Charge collector structure for detecting radiation induced charge during integrated circuit processing

摘要

A method and structure for the evaluation of the density of charge induced to a semiconductor substrate during exposure to radiation as a result of integrated circuits processing procedures such as ion implantation and plasma etching is disclosed. A plurality of stacked gate field effect transistors, wherein each stacked has a charge collection capacitor attached to the gate, is fabricated on a semiconductor substrate. Each charge collection capacitor has an area that is different from every other charge collection capacitor. The to substrate is exposed to a radiation source. The threshold voltage for each of the stacked gate field effect transistors is measured. The difference in threshold voltage for the stacked gate transistors is proportional to the amount of charge induced during the exposure to the radiation and the density of the charge induced by the exposure to the radiation can be calculated from the comparison of the threshold voltage and the area of the charge collection capacitors.