Electrostatic discharge sensitivity tests for ISFET sensors

A set of tests using a standard electrostatic discharge (ESD) generator and a test setup to apply ESDs over ISFET-based chemical sensors in a reproducible way is proposed. The tests are used to study the ESD sensitivity of SiO2/Si3N4 gate ISFETs as well as to prove the effectiveness of a designed protection system based on an integrated platinum ring electrode and a protective element. It is shown that ISFETs show high sensitivity to ESD when they are in contact with a solution and discharges are applied to ISFET contact pins or when ISFET contact pins are connected to the ground and discharges are applied to a solution drop deposited on the gate zone. These tests emulate typical situations occurring while an operator is handling sensors and serve to determine in which of these situations it is recommendable for lab personnel to use static control measures like wrist straps to ground lab personnel. These tests in which ISFETs showed maximum sensitivity to ESD were used to study the performance of the designed protection system.