Developmental Research of an Apparatus for In-line Monitoring of Contamination on Si Wafer Surface

在MOS器件的制造中，制备化学清洁的硅表面是非常重要的。然而，在制造过程之前，空气中已经存在的有机材料可能会污染硅片表面。这些材料不能通过热退火完全去除，最终会影响MOS器件的电性能。因此，为了制造高质量、高可靠性的MOS器件，我们需要在器件制造过程中原位、快速地测定硅片表面的有机污染水平。在本研究中，开发了一种红外监测系统，用于快速检测和表征硅片表面的有机污染。红外光通过硅片传播，内部反射多次，这使得检测硅片表面的少量表面污染成为可能。我们进行了一项实验，证明了用适度的手段在300 mm直径的多重内反射（MIR）几何结构的硅晶片上红外吸收监测有机污染物的可行性。本实验的主要目的是展示本系统对有机污染的检测极限，然后将其与报道的对MOS器件电性能没有明显影响的污染水平上限（即10^<12>碳原子/cm^2）进行比较。我们发现，本系统可以检测硅片表面的碳氢化合物污染，污染水平低于10^<11>碳原子/cm^2。目前的研究结果表明，所提出的监测系统有利于高质量电子器件的制造。

In the fabrication of MOS devices, preparing chemically clean silicon surfaces is quite important. However, organic materials already present in the air may contaminate Si wafer surfaces prior to fabrication processes. Those materials cannot be completely removed by thermal annealing, and eventually affect the electrical performance of MOS devices. To fabricate high-quality, high-reliable MOS devices, therefore, we need an in-situ, rapid determination of the level of organic contamination on Si wafer surfaces during the fabrication process of the devices. In this study, an IR monitoring system has been developed for the rapid detection and characterization of organic contamination on Si wafer surfaces. IR light propagates through the Si wafer, internally reflecting many times, which makes it possible to detect small amounts of surface contamination on the wafer surface.We have performed an experiment demonstrating the feasibility of infrared absorption monitoring of organic contaminants on a 300-mm-diameter Si wafer in the multiple internal reflection (MIR) geometry with modest means. The main purpose of the experiment is to show the detection limit of the present system for organic contamination and then to compare it with the reported upper limit of the contamination level that has no appreciable effect on the electrical performance of MOS devices, that is, 10^<12> carbon atoms/cm^2 . We found that the present system allows for the detection of hydrocarbon contamination on Si wafer surfaces with a contamination level of below 10^<11> carbon atoms /cm^2. The present results demonstrate that the proposed monitoring system is quite beneficial to the fabrication of high-quality electronic devices.