Specific Process Knowledge/Thin Film deposition/ALD/TiO2 deposition using ALD: Difference between revisions
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<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="200px" heights="200px" perrow="5"> | <gallery caption="Titanium dioxide thickness as function of number of cycles" widths="200px" heights="200px" perrow="5"> | ||
image:TiO2 150C 1200 cycles Si_HF_treated.jpg| Temperature 150 <sup>o</sup>C. | image:TiO2 150C 1200 cycles Si_HF_treated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles, HF treated. | ||
image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature | image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles. | ||
image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature | image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature 250 <sup>o</sup>C, 750 cycles. | ||
image:TiO2 1000 cycles 300C Si_HF.jpg| Temperature | image:TiO2 1000 cycles 300C Si_HF.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles, HF treated. | ||
image:TiO2 1000 cycles 300C Si_un.jpg| Temperature | image:TiO2 1000 cycles 300C Si_un.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles. | ||
image:TiO2 350C 1250 cycles Si_HF_treated.jpg| Temperature 350 <sup>o</sup>C. | image:TiO2 350C 1250 cycles Si_HF_treated.jpg| Temperature 350 <sup>o</sup>C, 1250 cycles, HF treated. | ||
</gallery> | </gallery> | ||
Revision as of 14:23, 2 July 2015
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The ALD window for titanium dioxide (TiO2) ranges from 120 oC to 350 oC.
A low temperatures between 120 oC and 150 oC an anatase TiO2 layer is grown in the ALD, and at higher temperatures between 300 oC and 350 oC an amorphous TiO2 layer is grown. At temperatures between 150 oC and 300 oC the TiO2 layer will be a mixture of both anatase and amorphous TiO2.
For Si wafers, anatase TiO2 is best grown on wafers without native oxide (removed using BHF), and amorphous TiO2 is best grown on wafers with native oxide.
XPS measurements shows that at temperaturs below 120 oC the TiO2 layer will be contaminated with about 1-3 % chlorine molecules from the TiCl4 precursor. This can be seen as small white dots in SEM images of the anatase TiO2 layers.
Recipe: TiO2
Temperature: 120 oC - 350 oC
| TiCl4 | H2O | |
|---|---|---|
| Nitrogen flow | 150 sccm | 200 sccm |
| Pulse time | 0.1 s | 0.1 s |
| Purge time | 3.0 s | 4.0 s |
In the graphs below the TiO2 thickness as function of the number of cycles for deposition temperatures between 150 oC and 350 oC can be seen. From the equations the number of cycles required for a certain thickess can be calculated.
- Titanium dioxide thickness as function of number of cycles
-
Temperature 150 oC. -
Temperature 250 oC. -
Temperature 350 oC.
Some some SEM images of TiO2 deposited on a silicon surface at different temperatures between 150 oC and 120 oC are shown below:
- Titanium dioxide thickness as function of number of cycles
-
Temperature 150 oC, 1200 cycles, HF treated. -
Temperature 150 oC, 1200 cycles. -
Temperature 250 oC, 750 cycles. -
Temperature 300 oC, 1000 cycles, HF treated. -
Temperature 300 oC, 1000 cycles. -
Temperature 350 oC, 1250 cycles, HF treated.
Below some SEM images of anatase TiO2 deposited at 120 oC on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO2 layer of about 25 nm. From the SEM images it is seen that the TiO2 layer covers the trenches very well.
Below some SEM images of amorphous TiO2 deposited at 300 oC on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO2 layer of about 26 nm. From the SEM images it is seen that the TiO2 layer covers the trenches very well.
Evgeniy Shkondin, DTU Danchip, 2014.