Uzoma Paul C, Shabbir Salman, Hu Huan, Okonkwo Paul C, Penkov Oleksiy V
ZJU-UIUC Institute, International Campus, Zhejiang University, Haining 314400, China.
Department of Polymer and Textile Engineering, Federal University of Technology, P.M.B. 1526, Owerri 460114, Nigeria.
Nanomaterials (Basel). 2021 Oct 20;11(11):2782. doi: 10.3390/nano11112782.
The development of microelectronics is always driven by reducing transistor size and increasing integration, from the initial micron-scale to the current few nanometers. The photolithography technique for manufacturing the transistor needs to reduce the wavelength of the optical wave, from ultraviolet to the extreme ultraviolet radiation. One approach toward decreasing the working wavelength is using lithography based on beyond extreme ultraviolet radiation (BEUV) with a wavelength around 7 nm. The BEUV lithography relies on advanced reflective optics such as periodic multilayer film X-ray mirrors (PMMs). PMMs are artificial Bragg crystals having alternate layers of "light" and "heavy" materials. The periodicity of such a structure is relatively half of the working wavelength. Because a BEUV lithographical system contains at least 10 mirrors, the optics' reflectivity becomes a crucial point. The increasing of a single mirror's reflectivity by 10% will increase the system's overall throughput six-fold. In this work, the properties and development status of PMMs, particularly for BEUV lithography, were reviewed to gain a better understanding of their advantages and limitations. Emphasis was given to materials, design concepts, structure, deposition method, and optical characteristics of these coatings.
微电子学的发展始终由减小晶体管尺寸和提高集成度驱动，从最初的微米级发展到当前的几纳米级。制造晶体管的光刻技术需要将光波波长从紫外线降低到极紫外线辐射。一种降低工作波长的方法是使用基于波长约为7纳米的超越极紫外线辐射（BEUV）的光刻技术。BEUV光刻依赖于先进的反射光学元件，如周期性多层膜X射线镜（PMM）。PMM是具有“轻”、“重”材料交替层的人造布拉格晶体。这种结构的周期约为工作波长的一半。由于一个BEUV光刻系统至少包含10面镜子，光学元件的反射率成为关键因素。单个镜子的反射率提高10%将使系统的整体吞吐量提高六倍。在这项工作中，对PMM的特性和发展现状进行了综述，特别是对于BEUV光刻，以更好地了解其优点和局限性。重点介绍了这些涂层的材料、设计概念、结构、沉积方法和光学特性。
