Specific Process Knowledge/Thin Film deposition/ALD/TiO2 deposition using ALD: Difference between revisions

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image:TiO2 350C 1250 cycles Si_HF_treated.jpg| Temperature 350 <sup>o</sup>C, 1250 cycles, HF treated.
image:TiO2 350C 1250 cycles Si_HF_treated.jpg| Temperature 350 <sup>o</sup>C, 1250 cycles, HF treated.
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Below some SEM images of anatase TiO<sub>2</sub> deposited at 120 <sup>o</sup>C 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 TiO<sub>2</sub> layer of about 25 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  
Below some SEM images of anatase TiO<sub>2</sub> deposited at 120 <sup>o</sup>C 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 TiO<sub>2</sub> layer of about 25 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  


<gallery caption="" widths="250px" heights="250px" perrow="5">
<gallery caption="Anatase titanium dioxide deposited on Si trenches" widths="250px" heights="250px" perrow="3">
image:SEM-TiO2-120C-1.jpg|
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Below some SEM images of amorphous TiO<sub>2</sub> deposited at 300 <sup>o</sup>C 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 TiO<sub>2</sub> layer of about 26 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  
Below some SEM images of amorphous TiO<sub>2</sub> deposited at 300 <sup>o</sup>C 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 TiO<sub>2</sub> layer of about 26 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  


<gallery caption="" widths="250px" heights="250px" perrow="5">
<gallery caption="Amorphous titanium dioxide deposited on Si trenches" widths="250px" heights="250px" perrow="3">
image:TiO2 trenches-300C-1.jpg|
image:TiO2 trenches-300C-1.jpg|
image:TiO2 trenches-300C-2.jpg|
image:TiO2 trenches-300C-2.jpg|

Revision as of 10:09, 3 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.

TiO2 standard recipe

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

TiO2 deposition rates

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. All result have been obtained for Si wafers with native oxide.

  • Titanium dioxide thickness as function of number of cycles
  • Temperature 150 oC.
    Temperature 150 oC.
  • Temperature 250 oC.
    Temperature 250 oC.
  • Temperature 350 oC.
    Temperature 350 oC.

TiO2 results

Some some SEM images of TiO2 deposited on a Si surface at different temperatures between 150 oC and 350 oC are shown below. Some of samples have been treated with HF (hydrofluoric acid) to remove the native oxide layer silicon samples just before the ALD deposition.

  • Titanium dioxide deposited at different temperatures on a Si surface
  • Temperature 150 oC, 1200 cycles, HF treated.
    Temperature 150 oC, 1200 cycles, HF treated.
  • Temperature 150 oC, 1200 cycles.
    Temperature 150 oC, 1200 cycles.
  • Temperature 250 oC, 750 cycles.
    Temperature 250 oC, 750 cycles.
  • Temperature 300 oC, 1000 cycles, HF treated.
    Temperature 300 oC, 1000 cycles, HF treated.
  • Temperature 300 oC, 1000 cycles.
    Temperature 300 oC, 1000 cycles.
  • Temperature 350 oC, 1250 cycles, HF treated.
    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.

  • Anatase titanium dioxide deposited on Si trenches

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.

  • Amorphous titanium dioxide deposited on Si trenches

Evgeniy Shkondin, DTU Danchip, 2014.

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