Development of local-strain technology for crystalline Ge and its application to transistors

为了建立应变Ge沟道的技术，在应力源形成之后，通过拉曼光谱研究了应变对几何和热处理参数的依赖性。缺陷的产生，转化和分布也澄清了光致发光。为了制备Ge-MOSFET，提出了一种超薄SiO2/GeO 2双层Ge表面钝化方法，该方法不需要破坏真空，其界面态密度（Dit）与SiO2/Si相同。为了消除SiO2/GeO 2结构中慢陷阱的影响，提出了一种在各固定温度下优化偏压条件的深能级瞬态谱方法，对GeO 2/Ge结构进行了精确的测量。根据应变评估的结果，一个好的Ge-MOSFET的制造温度应低于500 ℃。因此，开发了一种低温工艺用于Ge-MOSFET的制造，通过该工艺，Ge晶体管的操作得到了批准。特别地，p-MOSFET的沟道迁移率比Si晶体管的沟道迁移率高四倍。

To establish the technology of a strained Ge channel, after stressor formation, the dependences of strain on geometric and thermal treatment parameters were investigated by Raman spectroscopy. Defect generation, transformation, and distribution were also clarified by photoluminescence. To fabricate Ge-MOSFET, an ultra-thin SiO2/GeO2bilayer Ge-surface passivation method was developed without vacuum breaking, which showed a low interface states density (Dit) in the same degree of that for SiO2/Si. To eliminate the influence of slow-traps in the SiO2/GeO2structure, a deep level transient spectroscopy method was developed with optimized bias condition at each fixed-temperature, by which an accurate Ditevaluation was performed for GeO2/Ge. According to the result of strain evaluation, a good-quality Ge-MOSFET should be fabricated at a temperature less than 500 oC. Therefore, a low-temperature process was developed for Ge-MOSFET fabrication, by which the operation of Ge transistors was approved. Particularly, the channel mobility of p-MOSFET was four times higher than that of a Si transistor.