High-voltage pixel sensors for ATLAS upgrade

I Perić ,M George,F Bompard,D Fougeron,P Pangaud,M Garcia-Sciveres,D Hynds,A La Rosa,P Breugnon,F Huegging ,A Rozanov ,J C Clémens ,J Große-Knetter ,J Liu ,J Rieger ,J Weingarten ,M Barbero ,B Ristić ,D Ferrère ,H Pernegger ,M D M Capeans Garrido ,S Feigl ,Christian Kreidl ,P Fischer ,A Miucci ,C M Buttar ,D Muenstermann ,G Iacobucci ,M Backhaus ,M Nessi ,N Wermes ,R L Bates ,Sergio González Sevilla ,T Hemperek ,T Obermann ,A Quadt ,A Blue ,Hans Krüger

doi:10.1016/j.nima.2014.06.035

Abstract

The high-voltage (HV-) CMOS pixel sensors offer several good properties: a fast charge collection by drift, the possibility to implement relatively complex CMOS in-pixel electronics and the compatibility with commercial processes. The sensor element is a deep n-well diode in a p-type substrate. The n-well contains CMOS pixel electronics. The main charge collection mechanism is drift in a shallow, high field region, which leads to a fast charge collection and a high radiation tolerance. We are currently evaluating the use of the high-voltage detectors implemented in 180nm HV-CMOS technology for the high-luminosity ATLAS upgrade. Our approach is replacing the existing pixel and strip sensors with the CMOS sensors while keeping the presently used readout ASICs. By intelligence we mean the ability of the sensor to recognize a particle hit and generate the address information. In this way we could benefit from the advantages of the HV sensor technology such as lower cost, lower mass, lower operating voltage, smaller pitch, smaller clusters at high incidence angles. Additionally we expect to achieve a radiation hardness necessary for ATLAS upgrade. In order to test the concept, we have designed two HV-CMOS prototypes that can be readout in two ways: using pixel and strip readout chips. In the case of the pixel readout, the connection between HV-CMOS sensor and the readout ASIC can be established capacitively.

Highlights

High-voltage CMOS active pixel detectors are a family of active pixel detectors that unifies several good properties: fast charge collection by drift, CMOS in-pixel electronics and the compatibility with commercial processes
High-voltage CMOS active pixel detectors are a family of active pixel detectors that can be implemented in standard CMOS (HV) processes and that relay on the use of high voltage to deplete the sensor diodes and improve the charge collection efficiency
HV-CMOS sensors are based on the so-called “smart diode” structure, where a collection electrode (n-well) occupies about 50% of the pixel area, and CMOS electronics is implemented inside the electrode

Summary

Introduction

High-voltage CMOS active pixel detectors are a family of active pixel detectors that unifies several good properties: fast charge collection by drift, CMOS in-pixel electronics and the compatibility with commercial processes. In contrast to other CMOS monolithic detectors, the collection electrode of a HV-CMOS pixel is large – it occupies about 50% of the pixel area Fig. 1 (the pixel size is 33 μm Â 125 μm and the diode size 19 μm Â 110 μm) Because of this we expect an efficient charge collection with small signal degradation after high irradiation doses. Hybrid pixel detectors based on active HV-CMOS sensors and capacitive chip to chip signal transmission [3,4]. With all these detector types we have measured sufficient signal to noise ratios ( 4 20), even after irradiation with neutrons to 1015 neq=cm2 [7]. In this publication we present the results obtained with the second prototype

Intelligent sensor concept

Test detectors

Novel address scheme

Experimental results

10 Pixel Column

Conclusion and outlook