Method of selective etching

Claim 1

A method of manufacturing a silicon semiconductor device comprising the steps of a. preparing a silicon substrate whose one principal surface is covered with a silicon nitride film, b. depositing an aluminum layer on said film, c. forming on said aluminum layer a photoresist layer having a desired geometrical pattern, d. engraving said aluminum layer in accordance with said pattern with said photoresist layer as a mask, e. heating the surface of said aluminum layer thus engraved in an oxidizing atmosphere at a temperature in the range of about 500* C. to 600* C. thereby to make the surface etching-proof, and f. subjecting the exposed portion of said nitride film not covered with the etching-proof aluminum oxide layer to a solution whose major ingredient is hydrofluoric acid, thereby forming in said exposed portion a hole and exposing the semiconductor substrate there-through.

Claim 3

A method of manufacturing a semiconductor device comprising the steps of covering a surface of a semiconductor substrate with a silicon nitride film; forming a photoresist layer having a desired geometrical pattern on said silicon nitride film; depositing a layer of a metal selected from the group consisting of aluminum, titanium and chromium on the surface of said silicon nitride film and said photoresist layer; removing said photoresist layer and the layer of said metal deposited on said photoresist layer while leaving the layer of said metal deposited on the silicon nitride film substantially intact; heating the combination thus obtained in an oxidizing atmosphere at a temperature in the range of 500* C. to 1,300* C. to oxidize at least the surface of said layer of a metal; and subjecting the exposed portion of said nitride film to a solution the major ingredient of which is hydrofluoric acid.

Claim 4

A method of manufacturing a semiconductor device comprising the steps of depositing a layer of aluminum oxide on a silicon nitride film by thermally decomposing an aluminum organic compound at about 400* C.; removing a selective portion of said layer of aluminum oxide; heating the remaining layer of aluminum oxide at a temperature of at least about 600* C.; then subjecting the exposed portion of said nitride film to a solution the major ingredient of which is hydrofluoric acid.

Claim 5

A method of selectively etching a material containing a silicon nitride film comprising the steps of preparing a layer of a metal selected from the group consisting of titanium and chromium on a portion of the surface of said material, the material being exposed partially in accordance with a geometric pattern; heating the combination thus obtained in an oxidizing atmosphere at a temperature in the range of 800* C. to 1,300* C. so as to oxidize at least the surface part of said layer of the metal; then subjecting the exposed portion of said material to an etchant containing hydrofluoric acid as the major ingredient, against which said layer and said material have a high and a low etching resistance, respectively, and etching said material selectively in accordance with said pattern.