Patent ID: 8216905

Claim:
A method of preparing an active pixel cell on a substrate, comprising: creating a shallow trench isolation (STI) structure on the substrate, wherein during a creation of the STI structure a first stress is exerted on the substrate; measuring the first stress by using Raman Spectroscopy, wherein the first stress is reflected by Raman peak shift data; selecting a second stress of a film for a stress layer, wherein the second stress is used to counter first stress due to the creation of the STI structure; and depositing the stress layer with the second stress von the substrate, wherein the stress layer covers devices of the active pixel cell that are formed on the substrate and the formed devices include a photodiode next to the STI and a transistor, the deposition of the stress layer results in the second stress being exerted on the substrate and the second stress counters the first stress, and reduces dark current and white cell counts.