Onto Innovation Inc.
TARGET FOR OPTICAL MEASUREMENT OF TRENCHES

Abstract:

A metrology target is designed for measuring a feature at the bottom of a trench in a device under test, such as a tungsten recess vertical profile in a wordline in a three-dimensional (3D) NAND. The metrology target follows the design rules for the device under test and includes a tier stack with a plurality of tier stack pairs including, each including a conductor layer, such as tungsten, and an insulator layer, such as silicon dioxide and a trench that extends through the tier stack pairs. The metrology target includes a via that extends through the tier stack pairs and is positioned a lateral distance to the trench to promote access of light to a bottom of the trench, via plasmonic resonance, for measurement of a characteristic of the trench, such as the tungsten recess at the bottom of the wordline slit.