Negative tone i-line photoresist with controlled undercut profile designed for metal deposition to form metal interconnects

Metal deposition on a substrate using the lift-off process plays a vital role in the semiconductor industry to generate metal interconnects. The metal deposition on the substrate can be carried out using the process of evaporation or sputtering. In the metal lift-off process, the substrate is first patterned with resist followed by metal deposition using either the evaporation or sputtering process and eventually the photoresist is removed using a remover solvent. In both the deposition techniques, a unique undercut profile of the photoresist is desired. For metal deposition using the evaporation process, the photoresist is required to have a 're-entrant' profile. On the other hand, for deposition using the sputtering process, the photoresist is desired to have a 'T-shaped' profile typically achieved using a bi-layer process. The AZ® LNR-003 formulation is a chemically amplified negative tone photoresist developed by EMD Performance Materials Corp. designed to generate a T-shaped profile, suitable for the metal deposition using the sputtering process. The undercut profile can be tailored by modifying the process conditions such as post applied bake temperature, post exposure bake temperature and development conditions. The formulation comprises of a specific combination of photoacid generator, quencher and additive which generates the 'T-Shaped profile'. The AZ® LNR-003 photoresist can replace the bi-layer process used at present in the semiconductor industry to generate the 'T-shaped' profile with a single layer step.