A layer is formed over a wafer. The layer contains a material that is sensitive to an extreme ultraviolet (EUV) radiation. A first baking process is performed to the layer. The first baking process is performed with a first humidity level that is greater than about 44%. After the first baking process, the layer is exposed to EUV radiation. A second baking process is performed to the layer. The second baking process is performed with a second humidity level that is greater than about 44%. The layer is rinsed with a liquid that contains water before the second baking process or after the second baking process. After the exposing, the layer is developed with a developer solution that contains water.