In the fabrication of 40nm BSI CMOS Image Sensors, the Sacrificial Lower OCL Reflow step is critical for defining the three-dimensional optical profile of the lower microlens array P1.While the preceding coat, expose, and develop steps define the lateral footprint of the sacrificial photoresist as discrete vertical cylinders, this reflow step physically reshapes them into continuous convex lenses P1.This transformation is strictly necessary to prepare the precise geometric profile that will be p