Figure 3: 1.3µm Oxide Uniformity by Date
Figure 6: Interval plot of Nf vs. furnace. No significant difference
in refractive index was observed between pyrolytic and Steamer
derived oxide.
Figure 4: Run-to-Run Variation: Thickness
Figure 7: Film stress by wafer position 1um steamer oxide
Figure 5: Run-to-Run Variation: Standard Deviation Percentage
The top chart illustrates the run-to-run comparison of 5 runs
spaced over three weeks. The bottom chart shows wafer-to-wafer and within-wafer comparisons. This shows variation of
less than 60 angstroms or 0.6% over multiple runs and locations across the furnace.
cycle time at 3.5µm from 27.9 hours to 26 hours, or 7.3%, including
ramp up and ramp down (see Figure 1).
Film uniformity also improved across the furnace. In torch-based
operations, the steam flow rate is kept to the minimum needed
to grow the oxide since higher flow rates increase costs, particles,
maintenance, and the thermal load. However, when using the
Steamer, increased flow rate only marginally increases the power
and DI water requirements. Since the steam is delivered at slightly
above the condensation point, there is no thermal loading or
shadow generated in the tube. This increased steam flow rate can
