Investigation of Ni-based silicide formation by different dynamic surface annealing approaches
Sub-melt millisecond anneal (MSA) is one of major anneal techniques for forming ultra-shallow and highly activated junctions. Besides post-implant anneal for source/drain and source/drain extensions, MSA has also attracted increased interests in nickel-silicide formation recently. During the silicidation process, desired Ni diffusion in forming silicides is competing with un-wanted Ni diffusion along defects paths. The latter will cause higher junction leakage and/or source/drain leakage. Since the activation energy for the un-wanted diffusion is lower, higher process temperature with shorter duration is beneficial for minimizing the un-wanted diffusion. Furthermore, MSA allows high process temperature to be used for silicide formation, which can re-activate some dopants, such as arsenic and phosphors. These dopants are easily deactivated during lower temperature thermal processes post source/drain formation such as silicide block film deposition; therefore, transistor performance can be improved by using MSA for silicidation processes. In this work, dynamic surface annealing (DSA), which is one form of MSA techniques, was applied to form Ni-based silicides. The impacts of different combinations of soak RTA and DSA for thermal steps before and after selective nickel/NiSi strip were examined. One step DSA has been demonstrated effective reduction of Nickel piping by e-beam inspection count, improved NiSi resistance and junction leakage w/o device performance degradation.
Laser annealing applications for semiconductor devices manufacturing
Abstract In the history of semiconductor device fabrication, annealing is one of the critical process steps used to achieve the targeted device performance. Thermal budget requirements in most semiconductor manufacturing process steps have always followed a downward trend through either a reduction of the time spent at high temperature or a lowering of the peak temperature. This was driven at first by the traditional shrinking of structure dimensions which naturally required reducing species diffusion. From the last decade, performance improvements started to be driven essentially by the introduction of new materials (e.g., SiGe alloy, high-k/metal gate stack) and device architecture changes (e.g., 2D planar to 3D FinFET). The current development trend is leading toward 3D integrated circuits to answer the growing demand for increased functionality and performance. Such new drivers impact the whole supply chain, and low thermal budget solutions are now key to manage local strain and stress; limit species diffusion and interdiffusion; and control layer deposition, etch, and quality. In this regard, for a wide variety of applications, laser exhibits superior performance and a more cost-effective solution than nonlaser technologies. Moreover, laser provides flexible, higher throughput to process various materials. Trends regarding laser annealing are expected to experience fast growth, driven by 3D integration applications. In this chapter, we will review the most promising applications for laser annealing from the recent published literature with a focus on realistic candidates for integration in a high-volume semiconductor manufacturing flow, based on electrically relevant results. The first section will be dedicated to power devices, the second section to CMOS logic and 3D integration, and the final section to memory.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.