A method of forming an image sensor device includes forming a light sensing region at a front surface of a silicon substrate and a patterned metal layer there over. Thereafter, the method also includes performing an ion implantation process to the back surface of the silicon substrate and performing a green laser annealing process to the implanted back surface of the silicon substrate. The green laser annealing process uses an annealing temperature greater than or equal to about 1100° C. for a duration of about 100 to about 400 nsec. After performing the green laser annealing process, a silicon polishing process is performed on the back surface of the silicon substrate.