Chipworks published iPhone 4 teardown report and identified its 5MP BSI sensor as made by Omnivision, likely part number is OV5642. The pixel size is 1.4 µm and the sensor is manufactured at 130 nm process generation.
Update June 24, 2010: I received a mail from Chipworks saying:
"The sensor in the iPhone is believed to be the OmniVision 1.7 as disclosed by Apple. We made an error in our post describing it as 1.4 and have fixed it.
We are expected to have the camera module in our RE labs today and will fully confirm the device. (It was torn down in California)."
Below is OV5642 die photo:
Update #2: EETimes published UBM TechInsights findings from its iPhone 4 teardown:
"The phone's front-facing five-Mpixel camera is either the OV5650 or the OV5653 based on specifications and preliminary die photos inspection. The image sensors have appeared in handsets the group has examined, however it is a relatively modern choice compared to image sensors in past iPhones, and it supports backside illumination.
"Typically Apple uses older image sensors to save a few dollars," said Steve Bitton, a product manager with UBM TechInsights working on the iPhone 4 teardown.
Update #3: UBM TechInsights published iPhone 4 sensor photo with following comments:
"By examining the image sensor package and by comparing the die photo and specifications to our die image library, we have identified the 5 MP image sensor as the Omnivision OV5650 with backside illumination technology."
Here is the die photo: