CMOS-Based Ion Image Sensors for Eliminating Optical Contamination

Ion measurements in existing ion sensors fluctuate significantly owing to the incident light. Therefore, a light shield is required, which critically limits the applicability of ion sensors. In this study, two sophisticated methods to eliminate optical signal contamination occurring during ion imaging were proposed and demonstrated. The first method involved the design of two pixels with different characteristics, which comparatively eliminated the interference of light. The second method to measure the voltage due to photoelectrons and subtracted it from the output. Two types of sensors based on the proposed methods were designed and fabricated. Based on functional validation, both methods achieved accurate ion measurements under light irradiation without any fluctuations caused by optical contamination. Notably, the proposed methods eliminated optical contamination without degrading ion sensing spatial resolution. The proposed methods demonstrate a novel application of ion imaging without light shielding.