Study of Alignment &amp; Overlay Strategy in 14 nm Lithography Process

Lai, Lulu; Qian, Rui; Liu, Biqiu; Guo, Xiaojun; Zhang, Cong; Huang, Jun; J, Yu Zhang

doi:10.1109/cstic49141.2020.9282422

Cited by 1 publication

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“…Moreover, after some processes such as etching and CMP, the alignment marks may suffer from a certain degree of deformation or asymmetry, and the damages to alignment marks such as erosion, dishing and contamination may negatively affect the alignment accuracy. In this regard, the sub-segmentation structure splits the marks into smaller structures, and the structural variations brought by the processes are limited within small ranges, so the deformation will be greatly weakened, reducing the influence on the alignment error [38][39][40] . Figure 8 shows some examples of sub-segmentation alignment marks, and they are also known as POLAR marks 39 .…”

Section: Development Of Alignment Marks and Efficient Methods For Mar...mentioning

confidence: 99%

Review of overlay error and controlling methods in alignment system for advanced lithography

Hao¹,

Qi²

2022

Thirteenth International Conference on Information Optics and Photonics (CIOP 2022)

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Acting as one of the three critical indicators to evaluate the performance of lithography scanners, overlay has been a vital factor which seriously affects the electric property, life span and reliability of integrated circuits (IC). With continuous developments of technology nodes and applications of resolution enhancement technologies (RET), current resolution of the scanners has shrunk to 7 nm and beyond, proposing more stringent requirements for measuring, monitoring and correcting the overlay error. To ensure that the overlay budget fully met by the scanner, advanced optical technologies and holistic alignment approaches have been gradually applied to the alignment system of the scanner, revealing that an integrated methodology in which multiple technologies are adopted proved to be valid and effective in reducing the overlay error in present technology nodes.In this article, the exact concept of overlay error is provided, and on this basis different methods to describe the overlay error are comprehensively analyzed from the perspectives of classifications, sources, quality control and correcting models. Then the systematic relationship between alignment and overlay is illustrated. Recent improvements in the alignment system are also the key points here to systematically reduce the overlay error, including the optimization of the alignment optical path, mark types and design procedures, as well as the application of optimal color weighting (OCW), wafer alignment model mapping (WAMM) and sampling scheme optimization (SSO) algorithms. Based on the combined application and iteration of these technologies, it is believed that the on-product overlay (OPO) can be further compressed to support the continuous tightening of the overlay budget in the industry of IC.

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Section: Development Of Alignment Marks and Efficient Methods For Mar...mentioning

confidence: 99%