Process for making air bridges for integrated circuits

Claim 1

The method of making an evaporated metallic air bridge on a semiconductor body between spaced contacts on an existing metallization, comprising the following steps: (1) photolithographically patterning a first uniform layer of photoresist coating said semiconductor body over said metallization to create two openings with steep sides at said two contacts with a photoresist strip of uniform thickness between said openings, (2) hard baking said photoresist strip to cause momentary softening to allow surface tension within said strip to reduce the slope of said openings at said contacts and create a gradually curving arcuate profile between contacts, said heating further polymerizing said photoresist for increased resistance to photoresist solvent and developer, and for reduced sensitivity to illumination, (3) photolithographically patterning a second layer of photoresist and a contrast enhancement layer coating said semiconductor body to create a third opening to expose said contacts and said hard baked strip of photoresist, the contrast enhancement layer creating a lip around said third opening to permit lift-off of unwanted portions of a second metal deposition outside said third opening, (4) forming a second metallization by evaporation over said semiconductor body, the deposition coating the exposed hard baked layer of photoresist and the exposed contact regions within said third opening to form an arch and coating areas surrounding said third opening, and (5) dissolving said second photoresist layer, the hard baked first layer of photoresist, and lifting off the portions of second metallization surrounding said third opening to form an air bridge.

Claim 2

The method of making an evaporated metallic air bridge on a semiconductor body between spaced contacts on an existing metallization, comprising the following steps: (1) photolithographically patterning a first uniform layer of photoresist coating said semiconductor body over said metallization to create two openings with steep sides at said two contacts with a photoresist strip of uniform thickness between said openings, (2) hard baking said photoresist strip to cause momentary softening to allow surface tension within said strip to reduce the slope of said openings at said contacts and create a gradually curving arcuate profile between contacts, said heating further polymerizing said photoresist for increased resistance to photoresist solvent and developer, and for reduced sensitivity to illumination, (3) photolithographically patterning a second layer of photoresist and a contrast enhancement layer coating said semiconductor body to create a third opening to expose said contacts and said hard baked strip of photoresist, the contrast enhancement layer creating a lip around said third opening to permit lift-off of unwanted portions of a second metal deposition outside said third opening, (4) forming a second metallization by evaporation over said semiconductor body, the deposition coating the exposed hard baked layer of photoresist and the exposed contact regions within said third opening to form an arch and coating areas surrounding said third opening, and (5) dissolving said second photoresist layer, the hard baked first layer of photoresist, and lifting off the portions of second metallization surrounding said third opening to form an air bridge.