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

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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 grown 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. 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 amorphous TiO<sub>2</sub> layer is grown in the ALD, and at higher temperatures between 300 <sup>o</sup>C and 350 <sup>o</sup>C an anatase TiO<sub>2</sub> layer is grown. 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 amorphous and anatase TiO<sub>2</sub>.


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, amorphous TiO<sub>2</sub> is best grown on wafers with native oxide, and anatase TiO<sub>2</sub> is best grown on wafers without native oxide (removed using HF).


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. This can be seen as small white dots in SEM images of the anatase TiO<sub>2</sub> layers.


====TiO<sub>2</sub> standard recipe====


<b>Recipe</b>: TiO2
<b>Recipe</b>: TiO2
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!Purge time
!Purge time
|3.0 s
|4.0 s
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|5.0 s
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In the graphs below the TiO<sub>2</sub> thickness as function of the 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 dioxide thickness as function of number of cycles" widths="300px" heights="300px" perrow="5">
====TiO<sub>2</sub> deposition rates====
 
In the graphs below the TiO<sub>2</sub> thickness as function of the 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 to be deposited can be calculated. All results have been obtained for Si wafers with native oxide. 
 
<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="300px" heights="300px" perrow="3">
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 250 <sup>o</sup>C.
image:ALD_TiO2_grow_rate_250C.jpg| Temperature 250 <sup>o</sup>C.
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</gallery>
</gallery>


Some some SEM images of TiO<sub>2</sub> deposited on a silicon surface at different temperatures between 150 <sup>o</sup>C and 120 <sup>o</sup>C are shown below:
Evgeniy Shkondin, DTU Danchip, April-May 2014.


<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="200px" heights="200px" perrow="5">
 
====TiO<sub>2</sub> results====
 
Some some SEM images of TiO<sub>2</sub> deposited on a Si surface at different temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C are shown below. Some of samples have been treated with HF (hydrofluoric acid) to remove the native oxide layer just before the ALD deposition.
 
<gallery caption="Titanium dioxide deposited at different temperatures on a Si surface" widths="250px" heights="180px" perrow="3">
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_HF_treated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles, HF treated.
image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles.
image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles.
image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature 250 <sup>o</sup>C, 750 cycles.
image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature 250 <sup>o</sup>C, 750 cycles.
</gallery>
<gallery caption="" widths="250px" heights="180px" perrow="5">
image:TiO2 1000 cycles 300C Si_HF.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles, HF treated.
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 300 <sup>o</sup>C, 1000 cycles.
image:TiO2 1000 cycles 300C Si_un.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles.
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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 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.  
XPS measurements of TiO<sub>2</sub> deposited at 120 <sup>o</sup>C and 300 <sup>o</sup>C are shown below. From the XPS measurements it can be calculated that at temperatures 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. This can be also seen as small white dots in the SEM image of the amorphous TiO<sub>2</sub> layers above.
 
[[image:XPS_TiO2.jpg|320x320px|left|thumb|XPS measurements of titanium dioxide.]]
 
<br clear="all" />
 
Evgeniy Shkondin, DTU Danchip, 2014.


<gallery caption="" widths="250px" heights="250px" perrow="5">
image:SEM-TiO2-120C-1.jpg|
image:SEM-TiO2-120C-2.jpg|
image:SEM-TiO2-120C-3.jpg|
</gallery>


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.
====TiO<sub>2</sub> deposition on trenches====


<gallery caption="" widths="250px" heights="250px" perrow="5">
For TiO<sub>2</sub> deposition on trenches more information can be found here:
image:TiO2 trenches-300C-1.jpg|
image:TiO2 trenches-300C-2.jpg|
image:TiO2 trenches-300C-3.jpg|
</gallery>


Evgeniy Shkondin, DTU Danchip, 2014.
*[[Specific Process Knowledge/Thin Film deposition/ALD/TiO2 deposition using ALD/TiO2 deposition on trenches using ALD|TiO<sub>2</sub> deposition on trenches using ALD]]

Latest revision as of 10:27, 19 June 2023

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

For Si wafers, amorphous TiO2 is best grown on wafers with native oxide, and anatase TiO2 is best grown on wafers without native oxide (removed using HF).


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 4.0 s 5.0 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 to be deposited can be calculated. All results 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.

Evgeniy Shkondin, DTU Danchip, April-May 2014.


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 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.

XPS measurements of TiO2 deposited at 120 oC and 300 oC are shown below. From the XPS measurements it can be calculated that at temperatures below 120 oC the TiO2 layer will be contaminated with about 1-3 % chlorine molecules from the TiCl4 precursor. This can be also seen as small white dots in the SEM image of the amorphous TiO2 layers above.

XPS measurements of titanium dioxide.


Evgeniy Shkondin, DTU Danchip, 2014.


TiO2 deposition on trenches

For TiO2 deposition on trenches more information can be found here:

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