  The optimization of silicon photodiode-based CMOS sensors with
backside-illumination for 300-1000 nm wavelength range was studied. It was
demonstrated that a single hole on a photodiode increases the optical
efficiency of the pixel in near-infrared wavelengths. A hole with optimal
dimensions enhanced optical absorption by 60% for a 3 $\mu$m thick Si
photodiode, which is 4 orders better than that for comparable flat photodiodes.
We have shown that there is an optimal size and depth of the hole that exhibits
maximal absorption in blue, green, red, and infrared. Crosstalk was
successfully reduced by employing thin trenches between pixels of 1.12
$\mu{m^2}$ in size.
