Graded Multilayer Film Design Method of Anamorphic Magnification Extreme Ultraviolet Lithography Objective System

Mo Liu; Yanqiu Li

doi:10.3788/AOS202040.0522001

Journals >Acta Optica Sinica >Volume 40 >Issue 5 >Page 0522001 > Article

Acta Optica Sinica
Vol. 40, Issue 5, 0522001 (2020)

Graded Multilayer Film Design Method of Anamorphic Magnification Extreme Ultraviolet Lithography Objective System

Mo Liu and Yanqiu Li^*

Author Affiliations

Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

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DOI: 10.3788/AOS202040.0522001 Cite this Article Set citation alerts

Mo Liu, Yanqiu Li. Graded Multilayer Film Design Method of Anamorphic Magnification Extreme Ultraviolet Lithography Objective System[J]. Acta Optica Sinica, 2020, 40(5): 0522001 Copy Citation Text

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Fig. 1. Thickness distribution of multilayer films. (a) Regular multilayer films; (b) laterally graded multilayer films

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Fig. 2. Mo/Si regular film reflectivity versus incident angle^[4]

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Fig. 3. Optical path of anamorphic magnification EUV lithography objective system in yz plane when M_H=4 and M_L=8

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Fig. 4. Image field and field points F₁--F₉

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Fig. 5. Flow chart of progressive optimization design for graded multilayer films

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Fig. 6. Reflectivity distribution of M1, M2, M3, and M5 mirrors when single mirror is added with progressively optimized laterally graded multilayer films, and remaining mirrors are all bare mirrors (assuming ideal reflection).(a) M1; (b) M2; (c) M3; (d) M5

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Fig. 7. Reflectivity distribution and wavefront aberration distribution of film-containing objective system in final multilayer film design scheme. (a) F₂, reflectivity; (b) F₉, reflectivity; (c) F₂, wavefront aberration; (d) F₉, wavefront aberration

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Parameter	Specification
Wavefront aberration/λ	0.05670
Wavelength /nm	13.5
Field of view /(mm×mm)	26×1
M_H	4
M_L	8
NA	0.6
Range of incident angle	<6°

Table 1. Performance indexes of anamorphic magnification EUV lithography objective system after optimization

Mirror	Diameter /mm	Incident angle range /(°)	Average incident angle /(°)
M1	483.29	11.56--19.46	15.94
M2	229.61	20.58--35.11	27.38
M3	65.77	9.34--19.08	13.76
M4	252.32	4.32--7.18	5.30
M5	288.56	1.36--17.92	10.71
M6	700.88	0.60--6.13	3.85

Table 2. Range of incident angle and average incident angle of anamorphic magnification EUV lithography objective system with NA=0.6

Mirror	Minimum reflectivity /%
Mirror	Optimized M1,M2,M3,M5 with laterally graded multilayer films	Optimized M1,M2,M3,M5 with progressively optimized graded multilayer films
M1	70.44	70.50
M2	46.53	47.18
M3	67.31	71.89
M4	72.31	72.31
M5	71.62	71.89
M6	71.48	71.48

Table 3. Minimum reflectivity distribution of M1--M6 mirrors

Mirror	C₀	C₂	Y₀
M1	1.010	5.964×10^-7	-32.15
M2	1.068	8.549×10^-6	-10.20
M3	1.201	-1.299×10^-6	-355.30
M5	0.987	2.148×10^-6	-16.98

Table 4. Laterally graded multilayer film parameters of mirrors M1, M2, M3, M5

Mirror	C₀	C₂	Y₀
M1M2M3M5	1.01017001.06762301.19206150.9824070	5.964×10^-78.549×10^-7-1.299×10^-72.148×10^-7	-32.15-10.20-355.30-16.98

Table 5. Gradient variation parameters of laterally graded multilayer films with progressive optimization design

Field point	Condition	Wavefront aberration/λ	Strehl
F₂	System without coating	0.0307	0.964
	System with coating	0.0598	0.868
F₉	System without coating	0.0559	0.884
	System with coating	0.0872	0.741

Table 6. Wavefront aberrations and Strehl of bare mirror system and film-containing objective system at center and edge field points

Mo Liu, Yanqiu Li. Graded Multilayer Film Design Method of Anamorphic Magnification Extreme Ultraviolet Lithography Objective System[J]. Acta Optica Sinica, 2020, 40(5): 0522001

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