Effect of ultrathin GeO_x interfacial layer formed by thermal oxidation on Al_2O_3 capped Ge

We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer （OBL） to form an ultrathin GeOx interracial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. The GeOx interfacial layer is formed in oxidation reaction by oxygen passing through the Al2O3 OBL, in which theAl2O3 layer could restrain the oxygen diffusion and suppress the GeO desorption during thermal treatment. The thickness of the GeOx interfacial layer would dramatically decrease as the thickness of Al2O3 OBL increases, which is beneficial to achieving an ultrathin GeOx interfacial layer to satisfy the demand for small equivalent oxide thickness （EOT）. In addition, the thickness of the GeOx interfacial layer has little influence on the passivation effect of the Al2O3/Ge interface. Ge （100） p-channel metal- oxide-semiconductor field-effect transistors （pMOSFETs） using the Al2O3/GeOx/Ge gate stacks exhibit excellent electrical characteristics; that is, a drain current on-off （Ionloft） ratio of above 1 104, a subthreshold slope of - 120 mV/dec, and a peak hole mobility of 265 cm2/V.s are achieved.     

超短沟道绝缘层上硅平面场效应晶体管中热载流子注入应力导致的退化对沟道长度的依赖性

随着场效应晶体管(MOSFET)器件尺寸的进一步缩小和器件新结构的引入, 学术界和工业界对器件中热载流子注入(hot carrier injections, HCI)所引起的可靠性问题日益关注. 本文研究了超短沟道长度(L=30–150 nm)绝缘层上硅(silicon on insulator, SOI)场效应晶体管在HCI应力下的电学性能退化机理. 研究结果表明, 在超短沟道情况下, HCI 应力导致的退化随着沟道长度变小而减轻. 通过研究不同栅长器件的恢复特性可以看出, 该现象是由于随着沟道长度的减小, HCI应力下偏压温度不稳定性效应所占比例变大而导致的. 此外, 本文关于SOI器件中HCI应力导致的退化和器件栅长关系的结果与最近报道的鳍式场效晶体管(FinFET)中的结果相反. 因此, 在超短沟道情况下, SOI平面MOSFET器件有可能具有比FinFET器件更好的HCI可靠性.     

Equivalent oxide thickness scaling of Al2O3/Ge metal-oxide-semiconductor capacitors with ozone post oxidation

Aluminum-oxide films deposited as gate dielectrics on germanium （Ge） by atomic layer deposition were post oxidized in an ozone atmosphere. No additional interfacial layer was electron microscopy and X-ray photoelectron spectroscopy detected by the high-resolution cross-sectional transmission measurements made after the ozone post oxidation （OPO） treatment. Decreases in the equivalent oxide thickness of the OPO-treated Al2O3/Ge MOS capacitors were confirmed. Furthermore, a continuous decrease in the gate leakage current was achieved with increasing OPO treatment time. The results can be attributed to the film quality having been improved by the OPO treatment.