Nuclear Instruments and Methods in Physics Research A 583 (2007) 153–156 Laser characterisation of a 3D single-type column p-type prototype module read out with ATLAS SCT electronics T. Ehrich a , S. Ku¨hn a,Ã , M. Boscardin b , G.-F. Dalla Betta b , S. Eckert a , K. Jakobs a , M. MaaXen a , U. Parzefall a , C. Piemonte b , A. Pozza b , S. Ronchin b , N. Zorzi b a Physikalisches Institut, Universita ¨ t Freiburg, Hermann-Herder Str. 3, 79104 Freiburg, Germany b ITC-irst Trento, Microsystems Division, via Sommarive, 18 38050 Povo di Trento, Italy Available online 31 August 2007 Abstract In this paper measurements of a 3D single-type column (3D-stc) microstrip silicon device are shown. The 3D-stc sensor has n-type columns in p-type substrate. It has been connected to an ATLAS SCT ABCD3T chip and is readout with ATLAS SCT electronics at 40 MHz. Spatial measurements were done with a laser setup to investigate the expected low field region in 3D devices. An influence of the p-stops on the collected charge has been observed. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Wk; 29.40.Gx Keywords: Silicon detectors; 3D detectors; Charge collection; p Bulk 1. Introduction For future high luminosity colliders, especially for a proposed upgrade of the LHC [1], the SLHC, extremely radiation hard silicon detectors are needed. For 3D devices columns are etched into the silicon perpendicular to the sensor surface [2]. An advantage of 3D sensors is that they have a lower full depletion voltage than planar devices. The electric field is parallel to the sensor surface. Additionally the collection length is shorter, which is a very important advantage to reduce charge trapping after irradiation. A sensor design of single-type columns (stc) 3D sensors was introduced by ITC-irst, Trento [3]. The main advantage of 3D-stc sensors is fabrication process simpli- fication. A drawback is the existence of low field regions between neighbouring strips. Electrons created in the low field region move slowly until they reach higher field regions and a long collection time is needed to collect all these charges [3]. For irradiated detectors, long drift times would lead to increased trapping and hence signal loss [4]. One goal of our measurements with the laser test setup was to measure the extension and effect of these low field regions. 2. Device under test and laser setup 2.1. Device under test The tested device is a FZ n-in-p microstrip 3D-stc sensor. It has n-doped columns of 10 mm diameter and 150 mm depth, which are neither filled nor metallised. Ten columns are connected to one microstrip. The device has 64 AC-coupled strips and a nominal resistivity of 5 kO cm. The distance between columns within one strip is 100 mm. The strip pitch is 80 mm. The device has a size of approx. 1:6  5 mm 2 and is 500 mm thick. There are common p-stops around each strip. In Fig. 1 a schematic cross- section of a sensor is shown. The advantage of this n-in-p device is that electrons are collected. Electrons have a higher mobility than holes and are less affected by trapping, which is very important for detectors for high luminosity colliders. ARTICLE IN PRESS www.elsevier.com/locate/nima 0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.08.205 Ã Corresponding author. Tel.: +49 761 2035854; fax: +49 761 2035931. E-mail address: susanne.kuehn@physik.uni-freiburg.de (S. Ku¨hn).