Etching method and etching composition useful for the method

Abstract

In etching of silicon nitride with a phosphorus type, if etching is carried for a long time, silicon oxide tends to precipitate, and it has been impossible to constantly carry out the etching for a long period of time. By an etching method for silicon nitride using a composition comprising a phosphorus compound, a boron compound, a silicon compound and/or their fluorides thereof, there will be no precipitation of silicon oxide even when the composition is used for a long time. It is particularly preferred to further add nitric acid and/or a nitrate, whereby stability of selectivity will be increased.

1 . An etching method for silicon nitride, which comprises etching silicon nitride with a composition comprising a phosphorus compound and/or a fluoride thereof, a boron compound and/or a fluoride thereof, a silicon compound and/or a fluoride thereof, and water. 
     
     
         2 . The etching method for silicon nitride according to  claim 1 , wherein the phosphorus compound and/or a fluoride thereof is at least one member selected from the group consisting of phosphoric acid, phosphorus fluoride, phosphorus trifluoride, phosphorus pentafluoride, fluorophosphoric acid and a fluorophosphate. 
     
     
         3 . The etching method for silicon nitride according to  claim 1 , wherein the boron compound and/or a fluoride thereof is at least one member selected from the group consisting of boric acid, a borate, boron fluoride, boron trifluoride, fluoroboric acid and a fluoroborate. 
     
     
         4 . The etching method for silicon nitride according to  claim 1 , wherein the silicon compound and/or a fluoride thereof is at least one member selected from the group consisting of a silicon halide, hexafluorosilicic acid, a hexafluorosilicate, an alkoxysilane, an alkylsilane, silicic acid, a silicate, silicon fluoride, silicon chloride, ammonium hexafluorosilicate, tetraethoxysilane, tetramethoxysilane and methyltrimethoxysilane. 
     
     
         5 . The etching method for silicon nitride according to  claim 1 , wherein the boron content in the composition is from 0.001 to 10 wt %. 
     
     
         6 . The etching method for silicon nitride according to  claim 1 , wherein the silicon content in the composition is from 0.001 to 0.01 wt %. 
     
     
         7 . The etching method for silicon nitride according to  claim 1 , wherein the fluorine content in the composition is from 0.010 to 0.050 wt %. 
     
     
         8 . The etching method for silicon nitride according to  claim 1 , wherein the composition further contains nitric acid and/or a nitrate. 
     
     
         9 . The etching method for silicon nitride according to  claim 1 , wherein etching is carried out at a temperature of from 120° C. to 180° C. 
     
     
         10 . The etching method for silicon nitride according to  claim 1 , wherein at least one member selected from the group consisting of a phosphorus compound and/or a fluoride thereof, a boron compound and/or a fluoride thereof, a silicon compound and/or a fluoride thereof, nitric acid and/or a nitrate, and water, is additionally added. 
     
     
         11 . An etching composition for silicon nitride as defined in  claim 1 .