Lithography overlay control improvement using patterned wafer geometry for sub-22nm technology nodes

Peterson, Joel; Rusk, Gary; Veeraraghavan, S.; Huang, Chung‐Che; Koffas, Telly; Kimani, Peter K.; Sinha, Jaydeep K.

doi:10.1117/12.2086525

Cited by 4 publications

(2 citation statements)

References 4 publications

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“…The resolution, overlay, and throughput are the three critical indicators of photolithography equipment [1,2]. The overlay error beyond the limitation may cause gross deviation of the IC components and devices, and lead to short circuits, open circuits and other problems [3][4][5]. According to the International Technology Roadmap for Semiconductors (ITRS) and other institutes, for process nodes of 10 nm and 7 nm, the overlay accuracy is required to be below 3 nm and 2 nm [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Adaptive Weighted Error-Correction Method Based on the Error Distribution Characteristics of Multi-Channel Alignment

Song,

Wang,

et al. 2024

Sensors

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As process nodes of advanced integrated circuits continue to decrease below 10 nm, the requirement for overlay accuracy is becoming stricter. The alignment sensor measures the position of the alignment mark relative to the wafer; thus, sub-nanometer alignment position accuracy is vital. The Phase Grating Alignment (PGA) method is widely used due to its high precision and stability. However, the alignment error caused by the mark asymmetry is the key obstacle preventing PGA technology from achieving sub-nanometer alignment accuracy. This error can be corrected using many methods, such as process verification and multi-channel weighted methods based on multi-diffraction, multi-wavelength and multi-polarization state alignment sensors. However, the mark asymmetry is unpredictable, complex and difficult to obtain in advance. In this case, the fixed-weight method cannot effectively reduce the alignment error. Therefore, an adaptive weighted method based on the error distribution characteristic of a multi-channel is proposed. Firstly, the simulation result proves that the error distribution characteristic of the multi-alignment result has a strong correlation with the mark asymmetry. Secondly, a concrete method of constructing weight values based on error distribution is described. We assume that the relationship between the weight value of each channel and the deviations of all channels’ results is second-order linear. Finally, without other prior process correction in the simulation experiment, the residual error’s Root Mean Square (RMS) of fixed weighted method is 14.0 nm, while the RMS of the adaptive weighted method is 0.01 nm, when dealing with five typical types of mark asymmetry. The adaptive weighted method exhibits a more stable error correction effect under unpredictable and complicated mark asymmetry.

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Section: Introductionmentioning

confidence: 99%

Adaptive Weighted Error-Correction Method Based on the Error Distribution Characteristics of Multi-Channel Alignment

Song,

Wang,

et al. 2024

Sensors

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show abstract

“…The overlay confined to a reasonable range would not lead to serious consequences. However, the error beyond the limitation may cause vital deviation of the components and devices from theoretical designed structures, which would result in short circuit, open circuit and other types of faults 6,7 . Generally the acceptable maximum value of overlay is 1/3 of the critical dimension (CD) 8 .…”

Section: Introductionmentioning

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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Overlay control solution for high aspect ratio etch process induced overlay error

Zhang

Feng

et al. 2022

Journal of Vacuum Science &Amp; Technology B

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In the semiconductor manufacturing process, especially in the high aspect ratio etch process of 3D NAND, overlay remains a constraint in an increasing device yield. With the increase in 3D layers, the etch process shows extreme inconsistency for different lots with different etch chambers, which makes it difficult to control within the budget. This article gives a systematic analysis on how the overlay feedback model reduces the overlay and which method should be used to reduce the etch-induced overlay residue. The linear and nonlinear inter- and intrafield models are used, and the overlay reduction performance is limited. Then, a correction per exposure (CPE) method is used, which shows the minimum residue. The feedforward overlay method together with the linear and nonlinear CPE method shows the best performance with only 20%–30% overlay residue. Two methods are recommended during the CPE model applied to control overfitting. One is to choose the best CPE order by judging the mark number of each exposure field, and the other is to define the fitting parameter range in a suitable range. Different CPE models are used and compared, and the verification results demonstrate that the suggested method has a great overlay fitting performance and overlay residue even if some parameters are excluded. That is, the study shows a method to balance the process variation, machine performance, feedback model, and metrology data.

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Lithography overlay control improvement using patterned wafer geometry for sub-22nm technology nodes

Cited by 4 publications

References 4 publications

Adaptive Weighted Error-Correction Method Based on the Error Distribution Characteristics of Multi-Channel Alignment

Adaptive Weighted Error-Correction Method Based on the Error Distribution Characteristics of Multi-Channel Alignment

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

Overlay control solution for high aspect ratio etch process induced overlay error

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