Superconformal Growth of Thin Films by Two-Component CVD

非技术描述：集成电路需要多层次的晶体管微观布线，即需要十层或更多层的垂直柱和水平排铜将所有晶体管互连成一个功能芯片。对于每一层，需要先进的图案和蚀刻方法来创建尺寸远低于1微米的圆柱形和沟槽形开口。在越来越小的尺寸尺度上制造这种精致的结构，没有任何被困的空隙空间或沿中线的低密度材料的“接缝”，是一个重大挑战。该项目探索了一种完成填充步骤的新方法：在特殊条件下，使用两种化学物质从气相沉积材料，导致开口底部的生长速度比顶部快，称为超共形生长。在填充过程中，沉积的材料形成一个v型的轮廓，顶点从底部向上移动，提供一个完美的填充结构。该研究项目与各种教育活动相结合：让研究生参与研究的各个方面，指导本科生进行高级项目，并将研究成果传播给科技界。技术描述：本研究项目开发了一种创新的方法，以超共形方式沉积薄膜材料在高长宽比（深度：宽度）的开口内，如衬底中的沟槽和通孔，从而实现完整和无空隙的填充。这种超适形生长是各种纳米级制造工艺所需要的。在这个项目中，生长通过化学气相沉积进行，使用两种反应物在相对较低的温度下进行，通常低于300摄氏度。存在一种动力学机制，其中物种运输和表面反应速率的竞争导致超适形生长。项目任务包括(1)演示和评估各种材料和各种开口的超适形填充方法；(2)建立一个数学模型，可以预测一般的超适形生长条件；(3)确定为了消除低密度物质的生长，需要在结构内何种化学物质分布。这些实验产生了详细的动力学数据，并根据基于扩散的模型进行了测试。该过程的原子尺度机制是通过对薄膜表面的原位分析、粒子传输和填充剖面的详细计算以及对反应副产物作用的严格检查来确定的。

Non-Technical Description: Integrated circuits require multi-level microscopic wiring of transistors, i.e., ten or more layers of vertical columns and horizontal rows of copper are needed to interconnect all the transistors into a functional chip. For each layer, advanced patterning and etching methods are required to create cylindrical and trench-shaped openings with dimensions well below one micrometer. Fabricating this exquisite structure on ever-smaller size scales, without any trapped void space or "seam" of low-density material along the centerline, is a significant challenge. This project explores a new method to accomplish the filling step: a material is deposited from the gas phase using two chemical species under special conditions that cause the growth rate to be faster at the bottom of the opening than at the top, termed as superconformal growth. During the filling process, the deposited material forms a V-shaped profile and the apex moves up from the bottom to afford a perfectly filled structure. The research project is integrated with various educational activities: involving graduate students in every aspect of the research, supervising undergraduate students on senior projects, and disseminating the research findings to the scientific and technical communities. Technical Description: This research project develops an innovative approach to deposit thin film materials in a superconformal fashion inside of high aspect ratio (depth : width) openings such as trenches and vias in a substrate, leading to complete and void-free filling. Such superconformal growth is needed for a wide variety of nanoscale fabrication processes. In this project, growth proceeds by chemical vapor deposition using two reactants at a relatively low temperature, generally below 300 degrees C. A kinetic regime exists where the competitions in species transport and surface reaction rates lead to the superconformal growth. The project tasks include (1) to demonstrate and evaluate the superconformal filling method for a variety of materials and in various openings; (2) to create a mathematical model of the effect that can predict superconformal growth conditions in general; and (3) to determine what distribution of chemical species within the structure is needed to eliminate the growth of low-density material. These experiments generate detailed kinetic data that are tested against a diffusion-based model. The atomic-scale mechanisms of the process are determined using in-situ analyses of the film surface, detailed calculations of particle transport and filling profiles, and a critical examination of the role of reaction byproducts.