Proton Irradiation Damage in a CMOS Image Sensor : Proton Irradiation Damage in a CMOS Image Sensor

Requires: Victory Process/Victory Mesh/Victory Device/REM
Minimum Versions: Victory Process 7.30.4.R, Victory Mesh 1.4.6.R, Victory Device 1.14.1.R

This examples demonstrates Proton Irradiation Damage in a CMOS Image Sensor

This example uses Victory Process Cell mode to create a CMOS image sensor (CIS) complete with two pass transistors. The image sensor was then irradiated with a damaging fluence of protons in several stages, and the damage effects on the performance of the image sensor were monitored.

In order to speed up the process simulation, initially 1D Monte-Carlo implant simulations were stored as data files and imported into Victory Process Cell mode using the Profile statement. Other implants used the 3D Monte-Carlo BCA simulator in the normal way.

During Device simulations, the level of electron depletion in the active section of the image sensor was monitored using the Probe n.conc statement. Electrostatic potentials were also monitored using this method.

The image sensor was pulsed into deep electron depletion, and then monitored with time, to see how long it took for thermal generation to re-fill the active region of the image sensor. The longer the time for thermal generation to refill the depleted active region, the more versitile the image sensor will be.

Once a baseline time was established for the un-damaged image sensor, the sensor was subject to proton fluxes of 1e10, 1e11 and 1e12 proton/cm2 and the dark recovery time was re-tested to observe the effects of the proton induced damage. In this example, rather than use LOOP statements, the internal Design of Experiments (DoE) feature of deckbuild was used, using the sweep parameter to define the levels of proton irradiation per cm2. It was found that the damage was slight but noticable for a flux of 1e10 protons/cm2 but the final proton flux of 1e12/cm2 was sufficient to render the image sensor non operational. When viewing the electrical results, it must be bourne in mind that the proton damage also damages the pass transistors, which effects the whole operation of the sensor.

The proton flux is set up using the radiation proton energy=1.8 fluence=<p/cm2> statement, with the total fluence being the variable in the Design of Experiments. The damage rate and non ionizing energy loss are set on the material dam.proton=1e3 dam.niel=3.1 statement. The capture cross sections for the proton damage created defects is set using the defects fluence.model statement.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.