Understanding the Transport Properties of Silicon Grain Boundaries and How They Relate to I.C. Applications of Polysilicon

摘要

Silicon integrated circuit technology utilizes polycrystalline silicon (polysilicon) for a variety of purposes ranging from gates and conductor lines to resistors and, recently, even active devices. The structural, chemical, and electrical properties of silicon grain boundaries play a fundamental role in determining the operational characteristics of these polysilicon elements. In many cases process control problems, such as the extreme sensitivity of poly resistivity to dopant level variations, can be traced directly back to the fundamental nature of the double depletion layers that surround most silicon grain boundaries. In the past 10 years studies of the fundamental transport properties of single grain boundaries have provided us with a clear theoretical picture for predicting the current flow across such structures. Our present state of understanding in this area is reviewed. Despite this level of progress, predicting the electrical properties of a real polycrystalline film remains a difficult task. Inhomogeneities in the structure of single boundaries, crystallographic dependence of potential barrier heights, grain boundary dopant segregation and diffusion, plus other effects are the source of the complex properties of a typical real-world polysilicon device. (ERA citation 12:043634)