Method of forming dual size microlenses for image sensors

A method of forming microlenses for a complementary metal oxide semiconductor (CMOS) image sensor having at least one large-area pixel and at least one small-area pixel, the method comprising:

• applying a uniform layer of photoresist material on a light incident side of the image sensor over the at least one large-area pixel and over the at least one small-area pixel;
• exposing the layer of photoresist material to a pattern of light and developing the exposed layer to simultaneously:
• form the photoresist material into a first block disposed over the at least one large area pixel and into a second block disposed over the at least one small area pixel;
• and
• form at least one void in the second block to reduce a volume of the photoresist material included in the second block;
• and
• reflowing the first block and second block of photoresist material to form a respective first microlens and second microlens, wherein the first microlens has substantially the same effective focal length as the second microlens.