Plasma etcher having isotropic subchamber with gas outlet for producing uniform etching

Claim 1

In an etcher for etching surfaces of articles with a gaseous discharge plasma generated within an etching chamber provided with a plurality of electrodes, a plasma etcher comprising (i) an etching chamber containing at least a pair of electrodes, one of said electrodes being arranged to support thereon articles to be etched; (ii) means defining a gas inlet which serves to introduce a gas directly into said etching chamber; (iii) means for effecting an isotropic emission of gas from said etching chamber including a joint part forming a restricted passage which is isotropically disposed outside an outer fringe of the electrode for supporting said articles and into and through which said gas can flow from said etching chamber; (iv) an isotropically-configured subchamber which is coupled with said etching chamber through said joint part and which has a capacity as well as a fluid conductance greater than that of said joint part, said subchamber having an annular configuration and said passage formed by said joint part being restricted to an extent necessary to restrain the gas pressure in said etching chamber in the vicinity of said passage from becoming substantially lower than the gas pressure in other parts of said etching chamber; and (v) means defining a gas outlet provided in said subchamber for accommodating the outflow of gas.