Hints, Tips and Solutions

Q: Which are the key parameters for tuning RTA simulations when using the new Stanford diffusion models in ATHENA version 4.0?

A: For RTA applications it is recommended to use the new set of models from Stanford University included in ATHENA version 4.0. These models include effects of <311> defect clusters, dislocation loops and high concentration effects. To enable all these models the syntax used is:

METHOD FULL.CPL CLUSTER.DAM V.LOOP.SINK \

I.LOOP.SINK HIGH.CONC

The syntax METHOD NEWTON is also recommended to improve the speed of simulations.

Since these models are an extension of the existing FULL.CPL models many of the same tuning parameters apply. Previous simulations [1] have shown how the surface recombination rate of intersititials KSURF.0 is a key tuning parameter for reverse short channel effect where damage enhanced diffusion is significant. This is also true in the <311> cluster models.

In RTA simulations with the FULL.CPL model all point defects are created by the implantation. They are at a maximum at t=0 of the RTA and their concentration decays rapidly with time due to diffusion and recombination. As documented in [2], one key effect of the <311>cluster model is that the free point defect concentration is not created at the time of the implant. The implant creates some interstitials but also creates <311> defect clusters. These clusters decay with time releasing point defects over an extended period of time. This effect is particularly apparent at low temperatures.

Clearly then a key parameter for tuning RTA effects is the time constant for the dissolution of <311> clusters to interstitials. This is controlled by the syntax:

CLUSTER SILICON TAU.311.0=<val> TAU.311.E=<val>

Measured data [3] shows that the enhanced diffusivity due to point defects extends over minutes at 800C. Figure 1 shows ATHENA results matched to the measured data in Figure 2 of [3]. In this case the value of TAU.311.0 is adjusted to show lower diffusion in the first 15seconds than the FULL.CPL model predicts. For comparison a lower value of TAU.311.0 is used in Figure 2. It is clear that this does not match the data in [3] as a significant part of the complete diffusion is in the first 15 seconds.


Figure 1. RTA of a 5.0e13 phosphorus implant matched to experimental data in [3].


Figure 2. The effect of lower TAU.311.0 is to speed up the diffusion over the initial time period.

References

[1] Hints and Tips, Simulation Standard December 1995

[2] S. Crowder and P. Griffin, Simulation Standard August 1996

[3] M. Giles, J. Electrochem Soc. Vol 138 p1160 (1991)