Institute of Solid State Physics
|
|
|
Advanced process nodes for analog radiation-tolerant integrated circuits. Microelectronic devices exist in an out-of-equilibrium meta-stable state. There are typically sharp concentration gradients and strained layers at interfaces in a device. Interfaces between materials often have high defect densities. When the devices are irradiated by x-rays the x-rays can break bonds and detach hydrogen at the Si-SiO2 interface or rearrange the atoms in the amorphous oxide. This can increase the defect density at the interface and in the oxide. The x-rays can also excit electrons that get trapped in the defects. Charges in SiO2 can be trapped for years similar to the way charges are trapped in flash memory devices. These trapped charges cause threshold voltage shifts and Coulomb scattering that decreases the mobility. The sensitivity of semiconductor devices to ionizing radiation depends on details of the technology. In this master, 28 nm MOS transistors will be investigated. This is the last technolgy node that used a planar MOSFET geometry. The devices will be measured before and after x-ray irradiation and they will be modelled with state-of-the-art TCAD software. This master project is being done in collaboration with Alicja Michalowska-Forsyth of the Institute of Electronics. |
