Noise characteristics of stacked CMOS active pixel sensor for charged particles

Abstract

The noise characteristics of a stacked CMOS active pixel sensor (SCAPS) for incident charged particles have been analyzed under 4.5 keV Si + ion irradiation. The source of SCAPS dark current was found to change from thermal to electron leakage with decreasing device temperature. Leakage current at charge integration part in a pixel has been reduced to 0.1 electrons s À1 at 77 K. The incident ion signals are computed by subtracting reset frame values from each frame using a non-destructive readout operation. With increase of irradiated ions, the dominant noise source changed from read noise, and shot noise from the incident ions, to signal frame fixed-pattern noise from variations in sensitivity between pixels. Pixel read noise is equivalent to ten incident ions. The charge of an incident ion is converted to 1.5 electrons in the pixel capacitor. Shot noise corresponds to the statistical fluctuation of incident ions. Signal frame fixed-pattern noise is 0.7% of the signal. By comparing full well conditions to noise floor, a dynamic range of 80 dB is achieved. SCPAS is useful as a two-dimensional detector for microanalyses such as stigmatic secondary ion mass spectrometry. #

Microscopic oxygen isotopic homogeneity/heterogeneity in the matrix of the Vigarano CV3 chondrite

“…Because the SCAPS is composed of a pixelled array of ϳ600 ϫ 600 independent microdetectors, simultaneous two-dimensional detection can be achieved. The SCAPS is suitable for high-precision-isotope imaging, isotopography, because of its direct ion-capability, high sensitivity, low noise, and wide dynamic range Kunihiro et al, 2001;Takayanagi et al, 2003). Secondary ion intensities can be determined within twice the Poisson statistical error.…”

Analysis of the noise properties of a solid‐state SCAPS ion imager and development of software noise reduction

“…The basic noise properties of SCAPS have been described previously 3. The raw signal image output from a solid‐state imager include two kinds of noises: fixed pattern noise (FPN) and random noise.…”

“…Dark current can be reduced to negligible level by cooling the imager at 77 K using liquid N 2 3. Reset noise suppression, using nondestructive readout correlated double sampling (NDRO‐CDS), is used to decrease the internal read noise and FPN.…”

Dark current reduction in stacked-type CMOS-APS for charged particle imaging

“…Fig. 4 shows a measurement result of temperature dependence of the dark current in a charged particle imager with a conventional pixel structure that consists of n-MOS transistors located in a common p-well [6]. The dark current depends on thermal generation model with activation energy of about 0.55 eV from 200 K to room temperature.…”