Simulation and development of triple-junction color sensors using CMOS-compatible processing

• Main Author: Chen, Jun
• Other Authors: Ram Singh Rana
• Format: Theses and Dissertations
• Published: 2008
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Electronic circuits
• Online Access: https://hdl.handle.net/10356/3748
• Institution: Nanyang Technological University

Color sensor can be used to verify position of objects, recognize color sequence. Conventional color sensors employ three identical photodiodes with red, green, and blue optical filters deposited on their surface. This approach leads to an increased occupied silicon area. The color sensor with vertically stacked triple-junction structure (investigated in this thesis) can overcome these restrictions. The operation of the color sensor relies on the wavelength dependence of light absorption in silicon. The thorough design of the color sensor included more successive steps. Initially, theoretical calculations were performed to find the depth and depletion region width of each junction required to optimize their spectral responsivity. Once these main features were established, the doping concentrations for each junction were determined and the complete fabrication process was designed. Then TSUPREM-IV was used to simulate the whole process of the device; MEDICI was used to simulate the device optical and electrical characteristics. Afterwards, the mask layout, process run sheets based on two basic models: abrupt junction model and linearly graded junction model, were designed and confirmed. The practical fabrication of the color sensors has been carried out in MFL, using the modified 2?m CMOS process. Finally, the fabricated sensors have been characterized.