Characterization Of Ni (Si, Ge) Films Under Microwave Annealing And Theoretical Study Of Microwave Annealing

Low thermal budget processing is highly desirable in the formation of ultra-shallow junction source/drain and high-k/metal-gate gate stack used in sub-100nm MOSFET in the traditional gate-first device process flow, therefore the demand for advanced annealing techniques which can get low thermal budget have been kept increasing. Microwave annealing, which is thought to be an alternative technique to get low thermal budget, is drawing more and more attention and is widely used in the semiconductor process investigations these years. Even lots of work have been carried out to investigate its possible application in the semiconductor industry and great results have been gat, little was done to investigate the heating mechanisms of MWA. In this work, we explore the heating mechanisms of MWA and reveal why low thermal budget can be gat under MWA by investigating the different phase formation and temperature behavior of an ultrathin Ni on an epitaxially grown Si0.81Ge0.19layer annealed by MWA and RTP. The material system Ni/epi-Si1-xGex is chosen because upon treatment by RTP, the silicide formation and morphology stability have been well characterized thermodynamically and structurally. Moreover, this material system is relevant for the state-of-the-art CMOS technologies where an epi-Si1-xGex layer is present in the source/drain regions of p-type channel MOS devices for hole mobility enhancement. The investigation details include the following sections:The samples were divided in two groups, the first group of samples was annealed by MWA and the second group of samples was annealed by RTP emulating the temperature-time curves obtained for the MWA samples. Phase formation, resistivity mapping, morphology analysis, and composition evaluation indicate that the formation of low-resistivity NiSi1-xGex by means of MWA occurs at lower temperature than by RTP. Under similar annealing conditions, more severe strain relaxation and defect generation are therefore found in the remaining Sio0.81Ge0.19layers treated by MWA. These results indicate that low thermal budget can be gat by MWA and the heating mechanisms of it differ from RTP, for silicidation under MWA is in essence also due to thermal effects.Then the conductivity loss and dielectric loss were investigated, which play important roles in the microwave absorption.When neglecting heat conduction across the interfaces, and ignoring heat losses due to thermal radiation and convection from the surfaces, absorption formulas were gat for good conductor thin films and lay stacks of two neighbouring good conductor films in microwave filed, which can be used to calculate the absorbed microwave energy. They show that the temperature of Ni film is much higher than the silicon substrate when heated separately or as lay stacks. Even the real temperature difference can’t be that big when heat conduction across the interfaces and heat losses due to thermal radiation and convection from the surfaces are taken into consideration, it’s still reasonable to think that the higher temperature of Ni film will promote the reaction between Ni and Si0.81Ge0.19when the higher temperature is dissipating by heat conduction and heat losses, and that’s also why low thermal budget can be gat by MWA.For the dielectric loss arises from the absorption of microwave by defects, it’s found that the defect density is too low to contribute to a higher temperature in our materials. However, for the position of defects is where the reaction and diffusion take place, the local absorption of microwave energy by defects can contribute to a local higher temperature and then promote the reaction and diffusion, so it still can’t be neglected.