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

A method to profile the effects of radiation by the measurement of a density of an electrical charge per unit area induced to a semiconductor substrate by said radiation having a magnitude comprising the steps of:

• a) fabricating a plurality of stacked gate field effect transistors each having a drain, a source, a floating gate to accumulate and retain said electrical charge, and a gate;
• b) fabricating a plurality of charge collection capacitors wherein each charge collection capacitor is connected to the gate of one of said plurality of stacked gate field effect transistors and wherein each charge collection capacitor has an area that is unequal to the area of any of the other charge collection capacitors of the plurality of charge collection capacitors;
• c) exposing said plurality of stacked gate field effect transistors and the plurality of charge collection capacitors to the radiation;
• d) contacting each stacked gate field effect transistor with a threshold voltage measuring apparatus;
• e) measuring and recording a threshold voltage parameter for each of the stacked gate field effect transistors;
• f) comparing said threshold voltage parameter of each stacked gate field effect transistor with the area of each charge collection capacitor attached to said stacked gate field effect transistor;
• g) determining a change in the threshold voltage parameter between each of the plurality of stacked gate field effect transistors versus the change in area for each of the charge collection capacitors attached to the stacked gate field effect transistors, which is the density of said electrical charge induced per unit area of exposure to said radiation;
• h) examining said semiconductor substrate to identify any damage to said semiconductor substrate as a result of said electrical charge;
• i) modifying said magnitude of radiation;
• and
• j) repeating said method to measure said density of said electrical charge to establish a profile of said modifying of fabrication parameters versus amount of damage to said semiconductor substrate as a result of said electrical charge induced by said radiation.