Mechanisms of Stress and Structure Evolution During Processing of Polycrystalline Thin Films

多晶膜用于广泛的微米和纳米级器件和系统中，其中它们的应力状态和晶粒结构深刻地影响它们的性能、性质和可靠性。 在膜形成和随后的处理过程中的应力和结构演化是强耦合的。 应力演化的原位测量揭示了一系列复杂的现象，包括拉伸和压缩应力状态之间的演化，以及生长中断期间明显可逆的应力变化。非原位和原位表征的晶粒结构和表面形貌也揭示了复杂的过程，其中包括晶粒生长和纹理演变过程中和之后的岛屿合并，网络形成过程中的岛屿合并，保留深沟在晶界，和膜岛合并过程中和之后的表面形貌的变化。 这种现象在目前对应力和结构演化之间联系的理解中没有得到解释。 在这个程序中，应力演化将在一系列条件下的一系列材料的沉积过程中进行研究。 使用不同的材料和沉积温度将允许观察到的行为是中间的那些已经成为先前研究的重点。 使用具有较高熔化温度的材料还将允许淬火表面和晶粒结构以用于非原位表征。 将在沉积期间和沉积中断期间使用光散射技术监测表面形貌。原子沉积通量的入射角也将变化，以便可控地促进不同水平的表面粗糙度。 形成膜的初始岛的尺寸和间距也将使用模板去湿技术来改变。通过这些研究，将开发的理解，这将允许多晶薄膜的结构和性能的应用特定的工程和从他们的微/纳米结构图案。为我们的手机、计算机和互联网供电的电气设备和集成电路是使用在硅等材料的平坦表面上形成的非常薄的金属和半导体层制造的。 然后在这些薄膜中制作非常小的图案，以创建数百万个连接起来的设备，以制造设备的电路。 有时，这些设备的部件在工作时会发生物理移动。 不同材料的层或膜通常通过基本上将原子喷射到平坦表面上来制成。 一旦原子到达表面，它们就会四处移动形成小晶体，这些晶体会生长，直到它们相互碰撞形成连续的薄膜。这些晶体形成和生长的方式可能会有很大的不同，这取决于原子是如何喷射的，以及使用了哪些原子。 这些变化强烈地影响着薄膜的性质，包括电子在其中移动的难易程度，或者移动部件的难易程度。 这使得制造复杂的集成电路非常困难，并限制了可以制造的东西。 该研究计划的重点是了解为什么会发生这些变化，以及如何控制它们，以便制造新的设备和电路。 为了做到这一点，研究人员将改变原子的喷射方式，并测量薄膜的性质和结构在形成过程中的变化。

TECHNICAL SUMMARY Polycrystalline films are used in a wide range of micro- and nano-scale devices and systems in which their stress state and grain structure profoundly affect their performance, properties and reliability. Stress and structure evolution during film formation and subsequent processing are known to be strongly coupled. In-situ measurements of stress evolution have revealed a complex range of phenomenology, including evolution between tensile and compressive stress states, and apparently reversible stress changes during growth interruptions. Both ex-situ and in-situ characterization of grain structures and surface topography have also revealed complex processes that include grain growth and texture evolution during and after island coalescence, network formation during island coalescence, retention of deep trenches at grain boundaries, and changes of surface topography during and after film island coalescence. This phenomenology is not accounted for in current understandings of the linkage between stress and structure evolution. In this program, stress evolution will be studied during deposition of a range of materials under a range of conditions. Use of different materials and deposition temperatures will allow observations of behavior that are intermediate to those that have been the focus of prior studies. Use of materials with higher melting temperatures will also allow quenching of surface and grain structures for ex-situ characterization. Surface topography will be monitored during deposition, and during interruptions of depositions, using light scattering techniques. The angle of incidence of the atomic deposition flux will also be varied in order to controllably promote different levels of surface roughness. The size and spacing of the initial islands from which films are formed will also be varied using templated dewetting techniques. Through these studies, understandings will be developed that will allow application-specific engineering of structures and properties of polycrystalline thin films and the micro/nanostructures patterned from them. NON-TECHNICAL SUMMARY The electrical devices and integrated circuits that power our cell phones, computers, and the Internet are created using very thin layers of metals and semiconductors that are formed on flat surfaces of materials like silicon. Extremely small patterns are then made in these films to create millions of devices that are connected to make circuits of devices. Sometimes the devices have parts that physically move as they work. Layers, or films, of different materials are usually made by essentially spraying atoms onto a flat surface. Once the atoms arrive on the surface, they move around to form small crystals and these crystals grow until they run into each other to form a continuous film. The way these crystals form and grow can vary tremendously, depending on how the atoms are sprayed and on which atoms are used. These variations strongly affect the properties of a film, including how easily electrons can move through them or how easily the moving parts can be moved. This makes it very difficult to make complex integrated circuits and limits what can be made. This research program focuses on understanding why these variations occur and on how they can be controlled, so that new devices and circuits can be made. To do this, the researchers will change the way the atoms are sprayed and measure how the properties and structure of films change, while they are being formed.