Stabilization of flatband voltages and threshold voltages in hafnium oxide based silicon transistors for cmos

Abstract

The present invention provides a metal stack structure that stabilizes the flatband voltage and threshold voltages of material stacks that include a Si-containing conductor and a Hf-based dielectric. This present invention stabilizes the flatband voltages and the threshold voltages by introducing a rare earth metal-containing layer into the material stack that introduces, via electronegativity differences, a shift in the threshold voltage to the desired voltage. Specifically, the present invention provides a metal stack comprising: a hafnium-based dielectric; a rare earth metal-containing layer located atop of, or within, said hafnium-based dielectric; an electrically conductive capping layer located above said hafnium-based dielectric; and a Si-containing conductor.

1 . An n-metal oxide semiconductor field effect transistor (n-MOSFET) material stack comprising:
 a hafnium-based dielectric;   a rare earth-containing layer comprising an oxide or nitride of at least one element from Group IIIB of the Periodic Table of Elements located atop of; or within, said hafnium-based dielectric;   an electrically conducting capping layer located above said hafnium-based dielectric; and   a Si-containing conductor located above said electrically conducting capping layer, wherein said rare-earth-containing layer introduces via electronegativity differences a negative shift in threshold voltage.   
   
   
       2 . The n-MOSFET material stack of  claim 1  further comprising a chemox layer located beneath said Hf-based dielectric. 
   
   
       3 . The n-MOSFET material stack of  claim 1  wherein said Hf-based dielectric comprises hafnium oxide, hafnium silicate, hafnium silicon oxynitride, a mixture of hafnium oxide and zirconium oxide or multilayers thereof. 
   
   
       4 . The n-MOSFET material stack of  claim 3  wherein said Hf-based dielectric comprises hafnium oxide. 
   
   
       5 . The n-MOSFET material stack of  claim 1  wherein said Group IIIB element is one of La, Ce, Y, Sm, Er and Tb. 
   
   
       6 . The n-MOSFET material stack of  claim 5  wherein said Group IIIB element is La and said rare earth metal-containing layer is La 2 O 3  or LaN. 
   
   
       7 . The n-MOSFET material stack of  claim 1  wherein said electrically conductive capping layer comprises a metal nitride or metal silicon nitride, wherein said metal is from Group IVB or VB of the Periodic Table of Elements. 
   
   
       8 . The n-MOSFET material stack of  claim 8  wherein said electrically conductive capping layer comprises TiN, TaN, a ternary alloy of Ti—La—N, a ternary alloy of Ta—La—N or a stack with a ternary alloy of Ti—La—N or Ta—La—N wherein said rare earth metal-containing layer is present in said electrically conductive capping layer. 
   
   
       9 . The n-MOSFET material stack of  claim 1  comprising an optional chemox layer, HfO 2  or Hf silicate as said Hf-based dielectric, a metal nitride layer including at least one rare earth metal or rare earth-like material, and polySi as the Si-containing gate conductor, wherein said metal nitride layer is used as both said rare earth-containing layer and said electrically conducting capping layer. 
   
   
       10 . The n-MOSFET material stack of  claim 1  comprising optionally a SiO 2  chemox layer, HfO 2  or Hf silicate as said Hf-based dielectric, a La containing material as the rare earth metal-containing layer, TiN as the electrically conductive capping layer, and n-doped Si as the Si-containing conductor. 
   
   
       11 . An n-MOSFET material stack comprising:
 a hafnium-based dielectric containing a concentration gradient of a rare earth metal comprising at least one element from Group IIIB of the Periodic Table of Elements located atop of, or within, said hafnium-based dielectric;   an electrically conductive capping layer located above said hafnium-based dielectric; and   a Si-containing conductor, wherein said rare-earth-containing metal introduces via electronegativity differences a negative shift in threshold voltage.   
   
   
       12 . The n-MOSFET material stack of  claim 11  further comprising a chemox layer located beneath said Hf-based dielectric. 
   
   
       13 . The n-MOSFET material stack of  claim 11  wherein said Hf-based dielectric comprises hafnium oxide, hafnium silicate, hafnium silicon oxynitride, a mixture of hafnium oxide and zirconium oxide or multilayers thereof. 
   
   
       14 . The n-MOSFET material stack of  claim 13  wherein said Hf-based dielectric comprises hafnium oxide. 
   
   
       15 . The n-MOSFET material stack of  claim 11  wherein said Group IIIB element is one of La, Ce, Y, Sm, Er and Tb. 
   
   
       16 . The n-MOSFET material stack of  claim 15  wherein said Group IIIB element is La. 
   
   
       17 . The n-MOSFET material stack of  claim 11  wherein said electrically conductive capping layer comprises a metal nitride or metal silicon nitride, wherein said metal is from Group IVB or VB of the Periodic Table of Elements. 
   
   
       18 . The n-MOSFET material stack of  claim 11  comprising an optional chemox layer, HfO 2  or Hf silicate as said Hf-based dielectric, a metal nitride layer including at least one rare earth metal or rare earth-like metal, and polySi as the Si-containing gate conductor, wherein said metal nitride layer is used as both said rare earth-containing metal and said electrically conducting capping layer. 
   
   
       19 . The n-MOSFET material stack of  claim 11  comprising optionally a SiO 2  chemox layer, HfO 2  or Hf silicate as said Hf-based dielectric, a La containing material as the rare earth metal-containing metal, TiN as the electrically conductive capping layer, and n-doped Si as the Si-containing conductor. 
   
   
       20 . An n-MOSFET material stack comprising:
 a hafnium-based dielectric containing foreign atoms having a valence and electronegativity different from hafnium located atop of, or within, said hafnium-based dielectric, said foreign atoms comprising a rare earth metal from Group IIIB of the Periodic Table of Elements;   an electrically capping layer located above said hafnium-based dielectric; and   a Si-containing conductor, wherein said foreign atoms provide a negative shift in threshold voltage.   
   
   
       21 . The n-MOSFET material stack of  claim 20  wherein said Hf-based dielectric comprises hafnium oxide, hafnium silicate, hafnium silicon oxynitride, a mixture of hafnium oxide and zirconium oxide or multilayers thereof. 
   
   
       22 . The n-MOSFET material stack of  claim 20  wherein said Hf-based dielectric comprises hafnium oxide. 
   
   
       23 . The n-MOSFET material stack of  claim 20  wherein said Group IIIB element is one of La, Ce, Y, Sm, Er and Tb. 
   
   
       24 . The n-MOSFET material stack of  claim 23  wherein said Group IIIB element is La. 
   
   
       25 . A semiconductor structure comprising:
 a patterned n-MOSFET material stack located on a surface of a semiconductor substrate, said patterned n-MOSFET material stack comprising a hafnium-based dielectric; a rare earth-containing layer located on atop of, or within, said hafnium-based dielectric; an electrically conductive capping layer located above said hafnium-based dielectric; and a Si-containing conductor, wherein said rare-earth-containing layer introduces electronegativity into said hafnium-based dielectric to provide a negative shift in threshold voltage, and an alignment of a Fermi level of the Si-containing electrode with a conduction band of said semiconductor substrate.