Development of Low-Resistivity Contact Materials for Future ULSIs

我们研究了未来ULSI器件中极低电阻率欧姆接触的形成技术，如控制金属/硅界面的肖特基势垒高度、极高杂质掺杂和使用氢端结控制表面反应。本研究的主要结果如下：(1)在金属/硅界面处引入SiGe夹层，以控制界面势垒高度。在Ti/SiGe/Si（100）的情况下，在580、700和750的温度下快速退火30秒，制备出Ti_5Ge_3、C49-TiSi_2和C54-Ti(Si_1-_yGe_y)_2，发现C54-Ti(Si_1-_yGe_y)_2和C54-TiSi_2都是低电阻相。此外，Ti/SiGe/Si （10o）体系的带隙缩小和肖特基势垒高度降低，这是由于金属/SiGe界面固相反应形成了富锗的SiGe层。(2)开发了采用h端终止处理的触点形成工艺，并证实能形成具有良好电特性的界面。在Ti/p-SiGe/p-Si（100）触点的情况下，可以发现通过RTA工艺退火30秒后，陷阱密度降低，形成了接近理想的界面。另一方面，通过RTA观察到n型样品的泄漏电流增加。(3)为了明确金属/硅界面的最大掺杂浓度，研究了接触电阻率与B掺杂浓度之间的关系。实现了2 × 10^<20> cm^<-3>左右的掺杂浓度，这与B原子在Si中的固溶度非常接近，接触电阻率可以用包含杂质能带形成影响的理论计算来解释。

We have investigated the formation technology of ohmic contacts with very low resistivity for future ULSI devices, such as the control of Schottky barrier heights at metal/Si interfaces, the very-high impurity doping and the surface reaction control using hydrogen termination. The main results obtained by this study are as follows :(1) We have introduced a SiGe interlayer at the metal/Si interface in order to control the interfacial barrier height. In the case of Ti/SiGe/Si (1O0) , Ti_5Ge_3, C49-TiSi_2 and C54-Ti (Si_1-_yGe_y) _2 are produced at 580ﾟC, 700ﾟC and >750ﾟC by rapid thermal annealing for 30 sec. It is found that C54-Ti(Si_1-_yGe_y)_2 is a low resistivity phase as well as C54-TiSi_2. Furthermore, the bandgap narrowing and the lowering of Schottky barrier heights are observed for Ti/SiGe/Si (l0O) systems, since Ge-rich SiGe layers are formed as a result of solid-phase reaction at the metal/SiGe interface.(2) The contact formation process using H-termination treatments has been developed and it is confirmed to be able to form interfaces with good electrical characteristics. In the case of Ti/p-SiGe/p-Si (100) contacts, it can be found that the trap density is reduced and a nearly idealistic interface is formed by annealing for 30 sec using RTA processes. On the other hand, an increase in leakage current is observed by RTA for n-type samples.(3) The correlation between contact resistivities and B doping concentrations has been examined in order to clarify a maximum doping concentration at metal/Si interfaces. The doping concentration about 2x10^<20> cm^<-3> is realized, which is very close to the solid solubility of B atoms in Si, and the contact resistivity can be explained by the theoretical calculation including the effect of impurity band formation.