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在电阻率比较高的P-N结隔离外延中,许多同志都发现一种“自隔离”现象。在SiCl_4中不掺杂或掺杂很少的情况下,外延之后,埋层区之间正、反向好象都有一定的耐压,有时漏电流很小(比如100伏小于1微安),有时漏电流很大,与常见的沟道漏电相似,用显微热探针测量N~+区上边的外延层是N型,其余好象是P型。由于电阻率较高,热探针有时并不明显。对于这种“隔离”的本质,一般有两种看法。一种看法是外延时衬底中的杂质高速扩散,已经形成了P-N结隔离;另一种看法则认为这是一种耗尽层的高电阻隔离,即由于掺杂很少,外延电阻率很高,隔离墙区的电阻也很大。这种看法的依据是:
In the relatively high resistivity P-N junction isolation, many comrades found a “self-isolation” phenomenon. In SiCl_4 without doping or doping case, the epitaxial, the buried layer between the positive and negative seems to have a certain pressure, and sometimes leakage current is very small (for example, 100 V is less than 1 μA) , And sometimes the leakage current is large. Similar to the common channel leakage, the epitaxial layer above the N ~ + region is measured by the micropore probe and the rest appears to be P-type. Due to the higher resistivity, the thermal probe is sometimes not obvious. There are two generalities about the nature of this “isolation.” One view is that the diffusion of impurities in the epitaxial substrate at a high rate has resulted in the formation of PN junction isolation. Another view is that this is a depletion layer of high-resistance isolation, ie, due to the low doping, the epitaxial resistivity High, the resistance of the wall area is also great. The basis of this view is: