Sensor design optimization of innovative low-power, large area MAPS for HEP and applied science

Abstract

Fully depleted Monolithic Active Pixels (MAPS) represent a state-of-the-art detector technology and profit from a low material budget and cost for high energy physics (HEP) experiments and other fields of research like medical imaging and astro-particle physics. Compared to the MAPS currently in use, fully depleted pixel sensors have the advantage of charge collection by drift, which enables a fast and uniform response overall the pixel matrix. The functionality of these devices has been shown in previous proof-of-concept productions. In this article we describe the optimization of the test pixel designs, that will be implemented in the first engineering run of the demonstrator chip of the ARCADIA project. These optimization procedures include radiation damage models, that have been employed in Technology Computer Aided Design (TCAD) simulations to predict the sensors behavior in different working environments.

Impact of X-ray induced radiation damage on FD-MAPS of the ARCADIA project

“…This effect is clearly visible in the comparison of the electron density shown in figure 1, before (a) and after (b) the introduction of surface damage. The absolute strength of this effect has been found in simulation studies to be dependent on the gap between the n-and pwell implantation within the low-doped epitaxial (ntype) layer and the concentration, of the positive oxide charges, which increases with the expected dose [3].…”

“…Sector 3 expresses a larger noise level than sector 2, which is intuitively not expected. A possible explanation could be an increased depletion voltage due to the larger pwell (as seen in simulation studies [3,4]), which might differ between measurements and simulations due to uncertainties in the lateral spreading of implanted regions of about ±1 μm. A higher depletion voltage would increase the pixel capacitance at a fixed backside voltage thus result in a larger noise level.…”

“…This prototype has arrived in May 2021 and is currently under test, together with additional test structures of pixel and strip arrays with different pitches and sensor geometries. In preparation of this first engineering run the sensor design has been studied in detail in extensive simulation campaigns [3,4]. These were conducted in order to select most promising designs for low in-pixel capacitance and fast charge collection.…”