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 including a conductor; a semiconductor and an interfacial dielectric layer disposed between and in contact with both the conductor and the semiconductor, wherein the conductor is a conductive metal oxide, and the interfacial dielectric layer has a thickness in the range 0.2 nm to 4 nm 7 and comprises one of: WO3, TiO2, MgO, Al2O3, HfO2, ZrO2, Ta2O5, V2O5, BaZrO3, La2O3, Y2O3, HfSiO4, ZrSiO4, CoO, NiO, GaO, SrTiO3, or (Ba,Sr)TiO3.
2. The electrical contact structure of claim 1 , wherein the conductive metal oxide has a thickness in the range 0.5 nm to 3 nm and comprises one of: WO2, (Nb,Sr)TiO3, (Ba,Sr)TiO3, SrRuO3, MoO2, OsO2, RhO2, RuO2, IrO2, ReO3, ReO2, LaCuO3, Ti2O3, TiO, V2O3, VO, Fe3O4, ZnO, indium tin oxide (ITO), aluminum-doped zinc-oxide (AZO), InSnO, or CrO2.
3. The electrical contact structure of claim 1 , wherein a junction between the conductive metal oxide and the interfacial dielectric layer is chemically stable up to a temperature of 450° C.
4. The electrical contact structure of claim 1 , wherein the semiconductor is a III-V compound semiconductor.
5. The electrical contact structure of claim 1 , wherein the semiconductor is a semiconductor comprising one or several of the group IV elements silicon, germanium, carbon, or tin.
6. The electrical contact structure of claim 1 , wherein the semiconductor is a silicon source or drain region of a field effect transistor, said silicon is doped n-type to a concentration in excess of 10 20 cm-3, the interfacial dielectric layer is V 2 O 5 with a thickness of between 0.2 nm and 3.0 nm, and the conductive metal oxide is conductive vanadium oxide with a composition intermediate between VO and VO2 and a thickness of between 0.5 nm and 5.0 nm.
7. The electrical contact structure of claim 1 , wherein the semiconductor is a silicon source or drain region of a field effect transistor, said silicon is doped n-type to a concentration in excess of 10 20 cm −3 , the interfacial dielectric layer is TiO2 with a thickness of between 0.2 nm and 3.0 nm, and the conductive metal oxide is conductive tungsten oxide (e.g., WO 2 ) with a thickness of between 0.5 nm and 5.0 nm.
8. A method of forming an electrical contact structure, comprising depositing by one of atomic layer deposition, chemical vapor deposition, or physical vapor deposition, to a thickness in the range 0.2 nm to 4 nm, an interfacial dielectric layer on a semiconductor and thereafter forming a conductor on the interfacial dielectric layer such that the interfacial dielectric layer is thereby disposed between and in contact with both the conductor and the semiconductor, wherein the conductor is a conductive metal oxide and the interfacial dielectric layer comprises a metal oxide.
9. A method of forming an electrical contact structure, comprising depositing and subsequently oxidizing a metal layer on a semiconductor, and subsequently forming a conductive metal oxide conductor over the oxidized metal layer such that the oxidized metal layer forms an interfacial dielectric layer disposed between and in contact with both the conductor and the semiconductor and has a thickness in the range 0.2 nm to 4 nm.
10. The method of either claim 8 or claim 9 , wherein the interfacial dielectric layer comprises TiO2.
11. The method of either claim 8 or claim 9 , wherein the interfacial dielectric layer comprises V2O5.
12. The method of claim 10 , wherein the conductive metal oxide comprises conductive tungsten oxide and the conductive tungsten oxide is formed by reaction of a tungsten metal layer with the TiO2 interfacial dielectric layer and has a composition intermediate between WO2 and WO2.95.
13. The method of claim 11 , wherein the conductive metal oxide comprises conductive vanadium oxide and the conductive vanadium oxide is formed by reaction of vanadium metal with the V2O5 interfacial dielectric layer and has a composition intermediate between VO and VO2.
14. The method of claim 10 , wherein the conductive metal oxide is a conductive mixed oxide layer comprising a mixture of tungsten and titanium oxides formed by the reaction of tungsten metal layer with the TiO2 interfacial dielectric layer on top of some remaining thickness of the TiO2 interfacial dielectric layer.