Modeling UV response of rear-surface sensitized charge-coupled devices

• Published in: Applied physics letters 1987-05, Vol.50 (18), p.1275-1277
• Main Authors: PECKERAR, M. C, BOSIERS, J. T, MCCARTHY, D, SAKS, N. S, MICHELS, D. J
• Format: Article
• Language: English
• Subjects: Applied sciences; Charge transfer devices; Electronics; Exact sciences and technology; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.97882

Rear-surface illuminated charge-coupled devices (CCD’s) are typically insensitive to radiation whose depth of penetration is less than 1000 Å. This is due to the presence of immobile charges either in the rear-surface native oxide or at the native oxide/semiconductor interface. These fixed charges channel signal charge away from the front-surface confinement minima. The result is a loss of detective quantum efficiency (DQE), which is defined as the number of signal charges actually collected divided by the number produced. The CCD can be sensitized to shallow-penetrating radiation through the use of ion implantation techniques. To model the sensitization process, four factors must be accounted for. They are: the extent of the rear-surface depletion created by the fixed charge, Debye length spreading of the mobile charge background in the semiconductor, the position of the implant maximum, and the gradient of the active implant charge before the implant maximum is reached. By judicious manipulation of these factors DQE’s as high as 20% (uncorrected for UV reflection loss) have been obtained at 1216 Å.