Monitor structure for photoresist thickness in trench

Abstract

A method of forming a microelectronic device includes forming positive tone photoresist on the microelectronic device, filling a trench, extending over a top surface adjacent to the trench, and covering a thickness monitor on a substrate containing the microelectronic device. The photoresist in and over the trench is exposed at a trench energy dose, and the photoresist in the monitor area is exposed at a monitor energy dose that is less than the trench energy dose. The photoresist is developed, leaving photoresist in the trench having an in-trench thickness less than the depth of the trench and leaving an in-monitor thickness of the photoresist on the monitor area less than an unexposed thickness. The in-monitor thickness of the photoresist on the monitor area may be measured and the measured thickness value may be used with a calibration chart to estimate the in-trench thickness of the photoresist.