Mechanism and Kinetics of Selective Tungsten Chemical Vapor Deposition

本项目的目的是阐明六氟化钨和六氯化钨非均相化学气相沉积中吸附、解吸、表面反应、扩散、钨成核和薄膜生长的机理，并基于这些机理建立基本的、非经验的反应速率表达式。将采用一种基于互补超高真空（UHV）技术的实验方法，以便在定义良好的条件下分离和单独检查各种反应步骤。程序升温解吸和反应光谱（TPD/TPRS）将用于分离吸附、分解和解吸，并确定每个步骤的速率常数。基于TPD/TPRS研究和扫描动力学光谱（SKS）实验提出的机制的速率表达式将与生长速率曲线进行比较。将研究清洁的硅和清洁的钨表面，分别建立在没有可能作为毒物或促进剂的化学物质的情况下，硅还原和氢还原反应的行为。然后将系统地介绍杂质、掺杂剂和表面绝缘层，并量化它们对沉积反应的影响。这项研究的成功完成将导致对钨沉积反应的更大的基本理解，特别是关于选择性沉积的限制，在硅上表现出的自限制生长行为。以及有意促进或毒害表面反应的方法。由于半导体器件的横向和纵向尺寸不断缩小，以驱动更快、更可靠的集成微电路，因此对材料提出了新的要求，这一提议的研究受到了推动。钨所具有的特性使其成为非常大规模集成电路中许多技术重要应用的有吸引力的候选者。一些制造商已经将钨互连集成到他们的电路中，但现有的技术在质量控制和非常精细结构的生产方面还有很大的改进空间。

The objectives of this project are to elucidate the mechanisms of adsorption, desorption, surface reaction, diffusion, tungsten nucleation and film growth in the heterogeneous chemical vapor deposition of tungsten hexafluoride and tungsten hexachloride and to develop fundamentally based, non-empirical reaction rate expressions based on these mechanisms. An experimental approach based on complementary ultrahigh vacuum (UHV) techniques will be employed so that the various reaction steps can be isolated and examined individually under well-defined conditions. Temperature-programmed desorption and reaction spectroscopy (TPD/TPRS) will be used to separate adsorption from decomposition and desorption and to determine the rate constants for each step. Rate expressions based on mechanisms suggested by the TPD/TPRS studies and scanning kinetic spectroscopy (SKS) experiments will be compared to growth rate curves. Clean silicon and clean tungsten surfaces will be investigated to establish behavior of the silicon reduction and hydrogen reduction reactions, respectively, in the absence of chemical species which may act as poisons or promoters. Impurities, dopants and surface insulating layers will then be introduced systematically and their effects on the deposition reactions will be quantified. Successful completion of this research will lead to a greater fundamental understanding of the tungsten deposition reactions, particularly with respect to the limits of selective deposition, the self- limiting growth behavior exhibited on silicon, and to methods for intentionally promoting or poisoning the surface reactions. The proposed research is motivated by new demands placed on materials as lateral and vertical dimensions in semiconductor devices continue to shrink in the drive for faster, more reliable integrated microcircuits. Tungsten possesses properties which make it an attractive candidate for a number of technologically- important applications in very large scale integration (VLSI) circuits. Some manufacturers are already incorporating tungsten interconnects into their circuits, but existing technology leaves much room for improvement in quality control and production of very fine structures.