Thermal aberration control for low-k1 lithography

Uehara, Yusaku; Matsuyama, Tomoyuki; Nakashima, Toshiharu; Ohmura, Yasuhiro; Ogata, Taro; Suzuki, Kosuke; Tokuda, Noriaki

doi:10.1117/12.711440

Cited by 7 publications

(3 citation statements)

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“…The transmitted laser energy, though as low as a few watts, will cause unwanted thermal aberrations [1][2][3], and the nonuniform distribution of energy, for example, under dipole illumination conditions, makes it worse and more complicated [4,5]. Previous studies attributed thermal aberrations to three temperature effects: thermal deformation of lens surface, change of refractive index, and stress-birefringence [6].…”

Section: Introductionmentioning

confidence: 96%

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Chen

Yang

et al. 2013

Appl. Opt.

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Precision optical systems that utilize laser beams as working media usually suffer from thermal aberrations caused by absorbed energy. Based on a specially designed three-lens system, the causes and contributions of mechanical structures to the system's thermal aberrations are studied. The contribution of three thermal effects, surface deformation, change of refractive index, and stress birefringence on the system's thermal aberrations, is analyzed respectively through an integrated optomechanical simulation method. The impact of the structure's thermal dissipating capability and structure configuration on the system's thermal aberrations is analyzed, too. Experiments have been carried out to validate the correctness and accuracy of the simulation method. Both the simulated and tested results can provide a reference for structure design and thermal aberration analysis of the similar optical systems.

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Section: Introductionmentioning

confidence: 96%

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Chen

Yang

et al. 2013

Appl. Opt.

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“…To correct assembling errors like tilt and decentration, adjusting mechanisms are employed, which are also helpful for the compensation of low order rotational symmetrical aberrations, which indicate piston Z1, defocus Z4 and primary spherical Z9. The projection objective always performs well at the beginning, during the working hours, due to the fact that all materials have good absorption at such a short wavelength, the energy absorbed by the projection lens causes significant rise in temperature, which brings surface deformation and refractive index change, and this produces so called thermal aberration [4][5][6]. While as time goes on, the heat accumulates in the illuminated zone, thermal aberrations become dominant to make the optical performance bad.…”

Section: Introductionmentioning

confidence: 99%

Simulation Research on the Thermal Effects in Dipolar Illuminated Lithography

Yao

Gong

2016

Journal of the Optical Society of Korea

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The prediction of thermal effects in lithography projection objective plays a significant role in the real-time dynamic compensation of thermal aberrations. For the illuminated lithography projection objective, this paper applies finite element analysis to get the temperature distribution, surface deformation and stress data. To improve the efficiency, a temperature distribution function model is proposed to use for the simulation of thermal aberrations with the help of optical analysis software CODE V. SigFit is approved integrated optomechanical analysis software with the feature of calculating OPD effects due to temperature change, and it is utilized to prove the validation of the temperature distribution function. Results show that the impact of surface deformation and stress is negligible compared with the refractive index change; astigmatisms and 4-foil aberrations dominate in the thermal aberration, about 1.7 λ and 0.45 λ. The system takes about one hour to reach thermal equilibrium and the contrast of the imaging of dense lines get worse as time goes on.

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“…Thus, thermal aberration induced by lens heating becomes more and more important. As a result of laser absorption, lens heating, which leads to temperature rise and inhomogeneous thermal distribution, results in thermal elastic deformation, refractive index change, and thermal stress [2][3][4]. Among these three main reasons, refractive index change caused by inhomogeneous thermal distribution is a dominating factor for projection lens performance degeneration [4,5].…”

Section: Introductionmentioning

confidence: 99%

Analysis and experiments of the thermal–optical performance for a kinematically mounted lens element

Zhang

et al. 2014

Appl. Opt.

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In order to evaluate the thermal-optical performance of a kinematic mounting applied in lithographic projection lens, the optical surface figure and wavefront changes of the lens element under a certain thermal load are investigated with both experimental and numerical simulation methods. From the experimental and numerical results, the temperature on the edge of the lens element rises up to 22.51°C, and the center of lens is 5.3°C higher. As a result, this thermal nonuniformity leads to a 9.622 nm RMS change of the optical surface figure and 71.905 nm RMS change of the index inhomogeneity, consisting mainly of Z4, Z9, and Z16. Because of the radial flexibility of the supporting legs of the kinematic mounting, aberrations such as pri trefoil and sec trefoil are less than 2% of the total wavefront changes, and other nonaxisymmetric aberrations are negligible. The Zernike coefficient differences between experiments and simulation are less than 2 nm, which supports the correctness of our method. The kinematic mounting shows good thermal adaptability, and the method for evaluation of the thermal-optical characteristics is proved effective.

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Thermal aberration control for low-k1 lithography

Cited by 7 publications

References 0 publications

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Simulation Research on the Thermal Effects in Dipolar Illuminated Lithography

Analysis and experiments of the thermal–optical performance for a kinematically mounted lens element

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