FABRICATION OF SEMICONDUCTOR DEVICE

摘要

PURPOSE:To etch a plurality of layer insulation films at a desired etching rate ratio with high controllability by employing an etching liquid containing speci fied quantity of hydrofluoric acid and ammonium fluoride. CONSTITUTION:A BPSG layer 21 is etched back for 1.5-2min using an etching liquid containing 1.6-6wt.% of hydrofluoric acid and 2.5-10wt.% of ammonium fluoride thus exposing an MTO layer 20 on a polysilicon layer 16. The etching rate for the BPSG layer 21 is set 1.1-1.2 times as high as that for the MTO layer 20 so that even a thick BPSG layer is etched back sufficiently and selectively thus sustaining planarity on the surface. This method planarizes the surface while enhancing the step coverage.