Abstract A method of precision etching for semiconductor device fabrication using the preferential characteristics of certain etchants for particular crystallographic planes of monocrystalline material. In particular, silicon is precisely etched by disposing etch masks on surfaces parallel to the (100) plane with the mask edges parallel to the lines of intersection of the (111) planes with the (100) plane, and using alkali hydroxide etches as well as certain organic reagents, which have substantially lower etch rates with respect to the (110) and (111) planes. Also, undercutting at intersections of the mask boundaries which expose the (110) plane is avoided by shaping the mask to compensate therefor. A suitable etchant formulation contains 50 parts by volume of water, 15 parts by volume of npropanol and has molar concentration of hydroxide of about 5.3.
The process in accordance with claim 1 in which the adjoining edges of said etch resistant mask defining unmasked portions of said slice surface have a width sufficient to enable penetration by the etching process through the silicon slice, said etching process being self-terminating.
Claim 2
Dependent Claim
21 words
The process in accordance with claim 1 in which the mask is shaped to a compensating form at its outside corners.
Claim 3
Dependent Claim
125 words
The process of shaping by anisotropic chemical etching a monocrystalline slice of silicon semiconductor material having as low order crystallographic planes the (100), (111) and (110), said slice having its two major surfaces in said (100) plane, forming an etch resistant mask of silicon oxide on one of said major surfaces, the edges of said mask being parallel to the lines of intersection between the (100) and the (111) plane, applying an etchant comprising a solution of potassium hydroxide, water, and n-propanol having the relative proportions of about 15 grams of potassium hydroxide, 50 milliliters of water and 15 milliliters of n-propanol, corresponding to molar concentration of said hydroxide of about 5.3, said solution being applied to said slice at a temperature of about 85*C.