Historical overview of silicon crystal pulling development

The first silicon single crystals were grown by crucible pulling in 1950, 2 years after the invention of the transistor, which was first made from germanium. Two years later, the crucible-free float zone pulling was invented. In this stage, the low purity of the starting polysilicon for the crystal pulling was the biggest problem. A great help in the purification of polysilicon were the very low distribution coefficients of most of the impurities. This effect was used in the refining of silicon by repeated crucible-free zone melting (zone refining). However, boron cannot be sufficiently removed by this technique. Since 1961, the raw silicon is first transformed into a silane, then the silane is purified by distillation and adsorption, and finally retransformed to elemental silicon by chemical vapor deposition. This purification technique yields a polysilicon that needs no further purification by zone refining. A big step forward was the invention of the dislocation-free crystal growth in 1958, an absolute necessity for the manufacturing of highly integrated devices. The first crystals were small with about 0.5 " diameter and about 100 g weight. Predominantly for economical reasons, the size of the crucible pulled crystals increased stepwise about every 4 years to 12 " diameter (for 300 mm wafers) and to 250 kg in weight until today. The maximum diameter of Boat zone grown crystals is only 6 " at present, because there was no need for larger Boat zone-Si diameters in the past. But this has changed recently. (C) 2000 Elsevier Science S.A. All rights reserved.