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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 grow in the ALD, and at higher temperatures between 300 ^oC and 350 ^oC and amorphous TiO₂ layer is grown in the ALD. At temperatures between 150 ^oC and 300 ^oC the TiO₂ layer will be a mixture of both anatase and amorphous TiO₂.

SEM images of both anatase and amorphous TiO₂ are shown below.

For Si wafers, anatase TiO₂ is best grown wafers without native oxide (do an BHF etch), 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.

All results shown on this page have been obtained using the "TiO2" recipe on new Si(100) wafers with native oxide:

Recipe: TiO2

Temperature: 150 ^oC - 350 ^oC

	TMA	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 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 oxide thickness as function of number of cycles
Temperature 150 ^oC.
Temperature 200 ^oC.
Temperature 250 ^oC.

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 \mum, 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 anatase TiO₂ deposited at 300 ^oC on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 \mum, 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.

@@ Line 55: / Line 55: @@
 </gallery>
-Below some SEM images of anatase TiO<sub>2</sub> deposited on trenches are shown.
+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 \mum, 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="Anatase TiO<sub>2</sub> deposited on a Si sample with trenches. Temperature = 120 <sup>o</sup>C, number of cycles = 500. Trench width = 200 nm, trench depth = 4 \mum, i.e. the aspect ratio is 1:20. It is seen that the TiO<sub>2</sub> covrets the trenches very well" widths="350px" heights="350px" perrow="5">
+<gallery caption="" widths="250px" heights="250px" perrow="5">
 image:SEM-TiO2-120C-1.jpg|
 image:SEM-TiO2-120C-2.jpg|
@@ Line 63: / Line 63: @@
 </gallery>
-Below some SEM images of amorphous TiO<sub>2</sub> deposited on trenches are shown
+Below some SEM images of anatase 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 \mum, 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="Amorphous TiO<sub>2</sub> deposited a Si sample with trenches. Temperature = 300 <sup>o</sup>C, number of cycles = 500. Trench width = 200 nm, trench depth = 4 \mum, i.e. the aspect ratio is 1:20. It is seen that the TiO<sub>2</sub> covrets the trenches very well" widths="350px" heights="350px" perrow="5">
+<gallery caption="" widths="250px" heights="250px" perrow="5">
 image:TiO2 trenches-300C-1.jpg|
 image:TiO2 trenches-300C-2.jpg|