CMOS position-sensitive photodetectors (PSDs) for integrated sensor systems

Implementations and test results of one single-axis and 2- axis CMOS PSDs as well as a BiCMOS integrated receiver channel are presented. The single-axis PSD has a conventional LEP structure. It uses the well-substrate junction as a photodetector and pinched well as current dividing layer. An interelectrode resistance, NEP and position sensing accuracy of 152 k(Omega) , 1.6 pW/(root)Hz (850 nm) and 0.1%rms are achieved with the detector measuring 5 X 0.2 mm2. The first 2-axis PSD is a tetralateral LEP but instead of having strip-like continuous edge-electrodes it has electrodes composed of 100 discrete contacts, each of which is connected to the output current line using MOS switches. Linear position response is provided by disconnecting one opposite pair of the electrodes from preamplifier inputs and measuring one dimension at a time. An interelectrode resistance, NEP and accuracy of 4.5 k(Omega) , 10 pW/(root)Hz and 0.07%rms were achieved with this PSD using the alternate measurement mode. The second 2-axis PSD has an operating principle similar to a basic LEP but is composed of an array of phototransistors and polysilicon resistors. The NEP and position sensing nonlinearity of the sensor were 0.5 pW/(root)Hz and 0.04%rms, respectively. The third 2-axis PSD has the same construction as the second one but the phototransistors and polysilicon resistors were replaced with well-substrate photodiodes and pmos transistors, respectively. By driving one or more adjacent transistors in off-state the LEP mode can be changed to a segmented PSD mode providing the means to combine the high lateral sensitivity of the segmented mode with the large and linear measurement fields of the LEP. The BiCMOS receiver channel is composed of a transimpedance preamplifier, voltage amplifiers, gain control and offset cancellation blocks and a synchronous detector. The transimpedance at four different gains for a signal frequency ranging typically from 5 kHz to 10 kHz were 7 M(Omega) , 33 M(Omega) , 143 M(Omega) and 488 M(Omega) . The measured noise current density was lower than 0.3 pA(root)Hz, and the area and power consumption were 2.9 X 0.45 mm2 and 37 mW, respectively. As the achieved results fulfill the demands set for a typical signal conditioning channel of a PSD sensor system, the properties appear to be suitable for integrated PSD systems.

[1]  Y. Morikawa,et al.  A small-distortion two-dimensional position-sensitive detector (PSD) with on-chip MOSFET switches☆ , 1992 .

[2]  Y. Morikawa,et al.  A small distortion two-dimensional position-sensitive detector (PSD) with on-chip MOSFET switches , 1991, TRANSDUCERS '91: 1991 International Conference on Solid-State Sensors and Actuators. Digest of Technical Papers.

[3]  Pietro Perona,et al.  A Current-Mode Position Sensitive Circuit , 1993, ESSCIRC '93: Nineteenth European Solid-State Circuits Conference.

[4]  Peter Seitz,et al.  Industrial CMOS technology for the integration of optical metrology systems (photo-ASICs) , 1992 .

[5]  S. Middelhoek,et al.  Two-dimensional position-sensitive photodetector with high linearity made with standard i.c.-technology , 1979 .

[6]  Tarmo Ruotsalainen,et al.  Photodiodes for high-frequency applications implemented in CMOS and BiCMOS processes , 1997, Other Conferences.

[7]  Giovanni Verzellesi,et al.  On the electro-optical characteristics of CMOS compatible photodiodes , 1991, [1991 Proceedings] 6th Mediterranean Electrotechnical Conference.

[8]  Risto Myllylä,et al.  A high-resolution lateral displacement sensing method using active illumination of a cooperative target and a focused four-quadrant position-sensitive detector , 1995 .

[9]  J. A. Connelly,et al.  Producing phototransistors in a standard digital CMOS technology , 1996, 1996 IEEE International Symposium on Circuits and Systems. Circuits and Systems Connecting the World. ISCAS 96.

[10]  Timo Rahkonen,et al.  CMOS photodetectors for industrial position sensing , 1994 .

[11]  Juha Kostamovaara,et al.  High accuracy CMOS position-sensitive photodetector (PSD) , 1997 .

[12]  P. Aubert,et al.  Monolithic optical position encoder with on-chip photodiodes , 1988 .

[13]  Y. Hatanaka,et al.  A reduced capacitance concept for high-speed optical position-sensitive devices (PSDs) , 1990 .

[14]  Brian F. Alexander,et al.  Elimination of systematic error in subpixel accuracy centroid estimation [also Letter 34(11)3347-3348(Nov1995)] , 1991 .