The design methodology for the development of 3D integrated edgeless pixel detectors with in-pixel processing using
Electronic Design Automation (EDA) tools is presented. A large area 3 tier 3D detector with one sensor layer and two
ASIC layers containing one analog and one digital tier, is built for x-ray photon time of arrival measurement and imaging.
A full custom analog pixel is 65μm x 65μm. It is connected to a sensor pixel of the same size on one side, and on the other
side it has approximately 40 connections to the digital pixel. A 32 x 32 edgeless array without any peripheral functional
blocks constitutes a sub-chip. The sub-chip is an indivisible unit, which is further arranged in a 6 x 6 array to create the
entire 1.248cm x 1.248cm ASIC. Each chip has 720 bump-bond I/O connections, on the back of the digital tier to the
ceramic PCB. All the analog tier power and biasing is conveyed through the digital tier from the PCB.
The assembly has no peripheral functional blocks, and hence the active area extends to the edge of the detector. This was
achieved by using a few flavors of almost identical analog pixels (minimal variation in layout) to allow for peripheral
biasing blocks to be placed within pixels. The 1024 pixels within a digital sub-chip array have a variety of full custom,
semi-custom and automated timing driven functional blocks placed together. The methodology uses a modified mixed-mode
on-top digital implementation flow to not only harness the tool efficiency for timing and floor-planning but also to
maintain designer control over compact parasitically aware layout. The methodology uses the Cadence design platform,
however it is not limited to this tool.
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