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人们总是希望所制作的半导体器件质量高,可靠性好。为了实现这些目标,栅氧化层的击穿强度和阈值电压重复可控是基本的必要条件。人们发现,碱离子是造成表面电位不稳定的主要原因,因此,在制作高击穿电压的二氧化硅绝缘体时,去除这类可动离子显得特别重要,人们已经发现,在热氧化工艺中掺入百分之几的HCl气体时就能有效地吸除这类碱离子。进一步的研究工作是在初始氧化层生长以后,再在百分之几的HCl和O_2的混合气体中对二氧化硅进行高温处理。这种工艺称为两步HCl处理工艺。业已发现,采用两步HCl栅氧化工艺,面积为20,000平方密耳的电容器的薄氧化层的击穿电场比标准的一步栅氧化工艺提高了百分之五十六。大面积电容器上缺陷密度减小将会使超大规模集成电路的制造工艺得到显著改善。
People always hope that the semiconductor devices produced by high quality, good reliability. In order to achieve these goals, the gate oxide breakdown strength and threshold voltage repeatedly controllable is a basic prerequisite. It has been found that alkali ions are the main cause of surface potential instabilities. Therefore, it is particularly important to remove such movable ions during the fabrication of high breakdown voltage silicon dioxide insulators. It has been found that in the thermal oxidation process, Into a few percent HCl gas will be able to effectively absorb such alkali ions. Further research work is to heat the silicon dioxide in a few percent of the mixture of HCl and O 2 after the initial growth of the oxide layer. This process is called a two-step HCl process. It has been found that the breakdown electric field of a thin oxide layer of a 20,000 square mil capacitor using a two-step HCl gate oxidation process has increased by fifty-six percent over a standard one-step gate oxidation process. Decreasing the density of defects on large area capacitors will result in a significant improvement in the fabrication process for very large scale integrated circuits.