Effect of Molecular Weights of 193nm Resist Polymers on the Negative Tone Development Process

The effect of molecular weights of 193nm resist polymers on the negative tone development (NTD) process was studied in three different solvent developers. By optimizing the polymer structures for the NTD process, it was possible to improve the dissolution rate of 193 nm resist polymers in the NTD process to give higher dissolution rate contrasts in a wide range of molecular weights. Contrary to the conventional positive tone development process, the NTD process yielded faster photospeeds with higher molecular weights. It was also found that the critical dimension uniformity (CDU) of 193 nm resists can be optimized in the NTD process by optimizing the molecular weights of the resist polymers. The optimum Mw for the best CDU was different for different developers and could be different for different resist formulations. In addition to the resist polymers and developers, it will be necessary to optimize other imaging materials for the NTD process in order to maximize the full benefits of the NTD process.