Metal lift-off systems and methods using liquid solvent and frozen gas

A method of fabricating an infrared imaging device, comprising:

• patterning a layer of photoresist on a surface of a wafer to define metal feature areas and residual metal areas;
• depositing a metal layer over the patterned layer of photoresist, the metal layer comprising metal feature portions in the metal feature areas and residual metal in the residual metal areas;
• flooding the wafer with a low-pressure solvent;
• spraying the surface of the wafer with a high-pressure solvent to remove the photoresist and the residual metal from the surface of the wafer;
• securing the wafer on a platen that can be rotated to at least a first position and a second position;
• spraying the surface of the wafer with a stream of frozen gas particles, with the wafer on the platen in the first position, to remove metal flaps from edges of the metal feature portions;
• rotating the platen to the second position;
• and
• spraying the surface of the wafer with a second stream of frozen gas particles, with the wafer on the platen in the second position, to remove metal flaps from edges of the metal feature portions;
• wherein the metal feature portions comprise reflectors of an array of microbolometers.

A method of fabricating an array of microbolometers comprising:

• depositing a first layer of photo-resist on a surface of a wafer;
• depositing a second layer of photo-resist on the wafer;
• developing the first and second layers of photo-resist to define metal feature areas and residual metal areas, wherein undercuts form in the first layer of photo-resist at edges of the metal feature areas;
• depositing a layer of metal over the first and second layers of photo-resist, wherein the layer of metal comprises residual metal portions in the residual metal areas, metal feature portions in the metal feature areas, and residual flaps in the undercuts, wherein the metal feature portions include legs of the array of microbolometers;
• flooding the wafer in a solvent and spraying the surface of the wafer with a high-pressure solvent, wherein the flooding with the solvent and the spraying with the high-pressure solvent removes the first and second layers of photo-resist and the residual metal portions;
• positioning the wafer in a plurality of orientations;
• and
• spraying the surface of the wafer with a stream of frozen CO2 particles while the wafer is in each of the orientations, wherein the spraying with the stream of frozen CO2 particles removes the residual flaps remaining after the flooding with the solvent and the spraying with the high-pressure solvent.