Nitric acid oxidation of Si to form ultrathin silicon dioxide layers with a low leakage current density
Nitric acid oxidation of Si to form ultrathin silicon dioxide layers with a low leakage current density
复制标题
DOI：
10.1063/1.1621720
复制
发表时间：
2003-12-01
影响因子：
3.2
通讯作者：
Iwasa, H
中科院分区：
文献类型：
--
作者：
Kobayashi, H;Asuha;Iwasa, H
具有优异电特性的超薄二氧化硅（SiO2）层可以使用Si的硝酸氧化（NAOS）方法形成，即，通过将Si浸入硝酸（HNO 3）溶液中。用61wt%HNO3在113 ℃的沸腾温度下形成的SiO2层具有1.3nm的厚度，具有相当高的漏电流密度。当SiO2层在68wt%HNO3中形成时（即，与水的共沸混合物），另一方面，漏电流密度（例如，1.5尽管SiO2的厚度几乎相同，为1.4nm，但在正向栅极偏压V-G为1V时的A/cm（2）变得与热生长SiO2层的A/cm（2）一样低。由于NAOS氧化物层的漏电流密度相对较低，因此可以测量电容-电压（C-V）曲线，而不管NAOS氧化物厚度如何。然而，在C-V曲线中存在驼峰，表明存在高密度界面态。傅里叶变换红外吸收测量表明，SiO2层的原子密度增加了7%，在硝酸浓度从61到68重量%的增加。价带谱的测量澄清，这种浓度的增加导致的增强的价带不连续性在Si/SiO2界面从4.1到4.3 eV。当在400 degreesC下在氢中对金属氧化物半导体二极管进行金属化后退火（PMA）处理时，漏电流密度显著增加，并且这种增加归因于Al电极与化学SiO2层之间的反应，导致SiO2厚度减小。另一方面，在200 ℃氢气中使用PMA，SiO2厚度仅略微降低至1.3 nm。在这种情况下，漏电流密度大大降低（例如，0.4 A/cm（2）（V-G=-1 V）和5 × 10（-3）A/cm（2）（V-G=-1 V），因此它变成具有相同厚度的热生长SiO2层的1/3-1/10。在200 ℃ PMA处理后，C-V曲线中的驼峰消失，表明界面态的消除，界面态钝化是漏电流密度降低的原因之一。价带谱的测量结果表明，PMA的漏电流密度降低的另一个原因是在Si/SiO2界面处的带不连续性的增加，和SiO2间隙状态的消除。(C)2003年，美国物理学会。
Ultrathin silicon dioxide (SiO2) layers with excellent electrical characteristics can be formed using the nitric acid oxidation of Si (NAOS) method, i.e., by immersion of Si in nitric acid (HNO3) solutions. The SiO2 layer formed with 61 wt % HNO3 at its boiling temperature of 113degreesC has a 1.3 nm thickness with a considerably high density leakage current. When the SiO2 layer is formed in 68 wt % HNO3 (i.e., azeotropic mixture with water), on the other hand, the leakage current density (e.g., 1.5 A/cm(2) at the forward gate bias, V-G, of 1 V) becomes as low as that of thermally grown SiO2 layers, in spite of the nearly identical SiO2 thickness of 1.4 nm. Due to the relatively low leakage current density of the NAOS oxide layer, capacitance-voltage (C-V) curves can be measured in spite of the ultrathin oxide thickness. However, a hump is present in the C-V curve, indicating the presence of high-density interface states. Fourier transformed infrared absorption measurements show that the atomic density of the SiO2 layers increases by 7% with an increase in the HNO3 concentration from 61 to 68 wt %. Measurements of valence band spectra clarify that this concentration increase causes the enhancement of the valence band discontinuity at the Si/SiO2 interface from 4.1 to 4.3 eV. When postmetallization annealing (PMA) treatment is performed at 400degreesC in hydrogen on metal-oxide-semiconductor diodes, the leakage current density markedly increases, and this increase is attributed to a reaction between the Al electrode and the chemical SiO2 layer, resulting in a decrease in the SiO2 thickness. With PMA at 200degreesC in hydrogen, on the other hand, the SiO2 thickness decreases only slightly to 1.3 nm. In this case, the leakage current density greatly decreases (e.g., 0.4 A/cm(2) at V-G=1 V and 5x10(-3) A/cm(2) at V-G=-1 V), and consequently it becomes 1/3-1/10 of those for thermally grown SiO2 layers with the same thickness. The hump in the C-V curves disappears after PMA at 200degreesC, indicating the elimination of interface states, and the interface state passivation is attributed to one of the reasons for the decrease in the leakage current density. Measurements of the valence band spectra show that another reason for the decrease in the leakage current density by PMA are an increase in the band discontinuity at the Si/SiO2 interface, and the elimination of SiO2 gap states. (C) 2003 American Institute of Physics.