The Monopix chips: depleted monolithic active pixel sensors with a column-drain read-out architecture for the ATLAS Inner Tracker upgrade

Abstract

A: Two different depleted monolithic CMOS active pixel sensor (DMAPS) prototypes with a fully synchronous column-drain read-out architecture were designed and tested: LF-Monopix and TJ-Monopix. These chips are part of a R&D effort towards a suitable implementation of a CMOS DMAPS for the HL-LHC ATLAS Inner Tracker. LF-Monopix was developed using a 150nm CMOS process on a highly resistive substrate (>2 kΩ cm), while TJ-Monopix was fabricated using a modified 180 nm CMOS process with a 1 kΩ cm epi-layer for depletion. The chips differ in their front-end design, biasing scheme, pixel pitch, dimensions of the collecting electrode relative to the pixel size (large and small electrode design, respectively) and the placement of read-out electronics within such electrode.Both chips were operational after thinning down to 100 µm and additional back-side processing in LF-Monopix for total bulk depletion. The results in this work include measurements of their leakage current, noise, threshold dispersion, response to minimum ionizing particles and efficiency in test beam campaigns. In addition, the outcome from measurements after irradiation with neutrons up to a dose of 1 × 10 15 n eq /cm 2 and its implications for future designs are discussed.

CACTUS: a depleted monolithic active timing sensor using a CMOS radiation hard technology

“…The BV measured on version A is 230 V. The BV measured on version B is around 350 V. The value for version A was also confirmed on other thinned and non-thinned sensors. According to previous tests with similar structures and the same substrate resistivities on the same process, these voltages are enough to fully deplete thinned substrates (−15 V needed for 100 µm and −60 V for 200 µm [15]). The ability to bias the sensor with higher voltages is beneficial to compensate for the charge losses after neutron irradiation [16].…”

Progress on the radiation tolerance of CMOS Monolithic Active Pixel Sensors

“…The readout of the pixels is done by a column drain architecture. During tests, the sensor demonstrated a gain of ∼ 400 µV/e [121]. The threshold before irradiation was 350 e with a dispersion of 35 e and a noise of 16 e ENC.…”

“…LF-Monopix is a depleted MAPS (DMAPS) prototype program [120,121,130] aiming for ATLAS. The concept of the sensor relies on sizeable 250 × 50 µm pixels with high fill factor diodes.…”

Recent measurements on MiniMALTA, a radiationhard CMOS sensor with small collection electrodesfor ATLAS

“…It features a 512 × 512 matrix of 36.4 × 36.4 µm 2 pixels with a small (3 µm wide) collection electrode electrode with an approximate input capacitance of 5 fF. It features low noise (<20 ENC) and low power consumption (<70 mW/cm 2 ).The key difference between MALTA and the other TowerJazz DMAPS for the ITk, Monopix, is the asynchronous read out architecture which features a 40 bit parallel data bus for high hit rates, and an overall read out speed of 5 Gbit/s [3]. (c) MALTA in-pixel efficiency, threshold = 400 e − , φ = 5e14n eq /cm 2 [4].…”