采用SiGe虚拟衬底高迁移率应变硅材料的制备和表征

研究了生长在弛豫Si0.79Ge0.21/梯度Si1-xGex/Si虚拟衬底上的应变硅材料的制备和表征,这一结构是由减压外延气相沉积系统制作的.根据双晶X射线衍射计算出固定组分SiGe层的Ge浓度和梯度组分SiGe层的梯度,并由二次离子质谱仪测量验证.由原子力显微术和喇曼光谱测试结果得到应变硅帽层的表面粗糙度均方根和应变度分别为2.36nm和0.83%;穿透位错密度约为4×104cm-2.此外,发现即使经受了高热开销过程,应变硅层的应变仍保持不变.分别在应变硅和无应变的体硅沟道上制作了nMOSFET器件,并对它们进行了测量.相对于同一流程的体硅MOSFET,室温下观测到应变硅器件中电子的低场迁移率显著增强,约为85%.

Fabrication and Characterization of Strained Si Material Using SiGe Virtual Substrate for High Mobility Devices

The fabrication and characterization of strained-Si material grown on a relaxed Si0.79Ge0.21/graded Si1-xGex/Si virtual substrate,using reduced pressure chemical vapor deposition,are presented.The Ge concentration of the constant composition SiGe layer and the grading rate of the graded SiGe layer are estimated with double-crystal X-ray diffraction and further confirmed by SIMS measurements.The surface root mean square roughness of the strained Si cap layer is 2.36nm,and the strain is about 0.83% as determined by atomic force microscopy and Raman spectra,respectively.The threading dislocation density is on the order of 4e4cm-2.Furthermore,it is found that the stress in the strained Si cap layer is maintained even after the high thermal budget process.nMOSFET devices are fabricated and measured in strained-Si and unstrained bulk-Si channels.Compared to the co-processed bulk-Si MOSFETs at room temperature,a significant low vertical field mobility enhancement of about 85% is observed in the strained-Si devices.