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The ALD window for titanium dioxide (TiO<sub>2</sub>) ranges from 120 <sup>o</sup>C to 350 <sup>o</sup>C.  
The ALD window for titanium dioxide (TiO<sub>2</sub>) ranges from 120 <sup>o</sup>C to 350 <sup>o</sup>C.  


A low temperatures between 120 <sup>o</sup>C and 150 <sup>o</sup>C an anatase TiO<sub>2</sub> layer is grow in the ALD, and at higher temperatures between 300 <sup>o</sup>C and 350 <sup>o</sup>C and amorphous TiO<sub>2</sub> layer is grown in the ALD. At temperatures between 150 <sup>o</sup>C and 300 <sup>o</sup>C the TiO<sub>2</sub> layer will be a mixture of both anatase and amorphous TiO<sub>2</sub>.
A low temperatures between 120 <sup>o</sup>C and 150 <sup>o</sup>C an anatase TiO<sub>2</sub> layer is grow in the ALD, and at higher temperatures between 300 <sup>o</sup>C and 350 <sup>o</sup>C an amorphous TiO<sub>2</sub> layer is grown in the ALD. At temperatures between 150 <sup>o</sup>C and 300 <sup>o</sup>C the TiO<sub>2</sub> layer will be a mixture of both anatase and amorphous TiO<sub>2</sub>.


SEM images of both anatase and amorphous TiO<sub>2</sub> are shown below.
For Si wafers, anatase TiO<sub>2</sub> is best grown on wafers without native oxide (removed using BHF), and amorphous TiO<sub>2</sub> is best grown on wafers with native oxide.
 
For Si wafers, anatase TiO<sub>2</sub> is best grown wafers without native oxide (do an BHF etch), and amorphous TiO<sub>2</sub> is best grown on wafers with native oxide.


XPS measurements shows that at temperaturs below 120 <sup>o</sup>C the TiO<sub>2</sub> layer will be contaminated with about 1-3 % chlorine molecules from the TiCl<sub>4</sub> precursor.
XPS measurements shows that at temperaturs below 120 <sup>o</sup>C the TiO<sub>2</sub> layer will be contaminated with about 1-3 % chlorine molecules from the TiCl<sub>4</sub> precursor.
All results shown on this page have been obtained using the "TiO2" recipe on new Si(100) wafers with native oxide:


<b>Recipe</b>: TiO2
<b>Recipe</b>: TiO2


<b>Temperature</b>: 150 <sup>o</sup>C - 350 <sup>o</sup>C
<b>Temperature</b>: 120 <sup>o</sup>C - 350 <sup>o</sup>C


{| border="2" cellspacing="2" cellpadding="5"  align="none"
{| border="2" cellspacing="2" cellpadding="5"  align="none"
|-  
|-  
|
|
!TMA
!TiCl<sub>3</sub>
!H<sub>2</sub>O
!H<sub>2</sub>O
|-
|-
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In the graphs below the TiO<sub>2</sub> thickness as function of number of cycles for deposition temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C can be seen. From the equations the number of cycles required for a certain thickess can be calculated.  
In the graphs below the TiO<sub>2</sub> thickness as function of number of cycles for deposition temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C can be seen. From the equations the number of cycles required for a certain thickess can be calculated.  


<gallery caption="Titanium oxide thickness as function of number of cycles" widths="220px" heights="220px" perrow="5">
<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="220px" heights="220px" perrow="5">
image:ALD_TiO2_grow_rate_150C.jpg| Temperature 150 <sup>o</sup>C.
image:ALD_TiO2_grow_rate_150C.jpg| Temperature 150 <sup>o</sup>C.
image:ALD_TiO2_grow_rate_250C.jpg| Temperature 200 <sup>o</sup>C.
image:ALD_TiO2_grow_rate_250C.jpg| Temperature 200 <sup>o</sup>C.
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</gallery>
</gallery>


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.  
 
SEM images of both anatase and amorphous TiO<sub>2</sub> are shown below.
 
 
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="" widths="250px" heights="250px" perrow="5">
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</gallery>
</gallery>


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.  
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 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="" widths="250px" heights="250px" perrow="5">
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