface underlies the second gate dielectric 22 B.
- the embedded semiconductor material portion 50 contacts bottom surfaces of the first and second gate dielectrics ( 22 A, 22 B).
- the present invention can be practiced with any number of gate structures or without any gate structure. Further, shallow trench isolation structures including a dielectric material can be employed in each of the first and second exemplary structures.
Abstract
Description
- This application is a divisional of U.S. patent application Ser. No. 12/561,704, filed on Sep. 17, 2009 the entire content and disclosure of which is incorporated herein by reference.
- This invention was made with United States government support under Contract No. FA8650-08-C-7806 awarded by Defense Advanced Research Projects Agency (DARPA). The United States government has certain rights in this invention.
- This invention relates to methods of laterally offsetting sidewalls of a trench in a semiconductor substrate relative to sidewalls of overlying structures and structures formed by the same.
- Etching in a vertical direction is an integral component of semiconductor processing technology. An isotropic etch employs wet chemicals or reactant gases that etch a material isotropically. The etch rate of isotropic etch processes are difficult to control on a nanoscale, i.e., on a scale from 0.1 nm to 10 nm, because the etch rate is sensitive to temperature and/or supply of etchant.
- Plasma processing provides a more precise control of the etch rate. Plasma etch chambers are designed to etch anisotropically in a vertical direction. Advanced semiconductor chips require a high degree of profile control, where the extent of vertical etching may be difficult to control. The ion energy due to the plasma self-bias potential is the ultimately lowest ion energy attainable in plasma reactors, while still enabling a reasonable degree of vertical etching.
- Known plasma-etch-based solutions to recessing silicon on a nanoscale generate a post-etch profile in which lateral silicon erosion in the horizontal direction can be up to about ⅓ of the silicon erosion in the vertical direction, i.e., in the direction of the impinging plasma. The amount of lateral etching relative to the depth of a trench formed by a plasma etch is limited. This constraint makes it difficult to enable useful features in semiconductor technology such as tunnel field effect transistor (FET) having strained semiconductor-on-insulator (SSOI) features, which may be a crucial component in obtaining sub-threshold slope characteristics below the classical limit of 60 mV/decade.
- In an embodiment of the present invention, a trench is formed by an anisotropic etch in a semiconductor material layer employing a masking layer. An adsorbed fluorine layer is formed on the exposed surfaces of a semiconductor structure including the bottom surface and the sidewalls of the trench at a cryogenic temperature. A sputtering process performed at a cryogenic temperature removes horizontal portions of the adsorbed fluorine layer so that the remaining adsorbed fluorine layer is present only on vertical sidewalls of the semiconductor structure including the sidewalls of the trench. The temperature of the semiconductor structure is raised above the cryogenic temperature to enable reaction of the adsorbed fluorine layer with the semiconductor material in a lateral direction. The adsorbed fluorine layer removes a controlled amount of the underlying semiconductor material by chemically reacting and removing the semiconductor material. The amount of removal of the semiconductor material is in the range of monolayers of the semiconductor material, thereby providing a lateral etch by a nanoscale dimension.
- In another embodiment of the present invention, a trench is formed by an anisotropic etch in a semiconductor material layer employing a masking layer, which can be gate spacers. The crystallographic orientations of the sidewalls of the trench are selected to provide a lower oxidation rate than the crystallographic orientation of the bottom surface of the trench. A contiguous oxide liner having a thicker bottom portion relative to thinner sidewall portions is formed by oxidation. The contiguous oxide liner is isotropically etched to remove the thinner sidewall portions. The semiconductor material is laterally etched by a plasma-based etch at a controlled rate in a chemistry that is somewhat selective to the oxide layer atop the horizontal surface, thereby preventing etch of the semiconductor material underneath the oxide layer. The remaining horizontal portion of the contiguous oxide is subsequently removed, and the trench can be filled with a different semiconductor material to provide stress to neighboring semiconductor regions, which can include a channel of a field effect transistor.
- According to an aspect of the present invention, a method of forming a semiconductor structure is provided. The method includes forming a trench in a semiconductor material layer, and forming an adsorbed fluorine layer on vertical surfaces of the trench, while horizontal surfaces of the trench do not have adsorbed fluorine thereupon.
- According to another aspect of the present invention, another method of forming a semiconductor structure is provided. The method includes forming a trench in a semiconductor material layer; forming a contiguous semiconductor oxide liner on sidewalls and a bottom surface of the trench; exposing sidewall surfaces of the trench by removing vertical portions of the contiguous semiconductor oxide liner while a remaining horizontal semiconductor oxide portion of the contiguous semiconductor oxide liner overlies a portion of the semiconductor material layer located underneath the trench; and laterally etching the sidewall surfaces of the trench while the remaining horizontal semiconductor oxide portion covers the portion of the semiconductor material layer located underneath the trench.
- According to yet another aspect of the present invention, a semiconductor structure is provided. The semiconductor structure includes a gate structure located on a semiconductor material layer including a first semiconductor material, the gate structure including a gate dielectric, a gate conductor, and a gate spacer; a semiconductor material portion embedded in the semiconductor material layer, the semiconductor material portion including a second semiconductor material that is different from the first semiconductor material; and a non-planar interface region between the first semiconductor material and the second semiconductor material, wherein the non-planar interface region includes a first horizontal interface portion at a first depth from the gate dielectric, a second horizontal interface portion at a second depth from the gate dielectric, and a non-horizontal interface portion adjoined to the first horizontal interface portion and the second horizontal interface portion and underlying the gate spacer.
- According to still another aspect of the present invention, another semiconductor structure is provided. The semiconductor structure includes a trench in a semiconductor material layer; and an adsorbed fluorine layer located on vertical surfaces of the trench, while horizontal surfaces of the trench do not have adsorbed fluorine thereupon.
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FIG. 1 is a vertical cross-sectional view of a first exemplary structure before formation of a trench according to a first embodiment of the present invention. -
FIG. 2 is a vertical cross-sectional view of the first exemplary structure after forming a trench according to the first embodiment of the present invention. -
FIG. 3 is a vertical cross-sectional view of the first exemplary structure after forming a contiguous adsorbed fluorine layer according to the first embodiment of the present invention. -
FIG. 4 is a vertical cross-sectional view of the first exemplary structure after removal of horizontal portions of the contiguous adsorbed fluorine layer to provide adsorbed fluorine layer present only on vertical surfaces according to the first embodiment of the present invention. -
FIG. 5 is a vertical cross-sectional view of the first exemplary structure after lateral etching of the sidewalls of the trench according to the first embodiment of the present invention. -
FIG. 6 is a vertical cross-sectional view of the first exemplary structure after formation of an embedded semiconductor material portion according to the first embodiment of the present invention. -
FIG. 7 is a vertical cross-sectional view of a second exemplary structure after forming a contiguous semiconductor oxide liner according to a second embodiment of the present invention. -
FIG. 8 is a vertical cross-sectional view of the second exemplary structure after removing vertical portions of the contiguous semiconductor oxide liner according to the second embodiment of the present invention. -
FIG. 9 is a vertical cross-sectional view of the second exemplary structure after laterally etching a semiconductor material employing a horizontal semiconductor oxide portion according to the second embodiment of the present invention. -
FIG. 10 is a vertical cross-sectional view of the second exemplary structure after removing the horizontal semiconductor oxide portion according to the second embodiment of the present invention. -
FIG. 11 is a vertical cross-sectional view of the second exemplary structure after formation of an embedded semiconductor material portion according to the second embodiment of the present invention. -
FIG. 12 is a vertical cross-sectional view of a variation of the second exemplary structure after formation of an embedded semiconductor material portion according to the second embodiment of the present invention. - As stated above, the present invention relates to methods of laterally offsetting sidewalls of a trench in a semiconductor substrate relative to sidewalls of overlying structures and structures formed by the same, which are now described in detail with accompanying figures. The drawings are not necessarily drawn to scale.
- Referring to
FIG. 1 , a first exemplary structure according to a first embodiment of the present invention includes asubstrate 8, afirst gate structure 20A located on a top surface of thesubstrate 8, and asecond gate structure 20B located on the top surface of thesubstrate 8 and laterally spaced from thefirst gate structure 20A. Thesubstrate 8 includes asemiconductor material layer 10, which is comprised of a semiconductor material. The semiconductor material of thesemiconductor material layer 10 can be selected from, but is not limited to, silicon, germanium, silicon-germanium alloy, silicon carbon alloy, silicon-germanium-carbon alloy, gallium arsenide, indium arsenide, indium phosphide, III-V compound semiconductor materials, II-VI compound semiconductor materials, organic semiconductor materials, and other compound semiconductor materials. Preferably, the semiconductor material of thesemiconductor material layer 10 is a single crystalline material. For example, thesemiconductor material layer 10 can be a single crystalline silicon layer. Thesubstrate 8 may include a buriedinsulator layer 9. Further, thesubstrate 8 may include a handle substrate (not shown) located beneath the buriedinsulator layer 9, if present. - The
first gate structure 20A can include a first gate dielectric 22A, afirst gate conductor 24A, afirst gate spacer 26A, and a firstdielectric cap 28A. Thesecond gate structure 20B can include a second gate dielectric 22B, asecond gate conductor 24B, asecond gate spacer 26B, and a seconddielectric cap 28B. The first and second gate dielectrics (22A, 22B) can be a silicon-oxide-based gate dielectric material or a high dielectric constant (high-k) dielectric material such as a dielectric metal oxide, having a dielectric constant greater than 4.0. The first and second gate conductors (24A, 24B) can be a doped semiconductor material, a metallic material, or a combination thereof. The first and second gate dielectrics (26A, 26B) can be a dielectric material such as silicon nitride, silicon oxynitride, or a combination of silicon oxide and silicon nitride. Preferably, the outer surfaces of the first and second gate dielectrics (26A, 26B) include a semiconductor nitride or a semiconductor oxynitride such as silicon nitride or silicon oxynitride. The first and second dielectric caps (28A, 28B) can be a dielectric material such as silicon nitride, silicon oxynitride, or a combination of silicon oxide and silicon nitride. Preferably, the top surfaces of the first and second dielectric caps (28A, 28B) include a semiconductor nitride or a semiconductor oxynitride such as silicon nitride or silicon oxynitride. - Referring to
FIG. 2 , atrench 30 is formed by etching an exposed portion of thesemiconductor material layer 10 between the first and second gate structures (20A, 20B). Thetrench 30 can be formed by an anisotropic etch that etches the semiconductor material of thesemiconductor material layer 10 selective to the dielectric materials of the first and second gate spacers (26A, 26B) and the first and second dielectric caps (28A, 28B). If the buriedinsulator layer 9 is present, the depth of thetrench 30 is selected to be less than the depth of the buriedinsulator layer 9. Thetrench 30 has a bottom surface and sidewalls. The bottom surface of thetrench 30 is a horizontal surface, and the sidewalls of thetrench 30 are typically substantially vertical. The periphery of the sidewalls of thetrench 30 can coincide with outer peripheries of the first and second gate spacers (26A, 26B) at which the outer sidewalls of the first and second gate spacers (26A, 26B) contact a top surface of thesemiconductor material layer 10. - Referring to
FIG. 3 , the first exemplary structure is placed in a cryogenic environment, which has an ambient temperature below −40 degrees Celsius, and preferably below −100 degrees Celsius. Placement of the first exemplary structure in a cryogenic environment can be effected by providing a cryogenic chamber and inserting the first exemplary structure into the cryogenic chamber. Preferably, the cryogenic chamber is a vacuum enclosure that provides a cryogenic temperature and low residual gas pressure. - After the first exemplary structure is cooled below −40 degrees Celsius, and preferably below −100 degrees Celsius, the cryogenic chamber is filled with a fluorine-containing gas. The fluorine-containing gas includes any gas that contains fluorine atoms that adsorb to a surface at a cryogenic temperature. For example, the fluorine-containing gas can be, but is not limited to F2, CClF3, CF4, SF6, XeF2, CHF3, CH2F2, CH3F, C4F6, C5F8, C4F8 or any combination thereof. A contiguous adsorbed
fluorine layer 80 is formed on exposed surfaces of the first exemplary semiconductor structure at the cryogenic temperature because the fluorine-containing gas is adsorbed on the cold surfaces of the first exemplary structure. The surfaces on which the contiguous adsorbedfluorine layer 80 is formed include the bottom surface and the sidewalls of thetrench 30. Typically, the contiguous adsorbedfluorine layer 80 contiguously extends over all of the exposed surfaces of the first exemplary semiconductor structure without a hole or a discontinuity. Thus, the contiguous adsorbedfluorine layer 80 is formed on all surfaces of thetrench 30, i.e., on horizontal and vertical surfaces of thetrench 30. The contiguous adsorbedfluorine layer 80 can be a monolayer of fluorine atoms that are atomically bonded to an underlying semiconductor material in thesemiconductor material layer 10. - Referring to
FIG. 4 , horizontal portions of the contiguous adsorbedfluorine layer 80 are removed to provide adsorbed fluorine layers 82 that are present only on vertical surfaces of the first exemplary semiconductor structure. For example, the cryogenic chamber can be equipped with sputtering capability to provide ions that impinge upon the first exemplary structure in a direction that is substantially normal to thebottom surface 31 of thetrench 30. Ions that can be employed to sputter and remove horizontal portions of the contiguous adsorbedfluorine layer 80 include, but are not limited to, Kr, He, Ne, Ar, Xe, H2, N2, and O2. The ion sputtering destroys the chemical bonding between the adsorbed atoms and the underlying semiconductor material so that the horizontal surface of thetrench 30 does not have adsorbed fluorine thereupon after the sputtering. Horizontal portions of the contiguous adsorbedfluorine layer 80 are thus removed, and vertical portions of the contiguous adsorbedfluorine layer 80 remain to constitute the adsorbed fluorine layers 82, which cover all of the vertical sidewalls of thetrench 30 and a lower portion of the outer sidewalls of the first and second gate spacers (26A, 26B). Each of the adsorbed fluorine layers 82 contiguously extends over a vertical portion of an outer surface of one of the first and second gate spacers (26A, 26B). Preferably, the sputtering is performed at a cryogenic temperature below −40 degrees Celsius, and preferably below −100 degrees Celsius. - Alternately, the sputtering can be performed in another cryogenic chamber after transporting the first exemplary semiconductor structure into the other cryogenic chamber. Preferably, the ambient conditions of the first exemplary structure is maintained at a cryogenic temperature and in vacuum or in an inert ambient to prevent the contiguous adsorbed
fluorine layer 80 from becoming volatile. After transfer of the first exemplary structure into the other chamber, ions impinge upon the first exemplary structure in a direction that is substantially normal to thebottom surface 31 of thetrench 30 to remove the horizontal portions of the contiguous adsorbedfluorine layer 80. The remaining vertical portions of the contiguous adsorbedfluorine layer 80 constitute the adsorbed fluorine layers 82, which cover all of the vertical sidewalls of thetrench 30 and a lower portion of the outer sidewalls of the first and second gate spacers (26A, 26B). The horizontal bottom surface of thetrench 30 does not have adsorbed fluorine thereupon. Each of the adsorbed fluorine layers 82 contiguously extends over a vertical portion of an outer surface of one of the first and second gate spacers (26A, 26B). Preferably, the sputtering is performed at a cryogenic temperature below −40 degrees Celsius, and preferably below −100 degrees Celsius. - Referring to
FIG. 5 , the temperature of the first exemplary structure is raised above −40 degrees Celsius. For example, the first exemplary structure may be exposed to an ambient at a room temperature between 5 degrees Celsius and 35 degrees Celsius. As the temperature of the first exemplary structure is raised, the sidewalls of thetrench 30 are laterally etched by the adsorbed fluorine layers 82. Specifically, the adsorbed fluorine layers 82 and the vertical surfaces of thetrench 30 are subjected to a temperature at which the adsorbed fluorine layers 82 etch the underlying semiconductor material on the vertical surfaces of thetrench 80 by reacting with the underlying semiconductor material of thesemiconductor material layer 10. The amount of etched semiconductor material is measured in monolayers, and is typically from 1 to 4 atomic layers of the semiconductor material in thesemiconductor material layer 10. Thus, the lateral recess width RW is from 0.3 nm to 1.5 nm depending on the crystallographic orientation of the semiconductor material at the sidewalls of thetrench 30. - Referring to
FIG. 6 , an embeddedsemiconductor material portion 50 is formed by filling thetrench 30 with another semiconductor material, which is typically a different material than the semiconductor material of thesemiconductor material layer 10. The semiconductor material of the embeddedsemiconductor material portion 50 can generate mechanical stress in a portion of thesemiconductor material layer 10 located around the embeddedsemiconductor material portion 50. - The semiconductor material of the
semiconductor material layer 10 and the semiconductor material of the embeddedsemiconductor material portion 50 can be single crystalline semiconductor materials that are epitaxially aligned to each other. The material of the embedded semiconductor material portion can be selected from, but is not limited to, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy. The vertical interfaces between thesemiconductor material layer 10 and the embeddedsemiconductor material portion 50 are laterally offset by the lateral recess width RW from outer peripheries of the first and second gate spacers (26A, 26B) at which the first and second gate spacers (26A, 26B) contact the embeddedsemiconductor material portion 50. - A second exemplary structure according to a second embodiment of the present invention is derived from the first exemplary structure in
FIG. 2 according to the first embodiment of the present invention. In the second exemplary structure, a limitation is imposed on the crystallographic orientation of the bottom surface of thetrench 30 and the crystallographic orientations of the sidewalls of thetrench 30 at a step corresponding toFIG. 2 . Specifically, the bottom surface of thetrench 30 has a crystallographic orientation that provides a greater oxidation rate for the semiconductor material of thesemiconductor material layer 10 than crystallographic orientations of the sidewalls of thetrench 30. For example, if thesemiconductor material layer 10 is a single crystalline silicon layer and the bottom surface of thetrench 30 has a <111> orientation, and the sidewall surfaces of thetrench 30 can have <110> orientation. Alternately, if thesemiconductor material layer 10 is a single crystalline silicon layer and the bottom surface of thetrench 30 has a <110> orientation, and the sidewall surfaces of thetrench 30 can have a <100> orientation. In general, any combination of crystallographic orientations for the bottom surface and sidewalls of thetrench 30 can be employed as long as the bottom surface of thetrench 30 has a higher oxidation rate than the sidewalls of thetrench 30. Alternatively, the bottom of said trench can by oxidized to a greater depth than the sidewalls by exposing the structure to an oxygen plasma, where the ion energy is greater than the plasma potential alone. Due to the geometry of the reactor, high energy ions will react with the bottom trench forming an oxide of thickness t1, whereas the sidewalls of the trench only react with plasma neutrals and scattered ions, forming a thinner oxide of thickness t2. Gate structures can be masked during this process. In this case, the crystallographic orientation of the bottom surface of the trench need not have a greater oxidation rate for thermal oxidation than sidewall surfaces of the trench because the geometry employed in the plasma oxidation induces greater oxidation rate on the bottom surfaces of the trench than on the sidewall surfaces of the trench. - Referring to
FIG. 7 , after atrench 30 is formed in thesemiconductor material layer 10 of the second exemplary structure at a step corresponding toFIG. 2 , a contiguoussemiconductor oxide liner 40 is formed on all exposed surfaces of thetrench 30 including the sidewalls and the bottom surface of thetrench 30. The contiguoussemiconductor oxide liner 40 is formed by converting the semiconductor material in thesemiconductor material layer 10 into a semiconductor oxide. For example, if the semiconductor material in thesemiconductor material layer 10 is silicon, the semiconductor oxide is silicon oxide. Because of the differential between the oxidation rates of the bottom surface and sidewalls of thetrench 30, the first thickness t1 of the horizontal portion of the contiguoussemiconductor oxide liner 40 is greater than the second thickness t2 of the vertical portions of the contiguoussemiconductor oxide liner 40. - Referring to
FIG. 8 , vertical portions of the contiguoussemiconductor oxide liner 40 are removed, for example, by an isotropic etch. The isotropic etch can be a wet etch or a dry etch. In case a wet etch is employed, a dilute hydrofluoric acid can be employed to provide a slow etch rate if the contiguoussemiconductor oxide liner 40 includes silicon oxide, a germanium oxide, or silicon-germanium oxide. In case the isotropic etch is a dry etch, an etchant gas such as HCl, SF6, XeF2, CF4 or NF3 can be employed. - The duration of the etch is controlled so that the amount of removal of the contiguous
semiconductor oxide liner 40 is greater than the second thickness t2 and is lesser than the first thickness t1. Thus, sidewall surfaces 33 of the trench are exposed as vertical portions of the contiguoussemiconductor oxide liner 40 are removed by the etch process. A remaining horizontal semiconductor oxide portion of the contiguoussemiconductor oxide liner 40, which is herein referred to as a horizontalsemiconductor oxide portion 42, overlies the portion of thesemiconductor material layer 10 located underneath thetrench 42. Edges of the horizontalsemiconductor oxide portion 42 contact the sidewall surfaces 33 of thetrench 30 at this step. - Referring to
FIG. 9 , the exposed semiconductor material on the sidewall surfaces 33 of thetrench 30 is laterally etched while the horizontalsemiconductor oxide portion 42 covers the portion of thesemiconductor material layer 10 located underneath thetrench 30, thereby preventing etching of the semiconductor material underneath the bottom surface of thetrench 30. The sidewall surfaces 33 of thetrench 30 can be laterally etched by a dry etch or a wet etch. Preferably, the sidewall surfaces 33 of thetrench 30 are laterally etched by a plasma etch, which is a dry etch. In case a plasma etch is employed to etch the sidewall surfaces 33 of thetrench 30, the etch process can benefit from a precision control of the etch rate and enhanced uniformity of the etch rate, which are typically associated with the plasma etch. The sidewall surfaces 33 of thetrench 30 are laterally etched while the horizontalsemiconductor oxide portion 42 remains at the bottom of thetrench 30. Because the lateral etch makes the sidewall surfaces 33 of the trench recede from the original positions as the etch progresses, the horizontalsemiconductor oxide portion 42 does not cover a peripheral portion of the bottom surface of thetrench 30 as the lateral etch progresses. - Referring to
FIG. 10 , the horizontalsemiconductor oxide portion 42 is removed to expose the portion of thesemiconductor material layer 10 located underneath. The horizontalsemiconductor oxide portion 42 can be removed selective to thesemiconductor material layer 10. For example, if the horizontalsemiconductor oxide portion 42 includes silicon oxide, germanium oxide, or a silicon-germanium oxide, the horizontalsemiconductor oxide portion 42 can be removed by a wet etch employing a hydrofluoric acid (HF) solution or a dry etch employing HF in a vapor phase. - The center portion of the
trench 30 can have a first depth D1, and the peripheral portions of thetrench 30 can have a second depth D2. The central portion of thetrench 30 corresponds to the area over which the horizontalsemiconductor oxide portion 42 is present during the lateral etch of thetrench 30. The peripheral portions of the trench corresponds to the area over which the horizontalsemiconductor oxide portion 42 is not present during the lateral etch of thetrench 30. When the first depth D1 is not the same as the second depth D2, a firstnon-planar surface region 62A is formed on the side of thefirst gate stack 20A, and a secondnon-planar surface region 62B is formed on the side of thesecond gate stack 20B. Each of the first and second non-planar surface regions (62A, 62B) includes a sub-region having the first depth D1 and a sub-region having the second depth D2. - Referring to
FIG. 11 , an embeddedsemiconductor material portion 50 is formed by filling thetrench 30 with another semiconductor material, which is typically a different material than the semiconductor material of thesemiconductor material layer 10. The semiconductor material of the embeddedsemiconductor material portion 50 can generate mechanical stress in a portion of thesemiconductor material layer 10 located around the embeddedsemiconductor material portion 50. - The semiconductor material of the
semiconductor material layer 10 and the semiconductor material of the embeddedsemiconductor material portion 50 can be single crystalline semiconductor materials that are epitaxially aligned to each other. The material of the embedded semiconductor material portion can be selected from, but is not limited to, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy. - The embedded
semiconductor material portion 50 contacts thesemiconductor material layer 10 at a first horizontal interface located at the first depth D1 from the first and second gate dielectrics (22A, 22B) and at a second horizontal interface located at the second depth D2 from the first and second gate dielectrics (22A, 22B). A firstnon-planar interface region 63A is formed on the side of thefirst gate stack 20A, and a secondnon-planar interface region 63B is formed on the side of thesecond gate stack 20B. Each of the first and second non-planar interface regions (63A, 63B) includes a portion of a first horizontal interface, i.e., a “first horizontal interface portion,” a portion of a second horizontal interface, i.e., a “second horizontal interface portion,” and a non-horizontal interface portion adjoined to the first horizontal interface portion and the second horizontal interface portion. The firstnon-planar interface region 63A underlies thefirst gate spacer 26A, and the secondnon-planar interface region 63B underlies thesecond gate spacer 26B. - Further, the embedded
semiconductor material portion 50 contacts thesemiconductor material layer 10 at a first vertical interface located underneath thefirst gate spacer 26A and at second vertical interface located underneath thesecond gate spacer 26B. In other words, the first vertical interface underlies thefirst gate spacer 26A, and the second vertical interface underlies thesecond gate spacer 26B. - Referring to
FIG. 12 , a variation of the second exemplary structure is shown, in which the first vertical interface and the second vertical interface between the embeddedsemiconductor material portion 50 contacts thesemiconductor material layer 10 can be moved further from the outer peripheries of the first and second gate spacers (26A, 26B). The lateral offset LO is the most proximal lateral distance between each of the first and second vertical interfaces and the outer peripheries of the first and second gate spacers (26A, 26) at which the first and second gate spacers contact the embeddedsemiconductor material portion 50. The lateral offset LO can be increased by increasing the time period of the lateral etch of the sidewall surfaces 33 of thetrench 30 at a step corresponding toFIG. 9 . - In the variation of the second exemplary structure, the lateral offset LO is greater than the lateral width of the bottom portions of the first and second gate spacers (26A, 26B). Correspondingly, the first vertical interface underlies the
first gate dielectric 22A, and the second vertical interface underlies thesecond gate dielectric 22B. The embeddedsemiconductor material portion 50 contacts bottom surfaces of the first and second gate dielectrics (22A, 22B). - The present invention can be practiced with any number of gate structures or without any gate structure. Further, shallow trench isolation structures including a dielectric material can be employed in each of the first and second exemplary structures.
- While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms and details can be made without departing from the spirit and scope of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.
Claims (20)
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US13/442,008 US20120193715A1 (en) | 2009-09-17 | 2012-04-09 | Structure with isotropic silicon recess profile in nanoscale dimensions |
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US12/561,704 US8232171B2 (en) | 2009-09-17 | 2009-09-17 | Structure with isotropic silicon recess profile in nanoscale dimensions |
US13/442,008 US20120193715A1 (en) | 2009-09-17 | 2012-04-09 | Structure with isotropic silicon recess profile in nanoscale dimensions |
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US13/442,011 Abandoned US20120193680A1 (en) | 2009-09-17 | 2012-04-09 | Structure with isotropic silicon recess profile in nanoscale dimensions |
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US9620376B2 (en) | 2015-08-19 | 2017-04-11 | Lam Research Corporation | Self limiting lateral atomic layer etch |
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KR101675388B1 (en) | 2010-08-25 | 2016-11-11 | 삼성전자 주식회사 | Fabricating method of semiconductor device |
GB2486427B (en) * | 2010-12-14 | 2013-08-07 | Converteam Technology Ltd | A layered material for a vacuum chamber |
KR101873911B1 (en) * | 2011-06-07 | 2018-07-04 | 삼성전자주식회사 | Semiconductor devices including contact structure and methods of fabricating the same, and an electronic system including the same |
CN102881591B (en) * | 2011-07-15 | 2015-12-16 | 中芯国际集成电路制造(北京)有限公司 | The manufacture method of semiconductor device |
US9698281B2 (en) * | 2012-08-22 | 2017-07-04 | Robert Bosch Gmbh | CMOS bolometer |
US9054217B2 (en) * | 2013-09-17 | 2015-06-09 | Samsung Electronics Co., Ltd. | Method for fabricating semiconductor device having an embedded source/drain |
CN105225962A (en) * | 2015-09-22 | 2016-01-06 | 上海华力微电子有限公司 | A kind of method improving performance of semiconductor device |
KR102350485B1 (en) * | 2017-08-18 | 2022-01-14 | 삼성전자주식회사 | Semiconductor device |
US10811269B2 (en) * | 2018-02-19 | 2020-10-20 | Tokyo Electron Limited | Method to achieve a sidewall etch |
US11087989B1 (en) * | 2020-06-18 | 2021-08-10 | Applied Materials, Inc. | Cryogenic atomic layer etch with noble gases |
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- 2012-04-09 US US13/442,011 patent/US20120193680A1/en not_active Abandoned
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US20120193680A1 (en) | 2012-08-02 |
US20110062494A1 (en) | 2011-03-17 |
US8232171B2 (en) | 2012-07-31 |
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