Humidity control in EUV lithography

A semiconductor fabrication system, comprising:

• a photoresist coating tool configured to introduce water to a photoresist layer and to coat the photoresist layer over a wafer;
• a baking tool configured to bake the photoresist layer at a humidity setting greater than about 44%;
• an exposure tool configured to expose the photoresist layer to extreme ultraviolet (EUV) light;
• a rinsing tool configured to rinse the photoresist layer with a liquid that contains water;
• a developing tool configured to develop the photoresist layer with a developer solution that contains water;
• and
• one or more controllers configured to control:
• an amount of water introduced to the photoresist layer by the photoresist coating tool, the humidity setting of the baking tool, an amount of water in the liquid for the rinsing tool, and an amount of water in the developer solution for the developer tool, wherein at least some of the one or more controllers are integrated into one or more of:
• the photoresist coating tool, the baking tool, the rinsing tool, or the developing tool.

A method, comprising:

• forming a photoresist layer over a substrate;
• performing a pre-exposure baking process to the photoresist layer in a controlled environment having a humidity level greater than about 44%;
• performing an exposure process to the photoresist layer;
• performing a post-exposure baking process to the photoresist layer in the controlled environment;
• performing a rinsing process to the photoresist layer with a water-containing liquid before the pre-exposure baking process or after the post-exposure baking process;
• and
• performing a photoresist developing process using a developer solution that contains water.