Sealed nitride layer for integrated circuits

A method of forming an integrated circuit, the method comprising:

• forming a layer of oxide over a surface of a substrate;
• forming a first layer of nitride overlaying the layer of oxide;
• forming a contact opening through the first layer of nitride and the oxide layer to expose a portion of the surface of the substrate;
• forming a second layer of nitride overlaying the first layer of nitride, the second layer of nitride also overlaying the exposed portion of the surface of the substrate in the contact opening and sidewalls of the contact opening;
• and
• using a reactive ion etch (RIE etch) without a mask on the substrate for a pre-determined amount of time to remove a portion of the second layer of nitride overlaying the surface of the substrate in the contact opening without removing the portions of the second nitride layer overlaying the sidewalls of the contact opening and without removing portions of the first nitride layer overlaying the oxide layer, wherein the oxide layer is sealed by the first and second nitride layers.

A method of forming semiconductor devices in an integrated circuit comprising:

• forming a plurality of device regions of a first conductivity type in a substrate adjacent a surface of the substrate;
• forming an oxide layer over a surface of a substrate;
• patterning the oxide layer to expose pre-selected portions of the surface of the substrate;
• forming a first layer of nitride overlaying the oxide layer and the exposed portions of the surface of the substrate;
• implanting ions of a second conductivity type through the layer of nitride into the substrate to form device regions of the second conductivity type, wherein remaining portions of the oxide layer under the nitride layer selectively stop the ions from entering the substrate to selectively define edges of the device regions of the second conductivity type;
• forming contact openings to expose a portion of each of the device regions of the first and second conductivity type in the substrate;
• forming a second layer of nitride over the first layer of nitride, the second layer of nitride also overlaying the exposed portions of each of the device regions in their associated contact openings and sidewalls of each of the contact openings;
• and
• exposing the substrate to a reactive ion etch (RIE etch) for a pre-determined amount of time to remove portions of the second layer of nitride adjacent a surface of each device region in an associated contact opening, wherein the substrate is not exposed to RIE etch long enough to remove all of the portions of the second nitride layer overlaying the respective sidewalls of each of the contact openings and portions of the first layer of nitride overlaying the oxide layer so that the oxide layer remains sealed by the first and second layers of nitride.