Short Time Annealing

Abstract

Short time annealing has recently become of interest in silicon processing as a technique to activate ion implanted dopants, remove defects, and regrow amorphized silicon, with minimal diffusion of the dopant atoms. Short time annealing is carried out using a variety of energy sources ranging from arc lamps and resistance heaters with heating times of a few tens of seconds, to laser, electron, and ion sources with heating times of a few milliseconds down to nanoseconds. The annealing processes are grouped according to the time durations of the anneal and with reference to the thermal response time of the silicon. These are designated as adiabatic for < 10−6 sec; thermal flux for 10−6–10−2 sec, and isothermal for > 10−2 sec. Processes in the adiabatic regime result in surface melting, regrowth of silicon free of extended defects, and complete dopant activation. However, the dopant diffuses throughout the melt zone. In the thermal flux and isothermal annealing regimes the dopant can be activated, and amorphous silicon regrown epitaxially with little dopant diffusion. In the limited results reported to date, the complete removal of extended defects has not been achieved. Further investigation may yield new results in extended defect removal.

Chemically derived ferroelectric calcium modified lead titanate thin films deposited from aquo-diol-solvent solutions

“…and ferroelectric properties. We have found, along with other authors [ 19,20], that films crystallized with rapid heating have a better ferroelectric response than films treated in an oven with slow heating rates. Ra-…”

Evolution of dopants and defects in silicon under various annealing sequences

“…Permitting only 15% of the first 100μs of a thermal sequence to dwell within Tpeak -50°C (as in type A) is far more effective at defect free activation than it is to first heat up "slowly" over a millisecond and then spend as much as 50% of the exposure duration within Tpeak -50°. In conclusion, Sedgwick [18] remarked nearly three decades ago that extrapolation of the temperature dependence of dislocation loop removal rates to very short times may not be valid because it is based on defects "that are first formed and then dissolved" -and that in the future, short time annealing may produce different results.…”

“…Within 60μs accumulated duration at 1030°C (or within 9μs of time above 980°C), an exponential diffusion tail characteristic of enhanced diffusion is observed. The 20Å diffusion at 1x10 18 /cm 2 within 9μs near 1000°C indicates an average diffusivity enhancement in the range of at least 10 6 . The 1ms 1230°C also suffers the same fate and demonstrates a similar exponential tail.…”

“…With a micro-probe tip radius of only 3μm and probe spacing of 5μm, the micro-probe is able to provide reliable Rs readings in the middle of the exposed field without the measurement artifacts from proximity to exposure edges that are observed with standard 4-point probe with probe spacing comparable to exposure field dimensions. The pulsed laser, CW laser and lamps provide surface heating rates in the adiabatic, thermal flux or isothermal heating regimes [18] and will be referred to as anneal types A, B and C, respectively in this paper. The peak temperature reached by the silicon surface with anneal types A and B can be affected either by changing the pulse energy or CW-laser power, respectively.…”

Shallow junctions-modeling the dominance of point defect charge states during transient diffusion

“…The result is that pn junction deplhs are deeper than expected due to anomalous transient-enhanced diffusion (8,9). The amount of anomalous transient displacement during ann ealing seems to be greater for dopants thaI diffuse primarily by an inlerstitialcy mechanism (B and P) (7,10,11), compared to vacancy diffusers (As and Sb) (7,11,12).…”