• Chinese Journal of Lasers
  • Vol. 48, Issue 20, 2005001 (2021)
Xiaozhe Ma1、2, Fang Zhang1、*, and Huijie Huang1、2、**
Author Affiliations
  • 1Laboratory of Information Optics and Optoelectronic 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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    DOI: 10.3788/CJL202148.2005001 Cite this Article Set citation alerts
    Xiaozhe Ma, Fang Zhang, Huijie Huang. Correction Technology for Illumination Field Intensity Profile in Photolithography Machine[J]. Chinese Journal of Lasers, 2021, 48(20): 2005001 Copy Citation Text show less

    Abstract

    Objective The step-and-scan photolithography machine is the main equipment for manufacturing integrated circuits used in the key layer preparation. The exposure system of the photolithography machine consists of the illumination system and projection objective. The illumination system is the core of the subsystems, therefore, it is used for several purposes, and it generates an illumination field with a specific intensity profile. The critical dimension uniformity is determined using the uniformity of the dose energy in the scanned exposure field. In and below 28 nm node, the top-Gaussian illumination is an important technology for reducing the influence of the pulse quantization error on dose energy. Considering the matching and consistency of the photolithography machine and the moving range of the wafer platform, the requirements and tolerances of the top-Gaussian illumination field are relatively strict. However, owing to limitations in design, manufacturing, and installation for the microlens arrays, diffuser, and Fourier transform lens (FTL), the dimensions of the top-Gaussian illumination field in scan direction are relatively difficult to meet the requirements directly. The performance of optical elements, such as coating transmittance, may degrade the performance of the top-Gaussian illumination field after long-term use. The general correction methods are focused on the uniformity correction of the illumination field. Therefore, in this study, a correction technology for the intensity profile of the illumination field is proposed. A corrector designed and optimized by this technology can correct the intensity profile and integral uniformity of the illumination field simultaneously. The energy loss can be decreased by considering the dimension tolerances of the intensity profile in the scan direction as boundary conditions during the optimization.

    Methods The design process of the corrector includes the intensity profile and integral uniformity corrections. The corrector is located at the front of the rear focal plane of FTL with a defocus distance. The illumination field on the rear focal plane of FTL should be transferred to the defocus plane during the design and optimization process. For the conventional illumination mode, the intensity distribution of a field point on the rear focal plane of FTL at the corrector plane is shown in Fig. 5. The intensity profile correction in the scan direction is coupled with the integral uniformity correction in the nonscan direction. Conducting a few iterations of the optimization during the design of the corrector is necessary. To reduce the number of iterations, the integral uniformity of the illumination field in the nonscan direction is corrected. Then, the intensity profile of the illumination field in the scan direction is corrected. Additionally, the dimension tolerances of the intensity profile in the scan direction should be included in optimizing the corrector to reduce the energy loss of the correction of the illumination field.

    Results and Discussions To verify the feasibility of this technology, correctors are designed for three unsatisfied top-Gaussian illumination fields. Moreover, the transmittance distributions of the correctors are optimized through the simulated annealing algorithm. Fig. 10 shows the transmittance distributions of the designed and optimized correctors. The correctors’ abilities are tested through simulations in LightTools software. The integral uniformities of the three top-Gaussian illumination fields in the nonscan direction are less than 0.29% after correction (Table 6 and Table 7). The dimensions DY_97, DY_50, DY_003, and DY_25~75 of the three illumination fields in the scan direction are [3.79 mm, 4.39 mm], [13.18 mm, 13.58 mm], [23.3 mm, 23.4 mm], and [3.05 mm, 3.44 mm] after corrections, respectively. The correction results show that the integral uniformities and intensity profiles are meet the requirements. The energy loss introduced by the correction is reduced by an average of 4.09%. Furthermore, the time taken by algorithm is less than 10 s (CPU: Intel Core i7-10750H, SDRAM: 16 GB). The consistency of the algorithm and simulation results shows the feasibility and veracity of the proposed technology.

    Conclusions In this study, a correction technology for the intensity profile of the illumination field in a photolithography machine is proposed. To reduce the number of iterations, the integral uniformity in the nonscan direction of the illumination field should be corrected. Then, the intensity distribution of the illumination field in the scan direction is corrected by the proposed technology. The tolerances of the dimensions of the intensity distribution in the scan direction are taken as the boundary conditions during the optimization to reduce the energy loss of the illumination field. According to three unsatisfied top-Gaussian illumination fields, the correctors are designed and optimized in a relatively short time. The integral uniformities in the nonscan direction and the dimensions of the intensity profiles in the scan direction are satisfied with the requirements after correction.

    Xiaozhe Ma, Fang Zhang, Huijie Huang. Correction Technology for Illumination Field Intensity Profile in Photolithography Machine[J]. Chinese Journal of Lasers, 2021, 48(20): 2005001
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