Stratified gate dielectric stack for gate dielectric leakage reduction

Abstract

A stratified gate dielectric stack includes a first high dielectric constant (high-k) gate dielectric comprising a first high-k dielectric material, a band-gap-disrupting dielectric comprising a dielectric material having a different band gap than the first high-k dielectric material, and a second high-k gate dielectric comprising a second high-k dielectric material. The band-gap-disrupting dielectric includes at least one contiguous atomic layer of the dielectric material. Thus, the stratified gate dielectric stack includes a first atomic interface between the first high-k gate dielectric and the band-gap-disrupting dielectric, and a second atomic interface between the second high-k gate dielectric and the band-gap-disrupting dielectric that is spaced from the first atomic interface by at least one continuous atomic layer of the dielectric material of the band-gap-disrupting dielectric. The insertion of the band-gap disrupting dielectric results in lower gate leakage without resulting in any substantial changes in the threshold voltage characteristics and effective oxide thickness.

What is claimed is: 
     
         1 . A semiconductor structure comprising a field effect transistor, said field effect transistor (FET) including a stratified gate dielectric stack comprising:
 a first high dielectric constant (high-k) gate dielectric comprising a first high-k dielectric material and located on a semiconductor substrate;   a band-gap-disrupting dielectric comprising a dielectric material having a different band gap than said first high-k gate dielectric; and   a second high-k gate dielectric comprising a second high-k dielectric material having a different band gap than said band-gap-disrupting dielectric, wherein a first atomic interface between said band-gap-disrupting dielectric and said first high-k gate dielectric is spaced from a second atomic interface between said band-gap-disrupting dielectric and said second high-k gate dielectric by at least one continuous atomic layer of said dielectric material of said band-gap-disrupting dielectric.   
     
     
         2 . The semiconductor structure of  claim 1 , wherein said first high-k dielectric material is substantially free of said dielectric material of said band-gap-disrupting dielectric. 
     
     
         3 . The semiconductor structure of  claim 2 , wherein said second high-k dielectric material is substantially free of said dielectric material of said band-gap-disrupting dielectric. 
     
     
         4 . The semiconductor structure of  claim 3 , wherein said dielectric material of said band-gap-disrupting dielectric is substantially free of said first high-k dielectric material and said second high-k dielectric material. 
     
     
         5 . The semiconductor structure of  claim 1 , wherein said stratified gate dielectric stack provides a same shift to a work function of said a gate electrode of said field effect transistor as a hypothetical gate dielectric stack derived by omitting said band-gap-disrupting dielectric from said stratified gate dielectric stack. 
     
     
         6 . The semiconductor structure of  claim 1 , wherein said dielectric material of said band-gap-disrupting dielectric is selected from La 2 O 3 , Al 2 O 3 , TiO 2 , La 2 O u N v , Al 2 O u N v , TiO u N v , and an alloy thereof, wherein each value of u is independently from 0.5 to 3 and each value of v is independently from 0 to 2. 
     
     
         7 . The semiconductor structure of  claim 6 , wherein said first high-k dielectric material is selected from HfO 2 , ZrO 2 , HfO x N y , ZrO x N y , and alloys thereof, wherein each value of x is independently from 0.5 to 3 and each value of y is independently from 0 to 2. 
     
     
         8 . The semiconductor structure of  claim 1 , wherein said first high-k gate dielectric is a first U-shaped high-k gate dielectric, said band-gap-disrupting dielectric is a U-shaped band-gap-disrupting dielectric, and said second high-k dielectric is a U-shaped band-gap-disrupting dielectric, wherein topmost surfaces of said first U-shaped high-k gate dielectric, said U-shaped band-gap-disrupting dielectric, and said U-shaped band-gap-disrupting dielectric are located within a same horizontal plane. 
     
     
         9 . The semiconductor structure of  claim 1 , wherein each of said first atomic interface and said second atomic interface comprises a horizontal atomic interface portion and a pair of vertical atomic interface portions that are parallel to each other. 
     
     
         10 . The semiconductor structure of  claim 1 , wherein said stratified gate dielectric stack further comprises an interfacial dielectric comprising a dielectric oxide of a semiconductor material of said semiconductor substrate and contacting said first high-k gate dielectric. 
     
     
         11 . The semiconductor structure of  claim 1 , wherein said second high-k dielectric material is the same as said first high-k dielectric material. 
     
     
         12 . The semiconductor structure of  claim 1 , wherein said second high-k dielectric material is different from said first high-k dielectric material. 
     
     
         13 . The semiconductor structure of  claim 1 , further comprising a gate spacer contacting outer sidewalls of said first high-k gate dielectric. 
     
     
         14 . The semiconductor structure of  claim 1 , further comprising a gate electrode, said gate electrode comprising:
 a work function material portion embedded within said second high-k dielectric; and   a conductive material portion embedded within said work function material portion.   
     
     
         15 . The semiconductor structure of  claim 1 , further comprising an additional high-k gate dielectric located on said second high-k gate dielectric and comprising an additional high-k dielectric material that is different from said second high-k dielectric material and is selected from La 2 O 3 , Al 2 O 3 , TiO 2 , HfO 2 , ZrO 2 , La 2 O s N t , Al 2 O s N t , TiO S N t , HfO s N t , ZrO s N t  and an alloy thereof, wherein each value of s is independently from 0.5 to 3 and each value of t is independently from 0 to 2. 
     
     
         16 . The semiconductor structure of  claim 1 , further comprising an additional high-k gate dielectric contacting said first high-k gate dielectric and comprising an additional high-k dielectric material that is different from said first high-k dielectric material and is selected from La 2 O 3 , Al 2 O 3 , TiO 2 , HfO 2 , ZrO 2 , La 2 O s′ N t′ , Al 2 O s′ N t′ , TiO s′ N t′ , HfO s′ N t′ , ZrO s′ N t′  and an alloy thereof, wherein each value of s′ is independently from 0.5 to 3 and each value of t′ is independently from 0 to 2. 
     
     
         17 . The semiconductor structure of  claim 1 , wherein said band-gap-disrupting dielectric comprises a horizontal portion and vertical portions and has a substantially same thickness throughout. 
     
     
         18 . The semiconductor structure of  claim 1 , wherein said band-gap-disrupting dielectric is a planar layer having a same thickness throughout. 
     
     
         19 . The semiconductor structure of  claim 18 , wherein a vertical portion of said second high-k gate dielectric contacts a sidewall of said first high-k gate dielectric. 
     
     
         20 . The semiconductor structure of  claim 1 , further comprising an interfacial dielectric comprising a dielectric material including a semiconductor material of said semiconductor substrate and at least one of oxygen and nitrogen. 
     
     
         21 . The semiconductor structure of  claim 1 , wherein said semiconductor substrate is a bulk semiconductor substrate and said field effect transistor is a planar field effect transistor. 
     
     
         22 . The semiconductor structure of  claim 1 , wherein said semiconductor substrate is a semiconductor-on-insulator substrate and said field effect transistor is a planar field effect transistor. 
     
     
         23 . The semiconductor structure of  claim 1 , wherein said semiconductor substrate comprises a semiconductor fin formed on a bulk semiconductor substrate. 
     
     
         24 . The semiconductor structure of  claim 1 , wherein said semiconductor substrate comprises a semiconductor fin formed on a stack, from bottom to top, of a handle substrate and a buried insulator layer. 
     
     
         25 . The semiconductor structure of  claim 1 , further comprising a gate spacer contacting sidewalls of each of said first high-k dielectric, said band-gap-disrupting dielectric, and said second high-k dielectric.