Omnivision BSI Backside Implant Optimizations

Omnivision BSI pixel uses P+ backside implant to passivate the backside surface. The recently published WO/2009/099491 patent application gives some details of its optimization process. The figure below shows the location of the backside P+ implant 220:

First, Omnivision optimizes the P+ layer depth, making few implants with different energies:

The sensitivity for the different depths is shown below:

Next step is the optimization of the P+ implant dosage. The three tested dosages are shown here:

The pixel sensitivity vs dosage is shown below:

One more step is optimization of the silicon layer thickness:

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