Selective polycrystalline silicon removal combining dry etching and wet etching process for 3D multilayer device fabrication

Abstract

Polycrystalline silicon (polysilicon) is generally regarded as structure material and dummy material in 3D multilayer structure semiconductor manufacturing. The selective removal of polysilicon is therefore an essential process for 3D memory device fabrication, which requires the combination of patterning and deep hole etching. In this work, we developed a polysilicon removal method combining dry etching and wet etching steps for hole structure with aspect ratio 10:1 in multilayer device application. Dry etching process opening hard mask layers was found to form block layer against wet etching process aiming to remove dummy polysilicon. Chlorine and hydrogen bromide (Cl₂/HBr) based plasma was selected for dry etching process after hard mask opening procedure to form polysilicon surface without blocking layer, enabling wet etching process to effectively remove dummy polysilicon.