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所谓外延“自隔离”现象,在我们的实验中也得到了证实,这确实是一种有趣的现象。这种现象是:在不掺杂及系统(如加热体)特别清洁的情况下,利用我们自产的SiCl_4,在N型衬底上生长的外延层为N型,在p=8～13欧姆·厘米的P型衬底上生长的外延层仍是P型,可用热探针检查证实。另外还发现,在p=8～13欧姆·厘米的基片上扩有锑埋层的岛上,经外延生长后,发现岛与岛之间有“自然”隔离现象。我认为应对此现象作进一步的研究,做成电路,并考查其可靠性,以确定其实用价值。下面就“外延自隔离技术”一文的几个问题提出一些看法(1)“对于不掺杂的与衬底同类型的外延……显然外延层的杂质主要来自衬底杂质的外扩散。”还必须强调系统(如加热体)没有任何杂质污染的条件。(2)用三探针测量击穿电压是不够确切的。因为外延生长形成自隔离后,中间隔有p~-墙,而所用的三探针最外两针之间有大约5毫米的距离(见图),因此,测出的击穿电压是不真实的。如果要测量埋层上n岛的电阻率,只有放置同样条件扩过锑埋层的样片。
The so-called phenomenon of “self-isolation” has also been confirmed in our experiments. This is indeed an interesting phenomenon. The phenomenon is that the epitaxial layer grown on the N-type substrate is N-type without doping and with special cleaning of the system (eg, heating body), using our own SiCl 4, and at p = 8-13 ohms The epitaxial layer grown on a centimeter P-type substrate is still P-type and can be confirmed by thermal probe examination. In addition, it was also found that there was a “natural” isolation between the island and the island after epitaxial growth on an island of antimony buried layer on a substrate of p = 8 to 13 ohm.cm. I think this phenomenon should be further studied, made a circuit, and test its reliability, to determine its practical value. Here are some observations on the issue of “epitaxial self-isolation”: (1) “For the undoped epitaxy of the same type as the substrate ... it is clear that the impurities in the epitaxial layer are mainly due to the out-diffusion of the substrate impurities.” Must emphasize the system (such as heating body) without any impurity contamination conditions. (2) It is not exact enough to measure breakdown voltage with three probes. Since the epitaxial growth is formed after isolation, there is a gap between the p ~ - walls and the distance between the outermost two needles of the three probes used is about 5 mm (see figure), so the measured breakdown voltage is not true of. If you want to measure the resistivity of the island on the buried layer, only place the sample under the same conditions to extend the buried antimony layer.