Speaker
Description
Depleted CMOS Active Pixel Sensors (DMAPS) provide interesting solutions in environments where timing precision and radiation tolerance are needed, by achieving a sizable fully depleted sensitive layer with strong drift field. They also have the advantage of using commercial processes and do not need hybridization, which eases production at relatively low cost. Developments have recently followed several lines and concepts, and the focus of this talk will be DMAPS Monopix developments in two technologies, LFoundry 150 nm CMOS and TowerJazz 180 nm CMOS processes.
The development of DMAPS in LFoundry 150 nm relies on using a large collection electrode to achieve a depleted sensitive layer by combining high resistive substrate (> 2 kΩ.cm) as sensitive layer and high bias voltage (> 200 V). Its sensor structure mimics the standard planar sensor, and it incorporates a large-area implant as the collection node, thus is an intrinsically radiation-hard structure with uniform drifting field. The in-pixel electronics is integrated in the collection well thanks to the multiple nested wells offered by the foundry.
The TowerJazz development line uses a small collection well, and the resulting sensor capacitance can be as small as ~ 5 fF, a value typically at least an order of magnitude smaller than in the case of the large electrode design. A major benefit of small sensor capacitance is the possibility to employ a very low power analog front-end design (~ 1 µW/pixel) yet keep a low electronic noise value. In order to achieve a fully depleted sensitive layer, together with enhanced lateral collection field, dedicated process modifications are needed in this process.
This talk will focus on large scale demonstrators fabricated in the two processes, named LF-Monopix and TJ-Monopix, both using a synchronous architecture based on column drain as was utilized in the FE-I3 pixel chip currently used in the ATLAS pixel detector. Characterization results will be given, in particular for what concerns the behavior of the chips in both technologies after irradiation. A new design has recently been submitted (LF-Monopix2) / is about to be submitted (TJ-Monopix2) and a focus will be brought to the design of these new prototypes.
