Design of Reflective Projection Optics Used in Lithographic Focusing and Leveling System

Fig. 3. Simulated projection grate and its imaging with different aberrations. (a) Projection grate; (b)imaging with no aberration; (c) imaging with 0.95 magnification; (d)imaging with 5 mrad tele-centricity; (e) imaging with 0.08 distortion; (f) imaging with 0.70 modulation transfer function (MTF)

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Fig. 4. Measurement accuracy of system with different aberrations. (a) Magnification; (b) tele-centricity; (c) distortion; (d) MTF value

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Fig. 5. Spot diagram of projection system

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Fig. 6. MTF curve of projection system

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Fig. 7. Distortion of projection system

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Table 1. Requirement for system performance index
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Table 1. Requirement for system performance index
Parameter Value
Field /(mm×mm) 3×26
Tele-centricity /mrad <0.2
NA 0.065
Magnification -1±0.001
Wavelength range /nm 600-1000
Distortion /% <0.01
MTF(@33 lp/mm) >0.60

Table 2. Structure parameter of the system
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Table 2. Structure parameter of the system
Element Parameter Value /mm
M₁ Semi-diameter 70.000
Radius 384.389
M₂ Semi-diameter 20.000
Radius 192.182
l₁ TTHI 100.000
l₂ TTHI 289.381
l₃ TTHI 193.738
l₄ TTHI 193.738
l₅ TTHI 269.381
l₆ TTHI 120.000

Table 3. Tolerances distribution of the reflection projection system

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Table 3. Tolerances distribution of the reflection projection system

Surface	Radius /mm	TILTX/(°)	TILTY/(°)	DECX/mm	DECY/mm	Irregularity /fringe	Position /mm	Abbe /%
M1	±0.1	±0.01	±0.01	±0.05	±0.05	±0.1	±0.05	1.00
M2	±0.1	±0.01	±0.01	±0.05	±0.05	±0.1	±0.05	1.00
Mirror1	-	±0.01	±0.01	-	-	±0.1	±0.05	-
Mirror2	-	±0.01	±0.01	-	-	±0.1	±0.05	-

Table 4. Effect of tolerances on MTF

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Table 4. Effect of tolerances on MTF

Type	Object	Value /mm	Criterion	Change
TTHI	l₅	0.05	0.732679	-0.00921
TETY	M1	-0.01	0.735228	-0.00666
TSTY	M1	-0.01	0.735228	-0.00666
TETY	M1	0.01	0.735408	-0.00648
TTHI	l₅	-0.05	0.735733	-0.00615
TTHI	l₁	0.05	0.737226	-0.00466
TSDX	M1	0.05	0.737690	-0.00419
TEDX	M1	0.05	0.737690	-0.00419
TEDX	M1	-0.05	0.737799	-0.00409
TTHI	l₁	-0.05	0.739291	-0.00259

Table 5. Monte Carlo analysis results
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Table 5. Monte Carlo analysis results
Percent /% MTF
90 >0.722339
80 >0.729696
50 >0.734511
20 >0.738964
10 >0.740203

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Shengsheng Sun, Dan Wang, Yuejing Qi, Mingcheng Zong. Design of Reflective Projection Optics Used in Lithographic Focusing and Leveling System[J]. Acta Optica Sinica, 2020, 40(15): 1522002

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