Method for the manufacture of a monolithic, static memory cell

Abstract

Production of high bit density memory cells using six selective, vertically aligned, reactive plasma etching steps. A gate oxide layer is applied to the boundary surface of the semiconductor layer and has a polysilicon layer which is highly doped and covered with a first intermediate oxide layer. A drive line and the gate are first formed. Sections of the drive line at the ends thereof are removed by isotropic etching and the resulting recesses are filled in a thermal oxidation step. The portion of the gate oxide layer adjacent the structured parts is removed by a second etching step. A second polysilicon layer is deposited, highly doped and covered with a second intermediate oxide layer. Another drive line having a part contacting a doped region in the semiconductor layer, the region being formed by ion implantation, is structured by a third etching step. A recess is then formed by a fourth etching step and an isotropic etching step is performed to remove those parts of the drive line which extend to the last-mentioned recess. A fifth etching step is performed for removing the oxide layer covering the boundary surface of the semiconductor layer within the recess. A third, silicon layer is deposited and covered with a third intermediate oxide layer. Another recess is formed in the third intermediate oxide layer above the recess provided by the fourth etching in a sixth etching step. A conductive coating is then applied to the third polysilicon layer and is provided with an electrical terminal.