Method of forming strontium titanate films

Abstract

Embodiments of the current invention include methods of forming a strontium titanate (SrTiO 3 ) film using atomic layer deposition (ALD). More particularly, the method includes forming a plurality of titanium oxide (TiO 2 ) unit films using ALD and forming a plurality of strontium oxide (SrO) unit films using ALD. The combined thickness of the TiO 2 and SrO unit films is less than approximately 5 angstroms. The TiO 2 and SrO units films are then annealed to form a strontium titanate layer.

1 . A method for forming a capacitive device, comprising:
 a. forming a Sr-containing and Ti-containing film on a substrate by:
 i. forming an SrO film on the substrate from one or more SrO unit films; 
 ii. forming a TiO 2  film from one or more TiO 2  unit films on the previously formed SrO film; 
 iii. forming one or more SrO unit films on the previously formed TiO 2  film if the combined total thickness of all previously formed SrO films and all previously formed TiO 2  films has not reached a desired value; 
 iv. forming one or more TiO 2  unit films on the previously formed SrO film if the combined total thickness of all previously formed SrO films and all previously formed TiO 2  films has not reached a desired value; 
 v. wherein the ratio of all of the SrO films and all of the TiO 2  films is 3:2; and 
   b. applying multiple pre-saturation pulses of a Ti-precursor without a pulse of an oxidant between the Ti-precursor pulses during the formation of the first TiO 2  unit film.   
     
     
         2 . The method of  claim 1  further comprising a first SrO unit film formed on a first conductive layer disposed on the substrate. 
     
     
         3 . The method of  claim 2 , wherein the plurality of SrO unit films are formed on the first SrO unit film. 
     
     
         4 . The method of  claim 1 , wherein the plurality of TiO 2  unit films are formed on the first TiO 2  unit film. 
     
     
         5 . The method of  claim 1 , wherein the plurality of SrO unit films comprise a multiple of three monolayers. 
     
     
         6 . The method of  claim 1 , wherein the plurality of TiO 2  films comprise a multiple of two monolayers. 
     
     
         7 . The method of  claim 2 , wherein the first conductive layer comprises one of molybdenum or molybdenum oxide. 
     
     
         8 . The method of  claim 2 , wherein forming the first SrO unit film on the first conductive layer is achieved by applying multiple pre-saturation pulses without a pulse of an oxidant between the Sr-precursor pulses during the formation of the first SrO 2  unit film within an atomic layer deposition tool. 
     
     
         9 . The method of  claim 8 , wherein the number of pre-saturation pulses may be in the range of 50-200 pulses. 
     
     
         10 . The method of  claim 1  further comprising annealing the plurality of SrO unit films and the plurality of TiO 2  films to form a strontium titanate film. 
     
     
         11 . The method of  claim 10 , wherein the strontium titanate film has a high-k dielectric constant greater than 45. 
     
     
         12 . The method of  claim 1 , wherein steps iii) and iv) are repeated.