Novel ATHENA mark design to enhance alignment quality in double patterning with spacer process

Abstract

DPS (Double Patterning with Spacer) has been one of the most promising solutions in flash memory device manufacturing. Apart from the process complexity inherent with the DPS process, the DPS process also requires more engineering efforts on alignment technique compared to the single patterning. Since the traditional alignment marks defined by the core mask has been altered hence the alignment mark recognition could be challenging for the subsequent process layers.This study characterizes the process influence on the traditional ASML VSPM (Versatile Scribelane Primary Marks) alignment mark, and various types of sub-segmentations within VSPM marks were carried out to enable the alignment and find out the best performing alignment marks. The design of the transverse and vertical sub-segmentations within the VSPM marks is aimed to enhance the alignment signal strength and mark detectability. Alignment indicators of WQ (Wafer Quality), MCC (Multiple Correlation Coefficient) and ROPI (Residual Overlay Performance Indicator) were used to judge the alignment performance and stability. A good correlation was established between sub-segmentations and wafer alignment signal strength.

New alignment mark designs in single patterning and self-aligned double patterning

“…Such requirements require lots of challenges in SADP process, because the first printed mandrel pattern will be removed after spacer process. As a result, there exist huge differences of alignment marks between SADP process and traditional single lithography [8,9].…”

Analytic Design of Segmented Phase Grating for Optical Sensing in High-Precision Alignment System

“…In this case, the diffraction efficiency supported by the 5th order light signal is rather inadequate for a robust positioning. A segmented phase grating structure is designed to improve the light signals received at high odd orders [ 13 , 14 , 15 , 16 , 17 ]. For the 5th order, the grating ridge is further equally divided into five parts, as three ridges and two grooves, which is labeled as AH53 by taking the naming rule in [ 15 ] (p. 854).…”