Characterization of CMOS position sensitive solid-state photomultipliers

We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide–semiconductor (CMOS) process. While only needing four signal output channels to readout, the device provides spatial information on the micro-pixel level. Four variations of the PS-SSPM were fabricated, however, we only show the characterization results from two. These two PS-SSPMs were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5×1.5 mm2, however, each device has different micro-pixel geometries and a different micro-pixel electrical readout for event position sensing. The FWHM energy resolution at 511 keV was measured as a function of bias using a 1×1×20 mm3 LYSO crystal. The energy resolution was ∼13–14% for both PS-SSPM designs. The LYSO scintillator coincidence timing resolution was measured with results ranging from 2.1 to 1.0 ns between the two PS-SSPMs. Spatial resolution studies were conducted using a focused (∼15 μm beam spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, its X and Y FWHM spatial resolution was measured to be 70 μm. Lastly, we demonstrate the PS-SSPM imaging capabilities using a LYSO scintillator array having 500×500 μm2 pixels.