MIS capacitor and method of formation
An MIS capacitor with low leakage and high capacitance is disclosed. A layer of hemispherical grained polysilicon (HSG) is formed as a lower electrode. Prior to the dielectric formation, the hemispherical grained polysilicon layer may be optionally subjected to a nitridization or anneal process. A dielectric layer of aluminum oxide (Al 2 O 3 ), or a composite stack of interleaved layers of aluminum oxide and other metal oxide dielectric materials, is fabricated over the hemispherical grained polysilicon layer and after the optional nitridization or anneal process. The dielectric layer of aluminum oxide (Al 2 O 3 ) or the aluminum oxide composite stack may be optionally subjected to a post-deposition treatment to further increase the capacitance and decrease the leakage current. A metal nitride upper electrode is formed over the dielectric layer or the composite stack by a deposition technique or by atomic layer deposition.
1. A capacitor comprising:
a first electrode comprising a material selected from the group consisting of hemispherical grained polysilicon, silica, germanium and silicon;
a dielectric layer formed adjacent said first electrode, said dielectric layer comprising aluminum oxide;
a first silicon-doped aluminum-containing interfacial layer at the interface between said first electrode and said dielectric layer;
a metal nitride second electrode formed over said dielectric layer; and
a second silicon-doped aluminum-containing interfacial layer at the interface between said metal nitride second electrode and said dielectric layer.
2. The capacitor of claim 1 , wherein said dielectric layer further comprises a dielectric material adjacent said aluminum oxide.
3. The capacitor of claim 2 , wherein said dielectric material is selected from the group consisting of tantalum oxide, zirconium oxide, hafnium oxide, hafnium-aluminum-oxygen alloys and lanthanum-aluminum-oxygen alloys.
4. The capacitor of claim 1 , wherein said dielectric layer comprises interleaved layers of aluminum oxide and tantalum oxide.
5. The capacitor of claim 4 , wherein said dielectric layer is an annealed ALD aluminum oxide layer.
6. The capacitor of claim 1 , wherein said metal nitride second electrode is a tungsten nitride layer or a titanium nitride layer.
7. The capacitor of claim 6 , wherein said ALD titanium nitride layer is a nitridized ALD titanium nitride layer.