A process modification for CMOS monolithic active pixel sensors for enhanced depletion, timing performance and radiation tolerance

• DOI: 10.1016/j.nima.2017.07.046
• Publication Date: 2017-07-31T13:16:59Z
• Authors: W. Snoeys; G. Aglieri Rinella; H. Hillemanns; T. Kugathasan; M. Mager; L. Musa; P. Riedler; F. Reidt; J. Van Hoorne; A. Fenigstein; T. Leitner
• Keywords: SIGNAL (programming language)

For the upgrade of its Inner Tracking System, ALICE experiment plans to install a new tracker fully constructed with monolithic active pixel sensors implemented in standard 180 nm CMOS imaging sensor process, deep pwell allowing full within pixel. Reverse substrate bias increases tolerance non-ionizing energy loss (NIEL) well beyond 10131MeVneq∕cm2, but does not allow depletion sensitive layer and hence charge collection by drift, mandatory for more extreme radiation tolerance. This paper describes process modification deplete epitaxial even small electrode. It uses low dose blanket high n-type implant array require significant circuit or layout changes so that same design can be fabricated both modified process. When exposed 55Fe source at reverse −6 V, pixels variant respectively yield signal about 115 mV, 110 mV 90 output follower circuit. Signal rise times heavily affected speed this are 27.8+∕−5 ns, 23.2+∕−4.2 22.2+∕−3.7 ns rms, respectively. In different setup, single from 90Sr only degrades less than 20% after 1015 1MeVneq∕cm2 irradiation, while time 16+∕−2 19+∕−2.8 rms. From no useful could extracted exposure. These first results indicate maintains capacitance, improves timing performance NIEL least an order magnitude.