000268588 001__ 268588
000268588 005__ 20190812204806.0
000268588 0247_ $$2doi$$a10.1117/12.2511301
000268588 02470 $$a10.1117/12.2511301$$2DOI
000268588 037__ $$aCONF
000268588 245__ $$aOptical-stack optimization for improved SPAD photon detection efficiency
000268588 260__ $$c2019-02-22
000268588 269__ $$a2019-02-22
000268588 336__ $$aConference Papers
000268588 490__ $$aProceedings SPIE$$v10926
000268588 520__ $$aSingle-photon avalanche diodes (SPADs) are direct photon-to-digital detectors that enable scalable arrays with Poisson-limited signal-to-noise ratio and picosecond timing resolution. However, SPAD detectors require a guard-ring structure to prevent lateral edge breakdown. The guard ring, in addition to pixel electronics, reduces the sensitive area within the pixel, often below 50%. We present the simulation, design and characterization of microlens structures to increase the effective fill factor and SPAD photon detection efficiency. The main challenges in designing microlenses for SPADs are a relatively large SPAD pitch and a low native fill factor, requiring high microlens efficiency over a wide angular distribution of light. In addition, we addressed the requirements of several designs in the same technology, featuring native fill factors which range from 10.5% to 28%, by carrying out the microlens fabrication at wafer reticle level. The fabrication process starts with creating a photoresist microlens master, used to fabricate a mould for microlens imprints. After dispensing a UV curable hybrid polymer on top of the SPAD array, the mould is used to imprint the microlens array shape, and then cured with UV exposure. By using microlenses, we were able to increase the initial fill factor to more than 84% effective fill factor for a 28.5 μm pixel pitch. We also explore the influence of the passivation layer on the SPAD photon detection efficiency.
000268588 700__ $$g239007$$0253747$$aAntolović, Ivan Michel
000268588 700__ $$0250407$$aUlku, Arin Can
000268588 700__ $$g285706$$aKizilkan, Ekin
000268588 700__ $$0285706$$aLindner, Scott$$g230892
000268588 700__ $$aZanella, Frédéric
000268588 700__ $$aFerrini, Rolando$$0240343$$g134470
000268588 700__ $$aSchnieper, Marc
000268588 700__ $$aCharbon, Edoardo$$0240305$$g146991
000268588 700__ $$aBruschini, Claudio$$0243229$$g109304
000268588 7112_ $$aQuantum Sensing and Nano Electronics and Photonics XVI$$cSan Francisco, CA, USA$$dFebruary 2-7, 2019
000268588 773__ $$q99$$j10926$$tQuantum Sensing and Nano Electronics and Photonics XVI
000268588 8560_ $$falessandra.bianchi@epfl.ch
000268588 909C0 $$xU12178$$pAQUA$$0252106$$zMarselli, Béatrice
000268588 909CO $$pconf$$pSTI$$ooai:infoscience.epfl.ch:268588
000268588 960__ $$aclaudio.bruschini@epfl.ch
000268588 961__ $$aalessandra.bianchi@epfl.ch
000268588 973__ $$aEPFL$$rREVIEWED
000268588 980__ $$aCONF
000268588 981__ $$aoverwrite