Enhancing step coverage by creating a tapered profile through three dimensional resist pull back

The method of forming an electrical contact to an integrated circuit device structure comprising:

• providing an insulating layer overlying said integrated circuit device structure;
• forming and patterning a photoresist layer on top of said insulating layer with openings in said photoresist layer where the desired said tapered opening is to be located;
• isotropically etching through said openings a portion of said insulating layer vertically and horizontally;
• pulling back said photoresist layer via a pure isotropic etch wherein said photoresist layer is eroded from the portion of said photoresist layer in contact with said insulating layer forming an overhang photoresist profile and leaving a step at the top of said insulating layer underneath said overhang photoresist profile;
• anisotropically etching remainder of said opening through said insulating layer wherein said overhang photoresist profile is etched away exposing said insulating layer step which is smoothed into said tapered opening having positive sloped sidewalls;
• wherein said anisotropic etch is performed using a first step with low selectivity of said photoresist to said insulating layer of between about 2:1 to 3:1 and followed by a second step using higher selectivity of said photoresist to said insulating layer;
• and
• completing said contact to said integrated circuit device structure by filling said electrical contact opening with metallurgy.

The method of forming an electrical contact through an oxide/spin-on-glass/oxide sandwich layer to the underlying metallurgy layer of an integrated circuit comprising:

• forming and patterning a photoresist layer on top of said sandwich layer to leave openings in the photoresist layer at the locations of the desired said electrical contact;
• isotropically etching a portion of said sandwich layer vertically and horizontally through said photoresist layer openings and stopping said etching before said spin-on-glass portion of said sandwich layer is reached;
• pulling back said photoresist layer by a pure isotropic etch wherein said photoresist layer is eroded from the portion of said photoresist layer in contact with said insulating layer forming an overhang photoresist profile and leaving a step at the top of said sandwich layer underneath said overhang photoresist profile;
• anisotropically etching remainder of said electrical contact opening through said sandwich layer wherein said overhang photoresist profile is etched away exposing said sandwich layer step which is smoothed into said tapered opening having positive sloped sidewalls;
• wherein said anisotropic etch is performed using a first step with low selectivity of said photoresist to said insulating layer of between about 2:1 to 3:1 and followed by a second step using higher selectivity of said photoresist to said insulating layer;
• and completing said electrical contact to said metallurgy layer by filling said electrical contact opening with a second metallurgy.