Method for Profile Reconstruction of Phase Defects in Extreme Ultraviolet Lithography Mask

Wei Cheng; Sikun Li; Xiangzhao Wang; Zinan Zhang

doi:10.3788/AOS202040.1005001

Acta Optica Sinica, Volume. 40, Issue 10, 1005001(2020)

Method for Profile Reconstruction of Phase Defects in Extreme Ultraviolet Lithography Mask

Wei Cheng^1,2, Sikun Li^1,2、*, Xiangzhao Wang^1,2、**, and Zinan Zhang^1,2

¹Laboratory of Information Optics and Opt-electronic Technology, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

²Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

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Figures & Tables(21)

Fig. 1. Schematic of defected multilayer film in EUV lithography. (a) Bump defect; (b) pit defect

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Fig. 2. Schematic of illumination angle

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Fig. 3. Flowchart of FP reconstructing complex amplitude

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Fig. 4. Schematic of CNN

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Fig. 5. Schematic of MLP

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Fig. 6. Flowchart of bottom profile parameter reconstruction of defects

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Fig. 7. Schematic of FP reconstructing complex amplitude

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Fig. 8. Reconstruction results of complex amplitude of aerial image. (a) Reconstructed amplitude; (b) reconstructed phase

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Fig. 9. Comparison of amplitudes of aerial images. (a) Reconstructed amplitude of aerial image; (b) simulated amplitude of aerial image (NA_obj=0.0825); (c) simulated amplitude of aerial image (NA_obj=0.1320); (d) difference between those in Fig. 9(a) and Fig. 9(c)

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Fig. 10. Central longitudinal sections of amplitude and phase of aerial images of mask blanks with bump defect. (a)(c) ω_bot=20 nm; (b)(d) h_bot=20 nm

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Fig. 11. Central longitudinal sections of amplitude and phase of aerial images of mask blanks with pit defect. (a)(c) ω_bot=20 nm; (b)(d) h_bot=-20 nm

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Fig. 12. Central values of aerial images of mask blanks with bump defects. (a) Amplitude; (b) phase

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Fig. 13. Central values of aerial images of mask blanks with pit defects. (a) Amplitude; (b) phase

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Fig. 14. Reconstruction results of bottom profile parameters of bump defects. (a) Reconstructed ω_bot using CNN; (b) reconstructed h_bot using MLP; (c) reconstructed h_bot using MLP when input ω_bot is real; (d) reconstructed h_bot using CNN

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Fig. 15. Reconstruction results of bottom profile parameters of pit defects. (a) Reconstructed ω_bot using CNN; (b) reconstructed h_bot using MLP; (c) reconstructed h_bot using MLP when input ω_bot is real; (d) reconstructed h_bot using CNN

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Fig. 16. Comparison of aerial images without and with noise. (a) Aerial image without noise; (b) aerial image with noise; (c) noise

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Fig. 17. Reconstruction results of bottom profile parameters of bump defects when measured aerial images are with noise. (a) Reconstructed ω_bot using CNN; (b) reconstructed h_bot using MLP

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Fig. 18. Reconstruction results of bottom profile parameters of pit defects when measured aerial images are with noise. (a) Reconstructed ω_bot using CNN; (b) reconstructed h_bot using MLP

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Table 1. Parameter setting for simulation

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Table 1. Parameter setting for simulation

Simulation object	Submodule	Parameter
Mask	Multilayer	40 pairs of Mo/Si bilayerMo/Si thickness: 4.17 nm/2.78 nmRefractive index: Mo: 0.923800-0.006435j, Si: 0.9990000-0.0018265j
Mask	Substrate	SiO₂ thickness: 20 nm
Optics	Illumination	Wavelength: 13.5 nm Chief ray angle: 6°
Optics	Projection	900× magnification, NA_obj=0.0825

Table 2. Illumination angle of coherent light
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Table 2. Illumination angle of coherent light
Angle l₁ l₂ l₃ l₄ l₅ l₆ l₇ l₈ l₉
$\begin{matrix} {θ_{r}}_{} \end{matrix}$ /(°) 0 2.03 2.03 2.03 2.03 2.84 2.84 2.84 2.84
φ /(°) 0 0 90 180 -90 45 135 -135 -45

Table 3. Reconstruction results of defects

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Table 3. Reconstruction results of defects

$\begin{matrix} {h_{top}}_{} \end{matrix}$ /nm	$\begin{matrix} {ω_{top}}_{} \end{matrix}$ /nm	$\begin{matrix} {h_{bot}}_{} \end{matrix}$ /nm	$\begin{matrix} {ω_{bot}}_{} \end{matrix}$ /nm	RMSE of $\begin{matrix} {h_{bot}}_{} \end{matrix}$ /nm	RMSE of $\begin{matrix} {ω_{bot}}_{} \end{matrix}$ /nm
1	40	Rand (5, 50)	Rand (5, 50)	3.8670	0.4491
1	40	Rand (5, 50)	Rand (15, 50)	1.1109	0.2935
1	50	Rand (5, 50)	Rand (5, 50)	3.7050	0.5495
1	50	Rand (5, 50)	Rand (15, 50)	0.7470	0.2768
2	40	Rand (5, 50)	Rand (5, 50)	2.8543	0.5905
2	40	Rand (5, 50)	Rand (15, 50)	0.9598	0.3599
2	50	Rand (5, 50)	Rand (5, 50)	3.7503	0.5176
2	50	Rand (5, 50)	Rand (15, 50)	1.1889	0.3732
3	30	Rand (5, 50)	Rand (5, 50)	2.3104	0.4316
3	30	Rand (5, 50)	Rand (15, 50)	1.3697	0.3489
-1	40	Rand (-5, -50)	Rand (5, 50)	2.0551	0.4495
-1	40	Rand (-5, -50)	Rand (15, 50)	1.3201	0.4318
-1	50	Rand (-5, -50)	Rand (5, 50)	0.9077	0.4087
-1	50	Rand (-5, -50)	Rand (15, 50)	0.7979	0.4170
-2	40	Rand (-5, -50)	Rand (5, 50)	1.8740	0.4321
-2	40	Rand (-5, -50)	Rand (15, 50)	1.3026	0.4324
-2	50	Rand (-5, -50)	Rand (5, 50)	1.5330	0.4564
-2	50	Rand (-5, -50)	Rand (15, 50)	0.9527	0.3922
-3	30	Rand (-5, -50)	Rand (5, 50)	2.0017	0.3925
-3	30	Rand (-5, -50)	Rand (15, 50)	1.0076	0.4260

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Wei Cheng, Sikun Li, Xiangzhao Wang, Zinan Zhang. Method for Profile Reconstruction of Phase Defects in Extreme Ultraviolet Lithography Mask[J]. Acta Optica Sinica, 2020, 40(10): 1005001

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