Method for making a semiconductor device having a high-k gate dielectric

Abstract

A method for making a semiconductor device is described. That method comprises forming a high-k gate dielectric layer on a substrate. After removing impurities from that layer, and increasing its oxygen content, a gate electrode is formed on the high-k gate dielectric layer.

What is claimed is:  
     
         1 . A method for making a semiconductor device comprising: 
 forming on a substrate a high-k gate dielectric layer;    removing impurities from the high-k gate dielectric layer, and increasing the oxygen content of the high-k gate dielectric layer; and then    forming a gate electrode on the high-k gate dielectric layer.    
     
     
         2 . The method of  claim 1  wherein the high-k gate dielectric layer is formed by atomic layer chemical vapor deposition, and wherein the high-k gate dielectric layer comprises a material selected from the group consisting of hafnium oxide, hafnium silicon oxide, lanthanum oxide, zirconium oxide, zirconium silicon oxide, titanium oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate.  
     
     
         3 . The method of  claim 1  wherein a wet chemical treatment is applied to the high-k gate dielectric layer to remove impurities from that layer and to increase the oxygen content of that layer.  
     
     
         4 . The method of  claim 3  wherein the wet chemical treatment comprises exposing the high-k gate dielectric layer to a solution that comprises a source of hydroxide at a sufficient temperature for a sufficient time to remove impurities from the high-k gate dielectric layer and to increase the oxygen content of the high-k gate dielectric layer.  
     
     
         5 . The method of  claim 4  wherein the source of hydroxide is selected from the group consisting of deionized water, hydrogen peroxide, ammonium hydroxide, and a tetraalkyl ammonium hydroxide.  
     
     
         6 . The method of  claim 5  wherein the source of hydroxide is tetramethyl ammonium hydroxide.  
     
     
         7 . The method of  claim 6  wherein the gate electrode comprises polysilicon.  
     
     
         8 . A method for making a semiconductor device comprising: 
 forming on a substrate a high-k gate dielectric layer;    applying a wet chemical treatment to the high-k gate dielectric layer to remove impurities from the high-k gate dielectric layer, and to increase the oxygen content of the high-k gate dielectric layer; and then    forming a layer that comprises polysilicon on the high-k gate dielectric layer.    
     
     
         9 . The method of  claim 8  wherein the high-k gate dielectric layer is formed by atomic layer chemical vapor deposition, and is between about 5 angstroms and about 40 angstroms thick.  
     
     
         10 . The method of  claim 9  wherein the high-k gate dielectric layer comprises a material selected from the group consisting of hafnium oxide, zirconium oxide, titanium oxide, and aluminum oxide.  
     
     
         11 . The method of  claim 10  wherein the wet chemical treatment comprises exposing the high-k gate dielectric layer to a solution that comprises a source of hydroxide at a sufficient temperature for a sufficient time to remove chlorine from the high-k gate dielectric layer and to increase the oxygen content of the high-k gate dielectric layer.  
     
     
         12 . The method of  claim 11  wherein the source of hydroxide is selected from the group consisting of deionized water, hydrogen peroxide, ammonium hydroxide, and a tetraalkyl ammonium hydroxide.  
     
     
         13 . A method for making a semiconductor device comprising: 
 forming a high-k gate dielectric layer on a substrate, the high-k gate dielectric layer being less than about 60 angstroms thick and comprising a material selected from the group consisting of hafnium oxide, zirconium oxide, titanium oxide, and aluminum oxide;    exposing the high-k gate dielectric layer to a solution that comprises a source of hydroxide at a sufficient temperature for a sufficient time to remove chlorine from the high-k gate dielectric layer and to increase the oxygen content of the high-k gate dielectric layer;    forming a layer that comprises polysilicon on the high-k gate dielectric layer; and    etching the polysilicon containing layer and the high-k gate dielectric layer.    
     
     
         14 . The method of  claim 13  wherein the high-k gate dielectric layer is formed by atomic layer chemical vapor deposition and is between about 5 angstroms and about 40 angstroms thick.  
     
     
         15 . The method of  claim 14  wherein the source of hydroxide is selected from the group consisting of deionized water, hydrogen peroxide, ammonium hydroxide, and a tetraalkyl ammonium hydroxide.  
     
     
         16 . The method of  claim 15  wherein the high-k gate dielectric layer is exposed to a solution that comprises hydrogen peroxide at a temperature that is between about 15° C. and about 40° C. for at least about one minute.  
     
     
         17 . The method of  claim 15  wherein the high-k gate dielectric layer is exposed to a solution that comprises hydrogen peroxide and ammonium hydroxide at a temperature that is between about 15° C. and about 40° C. for at least about one minute.  
     
     
         18 . The method of  claim 15  wherein the high-k gate dielectric layer is exposed to a solution that comprises ammonium hydroxide at a temperature that is between about 15° C. and about 90° C. for at least about one minute.  
     
     
         19 . The method of  claim 15  wherein the high-k gate dielectric layer is exposed to a solution that comprises tetramethyl ammonium hydroxide at a temperature that is between about 15° C. and about 90° C. for at least about one minute.  
     
     
         20 . The method of  claim 15  wherein the high-k gate dielectric layer is exposed to a solution that comprises deionized water at a temperature of at least about 35° C. for at least about one minute.  
     
     
         21 . The method of  claim 15  wherein the source of hydroxide acts as an oxidizer and wherein the oxygen content of the high-k gate dielectric layer is increased by at least about 10 percent, when the high-k gate dielectric layer is exposed to the solution that includes the source of hydroxide.  
     
     
         22 . The method of  claim 15  wherein the chlorine content of the high-k gate dielectric layer is decreased by at least about 80 percent, when the high-k gate dielectric layer is exposed to the solution that includes the source of hydroxide.  
     
     
         23 . The method of  claim 15  wherein the high-k gate dielectric layer is partially etched, when the high-k gate dielectric layer is exposed to the solution that includes the source of hydroxide.  
     
     
         24 . The method of  claim 15  wherein at least about 10% of the high-k gate dielectric layer is partially etched, when the high-k gate dielectric layer is exposed to the solution that includes the source of hydroxide.  
     
     
         25 . The method of  claim 15  wherein less than about 3 angstroms of oxide grows on the substrate, when the high-k gate dielectric layer is exposed to the solution that includes the source of hydroxide.  
     
     
         26 . The method of  claim 15  further comprising forming a second high-k gate dielectric layer, and exposing the second high-k gate dielectric layer to a second solution that includes a source of hydroxide, prior to forming the layer that comprises polysilicon.