Research On Key Technologies Of EUV Lithography Mask Detection Based On Multi-wavelength Iterative Algorithm

Extreme Ultraviolet(EUV)(?= 13.5nm)lithography is the next-generation lithography technology in the world promising to achieve a minimum of 22nm.The lithography mask in the production process into the nm level of dust pollution,impurity particles,drums,pits appear in the substrate surface or buried in the multi-layer film or mask surface,will result in photolithographic samples of serious defects.Optical non-interferometric phase retrieval detection is based on the measurement of light intensity information totally.The optical path of the system is simple and the resolution of the instrument is reduced without loss of relevant information,which is an important way to realize the detection of extreme ultraviolet mask defects.Based on the existing theory of non-interferometric phase retrieval,the defect detection method based on iterative algorithm is studied for the retrieval of defect phase information.Based on the traditional multi-wavelength iterative algorithm,a fast convergence iterative algorithm of phase retrieval-multi-wavelength gradient iterative algorithm is proposed,which is programmed by matlab.The angular transfer function and gradient acceleration function are introduced.The simulation results show that the retrievals of the Gaussian phase plane of[-0.84,0]and the "lena" phase plane of[-?,0],respectively,with the relative rms values of 10-3 order of magnitude,indicating the feasibility of the method.And compared with the traditional multi-wavelength iterative phase retrieval algorithm,the convergence speed is more than 2 times faster than that of the traditional algorithm and has higher retrieval accuracy.Finally,the influence of wavelength number,range,transmission distance and phase retrieval interval on the algorithm performance are discussed.An experimental setup based on the multi-wavelength gradient iterative algorithm is proposed to reconstruct the information of the wavefront phase of the incident light,and the calculated value of the intensity information of the output plane is compared with the measured value,which shows the correctness of the algorithm.The phase plane of the two transmissive elements is experimented respectively:resolution board with a certain width of the three lines and the letter e-chip,and the experimental results are in accordance with the expectation.