Boron-enhanced-diffusion of boron: The limiting factor for ultra-shallow junctions

ABSTRACT2. 0 keV 11B+, 2.2 keV 49BF2+ ion implanted and 1.0 kV Plasma Doped (PLAD) wafers of a dose of 1E15/cm2 were annealed at various times and temperatures in a variety of ambiente: 600 to 50,000 ppm O2 in N2; 5% NH3 in N2; N2O; N2 or Ar, in order to investigate the effects of the annealing ambient on the formation of ultra-shallow junctions. RGA data was collected during some (if the anneals to assist in identifying the complex surface chemistry responsible for boron out-diffusion. Subsequent to the anneals, ellipsometric, XPS, four-point probe sheet resistance and SJJVIS measurements were performed to further elucidate the effects of the different ambients on the r etained boron dose, the sheet resistance value, the RTP grown oxide layer and the junction depth. In the cases where oxygen was present, e.g. N2O and O2 in N2, an oxidation enhanced diffusion of the boron was observed. This was most dramatic for the N2O anneals, which at 1050°C 10s diffused the boron an additional 283 to 427 Å, depending on the particular doping condition and species. For the case of BF2 implants and PLAD, anneals in 5% NH3 in N2 reduced the junction depth by a nitridation reduced diffusion mechanism. RGA data indicated that the out-diffusion mechanisms for B and BF2 implanted wafers are different, with the BF2 exhibiting dopant loss mechanisms during the 950°C anneals, producing F containing compounds. B implants did not show doping loss mechanisms, ais observed by the RGA, until the 1050°C anneals and these signals did not contain F containing compounds. Equivalent effective energy boron implants of 8.9 keV BF2 vs. 2.0 keV B, however, indicated that the overall effect of the F in the BF2 implants is very beneficial in the creation of ultra-shallow junctions (compared to B implants): reducing the junction depth by 428 Å, and increasing the electrical activation (determined by SRP) by 11.7%, even though the retained dose (resulting from an increased out-diffusion of B), was decreased by 5.4%.

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Ultra Shallow Junction Formation by RTA at High Temperature for Short Heating Cycle Time

MRS Proceedings ◽

10.1557/proc-532-3 ◽

1998 ◽

Vol 532 ◽

Cited By ~ 13

Author(s):

S. Saito ◽

S. Shishiguchi ◽

A. Mineji ◽

T. Matsuda

Keyword(s):

Beam Current ◽

Process Conditions ◽

Key Factors ◽

Enhanced Diffusion ◽

Junction Formation ◽

Shallow Junctions ◽

Ultra Shallow Junctions ◽

Ion Species ◽

Temperature Time ◽

Short Heating

ABSTRACTIn accordance with decrease of device size, ultra shallow junctions are required for realizing superior device performance. Enhanced diffusion caused by implantation is a crucial factor to realize ultra shallow junctions. Not only implant but also RTA conditions are key factors to suppress enhanced diffusion. In this paper, process conditions to minimize enhanced diffusion are discussed. Implant ion species, energy, dose and beam current parameters are investigated for implantation and temperature, time and ramping rate parameters are investigated for RTA. Important result is that optimization of not only implant but also RTA conditions should be carried out in order to fabricate ultra shallow junctions.

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Vacancy-type defects in ultra-shallow junctions fabricated using plasma doping studied by positron annihilation

2010 International Workshop on Junction Technology Extended Abstracts ◽

10.1109/iwjt.2010.5474912 ◽

2010 ◽

Author(s):

Akira Uedono ◽

Kazuo Tsutsui ◽

Shoji Ishibashi ◽

Hiromichi Watanabe ◽

Shoji Kubota ◽

...

Keyword(s):

Positron Annihilation ◽

Plasma Doping ◽

Shallow Junctions ◽

Ultra Shallow Junctions

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Ultra-Shallow Junctions by Ion Implantation and Rapid Thermal Annealing: Spike-Anneals, Ramp Rate Effects

MRS Proceedings ◽

10.1557/proc-568-19 ◽

1999 ◽

Vol 568 ◽

Cited By ~ 17

Author(s):

Aditya Agarwal ◽

Hans-J. Gossmann ◽

Anthony T. Fiory

Keyword(s):

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Driving Forces ◽

Recent Experimental Data ◽

Enhanced Diffusion ◽

Temperature Ramp ◽

Rate Effects ◽

Low Energies ◽

Ultra Shallow Junctions ◽

P Type

ABSTRACTOver the last couple of years rapid thermal annealing (RTA) equipment suppliers have been aggressively developing lamp-based furnaces capable of achieving ramp-up rates on the order of hundreds of degrees per second. One of the driving forces for adopting such a strategy was the experimental demonstration of 30nm p-type junctions by employing a ramp-up rate of ≈400°C/s. It was subsequently proposed that the ultra-fast temperature ramp-up was suppressing transient enhanced diffusion (TED) of boron which results from the interaction of the implantation damage with the dopant. The capability to achieve very high temperature ramp-rates was thus embraced as an essential requirement of the next generation of RTA equipment.In this paper, recent experimental data examining the effect of the ramp-up rate during spike-and soak-anneals on enhanced diffusion and shallow junction formation is reviewed. The advantage of increasing the ramp-up rate is found to be largest for the shallowest, 0.5-keV, B implants. At such ultra-low energies (ULE) the advantage arises from a reduction of the total thermal budget. Simulations reveal that a point of diminishing return is quickly reached when increasing the ramp-up rate since the ramp-down rate is in practice limited. At energies where TED dominates, a high ramp-up rate is only effective in minimizing diffusion if the implanted dose is sufficiently small so that the TED can be run out during the ramp-up portion of the anneal; for larger doses, a high ramp-up rate only serves to postpone the TED to the ramp-down duration of the anneal. However, even when TED is minimized at higher implant energies via high ramp-up rates, the advantage is unobservable due to the rather large as-implanted depth. It appears then that while spike anneals allow the activation of ULE-implanted dopants to be maximized while minimizing their diffusion the limitation imposed by the ramp-down rate compromises the advantage of very aggressive ramp-up rates.

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