Epitaxial Silicon Technology is a single-volume, in-depth review of all the silicon epitaxial growth techniques. This technology is being extended to the growth of epitaxial layers on insulating substrates by means of a variety of lateral seeding approaches. This book is divided into five chapters, and the opening chapter describes the growth of silicon layers by vapor-phase epitaxy, considering both atmospheric and low-pressure growth. The second chapter discusses molecular-beam epitaxial growth of silicon, providing a unique ability to grow very thin layers with precisely controlled doping characteristics. The third chapter introduces the silicon liquid-phase epitaxy, in which the growth of silicon layers arose from a need to decrease the growth temperature and to suppress autodoping. The fourth chapter addresses the growth of silicon on sapphire for improving the radiation hardness of CMOS integrated circuits. The fifth chapter deals with the advances in the application of silicon epitaxial growth. This chapter also discusses the formation of epitaxial layers of silicon on insulators, such as silicon dioxide, which do not provide a natural single crystal surface for growth. Each chapter begins with a discussion on the fundamental transport mechanisms and the kinetics governing the growth rate, followed by a description of the electrical properties that can be achieved in the layers and the restrictions imposed by the growth technique upon the control over its electrical characteristics. Each chapter concludes with a discussion on the applications of the particular growth technique. This reference material will be useful for process technologists and engineers who may need to apply epitaxial growth for device fabrication.

This book, a continuation of the series “Advances in Materials Research,” is intended to provide the general basis of the science and technology of crystal growth of silicon for solar cells. In the face of the destruction of the global environment,the degradationofworld-widenaturalresourcesandtheexha- tion of energy sources in the twenty-?rst century, we all have a sincere desire for a better/safer world in the future. In these days, we strongly believe that it is important for us to rapidly developanewenvironment-friendlycleanenergyconversionsystemusingsolar energyastheultimatenaturalenergysource. Forinstance,mostofournatural resources and energy sources will be exhausted within the next 100 years. Speci?cally, the consumption of oil, natural gas, and uranium is a serious problem. Solar energy is the only ultimate natural energy source. Although 30% of total solar energy is re?ected at the earth’s surface, 70% of total solar energy can be available for us to utilize. The available solar energy amounts to severalthousand times larger than the world’s energy consumption in 2000 of about 9,000 Mtoe (M ton oil equivalent). To manage 10% of the world’s energy consumption at 2050 by solar energy, we must manufacture 40 GW solar cells per year continuously for 40 years. The required silicon feedstock is about 400,000 ton per year. We believe that this is an attainable target, since it can be realized by increasing the world production of silicon feedstock by 12times asmuchasthe presentproductionat2005.

The work performed during the first quarter included the development of epitaxial baseline solar cell structures grown on conventional single crystal substrates and initial studies of epitaxial growth and the fabrication of solar cells on one type of polycrystalline substrate (Wacker SILSO). Details of the growth and fabrication procedures for the baseline solar cells are given along with measured cell parameters. The results show that solar cells fabricated on epitaxial layers of about one mil thickness can produce AM-1 efficiency of 12%. Reproducibility of these results was established and the direction to be taken for higher efficiency is identified. Growth studies on polycrystalline substrates were started and x-ray topographic studies of the epitaxial layers showed encouraging results in that a substantially lower defect density was noted in the grown layer. Initial results on epitaxial solar cells fabricated on polycrystalline substrates are discussed along with some limitations associated with the use of this material.

Low temperature processes for semiconductors have been recently under intensive development to fabricate controlled device structures with minute dimensions in order to achieve the highest device performance and new device functions as well as high integration density. Comprising reviews by experts long involved in the respective pioneering work, this volume makes a useful contribution toward maturing the process of low temperature epitaxy as a whole.