J. Grabmaier – författare

1.1 The Role of Silicon as a Semiconductor Silicon is unchallenged as a semiconductor base material in our present electronics indu­ stry. The reasons why it qualifies so strongly for this particular purpose are manyfold. The attractive combination of physical (electrical) properties of silicon and the unique properties of its native oxide layer have been the original factors for its breathtaking evolution in device technology. The majority of reasons, however, for its present status are correlated with industrial prosessing in terms of charge units ( economy), reliability (reproducibility), and flexibility, but also its availability. The latter point, in particular, plays an important role in the different long-term projects on the terrestrial application of solar cells. Practically inexhaustive resources of silicon dioxide form a sound basis even for the most pretentious programs on future alternatives to relieve the present situation in electrical power generation by photovol­ taics. Assuming a maximum percentage of 10% to be replaced by the year 2000 would roughly mean a cumulative annual production of 2 million metric tons of crude silicon (based on present solar cell standards)!). To illustrate the orders of magnitude that have to be discussed in pertinent programs: Today, the industrial silicon capacity of non-communistic countries (including ferrosili­ con and other alloys by their relative Si-content) amounts to some 2 million tons per year.

1.1 The Role of Silicon as a Semiconductor Silicon is unchallenged as a semiconductor base material in our present electronics indu­ stry. The reasons why it qualifies so strongly for this particular purpose are manyfold. The attractive combination of physical (electrical) properties of silicon and the unique properties of its native oxide layer have been the original factors for its breathtaking evolution in device technology. The majority of reasons, however, for its present status are correlated with industrial prosessing in terms of charge units ( economy), reliability (reproducibility), and flexibility, but also its availability. The latter point, in particular, plays an important role in the different long-term projects on the terrestrial application of solar cells. Practically inexhaustive resources of silicon dioxide form a sound basis even for the most pretentious programs on future alternatives to relieve the present situation in electrical power generation by photovol­ taics. Assuming a maximum percentage of 10% to be replaced by the year 2000 would roughly mean a cumulative annual production of 2 million metric tons of crude silicon (based on present solar cell standards)!). To illustrate the orders of magnitude that have to be discussed in pertinent programs: Today, the industrial silicon capacity of non-communistic countries (including ferrosili­ con and other alloys by their relative Si-content) amounts to some 2 million tons per year.

In the first contribution to this volume we read that the world-wide production of single­ crystal silicon amounts to some 2000 metric tons per year. Given the size of present-day silicon-crystals, this number is equivalent to 100000 silicon-crystals grown every year by either the Czochralski (80%) or the floating-zone (20%) technique. But, to the best of my knowledge, no coherent and comprehensive article has been written that deals with "the art and science", as well as the practical and technical aspects of growing silicon­ crystals by the Czochralski technique. The same could be said about the floating-zone technique were it not for the review article by W. Dietze, W. Keller and A. Miihlbauer which was published in the preceding Volume 5 ("Silicon") of this series (and for a monograph by two of the above authors published about the same time). As editor of this volume I am very glad to have succeeded in persuading two scien­ tists, W. Zulehner and D. Huber, of Wacker-Chemitronic GmbH - the world''s largest producer of silicon-crystals - to write a comprehensive article about the practical and scientific aspects of growing silicon-crystals by the Czochralski method and about silicon­ wafer manufacture. I am sure that many scientists or engineers who work with silicon­ crystals -be it in the laboratory or in a production environment - will profit from the first article in this volume.