Large Range And High Precision Lithography Alignment Technologybased On Composite Gratings

With the significant development of micro/nano technology, there is an increasing demand for improving the lithography resolution since the characteristic size of the structure is down to sub micrometer and nanometer. The previous methods to improve the resolution are trying to alleviate the wavelength and raise the numerical aperture. Nonetheless, the traditional methods are limited to the technology and cost when the resolution reaches 32 nm. Under those conditions, the technologies of nanoimprint and surface plasma lithography are rapidly progressing due to the low cost and high precision. Particularly, nanoimprint is the most potential method for improving the resolution when it comes down to 22 nm.Alignment which is one of the three core technologies in lithography mainly focuses on projective exposure system previously. Nevertheless, it is difficult to meet the demand for the high precision of micro/nano devices when the alignment technology is limited in close/contact lithography such as nanoimprint and surface plasma lithography. Therefore it is vital to research on the precise alignment technology in relation to the characteristics of contacting lithography methods such as nanoimprint.According to the recent trend of alignment technology, this paper proposes two novel alignment methods to meet the demand for high precision and efficiency in contacting lithography. Based on the previous research, the methods could complete the coarse alignment and precise alignment in both X and Y direction simultaneously through utilizing the specially designed gratings.Based on the theory of scalar diffraction, this paper analyzes the imaging patterns modulated by overlapped gratings and explores the principle of Moiré fringes in detail. In addition, we design two complicated grating marks and develop the alignment model based on double gratings. The methods could achieve the instant 2D alignment through 2D gratings and complete the coarse and precise alignment through complicated gratings.Both simulations and experiments are conducted to verify the effectiveness of the proposed two methods. To be concluded, the precision of the proposed method which utilizes the 2D Ronchi gratings can reach 22 nm, and the repeatability is 20 nm. The precision of the proposed method which utilizes the complicated gratings can reach 14 nm, and the repeatability is 15 nm.