Carbon addition for low resistivity in situ doped silicon epitaxy

Abstract

Embodiments of the present invention generally relate to methods of forming epitaxial layers and devices having epitaxial layers. The methods generally include forming a first epitaxial layer including phosphorus and carbon on a substrate, and then forming a second epitaxial layer including phosphorus and carbon on the first epitaxial layer. The second epitaxial layer has a lower phosphorus concentration than the first epitaxial layer, which allows for selective etching of the second epitaxial layer and undesired amorphous silicon or polysilicon deposited during the depositions. The substrate is then exposed to an etchant to remove the second epitaxial layer and undesired amorphous silicon or polysilicon. The carbon present in the first and second epitaxial layers reduces phosphorus diffusion, which allows for higher phosphorus doping concentrations. The increased phosphorus concentrations reduce the resistivity of the final device. The devices include epitaxial layers having a resistivity of less than about 0.381 milliohm-centimeters.

We claim: 
     
         1 . A device, comprising:
 a substrate; and   an epitaxially-grown film disposed on the substrate, the epitaxially-grown film comprising a first dopant and carbon, wherein the first dopant is present within the epitaxially-grown film in a concentration of about 1×10 19  atoms per cubic centimeter to about 2.5×10 21  atoms per cubic centimeter, and the carbon is present within the epitaxially-grown film in a concentration less than about 0.5 atomic percent, and further wherein the epitaxially-grown film has a resistivity less than about 0.381 milliohm-centimeters.   
     
     
         2 . The device of  claim 1 , wherein the first dopant is phosphorus. 
     
     
         3 . The device of  claim 1 , wherein the carbon is present within the epitaxially-grown film in a concentration within a range from about 0.1 atomic percent to about 0.3 atomic percent. 
     
     
         4 . The device of  claim 1 , wherein the substrate is a monocrystalline substrate. 
     
     
         5 . The device of  claim 4 , wherein the substrate comprises silicon. 
     
     
         6 . The device of  claim 4 , wherein the epitaxially-grown film comprises silicon. 
     
     
         7 . The device of  claim 1 , wherein the epitaxially-grown film has a resistivity less than about 0.345 milliohm-centimeters. 
     
     
         8 . The device of  claim 2 , wherein the carbon concentration is within a range from about 0.2 atomic percent to about 0.3 atomic percent. 
     
     
         9 . A device, comprising:
 a substrate; and   an epitaxially-grown film disposed on the substrate, the epitaxially-grown film comprising phosphorus and carbon, wherein the phosphorus is present within the epitaxially-grown film in a concentration of about 5×10 20  atoms per cubic centimeter or greater, and the carbon is present within the epitaxially-grown film in a concentration within a range from about 0.1 atomic percent to about 0.3 atomic percent, and further wherein the epitaxially-grown film has a resistivity less than about 0.381 milliohm-centimeters.   
     
     
         10 . The device of  claim 9 , wherein the substrate is a monocrystalline substrate. 
     
     
         11 . The device of  claim 10 , wherein the substrate comprises silicon. 
     
     
         12 . The device of  claim 9 , wherein the epitaxially-grown film comprises silicon. 
     
     
         13 . The device of  claim 9 , wherein the epitaxially-grown film has a resistivity less than about 0.345 milliohm-centimeters. 
     
     
         14 . The device of  claim 13 , wherein the carbon concentration is within a range from about 0.2 atomic percent to about 0.3 atomic percent. 
     
     
         15 . The device of  claim 9 , wherein the carbon concentration is within a range from about 0.2 atomic percent to about 0.3 atomic percent. 
     
     
         16 . A device, comprising:
 a monocrystalline silicon substrate; and   an epitaxially-grown silicon film disposed on the monocrystalline silicon substrate, the epitaxially grown silicon film comprising phosphorus and carbon, wherein the phosphorus is present within the epitaxially-grown silicon film in a concentration of about 5×10 20  atoms per cubic centimeter or greater, and the carbon is present within the epitaxially-grown silicon film in a concentration within a range from about 0.1 atomic percent to about 0.3 atomic percent, and further wherein the epitaxially-grown silicon film has a resistivity less than about 0.381 milliohm-centimeters.   
     
     
         17 . The device of  claim 16 , wherein the epitaxially-grown silicon film has a resistivity less than about 0.345 milliohm-centimeters. 
     
     
         18 . The device of  claim 17 , wherein the carbon concentration is within a range from about 0.2 atomic percent to about 0.3 atomic percent. 
     
     
         19 . The device of  claim 16 , wherein the monocrystalline silicon substrate comprises a source or drain feature, and the epitaxially-grown silicon film is disposed on the source or drain feature. 
     
     
         20 . The device of  claim 16 , wherein the epitaxially-grown silicon film has a haze of about 1 part per million or less.