Tutorials Manual
Tutorials Manual
Tutorials Manual
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Chemkin 4.1.1<br />
Chapter 4: Materials Problems<br />
4.1.2.3 Project Results<br />
Figure 4-3 shows that the predicted deposition rate increases with increasing<br />
SiF 4 /NH 3 ratio, as expected under these conditions of excess ammonia. Although this<br />
particular plot shows the growth rate of Si(D), choosing to plot the growth rate of N(D),<br />
BULK1 or BULK2 would give essentially the same result.<br />
Figure 4-3<br />
Steady-state Thermal CVD—Deposition Rate vs. SiF 4 Mole Fraction<br />
In studying a CVD system, it is often useful to know the relative importance of gasphase<br />
and surface reactions. For this system, the model shows that very little gasphase<br />
decomposition occurs under these conditions. Figure 4-4 shows the total rates<br />
of production (ROPs) for SiF 4 and NH 3 due to gas-phase and surface reactions. In<br />
these cases, the negative numbers indicate that these are really loss rates rather than<br />
production rates. However, these results clearly show that surface reactions (rather<br />
than gas reactions) dominate the decomposition of these starting materials.<br />
Sensitivity analysis gives complementary information to the ROP analysis. Figure 4-5<br />
shows the silicon nitride growth rate is most sensitive to surface reaction #2, which is<br />
the reaction of SiF 4 at the surface. Figure 4-6 shows that the NH_NH2(S) site fraction<br />
is much larger than the site fractions of the other surface species.<br />
© 2007 Reaction Design 120 RD0411-C20-000-001
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