Tapered opening sidewall with multi-step etching process

In the method of fabrication of a metal oxide semiconductor field effect integrated circuit having a feature size of about one micrometer or less wherein the semiconductor integrated circuit structure having device elements is covered with a silicon oxide layer and a silicate glass layer, a process for forming tapered contact openings to device elements comprising:

• forming a resist masking layer over the said silicate glass layer having openings therein in the areas where the said contact openings are desired;
• anisotropically etching into said silicate glass layer through a first thickness to form a first opening using said resist masking layer as a mask;
• isotropic etching through a second thickness portion of said silicate glass layer to substantially uniformly enlarge said first opening while using unchanged said resist layer;
• anisotropically etching through the remaining thickness of said silicate glass layer to the semiconductor substrate to form said tapered opening with a metal step coverage improvement between about 20 to 60% ;
• and removing the said resist layer.

In the method of fabrication of a metal oxide semiconductor field effect integrated circuit having a feature size of about one micrometer or less wherein the semiconductor integrated circuit structure having device elements is covered with a composite layer composed of a silicon oxide layer, spin-on-glass and a silicon oxide layer, a process for forming tapered contact openings to device elements comprising:

• forming a resist masking layer over the said composite layer having openings therein in the areas where the said openings are desired;
• anisotropically etching into said composite layer through a first thickness to form a first opening using said resist masking layer as a mask;
• isotropic etching through a second thickness portion of said composite layer to substantially uniformly enlarge said first opening while using unchanged said resist layer;
• anisotropically etching through the remaining thickness of said composite layer to the desired conductive layer forming part of said device elements to form said tapered opening with a metal step coverage improvement between about 20 to 60%;
• and
• removing the said resist layer.