Patent ID: 7334211
Filing Date: 2008-02-19
Classification: G06F,H01L

Abstract:
1. A method of designing with a simulation a CMOS image sensor integrated circuit having a photodetector using energy of photons reaching the photodetector to excite electrons; a transfer device with a first terminal coupled to the photodetector, a second terminal coupled to the corresponding node, and a control terminal causing a transfer of the electrons from the first terminal to the second terminal in response to receiving a control signal of sufficient value; a p-type region having a concentration stronger than a background concentration and having a lateral position at least partly under the control terminal of the transfer device; the simulation comprising: selecting design parameters of a surface p-type region laterally positioned at the photodetector; selecting design parameters of the transfer device; selecting design parameters for a first n-type region and a second n-type region of the photodetector, the first n-type region at a first depth range in the integrated circuit and receiving the electrons excited by the photons, and the second n-type region at a second depth range wherein the first depth range includes depths deeper than the second depth range, the second n-type region being adjacent to the first n-type region and receiving the electrons from the first n-type region; selecting design parameters of the p-type region; filling the photodetector with electrons to a maximum capacity; verifying that the maximum capacity of the photodetector meets a design specification of the integrated circuit; and verifying that raising the control voltage on the control terminal, without exceeding a voltage tolerance of a dielectric, transfers the electrons from the photodetector to the corresponding node to be measured and removed.