A New Technique for Monitoring Metallic Contamination During Aqueous Semiconductor Wafer Processing

随着器件和互连尺寸的不断缩小，微电子产业面临着多项严峻的技术挑战。一个重要的挑战是在加工过程中降低晶圆表面的金属污染水平。在16mb动态随机存取存储器（DRAM）的制造过程中，1010个金属原子/crn2的容差限制以及金属污染物使超薄（40）极氧化物短路的能力都证明了这一点。硅片表面的污染程度在很大程度上取决于化学工艺溶液中微量金属杂质的沉积和溶解之间的权衡。这种权衡涉及许多基本的物理和化学过程，包括表面化学反应、体扩散和对流。尽管污染物的潜在来源、沉积机制和运移至关重要，但人们对它们仍知之甚少。由于在测量表面污染水平方面存在分析困难，对这些问题的研究受到了阻碍。我们建议开发一种新的原位间接监测化学工艺水溶液中金属污染物沉积和溶解的技术。该方法采用空间分辨吸收光谱来检测晶圆表面附近边界层的浓度梯度，灵敏度限制在ppb范围内。我们将利用该技术监测缓冲氧化物蚀刻剂（BOE）中Cu的沉积速率，并监测标准化学工艺溶液SC-1中Cu的溶解速率。实验测量将辅以计算机模拟金属污染物沉积和溶解在水晶圆加工过程中使用实际的过程几何。所提出的模型将包括扩散、对流和化学表面过程，使用随时间变化的三维有限差分解来控制动量和质量传输方程。表面化学过程和大块传输速率的实验测定对于正确预测金属污染物沉积和溶解速率至关重要。除了作为原位传感器的潜在应用之外，实验技术还可以用于金属污染物沉积和溶解过程中发生的各种基本物理和化学过程的研究。通过紫外光照射表面和电化学控制表面，可以测量沉积开始的电位。这将允许确定能斯特方程对化学过程中金属污染物沉积预测的适用性。＊＊＊

9634058 Suni As device and interconnect sizes continuously shrink, the microelectronics industry faces a number of serious technological challenges. One important challenge is to decrease the level of metallic contamination on wafer surfaces during processing. This is evidenced both by the tolerance limit of 1010 metal atoms/crn2 during fabrication of 16-MB dynamic random access memory(DRAM) and by the ability of metallic contaminants to short-circuit ultrathin((40() gate oxides . The level of contamination on the wafer surface is determined to a large extent by the tradeoff between deposition and dissolution of trace metallic impurities in aqueous chemical process solutions. This tradeoff involves a number of fundamental physical and chemical processes, including surface electroless reaction, bulk diffusion and convection. The potential sources, deposition mechanism(s) and transport of contaminants are still poorly understood despite their critical importance. Study of these problems has been hampered by analytical difficulties in measuring the level of surface contamination. We propose to develop a new in situ technique for indirect monitoring of metal contaminant deposition and dissolution in aqueous chemical process solutions. This employs spatially resolved absorption spectroscopy to detect concentration gradients in the boundary layer near the wafer surface with sensitivity limits in the ppb range. We will employ this technique to monitor the rate of Cu(( deposition from a buffered oxide etchant(BOE) and to monitor the rate of Cu dissolution in a standard chemical process solution SC-1. The experimental measurements will be complemented by computer modeling of metal contaminant deposition and dissolution during aqueous wafer processing using realistic process geometries. The proposed model will include diffusion, convection and electroless surface processes using time-dependent, three-dimensional finite difference solution of the governing momentum and mass transport equation s. Experimental determination of the rates of surface electroless processes and bulk transport are essential to correctly predict rates of metal contaminant deposition and dissolution. Besides potential applications as an in situ sensor, the experimental technique can be employed in a variety of studies of the fundamental physical and chemical processes occurring during metal contaminant deposition and dissolution. By illuminating the surface with ultraviolet light and controlling the surface electrochemically, the potential at which deposition is initiated can be measured. This will allow determination of the applicability of the Nernst equation to the prediction of metal contaminant deposition by electroless processes. ***