X-ray-based overlay metrology using reciprocal space slicing analysis

Zhang, Jiahao; Chen, Xiuguo; Yang, Tianjuan; Liu, Shiyuan

doi:10.1364/ol.505346

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…In 2018, Veldman et al enlightened a method of extraction based on the displacement of intensity minima in the scattering diagram of a sample [20]. More recently, Zhang et al proposed a similar method but with a limited number of sample rotations, using reciprocal space slicing (RSS) [21].…”

Section: Introductionmentioning

confidence: 99%

Small angle x-ray scattering overlay metrology for advanced nodes

Choisnet,

Freychet,

Blancquaert

et al. 2024

Metrology, Inspection, and Process Control XXXVIII

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With a sub-nanometric resolution required for nodes below 14 nm, according to the International Roadmap for Devices and Systems (IRDS), exploring new overlay characterization methods is key to drive further component size reduction and develop better-performing technologies. In this work, we present our first Small-Angle X-ray Scattering (SAXS) results of overlay measurements on stacks of silicon line gratings. Our method, novel for SAXS overlay measurements, is based on inverse problem resolution and reconstructs the in-depth profile (approximated as a stack of trapezoids) of the structure. We are thus able to extract overlay with SAXS with a very fine sensitivity, high precision and sub-nanometric resolution that suit the requirements for advanced technological nodes. We compared these results with those of Scanning Electron Microscopy (SEM) contour-based on product overlay. The reconstructed structures are compared to profiles obtained with Scanning Transmission Electron Microscopy (STEM). From the differences between these multi-scale techniques we can conclude on the high potential of SAXS to become a complementary to those existing, and assess its potential for advanced technology nodes.

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Section: Introductionmentioning

confidence: 99%

Small angle x-ray scattering overlay metrology for advanced nodes

Choisnet,

Freychet,

Blancquaert

et al. 2024

Metrology, Inspection, and Process Control XXXVIII

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show abstract

“…Jiahao Zhang proposed a high-precision X-ray-based overlay metrology using reciprocal space-slicing analysis (RSS). This method has demonstrated robustness against asymmetric overlay marks [23]. However, the wafer surface is coated with photoresist during the alignment process.…”

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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“…For single exposure, the overlay budget typically amounts to a quarter of the half pitch, while for double patterning, the overlay budget is one-sixth of the half pitch [5]. Currently, the accuracy required for measuring overlay needs to meet the demand of the sub-nanometer level for chip manufacturing [10]. The control of overlay mainly involves three steps: alignment, after-development inspection (ADI), and after-etch inspection (AEI) [11].…”

Section: Introductionmentioning

confidence: 99%

Mitigating the Impact of Asymmetric Deformation on Advanced Metrology for Photolithography

Yang,

Yao,

Cao

et al. 2024

Applied Sciences

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Controlling overlay in lithography is crucial for improving the yield of integrated circuit manufacturing. The process disturbances can cause undesirable morphology changes of overlay targets (such as asymmetric grating), which can significantly impact the accuracy of overlay metrology. It is essential to decouple the overlay target asymmetry from the wafer deformation, ensuring that the overlay metrology is free from the influence of process-induced asymmetry (e.g., grating asymmetry and grating imbalance). Herein, we use an asymmetric grating as a model and show that using high-diffraction-order light can mitigate the impact of asymmetric grating through the rigorous coupled-wave analysis (RCWA) method. In addition, we demonstrate the diffraction efficiency as a function of the diffraction order, wavelength, and pitch, which has guiding significance for improving the measurement accuracy of diffraction-based overlay (DBO) metrology.

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X-ray-based overlay metrology using reciprocal space slicing analysis

Cited by 5 publications

References 18 publications

Small angle x-ray scattering overlay metrology for advanced nodes

Small angle x-ray scattering overlay metrology for advanced nodes

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

Mitigating the Impact of Asymmetric Deformation on Advanced Metrology for Photolithography

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