Student Travel Support for the International Symposium on Si-Heterostructures, Barga, Italy, September 9-12, 1997

9531816皮尔索尔该项目的目标是通过非侵入性监测实现对气相薄膜沉积的新的基本了解，并确定这些信息如何改进对气相半导体工艺中的化学成分的实时控制。几乎所有的半导体制造都涉及到通过气相化学来刻蚀或沉积薄膜。人们普遍认为，现场、非侵入性的过程监控和实时控制将提高制造产量和生产能力，需要更多的研究来开发合适的方法。例如，在最近(1994年8月)的评论中，《半导体国际》的编辑评论说，“实时监控仍然是一个非常可取的目标，但有些遥远”。关键是一种强大的定量技术，它可以跟踪发生在半导体晶片表面或附近的化学反应。一种基于紫外光谱的方法是拟议工作的重点。控制策略的同步测试将决定测量结果是否有足够的信息可供实际使用。实验环境将是现有的化学束外延反应堆，具有校准的流量、压力和晶片温度监测。它支持从超高真空(10-10Torr)到10-4Torr压力的加工条件。共置的化学气相沉积反应器允许在10-4Torr到大气压的压力范围内进行额外的实验。实验将确定在实际操作条件下，紫外光谱能否提供多种化学成分的阳性鉴定和定量。这种方法具有足够的灵敏度，可用于气体密度最低的超高真空沉积条件。定量依赖于光学信号的准确基线，因此新的无云窗将与补偿光源强度和光学透明度漂移的技术结合使用。机理建模将为待测参数的估计和反馈控制提供依据。将使用基于线性和非线性模型的控制方法。最初的工作将测试该系统跟踪1至3种稀释物组成超过另一种的时变设定点的能力，并在晶片表面提供均匀的温度。然后，该系统将被用来控制GaAs与Al和In的化合物的沉积。为了优化信息含量，实验将确定紫外光应该位于哪里(相对于晶片表面)。控制策略的有效性将通过对沉积的薄膜进行独立(离线)化学分析来衡量。***

9531816 Pearsall The goal of this project is to achieve new fundamental understanding of thin film deposition from the gas phase through non-invasive monitoring and to determine how this information can improve real-time control of chemistry in gas-phase semiconductor processing. Nearly all semiconductor manufacturing involves etching or deposition of thin films via gasphase chemistry. There is wide agreement that in-situ, non-invasive process monitoring and real-time control will improve manufacturing yield and throughput, and that more research is needed to develop suitable methods. For example, in recent (8/94) review the editor of Semiconductor International remarked, "Real-time monitoring remains a highly desirable, but somewhat distant goal". The key is a robust, quantitative technique that tracks the chemical reactions occurring at or near the surface of a semiconductor wafer. A method based on ultra-violet (UV) spectroscopy is focus of the proposed work. Simultaneous tests of control strategies will determine whether the measurements have enough information to be of practical use. The experimental environment will be an existing chemical beam expitaxy reactor with calibrated flow, pressure, and wafer temperature monitoring. It supports processing conditions from ultra-high vacuum (10-10 Torr) to 10-4 Torr pressure. A co-located chemical vapor deposition reactor allows additional experiments in the pressure range 10-4 Torr to atmospheric pressure. Experiments will determine whether UV spectroscopy can provide positive identification and quantitation of multiple chemical components at realistic operating conditions. This method has sufficient sensitivity to be used in ultra-high vacuum deposition conditions where the gas density is lowest. Quantitation depends on an accurate baseline for the optical signal, so a new nonclouding window will be used in combination with techniques that compensate for drift in source intensity and optical transparency. Mechanis tic modeling will provide the basis for estimation of unmeasured parameters and for feedback control. Linear and non-linear model-based control methods will be used. Initial work will test the system's ability to track time-varying setpoints for compositions of 1 to 3 dilute reactants in an excess of another, and to provide uniform temperature across the wafer surface. The system will then be used to control deposition of compounds of GaAs with Al and In. Experiments will determine where the UV beam should be located (relative to the wafer surface) in order to optimize the information content. The efficacy of the control strategy will be measured by independent (off-line) chemical analysis of the deposited film. ***