Method of manufacturing a semiconductor device with a fast bipolar transistor
 The invention relates to a method of manufacturing a discrete or integrated bipolar transistor comprising a base (1A), an emitter (2) and a collector (3). The base (1A) and a connecting region (1B) of the base (1A) are formed by providing a semiconductor body (10) with a doped semiconducting layer (1) which locally borders on a monocrystalline part (3) of the semiconductor body which forms the collector (3). Outside said base, the layer (1) borders on a non-monocrystalline part (4) of the semiconductor body (10) and forms a non-monocrystalline connecting region (1B) of the base (1A). By means of a mask (5), the doping concentration of the layer (1) outside the mask (5) is selectively increased, resulting in a highly conducting connection region (1B) and a very fast transistor. In the known method, an ion implantation is used for this purpose. In a method in accordance with the invention, this is achieved by bringing the semiconductor body (10) into contact with a gaseous substance (40) comprising a doping element, and heating the semiconductor body (10) in such a manner that the doping elements penetrate into the semiconducting layer (1). Such a method surprisingly results in a much faster transistor. It has been found that this enables, on the one hand, a much smaller diffusion in the thickness direction of the doping of the base (1A) to be achieved, which results in a much faster transistor, particularly, if the base (1A) contains SiGe. On the other hand, the lateral diffusion from the connecting region (1B) to the base (1A) is particularly strongly suppressed. This too has a beneficial effect on the speed of the transistor. The supply of the gaseous substance (40), for example diborane, preferably takes place at a temperature between 800 and 950.degree. C. for one to several minutes. Subsequently, a slightly longer diffusion step can be carried out, for example, at 850.degree. C. 
U.S. Philips Corporation
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Cornelis E. Wiebe B. Catharina H. H. Doede
Timmering De Boer Emons Terpstra