Application of Greek cross structures for process development of electrochemical sensors

Using a test structure chip designed to assist in process development for reference electrode fabrication for integrated electrochemical sensors, this paper reports measurements of Greek cross test structures and compares them to measurements of bridge resistor structures on the same chip. The correct application of these structures requires careful consideration of the measurement parameters to provide accurate results and different force current values have been investigated. Results from platinum structures suggest there is measureable variation in the feature size when Greek cross results are used to extract electrical critical dimension from the bridge resistor measurements. Similar measurements of silver structures were less conclusive. While the bridge structures show a significant effect of oxidation of silver which has been exposed to air since fabrication, the Greek cross results are highly variable and may not be reliable.