Process for anisotropic etching of silicon plates

A process of anisotropically etching a silicon plate having a thickness dimension which is the smallest of three mutually perpendicular dimensions of the plate and having first and second portions of opposite conductivity types (p, n) adjoining each other along a mutual boundary surface essentially perpendicular to the thickness dimension of the plate, said first plate portion being monocrystalline, said process including modifying the front side of said plate at the external surface of said monocrystalline second portion of the plate through gaps of at least one inorganic masking layer, said modifying being performed by a process step of etching a topographic configuration extending into said monocrystalline first plate portion from the plate side provided by it and stopping short of said boundary, a process step of depositing metallization on said first plate portion or a sequential combination of said process steps in the order named, a step of providing a passivating layer protecting the exposed surface of the first plate portion, and a process step of etching the side of said plate presented by said second plate portion, characterized in that

• the etching steps are performed with an etchant mixture containing, as an etchant, an organically substituted ammonium hydroxide of the formula NR.sub.4 OH in aqueous solution or in water-free state, wherein R designates an alkyl group containing not more than four carbon atoms, said etchant mixture including as an additive a complexing agent, an inhibitor, or a wetting agent, or two or more additives selected from complexing agents, inhibitors and wetting agents.