Method for fabricating different gate oxide thickness within the same chip

Abstract

A semiconductor structure having silicon dioxide layers of different thicknesses is fabricated by forming a sacrificial silicon dioxide layer on the surface of a substrate; implanting nitrogen ions through the sacrificial silicon dioxide layer into first areas of the semiconductor substrate; implanting chlorine and/or bromine ions through the sacrificial silicon dioxide layer into second areas of the semiconductor substrate where silicon dioxide having the highest thickness is to be formed; removing the sacrificial silicon dioxide layer; and then growing a layer of silicon dioxide on the surface of the semiconductor substrate. The growth rate of the silicon dioxide will be faster in the areas containing the chlorine and/or bromine ions and therefore the silicon dioxide layer will be thicker in those regions as compared to the silicon dioxide layer in the regions not containing the chlorine and/or bromine ions. The growth rate of the silicon dioxide will be slower in the areas containing the nitrogen ions and therefore the silicon dioxide layer will be thinner in those regions as compared to the silicon dioxide layer in the regions not containing the nitrogen ions. Also provided are structures obtained by the above process.

What is claimed is:  
     
         1 . A method for simultaneously fabricating different oxide thicknesses on the same semiconductor substrate which comprises: 
 forming a sacrificial silicon dioxide layer on the surface of a semiconductor substrate;    implanting nitrogen ions through the sacrificial silicon oxide layer into at least one first area of the semiconductor substrate to be oxidized while masking the other areas of the semiconductor substrate; and    wherein the nitrogen ions retard the oxidation rate of the semiconductor substrate;    implanting second ions selected from the group consisting of chlorine ions, bromine ions, and mixtures thereof through the sacrificial silicon dioxide layer into at least one second area of the semiconductor substrate to be oxidized while masking the other areas of the semiconductor substrate;    and wherein the second ions increase the oxidation rate of the semiconductor substrate;    removing the sacrificial silicon dioxide layer;    and then growing a layer of silicon dioxide on the surface of the semiconductor substrate wherein the growth rate of the silicon dioxide will be faster in the second area containing the second ions;    and wherein the growth rate of the silicon dioxide will be slower in the first areas containing the nitrogen ions;    and wherein the silicon dioxide layer will be thicker in the second areas compared to the silicon dioxide in the first areas not containing the second ions;    and wherein the silicon dioxide layer will be thinner in the first areas compared to the silicon dioxide in the areas not containing the nitrogen ions.    
     
     
         2 . The method of  claim 1  wherein nitrogen ions are implanted prior to implanting second ions.  
     
     
         3 . The method of  claim 1  wherein second ions are implanted prior to implanting nitrogen ions.  
     
     
         4 . The method of  claim 1  wherein the dosage of the nitrogen ions is about 2×10 13  to about 2×10 15  atoms/cm 2 .  
     
     
         5 . The method of  claim 1  wherein the nitrogen ions are implanted at an energy of about 1 to about 15 keV.  
     
     
         6 . The method of  claim 1  wherein the substrate is silicon or SOI substrate.  
     
     
         7 . The method of  claim 1  wherein the second ions are chlorine ions.  
     
     
         8 . The method of  claim 1  wherein the dosage of the second ions is about 2×10 13  to about 2×10 15  atoms/cm 2 .  
     
     
         9 . The method of  claim 1  wherein the second ions are implanted at an energy of about 1 to about 15 keV.  
     
     
         10 . The method of  claim 1  wherein at least one of the nitrogen ions and second ions are implanted in at least two different areas of at least two different dosages.  
     
     
         11 . A semiconductor device obtained by the process of  claim 1 .  
     
     
         12 . A semiconductor structure comprising: 
 a semiconductor substrate containing selected first areas with implanted nitrogen ions;    selected second areas with second implanted ions selected from the group consisting of chlorine, bromine, and mixtures thereof;    a silicon dioxide layer of differing thickness wherein the dioxide layer above the portion of the substrate having the second implanted ion is thicker than the thickness of the silicon dioxide above the first areas.    
     
     
         13 . The semiconductor structure of  claim 12  wherein the dosage of the nitrogen ions is about 2×10 13  to about 2×10 15  atoms/cm 2 .  
     
     
         14 . The semiconductor structure of  claim 12  wherein the dosage of the second ions is about 2×10 13  to about 2×10 15  atoms/c 2 .  
     
     
         15 . The semiconductor structure of  claim 12  wherein the second ions are chlorine.  
     
     
         16 . The semiconductor structure of  claim 12  wherein the substrate is silicon or SOI substrate.  
     
     
         17 . The semiconductor structure of  claim 12  which further includes silicon dioxide above areas of the semiconductor substrate that are non-implanted areas.  
     
     
         18 . The semiconductor structure of  claim 12  wherein the silicon dioxide layer above the portion of the substrate having the nitrogen implanted ion is thinner than the thickness of the silicon dioxide above the areas not having the nitrogen implanted ions.  
     
     
         19 . The semiconductor structure of  claim 12  wherein the silicon dioxide layer above the portion of the substrate having the chlorine or bromine ion is thicker than the thickness of the silicon dioxide above the areas not having the chlorine or bromine implanted ions.