Etching a semiconductor material and automatically stopping same

Claim 1

A method of etching material from one surface of a silicon substrate formed with a first region adjacent said one surface and a second region spaced from said one surface, said second region being doped with N type impurity atoms in a concentration high enough to significantly retard a chemical reaction between the silicon and a refractory metal hexafluoride, said method comprising: masking said one of said surfaces to expose a surface area of said substrate where said silicon is to be etched; exposing said substrate to a gaseous refractory metal hexafluoride at a temperature of at least about 550° C. whereby said hexafluoride reacts with the silicon in said first region to replace the silicon with the refractory metal of said hexafluoride, and maintaining said reaction until all of the silicon in said first region has been replaced with the refractory metal of said hexafluoride; and etching said refractory metal from said first region of said substrate with an etchant that does not substantially react with the semiconductor material.

Claim 2

A method of etching material from one surface of a silicon substrate formed with a first region adjacent said one surface and a second region spaced from said one surface, said second region being doped with N type impurity atoms in a concentration high enough to significantly retard a chemical reaction between the silicon and a refractory metal hexafluoride, said method comprising: masking said one of said surfaces to expose a surface area of said substrate where said silicon is to be etched; exposing said substrate to a gaseous refractory metal hexafluoride at a temperature of at least about 550° C. whereby said hexafluoride reacts with the silicon in said first region to replace the silicon with the refractory metal of said hexafluoride, and maintaining said reaction until all of the silicon in said first region has been replaced with the refractory metal of said hexafluoride; and etching said refractory metal from said first region of said substrate with an etchant that does not substantially react with the semiconductor material.

Claim 6

A method in accordance with claims 1 or 2 wherein said substrate is exposed to a refractory metal hexafluoride selected from the group consisting of tungsten hexafluoride and molybdenum hexafluoride.

Claim 7

A method in accordance with claims 1 or 2 wherein said substrate is exposed to tungsten hexafluoride.

Claim 10

A method of etching material from one surface of a silicon substrate formed with a first region adjacent said one surface and a second region spaced from said one surface doped with phosphorus atoms in a concentration of at least about 10 19 atoms/cm 3 , said method comprising: forming an oxide mask on said one surface to expose a surface area of said substrate where said silicon is to be etched; and raising the temperature of said substrate to a temperature of at least about 550° C. and exposing it to a refractory metal hexafluoride selected from the group consisting of tungsten hexafluoride and molybdenum hexafluoride for a period of time sufficient for the refractory metal of said hexafluoride to replace the silicon atoms in said first region of said substrate whereupon the reaction between said hexafluoride and said silicon stops at said second region.

Claim 11

A method of etching material from one surface of a silicon substrate formed with a first region adjacent said one surface and a second region spaced from said one surface doped with phosphorus atoms in a concentration of at least about 10 19 atoms/cm 3 , said method comprising: forming an oxide mask on said one surface to expose a surface area of said substrate where said silicon is to be etched; and raising the temperature of said substrate to a temperature of at least about 550° C. and exposing it to a refractory metal hexafluoride selected from the group consisting of tungsten hexafluoride and molybdenum hexafluoride for a period of time sufficient for the refractory metal of said hexafluoride to replace the silicon atoms in said first region of said substrate whereupon the reaction between said hexafluoride and said silicon stops at said second region.