Target for optical measurement of grooves

A metrology target is designed to measure a feature at the bottom of a trench in a device under test, such as a tungsten recess vertical profile in a word line in a three-dimensional (3D) NAND. The metrology target follows a design rule of the device under test and includes a stack of stacks having a plurality of stack-of-stack pairs, each stack-of-stack pair including a conductor layer, such as tungsten, and an insulator layer, such as silicon dioxide, and trenches extending through the stack-of-stack pairs. The metrology target includes a through-hole extending through the stacked stack pair and positioned at a lateral distance from the trench to promote light via plasmon resonance to reach the bottom of the trench for measuring a characteristic of the trench, such as a tungsten recess at the bottom of a word line slit. 一种计量目标被设计用于测量待测装置中的沟槽的底部处的特征，诸如三维(3D)NAND中的字线中的钨凹陷部竖直轮廓。该计量目标遵循该待测装置的设计规则，并且包括层叠堆叠，该层叠堆叠具有多个层叠堆叠对以及延伸穿过这些层叠堆叠对的沟槽，每个层叠堆叠对包括导体层(诸如钨)和绝缘体层(诸如二氧化硅)。该计量目标包括通孔，该通孔延伸穿过该层叠堆叠对，并且被定位成与该沟槽相距一定横向距离以经由