Semiconductor Silicon: The Extraordinary Made Ordinary
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Semiconductor Silicon: The Extraordinary Made Ordinary Harry J. Leamy and Jack H. Wernick We humans have employed and improved materials for millennia, but it required the Industrial Revolution of the last century to birth the systematic, science-based development of materials. During this time, effort expended in understanding the process-microstructureproperties relationships of materials conferred great economic and military advantage upon the successful. The introduction of machine power in this era created great leverage for improvements in the strength, ductility, corrosion resistance, formability, and similar properties of materials. Response to this opportunity led to the emergence of the materials profession. Stimulated by opportunity, materials scientists and engineers of the day met many of the challenges by first understanding and then controlling the composition and microstructure of materials. In the process, they defined the materials-engineering profession and left their names as a part of its vocabulary: Martens(ite), Bain(ite), Austen(ite), Schmid, Bessemer, Charpy, and Jomminy, to name a few. In fact the understanding and control of microstructure is the hallmark of materials science and engineering. Of course the ancient art of finding, mining, concentrating, and refining materials from the earth's crust does not apply to this definition since we wish to focus on the engineering of materials. Five decades ago, a new chapter in the evolution of this profession began by the invention of the transistor. This invention and the development of integrated circuitry that followed from it spawned a new era of materials achievement, again stimulated by the enormous economic and performance gains available. In this arena however, the object of the game was to completely eliminate microstructure while doing away with impurities, save for a desired few, to levels previously unimagined. Today a material thus prepared is a blank slate upon which we can write the microstructure of an integrated circuit. The story of integrated-circuit fabrication is by now a very familiar one. Its telling employs vocabulary such as diffusion, ion implantation, lithography, oxidation, metallization, and passivation. The story's theme suggests that advances
MRS BULLETIN/MAY 1997
Figure 1. Semiconductor silicon rivals steel as an enabling material fora new era. This era, the information age, was born with the invention of the transistor and continues, 50 years later, to log exponential growth. This growth is supported by the ability of the materials community to keep pace with the requirements imposed on this material, the specifications of which exceed those for any other inorganic material (animal, vegetable, mineral) by at least two orders of magnitude. Photograph by Kelly James, Salem, Oregon. Courtesy of Mitsubishi Silicon America.
in lithography lead to geometric improvements in performance, both computational and economic, of the product circuits, which are essential ingredients in the ongoing information r
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