US20160005883A1 - Silicon carbide semiconductor device - Google Patents
Silicon carbide semiconductor device Download PDFInfo
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- US20160005883A1 US20160005883A1 US14/668,299 US201514668299A US2016005883A1 US 20160005883 A1 US20160005883 A1 US 20160005883A1 US 201514668299 A US201514668299 A US 201514668299A US 2016005883 A1 US2016005883 A1 US 2016005883A1
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 239000004065 semiconductor Substances 0.000 title claims abstract description 33
- 229910010271 silicon carbide Inorganic materials 0.000 title claims description 44
- 239000010410 layer Substances 0.000 claims abstract description 158
- 229910052751 metal Inorganic materials 0.000 claims abstract description 48
- 239000002184 metal Substances 0.000 claims abstract description 48
- 239000011229 interlayer Substances 0.000 claims abstract description 41
- 239000000758 substrate Substances 0.000 claims abstract description 30
- 230000005669 field effect Effects 0.000 claims abstract description 5
- 239000000463 material Substances 0.000 claims description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 12
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 229910021332 silicide Inorganic materials 0.000 claims description 7
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- -1 aluminum silicon copper Chemical compound 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 3
- LKTZODAHLMBGLG-UHFFFAOYSA-N alumanylidynesilicon;$l^{2}-alumanylidenesilylidenealuminum Chemical compound [Si]#[Al].[Si]#[Al].[Al]=[Si]=[Al] LKTZODAHLMBGLG-UHFFFAOYSA-N 0.000 claims description 3
- WPPDFTBPZNZZRP-UHFFFAOYSA-N aluminum copper Chemical compound [Al].[Cu] WPPDFTBPZNZZRP-UHFFFAOYSA-N 0.000 claims description 3
- YXTPWUNVHCYOSP-UHFFFAOYSA-N bis($l^{2}-silanylidene)molybdenum Chemical compound [Si]=[Mo]=[Si] YXTPWUNVHCYOSP-UHFFFAOYSA-N 0.000 claims description 3
- 239000011733 molybdenum Substances 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910021344 molybdenum silicide Inorganic materials 0.000 claims description 3
- 229910021334 nickel silicide Inorganic materials 0.000 claims description 3
- RUFLMLWJRZAWLJ-UHFFFAOYSA-N nickel silicide Chemical compound [Ni]=[Si]=[Ni] RUFLMLWJRZAWLJ-UHFFFAOYSA-N 0.000 claims description 3
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical group [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims description 3
- 229910021341 titanium silicide Inorganic materials 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims 6
- 229910044991 metal oxide Inorganic materials 0.000 abstract description 2
- 150000004706 metal oxides Chemical class 0.000 abstract 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 7
- 239000002019 doping agent Substances 0.000 description 6
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- 229910052681 coesite Inorganic materials 0.000 description 4
- 229910052906 cristobalite Inorganic materials 0.000 description 4
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 229910052682 stishovite Inorganic materials 0.000 description 4
- 229910052905 tridymite Inorganic materials 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 3
- 238000000231 atomic layer deposition Methods 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 239000005380 borophosphosilicate glass Substances 0.000 description 3
- 238000005530 etching Methods 0.000 description 3
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 3
- 238000002513 implantation Methods 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 239000005368 silicate glass Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/80—Field effect transistors with field effect produced by a PN or other rectifying junction gate, i.e. potential-jump barrier
- H01L29/808—Field effect transistors with field effect produced by a PN or other rectifying junction gate, i.e. potential-jump barrier with a PN junction gate, e.g. PN homojunction gate
- H01L29/8083—Vertical transistors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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 potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
- H01L21/048—Making electrodes
- H01L21/0485—Ohmic electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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 potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
- H01L21/048—Making electrodes
- H01L21/0495—Schottky electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0684—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape, relative sizes or dispositions of the semiconductor regions or junctions between the regions
- H01L29/0692—Surface layout
- H01L29/0696—Surface layout of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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 Table
- H01L29/1608—Silicon carbide
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/45—Ohmic electrodes
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- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/47—Schottky barrier electrodes
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/7801—DMOS transistors, i.e. MISFETs with a channel accommodating body or base region adjoining a drain drift region
- H01L29/7802—Vertical DMOS transistors, i.e. VDMOS transistors
- H01L29/7803—Vertical DMOS transistors, i.e. VDMOS transistors structurally associated with at least one other device
- H01L29/7806—Vertical DMOS transistors, i.e. VDMOS transistors structurally associated with at least one other device the other device being a Schottky barrier diode
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- H—ELECTRICITY
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- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/872—Schottky diodes
Definitions
- the present invention relates to a semiconductor power device, and particularly to a silicon carbide (SiC) semiconductor power device.
- SiC silicon carbide
- Power semiconductor devices should provide the minimum possible turn-on resistance, reverse leakage current and high switching speed at the rated breakdown voltage, to reduce the operational conduction loss and switching loss.
- the thickness of voltage supporting layer (a low doping concentration drift layer) of power devices made of SiC is one-tenth of that made of silicon at the same rated blocking voltage, and the theoretical conduction resistance of SiC power devices can be hundreds times lower than Si power devices.
- SiC metal oxide semiconductor field effect transistor MOSFET
- the wide bandgap of SiC also makes the turn-on voltage of body diode of SiC metal oxide semiconductor field effect transistor (MOSFET) reach to nearly 3V, which will result in a larger loss during switching and limit the switching speed.
- MOSFET metal oxide semiconductor field effect transistor
- the basal plane dislocations happened during epitaxial growth of SiC drift layer will expand into stacking faults due to recombination of carriers during the forward conducting of body diode.
- SiC MOSFET's may degrade or even fail due to these stacking faults. Therefore, a SiC MOSFET sometimes co-packages an reverse-parallel connected SiC Schottky diode exertnally to increase the operating speed, reduce switching loss and avoid reliability issues brought by stacking faults.
- U.S. Pat. No. 6,979,863 discloses a SiC MOSFET integrated with a Schottky diode.
- the source metal and the Schottky metal are adjacent to each other which require additional layers in the manufacturing process to individually fabricate source contacts and Schottky contacts.
- greater tolerances in design rules need to be reserved to avoid yield loss.
- an effective gate width per unit area of the SiC MOSFET and a current density of the device may be undesirably affected, with costs further increased.
- the SiC semiconductor device includes a substrate, an n-drift layer, a plurality of doped regions, a gate dielectric layer, a gate electrode, an inter-layer dielectric layer, a plurality of source openings, a plurality of junction openings, a plurality of gate openings, a first metal layer and a second metal layer.
- the substrate is heavily doped n-type.
- the n-drift layer is disposed on the substrate, and is lightly doped n-type compared to the substrate.
- the doped regions are disposed at the n-drift layer and spaced from each other, with a junction field effect transistor (JFET) region formed between the doped regions.
- JFET junction field effect transistor
- Each of the doped regions includes a p-well, a heavily doped n-type (n+) region located in the p-well, and a heavily doped p-type (p+) region located in the p-well and surrounded by the n+ region.
- the gate dielectric layer is arranged on the n-drift layer.
- the gate electrode is disposed on the gate dielectric layer.
- the inter-layer dielectric layer is disposed on the gate dielectric layer and the gate electrode.
- the source openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the n+ region and the p+ region.
- the source openings are separated by the gate electrode and the inter-layer dielectric layer.
- the junction openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the JFET region and the doped region.
- the junction openings are separated by the gate electrode and the inter-layer dielectric layer.
- the gate openings penetrate through the inter-layer dielectric layer to a surface portion of the gate electrode.
- the first metal layer is disposed at a bottom of the source openings to form an Ohmic contact with the surface portion of the n+ region and the p+ region.
- the second metal layer includes a first portion and a second portion.
- the first portion covers the junction openings and the source openings, is in contact and electrically connected with the first metal layer, and forms a Schottky contact with the surface portion of the JFET region.
- the second portion covers the gate openings and is electrically insulated from the first portion.
- the SiC semiconductor device includes a substrate, an n-drift layer, a plurality of first doped regions, a plurality of second doped regions, a gate dielectric layer, a gate electrode, an inter-layer dielectric layer, a plurality of source openings, a plurality of junction openings, a plurality of gate openings, a first metal layer and a second metal layer.
- the substrate is heavily doped n-type.
- the n-drift layer is disposed on the substrate, and is lightly doped n-type compared to the substrate.
- the first doped regions are disposed at the n-drift layer and, and each includes a first p-well, a first n+ region disposed in the first p-well, and a first p+ region disposed in the first p-well and surrounded by the first n+ region.
- the second doped regions and the first doped regions are disposed at an interval at the n-drift layer.
- a JFET region is formed between the first doped region and the second doped region.
- Each of the second doped regions includes a second p-well surrounding a non-p-well region, a second p+ region surrounding the non-p-well region and a part or all of the second p+ region overlapping with the second p-well.
- the gate dielectric layer is disposed on the n-drift layer.
- the gate electrode is disposed on the gate dielectric layer.
- the inter-layer dielectric layer is disposed on the gate dielectric layer and the gate electrode.
- the source openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the first n+ region and the first p+ region.
- the source openings are separated by the gate electrode and the inter-layer dielectric layer.
- the junction openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the second doped region.
- the junction openings are separated by the gate electrode and the inter-layer dielectric layer.
- the gate openings penetrate through the inter-layer dielectric layer to a surface portion of the gate electrode.
- the first metal layer is disposed at a bottom of the source openings, and forms an Ohmic contact with the surface portion of the first n+ region and the first p+ region.
- the second metal layer includes a first portion and a second portion.
- the first portion covers the junction openings and the source openings, is in contact and electrically connected with the first metal layer, and forms a Schottky contact with a surface portion of the non-p-well region.
- the second portion covers the gate openings and is electrically insulated from the first portion.
- the source openings and the junction openings are separately arranged.
- the first metal layer is formed at the bottom the source openings to form an Ohmic contact with only the n+ region (or the first n+ region) and the p+ region (or the first p+ region).
- FIG. 1 is a top view of the present invention
- FIG. 2A is an enlarged view of an area X in FIG. 1 according to a first embodiment of the present invention
- FIG. 2B is a sectional view along A-A of FIG. 2A ;
- FIG. 2C is a sectional view along B-B of FIG. 2A ;
- FIG. 2D is a sectional view along A-A of FIG. 2A according to another embodiment of the present invention.
- FIG. 3A is an enlarged view of an area Y in Fig.1 according to the first embodiment of the present invention.
- FIG. 3B is a sectional view along C-C of FIG. 3A ;
- FIG. 4 is an enlarged view of the area X in FIG. 1 according to a second embodiment of the present invention.
- FIG. 5 is a sectional view along D-D of FIG. 4 .
- FIG. 1 shows a top view of the present invention.
- FIG. 2A shows an enlarged view of an area X in FIG. 1 according to a first embodiment of the present invention.
- FIG. 2B shows a sectional view along A-A of FIG. 2A .
- FIG. 2C shows a sectional view along B-B of FIG. 2A .
- FIG. 3B shows an enlarged view of an area Yin FIG. 1 .
- FIG. 3B shows a sectional view along C-C of FIG. 3A . Referring to FIG. 1 , FIGS. 2A to 2C , and FIGS.
- a SiC semiconductor device 1 of the present invention includes a substrate 10 , an n-drift layer 11 , a plurality of doped regions 20 , a gate dielectric layer 41 , a gate electrode 42 , an inter-layer dielectric layer 43 , a plurality of source openings 51 , a plurality of junction openings 52 , a plurality of gate openings 53 , a first metal layer 61 , and a second metal layer 62 .
- the substrate 10 is a 4H-SiC substrate, and is heavily doped n-type with a concentration greater than 1E18cm ⁇ 3 .
- the n-drift layer 11 is arranged on the substrate 10 , and is n-type with a doping concentration smaller than that of the substrate 10 .
- the doping concentration of the n-drift layer 11 is between 1E14cm ⁇ 3 and 1E17cm ⁇ 3 .
- the doped regions 20 are disposed at an interval at the n-drift layer 11 , and each includes a p-well 21 , a heavily doped n-type (n+) region 22 , and a heavily doped p-type (p+) region 23 .
- the p-well 21 has a doping concentration smaller than 1E19cm ⁇ 3 .
- the n+ region 23 has a doping concentration greater than 1E19cm ⁇ 3 , and is disposed in the p-well 21 .
- the p+ region 23 has a doping concentration greater than 1E19cm ⁇ 3 , and is surrounded by the n+ region 22 and is in contact with the p-well 21 .
- phosphorous or nitrogen may be implanted as the n type dopant, and aluminum or boron may be implanted as the p type dopant, with implantation energy between 10 keV and 1400 keV.
- the p+ region 23 may be surrounded by the p-well 21 and the n+ region 22 , and a part or all of the p+ region 23 overlaps with the p-well 21 .
- a junction field effect transistor (JFET) region 30 is formed between the doped regions 20 .
- the gate dielectric layer 41 is disposed on the n-drift layer 11 , and may be made of a material such as SiO 2 , nitride-containing SiO 2 or Al 2 O 3 by thermal oxidation, chemical vapor deposition (CVD) or atomic layer deposition (ALD).
- the gate electrode 42 is disposed on the gate dielectric layer 41 , and corresponds above the JFET region 30 .
- the gate electrode 42 may be made of a material such as heavily doped n-type poly-Si with phosphorous as a dopant, or a heavily doped p-type poly-Si with boron as a dopant.
- the inter-layer dielectric layer 43 is disposed on the gate dielectric layer 41 and the gate electrode 42 , and is made of a material such as tetra-ethyl-ortho-silicate (TEOS), boro-phospho-silicate-glass (BPSG), oxynitride, undoped silicate glass (USG) or silicon rich nitride (SRN).
- TEOS tetra-ethyl-ortho-silicate
- BPSG boro-phospho-silicate-glass
- oxynitride undoped silicate glass
- USG undoped silicate glass
- SRN silicon rich nitride
- the source openings 51 are formed by etching, and penetrate through the inter-layer dielectric layer 43 and the gate dielectric layer 41 to a surface portion of the n+ region 22 and the p+ region 23 .
- the source openings 51 are separated by the gate electrode 42 and the inter-layer dielectric layer 43 .
- the junction openings 52 are similarly formed by etching, and penetrate through the inter-layer dielectric layer 43 and the gate dielectric layer 41 to a surface portion of the JFET region 30 and the doped region 20 .
- the junction openings 52 are separated by the gate electrode 42 and the inter-layer dielectric layer 43 . Referring to FIGS.
- the gate openings 53 penetrate through the inter-layer dielectric layer 43 to a surface portion of the gate electrode 42 .
- the gate openings 53 are also formed by etching.
- a field oxide layer 44 is further provided between the gate electrode 42 and the n-drift layer 11 .
- the first metal layer 61 is disposed at a bottom of the source openings 51 , and is a silicide or a combination of silicides of a material selected from a group consisting of nickel, titanium and aluminum. acted with SiC at an annealing temperature higher than 900° C. to form silicides. The unreacted materials are then removed by wet processes to have the first metal layer 61 remained at the bottom of the source openings 51 . At the bottom of the source openings 51 , the first metal layer 61 forms an Ohmic contact with the surface portion of the n+ region 22 and the p+ region 23 .
- the second metal layer 62 may be made of a material such as titanium, molybdenum, nickel, aluminum, titanium silicide, molybdenum silicide, nickel silicide, aluminum silicide, titanium nitride, an aluminum copper alloy or an aluminum silicon copper alloy by PVD or CVD.
- the second metal layer 62 includes a first portion 621 and a second portion 622 .
- the first portion 621 covers the junction openings 52 and the source openings 51 , is in contact and electrically connected with the first metal layer 61 in the source openings 51 , and forms a Schottky contact with the surface portion of the JFET region 30 in the junction openings 52 .
- the second portion 622 covers the gate openings 53 , and is not in contact with and electrically insulated from the first portion 621 .
- the SiC semiconductor device 1 further includes a drain 70 .
- the drain 70 is disposed at one side of the substrate 10 opposite to the n-drift layer 11 . Accordingly, the SiC semiconductor device 1 forms a MOSFET integrated with an anti-parallelly connected junction barrier controlled Schottky rectifer.
- the SiC semiconductor device 1 is a design with a quadrilateral p-well 21 at the center and four junction openings 52 each being a quarter of a rounded rectangle at a corner to form a unit cell, thereby effectively utilizing the area of the device.
- the unit cell may have a planar contour of a square, a hexagon or a long strip.
- the planar contour of the junction openings 52 may be a triangle, a hexagon, an octagon or a circle, and may have a design adjustable according to the actual area of the device.
- FIG. 4 shows an enlarged view of the area X in FIG. 1 according to a second embodiment of the present invention.
- FIG. 5 is a sectional view along D-D of Fig.4 .
- a SiC semiconductor device 1 is further provided by the present invention.
- the SiC semiconductor device 1 includes a substrate 10 , an n-drift layer 11 , a plurality of first doped regions 20 a, a JFET region 30 , a plurality of second doped regions 20 b, a gate dielectric layer 41 , a gate electrode 42 , an inter-layer dielectric layer 43 , a plurality of source openings 51 , a plurality of junction openings 52 , a plurality of gate openings 53 , a first metal layer 61 and a second metal layer 62 .
- the unit cell has a planar contour of a hexagon.
- the unit cell may be a rectangle, a quadrilateral or a long strip.
- the substrate 10 is a 4H-SiC substrate, and is heavily doped n-type with a concentration greater than 1E18cm ⁇ 3 .
- the n-drift layer 11 is disposed on the substrate 10 , and is n-type with a doping concentration smaller than that of the substrate 10 .
- the doping concentration of the n-drift layer 11 is between 1E14cm ⁇ 3 and 1E17cm ⁇ 3 .
- the first doped regions 20 a and the second doped regions 20 b are disposed at an interval at the n-drift layer 11 .
- the JFET region 30 is formed between the first doped regions 20 a and the second doped regions 20 b.
- Each of the first doped regions 20 a includes a first p-well 21 a, a first n+ region 22 a, and a first p+ region 23 a.
- the first n+ region 22 a is disposed in the first p-well 21 a.
- the first p+ region 23 a is surrounded by the first n+ region 22 a, and is contact with the first p-well 21 a .
- Each of the second doped regions 20 b includes a second p-well 21 b, a second n+ region 22 b and a second p+ region 23 b.
- the second p-well 21 b surrounds a non-p-well region 31 .
- the second n+ region 22 b is disposed in the second p-well 21 b.
- this embodiment includes the second n+ region 22 b, the second n+ region 22 b may be excluded in another embodiment, and operations of the SiC semiconductor device 1 are not affected.
- the doping concentrations and implantation energies of the first doped regions 20 a and the second doped regions 20 b may correspond to the doping concentrations and implantation energies of the doped regions 20 , and shall be omitted herein.
- the gate dielectric layer 41 is disposed on the n-drift layer 11 , and may be similarly made of a material such as SiO 2 , nitride-containing SiO 2 or Al 2 O 3 by thermal oxidation, CVD or ALD.
- the gate electrode 42 is disposed on the gate dielectric layer 41 .
- the gate electrode 42 may be made of a material such as heavily doped n-type poly-Si with phosphorous as a dopant, or a heavily doped p-type poly-Si with boron as a dopant.
- the inter-layer dielectric layer 43 is disposed on the gate dielectric layer 41 and the gate electrode 42 , and is made of a material such as TEOS, BPSG, oxynitride, USG or SRN. Further, in the second embodiment, positions and structures of the gate openings 53 are identical to those in the first embodiment, and may be referred from FIGS. 3A and 3B . Associated details shall be omitted herein.
- the source openings 51 of the second embodiment penetrate through the inter-layer dielectric layer 43 and the gate dielectric layer 41 to a surface portion of the first n+ region 22 a and the first p+ region 23 a to correspond above the first doped region 20 a.
- the source openings 51 are separated by the gate electrode 42 and the inter-layer dielectric layer 43 .
- the junction openings 52 penetrate through the inter-layer dielectric layer 43 and the gate dielectric layer 41 to a surface portion of the second p+ region 23 b of the second doped region 20 b and the non-p-well region 31 .
- the junction openings 52 are spaced by the gate electrode 42 and the inter-layer dielectric layer 43 .
- the gate openings 53 penetrate through the inter-layer dielectric layer 43 to a surface portion of the gate electrode 42 .
- the first metal layer 61 is disposed at the bottom of the source openings 51 , and forms an Ohmic contact with the the surface portion of first n+ region 22 a and the first p+ region 23 a.
- the second metal layer 62 includes a first portion 621 and a second portion 622 .
- the first portion 621 covers the junction openings 52 and the source openings 51 , is in contact and electrically connected with the first metal layer 61 , and forms a Schottky contact with a surface portion of the non-p-well region 31 .
- the second portion 622 covers the gate openings 53 , and is not in contact with and thus electrically insulated from the first portion 621 .
- the source openings and the junction openings are separately disposed.
- the source openings are first manufactured and the first metal layer is formed, and gate openings and the junction openings are manufactured, followed by forming the second metal layer, thereby forming a good Schottky contact by the second metal layer at the junction openings with SiC.
- the first metal layer is formed at the bottom of the source openings to form an Ohmic contact with only the n+ region (or the first n+ region) and the p+ region (or the first p+ region). As such, shorting between the lightly doped n-type n-drift layer and the first metal layer due to manufacturing variations can be avoided, thereby improving manufacturing yield.
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Abstract
Description
- The present invention relates to a semiconductor power device, and particularly to a silicon carbide (SiC) semiconductor power device.
- Power semiconductor devices should provide the minimum possible turn-on resistance, reverse leakage current and high switching speed at the rated breakdown voltage, to reduce the operational conduction loss and switching loss. The wide bandgap (Eg=3.26 eV), high threshold field of dielectric breakdown (2.2 MV/cm) and high thermal conductivity (4.9 W/cm-K) of silicon carbide (SiC) make it an ideal material for power switching devices. The thickness of voltage supporting layer (a low doping concentration drift layer) of power devices made of SiC is one-tenth of that made of silicon at the same rated blocking voltage, and the theoretical conduction resistance of SiC power devices can be hundreds times lower than Si power devices.
- However, the wide bandgap of SiC also makes the turn-on voltage of body diode of SiC metal oxide semiconductor field effect transistor (MOSFET) reach to nearly 3V, which will result in a larger loss during switching and limit the switching speed. Furthermore, the basal plane dislocations happened during epitaxial growth of SiC drift layer will expand into stacking faults due to recombination of carriers during the forward conducting of body diode. SiC MOSFET's may degrade or even fail due to these stacking faults. Therefore, a SiC MOSFET sometimes co-packages an reverse-parallel connected SiC Schottky diode exertnally to increase the operating speed, reduce switching loss and avoid reliability issues brought by stacking faults.
- In addition to externally connected with a Schottky diode, U.S. Pat. No. 6,979,863 discloses a SiC MOSFET integrated with a Schottky diode. In the SiC MOSFET of the above disclosure, the source metal and the Schottky metal are adjacent to each other which require additional layers in the manufacturing process to individually fabricate source contacts and Schottky contacts. Besides, to prevent the source metal erroneously contact to the drift layer and thus cause leakage current of the SiC MOSFET, greater tolerances in design rules need to be reserved to avoid yield loss. Thus, an effective gate width per unit area of the SiC MOSFET and a current density of the device may be undesirably affected, with costs further increased.
- It is a primary object of the present invention to provide a SiC MOSTFET device, which is integrated with a Schottky diode without involving an additional mask and provides preferred utilization efficiency.
- To achieve the above object, a SiC semiconductor device is provided. The SiC semiconductor device includes a substrate, an n-drift layer, a plurality of doped regions, a gate dielectric layer, a gate electrode, an inter-layer dielectric layer, a plurality of source openings, a plurality of junction openings, a plurality of gate openings, a first metal layer and a second metal layer.
- The substrate is heavily doped n-type. The n-drift layer is disposed on the substrate, and is lightly doped n-type compared to the substrate. The doped regions are disposed at the n-drift layer and spaced from each other, with a junction field effect transistor (JFET) region formed between the doped regions. Each of the doped regions includes a p-well, a heavily doped n-type (n+) region located in the p-well, and a heavily doped p-type (p+) region located in the p-well and surrounded by the n+ region. The gate dielectric layer is arranged on the n-drift layer. The gate electrode is disposed on the gate dielectric layer. The inter-layer dielectric layer is disposed on the gate dielectric layer and the gate electrode.
- The source openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the n+ region and the p+ region. The source openings are separated by the gate electrode and the inter-layer dielectric layer. The junction openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the JFET region and the doped region. The junction openings are separated by the gate electrode and the inter-layer dielectric layer. The gate openings penetrate through the inter-layer dielectric layer to a surface portion of the gate electrode. The first metal layer is disposed at a bottom of the source openings to form an Ohmic contact with the surface portion of the n+ region and the p+ region. The second metal layer includes a first portion and a second portion. The first portion covers the junction openings and the source openings, is in contact and electrically connected with the first metal layer, and forms a Schottky contact with the surface portion of the JFET region. The second portion covers the gate openings and is electrically insulated from the first portion.
- To achieve the above object, a SiC semiconductor device is further provided by the present invention. The SiC semiconductor device includes a substrate, an n-drift layer, a plurality of first doped regions, a plurality of second doped regions, a gate dielectric layer, a gate electrode, an inter-layer dielectric layer, a plurality of source openings, a plurality of junction openings, a plurality of gate openings, a first metal layer and a second metal layer. The substrate is heavily doped n-type. The n-drift layer is disposed on the substrate, and is lightly doped n-type compared to the substrate. The first doped regions are disposed at the n-drift layer and, and each includes a first p-well, a first n+ region disposed in the first p-well, and a first p+ region disposed in the first p-well and surrounded by the first n+ region. The second doped regions and the first doped regions are disposed at an interval at the n-drift layer. A JFET region is formed between the first doped region and the second doped region. Each of the second doped regions includes a second p-well surrounding a non-p-well region, a second p+ region surrounding the non-p-well region and a part or all of the second p+ region overlapping with the second p-well. The gate dielectric layer is disposed on the n-drift layer. The gate electrode is disposed on the gate dielectric layer. The inter-layer dielectric layer is disposed on the gate dielectric layer and the gate electrode.
- The source openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the first n+ region and the first p+ region. The source openings are separated by the gate electrode and the inter-layer dielectric layer. The junction openings penetrate through the inter-layer dielectric layer and the gate dielectric layer to a surface portion of the second doped region. The junction openings are separated by the gate electrode and the inter-layer dielectric layer. The gate openings penetrate through the inter-layer dielectric layer to a surface portion of the gate electrode. The first metal layer is disposed at a bottom of the source openings, and forms an Ohmic contact with the surface portion of the first n+ region and the first p+ region. The second metal layer includes a first portion and a second portion. The first portion covers the junction openings and the source openings, is in contact and electrically connected with the first metal layer, and forms a Schottky contact with a surface portion of the non-p-well region. The second portion covers the gate openings and is electrically insulated from the first portion.
- Thus, in the present invention, the source openings and the junction openings are separately arranged. Further, the first metal layer is formed at the bottom the source openings to form an Ohmic contact with only the n+ region (or the first n+ region) and the p+ region (or the first p+ region). As such, shorting between the lightly doped n-type n-drift layer and the first metal layer due to manufacturing variations can be avoided, thereby improving manufacturing yield.
- The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
-
FIG. 1 is a top view of the present invention; -
FIG. 2A is an enlarged view of an area X inFIG. 1 according to a first embodiment of the present invention; -
FIG. 2B is a sectional view along A-A ofFIG. 2A ; -
FIG. 2C is a sectional view along B-B ofFIG. 2A ; -
FIG. 2D is a sectional view along A-A ofFIG. 2A according to another embodiment of the present invention; -
FIG. 3A is an enlarged view of an area Y inFig.1 according to the first embodiment of the present invention; -
FIG. 3B is a sectional view along C-C ofFIG. 3A ; -
FIG. 4 is an enlarged view of the area X inFIG. 1 according to a second embodiment of the present invention; and -
FIG. 5 is a sectional view along D-D ofFIG. 4 . -
FIG. 1 shows a top view of the present invention.FIG. 2A shows an enlarged view of an area X inFIG. 1 according to a first embodiment of the present invention.FIG. 2B shows a sectional view along A-A ofFIG. 2A .FIG. 2C shows a sectional view along B-B ofFIG. 2A .FIG. 3B shows an enlarged view of an area YinFIG. 1 .FIG. 3B shows a sectional view along C-C ofFIG. 3A . Referring toFIG. 1 ,FIGS. 2A to 2C , andFIGS. 3A and 3B , aSiC semiconductor device 1 of the present invention includes asubstrate 10, an n-drift layer 11, a plurality ofdoped regions 20, agate dielectric layer 41, agate electrode 42, aninter-layer dielectric layer 43, a plurality ofsource openings 51, a plurality ofjunction openings 52, a plurality ofgate openings 53, afirst metal layer 61, and asecond metal layer 62. - Referring to
FIG. 2B , thesubstrate 10 is a 4H-SiC substrate, and is heavily doped n-type with a concentration greater than 1E18cm−3. The n-drift layer 11 is arranged on thesubstrate 10, and is n-type with a doping concentration smaller than that of thesubstrate 10. For example, the doping concentration of the n-drift layer 11 is between 1E14cm−3 and 1E17cm−3. The dopedregions 20 are disposed at an interval at the n-drift layer 11, and each includes a p-well 21, a heavily doped n-type (n+)region 22, and a heavily doped p-type (p+)region 23. The p-well 21 has a doping concentration smaller than 1E19cm−3. Then+ region 23 has a doping concentration greater than 1E19cm−3, and is disposed in the p-well 21. Thep+ region 23 has a doping concentration greater than 1E19cm−3, and is surrounded by then+ region 22 and is in contact with the p-well 21. In the embodiment, phosphorous or nitrogen may be implanted as the n type dopant, and aluminum or boron may be implanted as the p type dopant, with implantation energy between 10 keV and 1400 keV. In another embodiment, as shown inFIG. 2D , thep+ region 23 may be surrounded by the p-well 21 and then+ region 22, and a part or all of thep+ region 23 overlaps with the p-well 21. - Again referring to
FIG. 2B , a junction field effect transistor (JFET)region 30 is formed between thedoped regions 20. Thegate dielectric layer 41 is disposed on the n-drift layer 11, and may be made of a material such as SiO2, nitride-containing SiO2 or Al2O3 by thermal oxidation, chemical vapor deposition (CVD) or atomic layer deposition (ALD). Thegate electrode 42 is disposed on thegate dielectric layer 41, and corresponds above theJFET region 30. Thegate electrode 42 may be made of a material such as heavily doped n-type poly-Si with phosphorous as a dopant, or a heavily doped p-type poly-Si with boron as a dopant. Theinter-layer dielectric layer 43 is disposed on thegate dielectric layer 41 and thegate electrode 42, and is made of a material such as tetra-ethyl-ortho-silicate (TEOS), boro-phospho-silicate-glass (BPSG), oxynitride, undoped silicate glass (USG) or silicon rich nitride (SRN). - The
source openings 51 are formed by etching, and penetrate through theinter-layer dielectric layer 43 and thegate dielectric layer 41 to a surface portion of then+ region 22 and thep+ region 23. Thesource openings 51 are separated by thegate electrode 42 and theinter-layer dielectric layer 43. Referring toFIG. 2C , thejunction openings 52 are similarly formed by etching, and penetrate through theinter-layer dielectric layer 43 and thegate dielectric layer 41 to a surface portion of theJFET region 30 and the dopedregion 20. Thejunction openings 52 are separated by thegate electrode 42 and theinter-layer dielectric layer 43. Referring toFIGS. 3A and 3B , thegate openings 53 penetrate through theinter-layer dielectric layer 43 to a surface portion of thegate electrode 42. In the embodiment, thegate openings 53 are also formed by etching. Afield oxide layer 44 is further provided between thegate electrode 42 and the n-drift layer 11. - The
first metal layer 61 is disposed at a bottom of thesource openings 51, and is a silicide or a combination of silicides of a material selected from a group consisting of nickel, titanium and aluminum. acted with SiC at an annealing temperature higher than 900° C. to form silicides. The unreacted materials are then removed by wet processes to have thefirst metal layer 61 remained at the bottom of thesource openings 51. At the bottom of thesource openings 51, thefirst metal layer 61 forms an Ohmic contact with the surface portion of then+ region 22 and thep+ region 23. Thesecond metal layer 62 may be made of a material such as titanium, molybdenum, nickel, aluminum, titanium silicide, molybdenum silicide, nickel silicide, aluminum silicide, titanium nitride, an aluminum copper alloy or an aluminum silicon copper alloy by PVD or CVD. Thesecond metal layer 62 includes afirst portion 621 and asecond portion 622. Thefirst portion 621 covers thejunction openings 52 and thesource openings 51, is in contact and electrically connected with thefirst metal layer 61 in thesource openings 51, and forms a Schottky contact with the surface portion of theJFET region 30 in thejunction openings 52. Thesecond portion 622 covers thegate openings 53, and is not in contact with and electrically insulated from thefirst portion 621. - In one embodiment, the
SiC semiconductor device 1 further includes adrain 70. Thedrain 70 is disposed at one side of thesubstrate 10 opposite to the n-drift layer 11. Accordingly, theSiC semiconductor device 1 forms a MOSFET integrated with an anti-parallelly connected junction barrier controlled Schottky rectifer. - As shown in
FIG. 2A , in the first embodiment, for example, theSiC semiconductor device 1 is a design with a quadrilateral p-well 21 at the center and fourjunction openings 52 each being a quarter of a rounded rectangle at a corner to form a unit cell, thereby effectively utilizing the area of the device. In addition to the above shape, the unit cell may have a planar contour of a square, a hexagon or a long strip. In addition to the exemplary planar contour of a rounded rectangle, the planar contour of thejunction openings 52 may be a triangle, a hexagon, an octagon or a circle, and may have a design adjustable according to the actual area of the device. -
FIG. 4 shows an enlarged view of the area X inFIG. 1 according to a second embodiment of the present invention.FIG. 5 is a sectional view along D-D ofFig.4 . To achieve the above object, aSiC semiconductor device 1 is further provided by the present invention. TheSiC semiconductor device 1 includes asubstrate 10, an n-drift layer 11, a plurality of firstdoped regions 20 a, aJFET region 30, a plurality of seconddoped regions 20 b, agate dielectric layer 41, agate electrode 42, aninter-layer dielectric layer 43, a plurality ofsource openings 51, a plurality ofjunction openings 52, a plurality ofgate openings 53, afirst metal layer 61 and asecond metal layer 62. - In the second embodiment, for example, the unit cell has a planar contour of a hexagon. In other embodiments, the unit cell may be a rectangle, a quadrilateral or a long strip.
- In the second embodiment, the
substrate 10 is a 4H-SiC substrate, and is heavily doped n-type with a concentration greater than 1E18cm−3. The n-drift layer 11 is disposed on thesubstrate 10, and is n-type with a doping concentration smaller than that of thesubstrate 10. For example, the doping concentration of the n-drift layer 11 is between 1E14cm−3 and 1E17cm−3. - The first
doped regions 20 a and the seconddoped regions 20 b are disposed at an interval at the n-drift layer 11. TheJFET region 30 is formed between the firstdoped regions 20 a and the seconddoped regions 20 b. Each of the firstdoped regions 20 a includes a first p-well 21 a, afirst n+ region 22 a, and afirst p+ region 23 a. Thefirst n+ region 22 a is disposed in the first p-well 21 a. Thefirst p+ region 23 a is surrounded by thefirst n+ region 22 a, and is contact with the first p-well 21 a. Each of the seconddoped regions 20 b includes a second p-well 21 b, asecond n+ region 22 b and asecond p+ region 23 b. The second p-well 21 b surrounds a non-p-well region 31. Thesecond n+ region 22 b is disposed in the second p-well 21 b. A part or all of thesecond p+ region 23 b overlaps with the second p-well 21 b, is adjacent to thesecond n+ region 22 b, and extends to the non-p-well region 31. It should be noted that, although this embodiment includes thesecond n+ region 22 b, thesecond n+ region 22 b may be excluded in another embodiment, and operations of theSiC semiconductor device 1 are not affected. The doping concentrations and implantation energies of the firstdoped regions 20 a and the seconddoped regions 20 b may correspond to the doping concentrations and implantation energies of the dopedregions 20, and shall be omitted herein. - The
gate dielectric layer 41 is disposed on the n-drift layer 11, and may be similarly made of a material such as SiO2, nitride-containing SiO2 or Al2O3 by thermal oxidation, CVD or ALD. Thegate electrode 42 is disposed on thegate dielectric layer 41. Thegate electrode 42 may be made of a material such as heavily doped n-type poly-Si with phosphorous as a dopant, or a heavily doped p-type poly-Si with boron as a dopant. Theinter-layer dielectric layer 43 is disposed on thegate dielectric layer 41 and thegate electrode 42, and is made of a material such as TEOS, BPSG, oxynitride, USG or SRN. Further, in the second embodiment, positions and structures of thegate openings 53 are identical to those in the first embodiment, and may be referred fromFIGS. 3A and 3B . Associated details shall be omitted herein. - Accordingly, compared to the first embodiment, the
source openings 51 of the second embodiment penetrate through theinter-layer dielectric layer 43 and thegate dielectric layer 41 to a surface portion of thefirst n+ region 22 a and thefirst p+ region 23 a to correspond above the firstdoped region 20 a. Thesource openings 51 are separated by thegate electrode 42 and theinter-layer dielectric layer 43. Thejunction openings 52 penetrate through theinter-layer dielectric layer 43 and thegate dielectric layer 41 to a surface portion of thesecond p+ region 23 b of the seconddoped region 20 b and the non-p-well region 31. Thejunction openings 52 are spaced by thegate electrode 42 and theinter-layer dielectric layer 43. Thegate openings 53 penetrate through theinter-layer dielectric layer 43 to a surface portion of thegate electrode 42. - The
first metal layer 61 is disposed at the bottom of thesource openings 51, and forms an Ohmic contact with the the surface portion of firstn+ region 22 a and thefirst p+ region 23 a. Thesecond metal layer 62 includes afirst portion 621 and asecond portion 622. Thefirst portion 621 covers thejunction openings 52 and thesource openings 51, is in contact and electrically connected with thefirst metal layer 61, and forms a Schottky contact with a surface portion of the non-p-well region 31. Thesecond portion 622 covers thegate openings 53, and is not in contact with and thus electrically insulated from thefirst portion 621. It should be noted that, details of manufacturing processes for forming thesource openings 51, thejunction openings 52 and thegate openings 53 as well as the materials of thefirst metal layer 61 and thesecond metal layer 62 may be referred from the corresponding description of the first embodiment, and shall be omitted herein. - In conclusion, in the present invention, the source openings and the junction openings are separately disposed. In the manufacturing process, the source openings are first manufactured and the first metal layer is formed, and gate openings and the junction openings are manufactured, followed by forming the second metal layer, thereby forming a good Schottky contact by the second metal layer at the junction openings with SiC. Further, the first metal layer is formed at the bottom of the source openings to form an Ohmic contact with only the n+ region (or the first n+ region) and the p+ region (or the first p+ region). As such, shorting between the lightly doped n-type n-drift layer and the first metal layer due to manufacturing variations can be avoided, thereby improving manufacturing yield.
- While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
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US9246016B1 (en) | 2016-01-26 |
TWI528565B (en) | 2016-04-01 |
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