Mini-MALTA: radiation hard pixel designs for small-electrode monolithic CMOS sensors for the High Luminosity LHC

Abstract

A: Depleted Monolithic Active Pixel Sensor (DMAPS) prototypes developed in the TowerJazz 180 nm CMOS imaging process have been designed in the context of the ATLAS upgrade Phase-II at the HL-LHC. The pixel sensors are characterized by a small collection electrode (3 µm) to minimize capacitance, a small pixel size (36.4 × 36.4 µm), and are produced on high resistivity epitaxial p-type silicon. The design targets a radiation hardness of 1 × 10 15 1 MeV n eq /cm 2 , compatible with the outermost layer of the ATLAS ITK Pixel detector. This paper presents the results from characterization in particle beam tests of the Mini-MALTA prototype that implements a mask change or an additional implant to address the inefficiencies on the pixel edges. Results show full efficiency after a dose of 1 × 10 15 1 MeV n eq /cm 2 .

Latest Developments and Results of Radiation Tolerance CMOS Sensors with Small Collection Electrodes

“…3, the Mini-MALTA sensor, with 16 × 64 square pixels, has the matrix divided in 8 sectors with different pixel flavours, analog FE design, reset mechanism and electrode/well geometries. The left hand side has enlarged transistors to increase its gain and reduce the operational threshold [7]. The chip has an asynchronous read-out, with an improved slow-control with respect to MALTA and single serial data stream of 40Mbs or 1.2 Gpbs with 8b10b encoding.…”

“…The first two prototypes designed and issued were the large scale MALTA sensor [6] in January 2018, with a matrix of 512x512 and Mini-MALTA [7] in January 2019, a reduced-size prototype with a 16x64 pixel matrix. The pixel sensors presented on this paper have a small pixel size (36.4 x 36.4 µm2) and are produced on high resistivity epitaxial p-type silicon.…”

Vertex and tracking detector R&D for CLIC

“…In this way, the charge collection in the sensor and the sharing of the charge between individual pixels are reduced. The faster charge collection and higher single pixel charge simultaneously improve the radiation tolerance [15], the time-stamping capability and widen the efficient operation window to higher threshold values, which is especially relevant for thin sensors.…”

Depleted Monolithic Active Pixel Sensors in the LFoundry 150 nm and TowerJazz 180 nm CMOS Technologies

“…This requires more careful pixel layout design as well as further sensor engineering. Two different technological fixes have been proposed based on TCAD simulation [18], and both of them have been proven to be effective for improving the lateral field substantially in later tests with another chip [19].…”

“…Intensive R&D has also been performed on DMAPS design with a small electrode in order to enhance the radiation tolerance, and important lessons have been learned with the prototypes in the TowerJazz 180 nm CMOS technology, pointing out the weakness of the current design and the path for future improvements. Technological fixes as well as design optimization for the small electrode design have been implemented in a small scale test chip called MiniMALTA in TowerJazz, which has already shown significant improvements in both sensor charge collection property and circuit performance [19]. The design of next-generation Monopix chips in the two mentioned technologies are on-going, both of which feature optimized analog front-end electronics, smaller pixels and larger sensor format than their ancestors.…”