Optimization of Layout of Photosensitive CMOS VLSI Using Resolution Criteria

Abstract A prototype CCD array with a cell size of 5.5 μm, equipped with a vertical anti-blooming device (PSA), was developed at the enterprise of NPP Pulsar in the optoelectronics department. The PSA device allows you to eliminate local overshadowing in the image. However, cell reduction leads to the emergence of volumetric flow of charge carriers, which are added (“mixed”) to the useful signal charge packets. Such charge additives equalize the magnitudes of the charge packets in the neighboring cells and, thus, reduce the resolution value. The main characteristic of the resolution of a photodetector is the modulation transfer function - MTF. Its value depends on the magnitudes of charge packets accumulated in neighboring photodetector cells, which can be “distorted” due to electron fluxes in the bulk of the semiconductor. In practice, the resolution of the photodetector is estimated as the magnitude of the modulation of the cell signal at a frequency of the spatial input signal equal to half the Nyquist frequency. Therefore, modeling the dependence of the modulation transfer function on the topology, the bulk structure of the impurity profile, and the control voltages of the cell is an important task that has practical significance for designing a CCD. In this final qualifying work, a 5.5 μm photodetector cell was simulated, as well as an array of photodetector cells with different light shield configurations, and based on a comparison of the obtained modulation values, the topology parameters were selected from the point of view of the resolution criterion.