MIS contact structure with metal oxide conductor
An electrical contact structure (an MIS contact) includes one or more conductors (M-Layer), a semiconductor (S-Layer), and an interfacial dielectric layer (I-Layer) of less than 4 nm thickness disposed between and in contact with both the M-Layer and the S-Layer. The I-Layer is an oxide of a metal or a semiconductor. The conductor of the M-Layer that is adjacent to and in direct contact with the I-Layer is a metal oxide that is electrically conductive, chemically stable and unreactive at its interface with the I-Layer at temperatures up to 450° C. The electrical contact structure has a specific contact resistivity of less than or equal to approximately 10 −5 -10 −7 Ω-cm 2 when the doping in the semiconductor adjacent the MIS contact is greater than approximately 2×10 19 cm −3 and less than approximately 10 −8 Ω-cm 2 when the doping in the semiconductor adjacent the MIS contact is greater than approximately 10 20 cm −3 .
1. An electrical contact structure, comprising a conductor; a semiconductor layer; and an interfacial dielectric layer of less than 10 nm thickness disposed between and in contact with both the conductor and the semiconductor layer, wherein the conductor is a conductive metal oxide and the interfacial dielectric layer comprises a plurality of oxide layers, wherein at least one of the oxide layers of the interfacial dielectric layer is an oxide of a metal or an oxide of a semiconductor.
2. The electrical contact structure of claim 1 , wherein the electrical contact structure has a specific contact resistivity of less than or equal to approximately 10 −5 -10 −7 Ω-cm 2 .
3. The electrical contact structure of claim 2 , wherein at least one of the oxide layers of the interfacial dielectric layer comprises a material that would be an insulator or a semiconductor in its bulk state.
4. The electrical contact structure of claim 2 , wherein at least one of the oxide layers of the interfacial dielectric layer has a thickness in the range 0.2 nm to 4 nm and the conductive metal oxide layer has a thickness in the range 0.5 nm to 3 nm.
5. The electrical contact structure of claim 2 , wherein the junction between the conductive metal oxide layer and the interfacial dielectric layer is chemically stable up to a temperature of 400° C.
6. The electrical contact structure of claim 1 , wherein the semiconductor layer is a doped semiconductor with a doping larger than 10 19 cm −3 .
7. The electrical contact structure of claim 1 , wherein the semiconductor layer adjacent the interfacial dielectric layer is doped n-type to an active concentration greater than approximately 10 20 cm −3 and the electrical contact structure has a specific contact resistivity of less than approximately 1×10 −8 Ω-cm 2 .
8. The electrical contact structure of claim 1 wherein the conductive metal oxide layer is contacted by a thin metal layer of a metal different than that of the conductive metal oxide layer.
9. The electrical contact structure of claim 1 , wherein the conductive metal oxide layer is one of WO 2 or a mixture of tungsten oxides with compositions ranging between WO 2 and WO 2.95 , (Nb,Sr)TiO 3 , (Ba,Sr)TiO 3 , SrRuO 3 , MoO 2 , OsO 2 , RhO 2 , RuO 2 , IrO 2 , ReO 3 , ReO 2 , LaCuO 3 , Ti 2 O 3 , TiO, V 2 O 3 , VO, Fe 3 O 4 , ZnO, InSnO, ITO, AZO, and CrO 2 , or any of their doped or non-stoichiometric variants.
10. The electrical contact structure of claim 1 , wherein the interfacial dielectric layer comprises at least one of WO 3 , TiO 2 , SrTiO 3 , MgO, Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 , V 2 O 5 , BaZrO 3 , La 2 O 3 , Y 2 O 3 , HfSiO 4 , ZrSiO 4 , CoO, NiO, ZnO, GaO, SiO 2 , SrTiO 3 , (Ba,Sr)TiO 3 , ZnO, silicon oxide, and germanium oxide, or any of their doped or non-stoichiometric variants.
11. The electrical contact structure of claim 1 wherein the semiconductor layer comprises a semiconductor including one or more of the group IV elements silicon, germanium, carbon, or tin, or carbon nanotubes.
12. The electrical contact structure of claim 1 , wherein the interfacial dielectric layer comprises at least one of titanium silicate, TiSi x O y , or titanium silicon oxynitride.
13. The electrical contact structure of claim 1 , wherein the interfacial dielectric layer comprises an oxide of titanium and the conductive metal oxide layer comprises an oxide of ruthenium.
14. The electrical contact structure of claim 13 , wherein the interfacial dielectric layer comprises TiO 2 and the conductive metal oxide layer comprises RuO 2 .
15. The electrical contact structure of claim 2 , wherein the interfacial dielectric layer has a thickness in the range 0.2 nm to 10 nm.
16. The electrical contact structure of claim 1 , wherein the conductor comprises a stack of metals including at least a nitride of titanium, and the interfacial dielectric layer comprises at least one layer that is an oxide of a metal and at least one layer that is an oxide of a semiconductor.
17. The electrical contact structure of claim 16 , wherein the stack of metals includes a contact metal that is adjacent to and in direct contact with the interfacial dielectric layer, said contact metal comprising a metal oxide that is electrically conductive, chemically stable, and unreactive at its interface with the interfacial dielectric layer at temperatures up to 450° C.
18. The electrical contact structure of claim 17 , wherein the electrical contact structure comprises a source or drain region of a transistor.
19. The electrical contact structure of claim 18 , wherein the semiconductor layer comprises a doped semiconductor.
20. The electrical contact structure of claim 1 , wherein the conductor comprises a stack of metals including at least a first oxide of tungsten, and the interfacial dielectric layer comprises at least one layer that is a second oxide of tungsten different from the first oxide of tungsten.