Near-100% Quantum Efficiency of Delta Doped Large-Format UV-NIR Silicon Imagers

We have demonstrated a back surface process for back-illuminated high-purity p-channel charge-coupled devices (CCDs), enabling broadband coverage from the ultraviolet to near infrared (NIR). The process consists of the formation of a delta layer followed by a double layer antireflection (AR) coating. The process is performed below 450degC and is applied to fully fabricated CCDs with aluminum metallization. The delta doping process was demonstrated on 1 k times 1 k and 2 k times 4 k CCDs, which were found to exhibit low dark current and near reflection-limited quantum efficiency. Two broadband AR coatings were developed to cover the UV-visible and visible-NIR bands. These coatings consist of a double layer of Si_xN_y and SiO_x deposited by plasma enhanced chemical vapor deposition onto the back surface of a delta doped CCD. The thicknesses of the coating layers are adjusted for the desired bandpass.