Ziptronix announces industry’s lowest distortion capability for backside illuminated image sensor apps

RESEARCH TRIANGLE PARK, USA: Ziptronix Inc., the leading developer of direct bonding technology for advanced semiconductor applications, announced that recent collaborations with major image-sensor manufacturers have shown that the Ziptronix ZiBondTM direct bonding process contributes minimum distortion in backside illuminated (BSI) image sensors.

“In addition to confirming that the Ziptronix direct bonding technology delivers the lowest distortion of any process for manufacturing BSI image sensors, these results have tremendous bottom-line significance for image sensor makers,” said Ziptronix CEO Dan Donabedian. “Minimal distortion means pixels can be scaled smaller, and that means increased image sensor resolution, more die per wafer, improved image sensor yields and lower production costs.”

BSI image sensors are rapidly replacing frontside illuminated image sensors for applications such as digital cameras and smartphone cameras due to pixel scaling and other advantages enabled by not illuminating the photodiodes through the CMOS interconnect stack. BSI image sensor manufacturing typically requires bonding a silicon CMOS wafer to a non-CMOS handle wafer. Because this bonding technology does not involve a large coefficient of thermal expansion (CTE) mismatch, it does enable very low distortion which is required for scalable color filter array overlay on the exposed photodiodes after thinning of the bonded CMOS wafer.

Distortion of the wafer introduced during the bonding process can compromise the overlay and limit pixel scaling. ZiBond’s inherent capacity for high bond strength at low temperature effectively minimizes this distortion compared to the competing bond technologies, adhesive and copper thermo-compression. This directly enables submicron pixel scaling; for example, 0.9 micron pixel BSI image sensors have already been fabricated and work on 0.7 micron pixel BSI is underway.

Sony Corp., a leader in image sensor manufacturing, has recently licensed the Ziptronix ZiBond technology for BSI image sensor manufacturing. Several sources, including a Chipworks teardown published by technology blog network Engadget, have subsequently reported that Sony is supplying image sensors for the iPhone 4S.