US20130334484A1 - Atomic Layer Deposition of Hafnium and Zirconium Oxides for Memory Applications - Google Patents
Atomic Layer Deposition of Hafnium and Zirconium Oxides for Memory Applications Download PDFInfo
- Publication number
- US20130334484A1 US20130334484A1 US13/972,587 US201313972587A US2013334484A1 US 20130334484 A1 US20130334484 A1 US 20130334484A1 US 201313972587 A US201313972587 A US 201313972587A US 2013334484 A1 US2013334484 A1 US 2013334484A1
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- US
- United States
- Prior art keywords
- metal
- metal oxide
- oxide
- hafnium
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical class [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 229910001928 zirconium oxide Inorganic materials 0.000 title claims abstract description 29
- 229910052735 hafnium Inorganic materials 0.000 title claims description 74
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical group [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 title claims description 68
- 238000000231 atomic layer deposition Methods 0.000 title abstract description 103
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 288
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 256
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910000449 hafnium oxide Inorganic materials 0.000 claims abstract description 29
- 229910052726 zirconium Chemical group 0.000 claims description 69
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical group [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 64
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 28
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 26
- 239000002019 doping agent Substances 0.000 claims description 10
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 8
- 229910003134 ZrOx Inorganic materials 0.000 claims description 5
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(IV) oxide Inorganic materials O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 164
- 229910052751 metal Inorganic materials 0.000 abstract description 138
- 239000002184 metal Substances 0.000 abstract description 138
- 230000008569 process Effects 0.000 abstract description 114
- 239000000463 material Substances 0.000 abstract description 69
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000010410 layer Substances 0.000 description 239
- 239000010408 film Substances 0.000 description 73
- 239000007789 gas Substances 0.000 description 69
- 238000000151 deposition Methods 0.000 description 56
- 230000001590 oxidative effect Effects 0.000 description 52
- 239000007800 oxidant agent Substances 0.000 description 47
- 239000000758 substrate Substances 0.000 description 35
- 230000008021 deposition Effects 0.000 description 33
- NFHFRUOZVGFOOS-UHFFFAOYSA-N palladium;triphenylphosphane Chemical compound [Pd].C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1 NFHFRUOZVGFOOS-UHFFFAOYSA-N 0.000 description 26
- 239000002243 precursor Substances 0.000 description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 20
- -1 hafnium halide compound Chemical class 0.000 description 17
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 15
- 238000010926 purge Methods 0.000 description 15
- 150000001875 compounds Chemical class 0.000 description 14
- 239000000126 substance Substances 0.000 description 14
- 239000001301 oxygen Substances 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 13
- 239000012159 carrier gas Substances 0.000 description 12
- 125000004663 dialkyl amino group Chemical group 0.000 description 12
- 239000000203 mixture Substances 0.000 description 12
- 150000002363 hafnium compounds Chemical class 0.000 description 11
- 150000003755 zirconium compounds Chemical class 0.000 description 10
- 238000000137 annealing Methods 0.000 description 9
- 210000002381 plasma Anatomy 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000003795 chemical substances by application Substances 0.000 description 7
- 150000002926 oxygen Chemical class 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 5
- 229910007928 ZrCl2 Inorganic materials 0.000 description 5
- 239000003708 ampul Substances 0.000 description 5
- 210000004027 cell Anatomy 0.000 description 5
- 230000006870 function Effects 0.000 description 5
- 150000002736 metal compounds Chemical class 0.000 description 5
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 5
- 229920005591 polysilicon Polymers 0.000 description 5
- 239000010936 titanium Substances 0.000 description 5
- 229910052721 tungsten Inorganic materials 0.000 description 5
- 239000010937 tungsten Substances 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 4
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 239000012707 chemical precursor Substances 0.000 description 4
- ZYLGGWPMIDHSEZ-UHFFFAOYSA-N dimethylazanide;hafnium(4+) Chemical compound [Hf+4].C[N-]C.C[N-]C.C[N-]C.C[N-]C ZYLGGWPMIDHSEZ-UHFFFAOYSA-N 0.000 description 4
- ZWWCURLKEXEFQT-UHFFFAOYSA-N dinitrogen pentaoxide Chemical compound [O-][N+](=O)O[N+]([O-])=O ZWWCURLKEXEFQT-UHFFFAOYSA-N 0.000 description 4
- 239000007772 electrode material Substances 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- 229910052723 transition metal Inorganic materials 0.000 description 4
- 229940126062 Compound A Drugs 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- NLDMNSXOCDLTTB-UHFFFAOYSA-N Heterophylliin A Natural products O1C2COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC2C(OC(=O)C=2C=C(O)C(O)=C(O)C=2)C(O)C1OC(=O)C1=CC(O)=C(O)C(O)=C1 NLDMNSXOCDLTTB-UHFFFAOYSA-N 0.000 description 3
- 125000003282 alkyl amino group Chemical group 0.000 description 3
- 125000000217 alkyl group Chemical group 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- DWCMDRNGBIZOQL-UHFFFAOYSA-N dimethylazanide;zirconium(4+) Chemical compound [Zr+4].C[N-]C.C[N-]C.C[N-]C.C[N-]C DWCMDRNGBIZOQL-UHFFFAOYSA-N 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- INZDTEICWPZYJM-UHFFFAOYSA-N 1-(chloromethyl)-4-[4-(chloromethyl)phenyl]benzene Chemical compound C1=CC(CCl)=CC=C1C1=CC=C(CCl)C=C1 INZDTEICWPZYJM-UHFFFAOYSA-N 0.000 description 2
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910007930 ZrCl3 Inorganic materials 0.000 description 2
- CUJRVFIICFDLGR-UHFFFAOYSA-N acetylacetonate Chemical compound CC(=O)[CH-]C(C)=O CUJRVFIICFDLGR-UHFFFAOYSA-N 0.000 description 2
- 150000004703 alkoxides Chemical class 0.000 description 2
- GPBUGPUPKAGMDK-UHFFFAOYSA-N azanylidynemolybdenum Chemical compound [Mo]#N GPBUGPUPKAGMDK-UHFFFAOYSA-N 0.000 description 2
- CFJRGWXELQQLSA-UHFFFAOYSA-N azanylidyneniobium Chemical compound [Nb]#N CFJRGWXELQQLSA-UHFFFAOYSA-N 0.000 description 2
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 2
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 125000000058 cyclopentadienyl group Chemical group C1(=CC=CC1)* 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 2
- PDPJQWYGJJBYLF-UHFFFAOYSA-J hafnium tetrachloride Chemical compound Cl[Hf](Cl)(Cl)Cl PDPJQWYGJJBYLF-UHFFFAOYSA-J 0.000 description 2
- WHJFNYXPKGDKBB-UHFFFAOYSA-N hafnium;methane Chemical compound C.[Hf] WHJFNYXPKGDKBB-UHFFFAOYSA-N 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- 229910000457 iridium oxide Inorganic materials 0.000 description 2
- 239000003446 ligand Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000012705 liquid precursor Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- NFFIWVVINABMKP-UHFFFAOYSA-N methylidynetantalum Chemical compound [Ta]#C NFFIWVVINABMKP-UHFFFAOYSA-N 0.000 description 2
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 2
- 239000001272 nitrous oxide Substances 0.000 description 2
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 2
- NJPPVKZQTLUDBO-UHFFFAOYSA-N novaluron Chemical compound C1=C(Cl)C(OC(F)(F)C(OC(F)(F)F)F)=CC=C1NC(=O)NC(=O)C1=C(F)C=CC=C1F NJPPVKZQTLUDBO-UHFFFAOYSA-N 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 2
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 229910052707 ruthenium Inorganic materials 0.000 description 2
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 2
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
- HWEYZGSCHQNNEH-UHFFFAOYSA-N silicon tantalum Chemical compound [Si].[Ta] HWEYZGSCHQNNEH-UHFFFAOYSA-N 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 229910003468 tantalcarbide Inorganic materials 0.000 description 2
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 description 2
- 229910001936 tantalum oxide Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 229910001930 tungsten oxide Inorganic materials 0.000 description 2
- ZVWKZXLXHLZXLS-UHFFFAOYSA-N zirconium nitride Chemical compound [Zr]#N ZVWKZXLXHLZXLS-UHFFFAOYSA-N 0.000 description 2
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 229910003865 HfCl4 Inorganic materials 0.000 description 1
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 229910007938 ZrBr4 Inorganic materials 0.000 description 1
- 229910007932 ZrCl4 Inorganic materials 0.000 description 1
- 229910008047 ZrI4 Inorganic materials 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- UQZIWOQVLUASCR-UHFFFAOYSA-N alumane;titanium Chemical compound [AlH3].[Ti] UQZIWOQVLUASCR-UHFFFAOYSA-N 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 229940051881 anilide analgesics and antipyretics Drugs 0.000 description 1
- 150000003931 anilides Chemical class 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- VBCSQFQVDXIOJL-UHFFFAOYSA-N diethylazanide;hafnium(4+) Chemical compound [Hf+4].CC[N-]CC.CC[N-]CC.CC[N-]CC.CC[N-]CC VBCSQFQVDXIOJL-UHFFFAOYSA-N 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- NPEOKFBCHNGLJD-UHFFFAOYSA-N ethyl(methyl)azanide;hafnium(4+) Chemical compound [Hf+4].CC[N-]C.CC[N-]C.CC[N-]C.CC[N-]C NPEOKFBCHNGLJD-UHFFFAOYSA-N 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- FEEFWFYISQGDKK-UHFFFAOYSA-J hafnium(4+);tetrabromide Chemical compound Br[Hf](Br)(Br)Br FEEFWFYISQGDKK-UHFFFAOYSA-J 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000002085 persistent effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 1
- LSWWNKUULMMMIL-UHFFFAOYSA-J zirconium(iv) bromide Chemical compound Br[Zr](Br)(Br)Br LSWWNKUULMMMIL-UHFFFAOYSA-J 0.000 description 1
- XLMQAUWIRARSJG-UHFFFAOYSA-J zirconium(iv) iodide Chemical compound [Zr+4].[I-].[I-].[I-].[I-] XLMQAUWIRARSJG-UHFFFAOYSA-J 0.000 description 1
Images
Classifications
-
- H01L45/146—
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
- H10N70/24—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/881—Switching materials
- H10N70/883—Oxides or nitrides
- H10N70/8833—Binary metal oxides, e.g. TaOx
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/011—Manufacture or treatment of multistable switching devices
- H10N70/021—Formation of switching materials, e.g. deposition of layers
- H10N70/023—Formation of switching materials, e.g. deposition of layers by chemical vapor deposition, e.g. MOCVD, ALD
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/821—Device geometry
- H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/80—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays
Definitions
- Embodiments of the invention generally relate to memory devices and methods for manufacturing such memory devices.
- Nonvolatile memory elements are used in systems in which persistent storage is required. For example, digital cameras use nonvolatile memory cards to store images and digital music players use nonvolatile memory to store audio data. Nonvolatile memory is also used to persistently store data in computer environments. Nonvolatile memory is often formed using electrically-erasable programmable read only memory (EPROM) technology. This type of nonvolatile memory contains floating gate transistors that can be selectively programmed or erased by application of suitable voltages to their terminals.
- EPROM electrically-erasable programmable read only memory
- Resistive switching nonvolatile memory is formed using memory elements that have two or more stable states with different resistances.
- Bistable memory has two stable states.
- a bistable memory element can be placed in a high resistance state or a low resistance state by application of suitable voltages or currents. Voltage pulses are typically used to switch the memory element from one resistance state to the other.
- Nondestructive read operations can be performed to ascertain the value of a data bit that is stored in a memory cell.
- Resistive switching based on transition metal oxide switching elements formed of metal oxide films has been demonstrated. Although metal oxide films such as these exhibit bistability, the resistance of these films and the ratio of the high-to-low resistance states are often insufficient to be of use within a practical nonvolatile memory device. For instance, the resistance states of the metal oxide film should preferably be significant as compared to that of the system (e.g., the memory device and associated circuitry) so that any change in the resistance state change is perceptible. The variation of the difference in resistive states is related to the resistance of the resistive switching layer. Therefore, a low resistance metal oxide film may not form a reliable nonvolatile memory device.
- the resistance of the conductive lines may overwhelm the resistance of the metal oxide resistive switching element. Therefore, the state of the bistable metal oxide resistive switching element may be difficult or impossible to sense.
- the resistance of the resistive switching memory element (at least in its high resistance state) is preferably significant compared to the resistance of the current steering elements, so that the unvarying resistance of the current steering element does not dominate the resistance of the switching memory element, and thus reduce the measurable difference between the “on” and “off” states of the formed memory device (e.g., logic states of the device).
- insulator materials such as metal oxides (e.g., hafnium oxide) between metal electrodes to form a device that can be switched between two different stable resistance states by the application of appropriate voltages.
- metal oxides e.g., hafnium oxide
- the switching is enabled by the back and forth movement of charged oxygen vacancies between the electrodes under the influence of the applied electrical field.
- the interface between the electrode and the metal oxide bulk film is a region in which vacancies may be trapped and eventually be removed from the metal oxide bulk film. This is especially true when reactive metal surfaces or boundary regions have large structural changes relative to the metal oxide bulk film.
- Embodiments of the invention generally relate to nonvolatile memory devices and methods for manufacturing such memory devices.
- the methods for forming improved memory devices such as a ReRAM cells, provide optimized, atomic layer deposition (ALD) processes for forming a metal oxide film stack which contains a metal oxide buffer layer (e.g., metal-poor oxide, such that the metal is completely oxidized or substantially oxidized) disposed on or over a metal oxide bulk layer (e.g., metal-rich oxide, such that the metal is less oxidized than the metal-poor oxide).
- ALD atomic layer deposition
- the metal oxide bulk layer containing a metal-rich oxide material is less electrically resistive than the metal oxide buffer layer containing a metal-poor oxide material since the metal oxide bulk layer is less oxidized or more metallic than the metal oxide buffer layer.
- the metal oxide bulk layer contains a metal-rich hafnium oxide material and the metal oxide buffer layer contains a metal-poor zirconium oxide material.
- the metal oxide bulk layer contains a metal-rich zirconium oxide material and the metal oxide buffer layer contains a metal-poor hafnium oxide material.
- the described ALD processes are techniques for depositing ultra-thin metal oxide films due to practical advantages which includes simple and accurate thickness control, excellent reproducibility and uniformity, and capability to produce conformal films at sharp interfaces and trenches with high aspect ratio.
- metal oxide materials can be made metal-rich or metal-poor (metal deficient), which in turn tailors the oxygen defect content and type (vacancy vs. interstitial), resulting in an enhancement or reduction in defect density to facilitate carrier transport.
- a method for fabricating a resistive switching memory element such as a memory device, includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack contains a metal oxide buffer layer disposed on or over a metal oxide bulk layer.
- the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method further provides depositing the metal oxide buffer layer over the metal oxide bulk layer during a second ALD process, wherein the metal oxide buffer layer substantially contains M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the metal oxide bulk layer substantially contains a metal-rich hafnium oxide which has the chemical formula of HfO x , where x is within a range from about 1.70 to about 1.90, and the metal oxide buffer layer substantially contains a metal-poor, zirconium oxide material having the chemical formula of ZrO 2 .
- the metal oxide bulk layer substantially contains a metal-rich zirconium oxide which has the chemical formula of ZrO x , where x is within a range from about 1.70 to about 1.90
- the metal oxide buffer layer substantially contains a metal-poor, hafnium oxide material which has the chemical formula of HfO 2 .
- the metal oxide bulk layer contains a metal-rich oxide material which has the chemical formula of HfO x or ZrO x , where x is within a range from about 1.65 to about 1.95, such as from about 1.70 to about 1.90, such as from about 1.75 to about 1.85, for example, about 1.80.
- the metal oxide bulk layer may have a thickness within a range from about 5 ⁇ to about 100 ⁇ , such as from about 10 ⁇ to about 80 ⁇ , such as from about 15 ⁇ to about 50 ⁇ .
- the metal oxide buffer layer may have a thickness within a range from about 2 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 15 ⁇ .
- the first ALD process includes sequentially providing a metal source gas and an oxidizing agent during a metal-rich oxidizing ALD process.
- the metal source gas may contain a tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process.
- the tetrakis(dialkylamido) hafnium compound may be tetrakis(dimethylamido) hafnium.
- the metal source gas may contain a tetrakis(dialkylamido) zirconium compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process.
- the tetrakis(dialkylamido) zirconium compound may be tetrakis(dimethylamido) zirconium.
- the substrate may be maintained at a deposition temperature or a substrate temperature within a range from greater than 0° C. to about 20° C., such as from greater than 0° C. to about 15° C., such as from greater than 0° C. to about 10° C., such as from greater than 0° C. to about 5° C., for example about 1° C. during the metal-rich oxidizing ALD process.
- the second ALD process includes sequentially providing a metal source gas and an oxidizing agent during a metal-poor oxidizing ALD process.
- the metal source gas may contain the tetrakis(dialkylamido) zirconium compound and the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof during the metal-poor oxidizing ALD process.
- the metal source gas may contain the tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain the activated oxygen agent during the metal-poor oxidizing ALD process.
- the method further provides forming a silicon oxide layer on or over the lower electrode, and subsequently, forming the metal oxide bulk layer on or over the silicon oxide layer.
- the silicon oxide layer contains a silicon oxide material, such as native silicon oxides, silicon dioxide, dopant variants thereof, or combinations thereof.
- the silicon oxide layer may have a thickness within a range from about 2 ⁇ to about 40 ⁇ , such as from about 2 ⁇ to about 20 ⁇ , such as from about 5 ⁇ to about 10 ⁇ .
- a method for fabricating a resistive switching memory element includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack may contain a doped-metal oxide buffer layer disposed on or over a metal oxide bulk layer.
- the method provides that the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method includes depositing the doped-metal oxide buffer layer over the metal oxide bulk layer during a second ALD process, wherein the doped-metal oxide buffer layer substantially contains MM 1 O 4 or a mixture of MO 2 and M′O 2 , where M is the same metal selected for the metal oxide bulk layer, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the doped-metal oxide buffer layer substantially contains a mixture of MO 2 and M′O 2 , wherein M is hafnium and M′ is zirconium.
- the doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 0.25 at % (atomic percent) to about 25 at % and hafnium oxide at a concentration within a range from about 75 at % to about 99.75 at %.
- the doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 0.5 at % to about 20 at % and hafnium oxide at a concentration within a range from about 80 at % to about 99.5 at %.
- the doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 1 at % to about 15 at % and hafnium oxide at a concentration within a range from about 85 at % to about 99 at %.
- the doped-metal oxide buffer layer substantially contains a mixture of MO 2 and M′O 2 , wherein M is zirconium and M′ is hafnium.
- the doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 0.25 at % to about 25 at % and zirconium oxide at a concentration within a range from about 75 at % to about 99.75 at %.
- the doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 0.5 at % to about 20 at % and zirconium oxide at a concentration within a range from about 80 at % to about 99.5 at %.
- the doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 1 at % to about 15 at % and zirconium oxide at a concentration within a range from about 85 at % to about 99 at %.
- the doped-metal oxide buffer layer may have a thickness within a range from about 2 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 30 ⁇ .
- the metal oxide bulk layer may have a thickness within a range from about 5 ⁇ to about 100 ⁇ , such as from about 10 ⁇ to about 80 ⁇ , such as from about 15 ⁇ to about 50 ⁇ .
- the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a metal-poor oxide layer during a deposition step of a metal-poor oxidizing ALD process, and subsequently doping the metal-poor oxide layer while forming the doped-metal oxide buffer layer during a doping step of the metal-poor oxidizing ALD process.
- the method may further include repeating the deposition and doping steps of the metal-poor oxidizing ALD process while forming the doped-metal oxide buffer layer.
- the metal-poor oxide layer may be exposed to a second metal source gas and the oxidizing agent during the doping step of the metal-poor oxidizing ALD process.
- a method for fabricating a resistive switching memory element includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack contains a metal oxide buffer laminate disposed on or over a metal oxide bulk layer.
- the method further provides that the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method also provides depositing the metal oxide buffer laminate over the metal oxide bulk layer during a second ALD process, wherein the metal oxide buffer laminate substantially contains a plurality metal-poor oxide layers of MO 2 and M′O 2 , where M is the same metal selected for the metal oxide bulk layer, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a first metal-poor oxide layer during a first step of a metal-poor oxidizing ALD process, and subsequently, sequentially providing a second metal source gas and the oxidizing agent while forming a second metal-poor oxide layer on the first metal-poor layer during a second step of the metal-poor oxidizing ALD process.
- the method further provides repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of first and second metal-poor oxide layers contained within the metal oxide buffer laminate.
- Each of the first and second metal source gases may independently contain an organic-metallic compound.
- the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof.
- Each of the metal-poor oxide layers may independently have a thickness within a range from about 2 ⁇ to about 20 ⁇ , such as from about 2 ⁇ to about 10 ⁇ , such as from about 3 ⁇ to about 7 ⁇ , for example, about 5 ⁇ .
- the metal oxide buffer laminate may have a thickness within a range from about 2 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 30 ⁇ .
- the metal oxide bulk layer may have a thickness within a range from about 5 ⁇ to about 100 ⁇ , such as from about 10 ⁇ to about 80 ⁇ , such as from about 15 ⁇ to about 50 ⁇ .
- a method for fabricating a resistive switching memory element includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack may contain a metal oxide buffer laminate disposed on or over a metal oxide bulk laminate.
- the method further includes forming the metal oxide bulk laminate by sequentially providing a first metal source gas and a first oxidizing agent while forming a first metal-rich oxide layer during a first step of a metal-rich oxidizing ALD process, wherein the first metal-rich oxide layer substantially contains MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method further includes sequentially providing a second metal source gas and the first oxidizing agent while forming a second metal-rich oxide layer on the first metal-rich oxide layer during a second step of the metal-rich oxidizing ALD process, wherein the second metal-rich oxide layer substantially contains MO 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the method further includes repeating the first and second steps of the metal-rich ALD process while forming a plurality of the first and second metal-rich oxide layers contained within the metal oxide bulk laminate.
- the method further includes forming the metal oxide bulk laminate by sequentially providing the first metal source gas and a second oxidizing agent while forming a first metal-poor oxide layer during a first step of a metal-poor oxidizing ALD process, wherein the first metal-poor oxide layer substantially contains MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method further includes sequentially providing the second metal source gas and the second oxidizing agent while forming a second metal-poor oxide layer on the first metal-poor oxide layer during a second step of the metal-poor oxidizing ALD process, wherein the second metal-poor oxide layer substantially contains M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the method further includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of the first and second metal-poor oxide layers contained within the metal oxide buffer laminate.
- FIG. 1 is a flowchart illustrating a method to form a memory device, as described by embodiments herein;
- FIG. 2A depicts a memory device which may be formed by a method illustrated in FIG. 1 , as described by embodiments herein;
- FIGS. 2B-2E depict various metal oxide film stacks which may be formed within the memory device illustrated in FIG. 2A , as described by other embodiments herein;
- FIG. 3 depicts a memory array of resistive switching memory devices, as described by another embodiment herein.
- Embodiments of the invention generally relate to nonvolatile memory devices and methods for manufacturing such memory devices.
- the invention teaches a novel process to form a metal oxide film stacks for an improved ReRAM cell.
- the metal oxide film stacks contains a metal oxide buffer layer disposed on or over a metal oxide bulk layer, such that the metal in both metal oxide layers are different metals (e.g., Hf vs Zr) and have different states of oxidation, such as metal-rich and metal-poor oxide materials.
- the metal oxide bulk layer and the metal oxide buffer layer are formed by different ALD processes.
- the metal oxide bulk layer contains a metal-rich hafnium oxide material and the metal oxide buffer layer contains a metal-poor zirconium oxide material.
- the metal oxide bulk layer contains a metal-rich zirconium oxide material and the metal oxide buffer layer contains a metal-poor hafnium oxide material.
- FIG. 1 is a flowchart illustrating a method for manufacturing or otherwise forming various memory devices, as described by embodiments herein, such as process 100 which may be utilized to form resistive switching memory elements/devices, such as memory device 200 , as depicted in FIG. 2A .
- process 100 may be used to form memory device 200 and includes forming lower electrode 220 on or over substrate 210 during step 110 , optionally forming silicon oxide layer 222 on or over lower electrode 220 during step 120 , forming metal oxide film stack 230 on or over silicon oxide layer 222 or lower electrode 220 by ALD processes during step 130 , depositing upper electrode 260 on or over metal oxide film stack 230 during step 140 , and optionally annealing memory device 200 during step 145 .
- FIGS. 2B-2E depict a variety of metal oxide film stacks 230 formed by different ALD techniques during step 130 , as described by embodiments herein.
- a variety of metal oxide film stacks 230 may be formed by different ALD techniques during step 130 of process 100 , and contained within memory device 200 depicted in FIG. 2A .
- Each of the metal oxide film stacks 230 depicted in FIGS. 2B-2E may be disposed between lower electrode 220 and upper electrode 260 of memory device 200 . Therefore, any of the particular lower layers depicted in each of the metal oxide film stacks 230 may be on or over lower electrode 220 .
- upper electrode 260 may be on or over any of the particular upper layers depicted in each of the metal oxide film stacks 230 .
- Silicon oxide layer 222 may be deposited, formed, or otherwise disposed on or over lower electrode 220 .
- metal oxide film stack 230 contains metal oxide buffer layer 234 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2B .
- Metal oxide bulk layer 232 may substantially contain a metal-rich oxide material having a generic chemical formula of MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- metal oxide buffer layer 234 substantially contains a metal-poor oxide material having a generic chemical formula of M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- metal oxide film stack 230 contains doped-metal oxide buffer layer 236 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2C .
- Doped-metal oxide buffer layer 236 substantially contains MM 1 O 4 or a mixture of MO 2 and M′O 2 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2D .
- Metal oxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO 2 and M′O 2 , such as metal-poor oxide layers 242 and 244 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk laminate 250 , as depicted in FIG. 2E .
- a plurality of metal-rich oxide layers 252 and 254 are contained within metal oxide bulk laminate 250 .
- Metal-rich oxide layer 252 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95, while metal-rich oxide layer 254 may substantially contain M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- process 100 further provides step 120 which includes optionally forming silicon oxide layer 222 on or over lower electrode 220 , and subsequently, forming metal oxide bulk layer 232 on or over silicon oxide layer 222 , as depicted in FIGS. 2B-2E .
- Silicon oxide layer 222 contains a silicon oxide material, such as native silicon oxides, silicon dioxide, dopant variants thereof, or combinations thereof. Silicon oxide layer 222 may contain a single layer or multiple layers of the same or different silicon oxide materials. Usually, silicon oxide layer 222 may be continuously formed, deposited, or otherwise disposed on or over lower electrode 220 or other underlying surfaces. Alternatively, silicon oxide layer 222 may also be discontinuously formed, deposited, or otherwise disposed on or over lower electrode 220 or other underlying surfaces. Silicon oxide layer 222 may have a thickness within a range from about 2 ⁇ to about 40 ⁇ , such as from about 2 ⁇ to about 20 ⁇ , such as from about 5 ⁇ to about 10 ⁇ .
- a method for fabricating a resistive switching memory device or element includes forming metal oxide film stack 230 on or over silicon oxide layer 222 or lower electrode 220 disposed on substrate 210 , wherein metal oxide film stack 230 contains metal oxide buffer layer 234 disposed on or over metal oxide bulk layer 232 .
- Metal oxide bulk layer 232 is less electrically resistive than metal oxide buffer layer 234 since metal oxide bulk layer 232 is less oxidized or more metallic than metal oxide buffer layer 234 . Therefore, metal oxide bulk layer 232 is metal-rich and more leaky relative to metal oxide buffer layer 234 which has a metal-poor.
- metal oxide film stack 230 contains metal oxide buffer layer 234 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2B .
- Metal oxide film stack 230 may be formed by depositing metal oxide bulk layer 232 over lower electrode 220 during a first ALD process, such as a metal-rich oxidizing ALD process at step 130 of process 100 .
- Metal oxide bulk layer 232 may substantially contain a metal-rich oxide material having a generic chemical formula of MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- Step 130 of process 100 further provides a method which includes depositing metal oxide buffer layer 234 over metal oxide bulk layer 232 during a second ALD process, such as a metal-poor oxidizing ALD process, wherein metal oxide buffer layer 234 may substantially contain a metal-poor oxide material having a generic chemical formula of M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- metal oxide bulk layer 232 may substantially contain a metal-rich, hafnium oxide material having the generic chemical formula of HfO x , where x is within a range from about 1.70 to about 1.90, and metal oxide buffer layer 234 may substantially contain a metal-poor, zirconium oxide material having the generic chemical formula of ZrO 2 .
- metal oxide bulk layer 232 may substantially contain a metal-rich, zirconium oxide material having the generic chemical formula of ZrO x , where x is within a range from about 1.70 to about 1.90
- metal oxide buffer layer 234 may substantially contain a metal-poor, hafnium oxide material having the generic chemical formula of HfO 2 .
- metal oxide bulk layer 232 substantially contains a metal-rich oxide material having the generic chemical formula of HfO x or ZrO x , where x is within a range from about 1.65 to about 1.95, such as from about 1.70 to about 1.90, such as from about 1.75 to about 1.85, for example, about 1.80.
- Metal oxide bulk layer 232 may have a thickness within a range from about 5
- Metal oxide buffer layer 234 may have a thickness within a range from about 2 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 15 ⁇ .
- the first ALD process such as the metal-rich oxidizing ALD process, includes sequentially providing a metal source gas and an oxidizing agent into the deposition chamber while sequentially exposing the surfaces of the substrate or device to the chemical reagents/precursors.
- the metal source gas may contain a hafnium precursor, such as a tetrakis(dialkylamido) hafnium compound or a hafnium halide compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process.
- the tetrakis(dialkylamido) hafnium compound may be tetrakis(dimethylamido) hafnium or the hafnium halide compound may be hafnium tetrachloride.
- the metal source gas may contain a zirconium precursor, such as a tetrakis(dialkylamido) zirconium compound or a zirconium halide compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process.
- the tetrakis(dialkylamido) zirconium compound may be tetrakis(dimethylamido) zirconium or the zirconium halide compound may be zirconium tetrachloride.
- substrate 210 and/or memory device 200 may be maintained at a deposition temperature or a substrate temperature within a range from greater than 0° C. to about 20° C., such as from greater than 0° C. to about 15° C., such as from greater than 0° C. to about 10° C., such as from greater than 0° C. to about 5° C., for example about 1° C. during the metal-rich oxidizing ALD process.
- the second ALD process such as a metal-poor oxidizing ALD process, includes sequentially providing a metal source gas and an oxidizing agent into the deposition chamber while sequentially exposing the surfaces of the substrate or device to the chemical reagents/precursors.
- the metal source gas may contain the tetrakis(dialkylamido) zirconium compound or the zirconium halide compound and the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof during the metal-poor oxidizing ALD process.
- the metal source gas may contain the tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain the activated oxygen agent during the metal-poor oxidizing ALD process.
- metal oxide film stack 230 contains doped-metal oxide buffer layer 236 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2C .
- Doped-metal oxide buffer layer 236 substantially contains MM 1 O 4 or a mixture of MO 2 and M′O 2 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- a method for fabricating a resistive switching memory device or element includes forming metal oxide film stack 230 at step 130 of process 100 on or over lower electrode 220 disposed on substrate 210 , wherein metal oxide film stack 230 may contain doped-metal oxide buffer layer 236 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2C .
- the method provides that metal oxide film stack 230 may be formed by depositing metal oxide bulk layer 232 over lower electrode 220 during a first ALD process, such as a metal-rich oxidizing ALD process at step 130 of process 100 .
- Metal oxide bulk layer 232 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method includes depositing doped-metal oxide buffer layer 236 over metal oxide bulk layer 232 during a second ALD process, wherein doped-metal oxide buffer layer 236 may substantially contain MM 1 O 4 or a mixture of MO 2 and M′O 2 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- doped-metal oxide buffer layer 236 may substantially contain a mixture of MO 2 and M′O 2 , wherein M is hafnium and M′ is zirconium.
- Doped-metal oxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 0.25 at % (atomic percent) to about 25 at % and hafnium oxide at a concentration within a range from about 75 at % to about 99.75 at %.
- doped-metal oxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 0.5 at % to about 20 at % and hafnium oxide at a concentration within a range from about 80 at % to about 99.5 at %.
- doped-metal oxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 1 at % to about 15 at % and hafnium oxide at a concentration within a range from about 85 at % to about 99 at %.
- doped-metal oxide buffer layer 236 may substantially contain a mixture of MO 2 and M′O 2 , wherein M is zirconium and M′ is hafnium.
- Doped-metal oxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 0.25 at % to about 25 at % and zirconium oxide at a concentration within a range from about 75 at % to about 99.75 at %.
- doped-metal oxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 0.5 at % to about 20 at % and zirconium oxide at a concentration within a range from about 80 at % to about 99.5 at %.
- doped-metal oxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 1 at % to about 15 at % and zirconium oxide at a concentration within a range from about 85 at % to about 99 at %.
- doped-metal oxide buffer layer 236 may have a thickness within a range from about 2 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 30 ⁇ .
- Metal oxide bulk layer 232 may have a thickness within a range from about 5 ⁇ to about 100 ⁇ , such as from about 10 ⁇ to about 80 ⁇ , such as from about 15 ⁇ to about 50 ⁇ .
- the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a metal-poor oxide layer during a deposition step of a metal-poor oxidizing ALD process, and subsequently doping the metal-poor oxide layer while forming doped-metal oxide buffer layer 236 during a doping step of the metal-poor oxidizing ALD process.
- the method may further include repeating the deposition and doping steps of the metal-poor oxidizing ALD process while forming doped-metal oxide buffer layer 236 .
- the metal-poor oxide layer may be exposed to a second metal source gas and the oxidizing agent during the doping step of the metal-poor oxidizing ALD process.
- metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk layer 232 , as depicted in FIG. 2D .
- Metal oxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO 2 and M′O 2 , such as metal-poor oxide layers 242 and 244 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- a method for fabricating a resistive switching memory device or element includes forming metal oxide film stack 230 at step 130 of process 100 on or over lower electrode 220 disposed on substrate 210 , wherein metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk layer 232 .
- Process 100 further provides a method for forming metal oxide film stack 230 by depositing metal oxide bulk layer 232 over lower electrode 220 during a first ALD process, wherein metal oxide bulk layer 232 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- metal oxide buffer laminate 240 on or over metal oxide bulk layer 232 during a second ALD process, wherein metal oxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO 2 and M′O 2 , such as metal-poor oxide layers 242 and 244 , where M is the same metal selected for metal oxide bulk layer 232 , M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a first metal-poor oxide layer, such as metal-poor oxide layer 242 , during a first step of a metal-poor oxidizing ALD process, and subsequently, sequentially providing a second metal source gas and the oxidizing agent while forming a second metal-poor oxide layer, such as metal-poor oxide layer 244 , on the first metal-poor layer during a second step of the metal-poor oxidizing ALD process.
- Process 100 further provides a method which includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of metal-poor oxide layers 242 and 244 contained within metal oxide buffer laminate 240 .
- the first metal source gas and the second metal source gas independently contain the respective metal source precursor, such as an organic-metallic compound.
- the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof.
- Metal oxide buffer laminate 240 contains a plurality of sequentially stacked metal-poor oxide layers 242 and 244 , such that metal oxide buffer laminate 240 contains at least 2 layers of metal-poor oxide layer 242 sequentially stacked with at least 2 layers of metal-poor oxide layer 244 . In some examples, metal oxide buffer laminate 240 contains at least 2 layers of each metal-poor oxide layer 242 and 244 , but may contain from 3 layers to about 50 layers or more of each metal-poor oxide layer 242 and 244 .
- metal-poor oxide layers 242 and 244 may independently have a thickness within a range from about 2 ⁇ to about 20 ⁇ , such as from about 2 ⁇ to about 10 ⁇ , such as from about 3 ⁇ to about 7 ⁇ , for example, about 5 ⁇ . Therefore, metal oxide buffer laminate 240 may have a total final thickness within a range from about 5 ⁇ to about 80 ⁇ , such as from about 5 ⁇ to about 50 ⁇ , such as from about 5 ⁇ to about 30 ⁇ . Generally, metal oxide bulk layer 232 may have a thickness within a range from about 5 ⁇ to about 100 ⁇ , such as from about 10 ⁇ to about 80 ⁇ , such as from about 15 ⁇ to about 50 ⁇ .
- metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk laminate 250 , as depicted in FIG. 2E .
- a plurality of metal-rich oxide layers 252 and 254 are contained within metal oxide bulk laminate 250 .
- Metal-rich oxide layer 252 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95, while metal-rich oxide layer 254 may substantially contain M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- a method for fabricating a resistive switching memory device or element includes forming metal oxide film stack 230 at step 130 of process 100 on or over lower electrode 220 disposed on substrate 210 , wherein metal oxide film stack 230 contains metal oxide buffer laminate 240 disposed on or over metal oxide bulk laminate 250 .
- the method further includes forming metal oxide bulk laminate 250 by sequentially providing a first metal source gas and a first oxidizing agent while forming a first metal-rich oxide layer, such as metal-rich oxide layer 252 , during a first step of a metal-rich oxidizing ALD process, wherein metal-rich oxide layer 252 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method further includes sequentially providing a second metal source gas and the first oxidizing agent while forming a second metal-rich oxide layer, such as metal-rich oxide layer 254 , on or over metal-rich oxide layer 252 during a second step of the metal-rich oxidizing ALD process, wherein metal-rich oxide layer 254 may substantially contain M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the method further includes repeating the first and second steps of the metal-rich ALD process while forming a plurality of the first and second metal-rich oxide layers, such as metal-rich oxide layers 252 and 254 , contained within metal oxide bulk laminate 250 .
- the method further includes forming metal oxide buffer laminate 240 by sequentially providing the first metal source gas and a second oxidizing agent while forming a first metal-poor oxide layer, such as metal-poor oxide layer 242 , during a first step of a metal-poor oxidizing ALD process, wherein metal-poor oxide layer 242 may substantially contain MO x , where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- the method further includes sequentially providing the second metal source gas and the second oxidizing agent while forming a second metal-poor oxide layer, such as metal-poor oxide layer 244 , on metal-poor oxide layer 242 during a second step of the metal-poor oxidizing ALD process, wherein metal-poor oxide layer 244 may substantially contain M′O 2 , where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- the method during step 130 further includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of the first and second metal-poor oxide layers, such as metal-poor oxide layers 242 and 244 , contained within metal oxide buffer laminate 240 .
- the metal-poor oxidizing (second) ALD process includes sequentially pulsing, introducing, or otherwise providing a metal source gas and an oxidizing agent, such as ozone, into the deposition chamber and exposing the exposed surface of the processing substrate.
- a metal source gas and an oxidizing agent such as ozone
- the metal source gas and the oxidizing agent may be sequentially pulsed, introduced, or otherwise provided during the metal-poor oxidizing (second) ALD process.
- the metal-poor oxidizing (second) ALD process provides that the metal source gas may contain a tetrakis(dialkylamino) metal compound, where the metal is hafnium or zirconium and the oxidizing agent may contain ozone.
- the tetrakis(dialkylamino) metal compound may be a tetrakis(dialkylamino) hafnium compound, such as tetrakis(dimethylamino) hafnium.
- the tetrakis(dialkylamino) metal compound may be a tetrakis(dialkylamino) zirconium compound, such as tetrakis(dimethylamino) zirconium.
- the metal-rich oxidizing (first) ALD process includes sequentially pulsing, introducing, or otherwise providing a metal source gas and an oxidizing agent, wherein the oxidizing agent may be different than the oxidizing agent utilized during the metal-poor oxidizing (second) ALD process.
- the oxidizing agent may contain or be water during the metal-rich oxidizing (first) ALD process while the oxidizing agent may contain or be ozone during the metal-poor oxidizing (second) ALD process.
- metal oxide film stack 230 may be deposited or otherwise formed using a variety of deposition techniques, but in many embodiments described herein, all of the materials and/or layers of metal oxide film stack 230 may be deposited using thermal ALD processes and/or plasma-enhanced ALD (PE-ALD).
- PE-ALD plasma-enhanced ALD
- a metal-rich oxide material may be formed by a metal-rich oxidizing (first) ALD process utilizing water and a metal-poor oxide material may be formed by a metal-poor oxidizing (second) ALD process utilizing an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof.
- the ALD processes described herein may include heating the substrate or the substrate carrier/pedestal to a deposition temperature within a range from about 50° C. to about 500° C., such as from about 200° C. to about 350° C., such as from about 250° C. to about 300° C.
- the deposition temperature during a metal-poor oxidizing (second) ALD process may be about 275° C.
- the deposition temperature during a metal-rich oxidizing (first) ALD process may be about 250° C.
- a method of process 100 for forming memory device 200 on the surface of substrate 210 includes forming lower electrode 220 containing polysilicon disposed on or over substrate 210 (step 110 ), optionally forming silicon oxide layer 222 on or over lower electrode 220 (step 120 ), forming metal oxide film stack 230 on or over silicon oxide layer 222 and/or lower electrode 220 (step 130 ), optionally annealing the substrate, depositing upper electrode 260 on or over metal oxide film stack 230 (step 140 ), and optionally annealing the substrate (step 145 ), such as a post electrode anneal.
- Metal oxide film stack 230 generally contains at least one metal oxide buffer layer 234 and optionally, may contain additionally layers.
- lower electrode 220 contains an n-type polysilicon material and upper electrode 260 contains titanium nitride or derivative thereof.
- FIG. 2A depicts memory device 200 containing metal oxide film stack 230 disposed between at least two electrodes, such as lower electrode 220 and upper electrode 260 , and lower electrode 220 is disposed or otherwise supported on substrate 210 .
- Substrate 210 supports lower electrode 220 while depositing and forming each of the layers within memory device 200 —and for subsequent manufacturing processes.
- Substrate 210 may be wafer or other substrate and contain silicon, doped silicon, Group III-V materials (e.g., GaAs), or derivates thereof. In most examples described herein, substrate 210 is a crystalline silicon wafer that may be doped with a dopant element.
- Lower electrode 220 may contain a doped silicon material, for example p-type or n-type (N+) doped polysilicon. Lower electrode 220 may be deposited or otherwise formed on or over substrate 210 during step 110 .
- Lower electrode 220 and upper electrode 260 may independently contain or be formed of one material or multiple materials and generally contain or formed of different conductive materials relative to each other. Numerous exemplary electrode materials that may be useful for lower electrode 220 and upper electrode 260 are provided in the written description herein. These electrode materials are only exemplary and should not be limited in scope relative to the variety of materials that may be independently contained within lower electrode 220 and upper electrode 260 . In some embodiments, lower electrode 220 and upper electrode 260 have work functions that differ by an energy level within a range from about 0.1 eV to about 1 eV, such as, from about 0.4 eV to about 0.6 eV.
- lower electrode 220 may contain a n-type polysilicon material which has a work function within a range from about 4.1 eV to about 4.15 eV and upper electrode 260 may contain a titanium nitride material which has a work function within a range from about 4.5 eV to about 4.6 eV.
- exemplary electrode materials that may be contained within lower electrode 220 and/or upper electrode 260 include p-type polysilicon (about 4.9 eV to about 5.3 eV), transition metals, transition metal alloys, transition metal nitrides, transition metal carbides, tungsten (about 4.5 eV to about 4.6 eV), tantalum nitride (about 4.7 eV to about 4.8 eV), molybdenum oxide (about 5.1 eV), molybdenum nitride (about 4.0 eV to about 5.0 eV), iridium (about 4.6 eV to about 5.3 eV), iridium oxide (about 4.2 eV), ruthenium (about 4.7 eV), and ruthenium oxide (about 5.0 eV).
- p-type polysilicon about 4.9 eV to about 5.3 eV
- transition metals transition metal alloys
- transition metal nitrides transition metal carbides
- tungsten about
- exemplary electrode materials for lower electrode 220 and/or upper electrode 260 include a titanium/aluminum alloy (about 4.1 eV to about 4.3 eV), nickel (about 5.0 eV), tungsten nitride (about 4.3 eV to about 5.0 eV), tungsten oxide (about 5.5 eV to about 5.7 eV), aluminum (about 4.2 eV to about 4.3 eV), copper or silicon-doped aluminum (about 4.1 eV to about 4.4 eV), copper (about 4.5 eV), hafnium carbide (about 4.8 eV to about 4.9 eV), hafnium nitride (about 4.7 eV to about 4.8 eV), niobium nitride (about 4.95 eV), tantalum carbide (about 5.1 eV), tantalum silicon nitride (about 4.4 eV), titanium (about 4.1 eV to about 4.4 eV), vanadium carbide
- upper electrode 260 may contain metals, metal carbides, metal oxides, or metal nitrides, which include, for example, platinum, palladium, ruthenium, ruthenium oxide, iridium, iridium oxide, titanium, titanium nitride, tungsten, tungsten oxide, tungsten nitride, tungsten carbide, tantalum, tantalum oxide, tantalum nitride, tantalum silicon nitride, tantalum carbide, molybdenum, molybdenum oxide, molybdenum nitride, titanium aluminum alloys, nickel, aluminum, doped aluminum, aluminum oxide, copper, hafnium carbide, hafnium nitride, niobium nitride, vanadium carbide, vanadium nitride, zirconium nitride, derivatives thereof, or combinations thereof.
- Memory device 200 containing upper electrode 260 deposited, formed, or otherwise disposed on or over metal oxide film stack 230 may optionally be exposed to a second annealing process, such as a post electrode anneal, during step 145 of process 100 .
- the post electrode anneal occurs subsequent to the formation of upper electrode 260 .
- memory device 200 including upper electrode 260 and metal oxide film stack 230 , may be heated to an annealing temperature within a range from about 400° C. to about 1,200° C., such as from about 500° C. to about 900° C., or from about 700° C. to about 800° C., for example, about 750° C.
- memory device 200 may be heated for a time period within a range from about 10 seconds to about 5 minutes, such as from about 20 seconds to about 4 minutes, or from about 40 seconds to about 2 minutes during the post upper electrode anneal of step 145 .
- the post electrode anneal may be conducted within an annealing chamber, vacuum chamber, deposition chamber, or other processing chamber that provides heat to the layers contained within memory device 200 , such as metal oxide film stack 230 and upper electrode 260 .
- memory device 200 containing upper electrode 260 may be heated to an annealing temperature within a range from about 700° C. to about 800° C. for a time period within a range from about 40 seconds to about 2 minutes during the post upper electrode anneal at step 145 .
- the annealing temperature of about 750° C. for about 1 minute is used during the annealing process.
- FIG. 3 depicts a memory array 300 of resistive switching memory devices 310 , as described by embodiments herein.
- Each memory device 310 contains at least one switching memory element 312 , and may contain multiple switching memory elements 312 .
- memory devices 310 may be a plurality of memory devices 200 , depicted in FIG. 2A .
- Each memory device 200 may independently contain any of the metal oxide film stacks 230 illustrated in FIGS. 2B-2E .
- Memory array 300 may be part of a larger memory device or other integrated circuit structure, such as a system on a chip type device. Read and write circuitry is connected to switching memory devices 310 using electrodes 322 and electrodes 324 .
- Electrodes such as upper electrodes 322 and lower electrodes 324 , are sometimes referred to as word lines and bit lines, and are used to read and write data into the memory elements 312 in the switching memory devices 310 .
- Individual switching memory devices 310 or groups of switching memory devices 310 can be addressed using appropriate sets of electrodes 322 and 324 .
- the memory elements 312 in the switching memory devices 310 may be formed from a plurality of layers 314 a , 314 b , 314 c , and 314 d containing various materials, as indicated schematically in FIG. 3 .
- memory arrays such as memory array 300 can be stacked in a vertical fashion to make multilayer memory array structures.
- resistive-switching memory elements/devices generally have a structure in which resistive-switching insulating layers are surrounded by two conductive electrodes.
- memory elements may have electrodes of different materials (e.g., one electrode containing a doped silicon material and the other electrode containing a titanium nitride material) surrounding a resistive-switching layer of a metal oxide (e.g., hafnium oxide) having a thickness within a range from about 20 ⁇ to about 100 ⁇ , and a coupling layer that is substantially thinner than the resistive-switching layer (e.g., less than 25% the thickness of the resistive-switching layer).
- a metal oxide e.g., hafnium oxide
- the coupling layer may be a metallic material such as titanium. Memory elements including the coupling layer have exhibited improved switching characteristics (e.g., lower set, reset, and forming voltages, and better retention).
- the resistive-switching layer includes a higher bandgap material (e.g., a material having a bandgap greater than 4 eV such as hafnium oxide, aluminum oxide, tantalum oxide, yttrium oxide, zirconium oxide, cerium oxide, alloys thereof, derivatives thereof, or combinations thereof), however other resistive-switching layers may include materials having a bandgap less than 4 eV (e.g., titanium oxide).
- the exemplary ALD processes for depositing or otherwise forming the metal oxide materials contained within metal oxide film stack 230 and other materials and/or layers contained within memory device 200 are typically conducted in a deposition chamber, such as an ALD chamber.
- the deposition chamber may maintain an internal pressure of less than 760 Torr, such as within the range from about 10 mTorr to about 10 Torr, such as from about 100 mTorr to about 1 Torr, for example, about 350 mTorr.
- the temperature of the substrate or the substrate carrier/pedestal is usually maintained within the range from about 50° C. to about 1,000° C., such as from about 100° C. to about 500° C., such as from about 200° C. to about 400° C., or such as from about 250° C. to about 300° C.
- the metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a flow rate within the range from about 0.1 sccm to about 200 sccm, such as from about 0.5 sccm to about 50 sccm, from about 1 sccm to about 30 sccm, for example, about 10 sccm.
- the metal source gas may be provided along with a carrier gas, such as argon or nitrogen.
- the carrier gas may have a flow rate within the range from about 1 sccm to about 300 sccm, such as from about 2 sccm to about 80 sccm, from about 5 sccm to about 40 sccm, for example, about 20 sccm.
- the metal source gas may be pulsed or otherwise provided into the deposition chamber at a rate within a range from about 0.01 seconds to about 10 seconds, depending on the particular process conditions, metal source gas or desired composition of the deposited metal oxide material.
- the metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 10 seconds, such as from about 1 second to about 5 seconds, for example, about 3 seconds.
- the metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.05 seconds to about 2 seconds, such as from about 0.1 seconds to about 1 second, for example, about 0.5 seconds.
- the metal source gas is a hafnium precursor which is a tetrakis(dialkylamino) hafnium compound, such as tetrakis(dimethylamino) hafnium ((Me 2 N) 4 Hf or TDMAH), tetrakis(diethylamino) hafnium ((Et 2 N) 4 Hf or TDEAH), or tetrakis(ethylmethylamino) hafnium ((EtMeN) 4 Hf or TEMAH).
- tetrakis(dialkylamino) hafnium compound such as tetrakis(dimethylamino) hafnium ((Me 2 N) 4 Hf or TDMAH), tetrakis(diethylamino) hafnium ((Et 2 N) 4 Hf or TDEAH), or tetrakis(ethylmethylamino) hafnium ((EtM
- the metal source gas is generally dispensed into a deposition chamber by introducing a carrier gas through an ampoule containing the metal source or precursor.
- An ampoule unit may include an ampoule, a bubbler, a canister, a cartridge, or other container used for storing, containing, or dispersing chemical precursors.
- the ampoule may contain a liquid precursor (e.g., TDMAH or TDEAH) and be part of a liquid delivery system containing injector valve system used to vaporize the liquid precursor with a heated carrier gas.
- the ampoule may be heated to a temperature of about 100° C. or less, such as within a range from about 30° C. to about 90° C., for example, about 50° C.
- the oxidizing agent (e.g., O 2 , O 3 , H 2 O) may be pulsed, introduced, or otherwise provided into the deposition chamber at a flow rate within a range from about 0.01 seconds to about 10 seconds, depending on the particular process conditions, oxygen source gas or oxidizing agent or desired composition of the deposited metal oxide material.
- the oxidizing agent may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.001 seconds to about 1 second, such as from about 0.001 seconds to about 0.1 seconds, for example, about 0.05 seconds.
- the oxidizing agent may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.5 second to about 10 seconds, such as from about 1 second to about 3 seconds, for example, about 2 seconds.
- the oxidizing agent may contain or be formed of or generated from an oxygen source that includes oxygen (O 2 ), atomic oxygen (O), ozone (O 3 ), nitrous oxide (N 2 O), nitric oxide (NO), nitrogen dioxide (NO 2 ), dinitrogen pentoxide (N 2 O 5 ), hydrogen peroxide (H 2 O 2 ), derivatives thereof, plasmas thereof, or combinations thereof.
- Ozone may be formed inside or outside of the deposition chamber, such as the ALD chamber.
- the oxidizing agent contains ozone formed by an ozone generator positioned outside of the interior of the deposition chamber. Ozone is generated and then flowed or directed into the deposition chamber and exposed along with the metal source gas to the substrate surface.
- the oxidizing agent contains ozone formed by a plasma generated within the interior of the deposition chamber. Oxygen gas flowed or directed into the deposition chamber, then ignited or formed into ozone and/or atomic oxygen before being sequentially exposed along with the metal source gas to the substrate surface.
- a carrier gas or a purge gas may be provided at the same time as the metal source gas and/or the oxygen source, but is also provided between the pulses of the metal source gas and/or the oxygen source.
- the carrier gas or purge gas may continuous flow during the ALD process or may be intermediately and/or sequentially pulsed, introduced, or otherwise provided during the ALD.
- the carrier gas or purge gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 30 seconds, depending on the particular process conditions, source gases, or desired composition of the deposited metal oxide material.
- the carrier gas or a purge gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 30 seconds, such as from about 2 seconds to about 20 seconds, for example, about 10 seconds or about 15 seconds.
- the carrier gas or purge gas may contain nitrogen, argon, helium, hydrogen, a forming gas, oxygen, mixtures thereof, or combinations thereof.
- the carrier gas or the purge gas may be sequentially pulsed, introduced, or otherwise provided after each pulse of the metal source gas and each pulse of the oxidizing agent during the ALD cycle.
- the pulses of purge gas or carrier gas are typically pulsed, introduced, or otherwise provided at a flow rate within a range from about 2 standard liters per minute (slm) to about 22 slm, such as about 10 slm.
- the specific purge gas flow rates and duration of process cycles are obtained through experimentation. In one example, a 300 mm diameter wafer requires about twice the flow rate for the same duration as a 200 mm diameter wafer in order to maintain similar throughput.
- Precursors at ambient temperature and pressure may be gas, liquid, or solid. However, volatilized precursors are used within the ALD chamber.
- Organic-metallic compounds contain at least one metal atom and at least one organic-containing functional group, such as amides, alkyls, alkoxyls, alkylaminos, anilides, or derivatives thereof. Precursors may include organic-metallic, organometallic, inorganic, or halide compounds.
- the metal source gas is formed from or contains a tetrakis(dialkylamino) metal compound, such as a tetrakis(dialkylamino) hafnium compound or a tetrakis(dialkylamino) zirconium compound.
- Tetrakis(dialkylamino) metal compounds are useful for depositing metal oxides contained within metal oxide film stack 230 and other materials and/or layers within memory device 200 during ALD processes.
- the metal source gas contains or is formed from exemplary hafnium precursors which include hafnium compounds containing ligands such as halides, alkylaminos, cyclopentadienyls, alkyls, alkoxides, derivatives thereof, or combinations thereof.
- hafnium alkylamino compounds useful as hafnium precursors include tetrakis(dialkylamino) hafnium compounds, such as (RR′N) 4 Hf, where R or R′ are independently hydrogen, methyl, ethyl, propyl, or butyl.
- Hafnium halide compounds useful as hafnium precursors may include HfCl 4 , HfI 4 , and HfBr 4 .
- Exemplary hafnium precursors useful for depositing hafnium oxides and other hafnium-containing materials contained within metal oxide film stack 230 and other materials and/or layers within memory device 200 during ALD processes include (Et 2 N) 4 Hf, (Me 2 N) 4 Hf, (MeEtN) 4 Hf, ( t BuC 5 H 4 ) 2 HfCl 2 , (C 5 H 5 ) 2 HfCl 2 , (EtC 5 H 4 ) 2 HfCl 2 , (Me 5 C 5 ) 2 HfCl 2 , (Me 5 C 5 )HfCl 3 , ( i PrC 5 H 4 ) 2 HfCl 2 , ( i PrC 5 H 4 )HfCl 3 , ( t BuC 5 H 4 ) 2 HfMe 2 , (acac) 4 Hf, (hfac) 4 Hf, (tfac) 4 Hf, (thd) 4 Hf, (
- the metal source gas contains or is formed from exemplary zirconium precursors which include zirconium compounds containing ligands such as halides, alkylaminos, cyclopentadienyls, alkyls, alkoxides, derivatives thereof, or combinations thereof.
- zirconium alkylamino compounds useful as zirconium precursors include tetrakis(dialkylamino) zirconium compounds, such as (RR′N) 4 Zr, where R or R′ are independently hydrogen, methyl, ethyl, propyl, or butyl.
- Zirconium halide compounds useful as zirconium precursors may include ZrCl 4 , ZrI 4 , and ZrBr 4 .
- Exemplary zirconium precursors useful for depositing zirconium oxides and other zirconium-containing materials contained within metal oxide film stack 230 and other materials and/or layers within memory device 200 during ALD processes include (Et 2 N) 4 Zr, (Me 2 N) 4 Zr, (MeEtN) 4 Zr, ( t BuC 5 H 4 ) 2 ZrCl 2 , (C 5 H 5 ) 2 ZrCl 2 , (EtC 5 H 4 ) 2 ZrCl 2 , (Me 5 C 5 ) 2 ZrCl 2 , (Me 5 C 5 )ZrCl 3 , ( i PrC 5 H 4 ) 2 ZrCl 2 , ( i Pr 5 H 4 )ZrCl 3 , ( t BuC 5 H 4 ) 2 ZrMe 2 , (acac) 4 Zr, (hfac) 4 Zr, (tfac) 4 Zr, (thd) 4 Zr, (NO
- the ALD processes are provided as exemplary ALD processes and should not be limited in scope relative to the variety of ALD processes that may be useful for depositing or otherwise forming the metal oxide materials contained within metal oxide film stack 230 and other materials and/or layers contained within memory device 200 .
- Chemical precursors, carrier gases, pulse times, exposure times, flow rates, temperatures, pressures, sequence orders, and other variables may be adjusted accordingly in order to form the desired thickness and stoichiometry of the metal oxide materials contained within metal oxide film stack 230 and other materials and/or layers contained within memory device 200 .
- “Atomic layer deposition” refers to the sequential introduction of two or more reactive compounds to deposit a layer of material on a substrate surface.
- the two, three or more reactive compounds may alternatively be introduced into a reaction zone of a deposition chamber.
- each reactive compound is separated by a time delay to allow each compound to adhere and/or react on the substrate surface.
- a first precursor or compound A is pulsed into the reaction zone followed by a first time delay.
- a second precursor or compound B is pulsed into the reaction zone followed by a second delay.
- a purge gas such as argon or nitrogen
- the purge gas may flow continuously throughout the deposition process so that only the purge gas flows during the time delay between pulses of reactive compounds.
- the reactive compounds are alternatively pulsed until a desired film or film thickness is formed on the substrate surface.
- the ALD process of pulsing compound A, purge gas, pulsing compound B and purge gas is a cycle.
- a cycle can start with either compound A or compound B and continue the respective order of the cycle until achieving a film with the desired thickness.
- a “pulse” as used herein is intended to refer to a quantity of a particular compound that is intermittently or non-continuously introduced into a reaction zone of a processing chamber.
- the quantity of a particular compound within each pulse may vary over time, depending on the duration of the pulse.
- the duration of each pulse is variable depending upon a number of factors such as, for example, the volume capacity of the deposition chamber employed, the vacuum system coupled thereto, and the volatility/reactivity of the particular compound itself.
- a “half-reaction” as used herein is intended to refer to a pulse of precursor step followed by a purge step.
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Abstract
Embodiments of the invention generally relate to nonvolatile memory devices and methods for manufacturing such memory devices. The methods for forming improved memory devices, such as a ReRAM cells, provide optimized, atomic layer deposition (ALD) processes for forming a metal oxide film stack having a metal oxide buffer layer disposed on or over a metal oxide bulk layer. The metal oxide bulk layer contains a metal-rich oxide material and the metal oxide buffer layer contains a metal-poor oxide material. The metal oxide bulk layer is less electrically resistive than the metal oxide buffer layer since the metal oxide bulk layer is less oxidized or more metallic than the metal oxide buffer layer. In one example, the metal oxide bulk layer contains a metal-rich hafnium oxide material and the metal oxide buffer layer contains a metal-poor zirconium oxide material.
Description
- This application is a continuation claiming priority to U.S. patent application Ser. No. 13/236,481, filed 19 Sep. 2011, which is entirely incorporated by reference herein for all purposes.
- 1. Field of the Invention
- Embodiments of the invention generally relate to memory devices and methods for manufacturing such memory devices.
- 2. Description of the Related Art
- Nonvolatile memory elements are used in systems in which persistent storage is required. For example, digital cameras use nonvolatile memory cards to store images and digital music players use nonvolatile memory to store audio data. Nonvolatile memory is also used to persistently store data in computer environments. Nonvolatile memory is often formed using electrically-erasable programmable read only memory (EPROM) technology. This type of nonvolatile memory contains floating gate transistors that can be selectively programmed or erased by application of suitable voltages to their terminals.
- As fabrication techniques improve, it is becoming possible to fabricate nonvolatile memory elements with increasingly smaller dimensions. However, as device dimensions shrink, scaling issues are posing challenges for traditional nonvolatile memory technology. This has led to the investigation of alternative nonvolatile memory technologies, including resistive switching nonvolatile memory.
- Resistive switching nonvolatile memory is formed using memory elements that have two or more stable states with different resistances. Bistable memory has two stable states. A bistable memory element can be placed in a high resistance state or a low resistance state by application of suitable voltages or currents. Voltage pulses are typically used to switch the memory element from one resistance state to the other. Nondestructive read operations can be performed to ascertain the value of a data bit that is stored in a memory cell.
- Resistive switching based on transition metal oxide switching elements formed of metal oxide films has been demonstrated. Although metal oxide films such as these exhibit bistability, the resistance of these films and the ratio of the high-to-low resistance states are often insufficient to be of use within a practical nonvolatile memory device. For instance, the resistance states of the metal oxide film should preferably be significant as compared to that of the system (e.g., the memory device and associated circuitry) so that any change in the resistance state change is perceptible. The variation of the difference in resistive states is related to the resistance of the resistive switching layer. Therefore, a low resistance metal oxide film may not form a reliable nonvolatile memory device. For example, in a nonvolatile memory that has conductive lines formed of a relatively high resistance metal such as tungsten, the resistance of the conductive lines may overwhelm the resistance of the metal oxide resistive switching element. Therefore, the state of the bistable metal oxide resistive switching element may be difficult or impossible to sense.
- Similar issues can arise from integration of the resistive switching memory element with current steering elements, such as diodes and/or resistors. The resistance of the resistive switching memory element (at least in its high resistance state) is preferably significant compared to the resistance of the current steering elements, so that the unvarying resistance of the current steering element does not dominate the resistance of the switching memory element, and thus reduce the measurable difference between the “on” and “off” states of the formed memory device (e.g., logic states of the device). However, since the power that can be delivered to a circuit containing a series of resistive switching memory elements and current steering elements is typically limited in most conventional nonvolatile memory devices (e.g., CMOS driven devices), it is desirable to form each of the resistive switching memory elements and current steering elements in the circuit so that the voltage drop across each of these elements is small, and thus resistance of the series connected elements does not cause the current to decrease to an undesirable level due to the fixed applied voltage (e.g., about 2-5 volts).
- As nonvolatile memory device sizes shrink, it is important to reduce the required currents and voltages that are necessary to reliably set, reset and/or determine the desired “on” and “off” states of the device to minimize resistive heating of the device and cross-talk between adjacent devices. Moreover, in cases where multiple formed memory devices are interconnected to each other and to other circuit elements it is desirable to minimize the device performance variation between one device to the next to assure that the performance of the formed circuit performs in a desirable manner.
- Current ReRAM structures use thin film stacks of insulator materials, such as metal oxides (e.g., hafnium oxide) between metal electrodes to form a device that can be switched between two different stable resistance states by the application of appropriate voltages. In one class of cells, specifically bipolar ReRAMs, the switching is enabled by the back and forth movement of charged oxygen vacancies between the electrodes under the influence of the applied electrical field. In order for the cell to be able to switch reproducibly for many thousands of cycles, it is necessary that there always be a sufficient concentration of vacancies in the bulk of the metal oxide film. The interface between the electrode and the metal oxide bulk film is a region in which vacancies may be trapped and eventually be removed from the metal oxide bulk film. This is especially true when reactive metal surfaces or boundary regions have large structural changes relative to the metal oxide bulk film.
- Therefore, there is a need for an effective interface that is separate from the electrode interface but does not substantially alter the switching properties of the metal oxide bulk film, as well as a need for an efficient and controllable process to form such metal oxide bulk film for a nonvolatile memory device.
- Embodiments of the invention generally relate to nonvolatile memory devices and methods for manufacturing such memory devices. The methods for forming improved memory devices, such as a ReRAM cells, provide optimized, atomic layer deposition (ALD) processes for forming a metal oxide film stack which contains a metal oxide buffer layer (e.g., metal-poor oxide, such that the metal is completely oxidized or substantially oxidized) disposed on or over a metal oxide bulk layer (e.g., metal-rich oxide, such that the metal is less oxidized than the metal-poor oxide). Therefore, the metal oxide bulk layer containing a metal-rich oxide material is less electrically resistive than the metal oxide buffer layer containing a metal-poor oxide material since the metal oxide bulk layer is less oxidized or more metallic than the metal oxide buffer layer. In one example, the metal oxide bulk layer contains a metal-rich hafnium oxide material and the metal oxide buffer layer contains a metal-poor zirconium oxide material. In another example, the metal oxide bulk layer contains a metal-rich zirconium oxide material and the metal oxide buffer layer contains a metal-poor hafnium oxide material.
- The described ALD processes are techniques for depositing ultra-thin metal oxide films due to practical advantages which includes simple and accurate thickness control, excellent reproducibility and uniformity, and capability to produce conformal films at sharp interfaces and trenches with high aspect ratio. By optimizing the ratio of metal precursor gas to oxidizer pulses, metal oxide materials can be made metal-rich or metal-poor (metal deficient), which in turn tailors the oxygen defect content and type (vacancy vs. interstitial), resulting in an enhancement or reduction in defect density to facilitate carrier transport.
- In many embodiments, a method for fabricating a resistive switching memory element, such as a memory device, is provided and includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack contains a metal oxide buffer layer disposed on or over a metal oxide bulk layer. In some embodiments of the method, the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. The method further provides depositing the metal oxide buffer layer over the metal oxide bulk layer during a second ALD process, wherein the metal oxide buffer layer substantially contains M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- In some examples described herein, the metal oxide bulk layer substantially contains a metal-rich hafnium oxide which has the chemical formula of HfOx, where x is within a range from about 1.70 to about 1.90, and the metal oxide buffer layer substantially contains a metal-poor, zirconium oxide material having the chemical formula of ZrO2. In other examples described herein, the metal oxide bulk layer substantially contains a metal-rich zirconium oxide which has the chemical formula of ZrOx, where x is within a range from about 1.70 to about 1.90, and the metal oxide buffer layer substantially contains a metal-poor, hafnium oxide material which has the chemical formula of HfO2. In additional examples, the metal oxide bulk layer contains a metal-rich oxide material which has the chemical formula of HfOx or ZrOx, where x is within a range from about 1.65 to about 1.95, such as from about 1.70 to about 1.90, such as from about 1.75 to about 1.85, for example, about 1.80. The metal oxide bulk layer may have a thickness within a range from about 5 Å to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å. The metal oxide buffer layer may have a thickness within a range from about 2 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 15 Å.
- In other embodiments, the first ALD process includes sequentially providing a metal source gas and an oxidizing agent during a metal-rich oxidizing ALD process. In some examples, the metal source gas may contain a tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process. For example, the tetrakis(dialkylamido) hafnium compound may be tetrakis(dimethylamido) hafnium. In other examples, the metal source gas may contain a tetrakis(dialkylamido) zirconium compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process. For example, the tetrakis(dialkylamido) zirconium compound may be tetrakis(dimethylamido) zirconium. In one embodiment described herein, the substrate may be maintained at a deposition temperature or a substrate temperature within a range from greater than 0° C. to about 20° C., such as from greater than 0° C. to about 15° C., such as from greater than 0° C. to about 10° C., such as from greater than 0° C. to about 5° C., for example about 1° C. during the metal-rich oxidizing ALD process.
- In other embodiments, the second ALD process includes sequentially providing a metal source gas and an oxidizing agent during a metal-poor oxidizing ALD process. In some examples, the metal source gas may contain the tetrakis(dialkylamido) zirconium compound and the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof during the metal-poor oxidizing ALD process. In other examples, the metal source gas may contain the tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain the activated oxygen agent during the metal-poor oxidizing ALD process.
- In some embodiments, the method further provides forming a silicon oxide layer on or over the lower electrode, and subsequently, forming the metal oxide bulk layer on or over the silicon oxide layer. The silicon oxide layer contains a silicon oxide material, such as native silicon oxides, silicon dioxide, dopant variants thereof, or combinations thereof. The silicon oxide layer may have a thickness within a range from about 2 Å to about 40 Å, such as from about 2 Å to about 20 Å, such as from about 5 Å to about 10 Å.
- In another embodiment described herein, a method for fabricating a resistive switching memory element is provided and includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack may contain a doped-metal oxide buffer layer disposed on or over a metal oxide bulk layer. The method provides that the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. The method includes depositing the doped-metal oxide buffer layer over the metal oxide bulk layer during a second ALD process, wherein the doped-metal oxide buffer layer substantially contains MM1O4 or a mixture of MO2 and M′O2, where M is the same metal selected for the metal oxide bulk layer, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- In many examples, the doped-metal oxide buffer layer substantially contains a mixture of MO2 and M′O2, wherein M is hafnium and M′ is zirconium. The doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 0.25 at % (atomic percent) to about 25 at % and hafnium oxide at a concentration within a range from about 75 at % to about 99.75 at %. In some examples, the doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 0.5 at % to about 20 at % and hafnium oxide at a concentration within a range from about 80 at % to about 99.5 at %. In other examples, the doped-metal oxide buffer layer may contain zirconium oxide at a concentration within a range from about 1 at % to about 15 at % and hafnium oxide at a concentration within a range from about 85 at % to about 99 at %.
- In other examples, the doped-metal oxide buffer layer substantially contains a mixture of MO2 and M′O2, wherein M is zirconium and M′ is hafnium. The doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 0.25 at % to about 25 at % and zirconium oxide at a concentration within a range from about 75 at % to about 99.75 at %. In some examples, the doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 0.5 at % to about 20 at % and zirconium oxide at a concentration within a range from about 80 at % to about 99.5 at %. In other examples, the doped-metal oxide buffer layer may contain hafnium oxide at a concentration within a range from about 1 at % to about 15 at % and zirconium oxide at a concentration within a range from about 85 at % to about 99 at %.
- In some embodiments, the doped-metal oxide buffer layer may have a thickness within a range from about 2 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 30 Å. The metal oxide bulk layer may have a thickness within a range from about 5 Å to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å.
- In another embodiment, the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a metal-poor oxide layer during a deposition step of a metal-poor oxidizing ALD process, and subsequently doping the metal-poor oxide layer while forming the doped-metal oxide buffer layer during a doping step of the metal-poor oxidizing ALD process. The method may further include repeating the deposition and doping steps of the metal-poor oxidizing ALD process while forming the doped-metal oxide buffer layer. The metal-poor oxide layer may be exposed to a second metal source gas and the oxidizing agent during the doping step of the metal-poor oxidizing ALD process.
- In another embodiment described herein, a method for fabricating a resistive switching memory element is provided and includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack contains a metal oxide buffer laminate disposed on or over a metal oxide bulk layer. The method further provides that the metal oxide film stack may be formed by depositing the metal oxide bulk layer over the lower electrode during a first ALD process, wherein the metal oxide bulk layer substantially contains MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. The method also provides depositing the metal oxide buffer laminate over the metal oxide bulk layer during a second ALD process, wherein the metal oxide buffer laminate substantially contains a plurality metal-poor oxide layers of MO2 and M′O2, where M is the same metal selected for the metal oxide bulk layer, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
- In many examples, the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a first metal-poor oxide layer during a first step of a metal-poor oxidizing ALD process, and subsequently, sequentially providing a second metal source gas and the oxidizing agent while forming a second metal-poor oxide layer on the first metal-poor layer during a second step of the metal-poor oxidizing ALD process. The method further provides repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of first and second metal-poor oxide layers contained within the metal oxide buffer laminate. Each of the first and second metal source gases may independently contain an organic-metallic compound. In some examples, the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof. Each of the metal-poor oxide layers may independently have a thickness within a range from about 2 Å to about 20 Å, such as from about 2 Å to about 10 Å, such as from about 3 Å to about 7 Å, for example, about 5 Å. Also, the metal oxide buffer laminate may have a thickness within a range from about 2 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 30 Å. The metal oxide bulk layer may have a thickness within a range from about 5 Å to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å.
- In other embodiments described herein, a method for fabricating a resistive switching memory element is provided and includes forming a metal oxide film stack on or over a lower electrode disposed on a substrate, wherein the metal oxide film stack may contain a metal oxide buffer laminate disposed on or over a metal oxide bulk laminate. The method further includes forming the metal oxide bulk laminate by sequentially providing a first metal source gas and a first oxidizing agent while forming a first metal-rich oxide layer during a first step of a metal-rich oxidizing ALD process, wherein the first metal-rich oxide layer substantially contains MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95.
- Subsequently, the method further includes sequentially providing a second metal source gas and the first oxidizing agent while forming a second metal-rich oxide layer on the first metal-rich oxide layer during a second step of the metal-rich oxidizing ALD process, wherein the second metal-rich oxide layer substantially contains MO2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. Thereafter, the method further includes repeating the first and second steps of the metal-rich ALD process while forming a plurality of the first and second metal-rich oxide layers contained within the metal oxide bulk laminate.
- Additionally, the method further includes forming the metal oxide bulk laminate by sequentially providing the first metal source gas and a second oxidizing agent while forming a first metal-poor oxide layer during a first step of a metal-poor oxidizing ALD process, wherein the first metal-poor oxide layer substantially contains MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. Subsequently, the method further includes sequentially providing the second metal source gas and the second oxidizing agent while forming a second metal-poor oxide layer on the first metal-poor oxide layer during a second step of the metal-poor oxidizing ALD process, wherein the second metal-poor oxide layer substantially contains M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. Thereafter, the method further includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of the first and second metal-poor oxide layers contained within the metal oxide buffer laminate.
- So that the manner in which the above recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
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FIG. 1 is a flowchart illustrating a method to form a memory device, as described by embodiments herein; -
FIG. 2A depicts a memory device which may be formed by a method illustrated inFIG. 1 , as described by embodiments herein; -
FIGS. 2B-2E depict various metal oxide film stacks which may be formed within the memory device illustrated inFIG. 2A , as described by other embodiments herein; and -
FIG. 3 depicts a memory array of resistive switching memory devices, as described by another embodiment herein. - To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
- Embodiments of the invention generally relate to nonvolatile memory devices and methods for manufacturing such memory devices. The invention teaches a novel process to form a metal oxide film stacks for an improved ReRAM cell. The metal oxide film stacks contains a metal oxide buffer layer disposed on or over a metal oxide bulk layer, such that the metal in both metal oxide layers are different metals (e.g., Hf vs Zr) and have different states of oxidation, such as metal-rich and metal-poor oxide materials. The metal oxide bulk layer and the metal oxide buffer layer are formed by different ALD processes. In one example, the metal oxide bulk layer contains a metal-rich hafnium oxide material and the metal oxide buffer layer contains a metal-poor zirconium oxide material. In another example, the metal oxide bulk layer contains a metal-rich zirconium oxide material and the metal oxide buffer layer contains a metal-poor hafnium oxide material.
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FIG. 1 is a flowchart illustrating a method for manufacturing or otherwise forming various memory devices, as described by embodiments herein, such asprocess 100 which may be utilized to form resistive switching memory elements/devices, such asmemory device 200, as depicted inFIG. 2A . In one embodiment,process 100 may be used to formmemory device 200 and includes forminglower electrode 220 on or oversubstrate 210 duringstep 110, optionally formingsilicon oxide layer 222 on or overlower electrode 220 duringstep 120, forming metaloxide film stack 230 on or oversilicon oxide layer 222 orlower electrode 220 by ALD processes duringstep 130, depositingupper electrode 260 on or over metaloxide film stack 230 duringstep 140, and optionally annealingmemory device 200 duringstep 145.FIGS. 2B-2E depict a variety of metal oxide film stacks 230 formed by different ALD techniques duringstep 130, as described by embodiments herein. - In many embodiments, a variety of metal oxide film stacks 230, as depicted in
FIGS. 2B-2E , may be formed by different ALD techniques duringstep 130 ofprocess 100, and contained withinmemory device 200 depicted inFIG. 2A . Each of the metal oxide film stacks 230 depicted inFIGS. 2B-2E may be disposed betweenlower electrode 220 andupper electrode 260 ofmemory device 200. Therefore, any of the particular lower layers depicted in each of the metal oxide film stacks 230 may be on or overlower electrode 220. Similarly,upper electrode 260 may be on or over any of the particular upper layers depicted in each of the metal oxide film stacks 230.Silicon oxide layer 222 may be deposited, formed, or otherwise disposed on or overlower electrode 220. - In one embodiment, metal
oxide film stack 230 contains metaloxide buffer layer 234 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2B . Metaloxide bulk layer 232 may substantially contain a metal-rich oxide material having a generic chemical formula of MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. Also, metaloxide buffer layer 234 substantially contains a metal-poor oxide material having a generic chemical formula of M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In another embodiment, metal
oxide film stack 230 contains doped-metaloxide buffer layer 236 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2C . Doped-metaloxide buffer layer 236 substantially contains MM1O4 or a mixture of MO2 and M′O2, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In another embodiment, metal
oxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2D . Metaloxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO2 and M′O2, such as metal-poor oxide layers 242 and 244, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In another embodiment, metal
oxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk laminate 250, as depicted inFIG. 2E . A plurality of metal-rich oxide layers oxide bulk laminate 250. Metal-rich oxide layer 252 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95, while metal-rich oxide layer 254 may substantially contain M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In various embodiments,
process 100 further providesstep 120 which includes optionally formingsilicon oxide layer 222 on or overlower electrode 220, and subsequently, forming metaloxide bulk layer 232 on or oversilicon oxide layer 222, as depicted inFIGS. 2B-2E .Silicon oxide layer 222 contains a silicon oxide material, such as native silicon oxides, silicon dioxide, dopant variants thereof, or combinations thereof.Silicon oxide layer 222 may contain a single layer or multiple layers of the same or different silicon oxide materials. Usually,silicon oxide layer 222 may be continuously formed, deposited, or otherwise disposed on or overlower electrode 220 or other underlying surfaces. Alternatively,silicon oxide layer 222 may also be discontinuously formed, deposited, or otherwise disposed on or overlower electrode 220 or other underlying surfaces.Silicon oxide layer 222 may have a thickness within a range from about 2 Å to about 40 Å, such as from about 2 Å to about 20 Å, such as from about 5 Å to about 10 Å. - In many embodiments, a method for fabricating a resistive switching memory device or element, such as
memory device 200, is provided and includes forming metaloxide film stack 230 on or oversilicon oxide layer 222 orlower electrode 220 disposed onsubstrate 210, wherein metaloxide film stack 230 contains metaloxide buffer layer 234 disposed on or over metaloxide bulk layer 232. Metaloxide bulk layer 232 is less electrically resistive than metaloxide buffer layer 234 since metaloxide bulk layer 232 is less oxidized or more metallic than metaloxide buffer layer 234. Therefore, metaloxide bulk layer 232 is metal-rich and more leaky relative to metaloxide buffer layer 234 which has a metal-poor. - In one embodiment, metal
oxide film stack 230 contains metaloxide buffer layer 234 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2B . Metaloxide film stack 230 may be formed by depositing metaloxide bulk layer 232 overlower electrode 220 during a first ALD process, such as a metal-rich oxidizing ALD process atstep 130 ofprocess 100. Metaloxide bulk layer 232 may substantially contain a metal-rich oxide material having a generic chemical formula of MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. Step 130 ofprocess 100 further provides a method which includes depositing metaloxide buffer layer 234 over metaloxide bulk layer 232 during a second ALD process, such as a metal-poor oxidizing ALD process, wherein metaloxide buffer layer 234 may substantially contain a metal-poor oxide material having a generic chemical formula of M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In some examples described herein, metal
oxide bulk layer 232 may substantially contain a metal-rich, hafnium oxide material having the generic chemical formula of HfOx, where x is within a range from about 1.70 to about 1.90, and metaloxide buffer layer 234 may substantially contain a metal-poor, zirconium oxide material having the generic chemical formula of ZrO2. In other examples described herein, metaloxide bulk layer 232 may substantially contain a metal-rich, zirconium oxide material having the generic chemical formula of ZrOx, where x is within a range from about 1.70 to about 1.90, and metaloxide buffer layer 234 may substantially contain a metal-poor, hafnium oxide material having the generic chemical formula of HfO2. In some additional examples, metaloxide bulk layer 232 substantially contains a metal-rich oxide material having the generic chemical formula of HfOx or ZrOx, where x is within a range from about 1.65 to about 1.95, such as from about 1.70 to about 1.90, such as from about 1.75 to about 1.85, for example, about 1.80. - Metal
oxide bulk layer 232 may have a thickness within a range from about 5 - A to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å. Metal
oxide buffer layer 234 may have a thickness within a range from about 2 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 15 Å. - In other embodiments, the first ALD process, such as the metal-rich oxidizing ALD process, includes sequentially providing a metal source gas and an oxidizing agent into the deposition chamber while sequentially exposing the surfaces of the substrate or device to the chemical reagents/precursors. In some examples, the metal source gas may contain a hafnium precursor, such as a tetrakis(dialkylamido) hafnium compound or a hafnium halide compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process. In one example, the tetrakis(dialkylamido) hafnium compound may be tetrakis(dimethylamido) hafnium or the hafnium halide compound may be hafnium tetrachloride. In other examples, the metal source gas may contain a zirconium precursor, such as a tetrakis(dialkylamido) zirconium compound or a zirconium halide compound and the oxidizing agent may contain water during the metal-rich oxidizing ALD process. For example, the tetrakis(dialkylamido) zirconium compound may be tetrakis(dimethylamido) zirconium or the zirconium halide compound may be zirconium tetrachloride.
- In one embodiment described herein,
substrate 210 and/ormemory device 200 may be maintained at a deposition temperature or a substrate temperature within a range from greater than 0° C. to about 20° C., such as from greater than 0° C. to about 15° C., such as from greater than 0° C. to about 10° C., such as from greater than 0° C. to about 5° C., for example about 1° C. during the metal-rich oxidizing ALD process. - In other embodiments, the second ALD process, such as a metal-poor oxidizing ALD process, includes sequentially providing a metal source gas and an oxidizing agent into the deposition chamber while sequentially exposing the surfaces of the substrate or device to the chemical reagents/precursors. In some examples, the metal source gas may contain the tetrakis(dialkylamido) zirconium compound or the zirconium halide compound and the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof during the metal-poor oxidizing ALD process. In other examples, the metal source gas may contain the tetrakis(dialkylamido) hafnium compound and the oxidizing agent may contain the activated oxygen agent during the metal-poor oxidizing ALD process.
- In another embodiment, metal
oxide film stack 230 contains doped-metaloxide buffer layer 236 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2C . Doped-metaloxide buffer layer 236 substantially contains MM1O4 or a mixture of MO2 and M′O2, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In another embodiment described herein, a method for fabricating a resistive switching memory device or element, such as
memory device 200, is provided and includes forming metaloxide film stack 230 atstep 130 ofprocess 100 on or overlower electrode 220 disposed onsubstrate 210, wherein metaloxide film stack 230 may contain doped-metaloxide buffer layer 236 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2C . The method provides that metaloxide film stack 230 may be formed by depositing metaloxide bulk layer 232 overlower electrode 220 during a first ALD process, such as a metal-rich oxidizing ALD process atstep 130 ofprocess 100. - Metal
oxide bulk layer 232 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. The method includes depositing doped-metaloxide buffer layer 236 over metaloxide bulk layer 232 during a second ALD process, wherein doped-metaloxide buffer layer 236 may substantially contain MM1O4 or a mixture of MO2 and M′O2, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In many examples, doped-metal
oxide buffer layer 236 may substantially contain a mixture of MO2 and M′O2, wherein M is hafnium and M′ is zirconium. Doped-metaloxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 0.25 at % (atomic percent) to about 25 at % and hafnium oxide at a concentration within a range from about 75 at % to about 99.75 at %. In some examples, doped-metaloxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 0.5 at % to about 20 at % and hafnium oxide at a concentration within a range from about 80 at % to about 99.5 at %. In other examples, doped-metaloxide buffer layer 236 may contain zirconium oxide at a concentration within a range from about 1 at % to about 15 at % and hafnium oxide at a concentration within a range from about 85 at % to about 99 at %. - In other examples, doped-metal
oxide buffer layer 236 may substantially contain a mixture of MO2 and M′O2, wherein M is zirconium and M′ is hafnium. Doped-metaloxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 0.25 at % to about 25 at % and zirconium oxide at a concentration within a range from about 75 at % to about 99.75 at %. In some examples, doped-metaloxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 0.5 at % to about 20 at % and zirconium oxide at a concentration within a range from about 80 at % to about 99.5 at %. In other examples, doped-metaloxide buffer layer 236 may contain hafnium oxide at a concentration within a range from about 1 at % to about 15 at % and zirconium oxide at a concentration within a range from about 85 at % to about 99 at %. In some embodiments, doped-metaloxide buffer layer 236 may have a thickness within a range from about 2 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 30 Å. Metaloxide bulk layer 232 may have a thickness within a range from about 5 Å to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å. - In another embodiment, the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a metal-poor oxide layer during a deposition step of a metal-poor oxidizing ALD process, and subsequently doping the metal-poor oxide layer while forming doped-metal
oxide buffer layer 236 during a doping step of the metal-poor oxidizing ALD process. The method may further include repeating the deposition and doping steps of the metal-poor oxidizing ALD process while forming doped-metaloxide buffer layer 236. The metal-poor oxide layer may be exposed to a second metal source gas and the oxidizing agent during the doping step of the metal-poor oxidizing ALD process. - In another embodiment, metal
oxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk layer 232, as depicted inFIG. 2D . Metaloxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO2 and M′O2, such as metal-poor oxide layers 242 and 244, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In another embodiment described herein, a method for fabricating a resistive switching memory device or element, such as
memory device 200, is provided and includes forming metaloxide film stack 230 atstep 130 ofprocess 100 on or overlower electrode 220 disposed onsubstrate 210, wherein metaloxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk layer 232.Process 100 further provides a method for forming metaloxide film stack 230 by depositing metaloxide bulk layer 232 overlower electrode 220 during a first ALD process, wherein metaloxide bulk layer 232 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. The methods ofprocess 100 also provides depositing metaloxide buffer laminate 240 on or over metaloxide bulk layer 232 during a second ALD process, wherein metaloxide buffer laminate 240 may substantially contain a plurality metal-poor oxide layers of MO2 and M′O2, such as metal-poor oxide layers 242 and 244, where M is the same metal selected for metaloxide bulk layer 232, M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In many examples, the second ALD process further includes sequentially providing a first metal source gas and an oxidizing agent while forming a first metal-poor oxide layer, such as metal-
poor oxide layer 242, during a first step of a metal-poor oxidizing ALD process, and subsequently, sequentially providing a second metal source gas and the oxidizing agent while forming a second metal-poor oxide layer, such as metal-poor oxide layer 244, on the first metal-poor layer during a second step of the metal-poor oxidizing ALD process.Process 100 further provides a method which includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of metal-poor oxide layers 242 and 244 contained within metaloxide buffer laminate 240. The first metal source gas and the second metal source gas independently contain the respective metal source precursor, such as an organic-metallic compound. In some examples, the oxidizing agent may contain an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof. - Metal
oxide buffer laminate 240 contains a plurality of sequentially stacked metal-poor oxide layers 242 and 244, such that metaloxide buffer laminate 240 contains at least 2 layers of metal-poor oxide layer 242 sequentially stacked with at least 2 layers of metal-poor oxide layer 244. In some examples, metaloxide buffer laminate 240 contains at least 2 layers of each metal-poor oxide layer poor oxide layer oxide buffer laminate 240 may have a total final thickness within a range from about 5 Å to about 80 Å, such as from about 5 Å to about 50 Å, such as from about 5 Å to about 30 Å. Generally, metaloxide bulk layer 232 may have a thickness within a range from about 5 Å to about 100 Å, such as from about 10 Å to about 80 Å, such as from about 15 Å to about 50 Å. - In another embodiment, metal
oxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk laminate 250, as depicted inFIG. 2E . A plurality of metal-rich oxide layers oxide bulk laminate 250. Metal-rich oxide layer 252 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95, while metal-rich oxide layer 254 may substantially contain M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. - In other embodiments described herein, a method for fabricating a resistive switching memory device or element, such as
memory device 200, is provided and includes forming metaloxide film stack 230 atstep 130 ofprocess 100 on or overlower electrode 220 disposed onsubstrate 210, wherein metaloxide film stack 230 contains metaloxide buffer laminate 240 disposed on or over metaloxide bulk laminate 250. The method further includes forming metaloxide bulk laminate 250 by sequentially providing a first metal source gas and a first oxidizing agent while forming a first metal-rich oxide layer, such as metal-rich oxide layer 252, during a first step of a metal-rich oxidizing ALD process, wherein metal-rich oxide layer 252 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. - Subsequently, during
step 130, the method further includes sequentially providing a second metal source gas and the first oxidizing agent while forming a second metal-rich oxide layer, such as metal-rich oxide layer 254, on or over metal-rich oxide layer 252 during a second step of the metal-rich oxidizing ALD process, wherein metal-rich oxide layer 254 may substantially contain M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. Thereafter, the method further includes repeating the first and second steps of the metal-rich ALD process while forming a plurality of the first and second metal-rich oxide layers, such as metal-rich oxide layers oxide bulk laminate 250. - Additionally, during
step 130, the method further includes forming metaloxide buffer laminate 240 by sequentially providing the first metal source gas and a second oxidizing agent while forming a first metal-poor oxide layer, such as metal-poor oxide layer 242, during a first step of a metal-poor oxidizing ALD process, wherein metal-poor oxide layer 242 may substantially contain MOx, where M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95. - Subsequently, during
step 130, the method further includes sequentially providing the second metal source gas and the second oxidizing agent while forming a second metal-poor oxide layer, such as metal-poor oxide layer 244, on metal-poor oxide layer 242 during a second step of the metal-poor oxidizing ALD process, wherein metal-poor oxide layer 244 may substantially contain M′O2, where M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium. Thereafter, the method duringstep 130 further includes repeating the first and second steps of the metal-poor oxidizing ALD process while forming a plurality of the first and second metal-poor oxide layers, such as metal-poor oxide layers 242 and 244, contained within metaloxide buffer laminate 240. - The metal-poor oxidizing (second) ALD process includes sequentially pulsing, introducing, or otherwise providing a metal source gas and an oxidizing agent, such as ozone, into the deposition chamber and exposing the exposed surface of the processing substrate. In some examples, the metal source gas and the oxidizing agent may be sequentially pulsed, introduced, or otherwise provided during the metal-poor oxidizing (second) ALD process.
- The metal-poor oxidizing (second) ALD process provides that the metal source gas may contain a tetrakis(dialkylamino) metal compound, where the metal is hafnium or zirconium and the oxidizing agent may contain ozone. In some examples, the tetrakis(dialkylamino) metal compound may be a tetrakis(dialkylamino) hafnium compound, such as tetrakis(dimethylamino) hafnium. In other examples, the tetrakis(dialkylamino) metal compound may be a tetrakis(dialkylamino) zirconium compound, such as tetrakis(dimethylamino) zirconium.
- In other embodiments, the metal-rich oxidizing (first) ALD process includes sequentially pulsing, introducing, or otherwise providing a metal source gas and an oxidizing agent, wherein the oxidizing agent may be different than the oxidizing agent utilized during the metal-poor oxidizing (second) ALD process. For example, the oxidizing agent may contain or be water during the metal-rich oxidizing (first) ALD process while the oxidizing agent may contain or be ozone during the metal-poor oxidizing (second) ALD process.
- Some of the materials and/or layers of metal
oxide film stack 230 may be deposited or otherwise formed using a variety of deposition techniques, but in many embodiments described herein, all of the materials and/or layers of metaloxide film stack 230 may be deposited using thermal ALD processes and/or plasma-enhanced ALD (PE-ALD). In one embodiment, a metal-rich oxide material may be formed by a metal-rich oxidizing (first) ALD process utilizing water and a metal-poor oxide material may be formed by a metal-poor oxidizing (second) ALD process utilizing an activated oxygen agent, such as ozone, atomic oxygen, oxygen plasma, derivatives thereof, or combinations thereof. - The ALD processes described herein may include heating the substrate or the substrate carrier/pedestal to a deposition temperature within a range from about 50° C. to about 500° C., such as from about 200° C. to about 350° C., such as from about 250° C. to about 300° C. In one example, the deposition temperature during a metal-poor oxidizing (second) ALD process may be about 275° C. In another example, the deposition temperature during a metal-rich oxidizing (first) ALD process may be about 250° C.
- In one example, a method of
process 100 for formingmemory device 200 on the surface ofsubstrate 210 includes forminglower electrode 220 containing polysilicon disposed on or over substrate 210 (step 110), optionally formingsilicon oxide layer 222 on or over lower electrode 220 (step 120), forming metaloxide film stack 230 on or oversilicon oxide layer 222 and/or lower electrode 220 (step 130), optionally annealing the substrate, depositingupper electrode 260 on or over metal oxide film stack 230 (step 140), and optionally annealing the substrate (step 145), such as a post electrode anneal. Metaloxide film stack 230 generally contains at least one metaloxide buffer layer 234 and optionally, may contain additionally layers. In many examples,lower electrode 220 contains an n-type polysilicon material andupper electrode 260 contains titanium nitride or derivative thereof. -
FIG. 2A depictsmemory device 200 containing metaloxide film stack 230 disposed between at least two electrodes, such aslower electrode 220 andupper electrode 260, andlower electrode 220 is disposed or otherwise supported onsubstrate 210.Substrate 210 supportslower electrode 220 while depositing and forming each of the layers withinmemory device 200—and for subsequent manufacturing processes.Substrate 210 may be wafer or other substrate and contain silicon, doped silicon, Group III-V materials (e.g., GaAs), or derivates thereof. In most examples described herein,substrate 210 is a crystalline silicon wafer that may be doped with a dopant element.Lower electrode 220 may contain a doped silicon material, for example p-type or n-type (N+) doped polysilicon.Lower electrode 220 may be deposited or otherwise formed on or oversubstrate 210 duringstep 110. -
Lower electrode 220 andupper electrode 260 may independently contain or be formed of one material or multiple materials and generally contain or formed of different conductive materials relative to each other. Numerous exemplary electrode materials that may be useful forlower electrode 220 andupper electrode 260 are provided in the written description herein. These electrode materials are only exemplary and should not be limited in scope relative to the variety of materials that may be independently contained withinlower electrode 220 andupper electrode 260. In some embodiments,lower electrode 220 andupper electrode 260 have work functions that differ by an energy level within a range from about 0.1 eV to about 1 eV, such as, from about 0.4 eV to about 0.6 eV. In some examples,lower electrode 220 may contain a n-type polysilicon material which has a work function within a range from about 4.1 eV to about 4.15 eV andupper electrode 260 may contain a titanium nitride material which has a work function within a range from about 4.5 eV to about 4.6 eV. Other exemplary electrode materials that may be contained withinlower electrode 220 and/orupper electrode 260 include p-type polysilicon (about 4.9 eV to about 5.3 eV), transition metals, transition metal alloys, transition metal nitrides, transition metal carbides, tungsten (about 4.5 eV to about 4.6 eV), tantalum nitride (about 4.7 eV to about 4.8 eV), molybdenum oxide (about 5.1 eV), molybdenum nitride (about 4.0 eV to about 5.0 eV), iridium (about 4.6 eV to about 5.3 eV), iridium oxide (about 4.2 eV), ruthenium (about 4.7 eV), and ruthenium oxide (about 5.0 eV). Other exemplary electrode materials forlower electrode 220 and/orupper electrode 260 include a titanium/aluminum alloy (about 4.1 eV to about 4.3 eV), nickel (about 5.0 eV), tungsten nitride (about 4.3 eV to about 5.0 eV), tungsten oxide (about 5.5 eV to about 5.7 eV), aluminum (about 4.2 eV to about 4.3 eV), copper or silicon-doped aluminum (about 4.1 eV to about 4.4 eV), copper (about 4.5 eV), hafnium carbide (about 4.8 eV to about 4.9 eV), hafnium nitride (about 4.7 eV to about 4.8 eV), niobium nitride (about 4.95 eV), tantalum carbide (about 5.1 eV), tantalum silicon nitride (about 4.4 eV), titanium (about 4.1 eV to about 4.4 eV), vanadium carbide (about 5.15 eV), vanadium nitride (about 5.15 eV), and zirconium nitride (about 4.6 eV). For some embodiments described herein, the higher work function electrode receives a positive pulse (as measured compared to a common reference potential) during a reset operation, although other materials and configurations are possible. - In other embodiments, the higher work function electrode receives a negative pulse during a reset operation. In some examples,
upper electrode 260 may contain metals, metal carbides, metal oxides, or metal nitrides, which include, for example, platinum, palladium, ruthenium, ruthenium oxide, iridium, iridium oxide, titanium, titanium nitride, tungsten, tungsten oxide, tungsten nitride, tungsten carbide, tantalum, tantalum oxide, tantalum nitride, tantalum silicon nitride, tantalum carbide, molybdenum, molybdenum oxide, molybdenum nitride, titanium aluminum alloys, nickel, aluminum, doped aluminum, aluminum oxide, copper, hafnium carbide, hafnium nitride, niobium nitride, vanadium carbide, vanadium nitride, zirconium nitride, derivatives thereof, or combinations thereof. In many examples,upper electrode 260 contains titanium, titanium nitride, alloys thereof, or combinations thereof. -
Memory device 200 containingupper electrode 260 deposited, formed, or otherwise disposed on or over metaloxide film stack 230 may optionally be exposed to a second annealing process, such as a post electrode anneal, duringstep 145 ofprocess 100. The post electrode anneal occurs subsequent to the formation ofupper electrode 260. During the post electrode anneal,memory device 200, includingupper electrode 260 and metaloxide film stack 230, may be heated to an annealing temperature within a range from about 400° C. to about 1,200° C., such as from about 500° C. to about 900° C., or from about 700° C. to about 800° C., for example, about 750° C. Generally,memory device 200 may be heated for a time period within a range from about 10 seconds to about 5 minutes, such as from about 20 seconds to about 4 minutes, or from about 40 seconds to about 2 minutes during the post upper electrode anneal ofstep 145. The post electrode anneal may be conducted within an annealing chamber, vacuum chamber, deposition chamber, or other processing chamber that provides heat to the layers contained withinmemory device 200, such as metaloxide film stack 230 andupper electrode 260. - In some examples,
memory device 200 containingupper electrode 260 may be heated to an annealing temperature within a range from about 700° C. to about 800° C. for a time period within a range from about 40 seconds to about 2 minutes during the post upper electrode anneal atstep 145. In one example, the annealing temperature of about 750° C. for about 1 minute is used during the annealing process. -
FIG. 3 depicts amemory array 300 of resistiveswitching memory devices 310, as described by embodiments herein. Eachmemory device 310 contains at least oneswitching memory element 312, and may contain multiple switchingmemory elements 312. In some embodiments,memory devices 310 may be a plurality ofmemory devices 200, depicted inFIG. 2A . Eachmemory device 200 may independently contain any of the metal oxide film stacks 230 illustrated inFIGS. 2B-2E .Memory array 300 may be part of a larger memory device or other integrated circuit structure, such as a system on a chip type device. Read and write circuitry is connected to switchingmemory devices 310 usingelectrodes 322 andelectrodes 324. Electrodes, such asupper electrodes 322 andlower electrodes 324, are sometimes referred to as word lines and bit lines, and are used to read and write data into thememory elements 312 in the switchingmemory devices 310. Individualswitching memory devices 310 or groups of switchingmemory devices 310 can be addressed using appropriate sets ofelectrodes memory elements 312 in the switchingmemory devices 310 may be formed from a plurality oflayers FIG. 3 . In addition, memory arrays such asmemory array 300 can be stacked in a vertical fashion to make multilayer memory array structures. - According to various embodiments described herein, resistive-switching memory elements/devices generally have a structure in which resistive-switching insulating layers are surrounded by two conductive electrodes. In some embodiments, memory elements may have electrodes of different materials (e.g., one electrode containing a doped silicon material and the other electrode containing a titanium nitride material) surrounding a resistive-switching layer of a metal oxide (e.g., hafnium oxide) having a thickness within a range from about 20 Å to about 100 Å, and a coupling layer that is substantially thinner than the resistive-switching layer (e.g., less than 25% the thickness of the resistive-switching layer). In some embodiments, the coupling layer may be a metallic material such as titanium. Memory elements including the coupling layer have exhibited improved switching characteristics (e.g., lower set, reset, and forming voltages, and better retention). In some embodiments, the resistive-switching layer includes a higher bandgap material (e.g., a material having a bandgap greater than 4 eV such as hafnium oxide, aluminum oxide, tantalum oxide, yttrium oxide, zirconium oxide, cerium oxide, alloys thereof, derivatives thereof, or combinations thereof), however other resistive-switching layers may include materials having a bandgap less than 4 eV (e.g., titanium oxide).
- The exemplary ALD processes for depositing or otherwise forming the metal oxide materials contained within metal
oxide film stack 230 and other materials and/or layers contained withinmemory device 200 are typically conducted in a deposition chamber, such as an ALD chamber. The deposition chamber may maintain an internal pressure of less than 760 Torr, such as within the range from about 10 mTorr to about 10 Torr, such as from about 100 mTorr to about 1 Torr, for example, about 350 mTorr. The temperature of the substrate or the substrate carrier/pedestal is usually maintained within the range from about 50° C. to about 1,000° C., such as from about 100° C. to about 500° C., such as from about 200° C. to about 400° C., or such as from about 250° C. to about 300° C. - The metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a flow rate within the range from about 0.1 sccm to about 200 sccm, such as from about 0.5 sccm to about 50 sccm, from about 1 sccm to about 30 sccm, for example, about 10 sccm. The metal source gas may be provided along with a carrier gas, such as argon or nitrogen. The carrier gas may have a flow rate within the range from about 1 sccm to about 300 sccm, such as from about 2 sccm to about 80 sccm, from about 5 sccm to about 40 sccm, for example, about 20 sccm.
- The metal source gas may be pulsed or otherwise provided into the deposition chamber at a rate within a range from about 0.01 seconds to about 10 seconds, depending on the particular process conditions, metal source gas or desired composition of the deposited metal oxide material. In one embodiment, such as for forming a metal-poor oxide material, the metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 10 seconds, such as from about 1 second to about 5 seconds, for example, about 3 seconds. In another embodiment, such as for forming a metal-rich oxide material, the metal source gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.05 seconds to about 2 seconds, such as from about 0.1 seconds to about 1 second, for example, about 0.5 seconds. In many examples, the metal source gas is a hafnium precursor which is a tetrakis(dialkylamino) hafnium compound, such as tetrakis(dimethylamino) hafnium ((Me2N)4Hf or TDMAH), tetrakis(diethylamino) hafnium ((Et2N)4Hf or TDEAH), or tetrakis(ethylmethylamino) hafnium ((EtMeN)4Hf or TEMAH).
- The metal source gas is generally dispensed into a deposition chamber by introducing a carrier gas through an ampoule containing the metal source or precursor. An ampoule unit may include an ampoule, a bubbler, a canister, a cartridge, or other container used for storing, containing, or dispersing chemical precursors. In another example, the ampoule may contain a liquid precursor (e.g., TDMAH or TDEAH) and be part of a liquid delivery system containing injector valve system used to vaporize the liquid precursor with a heated carrier gas. Generally, the ampoule may be heated to a temperature of about 100° C. or less, such as within a range from about 30° C. to about 90° C., for example, about 50° C.
- The oxidizing agent (e.g., O2, O3, H2O) may be pulsed, introduced, or otherwise provided into the deposition chamber at a flow rate within a range from about 0.01 seconds to about 10 seconds, depending on the particular process conditions, oxygen source gas or oxidizing agent or desired composition of the deposited metal oxide material. In one embodiment, such as for forming a metal-poor oxide material, the oxidizing agent may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.001 seconds to about 1 second, such as from about 0.001 seconds to about 0.1 seconds, for example, about 0.05 seconds. In another embodiment, such as for forming a metal-rich oxide material, the oxidizing agent may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 0.5 second to about 10 seconds, such as from about 1 second to about 3 seconds, for example, about 2 seconds.
- The oxidizing agent may contain or be formed of or generated from an oxygen source that includes oxygen (O2), atomic oxygen (O), ozone (O3), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), dinitrogen pentoxide (N2O5), hydrogen peroxide (H2O2), derivatives thereof, plasmas thereof, or combinations thereof. Ozone may be formed inside or outside of the deposition chamber, such as the ALD chamber. In one example, the oxidizing agent contains ozone formed by an ozone generator positioned outside of the interior of the deposition chamber. Ozone is generated and then flowed or directed into the deposition chamber and exposed along with the metal source gas to the substrate surface. In another example, the oxidizing agent contains ozone formed by a plasma generated within the interior of the deposition chamber. Oxygen gas flowed or directed into the deposition chamber, then ignited or formed into ozone and/or atomic oxygen before being sequentially exposed along with the metal source gas to the substrate surface.
- A carrier gas or a purge gas may be provided at the same time as the metal source gas and/or the oxygen source, but is also provided between the pulses of the metal source gas and/or the oxygen source. The carrier gas or purge gas may continuous flow during the ALD process or may be intermediately and/or sequentially pulsed, introduced, or otherwise provided during the ALD. The carrier gas or purge gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 30 seconds, depending on the particular process conditions, source gases, or desired composition of the deposited metal oxide material. In one embodiment, the carrier gas or a purge gas may be pulsed, introduced, or otherwise provided into the deposition chamber at a rate within a range from about 1 second to about 30 seconds, such as from about 2 seconds to about 20 seconds, for example, about 10 seconds or about 15 seconds.
- The carrier gas or purge gas may contain nitrogen, argon, helium, hydrogen, a forming gas, oxygen, mixtures thereof, or combinations thereof. The carrier gas or the purge gas may be sequentially pulsed, introduced, or otherwise provided after each pulse of the metal source gas and each pulse of the oxidizing agent during the ALD cycle. The pulses of purge gas or carrier gas are typically pulsed, introduced, or otherwise provided at a flow rate within a range from about 2 standard liters per minute (slm) to about 22 slm, such as about 10 slm. The specific purge gas flow rates and duration of process cycles are obtained through experimentation. In one example, a 300 mm diameter wafer requires about twice the flow rate for the same duration as a 200 mm diameter wafer in order to maintain similar throughput.
- Many precursors are within the scope of embodiments of the invention for depositing the dielectric materials described herein. One important precursor property is to have a favorable vapor pressure. Precursors at ambient temperature and pressure may be gas, liquid, or solid. However, volatilized precursors are used within the ALD chamber. Organic-metallic compounds contain at least one metal atom and at least one organic-containing functional group, such as amides, alkyls, alkoxyls, alkylaminos, anilides, or derivatives thereof. Precursors may include organic-metallic, organometallic, inorganic, or halide compounds.
- In one embodiment, the metal source gas is formed from or contains a tetrakis(dialkylamino) metal compound, such as a tetrakis(dialkylamino) hafnium compound or a tetrakis(dialkylamino) zirconium compound. Tetrakis(dialkylamino) metal compounds are useful for depositing metal oxides contained within metal
oxide film stack 230 and other materials and/or layers withinmemory device 200 during ALD processes. - In some examples, the metal source gas contains or is formed from exemplary hafnium precursors which include hafnium compounds containing ligands such as halides, alkylaminos, cyclopentadienyls, alkyls, alkoxides, derivatives thereof, or combinations thereof. Hafnium alkylamino compounds useful as hafnium precursors include tetrakis(dialkylamino) hafnium compounds, such as (RR′N)4Hf, where R or R′ are independently hydrogen, methyl, ethyl, propyl, or butyl. Hafnium halide compounds useful as hafnium precursors may include HfCl4, HfI4, and HfBr4. Exemplary hafnium precursors useful for depositing hafnium oxides and other hafnium-containing materials contained within metal
oxide film stack 230 and other materials and/or layers withinmemory device 200 during ALD processes include (Et2N)4Hf, (Me2N)4Hf, (MeEtN)4Hf, (tBuC5H4)2HfCl2, (C5H5)2HfCl2, (EtC5H4)2HfCl2, (Me5C5)2HfCl2, (Me5C5)HfCl3, (iPrC5H4)2HfCl2, (iPrC5H4)HfCl3, (tBuC5H4)2HfMe2, (acac)4Hf, (hfac)4Hf, (tfac)4Hf, (thd)4Hf, (NO3)4Hf, (tBuO)4Hf, (iPrO)4Hf, (EtO)4Hf, (MeO)4Hf, or derivatives thereof. - In other examples, the metal source gas contains or is formed from exemplary zirconium precursors which include zirconium compounds containing ligands such as halides, alkylaminos, cyclopentadienyls, alkyls, alkoxides, derivatives thereof, or combinations thereof. Zirconium alkylamino compounds useful as zirconium precursors include tetrakis(dialkylamino) zirconium compounds, such as (RR′N)4Zr, where R or R′ are independently hydrogen, methyl, ethyl, propyl, or butyl. Zirconium halide compounds useful as zirconium precursors may include ZrCl4, ZrI4, and ZrBr4. Exemplary zirconium precursors useful for depositing zirconium oxides and other zirconium-containing materials contained within metal
oxide film stack 230 and other materials and/or layers withinmemory device 200 during ALD processes include (Et2N)4Zr, (Me2N)4Zr, (MeEtN)4Zr, (tBuC5H4)2ZrCl2, (C5H5)2ZrCl2, (EtC5H4)2ZrCl2, (Me5C5)2ZrCl2, (Me5C5)ZrCl3, (iPrC5H4)2ZrCl2, (iPr5H4)ZrCl3, (tBuC5H4)2ZrMe2, (acac)4Zr, (hfac)4Zr, (tfac)4Zr, (thd)4Zr, (NO3)4Zr, (tBuO)4Zr, (PrO)4Zr, (EtO)4Zr, (MeO)4Zr, or derivatives thereof. - The ALD processes, as disclosed herein by the written description, are provided as exemplary ALD processes and should not be limited in scope relative to the variety of ALD processes that may be useful for depositing or otherwise forming the metal oxide materials contained within metal
oxide film stack 230 and other materials and/or layers contained withinmemory device 200. Chemical precursors, carrier gases, pulse times, exposure times, flow rates, temperatures, pressures, sequence orders, and other variables may be adjusted accordingly in order to form the desired thickness and stoichiometry of the metal oxide materials contained within metaloxide film stack 230 and other materials and/or layers contained withinmemory device 200. - “Atomic layer deposition” as used herein refers to the sequential introduction of two or more reactive compounds to deposit a layer of material on a substrate surface. The two, three or more reactive compounds may alternatively be introduced into a reaction zone of a deposition chamber. Usually, each reactive compound is separated by a time delay to allow each compound to adhere and/or react on the substrate surface. In one aspect, a first precursor or compound A is pulsed into the reaction zone followed by a first time delay. Next, a second precursor or compound B is pulsed into the reaction zone followed by a second delay. During each time delay a purge gas, such as argon or nitrogen, may be pulsed or otherwise provided into the deposition chamber to purge the reaction zone or otherwise remove any residual reactive compound or by-products from the reaction zone. Alternatively, the purge gas may flow continuously throughout the deposition process so that only the purge gas flows during the time delay between pulses of reactive compounds. The reactive compounds are alternatively pulsed until a desired film or film thickness is formed on the substrate surface. In either scenario, the ALD process of pulsing compound A, purge gas, pulsing compound B and purge gas is a cycle. A cycle can start with either compound A or compound B and continue the respective order of the cycle until achieving a film with the desired thickness.
- A “pulse” as used herein is intended to refer to a quantity of a particular compound that is intermittently or non-continuously introduced into a reaction zone of a processing chamber. The quantity of a particular compound within each pulse may vary over time, depending on the duration of the pulse. The duration of each pulse is variable depending upon a number of factors such as, for example, the volume capacity of the deposition chamber employed, the vacuum system coupled thereto, and the volatility/reactivity of the particular compound itself. A “half-reaction” as used herein is intended to refer to a pulse of precursor step followed by a purge step.
- While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (20)
1. A resistive switching memory element comprising:
a first electrode; and
a metal oxide film stack disposed over the first electrode;
wherein the metal oxide film stack comprises a metal oxide buffer layer and a metal oxide bulk layer,
wherein the metal oxide buffer layer is disposed between the metal oxide bulk layer and the first electrode.
wherein the metal oxide bulk layer comprises MOx;
wherein M is hafnium or zirconium and x is within a range from about 1.65 to about 1.95;
wherein the metal oxide buffer layer comprises M′O2; and
wherein M′ is zirconium if M is hafnium or M′ is hafnium if M is zirconium.
2. The resistive switching memory element of claim 1 , wherein the metal oxide bulk layer comprises HfOx, where x is within a range from about 1.70 to about 1.90, and wherein the metal oxide buffer layer comprises ZrO2.
3. The resistive switching memory element of claim 2 , wherein the metal oxide bulk layer has a thickness within a range from about 15 Å to about 50 Å, and wherein the metal oxide buffer layer has a thickness within a range from about 5 Å to about 15 Å.
4. The resistive switching memory element of claim 1 , wherein the metal oxide bulk layer comprises ZrOx, where x is within a range from about 1.70 to about 1.90, and wherein the metal oxide buffer layer comprises HfO2.
5. The resistive switching memory element of claim 4 , wherein the metal oxide bulk layer has a thickness within a range from about 15 Å to about 50 Å, and wherein the metal oxide buffer layer has a thickness within a range from about 5 Å to about 15 Å.
6. The resistive switching memory element of claim 1 , wherein the metal oxide buffer layer is less electrically resistive than the metal oxide bulk layer.
7. The resistive switching memory element of claim 1 , wherein the metal oxide buffer layer further comprises a dopant.
8. The resistive switching memory element of claim 7 , wherein the dopant is hafnium oxide if M′ is zirconium or the dopant is zirconium oxide if M′ is hafnium.
9. The resistive switching memory element of claim 7 , wherein the dopant is zirconium oxide and M′ is hafnium, and wherein a concentration of zirconium oxide in the metal oxide buffer layer is between about 0.25% atomic and 25% atomic.
10. The resistive switching memory element of claim 7 , wherein the dopant is zirconium oxide and M′ is hafnium, and wherein a concentration of zirconium oxide in the metal oxide buffer layer is between about 1% atomic and 15% atomic.
11. The resistive switching memory element of claim 7 , wherein the dopant is hafnium oxide and M′ is zirconium, and wherein a concentration of hafnium oxide in the metal oxide buffer layer is between about 0.25% atomic and 25% atomic.
12. The resistive switching memory element of claim 7 , wherein the dopant is hafnium oxide and M′ is zirconium, and wherein a concentration of hafnium oxide in the metal oxide buffer layer is between about 1% atomic and 15% atomic.
13. The resistive switching memory element of claim 7 , wherein the metal oxide buffer layer has a thickness of between 2 Å and 80 Å.
14. The resistive switching memory element of claim 1 , wherein the metal oxide buffer layer is a laminate comprising one or more layers of M′O2 and one or more layers of MO2.
15. The resistive switching memory element of claim 1 , wherein the metal oxide bulk layer is a laminate comprising one or more layers of M′O2 and one or more layers of MOx.
16. The resistive switching memory element of claim 1 , further comprising a silicon oxide layer and a second electrode;
wherein the silicon oxide layer, the metal oxide bulk layer, and the metal oxide buffer layer are disposed between the first electrode and the second electrode; and
wherein the silicon oxide layer is disposed between the second electrode and the metal oxide bulk layer.
17. The resistive switching memory element of claim 16 , wherein the silicon oxide layer has a thickness of between about 2 Å and 40 Å.
18. The resistive switching memory element of claim 1 , wherein x is within a range from about 1.70 to about 1.90.
19. The resistive switching memory element of claim 1 , wherein x is within a range from about 1.75 to about 1.85.
20. A resistive switching memory element comprising:
a first electrode;
a metal oxide buffer layer; and
a metal oxide bulk layer;
wherein the metal oxide buffer layer is disposed between the metal oxide bulk layer and the first electrode;
wherein the metal oxide bulk layer comprises HfOx;
wherein x is within a range from about 1.65 to about 1.95; and
wherein the metal oxide buffer layer comprises ZrO2.
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US13/972,587 US20130334484A1 (en) | 2011-09-19 | 2013-08-21 | Atomic Layer Deposition of Hafnium and Zirconium Oxides for Memory Applications |
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US13/236,481 US8546275B2 (en) | 2011-09-19 | 2011-09-19 | Atomic layer deposition of hafnium and zirconium oxides for memory applications |
US13/972,587 US20130334484A1 (en) | 2011-09-19 | 2013-08-21 | Atomic Layer Deposition of Hafnium and Zirconium Oxides for Memory Applications |
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US20130071984A1 (en) | 2013-03-21 |
WO2013043561A1 (en) | 2013-03-28 |
US8546275B2 (en) | 2013-10-01 |
KR20140074954A (en) | 2014-06-18 |
JP2014528176A (en) | 2014-10-23 |
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