Ultrashallow junctions formed by C coimplantation with spike plus submelt laser annealing

Abstract

A leading candidate for the formation of the ultrashallow junctions needed for L g ഛ 45 nm devices is the combination of coimplantation of a diffusion-retarding species such as carbon with a high temperature, millisecond annealing process after the conventional spike annealing. C coimplantation with B + for p-type metal-oxide semiconductor and P + for n-type metal-oxide semiconductor combined with conventional spike annealing produces reduced junction depths and improved dopant activation and profile abruptness, compared to similar implants without the coimplanted species. Addition of submelt laser annealing may further improve junction activation, but the dominant impact is gate depletion reduction, in that way, delaying the need to introduce metal gates. Devices show that the overlap capacitance is reduced, consistent with the shallower junction depths and reduced lateral diffusion. The improved dopant activation manifests itself in reduced series resistance and improved I on values. Finally, scanning spreading resistance microscopy measurements confirm the shallow junction depths and reduced lateral diffusion.

Impact of carbon co-implantation on boron distribution and activation in silicon studied by atom probe tomography and spreading resistance measurements

“…The most promising approach to realize precisely designed carrier distribution in devices is co-implantation with a different species. [4][5][6][7] However, mutual interactions that occur between the dopants and the co-implanted ions during annealing processes have not been sufficiently investigated. It is therefore necessary to form a deeper understanding of dopant behavior at the atomic level.…”

Microwave Annealing of Phosphorus and Cluster Carbon Implanted (100) and (110) Si

“…Figures 6 shows the SIMS profiles of P, in the presence of the C profiles, for different annealing conditions. It is well known that P diffusion can be strongly reduced by co-implants with C. 19 In Figure 6 we can see that the RTA anneal at 1000 • C for 10 s resulted in a clearly deeper diffused P profile than the MWA anneals, where the annealed P profiles closely follow the as-implanted case. Figure 7 shows the relationship of Rs and junction depth X j .…”

Suppression of boron diffusion in deep submicron devices

“…Unfortunately, the high diffusivity of boron in Si due to the transient enhanced diffusion leads to limited usefulness of the boron halo implants in narrow n-FET devices, as reported by Gossman. 3 One of the ways to reduce boron diffusion is to use a carbon co-implant, as was reported earlier by Felch et al 4 and Lee et al 5 using secondary ion mass spectrometry (SIMS). However, these results provide no information about dopant diffusion in the lateral dimension, which impacts the optimization of the device performance.…”