A silicon metal-semiconductor-metal photodetector macromodel for circuit simulations Lucio Pancheri a, * , Mauro Scandiuzzo b , Gian-Franco Dalla Betta a , David Stoppa b , Fabrizio De Nisi b , Lorenzo Gonzo b , Andrea Simoni b a Department of Information and Communication Technologies, University of Trento, Via Sommarive 14, 38050 Povo, Trento, Italy b ITC-IRST, Centro per la Ricerca Scientifica e Tecnologica, via Sommarive 18, 38050 Povo, Trento, Italy Received 21 November 2003; received in revised form 15 July 2004; accepted 20 August 2004 Available online 8 October 2004 The review of this paper was arranged by Prof. S. Cristoloveanu Abstract In this paper, numerical device simulations are used to get insight into the DC and dynamic behavior of a CMOS metal-semi- conductor-metalphotodetector,tobeusedasamixingdeviceforactivepixelsbasedonadifferentialread-outconcept.Onthebasis ofsimulationresults,asimpleelectricalmacromodelofthephotosensorhasbeendefinedandimplementedintheCadencepackage usingSpectreAHDL.Theproposedmacromodelisshowntoaccuratelyreproducethenumericaldevicesimulationpredictionsinall the considered operation modes. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: MSM photodetector; Silicon; CMOS; Macromodel; Circuit simulation 1. Introduction Active 3D vision systems can be used in a variety of applications, including industrial applications, automo- tive, process control and robotic guidance. One of the techniques employed in 3D measurements is Indirect Time-of-flight(I-TOF),whichavoidstheuseofcomplex scanning systems and exhibits a good measuring range. Scannerless I-TOF systems have been developed using CCD cameras and microchannel plates for light detec- tion and amplification. In spite of the good resolution obtained,thesesystemshavethedisadvantageofrequir- ing expensive opto-electronic components. The recent progresses in Indirect-time of flight (I-TOF) systems, driven by the effort of lowering the overall cost of the system, have been based on the integration of photo- detectors (PDs) and electronic read-out circuits on the same chip [1–6]. The use of inherently mixing detectors (IMDs) as sensing element together with a differential read-outchannelhasrecentlybeenproposedtoimprove the overall system performance [7,8]. Among other IMDs are Metal-Semiconductor-Metal (MSM) devices, which exhibit high bandwidth and good noise suppres- sion [9]. ThemaineffortsinthedevelopmentofMSMdevices havesofarbeenconcernedwithcompound(III–V)semi- conductors [10–12],butsomesilicon-baseddeviceshave also been proposed both in SOI [13,14] and in CMOS compatible technology [15–17]. In fact, the integration of MSM photosensors in standard CMOS processes canbedifficult,duetoseveralconstraints.Inparticular, themetalelectrodematerialissetbythetechnologyand 0038-1101/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.sse.2004.08.010 * Corresponding author. Tel.: +39 0461 883920; fax: +39 0461 882093. E-mail address: lucio.pancheri@dit.unitn.it (L. Pancheri). www.elsevier.com/locate/sse Solid-State Electronics 49 (2005) 175–181