G F Dalla Betta 050613 Standard and Slim

G. -F. Dalla Betta 05/06/13 Standard and Slim Edge Pixel Sensors Gian-Franco Dalla Betta DII, Università di Trento INFN – Padova, Gruppo Collegato di Trento Tel. : +39 -0461283904, e-mail: gianfranco. dallabetta@unitn. it

05/06/13 G. -F. Dalla Betta Outline • Status : • Last Vipix batch from 2012 • FBK restarting with 6’’ wafers • Pixel sensors with active edge • First batch (PAE) • Further experience at FBK • Plan for a new batch …

05/06/13 G. -F. Dalla Betta The 2012 batch (p-on-n) • • 13 wafers <111>, 200 mm Poly-Si gettering No process splits • Alignment marks compatible with both bump bonding (IZM) and vertical integration (T-Micro) • • 32 x 128 (54+54 FP) 128 x 128 (9+9 FP) 96 Px 128 (7) Test structures

05/06/13 G. -F. Dalla Betta Preliminary Results Test diode, 4 mm 2 • Very good leakage current (~0. 2 n. A/cm 2) • Very low depletion voltage (~2 V)

G. -F. Dalla Betta 05/06/13 Active edge sensors: first batch (PAE) n- substrate Initial process 2000 x • Wafer bonding (@SINTEF) • Trench etching with DRIE and thick oxide mask: Aspect ratio ~1/20, deep etching (>200 um) • Trench doping by thermal diffusion • Trench filling with poly-Si (width ~10 um) • Lithography on severe topography: Even after filling, trenches still represent a major obstacle for photoresist spin-coating. G. F. Dalla Betta et al. , NSS 2011, N 25 -04 4. 2 um 9. 4 um 1. 2 um 14. 3 um Improved process

05/06/13 G. -F. Dalla Betta Main Design Issues • Wafer layout with strips, pixels, and diodes • Back-side not accessible: bulk contacts and pads on the front side • Gap between n and p regions: trade-off between edge sensitivity and breakdown voltage (possibly increased with field plates and/or floating rings) Bulk contacts Trench Bulk pad Field plate Bulk pad Bulk contacts Trench Bias line DC pads AC pads Gap

05/06/13 G. -F. Dalla Betta Electrical Characterization no FP 5 mm gap n+ Field plate n/p gap p+ Trench edge n- substrate FP=5 um gap

05/06/13 G. -F. Dalla Betta Edge Sensitivity (1) Position resolved laser setup at Uni. TN Layout Charge signal map @40 V • Preliminary setup (laser spot size and alignment to be optimized) • Good charge collection efficiency edge up to few microns from the edge

G. -F. Dalla Betta Edge Sensitivity (2) 05/06/13 M. Povoli et al. , Pisa Meeting 2012 Synchrotron X-rays (15 ke. V) at Diamond, UK Spot size ~3 mm, scan step 5 mm, different bias 2 diodes with common edge It confirms the good sensitivity up to a few mm from the physical edge

G. -F. Dalla Betta 05/06/13 Further experience at FBK (1) Edgeless pixels (p-on-n) for ALICE on epitaxial wafers (collaboration with CERN and INFN Bari and Trieste) I. Rachevskaya et al. , Trento Workshop 2013

G. -F. Dalla Betta 05/06/13 Further experience at FBK (2) Edgeless pixels (n-on-p) for ATLAS upgrade (collaboration with LPNHE, Geneve and INFN Trieste) G. Giacomini et al. , Trento Workshop 2013

G. -F. Dalla Betta 05/06/13 Plans for a new batch • Vipix has a credit with FBK for one batch, that could now be oriented to the new Pix. FEL project • FBK technology is sufficiently mature to make active edge pixels, although there has been no direct experience on 6’’ so far • For X-rays, sensor thickness should be not too small • Epi wafers are not an option • Need for wafer bonding (external service) • Trench etching and poly-Si filling to be optimized • Support wafer removal to be engineered