DBI Enables CIS Evolution

Paul Enquist from Xperi (Ziptronix, Invensas) publishes an article "Direct Bond Technology Enables CMOS Image Sensor Evolution." Few quotes:

"A hybrid bond improvement in direct bond technology that allowed the elimination of TSVs and associated cost and die area by enabling scalable interconnection between two stacked wafers as part of the direct bond process was initially mass produced by Sony to deliver a third generation 1.4-µm pixel, 12-Mpixel BSI CIS in the 2016 iPhone 6S. A 14-µm hybrid bond interconnect pitch was used outside the pixel array for row/column interconnect and an electrically isolated 6-µm hybrid bond interconnect pitch was used within the pixel array.

Earlier this year, a fourth generation BSI using two iterations of the second-generation direct bond plus TSV interconnect was subsequently used to mass produce a three-layer stack of photodiode, 1-Gb DRAM memory, and logic. The DRAM buffering enabled unpresented performance of 960 fps at 1080p with a 1.4-µm pixel, 12-Mpixel BSI CIS used in the Samsung Galaxy S9. Also this year, Sony announced a fifth generation BSI CIS using a hybrid bond with a per pixel interconnect underneath the pixel array not possible with TSV technology. This enabled a 6.9-µm pixel, 1.5-Mpixels at 660 fps with a dedicated subthreshold ADC per pixel and a global shutter with and -75 dB parasitic light sensitivity.

Direct and hybrid bond technology has thus played an enabling role in the realization of BSI and stacked BSI with multiple generational variations of BSI CIS as summarized in Figure 1. The development of these technologies has been led by Xperi for over 15 years resulting in a substantial intellectual property portfolio that has been licensed to CIS industry leaders. The direct bond technology and hybrid bond technologies have been trademarked as ZiBond and DBI, respectively."