Improvement of leakage current characteristics of MOS devices by use of catalytic of platinum

我们提出了一种降低流过二氧化硅(SiO_2)层的漏电流密度的新方法。在这种方法中，在SiO_2层上沉积~3 nm厚的铂(PT)层，然后在~300℃的氧气中进行热处理，然后在去除铂层后沉积铝电极，得到&lt；Al/SiO_2/Si(100)&gt；MOS结构。解离的氧离子(O)被注入到SiO_2层中，并与SiO_2中的亚氧化物等缺陷态以及Si/SiO_2界面上的Si悬挂键界面态反应。该反应导致作为电流路径工作的缺陷态的消除。由于较高的电场促进了SiO_2层薄层中O离子的迁移，选择性地在薄层部分发生氧化，从而改善了SiO_2层厚度的均匀性，从而降低了漏电流密度。当施加相对于铂层的正偏压时，界面态密度变低。我们发现，在硝酸共沸溶液中浸渍硅形成的厚度为~1.4 nm的SiO_2层的漏电流密度与高温下生长的热SiO_2层的漏电流密度一样低或略低。因此，我们首次成功地观测到了超薄化学SiO_2层的电容-电压曲线。当沉积Al层并在氢气中加热200℃时，漏电流密度大大降低到相同厚度的热SiO_2层的1/20~1/4。结果表明，漏电流密度的降低是由于1)界面态的消除，2)SiO_2带隙的消除，3)SiO_2层禁带能的展宽。

We have developed a new method of decreasing a leakage current density flowing through silicon dioxide (SiO_2) layers. In this method, a platinum (Pt) layer of 〜 3 nm thickness is deposited on a SiO_2 layer, followed by heat treatment at 〜 300 ℃ in oxygen, and after the removal of the Pt layer, an alminum electrode is deposited, resulting in the <Al/SiO_2/Si(100)> MOS structure. Dissociated oxygen ions (O) are injected into the SiO_2 layer, and the ions react with defect states such as suboxide species in SiO_2 and Si dangling bond interface states at the Si/SiO_2 interface. The reaction results in the elimination of the defect states which work as a current path. Since the migration of O ions is enhanced in thin parts of the SiO_2 layer because of a high electrical field, oxidation selectively occurs in the thin part, leading to the improvement of the SiO_2 thickness uniformity and hence decreasing the leakage current density. When a positive bias voltage is applied to Si with respect to the Pt layer, the interface state density becomes lower.We have found that SiO_2 layers of 〜 1.4 nm thickness formed by immersion of Si in an azeotropic solution of nitric acid possess a leakage current density as low as or slightly lower than those for thermal SiO_2 layers grown at high temperatures. Consequently, we have succeeded in the observation of a capacitance-voltage curve for ultrathin chemical SiO_2 layers for the first time. When an Al layers deposited and the specimen is heated at 200℃ in hydrogen, the leakage current density is greatly decreased to 1/20 〜 1/4 of those for thermal SiO_2 layers of the same thickness. It is concluded that the decrease in the leakage current density results from 1) elimination of interface states, 2) elimination of SiO_2 gap-states, and 3) widening of the band-gap energy of the SiO_2 layer.